Diarylpropionitrile inhibits melanogenesis via protein kinase A/cAMP-response element-binding protein/microphthalmia-associated transcription factor signaling pathway in a-MSH-stimulated B16F10 melanoma cells

Diarylpropionitrile (DPN), a selective agonist for estrogen receptor I3 (ERI3), has been reported to regulate various hormonal responses through activation of ERI3 in tissues including the mammary gland and brain. However, the effect of DPN on melanogenesis independent of ERI3 has not been studied. The aim of this study is to examine the possibility of anti-melanogenic effect of DPN and its underlying mechanism. Melanin contents and cellular tyrosinase activity assay indicated that DPN inhibited melanin biosynthesis in alpha-melanocyte stimulating hormonestimulated B16F10 melanoma cell line. However, DPN had no direct influence on in vitro tyrosinase catalytic activity. On the other hand, 17I3-estradiol had no effect on inhibition of melanogenesis, suggesting that the DPN-mediated suppression of melanin production was not related with estrogen signaling pathway. Immunoblotting analysis showed that DPN down-regulated the expression of microphthalmiaassociated transcription factor (MITF), a central transcription factor of melanogenesis and its down-stream genes including tyrosinase, tyrosinase-related protein (TRP)1, and TRP-2. Also, DPN attenuated the phosphorylation of protein kinase A (PKA) and cAMP-response element-binding protein (CREB). Additionally, DPN suppressed the melanin synthesis in UVB-irradiated HaCaT conditioned media culture system suggesting that DPN has potential as an anti-melanogenic activity in physiological conditions. Collectively, our data show that DPN inhibits melanogenesis via downregulation of PKA/CREB/MITF signaling pathway.