HSP70 inducers from Chinese herbs and their effect on melanin production.

Skin hyperpigmentation disorders as a result of abnormal melanin production induced by ultraviolet (UV) irradiation are both a clinical and a cosmetic problem. This melanin production is mediated by tyrosinase whose expression is positively regulated by microphthalmia-associated transcription factor (MITF). We recently found that expression of heat shock protein 70 (HSP70) inhibits melanin production. In this study, we searched for HSP70 inducers from Chinese herbs and selected an ethanol extract of Eupatorium lindleyanum (E. lindleyanum). Not only melanin production but also the activity and expression of tyrosinase were significantly suppressed in cells treated with E. lindleyanum extract as well as in HSP70-overexpressing cells. The expression of MITF was clearly suppressed in cells treated with E. lindleyanum extract but not in HSP70-overexpressing cells. These results suggest that E. lindleyanum extract suppresses the expression of tyrosinase and melanin production through both HSP70-dependent and HSP70-independent mechanisms.