α-Methyl-p-Tyrosine Inhibits Latanoprost-Induced Melanogenesis In Vitro

Abstract

The PGF2α derivative, latanoprost, is a recent anti-glaucoma drug that has been reported to induce a discrete incidence of increased iris pigmentation in men. The present experiments were made in order to study whether this phenomenon could be influenced by the tyrosinase inhibitor, α-methyl-p-tyrosine. Melanin content, melanin production and tyrosinase activity of cultured uveal melanocytes derived from irides of brown or brown-blue color were measured after adding latanoprost at different molar concentration with or without α-methyl-p-tyrosine (10−5m). It was shown that latanoprost stimulated melanin content, melanin production and tyrosinase activity in a molar range between 10−7and 10−5min uveal melanocytes derived from irides of both brown and brown-blue color. The effect seemed to be more pronounced in melanocytes derived from irides of brown-blue color. The adding of α-methyl-p-tyrosine completely prevented latanoprost-induced stimulation of melanin production in uveal melanocytes derived from irides of both colors. These results suggest that latanoprost-induced stimulation of melanin production, follows the metabolic pathway involving tyrosinase activity and may be relevant for the therapeutic application of latanoprost in glaucoma in order to reduce its side-effect resulting in increased iris pigmentation.