Preventive effect of Rhus javanica extract on UVB-induced skin inflammation and photoaging

Rhus javanica has long been used in traditional medicines, and found to possess bioactive properties. In this study, we sought to investigate whether Rhus javanica extract (RJE) has preventive effects against UVB-induced inflammation and photoaging. RJE was identified as a promising candidate based on an MMP-1 promoter assay, and we confirmed suppressive effects on UVB-induced COX-2 and MMP-1 expression (67.6% and 80.9%, respectively) in immortalized human keratinocyte HaCaT cells. RJE suppressed both UVB-induced mitogen activated protein kinase (MAPK) and Akt signalling pathways as well as EGFR activity. RJE significantly suppressed repetitive UVB-induced wrinkle formation and COX-2 and MMP-13 expression in vivo. Among the compounds identified, syringic acid was found to exhibit the strongest inhibitory effect on UVB-induced MMP-1 promoter activity (45.2%). These results demonstrate that RJE has potent preventive activity for skin inflammation and photoaging which occurs via suppression of pathways related to EGFR.