title: Inhibition of melanogenesis in response to oxidative stress: transient downregulation of melanocyte differentiation markers and possible involvement of microphthalmia transcription factor.
abstract: H(2)O(2) and other reactive oxygen species are key regulators of many intracellular pathways. Within mammalian skin, H(2)O(2) is formed as a byproduct of melanin synthesis, and following u.v. irradiation. We therefore analyzed its effects on melanin synthesis. The activity of the rate-limiting melanogenic enzyme, tyrosinase, decreased in H(2)O(2)-treated mouse and human melanoma cells. This inhibition was concentration- and time-dependent in the B16 melanoma model. Maximal inhibition (50-75%) occurred 8-16 hours after a 20 minute exposure to 0.5 mM H(2)O(2). B16 cells withstand this treatment adequately, as shown by a small effect on glutathione levels and a rapid recovery of basal lipid peroxidation levels. Enzyme activities also recovered, beginning to increase 16-20 hours after the treatment. Inhibition of enzyme activities reflected decreased protein levels. mRNAs for tyrosinase, tyrosinase-related protein 1, dopachrome tautomerase, silver protein and melanocortin 1 receptor also decreased after H(2)O(2) treatment, and recovered at different rates. Downregulation of melanocyte differentiation markers mRNAs was preceded by a decrease in microphthalmia transcription factor (Mitf) gene expression, which was quantitatively similar to the decrease achieved using 12-O-tetradecanoylphorbol-13-acetate. Recovery of basal Mitf mRNA levels was also observed clearly before that of tyrosinase. Therefore, oxidative stress may lead to hypopigmentation by mechanisms that include a microphthalmia-dependent downregulation of the melanogenic enzymes.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia, Apto 4021, Campus de Espinardo, 30100 Murcia, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Jiménez-Cervantes
authors.forename: M
authors.initials: M
authors.lastname: Martínez-Esparza
authors.forename: C
authors.initials: C
authors.lastname: Pérez
authors.forename: N
authors.initials: N
authors.lastname: Daum
authors.forename: F
authors.initials: F
authors.lastname: Solano
authors.forename: J C
authors.initials: JC
authors.lastname: García-Borrón
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects; D008543:Melanins / Q000378:metabolism; D008544:Melanocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008545:Melanoma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor; D014442:Monophenol Monooxygenase / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects; D010088:Oxidoreductases; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors; D014407:Tumor Cells, Cultured; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D015415:Biomarkers; D004268:DNA-Binding Proteins; C497234:MITF protein, human; D008543:Melanins; D008562:Membrane Glycoproteins; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D011506:Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D014446:Tyrosine 3-Monooxygenase; C489799:TYRP1 protein, human; C079621:Tyrp1 protein, mouse; C064056:tyrosinase-related protein-1; D014442:Monophenol Monooxygenase; D005978:Glutathione