Associations between nitric oxide synthase genes and exhaled NO-related phenotypes according to asthma status

Effect of nitric oxide synthase gene polymorphism on inflammatory response in patients with chronic obstructive pulmonary disease

This study aimed to investigate the association between nitric oxide synthase gene polymorphisms and the inflammatory responses in patients with 'fast-' and 'slow-' developing chronic obstructive pulmonary disease (COPD). In the main process, 190 patients with slow-developing COPD, 94 patients with fast-developing COPD and 105 healthy volunteers were selected for inclusion. Endothelial nitric oxide synthase (eNOS) was detected using western-blot eNOS sites, and inducible nitric oxide synthase (iNOS) was detected through SNPshot. T helper 17 cells (Th17) and regulator T (Treg) cells were detected via flow cytometry, and interferon-gamma, tumour necrosis factor-alpha, interleukin (IL)-17, IL-10, IL-6, IL-4 and IL-2 were detected using a cytometric bead array. The final results and conclusions drawn from the tests suggest that Th17/Treg-mediated immune inflammation plays an important role in the pathogenesis of COPD, but whether it affects the development of COPD needs further investigation. Overall, COPD patients with a young age of onset, young age of smoking initiation and small body mass index, as well as COPD patients with CC at rs3729508 in the iNOS gene and non-GG at rs7830 in the eNOS gene, may be more likely to contract fast-developing COPD.

Male-biased association of endothelial nitric oxide synthase Asp298Glu substitution (NOS3-c.894G/T) with asthma risk and severity

OBJECTIVE

The nitric-oxide pathway plays a crucial role in the pathogeneses of asthma and NOS3-encoded endothelial nitric oxide synthase is one of the main components of the pathway. Variants of NOS3 are known to contribute to asthma development and pathophysiology.

METHODS

We investigated the association of NOS3-c.894G/T (rs1799983) with asthma risk and severity by studying frequencies of its genotypes and alleles in 555 asthmatics (93 intermittent, 240 mild, 158 moderate, and 64 severe asthma cases) and 351 control participants using the PCR-FRLP method, logistic regression analysis and generalized ordered logit estimates.

RESULTS

GT genotype (OR_adj: 1.39; CI: 1.04-1.85; p = 0.026), dominant model GT + TT (OR_adj: 1.41; CI: 1.07-1.87; p = 0.015), and T allele (OR_adj: 1.32; CI: 1.05-1.67; p = 0.018) was associated with increased ORs in asthmatics. Also, the frequency of GT + TT (OR_adj: 1.55; CI: 1.01-2.38; p = 0.044) was significantly higher in males. Furthermore, GT genotype (OR_adj: 1.39; CI: 1.04-1.85; p = 0.024), GT + TT (OR_adj: 1.42; CI: 1.07-1.87; p = 0.014), and T allele (OR_adj: 1.32; CI: 1.05-1.66; p = 0.018) in total population and GT + TT (OR_adj: 1.56; CI: 1.02-2.37; p = 0.04) in males were significantly associated with increased risk of severe, moderate, mild, intermittent asthma vs. controls. Also, GT genotype (OR_adj: 1.39; CI: 1.02-1.91; p = 0.039) was significantly more frequent in severe, moderate grades vs. lower severity grades in the total population. Frequencies of GT genotype (OR_adj: 1.77; CI: 1.05-3.00; p = 0.032) and GT + TT (OR_adj: 1.74; CI: 1.04-2.90; p = 0.036) in total population and GT genotype (OR_adj: 2.40; CI: 1.16-4.97; p = 0.018) and GT + TT (OR_adj: 2.30; CI: 1.12-4.74; p = 0.023) in male subpopulation were significantly higher in severe cases compared to lower grades.

CONCLUSIONS

NOS3-c.894G/T may be associated with asthma risk and its severer grades, with greater effects in men.

Gene-Folic Acid Interactions and Risk of Conotruncal Heart Defects: Results from the National Birth Defects Prevention Study

Conotruncal heart defects (CTDs) are heart malformations that affect the cardiac outflow tract and typically cause significant morbidity and mortality. Evidence from epidemiological studies suggests that maternal folate intake is associated with a reduced risk of heart defects, including CTD. However, it is unclear if folate-related gene variants and maternal folate intake have an interactive effect on the risk of CTDs. In this study, we performed targeted sequencing of folate-related genes on DNA from 436 case families with CTDs who are enrolled in the National Birth Defects Prevention Study and then tested for common and rare variants associated with CTD. We identified risk alleles in maternal MTHFS (OR_meta = 1.34; 95% CI 1.07 to 1.67), maternal NOS2 (OR_meta = 1.34; 95% CI 1.05 to 1.72), fetal MTHFS (OR_meta = 1.35; 95% CI 1.09 to 1.66), and fetal TCN2 (OR_meta = 1.38; 95% CI 1.12 to 1.70) that are associated with an increased risk of CTD among cases without folic acid supplementation. We detected putative de novo mutations in genes from the folate, homocysteine, and transsulfuration pathways and identified a significant association between rare variants in MGST1 and CTD risk. Results suggest that periconceptional folic acid supplementation is associated with decreased risk of CTD among individuals with susceptible genotypes.

Genetic Variants Associated with Bronchial Asthma Specific to the Population of the Russian Federation

Bronchial asthma (BA) is a disease that still lacks an exhaustive treatment protocol. In this regard, the global medical community pays special attention to the genetic prerequisites for the occurrence of this disease. Therefore, the search for the genetic polymorphisms underlying bronchial asthma has expanded considerably. As the present study progressed, a significant amount of scientific medical literature was analyzed and 167 genes reported to be associated with the development of bronchial asthma were identified. A group of participants (n = 7,303) who had voluntarily provided their biomaterial (venous blood) to be used in the research conducted by the Federal Medical Biological Agency of Russia was formed to subsequently perform a bioinformatic verification of known associations and search for new ones. This group of participants was divided into four cohorts, including two sex-distinct cohorts of individuals with a history of asthma and two sex-distinct cohorts of apparently healthy individuals. A search for polymorphisms was made in each cohort among the selected genes, and genetic variants were identified whose difference in occurrence in the different cohorts was statistically significant (significance level less than 0.0001). The study revealed 11 polymorphisms that affect the development of asthma: four genetic variants (rs869106717, rs1461555098, rs189649077, and rs1199362453), which are more common in men with bronchial asthma compared to apparently healthy men; five genetic variants (rs1923038536, rs181066119, rs143247175, rs140597386, and rs762042586), which are more common in women with bronchial asthma compared to apparently healthy women; and two genetic variants (rs1219244986 and rs2291651) that are rare in women with a history of asthma.

Blood eosinophil counts in the general population and airways disease: a comprehensive review and meta-analysis

BACKGROUND

The clinical context for using blood eosinophil (EOS) counts as treatment-response biomarkers in asthma and COPD requires better understanding of EOS distributions and ranges. We describe EOS distributions and ranges published in asthma, COPD, control (non-asthma/COPD) and general populations.

METHODS

We conducted a comprehensive literature review and meta-analysis of observational studies (January 2008 to November 2018) that included EOS counts in asthma, severe asthma, COPD, control and general populations. Excluded studies had total sample sizes <200, EOS as inclusion criterion, hospitalised population only and exclusively paediatric participants.

RESULTS

Overall, 91 eligible studies were identified, most had total-population-level data available: asthma (39 studies), severe asthma (12 studies), COPD (23 studies), control (seven studies) and general populations (14 studies); some articles reported data for multiple populations. Reported EOS distributions were right-skewed (seven studies). Reported median EOS counts ranged from 157-280 cells·µL-1 (asthma, 22 studies); 200-400 cells·µL-1 (severe asthma, eight studies); 150-183 cells·µL-1 (COPD, six studies); and 100-160 cells·µL-1 (controls, three studies); and 100-200 cells·µL-1 (general populations, six studies). The meta-analysis showed that observed variability was mostly between studies rather than within studies. Factors reportedly associated with higher blood EOS counts included current smoking, positive skin-prick test, elevated total IgE, comorbid allergic rhinitis, age ≤18 years, male sex, spirometric asthma/COPD diagnosis, metabolic syndrome and adiposity.

CONCLUSION

EOS distribution and range varied by study population, and were affected by clinical factors including age, smoking history and comorbidities, which, regardless of severity, should be considered during treatment decision-making.

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.

Exhaled breath analysis in disease detection

Investigating the use of exhaled breath analysis to diagnose and monitor different diseases has attracted much interest in recent years. This review introduces conventionally used methods and some emerging technologies aimed at breath analysis and their relevance to lung disease, airway inflammation, gastrointestinal disorders, metabolic disorders and kidney diseases. One section correlates breath components and specific diseases, whereas the other discusses some unique ideas, strategies, and devices to analyze exhaled breath for the diagnosis of some common diseases. This review aims to briefly introduce the potential application of exhaled breath analysis for the diagnosis and screening of various diseases, thereby providing a new avenue for the detection of non-invasive diseases.

Lower fractional exhaled nitric oxide levels are associated with depressive symptom in males: A population-based cross-sectional study

BACKGROUND

We examined cross-sectional associations between depression and both inflammatory markers and fractional exhaled nitric oxide (FeNO).

METHODS

This cross-sectional study is a secondary analysis of the data of the Iwaki Health Promotion Project 2016 (1,148 subjects). We analyzed the subjects' characteristics and laboratory data including plasma interleukin (IL)-6, high-sensitivity C-reactive protein (hs-CRP), and FeNO. The subjects with Center for Epidemiologic Studies Depression Scale scores ≥16 were assigned to the depression group. We performed a multivariate logistic regression analysis to determine whether inflammatory markers and FeNO were associated with depression.

RESULTS

We assessed 1,099 subjects (430 males, 669 females). The depression group was 237 subjects (21.5%) [84 males (19.5%), 153 females (22.9%)]. The non-depression group was 862 subjects (346 males and 516 females). There were no significant differences in IL-6, hs-CRP, or FeNO between both groups. However, the multivariate logistic regression analysis indicated that lower FeNO was significantly associated with depression in males after adjusting for possible confounding factors (age, BMI, comorbidities, high-sensitivity troponin T, FEV₁%, asthma, antidepressant use, smoker and alcohol drinker) (per 1 bpm increase, OR: 0.982; 95%CI: 0.967-0.998; p = 0.032).

CONCLUSION

Our findings indicate that lower FeNO may be associated with depression in males.

[Usefulness of measurement of nitric oxide in exhaled air in diagnostics and treatment of allergic rhinitis and asthma in children and adolescents]

Nitric oxide is produced by enzymes called nitric oxide synthases. It fulfills many important functions in the human body, but produced in excess amount has a proinflammatory activity. Fractional exhaled nitric oxide measurements are used in the diagnosis and monitoring of eosinophilic inflammation in the lower airways, but should not be used as an independent parameter to make a diagnosis of asthma or for the monitoring of asthma treatment. Evaluation of fractional exhaled nitric oxide concentrations is also used to determine the pathogenesis of symptoms in patients with rhinitis. In addition, they are helpful in detecting and monitoring eosinophilic inflammation in the lower respiratory tract that coexists with inflammation in the upper airways. Fractional exhaled nitric oxide concentrations may be abnormal (lowered or elevated) in other chronic diseases, such as cystic fibrosis, primary ciliary dyskinesia and inflammatory bowel diseases. Many factors, e.g. atopy, genetic polymorphisms of NOS, and the lipid profile affect the fractional exhaled nitric oxide measurement. Nasal nitric oxide measurement is useful in assessing the prevalence and severity of eosinophilic inflammation in the upper respiratory tract.

Exhaled breath NOx levels in a middle-aged adults population-based study: reference values and association with the smoking status

BACKGROUND

Biomarkers in exhaled breath condensate (EBC) are potentially sensitive indicators of early biochemical changes in airways following exposure to pneumotoxic substances, particularly in susceptible subjects. NOx are the stable end products of the nitrite-nitrate-NO oxidative stress pathway and can be used to monitor airway inflammatory diseases, especially in asthma. Nevertheless, population-based surveys are needed to better interpret EBC NOx levels in clinical studies. The aim of this study was to establish reference values of EBC NOx in a large group of middle-aged, healthy adults of a sample of the general population with particular focus on the smoking status.

METHODS

The EBC NOx levels were analysed from 2872 subjects among the ELISABET population-based cross sectional study including a representative sample of men and women aged from 40 to 66 years olds conducted in northern France, which included comprehensive questionnaires by interview and spirometry data. Healthy participants were defined as participants with no self-reported respiratory disease.

RESULTS

For the healthy subjects (n = 1251), the median NOx concentration (IQR) was equal to 7.2  μM (3.12) and concentrations of NOx in EBC did not differ significantly according to smoking status. The upper fifth percentile (95%) (ULN) of NOx concentrations among healthy subjects was equal to 13.6  μM, ranging from 12.7  μM (smokers) to 14.4  μM (ex smokers). Among subjects with EBC NOx values higher than the ULN and compared with subjects that had EBC NOx values lower than the ULN, we found a significant higher proportion of subjects with current asthma (10.5% vs 6.5%) or with chronic bronchitis symptoms (7.6% vs 3.3%).

CONCLUSION

This population-based study has provided the distribution and the upper limit reference value of a nitrosative stress biomarker (NOx) in EBC of middle aged, healthy adults. EBC NOx levels were not associated with smoking status.

Genetic and epigenetic susceptibility of airway inflammation to PM2.5 in school children: new insights from quantile regression

BACKGROUND

The fractional concentration of exhaled nitric oxide (FeNO) is a biomarker of airway inflammation that has proved to be useful in investigations of genetic and epigenetic airway susceptibility to ambient air pollutants. For example, susceptibility to airway inflammation from exposure to particulate matter with aerodynamic diameter < =2.5 μm (PM_2.5) varies by haplotypes and promoter region methylation in inducible nitric oxide synthase (iNOS encoded by NOS2). We hypothesized that PM2.5 susceptibility associated with these epigenetic and genetic variants may be greater in children with high FeNO from inflamed airways. In this study, we investigated genetic and epigenetic susceptibility to airborne particulate matter by examining whether the joint effects of PM2.5, NOS2 haplotypes and iNOS promoter methylation significantly vary across the distribution of FeNO in school children.

METHODS

The study included 940 school children in the southern California Children's Health Study who provided concurrent buccal samples and FeNO measurements. We used quantile regression to examine susceptibility by estimating the quantile-specific joint effects of PM_2.5, NOS2 haplotype and methylation on FeNO.

RESULTS

We discovered striking differences in susceptibility to PM_2.5 in school children. The joint effects of short-term PM_2.5 exposure, NOS2 haplotypes and methylation across the FeNO distribution were significantly larger in the upper tail of the FeNO distribution, with little association in its lower tail, especially among children with asthma and Hispanic white children.

CONCLUSION

School-aged children with higher FeNO have greater genetic and epigenetic susceptibility to PM_2.5, highlighting the importance of investigating effects across the entire distribution of FeNO.

Inducible nitric oxide synthase expression is increased in the alveolar compartment of asthmatic patients

INTRODUCTION

Increased exhaled nitric oxide (NO) levels in asthma are suggested to be through inducible NO synthase (iNOS). The aim of this study was to investigate the expression of iNOS in bronchoalveolar lavage (BAL) cells and tissue from central and peripheral airways and compare it with the exhaled bronchial and alveolar NO levels in patients with asthma vs a control group.

METHODS

Thirty-two patients with asthma (defined as controlled or uncontrolled according to Asthma Control Test score cut-off: 20) and eight healthy controls were included. Exhaled NO was measured, and alveolar concentration and bronchial flux were calculated. iNOS was measured in central and peripheral lung biopsies, as well as BAL cells. Bronchoalveolar lavage macrophages were stimulated in vitro, and iNOS expression and NO production were investigated.

RESULTS

Expression of iNOS was increased in central airway tissue and the alveolar compartment in uncontrolled as compared to controlled asthmatics and healthy controls. There were no differences, however, in iNOS mRNA levels in total BAL cells in uncontrolled as compared to controlled asthma. Bronchoalveolar lavage cell mRNA levels of iNOS or iNOS expression in central and alveolar tissue did not relate to alveolar NO, nor to bronchial flux of NO. In vitro stimulation with leukotriene D₄ increased iNOS mRNA levels and NO production in cultured BAL macrophages.

CONCLUSION

The levels of both bronchial and alveolar iNOS are increased in uncontrolled as compared to controlled asthma. However, levels of iNOS in BAL macrophages were not reflected by alveolar NO. Both central and distal iNOS levels may reflect responsiveness to steroid treatment.

6q12 and 11p14 variants are associated with postnatal exhaled nitric oxide levels and respiratory symptoms

BACKGROUND

Exhaled nitric oxide (eNO) is a biomarker of airway inflammation and seems to precede respiratory symptoms, such as asthma, in childhood. Identifying genetic determinants of postnatal eNO levels might aid in unraveling the role of eNO in epithelial function or airway inflammation and disease.

OBJECTIVE

We sought to identify genetic determinants of early postnatal eNO levels and subsequent respiratory symptoms during the first year of life.

METHODS

Within a population-based birth cohort, eNO levels were measured in healthy term infants aged 5 weeks during quiet tidal breathing in unsedated sleep. We assessed associations of single nucleotide polymorphisms with eNO levels in a genome-wide association study and subsequent symptoms of lower respiratory tract infections during the first year of life and asked whether this was modified by prenatal and early-life environmental factors.

RESULTS

We identified thus far unknown determinants of infant eNO levels: rs208515 (P = 3.3 × 10^-8), which is located at 6q12, probably acting in "trans" and explaining 10.3% of eNO level variance, and rs1441519 (P = 1.6 × 10^-6), which is located at 11p14, potentially affecting nitric oxide synthase 3 (NOS3) expression, as shown by means of in vitro functional analyses. Moreover, the 6q12 locus was inversely associated with subsequent respiratory symptoms (P < .05) and time to recovery after first respiratory symptoms during the first year of life (P < .05).

CONCLUSION

The identification of novel genetic determinants of infant eNO levels might implicate that postnatal eNO metabolism in healthy infants before first viral infections and sensitization is related to mechanisms other than those associated with asthma, atopy, or increased risk thereof later in life.

Evaluation and treatment of critical asthma syndrome in children

The heterogeneity of asthma is illustrated by the significantly different features of pediatric asthma compared to adult asthma. One phenotype of severe asthma in pediatrics includes atopy, lack of reduction in lung function, and absence of gender bias as the main characteristics. Included in the NIH NAEPP EPR-3 are recommendations for the treatment and management of severe pediatric asthma and critical asthma syndrome, such as continuous nebulization treatments, intubation and mechanical ventilation, heliox, and magnesium sulfate. In addition, epinephrine, intravenous immunoglobulin, intravenous montelukast, extracorporeal membrane oxygenation, and many biological modulators currently under investigation are additional current and/or future treatment modalities for the severe pediatric asthmatic. But, perhaps the most important strategy for managing the severe asthmatic is preventative treatment, which can significantly decrease impairment and risk, particularly for severe acute exacerbations requiring emergency care and/or hospitalization. In order for preventative therapy to be successful, several challenges must be met, including selecting the correct therapy for each patient and then ensuring compliance or adherence to a treatment plan. The heterogeneity of asthma renders the former difficult in that not all patients will respond equally to the same treatment; the latter is only helpful if the correct treatment is employed. Strategies to ensure compliance include education of caregivers and patients and their families. As newer medications are introduced, options for individualized or customized medicine increase, and this may pave the way for significant decreases in morbidity and mortality in severe pediatric asthma.

[Genetic and biochemical mechanisms of involvement of antioxidant defense enzymes in the development of bronchial asthma]

In the present review we have analyzed and summarized recent literature data on genetic and biochemical mechanisms responsible for involvement of antioxidant defense enzymes in the etiology and pathogenesis of bronchial asthma. It has been shown that the mechanisms of asthma development are linked with genetically determined abnormalities in the functioning of antioxidant defense enzymes. These alterations are accompanied by a systemic imbalance between oxidative and anti-oxidative reactions with the shift of the redox state toward increased free radical production and oxidative stress, a key element in the pathogenesis of bronchial asthma.

A common variant in RAB27A gene is associated with fractional exhaled nitric oxide levels in adults

BACKGROUND

Exhaled nitric oxide (FeNO) is a biomarker for eosinophilic inflammation in the airways and for responsiveness to corticosteroids in asthmatics.

OBJECTIVE

We sought to identify in adults the genetic determinants of fractional exhaled nitric oxide (FeNO) levels and to assess whether environmental and disease-related factors influence these associations.

METHODS

We performed a genome-wide association study of FeNO through meta-analysis of two independent discovery samples of European ancestry: the outbred EGEA study (French Epidemiological study on the Genetics and Environment of Asthma, N = 610 adults) and the Hutterites (N = 601 adults), a founder population living on communal farms. Replication of main findings was assessed in adults from an isolated village in Sardinia (Talana study, N = 450). We then investigated the influence of asthma, atopy and tobacco smoke exposure on these genetic associations, and whether they were also associated with FeNO values in children of the EAGLE (EArly Genetics & Lifecourse Epidemiology, N = 8858) consortium.

RESULTS

We detected a common variant in RAB27A (rs2444043) associated with FeNO that reached the genome-wide significant level (P = 1.6 × 10(-7) ) in the combined discovery and replication adult data sets. This SNP belongs to member of RAS oncogene family (RAB27A) and was associated with an expression quantitative trait locus for RAB27A in lymphoblastoid cell lines from asthmatics. A second suggestive locus (rs2194437, P = 8.9 × 10(-7) ) located nearby the sodium/calcium exchanger 1 (SLC8A1) was mainly detected in atopic subjects and influenced by inhaled corticosteroid use. These two loci were not associated with childhood FeNO values.

CONCLUSIONS AND CLINICAL RELEVANCE

This study identified a common variant located in RAB27A gene influencing FeNO levels specifically in adults and with a biological relevance to the regulation of FeNO levels. This study provides new insight into the biological mechanisms underlying FeNO levels in adults.

Role of polymorphisms of inducible nitric oxide synthase and endothelial nitric oxide synthase in idiopathic environmental intolerances

Oxidative stress and inflammation play a pathogenetic role in idiopathic environmental intolerances (IEI), namely, multiple chemical sensitivity (MCS), fibromyalgia (FM), and chronic fatigue syndrome (CFS). Given the reported association of nitric oxide synthase (NOS) gene polymorphisms with inflammatory disorders, we aimed to investigate the distribution of NOS2A −2.5 kb (CCTTT)_n as well as Ser608Leu and NOS3 −786T>C variants and their correlation with nitrite/nitrate levels, in a study cohort including 170 MCS, 108 suspected MCS (SMCS), 89 FM/CFS, and 196 healthy subjects. Patients and controls had similar distributions of NOS2A Ser608Leu and NOS3 −786T>C polymorphisms. Interestingly, the NOS3 −786TT genotype was associated with increased nitrite/nitrate levels only in IEI patients. We also found that the NOS2A −2.5 kb (CCTTT)₁₁ allele represents a genetic determinant for FM/CFS, and the (CCTTT)₁₆ allele discriminates MCS from SMCS patients. Instead, the (CCTTT)₈ allele reduces by three-, six-, and tenfold, respectively, the risk for MCS, SMCS, and FM/CFS. Moreover, a short number of (CCTTT) repeats is associated with higher concentrations of nitrites/nitrates. Here, we first demonstrate that NOS3 −786T>C variant affects nitrite/nitrate levels in IEI patients and that screening for NOS2A −2.5 kb (CCTTT)_n polymorphism may be useful for differential diagnosis of various IEI.

[Genetic and environmental factors of asthma and allergy: Results of the EGEA study]

INTRODUCTION AND METHODS

The EGEA study (epidemiological study on the genetics and environment of asthma, bronchial hyperresponsiveness and atopy), which combines a case-control and a family-based study of asthma case (n=2120 subjects) with three surveys over 20 years, aims to identify environmental and genetic factors associated with asthma and asthma-related phenotypes. We summarize the results of the phenotypic characterization and the investigation of environmental and genetic factors of asthma and asthma-related phenotypes obtained since 2007 in the EGEA study (42 articles).

RESULTS

Both epidemiological and genetic results confirm the heterogeneity of asthma. These results strengthen the role of the age of disease onset, the allergic status and the level of disease activity in the identification of the different phenotypes of asthma. The deleterious role of active smoking, exposure to air pollution, occupational asthmogenic agents and cleaning products on the prevalence and/or activity of asthma has been confirmed. Accounting for gene-environment interactions allowed the identification of new genetic factors underlying asthma and asthma-related traits and better understanding of their mode of action.

CONCLUSION

The EGEA study is contributing to the advances in respiratory research at the international level. The new phenotypic, environmental and biological data available in EGEA study will help characterizing the long-term evolution of asthma and the factors associated to this evolution.

Fraction of exhaled nitric oxide values in childhood are associated with 17q11.2-q12 and 17q12-q21 variants

BACKGROUND

The fraction of exhaled nitric oxide (Feno) value is a biomarker of eosinophilic airway inflammation and is associated with childhood asthma. Identification of common genetic variants associated with childhood Feno values might help to define biological mechanisms related to specific asthma phenotypes.

OBJECTIVE

We sought to identify the genetic variants associated with childhood Feno values and their relation with asthma.

METHODS

Feno values were measured in children age 5 to 15 years. In 14 genome-wide association studies (N = 8,858), we examined the associations of approximately 2.5 million single nucleotide polymorphisms (SNPs) with Feno values. Subsequently, we assessed whether significant SNPs were expression quantitative trait loci in genome-wide expression data sets of lymphoblastoid cell lines (n = 1,830) and were related to asthma in a previously published genome-wide association data set (cases, n = 10,365; control subjects: n = 16,110).

RESULTS

We identified 3 SNPs associated with Feno values: rs3751972 in LYR motif containing 9 (LYRM9; P = 1.97 × 10(-10)) and rs944722 in inducible nitric oxide synthase 2 (NOS2; P = 1.28 × 10(-9)), both of which are located at 17q11.2-q12, and rs8069176 near gasdermin B (GSDMB; P = 1.88 × 10(-8)) at 17q12-q21. We found a cis expression quantitative trait locus for the transcript soluble galactoside-binding lectin 9 (LGALS9) that is in linkage disequilibrium with rs944722. rs8069176 was associated with GSDMB and ORM1-like 3 (ORMDL3) expression. rs8069176 at 17q12-q21, but not rs3751972 and rs944722 at 17q11.2-q12, were associated with physician-diagnosed asthma.

CONCLUSION

This study identified 3 variants associated with Feno values, explaining 0.95% of the variance. Identification of functional SNPs and haplotypes in these regions might provide novel insight into the regulation of Feno values. This study highlights that both shared and distinct genetic factors affect Feno values and childhood asthma.

Haplotypes of the inducible nitric oxide synthase gene are strongly associated with exhaled nitric oxide levels in adults: a population-based study

BACKGROUND

Previous genetic association studies have reported evidence for association of single-nucleotide polymorphisms (SNPs) in the NOS2 gene, encoding inducible nitric oxide synthase (iNOS), to variation in levels of fractional exhaled nitric oxide (FENO) in children and adults. In this study, we evaluated 10 SNPs in the region of chromosome 17 from 26.07 Mb to 26.13 Mb to further understand the contribution of NOS2 to variation in levels of FENO.

METHODS

In a cohort of 5912 adults 25-75 years of age, we investigated the relationship between NOS2 haplotypes and FENO, and effect modification by asthma.

RESULTS

Seven common (frequency ≥5%) haplotypes (H1-H7) were inferred from all possible haplotype combinations. One haplotype (H3) was significantly associated with lower levels of FENO: -5.8% (95% CI -9.8 to -1.7; p=0.006) compared with the most common baseline haplotype H1. Two haplotypes (H5 and H6) were significantly associated with higher levels of FENO: +10.7% (95% CI 5.0 to 16.7; p=0.0002) and +14.9% (95% CI 10.6 to 19.3; p=7.8×10(-13)), respectively. The effect of haplotype H3 was mainly seen in subjects with asthma (-21.6% (95% CI -33.5 to -5.9)) and was not significant in subjects without asthma (-4.2% (95% CI -8.4 to 0.2)). The p value for interaction between H3 and asthma status was 0.004.

CONCLUSIONS

Our findings suggest that several common haplotypes in the NOS2 gene contribute to variation in FENO in adults. We also saw some evidence of effect modification by asthma status on haplotype H3.

Airway nitric oxide and psychological processes in asthma and health: a review

OBJECTIVE

The fraction of exhaled nitric oxide (FeNO) has been widely used as a marker of airway inflammation in asthma in recent years. However, NO serves multiple functions throughout the organism, and various influences on FeNO levels beyond inflammation have been documented. Emerging literature indicates that psychological processes are systematically linked to FeNO.

DATA SOURCES

Academic Search Complete, PubMed, PsychArticles, and PsychInfo databases.

STUDY SELECTIONS

Relevant studies were identified using keywords exhaled nitric oxide paired with psychological stress, stress psychology, emotion, major depression, anxiety, or psychopathology. Studies measuring FeNO during naturalistic observation of emotion and stress, laboratory stress and emotion-induction protocols, and correlational designs using psychological questionnaires were included.

RESULTS

Acute stress, anxiety, and negative affect have been repeatedly linked with higher FeNO levels, whereas more prolonged states of stress, in particular depression, have been associated with lower FeNO levels. The literature on FeNO is paralleled by research on NO in the cardiovascular and central nervous systems, which also shows systematic associations with psychosocial variables. Potential mechanisms of association include stimulation of NO release from different cells, including the epithelia and macrophages, through noradrenaline, interferon-γ, or vascular endothelial growth factor, changes in oxidative stress or arginase levels, or facilitation of diffusion by mechanical factors.

CONCLUSION

Psychosocial factors may need to be considered in the interpretation of longitudinal FeNO changes in monitoring and management of patients with asthma. The distinction between constitutive and inducible sources of NO will be essential for future research.

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.

Polymorphisms in nitric oxide synthase and endothelin genes among children with obstructive sleep apnea

Background

Obstructive sleep apnea (OSA) is associated with adverse and interdependent cognitive and cardiovascular consequences. Increasing evidence suggests that nitric oxide synthase (NOS) and endothelin family (EDN) genes underlie mechanistic aspects of OSA-associated morbidities. We aimed to identify single nucleotide polymorphisms (SNPs) in the NOS family (3 isoforms), and EDN family (3 isoforms) to identify potential associations of these SNPs in children with OSA.

Methods

A pediatric community cohort (ages 5–10 years) enriched for snoring underwent overnight polysomnographic (NPSG) and a fasting morning blood draw. The diagnostic criteria for OSA were an obstructive apnea-hypopnea Index (AHI) >2/h total sleep time (TST), snoring during the night, and a nadir oxyhemoglobin saturation <92%. Control children were defined as non-snoring children with AHI <2/h TST (NOSA). Endothelial function was assessed using a modified post-occlusive hyperemic test. The time to peak reperfusion (Tmax) was considered as the indicator for normal endothelial function (NEF; Tmax<45 sec), or ED (Tmax≥45 sec). Genomic DNA from peripheral blood was extracted and allelic frequencies were assessed for, NOS1 (209 SNPs), NOS2 (122 SNPs), NOS3 (50 SNPs), EDN1 (43 SNPs), EDN2 (48 SNPs), EDN3 (14 SNPs), endothelin receptor A, EDNRA, (27 SNPs), and endothelin receptor B, EDNRB (23 SNPs) using a custom SNPs array. The relative frequencies of NOS-1,-2, and −3, and EDN-1,-2,-3,-EDNRA, and-EDNRB genotypes were evaluated in 608 subjects [128 with OSA, and 480 without OSA (NOSA)]. Furthermore, subjects with OSA were divided into 2 subgroups: OSA with normal endothelial function (OSA-NEF), and OSA with endothelial dysfunction (OSA-ED). Linkage disequilibrium was analyzed using Haploview version 4.2 software.

Results

For NOSA vs. OSA groups, 15 differentially distributed SNPs for NOS1 gene, and 1 SNP for NOS3 emerged, while 4 SNPs for EDN1 and 1 SNP for both EDN2 and EDN3 were identified. However, in the smaller sub-group for whom endothelial function was available, none of the significant SNPs was retained due to lack of statistical power.

Conclusions

Differences in the distribution of polymorphisms among NOS and EDN gene families suggest that these SNPs could play a contributory role in the pathophysiology and risk of OSA-induced cardiovascular morbidity. Thus, analysis of genotype-phenotype interactions in children with OSA may assist in the formulation of categorical risk estimates.