NOS1 polymorphism is associated with atopy but not exhaled nitric oxide levels in healthy children

Nitric Oxide Synthase 2 Promoter Polymorphism Is a Risk Factor for Allergic Asthma in Children

Background and Objectives: In paediatric population, atopic asthma is associated with increased eosinophil counts in patients, that correlate with the airway inflammation measured by the concentration of nitric oxide in exhaled air (FeNO). As the FeNO level is a biomarker of atopic asthma, we assumed that polymorphisms in nitric synthases genes may represent a risk factor for asthma development. The purpose of this study was to analyse the association of NOS genetic variants with childhood asthma in the Polish population. Materials and methods: In study we included 443 children—220 patients diagnosed with atopic asthma and 223 healthy control subjects. We have genotyped 4 single nucleotide polymorphisms (SNP) from 3 genes involved in the nitric oxide synthesis (NOS1, NOS2 and NOS3). All analyses were performed using polymerase chain reaction with restriction fragments length polymorphism (PCR-RFLP). Results: We observed significant differences between cases and controls in SNP rs10459953 in NOS2 gene, considering both genotypes (p = 0.001) and alleles (p = 0.0006). The other analyzed polymorphisms did not show association with disease. Conclusions: According to our results, 5′UTR variant within NOS2 isoform may have an impact of asthma susceptibility in the population of Polish children. Further functional studies are required to understand the role of iNOS polymorphism in NOS2 translation and to consider it as a novel risk factor in childhood asthma. The next step would be to apply this knowledge to improve diagnosis and develop novel personalized asthma therapies.

Polymorphism of Nitric Oxide Synthase 1 Affects the Clinical Phenotypes of Ischemic Stroke in Korean Population

Objective

To investigate whether four single nucleotide polymorphisms (SNPs) rs2293054 [Ile734Ile], rs1047735 [His902His], rs2293044 [Val1353Val], rs2682826 (3'UTR) of nitric oxide synthase 1 (NOS1) are associated with the development and clinical phenotypes of ischemic stroke.

Methods

We enrolled 120 ischemic stroke patients and 314 control subjects. Ischemic stroke patients were divided into subgroups according to the scores of the National Institutes of Health Stroke Survey (NIHSS, <6 and ≥6) and Modified Barthel Index (MBI, <60 and ≥60). SNPStats, SNPAnalyzer, and HelixTree programs were used to calculate odds ratios (ORs), 95% confidence intervals (CIs), and p-values. Multiple logistic regression models were performed to analyze genetic data.

Results

No SNPs of the NOS1 gene were found to be associated with ischemic stroke. However, in an analysis of clinical phenotypes, we found that rs2293054 was associated with the NIHSS scores of ischemic stroke patients in codominant (p=0.019), dominant (p=0.007), overdominant (p=0.033), and log-additive (p=0.0048) models. Also, rs2682826 revealed a significant association in the recessive model (p=0.034). In allele frequency analysis, we also found that the T alleles of rs2293054 were associated with lower NIHSS scores (p=0.007). Respectively, rs2293054 had a significant association in the MBI scores of ischemic stroke in codominant (p=0.038), dominant (p=0.031), overdominant (p=0.045), and log-additive (p=0.04) models.

Conclusion

These results suggest that NOS1 may be related to the clinical phenotypes of ischemic stroke in Korean population.

Pooled Sequencing of Candidate Genes Implicates Rare Variants in the Development of Asthma Following Severe RSV Bronchiolitis in Infancy

Severe infection with respiratory syncytial virus (RSV) during infancy is strongly associated with the development of asthma. To identify genetic variation that contributes to asthma following severe RSV bronchiolitis during infancy, we sequenced the coding exons of 131 asthma candidate genes in 182 European and African American children with severe RSV bronchiolitis in infancy using anonymous pools for variant discovery, and then directly genotyped a set of 190 nonsynonymous variants. Association testing was performed for physician-diagnosed asthma before the 7^th birthday (asthma) using genotypes from 6,500 individuals from the Exome Sequencing Project (ESP) as controls to gain statistical power. In addition, among patients with severe RSV bronchiolitis during infancy, we examined genetic associations with asthma, active asthma, persistent wheeze, and bronchial hyperreactivity (methacholine PC₂₀) at age 6 years. We identified four rare nonsynonymous variants that were significantly associated with asthma following severe RSV bronchiolitis, including single variants in ADRB2, FLG and NCAM1 in European Americans (p = 4.6x10^-4, 1.9x10^-13 and 5.0x10^-5, respectively), and NOS1 in African Americans (p = 2.3x10^-11). One of the variants was a highly functional nonsynonymous variant in ADRB2 (rs1800888), which was also nominally associated with asthma (p = 0.027) and active asthma (p = 0.013) among European Americans with severe RSV bronchiolitis without including the ESP. Our results suggest that rare nonsynonymous variants contribute to the development of asthma following severe RSV bronchiolitis in infancy, notably in ADRB2. Additional studies are required to explore the role of rare variants in the etiology of asthma and asthma-related traits following severe RSV bronchiolitis.

Exhaled nitric oxide and the management of childhood asthma--yet another promising biomarker "has been" or a misunderstood gem

Childhood asthma is a common chronic condition. Approximately five percent of all children in western countries are prescribed treatment with inhaled corticosteroids (ICS) to prevent asthma symptoms. Current guidelines advocate titrating ICS dose to symptoms but this approach is not without problem, e.g. how to discern asthmatic from non-asthmatic symptoms? And when to reduce ICS dose? This review describes the strengths and weaknesses of fractional exhaled nitric oxide (FENO) as an objective index for individualising asthma control in children. Epidemiological and mechanistic evidence suggest that FENO should be a promising biomarker for eosinophilic airway inflammation (a hall mark for asthma) but somewhat surprisingly, clinical trials in children have not consistently found benefit from adding FENO to a symptom-based approach to ICS treatment in children. There are a number of reasons why FENO has apparently failed to translate from promising biomarker to clinically useful tool, and one reason may be a lack of understanding of what merits a significant intrasubject change in FENO. This review describes the rise and apparent fall of FENO as biomarker for asthma and then focuses on more recent evidence which suggest that FENO may prove to have a role in the management of childhood asthma, and in particular preventing exacerbations.

Nitric oxide synthase polymorphisms, gene expression and lung function in chronic obstructive pulmonary disease

Background

Due to the pleiotropic effects of nitric oxide (NO) within the lungs, it is likely that NO is a significant factor in the pathogenesis of chronic obstructive pulmonary disease (COPD). The aim of this study was to test for association between single nucleotide polymorphisms (SNPs) in three NO synthase (NOS) genes and lung function, as well as to examine gene expression and protein levels in relation to the genetic variation.

Methods

One SNP in each NOS gene (neuronal NOS (NOS1), inducible NOS (NOS2), and endothelial NOS (NOS3)) was genotyped in the Lung Health Study (LHS) and correlated with lung function. One SNP (rs1800779) was also analyzed for association with COPD and lung function in four COPD case–control populations. Lung tissue expression of NOS3 mRNA and protein was tested in individuals of known genotype for rs1800779. Immunohistochemistry of lung tissue was used to localize NOS3 expression.

Results

For the NOS3 rs1800779 SNP, the baseline forced expiratory volume in one second in the LHS was significantly higher in the combined AG + GG genotypic groups compared with the AA genotypic group. Gene expression and protein levels in lung tissue were significantly lower in subjects with the AG + GG genotypes than in AA subjects. NOS3 protein was expressed in the airway epithelium and subjects with the AA genotype demonstrated higher NOS3 expression compared with AG and GG individuals. However, we were not able to replicate the associations with COPD or lung function in the other COPD study groups.

Conclusions

Variants in the NOS genes were not associated with lung function or COPD status. However, the G allele of rs1800779 resulted in a decrease of NOS3 gene expression and protein levels and this has implications for the numerous disease states that have been associated with this polymorphism.

Effects of age, gender, and environmental exposures on exhaled nitric oxide level in healthy 12 to 18 years Qatari children

CONTEXT:

Fractional exhaled nitric oxide (FENO) is a useful noninvasive diagnostic tool for asthma and some other pediatric respiratory diseases. Factors affecting FENO level are variable in different populations and studies.

AIMS:

To estimate the normal values of exhaled nitric oxide for Qataris 12 to 18 years of age. Other objectives were to measure the correlation of anthropometric and other potential factors with FENO levels.

SETTINGS AND DESIGN:

Community-based, cross-sectional study.

METHODS:

A total of 438 Qatari national school children from both genders were randomly recruited in cross-sectional study. Of them, 203 were non-atopic and hence included in the statistical analysis. Questionnaires including personal data, demographic data, and other factors that may affect FENO level were distributed.

STATISTICAL ANALYSIS USED:

Comparison of means done using t-test. We performed Spearman's rho test to measure correlations. Data analysis was done using PASW 18.0 Release 18.0.0, 2009.

RESULTS:

The geometric mean of FENO levels for all subjects was 14.1 ppb (upper level CI 95% - 36.3 ppb). FENO was significantly higher in males (R² = −0.254, P<0.0001) and was negatively correlated with increasing age for the whole study population (P=0.036). This decline was interrupted by a significant upraise at the age of 15 years (P=0.0462) which seems to be driven by the males (P=0.0244). FENO levels were lower in subjects exposed to cats (P=0.019). We could not find significant correlation between FENO and other factors studied.

CONCLUSIONS:

Estimated FENO level with 95% CI in Qatari children, which is probably close to those in other Gulf countries, will be helpful clinically. The lower level of FENO with female gender, increasing age, and exposure to cats needs to be further studied to establish the association and to understand the underlying mechanisms.

Genetic variations in nitric oxide synthase and arginase influence exhaled nitric oxide levels in children

BACKGROUND

Exhaled nitric oxide (FeNO) is a biomarker of airway inflammation. In the nitric oxide (NO) synthesis pathway, nitric oxide synthases (encoded by NOS1, NOS2A, and NOS3) and arginases (encoded by ARG1 and ARG2) compete for L-arginine. Although FeNO levels are higher in children with asthma/allergy, influence of these conditions on the relationships between variations in these genes and FeNO remains unknown. The aims of the study were to evaluate the role of genetic variations in nitric oxide synthases and arginases on FeNO in children and to assess the influence of asthma and respiratory allergy on these genetic associations.

METHODS

Among children (6-11 years) who participated in the southern California Children's Health Study, variations in these five genetic loci were characterized by tagSNPs. FeNO was measured in two consecutive years (N = 2298 and 2515 in Years 1 and 2, respectively). Repeated measures analysis of variance was used to evaluate the associations between these genetic variants and FeNO.

RESULTS

Sequence variations in the NOS2A and ARG2 loci were globally associated with FeNO (P = 0.0002 and 0.01, respectively). The ARG2 association was tagged by intronic variant rs3742879 with stronger association with FeNO in asthmatic children (P-interaction = 0.01). The association of a NOS2A promoter haplotype with FeNO varied significantly by rs3742879 genotypes and by asthma.

CONCLUSION

Variants in the NO synthesis pathway genes jointly contribute to differences in FeNO concentrations. Some of these genetic influences were stronger in children with asthma. Further studies are required to confirm our findings.

The effects of NOS1 gene on asthma and total IgE levels in Taiwanese children, and the interactions with environmental factors

Asthma is a complex disorder, which is known to be affected by interactions between genetic and environmental factors. The aim of this study was to investigate the three microsatellite polymorphisms of GT repeats in intron 2, AAT repeats in intron 20, and CA repeats in exon 29 of the NOS1 gene in 155 asthmatic children and 301 control children, and the interaction with environmental factors in southern Taiwan. Total serum IgE, phadiatop test and genetic polymorphisms were measured. The genotype frequency of 14/14-AAT repeats of the NOS1 gene was significantly higher in the asthmatic group (p = 0.01). Total IgE concentrations were higher in asthmatic children (p = 0.015) carrying the NOS1 14/14-AAT genotype than in subjects with other polymorphisms. The gene and environmental interaction effects were 3.83-fold, 6.86-fold, and 8.04-fold (all corrected p-values <0.001) between subjects carrying at least one NOS1 14-AAT allele and exposure to cockroaches, high levels of total IgE, and positive response against the phadiatop test in asthmatic children. The findings of this study provide strong evidence that NOS1 gene with 14-AAT tandem repeats has a significant effect in asthmatic children. Environmental factors and atopic status will enhance the asthmatic risk for children who carry NOS1 susceptible allele.

Environmental exposures, nitric oxide synthase genes, and exhaled nitric oxide in asthmatic children

Exhaled nitric oxide (FeNO), a measure of airway inflammation, is being explored as a tool to guide asthma management in children. Investigators have identified associations of genetic polymorphisms in nitric oxide synthase genes (NOS1 and NOS3) with FeNO levels; however, none have explored whether these polymorphisms modify the relationship of environmental exposures with FeNO. The objective of this project was to evaluate the association of NOS polymorphisms and environmental exposures with FeNO levels among children with asthma. We conducted a 12-month prospective cohort study of 225 tobacco-smoke exposed children (6-12 years) with doctor-diagnosed asthma. We assessed environmental exposures (tobacco, indoor allergens, & airborne particulates), polymorphisms in NOS1 (an intronic AAT tandem repeat) and NOS3 (G894T), and FeNO levels. There was no association of NOS1 or NOS3 polymorphisms with FeNO levels. There were no significant interactions of environmental exposures and the NOS1 polymorphism with FeNO levels. In contrast, there was an interaction of the NOS3 polymorphism and airborne nicotine concentration with FeNO levels (P = 0.01). Among GG genotype individuals, nicotine exposure did not affect FeNO levels; however, among individuals with at least one T allele, higher nicotine exposure was associated with lower FeNO levels (approximately 5 ppb decrease from the lowest to the highest quartile). We conclude that genetic differences may explain some of the conflicting results in studies of the effects of tobacco smoke exposure on FeNO levels and may make FeNO interpretation difficult for a subset of children with asthma.

A NOS1 gene polymorphism associated with asthma and specific immunoglobulin E response to mite allergens in a Colombian population

BACKGROUND

Nitric oxide (NO) is involved in asthma pathogenesis and is synthesized by three isoforms of NO synthase, one of them encoded by NOS1 gene. The CA-repeat and the C5266T SNP in NOS1 exon 29 have been associated with asthma and IgE levels. We thought to test the association of asthma and asthma-related phenotypes with the exon 29 CA-repeat and the C5266T SNP in a Colombian population sample.

METHODS

The CA-repeat and the C5266T SNP were genotyped in 167 asthmatics and 166 controls using PCR-based fragment length polymorphism and TaqMan assay. We also determined total and mite-specific IgE against Blomia tropicalis and Dermatophagoides pteronyssinus.

RESULTS

Three new CA-repeat alleles, 14, 23 and 24 repeats were detected. Allele comprising 16 repeats was associated with asthma (OR: 1.90 (CI 1.22-2.97, p(c) = 0.028) and low total (p(c) = 0.02) and specific IgE to B. tropicalis (p(c) < 0.0001) and D. pteronyssinus (p(c) < 0.0001). We found no association of the C5266T SNP and asthma or IgE levels.

CONCLUSION

NOS1 exon 29 CA-repeat may be a risk factor for asthma susceptibility and mite specific IgE response in a Colombian population.

Candidate gene association studies and evidence for gene-by-gene interactions

Candidate gene studies in asthma are a powerful and valuable tool in asthma genetics. Although the quality of small-scale, freely associating studies has been questionable, increasingly serious efforts are made to establish, replicate, and verify association results. Association studies may help us to better understand the mechanisms underlying asthma. They may create hypotheses and help to direct functional studies to targets that are likely to give valuable results. However, they should not be over-interpreted; only biologic proof can verify associations between genetic variations and a certain disease outcome. The insight that gene-by-gene and gene-by-environment interactions may be crucial for understanding and pinpoint the complex mechanisms of genetic regulation of multifactorial diseases has gained momentum in the last years when technical improvement allowed for the effective genotyping and analysis of great numbers of polymorphisms in large populations. It can be expected that from this area of research new and exciting results will follow soon.

Robust estimation of experimentwise P values applied to a genome scan of multiple asthma traits identifies a new region of significant linkage on chromosome 20q13

Over 30 genomic regions show linkage to asthma traits. Six asthma genes have been cloned, but the putative loci in many linked regions have not been identified. To search for asthma susceptibility loci, we performed genomewide univariate linkage analyses of seven asthma traits, using 202 Australian families ascertained through a twin proband. House-dust mite sensitivity (Dpter) exceeded the empirical threshold for significant linkage at 102 cM on chromosome 20q13, near marker D20S173 (empirical pointwise P = .00001 and genomewide P = .005, both uncorrected for multiple-trait testing). Atopy, bronchial hyperresponsiveness (BHR), and forced expiratory volume in 1 s (FEV1) were also linked to this region. In addition, 16 regions were linked to at least one trait at the suggestive level, including 12q24, which has consistently shown linkage to asthma traits in other studies. Some regions were expected to be false-positives arising from multiple-trait testing. To address this, we developed a new approach to estimate genomewide significance that accounts for multiple-trait testing and for correlation between traits and that does not require a Bonferroni correction. With this approach, Dpter remained significantly linked to 20q13 (empirical genomewide P = .042), and airway obstruction remained linked to 12q24 at the suggestive level. Finally, we extended this method to show that the linkage of Dpter, atopy, BHR, FEV1, asthma, and airway obstruction to chromosome 20q13 is unlikely to be due to chance and may result from a quantitative trait locus in this region that affects several of these traits.