Photoprotective effects of 2S,3R-6-methoxycarbonylgallocatechin isolated from Anhua dark tea on UVB-induced inflammatory responses in human keratinocytes

Ultraviolet B (UVB) induces inflammation and causes skin aging. The signs of skin aging, such as wrinkles, discolored spots, loss of skin moisture, and disruption of the skin barrier, are mostly caused by inflammatory signaling among various skin layers. The cells on the outermost surface of the skin are keratinocytes; these cells protect the skin against environmental stress and play an important role in immunomodulation by secreting cytokines in response to environmental stress. In the present study, we found that UVB activates STAT1 to mediate inflammatory signaling, yet STAT1 (S272) and STAT (Y702) shows different responses against UVB exposure. Anhua drak tea is a post-fermented dark tea produced in Anhua and Xinhua country in Hunan province of China. Treatment with 2S,3R-6-methoxycarbonylgallocatechin (MCGE), an epigallocatechin gallate derivative isolated from black tea (Anhua dark tea), effectively suppresses STAT1 activation and inflammatory cytokines, and activates Nrf2 pathway to protect cells from reactive oxygen species production in UVB exposed keratinocyte cells (HaCaT). Interestingly, the effects of MCGE were independent on MAPK signaling pathway. Moreover, MCGE regulates inflammatory cytokines in monocyte-keratinocyte (THP-1, HaCaT) co-culture and macrophage differentiation models. These results suggest that MCGE potentially can be used as a photo-protective agent against UVB-induced inflammatory responses.