title: Enzymatic recognition of DNA damage induced by UVB-photosensitized titanium dioxide and biological consequences in Saccharomyces cerevisiae: evidence for oxidatively DNA damage generation.
abstract: Although titanium dioxide (TiO(2)) has been considered to be biologically inert, finding use in cosmetics, paints and food colorants, recent reports have demonstrated that when TiO(2) is attained by UVA radiation oxidative genotoxic and cytotoxic effects are observed in living cells. However, data concerning TiO(2)-UVB association is poor, even if UVB radiation represents a major environmental carcinogen. Herein, we investigated DNA damage, repair and mutagenesis induced by TiO(2) associated with UVB irradiation in vitro and in vivo using Saccharomyces cerevisiae model. It was found that TiO(2) plus UVB treatment in plasmid pUC18 generated, in addition to cyclobutane pyrimidine dimers (CPDs), specific damage to guanine residues, such as 8-oxo-7,8-dihydroguanine (8-oxoG) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG), which are characteristic oxidatively generated lesions. In vivo experiments showed that, although the presence of TiO(2) protects yeast cells from UVB cytotoxicity, high mutation frequencies are observed in the wild-type (WT) and in an ogg1 strain (deficient in 8-oxoG and FapyG repair). Indeed, after TiO(2) plus UVB treatment, induced mutagenesis was drastically enhanced in ogg1 cells, indicating that mutagenic DNA lesions are repaired by the Ogg1 protein. This effect could be attenuated by the presence of metallic ion chelators: neocuproine or dipyridyl, which partially block oxidatively generated damage occurring via Fenton reactions. Altogether, the results indicate that TiO(2) plus UVB potentates UVB oxidatively generated damage to DNA, possibly via Fenton reactions involving the production of DNA base damage, such as 8-oxo-7,8-dihydroguanine.
authors.affiliation: Laboratório de Diagnóstico Molecular e Hematologia, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde - Ilha do Fundão, CEP 21941-540, Rio de Janeiro, Brazil. alicia.pinto@incqs.fiocruz.br
authors.forename: A Viviana
authors.initials: AV
authors.lastname: Pinto
authors.forename: Elder L
authors.initials: EL
authors.lastname: Deodato
authors.forename: Janine S
authors.initials: JS
authors.lastname: Cardoso
authors.forename: Eliza F
authors.initials: EF
authors.lastname: Oliveira
authors.forename: Sérgio L
authors.initials: SL
authors.lastname: Machado
authors.forename: Helena K
authors.initials: HK
authors.lastname: Toma
authors.forename: Alvaro C
authors.initials: AC
authors.lastname: Leitão
authors.forename: Marcelo
authors.initials: M
authors.lastname: de Pádula
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000235:genetics; D009154:Mutation; D018384:Oxidative Stress / Q000235:genetics*; D010787:Photosensitivity Disorders; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics; D014025:Titanium / Q000633:toxicity*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: C009495:titanium dioxide; D000080242:8-Hydroxy-2'-Deoxyguanosine; D014025:Titanium; D003849:Deoxyguanosine