West Matthew B, Rokosh Gregg, Obal Detlef, Velayutham Murugesan, Xuan Yu-Ting, Hill Bradford G, Keith Rachel J, Schrader Jürgen, Guo Yiru, Conklin Daniel J, Prabhu Sumanth D, Zweier Jay L, Bolli Roberto, Bhatnagar Aruni
Institute of Molecular Cardiology, University of Louisville, Louisville, KY, USA.
Circulation. 2008 Nov 4;118(19):1970-8. doi: 10.1161/CIRCULATIONAHA.108.791533. Epub 2008 Oct 20.
Inducible nitric oxide synthase (iNOS) is an obligatory mediator of the late phase of ischemic preconditioning, but the mechanisms of its cardioprotective actions are unknown. In addition, it remains unclear whether sustained elevation of iNOS in myocytes provides chronic protection against ischemia/reperfusion injury.
Constitutive overexpression of iNOS in transgenic mice (alpha-myosin heavy chain promoter) did not induce contractile dysfunction and did not affect mitochondrial respiration or biogenesis, but it profoundly decreased infarct size in mice subjected to 30 minutes of coronary occlusion and 24 hours of reperfusion. In comparison with wild-type hearts, isolated iNOS-transgenic hearts subjected to ischemia for 30 minutes followed by 40 minutes of reperfusion displayed better contractile recovery, smaller infarct size, and less mitochondrial entrapment of 2-deoxy-[(3)H]-glucose. Reperfusion-induced loss of NAD(+) and mitochondrial release of cytochrome c were attenuated in iNOS-transgenic hearts, indicating reduced mitochondrial permeability transition. The NO donor NOC-22 prevented permeability transition in isolated mitochondria, and mitochondrial permeability transition-induced NAD(+) loss was decreased in wild-type but not iNOS-null mice treated with the NO donor diethylene triamine/NO 24 hours before ischemia and reperfusion ex vivo. iNOS-mediated cardioprotection was not abolished by atractyloside. Reperfusion-induced production of oxygen-derived free radicals (measured by electron paramagnetic resonance spectroscopy) was attenuated in iNOS-transgenic hearts and was increased in wild-type hearts treated with the mitochondrial permeability transition inhibitor cyclosporin A.
Cardiomyocyte-restricted expression of iNOS provides sustained cardioprotection. This cardioprotection is associated with a decrease in reperfusion-induced oxygen radicals and inhibition of mitochondrial swelling and permeability transition.
诱导型一氧化氮合酶（iNOS）是缺血预处理后期的一种必需介质，但其心脏保护作用的机制尚不清楚。此外，心肌细胞中iNOS的持续升高是否能提供针对缺血/再灌注损伤的慢性保护仍不明确。
在转基因小鼠（α-肌球蛋白重链启动子）中组成性过表达iNOS不会诱导收缩功能障碍，也不影响线粒体呼吸或生物发生，但它能显著减小经历30分钟冠状动脉闭塞和24小时再灌注的小鼠的梗死面积。与野生型心脏相比，离体的iNOS转基因心脏在经历30分钟缺血后再灌注40分钟，表现出更好的收缩恢复、更小的梗死面积以及更少的2-脱氧-[(3)H]-葡萄糖的线粒体摄取。再灌注诱导的NAD(+)损失和细胞色素c的线粒体释放在iNOS转基因心脏中减弱，表明线粒体通透性转换降低。NO供体NOC-22可防止离体线粒体发生通透性转换，并且在缺血和再灌注前24小时用NO供体二亚乙基三胺/NO处理的野生型小鼠而非iNOS基因敲除小鼠中，线粒体通透性转换诱导的NAD(+)损失减少。iNOS介导的心脏保护作用不会被苍术苷消除。再灌注诱导的氧自由基产生（通过电子顺磁共振光谱法测量）在iNOS转基因心脏中减弱，而在用线粒体通透性转换抑制剂环孢素A处理的野生型心脏中增加。
心肌细胞限制性表达iNOS可提供持续的心脏保护。这种心脏保护作用与再灌注诱导的氧自由基减少以及线粒体肿胀和通透性转换的抑制有关。
