Effect of Zanthoxylum piperitum Extract on Human Skin Protection from UVB by Regulation of COP1 and PPAR-α

Ultraviolet (UV) irradiation from the sun is the primary environmental factor that causes skin damages including skin cancer and premature skin aging. Because, even the most powerful sunscreen can’t always afford enough protection, it is necessary to enhance the defensive power of skin against UV. Recently, constitutive photomorphogenic protein-1 (COP1) has shown to contribute to the regulation of UVB response of keratinocytes. In this study, we represent that COP1 and its associated protein, de-etiolated 1 (DET1), might participate in photoaging process in human skin as Arabidopsis COP1 does sun-protective function in plants. After UVB irradiation, the decrease of COP1 and DET1 mRNA expression was followed by the increase of c-Jun total protein. Moreover, transfection with DNA vectors expressing COP1 and DET1 down-regulated the c-Jun total protein. We found that Zanthoxylum piperitum extract (ZE) up-regulated the expression of COP1 and DET1 on human keratinocytes, and inhibited the expression of MMP1 which is one of the genes regulated by c-Jun signal. In addition, ZE has been reported to stimulate PPAR-α and strengthen the skin barrier. We found that ZE decreased the UVB-induced IL-6 and IL-8 in NHEK cells. In human study, ZE protected skin against UV-B induced erythema and erythema-induced pigmentation. These results indicate that ZE could be useful for the protection against the adverse effects of UV irradiation through various mechanisms.