Recent epidemiological studies indicate beneficial effects of moderate ethanol consumption on heart in particular in regard to coronary heart disease. Although most of the studies focused on the effect of moderate consumption on atherosclerosis, evidence suggesting direct beneficial effect on the muscle resistance to post-ischemic reperfusion injury has also been obtained. The molecular mechanism that account for the direct effect on the muscle are not understood. Protein kinase C (PKC)-mediated signal transduction system has been found to be affected by ethanol. Because this signal transduction system regulates protection of the heart from ischemia and post-ischemic reperfusion injury, ethanol-induced changes in components of this signaling system may account for at least some of the beneficiary effects of moderate alcohol consumption. A useful model to study the effects of ethanol on signal transduction systems in heart is a tissue culture model of rat primary cardiac myocytes. Primary cardiac myocytes have many characteristics of cardiac cells in intact heart, including intracellular structures; contractility, responses to hormone stimuli and, relevant to this study, modulation of ischemia-induced injury by short ischemic pre-treatments (preconditioning) as well as by PKC activation. Moreover, in this cell model the environment of primary cardiac cells can be controlled without complicating neuronal and hormonal influences. Therefore, we propose to identify the mechanism by which ethanol exerts protective effect from ischemia, hypoxia and re-oxygenation injury of cardiac myocytes. Using this culture, we have already found that PKC-mediated signal transduction is specifically activated by ethanol. We also found that activation of only one PKC isozyme by preconditioning or PMA is required for the protection of cardiac myocytes from hypoxia-induced death. Here, we plan to identify the PKC isozyme(s) responsible for the ethanol- induced protection of myocytes from this injury, to identify the molecular mechanism leading to this protection, and to identify the mechanism by which PKC isozyme activation by ethanol occurs. Together, these studies will help elucidating the molecular basis for cardio- protection by ethanol.
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