Oxidative Stress Na Channel Gating and Arrhythmias

描述(由申请人提供)：在心肌梗死的背景下，由室颤(VF)引起的心源性猝死仍然是一个主要的公共卫生问题。虽然缺血性室颤的机制尚不清楚，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腺素途径的产物而产生的高活性的伽马酮醛(异酮，IsoKs)可以诱导HEK细胞中表达的HH1Na通道失活的缓慢恢复，这些效应可以通过t-丁基过氧化氢氧化这些细胞来模拟。初步数据显示，在犬梗死心脏边缘区域，F2-异前列腺素水平增加。因此，有人建议进行研究，以确定犬梗死心脏心外膜交界区组织中IsoKs过度产生的程度。我们还将利用突变方法来确定IsoKs是否直接加成Na通道和Detemine，后者加成赖氨酰残基，介导IsoKs的作用。我们还将首先在表达希尔Na通道的HEK细胞中探索新的药理药物来缓解这些影响。这些药物包括(A)可截断IsoKs加成到蛋白质上的亲脂类似物吡哆胺和2-羟基苯胺，以及(B)维生素E琥珀酸酯，这是一种新型高效、快速作用的维生素E形式，已被发现能有效防止由IsoKs和细胞内氧化引起的钠通道门控变化，然后将在犬心肌梗死模型中进行测试，以评估它们防止或缓解体内钠通道重构的能力。这些研究将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.