Platelet adherence to subendothelium of human arteries in pulsatile and steady flow

Platelet adherence to human artery subendothelium was investigated in pulsatile and steady flow in an annular perfusion chamber. The platelet adhesion was larger in steady flow than in pulsatile flow. The ratio of contact platelets to spread platelets was higher in pulsatile flow. The number of adherent platelets increased at increasing platelet number, red cell concentration, perfusion time, and flow velocity in both systems. The difference in platelet adherence in the two flow systems decreased at increasing adhesion, indicating that saturation occurred. The experiments indicate that for comparative studies of platelet adhesion in steady flow at a physiological red cell concentration and a shear rate as observed in small arteries, it is preferable to apply subnormal platelet counts and perfusion times shorter than 5 min

Impact of vascular thromboxane prostanoid receptor activation on hemostasis, thrombosis, oxidative stress, and inflammation

The activation of thromboxane prostanoid (TP) receptor on platelets, monocytes/macrophages, endothelial cells, and vascular smooth muscle cells (SMC) plays important roles in regulating platelet activation and vascular tone and in the pathogenesis of thrombosis and vascular inflammation. Oxidative stress and vascular inflammation increase the formation of TP receptor agonists, which promote initiation and progression of atherogenesis and thrombosis. Furthermore, TP receptor activation promotes angiogenesis and vessel wall constriction. Besides thromboxane A2 and its endoperoxide precursors, prostaglandin G2 and H2 , isoprostanes, and 20-hydroxyeicosatetraenoic acid also activate TP receptor as autocrine or paracrine ligands. These additional TP activators play a role in pathological conditions such as diabetes, obesity, and hypertension, and their biosynthesis is not inhibited by aspirin, at variance with that of thromboxane A2 . The understanding of TP receptor function increased our current knowledge of the pathogenesis of atherosclerosis and thrombosis, highlighting the great impact that this receptor has in cardiovascular disorders

Collagen surfaces to measure thrombus formation under flow: possibilities for standardization

Stemcel biology/Regenerative medicine (incl. bloodtransfusion

EV-077 in vitro inhibits platelet aggregation in type-2 diabetics on aspirin

INTRODUCTION: This study aimed to characterize the in vitro effect of EV-077, a compound that antagonises the binding of prostanoids and isoprostanes to the thromboxane receptor (TP) and inhibits the thromboxane synthase (TS), on platelet aggregation of patients with type-2 diabetes and coronary artery disease (CAD) on chronic aspirin treatment. The effect of EV-077 on 8-iso-PGE(2)-mediated TP receptor contraction of human arteries was also investigated. MATERIALS AND METHODS: Fifty-two type-2 diabetics with CAD on chronic aspirin (100mg) treatment were studied. Arachidonic acid-induced platelet aggregation was measured by impedance aggregometry in platelet-rich plasma (PRP) and whole blood anticoagulated with hirudin, and by light transmission aggregometry in citrate-anticoagulated PRP following 10-min in vitro exposure to EV-077 (100nmol/l) or control. The effect of EV-077 was measured on isometric contraction of 24 human umbilical arteries induced by isoprostane 8-iso-PGE(2). RESULTS: Arachidonic acid (1mmol/l) induced substantial aggregation in hirudin-anticoagulated whole blood (63\ub14AU), which was significantly reduced by in vitro exposure to EV-077 (38\ub13AU, P<0.001). Virtually no arachidonic acid-induced aggregation in citrate-anticoagulated or hirudin-anticoagulated PRP was observed. EV-077 potently, competitively and reversibly inhibited TP mediated contraction of umbilical arteries by 8-iso-PGE(2) (P<0.01). CONCLUSIONS: Aspirin did not completely inhibit arachidonic acid-induced platelet aggregation in whole blood from type-2 diabetics with CAD. This aggregation is likely induced by prostanoids and/or isoprostanes produced by leukocytes, because it was significantly reduced by EV-077. The TP receptor-mediated contraction of human arteries induced by isoprostane 8-iso-PGE(2) was effectively inhibited by EV-077