Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Roles and interactions among protease-activated receptors and P2ry12 in hemostasis and thrombosis. 2093 Jan 20

For more than 10 years, dual antiplatelet therapy with aspirin and clopidogrel has remained the cornerstone of treatment for patients with acute coronary syndrome (ACS). The novel oral P2Y purinoceptor 12 (P2Y12)-receptor inhibitors prasugrel and ticagrelor were approved by the FDA for clinical use in 2009 and 2011, respectively. These agents have a faster-acting, more-potent, and more-predictable antiplatelet effect than clopidogrel, which translates into improved clinical outcomes in patients with ACS, albeit at the expense of an increased risk of bleeding. However, some patients continue to experience adverse ischaemic events despite treatment with aspirin and a P2Y12-receptor antagonist, because platelets can remain activated via pathways not inhibited by these agents, such as the protease-activated receptor (PAR)-1 platelet activation pathway stimulated by thrombin. Emerging antiplatelet therapies that might address these limitations include intravenous P2Y12 antagonists, oral PAR-1 antagonists, and thromboxane-receptor inhibitors. In this Review, we provide an overview of these novel antiplatelet drugs, including newly approved agents and emerging compounds currently under clinical development, and also discuss evolving concepts and unmet needs related to antiplatelet therapy for the treatment of ACS.
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PMID:Novel antiplatelet agents in acute coronary syndrome. 2528 81