7-Dehydrocholesterol enhances ultraviolet A-induced oxidative stress in keratinocytes: roles of NADPH oxidase, mitochondria, and lipid rafts.
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.
Valencia
Antonio
A
Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Thier-224, 55 Fruit Street, Boston, MA 02114, USA.
Rajadurai
Anpuchchelvi
A
Carle
A Bjorn
AB
Kochevar
Irene E
IE
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*
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