title: A structural and dynamic investigation of the facilitating effect of glycoprotein IIb/IIIa inhibitors in dissolving platelet-rich clots.
abstract: 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 microm/min for rtPA binding velocity, P=0.04, and 1.2 +/- 0.6 versus 2.8 +/- 0.2 microm/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 micromol/L) or eptifibatide (1 micromol/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.
authors.affiliation: Department of Cardiology, Pitié-Salpêtrière Hospital, Paris, France. jean-philippe.collet@psl.ap-hop-paris.fr
authors.forename: J Ph
authors.initials: JP
authors.lastname: Collet
authors.forename: G
authors.initials: G
authors.lastname: Montalescot
authors.forename: C
authors.initials: C
authors.lastname: Lesty
authors.forename: J W
authors.initials: JW
authors.lastname: Weisel
mesh_terms: D000077284:Abciximab; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D003018:Clot Retraction; D000077542:Eptifibatide; D005337:Fibrin / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005342:Fibrinolysis / Q000187:drug effects* / Q000502:physiology; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D010455:Peptides / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors*; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D010959:Tissue Plasminogen Activator / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000911:Antibodies, Monoclonal; D005456:Fluorescent Dyes; D007140:Immunoglobulin Fab Fragments; D010455:Peptides; D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005337:Fibrin; D010959:Tissue Plasminogen Activator; D016650:Fluorescein-5-isothiocyanate; D000077542:Eptifibatide; D000077284:Abciximab