Mechanisms of nitric oxide control in endothelial and cardiac dysfunction

The central goal of this thesis was to understand the functional relevance of genetic polymorphisms in cardiovascular diseases. Endothelial nitric oxide synthase (eNOS, NOS3) is a critical regulator of cardiovascular function and is altered in a number of cardiovascular diseases. The mechanistic contributions of genetic polymorphisms in the NOS3 gene have not been completely understood. Another important goal was to understand the mechanistic aspects of sepsis related cardiac failure. Reactive nitrogen species have been implicated along with impaired mitochondrial function. The exact mechanisms, interplay of these mediators and their time course is not completely understood.; Intact endothelial function is a major regulator of cardiovascular function. Alterations in the endothelial nitric oxide (NO) production via endothelial nitric oxide synthase (eNOS, NOS3) have been implicated in vascular dysfunction. Moreover many genetic polymorphisms have been studied for their association with diseases and it has been established that NOS3 genetic polymorphisms may be a predisposing risk factor. These clinical studies are valuable, but fail to provide mechanistic insights. We have employed a relevant primary cell culture model to study the relevance of genetic polymorphisms.; Increased nitric oxide (NO) production and altered mitochondrial function are implicated as contributing mechanisms to sepsis-induced cardiac dysfunction. NO production is amplified during sepsis due to enhanced expression of inducible nitric oxide synthase (NOS2), which is regulated by calcineurin. Peroxynitrite, alters mitochondrial morphology and function, in part, through protein nitration. We tested the hypothesis that calcineurin inhibitors would attenuate NO production during endotoxemia, and resulting in preservation of myocardial mitochondrial morphology and cardiac function. LPS treatment resulted in reduced contractility and prolonged relaxation times, altered myocardial mitochondrial morphology, and increases in NOS2 protein expression and protein nitration. Cyclosporin A (CsA) pre-treatment normalized all measured parameters; FK506 failed to inhibit NOS2 expression or mitochondrial swelling, but reduced tissue nitration and preserved cardiac function. Enhanced myocardial protein nitration was associated with increased mitochondrial swelling and cardiac dysfunction. Thus, altered reactive nitrogen species apparently play an important role in sepsis related cardiac failure. (Abstract shortened by UMI.)...