title: Association of redox-active iron bound to high molecular weight structures in nuclei with inhibition of cell growth by H2O2.
abstract: Perturbations to Fe species contributing to generation of DNA single-strand breaks (SSBs) and inhibition of growth by H2O2 were studied in HL-60 cells made Fe-deficient by 24 h pretreatment with 144 microM bathophenanthroline disulfonic acid and 400 microM ascorbic acid (Free Radic. Biol. Med. 20: 399; 1996). The diffusion distance for SSB generation (d) in Fe-deficient cells, measured via inhibition with the *OH scavenger Me2SO using alkaline elution, was 6.5 nm. This is similar to the d for Fe-normal cells reported previously. After 1 and 3 h in fresh RPMI 1640 medium containing 10% serum, SSB generation increased from 29 to 56 and 93% of control Fe-normal cells, respectively. The d of the major contributor to SSB generation at these two treatment times was 1.9 nm. This d resembled the d for Fe-ATP as determined in isolated Ehrlich cell nuclei. The association of ATP with Fe2+ was further supported by decreased SSB generation in cells in which ATP synthesis was inhibited. In contrast to SSB generation, H2O2-induced inhibition of growth of Fe-deficient cells treated immediately after placing in fresh medium was not appreciably different from Fe-normal cells. However, after 3 h, an approximately 70% greater concentration of H2O2 than for control, Fe-normal cells was required to inhibit growth. This increase in H2O2 concentration was associated with decreased generation of SSBs by H2O2 in isolated HL-60 cell nuclei. Thus, Fe bound to nuclear structures is more closely associated with inhibition of cell growth than apparent Fe-ATP species. In parallel experiments, changes in total cellular Fe assayed by ashing and complexing with ferrozine were consistent with a non-transferrin mode of acquisition. These short-term changes appear due to processes accompanying reestablishment of the Fe content and distribution normally observed during long-term growth.
authors.affiliation: Department of Chemistry, University of Wisconsin-Milwaukee, USA.
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: R W
authors.initials: RW
authors.lastname: Byrnes
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001205:Ascorbic Acid / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects* / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D004249:DNA Damage; D004058:Diffusion; D005609:Free Radicals / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D000090463:Iron Deficiencies; D008670:Metals / Q000378:metabolism; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010618:Phenanthrolines / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D005609:Free Radicals; D008670:Metals; D010618:Phenanthrolines; C017049:bathophenanthroline disulfonic acid; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D007501:Iron; D001205:Ascorbic Acid