Roles and interactions among protease-activated receptors and P2ry12 in hemostasis and thrombosis

• DOI: 10.1073/pnas.1013309107
• Publication Date: 2010-10-08T03:01:59Z
• Authors: Ivo Cornelissen; Daniel Palmer; Tovo David; Lisa Wilsbacher; Cherry Concengco; Pamela Conley; Anjali Pandey; Shaun R. Coughlin
• Keywords: Blood Platelets; Male; Mice, Knockout; 0301 basic medicine; Hemostasis; Receptors, Proteinase-Activated; Thrombin; Cell Cycle Proteins; Thrombosis; In Vitro Techniques; Models, Biological; Receptors, Purinergic P2Y12; Adenosine Diphosphate; Mice; 03 medical and health sciences; Animals; Humans; Female; Receptors, Thrombin; Cell Adhesion Molecules; Adaptor Proteins, Signal Transducing; Signal Transduction

Toward understanding their redundancies and interactions in hemostasis and thrombosis, we examined the roles of thrombin receptors (protease-activated receptors, PARs) and the ADP receptor P2RY12 (purinergic receptor P2Y G protein-coupled 12) in human and mouse platelets ex vivo and in mouse models. Par3 −/− and Par4 +/− mouse platelets showed partially decreased responses to thrombin, resembling those in PAR1 antagonist-treated human platelets. P2ry12 +/− mouse platelets showed partially decreased responses to ADP, resembling those in clopidogrel-treated human platelets. Par3 −/− mice showed nearly complete protection against carotid artery thrombosis caused by low FeCl 3 injury. Par4 +/− and P2ry12 +/− mice showed partial protection. Increasing FeCl 3 injury abolished such protection; combining partial attenuation of thrombin and ADP signaling, as in Par3 −/− : P2ry12 +/− mice, restored it. Par4 −/− mice, which lack platelet thrombin responses, showed still better protection. Our data suggest that ( i ) the level of thrombin driving platelet activation and carotid thrombosis was low at low levels of arterial injury and increased along with the contribution of thrombin-independent pathways of platelet activation with increasing levels of injury; ( ii ) although P2ry12 acts downstream of PARs to amplify platelet responses to thrombin ex vivo, P2ry12 functioned in thrombin/PAR-independent pathways in our in vivo models; and ( iii ) P2ry12 signaling was more important than PAR signaling in hemostasis models; the converse was noted for arterial thrombosis models. These results make predictions being tested by ongoing human trials and suggest hypotheses for new antithrombotic strategies.