We have reported that the activation of protein kinase C (PKC) and its B1 or 2 isoforms in the myocardium and the vascular cells by diabetes or hyperglycemia are responsible for many of the vascular complications. In the heart, we have reported that PKCB1 and B2 activations are sustained for years in diabetic rats, mice and dogs and failed human hearts. We have reported that transgenic mice overexpressing PKCB2 isoforms specifically to the myocardium developed cardiac hypertrophy, fibrosis and heart failure. Isolated cardiornyocytes from PKCB transgenic mice contracted poorly which was corrected by specific inhibitor (LY333531) to PKCB isoforms. We found that PKCP isoforms activation is associated with decreased expression of eNOS and VEGF, but increased matrix proteins, activation of MAP kinase pathways, and phosphorylation of troponin-I in the myocardium. We postulate that the activation of PKC B1, B2, or delta isoforms by hyperglycemia or free fatty acids induced by the loss of insulin actions in diabetes is responsible for the poor contractility, hypertrophy and fibrosis observed in diabetic cardiornyopathy. PKCB or Beta isoform activation are mediating their actions by direct phosphorylation of contractility proteins or altering the expression of growth factors and extracellular proteins. We will test this hypothesis by using transgenic mice overexpressing either PKCB2 or delta isoforms or PKCP isoform null mice and in the cultured cardiomyocytes. PKC isoforms specific effects on gene expression and biological functions in response to glucose and insulin will be studied using adenoviral vectors containing the wild type or dominant- negative mutants of various PKC isoforms.
The specific aims are: 1) Determine the effects of glucose and insulin in isolated rat or mouse cardiomyocytes on changes in signaling gene expression, protein synthesis and contractility. 2) Evaluate whether diabetes in PKCB isoforms null mouse will cause changes in signaling, gene expression, functions, and histopathologies as observed in wild type in vivo. 3) Characterize the molecular and functional differences in the myocardium of transgenic mice overexpression PKCB2 and delta isoform in diabetic and non-diabetic states.
