DNA Methylation in the Arginase–Nitric Oxide Synthase Pathway Is Associated with Exhaled Nitric Oxide in Children with Asthma

Abstract

Rationale: Genetic variation in arginase (ARG) and nitric oxide synthase (NOS) has been associated with exhaled nitric oxide (FeNO) levels in children. Little is known about whether epigenetic variation in these genes modulates FeNO. Objectives: To evaluate whether DNA methylation in ARG and NOS genes is associated with FeNO. Methods: A subset of 940 participants in the Children's Health Study were selected for this study. Children were eligible if they had FeNO measurements and buccal cells collected on the same day. CpG loci located in the promoter regions of NOS1, NOS2A, NOS3, ARG1, and ARG2 genes were analyzed. Multiple loci in each gene were evaluated individually and averaged together. DNA methylation was measured using a bisulfite-polymerase chain reaction pyrosequencing assay. Linear regression models were used to investigate the association between DNA methylation and FeNO and whether associations differed by asthma status. Measurements and Main Results: DNA methylation in ARG2 was significantly associated with FeNO. A 1% increase in average DNA methylation of ARG2 was associated with a 2.3% decrease in FeNO (95% confidence interval, 24 to 20.6). This association was significantly larger in children with asthma (%diff ¼ 28.7%) than in children with no asthma (%diff ¼ 21.6%; p int ¼ 0.01). Differences in FeNO by asthma status were also observed for ARG1 (%diff asthma ¼ 24.4%; %diff non-asthma ¼ 0.3%; p int ¼ 0.02). DNA methylation in NOS genes was not associated with FeNO. Conclusions: DNA methylation in ARG1 and ARG2 is associated with FeNO in children with asthma and suggests a possible role for epigenetic regulation of nitric oxide production.Keywords: arginase; nitric oxide synthase; FeNO; asthma Nitric oxide (NO) is involved in the pathophysiology of allergic airway diseases. Fractional concentration of NO (FeNO) is measurably higher in children with eosinophilic airway inflammation and active asthma or allergic airway diseases, conditions in which airway inflammation plays a prominent role (1-3). Based on the findings in children, FeNO has been suggested as a biomarker that reflects important aspects of airway inflammation that may be useful in the management of some children with asthma (4).NO is synthesized from L-arginine by three NO synthase (NOS) isoforms: (1) neuronal NOS (nNOS encoded by NOS1); (2) endothelial NOS (eNOS encoded by NOS3); and (3) inducible NOS (iNOS encoded by NOS2A). The availability of intracellular L-arginine is a rate-limiting factor in NO production (5). Arginase (ARG) competes with NOS for the common substrate L-arginine. In humans, two isoforms of ARG (encoded by ARG1 and ARG2) are recognized. All three NOS isoforms are expressed in airway epithelium (6-8). Among ARG isoforms, ARGI is located in the cytosol, whereas ARGII is located in the mitochondrial matrix (8). Both isoforms are expressed in the airway epithelium, smooth muscle, and peribronchial and perivascular connective tissues (9, 10). Therefore, differences in ARG and NOS expression levels or function caused ...

Paediatrics in Amsterdam

“…BUKVIC et al [46] reported endotoxin exposure to be associated with a decreased risk of asthma in the whole population of investigated Croatian children but the effect of endotoxin exposure on asthma was found to differ among children with different variants of the MD-2 gene. Recent epigenetic studies have found DNA methylation in ARG1 and ARG2 to be associated with FeNO in children with asthma, thereby suggesting a possible role for epigenetic regulation of nitric oxide production [47]. Increased CD14 methylation from 2-10 yrs of age in children from a Norwegian birth cohort was found to be inversely correlated with soluble CD14 levels at 10 yrs of age [48].…”

Epigenetics and prenatal influences on asthma and allergic airways disease

“…While animal studies have begun to decipher the role of epigenetic regulation of gene expression associated with the development of allergic airway disease in the lung, several recent publications in human cohorts have examined DNA methylation in cells outside of the lung: peripheral blood [62], buccal cells [63,64] and nasal cells [65]. These early studies have only demonstrated statistical association of DNA methylation and specific exposure or asthma phenotype, but have not elucidated the role of DNA methylation in the control of gene expression in human asthma.…”

“…These early studies have only demonstrated statistical association of DNA methylation and specific exposure or asthma phenotype, but have not elucidated the role of DNA methylation in the control of gene expression in human asthma. BRETON et al [63] demonstrated that DNA methylation in promoters of two arginase genes (Arg1 and Arg2) is associated with exhaled NO in children with asthma from the Children's Health Study and indicates a role for epigenetic regulation of nitric oxide production. In a pilot study in the Columbia Center for Children's Environmental Health cohort, KURIAKOSE et al [64] found that iNOS methylation was not significantly associated with exhaled NO fraction (FeNO), but was inversely associated with bronchial NO flux.…”

Advances in pediatric asthma in 2011: Moving forward

“…They propose that new methods that quantify the complexity of asthma over time might provide additional information on predicting asthma exacerbations. Breton et al 97 reported that DNA methylation in the ARG1 and ARG2 promoters is associated with FENO levels in children with asthma and indicates a role for epigenetic regulation of nitric oxide J ALLERGY CLIN IMMUNOL VOLUME 129, NUMBER 1 production. On a review of biomarkers in the assessment of airways disease, Taylor 98 states that successful application of a biomarker result is critically dependent on the specific question being addressed and the performance characteristics of the biomarker in relation to that question in the context of pretest probabilities.…”