Abstract
BackgroundDNA methylation may mediate effects of air pollution on cardiovascular disease. The association between long-term air pollution exposure and DNA methylation in monocytes, which are central to atherosclerosis, has not been studied. We investigated the association between long-term ambient air pollution exposure and DNA methylation (candidate sites and global) in monocytes of adults (aged ≥55).MethodsOne-year average ambient fine particulate matter (PM2.5) and oxides of nitrogen (NOX) concentrations were predicted at participants’ (n = 1,207) addresses using spatiotemporal models. We assessed DNA methylation in circulating monocytes at 1) 2,713 CpG sites associated with mRNA expression of nearby genes and 2) probes mapping to Alu and LINE-1 repetitive elements (surrogates for global DNA methylation) using Illumina’s Infinium HumanMethylation450 BeadChip. We used linear regression models adjusted for demographics, smoking, physical activity, socioeconomic status, methyl-nutrients, and technical variables. For significant air pollution-associated methylation sites, we also assessed the association between expression of gene transcripts previously associated with these CpG sites and air pollution.ResultsAt a false discovery rate of 0.05, five candidate CpGs (cg20455854, cg07855639, cg07598385, cg17360854, and cg23599683) had methylation significantly associated with PM2.5 and none were associated with NOX. Cg20455854 had the smallest p-value for the association with PM2.5 (p = 2.77 × 10−5). mRNA expression profiles of genes near three of the PM2.5-associated CpGs (ANKHD1, LGALS2, and ANKRD11) were also significantly associated with PM2.5 exposure. Alu and LINE-1 methylation were not associated with long-term air pollution exposure.ConclusionsWe observed novel associations between long-term ambient air pollution exposure and site-specific DNA methylation, but not global DNA methylation, in purified monocytes of a multi-ethnic adult population. Epigenetic markers may provide insights into mechanisms underlying environmental factors in complex diseases like atherosclerosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-016-0202-4) contains supplementary material, which is available to authorized users.
Highlights
DNA methylation may mediate effects of air pollution on cardiovascular disease
We evaluated the association between long-term exposure to ambient air pollution and global and candidate CpG site DNA methylation in circulating monocytes of 1,207 participants from the Multi-Ethnic Study of Atherosclerosis (MESA)
We found five expression-associated methylation sites (eMS) had methylation significantly (FDR
Summary
DNA methylation may mediate effects of air pollution on cardiovascular disease. The association between long-term air pollution exposure and DNA methylation in monocytes, which are central to atherosclerosis, has not been studied. We investigated the association between long-term ambient air pollution exposure and DNA methylation (candidate sites and global) in monocytes of adults (aged ≥55). Many prior studies focused on the effect of air pollution exposure on the risk of cardiovascular mortality and morbidity. Associations between air pollution and cardiovascular disease have been identified in other countries, including Europe and China. Much uncertainty exists regarding underlying biological mechanisms for this association, DNA methylation has been postulated to mediate the effects of air pollution on cardiovascular disease (CVD) [17]
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