Effects Of Ginsenoside Rb1 On Melanogenesis In Human Epidermal Melanocytes

Objective: The colour of skin is mainly due to the presence of a pigment known as melanin. The melanocytes produce melanin and distribute it to neighbouring keratinocytes, therefore are responsible for the pigmentation of skin. The insufficient melanogenesis in melanocytes may result in hypopigmentation of the skin, and promotion of the melanogenesis in melanocytes is a strategy in treating depigmenting disorders. Tyrosinase is a key enzyme in melanogenesis in melanocytes. Recent studies showed that tyrosinase is mainly regulated by microphthalmia-associated transcription factor (MITF), which expression is regulated by upstream proteins such as cAMP response element binding protein (CREB). Ginsenoside Rb1 is one of the main active ingredients of Traditional Chinese Medicine Panax ginseng C A Meyer which has been used in treating hypopigmentation disorders such as vitiligo. In recent years, it has been reported that ginsenoside Rb1 has multiple actions such as anti-forgetful, anti-ageing, anti-oxidative, anti-apoptosis and promoting the nerve fiber formation and maintain its function. Both neural cell and melanocytes originate from the neural crest, however, the effects of ginsenoside Rb1 on melanocyte and its main function, melanogenesis, have not yet been studied. In the present study, we investigate the effects of ginsenoside Rb1 on melanogenesis in human melanocytes and underlying mechanism, in order to probe into its potential usefulness in treating depigmenting disorders.Methods: Melanocytes were primarily cultured and subcultured, after that, the 2-5th generation of melanocytes was selected to carry on the experiments. Effects of ginsenoside Rb1 on cell viability, tyrosinase activity and cellular melanin content in cultured melanocytes were measured by MTT method, oxidative DOPA reaction, and NaOH method, respectively. The expression of tyrosinase and MITF and the activation of CREB were tested by Western Blot analysis. Results: Treatment with 25-100μM of ginsenoside Rb1 for 72h significantly increased cellular melanin content and tyrosinase activity in a dose-dependant manner, while the cell viability of melanocytes remains unchanged. Treatment with 100μM of ginsenoside Rb1 for 72h significantly increased the expression of tyrosinase and MITF, and the activation of CREB. Pretreatment with 10μM of H-89, a selective inhibitor of PKA, significantly blocked the ginsenoside Rb1-induced activation of CREB and expression increase of MITF and tyrosinase, and subsequently the increase of tyrosinase activity and melanin content.Conclusions: Ginsenoside Rb1 could promote the melanogenesis and tyrosinase activity in normal human melanocytes. And the activation of PKA/CREB/MITF/ tyrosinase signaling pathway may contribute to the pro-melanogenesis activity of ginsenoside Rb1.