Alcohol extract from Vernonia anthelmintica (L.) willd seed enhances melanin synthesis through activation of the p38 MAPK signaling pathway in B16F10 cells and primary melanocytes

Ethnopharmacological relevanceVernonia anthelmintica (L.) willd has been used in folk medicine to treat leukoderma in China for centuries. The promoting activities of its extract (AVE) in melanogenesis and possible signaling pathways were investigated in this article.Materials and methodsThe improving activities of AVE were examined by melanin synthesis, tyrosinase activity assay and Western blot in B16F10 mouse melanoma cells and normal human primary melanocytes (NHMC).ResultsAVE increased the tyrosinase activity and melanin content in a dosage-dependent manner at concentrations of 1-40 μg/ml and treatment with 20 μg/ml AVE enhanced the expression of tyrosinase time-dependently in both B16F10 cells and NHMC. Whether AVE affects the expression of microphthalmia-associated transcription factor (MITF), which is required for tyrosinase expression, was investigated. Our results showed that AVE induced MITF protein expression up-regulation. Besides, Western blot analysis revealed that AVE promoted the level of phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) markedly at 0-6 h, while the level of phosphorylation of CREB at 0-2 h. The special p38 MAPK inhibitor, SB203580, and protein kinase A (PKA) inhibitor, H89, both attenuated the AVE-induced up-regulation of MITF and tyrosinase expression in B16F10 cells and NHMC. However, SB203580 could significantly decrease the melanin biosynthesis induced by AVE, but not H89.ConclusionAVE exerts its improving effect on melanogenesis mainly by p38 MAPK activation and MITF induction of tyrosinase.

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