title: Pigmented melanocytes are protected against ultraviolet-A-induced membrane damage.
abstract: The dominant skin pigment melanin is believed to protect human skin against several harmful effects of ultraviolet radiation. It is not clear, however, how melanin located inside melanin-producing melanocytes modulates the effect of ultraviolet radiation on melanocytes themselves. We have determined membrane damage in pigmented and unpigmented albino mouse melanocytes after ultraviolet A radiation, which is suspected to induce melanoma. Unpigmented cells were much more susceptible to ultraviolet-A-induced membrane permeability than pigmented cells. Unpigmented cells were also more susceptible to ultraviolet-A-induced lipid peroxidation than strongly pigmented cells. Furthermore, unpigmented cells were much more susceptible to ultraviolet-A-induced depletion of glutathione than pigmented cells. Reduced glutathione is known to be a major antioxidant of unpigmented skin cells such as fibroblasts and keratinocytes. To examine whether or not glutathione is also a major antioxidant in melanocytes, melanocytes were depleted of glutathione by means of buthionine sulfoximine. We found that depletion of glutathione in pigmented melanocytes did not change lipid damage induced by ultraviolet A radiation. In unpigmented melanocytes, however, depletion of glutathione significantly increased lipid damage induced by ultraviolet A radiation. Thus, pigmented melanocytes apparently contain antioxidants more potent than glutathione, protecting them from ultraviolet-A-induced membrane damage.
authors.affiliation: Department of Biophysics, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway. egil.kvam@labmed.uio.no
authors.forename: Egil
authors.initials: E
authors.lastname: Kvam
authors.forename: Jostein
authors.initials: J
authors.lastname: Dahle
mesh_terms: D000417:Albinism; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000528:radiation effects; D005978:Glutathione / Q000378:metabolism; D015227:Lipid Peroxidation / Q000528:radiation effects; D008543:Melanins / Q000096:biosynthesis; D008544:Melanocytes / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D017382:Reactive Oxygen Species / Q000378:metabolism; D012880:Skin Pigmentation / Q000528:radiation effects*; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014443:Tyrosine / Q000494:pharmacology; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D008543:Melanins; D017382:Reactive Oxygen Species; D017392:Thiobarbituric Acid Reactive Substances; D014443:Tyrosine; D005978:Glutathione