Ethanol on Excitation-Contraction in Cardiac Cells

描述（由申请人提供）：慢性酒精中毒是人类心肌病的主要原因，并会导致各种变化，干扰乙醇喂养的动物模型心脏的收缩功能。酒精性心肌病的特征包括心输出量减少、心肌收缩力受损和房性心律失常。酒精在急性给药期间也有直接的心脏抑制作用。酒精性心脏病的一些特征可能反映了这些急性乙醇作用引起的适应性变化。我们在之前的资助期间的研究已经确定了兴奋-收缩（E-C）耦合级联内的许多急性乙醇作用的目标，包括肌膜Na和Ca2通道，它们会导致驱动收缩的胞质Ca2（[Ca2]i）瞬变的抑制。我们还发现了乙醇喂养大鼠心脏中 E C 耦合的特定变化，这表明 L 型 Ca2 通道中存在选择性损伤及其受 cAMP 依赖性蛋白激酶的调节。在此提出的工作中，我们将进一步研究受急性乙醇影响的 E C 耦合元素，以期阐明哪些元素可能导致 [Ca2 ]i 瞬变不足。然而，拟议研究的主要目的是表征长期乙醇消耗后 EC 耦合的变化，并确定这些变化的机制以及它们如何导致心脏功能缺陷。具体来说，我们将研究以下相关假设：通道亚基异构体组成和/或表达的改变导致通道有缺陷，无论是（1）基础通道特性，（2）与细胞内Ca2释放途径的耦合，（3）正常cAMP依赖性信号传导途径的调节，和/或（4）心肌细胞内的定位。这些实验将结合[Ca2]i 成像、电生理学和分子生物学方法。拟议的工作将为长期乙醇消耗引起的心脏功能障碍引起的 EC 耦合变化提供新的见解。这些发现还可能对阐明与心脏中其他异常适应性过程的发展相关的因果因素具有更广泛的影响，这些异常适应性过程最终导致心力衰竭

DESCRIPTION (provided by applicant): Chronic alcoholism is a major cause of cardiomyopathy in humans and leads to a variety of changes that interfere with contractile function in the hearts of ethanol-fed animal models. Features of alcoholic cardiomyopathy include decreased cardiac output, impaired myocardial contractility and atrial dysrhythmias. There are also direct cardiodepressant effects of alcohol during acute administration. Some of the features of alcoholic heart disease may reflect adaptive changes induced by these acute ethanol actions. Our studies during the previous granting period have identified a number of targets of acute ethanol action within the excitation-contraction (E-C) coupling cascade, including sarcolemmal Na+ and Ca2+ channels, which lead to depression of the cytosolicCa2+ ([Ca2+]i) transients that drive contraction. We have also identified specific changes in E C coupling in the hearts of ethanol-fed rats, which suggest a selective lesion in the L-type Ca2+ channel and its regulation by cAMP-dependent protein kinase. In the work proposed here, we will further investigate the elements of E C coupling that are affected by acute ethanol, with a view to elucidating which of these is likely to contribute to the deficient [Ca2+]i transients. However, the principal aims of the proposed studies will be to characterize the changes in E C coupling following chronic ethanol consumption, and to determine the mechanism of these changes and how they lead to deficiencies in cardiac function. Specifically, we will investigate the following linked hypotheses: Alterations in the channel subunit isoform composition and/or expression leads to a channel that is defective, either in (1) basal channel properties, (2) coupling to intracellular Ca2+ release pathways, (3) regulation by the normal cAMP-dependent signaling pathway, and/or (4) localization within the cardiomyocyte. These experiments will utilize a combination of [Ca2+]i imaging, electrophysiology and molecular biology approaches. The proposed work will yield new insights into the changes in E C coupling that underlie cardiac dysfunction induced by chronic ethanol consumption. These findings may also have broader implications in elucidating the causal factors associated with the development of other aberrant adaptive processes in the heart, which eventually lead to cardiac failure