In hearts with volume overload, a complex sequence of compensatory events result in a continual state of extra cellular matrix (ECM) remodeling and by changes in myocyte function and eventually leads to congestive heart failure (HF). Increasing evidence suggests that reactive oxygen (ROS) and nitrogen (RNS) species, collectively termed reactive inflammatory species (RIS), and the enzymes that regulate their bioavailability are associated with contractile failure and myocardial structural damage in end-stage HF models. However, the relationship between RIS and the temporal progression of HF has not been extensively studied. Using an aortocaval fistula (ACF) model in the rat, 3 key, clinically relevant, time points in the temporal progression of volume overload have been rigorously defined in vivo: acute (2-5 days), chronic compensated (4-8 weeks), and chronic decompensated (15-21 weeks). Preliminary studies indicate increased tyrosine nitration of myofilament proteins, matrix degrading enzymes and signaling molecules during the acute phase of HF. An imbalance between RIS generating enzymes and antioxidant defenses was also observed acute stage and during the transition to decompensated HF. Moreover, we have found that RIS cause contractile dysfunction in isolated adult cardiac myocytes. This led to the hypothesis that RIS are important mediators of adverse LV remodeling and contractile dysfunction that underlie the development and progression of volume overload-induced HF.
Aim 1 will establish a link between reactive inflammatory species and the development and progression of volume overload-induced CHF. RIS will be measured using a combination of microdialysis, ESR (electron spin resonance) and standard biochemical assays. A series of pharmacological interventions and transgenic approaches (iNOS(-/-), myeloperoxidase (-/-), SOD overexpressors) will be used to manipulate RIS levels in vivo. A proteomics approach will used to identify RIS-modulated proteins.
Aim 2 will determine the mechanisms by which RIS contribute to LV remodeling in ACF-induced HF, with particular focus on ECM turnover in vivo and the regulation matrix metalloproteinase (MMP) activation by cardiac fibroblasts in vitro.
Aim 3 will use video edge microscopy, fluorescent Ca 2+ imaging and immunocytochemistry to determine whether altered susceptibility to RIS during HF progression contributes to cardiomyocyte. The proposed investigations are fundamentally important to the development of therapeutic strategies targeted to oxidant-induced injury and may have important implications in the treatment of HF.
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