Fine particulate matter exposure induces DNA damage by downregulating Rad51 expression in human bronchial epithelial Beas-2B cells in vitro

Although an accumulating body of evidence suggests that fine particulate matter (PM2.5) can cause lung injury and lung cancer, the underlying mechanisms are not yet clear. In this study, multiple endpoints associated with the cellular response to PM2.5 exposure, including the cell proliferation rate, cell apoptosis, malondialdehyde (MDA) content and DNA damage, were evaluated in human bronchial epithelial Beas-2B cells. The mRNA expression profile in PM2.5-treated cells was analyzed by transcriptome sequencing. The DNA repair gene Rad51 was then selected for further analysis. We found that the viability and growth of Beas-2B cells decreased while cell apoptosis increased in a dose-dependent manner after PM2.5 exposure. The comet assay showed that PM2.5 exposure induced evident DNA damage in PM2.5-treated cells. The MDA content in the treated cells was increased, indicating that PM2.5 exposure promoted lipid peroxidation. Furthermore, Rad51 expression was downregulated in PM2.5-treated cells, which may have contributed to the PM2.5-induced DNA damage in Beas-2B cells. Upregulation of Rad51 expression could rescue the negative impact of PM2.5 exposure in Beas-2B cells. Taken together, our research demonstrates that PM2.5 exposure induces DNA damage and impairs the DNA repair process by downregulating Rad51 expression in Beas-2B cells. This finding is expected to provide new insight into the genotoxicity of PM2.5 exposure.