Ability of Different Glycoprotein IIb-IIIa Ligands to Support Platelet Aggregation Induced by Activating Antibody CRC54

Abstract

The ability of different ligands of glycoprotein (GP) IIb-IIIa (alphaIIb/beta3-integrin) to support platelet aggregation stimulated by activating anti-GP IIb-IIIa monoclonal antibody (monoAB) CRC54 has been investigated. Antibody CRC54 stimulated aggregation of washed platelets not only in the presence of fibrinogen, the main GP IIb-IIIa ligand, but also in the presence of von Willebrand factor (vWF). Unlike these ligands, fibronectin failed to support CRC54-induced aggregation. Fibrinogen and vWF dependent platelet aggregation was completely suppressed by GP IIb-IIIa antagonists--preparations Monafram (F(ab')2 fragments of monoAB that blocked GP IIb-IIIa receptor activity) and aggrastat (RGD-like peptidomimetic). However, aggregation stimulated in the presence of vWF was also completely inhibited by monoAB AK2 directed against GP Ib and capable of blocking its binding with vWF. CRC54-induced aggregation of platelets from patient with GP Ib deficiency in the presence of vWF was significantly lower than aggregation of platelets from normal donors and was not inhibited by anti-GP Ib antibody but still blocked by GP IIb-IIIa antagonist Monafram. Monafram also suppressed CRC54-stimulated platelet adhesion to plastic-adsorbed fibrinogen, vWF, and fibronectin. Unlike CRC54-induced platelet aggregation supported by fluid phase vWF, CRC54-induced adhesion to adsorbed vWF was not affected by anti-GP Ib antibody. Aggregation induced by CRC54 in the presence of fibrinogen and vWF was only partially suppressed by prostaglandin E1, an inhibitor of platelet activation, and was associated with serotonin release from platelet granules only when Ca2+ concentration was decreased from 1 mM (physiological level) to 0.1 mM. The data indicate that vWF supports CRC54-induced platelet aggregation via interaction with two receptors--GP IIb-IIIa and GP Ib. Aggregation induced by CRC54 in the presence of vWF or fibrinogen is only partially dependent on platelet activation and is accompanied with granule secretion only at low Ca2+ concentrations.

Antiplatelet and antithrombotic activity of indole‐3‐carbinol in vitro and in vivo

“…The platelet membrane in which GP IIb/IIIa exists as a complex is very important in platelet plug formation after vascular injury (Wang et al, 2006). This complex acts as a receptor for fibrinogen, fibronectin, von Willebrand factor and vitronectin, and its binding of these adhesive proteins mediates platelet aggregation, adhesion and spreading (Naimushin and Mazurov, 2005;Wijeyewickrema et al, 2005). Flow cytometric analysis showed that indole-3-carbinol inhibited the population of FITC fibrinogen bound GP IIb/IIIa in a concentration-dependent manner, suggesting indole-3-carbinol may disrupt the fibrinogen binding to GP IIb/IIIa receptor on platelet surface, suggesting that the inhibitory effect of indole-3-carbinol on platelet aggregation may be mediated by blockage of fibrinogen binding to GP IIb/IIIa receptor.…”

Endothelium, Platelets, and Coagulation Factors as the Three Vital Components for Diagnosing Bleeding Disorders: A Simplified Perspective with Clinical Relevance

“…Platelet aggregation is investigated using an aggregometer which works on the principle that the transmission of light increases as platelets aggregate [ 46 , 47 ]. Another glycoprotein, activated integrin α IIb β 3, commonly known as gpIIb/IIIa on platelets, is responsible for platelet aggregation by cross-linking platelets with fibrinogen [ 48 ]. Defective gpIIb/IIIa on platelets results in inadequate aggregation, and this condition is called Glanzmann's thrombasthenia [ 49 ].…”

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“…Other studies revealed that platelet aggregation induced by MCF-7 cells is mediated in part through an ADPdependent mechanism and that these cells express platelet immunorelated glycoproteins GPIb, GPIIb/IIIa, GPIb/IX, and the integrin αv subunit on their surface [157]. Tumorinduced platelet aggregation is also regulated by plasma proteins, e.g., von Willebrand factor or fibrinogen [158,159]. Studies from Yokota et al [148] provided new insight into thrombin-mediated TF-dependent metastasis based on a hyperthrombotic mouse model with thrombomodulin deficiency (TM Pro mice).…”