One of the most serious secondary effects of alcohol abuse is the development of specific alcohol-induced cardiomyopathies which often lead to congestive heart failure. Previous findings suggest that one of the mechanisms underlying reduced cardiac function by ethanol (EtOH) may involve the direct suppression of cardiac excitation-contraction (E-C) coupling. Interestingly, this direct effect does not appear to involve alterations in the trigger for cardiac contraction (via L-type Ca 2+ current) raising the possibility that the primary negative inotropic effects of EtOH might reside in an altered response to that trigger. The goal of this project is to investigate how EtOH affects Ca2+ release from internal stores in the sarcoplasmic reticulum (SR) during the cardiac cycle. This will be accomplished through measurement of Ca 2+ sparks, which are thought to represent the fundamental Ca 2+ release units responsible for contraction.
The Specific Aims of this project are: 1) to determine if the cardiodepressant effects of EtOH occur as the result of a direct suppression of SR Ca 2+ release; and 2) to investigate whether or not these changes in SR Ca 2+ release contribute to the depression in cardiac function that occurs in a chronic model of alcohol-induced cardiomyopathy. Ca 2+ sparks will be measured in rat ventricular myocytes with the Ca2+-sensitive fluorescent indicator fluo-4 using laser scanning confocal microscopy in combination with whole cell voltage clamp techniques. Some experiments will be performed in saponin-permeabilized myocytes exposed to different cytosolic Ca2+ concentrations in order to assess Ca 2+ sensitivity of Ca 2+ sparks activated purely by Ca 2+ in the absence of functional sarcolemmal Ca 2+ current. These methodological approaches will allow the investigation of how EtOH affects SR Ca 2+ release that occurs both as a result of its normal trigger (L-type Ca 2+ channels) and in response to the final common pathway for E-C coupling, direct activation by Ca 2+. In addition to the study of direct effects of EtOH on the physiological and biophysical processes responsible for SR Ca 2+ release, we will also correlate these changes in SR Ca 2+ signaling with the development of alcohol-induced cardiomyopathy in order to determine if the reduction of cardiac output at the whole organ level occurs as the result of a suppression of E-C coupling at the level of the SR. The results of this study will contribute to our understanding of the mechanisms by which EtOH interferes with SR Ca 2+ release and whether or not this mechanism involves the trigger for E-C coupling or the response to that trigger. More importantly, such information can then be applied to understanding how a reduction in SR function by EtOH might contribute to chronic suppression of overall cardiac function, leading to the development of cardiomyopathies and heart failure associated with long-term alcohol abuse.
| Cordeiro, Jonathan M; Malone, Jane E; Di Diego, Jose M et al. (2007) Cellular and subcellular alternans in the canine left ventricle. Am J Physiol Heart Circ Physiol 293:H3506-16 |
| Aistrup, Gary L; Kelly, James E; Piano, Mariann R et al. (2006) Biphasic changes in cardiac excitation-contraction coupling early in chronic alcohol exposure. Am J Physiol Heart Circ Physiol 291:H1047-57 |
| Wasserstrom, J Andrew; Aistrup, Gary L (2005) Digitalis: new actions for an old drug. Am J Physiol Heart Circ Physiol 289:H1781-93 |
