Xuan Y T, Tang X L, Qiu Y, Banerjee S, Takano H, Han H, Bolli R
Experimental Research Laboratory, Division of Cardiology, University of Louisville, Louisville, Kentucky 40292, USA.
Am J Physiol Heart Circ Physiol. 2000 Nov;279(5):H2360-71. doi: 10.1152/ajpheart.2000.279.5.H2360.
In conscious rabbits, a sequence of six 4-min coronary occlusion/4-min reperfusion cycles, which elicits late preconditioning (PC), caused rapid activation of calcium-dependent nitric oxide (NO) synthase (NOS) [cNOS; endothelial NOS (eNOS) and/or neuronal NOS (nNOS)], whereas calcium-independent NOS [inducible NOS (iNOS)] activity remained unchanged. The enhanced cNOS activity was associated with increased myocardial levels of NO(2) and/or NO(3) (NO(x)). Twenty-four hours after ischemic PC was induced, the opposite pattern was observed, i.e., there was a pronounced increase in cytosolic iNOS activity but no change in cNOS activity. The initial burst of ischemia-induced cNOS activity was not affected by pretreatment with the antioxidant N-2-mercaptopropionyl glycine (MPG), the protein kinase C (PKC) inhibitor chelerythrine, or the tyrosine kinase inhibitor lavendustin A, indicating that it is independent of the generation of oxidant species and the activation of PKC and tyrosine kinases. In contrast, the delayed upregulation of iNOS 24 h after PC was prevented by pretreatment with N(omega)-nitro-L-arginine, MPG, or chelerythrine before the PC ischemia, indicating that it is triggered by a signaling mechanism that involves the generation of NO, the formation of oxidant species, and the activation of PKC. Taken together, these results demonstrate that, in conscious animals, ischemic PC elicits a biphasic response in cardiac NOS activity, i. e., an immediate activation of cNOS (most likely eNOS) followed 24 h later by a delayed upregulation of iNOS. To our knowledge, this is the first study to directly measure NOS activity after brief myocardial ischemia in vivo. In conjunction with previous functional studies, the data support a distinctive role of NOS isoforms in late PC, with eNOS serving as the trigger on day 1 and iNOS as the mediator on day 2.
在清醒兔中，一系列六个4分钟冠状动脉闭塞/4分钟再灌注周期可引发延迟预处理（PC），该过程导致钙依赖性一氧化氮（NO）合酶（cNOS；内皮型NOS（eNOS）和/或神经元型NOS（nNOS））快速激活，而钙非依赖性NOS（诱导型NOS（iNOS））活性保持不变。增强的cNOS活性与心肌中NO₂和/或NO₃（NOₓ）水平升高有关。在诱导缺血性PC 24小时后，观察到相反的模式，即胞质iNOS活性显著增加而cNOS活性无变化。缺血诱导的cNOS活性的初始爆发不受抗氧化剂N-2-巯基丙酰甘氨酸（MPG）、蛋白激酶C（PKC）抑制剂白屈菜红碱或酪氨酸激酶抑制剂拉文达ustin A预处理的影响，表明其独立于氧化应激产物的产生以及PKC和酪氨酸激酶的激活。相反，在PC缺血前用Nⁿ-硝基-L-精氨酸、MPG或白屈菜红碱预处理可防止PC后24小时iNOS的延迟上调，表明其由涉及NO生成、氧化应激产物形成和PKC激活的信号机制触发。综上所述，这些结果表明，在清醒动物中，缺血性PC在心脏NOS活性中引发双相反应，即cNOS（最可能是eNOS）立即激活，随后24小时iNOS延迟上调。据我们所知，这是第一项在体内短暂心肌缺血后直接测量NOS活性的研究。结合先前的功能研究，这些数据支持NOS同工型在延迟PC中的独特作用，eNOS在第1天起触发作用，iNOS在第2天起介导作用。
