Propionibacterium acnes and peptidoglycan activate aryl hydrocarbon receptor and modify differentiation of SZ95 sebocytes in vitro

Individual acne comedones can undergo spontaneous remission in association with shrunken sebaceous glands (SGs) containing undifferentiated cells under unknown mechanisms. It is also still controversial whether sebum-induced follicular Propionibacterium acnes(P. acnes)interacts with the SGs. We explored the effects of P. acnes and peptidoglycan (PGN) on the aryl hydrocarbon receptor (AhR) activation, lipogenesis and differentiation in cultured human SZ95 sebocytes in vitro. Both formaldehyde-inactivated P. acnes and PGN upregulated mRNA levels of AhR charachteristic downstream genes CYP1A1, CYP1B1, CYP1A2, as well as significantly induced translocation of AhR protein from cytoplasm into nucleus. GSEA revealed pathways of downregulated lipogenesis and upregulated keratinization. In addition, P.acnes and PGN inhibited linoleic acid(LA)-induced neutral lipid synthesis and expressions of Keratin 7 and Mucin1/EMA (sebocyte markers) and increased the expression of Keratin 10 and involucrin (keratinocyte markers), which were abolished after AhR gene silencing. Moreover, inhibited expressions of lipogenesis-related genes such as SREBP1 were observed. In conclusion, we provide evidence that P. acnes can switch sebocytes into a keratinocyte-like differentiation with reduced lipogenesis via AhR, indicating that follicular P. acnes should not only be considered as acnegenic but also as a factor promoting acne remission through feedback regulation of sebum production. Overall design: Examination of total RNA from SZ95 sebocytes of three groups:LA,LA+p.acnes,LA+PGN.