Topical trans-4-aminomethylcyclohexanecarboxylic acid prevents ultravioletradiation-induced pigmentation

We have studied the effect of a plasmin inhibitor, trans-4-aminomethylcyclo hexanecarboxylic acid (trans-AMCHA), on skin pigmentation induced by ultrav iolet (UV) exposure in Weiser-Maples guinea pigs. When guinea pigs are expo sed to UV radiation (840 ml cm(-2)), skin pigmentation is clearly observed from seven days after exposure and continued to increase to 29 days. Post-e xposure applications of 2 and 3% solutions of trans-AMCHA to the exposed re gions prevent or inhibit the pigmentation process. When the skin is removed and stained by the Fontana-Masson method, melanin content in the basal lay er of UV-exposed epidermis is significantly reduced in the regions to which 2 and 3% trans-AMCHA solutions have been applied, compared with the vehicl e control. As plasmin is known to contribute to the release of arachidonic acid (AA) and the production of prostaglandins (PGs), we have examined the effects of trans-AMCHA on AA-induced pigmentation in guinea pig skin. Topic al application of trans-AMCHA causes a dose-dependent decrease in AA-induce d pigmentation. These results suggest that trans-AMCHA reduces melanocyte t yrosinase activity by suppressing the production of PGs, UV-induced melanog ens, through the suppression of the UV-induced increase in epidermal plasmi n activity. (C) 1998 Elsevier Science S.A. All rights reserved.