43

Background: Acne vulgaris is a common pilosebaceous disease associated with Propionibacterium acnes ( P. acnes). Resolution of comedones may occur in association with shrunken sebaceous glands (SGs) containing de-differentiated cells, however the role of P. acnes is unclear. Objectives: To investigate the effects of P. acnes on aryl hydrocarbon receptor (AhR) activation, lipogenesis and differentiation in cultured immortalized human SZ95 sebocytes. Materials & Methods: Cultured sebocytes were incubated with formalin-killed (f-) P. acnes (f- P. acnes) at different ratios of multiplicity of infection. The mRNA levels of the AhR downstream cytochrome P450 (CYP) genes were measured by quantitative RT-PCR, nuclear translocation of AhR by western blot and immunofluorescence, lipogenesis and keratinization by gene set enrichment analysis (GSEA), lipid related analysis by Oil red O staining and Nile red staining, and sebaceous differentiation-related gene expression by western blot. Results: f- P. acnes upregulated CYPs mRNA levels and induced translocation of AhR protein from the cytoplasm into the nucleus. GSEA revealed downregulation of lipogenesis and upregulation of keratinization. f- P. acnes inhibited linoleic acid-induced neutral lipid synthesis and expression of sebocyte markers, keratin 7 and mucin1/EMA, but increased expression of keratinocyte markers, keratin 10 and involucrin, which were abolished by AhR gene silencing. Inhibition of lipogenesis-related genes, such as sterol response element-binding protein, was also observed. Conclusion: f- P. acnes inhibits lipogenesis and induces terminal differentiation of sebocytes, into keratinocyte-like cells, via activation of the AhR pathway in vitro, suggesting that follicular P. acnes is not only acnegenic but also promotes acne remission through feedback regulation of sebum production.