Aqueous fraction from Cuscuta japonica seed suppresses melanin synthesis through inhibition of the p38 mitogen-activated protein kinase signaling pathway in B16F10 cells

Ethnopharmacological relevance: Semen cuscutae has been used traditionally to treat pimples and alleviate freckles and melasma in Korea. The present study aimed to investigate the inhibitory effect of Cuscuta japonica Choisy seeds on alpha-melanocyte-stimulating hormone (alpha-MSH)-induced melanogenesis. Materials and methods: The aqueous fraction from Semen cuscutae (AFSC) was used to determine anti-melanogenic effects by examination of cellular melanin contents. tyrosinase activity assay, cAMP assay and Western blot analysis for melanin synthesis-related signaling proteins in B16F10 mouse melanoma cells. Results: AFSC markedly inhibited alpha-MSH-induced melanin synthesis and tyrosinase activity, and also decreased alpha-MSH-induced expression of microphthalmia-associated transcription factor (MITF) and tyrosinase-related proteins (TRPs). Moreover, AFSC significantly decreased the level of phosphorylated p38 mitogen-activated protein kinase (MAPK) signaling through the down-regulation of alpha-MSH-induced cAMP. Furthermore, we confirmed that the specific inhibitor of p38 MAPK (SB203580)-mediated suppressed melanin synthesis and tyrosinase activity was further attenuated by AFSC. AFSC also further decreased SB203580-mediated suppression of MITF and TRP expression. Conclusions: These results indicate that AFSC inhibits p38 MAPK phosphorylation with suppressed cAMP levels and subsequently down-regulate MITF and TRP expression, which results in a marked reduction of melanin synthesis and tyrosinase activity in alpha-MSH-stimulated B16F10 cells. (c) 2012 Elsevier Ireland Ltd. All rights reserved.