The P2Y12 antagonists, 2-methylthioadenosine 5'-monophosphate triethylammonium salt and cangrelor (ARC69931MX), can inhibit human platelet aggregation through a Gi-independent increase in cAMP levels.
ADP plays an integral role in the process of hemostasis by signaling through two platelet G-protein-coupled receptors, P2Y1 and P2Y12. The recent use of antagonists against these two receptors has contributed a substantial body of data characterizing the ADP signaling pathways in human platelets. Specifically, the results have indicated that although P2Y1 receptors are involved in the initiation of platelet aggregation, P2Y12 receptor activation appears to account for the bulk of the ADP-mediated effects. Based on this consideration, emphasis has been placed on the development of a new class of P2Y12 antagonists (separate from clopidogrel and ticlopidine) as an approach to the treatment of thromboembolic disorders. The present work examined the molecular mechanisms by which two of these widely used adenosine-based P2Y12 antagonists (2-methylthioadenosine 5'-monophosphate triethylammonium salt (2MeSAMP) and ARC69931MX), inhibit human platelet activation. It was found that both of these compounds raise platelet cAMP to levels that substantially inhibit platelet aggregation. Furthermore, the results demonstrated that this elevation of cAMP did not require Gi signaling or functional P2Y12 receptors but was mediated through activation of a separate G protein-coupled pathway, presumably involving Gs. However, additional experiments revealed that neither 2MeSAMP nor ARC69931MX (cangrelor) increased cAMP through activation of A2a, IP, DP, or EP2 receptors, which are known to couple to Gs. Collectively, these findings indicate that 2MeSAMP and ARC69931MX interact with an unidentified platelet G protein-coupled receptor that stimulates cAMP-mediated inhibition of platelet function. This inhibition is in addition to that derived from antagonism of P2Y12 receptors.
From the Department of Pharmacology, University of Illinois, Chicago, Illinois 60612.
Subhashini
S
Srinivasan
From the Department of Pharmacology, University of Illinois, Chicago, Illinois 60612.
Fozia
F
Mir
From the Department of Pharmacology, University of Illinois, Chicago, Illinois 60612.
Jin-Sheng
JS
Huang
From the Department of Pharmacology, University of Illinois, Chicago, Illinois 60612.
Fadi T
FT
Khasawneh
From the Department of Pharmacology, University of Illinois, Chicago, Illinois 60612.
Stephen C-T
SC
Lam
From the Department of Pharmacology, University of Illinois, Chicago, Illinois 60612. Electronic address: gcl@uic.edu.
Guy C
GC
Le Breton
D000244:Adenosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D010974:Platelet Aggregation / Q000187:drug effects*; D058919:Purinergic P2 Receptor Antagonists; D043705:Receptor, Adenosine A2A / Q000378:metabolism; D044463:Receptor, PAR-1 / Q000378:metabolism; D044006:Receptors, Epoprostenol; D011971:Receptors, Immunologic / Q000378:metabolism; D011982:Receptors, Prostaglandin / Q000378:metabolism; D018078:Receptors, Prostaglandin E / Q000378:metabolism; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058925:Receptors, Purinergic P2Y12; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013873:Thionucleotides / Q000494:pharmacology*
C548576:P2RY12 protein, human; C545644:PTGER2 protein, human; C113936:PTGIR protein, human; D058919:Purinergic P2 Receptor Antagonists; D043705:Receptor, Adenosine A2A; D044463:Receptor, PAR-1; D044006:Receptors, Epoprostenol; D011971:Receptors, Immunologic; D011982:Receptors, Prostaglandin; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058925:Receptors, Purinergic P2Y12; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; C117446:cangrelor; C023427:guanosine 5'-O-(2-thiodiphosphate); D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C036293:prostaglandin D2 receptor; C008501:2-methylthio-ATP