Suppression of the inflammatory response by oxyresveratrol from the root bark of Roxb against ultraviolet B-induced keratinocytes mediated by regulating p38 MAPK and AP-1.

Oxyresveratrol is a polyphenolic compound present in the root bark of Roxb. Several studies have reported on its antioxidant, anti-inflammatory, and whitening properties. In this study, we report for the first time that oxyresveratrol alleviates the cytotoxicity of ultraviolet B (UVB) radiation in keratinocytes- . We performed resazurin cell viability, reactive oxygen species (ROS), and Griess assays to investigate the cytoprotective and free radical-scavenging capabilities of oxyresveratrol. The antioxidant effect was demonstrated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging assay. The inhibition of inflammatory and apoptotic proteins by oxyresveratrol in UVB-irradiated keratinocytes was investigated using western blotting. Pretreated cells with oxyresveratrol exhibited reduced cell death upon UVB exposure, which was mediated by its antioxidant activity. Oxyresveratrol protected cells by inhibiting the mitogen-activated protein kinase p38 and its downstream target, AP-1 transcription factor. These factors led to a decrease in UVB-induced cell inflammation through iNOS and COX-2 expression. Furthermore, the Bax/Bcl-2 ratio was significantly decreased by oxyresveratrol at 10 μM and thus reduced cell apoptosis, as demonstrated by the Hoechst 33342 staining assay. This study revealed the photoprotective effects of oxyresveratrol against UVB\ irradiation in keratinocytes. This strongly supports the benefits of using oxyresveratrol as an ingredient in skincare products for the prevention of sun-damaged skin.