The long-term goal of this proposal is to identify functions and determine mechanisms of the fibrinolytic system, and its inhibitors, in physiological and pathological processes utilizing cell-based and in vivo models. The availability of mice with deficiencies of genes of the fibrinolytic system has resulted in direct analyses of the role of these proteins in a number of biological events. Studies have indicated that a PAI-1 deficiency diminishes angiogenesis in tumor models. Further, our laboratory has shown that endothelial cell (EC) signaling and function are regulated by PAI-1/LRP interactions. The current application will further elucidate effects of PAI-1 on cell signaling pathways and determine the importance of PAI-1/LRP interactions in both cellular and physiological events. As a result of these observations, the following studies are proposed: (1.) Determine the effects of a PAI-1 deficiency on murine EC JAK/STAT signaling and cell cycle progression. These studies will assess STAT and JAK expression profiles and activation status in proliferating wild-type (WT) and PAI-1-/- EC as well as the extent of nuclear translocation of STAT. The addition of rPAI-1 and mutants will determine which functional domains of PAI-1 regulate the activation status of this pathway. Additional studies will determine effects on cell migration. Downstream effects on cell cycle progression will also be investigated. The hypothesis is that a PAI-1 deficiency will affect JAK/STAT signaling and downstream cell cycle progression, and that these effects are mediated by PAI-1/LRP interactions. (2.) Characterize early and late stage events of cardiac fibrosis in PAI-1-/- and uPA-/-/PAI-1-/- mice. Recent studies have shown that PAI-1-/- mice develop cardiac fibrosis, which may be mediated by dysregulated uPA or chronic activation of the Akt pathway, the result of altered PAI-1/LRP interactions. The studies proposed will initially characterize cardiac fibrosis in PAI-1-/- and uPA-/-/PAI-1-/- mice in order to differentiate effects from uPA activity and PAI-1 functions independent of uPA inhibition in cardiac fibrosis phenotypes. The hypothesis is that cardiac fibrosis will be regulated by urokinase activity and other functions of PAI-I which will be further pursued in future studies of mice expressing functional mutations of PAI-1.

Public Health Relevance

Plasminogen activator inhibitor-1 (PAI-1) is a multifunctional protein that can affect cell function through altering cell adhesion to extracellular matrix by interaction with vitronectin (VN) and/or regulating internalization of urokinase (uPA)/urokinase receptor (uPAR) through interaction with low density lipoprotein receptor related protein (LRP). Our laboratory has determined that cell signaling and resultant effects on cell proliferation are regulated by PAI-1/LRP interactions. Results from these studies will facilitate an understanding of the effects of PAI-1 on endothelial cell function and biology and serve to identify its mechanistic involvement in the angiogenic process.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-HEME-C (02))
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Link, Rebecca P
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University of Notre Dame
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Notre Dame
United States
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Gupta, Kamlesh K; Xu, Zhi; Castellino, Francis J et al. (2016) Plasminogen activator inhibitor-1 stimulates macrophage activation through Toll-like Receptor-4. Biochem Biophys Res Commun 477:503-8
Narasaki, R; Xu, Z; Liang, Z et al. (2012) The vitronectin-binding domain of plasminogen activator inhibitor-1 plays an important functional role in lipopolysaccharide-induced lethality in mice. J Thromb Haemost 10:2618-21
Ploplis, Victoria A (2011) Effects of altered plasminogen activator inhibitor-1 expression on cardiovascular disease. Curr Drug Targets 12:1782-9
Xu, Zhi; Castellino, Francis J; Ploplis, Victoria A (2010) Plasminogen activator inhibitor-1 (PAI-1) is cardioprotective in mice by maintaining microvascular integrity and cardiac architecture. Blood 115:2038-47
Balsara, Rashna D; Ploplis, Victoria A (2008) Plasminogen activator inhibitor-1: the double-edged sword in apoptosis. Thromb Haemost 100:1029-36
Balsara, R D; Xu, Z; Ploplis, V A (2007) Targeting plasminogen activator inhibitor-1: role in cell signaling and the biology of domain-specific knock-in mice. Curr Drug Targets 8:982-95
Xu, Zhi; Balsara, Rashna D; Gorlatova, Natalia V et al. (2004) Conservation of critical functional domains in murine plasminogen activator inhibitor-1. J Biol Chem 279:17914-20
Busuttil, S J; Ploplis, V A; Castellino, F J et al. (2004) A central role for plasminogen in the inflammatory response to biomaterials. J Thromb Haemost 2:1798-805
Ploplis, Victoria A; Balsara, Rashna; Sandoval-Cooper, Mayra J et al. (2004) Enhanced in vitro proliferation of aortic endothelial cells from plasminogen activator inhibitor-1-deficient mice. J Biol Chem 279:6143-51
Sato, Jun; Schorey, Jeffrey; Ploplis, Victoria A et al. (2003) The fibrinolytic system in dissemination and matrix protein deposition during a mycobacterium infection. Am J Pathol 163:517-31

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