title: The formation of DNA single-strand breaks and alkali-labile sites in human blood lymphocytes exposed to 365-nm UVA radiation.
abstract: The potency of UVA radiation, representing 90% of solar UV light reaching the earth's surface, to induce human skin cancer is the subject of continuing controversy. This study was undertaken to investigate the role of reactive oxygen species in DNA damage produced by the exposure of human cells to UVA radiation. This knowledge is important for better understanding of UV-induced carcinogenesis. We measured DNA single-strand breaks and alkali-labile sites in human lymphocytes exposed ex vivo to various doses of 365-nm UV photons compared to X-rays and hydrogen peroxide using the comet assay. We demonstrated that the UVA-induced DNA damage increased in a linear dose-dependent manner. The rate of DNA single-strand breaks and alkali-labile sites after exposure to 1J/cm(2) was similar to the rate induced by exposure to 1 Gy of X-rays or 25 μM hydrogen peroxide. The presence of either the hydroxyl radical scavenger dimethyl sulfoxide or the singlet oxygen quencher sodium azide resulted in a significant reduction in the UVA-induced DNA damage, suggesting a role for these reactive oxygen species in mediating UVA-induced DNA single-strand breaks and alkali-labile sites. We also showed that chromatin relaxation due to hypertonic conditions resulted in increased damage in both untreated and UVA-treated cells. The effect was the most significant in the presence of 0.5M Na(+), implying a role for histone H1. Our data suggest that the majority of DNA single-strand breaks and alkali-labile sites after exposure of human lymphocytes to UVA are produced by reactive oxygen species (the hydroxyl radical and singlet oxygen) and that the state of chromatin may substantially contribute to the outcome of such exposures.
authors.affiliation: Burnasyan Federal Medical Biophysical Center, Federal Medical Biological Agency, Moscow 123182, Russia; Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow 119991, Russia.
authors.forename: Andreyan N
authors.initials: AN
authors.lastname: Osipov
authors.affiliation: Burnasyan Federal Medical Biophysical Center, Federal Medical Biological Agency, Moscow 123182, Russia.
authors.forename: Nadezhda M
authors.initials: NM
authors.lastname: Smetanina
authors.affiliation: Burnasyan Federal Medical Biophysical Center, Federal Medical Biological Agency, Moscow 123182, Russia.
authors.forename: Margarita V
authors.initials: MV
authors.lastname: Pustovalova
authors.affiliation: Burnasyan Federal Medical Biophysical Center, Federal Medical Biological Agency, Moscow 123182, Russia; Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow 119991, Russia.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Arkhangelskaya
authors.affiliation: Chalk River Laboratories, Atomic Energy of Canada Limited, Chalk River, ON K0J1P0, Canada. Electronic address: klokovd@aecl.ca.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Klokov
mesh_terms: D000328:Adult; D063646:Carcinogenesis / Q000528:radiation effects; D002478:Cells, Cultured; D002843:Chromatin / Q000235:genetics; D020552:Comet Assay; D004247:DNA / Q000187:drug effects / Q000528:radiation effects; D053904:DNA Breaks, Single-Stranded / Q000187:drug effects* / Q000528:radiation effects*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers / Q000494:pharmacology; D006657:Histones / Q000235:genetics; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects*; D008214:Lymphocytes / Q000528:radiation effects; D008297:Male; D019810:Sodium Azide / Q000494:pharmacology*; D013472:Sunlight / Q000009:adverse effects; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014965:X-Rays / Q000009:adverse effects; D055815:Young Adult
chemical_list: D002843:Chromatin; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D006657:Histones; D004247:DNA; D019810:Sodium Azide; D006861:Hydrogen Peroxide; D004121:Dimethyl Sulfoxide
keywords: Comet assay; DNA single-stand breaks; Dose response; Free radicals; Human blood lymphocytes; UVA radiation