Interaction with damaged vessel wall in vivo in humans induces platelets to express CD40L resulting in endothelial activation with no effect of aspirin intake

Abstract

Activated platelets express CD40L on their plasma membrane and release the soluble fragment sCD40L. The interaction between platelet surface CD40L and endothelial cell CD40 leads to the activation of endothelium contributing to atherothrombosis. Few studies have directly demonstrated an increased expression of platelet CD40L in conditions of in vivo platelet activation in humans, and no data are available on its relevance for endothelial activation. We aimed to assess whether platelets activated in vivo at a localized site of vascular injury in humans express CD40L and release sCD40L, whether the level of platelet CD40L expression attained in vivo is sufficient to induce endothelial activation, and whether platelet CD40L expression is inhibited by aspirin intake. We used the skin-bleeding-time test as a model to study the interaction between platelets and a damaged vessel wall by measuring CD40L in the blood emerging from a skin wound in vivo in healthy volunteers. In some experiments, shed blood was analyzed before and 1 h after the intake of 500 mg of aspirin. Platelets from the bleeding-time blood express CD40L and release soluble sCD40L, in a time-dependent way. In vivo platelet CD40L expression was mild but sufficient to induce VCAM-1 expression and IL-8 secretion in coincubation experiments with cultured human endothelial cells. Moreover, platelets recovered from the bleedingtime blood activated endothelial cells; an anti-CD40L antibody blocked this effect. On the contrary, the amount of sCD40L released by activated platelets at a localized site of vascular injury did not reach the concentrations required to induce endothelial cell activation. Soluble monocyte chemoattractant protein-1, a marker of endothelium activation, was increased in shed blood and correlated with platelet CD40L expression. Aspirin intake did not inhibit CD40L expression by platelets in vivo. We concluded that CD40L expressed by platelets in vivo in humans upon contact with a damaged vessel wall activates endothelium; aspirin treatment does not inhibit this mechanism. bleeding time; flow cytometry; atherosclerosis; platelet activation CD40L (CD154) IS A TRIMERIC TRANSMEMBRANE PROTEIN of the tumor necrosis factor family expressed on several cell types, including activated CD4 ϩ T cells, mast cells, basophils, eosinophils, smooth muscle cells, and activated platelets. CD40L and its membrane receptor, CD40, represent a system involved in cell communication, with CD40L inducing activation of CD40-expressing cells. This interaction mediates signals leading to responses that have a key role in immune activation, inflammation, atherosclerosis, and thrombosis.Platelets constitutively express CD40 on their plasma membrane, whereas CD40L, cryptic in resting platelets, is exposed at their surface upon activation (1) from where it is then cleaved, producing a soluble fragment released in the circulation, sCD40L (20).Platelet surface CD40L is proinflammatory and procoagulant and can induce the activation of normal endothelium by ligation of CD40 o...

Review of experimental animal models of biliary acute pancreatitis and recent advances in basic research

“…CD40L is a transmembrane glycoprotein that belongs to the TNF family of cell surface interaction molecules 117 . Induced to express mainly on a CD4 + T cell subset, it has been found to activate platelets and to exert proinflammatory 117–120 and procoagulant effects 121,122 . Abdulla et al .…”

“…117 Induced to express mainly on a CD4 + T cell subset, it has been found to activate platelets and to exert proinflammatory [117][118][119][120] and procoagulant effects. 121,122 Abdulla et al examined responses in CD40L -/mice to AP induced by either Na-TC or caerulein, but observed no beneficial effects in CD40L -/mice compared with their littermates. 116…”

Platelet CD40 ligand and bleeding during P2Y12 inhibitor treatment in acute coronary syndrome

“…Platelet‐associated and platelet‐released CD40L may directly affect platelet function, as they enhance collagen‐induced platelet α IIb β 3 activation, secretion, and thrombus growth . Platelet‐associated CD40L also induces a procoagulant and proinflammatory state in the endothelium . Furthermore, the function of platelet‐associated CD40L may extend beyond the endothelium and platelets, as it is a key component of platelet‐leukocyte crosstalk, potentiating the recruitment of leukocytes to the site of vascular injury …”

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“…Such nano machines reproduce the behavior of platelets when a vessel wall is injured [25]. Platelets play an important role in maintaining the integrity of the endothelium by releasing some specific proangiogenic cytokines and growth factors.…”