Inhibitory effects of Stichopus japonicus extract on melanogenesis of mouse cells via ERK phosphorylation

Stichopus japonicus has been used as a folk medicine and as an ingredient in traditional food in East Asian countries. In recent years, the bioactive compounds found in S. japonicus have been reported to possess efficacy in wound healing and may be of potential use in the cosmeceutical, pharmaceutical and biomedical industries. Although the components and their functions require further investigation, S. japonicus extracts exhibit anti-inflammatory properties, and may be used for cancer prevention and treatment. Although several reports have examined different aspects of S. japonicus, the effects of S. japonicus extract on melanogenesis in the skin has not been reported to date. Therefore the present study aimed to investigate the effects of S. japonicus extract on melanogenesis. Treatment with a mixture of S. japonicus extracts (MSCE) reduced melanin synthesis and tyrosinase (TYR) activity in mouse melanocyte cells lines, B16F10 and Melan-A. In addition, MSCE treatment reduced the protein expression levels of TYR, tyrosinase-related protein-1 and tyrosinase-related protein-2. The reduced protein levels may be the result of decreased microphthalmia-associated transcription factor (MITF) expression, which is an important regulator of melanogenesis. The reduced expression level of MITF was associated with delayed phosphorylation of extracellular signal-regulated kinase (ERK) induced by MSCE treatment. A specific MEK inhibitor, PD98059, significantly blocked MSCE-mediated inhibition of melanin synthesis. In conclusion, these results indicate that MSCE may be useful as a potential skin-whitening compound in the skin medical industry.