title: Intracellular iron, but not copper, plays a critical role in hydrogen peroxide-induced DNA damage.
abstract: The role of intracellular iron, copper, and calcium in hydrogen peroxide-induced DNA damage was investigated using cultured Jurkat cells. The cells were exposed to low rates of continuously generated hydrogen peroxide by the glucose/glucose oxidase system, and the formation of single strand breaks in cellular DNA was evaluated by the sensitive method, single cell gel electrophoresis or "comet" assay. Pre-incubation with the specific ferric ion chelator desferrioxamine (0.1-5.0 mM) inhibited DNA damage in a time- and dose-dependent manner. On the other hand, diethylenetriaminepentaacetic acid (DTPA), a membrane impermeable iron chelator, was ineffective. The lipophilic ferrous ion chelator 1,10-phenanthroline also protected against DNA damage, while its nonchelating isomer 1,7-phenanthroline provided no protection. None of the above iron chelators produced DNA damage by themselves. In contrast, the specific cuprous ion chelator neocuproine (2,9-dimethyl-1,10-phenanthroline), as well as other copper-chelating agents, did not protect against H(2)O(2)-induced cellular DNA damage. In fact, membrane permeable copper-chelating agents induced DNA damage in the absence of H(2)O(2). These results indicate that, under normal conditions, intracellular redox-active iron, but not copper, participates in H(2)O(2)-induced single strand break formation in cellular DNA. Since BAPTA/AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester), an intracellular Ca(2+)-chelator, also protected against H(2)O(2)-induced DNA damage, it is likely that intracellular Ca(2+) changes are involved in this process as well. The exact role of Ca(2+) and its relation to intracellular transition metal ions, in particular iron, needs to be further investigated.
authors.affiliation: Laboratory of Biological Chemistry, University of Ioannina Medical School, Ioannina, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Barbouti
authors.forename: P T
authors.initials: PT
authors.lastname: Doulias
authors.forename: B Z
authors.initials: BZ
authors.lastname: Zhu
authors.forename: B
authors.initials: B
authors.lastname: Frei
authors.forename: D
authors.initials: D
authors.lastname: Galaris
mesh_terms: D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003300:Copper / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects*; D004277:DNA, Single-Stranded / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D005949:Glucose Oxidase / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D019169:Jurkat Cells / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction; D004369:Pentetic Acid / Q000494:pharmacology; D010618:Phenanthrolines / Q000494:pharmacology; D013997:Time Factors
chemical_list: D002614:Chelating Agents; D004277:DNA, Single-Stranded; D005029:Ethylenediamines; D007502:Iron Chelating Agents; D010618:Phenanthrolines; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D003300:Copper; D004369:Pentetic Acid; D006861:Hydrogen Peroxide; D007501:Iron; D005949:Glucose Oxidase; D002118:Calcium; C025205:1,10-phenanthroline