Stimulation of melanogenesis by scoparone in B16 melanoma cells

Aim： The effect of coumarin derivatives on melanogenesis was investigated in B16 murine melanoma cells. Methods： Melanin content and tyrosinase activity were analyzed spectrophotometrically. The expression of tyrosinase, tyrosinaserelated protein-1 （TRP-1） and tyrosinase-related protein-2 （TRP-2） were measured either by reverse transcription-polymerase chain reaction （RT-PCR） or Western blot. Results： Among the coumarin derivatives studied, scoparone （6,7- dimethoxycoumarin） was the most potent; the 6- or 7-methoxy group was found to be essential for the stimulation of melanogenesis. The melanin content was greatly increased by scoparone in a dose-dependent manner; there was no cytotoxicity at the effective concentrations. Scoparone increased enzyme activity as well as protein and mRNA expression of tyrosinase. In addition, mRNA of TRP-1 and TRP-2 were also increased after treatment with scoparone. H-89, an inhibitor of protein kinase A （PKA）, completely inhibited the scoparone-induced increase of melanogenesis and the tyrosinase protein. Conclusion： These results suggest that scoparone-induced stimulation of melanogenesis is likely to occur at the transcriptional level of melanogenesis-related enzymes through PKA signaling.