title: Radiation sources providing increased UVA/UVB ratios attenuate the apoptotic effects of the UVB waveband UVA-dose-dependently in hairless mouse skin.
abstract: UV radiation-induced epidermal apoptotic sunburn cells provide a mechanism for eliminating cells with irreparable DNA damage. The UVB (290-320 nm) waveband is mainly responsible, but the role of UVA (320-400 nm) is less clear, and possible waveband interactions have not been examined. Recent studies in mice reveal a protective role for UVA against UVB-induced inflammation and immunosuppression, mediated via cutaneous heme oxygenase (HO). As HO has antiapoptotic properties in other tissues, this study examines the effect of UVA/UVB waveband interaction on apoptosis in the Skh:hr-1 hairless mouse epidermis. Apoptosis was assessed by sunburn cell number, caspase-3-positive cell number, and degree of DNA fragmentation, in mice exposed to radiation sources providing a constant UVB dose with increasing proportions of UVA. The results indicated that as the UVA/UVB ratio was increased, both the sunburn cell and caspase-3-positive cell number decreased, and the degree of DNA fragmentation was reduced. Treatment of mice with the HO inhibitor, tin protoporphyrin-IX, markedly reduced the UVA antiapoptotic effect, confirming a major role for HO. The observations suggest that UVA reduces UVB-induced DNA damage, and may therefore have anti-photocarcinogenic properties that could be harnessed for better photoprotection in humans.
authors.affiliation: Faculty of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ibuki
authors.forename: Munif
authors.initials: M
authors.lastname: Allanson
authors.forename: Katie M
authors.initials: KM
authors.lastname: Dixon
authors.forename: Vivienne E
authors.initials: VE
authors.lastname: Reeve
mesh_terms: D000818:Animals; D017209:Apoptosis; D002273:Carcinogens / Q000737:chemistry; D053148:Caspase 3 / Q000378:metabolism; D004249:DNA Damage; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004817:Epidermis / Q000378:metabolism; D005260:Female; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D051379:Mice; D012867:Skin / Q000378:metabolism* / Q000528:radiation effects*; D013471:Sunburn; D014466:Ultraviolet Rays
chemical_list: D002273:Carcinogens; D004791:Enzyme Inhibitors; D006419:Heme Oxygenase (Decyclizing); D053148:Caspase 3