title: Investigation of the role of extracellular H2O2 and transition metal ions in the genotoxic action of ascorbic acid in cell culture models.
abstract: In the presence of oxygen, ascorbic acid (AA) is unstable in aqueous media and oxidises to dehydroascorbate (DHA), generating reactive intermediates such as ascorbate free radical and H2O2. It is proposed that the cytotoxicity of AA is due to the extracellular production of H2O2 and that this is mediated by transition metal ions present in cell media. Here we investigate the role of extracellular H2O2 and metal ions in the genotoxicity of AA in cell culture models. Our preliminary results confirmed that physiological concentrations of AA were not toxic to confluent human fibroblasts, although they inhibited the proliferation of cells at low density. No inhibition was observed with ascorbic acid 2-phosphate (AA2P), a vitamin C derivative that remains stable in culture media. Furthermore, high concentrations of AA induced DNA strand breakage in a dose-dependent manner, whereas DHA and AA2P were not genotoxic. The genotoxic effect of AA was transient, required the formation of extracellular H2O2 and the presence of intracellular iron, but not of extracellular transition metal ions. These observations further clarify the pro-oxidant effect of AA solutions in cell culture models. The possibility that intravenous administration of high-dose AA may cause a similar genotoxic effect in vivo is discussed.
authors: Radiation and Oxidative Stress Group, Department of Cancer Studies and Molecular Medicine, Biocentre, University of Leicester, Leicester LE1 7RH, UK. td13@le.ac.uk
authors: Tiago L
authors: TL
authors: Duarte
authors: Gabriela M
authors: GM
authors: Almeida
authors: George D D
authors: GD
authors: Jones
mesh_terms: D001205:Ascorbic Acid / Q000633:toxicity*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000187:drug effects* / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D009153:Mutagens / Q000633:toxicity*; D028561:Transition Elements / Q000378:metabolism
chemical_list: D008670:Metals; D009153:Mutagens; D028561:Transition Elements; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid