Sargahydroquinoic Acid Suppresses Hyperpigmentation by cAMP and ERK1/2-Mediated Downregulation of MITF in α-MSH-Stimulated B16F10 Cells

Hyperpigmentation diseases of the skin require topical treatment with depigmenting agents. We investigated the hypopigmented mechanisms of sargahydroquinoic acid (SHQA) in alpha-melanocyte-stimulating hormone (α-MSH)-stimulated B16F10 cells. SHQA reduced cellular tyrosinase (TYR) activity and melanin content in a concentration-dependent manner and attenuated the expression of TYR and tyrosinase-related protein 1 (TRP1), along with their transcriptional regulator, microphthalmia-associated transcription factor (MITF). SHQA also suppressed α-MSH-induced cellular production of cyclic adenosine monophosphate (cAMP), which inhibited protein kinase A (PKA)-dependent cAMP-responsive element-binding protein (CREB) activation. Docking simulation data showed a potential binding affinity of SHQA to the regulatory subunit RIIβ of PKA, which may also adversely affect PKA and CREB activation. Moreover, SHQA activated ERK1/2 signaling in B16F10 cells, stimulating the proteasomal degradation of MITF. These data suggest that SHQA ameliorated hyperpigmentation in α-MSH-stimulated B16F10 cells by downregulating MITF via PKA inactivation and ERK1/2 phosphorylation, indicating that SHQA is a potent therapeutic agent against skin hyperpigmentation disorders.