Inhibition of melanogenesis in response to oxidative stress: transient downregulation of melanocyte differentiation markers and possible involvement of microphthalmia transcription factor.
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.
Jiménez-Cervantes
C
C
Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia, Apto 4021, Campus de Espinardo, 30100 Murcia, Spain.
Martínez-Esparza
M
M
Pérez
C
C
Daum
N
N
Solano
F
F
García-Borrón
J C
JC
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
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