Platelet deposition induced by severely damaged vessel wall is inhibited by a boroarginine synthetic peptide with antithrombin activity

Thrombin plays a key role in platelet activation and thrombosis. Specific inhibition of thrombin appears to be one of the best approaches to prevent thrombus formation. We have studied the effects of a synthetic α-aminoboronic acid derivative - [Ac, (D) Phe-Pro-Boro-Arg-Hydrocloric acid] - on platelet deposition on severely damaged arterial wall. Platelet deposition was evaluated under well characterized rheological conditions in an original perfusion chamber and detected by autologous ¹¹¹In-labeled platelets. The study was performed 'in vivo' in a porcine model of arterial thrombosis triggered by severely damaged vessel wall at blood flow conditions mimicking mild stenosis (1690 s^-1) and patent (212 s^-1) vessels. In addition, ex-vivo platelet aggregation activity was evaluated by whole blood impedance aggregometry using collagen, ADP and thrombin as agonists. The synthetic α-aminoboronic peptide was intravenously administered as a bolus followed by continuous infusion. Ex vivo thrombin-induced whole blood platelet aggregation was totally abolished, while ADP- and Collagen-induced whole blood platelet aggregation was not modified. The effects of the synthetic antithrombin on platelet deposition were evaluated in native blood (non-anticoagulated) conditions and in combination with heparin. Under both experimental conditions, the synthetic peptide significantly inhibited platelet deposition at local flow conditions of both high (1690 s^-1) and low (212s^-1) shear rates. Our results suggest that specific inhibition of locally generated thrombin might be a good strategy to prevent platelet dependent arterial thrombus formation independently of the local flow shear rate of the area at risk.