Activation of p38 MAPK pathway contributes to the melanogenic property of apigenin in B16 cells.

We investigated the involvement of MAPK pathways in the melanogenic effect of apigenin in B16 cells. Apigenin treatment for 48 h dose (5-20 μm)-dependently up-regulated protein expression levels of microphthalmia-associated transcription factor (MITF) and melanogenic enzymes including tyrosinase, tyrosinase-related protein-1 (TRP-1) and TRP-2 and enhanced the phosphorylation of p38 MAPK, without affecting the phosphorylation of JNK or ERK MAPK. Treatment with 10 μm apigenin time (6-48 h)-dependently elevated the protein expressions of p-p38, MITF and melanogenic enzymes. Moreover, PD169316, a selective inhibitor of p38 kinase, suppressed the stimulatory effects of apigenin on tyrosinase activity and melanin synthesis, which were accompanied by decreased MITF protein expression. In conclusion, apigenin increased melanogenesis in B16 cells, at least in part, by activating the p38 MAPK pathway. The novel findings of this study shed light on the molecular mechanisms underlying the melanogenic activity of apigenin and suggest that apigenin/its derivatives may be potentially used for treating hypopigmentation disorders.