Oxidative DNA Damage Induced by Activation of Polychlorinated Biphenyls (PCBs): Implications for PCB-Induced Oxidative Stress in Breast Cancer
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- 作者：Gregory G. Oakley ; Udaya-sankar Devanaboyina ; Larry W. Robertson ; and Ramesh C. Gupta
- 刊名：Chemical Research in Toxicology
- 出版年：1996
- 出版时间：November 1996
- 年：1996
- 卷：9
- 期：8
- 页码：1285 - 1292
- 全文大小：390K
- 年卷期：v.9,no.8(November 1996)
- ISSN：1520-5010
文摘
We have previously reported that mono- and dichlorinated biphenyls(PCBs) can bemetabolized to dihydroxy compounds and further oxidized to reactivemetabolites which formadducts with nitrogen and sulfur nucleophiles including DNA [Amaro etal. (1996) Chem. Res.Toxicol. 9, 623-629; Oakley et al. (1996)Carcinogenesis 17, 109-114]. The formerstudiesalso demonstrated that during the metabolism of PCBs superoxide may beproduced. We havetherefore examined the abilities of PCB metabolites to induce freeradical-mediated oxidativeDNA damage using a newly developed, highly sensitive,32P-postlabeling assay for 8-oxodeoxyguanosine (8-oxodG) [Devanaboyina, U., and Gupta, R. (1996)Carcinogenesis 17, 917-924].The incubation of 3,4-dichloro-2',5'-dihydroxybiphenyl (100 
M)with calf thymus DNA (300g/mL) in the presence of the breast tissue and milk-associatedenzyme, lactoperoxidase (10mU/mL), and H2O2 (0.5 mM) resulted in asignificant increase in free radical-induced DNAdamage (253 8-oxodG/106 nucleotides) as compared tovehicle-treated DNA (118 8-oxodG/106nucleotides). Substituting CuCl2 (100 M) forlactoperoxidase/H2O2, however, resulted inasubstantial increase in 8-oxodG content (2669 8-oxodG/106nucleotides). FeCl3 was ineffective,suggesting that CuCl2 but not FeCl3 mediatesoxidation of PCB dihydroxy metabolites, resultingin oxidative DNA damage. The addition of catalase (100 U/mL) andsodium azide (0.1 M)reduced the effect of CuCl2 (849 and 8968-oxodG/106 nucleotides, respectively), whilesuperoxidedismutase (600 U/mL) moderately stimulated and glutathione (100 M)substantially stimulated8-oxodG formation (3014 and 4415 8-oxodG/106 nucleotides,respectively). The effect of variousbuffers as well as the effects of PCB structure on Cu(II)-mediatedoxidative DNA damage wereexamined. These results demonstrate that free radicals andoxidative DNA damage areproduced during oxidation of lower chlorinated biphenyls. Therelevance of the results isdiscussed in view of the recent report that increased oxidative DNAbase damage is detectedin the DNA of human breast tumor tissue.
M)with calf thymus DNA (300g/mL) in the presence of the breast tissue and milk-associatedenzyme, lactoperoxidase (10mU/mL), and H2O2 (0.5 mM) resulted in asignificant increase in free radical-induced DNAdamage (253 8-oxodG/106 nucleotides) as compared tovehicle-treated DNA (118 8-oxodG/106nucleotides). Substituting CuCl2 (100 M) forlactoperoxidase/H2O2, however, resulted inasubstantial increase in 8-oxodG content (2669 8-oxodG/106nucleotides). FeCl3 was ineffective,suggesting that CuCl2 but not FeCl3 mediatesoxidation of PCB dihydroxy metabolites, resultingin oxidative DNA damage. The addition of catalase (100 U/mL) andsodium azide (0.1 M)reduced the effect of CuCl2 (849 and 8968-oxodG/106 nucleotides, respectively), whilesuperoxidedismutase (600 U/mL) moderately stimulated and glutathione (100 M)substantially stimulated8-oxodG formation (3014 and 4415 8-oxodG/106 nucleotides,respectively). The effect of variousbuffers as well as the effects of PCB structure on Cu(II)-mediatedoxidative DNA damage wereexamined. These results demonstrate that free radicals andoxidative DNA damage areproduced during oxidation of lower chlorinated biphenyls. Therelevance of the results isdiscussed in view of the recent report that increased oxidative DNAbase damage is detectedin the DNA of human breast tumor tissue.