The overall objective of this proposal is to investigate the signaling mechanisms underlying the cardioprotective effect of fibroblast growth factor-2 (FGF2). The pathway(s) triggered by FGF2 to elicit protection in the heart during ischemia is unknown. However, evidence indicates that in many cell types, FGF2 can signal through protein kinase C (PKC), mitogen-activated protein kinase (MAPK), or nitric oxide (NO) and ATP-sensitive potassium (KATP) channels to mediate certain biological functions including cellular growth, vasodilation, and angiogenesis. All of these signaling pathways have also been shown to be important in cardioprotection. A broad multidisciplinary approach will be established that will combine diverse techniques (integrative physiology, molecular genetics, gene-targeted/transgenic mouse models, and pharmacology) and will integrate genetic information at the molecular level with physiological information at the whole organ/animal level. To ascertain the molecular mechanism(s) for FGF2-mediated cardioprotection, we will assess the patterns in activity of protein kinases (PKC and MAPK) that are either known to mediate FGF2 signaling or have been implicated in the development of cardioprotection. This will be done by determining which of these pathways is markedly altered prior to and during ischemia-reperfusion injury in wildtype and FGF2 transgenic mouse hearts and correlating these molecular/biochemical changes with post ischemic recovery of cardiac function and myocardial infarction. The effects of chronic cardiac expression of FGF2 upon nitric oxide synthase (NOS) mRNA, protein, enzymatic activity, and cellular distribution will be systematically defined for all three isoforms (eNOS, iNOS, and nNOS), providing for the first time a thorough characterization of these changes in the mouse heart. Furthermore, the effect of pharmacological inhibitors of PKC, MAPK, NOS, and KATP channels, on post-ischemic recovery of cardiac function and infarct size will be investigated and correlated with the biological actions of FGF2. Integration of these signaling pathways will be evaluted to determine whether activation occurs in a parallel or serial fashion to modulate FGF2-induced cardioprotection. The results from this proposal will provide important new insights into molecular and signaling mechanisms of FGF2-induced cardioprotection and should facilitate the development of novel pharmacological and/or gene therapeutic strategies that improve and enhance cardiac resistance to ischemia in susceptible cardiac patients. ? ?
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