MYOCYTE APOPTOSIS AND A TRANSGENIC HEART FAILURE MODEL

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Congestive heart failure is a major cause of morbidity and mortality in the United States. Little is known about the mechanisms by which specific etiologic agents can induce the sudden or gradual onset of ventricular dysfunction. In order to identify mechanisms that may contribute to the deterioration of ventricular function we have generated a transgenic animal model that targets expression of a non- infectious coxsackievirus cDNA to the ventricle. Preliminary data suggests that this unique transgenic model has many characteristics of cardiomyopathy including systolic and diastolic dysfunction, myocardial fibrosis, and induction of the embryonic program of gene expression. We have also shown that coxsackievirus B3 can infect mouse and rat myocytes in culture, and can induce a cytopathic effect that includes myocardial apoptosis. An integrated approach that uses cell culture combined with a transgenic animal model make it possible to address mechanisms by which a defined stimulus can adversely affect myocardial cells in culture and in an intact animal model of cardiomyopathy. In cell culture we propose to evaluate specific mechanisms by which coxsackieviral proteins can induce apoptosis and myofilament disruption. Functional significance of the findings in cell culture will then be evaluated in the transgenic mouse. These experiments are based on the following hypotheses: 1) that specific coxsackieviral proteins, such as protease 2A induce apoptosis and myofilament disruption in cultured cardiomyocytes, and 2) that low level cardiac specific expression of CVB proteins in transgenic mouse myocytes can induce abnormalities in excitation contraction coupling associated with ventricular dysfunction. The following specific aims are, therefore, proposed: 1) Determine whether CVB protease 2A is sufficient to induce viral mediated apoptosis and disruption of myofilaments in cultured neonatal ventricular myocytes, 2) Determine the mechanisms by which CVB3 induces a direct cytopathic effect in adult ventricular myocytes, 3) Examine the hemodynamic, and functional significance of cardiac specific expression of non-infectious CVB cDNA in transgenic mice, and 4) Determine whether cardiac expression of the replication deficient CVB3 genome leads to abnormal ventricular function that is associated with excitation contraction coupling abnormalities and altered contractility in the isolated ventricular myocyte. These experiments will facilitate our understanding of the mechanisms by which ventricular function deteriorates with expression of specific proteins that are associated with cardiomyopathy.