Abstract 634: Pigment Epithelium-Derived Factor (PEDF) Inhibits Occlusive Thrombus Formation in Rats
We have previously found that pigment epithelium-derived factor (PEDF), a glycoprotein with neuronal differentiating activity, inhibited tumor necrosis factor-a-, advanced glycation end product-, or angiotensin II-induced endothelial cell activation through its anti-oxidative properties, thus suggesting that PEDF may play a protective role against endothelial injury and atherosclerosis. However, the protective role of PEDF in thrombus formation, a critical process in atherosclerotic vascular diseases such as myocardial infarction and apoplexy, remains to be elucidated. In this study, we investigated whether and how PEDF could inhibit occlusive thrombus formation in rats. Occlusive thrombus formation was induced by treating rats with ligation and cuff placement at the left common artery. The occlusive thrombi were observed at the treated artery in a time-dependent manner; the average ratio of thrombus area to lumen area at the lesions (T/L ratio) reached 90 % 12–24h after treatment. Intravenous injection of PEDF dose-dependently inhibited thrombus formation at 12 h after the treatment; 30 mg PEDF treatment decreased the T/L ratio to about 60 % of control rats, which was prevented by the simultaneous treatment of anti-PEDF antibodies (Abs). Furthermore, intravenous injection of 30 mg PEDF significantly decreased the immunoreactive intensity of P-selectin, a marker of platelet activation, and the increase in NADPH oxidase activity and superoxide generation in thrombi. We further performed in vitro-experiments to examine whether the anti-thrombotic properties of PEDF were ascribed to its effects on platelets. In vitro, PEDF dose-dependently blocked the collagen-induced platelet activation; 100 nM PEDF decreased 2 mg/ml collagen-induced reactive oxygen species generation and platelet aggregation by about 80 % of the control, which was also blocked by the treatment with anti-PEDF Abs. These results demonstrate that PEDF could inhibit occlusive thrombus formation by blocking the platelet activation via suppression of NADPH oxidase-mediated superoxide generation. Our present study suggests that PEDF may be a novel therapeutic agent for the treatment of arterial thrombosis.