Although intravascular fibrin deposits and/or connective tissue accumulation are a common feature of vascular disorders, the underlying mechanisms remain obscure. The primary hypothesis of this proposal is that these changes result in part from a cytokine-mediated decrease in the fibrinolytic potential of cells of the vessel wall itself. This hypothesis will be tested by defining the fibrinolytic system of the vessel wall in vivo and determining whether it changes during experimentally induced or naturally occurring vascular disease. For example, the status of this system in endotoxemic mice, and in mice with bleomycin-mediated lung fibrosis, antibody-induced glomerulonephritis, and diet-induced atherosclerosis will be determined and compared to normal and diseased (e.g. atherosclerotic vessels) human tissues. The tissue distribution of tissue-plasminogen activator (t-PA), urokinase-PA (u-PA), PA-inhibitor 1 (PAI-1), PAI-2 and the u-PA receptor (u-PAR) will be investigated by employing specific antibodies in immunohistochemical studies to localize antigens, and specific cDNA probes in Northern blots and nuclease protection assays to quantitate mRNAs. In situ hybridization experiments will be performed using cRNA probes to each fibrinolytic component, and to von Willebrand's factor, in order to identify positive cells within the tissues, and to determine whether they are endothelial cells. The influence of infiltrating cells, and of cytokines released by them (e.g., tumor necrosis factor and transforming factor beta) on expression of this system during the progression of these diseases will be investigated. Finally, changes in the expression of these molecules in the tissues will be compared to changes in the blood to obtain insights into the origins of the plasma fibrinolytic components. These studies will begin to delineate the regulatory events controlling the individual fibrinolytic components in the tissues and blood under various conditions, and may contribute to our understanding of the influence of the fibrinolytic system on the prothrombotic state.
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