title: Induction of oxidative DNA damage by arsenite and its trivalent and pentavalent methylated metabolites in cultured human cells and isolated DNA.
abstract: Even though a well-known human carcinogen the underlying mechanisms of arsenic carcinogenicity are still not fully understood. For arsenite, proposed mechanisms are the interference with DNA repair processes and an increase in reactive oxygen species. Even less is known about the genotoxic potentials of its methylated metabolites monomethylarsonous [MMA(III)] and dimethylarsinous [DMA(III)] acid, monomethylarsonic [MMA(V)] and dimethylarsinic [DMA(V)] acid. Within the present study we compared the induction of oxidative DNA damage by arsenite and its methylated metabolites in cultured human cells and in isolated PM2 DNA, by frequencies of DNA strand breaks and of lesions recognized by the bacterial formamidopyrimidine-DNA glycosylase (Fpg). Only DMA(III) (> or =10 micro M) generated DNA strand breaks in isolated PM2 DNA. In HeLa S3 cells, short-term incubations (0.5-3 h) with doses as low as 10 nM arsenite induced high frequencies of Fpg-sensitive sites, whereas the induction of oxidative DNA damage after 18 h incubation was rather low. With respect to the methylated metabolites, both trivalent and pentavalent metabolites showed a pronounced induction of Fpg-sensitive sites in the nanomolar or micromolar concentration range, respectively, which was present after both short-term and long-term incubations. Furthermore MMA(III) and DMA(V) generated DNA strand breaks in a concentration-dependent manner. Taken together our results show that very low physiologically relevant doses of arsenite and the methylated metabolites induce high levels of oxidative DNA damage in cultured human cells. Thus, biomethylation of inorganic arsenic may be involved in inorganic arsenic-induced genotoxicity/carcinogenicity.
authors.affiliation: Institut für Lebensmittelchemie und Toxikologie, Universität Karlsruhe, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Schwerdtle
authors.forename: Ingo
authors.initials: I
authors.lastname: Walter
authors.forename: Iris
authors.initials: I
authors.lastname: Mackiw
authors.forename: Andrea
authors.initials: A
authors.lastname: Hartwig
mesh_terms: D001152:Arsenicals / Q000494:pharmacology*; D001435:Bacteriophages / Q000235:genetics; D002101:Cacodylic Acid / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D020552:Comet Assay; D004247:DNA / Q000187:drug effects*; D018736:DNA Adducts / Q000187:drug effects; D004249:DNA Damage; D019175:DNA Methylation / Q000187:drug effects; D004269:DNA, Bacterial / Q000187:drug effects; D043382:DNA-Formamidopyrimidine Glycosylase; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D009699:N-Glycosyl Hydrolases / Q000494:pharmacology; D009942:Organometallic Compounds / Q000494:pharmacology; D010084:Oxidation-Reduction
chemical_list: D001152:Arsenicals; D018736:DNA Adducts; D004269:DNA, Bacterial; D009942:Organometallic Compounds; C406082:monomethylarsonous acid; D004247:DNA; D002101:Cacodylic Acid; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; C020300:monomethylarsonic acid