Engagement of Glycoprotein IIb/IIIa (α _IIb β ₃ ) on Platelets Upregulates CD40L and Triggers CD40L-Dependent Matrix Degradation by Endothelial Cells

Abstract

Background-CD40L-CD40 interactions induce inflammatory signals in cells of the vascular wall. We evaluated the effects of glycoprotein (GP) IIb/IIIa (␣ IIb ␤ 3 ) engagement that occurs during platelet-endothelium interactions on CD40L surface exposure on platelets and initiation of proteolytic activity in human umbilical vein endothelial cells (HUVECs). Methods and Results-Transient (60-minute) adhesion of thrombin-prestimulated platelets enhanced HUVEC expression of urokinase-type plasminogen activator receptor and membrane type-1 matrix metalloproteinase (MT1-MMP) (reverse transcriptase-polymerase chain reaction, flow cytometry) and secretion of urokinase-type plasminogen activator, tissue-type plasminogen activator, and MMP-1 (ELISA) and induced proteolytic activity via MMP-2 and MMP-9 (gelatin zymography). These effects were abrogated by hindrance of physical platelet-endothelial contacts using transwell systems or inhibited by GRGDSP, mAbs anti-GP IIb/IIIa (7E3), anti-␣ v ␤ 3 (LM609), or anti-CD40L (TRAP1). In addition, MMP-2 and MMP-9 were inhibited by specific GP IIb/IIIa antagonists tirofiban, lamifiban, or integrelin. On endothelial cells, induction of proteolytic activity by activated platelets was mimicked by CD40 engagement using soluble CD40L but not affected by antibody clustering of ␣ v ␤ 3 . On platelets, CD40L and CD62P exposure was enhanced on adhesion to HUVECs or immobilized fibrinogen and was abrogated by GRGDSP or LM609. In suspension, cross-linking of GP IIb/IIIa by fibrinogen plus secondary mAb upregulated CD40L surface exposure. Consistently, bivalent mAb 7E3 upregulated CD40L, whereas ligation of GP IIb/IIIa by soluble fibrinogen alone or monovalent Fab-fragment c7E3 had no effect. Conclusions-Platelet adhesion via GP IIb/IIIa upregulates CD40L and CD62P surface exposure. Proteolytic activity of HUVEC is induced by the concerted action of ␤ 3 -integrin-mediated platelet adhesion and subsequent CD40L-induced signals in HUVECs. Effective anti-GP IIb/IIIa or anti-CD40L strategies might, therefore, contribute to plaque stabilization.

Effect of Atorvastatin on Risk of Recurrent Cardiovascular Events After an Acute Coronary Syndrome Associated With High Soluble CD40 Ligand in the Myocardial Ischemia Reduction with Aggressive Cholesterol Lowering (MIRACL) Study

“…25,26 High levels of sCD40L may reflect ongoing platelet activation at active culprit lesions that may lead to recurrent events. In fact, a recent study of patients undergoing percutaneous coronary intervention for the management of acute coronary syn- 17 However, the use of glycoprotein IIb/IIIa receptor antagonists or the use of percutaneous coronary intervention did not appreciably influence the results of the present study, because only 1% and 9% of patients received these forms of treatment, respectively, in the MIRACL Study.…”

Intracellular cyclophilin A is an important Ca2+ regulator in platelets and critically involved in arterial thrombus formation

“…17 Under inflammatory conditions, CyPA is released from immune cells and binds to its receptor, EMMPRIN (CD147), to modulate signal transduction of the target cell. [19][20][21][22][23][24] Recent studies provide evidence that CyPA is also present in the cytoplasm of platelets and can be released from granules upon platelet activation to bind to endothelial cells, monocytes, and macrophages via the CyPA receptor EMMPRIN (CD147), thereby inducing a signaling cascade into the target cell (eg, degranulation or expression of matrix metalloproteinases. 19,23,[25][26][27][28] The function of intracellular CyPA in platelets has not yet been explored.…”

Platelets, inflammation and anti-inflammatory effects of antiplatelet drugs in ACS and CAD

“…Along with the characterisation of MMP-2, MMP-9 was identified to be an inhibitor of platelet aggregation suggesting that the MMP-9/MMP-2-dependent bioregulatory system might be involved in platelet-platelet and plateletvessel wall interactions (17). Moreover, platelet adhesion via glycoprotein (GP) IIb/IIIa upregulates CD40L and P-selectin (CD62P) surface exposure leading to the assumption, that clinical benefits of GP IIb/IIIa antagonists in addition to the inhibition of thrombosis by blocking platelet aggregation also involve the inhibition of inflammation and thrombosis via blockade of CD40L release (18,19). While molecular interactions of leukocytes with activated endothelial cells are critical for the defense against microbial invasion and immune trafficking, platelets also contribute to leukocyte targeting-and regulated accumulation (20)(21)(22).…”