Oxidative Stress Na Channel Gating and Arrhythmias

描述（由申请人提供）：心肌梗死背景下室颤（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VF的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Na通道功能的机制尚未明确，但我们的初步研究形成了我们假设氧化应激起致病作用的基础。特别是，我们已经发现，作为自由基介导的脂质过氧化的异前列烷途径的产物产生的高反应性γ-酮醛（异缩酮，IsoKs）诱导从HEK细胞中表达的hH 1 Na通道失活中缓慢恢复，并且这些作用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，F2-异前列烷的水平在犬梗死心脏的边缘区增加。因此，提出了研究以确定在何种程度上IsoK在犬梗死心脏的心外膜边缘区的组织中过量产生。我们还将确定IsoKs是否直接加合Na通道和detemine，加合赖氨酰残基，介导IsoKs的作用，利用诱变方法。我们还将探索新的药理学药物，以减轻这些影响，首先在HEK细胞表达山钠通道。这些包括（a）吡哆胺和2-羟基苄胺的亲脂性类似物，其阻断IsoKs与蛋白质的加合，和（B）维生素E琥珀酸酯，一种新的有效和快速作用形式的维生素E。然后将在心肌梗塞的犬模型中测试发现有效地防止由IsoKs诱导的Na通道门控和细胞中的氧化的变化的试剂，以评估它们在体内防止或减轻Na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相关机制的理解，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.