One third of alcohol abusers manifest decreased cardiac contractility and muscle strength termed respectively alcoholic cardiomyopathy and myopathy, accounting for about 6 million persons in the US. In fact, the most common cause of cardiomyopathy with congestive heart failure is chronic alcoholism. However, the pathogenesis of these conditions still remains obscure. Studies in human alcoholics and animal models have demonstrated that chronic ethanol consumption increases oxidative stress and other cellular stress factors and enhances the susceptibility to apoptosis. In addition to our demonstration of a marked increase in the rate of apoptosis in human skeletal muscle and heart from alcoholic patients, we have also shown decreased cardiac function in alcohol-fed animals. Our preliminary data indicate that ethanol also interferes with the proliferation and differentiation o skeletal muscle satellite cells and other stem cells in culture. These findings suggest that ethanol-induced sensitization to apoptosis/necrosis may alter the delicate cellular equilibrium between survival and cell death. We hypothesize that chronic alcohol abuse sensitizes heart and muscle to mitochondrial apoptosis elicited by Ca2+ overload and Bid at least in part by enhancing oxidative/nitrosative stress. We propose that chronic alcohol abuse also affects renewal mediated by progenitor cells in skeletal muscle, an organ that has a robust capacity for regeneration. Thus we propose that an impaired balance between cell death and renewal are central to the development of alcoholic cardiomyopathy and skeletal myopathy.
The aims of this application are to i) evaluate stress response markers and apoptosis/necrosis in heart and skeletal muscle from human alcoholics and rats fed ethanol, with an emphasis on the mitochondrial stress pathways and ii) relate these parameters to the degree of alcoholic tissue injury, and iii) determine the effects of ethanol on progenitor cell number, proliferation and differentiation in skeletal muscle. We have available a collection of precisely annotated human heart and skeletal muscle tissues derived from patients on life support systems at the Hospital Clinic in Barcelona, Spain, and continue to obtain additional specimens. We have also established a productive collaboration with Dr. Pacher, the Chief of the Oxidative Stress and Tissue Injury Unit at NIAAA, who is a leader in research of oxidative/nitrosative stress in the cardiovascular system. Thus, the PIs'experience in calcium and Bcl-2 family protein-mediated mitochondrial stress and the pathologic aspects of human alcoholic cardiomyopathy and myopathy will be complemented by expertise in oxidative/nitrosative stress and by access to a unique human tissue resource. Furthermore, the studies will employ the recent advances in high resolution, high capacity and semi-automatic fluorescence imaging. We expect that the results of these studies will provide a unique bridge between the mechanisms underlying alcohol-induced tissue injury in animal models and in human alcoholics and will shed light on the pathogenesis of alcoholic cardiomyopathy and myopathy.
Chronic alcoholism is associated with heart and skeletal muscle disease, namely cardiomyopathy and myopathy. Cardiac and skeletal muscle cell death and renewal appear to be an important factor in the pathogenesis of these maladies, and an understanding of their mechanisms should offer opportunities to identify appropriate therapeutic targets. The combination of an access to a unique collection of annotated human heart and skeletal muscle samples, and expertise in (1) the clinical and basic research aspects of alcoholism, (2) both cell death and renewal research, (3) oxidative/nitrosative stress and (4) advanced fluorescence imaging measurements will provide this interdisciplinary collaboration with a unique opportunity to establish the mechanisms and significance of altered cell death and renewal in alcoholic heart and skeletal muscle.