Human atheromatous plaques stimulate thrombus formation by activating platelet glycoprotein VI

Abstract

Lipid-rich atherosclerotic plaques are vulnerable, and their rupture can cause the formation of a platelet- and fibrin-rich thrombus leading to myocardial infarction and ischemic stroke. Although the role of plaque-based tissue factor as stimulator of blood coagulation has been recognized, it is not known whether plaques can cause thrombus formation through direct activation of platelets. We isolated lipid-rich atheromatous plaques from 60 patients with carotid stenosis and identified morphologically diverse collagen type I- and type III-positive structures in the plaques that directly stimulated adhesion, dense granule secretion, and aggregation of platelets in buffer, plasma, and blood. This material also elicited platelet-monocyte aggregation and platelet-dependent blood coagulation. Plaques exposed to flowing blood at arterial wall shear rate induced platelets to adhere to and spread on the collagenous structures, triggering subsequent thrombus formation. Plaque-induced platelet thrombus formation was observed in fully anticoagulated blood (i.e., in the absence of tissue factor-mediated coagulation). Mice platelets lacking glycoprotein VI (GPVI) were unable to adhere to atheromatous plaque or form thrombi. Human platelet thrombus formation onto plaques in flowing blood was completely blocked by GPVI inhibition with the antibody 10B12 but not affected by integrin alpha2beta1 inhibition with 6F1 mAb. Moreover, the initial platelet response, shape change, induced by plaque was blocked by GPVI inhibition but not with alpha2beta1 antagonists (6F1 mAb or GFOGER-GPP peptide). Pretreatment of plaques with collagenase or anti-collagen type I and anti-collagen type III antibodies abolished plaque-induced platelet activation. Our results indicate that morphologically diverse collagen type I- and collagen type III-containing structures in lipid-rich atherosclerotic plaques stimulate thrombus formation by activating platelet GPVI. This platelet collagen receptor, essential for plaque-induced thrombus formation, presents a promising new anti-thrombotic target for the prevention of ischemic cardiovascular diseases.

Aegyptin, a Novel Mosquito Salivary Gland Protein, Specifically Binds to Collagen and Prevents Its Interaction with Platelet Glycoprotein VI, Integrin α2β1, and von Willebrand Factor

“…These findings are particularly relevant because the adhesive potential of platelets results from the sum of distinct pathways supported by coordinated receptor-ligand interactions specially adapted to respond to different environmental conditions (26). Also, fibrillar collagen is widely recognized as a particularly atherogenic molecule together with tissue factor (61)(62)(63). In addition, pepsin-digested collagen, which is readily recognized by aegyptin, displays pro-adhesive properties in vitro and possibly in vivo where matrix metalloprotease activity of infiltrating macrophages and activated smooth muscle cells has been reported (64).…”

Synergism between platelet collagen receptors defined using receptor-specific collagen-mimetic peptide substrata in flowing blood

“…Individually, receptor-binding peptides have been used as antagonists of ␣ 2 ␤ 1 and GpVI during platelet adhesion to collagen and to atherosclerotic plaque under higher shear. 10,25 Recently, GpVI-and ␣ 2 ␤ 1 -binding motifs were combined in triple-helical peptides, 26 revealing a need for high-affinity integrin-binding sites for full thrombus deposition, but these authors did not examine high shear or analyze thrombus morphology in detail. The present study was designed to extend our understanding of thrombus deposition on surfaces composed of discrete triple-helical peptides, to define the reactivity of collagen for VWF and for the platelet collagen receptors.…”

A functional genomics approach reveals novel quantitative trait loci associated with platelet signaling pathways

“…They are rapidly activated at sites of vascular injury or plaque rupture by a range of physiologic agonists, including collagen, present in the vessel wall and found in elevated levels in atherosclerotic plaques, 1 and adenosine diphosphate (ADP), released from activated platelets and damaged cells.…”