Oxidation of 5′-site guanine at GG and GGG sequences induced by a metabolite of carcinogenic heterocyclic amine PhIP in the presence of Cu(II) and NADH
Oxidation of 5′-site guanine at GG and GGG sequences induced by a metabolite of carcinogenic heterocyclic amine PhIP in the presence of Cu(II) and NADH
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DOI：
10.1093/carcin/23.5.855
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发表时间：
2002-05-01
期刊：
影响因子：
4.7
通讯作者：
Kawanishi, S
中科院分区：
文献类型：
--
作者：
Murata, M;Kawanishi, S
加合物的形成被认为是致癌性杂环胺引起DNA损伤的主要原因。通过电化学检测器与高效液相色谱联用的实验，我们发现2-氨基-1-甲基-6-苯基咪唑[4，5-B]吡啶（PhIP）的N-羟基代谢产物在Cu（II）存在下诱导8-羟基-2 '-脱氧鸟苷（8-OH-dG）的生成。内源性还原剂NADH的加入促进了8-OH-dG的形成。用P-32标记的DNA片段进行的实验表明，在Cu（II）和NADH存在下，该代谢物[PhIP（NHOH）]引起鸟嘌呤的8-羟基化，随后用甲酰氨基嘧啶-DNA糖基化酶处理导致GG和GGG序列的5 '-位点鸟嘌呤的链裂解。有趣的是，抗氧化酶SOD增强了DNA损伤的强度，胸腺嘧啶残基被附加到其鸟嘌呤为主的切割位点。过氧化氢酶和铜（I）特异性螯合剂浴铜灵可抑制DNA损伤，提示H2 O2和Cu（I）参与了DNA损伤。紫外-可见光谱研究表明，Cu（II）和SOD催化PhIP（NHOH）的自氧化反应。这些结果表明，Cu（II）依赖的自氧化PhIP（NHOH）加上NADH介导的还原其氧化产物形成氧化还原循环，导致氧化DNA损伤低浓度的PhIP（NHOH）。我们的结论是，除了DNA加合物的形成，氧化DNA损伤可能参与的致癌过程中的PhIP。
Adduct formation has been considered to be a major causal factor of DNA damage by carcinogenic heterocyclic amines. By means of experiments with an electrochemical detector coupled to a high-performance liquid chromatograph, we revealed that N-hydroxy metabolite of 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) induced the formation of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in the presence of Cu(II). Addition of an endogenous reductant NADH enhanced the 8-OH-dG formation. Experiments with P-32-labeled DNA fragments showed that this metabolite [PhIP(NHOH)] caused 8-hydroxylation of guanines in the presence of Cu(II) and NADH, and subsequent treatment with formamidopyrimidine-DNA glycosylase led to chain cleavages at the 5'-site guanine of GG and GGG sequences. Interestingly, antioxidant enzyme SOD enhanced the intensity of DNA damage, and thymine residues were appended to its guanine-predominant cleavage sites. Catalase and bathocuproine, a Cu(I)-specific chelator, inhibited the DNA damage, suggesting the involvement of H2O2 and Cu(I). A UV-visible spectroscopic study indicated that Cu(II) and SOD catalyze the autoxidation of PhIP(NHOH). These results suggest that Cu(II) -dependent autooxidation of PhIP(NHOH) coupled with NADH-mediated reduction of its oxidized product form redox cycle, resulting in oxidative DNA damage by low concentrations of PhIP(NHOH). We conclude that in addition to DNA adduct formation, oxidative DNA damage may be involved in the carcinogenic process of PhIP.