Rapid DNA methylation changes after exposure to traffic particles.
BACKGROUND
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.


OBJECTIVE
We evaluated whether particulate pollution modifies DNA methylation in heavily methylated sequences with high representation throughout the human genome.


METHODS
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.


RESULTS
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).


CONCLUSIONS
We found decreased repeated-element methylation after exposure to traffic particles. Whether decreased methylation mediates exposure-related health effects remains to be determined.
Baccarelli
Andrea
A
Laboratory of Environmental Epigenetics, Department of Environmental and Occupational Health, University of Milan, Via San Barnaba 8, 20122 Milan, Italy. andrea.baccarelli@unimi.it
Wright
Robert O
RO
Bollati
Valentina
V
Tarantini
Letizia
L
Litonjua
Augusto A
AA
Suh
Helen H
HH
Zanobetti
Antonella
A
Sparrow
David
D
Vokonas
Pantel S
PS
Schwartz
Joel
J
D000368:Aged; D000369:Aged, 80 and over; D020087:Alu Elements / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects*; D044127:Epigenesis, Genetic; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects*; D020084:Long Interspersed Nucleotide Elements / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000009:adverse effects*; D011446:Prospective Studies; D012621:Seasons; D014505:Urban Population; D001335:Vehicle Emissions / Q000633:toxicity*
D052638:Particulate Matter; D001335:Vehicle Emissions