Ventricular Remodeling in the Adapted Heart

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DESCRIPTION (provided by applicant): Following myocardial infarction (MI), there is a progressive myocardial remodeling characterized by left ventricular (LV) dilation, contractile dysfunction, myocyte hypertrophy and increased matrix protein formation. The proposed project will examine the molecular mechanism(s) of hypoxic preconditioning (HP)- mediated myocardial remodeling in the infarcted heart by studying cardioprotective parameters at the transcriptional and protein level. We have established the optimal hypoxic preconditioning stimulus in rat MI model (10%O2/90%NS) to initiate capillary/arteriolar formation, increased blood flow and ventricular function in the myocardium. To establish the role of such HP in potentiating the signal transduction process for ventricular remodeling we will examine (i) the expression of VEGF and its tyrosine kinase receptors VEGFR1 (Flt-1) and VEGFR2 (FIk-1), expression and activity of protein kinase C, MAP Kinases-Aim I (ii) the expression and activity of iNOS/eNOS will be determined along with the transcriptional regulation of these factors by NFkB, Stat1-Aim 2 (iii) the extent of endothelial cell (EC) survival and the extent of necrosis/apoptosis, anti-apoptotic proteins Bcl-2, survivin expression, PI-3-Kinase activity, and the extent of AKT/BAD phosphorylation -Aim 3. Our rat MI model subjected to HP before LAD occlusion has significant advantage to study the molecular mechanism of myocardial remodeling over several months. An obligatory role of FIk-1, iNOS and eNOS in VEGF mediated signaling in myocardial angiogenesis/remodeling will be established by the use of Flk1, iNOS-/- and eNOS-/- knockout mice. The endothelial cell proliferation will be studied by BrdU incorporation assay, cardiomyocyte and endothelial cell apoptosis will be studied by double antibody staining, capillary and arteriolar density will be determined by labeling endothelial and smoothe muscle cells using anti-rat CD31 and anti-smooth muscle actin respectively. The results of this study will establish whether protein kinase-C, MAP kinases, eNOS/iNOS/NO are involved in VEGF and/or receptors (FIk-1/FIt-1) mediated myocardial regulation of HP induced remodeling in rat MI model. The results will provide new information required for new therapeutic strategies to protect the heart in patients with cardiac stress or coronary heart disease.