Elucidation of ultraviolet radiation-induced physiological degradation pathway of eumelanin and pheomelanin

黑色素分为黑色真黑素和红色褐黑素。我们的研究旨在阐明紫外线诱导的两种黑色素的生理降解。以人的黑发和红发为研究对象，发现真黑素降解为PTCA（吡咯-2，3，5-三羧酸），而褐黑素则由苯并噻嗪结构转变为苯并噻唑结构。接下来，使用小鼠毛发和人类毛发以及合成的真黑素和褐黑素，我们发现UVA照射后黑色素的结构发生了类似的变化。最后，使用培养的黑素细胞和视网膜色素上皮细胞，我们表明，真黑素引起UVA或可见光照射后的交联结构。

Melanin is classified into black eumelanin and reddish pheomelanin. Our study aimed at elucidating UV-induced physiological degradation of both melanins. Using human black hair and red hair, we found that eumelanin is degraded to give PTCA (pyrrole-2,3,5-tricarboxylic acid) while pheomelanin is changed from benzothiazine to benzothiazole structure. Next, using mouse hair and human hair and synthetic eumelanin and pheomelanin, we found similar changes in structure of melanin upon UVA irradiation. Finally, using cultured melanocytes and retinal pigment epithelial cells, we showed that eumelanin gives rise to cross-linking structure upon UVA or visible light irradiation.