Temporal variability of global DNA methylation and hydroxymethylation in buccal cells of healthy adults: Association with air pollution

Abstract

Background: Epigenetic changes, such as DNA methylation, are observed in response to environmental exposure and in the development of several chronic diseases. Consequently, DNA methylation alterations might serve as indicators of early effects. In this context, the aim of this study was to assess the temporal variability of global DNA methylation and hydroxymethylation levels in buccal cells from healthy adult volunteers. Methods: Global DNA methylation (% 5mdC) and hydroxymethylation (% 5hmdC) levels in human buccal cells, collected from 26 healthy adults at different time points, were quantified by UPLC-MS/MS. Associations between % 5mdC and % 5hmdC, respectively, and short-term exposure (1-7 days) to air pollutants PM2.5 and PM10 were tested with mixed-effects models including various covariates. Results/Discussion: Dynamic short-term changes in DNA methylation and hydroxymethylation levels in buccal cells were observed, which were inversely associated with exposure to PM2.5 and PM10. An IQR increase in PM2.5 over a 7-day moving average period was significantly associated with a decrease of -1.47% (-1.74%, -1.20%) and -0.043% (-0.054%, -0.032%) in % 5mdC and % 5hmdC, respectively. Likewise, for PM10, a decrease of -1.42% (-1.70, -1.13) and -0.040% (-0.051%, -0.028%) was observed. Conclusion: Global DNA methylation and hydroxymethylatation varied over a time period of three weeks. The observed temporal variability was associated with exposure to ambient PM2.5 and PM10 levels. This should be taken into account when interpreting epigenetic alterations in buccal cells.