Site-specific DNA damage by phenylhydrazine and phenelzine in the presence of Cu(II) ion or Fe(III) complexes: roles of active oxygen species and carbon radicals.
Phenylhydrazine cleaved isolated DNA in the presence of Cu(II), Mn(III), hemin, Fe(III)-EDTA, or peroxidase/H2O2, while phenelzine cleaved in the presence of Cu(II). DNA cleavage by phenylhydrazine in the presence of Mn(III), hemin, or Fe(III)-EDTA occurred without marked site specificity. Inhibitory effects of scavengers of hydroxyl free radical (.OH) on the DNA damage suggest the involvement of .OH. On the other hand, Cu(II)-mediated DNA cleavage by phenylhydrazine or phenelzine was inhibited by catalase and bathocuproine, a Cu(I)-specific chelator, but not by .OH scavengers. The predominant cleavage site was the thymine residue of 5'-GTC-3' sequence. Since the cleavage pattern was similar to that induced by Cu(I) plus H2O2 but not to that induced by Cu(II) plus H2O2, it is speculated that the copper-oxygen complex derived from the reaction of H2O2 with Cu(I) participates in DNA damage by phenylhydrazine or phenelzine in the presence of Cu(II). A comparison between scavenger effects on the DNA damage and those on radical production detected with ESR suggests that carbon-centered radicals (phenyl radical, 2-phenylethyl radical) do not play an important role in Cu(II)-, hemin-, or Fe(III)-EDTA-mediated DNA damage by phenylhydrazine or phenelzine of relatively low concentrations (less than 0.5 mM). However, during the oxidation of a high concentration (10 mM) of phenylhydrazine by ferricyanide, phenyl radical seemed to cause DNA damage, especially the breakage of the deoxyribose phosphate backbone. The possibility that active oxygen species (copper-oxygen complex, .OH) are more important in DNA damage induced by hydrazines in vivo than carbon-centered radicals is discussed.
Yamamoto
K
K
Department of Public Health, Faculty of Medicine, Kyoto University, Japan.
Kawanishi
S
S
D002244:Carbon; D003300:Copper / Q000737:chemistry*; D004249:DNA Damage; D004578:Electron Spin Resonance Spectroscopy; D005292:Ferricyanides; D016166:Free Radical Scavengers; D005609:Free Radicals; D006427:Hemin / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010544:Peroxidases / Q000378:metabolism; D010624:Phenelzine / Q000633:toxicity*; D010659:Phenylhydrazines / Q000633:toxicity*
D005292:Ferricyanides; D016166:Free Radical Scavengers; D005609:Free Radicals; D010659:Phenylhydrazines; C030299:phenylhydrazine; D006427:Hemin; D002244:Carbon; D003300:Copper; D007501:Iron; D010544:Peroxidases; D010624:Phenelzine; D010100:Oxygen