Thom S R, Xu Y A, Ischiropoulos H
Institute for Environmental Medicine, University of Pennsylvania Medical Center, Philadelphia 19104, USA.
Chem Res Toxicol. 1997 Sep;10(9):1023-31. doi: 10.1021/tx970041h.
Carbon monoxide causes a perivascular oxidative injury in animals, and we tested the hypothesis that endothelial cells could be a source of the injurious oxidants. Studies were undertaken to assess whether exposure to carbon monoxide would cause cultured bovine pulmonary artery endothelial cells to liberate reactive species. Concentrations of carbon monoxide between 11 and 110 nM caused progressively higher concentrations of nitric oxide to be released by endothelial cells based on measurements of nitrite and nitrate. Intracellular production of peroxynitrite was indicated by elevated concentrations of nitrotyrosine, and extracellular liberation of peroxynitrite was indicated by oxidation of p-hydroxyphenylacetic acid and dihydrorhodamine-123. Carbon monoxide did not disturb mitochondrial function based on the rate of oxygen consumption, intracellular production of hydrogen peroxide, and the ability of cells to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Carbon monoxide also did not alter arginine transport by cells or nitric oxide synthase activity, but it was found to increase steady state levels of nitric oxide by competing for intracellular binding sites. Acute cytotoxicity from carbon monoxide, assessed as radioactive chromium leakage, was due to nitric oxide-derived oxidants. A delayed cell death, whose mechanism is not entirely clear, was also demonstrated by chromium leakage and uptake of vital stain. These findings offer a possible mechanism for adverse health effects caused by carbon monoxide at concentrations ranging from the relatively low levels in polluted environments to levels typically encountered with life-threatening poisoning. Carbon monoxide causes oxidative stress by a novel mechanism involving a competition for intracellular binding sites which increases steady state levels of nitric oxide and allows for generation of peroxynitrite by endothelium.
一氧化碳会在动物体内引发血管周围氧化损伤，我们检验了如下假设：内皮细胞可能是有害氧化剂的来源。我们开展了研究，以评估暴露于一氧化碳是否会导致培养的牛肺动脉内皮细胞释放活性物质。基于亚硝酸盐和硝酸盐的测量结果，11至110纳摩尔浓度的一氧化碳会使内皮细胞释放出浓度逐渐升高的一氧化氮。硝基酪氨酸浓度升高表明细胞内产生了过氧亚硝酸盐，对羟基苯乙酸和二氢罗丹明-123的氧化表明过氧亚硝酸盐释放到了细胞外。基于氧气消耗速率、细胞内过氧化氢的产生以及细胞还原3-(4,5-二甲基噻唑-2-基)-2,5-二苯基四氮唑溴盐的能力，一氧化碳并未干扰线粒体功能。一氧化碳也未改变细胞对精氨酸的转运或一氧化氮合酶的活性，但发现它通过竞争细胞内结合位点来增加一氧化氮的稳态水平。以放射性铬泄漏来评估，一氧化碳的急性细胞毒性是由一氧化氮衍生的氧化剂所致。铬泄漏和活体染色摄取也证明了存在一种延迟性细胞死亡，其机制尚不完全清楚。这些发现为一氧化碳在从污染环境中的相对低浓度到危及生命中毒时通常遇到的浓度范围内所造成的不良健康影响提供了一种可能的机制。一氧化碳通过一种新机制引起氧化应激，该机制涉及对细胞内结合位点的竞争，从而增加一氧化氮的稳态水平，并使内皮细胞生成过氧亚硝酸盐。
