A mechanism by which nitric oxide accelerates the rate of oxidative DNA damage in Escherichia coli.
A mechanism by which nitric oxide accelerates the rate of oxidative DNA damage in Escherichia coli.
复制标题
一氧化氮加速大肠杆菌氧化 DNA 损伤速率的机制。
DOI：
10.1046/j.1365-2958.2003.03530.x
复制
发表时间：
2003
影响因子：
3.6
通讯作者：
Imlay,JamesA
中科院分区：
文献类型：
--
作者：
Woodmansee,AnhN;Imlay,JamesA
一氧化氮 (NO) 的存在大大加快了过氧化氢 (H2O2) 杀死大肠杆菌的速度。工作人员提出，这种作用在吞噬细胞的杀菌过程中可能很重要。本研究的目的是确定这种协同作用的机制。死亡细胞的丝状化以及细胞渗透性铁螯合剂的保护表明，NO/H2O2 通过芬顿反应破坏细胞的 DNA 来杀死细胞。事实上，当 H2O2 暴露期间存在 NO 时，DNA 损伤的数量要多得多。在芬顿反应中，游离的细胞内铁将电子从外来供体转移到 H2O2，产生羟基自由基。尽管NO损坏了脱水酶的[Fe-S]簇，但这并没有增加游离铁的量，因此不是加速芬顿化学的原因。然而，一氧化氮也会阻碍呼吸，之前的研究表明这一事件会刺激氧化DNA损伤。由此产生的 NADH 积累加速了黄素还原酶对游离黄素的还原，这些还原的黄素通过将电子转移到游离铁来驱动芬顿化学。事实上，缺乏呼吸对苯二酚氧化酶的突变体对 H2O2 敏感，而 NO 没有任何进一步的影响。此外，缺乏黄素还原酶的突变体对 NO/H2O2 具有抗性，而过量生产的菌株则高度敏感。我们讨论了巨噬细胞攻击圈养细菌时 H2O2 和 NO 协同作用的可能性。
The presence of nitric oxide (NO) greatly accelerates the rate at which hydrogen peroxide (H2O2) killsEscherichia coli. Workers have suggested that this effect may be important in the process of bacteriocide by phagocytes. The goal of this study was to determine the mechanism of this synergism. The filamentation of the dead cells, and their protection by cell‐permeable iron chelators, indicated that NO/H2O2killed cells by damaging their DNA through the Fenton reaction. Indeed, the number of DNA lesions was far greater when NO was present during H2O2exposure. In the Fenton reaction, free intracellular iron transfers electrons from adventitious donors to H2O2, producing hydroxyl radicals. Although NO damaged the [Fe‐S] clusters of dehydratases, this did not increase the amount of free iron and was therefore not the reason for acceleration of Fenton chemistry. However, NO also blocked respiration, an event that previous studies have shown can stimulate oxidative DNA damage. The resultant accumulation of NADH accelerates the reduction of free flavins by flavin reductase, and these reduced flavins drive Fenton chemistry by transferring electrons to free iron. Indeed, mutants lacking the respiratory quinol oxidases were sensitive to H2O2, and NO did not have any further effect. Further, mutants that lack flavin reductase were resistant to NO/H2O2, and overproducing strains were hypersensitive. We discuss the possibility that H2O2and NO synergize when macrophages attack captive bacteria.