Anti-platelet effects of GPIIb/IIIa and P-selectin antagonism, platelet activation, and binding to neutrophils.
Platelet activation with GPIIb/IIIa binding to fibrinogen, aggregation and interaction with leukocytes constitute the principal mediator of thrombosis. Although the clinical benefits of GPIIb/IIIa antagonists have been documented, the relationship between their anti-platelet properties, platelet activation and binding to leukocytes is still debated. We investigated the effects of abciximab, tirofiban, roxifiban, and an anti-P-selectin blocking monoclonal antibody (Mab) on isolated human platelet aggregation using optical aggregometer, and on platelet P-selectin and GPIIb/IIIa expression, and platelet-neutrophil binding using flow cytometry. Thrombin at 0.025 U/ml induced maximal platelet aggregation (76.3 +/- 2.6%), P-selectin expression (88.5 +/- 4%), GPIIb/IIIa activation (PAC-1 binding, 86.2 +/- 8.9%) and platelet-neutrophil binding (58.0 +/- 6.4%). The GPIIb/IIIa antagonists inhibited in a concentration-dependent manner platelet aggregation (IC50 of 100 nM for abciximab and tirofiban and 50 nM for roxifiban) and PAC-1 binding, without any effect on P-selectin. None of these agents affected significantly platelet-neutrophil binding, whereas an anti-P-selectin Mab abolished this binding and amplified the effect of abciximab on platelet aggregation. These results indicate that the effects of these GPIIb/IIIa antagonists on platelet aggregation are not related to inhibition of platelet activation, as P-selectin levels and platelet-neutrophil binding remained unaffected, and highlight the participation of P-selectin with GPIIb/IIIa in platelet aggregation.
Laboratory of Experimental Pathology, Montreal Heart Institute and the University of Montreal, 5000 Belanger Street East, Montreal, Quebec H1T 1C8, Canada.
Alexandre
A
Caron
Jean-François
JF
Théorêt
Shaker A
SA
Mousa
Yahye
Y
Merhi
D000077284:Abciximab; D000578:Amidines / Q000494:pharmacology; D000704:Analysis of Variance; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002478:Cells, Cultured; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D007555:Isoxazoles / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D019007:P-Selectin / Q000187:drug effects*; D015539:Platelet Activation / Q000187:drug effects*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000077466:Tirofiban; D014443:Tyrosine / Q000031:analogs & derivatives / Q000494:pharmacology
D000578:Amidines; D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D007555:Isoxazoles; D019007:P-Selectin; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D014443:Tyrosine; D000077466:Tirofiban; C118235:roxifiban; D000077284:Abciximab