Mengeaud V, Ortonne J P
INSERM U.385, Faculté de Médecine, Nice, France.
Pigment Cell Res. 1994 Aug;7(4):245-54. doi: 10.1111/j.1600-0749.1994.tb00059.x.
Melanogenesis in melanoma cells can be enhanced by psoralens in the absence of UV light. Melanin biosynthesis is regulated by a number of melanocyte-specific proteins, including tyrosinase, DOPAchrome tautomerase (DCT), and tyrosinase-related protein-1 (TRP-1, gp75). To get more insight on the molecular mechanisms involved in psoralens-induced melanogenesis, we determined tyrosinase and DCT activities as well as mRNA and protein levels of tyrosinase, DCT, and TRP-1 in S91 mouse melanoma cells treated by 5-MOP. High concentration of 5-MOP (5 x 10(-5) M) induced a time-dependent increase of tyrosinase activity and melanin content, which was correlated to an increase of both mRNA and protein levels of tyrosinase. These results demonstrate that the 5-MOP stimulation of melanogenesis is related to increased tyrosinase synthesis. In addition, 5-MOP stimulated TRP-1 synthesis and induced a dose-dependent decrease of DCT activity without any modification in the expression of the protein. We explored then the signalling pathways involved in 5-MOP-induced melanogenesis and, particularly, the role of cyclic AMP and protein kinase C (PKC). A small stimulation of cyclic AMP production was observed in presence of 5-MOP. Furthermore, 1-oleoyl-2-acetylglycerol (OAG), a PKC activator, potentiated the 5-MOP stimulation of tyrosinase activity, while calphostin, a specific PKC inhibitor, inhibited the 5-MOP induction of tyrosinase activity. Phorbol-myristate acetate (PMA), described as a strong activator of PKC, inhibited also the effect of 5-MOP when used at long term. Taken together, these results demonstrate that in murine melanoma cells 5-MOP stimulates melanogenesis by increasing activity and synthesis of tyrosinase. Tyrosinase and TRP-1 expression are coordinately regulated by 5-MOP. Furthermore, a negative correlation between melanogenesis and DCT activity was observed under 5-MOP stimulation. At least, PKA and PKC systems appear to play an important role in the melanogenic effect of 5-MOP.
在没有紫外线的情况下，补骨脂素可增强黑色素瘤细胞中的黑色素生成。黑色素生物合成受多种黑素细胞特异性蛋白调控，包括酪氨酸酶、多巴色素互变异构酶（DCT）和酪氨酸酶相关蛋白1（TRP - 1，gp75）。为了更深入了解补骨脂素诱导黑色素生成所涉及的分子机制，我们测定了经5 - MOP处理的S91小鼠黑色素瘤细胞中酪氨酸酶和DCT的活性以及酪氨酸酶、DCT和TRP - 1的mRNA和蛋白水平。高浓度的5 - MOP（5×10⁻⁵ M）诱导酪氨酸酶活性和黑色素含量随时间增加，这与酪氨酸酶的mRNA和蛋白水平增加相关。这些结果表明，5 - MOP对黑色素生成的刺激与酪氨酸酶合成增加有关。此外，5 - MOP刺激TRP - 1合成并诱导DCT活性呈剂量依赖性降低，而蛋白表达无任何改变。然后我们探究了5 - MOP诱导黑色素生成所涉及的信号通路，特别是环磷酸腺苷（cAMP）和蛋白激酶C（PKC）的作用。在5 - MOP存在的情况下观察到cAMP产生有轻微刺激。此外，PKC激活剂1 - 油酰 - 2 - 乙酰甘油（OAG）增强了5 - MOP对酪氨酸酶活性的刺激，而PKC特异性抑制剂钙泊三醇抑制了5 - MOP对酪氨酸酶活性的诱导。长期使用时，被描述为PKC强激活剂的佛波酯 - 肉豆蔻酸乙酸酯（PMA）也抑制了5 - MOP的作用。综上所述，这些结果表明，在小鼠黑色素瘤细胞中，5 - MOP通过增加酪氨酸酶的活性和合成来刺激黑色素生成。5 - MOP协同调节酪氨酸酶和TRP - 1的表达。此外，在5 - MOP刺激下观察到黑色素生成与DCT活性之间呈负相关。至少，蛋白激酶A（PKA）和PKC系统似乎在5 - MOP的黑色素生成作用中起重要作用。
