Plasminogen activator inhibitor-1 (PAI-1) is the primary inhibitor of plasminogen activators in plasma, rapidly inactivating both tissue plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA). PAI-1 is a single-chain glycoprotein with a molecular weight of 47 kilodaltons. During fibrinolysis, tissue plasminogen activator (tPA) converts the inactive protein plasminogen into plasmin which plays a critical role in fibrinolysis by degrading fibrin and providing localized protease activity in a number of physiological functions. PAI-1 is synthesized in the liver and by endothelial cells, and its synthesis is regulated by several physiologic mediators, including endotoxin, interleukin-1, fibroblast growth factor-2, and lipids. Plasminogen activator inhibitor-1 is an important inhibitor of the fibrinolytic system, so elevated levels could suppress fibrinolysis and result in an increased risk of thrombosis. Increased PAI-1 levels have been shown to be associated with a number of atherosclerotic risk factors, PAI-1 has been shown to act as a prothrombic factor in both arterial and venous thromboembolic disorders. Increased levels of PAI-1 are associated with an increased incidence of acute coronary syndrome. PAI-1 levels are also increased in patients with chronic and acute coronary artery disease (CAD) and in patients who suffer restenosis after coronary angioplasty.

Synonyms: Serpin peptidase inhibitor, PAI-E, PLANH1