Yamamoto K, Kawanishi S
Department of Public Health, Faculty of Medicine, Kyoto University, Japan.
J Biol Chem. 1991 Jan 25;266(3):1509-15.
The mechanism of DNA damage by hydrazine in the presence of metal ions was investigated by DNA sequencing technique and ESR-spin trapping method. Hydrazine caused DNA damage in the presence of Mn(III), Mn(II), Cu(II), Co(II), and Fe(III). The order of inducing effect on hydrazine-dependent DNA damage (Mn(III) greater than Mn(II) approximately Cu(II) much greater than Co(II) approximately Fe(III)) was related to that of the accelerating effect on the O2 consumption rate of hydrazine autoxidation. DNA damage by hydrazine plus Mn(II) or Mn(III) was inhibited by hydroxyl radical scavengers and superoxide dismutase, but not by catalase. On the other hand, bathocuproine and catalase completely inhibited DNA damage by hydrazine plus Cu(II), whereas hydroxyl radical scavengers and superoxide dismutase did not. Hydrazine plus Mn(II) or Mn(III) caused cleavage at every nucleotide with a little weaker cleavage at adenine residues, whereas hydrazine plus Cu(II) induced piperidine-labile sites frequently at thymine residues, especially of the GTC sequence. ESR-spin trapping experiments showed that hydroxyl radical is generated during the Mn(III)-catalyzed autoxidation of hydrazine, whereas hydrogen atom adducts of spin trapping reagents are generated during Cu(II)-catalyzed autoxidation. The results suggest that hydrazine plus Mn(II) or Mn(III) generate hydroxyl free radical not via H2O2 and that this hydroxyl free radical causes DNA damage. A possibility that the hydrogen atom releasing compound participates in hydrazine plus Cu(II)-induced DNA damage is discussed.
采用DNA测序技术和电子自旋共振（ESR）自旋捕获法研究了在金属离子存在下肼对DNA的损伤机制。肼在Mn(III)、Mn(II)、Cu(II)、Co(II)和Fe(III)存在时会造成DNA损伤。对肼依赖性DNA损伤的诱导作用顺序（Mn(III)＞Mn(II)≈Cu(II)＞＞Co(II)≈Fe(III)）与对肼自氧化耗氧速率的加速作用顺序相关。肼加Mn(II)或Mn(III)引起的DNA损伤可被羟基自由基清除剂和超氧化物歧化酶抑制，但过氧化氢酶不能。另一方面，bathocuproine和过氧化氢酶可完全抑制肼加Cu(II)引起的DNA损伤，而羟基自由基清除剂和超氧化物歧化酶则不能。肼加Mn(II)或Mn(III)会导致每个核苷酸处的断裂，腺嘌呤残基处的断裂稍弱，而肼加Cu(II)则经常在胸腺嘧啶残基处，尤其是GTC序列处诱导产生哌啶敏感位点。ESR自旋捕获实验表明，在肼的Mn(III)催化自氧化过程中会产生羟基自由基，而在Cu(II)催化自氧化过程中会产生自旋捕获试剂的氢原子加合物。结果表明，肼加Mn(II)或Mn(III)不是通过H2O2产生羟基自由基，且这种羟基自由基会导致DNA损伤。本文还讨论了氢原子释放化合物参与肼加Cu(II)诱导的DNA损伤的可能性。
