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), αvβ3 Integrin, and GPIbα

Abstract

Although it has been reported that activated platelets can adhere to intact endothelium, the receptors involved have not been fully characterized. Also, it is not clear whether activated platelets bind primarily to matrix proteins at sites of endothelial cell denudation or directly to endothelial cells. Thus, this study was designed to further clarify the mechanisms of activated platelet adhesion to endothelium. Unstimulated human umbilical vein endothelial cell (HUVEC) monolayers were incubated with washed, stained, and thrombin-activated human platelets. To exclude matrix involvement, HUVEC were harvested mechanically and platelet binding was measured by flow cytometry. Before the adhesion assay, platelets or HUVEC were treated with different receptor antagonists. Whereas blockade of platelet β1 integrins, GPIbα, GPIV, P-selectin, and platelet-endothelial cell adhesion molecule (PECAM)-1 did not reduce platelet adhesion to HUVEC, blockade of platelet GPIIbIIIa by antibodies or Arg-Gly-Asp (RGD) peptides markedly decreased adhesion. Moreover, when platelets were treated with blocking antibodies to GPIIbIIIa-binding adhesive proteins, including fibrinogen and fibronectin, and von Willebrand factor (vWF), platelet binding was also reduced markedly. Addition of fibrinogen, fibronectin, or vWF further increased platelet adhesion, indicating that both endogenous platelet-exposed and exogenous adhesive proteins can participate in the binding process. Evaluation of the HUVEC receptors revealed predominant involvement of intercellular adhesion molecule (ICAM)-1 and αvβ3 integrin. Blockade of these two receptors by antibodies decreased platelet binding significantly. Also, there was evidence that a component of platelet adhesion was mediated by endothelial GPIbα. Blockade of β1 integrins, E-selectin, P-selectin, PECAM-1, vascular cell adhesion molecule (VCAM)-1 and different matrix proteins on HUVEC did not affect platelet adhesion. In conclusion, we show that activated platelet binding to HUVEC monolayers is mediated by a GPIIbIIIa-dependent bridging mechanism involving platelet-bound adhesive proteins and the endothelial cell receptors ICAM-1, αvβ3 integrin, and, to a lesser extent, GPIbα.

Ativação plaquetária em formas clínicas distintas da doença arterial coronariana (papel da P-selectina e de outros marcadores nas anginas estável e instável)

“…The pathophysiology of unstable angina is different from that of effort-induced angina due to increased myocardial oxigen demand 14 . The hypothesis of disease process in unstable angina has been strongly supported by results of previous studies [10][11][12][13][14][15][16] . The disease process of unstable angina appears to involve a transient thrombus formation mediated by a complex cascade of cellular interactions between the vascular endothelium and platelets at the atherosclerotic coronary artery 15 .…”

T helper type 1 lymphocytes drive inflammation in human atherosclerotic lesions

“…The Th1 polarization of T cell responses and the poor production of Th2 cytokines occurring within the plaque may represent local risk factors of thrombosis, which associate with platelet adhesion to dysfunctional endothelium. Besides prostaglandins and leukotrienes, activated platelets release cytokines and growth factors that contribute to migration and growth of smooth muscle cells and monocytes (52), which can amplify the inflammatory response and contribute to the remodeling of vessels.…”

Complete reversal of acid-induced acute lung injury by blocking of platelet-neutrophil aggregation

“…Platelet glycoprotein Ibα (GPIbα) (15) and GPIIb/GPIIIa (CD41/CD61, α IIb β 3 integrin) (16), endothelial P-selectin (17), and von Willebrand factor (18) have been shown to play important roles in platelet-endothelial interactions. Platelet depletion leads to diminished leukocyte recruitment in many models (19,20).…”