Venous thromboembolism (DVT/PE) is a major healthcare problem causing significant morbidity andmortality. According to the AHA, up to two million Americans are affected annually by deep venousthrombosis (DVT) and 200,000 die annually from one of its complications, pulmonary embolism (PE), morethan breast cancer and AIDs combined. We and others have demonstrated that a significant inflammatoryresponse occurs with venous thromboembolism and that this inflammation, through the production ofprocoagulant microparticles, leads to thrombus amplification. Plasminogen Activator lnhibitor-1 (PAI-1) isthe primary inhibitor of plasminogen activators in plasma. It is secreted in an active form from liver andendothelial cells and is stabilized by binding to vitronectin. It inactivats both tissue plasminogen activator(tPA) and urokinase-type plasminogen activator (uPA). PAI-1 levels are elevated by hyperlipidemia, andPAI-1 elevation appears to synergize with Factor V Leiden genetic abnormalities, a thrombophilic mutation ofFactor V (Leiden) which renders it resistent to proteolytic degradation. It is plausible that elevated PAI-1could suppress fibrinolysis and increase thrombosis. Studies on the role of elevated levels of PAI-1 tovenous thrombosis have been contradictory. The purpose of this proposal is to determine the role of PAI-1in venous thrombogenesis in a murine complete IVC ligtion venous thrombosis model (aim 1a) and a murineIVC stenosis-induced venous thrombosis model (aim 1b). Mice with PAI-1 deletion and PAI-1 overexpressionwill be studied, as will vitronectin deficient mice, mice with combined PAI-1/vitronectin deficiency,and wild type mice. We will also use pharmacologic PAI-1 inhibition. Thrombogenesis, vein wall/thrombusinflammation, the production of procoagulant microparticles, and thrombus/vein wall fibrosis will beevaluated. Additionally, we will determine the efficacy of PAI-1 inhibition after thrombogenesis, the roles ofplasmin generation, and the role of thrombin in venous thrombosis in both models (aim 1c). Finally, we willstudy levels of PAI-1 in Factor V Leiden heterozygous and homozygous mice, ApoE hyperlipidemic mice,Egr-1 null mice (the Egr-1 site in the PAI-1 promoter region is induced by hypoxia, a characteristic of venousstasis), and wild type mice in both models (aims 2a, 2b). These levels of PAI-1 will be correlated tothrombosis. The results of this proposal should better define the role of PAI-1 in venous thrombogenesis.
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