Ethanol on Excitation-Contraction in Cardiac Cells

描述(申请人提供)：慢性酒精中毒是人类心肌病的主要原因，并导致干扰乙醇喂养的动物模型心脏收缩功能的各种变化。酒精性心肌病的特征包括心输出量减少、心肌收缩能力受损和房性心律失常。在急性给药期间，酒精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酒精作用引起的适应性变化。我们在前一个授予期间的研究已经在兴奋-收缩(E-C)耦合级联中确定了一些急性乙醇作用的靶点，包括肌膜Na和Ca~(2+)通道，它们导致驱动收缩的胞浆Ca~(2+)([Ca~(2+)]_i)瞬变的抑制。我们还在乙醇喂养的大鼠心脏中发现了E-C偶联的特异性变化，这表明L钙通道存在选择性损伤，并受到cAMP依赖的蛋白激酶的调节。在本文提出的工作中，我们将进一步研究急性乙醇影响的EC偶联元件，以期阐明其中哪些元件可能导致[Ca~(2+)]i瞬变的缺陷。然而，拟议研究的主要目的将是描述慢性酒精摄入后E-C偶联的变化，并确定这些变化的机制以及它们如何导致心功能缺陷。具体地说，我们将研究以下相关假设：通道亚基亚基组成和/或表达的变化导致通道缺陷，包括(1)基本通道特性，(2)与细胞内钙释放途径的偶联，(3)正常cAMP依赖的信号通路的调节，和(或)(4)心肌细胞内的定位。这些实验将结合使用[钙]i成像、电生理学和分子生物学方法。这项拟议的工作将对慢性酒精摄入引起的心功能障碍的E-C偶联变化产生新的见解。这些发现还可能对阐明与心脏中其他异常适应过程的发展有关的原因因素具有更广泛的意义，这些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