Epigenome-wide association study on ambient PM_2.5 exposure in Han Chinese, the NSPT study

Ambient PM_2.5 exposure has been recognized as a major health risk and related to aging, cardiovascular, respiratory and neurologic diseases, and cancer. However, underlying mechanism of epigenetic alteration and regulated pathways still remained unclear. The study on methylome effect of PM_2.5 exposure was quite limited in Chinese population, and cohort-based study was absent. The study included blood-derived DNA methylation for 3365 Chinese participants from the NSPT cohort. We estimated individual PM_2.5 exposure level of short-medium-, medium- and long-term, based on a validated prediction model. We preformed epigenome-wide association studies to estimate the links between PM_2.5 exposure and DNA methylation change, as well as stratification and sensitive analysis to examined the robustness of the association models. A systematic review was conducted to obtain the previously published CpGs and examined for replication. We also conducted comparison on the DNA methylation variation corresponding to different time windows. We further conducted gene function analysis and pathway enrichment analysis to reveal related biological response. We identified a total of 177 CpGs and 107 DMRs associated with short-medium-term PM_2.5 exposure, at a strict genome-wide significance (P < 5 × 10^-8). The effect sizes on most CpGs tended to cease with the exposure of extended time scale. Associated markers and aligned genes were related to aging, immunity, inflammation and carcinogenesis. Enriched pathways were mostly involved in cell cycle and cell division, signal transduction, inflammatory pathway. Our study is the first EWAS on PM_2.5 exposure conducted in large-scale Han Chinese cohort and identified associated DNA methylation change on CpGs and regions, as well as related gene functions and pathways.