Ticagrelor attenuates the increase of extracellular vesicle concentrations in plasma after acute myocardial infarction compared to clopidogrel

Background Platelet P2Y12 antagonist ticagrelor reduces mortality after acute myocardial infarction (AMI) compared to clopidogrel, but the underlying mechanism is unknown. Because activated platelets, leukocytes, and endothelial cells release proinflammatory and prothrombotic extracellular vesicles (EVs), we hypothesized that the release of EVs is more efficiently inhibited by ticagrelor compared to clopidogrel. Objectives We compared EV concentrations and EV procoagulant activity in plasma of patients after AMI treated with ticagrelor or clopidogrel. Methods After percutaneous coronary intervention, 60 patients with first AMI were randomized to ticagrelor or clopidogrel. Flow cytometry was used to determine concentrations of EVs from activated platelets (CD61(+), CD62p(+)), fibrinogen(+), phosphatidylserine (PS+), leukocytes (CD45(+)), endothelial cells (CD31(+), 146(+)), and erythrocytes (CD235a(+)) in plasma at randomization, after 72 hours and 6 months of treatment. A fibrin generation test was used to determine EV procoagulant activity. Results Concentrations of platelet, fibrinogen(+), PS+, leukocyte, and erythrocyte EVs increased 6 months after AMI compared to the acute phase of AMI (P = .17). Conclusions Ticagrelor attenuates the increase of EV concentrations in plasma after acute myocardial infarction compared to clopidogrel. The ongoing release of EVs despite antiplatelet therapy might explain recurrent thrombotic events after AMI and worse clinical outcomes on clopidogrel compared to ticagrelor.Peer reviewe

Randomized controlled trial protocol to investigate the antiplatelet therapy effect on extracellular vesicles (AFFECT EV) in acute myocardial infarction

Activated platelets contribute to thrombosis and inflammation by the release of extracellular vesicles (EVs) exposing P-selectin, phosphatidylserine (PS) and fibrinogen. P2Y12 receptor antagonists are routinely administered to inhibit platelet activation in patients after acute myocardial infarction (AMI), being a combined antithrombotic and anti-inflammatory therapy. The more potent P2Y12 antagonist ticagrelor improves cardiovascular outcome in patients after AMI compared to the less potent clopidogrel, suggesting that greater inhibition of platelet aggregation is associated with better prognosis. The effect of ticagrelor and clopidogrel on the release of EVs from platelets and other P2Y12-exposing cells is unknown. This study compares the effects of ticagrelor and clopidogrel on (1) the concentrations of EVs from activated platelets (primary end point), (2) the concentrations of EVs exposing fibrinogen, exposing PS, from leukocytes and from endothelial cells (secondary end points) and (3) the procoagulant activity of plasma EVs (tertiary end points) in 60 consecutive AMI patients. After the percutaneous coronary intervention, patients will be randomized to antiplatelet therapy with ticagrelor (study group) or clopidogrel (control group). Blood will be collected from patients at randomization, 48 hours after randomization and 6 months following the index hospitalization. In addition, 30 age- and gender-matched healthy volunteers will be enrolled in the study to investigate the physiological concentrations and procoagulant activity of EVs using recently standardized protocols and EV-dedicated flow cytometry. Concentrations of EVs will be determined by flow cytometry. Procoagulant activity of EVs will be determined by fibrin generation test. The compliance and response to antiplatelet therapy will be assessed by impedance aggregometry. We expect that plasma from patients treated with ticagrelor (1) contains lower concentrations of EVs from activated platelets, exposing fibrinogen, exposing PS, from leukocytes and from endothelial cells and (2) has lower procoagulant activity, when compared to patients treated with clopidogrel. Antiplatelet therapy effect on EVs may identify a new mechanism of action of ticagrelor, as well as create a basis for future studies to investigate whether lower EV concentrations are associated with improved clinical outcomes in patients treated with P2Y12 antagonists.Peer reviewe

Neurotrophin p75 receptor (p75NTR) promotes endothelial cell apoptosis and inhibits angiogenesis:implications for diabetes-induced impaired neovascularization in ischemic limb muscles

Diabetes impairs endothelial function and reparative neovascularization. The p75 receptor of neurotrophins (p75<sup>NTR</sup>), which is scarcely present in healthy endothelial cells (ECs), becomes strongly expressed by capillary ECs after induction of peripheral ischemia in type-1 diabetic mice. Here, we show that gene transfer-induced p75<sup>NTR</sup> expression impairs the survival, proliferation, migration, and adhesion capacities of cultured ECs and endothelial progenitor cells (EPCs) and inhibits angiogenesis in vitro. Moreover, intramuscular p75<sup>NTR</sup> gene delivery impairs neovascularization and blood flow recovery in a mouse model of limb ischemia. These disturbed functions are associated with suppression of signaling mechanisms implicated in EC survival and angiogenesis. In fact, p75<sup>NTR</sup> depresses the VEGF-A/Akt/eNOS/NO pathway and additionally reduces the mRNA levels ofITGB1 [beta (1) integrin], BIRC5 (survivin), PTTG1 (securin) and VEZF1. Diabetic mice, which typically show impaired postischemic muscular neovascularization and blood perfusion recovery, have these defects corrected by intramuscular gene transfer of a dominant negative mutant form of p75<sup>NTR</sup>. Collectively, our data newly demonstrate the antiangiogenic action of p75<sup>NTR</sup> and open new avenues for the therapeutic use of p75<sup>NTR</sup> inhibition to combat diabetes-induced microvascular liabilities

CD146 (Cluster of Differentiation 146)

International audienceCD146 (cluster of differentiation 146) is an adhesion molecule that is expressed by different cells constituting vessels, particularly endothelial cells. The last 30 years of research in this field have shown that CD146 plays a key role in the control of several vessel functions. Three forms of CD146 have been described, including 2 transmembrane isoforms and a soluble protein that is detectable in the plasma. These CD146 forms mediate pleiotropic functions through homophilic and heterophilic interactions with proteins present on surrounding partners. Several studies used neutralizing antibodies, siRNA, or genetically modified mice to demonstrate the involvement of CD146 in the regulation of angiogenesis, vascular permeability, and leukocyte transmigration. In this review, we will focus on the current knowledge of the roles of CD146 in vascular homeostasis and diseases associated with endothelial dysfunction

Soluble CD146, an innovative and non-invasive biomarker of embryo selection for in-vitro fertilization

International audienceAlthough progress was made in in vitro fertilization (IVF) techniques, the majority of embryos transferred fail to implant. Morphology embryo scoring is the standard procedure for most of IVF centres for choosing the best embryo, but remains limited since even the embryos classified as ªtop qualityº may not implant. As it has been shown that i) CD146 is involved in embryo implantation and ii) membrane form is shed to generate soluble CD146 (sCD146), we propose that sCD146 in embryo supernatants may constitute a new biomarker of embryo selection. Immunocytochemical staining showed expression of CD146 in early embryo stages and sCD146 was detected by ELISA and Western-blot in embryo supernatants from D2. We retrospectively studied 126 couples who underwent IVF attempt. The embryo culture medium from each transferred embryo (n = 222) was collected for measurement of sCD146 by ELISA. Significantly higher sCD146 concentrations were present in embryo supernatants that did not implant (n = 185) as compared to those that successfully implanted (n = 37) (1310 +/- 1152 pg.mL-1 vs. 845+/- 1173 pg.mL-1, p = 0.024). Sensitivity analysis performed on single embryo transfers (n = 71) confirmed this association (p = 0.0054). The computed ROC curve established that the optimal sCD146 concentration for embryo implantation is under 1164 pg.mL-1 (sensitivity: 76%, specificity: 48%, PPV: 25% and NPV: 92%). Over this sCD146 threshold, the implantation rate was significantly lower (9% with sCD146 levels >1164 pg.ml-1 vs. 22% with sCD146 levels 1164 pg.mL-1, p = 0.01). Among the embryos preselected by morphologic scoring, sCD146 determination could allow a better selection of the embryo(s), thus improving the success of elective single embryo transfer. This study establishes the proof of concept for the use of sCD146 as a biomarker for IVF by excluding the embryo with the highest sCD146 level. A multicentre prospective study will now be necessary to further establish its use in clinical practice

Microparticles and sudden cardiac death due to coronary occlusion. The TIDE (Thrombus and Inflammation in sudden DEath) study

International audienceAims: The pattern of coronary occlusion might contribute to the onset of ventricular arrhythmia and sudden cardiac death (SCD). We hypothesized that the concentrations of microparticles might differ between SCD and ST-elevation myocardial infarction (STEMI) patients without rhythmic disturbances. Methods and results: The study sample includes consecutive patients hospitalized in two French tertiary centres between 2006 and 2011 for SCD with angiographically-proven acute coronary occlusion ( n=23), for STEMI ( n=61) and for a planned percutaneous coronary angioplasty (PCI) ( n=35, controls). During PCI blood was collected in the arch of aorta (systemic blood) before and after the procedure and in the culprit coronary lesion with an aspiration catheter. Microparticles were analysed by flow cytometry in a blinded manner to quantify endothelial (CD144+), platelet (CD41+), leucocyte (CD11a+) and erythrocyte (CD235a+) derived microparticles. After multivariate analysis, intracoronary concentrations of endothelial-derived microparticles were significantly higher in SCD than in STEMI patients (129 (74–185) vs. 50 (21–118) nb/µl; p < 0.01). Intracoronary and systemic blood concentrations of platelet-derived microparticles were not different between SCD and controls, suggesting limited impact of cardiac massage and electric defibrillation in microparticle concentrations. Conclusion: The higher concentrations of endothelial-derived microparticles in SCD due to acute coronary occlusion compared with STEMI without rhythmic disturbances suggests different patterns of acute coronary occlusion

The Role of the Adhesion Receptor CD146 and Its Soluble Form in Human Embryo Implantation and Pregnancy

International audienceCD146 is an adhesion molecule essentially located in the vascular system, which has been described to play an important role in angiogenesis. A soluble form of CD146, called sCD146, is detected in the bloodstream and is known as an angiogenic factor. During placental development, CD146 is selectively expressed in extravillous trophoblasts. A growing body of evidence shows that CD146 and, in particular, sCD146, regulate extravillous trophoblasts migration and invasion both in vitro and in vivo . Hereby, we review expression and functions of CD146/sCD146 in the obstetrical field, mainly in pregnancy and in embryo implantation. We emphasized the relevance of quantifying sCD146 in the plasma of pregnant women or in embryo supernatant in the case of in vitro fertilization (IVF) to predict pathological pregnancy such as preeclampsia or implantation defect. This review will also shed light on some major results that led us to define CD146/sCD146 as a biomarker of placental development and paves the way toward identification of new therapeutic targets during implantation and pregnancy

Extracellular vesicles from T cells overexpress miR-146b-5p in HIV-1 infection and repress endothelial activation

International audienceHuman immunodeficiency virus type 1 (HIV-1) infection promotes a generalized activation of host responses that involves not only CD4 T cells, but also cells of the microenvironment, which are not directly infected, such as endothelial cells. The mechanisms triggering HIV-1-associated vascular alterations remain poorly understood. Extracellular vesicles (EVs), implicated in cell-to-cell communication, have been recently described as carriers of microRNAs (miRNAs). Here, we show that miR-146b-5p is upregulated in both CD4 T cells, CD4 T cell-derived EVs and circulating EVs obtained from antiretroviral therapy-naive HIV-1-infected patients. We further demonstrate that EVs from T cell line overexpressing miR-146b-5p mimics (miR-146b-EVs): 1) protect their miRNA cargo from RNase degradation, 2) transfer miR-146b-5p mimics into endothelial cells and 3) reduce endothelial inflammatory responses in vitro and in vivo in the lungs of mice through the downregulation of nuclear factor-κB-responsive molecules. These data advance our understanding on chronic inflammatory responses affecting endothelial homeostasis, in infectious and non-infectious diseases and pave the way for potential new anti-inflammatory strategies

Microparticles from ischemic muscle promotes postnatal vasculogenesis.

International audienceBACKGROUND: We hypothesized that microparticles (MPs) released after ischemia are endogenous signals leading to postischemic vasculogenesis. METHODS AND RESULTS: MPs from mice ischemic hind-limb muscle were detected by electron microscopy 48 hours after unilateral femoral artery ligation as vesicles of 0.1- to 1-microm diameter. After isolation by sequential centrifugation, flow cytometry analyses showed that the annexin V(+) MP concentration was 3.5-fold higher in ischemic calves than control muscles (1392+/-406 versus 394+/-180 annexin V(+) MPs per 1 mg; P<0.001) and came mainly from endothelial cells (71% of MPs are CD(144+)). MPs isolated from ischemic muscles induced more potent in vitro bone marrow-mononuclear cell (BM-MNC) differentiation into cells with endothelial phenotype than those isolated from control muscles. MPs isolated from atherosclerotic plaques were ineffective, whereas those isolated from apoptotic or interleukin-1beta-activated endothelial cells also promoted BM-MNC differentiation. Interestingly, MPs from ischemic muscles produced more reactive oxygen species and expressed significantly higher levels of NADPH oxidase p47 (6-fold; P<0.05) and p67 subunits (16-fold; P<0.001) than controls, whereas gp91 subunit expression was unchanged. BM-MNC differentiation was reduced by 2-fold with MPs isolated from gp91-deficient animals compared with wild-type mice (P<0.05). MP effects on postischemic revascularization were then examined in an ischemic hind-limb model. MPs isolated from ischemic muscles were injected into ischemic legs in parallel with venous injection of BM-MNCs. MPs increased the proangiogenic effect of BM-MNC transplantation, and this effect was blunted by gp91 deficiency. In parallel, BM-MNC proangiogenic potential also was reduced in ABCA1 knockout mice with impaired vesiculation. CONCLUSIONS: MPs produced during tissue ischemia stimulate progenitor cell differentiation and subsequently promote postnatal neovascularization