BMAL1 regulates Propionibacterium acnes-induced skin inflammation via REV-ERBα in mice

Acne vulgaris is a common skin disease, affecting over 80% of adolescents. Inflammation is known to play a central role in acne development. Here, we aimed to investigate the role of the central clock gene Bmal1 in acne-associated inflammation in mice. To this end, mice were injected intradermally with Propionibacterium acnes (P. acnes) to induce acne-associated skin inflammation. We found that Bmal1 and its target genes Rev-erbcr, Dbp, Per1 and Cry2 were down-regulated in the skin of P. acnes-treated mice, suggesting a role of Bmal1 in the condition of acne. Supporting this, Bmal1-deleted or jet-lagged mice showed exacerbated P. acnes-induced inflammation in the skin. Regulation of P. acnes-induced inflammation by Bmal1 was further confirmed in RAW264.7 cells and primary mouse keratinocytes. Transcriptomic and protein expression analyses suggested that Bmal1 regulated P. acnes-induced inflammation via the NF-kappa B/NLRP3 axis, which is known to be repressed by REV-ERBa (a direct target of BMAL1). Moreover, loss of Rev-erb alpha in mice exacerbated P. acnes-induced inflammation. In addition, Rev-erb alpha silencing attenuated the inhibitory effects of Bmal1 on P. acnes-induced inflammation. Bmal1 knockdown failed to modulate P. acnes-induced inflammation in Rev-erb alpha-silenced cells. It was thus proposed that Bmal1 restrained P. acnes-induced skin inflammation via its target REV-ERB alpha, which acts on the NF-kappa B/NLRP3 axis to repress inflammation. In conclusion, Bmal1 disruption is identified as a potential pathological factor of acne-associated inflammation. The findings increase our understanding of the crosstalk between skin clock and acne and suggest targeting circadian rhythms as a promising approach for management of acne.