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

Genetic susceptibility to airway inflammation and exposure to short-term outdoor air pollution

BACKGROUND

Air pollution is a large environmental health hazard whose exposure and health effects are unequally distributed among individuals. This is, at least in part, due to gene-environment interactions, but few studies exist. Thus, the current study aimed to explore genetic susceptibility to airway inflammation from short-term air pollution exposure through mechanisms of gene-environment interaction involving the SFTPA, GST and NOS genes.

METHODS

Five thousand seven hundred two adults were included. The outcome measure was fraction of exhaled nitric oxide (FeNO), at 50 and 270 ml/s. Exposures were ozone (O₃), particulate matter < 10 µm (PM₁₀), and nitrogen dioxide (NO₂) 3, 24, or 120-h prior to FeNO measurement. In the SFTPA, GST and NOS genes, 24 single nucleotide polymorphisms (SNPs) were analyzed for interaction effects. The data were analyzed using quantile regression in both single-and multipollutant models.

RESULTS

Significant interactions between SNPs and air pollution were found for six SNPs (p < 0.05): rs4253527 (SFTPA1) with O₃ and NO_x, rs2266637 (GSTT1) with NO₂, rs4795051 (NOS2) with PM₁₀, NO₂ and NO_x, rs4796017 (NOS2) with PM₁₀, rs2248814 (NOS2) with PM₁₀ and rs7830 (NOS3) with NO₂. The marginal effects on FeNO for three of these SNPs were significant (per increase of 10 µg/m³):rs4253527 (SFTPA1) with O₃ (β: 0.155, 95%CI: 0.013-0.297), rs4795051 (NOS2) with PM₁₀ (β: 0.073, 95%CI: 0.00-0.147 (single pollutant), β: 0.081, 95%CI: 0.004-0.159 (multipollutant)) and NO₂ (β: -0.084, 95%CI: -0.147; -0.020 (3 h), β: -0.188, 95%CI: -0.359; -0.018 (120 h)) and rs4796017 (NOS2) with PM₁₀ (β: 0.396, 95%CI: 0.003-0.790).

CONCLUSIONS

Increased inflammatory response from air pollution exposure was observed among subjects with polymorphisms in SFTPA1, GSTT1, and NOS genes, where O₃ interacted with SFTPA1 and PM10 and NO₂/NO_x with the GSTT1 and NOS genes. This provides a basis for the further exploration of biological mechanisms as well as the identification of individuals susceptible to the effects of outdoor air pollution.

Utility of fractional exhaled nitric oxide in interstitial lung disease

The majority of interstitial lung diseases (ILDs) develop rapidly and are associated with a poor prognosis. Therefore, new noninvasive markers are needed to guide the classification and prognostication of ILD. We enrolled 95 patients with ILD, including dermatomyositis-associated ILD (n =69), Sjögren's syndrome-associated ILD (n= 7), mixed connective tissue disease-associated ILD (n= 9), idiopathic pulmonary fibrosis (n= 5) and hypersensitivity pneumonitis (n= 5), 82 patients with connective tissue disease but without ILD as well as 24 healthy controls, then evaluated fractional exhaled nitric oxide (FeNO50; 50 ml s^-1) (Bisenkovet al2006Vestn. Khir. Im. I. I. Grek.1659-14), pulmonary function and high-resolution computed tomography (HRCT) scores. Blood samples were analyzed and bronchoalveolar lavage fluid parameters were measured. There was no significant difference in FeNO50 values between different subgroups of ILD patients or between different subgroups of ILD patients and healthy controls. However, we found that FeNO50 was negatively correlated with the HRCT score and positively correlated with forced vital capacity. FeNO50 values did not play a clinical role in the diagnosis, differential diagnosis or prognostication of ILD.

Exposure to traffic-related particle matter and effects on lung function and potential interactions in a cross-sectional analysis of a cohort study in west Sweden

OBJECTIVES

To investigate the long-term effects of source-specific particle matter (PM) on lung function, effects of Surfactant Protein A (SP-A) and glutathione S-transferase (GST) genes GSTP1 and GSTT1 gene variants and effect modification by single-nucleotide polymorphism (SNP) genotype.

DESIGN

Cohort study with address-based annual PM exposure assigned from annual estimates of size (PM₁₀, PM_2.5 and PM_BC) and source-specific (traffic, industry, marine traffic and wood burning) dispersion modelling.

SETTING

Gothenburg, Sweden.

PARTICIPANTS

The ADult-Onset asthma and NItric oXide Study had 6685 participants recruited from the general population, of which 5216 (78%) were included in the current study with information on all variables of interest. Mean age at the time of enrolment was 51.4 years (range 24-76) and 2427 (46.5%) were men.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV₁). Secondary outcome measures were effects and gene-environment interactions of SP-A and GSTT1 and GSTP1 genotypes.

RESULTS

Exposure to traffic-related PM₁₀ and PM_2.5 was associated with decreases in percent-predicted (% predicted) FEV₁ by -0.48% (95% CI -0.89% to -0.07%) and -0.47% (95% CI -0.88% to -0.07%) per IQR 3.05 and 2.47 µg/m³, respectively, and with decreases in % predicted FVC by -0.46% (95% CI -0.83% to -0.08%) and -0.47% (95% CI -0.83% to -0.10%). Total and traffic-related PM_BC was strongly associated with both FEV₁ and FVC by -0.53 (95% CI -0.94 to -0.13%) and -0.43% (95% CI -0.77 to -0.09%) per IQR, respectively, for FVC, and similarly for FEV₁. Minor allele carrier status for two GSTP1 SNPs and the GSTT1 null genotype were associated with decreases in % predicted lung function. Three SP-A SNPs showed effect modification with exposure to PM_2.5 from industry and marine traffic.

CONCLUSIONS

PM exposure, specifically traffic related, was associated with FVC and FEV₁ reductions and not modified by genotype. Genetic effect modification was suggested for industry and marine traffic PM_2.5.

Acute ingestion of beetroot juice increases exhaled nitric oxide in healthy individuals

Background and objective

Nitric oxide (NO) plays an important role in the airways’ innate immune response, and the fraction of exhaled NO at a flow rate of 50mL per second (F_ENO₅₀) has been utilized to capture NO. Deficits in NO are linked to loss of bronchoprotective effects in airway challenges and predict symptoms of respiratory infection. While beetroot juice supplements have been proposed to enhance exercise performance by increasing dietary nitrate consumption, few studies have examined the impact of beetroot juice or nitrate supplementation on airway NO in contexts beyond an exercise challenge, which we know influences F_ENO₅₀.

Methods

We therefore examined the influence of a beetroot juice supplement on F_ENO₅₀ in healthy males and females (n = 38) during periods of rest and in normoxic conditions. F_ENO₅₀, heart rate, blood pressure, and state affect were measured at baseline, 45 minutes, and 90 minutes following ingestion of 70ml beetroot juice (6.5 mmol nitrate). Identical procedures were followed with ingestion of 70ml of water on a control day.

Results

After beetroot consumption, average values of the natural log of F_ENO₅₀ (lnF_ENO₅₀) increased by 21.3% (Cohen’s d = 1.54, p < .001) 45 minutes after consumption and by 20.3% (Cohen’s d = 1.45, p < .001) 90 min after consumption. On the other hand, only very small increases in F_ENO₅₀ were observed after consumption of the control liquid (less than 1% increase). A small subset (n = 4) of participants completed an extended protocol lasting over 3 hours, where elevated levels of F_ENO₅₀ persisted. No significant changes in cardiovascular measures were observed with this small single dose of beetroot juice.

Conclusion

As NO serves a key role in innate immunity, future research is needed to explore the potential clinical utility of beetroot and dietary nitrate to elevate F_ENO₅₀ and prevent respiratory infection.

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.

Association of NOS2 and NOS3 gene polymorphisms with susceptibility to type 2 diabetes mellitus and diabetic nephropathy in the Chinese Han population

Inducible nitric oxide synthase (NOS2) and endothelial nitric oxide synthase (NOS3) gene play important roles in the susceptibility to type 2 diabetes mellitus (T2DM). The present study aims to detect the potential association of NOS2 and NOS3 gene polymorphisms with the susceptibility toT2DM and diabetic nephropathy (DN) in the Chinese Han population. Four hundred and ninety T2DM patients and 485 healthy controls were enrolled in this case-control study. The genotypes of NOS2 and NOS3 gene polymorphisms were analyzed by the polymerase chain reaction (PCR)-ligase detection reaction (LDR) method. Our data demonstrated that the NOS2 rs2779248 and NOS2 rs1137933 genetic polymorphisms were significantly associated with the increased susceptibility to T2DM in the heterozygote comparison, dominant model, and allele contrast; and NOS3 rs3918188 genetic polymorphism was significantly associated with the increased susceptibility to T2DM in the homozygote comparison and recessive model. The allele-C and genotype-TC of NOS2 rs2779248, allele-A and genotype-GA of NOS2 rs1137933 and genotype-AA of NOS3 rs3918188 genetic polymorphisms might be the risk factors for increasing the susceptibility to T2DM. And a significant haplotype effect of NOS2 rs10459953/C- rs1137933/G- rs2779248/T was found between T2DM cases and controls. Moreover, NOS3 rs1800783 polymorphism was significantly associated with the increased susceptibility to DN in the heterozygote comparison, recessive model and allele contrast. At last, a positive correlation of family history of diabetes with NOS3 rs11771443 polymorphism was found in DN. These preliminary findings indicate that the NOS2 rs2779248, NOS2 rs1137933, and NOS3 rs3918188 genetic polymorphisms are potentially related to the susceptibility to T2DM, and the rs1800783 polymorphism might be considered as genetic risk factors for diabetic nephropathy, and family history of diabetes was closely associated with rs11771443 polymorphism in DN, and the genetic variants might be used as molecular markers for evaluating the risk of T2DM and diabetic nephropathy. © 2016 IUBMB Life, 68(7):516-525, 2016.