HDL Interfere with the Binding of T Cell Microparticles to Human Monocytes to Inhibit Pro-Inflammatory Cytokine Production

BACKGROUND: Direct cellular contact with stimulated T cells is a potent mechanism that induces cytokine production in human monocytes in the absence of an infectious agent. This mechanism is likely to be relevant to T cell-mediated inflammatory diseases such as rheumatoid arthritis and multiple sclerosis. Microparticles (MP) generated by stimulated T cells (MPT) display similar monocyte activating ability to whole T cells, isolated T cell membranes, or solubilized T cell membranes. We previously demonstrated that high-density lipoproteins (HDL) inhibited T cell contact- and MPT-induced production of IL-1beta but not of its natural inhibitor, the secreted form of IL-1 receptor antagonist (sIL-1Ra). METHODOLOGY/PRINCIPAL FINDINGS: Labeled MPT were used to assess their interaction with monocytes and T lymphocytes by flow cytometry. Similarly, interactions of labeled HDL with monocytes and MPT were assessed by flow cytometry. In parallel, the MPT-induction of IL-1beta and sIL-1Ra production in human monocytes and the effect of HDL were assessed in cell cultures. The results show that MPT, but not MP generated by activated endothelial cells, bond monocytes to trigger cytokine production. MPT did not bind T cells. The inhibition of IL-1beta production by HDL correlated with the inhibition of MPT binding to monocytes. HDL interacted with MPT rather than with monocytes suggesting that they bound the activating factor(s) of T cell surface. Furthermore, prototypical pro-inflammatory cytokines and chemokines such as TNF, IL-6, IL-8, CCL3 and CCL4 displayed a pattern of production induced by MPT and inhibition by HDL similar to IL-1beta, whereas the production of CCL2, like that of sIL-1Ra, was not inhibited by HDL. CONCLUSIONS/SIGNIFICANCE: HDL inhibit both MPT binding to monocytes and the MPT-induced production of some but not all cytokines, shedding new light on the mechanism by which HDL display their anti-inflammatory functions

Platelets Alter Gene Expression Profile in Human Brain Endothelial Cells in an In Vitro Model of Cerebral Malaria

Platelet adhesion to the brain microvasculature has been associated with cerebral malaria (CM) in humans, suggesting that platelets play a role in the pathogenesis of this syndrome. In vitro co-cultures have shown that platelets can act as a bridge between Plasmodium falciparum-infected red blood cells (pRBC) and human brain microvascular endothelial cells (HBEC) and potentiate HBEC apoptosis. Using cDNA microarray technology, we analyzed transcriptional changes of HBEC in response to platelets in the presence or the absence of tumor necrosis factor (TNF) and pRBC, which have been reported to alter gene expression in endothelial cells. Using a rigorous statistical approach with multiple test corrections, we showed a significant effect of platelets on gene expression in HBEC. We also detected a strong effect of TNF, whereas there was no transcriptional change induced specifically by pRBC. Nevertheless, a global ANOVA and a two-way ANOVA suggested that pRBC acted in interaction with platelets and TNF to alter gene expression in HBEC. The expression of selected genes was validated by RT-qPCR. The analysis of gene functional annotation indicated that platelets induce the expression of genes involved in inflammation and apoptosis, such as genes involved in chemokine-, TREM1-, cytokine-, IL10-, TGFβ-, death-receptor-, and apoptosis-signaling. Overall, our results support the hypothesis that platelets play a pathogenic role in CM

Dosage des microparticules dans le syndrome coronaire aigu

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF

Les nouveaux anticoagulants oraux

Les traitements anticoagulants ont été limités pendant de nombreuses années à l’administration parentérale des héparines et l’administration per os des antagonistes de la vitamine K, dans la prévention et le traitement des événements thromboemboliques veineux (ETEV). Ces deux types de médicaments sont des inhibiteurs indirects de la coagulation. De nouveaux traitements anticoagulants oraux qui ne nécessitent pas de surveillance biologique et qui ont une action directe sur un facteur de la coagulation, thrombine (facteur II activé [a]) pour le dabigatran, facteur Xa pour le rivaroxaban et l’apixaban, sont actuellement en cours de développement avec un effet comparable à celui des anticoagulants classiques. Leur utilisation est pour le moment limitée à la prévention des ETEV en chirurgie orthopédique. De nombreuses études actuellement en cours vont permettre une transformation du traitement anticoagulant au long cours dans les prochaines années et dans d’autres indications

Antiplatelet Agents for Cancer Prevention: Current Evidences and Continuing Controversies

International audienceOver the past two decades, aspirin has emerged as a promising chemoprotective agent to prevent colorectal cancer (CRC). In 2016, the mounting evidence supporting its chemoprotective effect, from both basic science and clinical research, led the US Preventive Services Task Force to recommend regular use of low-dose aspirin in some subgroups of patients for whom the benefits are deemed to outweigh the risks. In contrast, data on the chemoprotective effect of aspirin against other cancers are less clear and remain controversial. Most data come from secondary analyses of cardiovascular prevention trials, with only a limited number reporting cancer outcomes as a prespecified endpoint, and overall unclear findings. Moreover, the potential chemoprotective effect of aspirin against other cancers has been recently questioned with the publication of 3 long-awaited trials of aspirin in the primary prevention of cardiovascular diseases reporting no benefit of aspirin on overall cancer incidence and cancer-related mortality. Data on the chemoprotective effects of other antiplatelet agents remain scarce and inconclusive, and further research to examine their benefit are warranted. In this narrative review, we summarize current clinical evidence and continuing controversies on the potential chemoprotective properties of antiplatelet agents against cancer

Cerebral malaria: Role of microparticles and platelets in alterations of the blood-brain barrier

Brain lesions of cerebral malaria (CM) are characterised by a sequestration of Plasmodium falciparum-parasitised red blood cells (PRBC), leucocytes and platelets within brain microvessels, by an excessive release of pro-inflammatory cytokines as well as by disruption of the blood-brain barrier (BBB). We evaluated the possibility that PRBC and platelets interact and induce functional alterations in brain endothelium. Using an in vitro model of endothelial lesion, we showed that platelets can act as bridges between PRBC and endothelial cells (EC) allowing the binding of PRBC to endothelium devoid of cytoadherence receptors. Furthermore, platelets potentiated the cytotoxicity of PRBC for brain EC by inducing an alteration of the integrity of their monolayer and increasing their apoptosis. These findings provide insights into the mechanisms by which platelets can be deleterious to the brain endothelium during CM. Another aspect of inflammatory and infectious diseases is that they often lead to activation of vascular and blood cells. Such activation results in an enhanced vesiculation, i.e. the release of circulating microparticles (MP). We thus explored plasma levels of endothelial MP in Malawian children with malaria. Plasma MP numbers were markedly increased on admission only in patients with severe malaria complicated with coma. Using the experimental mouse model of CM, we evaluated the pathogenic implications of MP using genetically deficient mice in which the capacity to vesiculate is impaired. Such mice, lacking the ABCA-1 gene, upon infection by Plasmodium berghei ANKA, showed complete resistance to CM. When purified from infected susceptible animals, MP were able to reduce normal plasma clotting time and to significantly enhance tumour necrosis factor release from naïve macrophages. Altogether these data provide a novel insight into the pathogenic mechanisms leading to the neurological syndrome. The finding that ABCA-1 gene deletion confers complete protection against cerebral pathology, linked to an impaired MP production, provides new potential targets for therapeutic amelioration of severe malaria.info:eu-repo/semantics/publishe

Absence of bleeding upon dual antiplatelet therapy in a patient with a immune GPVI deficiency

Acquired deficiencies in platelet glycoprotein VI are rare and have not been found associated with other defects. Here we report the case of a 64-year old male patient presenting an immune GPVI deficiency associated to a mutation in the alpha-actinin gene and who has been treated with dual anti platelet therapy without bleeding. Introduction: Glycoprotein (GP) VI, a pluripotent receptor interacting with collagen and fibrin(ogen) is responsible for thrombus formation, growth and stability (). It is co-expressed with the Fc receptor γ (FcRγ) chain (). GPVI is not critical for haemostasis since subjects with a GPVI deficiency usually present low or even no bleeding tendency (, ). Acquired GPVI deficiency due to antibody-induced GPVI depletion is the most frequent finding. At least 10 patients have been described with an acquired GPVI deficiency, most often associated to immune thrombocytopenia, moderate bleeding and impaired collagen-induced platelet aggregation (). Several mechanisms leading to the GPVI deficiency are proposed including antibody-triggered GPVI internalization and/or shedding of the extracellular domain (, ). We report the case of a patient presenting an acquired GPVI deficiency different from those previously described: (i) he is male whereas all previous cases were female, (ii) he is heterozygous for a mutation in α (alpha)-actinin-1 gene and (iii) he was treated with dual antiplatelet therapy with no haemorrhagic manifestation