Plasminogen activator inhibitor type 1: the two faces of the same coin

Purpose of review Plasminogen activator inhibitor type 1 is the primary inhibitor of plasminogen activators. It is often bound to vitronectin, an abundant component of extracellular matrix in many tissues. The aim of this review is to discuss the contradictory results reported concerning the impact of plasminogen activator inhibitor type 1 expression in the kidney and in the vessel wall during pathological conditions. Recent findings First described as a 'bad guy' promoting the persistence of fibrin deposition and the evolution towards organ fibrosis, plasminogen activator inhibitor type 1 was recently reported to serve an unexpected protective role during fibrin-dependent diseases, such as experimental glomerulonephritis, and during aortic atherosclerosis. Summary Plasminogen activator inhibitor type 1 is not only an inhibitor of plasmin generation. Recent data suggest that plasminogen activator inhibitor type 1 is required for the regulation of plasminogen activator-dependent, plasmin-independent processes, and that its expression in vivo critically modulates inflammation, potentially by its capacity to occupy vitronectin binding sites.