Mechanisms of platelet activation: Need for new strategies to protect against platelet-mediated atherothrombosis

Summary

Platelets are central mediators of haemostasis at sites of vascular injury, but they also mediate pathologic thrombosis. Activated platelets stimulate thrombus formation in response to rupture of an atherosclerotic plaque or endothelial cell erosion, promoting atherothrombotic disease. They also interact with endothelial cells and leukocytes to promote inflammation, which contributes to atherosclerosis. Multiple pathways contribute to platelet activation, and current oral antiplatelet therapy with aspirin and a P2Y₁₂ adenosine diphosphate (ADP) receptor antagonist target the thromboxane A₂ and ADP pathways, respectively. Both can diminish activation by other factors, but the extent of their effects depends upon the agonist, agonist strength, and platelet reactivity status. Although these agents have demonstrated significant clinical benefit, residual morbidity and mortality remain high. Neither agent is effective in inhibiting thrombin, the most potent platelet activator. This lack of comprehensive inhibition of platelet function allows continued thrombus formation and exposes patients to risk for recurrent thrombotic events. Moreover, bleeding risk is a substantial limitation of antiplatelet therapy, because these agents target platelet activation pathways critical for both protective haemostasis and pathologic thrombosis. Novel antiplatelet therapies that provide more complete inhibition of platelet activation without increasing bleeding risk could considerably decrease residual risk for ischemic events. Inhibition of the protease-activated receptor (PAR)-1 platelet activation pathway stimulated by thrombin is a novel, emerging approach to achieve more comprehensive inhibition of platelet activation when used in combination with current oral antiplatelet agents. PAR-1 inhibition is not expected to increase bleeding risk, as this pathway does not interfere with haemostasis.

Keywords

Antiplatelet therapy - haemostasis - inflammation - platelet activation - thrombosis

• References

• 1 Brass LF. Thrombin and platelet activation. Chest 2003; 124: 18S-25S.
• 2 Davi G, Patrono C. Platelet activation and atherothrombosis. N Engl J Med 2007; 357: 2482-2494.
• 3 Varga-Szabo D, Pleines I, Nieswandt B. Cell adhesion mechanisms in platelets. Arterioscler Thromb Vasc Biol 2008; 28: 403-412.
• 4 Offermanns S. Activation of platelet function through G protein-coupled receptors. Circ Res 2006; 99: 1293-1304.
• 5 Mann KG. Thrombin formation. Chest 2003; 124: 4S-10S.
• 6 Brummel KE, Paradis SG, Butenas S. et al. Thrombin functions during tissue factor-induced blood coagulation. Blood 2002; 100: 148-152.
• 7 Vu TK, Hung DT, Wheaton VI. et al. Molecular cloning of a functional thrombin receptor reveals a novel proteolytic mechanism of receptor activation. Cell 1991; 64: 1057-1068.
• 8 Coughlin SR. Protease-activated receptors in hemostasis, thrombosis and vascular biology. J Thromb Haemost 2005; 03: 1800-1814.
• 9 Leger AJ, Covic L, Kuliopulos A. Protease-activated receptors in cardiovascular diseases. Circulation 2006; 114: 1070-1077.
• 10 Landis RC. Protease activated receptors: clinical relevance to hemostasis and inflammation. Hematol Oncol Clin North Am 2007; 21: 103-113.
• 11 Martorell L, Martinez-Gonzalez J, Rodriguez C. et al. Thrombin and protease-activated receptors (PARs) in atherothrombosis. Thromb Haemost 2008; 99: 305-315.
• 12 De Candia E, Hall SW, Rutella S. et al. Binding of thrombin to glycoprotein Ib accelerates the hydrolysis of Par-1 on intact platelets. J Biol Chem 2001; 276: 4692-4698.
• 13 Brass LF, Zhu L, Stalker TJ. Novel therapeutic targets at the platelet vascular interface. Arterioscler Thromb Vasc Biol 2008; 28: s43-50.
• 14 Wegener KL, Partridge AW, Han J. et al. Structural basis of integrin activation by talin. Cell 2007; 128: 171-182.
• 15 Mondoro TH, White MM, Jennings LK. Active GPIIb-IIIa conformations that link ligand interaction with cytoskeletal reorganization. Blood 2000; 96: 2487-2495.
• 16 Moser M, Nieswandt B, Ussar S. et al. Kindlin-3 is essential for integrin activation and platelet aggregation. Nat Med 2008; 14: 325-330.
• 17 Patil S, Newman DK, Newman PJ. Platelet endothelial cell adhesion molecule-1 serves as an inhibitory receptor that modulates platelet responses to collagen. Blood 2001; 97: 1727-1732.
• 18 Nanda N, Andre P, Bao M. et al. Platelet aggregation induces platelet aggregate stability via SLAM family receptor signaling. Blood 2005; 106: 3028-3034.
• 19 Israels SJ, McMillan-Ward EM. CD63 modulates spreading and tyrosine phosphorylation of platelets on immobilized fibrinogen. Thromb Haemost 2005; 93: 311-318.
• 20 Goschnick MW, Lau LM, Wee JL. et al. Impaired “outside-in” integrin alphaIIbbeta3 signaling and thrombus stability in TSSC6-deficient mice. Blood 2006; 108: 1911-1918.
• 21 Prevost N, Woulfe DS, Jiang H. et al. Eph kinases and ephrins support thrombus growth and stability by regulating integrin outside-in signaling in platelets. Proc Natl Acad Sci U S A 2005; 102: 9820-9825.
• 22 Bouchard BA, Tracy PB. Platelets, leukocytes, and coagulation. Curr Opin Hematol 2001; 08: 263-269.
• 23 Heemskerk JW, Bevers EM, Lindhout T. Platelet activation and blood coagulation. Thromb Haemost 2002; 88: 186-193.
• 24 Siljander P, Farndale RW, Feijge MA. et al. Platelet adhesion enhances the glycoprotein VI-dependent procoagulant response: Involvement of p38 MAP kinase and calpain. Arterioscler Thromb Vasc Biol 2001; 21: 618-627.
• 25 Storey RF, Sanderson HM, White AE. et al. The central role of the P(2T) receptor in amplification of human platelet activation, aggregation, secretion and procoagulant activity. Br J Haematol 2000; 110: 925-934.
• 26 Gawaz M, Langer H, May AE. Platelets in inflammation and atherogenesis. J Clin Invest 2005; 115: 3378-3384.
• 27 May AE, Seizer P, Gawaz M. Platelets: inflammatory firebugs of vascular walls. Arterioscler Thromb Vasc Biol 2008; 28: s5-10.
• 28 Langer HF, Gawaz M. Platelet-vessel wall interactions in atherosclerotic disease. Thromb Haemost 2008; 99: 480-486.
• 29 von Hundelshausen P, Weber C. Platelets as immune cells: bridging inflammation and cardiovascular disease. Circ Res 2007; 100: 27-40.
• 30 Weyrich AS, Zimmerman GA. Platelets: signaling cells in the immune continuum. Trends Immunol 2004; 25: 489-495.
• 31 Subramaniam M, Frenette PS, Saffaripour S. et al. Defects in hemostasis in P-selectin-deficient mice. Blood 1996; 87: 1238-1242.
• 32 Massberg S, Enders G, Leiderer R. et al. Plateletendothelial cell interactions during ischemia/reperfusion: the role of P-selectin. Blood 1998; 92: 507-515.
• 33 Bombeli T, Schwartz BR, Harlan JM. Adhesion of activated platelets to endothelial cells: evidence for a GPIIbIIIa-dependent bridging mechanism and novel roles for endothelial intercellular adhesion molecule 1 (ICAM-1), alphavbeta3 integrin, and GPIbalpha. J Exp Med 1998; 187: 329-339.
• 34 Gawaz M, Neumann FJ, Dickfeld T. et al. Vitronectin receptor (alpha(v)beta3) mediates platelet adhesion to the luminal aspect of endothelial cells: implications for reperfusion in acute myocardial infarction. Circulation 1997; 96: 1809-1818.
• 35 Lincoff AM, Kereiakes DJ, Mascelli MA. et al. Abciximab suppresses the rise in levels of circulating inflammatory markers after percutaneous coronary revascularization. Circulation 2001; 104: 163-167.
• 36 Shiraki R, Inoue N, Kawasaki S. et al. Expression of Toll-like receptors on human platelets. Thromb Res 2004; 113: 379-385.
• 37 Zernecke A, Liehn EA, Fraemohs L. et al. Importance of junctional adhesion molecule-A for neointimal lesion formation and infiltration in atherosclerosisprone mice. Arterioscler Thromb Vasc Biol 2006; 26: e10-13.
• 38 Henn V, Slupsky JR, Grafe M. et al. CD40 ligand on activated platelets triggers an inflammatory reaction of endothelial cells. Nature 1998; 391: 591-594.
• 39 Slupsky JR, Kalbas M, Willuweit A. et al. Activated platelets induce tissue factor expression on human umbilical vein endothelial cells by ligation of CD40. Thromb Haemost 1998; 80: 1008-1014.
• 40 Santos-Martinez MJ, Medina C, Jurasz P. et al. Role of metalloproteinases in platelet function. Thromb Res 2008; 121: 535-542.
• 41 Lambert MP, Sachais BS, Kowalska MA. Chemokines and thrombogenicity. Thromb Haemost 2007; 97: 722-729.
• 42 von Hundelshausen P, Weber KS, Huo Y. et al. RANTES deposition by platelets triggers monocyte arrest on inflamed and atherosclerotic endothelium. Circulation 2001; 103: 1772-1777.
• 43 von Hundelshausen P, Koenen RR, Sack M. et al. Heterophilic interactions of platelet factor 4 and RANTES promote monocyte arrest on endothelium. Blood 2005; 105: 924-930.
• 44 Koenen RR, von Hundelshausen P, Nesmelova IV. et al. Disrupting functional interactions between platelet chemokines inhibits atherosclerosis in hyperlipidemic mice. Nat Med 2009; 15: 97-103.
• 45 Gawaz M, Brand K, Dickfeld T. et al. Platelets induce alterations of chemotactic and adhesive properties of endothelial cells mediated through an interleukin1-dependent mechanism. Implications for atherogenesis. Atherosclerosis 2000; 148: 75-85.
• 46 Krotz F, Sohn HY, Gloe T. et al. NAD(P)H oxidasedependent platelet superoxide anion release increases platelet recruitment. Blood 2002; 100: 917-924.
• 47 da Costa Martins PA, van Gils JM, Mol A. et al. Platelet binding to monocytes increases the adhesive properties of monocytes by up-regulating the expression and functionality of beta1 and beta2 integrins. J Leukoc Biol 2006; 79: 499-507.
• 48 Schober A, Manka D, von Hundelshausen P. et al. Deposition of platelet RANTES triggering monocyte recruitment requires P-selectin and is involved in neointima formation after arterial injury. Circulation 2002; 106: 1523-1529.
• 49 Zarbock A, Polanowska-Grabowska RK, Ley K. Platelet-neutrophil-interactions: linking hemostasis and inflammation. Blood Rev 2007; 21: 99-111.
• 50 Weyrich AS, Schwertz H, Kraiss LW. et al. Protein synthesis by platelets: historical and new perspectives. J Thromb Haemost 2009; 07: 241-246.
• 51 Lindemann S, Tolley ND, Dixon DA. et al. Activated platelets mediate inflammatory signaling by regulated interleukin 1beta synthesis. J Cell Biol 2001; 154: 485-490.
• 52 Evangelista V, Manarini S, Di Santo A. et al. De novo synthesis of cyclooxygenase-1 counteracts the suppression of platelet thromboxane biosynthesis by aspirin. Circ Res 2006; 98: 593-595.
• 53 Weyrich AS, Denis MM, Schwertz H. et al. mTORdependent synthesis of Bcl-3 controls the retraction of fibrin clots by activated human platelets. Blood 2007; 109: 1975-1983.
• 54 Mason KD, Carpinelli MR, Fletcher JI. et al. Programmed anuclear cell death delimits platelet life span. Cell 2007; 128: 1173-1186.
• 55 Leytin V, Allen DJ, Lyubimov E. et al. Higher thrombin concentrations are required to induce platelet apoptosis than to induce platelet activation. Br J Haematol 2007; 136: 762-764.
• 56 Leytin V, Allen DJ, Mykhaylov S. et al. Thrombintriggered platelet apoptosis. J Thromb Haemost 2006; 04: 2656-2663.
• 57 Schulman SP. Antiplatelet therapy in non-ST-segment elevation acute coronary syndromes. J Am Med Assoc 2004; 292: 1875-1882.
• 58 Patrono C. Aspirin as an antiplatelet drug. N Engl J Med 1994; 330: 1287-1294.
• 59 Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. Br Med J 2002; 324: 71-86.
• 60 Lewis Jr. HD, Davis JW, Archibald DG. et al. Protective effects of aspirin against acute myocardial infarction and death in men with unstable angina. Results of a Veterans Administration Cooperative Study. N Engl J Med 1983; 309: 396-403.
• 61 Schwartz L, Bourassa MG, Lesperance J. et al. Aspirin and dipyridamole in the prevention of restenosis after percutaneous transluminal coronary angioplasty. N Engl J Med 1988; 318: 1714-1719.
• 62 Popma JJ, Ohman EM, Weitz J. et al. Antithrombotic therapy in patients undergoing percutaneous coronary intervention. Chest 2001; 119: 321S-336S.
• 63 Collaborative overview of randomised trials of antiplatelet therapy--I: Prevention of death, myocardial infarction, and stroke by prolonged antiplatelet therapy in various categories of patients. Antiplatelet Trialists’ Collaboration. Br Med J 1994; 308: 81-106.
• 64 Cattaneo M. P2Y12 receptor antagonists: a rapidly expanding group of antiplatelet agents. Eur Heart J 2006; 27: 1010-1012.
• 65 A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee. Lancet 1996; 348: 1329-1339.
• 66 Yusuf S, Zhao F, Mehta SR. et al. Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation. N Engl J Med 2001; 345: 494-502.
• 67 Steinhubl SR, Berger PB, Mann 3rd JT. et al. Early and sustained dual oral antiplatelet therapy following percutaneous coronary intervention: a randomized controlled trial. J Am Med Assoc 2002; 288: 2411-2420.
• 68 Sabatine MS, Cannon CP, Gibson CM. et al. Addition of clopidogrel to aspirin and fibrinolytic therapy for myocardial infarction with ST-segment elevation. N Engl J Med 2005; 352: 1179-1189.
• 69 Chen ZM, Jiang LX, Chen YP. et al. Addition of clopidogrel to aspirin in 45,852 patients with acute myocardial infarction: randomised placebo-controlled trial. Lancet 2005; 366: 1607-1621.
• 70 Bhatt DL, Fox KA, Hacke W. et al. Clopidogrel and aspirin versus aspirin alone for the prevention of atherothrombotic events. N Engl J Med 2006; 354: 1706-1717.
• 71 Bhatt DL, Flather MD, Hacke W. et al. Patients with prior myocardial infarction, stroke, or symptomatic peripheral arterial disease in the CHARISMA trial. J Am Coll Cardiol 2007; 49: 1982-1988.
• 72 Wiviott SD, Braunwald E, McCabe CH, Montalescot G, Ruzyllo W, Gottlieb S. et al. Prasugrel versus clopidogrel in patients with acute coronary syndromes. N Engl J Med 2007; 357: 2001-2015.
• 73 Rao SV, Eikelboom JA, Granger CB. et al. Bleeding and blood transfusion issues in patients with non-STsegment elevation acute coronary syndromes. Eur Heart J 2007; 28: 1193-1204.
• 74 Rao SV, Jollis JG, Harrington RA. et al. Relationship of blood transfusion and clinical outcomes in patients with acute coronary syndromes. J Am Med Assoc 2004; 292: 1555-1562.
• 75 Rao SV, O’Grady K, Pieper KS. et al. Impact of bleeding severity on clinical outcomes among patients with acute coronary syndromes. Am J Cardiol 2005; 96: 1200-1206.
• 76 Angiolillo DJ, Fernandez-Ortiz A, Bernardo E. et al. Variability in individual responsiveness to clopidogrel: clinical implications, management, and future perspectives. J Am Coll Cardiol 2007; 49: 1505-1516.
• 77 De Miguel A, Ibanez B, Badimon JJ. Clinical implications of clopidogrel resistance. Thromb Haemost 2008; 100: 196-203.
• 78 Boersma E, Harrington RA, Moliterno DJ. et al. Platelet glycoprotein IIb/IIIa inhibitors in acute coronary syndromes: a meta-analysis of all major randomised clinical trials. Lancet 2002; 359: 189-198.
• 79 Derian CK, Damiano BP, Addo MF. et al. Blockade of the thrombin receptor protease-activated receptor-1 with a small-molecule antagonist prevents thrombus formation and vascular occlusion in nonhuman primates. J Pharmacol Exp Ther 2003; 304: 855-861.
• 80 Kato Y, Kita Y, Hirasawa-Taniyama Y. et al. Inhibition of arterial thrombosis by a protease-activated receptor 1 antagonist, FR171113, in the guinea pig. Eur J Pharmacol 2003; 473: 163-169.
• 81 Vandendries ER, Hamilton JR, Coughlin SR. et al. Par4 is required for platelet thrombus propagation but not fibrin generation in a mouse model of thrombosis. Proc Natl Acad Sci USA 2007; 104: 288-292.
• 82 Maurice P, Legrand C, Fauvel-Lafeve F. Platelet adhesion and signaling induced by the octapeptide primary binding sequence (KOGEOGPK) from type III collagen. Faseb J 2004; 18: 1339-1347.
• 83 Suh TT, Holmback K, Jensen NJ. et al. Resolution of spontaneous bleeding events but failure of pregnancy in fibrinogen-deficient mice. Genes Dev 1995; 09: 2020-2033.
• 84 Chackalamannil S, Wang Y, Greenlee WJ. et al. Discovery of a novel, orally active himbacine-based thrombin receptor antagonist (SCH 530348) with potent antiplatelet activity. J Med Chem 2008; 51: 3061-3064.
• 85 Chintala M, Vemulapalli S, Kurowski S. et al. SCH 530348, a novel oral antiplatelet agent, demonstrated no bleeding risk alone or in combination with aspirin and clopidogrel in Cynomolgus monkeys. Atheroscler Thromb Vasc Biol 2008; 28: e32-e149 Abstract P579.
• 86 Becker RC, Moliterno DJ, Jennings LK. et al. Safety and tolerability of SCH 530348 in patients undergoing non-urgent percutaneous coronary intervention: a randomised, double-blind, placebo-controlled phase II study. Lancet 2009; 373: 919-928.
• 87 Jennings LK, Earhart A, Becker RC. et al. H. Thrombin receptor antagonist (TRA;SCH530348) is a selective, potent inhibitor of PAR1 activity with predictable pharmacokinetics. Presented at American Heart Association Scientific Sessions. November 4–7; 2007; Orlando, FL: 2007
• 88 Goto S YT, Ikeda Y, Yamaguchi H. et al. Phase II trial of the novel antiplatelet agent, SCH 530348, in Japanese patients with non-ST segment elevation acute coronary syndromes (NSTE ACS). Eur Heart J 2008; 29 (Suppl): 829 Abstract P4767.
• 89 Shinohara Y, Shimizu K, Jensen P. A phase II safety study of novel antiplatelet agent, SCH 530348, in Japanese patients with prior ischemic stroke. Int J Stroke 2008; 03 (Suppl. 01) 139 Abstract PO01–193.
• 90 Trial to Assess the Effects of SCH 530348 in Preventing Heart Attack and Stroke in Patients With Atherosclerosis (TRA 2°P – TIMI 50) (Study P04737). 2008
• 91 Trial to Assess the Effects of SCH 530348 in Preventing Heart Attack and Stroke in Patients With Acute Coronary Syndrome (TRACER) (Study P04736AM1). 2008