title: Effect of UVA radiation on membrane fluidity and radical decay in human fibroblasts as detected by spin labeled stearic acids.
abstract: The ultraviolet A (UVA) radiation component of sunlight (320-400 nm) has been shown to be a source of oxidative stress to cells via generation of reactive oxygen species. We report here some consequences of the UVA irradiation on cell membranes detected by electron paramagnetic resonance (EPR) spectroscopy. Paramagnetic nitroxide derivatives of stearic acid bearing the monitoring group at different depths in the hydrocarbon chain were incorporated into human fibroblasts membranes to analyze two main characteristics: kinetics of the nitroxide reduction and membrane fluidity. These two characteristics were compared for control and UVA-irradiated (0-250 kJ/m(2)) cells. The term relative redox capacity (RRC) was introduced to characterize and to compare free radical reduction measured by EPR with some well-known viability/clonogenicity tests. Our results showed that UVA-irradiation produces a more rigid membrane structure, especially at higher doses. Furthermore, we found that trends agree in survival measured by neutral red (NR), trypan blue (TB), and clonogenic efficiency compared with RRC values measured by EPR for low and medium exposure doses. Above 100 kJ/m(2), differences between these tests were observed. Antioxidant effect was modeled by alpha-tocopherol-acetate treatment of the cells before UVA irradiation. While NR, TB and clonogenicity tests showed protection at the highest UVA doses (>100 kJ/m(2)), results obtained with EPR measurements, both membrane fluidity and kinetics, or using MTT test did not exhibit this protective effect.
authors.affiliation: Faculty of Medicine, Institute of Biophysics and Radiation Biology, Semmelweis University, Budapest VIII. PO Box 263, Puskin u. 9, Budapest 1444, Hungary.
authors.forename: Marianna
authors.initials: M
authors.lastname: Budai
authors.forename: Anne
authors.initials: A
authors.lastname: Reynaud-Angelin
authors.forename: Zsófia
authors.initials: Z
authors.lastname: Szabó
authors.forename: Sára
authors.initials: S
authors.lastname: Tóth
authors.forename: Györgyi
authors.initials: G
authors.lastname: Rontó
authors.forename: Evelyne
authors.initials: E
authors.lastname: Sage
authors.forename: Pál
authors.initials: P
authors.lastname: Gróf
mesh_terms: D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D005609:Free Radicals / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008560:Membrane Fluidity / Q000528:radiation effects*; D009589:Nitrogen Oxides / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D013113:Spin Labels; D013229:Stearic Acids / Q000378:metabolism*; D013696:Temperature; D014466:Ultraviolet Rays; D014810:Vitamin E / Q000494:pharmacology
chemical_list: D005609:Free Radicals; D009589:Nitrogen Oxides; D013113:Spin Labels; D013229:Stearic Acids; D014810:Vitamin E; C031183:stearic acid; C039900:nitroxyl