Endothelial microparticles released by activated protein C protect beta cells through EPCR/PAR1 and annexin A1/FPR2 pathways in islets.

Islet transplantation is associated with early ischaemia/reperfusion, localized coagulation and redox-sensitive endothelial dysfunction. In animal models, islet cytoprotection by activated protein C (aPC) restores islet vascularization and protects graft function, suggesting that aPC triggers various lineages. aPC also prompts the release of endothelial MP that bear EPCR, its specific receptor. Microparticles (MP) are plasma membrane procoagulant vesicles, surrogate markers of stress and cellular effectors. We measured the cytoprotective effects of aPC on endothelial and insulin-secreting Rin-m5f ß-cells and its role in autocrine and paracrine MP-mediated cell crosstalk under conditions of oxidative stress. MP from aPC-treated primary endothelial (EC) or ß-cells were applied to H2 O2 -treated Rin-m5f. aPC activity was measured by enzymatic assay and ROS species by dihydroethidium. The capture of PKH26-stained MP and the expression of EPCR were probed by fluorescence microscopy and apoptosis by flow cytometry. aPC treatment enhanced both annexin A1 (ANXA1) and PAR-1 expression in EC and to a lesser extent in ß-cells. MP from aPC-treated EC (eMaPC ) exhibited high EPCR and annexin A1 content, protected ß-cells, restored insulin secretion and were captured by 80% of ß cells in a phosphatidylserine and ANXA1-dependent mechanism. eMP activated EPCR/PAR-1 and ANXA1/FPR2-dependent pathways and up-regulated the expression of EPCR, and of FPR2/ALX, the ANXA1 receptor. Cytoprotection was confirmed in H2 O2 -treated rat islets with increased viability (62% versus 48% H2 O2 ), reduced apoptosis and preserved insulin secretion in response to glucose elevation (16 versus 5 ng/ml insulin per 10 islets). MP may prove a promising therapeutic tool in the protection of transplanted islets.

An Intravenous Bolus of Epa: Dha 6: 1 Protects Against Myocardial Ischemia-Reperfusion-Induced Shock.

INTRODUCTION: Enriching the diet with Omega-3 for several weeks improves myocardial resistance to ischemia-reperfusion (IR) in rats. However, patients with myocardial infarction requiring an emergency reperfusion cannot be pretreated with such a diet. The objective of our study was to describe the effects of an intravenous Omega-3 bolus before reperfusion in a rat model of myocardial IR. METHODS: In a rat model of acute myocardial IR, an intravenous Omega-3 bolus (EPA:DHA 6:1), associated or not with iodinated contrast media, was administered after a 30-min ischemia, before reperfusion. Hemodynamic parameters were assessed. Circulating procoagulant microparticles were phenotyped. Vascular and heart inflammation, superoxide anion, and nitric oxide were measured. Ex vivo vascular reactivity was performed with a pharmacological selective inhibitor of inductible nitric oxide synthase. Cardiac troponin I (cTn-I) plasma levels were measured. RESULTS: Compared with untreated IR rats, an Omega-3 bolus before reperfusion significantly decreased the IR syndrome, improving mean arterial pressure (114 ±â€Š9 vs. 61 ±â€Š17 mmHg 4 h after reperfusion, P < 0.05) and carotid blood flow, and decreasing plasma cTn-I levels after revascularization. These beneficial effects may be due to improved ex vivo mesenteric resistance artery sensitivity to phenylephrine, endothelial protection assessed by decreased endothelial CD54 microparticle release (9.1 ±â€Š2.5 vs. 4.8 ±â€Š2.0 nM Eq PhtdSer, P < 0.05) and reduced vascular inflammation and oxidative stress. CONCLUSIONS: In this rat model of myocardial IR, an intravenous Omega-3 bolus before reperfusion decreases IR-induced vascular failure and shock. These results open therapeutic perspectives as far as myocardial reperfusion process is concerned that deserve further explorations in humans.

ß cell membrane remodelling and procoagulant events occur in inflammation-driven insulin impairment: a GLP-1 receptor dependent and independent control.

Inflammation and hyperglycaemia are associated with a prothrombotic state. Cell-derived microparticles (MPs) are the conveyors of active procoagulant tissue factor (TF) and circulate at high concentration in diabetic patients. Liraglutide, a glucagon-like peptide (GLP)-1 analogue, is known to promote insulin secretion and ß-cell preservation. In this in vitro study, we examined the link between insulin impairment, procoagulant activity and plasma membrane remodelling, under inflammatory conditions. Rin-m5f ß-cell function, TF activity mediated by MPs and their modulation by 1 µM liraglutide were examined in a cell cross-talk model. Methyl-ß-cyclodextrine (MCD), a cholesterol depletor, was used to evaluate the involvement of raft on TF activity, MP shedding and insulin secretion as well as Soluble N-éthylmaleimide-sensitive-factor Attachment protein Receptor (SNARE)-dependent exocytosis. Cytokines induced a two-fold increase in TF activity at MP surface that was counteracted by liraglutide. Microparticles prompted TF activity on the target cells and a two-fold decrease in insulin secretion via protein kinase A (PKA) and p38 signalling, that was also abolished by liraglutide. Large lipid raft clusters were formed in response to cytokines and liraglutide or MCD-treated cells showed similar patterns. Cells pre-treated by saturating concentration of the GLP-1r antagonist exendin (9-39), showed a partial abolishment of the liraglutide-driven insulin secretion and liraglutide-decreased TF activity. Measurement of caspase 3 cleavage and MP shedding confirmed the contribution of GLP-1r-dependent and -independent pathways. Our results confirm an integrative ß-cell response to GLP-1 that targets receptor-mediated signalling and membrane remodelling pointing at the coupling of insulin secretion and inflammation-driven procoagulant events.