title: 7-Dehydrocholesterol enhances ultraviolet A-induced oxidative stress in keratinocytes: roles of NADPH oxidase, mitochondria, and lipid rafts.
abstract: Long wavelength solar UVA radiation stimulates formation of reactive oxygen species (ROS) and prostaglandin E(2) (PGE(2)), which are involved in skin photosensitivity and tumor promotion. High levels of 7-dehydrocholesterol (7-DHC), the precursor to cholesterol, cause exaggerated photosensitivity to UVA in patients with Smith-Lemli-Opitz syndrome (SLOS). Partially replacing cholesterol with 7-DHC in keratinocytes rapidly (<5 min) increased UVA-induced ROS, intracellular calcium, phospholipase A(2) activity, PGE(2), and NADPH oxidase activity. UVA-induced ROS and PGE(2) production were inhibited in these cells by depleting the Nox1 subunit of NADPH oxidase using siRNA or using a mitochondrial radical quencher, MitoQ. Partial replacement of cholesterol with 7-DHC also disrupted membrane lipid raft domains, although depletion of cholesterol, which also disrupts lipid rafts, did not affect UVA-induced increases in ROS and PGE(2). Phospholipid liposomes containing 7-DHC were more rapidly oxidized by a free radical mechanism than those containing cholesterol. These results indicate that 7-DHC enhances rapid UVA-induced ROS and PGE(2) formation by enhancing free radical-mediated membrane lipid oxidation and suggests that this mechanism might underlie the UVA photosensitivity in SLOS.
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Thier-224, 55 Fruit Street, Boston, MA 02114, USA.
authors.forename: Antonio
authors.initials: A
authors.lastname: Valencia
authors.forename: Anpuchchelvi
authors.initials: A
authors.lastname: Rajadurai
authors.forename: A Bjorn
authors.initials: AB
authors.lastname: Carle
authors.forename: Irene E
authors.initials: IE
authors.lastname: Kochevar
mesh_terms: D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D003684:Dehydrocholesterols / Q000494:pharmacology*; D015232:Dinoprostone / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000528:radiation effects*; D008055:Lipids / Q000737:chemistry*; D008081:Liposomes; D021962:Membrane Microdomains; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010743:Phospholipids / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D019082:Smith-Lemli-Opitz Syndrome / Q000378:metabolism / Q000473:pathology; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D003684:Dehydrocholesterols; D008055:Lipids; D008081:Liposomes; D010743:Phospholipids; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D002784:Cholesterol; C016705:7-dehydrocholesterol; D019255:NADPH Oxidases; D015232:Dinoprostone; D002118:Calcium