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Updated: May 22, 2026

Quantification of three DNA Lesions by Mass Spectrometry and Assessment of Their Levels in Tissues of Mice Exposed to Ambient Fine Particulate Matter
Published on: May 29, 2019
Particulate matter, DNA methylation in nitric oxide synthase, and childhood respiratory disease
Carrie V Breton1, Muhammad T Salam, Xinhui Wang
1Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA. Breton@usc.edu
Background:
Air pollutants have been associated with childhood asthma and wheeze. Epigenetic regulation of nitric oxide synthase--the gene responsible for nitric oxide production--may be affected by air pollutants and contribute to the pathogenesis of asthma and wheeze.
Objective:
Our goal was to investigate the association between air pollutants, DNA methylation, and respiratory outcomes in children.
Methods:
Given residential address and buccal sample collection date, we estimated 7-day, 1-month, 6-month, and 1-year cumulative average PM₂.₅ and PM₁₀ (particulate matter ≤ 2.5 and ≤ 10 µm aerodynamic diameter, respectively) exposures for 940 participants in the Children's Health Study. Methylation of 12 CpG sites in three NOS (nitric oxide synthase) genes was measured using a bisulfite-polymerase chain reaction Pyrosequencing assay. Beta regression models were used to estimate associations between air pollutants, percent DNA methylation, and respiratory outcomes.
Results:
A 5-µg/m³ increase in PM₂.₅ was associated with a 0.20% [95% confidence interval (CI): -0.32, -0.07] to 1.0% (95% CI: -1.61, -0.56) lower DNA methylation at NOS2A position 1, 0.06% (95% CI: -0.18, 0.06) to 0.58% (95% CI: -1.13, -0.02) lower methylation at position 2, and 0.34% (95% CI: -0.57, -0.11) to 0.89% (95% CI: -1.57, -0.21) lower methylation at position 3, depending on the length of exposure and CpG locus. One-year PM2.5 exposure was associated with 0.33% (95% CI: 0.01, 0.65) higher in average DNA methylation of 4 loci in the NOS2A CpG island. A 5-µg/m³ increase in 7-day and 1-year PM₂.₅ was associated with 0.6% (95% CI: 0.13, 0.99) and 2.8% (95% CI: 1.77, 3.75) higher NOS3 DNA methylation. No associations were observed for NOS1. PM₁₀ showed similar but weaker associations with DNA methylation in these genes.
Conclusions:
PM₂.₅ exposure was associated with percent DNA methylation of several CpG loci in NOS genes, suggesting an epigenetic mechanism through which these pollutants may alter production of nitric oxide.
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