title: The inhibitory effect of glycolic acid and lactic acid on melanin synthesis in melanoma cells.
abstract: Alpha-hydroxy acids (AHAs) such as glycolic acid (GA) and lactic acid (LA) have been reported to be effective in treating pigmentary lesions such as melasma, solar lentigines, and postinflammatory hyperpigmentation. The mechanism of this effect might be due to epidermal remodeling and accelerated desquamation, which would result in quick pigment dispersion. However, the direct effect of AHAs on melanin synthesis has not yet been well studied. To elucidate such a direct effect of AHAs on melanogenesis, we performed melanin assays, growth curve determinations, Northern and Western blotting for melanogenic proteins [tyrosinase, tyrosinase related protein (TRP)-1 and TRP-2], and tyrosinase and, 4-dihydroxyphenylalaninechrome tautomerase enzyme activity assays using mouse B16 and human melanoma cells. GA or LA (at doses of 300 or 500 microg/ml) inhibited melanin formation in similar dose-dependent manner, without affecting cell growth. Although the mRNA and protein expression or molecular size of tyrosinase, TRP-1 and TRP-2 were not affected, tyrosinase activity was inhibited. To see whether GA and/or LA directly inhibit tyrosinase catalytic function, the effect of GA and LA on human tyrosinase purified from the melanosome-rich large granule fraction of human melanoma cells was performed. GA or LA were shown to inhibit tyrosinase enzyme activity directly, but this effect was not due to the acidity of GA or LA, because adjusting the pH to 5.6 (the pH of GA and LA at concentrations of 2500 microg/ml), did not affect tyrosinase activity. Taken together, these results show that GA and LA suppress melanin formation by directly inhibiting tyrosinase activity, an effect independent of their acidic nature. GA and LA might work on pigmentary lesions not only by accelerating the turnover of the epidermis but also by directly inhibiting melanin formation in melanocytes.
authors.affiliation: Division of Dermatology, Department of Clinical and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Usuki
authors.forename: Akiko
authors.initials: A
authors.lastname: Ohashi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Sato
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Ochiai
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Ichihashi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Funasaka
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002455:Cell Division; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D006016:Glycolates / Q000494:pharmacology*; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000378:metabolism; D019344:Lactic Acid / Q000494:pharmacology*; D008543:Melanins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D006016:Glycolates; D008543:Melanins; C031149:glycolic acid; D019344:Lactic Acid; D014442:Monophenol Monooxygenase; D019746:Intramolecular Oxidoreductases; C042501:dopachrome isomerase