Citation
Polymorphisms in Candidate Genes for the Nitric Oxide Pathway in Sickle Cell Patients with Acute Chest Syndrome and Asthma

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Title:
Polymorphisms in Candidate Genes for the Nitric Oxide Pathway in Sickle Cell Patients with Acute Chest Syndrome and Asthma
Creator:
Duckworth, Laurie J D
Place of Publication:
[Gainesville, Fla.]
Florida
Publisher:
University of Florida
Publication Date:
Language:
english
Physical Description:
1 online resource (89 p.)

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Nursing Sciences
Nursing
Committee Chair:
Stechmiller, Joyce K.
Committee Members:
Feeg, Veronica
Johnson, Julie A.
Frazier, Lorraine
Lima, John
Graduation Date:
8/11/2007

Subjects

Subjects / Keywords:
Acute chest syndrome ( jstor )
Alleles ( jstor )
Asthma ( jstor )
Disease risks ( jstor )
Diseases ( jstor )
Introns ( jstor )
Lungs ( jstor )
Oxides ( jstor )
Sickle cell disease ( jstor )
Sickles ( jstor )
Nursing -- Dissertations, Academic -- UF
acute, asthma, cell, chest, disease, nitric, oxide, polymorphisms, sickle, syndrome, synthase
City of Jacksonville ( local )
Genre:
bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Nursing Sciences thesis, Ph.D.

Notes

Abstract:
Sickle cell disease (SCD) is one of the most common genetic diseases, affecting one in 600 African Americans. Acute chest syndrome (ACS) is the leading cause of mortality and the second most common cause of hospitalizations in patients with SCD accounting for nearly half of premature deaths. A number of recent studies have reported that asthma may increase the risk of ACS in children with sickle cell disease. Nitric oxide is thought to play a key role in the pathogenesis of ACS. The main objectives of this study were to test the hypotheses that polymorphisms in candidate genes; Arginase 1, nitric oxide synthase (NOS) genes; NOS1 and NOS3, associate with ACS in SCD patients and to characterize the association between physician-diagnosed asthma and ACS. A total of 134 participants between 5-21 years of age with SCD were enrolled. Associations between acute chest syndrome and asthma with the following polymorphisms were explored: the AAT in intron 13 (formerly intron 20) of the NOS1; T-786C and G894T and the repeat polymorphism in intron 4 of NOS3; and ARG I Pvu polymorphism. African Americans (n=74) comprised a cohort of healthy controls owing to non-Hardy-Weinberg equilibrium (HWE) in some variants. Physician-diagnosed asthma was determined by chart review, parental report, and medication use. Eighty five percent of participants with asthma had at least on episode of ACS compared to 14.6 % of participants without ACS; adjusted odds ratio (OR) (95%CI) 5.46 (2.20,13.5), P = ? 0.0001. Physician-diagnosed asthma correlated with the number of episodes of ACS (P ? 0.001). The NOS1 AAT repeat polymorphism associated with the risk of ACS (P = 0.001) in patients without physician-diagnosed asthma. No associations were found between the NOS3 T-786C polymorphism and ACS. Carriers of the ARG I minor allele were less likely to have asthma, 22/79 (28%) compared to WT homozygotes 6/47 (13%); p = 0.04. Findings from this study suggest that asthma is a major risk factor for ACS. The NOS1 AAT repeat polymorphism may contribute to ACS in SCD patients without asthma. Studies that further characterize the association between asthma, ACS, and NOS genes in children with sickle cell disease are warranted. ( en )
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis:
Thesis (Ph.D.)--University of Florida, 2007.
Local:
Adviser: Stechmiller, Joyce K.
Statement of Responsibility:
by Laurie J D Duckworth.

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UFRGP
Rights Management:
Copyright Duckworth, Laurie J D. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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CHAPTER 1
INTRODUCTION

Sickle cell disease (SCD) is one of the most common genetic diseases, affecting one in

600 African Americans. Acute chest syndrome (ACS) is the leading cause of mortality and the

second most common cause of hospitalizations in patients with sickle cell disease (SCD)

accounting for nearly half of premature deaths (Platt et al., 1994; Stuart, & Setty 2001; Buchanan

et al., 2004). Our current understanding of the pathophysiology and mechanisms leading to

ACS in SCD is limited and remains unclear. In a large prospective study infection and

pulmonary fat embolism were identified as causal in 38% of episodes, but in approximately 50%

of cases no cause was determined (Vichinsky et al., 2000).

Nitric oxide (NO) is thought to play a key role in the pathogenesis of ACS (Gladwin et

al., 1999). NO is formed through the hydrolysis of arginine to NO by nitric oxide synthase

(NOS). Arginine acts as a substrate for both NOS and arginase. The arginase and NOS pathways

can interfere with each other via substrate competition (Morris, 2002) (Fig 1-1). Recent studies

suggest that asthma may be related to decreased NO bioavailability (de Boer et al., 1999; Meurs,

Maarsingh, Zaagsma, 2003) rather than an overproduction due to inflammation

(Kharitonov&Barnes, 2007). This may occur as a result of the increased activity of arginase

(Meurs et al., 2002; Zimmermann et al., 2003). Notably, plasma concentrations of NO are

reduced during ACS as a consequence of reduced NO bioavailability (Morris et al., 2006)

(Morris, et al., 2004).

Compared to normal control subjects, arginine concentrations were lower and the activity

of arginase, the enzyme that hydrolyzes arginine to omithine and urea, was higher in patients

with asthma (Morris et al., 2004). Addtionally, arginase expression was strongly induced by IL-

4 and IL-13 in mice models of asthma and by Th 2 cytokines, which may contribute to NO









Theoretical Framework

Sickle Cell disease is the most common genetic disorder among African Americans.

Acute Chest syndrome is a leading cause of death in patients with SCD. The incidence of asthma

is greater in African Americans compared to Caucasians (Lugogo & Kraft, 2006). Racial

disparities in the morbidity and mortality associated with asthma can be staggering suggesting

that African Americans may receive substandard care with regard to diagnosis and treatment

(Ford, & McCaffrey, 2006). The reasons for this are unclear but may involve many factors

including; access to care, payment, and, educational resources. Theoretically, it stands to reason

that patients with SCD who also have asthma may be more susceptible to the complication of

ACS.

There is compelling evidence to support the central role of NO in the initiation of the

pathophysiological process in acute chest syndrome. Stuart et al (1999) found that serum NO

concentration metabolites were decreased during ACS with values lower than patients in steady

state, without ACS. Decreased NO production in patients with ACS may be the final common

pathway leading to ongoing hypoxemia, pulmonary hypertension, and acute lung injury. Patients

prone to develop ACS have decreased levels of FENo even during periods of stability (Sullivan et

al., 2001). This may be due to genetic variations in candidate genes that regulate NO, which

predispose patients to reduced NO production and recurring episodes of ACS. A growing body

of research suggests that decreased expression of NO synthase genes resulting in decreased NO

production is deleterious to the lung and may lead to acute chest syndrome (Hammerman et al.,

1999). Identifying these patients before developing ACS may decrease the morbidity and

mortality associated with this condition.

To date few modifiable risk factors for ACS have been identified. Several retrospective

studies have reported that having asthma may increase the risk of developing ACS in the SCD









deficiency in asthma (Zimmermann et al., 2003). Wechsler et al (2000), identified a group of

patients with asthma with low concentrations of FENo that was inversely related to the AAT

repeat polymorphism in intron 13 on the NOS1 gene.

Recent studies demonstrate that administration of inhaled NO has beneficial effects in

treating ACS (Stuart & Setty, 2001; Sullivan et al., 1999; Atz & Wessel, 1997). Sullivan et al

(2001) reported lower concentrations of exhaled nitric oxide (FENo) in children who previously

had ACS. Additionally, they reported that low FENo was associated with a repeat polymorphism

in intron 13 (formerly called intron 20) on the NOS1 gene (Sullivan, 2001). Other NOS genes

may also be associated with ACS. For example, the NOS3 T-786C polymorphism and

increased susceptibility to ACS in females with SCD was reported (Sharan et al., 2004). Chaar et

al., (2006) reported that the C-786 allele was associated with a decreased risk of ACS. Genes that

are involved in the regulation of NO may be important in ACS because of the central role NO

plays in airway inflammation and the pulmonary endothelium.

In addition to genetic factors, environmental factors may contribute to the susceptibility

of patients with SCD to develop ACS. A number of recent studies have reported that asthma may

increase the risk of ACS in patients with SCD (Boyd et al., 2004; Knight-Madden et al, 2005;

Bryant, 2005; Nordness, 2005; Sylvester et al., 2007). These reports were based on studies that

documented a link between SCD and airway hyperresponsiveness, lower airway obstruction,

reversibility, abnormal pulmonary function tests and the fact that corticosteroids and

bronchodilators, drugs commonly used in asthma, were beneficial in ACS (Santoli et al., 1998;

Koumbourlis et al., 2001) (Klings et al., 2006).

The purpose of this study was to characterize the association between asthma and SCD.

The second aim of this study was to determine associations between polymorphisms in candidate









exhaled nitric oxide (FENo) (Weschler et al., 2000). These findings are extremely important

given that FENO is now widely accepted as a marker for airway inflammation in patients with

asthma. Results from this study may help explain the phenotypic variability among asthmatics.

In a genetic association study, Gao and colleagues (2000) tested whether variants ofNOS1,

NOS2, and NOS3 were related to asthma. Neither NOS2 nor NOS3 variants showed any

association with asthma. They did however find an association between variants in NOS1 and

asthma. More specifically they described significant differences in 183 bp allele frequencies

between control and asthmatic subjects. Homozygous 183 bp alleles were strongly associated

with asthma.

Nitric Oxide Synthase 2 (iNOS)

NO derived from NOS2 induciblee NOS or iNOS) is involved in inflammatory diseases of

the airways (Barnes, 1995). NOS2 has been shown to be upregulated in asthmatics and is a

substantial source of NO in the airways (Xia, 1992). Konno et al investigated whether the 14-

repeat allele (CCTTT) of the NOS2 gene influences the development of atopy and asthma. Their

findings suggest that the CCTTT repeat polymorphism is associated with atopy but not with

asthma. A recent study in 230 families with asthma investigated the genetic association of iNOS

repeats with asthma. Four repeats were identified; (CCTTT)n promoter repeat, intron 2(GT)n

repeat, intron 4 (GT)n repeat, and an intron 5 (CA)n repeat. This study is the first to identify

repeat polymorphisms in the iNOS gene and their association with asthma. Individuals carrying

allele 4 of the promoter repeat had high serum IgE and nitric oxide levels, characteristic of

asthma. Individuals carrying allele 3 of the intron 4 (GT)n repeat had elevated blood eosinophils

and increased asthma severity (Batra et al., 2006).

Given the role of NOS2 in airway inflammation further genetic studies are warranted

exploring variants in the gene and how they may contribute to asthma pathology.









You/your child's DNA samples will remain in possession of the Nemours Children's Clinic

and stored in Jacksonville, FL. The results of this genetic research might be valuable for

commercial and/or intellectual property (for example, patent) purposes. If you decide to

participate in this genetic research, you are giving your/your child's sample to Nemours

Children's Clinic. Nemours Children's Clinic retains sole ownership of the research results, and

of any use or development of the research records (including your/your child's sample)

consistent with this consent. You will not receive any financial benefit that might come from the

research results.

WILL I HAVE ACCESS TO THE GENETIC INFORMATION?
You/your child will not be notified of individual results from DNA tests and no results will

appear in your/your child's medical records.


HOW ELSE MIGHT THESE SAMPLES BE USED?
The samples obtained in this study will be analyzed for genes of related to sickle cell

disease and other related diseases. Samples will not be shared with other investigators.

Your/your child's DNA samples will not be sold. It is possible that we may wish to contact

you/your child for further study. If you do not want yourself/your child to be re-contacted for

further study, please indicate by checking the box below:

I do not wish (my child) to be re-contacted
I do wish (my child) to be re-contacted

PARENT'S (LEGAL REPRESENTATIVE) STATEMENT OF CONSENT
By signing this form, you have not waived any of the legal rights which your child

otherwise would have as a participant in a research study.









A recent study in children with SCD was conducted to determine whether children with

SCD have restrictive lung disease and if so whether this abnormality increases with age. Sixty-

four children with SCD and 64 ethnic matched controls, ages 5-16 years were studied.

Compared to controls, children with SCD had lower mean forced expiratory volume (FEV 1),

lower forced vital capacity (FVC), and lower peak expiratory flow (PEF). The effect of age on

lung function differed significantly between the two groups. Findings from this study

demonstrate that children with SCD have a restrictive airway disease pattern and this

abnormality increases with age. A limitation of this study is that episodes of acute chest

syndrome were not reported for children with SCD (Sylvester et al., 2004).

In 2006, this same group of investigators tested the hypothesis that children with SCD and

a positive history of acute chest syndrome would have worse lung function compared to children

with SCD and no history of acute chest syndrome. Forty subjects were enrolled, 20 positive for

ACS, and 20 negative for ACS. The mean total lung capacity and residual volumes were

significantly higher in children who had no history of ACS. They did not however demonstrate

any differences in bronchodilator reversibility tests. Their findings suggest that children with

SCD and a positive history for ACS have significant differences in lung function as compared to

children with SCD and no history of ACS. These differences are consistent with restrictive

airway disease often seen in adults with SCD (Sylvester, 2006).

A cross-sectional study of 310 adults with SCD found that 90% of subjects showed a

restrictive airway disease pattern. Additionally, they reported that the presence of restrictive

airway disease was associated with a more severe clinical course (Klings et al., 2006).

Koumbourlis and colleagues investigated the prevalence and reversibility of lower airway

obstruction in children with SCD ages 5-18 years. Interestingly they found that obstructive









CHILDREN'S INFORMED ASSENT (for 6 to 12 year olds)
You are being asked to be in a research study. Before you decide whether you want to be in it,
we want to tell you about it so you can ask any questions you have about it.
The doctor in charge of the study is Dr. Lima. This doctor would like to find out if you have
certain genes that influence whether or not you develop acute chest syndrome (a lung disease
associated with sickle cell disease). Genes come from your mother and father and help make up
what you look like and how your body works.
If you decide to be in the study, here is what will happen. For this study, you will be asked to
gargle with a mouthwash.
To gargle, you will first wash out your mouth with water. You will then gargle some mouthwash
for one minute and spit the mouthwash into a tube. You can also choose to gargle the
mouthwash for shorter periods of time more than once until you have gargled mouthwash for one
minute.
You may feel burning or tingling from the mouthwash.
You don't have to do the study if you don't want to. If you are in the study, you can stop being it
at any time. Nobody will be upset at you if you don't want to be in the study or if you want to
stop being in the study. The doctors and their assistants will take care of you as they have in the
past. If you have any questions or don't like what is happening, please tell the doctor or assistant.
Your parent or guardian knows about this study. You have had the study explained to you and
you have been given a chance to ask questions about it. By writing your name below, you are
saying that you know what will happen to you in the study and that you want to be in it.


Child's Signature Signature of Witness


Researcher's Signature Date









antimicrobial properties against pathogens including viruses and mycobacterium (Xia & Zweir,

1997). Endogenous NO is produced from the amino acid L-arginine by the enzyme NO synthase

which has three isoforms. Two constitutive forms (cNOS); neuronal (nNOS or NOS1) and

endothelial (eNOS or NOS3) are found in small quantities and serve basal metabolic functions.

The third isoform, inducible (iNOS or NOS2) is mediated by inflammatory cytokines and

endotoxin and plays a major role in the inflammation seen in asthma. All three of these isoforms

are found in the respiratory tract (Kobzik et al., 1993; Robbins et al., 1994).

Historical Events Leading to the Discovery of Nitric Oxide

Nitric oxide was discovered by Joseph Priestley in 1772 as a clear, colorless gas. In 1980.

Furchgott (1980) discovered that endothelial cells produce endedothelium relaxing factor

(EDRF) in response to acetylcholine In 1987 Moncada & Higgs (1987) and Ignarro et al (1987)

discovered that EDRF is nitric oxide. Within a years time Moncada reported that NO is

synthesized from the amino acid L-arginine (Palmer, Ashton & Moncada, 1988). Nitric Oxide

was proclaimed as molecule of the year on the cover of Science magazine in 1992. (Koshland,

1992). Six years later, the importance of the nitric oxide discovery was recognized by awarding

the Nobel Prize in Physiology and Medicine to Furchgott, Ignarrao, and Murad (Williams, 1998).

By 1993 NO had been implicated in the pathogenesis of a multitude of diseases including,

hypertension, septic shock, and dememntia (Moncada & Higgs, 1993). The next ten years led to

multiple publications related to NO, on average over 6000 papers per year addressing all areas of

medicine, including diabetes, wound healing, neurotransmission, cancer, immune function,

infection, eye disease, and respiratory function (Yetik-Anacak & Catravas, 2006). Presently it is

difficult to find a disease that is not associated with nitric oxide. This is amazing in that nitric

oxide was considered as nothing more than an irritant and pollutant twenty years ago (Moncada

& Higgs, 1993).









Methods And Procedures


Study Design

A prospective descriptive correlation study design was utilized to investigate the

association between polymorphisms in NOS genes and the incidence of ACS and asthma in

children with sickle cell disease. Participants with a positive history of ACS served as cases,

those without served as controls. The diagram (Figure 2-1) illustrates the study protocol used in

this study.

Consent

Informed consent and children's assent was obtained in accordance with the requirements

and guidelines of the Institutional Review Boards at The University of Florida, Nemours

Children's Clinic, and Emory University. Participants and their guardians were approached in

person by the study coordinator or principal investigator. The purpose, risks, and benefits of the

study were explained and reviewed in detail. The participants right to withdraw from the study

at any time without penalty was discussed.

Demographic Information

General demographic information was collected from the participant and guardian

following informed consent. (Appendix B)

Medical History

A brief medical history checklist was completed by the study coordinator or PI following

informed consent (Appendix C).

Acute Chest Syndrome Diagnosis

The diagnosis of ACS was determined by history and chart review. ACS was defined by

the presence of multilobar infiltrates by chest radiograph and history of cough, hypoxemia, and

dyspnea. Patients with at least one episode of ACS were classified as cases. Patients with SCD









chest syndrome and found that within two hours of exposure there were increases in NOS 3

protein and NOS 3 enzyme activity. They suggested that alterations of NO production and

metabolism contribute to the pathogenesis of ACS. In a 30-center study, Vichinsky et al (2000)

studied 671 episodes of ACS in 538 patients with SCD to determine the cause. They reported

ACS is precipitated by fat embolism and a variety of lung infections including; chalmydia,

mycoplasm, and legionella. More importantly their results show that in more than 50% of cases

the cause of ACS was undetermined. They conclude that the etiology for ACS remains unclear.

Surprisingly, the incidence of asthma in this study is reported to be 2%, significantly lower than

what is generally seen in the African American population.

Similarities and Differences Between Asthma and ACS with Regard to Symptomology and
Lung Function

A number of recent studies have reported that asthma may increase the risk of ACS in

patients with SCD (Boyd et al., 2004; Knight-Madden et al., 2005; Bryant, 2005; Nordness et al.,

2005). These reports were based on studies that documented a link between SCD and airway

hyperresponsiveness, lower airway obstruction, reversibility, abnormal pulmonary function tests

and the fact that corticosteroids and bronchodilators, drugs commonly used in asthma, were

beneficial in ACS (Santoli et al., 1998; Koumbourlis et al., 2001; Klings et al., 2006). Several

papers are cited in the literature describing pulmonary function in patients with sickle cell

disease (Koumbourlis et al., 2001; Sylvester et al., 2004, 2006; Klings et al., 2006). Exposure to

repeated vaso-occlusive crisis undoubtedly has an impact on the pulmonary vasculature resulting

in airway damage. This type of injury results in restrictive airway disease as opposed to the

obstructive airway disease seen in asthmatics. Multiple episodes of vaso-occlusive crisis and

recurrent episodes of ACS may result in irreversible airway damage (Sylvester, 2004, 2006;

Klings, 2006).









polymorphism in the NOS1 gene and the arginase 1 gene, neither of which showed differences

with regard to HWE.

Figure 2-1. Diagram of study protocol.


*History of asthma was not reported for one participant









abnormal hemoglobin from the other parent will have another form of sickle cell disease, such as

thalassemia (Goldman, 2004).


Patients with sickle cell disease require continuous treatment, even when they are not

having a painful crisis. The purpose of treatment is to manage and control symptoms, and to try

to limit the frequency of crises. Supplementation with folic acid, an essential element in

producing red blood cells, is required because of the rapid red blood cell turnover. Analgesics

and hydration are mainstay treatments for patients during a sickle crisis. Treatment of pain is

critical. Non-narcotic medications may be effective, but many patients require narcotics.

Hydroxyurea was found to help some patients by reducing the frequency of painful crises and

episodes of acute chest syndrome. It also been shown to decrease the need for blood transfusions.

Newer drugs are being developed to manage sickle cell anemia. Some of these drugs work by

trying to induce the body to produce more fetal hemoglobin (in an attempt to decrease the

amount of sickling), or by increasing the binding of oxygen to sickle cells. To date, there are no

other commonly used drugs available for treatment (Hoffman, 2005).


Acute Chest Syndrome

Acute Chest Syndrome is a common complication of sickle cell disease and is the leading

cause of premature death in this population (Platt, 1994) (Stuart et al., 1994) (Buchanan et al.,

2004). ACS is characterized by the presence of multi-lobe infiltrates, cough, dyspnea, hypoxia,

and often chest pain. The pathophysiology of ACS is unclear but recent research indicates that

NO plays a central role in airway pathology associated with this condition (Hammerman et al.,

1999). This is not surprising when we take into account that the lung contains all three forms of

nitric oxide synthase (NOS), NOS 1, 2, and 3. Kharitonov et al (1995) demonstrated that oral

administration of L-arginine to healthy subjects increased exhaled nitric oxide (ENO) levels.









APPENDIX C
MEDICAL HISTORY

Date of birth

Hb type SS SC S beta thel S other

Baseline pulse ox

Premature birth yes no

Asthma yes no

Reactive airway disease yes no

On any long term Antisickling therapy yes no

Episodes of ACS

Dates






Medications

PRN Albuterol
ICS
Singulair
Salmeterol









was relatively high, 0.69, then declined to a risk of about 0.4 at 12 to 15 repeats (n = 87 alleles,

63%), followed by an increased risk at higher numbers of repeats (n=35 alleles, 25.4%). The r2

for the regression was 0.76; and the p values for coefficients of quadratic regression line: x and

x2, were 0.024 and 0.024, respectively. For SCD patients with physician-diagnosed asthma, the

mean SD risk of ACS was higher than in non-asthmatics: 0.87 0.09 vs. 0.49 0.12; p =

0.001, and was not associated with AAT repeat numbers. No associations were found between

the risk of ACS and the T-786C NOS3 polymorphism in either the asthma or the no-asthma

cohorts or by sex (Data not shown). A modest association was found between the A2/A1 ARG1

polymorphism and asthma (Table 4-4). Carriers of the Al allele (Al homozygotes and

heterozygotes) were less likely to have asthma, 22/79 (27.8%), compared to A2 homozygotes,

6/47 (12.8%) (Fisher's exact test: = 3.98; p = 0.04).









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primarily as an S-nitroso adduct of serum albumin. Proceedings of the National Academy
of Science U.S.A., 89, 7674-7677.

Storm Van's Gravesande, K., Mattes, J., Endlicher, A., & Alving, K. (2004). Effect of two doses
of budesonide on exhaled nitric oxide and urinary EPX excretion in asthmatic children.
Pneumologie, 58(7), 483-8

Stuart, M. J., & Setty, B.N. (1999) Sickle cell acute chest syndrome: pathogenesis and rationale
for treatment. Blood, 94, 1555-1560

Stuart, M. J.& B. N. Setty. (2001). Acute chest syndrome of sickle cell disease: new light on an
old problem. Current Opinions Hematology, 8, 111-122.

Styles, L. A., Schalkwijk, C.G., Aarsman, A.J., Vichinsky, E.P., Lubin, B.H., & Kuypers F.A.
(1996). Phospholipase A2 levels in acute chest syndrome of sickle cell disease. Blood, 87,
2573-2578.









compared to 14.6 % of participants without ACS; adjusted odds ratio (OR) (95%CI) 5.46

(2.20,13.5), P = < 0.0001. Physician-diagnosed asthma correlated with the number of episodes of

ACS (P < 0.001). The NOS1 AAT repeat polymorphism associated with the risk of ACS (P =

0.001) in patients without physician-diagnosed asthma. No associations were found between the

NOS3 T-786C polymorphism and ACS. Carriers of the ARG I minor allele were less likely to

have asthma, 22/79 (28%) compared to WT homozygotes 6/47 (13%); p = 0.04.

Findings from this study suggest that asthma is a major risk factor for ACS. The NOS1

AAT repeat polymorphism may contribute to ACS in SCD patients without asthma. Studies that

further characterize the association between asthma, ACS, and NOS genes in children with sickle

cell disease are warranted.









Laurie Duckworth MSN, ARNP
Nemours Children's Clinic
807 Children's Way
Jacksonville, FL 32207
(904) 390-3483
(904) 390-3600 (operator)
(800) SOS-KIDS


WHO CAN I TALK TO ABOUT MY RIGHTS AS A STUDY SUBJECT?
Tim Wysocki, Ph.D.
Chairperson
Nemours-Florida IRB
Nemours Children's Clinic
807 Children's Way
Jacksonville, FL 32207
(904) 390-3698

WHAT IS THE PURPOSE OF THIS STUDY?
Some patients with sickle cell anemia may develop a condition called acute chest

syndrome (ACS). This condition is believed to be caused by the sickle red blood cells clogging

the blood vessels in the lungs. After repeated episodes of ACS, the blood pressure in the blood

vessels between the heart and lungs can remain high permanently. This condition is called

pulmonary hypertension.

The doctors who take care of children with sickle cell anemia have noticed that certain

children have a greater tendency to develop repeated episodes of acute chest syndrome while

others do not develop this complication. The reason for this is not clear. Likewise, intensive

care doctors who care for children with the acute chest syndrome have noticed that these children

respond dramatically to an inhaled gas called nitric oxide (NO) when they are extremely ill. NO

is a gas that is made in the cells that line the pulmonary (lung) blood vessels and is normally

made in our own bodies. We believe that children with sickle cell anemia who are prone to ACS

may not make enough NO in their pulmonary (lung) blood vessels. Recent research has shown









presence of inflammatory cells and mediators. Sputum examination is noninvasive and is one of

the few methods available that can produce valuable information from the lower respiratory tract

(Busse, 1998). Sputum sampling in children may be impractical in that it is time consuming,

expensive, and requires cooperation from the child. Additionally, these measures may only

reflect the severity of disease at the time of measurement. (Ratnawati & Thomas, 2005).

The great advantage of FENO measurement is that sample collection is noninvasive and

can be performed repeatedly (Kissoon et al., 1999; Barnes, 1996). There are several analyzers

now commercially available that have the capability to measure FENO. Most of the studies done

to date measure nitric oxide using a chemiluminescence analyzer which detects the

photochemical reaction between NO and ozone in the analyzer. (Kharitonov et al., 1994,1996;

Kissoon et al., 1999; Smith et al., 2005) The beauty of this method is the ability to measure

FENO directly in line to the analyzer, in real time, or indirectly by obtaining an exhaled air

sample in a balloon to be later analyzed at a more convenient time. Levels of FENO are reported

in parts per billion (ppb). Until recently reported values for FENO have varied widely most

likely due to significant differences in sampling technique. Major differences relate to exhalation

flow rate and nasal contamination (Kissoon et al., 1999). The American Thoracic Society has

published guidelines for FENO measurement in adults and children (American Thoracic Society,

1999). Portable devices are currently being developed for at home monitoring of FENO in

patients with asthma.

Exhaled nitric oxide is reduced in patients receiving anti-inflammatory treatment (Massaro

et al., 1995; Kharitonov, et al., 1996, 2007). It is believed that glucocorticoids prevent the

induction of inducible NOS (iNOS/NOS2) by cytokines in epithelial cells. (Kharitonov et al.,

1996). Measuring FENO may be useful for monitoring whether anti-inflammatory therapy is









Fagan, J. K., Scheff, P.A., Hryhorczuk, D., Ramakrishnan, V., Ross, M., & Persky, V. (2001).
Prevalence of asthma and other allergic diseases in an adolescent population: association
with gender and race. Ann Allergy Asthma Immunol 86, 177-184.

Frostell, C., Hogman, M., Hedenstrom, H., & Hedenstierna, G. (1993). Is nitric oxide inhalation
beneficial to the asthmatic patient? Am Rev Respir Dis. 147:,A515.

Ford, J.G., & McCaffrey, L. (2006). Understanding disparities in asthma outcomes among
African Americans.Clin Chest Med. 27(3), 423-30.

Furchgott. R.F.,& Zawadzki, J.V. (1980). The obligatory role of endothelial cells in the
relaxation of arterial smooth muscle by acetylcholine. Nature. 288, 373-376.

Gaston, B., Drazen, J.M., Loscalzo, J., & Stamler, J.S. (1994). The biology of nitrogen oxides in
the airways. Am JRespir Crit Care Med. 149, 538-551.

Gaston, B., Drazen, J., & Jonsen, A. (1994). Relaxation of bronchial smooth muscle by S-
nitrosothiols invitro. JPharmacolExp Ther. 268, 978-985.

Getahun, D., Demissie, K., Rhoads, G.G. (2005). Recent trends in asthma hospitalization and
mortality in the United States. Journal ofAsthma. 42, 373-378.

Gladwin, M. T., Schechter, A. N., Shelhamer, J.H., & Ognibene, F.P., (1999). The acute chest
syndrome in sickle cell disease. Possible role of nitric oxide in its pathophysiology and
treatment. Am JRespir Crit Care Med, 159, 1368-1376.

Goldman L, & Ausiello D. (2004). Cecil Textbook of Medicine. 22nd ed. Philadelphia, Pa: WB
Saunders; 1030-1039.

Grasemann, H., et al. (1999). Simple tandem repeat of polymorphisms in the neuronal nitric
oxide synthase gene in different ethnic populations. Human Heredity, 139-141.

Grasemann, H., Yandava, C.N., & Drazen, J.M. (1999). Neuronal NO synthase (NOS1) is a
major candidate gene for asthma. Clinical and Experimental Allergy, 29, 39-41.

Grasemann, H., Storm vans's Gravesande, K., Buscher, R., Drazen, J.M., & Ratjen, F. (2003).
Effects of sex and of gene variants in constitutive nitric oxide synthase on exhaled nitric
oxide. American Journal ofRespiratory Critical Care, 167(8) ,1113-6.

Gustafsson, L.E. (1998). Exhaled nitric oxide as a marker in asthma. European Respiratory
Journal, 11(Suppl.), 4s-52s.

Hammerman, S.I., Klings, E.S., Hendra, K.P., Upchurch, G.R., Rishikof, D.C., Loscalzp, J., &
Farber, H.W. (1999). American Journal ofPhysiology, (Heart and Circulatory
Physiology), 277, 1579-1592.

Hart, C.M. (1999). Nitric oxide in lung disease. Chest, 111(5), 1407-1417.









Nitric Oxide Synthase 3 (eNOS)

Endothelial nitric oxide (eNOS) is expressed in the airway and pulmonary epithelium and

serves an important role in vasodilator tone (Shaul et al., 2002; Vallance & Moncada, 1989).

Genome screenings have identified gene linkages to eNOS and asthma. (Holgate, 1997; Lee et al

2000) demonstrated an association in polymorphisms of eNOS and angiotensin covering

enzyme in patients with asthma. A more recent study also looking at polymorphisms of eNOS

and angiotensin covering enzyme in patients with asthma found no relationship among

polymorphisms ofNOS3 and asthma (Yildiz et al., 2004). Finally, a study in 163 patients with

asthma found no relationship between the tandem repeat polymorphism in intron 4 and the

(G894T) variant of the NOS3 gene with atopic asthma (Holla et al., 2002). Although widely

discussed, there is a lack of research in the literature demonstrating as association among

polymorphisms in the NOS3 gene and asthma.

Nitric Oxide and Acute Chest Syndrome

Most of the morbidity associated with sickle cell disease stems from vaso-occlusive crisis

(Platt, 1994) (Vichinsky et al., 2000). Nitric oxide is a vasodilator (Busse, 1998). Could a

polymorphism in nitric oxide synthase genes interfere with or inhibit nitric oxide production?

Several studies are beginning to address this. Morris et al. (2000) found that there may indeed be

a relationship between L-arginine and the NO pathway. Their study attempted to sort out the

issue of substrate deficiency or substrate depletion. Sickle cell patients may experience lengthy

periods of vaso-occlusion, creating a constant demand for vasodilation mechanisms, i.e. NO

production. This overwhelming need or utilization may deplete the quantity of the substrate, L-

arginine, thereby decreasing overall NO production (Morris et al., 2000). Interestingly, Morris's

group studied 36 patients at steady state (period of wellness) and during vaso-occlusive crisis

(VOC). During steady state, L-arginine levels were normal. L-arginine levels were decreased









BIOGRAPHICAL SKETCH

Laurie Duckworth, native Floridian, grew up in Miami, Florida. She received her Bachelor

of Science in Nursing with honors from Florida State University in 1983 and began her career as

a registered nurse in the burn unit at Jackson Memorial Hospital, Miami, Florida. In 1985 she

relocated to Jacksonville, Florida and was employed as a pediatric intensive care nurse. In 1987

she joined Nemours Children's Clinic, Jacksonville, Florida as a registered nurse and clinic

coordinator. For the past 17 years she has served as a clinical research coordinator in the

Biomedical Research Department with a focus on pulmonary disorders, specifically asthma and

acute chest syndrome. She enrolled in the accelerated BSN to PhD program at the University of

Florida in 2001 and completed her Masters of Science in Nursing degree and received her license

as a nurse practitioner in 2003. She is a member of Sigma Theta Tau, Council for the

Advancement of Nursing Science, Florida Nurse Practitioners Association, Association of

Clinical Research Professionals, and the Florida Nurse's Association.

The summer of 2003 she was awarded a competitive grant from the National Institutes of

Nursing Research, National Institutes of Health for a fellowship in genetics and completed a

minor degree in genetics at Georgetown University. In 2006 she presented at the National

Congress for Nurse Scientists in Washington, D.C. As a nurse scientist, she realizes the

importance of how she may contribute to society through scientific research. She strongly

believes that dissemination of knowledge through research in a multidisciplinary setting will

enhance and contribute to evidence-based practice.









CHAPTER 5
DISCUSSION

Acute chest syndrome is the leading cause of mortality and the second most common cause

of hospitalizations in patients with sickle cell disease accounting for 25% of premature deaths

(Platt, 1994; Stuart & Setty, 1999; Buchanan et al., 2004). The prevalence of ACS in children

with SCD in our study was 64%, which was in reasonable agreement with a previous study4 that

reported prevalence rates of 61% in 0 to 9 year olds, and 46% in 10 to 19 year olds, suggesting

that our sample was representative of the SCD population. In the present study, we identified

physician-diagnosed asthma as an important risk factor for ACS in patients with SCD. The

prevalence of physician-diagnosed asthma in SCD in our study was 36% (48 of 133

participants), and is in good agreement with those reported in previous studies, which ranged

between 17% and 53% (Boyd et al., 2004; Knight-Madden et al., 2005; Bryant, 2005; Nordness

et al., 2005) Among SCD patients with physician-diagnosed asthma, 85.4% had at least one

episode of ACS compared to 14.6% for participants who did not experience an episode of ACS

(OR= 5.47; p <0.0001). The prevalence of physician-diagnosed asthma in non-ACS

participants is in excellent agreement with the prevalence of asthma in African American

children without SCD (Yeatts & Shy, 2001; Fagan et al., 2001; Koumbourlis et al., 1997).

Importantly, our data also show that the proportion of patients with SCD who have physician-

diagnosed asthma increases linearly as the number of ACS episodes increase (Figure 2). To our

knowledge our study is the first to show this relationship, and, given the mortality and morbidity

associated with ACS, underscores the importance of coordinated pulmonary and sickle cell

hematology care in diagnosing asthma in SCD. These data are also important because they

point to the testable hypothesis that the aggressive treatment of asthma may reduce the mortality

and morbidity of ACS in SCD patients.









LIST OF FIGURES


Figure page

1-1 Metabolic pathways for Arginine, Arginase, Nitric oxide synthase, and Nitric oxide......20

2-1 D iagram of study protocol. ...................................................................... ....................27

4-1 Comparison of distributions of alleles carrying AAT repeats in intron 13 on NOS 1
g e n e ................... ...................5...................5..........

4-2 Prevalence of physcian-diagnosed asthma and acute chest syndrome episodes ...............56

4-3 Risk of ACS and NOS 1 AAT repeats in intron 13 ............................ .................57









LIST OF ABBREVIATIONS

ACS acute chest syndrome

AAT intronic repeat NOS 1 gene

DNA deoxyribonucleic acid

FENO exhaled nitric oxide

ICS inhaled corticosteroid

NO nitric oxide

cNOS constitutive nitric oxide synthase

eNOS endothelial nitric oxide synthase (NOS3)

HWE Hardy-Weinberg equillibrium

iNOS inducible nitric oxide synthase (NOS2)

LABA long-acting beta agonists

OR odds ratio

PCR polymerase chain reaction

nNOS neuronal nitric oxide synthase (NOS1)

SABA short-acting beta agonists

SCD sickle cell disease

SNP single nucleotide polymorphism

NCC Nemours Children's Clinic









WHAT ARE THE POTENTIAL BENEFITS TO ME/MY CHILD OR OTHERS?
There is no direct medical benefit to you/your child for participating in this study.

Although you/your child may not benefit directly from this research, there may be a benefit to

society, in general, from the knowledge gained in connection with your/your child's participation

in this study.


IS BEING IN THE STUDY VOLUNTARY?
Being in this study is totally voluntary. Anyone who does take part in the study can stop

being in it at any time. There will be no change to the medical care given to anyone who decides

not to be in it or who stops being in it. The researchers will destroy the samples obtained from

anyone in the study if they are asked to do so.


WHAT ARE ALTERNATIVE TREATMENT OR PROCEDURES?
There are no alternative procedures for this study other than you/your child can choose not

to participate.


WHAT HAPPENS IF MY CHILD DEVELOPS PROBLEMS FROM BEING IN THE
STUDY?
In the event that your child suffers any injury directly resulting from these studies, you

may contact any of the investigators listed on the front of this form. In the event that your child's

participation in this study results in a medical problem, treatment will be made available. No

other compensation of any type is available through Dr. Sylvester, Dr. Lima, Dr. Kissoon, Dr.

Hsu Dr. Sullivan, Laurie Duckworth or Nemours Children's Clinic. Nemours Children's Clinic

will not pay for treatment if your child suffers any injury related to this study.

You are responsible for reporting any adverse effects) to the investigator in charge as soon

as possible.









Hoffman R, Benz Jr. EJ, & Shattil SJ, et al., (2005). Hematology: Basic Principles and Practice.
4th ed. Philladelphia, Pa: Churchill Livingston.

Holgate, S.T. (1997). The cellular and mediator basis of asthma in relation to natural history.
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Holla, L.I., Buckova, D., Kuhrova, V., Stejkalova, A., Francova, H., Znojil, V., & Vacha, J.
(2002). Prevalence of endothelial nitric oxide synthase gene polymorphisms in patients
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Ignarro, L.J., Buga. G.M., Wood, K.S., Byrns, R.E., & Chaudhuri,G.(1987). Endothelium
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Khairtonov, S.A., Yates, D.H., Robbins, R.A., et al. (1994). Increased nitric oxide in exhaled air
of asthmatic patients. Lancet, 343,133-135.

Kharitonov, S.A., Lubec, G., Lubec, B., Hjelm, M., & Barnes, P.J. (1995). Clinical Science
(Lond), 88, 135-139.

Kharitonov, S.A., Yates, D.H., Chung, K.F., & Barnes, P.J. (1996). Changes in the dose of
inhaled steroids affect exhaled nitric oxide levels in asthmatic patients. European
Respiratory Journal, 9, 196-201.

Kharitonov, S., & Barnes, P.J. (2007). Exhaled Biomarkers. Chest, 130,1541-1456.

Klings, E. S. Wyszynski, D.F., Nolan, V.G., & Steinberg, M.H.. (2006). Abnormal pulmonary
function in adults with sickle cell anemia. American Journal Respiratory Critical Care
Medicine, 173, 1264-1269.

Knight-Madden, J. M., T. S. Forrester, N. A. Lewis, & A. Greenough. (2005). Asthma in
children with sickle cell disease and its association with acute chest syndrome. Thorax 60,
206-210

Kobzik, L., Bredt Lowenstein, C.J., Drazen, J., Gaston, B., Sugarbaker, D.,& Stamler, J.S.
(1993). Nitric oxide synthase in human and rat lung: immunocytochemical and
histochemical localization. American Journal of Respiratory Cellular Molecular Biology.,
9, 371-377.

Koshland, D.E. (1992). The molecule of the year. Science, 258, (5090), 1861.














1.0- /* *
1.0 95% CI


co 0.8 /

CO,
0.6 -

/y = 0.178+0.097x
0 0.4
o /

0.2 -



0.0
0 2 4 6 8 10

Number of episodes (x)

Figure 4-2. Prevalence of physcian-diagnosed asthma and acute chest syndrome episodes. The
proportion of SCD patients having physician-diagnosed asthma was plotted against
the number of episodes of acute chest syndrome in children with sickle cell disease.
Reprinted with permission by Wiley-Liss. Duckworth, L. et al. (2007). Pediatric
Pulmonology, 42(4), 334









adequate as well as patient compliance. A recent paper in The New England Journal of Medicine

reported that in patients with chronic, persistent asthma, treatment with inhaled corticosteroids

could successfully be titrated with the use of FENo measurements. Thus FENo measurements may

help to minimize the potential long-term side effects related to inhaled corticosteroids (Smith et

al., 2005; Deykin, 2005) With new technology currently available, FENo measurements are easy

to perform, can be reproduced accurately, and provide immediate results on which the primary

care provider can act.

While several studies have described the value of FENo measurement as a useful indicator

of airway inflammation and asthma (Cicutto & Downey, 2004; Karitonov et al ,2007; Zeidler,

Kleerup, Tashkin, 2004; Smith et al., 2005), few studies have addressed the variance of these

levels in patients with asthma or acute chest syndrome. Genetic variation may contribute to the

variability in exhaled nitric oxide levels. A limited number of studies have reported the

contribution of genetic variants in candidate genes for the NO pathway and how they may

correlate with exhaled nitric oxide and asthma.

Storm and colleagues (2003) identified a strong association between a NOS3 gene variant,

G893T, and the variability of FENO levels in patients with asthma. FENO levels were lowest in

subjects with the TT genotype and were significantly higher in subjects with either the GT or GG

genotype. As mentioned previously, the number or trinucleotide repeats (AAT) in the NOS1

gene correlated with FENO values in patients with asthma however varied depending on

genotype (Wechsler et al., 2000). Grasemann et al (2003) investigated FENO in both NOS1 and

NOS3 genes. Specifically they studied the number of AAT repeats in intron 13 (formerly intron

20) of the NOS1 gene and the 894G/T mutation in the NOS3 gene. They found no genetic

association between FENO levels and the NOS 1 gene. However, they did report that females









LIST OF TABLES


Table page

4-1 Characteristics of self-identified African Americans with sickle cell disease who had
at least one episode of acute chest syndrome (cases) and individuals with no episodes
of acute chest syndrome e (controls). ............................................................................. 54

4-2 Comparison of Hardy-Weinberg Equilibria (HWE) and minor allele frequencies of
NOS 1, NOS 3 and ARG I polymorphisms in 134 patients with sickle cell disease
(SCD ) and 74 healthy controls................................................ ............................... 54

4-3 Influence of physician-diagnosed asthma on the risk of having at least one episode of
acute chest syndrome in patients with sickle cell disease (cases) compared to no
physician-diagnosed asthm a (controls)........................................ .......................... 55

4-4 Association between ARG1 A2/A1 polymorphism and asthma among SCD patients.....57









The association between ACS and two polymorphisms in the NOS3 gene: E298D and T-

786C, has been reported in 87 African Americans with SCD (Sharan et al., 2004). The C-786

allele was associated with an increased risk of ACS in females (n=45; relative risk=8.7). We

were not able to replicate these data in the present study. The reasons for this are unclear, but

may be related to small number of patients in our study who did not have physician-diagnosed

asthma. Whether or not participants in the study by Sharan et al had physician-diagnosed asthma

is not clear.

The etiology of ACS is not completely understood but is known to involve infection,

pulmonary infarctions and pulmonary fat embolism (Vinchinsky et al., 2000; Vinchinsky et al

1994). Free fatty acids released by the hydrolysis of phospholipids in embolized fat can cause

acute lung injury (Styles et al., 1996). Isoenzymes of phospholipase A2 (PLA2) hydrolyze

phospholipids at the sn-2 position to generate lysophospholipids and free fatty acids (Dennis,

1994). Both cytosolic PLA2 and secretary PLA2 (sPLA2) function to generate arachidonic acid

from phospholipids in inflammatory cells (Balsinde et al., 1994; Calabrese et al., 2000). Plasma

concentrations of secretary phospholipase (sPLA2) are elevated in ACS ) (Styles et al., 1996)

and have been proposed as accurate markers of ACS in patients in SCD crises (Styles et al.,

2000; Naprawa et al., 2005). Asthma is accompanied by increased production of arachidonic

acid and enhanced activity of cysLT (Calabrese et al., 2000). Thus, it may be postulated that the

asthma phenotype associated with ACS in SCD may be leukotriene-dependent, and therefore

may be responsive to the leukotriene modifiers: 5-lipoxygenase inhibitors or leukotriene receptor

antagonists. Additionally, earlier studies have shown that corticosteroids may provide some

benefit to patients with ACS (Bernini et al., 1998), although associated with rebound

vasoocclusive pain when stopped abruptly. Aggressive treatment with moderate to high doses









SCD have restrictive lung disease owing to repeated episodes of pulmonary vaso-occlusion,

which increases with age (Klings et al., 2006). Moreover, SABA and ICS are often prescribed to

patients with sickle cell lung disease. Although our study confirms the results of previous

studies that physician-diagnosed asthma is associated with ACS, and further shows that the risk

of physician-diagnosed asthma is strongly associated with the number of ACS episodes, it is not

clear that participants with physician-diagnosed asthma in our study had true asthma as defined

by conventional methods. Clearly, further studies are warranted to determine if obstructive lung

disease and asthma increase the risk of ACS in children with SCD.

In a pilot study of non-asthmatic children with SCD, we reported that FENo levels were

reduced in individuals with ACS compared to those without ACS and to a cohort of healthy

African American children (without SCD) (Sullivan et al., 2001). We also reported that levels of

FENo were inversely related to the allelic sum of AAT repeats in intron 13 of NOS1 gene, which

suggested a genetic link for ACS and led us to hypothesize that this repeat variant associated

with ACS. A specific aim of the present case-control study was to determine the association

between the AAT repeat polymorphism and ACS. We found that the risk of ACS in individuals

without physician-diagnosed asthma was reduced in alleles with 12 to 15 repeats compared to

alleles with < 12 or with alleles carrying 16 or more repeats. These data support the hypothesis

that the risk of ACS in SCD patients without asthma is associated with the AAT repeat

polymorphism, thereby implicating a genetic basis this disease. However, the association we

found, if true, was modest and may represent of false-positive association owing to small

numbers. The confounding influence of physician-diagnosed asthma on the risk of developing

ACS (Figure 3) reduced our numbers and our power to detect a true genetic association. Thus

we conclude that a larger study is warranted to replicate our findings.









During the mid 1990's several studies demonstrated that nitric oxide plays a key role in

physiological regulation of airway disease (Gaston & Jonsen, 1994; Shaul et al., 1994; Barnes,

1995; Kharitonov et al 1994,1995,1996; Massaro et al., 1995, 1996). More specifically,

numerous studies reported increased exhaled nitric oxide levels in patients with asthma (Alving

Weitzberg, & Lundberg, 1993; Kharitonov et al., 1994, 1996; Barnes, 1995; Massaro et al.,

1995). Nitric oxide is released by a variety of pulmonary cells including epithelial cells,

eosinophils, and macrophages (Yates, 2001). It is believed that elevated nitric oxide in the

airways is generated by inducible nitric oxide synthase (iNOS) mediated by inflammatory

cytokines and endotoxin (Asano et al., 1994).

There is compelling evidence to support the central role of NO in the initiation of the

pathophysiological processes in acute chest syndrome. Stuart and Setty (1999) observed that

serum concentration of NO metabolites were decreased during episodes of ACS with values

lower than controls and patients in steady state. Recent studies have shown that L-arginine levels

are low in patients with sickle cell disease (Lopez et al., 2003; Enwonwu, 1990), and decreased

to an even greater extent in patients who have sickle cell disease with evidence of ACS (Morris

et al., 2000). These findings support the key role of NO in the pulmonary endothelium and

airway inflammation.

Nitric Oxide Mechanisms of Action

Nitric oxide (NO) is a simple free radical gas. NO reacts with oxygen to form nitrite and

nitrates. Endogenous nitric oxide is produced from the amino acid L-arginine by the enzyme NO

synthase, which has three isoforms (Nathan, & Xia, 1994) (Figl-1). Two constitutive forms

(cNOS); neuronal (nNOS or NOS1) and endothelial (eNOS or NOS3) and are found in small

quantities and serve basal metabolic functions. The third isoform, inducible (iNOS or NOS2) is

mediated by inflammatory cytokines and endotoxin and plays an important role in the









CHAPTER 4
RESULTS

The primary aim of the study was to characterize the association between physician-

diagnosed asthma and acute chest syndrome. The secondary aim of this study was to test the

hypothesis that polymorphisms in candidate genes for the NO pathway associate with ACS in

SCD patients.

Descriptive Results

A total of 134 children with SCD participated. Forty-eight patients with SCD had no

history of having ACS (36%) (controls), 86 at least one episode of ACS (64%) (cases). Fifty

percent of cases had either 1 or 2 episodes. No differences in age or sex were observed between

cases and controls (Table 1). Ninety percent (n=121) of patients with SCD were homozygous for

PS globin (HbSS); 6% (n=8) were heterozygous (HbSC); 3% (n=4) patients had sickle beta

thalassemia (HbS3); and genotype data on one patient was missing. On average the age for the

first episode of ACS was 4.4 years; the median age was 3.5 years; and the range was <1 to 17

years old. There was no relationship between age and the number of ACS episodes (data not

shown). The prevalence of physician-diagnosed asthma in our study was 36.1% (48 of 133;

asthma status was not recorded in one participant). There was 100% concordance between

physician-diagnosed asthma and asthma reported by patients or guardians. All participants with

physician-diagnosed asthma were taking inhaled SABA; 68.8 % were on ICS (33/48); 2 and 3

participants were on LABA (salmeterol) and LTRA (montelukast) respectively.

Genotyping

The success rate of genotyping ranged between 95 and 100% (average rate was 97.6%).

Table 2 compares the minor allele frequencies of the polymorphisms in SCD and healthy

controls. In SCD participants, the NOS1 AAT repeat polymorphism and the ARGI variant were









population. Wechsler et al. identified a group of patients with asthma with low concentrations of

FENo that was inversely related to the number of AAT repeats in intron 13 on the NOS1 gene.

This study did not include patients with SCD (2000). A study in a SCD population reported that

the number of AAT repeats in intron 13 of the NOS 1 gene associated with FENo levels; lower

levels associated with a higher number of repeats (Sullivan, 2001)

The overall objective of this study was to determine whether patients with ACS and SCD

have one or more genetic polymorphisms in candidate genes for the nitric oxide pathway that

may predispose them to ACS. More specifically, the study will compare allele frequencies and

genotype distributions of polymorphisms in NOS 1, NOS 3, and Arginase 1 genes in children

with sickle cell disease and ACS with age, gender, and asthma. Additionally this study will

explore associations between asthma and ACS.









TABLE OF CONTENTS

page

A CK N O W LED G M EN T S ................................................................. ........... ............. .....

LIST OF TA BLES ..................... ......... ...............................................................................................

LIST OF FIGURES .................................. .. ..... ..... ................. .8

LIST OF A BBREV IA TION S ......... ............... ...........................................................9

A B S T R A C T ................................ ............................................................ 10

CHAPTER

1 INTRODUCTION ............... .......................................................... 12

B background and Significance .................................................................................. ............... 14
Acute Chest Syndrome and Nitric Oxide .................................... .......... .................. 14
N itric O xide Synthase Enzym es ......................................................................... ...... 15
Nitric Oxide, Airway Inflammation, ACS, And Asthma..............................................16
Significant ce of R research .......................... .......... ........................................... .......... ..... ... 16
R research A im s and H ypotheses.............................................................................. ............17
S p ecific A im 1 ......................................................................... 17
H y p oth esis ...................................... ................................................... 17
S p ecific A im 2 ........................................................................ 17
H y p oth esis ...................................... ................................................... 17
Significance to N using ........................ .. ........................ .. .... ........ ........ 17
T heoretical F ram ew ork .......... .................................................................... ........... .. 18

2 M A TER IA L S A N D M ETH O D S ........................................ .............................................21

S u b j e c ts ..........................................................................................................2 1
Sam ple and Setting .............. ......................... ......... ... ..................... 21
In clu sion C criteria ...............................21..............................
Exclusion Criteria ...................... ................... .... ......... 21
M ethods A nd P rocedures............................................................................. .....................22
S tu d y D e sig n .............................................................................2 2
C o n se n t ................................ .......................................................2 2
D em graphic Inform action ....................................................................... ..................22
M medical History ................................. ............................... ......... 22
A cute Chest Syndrom e D diagnosis ............................................................. ............... 22
A sth m a D iag n o sis......... ...... ........................ ............................................ .. .... ........ .. 2 3
Isolation of G enom ic D N A ..................................................................... ..................23
G en oty p in g ................................................................2 4
Statistical A nalysis................................................... 25









of inhaled corticosteroids and a leukotriene modifier (5-liopoxygenase inhibitor or LTRA) in

SCD patients with physician-diagnosed asthma and SCD may reduce the mortality and morbidity

associated with ACS.

Conclusions

In summary, our study confirmed that physician-diagnosed asthma is an important risk

factor for ACS in SCD patients, and further demonstrated that the incidence of physician-

diagnosed asthma was highly correlated with the number of episodes of ACS. Our study

suggests that the NOS1 AAT repeat polymorphism may contribute to the risk of ACS in patients

without physician-diagnosed asthma, and that the A2/A1 ARGI polymorphism may contribute to

the incidence of asthma in SCD patients. Further studies are warranted to determine if

aggressive treatment of physician-diagnosed asthma reduces the risk of ACS in SCD, and if the

AAT repeat polymorphism contributes to ACS. It is important to note that our sample is

representative of the general African American population in that 14.6% of children with

physician diagnosed asthma who did not have a history of ACS is consistent with the incidence

of asthma nationally.

Implications for Clinical Practice

Findings from this study suggest that asthma may be a significant risk factor in children

with SCD for developing ACS. Quite often in primary care settings an asthma diagnosis is not

assigned before the age of 2 years. More specifically we often see related diagnoses such as

reactive airway disease, coughing, or upper airway congestion. In children with SCD the average

age for the first ACS episode is between 2 to 4 years of age. Provider education regarding the

association between asthma and ACS may heighten awareness of asthma related symptoms in

infants and young children with SCD and result in more aggressive airway management.

Additionally, educating the caregivers of patients with SCD regarding asthma symptoms and









inflammation seen in asthma. All three of these isoforms are found in the respiratory tract

(Kobzik, 1993;Robbins, 1994). Synthesis of NO by cNOS is thought to be responsible for

vasodilator tone associated with regulation of blood pressure, neurotransmission, respiratory

function, cardiac contractility, and also plays a role in platelet aggregation (Nathan & Xia,

1994;Yates, 2001; Hammerman et al., 1999). NOS1 and NOS3 are regulated by intracellular

calcium concentration, whereas NOS2 is induced under inflammation independent of calcium

concentration. Agonists such as stress, bradykinin, acetylcholine, and histamine may activate

cNOS resulting in the release of pico molar levels of NO. Conversely, iNOS is generated by

cytokines present in the airway and produce nano molar levels of NO (Yates, 2001).

NO impacts vascular homeostasis in a variety of ways. Levels of NO may inhibit smooth

muscle cell proliferation, platelet aggregation, and platelet and monocyte adhesion to the

endothelium. Low levels, or decreased bioavailabilty of NO may lead to hypertension, coronary

artery disease, peripheral artery disease, sickle cell, or stroke (Puddu et al., 2005).

Nitric oxide acts as a vasodilator, bronchodilator, neurotransmitter, and mediator of

inflammation in the lung (Barnes, 1993). Due to its role in smooth muscle relaxation, NO

showed promise as a bronchodilator. A study in guinea pigs demonstrated that NO will limit

methacholine-induced bronchoconstriction however the effect is short-lived and requires high

levels of inhaled NO (Dupuy et al., 1992). A study in asthmatics revealed that inhalation of NO

has a small effect on airway caliber and resistance, thus not showing much promise as a

therapeutic agent (Frostell e tal, 1993). Smooth muscle exists in both the bronchi and pulmonary

vasculature within the lung. Numerous studies demonstrate that NO plays a key role in

pulmonary arterial vasoconstriction (Dinh-Xuan, 1992; Leeman & Naecje, 1995; Yetik-Anacak









asthma, 4 million children (6%) had an asthma attack within the last 12 months, African

American children were more likely to have had an asthma attack in the last 12 months, and

children in fair or poor health were more than six times as likely to have had and asthma attack

in the past 12 months (National Center for Health Statistics, 2003). This is staggering given that

the National Institutes of Health and the international Global Initiatives for Asthma have focused

on asthma treatment and asthma management (National Heart, Lung and Blood Institute, 2003).

A recent study conducted by the American Lung Association Asthma Clinical Research

Centers reported that the number of asthma episodes was highest in children less than 10 years of

age. Additionally they found that African American ethnicity and a past history of severe asthma

were risk factors for poor asthma control (McCoy, et al., 2006). Minority groups with diverse

ethnic backgrounds experience disparities in asthma care and management resulting in increased

mortality (Coultas, Gong, & Grad, 1993). Lieu et al (2002) found that African American

children had worse asthma status compared to Caucasian children based on the American

Academy of Pediatrics Children's Health Survey (AAP), experiencing a greater number of

symptom-days, and an increased number of school absences. Additionally they discovered that

African American and Latino children were less likely to be using inhaled corticosteroid

medication compared to Caucasians. Notably, this cross sectional study included 1000 subjects

between the ages 2-16 years with a diagnosis of asthma, participating in a managed care

Medicaid plan. Zoratti and colleagues (1998) examined patterns of asthma care in 464 African

Americans and 1609 Caucasians with participating in a managed care program. Compared with

Caucasians, African Americans had fewer visits to asthma specialists, filled fewer prescriptions

for inhaled steroids, and were more likely to visit the emergency room for treatment of asthma.









Table 4-1. Characteristics of self-identified African Americans with sickle cell disease who had
at least one episode of acute chest syndrome (cases) and individuals with no episodes
of acute chest syndrome (controls).
Characteristic Cases (ACS) Controls (No ACS)
Number 86 48
Mean SD age, years 12.6 4.64 14 + 8.9
Mean SD age at 1st ACS 4.4 + 3.6
episode, years
Percent female 49.3 50.0
Percent on Hydroxyurea
Current 5.8 10.4
Ever 12.7 16.6
Percent on chronic PRBC* 18.6 12.5
transfusion
Reprinted with permission by Wiley-Liss
Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 334.
*Packed Red Blood Cells. =Data from 70 participants


Table 4-2. Comparison of Hardy-Weinberg Equilibria (HWE) and minor allele frequencies of
NOS 1, NOS 3 and ARG I polymorphisms in 134 patients with sickle cell disease
(SCD) and 74 healthy controls


Gene Polymorphism Minor Allele Frequency
(reference SNP) Sickle Cell Disease Healthy
participants Controls
AAT repeats in intron 13 0.091 0.21
NOS 1 (WT, > 12; minor, < 12)
T-786C (rs2070744) =0.098 0.155
NOS3 G894T (rsl799983)= 0.14 0.121
27 bp repeat in intron 4 =
A=4 repeat 0.303 0.277
B=5 repeats 0.363 0.291
C=6 repeats 0.059 0.014
A2/A1 v(rs17599586) 0.133 0.142
ARG1
Reprinted with permission by Wiley-Liss
Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 335


= indicates polymorphisms not in HWE in patients with SCD
v Al is the T allele; which is not cut by Pvu II; A2 is the C allele, which is cut by Pvu II.









WHAT HAPPENS IF I DECIDE FOR MY CHILD NOT TO PARTICIPATE OR TO
WITHDRAW MY CHILD FROM THE STUDY?
If you decide that you do not want you/your child's samples to be studied any longer and

you wish your/your child's samples to be destroyed, you can notify the investigators listed on the

front of this form.

You understand that your consent for you/your child to participate in this study is given

voluntarily. You may withdraw yourself/your child from or decide not to participate in the study

at any time without prejudice. If you decide for yourself/your child to no longer participate in

this study, it will not affect your/your child's future health care at Nemours Children's Clinic.


CAN I/MY CHILD BE TAKEN OUT OF THE STUDY WITHOUT MY CONSENT?
Presently, there is no known reason for taking you/your child out of this study without

your consent. However, the study investigators can remove your sample from the study at any

time, for any reasons) deemed appropriate.


WHAT ARE THE COSTS FOR BEING IN THE STUDY?
There will be no charge to you or your insurance company for the tests involved in this

study.


HOW WILL PEOPLE BE PAID FOR BEING IN THIS STUDY?
You will not be paid for participating in this study. You will not receive, either now or in

the future, compensation, financial benefits, or any royalties which result from information

obtained from this study.


WILL I BE TOLD OF NEW FINDINGS WHILE THE STUDY IS IN PROGRESS?
Participants will be told of any significant new findings developed during the course of this

study that may relate to their willingness to continue participation in the study..









LIST OF REFERENCES


Akinbami, L.J., & Schoendorf, K.C.(2002). Trends in childhood asthma: prevalence, heath care
utilization, and mortality. Pediatrics: 110(2 Pt 1),315-322.

Alving, K., Weitzberg, E., & Lundberg, J.M. (1993). Increased amount of nitric oxide in exhaled
air of asthmatics. Eur Respir, 6,1268-1270.

Asano, K., Chee, C.B., Gaston, B., Lilly, C.M., Gerard, C., Drazen, J.M., & Stamler, J.S. (1994).
Constitutive and inducible nitric oxide synthase gene expression, regulation, and activity in
human lung epithelial cells. Proc Natl Acad Sci U.S.A., 91(21),10089-10093.

Atz, A.M., & Wessel, D.L. (1997). Inhaled nitric oxide in sickle cell disease with acute chest
syndrome. Anesthesiology. 87,998-990.

Balsinde, J.S., Barbour, E., Bianco, I.D.,& Dennis, E.A., (1994). Arachidonic acid mobilization
in P388D1 macrophages is controlled by two distinct Ca(2+)-dependent phospholipase A2
enzymes. Proc NatlAcad Sci U.S.A., 91,11060-11064.

Barnes, P.J., & Belvisi, M.G. (1993). Nitric oxide and lung disease. Thorax. 48,1034-1043.

Barnes, P.J. (1995). Nitric oxide in airway disease. Ann. Med., 27, 389-393.

Batra, J., Singh, T., Mabalirajan, U., Sinha, A., Prasad, R., Ghosh, B. (2006). Association of
inducible nitric oxide synthase with asthma severity, total serum immunoglobin E and
blood eosinophil levels. Thorax, 62, 16-22.

Bernini, J. C., Rogers, Z. R., Sandler, E. S., Reisch, J. S., Quinn, C. T., & Buchanan, G. R.,
(1998). Beneficial effect of intravenous dexamethasone in children with mild to
moderately severe acute chest syndrome complicating sickle cell disease. Blood 92,3082-
3089

Biernacki, W.A., Kharitonov, S.A., Diemacka, H.M., & Barnes, P.J. (2005) Effect of
Montelukast on exhaled leukotrienes and quality of life in asthmatic patients. Chest, 128,
1958-1963.

Boyd, J. H., Moinuddin, A., Strunk, R.C., & Debaun, M. R.(2004). Asthma and acute chest in
sickle-cell disease. Pediatr Pulmonology, 38, 229-232.

Boyd, J. H., Macklin, E. A., Strunk, R. C.,& Debaun. M. R.(2006). Asthma is associated with
acute chest syndrome and pain in children with sickle cell anemia. Blood, 108, 2923-2927.

Bryant, R. (2005). Asthma in the pediatric sickle cell patient with acute chest syndrome. J
Pediatr Health Care, 19, 157-162.

Buchanan, G.R., Debaun, C.T., & Steinberg, M..H. (2004). Sickle cell disease. Hematology AM
Soc Hematol. Educ. Program, 35-47.









7, and a 27-bp-repeat VNTR in intron 4. They found no associations between E298D or VNTR

and SCD. Interestingly, they did report that all patients homozygous for the -786C variant had a

tendency to develop a more severe clinical course. Limitations to this study include the small

sample size, n=73. A recent retrospective study by Sharan et al (2004) investigated eNOS

polymorphisms; E298D and T-786C, in patients with SCD. They concluded that the D298 allele

was not associated with SCD, however the C-786 allele was strongly associated with the risk of

ACS in female subjects.

Sullivan et al (2001) tested the hypothesis that exhaled nitric oxide levels (FENo) are

altered in subjects with SCD who have had at least one episode of ACS. They also tested the

hypothesis that the number of AAT repeats in intron 13 (formerly intron 20) of the NOS1 gene

correlates with FENo. They reported that (FENo) levels in patients who have a history of ACS are

approximately one-third those observed in healthy controls and in patients with SCD who have

not had ACS. Additionally, they found that low FENo was associated with a repeat

polymorphism in the NOS 1 gene. More specifically, they identified that high numbers of repeats

are inversely correlated with FENo levels. It is tempting to speculate that the low FENo seen in

SCD patients with ACS may have a genetic origin and may be due to polymorphisms in NOS

genes.

Grasemann et al., (1999) demonstrated significant differences in allele frequencies and

genotypes of the NOS 1 gene among ethnically diverse populations. The number of AAT repeats

in intron 20 (currently noted as intron 13) of the NOS1 gene ranged from 7-16 in Causcasians

and African Americans. Individuals homozygous for allele 10 were more common among

Caucasians (p = 0.0004), whereas those homozygous for allele 14 were more common among

African Americans (p<0.05). These findings suggest that ethnicity may have an impact on









Koumbourlis, A., Hurlet-Jensen, A.C., & Bye, M.R. (1997). Lung function in infants with sickle
cell disease. Pediatr Pulmonology, 24:277-281.

Koumbourlis, A. C., Zar, H.J., Hurlet-Jensen, A.,& Goldberg, M.R.. (2001). Prevalence and
reversibility of lower airway obstruction in children with sickle cell disease. Journal of
Pediatrics, 138, 188-192.

Leeman, M.,& Naeije, R. (1995). Nitric oxide and hypoxic pulmonary hypertension (editorial)
European Respiratory Journal, 8, 513-514.

Leong, M. A., Dampier, C., Varlotta, L., & Allen, J.L. (1997). Airway hyperreactivity in children
with sickle cell disease. JPediatr, 131:278-283.

Lieu, T.A., Lozano, P., Finkelstein, J.A., Chi, F.W. et al (2002). Racial/Ethnic variation in
asthma status and management practices among children in managed medicaid.
Pediatrics. 109(5), 857-865.

Lopez, B.L., Kreshak, A.A., Morris, C.R., Davis-Moon, L., Ballas, S.K., Ma, X.L. (2003). L-
arginine levels are diminished in adult acute vaso-occlusive sickle cell crisis in the
emergency department. Br. J. Haematol., 120, 552-534.

Lugogo, N.L., Kraft, M. (2006). Epidemiology of Asthma. Clin Chest Med, 27(1):1-15.

Luiking, Y.C., Poeze, M., Dejong, C.H., Ramsay, G., Deutz, N.E.(2004). Arginine availability in
sepsis. Critical Care Medicine, 32(10), 2135-2145.

Lum, A., LeMarchand, L. (1998). A simple mouthwash method for obtaining genomic DNA in
molecular epidemiological studies. Cancer Epidemiol Biomarkers Prev. 7(8): 719-724.

Mannino, D.M., Homa, D.M., Akinbami, L., Moorman, J.E., Gwynn, C., & Redd, S.C. (2002).
Surveillance for asthma-United States 1980-1999. MMAWR: Surveillance Summaries,
29;51(1),1-13.

Marsden, P., Heng, H., Duff, c., Shi, X., Tsui, L., & Hall, A. (1994) Localization of the human
gene for inducible nitric oxide synthase (NOS2) to chromosome 17ql 1.2-q12. Genomics,
19, 183-185.

Massaro, P.P., Gaston, B., Dieter, K., Fanta, C., Stamler, J.S., & Drazen, J.M. (1995). Expired
nitric oxide levels during treatment of acute asthma. American Journal Respiratory
Critical Care Medicine, 152,800-803.

Massaro, A.P., Mehta, S., Lilly, C.M., Kobzik, L., Reilly, J., Drazen, J.M. (1996). Elevated nitric
oxide concentrations in isolated lower airway gas of asthmatic subjects. American Journal
Respiratory Critical Care Medicine, 153, 1510-1514.

McCoy, K., Shade, D.M., Irvin, C.G., Mastronarde, J.G., Hanania, N.A., Castro, M., Anthonisen,
N.R. (2006). Predicting episodes of poor asthma control in treated patients with asthma.
Journal of Allergy and Clinical Immunology, 118(6), 1226-1233.









Potential future studies could target patients with SCD and physician diagnosed asthma

early in childhood prior to the first episode of ACS. The first episode of ACS usually occurs

between 2-5 years of age (Knorr, 2001). Subjects would be randomized to receive either

aggressive asthma management with moderate to high doses of inhaled corticosteroids (ICS) and

a leukotriene receptor atagonist or standard of care, then followed over a period of 3-5 years.

Subjects would be monitored for asthma symptoms, episodes of ACS, and genotyped for the

AAT repeat polymorphism in the NOS1 gene. In addition, exhaled nitric oxide collection and

pulmonary function testing would be employed to assess and monitor airway inflammation.

Given that exhaled nitric oxide is an accepted measure of airway inflammation in asthma,

utilizing this biomarker as a predictor or diagnostic tool to measure airway inflammation, may be

useful when managing sickle cell disease patients.

Randomized clinical trials are warranted to determine if aggressive treatment of

physician diagnosed asthma reduces the risk of ACS in SCD, and to determine whether

polymorphisms in candidate genes in the nitric oxide pathway contribute to ACS. Collaboration

among sickle cell centers for large clinical trials will be especially important for genome wide

association studies related to SCD and asthma. Studies of this nature require large numbers of

patients in order to identify genetic associations. Finally, stressing the importance for

cooperation between pulmonary and hematology clinics can only benefit future studies involving

SCD and asthma.









variants in the NOS1 gene and that these differences may be misinterpreted if not addressed in

future studies. This study did not report whether or not participants had a history of asthma.

NOS genes that are involved in the regulation of NO may be important in ACS because of

the central role NO plays in airway inflammation and the pulmonary endothelium.

NOS Genes and Association with Asthma

There is a plethora of research in the literature describing the key role of NO in the airway

epithelium. Patients with asthma have increased NO production in their airways (Kharitonov,

Yates, & Robbins, 1994; Massaro et al., 1996; Barnes, 1996; Piacentini et al., 1999). NOS genes

are located throughout the genome at 7q35-36 (NOS3) (Robinson et al., 1994), 12q24 (NOS1)

(Xu et al., 1993), and 17q12 (NOS2) (Marsden et al., 1994), all candidate loci for asthma

(Collaborative Study on the Genetics of Asthma, 1997; Daniels, 1996; Ober et al., 1998).

Nitric Oxide Synthase 1 (nNOS)

Genome-wide searches have established linkage between asthma and the NOS1 (nNOS)

gene (Collaborative Study on the Genetics of Asthma, 1997; Barnes, 1996; Ober et al., 1998).

Grasemann et al (2000) showed a genetic association between a polymorphism in the NOS1 gene

and asthma using a case control design. They demonstrated that frequencies for allele 17 and 18

of a CA repeat in exon 29 of the NOS 1 gene were significantly different between 490 asthmatic

and 350 control subjects. To confirm their findings they genotyped and additional 1131 control

subjects and verified that the frequencies of alleles 17 and 18 were nearly identical to those

found in their original control group. This study in particular is impressive given the sample

size, case-control design, and reproducibility. Findings from this study provide support for NOS 1

as a candidate gene for asthma.

A study in 97 mild asthmatic patients revealed that the size of the AAT repeat

polymorphism on intron 13 (formerly intron 20) of the NOS 1 gene was significantly related to












Body Protein
SFood
* Body Protein L. in .
- Protein L-Arginine

fumaa ASL NOS
Arginriao
sucrinate N OH L-Arine


ASS
aspartate


i 0

L-Citrulline 4".'


reatine

/-- C aiRii

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pot
SX -- .
Lrr tC
O ~


L-'




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NO
L-p
NO
LUNG -
S BLOOD
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KIDNEY
NO- URINE


yamines
',DC


rrtuiine .. _

Carb-mnol-

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L-glutmine


Figure 1-1. Metabolic pathways for Arginine, Arginase, Nitric oxide synthase, and Nitric oxide.
Reprinted with permission by Lippincott, Williams & Wilkins.


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The signing of this consent does not absolve doctors from responsibility for proper medical
care at all times.
My signature indicates that I consent and authorize Drs. Lima, Kissoon, Sullivan
and whomever they may designate as their assistants including Nemours
Children's Clinic, its employees and its agents to perform upon
(Name of Patient) the research described
above.
I am making a decision whether or not to have my child or myself participate in
this study. I have read, or had read to me in a language that I understand, all of
the above, asked questions and received answers concerning areas I did not
understand, and willingly give my consent for my/my child's participation in this
study. Upon signing this form, I will receive a signed and dated copy.


Name of Participant (Print) Birthdate Signature of Participant Date

If participant is less than 18 years of age the parent/legal representative must give consent:


Name of Signature of Date
Parent/Legal Representative Parent/Legal representative


Name of Witness Signature of Witness Date
I the undersigned, certify that to the best of my knowledge the
subject/parent/legal representative signing this consent had the study fully and
carefully explained. He/she clearly understands the nature, risks and benefits in
his/her child's participation in this project.


Signature of Investigator/Designee Date









ACKNOWLEDGMENTS

I sincerely thank my doctoral committee, Drs. Joyce Stechmiller, Julie Johnson, Veronica

Feeg, John Lima, and Lorraine Frazier, for their mentorship, guidance, and support. The

expertise of each member has contributed greatly to the completion of my dissertation. I could

not have succeeded without them.

As chair of my committee, Dr. Joyce Stechmiller has served as an extraordinary teacher

and mentor. Her encouragement and positive nature has given me the confidence to explore my

research interest and believe in my contribution to the science of the nursing profession. Special

thanks to Dr. John Lima who not only served as a mentor but whom also provided daily

encouragement throughout this process. I could not have succeeded without his guidance and

support.

I would like to thank Dr. Niranjan Kissoon for providing the opportunity to develop my

research interest in nitric oxide. Special recognition goes to Jainwei Wang for enduring endless

questions related to genotyping. Also, Hua Feng for navigating me through the statistical

analyses for this project. My co-workers for their patience and understanding over the past

several years, I could not have completed this task without your support. Finally, I thank my

friends for their love and support.









in HWE. The NOS3 polymorphisms were not in HWE, which was in contrast to healthy

controls, suggesting that genotyping of these variants was not in error, but was probably due to

the presence of disease in SCD patients. The minor allele frequency of the AAT repeat (< 12

repeats) was significantly higher in healthy controls compared to SCD patients, 0.21 vs. 0.091;

p< 0.001). The distribution of alleles carrying the number of AAT repeats in patients with SCD

was skewed to the right compared to healthy controls (X2=122; p< 0.0001) (Figure 2). The data

demonstrate that using a cut-off of < 12 repeats as suggested by Wechsler et al. in a mostly

Caucasian asthmatic cohort is reasonable for patients with SCD.

Asthma and Acute Chest Syndrome

Among SCD patients with physician-diagnosed asthma, 85.4% had at least one episode of

ACS compared to 14.6% of controls (odds= 5.85); whereas cases and controls were about evenly

distributed among participants without asthma (odds = 1.07). The adjusted OR (95%CI) is 5.47

(2.20,13.5), p = <0.0001 (Table 3). Figure 2 shows that the proportion of SCD patients who had

physician-diagnosed asthma was related to the number of episodes of ACS. The intercept of the

regression line was 0.178; the slope of the regression line was 0.097; and the correlation

coefficient, R, was 0.89, indicating that 79% (R2*100) of the variability in the proportion of

SCD patients with physician-diagnosed asthma is accounted for by the number of episodes of

ACS (p=0.001). Seven of 8 patients with 7 or more episodes of ACS had physician-diagnosed

asthma (one patient failed to report asthma status, his medical history was missing and he was on

asthma medications). Neither age nor gender contributed to the relationship (data not shown).

Genetic Associations

The association between the risk of ACS and the number of AAT repeats for the NOS1

gene in SCD patients is shown in Figure 3. The risk of ACS in participants without physician-

diagnosed asthma and who were carrying alleles with < 12 AAT repeats (n = 16 alleles; 11.6%)









during periods ofvaso-occlusive crisis and acute chest syndrome. These findings suggest that

there may be arginine depletion in response to demand, as opposed to intrinsic substrate

deficiency. (Morris et al., 2000). A similar study looked at L-arginine levels during VOC when

sickle cell patients presented to the emergency department. They studied 50 adult patients and

found arginine levels were significantly low compared to steady state (Lopez et al., 2003). These

findings indicate that L-arginine levels are diminished during periods of exacerbation.

L-Citrulline is an amino acid and a precursor for arginine (Fig 1-1). Waugh et al. (2001)

demonstrated that giving 1-citrulline 0.lg/kg orally twice daily elevated plasma arginine levels,

and increased symptoms of wellness in children with SCD. The oral citrulline supplements were

well tolerated and without side effects.

Arginase Genes and Asthma

Characterization of an asthma phenotype will likely be related to a complex interaction of

genes and their polymorphic variants. The pathogenetic mechanisms of and contributing genetic

factors in asthma continue to elude scientists. In a murine model, Zimmerman et al (2003) found

that among signature asthma genes, there was over expression of the genes encoding for the

uptake and metabolism of arginine, a basic amino acid, by arginase. Additionally their results

demonstrated regulation of arginase by IL-4 and IL-13, cytokines that activate inflammatory

pathways seen in asthma. Microarray analysis in murine models of asthma found high levels of

arginase I and arginase II activity in association with IL-4 and IL13 overexpression (Vercelli,

2003). Notably, arginine acts as a substrate for both arginase and NO synthase. The arginase and

NO synthase pathways may interfere with each other by way of competition for arginine

(Vercelli, 2003). Much of the literature regarding NO in asthma has focused on iNOS and

centered on the proinflammatory role of NO. Meurs and colleagues report that a deficiency of

NO caused by increased arginase activity and altered arginine levels is a contributing factor in









3 L ITE R A TU R E R E V IE W ........................................................................ .. .......................28

S ick le C ell D ise a se ........................................................................................................... 2 8
A cute Chest Syndrom e ........................ .. ........................ .. .... ........ ........ 29
A sth m a ................... ...................3...................0..........
N itric Oxide ................................... ................ ............................ ......... 31
Historical Events Leading to the Discovery of Nitric Oxide .......................................32
Nitric Oxide Mechanisms of Action.... ......................................33
Exhaled Nitric Oxide and Airway Disease............... .... ......................35
Associations between NOS Genetic Variants and ACS .................. ............................. 38
NOS Genes and Association with Asthma... ..................... ....................40
N itric O xide Synthase 1 (nN O S) ......................................................................... ..... 40
N itric O xide Synthase 2 (iN O S)........................................................... ............... 41
N itric Oxide Synthase 3 (eN O S) .............................................................................. 42
N itric Oxide and A cute Chest Syndrom e ........................................ .......... ............... 42
A rginase G enes and A sthm a.......................................................................... ...................43
Im p a ct o f G en etic s ............................................................................................................ 4 4
G genetic Influence ..................................... ......... ..................................... 44
Analysis Of Ethical, Social, Political, Economic, and/or Cultural Issues...........................45
Limited understanding of etiology of ACS ........................... .........................47
Similarities and Differences Between Asthma and ACS with Regard to Symptomology
an d L u n g F u n ctio n .................................................................................... ................ .. 4 8

4 R E S U L T S ....................................................................... ............................ ............... 5 1

D e scrip tiv e R e su lts ................................................................................................... 5 1
Genotyping .......................................................................... 51
Asthma and Acute Chest Syndrome .............................................. .....................52
G genetic A associations ................................................................... 52

5 D ISC U SSIO N ............................................ ........ .............................. 58

Study L im stations ........................................... 59
Implications for Clinical Practice .............................................. 62

6 F U T U R E W O R K .............................................................................................................. 6 4

APPENDIX

A C O N SE N T F O R M .............................................. .......................... ..................... 66

B DEMOGRAPHIC INFORMATION ................................. ................................. 77

C M EDICAL HISTORY ................................................. 78

L IST O F R E F E R E N C E S ....................................................................................................79

B IO G R A PH IC A L SK E T C H ................................................................................................... 89


6









We would also like to store some of your/your child's DNA in a bank (storage
facilities) so that it may be used in future studies of sickle cell disease.

WHO IS SPONSORING THIS STUDY?
This study is being sponsored by The American Lung Association who will pay Nemours

Children's Clinic for conducting this study.


WHO CAN BE IN THIS STUDY?
You may participate in this study if you have sickle cell disease. You may or may not

have had an ACS episode. You do no have to have sickle cell disease to participate, however,

you may participate as a healthy volunteer. You must be African American to participate.


HOW MANY OTHER PEOPLE WILL BE PARTICIPATING IN THIS STUDY?
This study will involve approximately 300 children, ages 6 and older, and adults from the

Jacksonville, Florida and Atlanta, Georgia area. This study lasts only as long as it takes for

you/your child to provide a buccal cell sample.

WHAT ARE THE PROCEDURES FOR THIS STUDY?

Buccal Samples

In order to provide a buccal sample, you/your child must not have eaten for one hour.

Then, you/your child will gargle a mouthful of water for the purpose of washing and spit out the

water. You/your child will receive a small bottle of mouthwash (Scope) and an empty tube,

which will be labeled with an identification number. You/your child will vigorously gargle a

mouthful of mouthwash for one minute and spit the gargled mouthwash into the coded tube. If

you/your child find it hard to gargle the mouthwash for one minute, you/your child can gargle

the mouthwash for shorter times, and repeat the procedure until you/your child have gargled for a

total of one minute (For example, you/your child can gargle a mouthful of mouthwash for 20









APPENDIX B
DEMOGRAPHIC INFORMATION

MR#:


DOB:


AGE:


SEX: M F


Date enrolled:


Date of DNA Collection:


Date of Consent:


Name:


Study #

RACE:








U SCD O HEALTHY


.nl


1i


6 7 8 9 10 11 12 13


14 15 16 17 18 19 20 21 22 23


AAT NUMBER

Figure 4-1. Comparison of distributions of alleles carrying AAT repeats in intron 13 on NOS 1
gene in healthy, 73 self-identified, healthy African Americans (n=146 alleles) and in
127 African Americans with sickle cell disease patients (n=254 alleles). Reprinted
with permission by Wiley-Liss. Duckworth, L. et al. (2007). Pediatric Pulmonology,
42(4), 335



Table 4-3. Influence of physician-diagnosed asthma on the risk of having at least one episode of
acute chest syndrome in patients with sickle cell disease (cases) compared to no
physician-diagnosed asthma (controls). (p value represents the chi square difference
between the asthma and no asthma groups)
Group, number (%)


Cases (ACS)
Controls (no ACS)
Total
Adjusted Odds Ratio
(95%CI)
p value


Physician-diagnosed
Asthma
41 (85.4)
7(14.6)
48 (100)
5.46
(2.20,13.5)
p <0.0001


No asthma

44(51.8)
41(48.2)
85 (100)
1.07


Reprinted with permission by Wiley-Liss
Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 335


_n l1


































To my children, Lindsay and Lesley Duckworth, for their love, support, and patience. To my
parents, Louis and Lorraine Doucette, for believing in me. To all who nurtured my intellectual
curiosity making this milestone possible.









seconds, and gargle another mouthful of mouthwash for 20 seconds and repeat the procedure one

more time). The gargled mouthwash contains buccal cells from your/your child's mouth.

WHAT HAPPENS AFTER THE SAMPLES ARE COLLECTED?

The buccal cells will be processed and your/your child's DNA will be stored in our

laboratory at the Nemours Children's Clinic in Jacksonville, FL. You/your child will not be

notified of individual results and no results will appear in your/your child's medical records.

For those patients who have sickle cell disease, information from the medical record may

be collected, for example, how many episodes of acute chest syndrome you have had, and

number of hospitalizations.

WHAT ARE THE POTENTIAL RISKS OR DISCOMFORTS?

Any treatment has potential risks. The most common risks of the treatment used in this

study are listed below. In addition, there is always the risk of very uncommon or previously

unknown side effects.

DNA Testing

Even though we will be careful to not reveal the results of the DNA testing on your/your

child's sample, there is a very small chance this information could accidentally become known to

you, your child, your doctor, or others. Presently we know of no risk to you/your child if the

genetic results become known.

Gargling with Mouthwash

You/your child may experience burning or tingling in your/his/her mouth from gargling

with the mouthwash for one minute. You/your child can minimize burning or tingling by

gargling for shorter periods of time on more occasions until he/she has gargled for one minute.









& Catravas, 2006). Basal levels of NO in pulmonary endothelial cells maintain dilation of the

pulmonary vascular bed (Pepko-Zaba et al., 1991).

NO is produced in the airways by inflammatory cells, most notably eosinophils,

macrophages, epithelial cells, and mast cells, all of which are relevant to asthma (Gustafsson,

1998). Epithelial cells stimulated by cytokines result in the induction of iNOS producing high

quantities of NO (Robbins, 1996). NO generated from epithelial cells may be a physiological

defense against infection and could influence susceptibility to airway disease given its

antimicrobial properties Decreased levels of NO in the airway may increase susceptibility to

infection (Hart, 1999). NO reacts with thiols to form S-nitorsothiols (Stamler et al., 1992). These

compounds have bronchodilator activity and may also contribute to airway homeostasis by their

antimicrobial and anti-inflammatory properties (Gaston, 1994)

Exhaled Nitric Oxide and Airway Disease

Airway inflammation plays a central role in the pathogenesis as well as symptomology of

asthma (Shelhamer et al.,1995; Obyrne, 1996) Exhaled nitric oxide (FENO) levels are elevated

in patients with asthma, however, there is a substantial amount of variance (Massaro et al., 1995,

1996; Kissoon et al., 1999; Rosias et al., 2004; Storm et al., 2004). Repeatable noninvasive

measurement of inflammation would be useful in order to assess severity and guide treatment in

patients with asthma. Measurement of exhaled nitric oxide levels is an exciting recent

development that may provide an indication of the degree of airway inflammation in asthmatics

as opposed to traditional pulmonary function test, which are indirect measures of airway flow.

Customary monitoring techniques for assessing asthma severity include peak expiratory flow

rates, spirometry, and responses to medications. Despite the importance of inflammation in

asthma, monitoring airway inflammation is not routine. This is due in large part to the fact that

only invasive techniques such as bronchoscopy can directly sample lung tissue and fluids for the









CHAPTER 3
LITERATURE REVIEW

Sickle Cell Disease

Sickle cell disease is an inherited blood disease that is characterized by defective

hemoglobin. It is one of the most prevalent genetic disorders and is the most common genetic

disease in the African American population. The genetic mutation associated with sickle cell

disease occurs in approximately one in every 600 African American births. This disease affects

millions worldwide and approximately 72,000 people in the United States (Platt, 1994). The

clinical course of the disease varies from patient to patient. Some patients have mild symptoms

while others are severely affected. The reasons for this are unclear.


Sickle cell anemia is caused by an abnormal type of hemoglobin called hemoglobin S.

Hemoglobin is a protein inside red blood cells that carries oxygen. Hemoglobin S, however,

distorts the red blood cells shape. The fragile, sickle-shaped cells deliver less oxygen to the

body's tissues, and can break into pieces that disrupt blood flow (Goldman, 2004). Hypoxia

enhances the sickled erythrocytes adherence to both the macrovascular and microvascular

endothelium. The pulmonary microcirculation is particularly vulnerable to deoxygenation

(Stuart & Setty, 1999).


Sickle cell anemia is inherited as an autosomal recessive trait. This means it occurs in

someone who has inherited hemoglobin S from both parents. Sickle cell disease is much more

common in certain ethnic groups, significantly affecting African Americans. Someone who

inherits hemoglobin S from one parent and normal hemoglobin (A) from the other parent will

have sickle cell trait. Someone who inherits hemoglobin S from one parent and another type of









Wechsler, M. E., Grasemann, H., Deykin, A., Silverman, E.K., Yandava, C.N., Israel, E., Wand,
M., & Drazen, J.M. (2000). Exhaled nitric oxide in patients with asthma: association with
NOS1 genotype. American Journal of Respiratory Critical Care Medicine, 162, 2043-
2047.

Williams, N. (1998). NO news is good news...but only for three Americans. Science, 282,
(5389), 610-611.

Xia, Y., & Zweir, J.L. (1997). Superoxide and peroxynitrite generation from inducible nitric
oxide synthase in macrophages. Proceeings of the National Academy of Sciences U.S.A.,
94, 6954-6958.

Yates, D.H. (2001). Role of exhaled nitric oxide in asthma. Immunology and Cell Biology, 79,
178-190.

Yeatts, K.B. & Shy, C.M. (2001). Prevalence and consequences of asthma and wheezing in
African-American and White adolescents. Journal ofAdolescent Health, 29, 314-319.

Yetik-Anacak, G., & Catravas, J.D. (2006). Nitric oxide and the endothelium: History and
impact on cardiovascular disease. Vascular Pharmacology, 45, 268-276.

Yildiz, P., Oflaz, H., Cine, N., Genchallac, H., Erginel-Unaltuna, N., Yildiz, A., & Yilmaz, V.
(2004). Endothelial dysfunction in patients with asthma : The role of polymorphisms of
ACE and endothelial genes. International Archives ofAllergy and Immunology, 41, 159-
166.

Zeidler, M.R., Kleerup, E.C., & Tashkin, D.P. (2004). Exhaled nitric oxide in the assessment of
asthma. Current Opinion in Pulmonary Medicine, 10(1), 31-6.

Zimmermann, N., King, N.E., Laporte J., Yang, M., Mishra, A., Pope, S.M., Muntel, E.E., Witte,
D.P., Pegg, A.A., Foster, P.S., Hamid, Q., & Rothenberg, M.E. (2003). Dissection of
experimental asthma with DNA microarray analysis identifies arginase in asthma
pathogenesis. Journal of Clinical Investigation, 111, 1863-1874.

Zimmermann, N., & RothenbergM.E. (2005). The arginine-rginase balance in asthma and lung
inflammation. European Journal ofPharmacology, 533, 253-263.

Zoratti, E.M., Havstad, S., Rodriguez, J., Robens-Paradise, Y., Lafata, J.E., & McCarthy, B.
(1998). Health service use by African Americans and Caucasians with asthma in a
managed care setting. American Journal ofRespiratory Critical Care Medicine, 158, 371-
377.









Busse, W.W., & Holgate, S.T. (1998). Evidence from induced sputum. Inflammatory
mechanisms in asthma. (pp. 75-81). New York, NY: Marcel Dekker Inc.

Busse, W.W., & Holgate, S.T. (1998). Mediator Functions of Epithelial Cells. Inflammatory
Mechanisms in Asthma. (p.479). New York, NY: Marcel Dekker Inc.

Calabrese, C., Triggiani, M., Marone, G., & Mazzarella, G. (2000). Arachidonic acid metabolism
in inflammatory cells of patients with bronchial asthma. Allergy 55 Suppl 61, 27-30.

Chaar, V., Tarer. V., Etienne-Julan, M., Diara, J., Elion, J., & Romana, M.(2006). ET-1 and
eNOS gene polymorphisms and susceptibility to acute chest syndrome an painful vaso-
occlusive crises in children with sickle cell anemia. Haematologica. 91(9) ,1277-1278.

Cicutto L.C., & Downey, G.P. (2004). Biological markers in diagnosing, monitoring, and
treating asthma: a focus on noninvasive measurements. AACNClin Issues, 15(1), 97-111.

Collaborative Study on the Genetics of Asthma (CSGA)(1997). A genome wide search for
asthma susceptibility loci in ethnically diverse populations. Nature Genetics, 15, 389-392.

Collins, F., Green, E., Guttmacher, A., & Guyer, M. (2003). A vision for the future ofgenomics
research. A blueprint for the genomic era. Nature. 422, 835-847.

Coultas, D., Gong, H., & Grad, R. (1993). Respiratory diseases in minorities of the United
States. Am J Respir Crit Care. (149), S93-131.

De Boer, J., Duyvendak, M., Schuurman, F., Pouw, F., Zaagmsaj., & Meurs, H.(1999). Role of
L-arginine in the deficiency of nitric oxide and airway hyperactivity after the allergen-
induced early asthmatic reaction in guinea pigs. Br JPharmacol 128, 1114-1120.

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Biol Chem 269, 13057-13060.

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757-762.

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NOS Polymorphisms. Pediatric Pulmonology, 42(4), 332-338.

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amino acids in plasma and urine. Am J Med Sci., 300(6), 366-371.









genes for the nitric oxide pathway. These genes code for enzymes that utilize arginine as a

substrate and regulate NO production. Therefore it is possible that genetic variants that regulate

NO production could contribute to ACS and asthma in SCD.

Background and Significance

Acute Chest Syndrome and Nitric Oxide

ACS is a common complication of sickle cell anemia. ACS is the second most common

cause of hospitalization in patients with sickle cell disease and is the leading cause of premature

deaths (Platt, 1994) (Vichinsky et al., 1997, 2000). It is characterized by the presence of a rapidly

progressing multi-lobe infiltrate, cough, hypoxemia and dyspnea. The etiology of ACS is

multifactorial and remains unclear. Our current understanding suggests that ACS may be a form

of acute lung injury that progresses to acute respiratory distress syndrome. This injury is thought

to be precipitated by sloughing of blood in the pulmonary microvascular resulting in pulmonary

infarction, fat embolisation, and infection (Vichinsky et al 1996) (Scully et al ,1997). There is

compelling evidence to support the central role of NO in the initiation of the pathophysiological

process in ACS. Stuart and Setty assessed plasma NO metabolites in 36 patients with SCD and

23 age-matched controls. They found that serum concentrations of NO metabolites were

decreased during acute chest syndrome with values lower than in controls and in patients at

steady state (Stuart & Setty, 1999). Hammerman and colleagues (1999) exposed cultured

pulmonary endothelial cells to the plasma of patients with sickle cell disease and acute chest

syndrome and found that within two hours of exposure there were increases in NOS 3 protein

and NOS 3 enzyme activity. They suggested that alterations of NO production and metabolism

contribute to the pathogenesis of ACS.









Mehta, S.R., Annan, A.A., Byrns, P.J.(2006). Opportunities to improve outcomes in sickle cell
disease. American Family Physician. 74(2), 303-306.

Meurs, H., McKay, S., Maarsingh, H., Hamer, M., Macic, L., Molendijk, N., Zaagsma, J. (2002).
Increased arginase activity underlies allergen-induced deficiency of cNOS derived nitric
oxide and airway hyperresonsiveness. British Journal ofPharmacology, 136:391-398.

Meurs, H., H. Maarsingh, and J. Zaagsma. (2003). Arginase and asthma: novel insights into
nitric oxide homeostasis and airway hyperresponsiveness. Trends in Pharmacological
Sciences, 24, 450-455.

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of Medicine, 329, 2002-2012.

Morris, C.R., Kuypers, F.A., Larkin, S., Vinchinsky, E.P., Styles, L.A.(2000). Patterns of
arginine and nitric oxide in patients with sickle cell disease with vaso-occlusive crisis and
acute chest syndrome. Journal of Pediatric Hematology Oncology, 22, 515-520.

Morris, S.(2002). Regulation of enzymes of the urea cycle and arginine metabolism. Annual
Review ofNutrition, 22:87-105.

Morris, C. R., M. Poljakovic, L. Lavrisha, L. Machado, F. A. Kuypers, and S. M. Morris, Jr.
(2004). Decreased arginine bioavailability and increased serum arginase activity in asthma.
American Journal ofRespiratory Critical Care Medicine, 170, 148-153.

Morris, C. R., F. A. Kuypers, S. K. Larkin, E. Vichinsky, and L. A. Styles. (2006). Patterns of
Arginine and Nitric Oxide in Patients With Sickle Cell Disease With Vaso-occlusive Crisis
and Acute Chest Sydrome. Journal of Pediatric Hematology Oncology, 515-520.

Naprawa, J. T., B. K. Bonsu, D. G. Goodman, and M. A. Ranalli. (2005). Serum biomarkers for
identifying acute chest syndrome among patients who have sickle cell disease and present
to the emergency department. Pediatrics, 116, e420-e425

Nathan, C., Xie, Q.W. (1994). Nitric oxide synthase : roles, tolls, and controls. Cell, 78, 915-
918.

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Diagnosis and Management of Asthma. Journal ofAllergy and Clinical Immunology,
(Suppl.1), 142-144.

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Centers for Disease Control and Prevention. National Center for Health Statistics. Series
10, Number 223:p. 4.

National Heart, Lung and Blood Institute (2003). National Asthma Education Program Expert
Panel Report: Guidelines for the Diagnosis and Management of Asthma. Bethesda (MD):
National Institutes of Health.


































2007 Laurie Jill Duckworth









Research Aims and Hypotheses


Specific Aim 1

To characterize the relationship between ACS and asthma in children with SCD.

Hypothesis

Asthma is a risk factor for ACS.

Specific Aim 2

To explore associations among polymorphisms in candidate genes of the nitric oxide

pathway and their association with asthma, ACS and SCD.

Hypothesis

Polymorphisms in candidate genes of the nitric oxide pathway predict asthma and ACS in

children with SCD.

Significance to Nursing

This study will explore associations between candidate genes in the NO pathway and the

incidence of asthma and acute chest syndrome in a sickle cell disease population. Gaining

insight into mechanisms of chronic disease that may impact complications associated with SCD

is vital to nursing care. Outpatient Sickle Cell Disease clinics are generally managed by nurses.

The nurse is often the first contact when patients experience pain or respiratory distress. Asthma

is the leading chronic illness in children, can be life threatening, and is more prevalent in the

African American population. Recent retrospective studies suggest that patients with SCD who

also have a history of asthma may be at increased risk for acute chest syndrome. Knowledge

regarding polymorphisms in NOS genes and historical evidence of asthma, thereby predisposing

patients to ACS, may heighten awareness and result in aggressive management and treatment for

asthma related symptoms.









their association with ACS may lead them to seek prompt medical attention for coughing

episodes and upper airway congestion, symptoms which may otherwise be viewed as the

common cold.

Sickle cell disease is clearly a genetic disease. Asthma on the other hand is a complex,

multifactorial disease. Children suffering from SCD who also have asthma may have several

specialists managing their care, for example a pulmonologist, hematologist, and primary care

provider. Enhancing communication between providers may lead to better outcomes for these

patients.










Mean SD = 0.87 i i ')'


X2
*






0. = 082 0.22x 4 0.03c2
1
I;?








Meai 8D = OA9 0.12
<12 12 13 14 15 16 >=17


AAT repeat number in intron 13 of NOS1


Sidde cell paTfents with asthma n=41
Sidce cell patient without asthma n=44
P=O.00 1
-- Quadratc regression line for SCDNA

Figure 4-3. Risk of ACS and NOS 1 AAT repeats in intron 13. The risk of ACS (1-
[controls/(cases+controls)]) is plotted against the number of NOS 1 AAT repeats in
patients with SCD with physician-diagnosed asthma (closed circles) and without
physician-diagnosed asthma (SCDNA). Reprinted with permission by Wiley-Liss.
Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 334.


Table 4-4. Association between ARG1 A2/A1 polymorphism and asthma among SCD patients.


Genotype


Number of SCD patients


Asthma No asthma


I


Odds'


Al carriers 6 22 0.27
A2 homozygotes 41 58 0.71
=Statistic likelihood ratio Fisher's exact test: 3.98; p= 0.04









the pathogenesis of asthma (Meurs, 2003). Using global micorarray analysis, Zimmermann et al

(2006) reported that asthmatic conditions involve metabolism of arginine by arginase. They

report that arginase I and arginase II genes are key regulators of processes associated with airway

tone and lung inflammation. Collectively these studies indicate the need for further investigation

of Arginase I and Arginase II genes and how they may relate to asthma and airway disease.

Impact of Genetics

In April 2003, sequencing of the human genome was completed. The consequences of this

landmark event will have a dramatic impact on the ability to understand the mechanisms of

disease and develop treatments specifically tailored to a patient's genetic profile (Collins et al.,

2003). Sickle cell disease (SCD) is one of the most common genetic diseases, affecting one in

600 African Americans. Despite its Mendelian inheritance the disease is phenotypically highly

variable. For example, some affected by the disease suffer from recurrent vaso-occlusive crisis

and die at a young age, while others seem minimally affected and enjoy a normal life span

(Buchanan,, Debaun, & Steinberg, 2004). Hence the need for identification of risk factors and

genetic variants that may predict outcomes and reduce mortality.

Acute chest syndrome (ACS) is the leading cause of mortality and the second most

common cause of hospitalizations in patients with sickle cell disease (SCD) accounting for

nearly half of premature deaths (Platt, 1994; Stuart & Setty, 2001; Buchanan, Debaun, &

Steinberg, 2004). Our current understanding of the pathophysiology and mechanisms leading to

ACS in SCD is limited and remains unclear. There is paucity in the literature describing

associations between ACS, airway disease, and genetic variation.

Genetic Influence

Studies investigating the influence of genetic variation in candidate genes in the NO

pathway are not unprecedented. The gene that encodes NOS 1 in humans is located on the long









times higher for African American males as compared to white males, and 2.5 times higher for

black females when compared to white females (Fagan et al., 2000). Over the past 10-15 years

research has led to a greater understanding of the mechanisms of asthma, thereby reducing

mortality and improving the quality of life for many patients suffering with asthma. However,

reasons for disparities in mortality among African Americans continue to elude scientists. Recent

studies have reported a relationship between asthma and ACS (Boyd et al., 2004) (Knight-

Madden et al., 2005 (Bryant, 2005) (Nordness et al., 2005). Many of the symptoms related to

ACS are also seen in asthma; dyspnea, cough, decreased oxygen saturation. Surprisingly, the

prevalence of asthma in these studies ranged from 45 to 53%, a striking increase over the

incidence of asthma generally seen in African Americans. What remains unclear is direction of

the causality of the relationship between ACS and Asthma. Do patients with asthma have more

episodes of ACS, or are patients with a history of ACS more likely to develop asthma?

Few studies address polymorphisms in NOS genes and how they may impact airway

disease, specifically asthma, in patients with SCD. Given that asthma is the leading chronic

illness in children and more prevalent in African Americans, it is important to explore

relationships among candidate genes in the NO pathway, asthma, sickle cell disease, and acute

chest syndrome. Recent studies citing the importance of arginase in asthma pathogensis

additionally warrant further research (Vercelli, 2003).

Nitric Oxide

Nitric oxide (NO) plays a major role in lung physiology and airway disease. This

ubiquitous gas is an unstable free radical that serves as a mediator for several physiological

events including vascular and airway smooth muscle tone, bronchodilation, and airway

inflammation (Barnes, 1995). Nitric oxide may also be necessary for ciliary action (Jain et al.,

1993) and is thought to aid in maintaining sterility in the lower respiratory tract due to its









arm of chromosome 12 in the region 12q24.2. Multiple genome wide screening studies in

different ethnic populations have shown linkage of this region to asthma (Grasemann et al.,

1999; Barnes, 1996; CSGA, 1997; Ober et al., 1998). Grasemann and colleagues (1999) found

significant differences in allele frequencies and genotypes of the NOS 1 gene among ethnically

diverse populations. They studied 305 American-Caucasian and 105 African -American healthy

subjects. The number of AAT repeats in intron 13 (formerly intron 20) ranged from 7-16. The

overall distribution of alleles differed significantly between groups. Individuals homozygous for

allele 10 were more common among Caucasians whereas those homozygous for allele 14 were

more common in African-American subjects. A study in 97 mild asthmatics revealed that the

size of the AAT repeat polymorphism on intron 13 (formerly intron 20) of the NOS 1 gene was

significantly associated with FENo (Weschler, 2000). The NOS3 gene is located at 7q35-36. A

recent study in SCD patients found a functional single nucleotide polymorphism (SNP) in the

NOS3 gene, T-786C, that associated with increased susceptibility to acute chest syndrome in

females (Sharan et al., 2004).

Analysis Of Ethical, Social, Political, Economic, and/or Cultural Issues

Asthma presents an enormous burden to both the individual and healthcare system. It is

estimated that 20 million persons in the United States suffer from asthma and asthma accounts

for more than 5.000 deaths annually (National Asthma Education and Prevention Program,

2002). In the last two decades there has been a rise in asthma hospitalizations and asthma

mortality (Akinbami & Schoenforf, 2002). Mortality associated with asthma peaked in 1998 and

has decreased over the past few years. This increase is more pronounced in African American,

and people of low socioeconomic background (Mannino et al.,1998). According to the National

Health Interview Survey, nine million children under the age of 18 years have been diagnosed

with asthma (13%), children in poor families (15%) were more likely to be diagnosed with









Nitric Oxide Synthase Enzymes

Nitric oxide synthase enzymes are expressed in the lung parenchyma. NOS 1 and 3 are

constitutive and regulated by intracellular calcium concentration. NOS 2 is induced under

inflammatory conditions, such as asthma, and is independent of calcium levels. Studies in pig

lungs suggest that exhaled nitric oxide originates at the alveolar surface rather than from the

pulmonary circulation and may be derived from NOS 3 expressed in the alveolar walls of normal

lungs (Kobzik et al., 1993). Airway epithelial cells express both NOS 1 and 3 and therefore

contribute to NO levels in the lower respiratory tract (Shaul et al., 1994; Asano et al., 1994).

Using exhaled nitric oxide (FENo) as a marker of NO production, Sullivan et al (2001) found that

the concentration of FENo was lower in children with SCD who had previously suffered from

acute chest syndrome as compared to children with sickle cell disease with no history of acute

chest syndrome and healthy controls. Additionally they demonstrated that the FENo levels are

significantly correlated with the number of NOS 1 AAT repeats. Given that FENO in healthy

controls is likely produced by NOS 1 and 3 at basal concentrations, the decreased level in

patients with ACS as compared to healthy controls suggest genetic variations in these genes. It

is tempting to speculate that the low FENo seen in SCD patients with ACS may have a genetic

origin and possibly may be due to polymorphisms in NOS genes. Finally, a study in 97 mild

asthmatic patients revealed that the size of the AAT repeat polymorphism on intron 13 of the

NOS 1 gene was significantly related to FENO (Weschler et al., 2000). A certain fraction or

phenotype of asthmatics had low FENo. Collectively these findings suggest and support the

hypothesis that genetic variation in NOS genes may contribute to airway disease predisposing

patients with SCD to ACS.









disease, reversible in nature, precedes the development of restrictive airway disease. The

limitations of this study include; small sample size, limited historical information, and subjective

information with regard to a history of asthma. These children were not identified as having

physician-diagnosed asthma (Koumbourlis et al., 2001)

Asthma is a chronic inflammatory disease of the airways. In susceptible individuals, this

inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness, and cough,

particularly at night and in early morning. These episodes are usually associated with widespread

but variable airflow obstruction that is often reversible either spontaneously or with treatment.

The inflammation also causes an associated increase in the existing bronchial

hyperressponiveness to a variety of stimuli (National Asthma Education and Prevention Program

Expert Panel, (2003).

ACS is characterized by the presence of multi-lobe infiltrates, cough, dyspnea, hypoxia,

and often chest pain (Hammermann, 1999). Many of the symptoms related to ACS are also seen

in asthma; dyspnea, coughs, and decreased oxygen saturation. Differentiating between asthma

and ACS may be difficult in patients with SCD. Further research is needed to establish an

objective assessment for primary care providers who are managing patients with SCD and

airway disease.









chi square goodness of fit tests. Differences in age among groups were determined using one-

way ANOVA with Bonferroni correction for multiple comparisons. Association between groups

with gender, allele, genotype, and the number of AAT repeats on NOS 1 were assessed using

chi-square test. The strength of associations between disease risk and genotype were evaluated

with Mantel-Haensze common odds ratios (OR) and 95% confidence intervals. The relationship

between risk of ACS and the number of AAT repeats in intron 13 of the NOS 1 gene in patients

with and without asthma was determined by simple linear regression. Associations between the

incidence of asthma and episodes of ACS were determined by logistic regression analysis with

age and gender as covariates.

The Hardy-Weinberg law is commonly used for calculating genotype frequencies from

allele frequencies. This law is the cornerstone of population genetics. In population genetics,

the Hardy-Weinberg principle is a relationship between the frequencies of alleles and the

genotype of a population. The occurrence of a genotype, perhaps one associated with a disease,

stays constant unless matings are non-random or inappropriate, or mutations accumulate.

Therefore, the frequency of genotypes and the frequency of alleles are said to be at "genetic

equilibrium". Genetic equilibrium is a basic principle of population genetics (Nussbaum,

McInnes, & Willard, 2004). This sudy tested for Hardy Wienberg Equillibrium (HWE) with 74

healthy African American control subjects. The reasons for testing HWE were to establish that

the allele frequencies in the study participants were consistent with an Arican American

population, and secondly to rule out genotyping error. Interestingly, the NOS 3 polymorphysims

were not in HWE when compared to the healthy control cohort. This suggest that

polymorphisms in this gene may be realted to the disease process. This was not however

confirmed with the results. In fact, associations were found between the AAT repeat









rpm for 5 minutes. The supernatant was drawn off, 1 ml of 70% alcohol was added and the

sample was centrifuged again at 14,000 rpm for 2 minutes. The final specimen was suspended in

10mM of Tris, pH 7.5 and rehydrated overnight.

Genotyping

DNA was extracted as previously described and the quantity of DNA determined by

spectrophotometry. (Lum & LeMarchand, 1998). Aliquots of DNA containing 500 ng were

prepared and stored at -200C in a secure and locked freezer, and labeled with the participant's

code number. Forward and reverse primers specific to polymorphic loci in the NOS 1 and NOS3

genes were used to isolate regions of interest. Polymerase chain reaction was utilized to identify

patient genotype.

Below is a listing of the various known polymorphic loci in the NOS 1 and NOS 3 genes

and the ARG 1 gene. (Grasemann Yandava, & Drazen, 1999). In previous studies the location

of the AAT repeat was reported as intron 20 (Sullian et al., 2001; Wechsler, et al., 2000).

However, according to homosapiens chromosome 12 genomic contig NT_009775, the AAT

repeat polymorphism locates in the region of intron 13 (complement 8267923-8271203) of the

human NOS 1 gene. Oligonucleotides were synthesized by Operon Technologies (Alameda, CA,

USA). The restriction enzymes were purchased from New England Biolabs (Ipswhich, MA,

USA).

NOS 1 (neuronal NOS)

ATT intronic repeat: intron 13 (complement 8267923 8271203)

Forward primer: 5'CTGGGGCAATGGTGTGT-3'

Reverse primer: 5'GAGTAAAATTAAGGGTCAGC-3'

NOS 3 (endothelial NOS) (Sharan et al., 2000)












POLYMORPHISMS IN CANDIDATE GENES FOR THE NITRIC OXIDE PATHWAY IN
SICKLE CELL PATIENTS WITH ACUTE CHEST SYNDROME AND ASTHMA



















By

LAURIE JILL DUCKWORTH


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2007









APPENDIX A
CONSENT FORM

THE NEMOURS CHILDREN'S CLINIC
JACKSONVILLE, FLORIDA
INFORMED WRITTEN CONSENT
You are being asked to volunteer in a research study. This form will explain the study. It

is important that you understand the study before deciding to be in it. You may ask the people in

charge of the study who are listed on this page questions about the study at any time.


WHAT IS THE TITLE OF THIS STUDY?
Polymorphisms of Nitric Oxide Synthase Genes in Sickle Cell Patients with Acute Chest

Syndrome

WHO ARE THE PEOPLE IN CHARGE OF THIS STUDY?


Principal Investigator:



Telephone number:

Sub-Investigators:


John Lima, Pharm.D.
Nemours Children's Clinic
807 Children's Way
Jacksonville, FL 32207
(904) 390-3483 (904) 390-3600 (operator)
(800) SOS-KIDS
Niranjan Kissoon, M.D.
Professor & Chief Pediatric Critical Care Medicine
University of Florida-Jacksonville
(904) 202-8758
Jim Sylvester, PhD
Nemours Children's Clinic
807 Children's Way
Jacksonville, FL 32207
(904) 390-3483 (904) 390-3600 (operator)
(800) SOS-KIDS
Kevin Sullivan, M.D.
Division of Pediatric Anesthesiology
Nemours Children's Clinic
807 Children's Way
Jacksonville, FL 32207
Phone Number: (904) 202-8332
Lewis Hsu, M.D.
Emory University
69 Butler St. SE
Atlanta, Georgia 30303
(404) 616-3545









Nitric Oxide, Airway Inflammation, ACS, And Asthma

The importance of NO as a marker for airway inflammation in asthma is well documented

(Barnes, 1995; Batra, et al 2007). Exhaled nitric oxide levels serve as a useful marker for

assessing asthma severity and medication compliance (Naprawa et al., 2005). Asthma is the

most common chronic disease of childhood in the United States. The incidence of asthma in the

African American population surpasses that of Caucasians, 17% vs 6% respectively (Yeatts &

Shy, 2001) (Boyd et al., 2006). Differences in asthma related symptoms complicate the

treatment and management of this disease in patients with SCD who may also have ACS. For

example, patients with SCD who have recurring airway dysfunction may not be identified as

asthmatic in that they are not evaluated for this condition. Sub specialists and Pediatricians may

focus on the child's SCD and manage upper respiratory conditions on a case-by-case basis. This

may leave the patients more vulnerable to an increased risk for ACS.

Significance of Research

The information gained from the proposed research may identify candidate genetic variants

in the NO pathway that increase the risk of patients with SCD to develop ACS. More

specifically, this research may determine whether polymorphisms in NOS genes and other genes

that encode proteins that regulate NO predispose patients with sickle cell disease to episodes of

acute chest syndrome. If the NOS genotype is suggestive of decreased NO production in the

lung, early intervention with treatment modalities such as oral arginine may prevent ACS and

thereby reduce morbidity and mortality associated with this complication. Findings from this

research may lead to screening of patients with SCD for the genetic variants associated with

ACS early in life resulting in aggressive management and particular attention to associated lung

diseases such as asthma which may put them at heightened risk for pulmonary complications.









Styles, L. A., Aarsman, A.J., Vichinsky, E.P., & Kuypers, F.A. (2000). Secretory phospholipase
A(2) predicts impending acute chest syndrome in sickle cell disease. Blood, 96, 3276-
3278.

Sullivan, K.J., Kissoon, N., Duckworth, L.J., Sandler, E., Freeman, B., & Bayne, E. (2001). Low
Exhaled Nitric Oxide and a Polymorphism in the NOS I Gene Is Associated with Acute
Chest Syndrome. American Journal of Respiratory Critical Care Medicine, 164, 2186-
2190.

Sylvester, K.P., Patey, R.A., Broughton, S., Rafferty, G.F., Rees, D., Thein, S.L., & Greenough,
A.(2007). Temporal Relationship of Asthma to Acute Chest Syndrome in Sickle Cell
Disease. Pediatric Pulmonology, 42, 103-106.

Sylvester, K.P., Patey, R.A., Milligan, P., Dick, M., Rafferty, G.F., Rees, D., Thein, S.L., &
Greenough, A. (2004). Pulmonary function abnormalities in children with sickle cell
disease. Thorax, 59, 67-70.

Sylvester, K. P., Patey, R.A., Milligan, P., Rafferty, G.F., Broughton, S., Rees, D., Thein, S.L., &
Greenough, A. (2006). Impact of acute chest syndrome on lung function of children with
sickle cell disease. JPediatr 149:17-22.

Vallance, P., Collier, J., & Moncada, S.(1989). Effects of endothelium derived nitric oxide on
peripheral arteriolar tone in man. Lancet, 2, 997-1000.

Vargas, A., Da Silva, M., Silla, L., & Chies, J. (2005). Polymorphisms of chemokine receptors
and eNOS in Brazilian patients with sickle cell disease. Tissue Antigens, 66, 683-690.

Vercelli, D. (2003). Arginase : marker, effector, or candidate gene for asthma ? The Journal of
Clinical Investigation, 111, 1815-1816.

Vichinsky, E., Styles, L. (1996). Sickle cell disease. Pulmonary complications. Hematology/
Oncology Clinics of North America, 10,1275-1287.

Vichinsky, E. P,. Neumayr, L., Earles, A.N., Williams, R., Lennette, E.T., Dean, D., Nickerson,
B., Orringer, E., McKie, V., Bellevue, R., Daeschner, C., & Manci, E.A. (2000). Causes
and outcomes of the acute chest syndrome in sickle cell disease. National Acute Chest
Syndrome Study Group. The New England Journal of Medicine, 342, 1855-1865.

Vichinsky, E., Williams, R., Das, M., Earles, A.N., Lewis, N., Adler, A., & McQuitty, J. (1994).
Pulmonary fat embolism: a distinct cause of severe acute chest syndrome in sickle cell
anemia. Blood, 83, 3107-3112.

Waugh, W.H., Daeschner, C.W., Files, B.A., McConnell, M.E., & Strandjord, S.E. (2001). Oral
citrulline as arginine precursor may be beneficial in sickle cell disease: early phase two
results. Journal of the National Medical Association, 93, 363-371.









that patients with ACS have lower amounts of NO in the air they exhale when compared to

sickle cell patients who have not had ACS.

We believe that sickle cell patients with ACS produce very low quantities of NO in the

pulmonary (lung) system. We believe that this may be because some children have different

types of the protein (amino acid) that produces NO than others. This protein is called nitric oxide

synthase (NOS). Humans have three different types of the enzyme that produces NO. We want to

examine whether or not there is a link between tendency to suffer from ACS, and the type of

enzyme the patient has. This can be determined by studying your DNA (Studying genes or DNA

is becoming more common in clinical research studies, but is still in an early stage. We know

that certain genes make you tall or short. Certain genes give you brown or black hair). This will

be important to know because if there is a genetic or inherited component that determines how

severe the sickle cell disease will be it could be important for screening and lead to treatment that

may help avoid complications in groups that are at high risk of having ACS.


WHAT IS THE PURPOSE OF COLLECTING THESE SAMPLES FOR DNA
ANALYSIS?
You/your child are being asked to take part in this research study because you/your child

have sickle cell disease, or are a healthy volunteer. Similarly, certain genes are associated with

sickle cell disease, and may be associated with whether or not you/your child may develop ACS.

Studying DNA from people who have sickle cell disease may help us better understand the

importance of those genes and how they are involved in causing ACS.

You/your child are being invited to provide a sample of your/your child's buccal cells

(cells from your/your child's mouth) to test for DNA or genes related to sickle cell disease.

Participation is voluntary. You/your child do not have to provide a sample for DNA analysis.









without a history of ACS were classified as controls. The age at which participants experienced

their first episode of ACS was recorded.

Asthma Diagnosis

Participants were classified as having asthma if it was diagnosed by a physician and if they

were currently prescribed one or more of the following asthma medications: inhaled short-acting

beta agonists (SABA), inhaled corticosteroids (ICS), long-acting beta agonists (LABA), a

leukotriene receptor antagonists (LTRA).

Isolation of Genomic DNA

Isolation of DNA was accomplished by a published, non-invasive method (Lum &

LeMarchand, 1998). At least one hour after eating, subjects rinsed their mouths with water, then

swished Scope mouthwash vigorously for one minute and emptied their oral contents into a

Sarstedt 50 ml Centrifugation tube with a screw cap for closure. Alternatively the study

participants could swish mouthwash for shorter duration on consecutive occasions until the

subject had swished mouthwash for one minute. The tubes were coded with the study ID

number, and mailed to the Cell and Molecular Biology Laboratory, Nemours Children's Clinic,

in Jacksonville Florida. Alternatively mouthwash samples were stored at -20 to -70 O C and sent

to Nemours in bulk shipment.

Mouthwash samples were centrifuged at 2700 rpm for 15 minutes. The supernatant was

poured off. Approximately 0.7ml of T10E10SDS0.5%PK100 g/ml was added to the concentrate. The

specimen was placed into a labeled and serum separator tube, and put in 50 0C incubator

overnight. 0.7ml of Phenol:Chloroform:Isoamyl Alcohol (25:24:1, pH 8.0) was added to the

serum separator tube, and centrifuged at 2700 rpm for 10 minutes. This step was repeated. The

supernatant was then placed in a labeled 2ml centrifuge tube. Approximately 0.7ml of 3M

Sodium Acetate and 0.7ml of Isopropyl was added to the sample and then centrifuged at 14000









CHAPTER 6
FUTURE WORK

Several recent studies have reported that asthma may increase the risk for ACS in patients

with SCD (Boyd, 2004; Bryant, 2005; Knight-Madden, 2004; Nordness, 2005, Sylvester et al.,

2007). If indeed children with concomitant asthma and SCD have increased episodes of ACS,

studies investigating aggressive asthma treatment may have an affect on the mortality and

morbidity associated with this disease. Treatment with bronchodilators and inhaled steriods are

the mainstay of asthma management and are consistent with asthma guidelines (National Asthma

Education and Prevention Program Expert Panel, 2002). Likewise, patients with SCD and airway

compromise are routinely treated with bronchodilators and inhaled steroids. (Vichinsky, 2006;

Handelman, 1991; Mehta, 2006). Unlike preventative treatment in asthma, these medications are

used primarily as supportive care strategies in patients with SCD.

To date there are no randomized clinical trials exploring aggressive asthma management in

patients with SCD. Additionally, no studies have been reported that associate NOS genotypes,

asthma, and SCD. It is interesting to hypothesize that aggressive asthma treatment in patients

with SCD may prevent or reduce the incidence of ACS. More intriguing is the possibility that

identifying genotypes associated with asthma and ACS early in life, in conjunction with

aggressive asthma management, may reduce mortality in patients with SCD.

Montelukast, a leukotriene receptor antagonsist, is frequently prescribed for the treatment

and management of asthma in adults and young children (Knorr, 2001) (Biernacki, 2005)

Montelukast is widely accepted and commonly prescribed by pediatricians given its safety

profile and compliance. Recent updates to the national asthma guidelines suggest that

combination therapy with Montelukast and inhaled corticosteroids may improve asthma control.









with 12 or more AAT repeats in NOS3 had lower FENO levels compared to females with fewer

than 12 AAT repeats, suggesting that gender and/or genetic variants in NOS3 may affect exhaled

nitric oxide levels. Collectively, these findings may offer a plausible explanation for differences

in asthma phenotype and may explain the variance in FENO values.

To date the only study reporting and association between FENO and NOS genotype in

patients with sickle cell disease and acute chest syndrome is that by Sullivan and colleagues

(2001). As mentioned, they found an inverse correlation between the number of repeats in NOS 1

and FENO levels. Further studies are warranted exploring associations between NOS genes,

variability in FENO, asthma, and SCD.

Associations between NOS Genetic Variants and ACS

Nitric oxide (NO) is thought to play a key role in the pathogenesis of ACS (Gladwin et al.,

1999). Plasma concentrations of NO are reduced during ACS as a consequence of reduced NO

bioavailability (Morris et al., 2006) (Morris et al., 2004). Recent studies demonstrate that

administration of inhaled NO has beneficial effects in treating ACS (Stuart & Setty, 2001;

Sullivan et al., 1999). Identifying genetic variants in NOS genes may be beneficial in predicting

susceptibility for developing ACS. Hammerman and colleagues (1999) investigated the theory

that alterations in endothelial cell production and metabolism of NO products might be

associated with ACS. They measured NO products from cultured pulmonary endothelial cells

exposed to plasma from sickle cell patients during crisis. They found that within two hours of

exposure there were increases in NOS3 protein and NOS3 enzyme activity suggesting that an

increase of toxic NO metabolites might contribute to the cellular and tissue damage seen in ACS.

In an attempt to clarify the genetic differences associated with the phenotypic diversity in

patients with SCD, Vargas et al (2006) analyzed three polymorphisms in the eNOS gene; the

single-nucleotide polymorphism (SNP) T-786C in the promoter region, the SNP E298D in exon









Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

POLYMORPHISMS IN CANDIDATE GENES FOR THE NITRIC OXIDE PATHWAY IN
SICKLE CELL PATIENTS WITH ACUTE CHEST SYNDROME AND ASTHMA

By

Laurie Jill Duckworth

August 2007

Chair: Joyce K. Stechmiller
Major: Nursing Sciences

Sickle cell disease (SCD) is one of the most common genetic diseases, affecting one in 600

African Americans. Acute chest syndrome (ACS) is the leading cause of mortality and the

second most common cause of hospitalizations in patients with SCD accounting for nearly half

of premature deaths. A number of recent studies have reported that asthma may increase the risk

of ACS in children with sickle cell disease. Nitric oxide is thought to play a key role in the

pathogenesis of ACS. The main objectives of this study were to test the hypotheses that

polymorphisms in candidate genes; Arginase 1, nitric oxide synthase (NOS) genes; NOS1 and

NOS3, associate with ACS in SCD patients and to characterize the association between

physician-diagnosed asthma and ACS. A total of 134 participants between 5-21 years of age

with SCD were enrolled. Associations between acute chest syndrome and asthma with the

following polymorphisms were explored: the AAT in intron 13 (formerly intron 20) of the

NOS1; T-786C and G894T and the repeat polymorphism in intron 4 of NOS3; and ARG I Pvu

polymorphism. African Americans (n=74) comprised a cohort of healthy controls owing to non-

Hardy-Weinberg equilibrium (HWE) in some variants.

Physician-diagnosed asthma was determined by chart review, parental report, and

medication use. Eighty five percent of participants with asthma had at least on episode of ACS









These findings suggest ethnic differences in asthma related health care within a managed care

plan and suggest that financial barriers to health care are not the only cause for disparities.

As noted by Joseph et al (2005), it is important to distinguish race as a risk marker for

asthma as opposed to a risk factor. Risk markers imply a relationship between race and a

measured variable, whereas risk factors include ancestry, more specifically genetic variations

that associate with disease. Despite asthma guidelines, medical advances, and managed care

programs; ethnic disparities in the morbidity and mortality of asthma persist. This is not to

suggest that adherence to guidelines would minimize disparities but rather supports the role of

genetic variation.

Limited understanding of etiology of ACS

As stated previously, pulmonary disease manifested as ACS is a common complication of

sickle cell anemia. ACS is the second most common cause of hospitalization in patients with

sickle cell disease and is the leading cause of premature deaths (Platt, 1994;Vichinsky, 1996,

2000). ACS is characterized by the presence of a rapidly progressing multi-lobe infiltrate, cough,

hypoxemia and dyspnea. The etiology of ACS is multifactorial and remains unclear. Our current

understanding suggests that ACS may be a form of acute lung injury that progresses to acute

respiratory distress syndrome. This injury is thought to be precipitated by sloughing of blood in

the pulmonary microvascular resulting in pulmonary infarction, fat embolisation, and infection

(Vichinsky, 1996; Scully et al., 1997). There is compelling evidence to support the central role of

NO in the initiation of the pathophysiological process in ACS. Stuart and Setty assessed plasma

NO metabolites in 36 patients with SCD and 23 age-matched controls. Serum concentrations of

NO metabolites were decreased during acute chest syndrome with values lower than in controls

and in patients at steady state (Stuart et al 1999). Hammerman and colleagues (1999) exposed

cultured pulmonary endothelial cells to the plasma of patients with sickle cell disease and acute









HOW WILL THE INFORMATION COLLECTED FROM AND ABOUT PEOPLE IN
THE STUDY BE PROTECTED?
All information will be maintained on a confidential basis. Your/your child's identity will

be protected to the extent permitted by law. Care will be taken to preserve the confidentiality of

all information. You/your child understand that a record of your/your child's progress while in

this study will be kept in a confidential file at Nemours Children's Clinic. The samples will be

coded with a unique identifying number and stored in a secure location. The confidentiality of

any central computer record will be carefully guarded and no information by which you/your

child can be identified will be released or published. However, information from this study will

be submitted to the American Lung Association and the Food and Drug Administration (FDA).

(It may be submitted to governmental agencies in other countries where the study drug

combination may be considered for approval.) Medical records which identify participants and

the signed consent form can be inspected by

* The sponsoring drug company or designee
* The U.S. Food and Drug Administration
* The U.S. Department of Health and Human Services
* Governmental agencies in other countries; and
* The Nemours Florida Institutional Review Board (a group of people who carefully review
the study activities and are responsible for protecting the safety and the rights of the
volunteers).

Because of the need to release information to these parties, absolute confidentiality cannot

be guaranteed. The results of this research project may be presented at meetings or in

publications; however, your child's identity will not be disclosed in those presentations.


WHO CONTROLS AND OWNS GENETIC MATERIALS?
The sample that you/your child provide will be stored for 10 years at Nemours Children's

Clinic.









-786 T to C polymorphism: (rs2070744)


Forward primer: 5'GCATGCACTCTGGCCTGAAGTG-3'

Reverse primer: 5'CAGGAAGCTGCCTTCCAGTGC-3'

223BP PCR product

Exon 7 G894T = Glu298Asp polymorphism: (rs1799983)

Forward primer: 5'CTGGAGATGAAGGCAGGAGAC-3'

Reverse primer: 5'CTCCATCCCACCCAGTCAATC-3'

267 BP PCR product

Intron 4 Deletion/Insertion of 27 BP

Forward primer: 5'AGGCCCTATGGTAGTGCCTT-3'

Reverse primer: 5'TCTCTTAGTGCTGTGGTCAC-3'

Amplified by PCR on 6% polyacrylamide gels

ARG1 gene (Pvu II polymorphism) (rs17599586)

5'ATCTGAGGTAATAGAGAAGC 3'

5'TGAAAGTAGTACAGACAGAC 3'



Statistical Analysis

Data analysis was performed using SPSS version 11.0. The statistical significance of

differences in allele frequencies and genotype distributions were determined by calculating odds

ratios and by using chi square analysis. The Hardy -Weinberg equilibrium (HWE) was

examined using the Markov chain method with a program for population genetics data analysis

(Genepop, School of Biomedical Sciences, Curtin University of Technology, France) as well as









CHAPTER 2
MATERIALS AND METHODS

This chapter is divided into three sections. The first section presents subject characteristics,

sampling method, and eligibility criteria. Second, the methods and procedures with specifics on

study design, protocol, and data collection are presented. Finally a description of data

management and statistical analyses of the two aims are reviewed.

Subjects

Sample and Setting

A convenience sample of 134 African American subjects with SCD were selected and

recruited from the Sickle Cell Disease Clinic, Emory University School of Medicine, Atlanta,

GA, and from the Hematology Clinics at the Nemours Children's Clinic, Jacksonville and

Orlando, Florida. All African American patients with SCD meeting eligibility criteria were

offered participation in the study.

Informed consent and children's assent were obtained in accordance with the requirements

and guidelines of the Institutional Review Boards at the participating centers. (Appendix A)

Inclusion Criteria

* African American
* > 5 years to 21 years of age
* Sickle Cell Disease diagnosis (HbSS, HbSC or HbSp)

Exclusion Criteria

Prematurity of birth resulting in Bronchopulmonary Dysplasia or Respiratory Distress

Syndrome

Blood transfusion within the past 30 days









The results in Figure 2 imply that proportion of patients with physician-diagnosed asthma

is caused, at least in part, by the number of ACS episodes experienced by patients with SCD.

The fact is we cannot determine causality from our data. It is possible that ACS may cause

asthma, or that having asthma increases the risk of ACS, or that causality is bidirectional.

The results of this study support a genetic component for both ACS and for asthma in

SCD. The higher number of AAT repeats may act to decrease the activity of NOS enzyme

leading to reduced production and availability of NO, which can increase the risk of ACS and

possibly asthma (Weschler et al., 2000). Arginase activity is increased in asthma, leading to

reduced arginine availability, which can exacerbate NO deficiency in SCD patients. If the A2

allele of ARG1 leads to high expression of arginase I compared to the Al allele, then A2

homozygotes would utilize arginine to a greater extent than Al carriers, resulting in less arginine

for NOS 1 to convert to NO.

Study Limitations

A major limitation of the present study is how asthma was defined. We used a diagnosis

of asthma by a pediatrician, self- or guardian-reported asthma and drug use to define asthma.

Self- or guardian-reported asthma was in complete agreement with physician-diagnosed asthma,

and all participants with physician-diagnosed asthma were on SABA, two-thirds were on ICS,

which supports the idea that they had true asthma. Additionally, we only offered study

participation to those who presented for their clinic appointments. This may have biased the

study in that children with ACS may be more likely to keep their scheduled appointments

compared to SCD patients who are stable. Earlier studies show pulmonary function

abnormalities in children and adults with SCD. However, the data are conflicting in that some

studies in children with SCD have obstructive lung disease (Koumbourlas et al., 2001; Leong et

al., 1997), while others have found restrictive lung disease (Sylvester et al., 2006). Adults with









Recent studies have shown that L-arginine levels are low in patients with sickle cell disease

(Lopez et al., 2003 Enwonwu et al., 1990), and decreased to an even greater extent in patients

who have sickle cell disease with evidence of ACS. (Morris et al ,2000).

Asthma

Asthma is a disease involving chronic inflammation of the airways. Airway inflammation

is a consistent finding in patients with mild, moderate, and severe asthma. Numerous studies

have reported elevated exhaled nitric oxide levels in patients with asthma (Kissoon et al., 1999)

(Kharitonov, 1994,1996) (Piacentini et al., 1999). The following definition of asthma is the

accepted definition as proposed in the National, Heart, Lung and Blood Institutes (NHLBI's)

National Asthma and Prevention Program (NAEPP) Expert Panel Report: Guidelines for the

Diagnosis and Management of Asthma Update 2002:

Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular

elements play a role, in particular, mast cells, eosinophils, T lymphocyutes, neutrophils, and

epithelial cells. In susceptible individuals, this inflammation causes recurrent episodes of

wheezing, breathlessness, chest tightness, and cough, particularly at night and in early morning.

These episodes are usually associated with widespread but variable airflow obstruction that is

often reversible either spontaneously or with treatment. The inflammation also causes an

associated increase in the existing bronchial hyperressponiveness to a variety of stimuli (National

Asthma Education and Prevention Program Expert Panel, (2003).

Asthma is one of the most common chronic diseases of industrialized nations and its

prevalence continues to increase throughout the world. Statistics form the Centers for Disease

Control reveal that the incidence of asthma in the United States is between 8-9 %. Asthma is the

leading chronic illness in children and the number one cause of school absences. Overall,

mortality rates for asthma have declined since 1995, however mortality rates continue to be 3




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1 POLYMORPHISMS IN CANDIDATE GENES FOR THE NITRIC OXIDE PATHWAY IN SICKLE CELL PATIENTS WITH ACU TE CHEST SYNDROME AND ASTHMA By LAURIE JILL DUCKWORTH A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2007

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2 2007 Laurie Jill Duckworth

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3 To my children, Lindsay and Lesley Duckworth, fo r their love, support, a nd patience. To my parents, Louis and Lorraine Doucette, for believi ng in me. To all who nurtured my intellectual curiosity making this milestone possible.

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4 ACKNOWLEDGMENTS I sincerely thank my doctoral committee, Dr s. Joyce Stechmiller, Julie Johnson, Veronica Feeg, John Lima, and Lorraine Frazier, for th eir mentorship, guidance, and support. The expertise of each member has contributed greatly to the completion of my dissertation. I could not have succeeded without them. As chair of my committee, Dr. Joyce Stechmille r has served as an extraordinary teacher and mentor. Her encouragement and positive nature has given me the confidence to explore my research interest and believe in my contribution to the science of the nursing profession. Special thanks to Dr. John Lima who not only served as a mentor but whom also provided daily encouragement throughout this process. I coul d not have succeeded without his guidance and support. I would like to thank Dr. Niranjan Kissoon for providing the opportunity to develop my research interest in nitric oxi de. Special recognition goes to Jainwei Wang for enduring endless questions related to genotypi ng. Also, Hua Feng for navigating me through the statistical analyses for this project. My co-workers for their patience and understanding over the past several years, I could not have completed this task without your support. Finally, I thank my friends for their love and support.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........7 LIST OF FIGURES................................................................................................................ .........8 LIST OF ABBREVIATIONS..........................................................................................................9 ABSTRACT....................................................................................................................... ............10 CHAPTER 1 INTRODUCTION..................................................................................................................12 Background and Significance.................................................................................................14 Acute Chest Syndrome and Nitric Oxide........................................................................14 Nitric Oxide Synthase Enzymes......................................................................................15 Nitric Oxide, Airway Inflammation, ACS, And Asthma................................................16 Significance of Research....................................................................................................... .16 Research Aims and Hypotheses..............................................................................................17 Specific Aim 1.................................................................................................................17 Hypothesis..................................................................................................................... ..17 Specific Aim 2.................................................................................................................17 Hypothesis..................................................................................................................... ..17 Significance to Nursing........................................................................................................ ..17 Theoretical Framework.......................................................................................................... .18 2 MATERIALS AND METHODS...........................................................................................21 Subjects....................................................................................................................... ............21 Sample and Setting..........................................................................................................21 Inclusion Criteria.............................................................................................................21 Exclusion Criteria............................................................................................................21 Methods And Procedures........................................................................................................22 Study Design...................................................................................................................22 Consent........................................................................................................................ ....22 Demographic Information...............................................................................................22 Medical History...............................................................................................................22 Acute Chest Syndrome Diagnosis...................................................................................22 Asthma Diagnosis............................................................................................................23 Isolation of Genomic DNA.............................................................................................23 Genotyping..................................................................................................................... .24 Statistical Analysis........................................................................................................... .......25

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6 3 LITERATURE REVIEW.......................................................................................................28 Sickle Cell Disease............................................................................................................ .....28 Acute Chest Syndrome...........................................................................................................29 Asthma......................................................................................................................... ...........30 Nitric Oxide................................................................................................................... .........31 Historical Events Leading to th e Discovery of Nitric Oxide..........................................32 Nitric Oxide Mechanisms of Action.............................................................................33 Exhaled Nitric Oxide and Airway Disease.............................................................................35 Associations between NOS Genetic Variants and ACS.........................................................38 NOS Genes and Association with Asthma.............................................................................40 Nitric Oxide Synthase 1 (nNOS).....................................................................................40 Nitric Oxide Synthase 2 (iNOS)......................................................................................41 Nitric Oxide Synthase 3 (eNOS).....................................................................................42 Nitric Oxide and Acute Chest Syndrome...............................................................................42 Arginase Genes and Asthma...................................................................................................43 Impact of Genetics............................................................................................................. .....44 Genetic Influence.............................................................................................................. ......44 Analysis Of Ethical, Social, Politic al, Economic, and/or Cultural Issues..............................45 Limited understanding of etiology of ACS............................................................................47 Similarities and Differences Between Asth ma and ACS with Regard to Symptomology and Lung Function..............................................................................................................48 4 RESULTS........................................................................................................................ .......51 Descriptive Results............................................................................................................ .....51 Genotyping..................................................................................................................... ........51 Asthma and Acute Chest Syndrome.......................................................................................52 Genetic Associations........................................................................................................... ...52 5 DISCUSSION..................................................................................................................... ....58 Study Limitations.............................................................................................................. ......59 Implications for Clinical Practice...........................................................................................62 6 FUTURE WORK....................................................................................................................64 APPENDIX A CONSENT FORM..................................................................................................................66 B DEMOGRAPHIC INFORMATION......................................................................................77 C MEDICAL HISTORY............................................................................................................78 LIST OF REFERENCES............................................................................................................. ..79 BIOGRAPHICAL SKETCH.........................................................................................................89

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7 LIST OF TABLES Table page 4-1 Characteristics of self-identified African Americans with sickle cell disease who had at least one episode of acute chest syndrom e (cases) and individuals with no episodes of acute chest syndrome (controls)....................................................................................54 4-2 Comparison of Hardy-Weinberg Equilibri a (HWE) and minor allele frequencies of NOS 1, NOS 3 and ARG I polymorphisms in 134 patients with sickle cell disease (SCD) and 74 healthy controls...........................................................................................54 4-3 Influence of physician-diagnosed asthma on th e risk of having at least one episode of acute chest syndrome in patients with sick le cell disease (cases) compared to no physician-diagnosed asthma (controls)..............................................................................55 4-4 Association between ARG1 A2/A1 poly morphism and asthma among SCD patients.....57

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8 LIST OF FIGURES Figure page 1-1 Metabolic pathways for Arginine, Arginase Nitric oxide synthase, and Nitric oxide......20 2-1 Diagram of study protocol.................................................................................................27 4-1 Comparison of distributions of allele s carrying AAT repeats in intron 13 on NOS 1 gene........................................................................................................................... .........55 4-2 Prevalence of physcian-diagnosed asth ma and acute chest syndrome episodes................56 4-3 Risk of ACS and NOS 1 AAT repeats in intron 13...........................................................57

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9 LIST OF ABBREVIATIONS ACS acute chest syndrome AAT intronic repeat NOS1 gene DNA deoxyribonucleic acid FENO exhaled nitric oxide ICS inhaled corticosteroid NO nitric oxide cNOS constitutive n itric oxide synthase eNOS endothelial nitric oxide synthase (NOS3) HWE Hardy-Weinberg equillibrium iNOS inducible nitric oxide synthase (NOS2) LABA long-acting beta agonists OR odds ratio PCR polymerase chain reaction nNOS neuronal nitric oxide synthase (NOS1) SABA short-acting beta agonists SCD sickle cell disease SNP single nucleotide polymorphism NCC Nemours Childrens Clinic

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10 Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy POLYMORPHISMS IN CANDIDATE GENES FOR THE NITRIC OXIDE PATHWAY IN SICKLE CELL PATIENTS WITH ACU TE CHEST SYNDROME AND ASTHMA By Laurie Jill Duckworth August 2007 Chair: Joyce K. Stechmiller Major: Nursing Sciences Sickle cell disease (SCD) is one of the most common genetic diseases, affecting one in 600 African Americans. Acute chest syndrome (ACS ) is the leading cause of mortality and the second most common cause of hospitalizations in patients with SCD accounting for nearly half of premature deaths. A number of recent studies have reported that asthma may increase the risk of ACS in children with sickle cell disease. Nitr ic oxide is thought to play a key role in the pathogenesis of ACS. The main objectives of this study were to test the hypotheses that polymorphisms in candidate genes; Arginase 1, ni tric oxide synthase (NOS) genes; NOS1 and NOS3, associate with ACS in SCD patients a nd to characterize the association between physician-diagnosed asthma and ACS. A total of 134 participants between 5-21 years of age with SCD were enrolled. Asso ciations between acute chest syndrome and asthma with the following polymorphisms were explored: the AAT in intron 13 (formerl y intron 20) of the NOS1; T-786C and G894T and the repeat polymorphism in intron 4 of NOS3; and ARG I Pvu polymorphism. African Americans (n=74) comprise d a cohort of healthy controls owing to nonHardy-Weinberg equilibrium (HWE) in some variants. Physician-diagnosed asthma was determined by chart review, parental report, and medication use. Eighty five per cent of participants with asthma had at least on episode of ACS

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11 compared to 14.6 % of participants without ACS; adjusted odds ratio (OR) (95%CI) 5.46 (2.20,13.5), P = 0.0001. Physician-diagnosed asthma correla ted with the number of episodes of ACS ( P 0.001). The NOS1 AAT repeat polymorphism associated with the risk of ACS ( P = 0.001) in patients without physician-diagnosed asth ma. No associations were found between the NOS3 T-786C polymorphism and ACS. Carriers of the ARG I minor allele were less likely to have asthma, 22/79 (28%) compared to WT homozygotes 6/47 (13%); p = 0.04. Findings from this study suggest that asthma is a major risk factor for ACS. The NOS1 AAT repeat polymorphism may cont ribute to ACS in SCD patients without asthma. Studies that further characterize the associati on between asthma, ACS, and NOS genes in children with sickle cell disease are warranted.

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12 CHAPTER 1 INTRODUCTION Sickle cell disease (SCD) is one of the most common genetic diseases, affecting one in 600 African Americans. Acute chest syndrome (ACS ) is the leading cause of mortality and the second most common cause of hospitalizations in patients with sickle cell disease (SCD) accounting for nearly half of premature deaths (P latt et al., 1994; Stuart, & Setty 2001; Buchanan et al., 2004). Our current understanding of the pathophysiology and mechanisms leading to ACS in SCD is limited and remains unclear. In a large prospective study infection and pulmonary fat embolism were identified as causal in 38% of episodes, but in approximately 50% of cases no cause was determined (Vichinsky et al., 2000). Nitric oxide (NO) is thought to play a key role in the pat hogenesis of ACS (Gladwin et al., 1999). NO is formed through the hydrolysis of arginine to NO by nitric oxide synthase (NOS). Arginine acts as a substrate for both NOS and arginase. The arginase and NOS pathways can interfere with each other via substrate comp etition (Morris, 2002) (Fig 1-1). Recent studies suggest that asthma may be rela ted to decreased NO bioa vailability (de Boer et al., 1999; Meurs, Maarsingh, Zaagsma, 2003) rather than an overproduction due to inflammation (Kharitonov&Barnes, 2007). This may occur as a result of the increased activity of arginase (Meurs et al., 2002; Zimmermann et al., 2003). Notably, plasma concentrations of NO are reduced during ACS as a consequence of redu ced NO bioavailability (Morris et al., 2006) (Morris, et al., 2004). Compared to normal control subjects, arginine concentrations were lower and the activity of arginase, the enzyme that hydrolyzes arginine to ornithine and urea, was higher in patients with asthma (Morris et al., 2004). Addtionall y, arginase expression wa s strongly induced by IL4 and IL-13 in mice models of asthma and by Th 2 cytokines, which may contribute to NO

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13 deficiency in asthma (Zimmermann et al., 2003). Wechsler et al (2000), identified a group of patients with asthma with low concentrations of FENO that was inversely related to the AAT repeat polymorphism in intron 13 on the NOS1 gene. Recent studies demonstrate that administrati on of inhaled NO has beneficial effects in treating ACS (Stuart & Sett y, 2001; Sullivan et al., 1999; Atz & Wessel, 1997). Sullivan et al (2001) reported lower concentratio ns of exhaled nitric oxide (FENO) in children who previously had ACS. Additionally, they reported that low FENO was associated with a repeat polymorphism in intron 13 (formerly called intron 20) on the NO S1 gene (Sullivan, 2001). Other NOS genes may also be associated with ACS. For example, the NOS3 T-786C polymorphism and increased susceptibility to ACS in females with SCD was reported (Sharan et al., 2004). Chaar et al., (2006) reported that the C-786 al lele was associated with a decr eased risk of ACS. Genes that are involved in the regulation of NO may be im portant in ACS because of the central role NO plays in airway inflammation a nd the pulmonary endothelium. In addition to genetic factors, environmenta l factors may contribute to the susceptibility of patients with SCD to develop ACS. A number of recent studies have reported that asthma may increase the risk of ACS in patients with SC D (Boyd et al., 2004; Kni ght-Madden et al 2005; Bryant, 2005; Nordness, 2005; Sylvester et al., 2 007). These reports were based on studies that documented a link between SCD and airway hy perresponsiveness, lower airway obstruction, reversibility, abnormal pulmonary function te sts and the fact that corticosteroids and bronchodilators, drugs commonly used in asthma, we re beneficial in ACS (Santoli et al., 1998; Koumbourlis et al., 2001) (Klings et al., 2006). The purpose of this study was to characteri ze the association betw een asthma and SCD. The second aim of this study was to determine as sociations between polymorphisms in candidate

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14 genes for the nitric oxide pathway. These genes code for enzymes that utilize arginine as a substrate and regulate NO production. Therefore it is possible that genetic variants that regulate NO production could contribute to ACS and asthma in SCD. Background and Significance Acute Chest Syndrome and Nitric Oxide ACS is a common complication of sickle ce ll anemia. ACS is the second most common cause of hospitalization in patients with sickle cell disease and is the leading cause of premature deaths (Platt, 1994) (Vichinsky et al., 1997, 2000). It is characterized by th e presence of a rapidly progressing multi-lobe infiltrate, cough, hypoxe mia and dyspnea. The etiology of ACS is multifactorial and remains unclear. Our current unde rstanding suggests that ACS may be a form of acute lung injury that progresses to acute resp iratory distress syndrome. This injury is thought to be precipitated by sloughing of blood in the pulmonary microvascular resulting in pulmonary infarction, fat embolisation, and infection (Vichins ky et al 1996) (Scully et al ,1997). There is compelling evidence to support the central role of NO in the init iation of the pathophysiological process in ACS. Stuart and Setty assessed pl asma NO metabolites in 36 patients with SCD and 23 age-matched controls. They found that serum concentrations of NO metabolites were decreased during acute chest syndrome with values lower than in controls and in patients at steady state (Stuart & Setty, 1999). Hammerman and colleagues (1999) exposed cultured pulmonary endothelial cells to the plasma of pa tients with sickle cell disease and acute chest syndrome and found that within two hours of expos ure there were increases in NOS 3 protein and NOS 3 enzyme activity. They suggested that alterations of NO production and metabolism contribute to the pathogenesis of ACS.

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15 Nitric Oxide Synthase Enzymes Nitric oxide synthase enzyme s are expressed in the lung parenchyma. NOS 1 and 3 are constitutive and regulated by intracellular calcium concentra tion. NOS 2 is induced under inflammatory conditions, such as asthma, and is independent of calcium le vels. Studies in pig lungs suggest that exhaled nitric oxide originates at the alveolar surface rather than from the pulmonary circulation and may be derived from NOS 3 expressed in the alveolar walls of normal lungs (Kobzik et al., 1993). Ai rway epithelial cells express bo th NOS 1 and 3 and therefore contribute to NO levels in the lo wer respiratory tract (Shaul et al., 1994; Asano et al., 1994). Using exhaled nitric oxide (FENO) as a marker of NO production, Su llivan et al (2001) found that the concentration of FENO was lower in children with SCD who had previously suffered from acute chest syndrome as compared to children with sickle cell di sease with no history of acute chest syndrome and healthy controls. Additionally they demonstrated that the FENO levels are significantly correlated with the number of NOS1 AAT repeat s. Given that FENO in healthy controls is likely produced by NOS 1 and 3 at basal concentrations, th e decreased level in patients with ACS as compared to healthy controls suggest genetic variations in these genes. It is tempting to speculate that the low FENO seen in SCD patients with ACS may have a genetic origin and possibly may be due to polymorphism s in NOS genes. Finally, a study in 97 mild asthmatic patients revealed that the size of th e AAT repeat polymorphism on intron 13 of the NOS 1 gene was significantly related to FENO (Weschler et al., 2000). A certain fraction or phenotype of asthmatics had low FENO. Collectively these findings suggest and support the hypothesis that genetic variation in NOS genes may contribute to airway disease predisposing patients with SCD to ACS.

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16 Nitric Oxide, Airway Inflammation, ACS, And Asthma The importance of NO as a marker for airway inflammation in asthma is well documented (Barnes, 1995; Batra, et al 2007). Exhaled nitric oxide levels serve as a useful marker for assessing asthma severity and medication compli ance (Naprawa et al., 2005). Asthma is the most common chronic disease of childhood in the Un ited States. The incidence of asthma in the African American population surpas ses that of Caucasians, 17% vs 6% respectively (Yeatts & Shy, 2001) (Boyd et al., 2006). Differences in asthma related symptoms complicate the treatment and management of this disease in pa tients with SCD who may also have ACS. For example, patients with SCD who have recurring airway dysfunction may not be identified as asthmatic in that they are not evaluated for th is condition. Sub specialists and Pediatricians may focus on the childs SCD and manage upper respirat ory conditions on a case-by-case basis. This may leave the patients more vulnerable to an increased risk for ACS. Significance of Research The information gained from the proposed rese arch may identify candidate genetic variants in the NO pathway that increase the risk of patients with SCD to develop ACS. More specifically, this research may determine whet her polymorphisms in NOS genes and other genes that encode proteins that regulat e NO predispose patients with sick le cell disease to episodes of acute chest syndrome. If the NOS genotype is suggestive of decreased NO production in the lung, early intervention with treat ment modalities such as oral arginine may prevent ACS and thereby reduce morbidity and mort ality associated with this co mplication. Findings from this research may lead to screening of patients with SCD for the genetic variants associated with ACS early in life resulting in aggressive manageme nt and particular atten tion to associated lung diseases such as asthma which may put them at heightened risk for pulmonary complications.

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17 Research Aims and Hypotheses Specific Aim 1 To characterize the relationship between AC S and asthma in children with SCD. Hypothesis Asthma is a risk factor for ACS. Specific Aim 2 To explore associations among polymorphisms in candidate genes of the nitric oxide pathway and their association with asthma, ACS and SCD. Hypothesis Polymorphisms in candidate genes of the nitr ic oxide pathway predic t asthma and ACS in children with SCD. Significance to Nursing This study will explore associations between candidate genes in the NO pathway and the incidence of asthma and acute chest syndrome in a sickle cell diseas e population. Gaining insight into mechanisms of chronic disease that may impact complications associated with SCD is vital to nursing care. Outpatient Sickle Ce ll Disease clinics are gene rally managed by nurses. The nurse is often the first contact when patients experience pain or respiratory distress. Asthma is the leading chronic illness in children, can be life threateni ng, and is more prevalent in the African American population. Rece nt retrospective stud ies suggest that patients with SCD who also have a history of asthma may be at increased risk for ac ute chest syndrome. Knowledge regarding polymorphisms in NOS genes and histor ical evidence of asthma, thereby predisposing patients to ACS, may heighten awareness and resu lt in aggressive management and treatment for asthma related symptoms.

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18 Theoretical Framework Sickle Cell disease is the most common genetic disorder among African Americans. Acute Chest syndrome is a leading cause of death in patients with SCD. The incidence of asthma is greater in African Americ ans compared to Caucasians (Lugogo & Kraft, 2006). Racial disparities in the morbidity and mortality associ ated with asthma can be staggering suggesting that African Americans may receive substandard care with regard to diagnosis and treatment (Ford, & McCaffrey, 2006). The reasons for this are unclear but may involve many factors including; access to care, paymen t, and, educational resources. Th eoretically, it stands to reason that patients with SCD who also have asthma ma y be more susceptible to the complication of ACS. There is compelling evidence to support the central role of NO in the initiation of the pathophysiological process in acute chest syndrome. Stuart et al (1999) found that serum NO concentration metabolites were d ecreased during ACS with values lower than patients in steady state, without ACS. Decreased NO production in patients with ACS ma y be the final common pathway leading to ongoing hypoxemia, pulmonary hypertension, and acute l ung injury. Patients prone to develop ACS have decreased levels of FENO even during periods of stability (Sullivan et al., 2001). This may be due to genetic variatio ns in candidate genes that regulate NO, which predispose patients to reduced NO production an d recurring episodes of ACS. A growing body of research suggests that decreased expression of NO synthase genes resulting in decreased NO production is deleterious to the lung and may lead to acute chest syndrome (Hammerman et al., 1999). Identifying these patients before deve loping ACS may decrease the morbidity and mortality associated with this condition. To date few modifiable risk factors for ACS have been identified. Several retrospective studies have reported that havi ng asthma may increase the risk of developing ACS in the SCD

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19 population. Wechsler et al. identified a group of patients with as thma with low concentrations of FENO that was inversely related to the number of AAT repeats in intron 13 on the NOS1 gene. This study did not include patients with SCD ( 2000). A study in a SCD popul ation reported that the number of AAT repeats in intron 13 of the NOS 1 gene associated with FENO levels; lower levels associated with a higher number of repeats (Sullivan, 2001) The overall objective of this study was to de termine whether patients with ACS and SCD have one or more genetic polymorphisms in candi date genes for the nitric oxide pathway that may predispose them to ACS. More specificall y, the study will compare allele frequencies and genotype distributions of polymorphisms in NO S 1, NOS 3, and Arginase 1 genes in children with sickle cell disease and ACS with age, gender, and asthma. Additionally this study will explore associations betw een asthma and ACS.

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20 Figure 1-1. Metabolic pathways fo r Arginine, Arginase, Nitric oxi de synthase, and Nitric oxide. Reprinted with permission by Lippincott, Williams & Wilkins. NOS L-Arginine L Ornithine L Citrulline L-Arginine NOS Arginase L-Ornithine L-Citrulline NO

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21 CHAPTER 2 MATERIALS AND METHODS This chapter is divided into three sections. The first section presents subject characteristics, sampling method, and eligibility criteria. Second the methods and procedures with specifics on study design, protocol, and data collection are presented. Finally a description of data management and statistical analyses of the two aims are reviewed. Subjects Sample and Setting A convenience sample of 134 African American subjects with SCD were selected and recruited from the Sickle Cell Disease Clinic, Emory University School of Medicine, Atlanta, GA, and from the Hematology Clinics at the Nemours Childrens Clinic, Jacksonville and Orlando, Florida. All African American patient s with SCD meeting eligibility criteria were offered participation in the study. Informed consent and childrens assent were obtained in accordance with the requirements and guidelines of the Institutional Review Boards at the participating centers. (Appendix A) Inclusion Criteria African American 5 years to 21 years of age Sickle Cell Disease diagnosis (HbSS, HbSC or HbS) Exclusion Criteria Prematurity of birth resulti ng in Bronchopulmonary Dyspla sia or Respiratory Distress Syndrome Blood transfusion within the past 30 days

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22 Methods And Procedures Study Design A prospective descriptive correlation study design was utilized to investigate the association between polymorphisms in NOS gene s and the incidence of ACS and asthma in children with sickle cell disease. Participants with a positive history of ACS served as cases, those without served as controls The diagram (Figure 2-1) illust rates the study protocol used in this study. Consent Informed consent and childrens assent was obtained in accordance with the requirements and guidelines of the Institutional Review Boards at The University of Florida, Nemours Childrens Clinic, and Emory University. Particip ants and their guardians were approached in person by the study coordinator or pr incipal investigator. The purpose, risks, and benefits of the study were explained and reviewed in detail. The participants ri ght to withdraw from the study at any time without pena lty was discussed. Demographic Information General demographic information was colle cted from the participant and guardian following informed consent. (Appendix B) Medical History A brief medical history checkli st was completed by the study coordinator or PI following informed consent (Appendix C). Acute Chest Syndrome Diagnosis The diagnosis of ACS was determined by hist ory and chart review. ACS was defined by the presence of multilobar infi ltrates by chest radiograph and history of cough, hypoxemia, and dyspnea. Patients with at least one episode of ACS were classified as cases. Patients with SCD

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23 without a history of ACS were clas sified as controls. The age at which participants experienced their first episode of ACS was recorded. Asthma Diagnosis Participants were classified as having asthma if it was dia gnosed by a physician and if they were currently prescribed one or more of the following asthma medicati ons: inhaled short-acting beta agonists (SABA), inhaled corticostero ids (ICS), long-acting be ta agonists (LABA), a leukotriene receptor antagonists (LTRA). Isolation of Genomic DNA Isolation of DNA was accomplished by a pub lished, non-invasive method (Lum & LeMarchand, 1998). At least one hour after eating, s ubjects rinsed their mouths with water, then swished Scope mouthwash vigorously for one minut e and emptied their oral contents into a Sarstedt 50 ml Centrifugation tube with a sc rew cap for closure. Alternatively the study participants could swish mouthwash for shorte r duration on consecutive occasions until the subject had swished mouthwash for one minute. The tubes were coded with the study ID number, and mailed to the Cell and Molecular Biology Laboratory Nemours Childrens Clinic, in Jacksonville Florida. Alternatively mouthwash samples were stored at to C and sent to Nemours in bulk shipment. Mouthwash samples were centrifuged at 2700 rpm for 15 minutes. The supernatant was poured off. Approximately 0.7ml of T10E10SDS0.5%PK100g/ml was added to the concentrate. The specimen was placed into a labeled and serum separator tube, and put in 50 oC incubator overnight. 0.7ml of Phenol:Chloroform:Isoamyl Alcohol (25:24:1, pH 8.0) was added to the serum separator tube, and centrif uged at 2700 rpm for 10 minutes. This step was repeated. The supernatant was then placed in a labeled 2ml centrifuge tube. Approximately 0.7ml of 3M Sodium Acetate and 0.7ml of Isopropyl was adde d to the sample and then centrifuged at 14000

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24 rpm for 5 minutes. The supernat ant was drawn off, 1 ml of 70% alcohol was added and the sample was centrifuged again at 14,000 rpm for 2 minutes. The final specimen was suspended in 10mM of Tris, pH 7.5 and rehydrated overnight. Genotyping DNA was extracted as previously describe d and the quantity of DNA determined by spectrophotometry. (Lum & LeMarchand, 1998) Aliquots of DNA containing 500 ng were prepared and stored at -20C in a secure and locked freezer, a nd labeled with th e participants code number. Forward and reverse primers spec ific to polymorphic loci in the NOS 1 and NOS3 genes were used to isolate regions of interest. Polymerase chain reaction was utilized to identify patient genotype. Below is a listing of the various known polym orphic loci in the NOS 1 and NOS 3 genes and the ARG 1 gene. (Grasemann Yandava, & Dr azen, 1999). In previous studies the location of the AAT repeat was reported as intron 20 (Su llian et al., 2001; Wechsler, et al., 2000). However, according to homosapiens chromo some 12 genomic contig NT_009775, the AAT repeat polymorphism locates in the region of intron 13 (complement 8267923-8271203) of the human NOS1 gene. Oligonucleotides were synt hesized by Operon Technologies (Alameda, CA, USA). The restriction enzymes were purchas ed from New England Bi olabs (Ipswhich, MA, USA). NOS 1 (neuronal NOS) ATT intronic repeat: intron 13 (complement 8267923 8271203) Forward primer: 5CTGGGGCAATGGTGTGT-3 Reverse primer: 5GAGTAAAATTAAGGGTCAGC-3 NOS 3 (endothelial NOS) (Sharan et al., 2000)

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25 -786 T to C polymorphism: (rs2070744) Forward primer: 5GCATGCACTCTGGCCTGAAGTG-3 Reverse primer: 5CAGGAAGCTGCCTTCCAGTGC-3 223BP PCR product Exon 7 G894T = Glu298Asp polymorphism : (rs1799983) Forward primer: 5CT GGAGATGAAGGCAGGAGAC-3 Reverse primer: 5CT CCATCCCACCCAGTCAATC-3 267 BP PCR product Intron 4 Deletion/Insertion of 27 BP Forward primer: 5AG GCCCTATGGTAGTGCCTT-3 Reverse primer: 5TC TCTTAGTGCTGTGGTCAC-3 Amplified by PCR on 6% polyacrylamide gels ARG1 gene (Pvu II polymorphism) (rs17599586) 5ATCTGAGGTAATAGAGAAGC 3 5TGAAAGTAGTACAGACAGAC 3 Statistical Analysis Data analysis was performed using SPSS vers ion 11.0. The statis tical significance of differences in allele frequenc ies and genotype distributions we re determined by calculating odds ratios and by using chi square analysis. The Hardy Weinberg equilibrium (HWE) was examined using the Markov chain method with a program for population genetics data analysis (Genepop, School of Biomedical Sciences, Curtin University of Technology, France) as well as

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26 chi square goodness of fit tests. Differences in age among groups were determined using oneway ANOVA with Bonferroni correction for multiple comparisons. Association between groups with gender, allele, genotype, and the number of AAT repeats on NOS 1 were assessed using chi-square test. The strength of associations between disease ri sk and genotype were evaluated with Mantel-Haensze comm on odds ratios (OR) and 95% confid ence intervals. The relationship between risk of ACS and the number of AAT rep eats in intron 13 of the NOS 1 gene in patients with and without asthma was determined by simple linear regression. Associations between the incidence of asthma and episodes of ACS were de termined by logistic regression analysis with age and gender as covariates. The Hardy-Weinberg law is commonly used for calculating genotype frequencies from allele frequencies. This law is the cornerstone of population genetics. In population genetics, the HardyWeinberg principle is a re lationship between the frequencies of alleles and the genotype of a population. The occurrence of a genot ype, perhaps one associated with a disease, stays constant unless matings are non-random or inappropriate, or mutations accumulate. Therefore, the frequency of genotypes and the freque ncy of alleles are said to be at "genetic equilibrium". Genetic equilibrium is a basic principle of population genetics (Nussbaum, McInnes, & Willard, 2004). This sudy tested fo r Hardy Wienberg Equillibrium (HWE) with 74 healthy African American control subjects. The r easons for testing HWE were to establish that the allele frequencies in the study participants were consiste nt with an Arican American population, and secondly to rule out genotyping error. Interes tingly, the NOS 3 polymorphysims were not in HWE when compared to the healthty control cohort. This suggest that polymorphisms in this gene may be realted to the disease process. This was not however confirmed with the results. In fact, associations were found between the AAT repeat

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27 polymorphism in the NOS1 gene and the arginase 1 gene, neither of which showed differences with regard to HWE. Figure 2-1. Diagra m of study protocol. *History of asthma was not reported for one participant *

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28 CHAPTER 3 LITERATURE REVIEW Sickle Cell Disease Sickle cell disease is an inherited blood disease that is characterized by defective hemoglobin. It is one of the most prevalent ge netic disorders and is the most common genetic disease in the African American population. Th e genetic mutation associ ated with sickle cell disease occurs in approximately one in every 600 African American births. This disease affects millions worldwide and approximately 72,000 peopl e in the United States (Platt, 1994). The clinical course of the disease varies from patie nt to patient. Some patients have mild symptoms while others are severely affected. The reasons for this are unclear. Sickle cell anemia is caused by an abnorma l type of hemoglobin called hemoglobin S. Hemoglobin is a protein inside red blood cells that carries oxygen. Hemoglobin S, however, distorts the red blood cells shape. The fragile sickle-shaped cells deliver less oxygen to the body's tissues, and can break into pieces th at disrupt blood flow (Goldman, 2004). Hypoxia enhances the sickled erythrocytes adherence to both the macrovascular and microvascular endothelium. The pulmonary microcirculation is particularly vulne rable to deoxygenation (Stuart & Setty, 1999). Sickle cell anemia is inherited as an autoso mal recessive trait. This means it occurs in someone who has inherited hemoglobin S from both parents. Sickle cell disease is much more common in certain ethnic groups, significantly affecting African Americans. Someone who inherits hemoglobin S from one parent and norma l hemoglobin (A) from the other parent will have sickle cell trait. Someone who inherits hemogl obin S from one parent and another type of

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29 abnormal hemoglobin from the other parent will have another form of sickle cell disease, such as thalassemia (Goldman, 2004). Patients with sickle cell disease require con tinuous treatment, even when they are not having a painful crisis. The purpose of treatment is to manage and control symptoms, and to try to limit the frequency of crises. Supplementation with folic acid, an essential element in producing red blood cells, is requir ed because of the rapid red bl ood cell turnover. Analgesics and hydration are mainstay treatments for patients during a sickle crisis. Treatment of pain is critical. Non-narcotic medications may be e ffective, but many patient s require narcotics. Hydroxyurea was found to help some patients by re ducing the frequency of painful crises and episodes of acute chest syndrome. It also been shown to decrease the need for blood transfusions. Newer drugs are being developed to manage sickle cell anemia. Some of these drugs work by trying to induce the body to produce more fetal hemoglobin (in an attempt to decrease the amount of sickling), or by increasing the binding of oxygen to sickle cells. To date, there are no other commonly used drugs availa ble for treatment (Hoffman, 2005). Acute Chest Syndrome Acute Chest Syndrome is a common complication of sickle cell disease and is the leading cause of premature death in this population (Pla tt, 1994) (Stuart et al., 1994) (Buchanan et al., 2004). ACS is characterized by the presence of multi-lobe infiltrates, cough, dyspnea, hypoxia, and often chest pain. The pathophysiology of ACS is unclear but recent re search indicates that NO plays a central role in airway pathology asso ciated with this condition (Hammerman et al., 1999). This is not surprising when we take into account that the lung cont ains all three forms of nitric oxide synthase ( NOS), NOS 1, 2, and 3. Kharitonov et al (1995) demonstr ated that oral administration of L-arginine to healthy subjects increased exhale d nitric oxide (ENO) levels.

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30 Recent studies have shown that L-arginine levels are low in patients with sickle cell disease (Lopez et al., 2003 Enwonwu et al., 1990), and decreased to an even greater extent in patients who have sickle cell diseas e with evidence of ACS. (Morris et al ,2000). Asthma Asthma is a disease involving chronic inflam mation of the airways. Airway inflammation is a consistent finding in patients with mild, moderate, and severe asthma. Numerous studies have reported elevated exhaled nitric oxide leve ls in patients with asthma (Kissoon et al., 1999) (Kharitonov, 1994,1996) (Piacentini et al., 1999). The following definition of asthma is the accepted definition as proposed in the National, Heart, Lung and Blood Institutes (NHLBIs) National Asthma and Prevention Program (NAEPP) Expert Panel Report: Guidelines for the Diagnosis and Management of Asthma Update 2002: Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role, in particular, mast cells, eosinophils, T lymphoc yutes, neutrophils, and epithelial cells. In susceptible individuals, this inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness, and cough, particularly at night and in early morning. These episodes are usually associated with widesp read but variable airflow obstruction that is often reversible either spontan eously or with treatment. The inflammation also causes an associated increase in the existi ng bronchial hyperressponiveness to a variety of st imuli (National Asthma Education and Prevention Program Expert Panel, (2003). Asthma is one of the most common chronic diseases of industrialized nations and its prevalence continues to increase throughout the world. Statistics form the Centers for Disease Control reveal that the incidence of asthma in the United States is between 8-9 %. Asthma is the leading chronic illness in children and the number one cause of school absences. Overall, mortality rates for asthma have declined since 1995, however mortality ra tes continue to be 3

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31 times higher for African American males as compared to white males, and 2.5 times higher for black females when compared to white females (F agan et al., 2000). Over the past 10-15 years research has led to a greater understanding of the mechanisms of asthma, thereby reducing mortality and improving the quality of life for many patients suffering with asthma. However, reasons for disparities in mortal ity among African Americans conti nue to elude scientists. Recent studies have reported a relationship between asthma and ACS (Boyd et al., 2004) (KnightMadden et al., 2005 (Bryant, 2005) (Nordness et al., 2005). Many of the symptoms related to ACS are also seen in asthma; dyspnea, cough, de creased oxygen saturation. Surprisingly, the prevalence of asthma in these studies range d from 45 to 53%, a st riking increase over the incidence of asthma generally seen in African Am ericans. What remains unclear is direction of the causality of the relationship between ACS and Asthma. Do patients with asthma have more episodes of ACS, or are patients with a hist ory of ACS more likely to develop asthma? Few studies address polymorphisms in NOS genes and how they may impact airway disease, specifically asthma, in patients with SCD. Given that asthma is the leading chronic illness in children and more prevalent in African Americans, it is important to explore relationships among candidate genes in the NO path way, asthma, sickle cell disease, and acute chest syndrome. Recent studies citing the impor tance of arginase in asthma pathogensis additionally warrant further research (Vercelli, 2003). Nitric Oxide Nitric oxide (NO) plays a major role in lung physiology and airway disease. This ubiquitous gas is an unstable fr ee radical that serves as a me diator for several physiological events including vascular and airway smoot h muscle tone, bronchodilation, and airway inflammation (Barnes, 1995). Nitr ic oxide may also be necessary for ciliary action (Jain et al., 1993) and is thought to aid in maintaining steri lity in the lower respiratory tract due to its

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32 antimicrobial properties against pathogens includ ing viruses and mycobacterium (Xia & Zweir, 1997). Endogenous NO is produced from the amino aci d L-arginine by the enzyme NO synthase which has three isoforms. Tw o constitutive forms (cNOS); neuronal (nNOS or NOS1) and endothelial (eNOS or NOS3) are found in small quantities and serve basa l metabolic functions. The third isoform, inducible (iNOS or NOS2) is mediated by inflammatory cytokines and endotoxin and plays a major role in the inflammation seen in asthma. All th ree of these isoforms are found in the respiratory tract (Kobzik et al., 1993; Robbins et al., 1994). Historical Events Leading to the Discovery of Nitric Oxide Nitric oxide was discovered by Joseph Priestle y in 1772 as a clear, colorless gas. In 1980. Furchgott (1980) discover ed that endothelial cells produ ce endedothelium relaxing factor (EDRF) in response to acetylcholine In 1987 M oncada & Higgs (1987) and Ignarro et al (1987) discovered that EDRF is nitric oxide. Within a years time Moncada reported that NO is synthesized from the amino acid L-arginine (P almer, Ashton & Moncada, 1988). Nitric Oxide was proclaimed as molecule of the year on the cover of Science magazine in 1992. (Koshland, 1992). Six years later, the importance of the ni tric oxide discovery was recognized by awarding the Nobel Prize in Physiology and Medicine to Furchgott, Ignarrao, and Murad (Williams, 1998). By 1993 NO had been implicated in the pathogen esis of a multitude of diseases including, hypertension, septic shock, and dememntia (Mon cada & Higgs, 1993). The next ten years led to multiple publications related to NO, on average ov er 6000 papers per year addressing all areas of medicine, including diabetes, wound healing, neurotransmission, cancer, immune function, infection, eye disease, and respiratory functi on (Yetik-Anacak & Catravas, 2006). Presently it is difficult to find a disease that is not associated with nitric oxide. This is amazing in that nitric oxide was considered as nothing more than an ir ritant and pollutant twenty years ago (Moncada & Higgs, 1993).

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33 During the mid 1990s several studies demonstrated that nitric oxide plays a key role in physiological regulation of airway disease (Gaston & Jonsen 1994; Shaul et al., 1994; Barnes, 1995; Kharitonov et al 1994,1995,1996; Massaro et al., 1995, 1996). More specifically, numerous studies reported increas ed exhaled nitric oxide levels in patients with asthma (Alving Weitzberg, & Lundberg, 1993; Kharitonov et al., 1994, 1996; Barnes, 1995; Massaro et al., 1995). Nitric oxide is released by a variety of pulmonary cells including epithelial cells, eosinophils, and macrophages (Yates, 2001). It is be lieved that elevated nitric oxide in the airways is generated by inducib le nitric oxide synthase (iNOS) mediated by inflammatory cytokines and endotoxi n (Asano et al.,1994). There is compelling evidence to support the central role of NO in the initiation of the pathophysiological processes in acute chest synd rome. Stuart and Setty (1999) observed that serum concentration of NO metabolites were decreased during episodes of ACS with values lower than controls and patients in steady state. Recent studies have shown that L-arginine levels are low in patients with sickle cell disease (L opez et al., 2003; Enwonwu, 1990), and decreased to an even greater extent in patients who have sickle cell disease with evidence of ACS (Morris et al., 2000). These findings support the key ro le of NO in the pulmonary endothelium and airway inflammation. Nitric Oxide Mechanisms of Action Nitric oxide (NO) is a simple free radical gas. NO reacts with oxygen to form nitrite and nitrates. Endogenous nitric oxide is produced fr om the amino acid L-arginine by the enzyme NO synthase, which has three isoforms (Nathan, & Xia, 1994) (Fig1-1). Two constitutive forms (cNOS); neuronal (nNOS or NOS1) and endothe lial (eNOS or NOS3) and are found in small quantities and serve basal metabolic functions. The third isoform, inducible (iNOS or NOS2) is mediated by inflammatory cytokines and endot oxin and plays an important role in the

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34 inflammation seen in asthma. All three of these isoforms ar e found in the respiratory tract (Kobzik, 1993;Robbins, 1994). Synthesis of NO by cNOS is thought to be responsible for vasodilator tone associated w ith regulation of blood pressure, neurotransmission, respiratory function, cardiac contractility, a nd also plays a role in platel et aggregation (Nathan & Xia, 1994;Yates, 2001; Hammerman et al., 1999). NOS1 and NOS3 are regulated by intracellular calcium concentration, whereas NOS2 is induc ed under inflammation i ndependent of calcium concentration. Agonists such as stress, bradyki nin, acetylcholine, and histamine may activate cNOS resulting in the release of pico molar le vels of NO. Conversely iNOS is generated by cytokines present in the ai rway and produce nano molar levels of NO (Yates, 2001). NO impacts vascular homeostasis in a variet y of ways. Levels of NO may inhibit smooth muscle cell proliferation, plat elet aggregation, and platelet and monocyte adhesion to the endothelium. Low levels, or decreased bioavailab ilty of NO may lead to hypertension, coronary artery disease, peripher al artery disease, sickle cell, or stroke (Puddu et al., 2005). Nitric oxide acts as a vasodilator, bronchod ilator, neurotransmitter, and mediator of inflammation in the lung (Barne s, 1993). Due to its role in smooth muscle relaxation, NO showed promise as a bronchodilator. A study in guinea pigs demonstrated that NO will limit methacholine-induced bronchoconstriction however th e effect is short-liv ed and requires high levels of inhaled NO (Dupuy et al., 1992). A study in asthmatics revealed that inhalation of NO has a small effect on airway caliber and resi stance, thus not showing much promise as a therapeutic agent (Frostell e tal, 1993). Smooth muscle exists in both the bronchi and pulmonary vasculature within the lung. Numerous studi es demonstrate that NO plays a key role in pulmonary arterial vasoconstr iction (Dinh-Xuan, 1992; Leeman & Naecje, 1995; Yetik-Anacak

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35 & Catravas, 2006). Basal levels of NO in pulmona ry endothelial cells ma intain dilation of the pulmonary vascular bed (P epko-Zaba et al., 1991). NO is produced in the airways by inflammatory cells, most notably eosinophils, macrophages, epithelial cells, and mast cells, all of which are relevant to asthma (Gustafsson, 1998). Epithelial cells stimulated by cytokines result in the in duction of iNOS producing high quantities of NO (Robbins, 1996). NO generated fr om epithelial cells may be a physiological defense against infection and could influence susceptibility to airway disease given its antimicrobial properties Decreased levels of NO in the airway may increase susceptibility to infection (Hart, 1999). NO reacts with thiols to fo rm S-nitorsothiols (Stamler et al., 1992). These compounds have bronchodilator acti vity and may also contribute to airway homeostasis by their antimicrobial and anti-inflamma tory properties (Gaston, 1994) Exhaled Nitric Oxide and Airway Disease Airway inflammation plays a cen tral role in the pathogenesi s as well as symptomology of asthma (Shelhamer et al.,1995; Obyrne, 1996) E xhaled nitric oxide (FENO) levels are elevated in patients with asthma, however, there is a subs tantial amount of variance (Massaro et al., 1995, 1996; Kissoon et al., 1999; Rosias et al., 2004; Storm et al., 2004). Repeatable noninvasive measurement of inflammation would be useful in order to assess severity and guide treatment in patients with asthma. Measurement of exhaled nitric oxide levels is an exciting recent development that may provide an indication of the degree of airway inflammation in asthmatics as opposed to traditional pulmonary function test, wh ich are indirect measures of airway flow. Customary monitoring techniques for assessing asth ma severity include peak expiratory flow rates, spirometry, and responses to medications Despite the importance of inflammation in asthma, monitoring airway inflammation is not routine. This is due in large part to the fact that only invasive techniques such as bronchoscopy can directly sample lung tissue and fluids for the

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36 presence of inflammatory cells and mediators. Sputum examination is noninvasive and is one of the few methods available that can produce valuable information from the lower respiratory tract (Busse, 1998). Sputum sampling in children may be impractical in that it is time consuming, expensive, and requires cooperation from the child. Additionally, these measures may only reflect the severity of diseas e at the time of measurement. (Ratnawati & Thomas, 2005). The great advantage of FENO measurement is that sample collection is noninvasive and can be performed repeatedly (Kissoon et al., 1999; Barnes, 1996). There are several analyzers now commercially available that have the capability to measure FENO. Most of the studies done to date measure nitric oxide using a ch emiluminescence analyzer which detects the photochemical reaction between NO and ozone in the analyzer. (Kharitonov et al., 1994,1996; Kissoon et al., 1999; Smith et al., 2005) The beauty of this method is the ability to measure FENO directly in line to the analyzer, in real time, or indirectly by obtaining an exhaled air sample in a balloon to be later analyzed at a more convenient time. Levels of FENO are reported in parts per billion (ppb). Until recently repor ted values for FENO have varied widely most likely due to significant differences in sampling t echnique. Major differences relate to exhalation flow rate and nasal contamination (Kissoon et al., 1999). The American Thoracic Society has published guidelines for FENO measurement in adu lts and children (American Thoracic Society, 1999). Portable devices are curre ntly being developed for at home monitoring of FENO in patients with asthma. Exhaled nitric oxide is reduced in patients receiving anti-inflammatory treatment (Massaro et al., 1995; Kharitonov, et al., 1996, 2007). It is believed that glucocorticoids prevent the induction of inducible NOS (iNOS/ NOS2) by cytokines in epithelial cells. (Kharitonov et al., 1996). Measuring FENO may be useful for mon itoring whether anti-inflammatory therapy is

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37 adequate as well as patient compliance. A recent paper in The New England Journal of Medicine reported that in patients with chronic, persistent asthma, treatment with inhaled corticosteroids could successfully be titrated with the use of FENO measurements. Thus FENO measurements may help to minimize the potential long-term side effects related to inhaled corticosteroids (Smith et al., 2005; Deykin, 2005). With new technology currently available, FENO measurements are easy to perform, can be reproduced accurately, and provide immediate results on which the primary care provider can act. While several studies have described the value of FENO measurement as a useful indicator of airway inflammation and asthma (Cicutto & Downey, 2004; Karitonov et al ,2007; Zeidler, Kleerup, Tashkin, 2004; Smith et al., 2005), few studies have addressed the variance of these levels in patients with asthma or acute chest syndrome. Genetic varia tion may contribute to the variability in exhaled nitric oxide levels. A limited number of studies have reported the contribution of genetic variants in candidate genes for the NO pathway and how they may correlate with exhaled nitric oxide and asthma. Storm and colleagues (2003) identified a strong association between a NOS3 gene variant, G893T, and the variability of FENO levels in patie nts with asthma. FENO levels were lowest in subjects with the TT genotype and were significantly higher in subjects with either the GT or GG genotype. As mentioned previously, the number or trinucleotide repeats (AAT) in the NOS1 gene correlated with FENO values in patient s with asthma however varied depending on genotype (Wechsler et al., 2000). Grasemann et al (2003) investigated FENO in both NOS1 and NOS3 genes. Specifically they studied the numbe r of AAT repeats in intron 13 (formerly intron 20) of the NOS1 gene and the 894G/T mutation in the NOS3 gene. They found no genetic association between FENO levels and the NOS1 ge ne. However, they did report that females

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38 with 12 or more AAT repeats in NOS3 had lower FENO levels compared to females with fewer than 12 AAT repeats, suggesting that gender and/or genetic variants in NOS3 may affect exhaled nitric oxide levels. Collectively, these findings may offer a plausible explanation for differences in asthma phenotype and may explain the variance in FENO values. To date the only study reporting and associ ation between FENO and NOS genotype in patients with sickle cell disease and acute ches t syndrome is that by Sullivan and colleagues (2001). As mentioned, they found an inverse corre lation between the number of repeats in NOS1 and FENO levels. Further studies are warranted exploring associations between NOS genes, variability in FENO, asthma, and SCD. Associations between NOS Genetic Variants and ACS Nitric oxide (NO) is thought to play a key role in the pathoge nesis of ACS (Gladwin et al., 1999). Plasma concentrations of NO are reduced during ACS as a consequence of reduced NO bioavailability (Morris et al., 2006) (Morris et al., 2004). Recent studies demonstrate that administration of inhaled NO ha s beneficial effects in trea ting ACS (Stuart & Setty, 2001; Sullivan et al., 1999). Identifying genetic variants in NOS genes may be beneficial in predicting susceptibility for developing ACS. Hammerman and colleagues (1999) inve stigated the theory that alterations in endothe lial cell production and metabo lism of NO products might be associated with ACS. They measured NO produc ts from cultured pulmonary endothelial cells exposed to plasma from sickle cell patients durin g crisis. They found that within two hours of exposure there were increases in NOS3 protei n and NOS3 enzyme activity suggesting that an increase of toxic NO metabolites might contribute to the cellular a nd tissue damage seen in ACS. In an attempt to clarify the genetic differen ces associated with the phenotypic diversity in patients with SCD, Vargas et al (2006) analyzed three polymorphisms in the eNOS gene; the single-nucleotide polymorphism (SNP) T-786C in the promoter region, the SNP E298D in exon

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39 7, and a 27-bp-repeat VNTR in intron 4. They found no associations between E298D or VNTR and SCD. Interestingly, they did report that all patients hom ozygous for the C variant had a tendency to develop a more severe clinical cour se. Limitations to this study include the small sample size, n=73. A recent retrospective study by Sharan et al (2004) investigated eNOS polymorphisms; E298D and T-786C, in patients with SCD. They concluded that the D298 allele was not associated with SCD, how ever the C-786 allele was strongl y associated with the risk of ACS in female subjects. Sullivan et al (2001) tested the hypothesis that exhaled nitric oxide levels (FENO) are altered in subjects with SCD who have had at least one episode of ACS. They also tested the hypothesis that the number of AAT repeats in in tron 13 (formerly intron 20) of the NOS1 gene correlates with FENO. They reported that (FENO) levels in patients who ha ve a history of ACS are approximately one-third those obser ved in healthy controls and in patients with SCD who have not had ACS. Additionally, they found that low FENO was associated with a repeat polymorphism in the NOS1 gene. More specifically they identified that high numbers of repeats are inversely correlated with FENO levels. It is tempting to speculate that the low FENO seen in SCD patients with ACS may have a genetic orig in and may be due to polymorphisms in NOS genes. Grasemann et al., (1999) demons trated significant differences in allele frequencies and genotypes of the NOS1 gene among ethnically dive rse populations. The number of AAT repeats in intron 20 (currently noted as intron 13) of the NOS1 gene ranged from 7-16 in Causcasians and African Americans. Indi viduals homozygous for allele 10 were more common among Caucasians (p = 0.0004), whereas those homozyg ous for allele 14 were more common among African Americans (p0.05). These findings suggest that ethnicity may have an impact on

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40 variants in the NOS1 gene and that these differen ces may be misinterpreted if not addressed in future studies. This study did not report whether or not participants had a history of asthma. NOS genes that are involved in the regulation of NO may be important in ACS because of the central role NO plays in airway in flammation and the pulmonary endothelium. NOS Genes and Association with Asthma There is a plethora of research in the literature describing the key role of NO in the airway epithelium. Patients with asthma have increas ed NO production in thei r airways (Kharitonov, Yates, & Robbins, 1994; Massaro et al., 1996; Ba rnes, 1996; Piacentini et al., 1999). NOS genes are located throughout the genome at 7q35-36 ( NOS3) (Robinson et al., 1994), 12q24 (NOS1) (Xu et al., 1993), and 17q12 (NOS2) (Marsden et al., 1994), all candidate loci for asthma (Collaborative Study on the Genetics of Asthma 1997; Daniels, 1996; Ob er et al., 1998). Nitric Oxide Synthase 1 (nNOS) Genome-wide searches have established lin kage between asthma and the NOS1 (nNOS) gene (Collaborative Study on th e Genetics of Asthma, 1997; Barnes, 1996; Ober et al., 1998). Grasemann et al (2000) showed a genetic association between a polymorphism in the NOS1 gene and asthma using a case control design. They de monstrated that frequencies for allele 17 and 18 of a CA repeat in exon 29 of the NOS1 gene were significantly different between 490 asthmatic and 350 control subjects. To confirm their findings they genotyped and additional 1131 control subjects and verified that the frequencies of alleles 17 and 18 were nearly identical to those found in their original control gr oup. This study in particular is impressive given the sample size, case-control design, and reproducibility. Fi ndings from this study provide support for NOS1 as a candidate gene for asthma. A study in 97 mild asthmatic patients reve aled that the size of the AAT repeat polymorphism on intron 13 (formerly intron 20) of the NOS 1 gene was significantly related to

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41 exhaled nitric oxide (FENO ) (Weschler et al., 2000). These fi ndings are extremely important given that FENO is now widely accepted as a marker fo r airway inflammation in patients with asthma. Results from this study may help explai n the phenotypic variability among asthmatics. In a genetic association study, Gao and collea gues (2000) tested whether variants of NOS1, NOS2, and NOS3 were related to asthma. Neither NOS2 nor NOS3 variants showed any association with asthma. They did however fi nd an association between variants in NOS1 and asthma. More specifically they described sign ificant differences in 183 bp allele frequencies between control and asthmatic subjects. Homo zygous 183 bp alleles were strongly associated with asthma. Nitric Oxide Synthase 2 (iNOS) NO derived from NOS2 (inducible NOS or iNOS) is involved in inflammatory diseases of the airways (Barnes, 1995). NOS2 has been show n to be upregulated in asthmatics and is a substantial source of NO in the airways (Xia, 1992). Konno et al inves tigated whether the 14repeat allele (CCTTT) of the NOS 2 gene influences the development of atopy and asthma. Their findings suggest that the CCTTT repeat polymorphi sm is associated with atopy but not with asthma. A recent study in 230 families with asthma investigated the genetic association of iNOS repeats with asthma. Four repe ats were identified; (CCTTT)n pr omoter repeat, intron 2(GT)n repeat, intron 4 (GT)n repeat, a nd an intron 5 (CA)n repeat. This study is the first to identify repeat polymorphisms in the iNOS gene and thei r association with asth ma. Individuals carrying allele 4 of the promoter repeat had high serum IgE and nitric oxide levels, characteristic of asthma. Individuals carrying allele 3 of the in tron 4 (GT)n repeat had elevated blood eosinophils and increased asthma severi ty (Batra et al., 2006). Given the role of NOS2 in airway inflamma tion further genetic st udies are warranted exploring variants in the ge ne and how they may contribute to asthma pathology.

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42 Nitric Oxide Synthase 3 (eNOS) Endothelial nitric oxide (eNOS ) is expressed in the airway and pulmonary epithelium and serves an important role in vasodilator tone (Shaul et al., 2002; Valla nce & Moncada, 1989). Genome screenings have identifi ed gene linkages to eNOS and as thma. (Holgate, 1997; Lee et al 2000) demonstrated an association in polymor phisms of eNOS and angiotensin coverting enzyme in patients with asthma. A more recen t study also looking at po lymorphisms of eNOS and angiotensin coverting enzyme in patie nts with asthma found no relationship among polymorphisms of NOS3 and asthma (Yildiz et al ., 2004). Finally, a study in 163 patients with asthma found no relationship between the tand em repeat polymorphism in intron 4 and the (G894T) variant of the NOS3 gene with atopic asthma (Holla et al., 2002). Although widely discussed, there is a lack of research in the literature demonstrating as association among polymorphisms in the NOS3 gene and asthma. Nitric Oxide and Acute Chest Syndrome Most of the morbidity associated with sickle cell disease stems from vaso-occlusive crisis (Platt, 1994) (Vichinsky et al., 2000). Nitric oxide is a vasodilator (Busse, 1998). Could a polymorphism in nitric oxide synthase genes interfe re with or inhibit nitr ic oxide production? Several studies are beginning to address this. Mo rris et al. (2000) found that there may indeed be a relationship between L-arginine and the NO pa thway. Their study attempted to sort out the issue of substrate deficiency or substrate depletion. Sickle cell patients may experience lengthy periods of vaso-occlusion, creating a constant demand for vasodilation mechanisms, i.e. NO production. This overwhelming need or utilizatio n may deplete the quantity of the substrate, Larginine, thereby decreasing ove rall NO production (Morris et al., 2000). Interestingly, Morriss group studied 36 patients at steady state (period of wellness) and during vaso-occlusive crisis (VOC). During steady state, L-arginine levels were normal. L-arginine levels were decreased

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43 during periods of vaso-occlusive crisis and acute chest syndrome. These findings suggest that there may be arginine depletion in response to demand, as opposed to intrinsic substrate deficiency. (Morris et al., 2000). A similar study looked at L-arginine le vels during VOC when sickle cell patients presented to the emergency department. They studied 50 adult patients and found arginine levels were signif icantly low compared to steady state (Lopez et al., 2003). These findings indicate that L-argini ne levels are diminished during periods of exacerbation. L-Citrulline is an amino acid and a precursor fo r arginine (Fig 1-1). Waugh et al. (2001) demonstrated that giving l-citrul line 0.1g/kg orally twice daily el evated plasma arginine levels, and increased symptoms of wellne ss in children with SCD. The oral citrulline supplements were well tolerated and without side effects. Arginase Genes and Asthma Characterization of an asthma phenotype will likely be related to a complex interaction of genes and their polymorphic variants. The pathog enetic mechanisms of and contributing genetic factors in asthma continue to elude scientists. In a murine mo del, Zimmerman et al (2003) found that among signature asthma genes, there was ov er expression of the genes encoding for the uptake and metabolism of arginine, a basic amin o acid, by arginase. Addi tionally their results demonstrated regulation of argina se by IL-4 and IL-13, cytokines that activate inflammatory pathways seen in asthma. Microa rray analysis in murine models of asthma found high levels of arginase I and arginase II activity in associ ation with IL-4 and IL 13 overexpression (Vercelli, 2003). Notably, arginine acts as a substrate for both arginase a nd NO synthase. The arginase and NO synthase pathways may interfere with each other by way of competition for arginine (Vercelli, 2003). Much of the literature regarding NO in asthma has focused on iNOS and centered on the proinflammatory role of NO. Meur s and colleagues report that a deficiency of NO caused by increased arginase acti vity and altered arginine levels is a contributing factor in

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44 the pathogenesis of asthma (Meurs, 2003). Using global micorarray analysis, Zimmermann et al (2006) reported that asthmatic conditions invol ve metabolism of argini ne by arginase. They report that arginase I an d arginase II genes are key regulators of processes associated with airway tone and lung inflammation. Collectively these studi es indicate the need for further investigation of Arginase I and Arginase II genes and how they may relate to asthma and airway disease. Impact of Genetics In April 2003, sequencing of the human genome was completed. The consequences of this landmark event will have a dramatic impact on the ability to understand the mechanisms of disease and develop treatments specifically tailored to a patients genetic profile (Collins et al., 2003). Sickle cell disease (SCD) is one of the most common genetic diseases, affecting one in 600 African Americans. Despite its Mendelian i nheritance the disease is phenotypically highly variable. For example, some affected by the disease suffer from recurrent vaso-occlusive crisis and die at a young age, while others seem mini mally affected and enjoy a normal life span (Buchanan,, Debaun, & Steinberg, 2004). Hence the need for identification of risk factors and genetic variants that may predict outcomes and reduce mortality. Acute chest syndrome (ACS) is the leadi ng cause of mortality and the second most common cause of hospitalizations in patients with sickle cell disease (SCD) accounting for nearly half of premature deaths (Platt, 1994; Stuart & Setty, 2001; Buchanan, Debaun, & Steinberg, 2004). Our current understanding of the pathophysiology and mechanisms leading to ACS in SCD is limited and remains unclear. Th ere is paucity in the literature describing associations between ACS, airway disease, and genetic variation. Genetic Influence Studies investigating the infl uence of genetic variation in candidate genes in the NO pathway are not unprecedented. The gene that encodes NOS 1 in humans is located on the long

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45 arm of chromosome 12 in the region 12q24.2. Multiple genome wide screening studies in different ethnic populations have shown linkage of this region to asthma (Grasemann et al., 1999; Barnes, 1996; CSGA, 1997; Ober et al., 1998). Grasemann and colleagues (1999) found significant differences in allele frequencies and genotypes of the NOS1 gene among ethnically diverse populations. They studi ed 305 American-Caucasian and 105 African American healthy subjects. The number of AAT repeats in intron 13 (formerly intron 20) ranged from 7-16. The overall distribution of allele s differed significantly between groups. Individuals homozygous for allele 10 were more common among Caucasians whereas those homozygous for allele 14 were more common in African-American subjects. A study in 97 mild asthmatics revealed that the size of the AAT repeat polymorphism on intron 13 (formerly intron 20) of the NOS 1 gene was significantly associated with FENO (Weschler, 2000). The NOS3 gene is located at 7q35-36. A recent study in SCD patients found a functional single nucleotide polymorphism (SNP) in the NOS3 gene, T-786C, that associated with increased susceptibility to acute chest syndrome in females (Sharan et al., 2004). Analysis Of Ethical, Social, Politica l, Economic, and/or Cultural Issues Asthma presents an enormous burden to both th e individual and health care system. It is estimated that 20 million persons in the United States suffer from asthma and asthma accounts for more than 5.000 deaths annually (Nationa l Asthma Education and Prevention Program, 2002). In the last two decades there has been a rise in asthma hospitaliz ations and asthma mortality (Akinbami & Schoenforf, 2002). Mortality associated with asthma peaked in 1998 and has decreased over the past few years. This in crease is more pronounced in African American, and people of low socioeconomic background (Ma nnino et al.,1998). Accord ing to the National Health Interview Survey, nine million children under the age of 18 years have been diagnosed with asthma (13%), children in poor families (1 5%) were more likely to be diagnosed with

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46 asthma, 4 million children (6%) had an asthma attack within the last 12 months, African American children were more likely to have had an asthma attack in the last 12 months, and children in fair or poor health were more than six times as likely to have had and asthma attack in the past 12 months (National Center for Health Sta tistics, 2003). This is staggering given that the National Institutes of Health and the internat ional Global Initiatives for Asthma have focused on asthma treatment and asthma management (N ational Heart, Lung a nd Blood Institute, 2003). A recent study conducted by the American Lung Association Asthma Clinical Research Centers reported that the number of asthma epis odes was highest in children less than 10 years of age. Additionally they found that African American ethnicity and a past hi story of severe asthma were risk factors for poor asthma control (McC oy, et al., 2006). Minority groups with diverse ethnic backgrounds experience disparities in asth ma care and management resulting in increased mortality (Coultas, Gong, & Grad, 1993). Lieu et al (2002) found that African American children had worse asthma status compared to Caucasian children based on the American Academy of Pediatrics Childrens Health Surv ey (AAP), experiencing a greater number of symptom-days, and an increased number of school absences. Additionally they discovered that African American and Latino children were less likely to be using inhaled corticosteroid medication compared to Caucasians. Notably, th is cross sectional study included 1000 subjects between the ages 2-16 years with a diagnosis of asthma, participating in a managed care Medicaid plan. Zoratti and co lleagues (1998) examined patterns of asthma care in 464 African Americans and 1609 Caucasians with participating in a managed care program. Compared with Caucasians, African Americans had fewer visits to asthma specialists, filled fewer prescriptions for inhaled steroids, and were more likely to vi sit the emergency room fo r treatment of asthma.

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47 These findings suggest ethnic differences in asth ma related health care within a managed care plan and suggest that financial barriers to he alth care are not the onl y cause for disparities. As noted by Joseph et al (2005), it is important to distinguis h race as a risk marker for asthma as opposed to a risk factor. Risk ma rkers imply a relationship between race and a measured variable, whereas risk factors include ancestry, more specifically genetic variations that associate with disease. Despite asthma guidelines, medical advances, and managed care programs; ethnic disparities in th e morbidity and mortality of asthma persist. This is not to suggest that adherence to guideli nes would minimize disparities bu t rather supports the role of genetic variation. Limited understanding of etiology of ACS As stated previously, pulmonary disease manifested as ACS is a common complication of sickle cell anemia. ACS is the second most co mmon cause of hospitalization in patients with sickle cell disease and is the leading cause of premature deaths (Platt, 1994;Vichinsky, 1996, 2000). ACS is characterized by the presence of a rapidly progressing multi-lobe infiltrate, cough, hypoxemia and dyspnea. The etiology of ACS is multifactorial and remains unclear. Our current understanding suggests that ACS may be a form of acute lung injury that progresses to acute respiratory distress syndrome. This injury is thought to be precipitat ed by sloughing of blood in the pulmonary microvascular resulting in pulmonary infarction, fat embolisation, and infection (Vichinsky, 1996; Scully et al., 1997). There is co mpelling evidence to support the central role of NO in the initiation of the pathophys iological process in ACS. Stua rt and Setty assessed plasma NO metabolites in 36 patients with SCD and 23 age-matched controls. Serum concentrations of NO metabolites were decreased during acute chest syndrome with values lower than in controls and in patients at steady state (Stuart et al 1999). Hammerman and colleagues (1999) exposed cultured pulmonary endothelial cells to the plasma of patients with sickle cell disease and acute

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48 chest syndrome and found that within two hours of exposure th ere were increases in NOS 3 protein and NOS 3 enzyme activity. They sugge sted that alterations of NO production and metabolism contribute to the pathog enesis of ACS. In a 30-center study, Vichinsky et al (2000) studied 671 episodes of ACS in 538 patients with SCD to determine the cause. They reported ACS is precipitated by fat embolism and a variet y of lung infections including; chalmydia, mycoplasm, and legionella. More importantly their results show that in more than 50% of cases the cause of ACS was undetermined. They conc lude that the etiology for ACS remains unclear. Surprisingly, the incidence of asthma in this stud y is reported to be 2%, significantly lower than what is generally seen in th e African American population. Similarities and Differences Between Asthma and ACS with Regard to Symptomology and Lung Function A number of recent studies have reported th at asthma may increase the risk of ACS in patients with SCD (Boyd et al., 2004; Knight-Madden et al., 2005; Bryant, 2005; Nordness et al., 2005). These reports were based on studies th at documented a link between SCD and airway hyperresponsiveness, lower airway obstruction, reversibility, a bnormal pulmonary function tests and the fact that cort icosteroids and bronchodilators, drugs commonly used in asthma, were beneficial in ACS (Santoli et al., 1998; Koumbour lis et al., 2001; Klings et al., 2006). Several papers are cited in the literatu re describing pulmonary function in patients with sickle cell disease (Koumbourlis et al., 2001; Sylvester et al., 2004, 2006; Klings et al., 2006). Exposure to repeated vaso-occlusive crisis undoubtedly has an impact on the pulmonary vasculature resulting in airway damage. This type of injury result s in restrictive airway disease as opposed to the obstructive airway disease seen in asthmatics. Multiple episodes of vaso-occlusive crisis and recurrent episodes of ACS may result in irreve rsible airway damage (Sylvester, 2004, 2006; Klings, 2006).

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49 A recent study in children with SCD was c onducted to determine whether children with SCD have restrictive lung disease and if so whet her this abnormality increases with age. Sixtyfour children with SCD and 64 ethnic matched controls, ages 5-16 years were studied. Compared to controls, children with SCD had lo wer mean forced expiratory volume (FEV 1), lower forced vital capacity (FVC), and lower peak expiratory flow (PEF). The effect of age on lung function differed significantly between th e two groups. Findings from this study demonstrate that children with SCD have a restrictive airway disease pattern and this abnormality increases with age. A limitation of this study is that episodes of acute chest syndrome were not reported for children with SCD (Sylvester et al., 2004). In 2006, this same group of investigators te sted the hypothesis that children with SCD and a positive history of acute chest syndrome woul d have worse lung function compared to children with SCD and no history of acute chest syndrom e. Forty subjects were enrolled, 20 positive for ACS, and 20 negative for ACS. The mean to tal lung capacity and re sidual volumes were significantly higher in children w ho had no history of ACS. They did not however demonstrate any differences in bronchodilator reversibility tests. Their findings suggest that children with SCD and a positive history for ACS have significan t differences in lung function as compared to children with SCD and no history of ACS. Thes e differences are consistent with restrictive airway disease often seen in a dults with SCD (Sylvester, 2006). A cross-sectional study of 310 adults with SCD found that 90% of subjects showed a restrictive airway disease patter n. Additionally, they reported that the presence of restrictive airway disease was associated with a more se vere clinical course (Klings et al., 2006). Koumbourlis and colleagues investigated the prev alence and reversibility of lower airway obstruction in children with SCD ages 5-18 year s. Interestingly they found that obstructive

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50 disease, reversible in nature, precedes the de velopment of restrictive airway disease. The limitations of this study include; small sample size limited historical information, and subjective information with regard to a history of asthma These children were not identified as having physician-diagnosed asthma (Koumbourlis et al., 2001) Asthma is a chronic inflammatory disease of th e airways. In susceptible individuals, this inflammation causes recurrent episodes of wheezi ng, breathlessness, chest tightness, and cough, particularly at night and in early morning. These episodes are usua lly associated with widespread but variable airflow obstruc tion that is often reversible either spontaneously or with treatment. The inflammation also causes an associat ed increase in the existing bronchial hyperressponiveness to a variety of stimuli (National Asthma Education and Prevention Program Expert Panel, (2003). ACS is characterized by the presence of mu lti-lobe infiltrates, cough, dyspnea, hypoxia, and often chest pain (Hammerma nn, 1999). Many of the symptoms related to ACS are also seen in asthma; dyspnea, coughs, and decreased oxygen saturation. Differentiating between asthma and ACS may be difficult in patients with SCD. Further research is needed to establish an objective assessment for primary care providers who are managing patients with SCD and airway disease.

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51 CHAPTER 4 RESULTS The primary aim of the study was to char acterize the association between physiciandiagnosed asthma and acute chest syndrome. The secondary aim of this study was to test the hypothesis that polymorphisms in candidate gene s for the NO pathway associate with ACS in SCD patients. Descriptive Results A total of 134 children with SCD participat ed. Forty-eight patients with SCD had no history of having ACS (36%) (contr ols), 86 at least one episode of ACS (64%) (cases). Fifty percent of cases had either 1 or 2 episodes. No differences in age or sex were observed between cases and controls (Table 1). Ninety percent (n=121) of patients with SCD were homozygous for S globin (HbSS); 6% (n=8) were heterozygous (HbSC); 3% (n=4) patients had sickle beta thalassemia (HbS); and genotype data on one patient was missing. On average the age for the first episode of ACS was 4.4 years; the median age was 3.5 years; and the range was <1 to 17 years old. There was no relationship between age and the number of ACS episodes (data not shown). The prevalence of physician-diagnosed asthma in our study was 36.1% (48 of 133; asthma status was not recorded in one part icipant). There was 100% concordance between physician-diagnosed asthma and asthma reported by pa tients or guardians. All participants with physician-diagnosed asthma were taking inhale d SABA; 68.8 % were on ICS (33/48); 2 and 3 participants were on LABA (salmeterol) and LTRA (montelukast) respectively. Genotyping The success rate of genotyping ranged between 95 and 100% (average rate was 97.6%). Table 2 compares the minor allele frequenc ies of the polymorphisms in SCD and healthy controls. In SCD participants, the NOS1 AAT re peat polymorphism and the ARGI variant were

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52 in HWE. The NOS3 polymorphisms were not in HWE, wh ich was in contrast to healthy controls, suggesting that genotyping of these variants was not in error, but was probably due to the presence of disease in SCD patients. The minor allele frequency of the AAT repeat (< 12 repeats) was significantly higher in healthy controls compared to SCD patients, 0.21 vs. 0.091; p< 0.001). The distribution of al leles carrying the numbe r of AAT repeats in patients with SCD was skewed to the right comp ared to healthy controls (2=122; p< 0.0001) (Figure 2). The data demonstrate that using a cut-off of < 12 repeats as suggested by Wechsler et al. in a mostly Caucasian asthmatic cohort is reasonable for patients with SCD. Asthma and Acute Chest Syndrome Among SCD patients with physician-diagnosed as thma, 85.4% had at le ast one episode of ACS compared to 14.6% of controls (odds= 5.85); whereas cases and contro ls were about evenly distributed among participants without asthma ( odds = 1.07). The adjusted OR (95%CI) is 5.47 (2.20,13.5), p = <0.0001 (Table 3). Figure 2 sh ows that the proportion of SCD patients who had physician-diagnosed asthma was rela ted to the number of episodes of ACS. The intercept of the regression line was 0.178; the slope of the re gression line was 0.097; and the correlation coefficient, R, was 0.89, indi cating that 79% (R2*100) of the variability in the proportion of SCD patients with physician-diagnosed asthma is accounted for by the number of episodes of ACS (p=0.001). Seven of 8 patients with 7 or more episodes of ACS had physician-diagnosed asthma (one patient failed to report asthma st atus, his medical history was missing and he was on asthma medications). Neither age nor gender contri buted to the relationship (data not shown). Genetic Associations The association between the risk of ACS a nd the number of AAT repeats for the NOS1 gene in SCD patients is shown in Figure 3. The risk of ACS in participants without physiciandiagnosed asthma and who were carrying alleles with < 12 AAT repeats (n = 16 alleles; 11.6%)

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53 was relatively high, 0.69, then declined to a risk of about 0.4 at 12 to 15 repeats (n = 87 alleles, 63%), followed by an increased risk at higher numb ers of repeats (n=35 alleles, 25.4%). The r2 for the regression was 0.76; and the p values for coefficients of quadratic regression line: x and x2, were 0.024 and 0.024, respectively. For SC D patients with physician-diagnosed asthma, the mean SD risk of ACS was higher than in non-asthmatics: 0.87 0.09 vs. 0.49 0.12; p = 0.001, and was not associated with AAT repeat numbers. No associations were found between the risk of ACS and the T-786C NOS3 polymorphism in either the asthma or the no-asthma cohorts or by sex (Data not s hown). A modest association was found between the A2/A1 ARG1 polymorphism and asthma (Table 4-4). Carri ers of the A1 allele (A1 homozygotes and heterozygotes) were less likely to have asthma, 22/79 (27.8%), compared to A2 homozygotes, 6/47 (12.8%) (Fishers exact test: = 3.98; p = 0.04).

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54 Table 4-1. Characteristics of self-identified Af rican Americans with sickle cell disease who had at least one episode of acute chest syndrom e (cases) and individuals with no episodes of acute chest syndrome (controls). Characteristic Cases (ACS) Controls (No ACS) Number 86 48 Mean SD age, years 12.6 4.64 14 8.9 Mean SD age at 1st ACS episode, years 4.4 3.6 -Percent female 49.3 50.0 Percent on Hydroxyurea Current Ever 5.8 12.7 10.4 16.6 Percent on chronic PRBC* transfusion 18.6 12.5 Reprinted with permission by Wiley-Liss Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 334. *Packed Red Blood Cells. Data from 70 participants Table 4-2. Comparison of Har dy-Weinberg Equilibria (HWE) and minor allele frequencies of NOS 1, NOS 3 and ARG I polymorphisms in 134 patients with sickle cell disease (SCD) and 74 healthy controls Minor Allele Frequency Gene Polymorphism (reference SNP) Sickle Cell Disease participants Healthy Controls NOS 1 AAT repeats in intron 13 (WT, 12; minor, < 12) 0.091 0.21 T-786C (rs2070744) 0.098 0.155 G894T (rs1799983) 0.14 0.121 27 bp repeat in intron 4 A=4 repeat 0.303 0.277 B=5 repeats 0.363 0.291 NOS 3 C=6 repeats 0.059 0.014 ARG1 A2/A1 (rs17599586) 0.133 0.142 Reprinted with permission by Wiley-Liss Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 335 indicates polymorphisms not in HWE in patients with SCD A1 is the T allele; which is not cut by Pvu II; A2 is the C allele, which is cut by Pvu II.

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55 Figure 4-1. Comparison of dist ributions of alleles carrying AAT repeats in intron 13 on NOS 1 gene in healthy, 73 self-identified, healt hy African Americans (n=146 alleles) and in 127 African Americans with sickle cell di sease patients (n=254 alleles). Reprinted with permission by Wiley-Liss. Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 335 Table 4-3. Influence of physiciandiagnosed asthma on the risk of having at least one episode of acute chest syndrome in patients with sick le cell disease (cases) compared to no physician-diagnosed asthma (controls). (p va lue represents the ch i square difference between the asthma and no asthma groups) Group, number (%) Physician-diagnosed Asthma No asthma Cases (ACS) 41 (85.4) 44 (51.8) Controls (no ACS) 7 (14.6) 41 (48.2) Total 48 (100) 85 (100) Adjusted Odds Ratio (95%CI) 5.46 (2.20,13.5) 1.07 p value p <0.0001 Reprinted with permission by Wiley-Liss Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 335

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56 Number of episodes (x) 0246810 Proportion having asthma, P(x) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Observed P(x) Linear probability model 95% CI x y 097 0 178 0 Figure 4-2. Prevalence of physci an-diagnosed asthma and acute chest syndrome episodes. The proportion of SCD patients having physiciandiagnosed asthma wa s plotted against the number of episodes of acute chest syndrom e in children with sickle cell disease. Reprinted with permission by Wiley-Li ss. Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 334

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57 Figure 4-3. Risk of ACS and NOS 1 AAT re peats in intron 13. The risk of ACS (1[controls/(cases+controls)]) is plotted agai nst the number of NO S1 AAT repeats in patients with SCD with physician-diagnosed asthma (closed circles) and without physician-diagnosed asthma (SCDNA). Reprinted with permission by Wiley-Liss. Duckworth, L. et al. (2007). Pediatric Pulmonology, 42(4), 334. Table 4-4. Association between ARG1 A2/A1 polymorphism and asthma among SCD patients. Number of SCD patients Genotype Asthma No asthma Odds A1 carriers 6 22 0.27 A2 homozygotes 41 58 0.71 Statistic likelihood ratio Fisher s exact test: 3.98; p= 0.04

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58 CHAPTER 5 DISCUSSION Acute chest syndrome is the leading cause of mortality and the second most common cause of hospitalizations in patients with sickle ce ll disease accounting for 25% of premature deaths (Platt, 1994; Stuart & Setty, 1999; Buchanan et al., 2004). The prevalence of ACS in children with SCD in our study was 64%, which was in reasonable agreement w ith a previous stiudy4 that reported prevalence rates of 61% in 0 to 9 year olds, and 46% in 10 to 19 year olds, suggesting that our sample was representative of the SCD popul ation. In the pres ent study, we identified physician-diagnosed asthma as an important risk factor for ACS in patients with SCD. The prevalence of physician-diagnosed asthma in SCD in our study was 36% (48 of 133 participants), and is in good agreement with those reported in previous studies, which ranged between 17% and 53% (Boyd et al., 2004; Kni ght-Madden et al., 2005; Bryant, 2005; Nordness et al., 2005) Among SCD patients with physicia n-diagnosed asthma, 85.4% had at least one episode of ACS compared to 14.6% for participan ts who did not experience an episode of ACS (OR = 5.47; p <0.0001). The prevalence of physician-diagnosed asthma in non-ACS participants is in excellent ag reement with the prevalence of asthma in African American children without SCD (Yeatts & Shy, 2001; Faga n et al., 2001; Koumbo urlis et al., 1997). Importantly, our data also show that the pr oportion of patients with SCD who have physiciandiagnosed asthma increases linearly as the number of ACS episodes increase (Figure 2). To our knowledge our study is the first to show this relationship, and, gi ven the mortality and morbidity associated with ACS, underscores the importan ce of coordinated pulmonary and sickle cell hematology care in diagnosing asthma in SCD. These data are also important because they point to the testable hypothesis that the aggressive treatment of asthma may reduce the mortality and morbidity of ACS in SCD patients.

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59 The results in Figure 2 imply that proportion of patients with physician-diagnosed asthma is caused, at least in part, by the number of ACS episodes experi enced by patients with SCD. The fact is we cannot determine causality from our data. It is possi ble that ACS may cause asthma, or that having asthma increases the risk of ACS, or that causality is bidirectional. The results of this study support a genetic component for both ACS and for asthma in SCD. The higher number of AAT repeats may act to decrease the activity of NOS1 enzyme leading to reduced production a nd availability of NO, which can increase the risk of ACS and possibly asthma (Weschler et al., 2000). Arginase activity is increased in asthma, leading to reduced arginine availability, wh ich can exacerbate NO deficiency in SCD patients. If the A2 allele of ARG1 leads to high expression of argi nase I compared to the A1 allele, then A2 homozygotes would utilize arginine to a greater extent than A1 carriers, resulting in less arginine for NOS 1 to convert to NO. Study Limitations A major limitation of the present study is how asthma was defined. We used a diagnosis of asthma by a pediatrician, se lfor guardian-reported asthma and drug use to define asthma. Selfor guardian-reported asthma was in comple te agreement with physician-diagnosed asthma, and all participants with physician-diagnosed as thma were on SABA, two-thirds were on ICS, which supports the idea that they had true asthma. Additionally, we only offered study participation to those who presen ted for their clinic appointments. This may have biased the study in that children with ACS may be more likely to keep their scheduled appointments compared to SCD patients who are stable. Earlier studies show pulmonary function abnormalities in children and adults with SCD. However, the data are conflicting in that some studies in children with SCD ha ve obstructive lung disease (K oumbourlas et al., 2001; Leong et al., 1997), while others have found restrictive lung disease (Sylvester et al., 2006). Adults with

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60 SCD have restrictive lung disease owing to re peated episodes of pulm onary vaso-occlusion, which increases with age (Klings et al., 2006). Moreover, SABA a nd ICS are often prescribed to patients with sickle cell lung disease. Alt hough our study confirms the results of previous studies that physician-diagnosed as thma is associated with ACS, and further shows that the risk of physician-diagnosed asthma is strongly associated with the numb er of ACS episodes, it is not clear that participants with phys ician-diagnosed asthma in our st udy had true asthma as defined by conventional methods. Clearly, further studies are warranted to determine if obstructive lung disease and asthma increase the risk of ACS in children with SCD. In a pilot study of non-asthmatic chil dren with SCD, we reported that FENO levels were reduced in individuals with ACS compared to those without ACS and to a cohort of healthy African American children (without SCD) (Sullivan et al., 2001). We also reported that levels of FENO were inversely related to the allelic sum of AAT repeats in intron 13 of NOS1 gene, which suggested a genetic link for ACS and led us to hy pothesize that this rep eat variant associated with ACS. A specific aim of the present casecontrol study was to determine the association between the AAT repeat polymorphi sm and ACS. We found that th e risk of ACS in individuals without physician-diagnosed asthma was reduced in alleles with 12 to 15 repeats compared to alleles with < 12 or with alleles carrying 16 or more repeats. These data s upport the hypothesis that the risk of ACS in SCD patients without asthma is asso ciated with the AAT repeat polymorphism, thereby implicating a genetic basis this disease. However, the association we found, if true, was modest and may represent of false-positive associ ation owing to small numbers. The confounding influence of physiciandiagnosed asthma on the risk of developing ACS (Figure 3) reduced our numbers and our power to detect a true genetic association. Thus we conclude that a larger study is warr anted to replicate our findings.

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61 The association between ACS and two polym orphisms in the NOS3 gene: E298D and T786C, has been reported in 87 African Americans with SCD (S haran et al., 2004). The C-786 allele was associated with an increased risk of ACS in females (n=45; relative risk=8.7). We were not able to replicate these data in the present study. The reasons for this are unclear, but may be related to small number of patients in our study who did not have physician-diagnosed asthma. Whether or not participants in the st udy by Sharan et al had physician-diagnosed asthma is not clear. The etiology of ACS is not completely unders tood but is known to involve infection, pulmonary infarctions and pulmonary fat embolis m (Vinchinsky et al., 2000; Vinchinsky et al 1994). Free fatty acids released by the hydrolysis of phospholipids in embolized fat can cause acute lung injury (Styles et al., 1996). Isoenzymes of phospholipase A2 (PLA2) hydrolyze phospholipids at the sn-2 position to generate lysophospholipids and free fatty acids (Dennis, 1994). Both cytosolic PLA2 and secretory PLA2 (sPLA2) function to generate arachidonic acid from phospholipids in inflammatory cells (Balsind e et al., 1994; Calabrese et al., 2000). Plasma concentrations of secretory phospholipase (sPLA2) are elevated in ACS ) (Styles et al., 1996) and have been proposed as accurate markers of AC S in patients in SCD crises (Styles et al., 2000; Naprawa et al., 2005). Asthma is acco mpanied by increased production of arachidonic acid and enhanced activity of cysLT (Calabrese et al., 2000). Thus, it may be postulated that the asthma phenotype associated with ACS in SC D may be leukotriene-dependent, and therefore may be responsive to the leukotriene modifiers: 5-lipoxygenase inhibitors or leukotriene receptor antagonists. Additionally, earlier studies have shown that corticosteroids may provide some benefit to patients with ACS (Bernini et al., 1998), although associated with rebound vasoocclusive pain when stopped abruptly. Aggr essive treatment with moderate to high doses

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62 of inhaled corticosteroids and a leukotriene modifier (5-liopo xygenase inhibitor or LTRA) in SCD patients with physician-diagnosed asthma a nd SCD may reduce the mortality and morbidity associated with ACS. Conclusions In summary, our study confirmed that physicia n-diagnosed asthma is an important risk factor for ACS in SCD patients, and further demonstrated that the incidence of physiciandiagnosed asthma was highly correlated with the number of episodes of ACS. Our study suggests that the NOS1 AAT repeat polymorphism may contribute to the risk of ACS in patients without physician-diagnosed asth ma, and that the A2/A1 ARGI pol ymorphism may contribute to the incidence of asthma in SCD patients. Fu rther studies are warrant ed to determine if aggressive treatment of physicia n-diagnosed asthma reduces the ri sk of ACS in SCD, and if the AAT repeat polymorphism contributes to ACS. It is important to note that our sample is representative of the general African American population in that 14.6% of children with physician diagnosed asthma who did not have a hist ory of ACS is consistent with the incidence of asthma nationally. Implications for Clinical Practice Findings from this study suggest that asthma may be a significant risk factor in children with SCD for developing ACS. Quite often in pr imary care settings an asthma diagnosis is not assigned before the age of 2 years. More specif ically we often see related diagnoses such as reactive airway disease, coughing, or upper airway congestion. In children with SCD the average age for the first ACS episode is between 2 to 4 years of age. Provider education regarding the association between asthma and ACS may heighten awareness of asthma related symptoms in infants and young children with SCD and result in more aggressive airway management. Additionally, educating the careg ivers of patients with SCD re garding asthma symptoms and

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63 their association with ACS may lead them to seek prompt medical attention for coughing episodes and upper airway congest ion, symptoms which may otherwise be viewed as the common cold. Sickle cell disease is clearly a genetic disease. Asthma on the other hand is a complex, multifactorial disease. Children suffering from SCD who also have asthma may have several specialists managing their care, for example a pulmonologist, hematologist, and primary care provider. Enhancing communication between providers may lead to better outcomes for these patients.

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64 CHAPTER 6 FUTURE WORK Several recent studies have re ported that asthma may increase the risk for ACS in patients with SCD (Boyd, 2004; Bryant, 2005; Knight-Ma dden, 2004; Nordness, 2005, Sylvester et al., 2007). If indeed children with concomitant asth ma and SCD have increased episodes of ACS, studies investigating aggressive asthma treatment may have an affect on the mortality and morbidity associated with this disease. Treatment with bronchodilators and inhaled steriods are the mainstay of asthma management and are cons istent with asthma guidelines (National Asthma Education and Prevention Program Expert Panel, 2002). Likewise, patients with SCD and airway compromise are routinely treated with bronchodila tors and inhaled steroids. (Vichinsky, 2006; Handelman, 1991; Mehta, 2006). Unlike preventative treatment in asthma, these medications are used primarily as supportive care st rategies in patients with SCD. To date there are no randomized clinical trials exploring aggressive asthma management in patients with SCD. Additionally, no studies have been reported that associate NOS genotypes, asthma, and SCD. It is intere sting to hypothesize that aggressi ve asthma treatment in patients with SCD may prevent or reduce the incidence of ACS. More intriguing is the possibility that identifying genotypes associated with asthma and ACS early in life, in conjunction with aggressive asthma management, may redu ce mortality in patients with SCD. Montelukast, a leukotriene receptor antagonsist, is frequently prescrib ed for the treatment and management of asthma in adults a nd young children (Knorr, 2001) (Biernacki, 2005) Montelukast is widely accepte d and commonly prescribed by pe diatricians given its safety profile and compliance. Recent updates to the national asthma guidelines suggest that combination therapy with Montelukast and inhale d corticosteroids may improve asthma control.

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65 Potential future studies could target patient s with SCD and physician diagnosed asthma early in childhood prior to the first episode of ACS. The first episode of ACS usually occurs between 2-5 years of age (Knorr, 2001). Subjec ts would be randomized to receive either aggressive asthma management with moderate to high doses of inhaled corticosteroids (ICS) and a leukotriene receptor atagonist or standard of care, then followed over a period of 3-5 years. Subjects would be monitored for asthma symp toms, episodes of ACS, and genotyped for the AAT repeat polymorphism in the NOS1 gene. In addition, exhaled nitric oxide collection and pulmonary function testing would be employed to assess and monitor airway inflammation. Given that exhaled nitric oxide is an accepted measure of ai rway inflammation in asthma, utilizing this biomarker as a predictor or diagnos tic tool to measure airway inflammation, may be useful when managing sickle cell disease patients. Randomized clinical trials are warranted to determine if aggressive treatment of physician diagnosed asthma reduces the risk of ACS in SCD, and to determine whether polymorphisms in candidate genes in the nitric oxide pathway contribute to ACS. Collaboration among sickle cell centers for large clinical trials will be especially important for genome wide association studies related to SCD and asthma. St udies of this nature re quire large numbers of patients in order to identify genetic associations. Finally, stressing the importance for cooperation between pulmonary and hematology clin ics can only benefit future studies involving SCD and asthma.

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66 APPENDIX A CONSENT FORM THE NEMOURS CHILDREN'S CLINIC JACKSONVILLE, FLORIDA INFORMED WRITTEN CONSENT You are being asked to volunteer in a research study. This form will explain the study. It is important that you understand th e study before deciding to be in it. You may ask the people in charge of the study who are listed on this page questions about the study at any time. WHAT IS THE TITLE OF THIS STUDY? Polymorphisms of Nitric Oxide Synthase Gene s in Sickle Cell Patients with Acute Chest Syndrome WHO ARE THE PEOPLE IN CH ARGE OF THIS STUDY? Principal Investigator: John Lima, Pharm.D. Nemours Childrens Clinic 807 Children's Way Jacksonville, FL 32207 Telephone number: (904) 3903483 (904) 390-3600 (operator) (800) SOS-KIDS Sub-Investigators: Niranjan Kissoon, M.D. Professor & Chief Pediatri c Critical Care Medicine University of Florida-Jacksonville (904) 202-8758 Jim Sylvester, PhD Nemours Children's Clinic 807 Children's Way Jacksonville, FL 32207 (904) 390-3483 (904) 390-3600 (operator) (800) SOS-KIDS Kevin Sullivan, M.D. Division of Pe diatric Anesthesiology Nemours Childrens Clinic 807 Children's Way Jacksonville, FL 32207 Phone Number: (904) 202-8332 Lewis Hsu, M.D. Emory University 69 Butler St. SE Atlanta, Georgia 30303 (404) 616-3545

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67 Laurie Duckworth MSN, ARNP Nemours Childrens Clinic 807 Children's Way Jacksonville, FL 32207 (904) 390-3483 (904) 390-3600 (operator) (800) SOS-KIDS WHO CAN I TALK TO ABOUT MY RIGHTS AS A STUDY SUBJECT? Tim Wysocki, Ph.D. Chairperson Nemours-Florida IRB Nemours Children's Clinic 807 Childrens Way Jacksonville, FL 32207 (904) 390-3698 WHAT IS THE PURPOSE OF THIS STUDY? Some patients with sickle cell anemia may develop a condition called acute chest syndrome (ACS). This condition is believed to be caused by the sickle red blood cells clogging the blood vessels in the lungs. After repeated episodes of ACS, the blood pressure in the blood vessels between the heart and lungs can remain high permanently. This condition is called pulmonary hypertension. The doctors who take care of children with si ckle cell anemia have noticed that certain children have a greater tendency to develop re peated episodes of acute chest syndrome while others do not develop this complication. The re ason for this is not clear. Likewise, intensive care doctors who care for children wi th the acute chest syndrome have noticed that these children respond dramatically to an inhaled gas called nitric oxide (NO) when they are extremely ill. NO is a gas that is made in the cells that line th e pulmonary (lung) blood vessels and is normally made in our own bodies. We believe that childre n with sickle cell anemia who are prone to ACS may not make enough NO in their pulmonary (lung) blood vessels. Recent research has shown

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68 that patients with ACS have lo wer amounts of NO in the air they exhale when compared to sickle cell patients who have not had ACS. We believe that sickle cell patients with ACS produce very low quantities of NO in the pulmonary (lung) system. We believe that this may be because some children have different types of the protein (amino acid) th at produces NO than others. This protein is called nitric oxide synthase (NOS). Humans have thr ee different types of the enzyme that produces NO. We want to examine whether or not there is a link between tendency to suffer from ACS, and the type of enzyme the patient has. This can be dete rmined by studying your DNA (Studying genes or DNA is becoming more common in clinical research studi es, but is still in an early stage. We know that certain genes make you tall or short. Certai n genes give you brown or black hair). This will be important to know because if there is a gene tic or inherited component that determines how severe the sickle cell disease will be it could be important for screening and lead to treatment that may help avoid complications in groups that are at high ri sk of having ACS. WHAT IS THE PURPOSE OF CO LLECTING THESE SAMPLES FOR DNA ANALYSIS? You/your child are being asked to take part in this research study because you/your child have sickle cell disease, or are a healthy voluntee r. Similarly, certain genes are associated with sickle cell disease, and may be associated with whether or not you/your child may develop ACS. Studying DNA from people who have sickle cell disease may help us better understand the importance of those genes and how th ey are involved in causing ACS. You/your child are being invited to provide a sample of your/your childs buccal cells (cells from your/your childs mouth) to test for DNA or genes related to sickle cell disease. Participation is voluntary You/your child do not have to pr ovide a sample for DNA analysis.

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69 We would also like to stor e some of your/your childs DNA in a bank (storage facilities) so that it may be used in future studies of sickle cell disease. WHO IS SPONSORING THIS STUDY? This study is being sponsored by The Ameri can Lung Association who will pay Nemours Childrens Clinic for conducting this study. WHO CAN BE IN THIS STUDY? You may participate in this study if you have sickle cell disease. You may or may not have had an ACS episode. You do no have to have sickle cell disease to participate, however, you may participate as a healthy volunteer. You must be African American to participate. HOW MANY OTHER PEOPLE WILL BE PART ICIPATING IN THIS STUDY? This study will involve approximately 300 children ages 6 and older, and adults from the Jacksonville, Florida and Atlanta, Georgia area. This study lasts only as long as it takes for you/your child to provide a buccal cell sample. WHAT ARE THE PROCEDUR ES FOR THIS STUDY? Buccal Samples In order to provide a buccal sample, you/your child must not have eaten for one hour. Then, you/your child will gargle a mouthful of water for the purpose of washing and spit out the water. You/your child will rece ive a small bottle of mouthwas h (Scope) and an empty tube, which will be labeled with an identification number. You/your child will vigorously gargle a mouthful of mouthwash for one minute and spit the garg led mouthwash into the coded tube. If you/your child find it hard to gargle the mouthw ash for one minute, you/your child can gargle the mouthwash for shorter times, and repeat the procedure until you/your child have gargled for a total of one minute (For example, you/your child can gargle a mouthful of mouthwash for 20

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70 seconds, and gargle another mouthful of mouthw ash for 20 seconds and repeat the procedure one more time). The gargled mouthwash contains buccal cells from your/your childs mouth. WHAT HAPPENS AFTER THE SAMPLES ARE COLLECTED? The buccal cells will be processed and your /your childs DNA will be stored in our laboratory at the Nemours Childrens Clinic in Jacksonville, FL. You/your child will not be notified of individual results a nd no results will appear in you r/your childs medical records. For those patients who have sick le cell disease, information from the medical record may be collected, for example, how many episodes of acute chest syndrom e you have had, and number of hospitalizations. WHAT ARE THE POTEN TIAL RISKS OR DISCOMFORTS? Any treatment has potential risks. The most common risks of the treatment used in this study are listed below. In additi on, there is always the risk of very uncommon or previously unknown side effects. DNA Testing Even though we will be careful to not reve al the results of th e DNA testing on your/your childs sample, there is a very small chance this information could accidentally become known to you, your child, your doctor, or others. Presently we know of no risk to you/your child if the genetic results become known. Gargling with Mouthwash You/your child may experience burning or ting ling in your/his/her mouth from gargling with the mouthwash for one minute. You/your child can minimize burning or tingling by gargling for shorter periods of time on more o ccasions until he/she has gargled for one minute.

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71 WHAT ARE THE POTENTIAL BENEFITS TO ME/MY CHILD OR OTHERS? There is no direct medical benefit to you/your child for participating in this study. Although you/your child may not benef it directly from this research there may be a benefit to society, in general, from the knowledge gained in connection with your/your childs participation in this study. IS BEING IN THE STUDY VOLUNTARY? Being in this study is totally voluntary. Anyone who does take part in the study can stop being in it at any time. There will be no change to the medical care given to anyone who decides not to be in it or who stops be ing in it. The researchers will destroy the samples obtained from anyone in the study if they are asked to do so. WHAT ARE ALTERNATIVE TR EATMENT OR PROCEDURES? There are no alternativ e procedures for this study other than you/your child can choose not to participate. WHAT HAPPENS IF MY CHILD DEVELO PS PROBLEMS FROM BEING IN THE STUDY? In the event that your child suffers any injury directly resulting from these studies, you may contact any of the investigator s listed on the front of this form In the event that your child's participation in this study results in a medical problem, treatment will be made available. No other compensation of any type is available th rough Dr. Sylvester, Dr. Lima, Dr. Kissoon, Dr. Hsu Dr. Sullivan, Laurie Duckworth or Nemours Childrens Clinic. Nemours Childrens Clinic will not pay for treatment if your child suffe rs any injury related to this study. You are responsible for reporting any adverse eff ect(s) to the investigator in charge as soon as possible.

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72 WHAT HAPPENS IF I DECIDE FOR MY CHILD NOT TO PARTICIPATE OR TO WITHDRAW MY CHILD FROM THE STUDY? If you decide that you do not want you/your ch ilds samples to be studied any longer and you wish your/your childs samples to be destroye d, you can notify the inve stigators listed on the front of this form. You understand that your consent for you/your child to participate in this study is given voluntarily. You may withdraw yourse lf/your child from or decide not to participate in the study at any time without prejudice. If you decide for yourself/your ch ild to no longer participate in this study, it will not affect your/your childs futu re health care at Nemours Childrens Clinic. CAN I/MY CHILD BE TAKEN OUT OF TH E STUDY WITHOUT MY CONSENT? Presently, there is no known reason for taki ng you/your child out of this study without your consent. However, the st udy investigators can remove your sample from the study at any time, for any reason(s) deemed appropriate. WHAT ARE THE COSTS FOR BEING IN THE STUDY? There will be no charge to you or your insu rance company for the te sts involved in this study. HOW WILL PEOPLE BE PAID FO R BEING IN THIS STUDY? You will not be paid for particip ating in this study. You will not receive, either now or in the future, compensation, financial benefits, or any royalties which result from information obtained from this study. WILL I BE TOLD OF NEW FINDINGS WH ILE THE STUDY IS IN PROGRESS? Participants will be told of any significant ne w findings developed during the course of this study that may relate to their willingness to continue participation in the study..

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73 HOW WILL THE INFORMATION COLLECTED FROM AND ABOUT PEOPLE IN THE STUDY BE PROTECTED? All information will be maintained on a confid ential basis. Your/your childs identity will be protected to the extent permitted by law. Care will be taken to preserve the confidentiality of all information. You/your child understand that a record of your/ your childs progress while in this study will be kept in a confidential file at Nemours Children's Clinic. The samples will be coded with a unique identifying number and stored in a secure location. The confidentiality of any central computer record will be carefu lly guarded and no information by which you/your child can be identified will be released or pub lished. However, information from this study will be submitted to the American Lung Association and the Food and Drug Administration (FDA). (It may be submitted to governmental agencies in other countries where the study drug combination may be considered for approval.) Me dical records which identify participants and the signed consent form can be inspected by The sponsoring drug company or designee The U.S. Food and Drug Administration The U.S. Department of Health and Human Services Governmental agencies in other countries; and The Nemours Florida Institutional Review Boar d (a group of people who carefully review the study activities and are res ponsible for protecting the sa fety and the rights of the volunteers). Because of the need to release information to these parties, absolu te confidentiality cannot be guaranteed. The results of this research project may be presented at meetings or in publications; however, your childs identity w ill not be disclosed in those presentations. WHO CONTROLS AND OWNS GENETIC MATERIALS? The sample that you/your child provide will be stored for 10 years at Nemours Children's Clinic.

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74 You/your childs DNA samples will remain in possession of the Nemours Children's Clinic and stored in Jacksonville, FL. The results of this genetic research might be valuable for commercial and/or intellectual property (for example, patent ) purposes. If you decide to participate in this genetic re search, you are giving your/your childs sample to Nemours Children's Clinic. Nemours Children's Clinic retains sole ownership of the research results, and of any use or development of the research records (including your/your childs sample) consistent with this consent. You will not receive any financial benefit that might come from the research results. WILL I HAVE ACCESS TO TH E GENETIC INFORMATION? You/your child will not be no tified of individual results fr om DNA tests and no results will appear in your/your ch ilds medical records. HOW ELSE MIGHT THESE SAMPLES BE USED? The samples obtained in this study will be anal yzed for genes of related to sickle cell disease and other related diseases. Samples w ill not be shared with other investigators. Your/your childs DNA samples will not be sold. It is possible that we may wish to contact you/your child for further study. If you do not wa nt yourself/your child to be re-contacted for further study, please indicate by checking the box below: I do not wish (my child) to be re-contacted I do wish (my child) to be re-contacted PARENT'S (LEGAL REPRESENTA TIVE) STATEMENT OF CONSENT By signing this form, you have not waived any of the legal rights which your child otherwise would have as a pa rticipant in a research study.

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75 The signing of this consent does not absolve doct ors from responsibility for proper medical care at all times. My signature indicates that I consent and authorize Drs. Lima, Kissoon, Sullivan and whomever they may designate as their assistants including Nemours Childrens Clinic, its employees and its agents to perform upon ________________________ ________(Name of Patient) the research described above. I am making a decision whethe r or not to have my child or myself participate in this study. I have read, or had read to me in a language that I understand, all of the above, asked questions and received answers concerning areas I did not understand, and willingly give my consent fo r my/my childs participation in this study. Upon signing this form, I w ill receive a signed and dated copy. ________________________ ________ ___________________ _______ Name of Participant (Print) Birthdate Signature of Participant Date If participant is less than 18 years of age th e parent/legal representative must give consent: ____________________________ ____________________ __________ Name of Signature of Date Parent/Legal Representative Parent/Legal representative ____________________________ ______________________ ___________ Name of Witness Signature of Witness Date I the undersigned, certify that to the best of my knowledge the subject/parent/legal representative signing this consent had the study fully and carefully explained. He/she clearly unders tands the nature, risks and benefits in his/her childs particip ation in this project. _____________________________ ___________ Signature of Investigator/Designee Date

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76 CHILDRENS INFORMED ASSENT (for 6 to 12 year olds) You are being asked to be in a research study. Before you decide whether you want to be in it, we want to tell you about it so you ca n ask any questions you have about it. The doctor in charge of the study is Dr. Lima. This doctor would like to find out if you have certain genes that influence whether or not you develop acute chest syndrome (a lung disease associated with sickle cell disease). Genes come from your mother and father and help make up what you look like and how your body works. If you decide to be in the study, here is what will happen. For this study, you will be asked to gargle with a mouthwash. To gargle, you will first wash out your mouth with water. You will then gargle some mouthwash for one minute and spit the mouthwash into a tube. You can also choose to gargle the mouthwash for shorter periods of time more than once until you have gargled mouthwash for one minute. You may feel burning or ting ling from the mouthwash. You dont have to do the study if you dont want to If you are in the study, you can stop being it at any time. Nobody will be upset at you if you dont want to be in the study or if you want to stop being in the study. The doctors and their assistants will take care of you as they have in the past. If you have any questions or dont like what is happening, please tell the doctor or assistant. Your parent or guardian knows about this study. You have ha d the study explained to you and you have been given a chance to ask questions about it. By writing your name below, you are saying that you know what will happen to you in the study and that you want to be in it. _______________________ _____________________ Childs Signature Signature of Witness _______________________ _____________________ Researchers Signature Date

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77 APPENDIX B DEMOGRAPHIC INFORMATION Name: MR#: Study # DOB: AGE: SEX: M F RACE: Date enrolled: Date of DNA Collection: Date of Consent:

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78 APPENDIX C MEDICAL HISTORY Date of birth ___________________ Hb type SS SC S beta thel S other Baseline pulse ox Premature birth yes no Asthma yes no Reactive airway disease yes no On any long term Antisickling therapy yes no Episodes of ACS Dates__________, ____________, ____________, _____________, _____________, ____________. _______________, _______________, _____________ Medications PRN Albuterol ICS __________________________ Singulair _______________________ Salmeterol____________

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79 LIST OF REFERENCES Akinbami, L.J., & Schoendorf, K.C.(2002). Trends in childhood asthma: prevalence, heath care utilization, and mortality. Pediatrics:110(2 Pt 1),315-322. Alving, K., Weitzberg, E., & Lundberg, J.M. (1993). Increased amount of nitr ic oxide in exhaled air of asthmatics. Eur Respir, 6,1268-1270. Asano, K., Chee, C.B., Gaston, B., Lilly, C.M., Gerard, C., Drazen, J.M., & Stamler, J.S. (1994). Constitutive and inducible nitric oxide synthase gene expression, regulation, and activity in human lung epithelial cells. Proc Natl Acad Sci U.S.A., 91(21),10089-10093. Atz, A.M., & Wessel, D.L. (1997). Inhaled nitric oxide in sickle cell di sease with acute chest syndrome. Anesthesiology. 87,998-990. Balsinde, J.S., Barbour, E., Bianco, I.D.,& Denni s, E.A., (1994). Arachidonic acid mobilization in P388D1 macrophages is controlled by two distinct Ca(2+)-dependent phospholipase A2 enzymes. Proc Natl Acad Sci U.S.A., 91,11060-11064. Barnes, P.J., & Belvisi, M.G. (1993) Nitric oxide and lung disease. Thorax. 48,1034-1043. Barnes, P.J. (1995). Nitric oxide in airway disease. Ann. Med., 27, 389-393. Batra, J., Singh, T., Mabalirajan, U., Sinha, A ., Prasad, R., Ghosh, B. (2006). Association of inducible nitric oxide syntha se with asthma severity, to tal serum immunoglobin E and blood eosinophil levels. Thorax, 62, 16-22. Bernini, J. C., Rogers, Z. R., Sandler, E. S., Reisch, J. S., Quinn, C. T., & Buchanan, G. R., (1998). Beneficial eff ect of intravenous dexamethasone in children with mild to moderately severe acute chest syndrome complicating sickle cell disease. Blood 92,30823089 Biernacki, W.A., Kharitonov, S.A., Diernacka, H.M., & Barnes, P.J. (2005) Effect of Montelukast on exhaled leukotrienes and qua lity of life in asthmatic patients. Chest, 128, 1958-1963. Boyd, J. H., Moinuddin, A., Strunk, R.C., & De baun, M. R.(2004). Asthma and acute chest in sickle-cell disease. Pediatr Pulmonology, 38, 229-232. Boyd, J. H., Macklin, E. A., Strunk, R. C.,& Debaun. M. R.(2006). Asthma is associated with acute chest syndrome and pain in ch ildren with sickle cell anemia. Blood, 108, 2923-2927. Bryant, R. (2005). Asthma in the pediatric si ckle cell patient with acute chest syndrome. J Pediatr Health Care, 19, 157-162. Buchanan, G.R., Debaun, C.T., & Steinberg, M..H. (2004). Sickle cell disease. Hematology AM Soc Hematol. Educ. Program, 35-47.

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80 Busse, W.W., & Holgate, S.T. (1998). Evidence from induced sputum. Inflammatory mechanisms in asthma. (pp. 75-81). New York, NY: Marcel Dekker Inc. Busse, W.W., & Holgate, S.T. (1998). Me diator Functions of Epithelial Cells. Inflammatory Mechanisms in Asthma. (p.479). New York, NY: Marcel Dekker Inc. Calabrese, C., Triggiani, M., Marone, G., & Mazzarella, G. (2 000). Arachidonic acid metabolism in inflammatory cells of patients with bronchial asthma. Allergy 55 Suppl 61, 27-30. Chaar, V., Tarer. V., Etienne-Julan, M., Diara, J., Elion, J., & Romana, M.(2006). ET-1 and eNOS gene polymorphisms and susceptibility to acute chest syndrome an dpainful vasoocclusive crises in children with sickle cell anemia. Haematologica. 91(9) ,1277-1278. Cicutto L.C., & Downey, G.P. (2004). Biological markers in diagnosing, monitoring, and treating asthma: a focus on noninvasive measurements. AACN Clin Issues, 15(1), 97-111. Collaborative Study on the Genetic s of Asthma (CSGA)(1997). A genome wide search for asthma susceptibility loci in ethnically diverse populations. Nature Genetics, 15, 389-392. Collins, F., Green, E., Guttmacher, A., & Guyer, M. (2003). A vision for the future of genomics research. A blueprint for the genomic era. Nature. 422, 835-847. Coultas, D., Gong, H., & Grad, R. (1993). Resp iratory diseases in minorities of the United States. Am J Respir Cr it Care. (149), S93-131. De Boer, J., Duyvendak, M., Schuurman, F., Pouw F., Zaagmsaj., & Meurs, H.(1999). Role of L-arginine in the deficiency of nitric oxide and airway hyperactivity after the allergeninduced early asthmatic reaction in guinea pigs. Br J Pharmacol 128, 1114-1120. Dennis, E. A. (1994). Diversity of group types, regulation, and function of phospholipase A2. J Biol Chem 269, 13057-13060. Deykin, A. (2005). Targeting biologic markers in asthma-is exhlaed nitric oxide the buls eye. The New England Journal of Medicine, 352 21, 2233-2235. Dinh-Xuan, A.T.(1992). Endothelial modul ation of pulmonary vascular tone. Eur Respir J. 5, 757-762. Duckworth, L., Hsu, L., Feng, H.., Wang, J., Sylv ester, J.E., Kissoon, N., Sandler, E., & Lima, J. (2007). Physician -Diagnosed Asthma and Ac ute Chest Syndrome: Associations with NOS Polymorphisms. Pediatric Pulmonology, 42(4), 332-338. Dupuy, P. M., Shore, S.A., Drazen, J.M., Fros tgell, C., Hill, W.A., & Zapol, W.M. (1992). Bronchodilator action of inhaled nitric oxide in guinea pigs. J Clin Invest. 90, 421-428. Enwonwu, C.O., Xu, S.X., Turner, E. (1990). Nitr ogen metabolism in sickle cell anemia: free amino acids in plasma and urine. Am J Med Sci., 300(6), 366-371.

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81 Fagan, J. K., Scheff, P.A., Hryhorczuk, D., Rama krishnan, V., Ross, M., & Persky, V. (2001). Prevalence of asthma and other allergic diseases in an a dolescent population: association with gender and race. Ann Allergy Asthma Immunol 86, 177-184. Frostell, C., Hogman, M., Hedenstrom, H., & Hede nstierna, G. (1993). Is nitric oxide inhalation beneficial to the asthmatic patien t? Am Rev Respir Dis. 147:,A515. Ford, J.G., & McCaffrey, L. (2006). Understa nding disparities in asthma outcomes among African Americans.Clin Chest Med. 27(3), 423-30. Furchgott. R.F.,& Zawadzki, J.V. (1980). The obligatory role of endot helial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature. 288, 373-376. Gaston, B., Drazen, J.M., Loscalzo, J., & Stamler, J.S. (1994). The biology of nitrogen oxides in the airways. Am J Respir Crit Care Med. 149, 538-551. Gaston, B., Drazen, J., & Jonsen, A. (1994). Relaxation of bronchial smooth muscle by Snitrosothiols invitro. J Pharmacol Exp Ther. 268, 978-985. Getahun, D., Demissie, K., Rhoads, G.G. (2005). Recent trends in asthma hospitalization and mortality in the United States. Journal of Asthma. 42, 373-378. Gladwin, M. T., Schechter, A. N., Shelhamer, J.H., & Ognibene, F.P ., (1999). The acute chest syndrome in sickle cell disease. Possible role of nitric oxide in its pathophysiology and treatment. Am J Respir Crit Care Med, 159, 1368-1376. Goldman L, & Ausiello D. (2004). Cecil Textbook of Medicine. 22nd ed. Philadelphia, Pa: WB Saunders; 1030-1039. Grasemann, H., et al. (1999). Simple tandem re peat of polymorphisms in the neuronal nitric oxide synthase gene in different ethnic populations. Human Heredity, 139-141. Grasemann, H., Yandava, C.N., & Drazen, J.M. (1999). Neuronal NO synthase (NOS1) is a major candidate gene for asthma. Clinical and Experimental Allergy, 29, 39-41. Grasemann, H., Storm vanss Gravesande, K., Buscher, R., Drazen, J.M., & Ratjen, F. (2003). Effects of sex and of gene vari ants in constitutive nitric oxi de synthase on exhaled nitric oxide. American Journal of Respiratory Critical Care, 167(8) ,1113-6. Gustafsson, L.E. (1998). Exhaled nitric oxide as a marker in asthma. European Respiratory Journal, 11(Suppl.), 4s-52s. Hammerman, S.I., Klings, E.S., Hendra, K.P., Up church, G.R., Rishikof, D.C., Loscalzp, J., & Farber, H.W. (1999). American Journal of Physiology, (Heart and Circulatory Physiology), 277, 1579-1592. Hart, C.M. (1999). Nitric oxide in lung disease. Chest, 111(5), 1407-1417.

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89 BIOGRAPHICAL SKETCH Laurie Duckworth, native Florid ian, grew up in Miami, Florida. She received her Bachelor of Science in Nursing with honors from Florida Stat e University in 1983 a nd began her career as a registered nurse in the burn un it at Jackson Memorial Hospital, Miami, Florida. In 1985 she relocated to Jacksonville, Florida and was employed as a pediatric intensive care nurse. In 1987 she joined Nemours Childrens Clinic, Jacksonville Florida as a register ed nurse and clinic coordinator. For the past 17 years she has serv ed as a clinical research coordinator in the Biomedical Research Department with a focus on pulmonary disorders, specifically asthma and acute chest syndrome. She enrolled in the acceler ated BSN to PhD program at the University of Florida in 2001 and completed her Masters of Scie nce in Nursing degree and received her license as a nurse practitioner in 2003. She is a member of Sigma Theta Tau, Council for the Advancement of Nursing Science, Florida Nurs e Practitioners Association, Association of Clinical Research Professionals, and th e Florida Nurses Association. The summer of 2003 she was awarded a competitive grant from the National Institutes of Nursing Research, National Institutes of Health for a fellowship in genetics and completed a minor degree in genetics at Georgetown Univer sity. In 2006 she pres ented at the National Congress for Nurse Scientists in Washington, D. C. As a nurse scientist, she realizes the importance of how she may contribute to societ y through scientific research. She strongly believes that dissemination of knowledge through research in a multidisciplinary setting will enhance and contribute to evidence-based practice.