Particulate matter-induced senescence of skin keratinocytes involves oxidative stress-dependent epigenetic modifications

Ambient air particulate matter (PM) induces senescence in human skin cells. However, the underlying mechanisms remain largely unknown. We investigated how epigenetic regulatory mechanisms participate in cellular senescence induced by PM with a diameter <2.5 (PM(2.5)) in human keratinocytes and mouse skin tissues. PM(2.5)-treated cells exhibited characteristics of cellular senescence. PM(2.5) induced a decrease in DNA methyltransferase (DNMT) expression and an increase in DNA demethylase (ten–eleven translocation; TET) expression, leading to hypomethylation of the p16(INK4A) promoter region. In addition, PM(2.5) led to a decrease in polycomb EZH2 histone methyltransferase expression, whereas the expression of the epigenetic transcriptional activator MLL1 increased. Furthermore, binding of DNMT1, DNMT3B, and EZH2 to the promoter region of p16(INK4A) decreased in PM(2.5)-treated keratinocytes, whereas TET1 and MLL1 binding increased, leading to decreased histone H3 lysine 27 trimethylation (H3K27Me3) and increased H3K4Me3 in the promoter of p16(INK4A). PM(2.5)-induced senescence involved aryl hydrocarbon receptor (AhR)-induced reactive oxygen species (ROS) production. ROS scavenging dampened PM(2.5)-induced cellular senescence through regulation of DNA and histone methylation. Altogether, our work shows that skin senescence induced by environmental PM(2.5) occurs through ROS-dependent the epigenetic modification of senescence-associated gene expression. Our findings provide information for the design of preventive and therapeutic strategies against skin senescence, particularly in light of the increasing problem of PM(2.5) exposure due to air pollution.