title: Characterization of DNA damage inflicted by free radicals from a mutagenic sunscreen ingredient and its location using an in vitro genetic reversion assay.
abstract: We describe an in vitro approach to assessing the potential genotoxicity of illuminated sunscreens. The photomutagenic sunscreen Padimate-O attacks DNA on illumination with simulated sunlight, producing strand breaks and lesions that are labile to N,N'-dimethylethylenediamine but few, if any, cyclobutane dimers or other direct photoproducts. The damage can be completely suppressed by the free radical quenchers Tris, ethanol, mannitol and dimethylsulfoxide, which is commonly used as a solvent in conventional photomutagenicity assays. Using a genetic reversion assay that depends on regenerating beta-galactosidase activity in photodamaged plasmids we find that GC base pairs are particularly susceptible to attack by Padimate-O.
authors.affiliation: Department of Biochemistry, University of Oxford, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: McHugh
authors.forename: J
authors.initials: J
authors.lastname: Knowland
mesh_terms: D010129:4-Aminobenzoic Acid / Q000737:chemistry / Q000633:toxicity; D001483:Base Sequence; D004249:DNA Damage; D016166:Free Radical Scavengers / Q000494:pharmacology; D005609:Free Radicals / Q000737:chemistry / Q000633:toxicity*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010777:Photochemistry; D010957:Plasmids / Q000187:drug effects / Q000235:genetics; D013473:Sunscreening Agents / Q000737:chemistry / Q000633:toxicity*; D062366:para-Aminobenzoates
chemical_list: D016166:Free Radical Scavengers; D005609:Free Radicals; D013473:Sunscreening Agents; D062366:para-Aminobenzoates; D010129:4-Aminobenzoic Acid; C041981:padimate-O