Guggulsterone inhibits melanogenesis in B16 murine melanoma cells by downregulating tyrosinase expression

In the present study, we investigated the effect of guggulsterone on melanogenesis in B16 melanoma cells and elucidated its possible mechanism of action. The effects of guggulsterone on melanogenesis were determined by assaying melanin synthesis and cellular tyrosinase activity in B16/F10 mouse melanoma cells. Guggulsterone dose-dependently inhibited isobutylmethylxanthine (IBMX)-induced melanogenesis and cellular tyrosinase activity with no cytotoxicity. Decreased melanin biosynthesis was accompanied by the reduced expression of melanogenesis-related genes, such as tyrosinase, microphthalmia-associated transcription factor, tyrosinase-related protein (TRP)-1 and TRP-2. Guggulsterone also inhibited α-melanocyte stimulating hormone- or forskolin-induced increases in melanogenesis, suggesting an action on the cAMP-dependent melanogenic pathway. Co-incubation with chenodeoxycholic acid, a well-known farnesoid-X receptor agonist, did not affect IBMX-induced melanogenesis. These results suggest that guggulsterone exerts a melanogenic inhibitory effect through the downregulation of tyrosinase expression.