title: Effects of ultraviolet light on melanocyte differentiation: studies with mouse neural crest cells and neural crest-derived cell lines.
abstract: To evaluate the etiologic role of ultraviolet (UV) radiation in acquired dermal melanocytosis (ADM), we investigated the effects of UVA and UVB irradiation on the development and differentiation of melanocytes in primary cultures of mouse neural crest cells (NCC) by counting the numbers of cells positive for KIT (the receptor for stem cell factor) and for the L-3,4-dihydroxyphenylalanine (DOPA) oxidase reaction. No significant differences were found in the number of KIT- or DOPA-positive cells between the UV-irradiated cultures and the non-irradiated cultures. We then examined the effects of UV light on KIT-positive cell lines derived from mouse NCC cultures. Irradiation with UVA but not with UVB inhibited the tyrosinase activity in a tyrosinase-positive cell line (NCCmelan5). Tyrosinase activity in the cells was markedly enhanced by treatment with alpha-melanocyte-stimulating hormone (alpha-MSH), but that stimulation was inhibited by UVA or by UVB irradiation. Irradiation with UVA or UVB did not induce tyrosinase activity in a tyrosinase-negative cell line (NCCmelb4). Levels of KIT expression in NCCmelan5 cells and in NCCmelb4 cells were significantly decreased after UV irradiation. Phosphorylation levels of extracellular signal-regulated kinase 1/2 in cells stimulated with stem cell factor were also diminished after UV irradiation. These results suggest that UV irradiation does not stimulate but rather suppresses mouse NCC. Thus if UV irradiation is a causative factor for ADM lesions, it would not act directly on dermal melanocytes but may act in indirect manners, for instance, via the overproduction of melanogenic cytokines such as alpha-MSH and/or endothelin-1.
authors.affiliation: Department of Dermatology, St Marianna University School of Medicine, Kawasaki, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Hosaka
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Soma
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kawa
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kaminaga
authors.forename: Kayoko
authors.initials: K
authors.lastname: Osumi
authors.forename: Shiho
authors.initials: S
authors.lastname: Ooka
authors.forename: Hidenori
authors.initials: H
authors.lastname: Watabe
authors.forename: Masaru
authors.initials: M
authors.lastname: Ito
authors.forename: Fumiko
authors.initials: F
authors.lastname: Murakami
authors.forename: Masako
authors.initials: M
authors.lastname: Mizoguchi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation; D002460:Cell Line; D002470:Cell Survival; D004396:Coloring Agents / Q000494:pharmacology; D004307:Dose-Response Relationship, Radiation; D019332:Endothelin-1 / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D008544:Melanocytes / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D014442:Monophenol Monooxygenase / Q000378:metabolism; D009432:Neural Crest / Q000166:cytology*; D010078:Oxazines; D010766:Phosphorylation; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D014466:Ultraviolet Rays; D014966:Xanthenes
chemical_list: D004396:Coloring Agents; D019332:Endothelin-1; D010078:Oxazines; D014966:Xanthenes; C005843:resazurin; D014442:Monophenol Monooxygenase; D019009:Proto-Oncogene Proteins c-kit; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases