title: Retinoic acid as modulator of UVB-induced melanocyte differentiation. Involvement of the melanogenic enzymes expression.
abstract: Retinoic acid (RA) is a hormone-like agent involved in the control of cell differentiation. The most characteristic feature of melanocyte differentiation, melanogenesis, is stimulated by UV radiations. Excessive chronic sun exposure results in irregular skin hypermelanosis that can be partially corrected by topical RA. The basic mechanisms underlying this effect of RA are unknown. To determine whether RA can directly modulate excessive melanin synthesis, we analyzed the in vitro effect of cis- and trans-RA on UVB-induced melanogenesis in S91 mouse melanoma cells and in normal human melanocytes (NHM). In both cells types, the two RA isoforms significantly decreased the UVB-stimulated melanogenesis in term of tyrosinase activity and melanin neosynthesis. To correlate changes in melanogenesis with the expression of melanogenic enzymes, we determined the neosynthesis rate of tyrosinase, tyrosinase-related protein-1 (TRP-1/gp 75) and tyrosinase-related protein-2 (TRP-2/DOPAchrome tautomerase). Here we show that UVB-induced melanogenesis in NHM is related to an increased synthesis of tyrosinase and TRP-1 and to a dramatic decrease of TRP-2 expression. RA inhibition of UVB-induced melanogenesis acts at the post-transcriptional level leading to a decreased tyrosinase and TRP-1 synthesis. We also show that in NHM, inhibition of TRP-2 following UVB-treatment is significantly reversed by RA. This demonstrates a negative correlation between melanogenesis and TRP-2 expression.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Unité U.385, Faculté de Médecine, Nice, France.
authors.forename: C
authors.initials: C
authors.lastname: Roméro
authors.forename: E
authors.initials: E
authors.lastname: Aberdam
authors.forename: C
authors.initials: C
authors.lastname: Larnier
authors.forename: J P
authors.initials: JP
authors.lastname: Ortonne
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000528:radiation effects; D004790:Enzyme Induction / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D019746:Intramolecular Oxidoreductases; D007535:Isomerases / Q000096:biosynthesis*; D008543:Melanins / Q000096:biosynthesis*; D008544:Melanocytes / Q000187:drug effects* / Q000201:enzymology / Q000528:radiation effects*; D008546:Melanoma, Experimental / Q000473:pathology; D008562:Membrane Glycoproteins; D051379:Mice; D014442:Monophenol Monooxygenase / Q000096:biosynthesis*; D010088:Oxidoreductases; D014176:Protein Biosynthesis; D012867:Skin / Q000166:cytology; D014212:Tretinoin / Q000494:pharmacology*; D014466:Ultraviolet Rays
chemical_list: D008543:Melanins; D008562:Membrane Glycoproteins; D014212:Tretinoin; D010088:Oxidoreductases; C489799:TYRP1 protein, human; C079621:Tyrp1 protein, mouse; C064056:tyrosinase-related protein-1; D014442:Monophenol Monooxygenase; D007535:Isomerases; D019746:Intramolecular Oxidoreductases; C042501:dopachrome isomerase