Oxidative Stress Na Channel Gating and Arrhythmias

描述（由申请人提供）：心肌梗塞引起的心室颤动（VF）导致的心源性猝死仍然是一个主要的公共卫生问题。虽然缺血性心室颤动的基本机制特征仍然不清楚，但越来越多的证据表明心脏钠 (Na) 通道与急性缺血心肌之间存在相互作用。虽然缺血可能改变钠离子通道功能的机制尚未明确，但我们的初步研究为我们的假设奠定了基础，即氧化应激起着致病作用。特别是，我们发现，作为自由基介导的脂质过氧化的异前列烷途径产物产生的高反应性γ-酮醛（异缩酮，IsoK）会诱导HEK细胞中表达的hH1 Na通道失活缓慢恢复，并且这些效应可以通过用叔丁基过氧化物氧化这些细胞来模拟。初步数据表明，犬梗塞心脏边缘区的 F2-异前列腺素水平升高。因此，建议进行研究以确定犬梗塞心脏心外膜边界区组织中 IsoK 过量产生的程度。我们还将确定 IsoK 是否直接加合 Na 通道，并利用诱变方法确定加合的赖氨酰残基介导 IsoK 的作用。我们还将探索新的药物制剂，首先在表达 hill Na 通道的 HEK 细胞中减轻这些影响。其中包括 (a) 吡哆胺和 2-羟基苄胺的亲脂类似物，可拦截 IsoK 与蛋白质的加合；(b) 维生素 E 琥珀酸酯，一种新型强效且快速起效的维生素 E 形式。发现可有效防止 IsoK 诱导的 Na 通道门控变化和细胞内氧化的药物将在犬心肌梗塞模型中进行测试，以评估其预防或减轻体内 Na 通道重塑的能力。这些研究应该提高我们对氧化损伤和心律失常之间联系机制的理解，并有可能确定新的抗心律失常治疗策略。

DESCRIPTION (provided by applicant): Sudden cardiac death due to ventricular fibrillation (VF) in the setting of myocardial infarction remains a major public health problem. While the seminal mechanistic features of ischemic VF remain obscure, growing evidence implicates an interaction between cardiac sodium (Na) channels and the acutely ischemic myocardium. While a mechanism whereby ischemia might alter Na channel function has not been clearly identified, our preliminary studies form the basis for our hypothesis that oxidative stress plays a causative role. In particular, we have found that highly reactive gamma-ketoaldehydes (isoketals, IsoKs) that are produced as products of the isoprostane pathway of free radical mediated lipid peroxidation induce slow recovery from inactivation of hH1 Na channels expressed in HEK cells and that these effects are mimicked by oxidation of these cells with t-butylperoxide. Preliminary data demonstrates that levels of F2-isoprostanes are increased in the border zone of the canine infarcted heart. Therefore, studies are proposed to determine to what extent IsoKs are overproduced in tissues from the epicardial border zone in canine infarcted hearts. We will also determine whether IsoKs directly adduct the Na channel and detemine, which adducted lysyl residues, mediate the effect of IsoKs, utilizing mutagenesis approaches. We will also explore novel pharmacologic agents to mitigate these effects first in HEK cells expressing hill Na channel. These include (a) lipophilic analogs of pyridoxamine and 2-hydroxybenzylamine, which intercept IsoKs from adducting to proteins, and (b) vitamin E succinate, a novel potent and rapid acting form of vitamin E. Agents found to effectively prevent the changes in Na channel gating induced by IsoKs and oxidation in the cells will then be tested in the canine model of myocardial infarction to assess their ability to prevent or mitigate Na channel remodeling in vivo. These studies should improve our understanding of the mechanisms linking oxidant injury and arrhythmias and have the potential to identify novel antiarrhythmic therapeutic strategies.