title: Tyrosinase-catalyzed metabolism of rhododendrol (RD) in B16 melanoma cells: production of RD-pheomelanin and covalent binding with thiol proteins.
abstract: RS-4-(4-Hydroxyphenyl)-2-butanol (rhododendrol, RD) was reported to induce leukoderma of the skin. To explore the mechanism underlying that effect, we previously showed that oxidation of RD with mushroom tyrosinase produces RD-quinone, which is converted to secondary quinone products, and we suggested that those quinones are cytotoxic because they bind to cellular proteins and produce reactive oxygen species. We then confirmed that human tyrosinase can oxidize both enantiomers of RD. In this study, we examined the metabolism of RD in B16F1 melanoma cells in vitro. Using 4-amino-3-hydroxy-n-butylbenzene as a specific indicator, we detected moderate levels of RD-pheomelanin in B16F1 cells exposed to 0.3 to 0.5 mM RD for 72 h. We also confirmed the covalent binding of RD-quinone to non-protein thiols and proteins through cysteinyl residues. The covalent binding of RD-quinone to proteins was 20- to 30-fold greater than dopaquinone. These results suggest that the tyrosinase-induced metabolism of RD causes melanocyte toxicity.
authors.affiliation: Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan.
authors.forename: Shosuke
authors.initials: S
authors.lastname: Ito
authors.forename: Masae
authors.initials: M
authors.lastname: Okura
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nakanishi
authors.forename: Makoto
authors.initials: M
authors.lastname: Ojika
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Wakamatsu
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Yamashita
mesh_terms: D000143:Acids / Q000378:metabolism; D000818:Animals; D016227:Benzoquinones / Q000378:metabolism; D055162:Biocatalysis; D000440:Butanols / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D002396:Catechols / Q000378:metabolism; D002417:Cattle; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D017613:Iodine Compounds / Q000378:metabolism; D008543:Melanins / Q000378:metabolism*; D008544:Melanocytes / Q000187:drug effects; D008546:Melanoma, Experimental / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D051379:Mice; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D041681:NIH 3T3 Cells; D010084:Oxidation-Reduction; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D000143:Acids; D016227:Benzoquinones; D000440:Butanols; D002396:Catechols; D017613:Iodine Compounds; D008543:Melanins; D013438:Sulfhydryl Compounds; C018362:pheomelanin; C115945:rhododendrol; D012710:Serum Albumin, Bovine; D004295:Dihydroxyphenylalanine; C010466:hydroiodic acid; C035157:dopaquinone; D014442:Monophenol Monooxygenase; D005978:Glutathione; C034221:catechol
keywords: 4-(4-hydroxyphenyl)-2-butanol; cysteine; glutathione; melanocyte toxicity; rhododendrol; sulfhydryl group; whitening agent/ tyrosinase