Effects of airborne particulate matter (PM10) from dust storm and thermal inversion on global DNA methylation in human peripheral blood mononuclear cells (PBMCs) in vitro

Scientists have considered epigenetic modifications as a possible mechanism to deal with adverse effects of air pollution. This study aimed to compare the effect of PM10 (PM with aerodynamic diameter ≤ 10 μm) from dust storm and inversion conditions on in vitro global methylation in human peripheral blood mononuclear cells (PBMCs). PM10 was sampled in Tehran, Iran, at a point impacted with dust storm and inversion. PM toxicity was determined using the MTT assay. PBMCs were extracted from whole blood of healthy males and treated separately with a mixture of pooled PM10 from inversion and dusty conditions at concentrations of 50-300 μg/mL for 4 h. Untreated cells were used as the negative control. Moreover, 5-methylsytosine (%5-mC) and 5-hydroxymethylcytosine (%5-hmC) were measured by the enzyme-linked immunosorbent assay (ELISA) method. Daily average PM10 concentrations in dusty and inversion days were 348.40 and 220.54 μg/m3, respectively. The mean of %5-mC (2.04 ± 1.49%) was estimated 12 times more than that of %5-hmC (0.17 ± 0.11%). PM10 resulting from the both sources caused DNA hypomethylation; however, this effect from inversion (median = 3%, IQR = 2.4%) was found to be significantly more than that from dust storm (median = 1.1%, IQR = 1.38%). Moreover, particles increased %5-hmC caused by PM10, which was significantly greater when resulting from inversion (0.23 ± 0.1%) than from dust storm (0.12 ± 0.09%). Furthermore, %5-mC and %5-hmC were significantly different at different PM10 concentrations (50-300 μg/mL) so that a significant difference was observed between %5-mC and %5-hmC at extreme concentrations. Results showed that PM10 from inversion caused a significantly more global methylation than that from dust storm. It can be concluded that measurement of 5-mC and 5-hmC as epigenetic modifications in environmental studies of DNA methylation can be a good procedure to determine health effects related to PM10 exposure.