A Structural and Dynamic Investigation of the Facilitating Effect of Glycoprotein IIb/IIIa Inhibitors in Dissolving Platelet-Rich Clots

Glycoprotein IIb/IIIa (GP IIb/IIIa) inhibitors were shown recently to facilitate the rate and the extent of pharmacological thrombolysis. However, their synergistic potential with rtPA in dissolving thrombotic vaso-occlusions is not fully understood. We have therefore developed a dynamic and structural approach for analysis of fibrinolysis to assess the inhibiting effect of platelets and the facilitating effect of GPIIb/IIIa inhibitors in dissolving platelet-rich clots (PRCs). Fluorescent rtPA was used to study the architecture of PRCs, to follow the progression of the rtPA binding front, and to measure the lysis-front velocity using confocal microscopy. Fibrinolysis resistance of PRCs was related to a reduction of both rtPA binding and lysis-front velocities of platelet-rich areas compared with platelet-poor areas (2.4±0.2 versus 3.5±0.4 &mgr;m/min for rtPA binding velocity, P =0.04, and 1.2±0.6 versus 2.8±0.2 &mgr;m/min for lysis-front velocity, P =0.008, in platelet-rich and platelet-poor areas, respectively). Fibrinolysis appeared heterogeneous, leaving platelet-rich areas un-lysed. Adding pharmacological concentrations of abciximab (0.068 &mgr;mol/L) or eptifibatide (1 &mgr;mol/L) before clotting decreased the average surface of platelet-rich areas by 64% (P =0.0005) and 72% (P =0.0007), respectively. The resulting equalization of rtPA binding rate and rtPA binding-front velocity between platelet-rich and platelet-poor areas led to a 3-fold increase of the lysis-front velocity in platelet-rich areas of either abciximab-PRC (P =0.006) or eptifibatide-PRC (P =0.03). The overall lysis rate of treated-PRC was increased by 74% compared with control-PRC (P <0.01). These results demonstrate that fibrinolysis resistance of PRCs is related primarily to the heterogeneity in the clot structure between platelet-rich and platelet-poor areas. GP IIb/IIIa inhibitors facilitate the rate and the extent of fibrinolysis by improving rtPA binding velocity and, subsequently, the lysis rate in platelet-rich areas. These findings provide new insights on the synergistic potential of GP IIb/IIIa inhibitors and fibrinolytic agents.

[1]  Assent investigators.  Efficacy and safety of tenecteplase in combination with enoxaparin, abciximab, or unfractionated heparin: the ASSENT-3 randomised trial in acute myocardial infarction , 2001, The Lancet.

[2]  M. Morice,et al.  Platelet glycoprotein IIb/IIIa inhibition with coronary stenting for acute myocardial infarction. , 2001, The New England journal of medicine.

[3]  P. Armstrong,et al.  Reperfusion therapy for acute myocardial infarction with fibrinolytic therapy or combination reduced fibrinolytic therapy and platelet glycoprotein IIb/IIIa inhibition: the GUSTO V randomised trial. , 2001 .

[4]  H. Pereira,et al.  Reperfusion therapy for acute myocardial infarction with fibrinolytic therapy or combination reduced fibrinolytic therapy and platelet glycoprotein IIb/IIIa inhibition: the GUSTO V randomised trial , 2001, The Lancet.

[5]  J. Soria,et al.  Effects of Abciximab on the Architecture of Platelet-Rich Clots in Patients With Acute Myocardial Infarction Undergoing Primary Coronary Intervention , 2001, Circulation.

[6]  J. Soria,et al.  Disaggregation of In Vitro Preformed Platelet-Rich Clots by Abciximab Increases Fibrin Exposure and Promotes Fibrinolysis , 2001, Arteriosclerosis, thrombosis, and vascular biology.

[7]  J. Soria,et al.  Influence of fibrin network conformation and fibrin fiber diameter on fibrinolysis speed: dynamic and structural approaches by confocal microscopy. , 2000, Arteriosclerosis, thrombosis, and vascular biology.

[8]  S. Mousa,et al.  Comparative in vitro efficacy of different platelet glycoprotein IIb/IIIa antagonists on platelet-mediated clot strength induced by tissue factor with use of thromboelastography: differentiation among glycoprotein IIb/IIIa antagonists. , 2000, Arteriosclerosis, thrombosis, and vascular biology.

[9]  C. Francis,et al.  Structural Studies of Fibrinolysis by Electron and Light Microscopy , 1999, Thrombosis and Haemostasis.

[10]  N. Kleiman,et al.  Platelet glycoprotein IIb/IIIa antagonists. What are the relevant issues concerning their pharmacology and clinical use? , 1999, Circulation.

[11]  P. Carmeliet,et al.  Plasminogen activator inhibitor-1 is a major determinant of arterial thrombolysis resistance. , 1999, Circulation.

[12]  E. Antman,et al.  Abciximab facilitates the rate and extent of thrombolysis: results of the thrombolysis in myocardial infarction (TIMI) 14 trial. The TIMI 14 Investigators. , 1999, Circulation.

[13]  C. Francis,et al.  Structural studies of fibrinolysis by electron microscopy. , 1998, Blood.

[14]  J. Burchenal,et al.  Randomized, placebo-controlled trial of platelet glycoprotein IIb/IIIa blockade with primary angioplasty for acute myocardial infarction. ReoPro and Primary PTCA Organization and Randomized Trial (RAPPORT) Investigators. , 1998, Circulation.

[15]  L. Jennings,et al.  Effect of Ca2+ on GP IIb-IIIa interactions with integrilin: enhanced GP IIb-IIIa binding and inhibition of platelet aggregation by reductions in the concentration of ionized calcium in plasma anticoagulated with citrate. , 1997, Circulation.

[16]  A. Rebuzzi,et al.  Differential suppression of thromboxane biosynthesis by indobufen and aspirin in patients with unstable angina. , 1997, Circulation.

[17]  I. Palacios,et al.  Restoration of coronary flow in myocardial infarction by intravenous chimeric 7E3 antibody without exogenous plasminogen activators. Observations in animals and humans. , 1997, Circulation.

[18]  H. Hemker,et al.  Inhibition of platelet-mediated, tissue factor-induced thrombin generation by the mouse/human chimeric 7E3 antibody. Potential implications for the effect of c7E3 Fab treatment on acute thrombosis and "clinical restenosis". , 1996, The Journal of clinical investigation.

[19]  S. Lord,et al.  Dissecting Clot Retraction and Platelet Aggregation , 1996, The Journal of Biological Chemistry.

[20]  D. Rijken,et al.  Superficial accumulation of plasminogen during plasma clot lysis. , 1995, Circulation.

[21]  R. Blinc,et al.  Finger-like lysing patterns of blood clots. , 1995, Biophysical journal.

[22]  R. Hantgan,et al.  Uncoupling fibrin from integrin receptors hastens fibrinolysis at the platelet-fibrin interface. , 1994, Blood.

[23]  C. Francis,et al.  Flow through clots determines the rate and pattern of fibrinolysis. , 1994, Thrombosis and haemostasis.

[24]  J. Kirkpatrick,et al.  Regulation of fibrinolysis by platelet-released plasminogen activator inhibitor 1: light scattering and ultrastructural examination of lysis of a model platelet-fibrin thrombus. , 1993, Blood.

[25]  G. FitzGerald,et al.  Inhibition of clot lysis and decreased binding of tissue-type plasminogen activator as a consequence of clot retraction. , 1992, Blood.

[26]  H. Gold,et al.  Pharmacodynamic study of F(ab')2 fragments of murine monoclonal antibody 7E3 directed against human platelet glycoprotein IIb/IIIa in patients with unstable angina pectoris. , 1990, The Journal of clinical investigation.

[27]  P. Bugelski,et al.  Utrastructural analysis of thrombolysis by streptokinase and tissue-type plasminogen activator of experimental coronary arterial thrombosis , 1989 .

[28]  Trial of abciximab with and without low-dose reteplase for acute myocardial infarction. Strategies for Patency Enhancement in the Emergency Department (SPEED) Group. , 2000, Circulation.

[29]  S. Diamond,et al.  Engineering design of optimal strategies for blood clot dissolution. , 1999, Annual review of biomedical engineering.

[30]  P. D. de Groot,et al.  The contribution of the three hypothesized integrin-binding sites in fibrinogen to platelet-mediated clot retraction. , 1998, Blood.

[31]  J. Burchenal,et al.  Randomized, placebo-controlled trial of platelet glycoprotein IIb/IIIa blockade with primary angioplasty for acute myocardial infarction. ReoPro and Primary PTCA Organization and Randomized Trial (RAPPORT) Investigators. , 1998, Circulation.

[32]  A. Pugh,et al.  Processing of Binary Images , 1983 .