Oxidative Stress Na Channel Gating and Arrhythmias

描述（由申请人提供）：心肌梗死后由心室颤动（VF）引起的心源性猝死仍然是一个主要的公共卫生问题。尽管缺血性室性心动过速的机制特征仍不清楚，但越来越多的证据表明，心脏钠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通道功能的机制尚未明确，但我们的初步研究为氧化应激起致病作用的假设奠定了基础。特别是，我们发现，自由基介导的脂质过氧化的异前列腺素途径产生的高活性γ -酮醛（异酮酸，IsoKs）诱导HEK细胞中表达的hH1 Na通道失活后缓慢恢复，并且这些作用可以通过过氧化t-丁基氧化这些细胞来模拟。初步数据表明，f2 -异前列腺素水平在犬梗死心脏边缘区增加。因此，研究被提出，以确定在多大程度上从心外膜边缘区在犬梗死心脏组织过量产生的isok。我们还将利用诱变方法确定isok是否直接加合Na通道，并确定哪些加合的赖氨酸残基介导了isok的作用。我们还将探索新的药物来减轻这些影响，首先在表达hill Na通道的HEK细胞。其中包括(a)吡哆胺和2-羟苄胺的亲脂性类似物，它们可以阻断isok内合到蛋白质中，以及(b)维生素E琥珀酸盐，一种新型的有效和快速作用的维生素E形式，可以有效预防由isok诱导的钠通道门控变化和细胞氧化，然后将在犬心肌梗死模型中进行测试，以评估它们在体内预防或减轻钠通道重塑的能力。这些研究将提高我们对氧化损伤和心律失常的机制的理解，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.