Depigmenting mechanisms of all-trans retinoic acid and retinol on B16 melanoma cells.

We assessed the effects of ATRA and retinol on melanogenesis in murine B16 melanoma cells. In the present study, ATRA and retinol inhibited melanin synthesis in melanoma cells stimulated by alpha-melanocyte stimulating hormone (alpha-MSH) or 3-isobutyl-1-methylxanthine (IBMX). To elucidate the target points of ATRA and retinol on melanogenesis, we performed western blotting for melanogenic proteins, such as tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2. ATRA inhibited the expression of tyrosinase and TRP-1, and retinol inhibited the expression of tyrosinase, in a dose-dependent manner. Neither ATRA nor retinol inhibited TRP-2 expression. There were no differences in melanogenic protein expression between the two stimulants tested, alpha-MSH and IBMX. Therefore, the depigmenting effect of ATRA and retinol might be due to inhibition of the signaling pathway between cAMP and tyrosinase transcription bound to tyrosinase expression. These results indicate that ATRA and retinol are candidate anti-melanogenic agents that they might be effective in hyperpigmentation disorders.