Particulate matter-induced atmospheric skin aging is aggravated by UVA and inhibited by a topical l-ascorbic acid...

Ambient particulate matter (PM) is a major contributor to environmental air pollution-associated skin damage. However, most published studies are observational or epidemiologic and have not mechanistically investigated the effects of air pollutants on cellular senescence and aging, particularly in combination with ultraviolet (UV) radiation. Herein, we analyzed whether UVA aggravates the PM-induced inflammatory cascade, which contributes to the aging of skin-derived cells. We hypothesized that cellular senescence is involved in PM&UVA-induced aging and tested whether an l-ascorbic acid compound (LAC), containing vitamin E and ferulic acid, can inhibit PM&UVA-induced aging. PM&UVA-exposed HDFs showed further elevated reactive oxygen species (ROS) levels detected by flow cytometry. We then demonstrated that PM induces MAPK signaling activation and the expression of AhR and NF-κB, responses that are both exacerbated by UVA. The levels of inflammatory cytokines, IL-1β and IL-6, were significantly higher in the PM&UVA-exposed group which resulted in increased transcription of MMPs, causing downregulation of type I collagen. Meanwhile, treatment with LAC reduced the levels of ROS and inflammatory cytokines. Additionally, PM&UVA-induced SA-β-gal production (staining assay) was reduced by LAC. These findings suggest a role of atmospheric pollution and UVA radiation in cellular senescence induction. Our findings also suggest a possible role of AhR inhibition by topical antioxidants to prevent atmospheric pollution-induced skin aging.