New tricks for old dogs - Nonthrombotic effects of thrombin in vessel wallbiology

Thrombin is a serine protease that potently activates platelets and catalyz es the conversion of fibrinogen to fibrin, Thrombin also exerts direct effe cts on vascular cells, such as smooth muscle cells, via interactions with m embers of the protease-activated receptor family. Evidence in several anima l models implicates thrombin-mediated signaling events in the response to i njury that typifies vascular lesion formation in atherosclerosis and resten osis. In this review, we examine the activation of protease-activated recep tors by thrombin, the downstream signaling events mediated by these recepto rs, and the physiological role of thrombin in vascular cells and vascular d isease.