Rapid DNA Methylation Changes after Exposure to Traffic Particles

TLDR

Particulate air pollution is linked to cardiovascular morbidity and mortality, and lower blood DNA methylation—associated with oxidative stress, aging, and atherosclerosis—may mediate these effects, though this relationship remains unclear. The study aimed to determine whether exposure to traffic‑derived particulate matter alters DNA methylation of LINE‑1 and Alu repetitive elements in elderly adults. Researchers quantified LINE‑1 and Alu methylation by qPCR‑pyrosequencing in 718 elderly participants and applied covariate‑adjusted mixed‑effects models to estimate the association between ambient black carbon, PM2.5, and sulfate exposures over 4‑hour to 7‑day windows. Higher recent exposure to black carbon and PM2.5 was associated with reduced LINE‑1 methylation (β ≈ −0.11 to −0.13 per SD increase), while Alu methylation showed no significant changes.

Abstract

Exposure to particulate air pollution has been related to increased hospitalization and death, particularly from cardiovascular disease. Lower blood DNA methylation content is found in processes related to cardiovascular outcomes, such as oxidative stress, aging, and atherosclerosis.We evaluated whether particulate pollution modifies DNA methylation in heavily methylated sequences with high representation throughout the human genome.We measured DNA methylation of long interspersed nucleotide element (LINE)-1 and Alu repetitive elements by quantitative polymerase chain reaction-pyrosequencing of 1,097 blood samples from 718 elderly participants in the Boston area Normative Aging Study. We used covariate-adjusted mixed models to account for within-subject correlation in repeated measures. We estimated the effects on DNA methylation of ambient particulate pollutants (black carbon, particulate matter with aerodynamic diameter < or = 2.5 microm [PM2.5], or sulfate) in multiple time windows (4 h to 7 d) before the examination. We estimated standardized regression coefficients (beta) expressing the fraction of a standard deviation change in DNA methylation associated with a standard deviation increase in exposure.Repetitive element DNA methylation varied in association with time-related variables, such as day of the week and season. LINE-1 methylation decreased after recent exposure to higher black carbon (beta = -0.11; 95% confidence interval [CI], -0.18 to -0.04; P = 0.002) and PM2.5 (beta = -0.13; 95% CI, -0.19 to -0.06; P < 0.001 for the 7-d moving average). In two-pollutant models, only black carbon, a tracer of traffic particles, was significantly associated with LINE-1 methylation (beta = -0.09; 95% CI, -0.17 to -0.01; P = 0.03). No association was found with Alu methylation (P > 0.12).We found decreased repeated-element methylation after exposure to traffic particles. Whether decreased methylation mediates exposure-related health effects remains to be determined.