In Vitro Impact of Pro-Senescent Endothelial Microvesicles on Isolated Pancreatic Rat Islets Function.

BACKGROUND: Ischemia-driven islet isolation procedure is one of the limiting causes of pancreatic islet transplantation. Ischemia-reperfusion process is associated with endothelium dysfunction and the release of pro-senescent microvesicles. We investigated whether pro-senescent endothelial microvesicles prompt islet senescence and dysfunction in vitro. MATERIAL AND METHODS: Pancreatic islets were isolated from male young rats. Replicative endothelial senescence was induced by serial passaging of primary porcine coronary artery endothelial cells, and microvesicles were isolated either from young passage 1 (P1) or senescent passage 3 (P3) endothelial cells. Islet viability was assessed by fluorescence microscopy, apoptosis by flow cytometry, and Western blot. Function was assessed by insulin secretion and islet senescence markers p53, p21, and p16 by Western blot. Microvesicles were stained by the PKH26 lipid fluorescent probe and their islet integration assessed by microscopy and flow cytometry. RESULTS: Regardless of the passage, half microvesicles were integrated in target islets after 24 hours incubation. Insulin secretion significantly decreased after treatment by senescent microvesicles (P3: 1.7 ± 0.2 vs untreated islet: 2.7 ± 0.2, P < .05) without altering the islet viability (89.47% ± 1.69 vs 93.15% ± 0.97) and with no significant apoptosis. Senescent microvesicles significantly doubled the expression of p53, p21, and p16 (P < .05), whereas young microvesicles had no significant effect. CONCLUSION: Pro-senescent endothelial microvesicles specifically accelerate the senescence of islets and alter their function. These data suggest that islet isolation contributes to endothelial driven islet senescence.

Significance of neutrophil microparticles in ischaemia-reperfusion: Pro-inflammatory effectors of endothelial senescence and vascular dysfunction.

Endothelial senescence is an emerging cause of vascular dysfunction. Because microparticles are effectors of endothelial inflammation and vascular injury after ischaemia-reperfusion, we examined leucocyte-derived microparticles of spleen origin as possible contributors. Microparticles were generated from primary rat splenocytes by either lipopolysaccharide or phorbol-myristate-acetate/calcium ionophore, under conditions mimicking innate and adaptive immune responses. Incubation of primary porcine coronary endothelial cells with either type of microparticles, but not with those from unstimulated splenocytes, leads to a similar threefold raise in senescence-associated ß-galactosidase activity within 48 hours, indicating accelerated senescence, to endothelial oxidative stress, and a fivefold and threefold increase in p21 and p16 senescence markers after 24 hours. After 12-hour incubation, the endothelial-dependent relaxation of coronary artery rings was reduced by 50%, at distinct optimal microparticle concentration. In vitro, microparticles were pro-thrombotic by up-regulating the local angiotensin system, by prompting tissue factor activity and a secondary generation of pro-coagulant endothelial microparticles. They initiated an early pro-inflammatory response by inducing phosphorylation of NF-κB, MAP kinases and Akt after 1 hour, and up-regulated VCAM-1 and ICAM-1 at 24 hours. Accordingly, VCAM-1 and COX-2 were also up-regulated in the coronary artery endothelium and eNOS down-regulated. Lipopolysaccharide specifically favoured the shedding of neutrophil- and monocyte-derived microparticles. A 80% immuno-depletion of neutrophil microparticles reduced endothelial senescence by 55%, indicating a key role. Altogether, data suggest that microparticles from activated splenocytes prompt early pro-inflammatory, pro-coagulant and pro-senescent responses in endothelial cells through redox-sensitive pathways. The control of neutrophil shedding could preserve the endothelium at site of ischaemia-reperfusion-driven inflammation and delay its dysfunction.

Thrombomodulin favors leukocyte microvesicle fibrinolytic activity, reduces NETosis and prevents septic shock-induced coagulopathy in rats.

BACKGROUND: Septic shock-induced disseminated intravascular coagulation is responsible for increased occurrence of multiple organ dysfunction and mortality. Immunothrombosis-induced coagulopathy may contribute to hypercoagulability. We aimed at determining whether recombinant human thrombomodulin (rhTM) could control exaggerated immunothrombosis by studying procoagulant responses, fibrinolysis activity borne by microvesicles (MVs) and NETosis in septic shock. METHODS: In a septic shock model after a cecal ligation and puncture-induced peritonitis (H0), rats were treated with rhTM or a placebo at H18, resuscitated and monitored during 4 h. At H22, blood was sampled to perform coagulation tests, to characterize MVs and to detect neutrophils extracellular traps (NETs). Lungs were stained with hematoxylin-eosin for inflammatory injury assessment. RESULTS: Coagulopathy was attenuated in rhTM-treated septic rats compared to placebo-treated rats, as attested by a significant decrease in procoagulant annexin A5+-MVs and plasma procoagulant activity of phospholipids and by a significant increase in antithrombin levels (84 ± 8 vs. 64 ± 6%, p < 0.05), platelet count (582 ± 157 vs. 319 ± 91 × 109/L, p < 0.05) and fibrinolysis activity borne by MVs (2.9 ± 0.26 vs. 0.48 ± 0.29 U/mL urokinase, p < 0.05). Lung histological injury score showed significantly less leukocyte infiltration. Decreased procoagulant activity and lung injury were concomitant with decreased leukocyte activation as attested by plasma leukocyte-derived MVs and NETosis reduction after rhTM treatment (neutrophil elastase/DNA: 93 ± 33 vs. 227 ± 48 and citrullinated histones H3/DNA: 96 ± 16 vs. 242 ± 180, mOD for 109 neutrophils/L, p < 0.05). CONCLUSION: Thrombomodulin limits procoagulant responses and NETosis and at least partly restores hemostasis control during immunothrombosis. Neutrophils might thus stand as a promising therapeutic target in septic shock-induced coagulopathy.

Evidence of Netosis in Septic Shock-Induced Disseminated Intravascular Coagulation.

INTRODUCTION: Neutrophils extracellular traps (NETs) have recently emerged as a new potential link between inflammation, immunity, and thrombosis and could play a key role in septic shock-induced disseminated intravascular coagulation (DIC) pathogenesis. The objective of our study was to investigate a potential link between NETosis and septic shock-induced DIC. METHODS: Twenty patients with septic shock (10 without and 10 with DIC according to JAAM 2006 score) were prospectively included in our study. Vascular cell activation was assessed by microparticle (MP) measurement. NETosis was investigated at days 1, 3, and 7 using two different approaches: probing and measurement of neutrophil DNA decompaction by neutrophil-side fluorescence light (NEUT-SFL) as recorded by an automated blood cell cytometer and the assessment of nucleosomes and NETs (DNA-bound myeloperoxidase, DNA-MPO). RESULTS: Endothelial-derived CD105-MPs, leucocyte-derived CD11a-MPs/leucocyte, and neutrophil-derived CD66b-MPs/neutrophil count ratios significantly increased in DIC compared with non-DIC patients, indicating on-going cell activation (P <0.05). NEUT-SFL, indicating DNA decompaction, was significantly higher in DIC patients. Circulating nucleosomes and DNA-MPO were increased in DIC patients (P <0.05). There were significant correlations between: nucleosomes and NETs (r = 0.397, P = 0.004), NEUT-SFL and nucleosomes (r = 0.243, P = 0.032), NEUT-SFL and DNA-MPO (r = 0.266, P = 0.024). CONCLUSION: NEUT-SFL, NETs, and elevated nucleosome concentrations were all correlated to DIC (P <0.05). We have shown that NETosis is significantly correlated to septic shock-induced DIC.

Early Detection of Disseminated Intravascular Coagulation During Septic Shock: A Multicenter Prospective Study.

OBJECTIVES: Inadequate stratification of septic shock patients may result in inappropriate treatment allocation in randomized clinical trials, especially regarding anticoagulant. We previously reported that endothelial-derived microparticles are relevant biomarkers of sepsis-induced disseminated intravascular coagulation. In this validation cohort, we assess microparticles as surrogates of cell activation to improve early disseminated intravascular coagulation diagnosis and patient stratification. DESIGN: Prospective observational study in septic shock patients. SETTINGS: Four medical ICUs in university hospitals. PATIENTS AND METHODS: Two hundred sixty-five patients with septic shock from four ICUs were consecutively enrolled. Disseminated intravascular coagulation was diagnosed according to Japanese Association for Acute Medicine 2006 score. Endothelial- and leukocyte-derived circulating procoagulant microparticles were isolated and quantified by prothrombinase assay at admission, day 3, and day 7. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: Two hundred fifty-nine patients were analyzed. Sixty-one had disseminated intravascular coagulation at admission, and 32 developed disseminated intravascular coagulation during the first 24 hours after admission. Multiple logistic regression model confirmed that endothelial cell-derived microparticles were associated with disseminated intravascular coagulation: CD105-microparticles (odds ratio, 2.13) and CD31-microparticles (odds ratio, 0.65) (p < 0.05). Furthermore, CD11a-microparticles to leukocyte ratio evidenced leukocyte activation (odds ratio, 1.59; p < 0.05). Prediction of disseminated intravascular coagulation was also analyzed after exclusion of patients with disseminated intravascular coagulation at admission. A new multiple logistic regression analysis demonstrated the association of CD105-microparticles (> 0.60 nM eq. PhtdSer; odds ratio, 1.67; p < 0.01), platelets count (≤ 127 g/L; odds ratio, 0.99; p < 0.01), and prothrombin time (≤ 58%; odds ratio, 0.98; p < 0.05) with disseminated intravascular coagulation. A combining score at admission is predictive of the absence of disseminated intravascular coagulation (area under the curve, 72.9%; specificity, 71.2%; sensitivity, 71.0%, with a negative predictive value of 93.1% and a positive predictive value of 31.0%). CONCLUSIONS: Procoagulant microparticles from endothelial cells and leukocytes reflect a vascular injury during sepsis-induced disseminated intravascular coagulation that precedes obvious activation of coagulation. A combination of prothrombin time, endothelium-derived CD105-microparticles, and platelet count at admission could predict the absence of disseminated intravascular coagulation and allow a better stratification in future randomized clinical trials.

Once versus twice daily injection of enoxaparin for thromboprophylaxis in bariatric surgery: effects on antifactor Xa activity and procoagulant microparticles. A randomized controlled study.

BACKGROUND: The optimal scheme of thromboprophylaxis in bariatric surgery remains uncertain, because clinical practice is different between countries and randomized trials are lacking. OBJECTIVES: The primary objective of this randomized multicenter study was to determine the optimal regimen of enoxaparin providing an antifactor Xa peak activity between .3 and .5 IU/mL at equilibrium and to evaluate the course of procoagulant microparticles (MPs). SETTING: University hospital. METHODS: A total of 164 patients scheduled for gastric bypass were allocated to 3 groups (A, B, and C) of enoxaparin treatment (4000, 6000, or 2×4000 IU, respectively). Antifactor Xa activity was measured before and 4 hours after each injection from D0 to D2. Doppler screening of the lower limbs was performed at D1, D9, and D30. Bleeding (BE) and thrombotic events (TE) were recorded during the first postoperative month. Total MPs were measured at D0, D9, and D30. MPs of leucocyte, platelet, and granulocyte origin were assessed in one third of the patients from each group. The 3 groups were compared by ANOVA. RESULTS: A total of 135 patients were analyzed. The equilibrium of antifactor Xa peak levels was obtained 52 hours after the presurgery injection and 12.8%, 56.4%, and 27.3% of the patients reached the target in groups A, B, and C, respectively (P<.001). No TE was detected. BE occurred in 1, 2, and 6 patients in groups A, B, and C, respectively). Total MPs remained unchanged over time. While no significant variation was observed in the other groups, platelet GP1 b(+)-MPs increased (P = .01) at D9 in group C, suggesting an incomplete control of anticoagulation leading to cell activation and procoagulant MP release that was confirmed by the higher MP levels measured at D30 (P = .04). CD66(+)-MPs were also highly elevated at J9 and D30 in group C indicating a granulocyte contribution. CONCLUSIONS: This study shows that a single dose of enoxaparin 6000 IU/d allowed most of the patients to reach the target range of antifactor Xa activity without increasing the bleeding risk, with the most likely efficient reduction of procoagulant MPs. (Surg Obes Relat Dis 2015;0:000-000.) © 2015 American Society for Metabolic and Bariatric Surgery. All rights reserved.

Medium-chain triglyceride supplementation exacerbates peritonitis-induced septic shock in rats: role on cell membrane remodeling.

BACKGROUND AND AIMS: Lipid emulsions for parenteral nutrition interfere with immunity and may alter the cell plasma membrane and microparticle release, thus modulating their biological effects. Our aim was to evaluate the effect of two lipid emulsions for parenteral nutrition containing either a mixture of long- and medium-chain triglycerides (LCTs and MCTs) or LCTs only, to assess their role on microparticle release and acute inflammation during septic shock in rats. METHODS AND RESULTS: Septic rats (cecal ligation and puncture) and sham rats were infused with 5% dextrose or a lipid emulsion during 22 h. After 18 h, rats were resuscitated during 4 h and hemodynamic parameters monitored. Circulating microparticles and their phenotype were measured by prothrombinase assay; heart and aorta were collected for Western blotting and electron paramagnetic resonance measurements. No significant effect of lipid emulsions was observed in sham rats. In septic rats, norepinephrine requirements were increased in MCT/LCT-infused rats compared with 5% dextrose- or LCT-infused rats (2.7 ± 0.2 vs. 1.9 ± 0.8 and 1.2 ± 0.3 µg/kg per minute, respectively; P < 0.05) with increased procoagulant microparticle generation (38.6 ± 5.8 vs. 18.8 ± 3.1 and 19.2 ± 3.0 nM equivalent phosphatidylserine [Eq PhtdSer]; P < 0.05), leukocyte- (17.4 ± 3.5 vs. 7.7 ± 1.8 and 6.0 ± 1.1 nM Eq PhtdSer; P < 0.05), platelet- (13.9 ± 2.5 vs. 4.4 ± 0.7 and 5.4 ± 1.3 nM Eq PhtdSer; P < 0.05), and endothelial-derived microparticles (16.9 ± 3.6 vs. 6.4 ± 1.4 and 5.6 ± 0.8 nM Eq PhtdSer; P < 0.05). The mixture of MCTs/LCTs significantly increased cardiac and vascular nitric oxide and superoxide anion production, phosphorylated IκB, and cyclooxygenase 2 expression compared with the lipid emulsion containing only LCTs. CONCLUSIONS: Compared with 5% dextrose, MCT/LCT supplementation during septic shock in rats induced deleterious effects with increased inflammation and cell activation, associated to vascular hyporeactivity. During septic shock, LCT supplementation seemed to be neutral compared with 5% dextrose infusion.

Lipid emulsions differentially affect LPS-induced acute monocytes inflammation: in vitro effects on membrane remodeling and cell viability.

The aim of this study was to assess how lipid emulsions for parenteral nutrition affect lipopolysaccharide (LPS)-induced acute monocyte inflammation in vitro. An 18 h long LPS induced human monocyte leukemia cell stimulation was performed and the cell-growth medium was supplemented with three different industrial lipid emulsions: Intralipid(®), containing long-chain triglycerides (LCT--soybean oil); Medialipid(®), containing LCT (soybean oil) and medium-chain triglycerides (MCT--coconut oil); and SMOFlipid(®), containing LCT, MCT, omega-9 and -3 (soybean, coconut, olive and fish oils). Cell viability and apoptosis were assessed by Trypan blue exclusion and flow cytometry respectively. Monocyte composition and membrane remodeling were studied using gas chromatography and NR12S staining. Microparticles released in supernatant were measured by prothrombinase assay. After LPS challenge, both cellular necrosis and apoptosis were increased (threefold and twofold respectively) and microparticle release was enhanced (sevenfold) after supplementation with Medialipid(®) compared to Intralipid(®), SMOFlipid(®) and monocytes in the standard medium. The monocytes differentially incorporated fatty acids after lipid emulsion challenge. Finally, lipid-treated cells displayed microparticles characterized by disrupted membrane lipid order, reflecting lipid remodeling of the parental cell plasma membrane. Our data suggest that lipid emulsions differentially alter cell viability, monocyte composition and thereby microparticle release. While MCT have deleterious effects, we have shown that parenteral nutrition emulsion containing LCT or LCT and MCT associated to n-3 and n-9 fatty acids have no effect on endotoxin-induced cell death and inflammation.

Liraglutide protects Rin-m5f ß cells by reducing procoagulant tissue factor activity and apoptosis prompted by microparticles under conditions mimicking Instant Blood-Mediated Inflammatory Reaction.

Instant Blood-Mediated Inflammatory Reaction (IBMIR) occurs at the vicinity of transplanted islets immediately after intraportal infusion and is characterized by cytokine secretion, tissue factor (TF) expression, and ß cell loss. Microparticles (MPs) are cellular effectors shed from the plasma membrane of apoptotic cells. Modulation of the properties of ß cell-derived MPs by liraglutide was assessed in a cellular model designed to mimic IBMIR oxidative and inflammatory conditions. Rin-m5f rat ß cells were stimulated by H2 O2 or a combination of IL-1ß and TNF-α. Cell-derived MPs were applied to naive Rin-m5f for 24 h. Apoptosis, MP release, TF activity, P-IκB expression, and MP-mediated apoptosis were measured in target cells. Direct protection by liraglutide was shown by a significant decrease in the oxidative stress-induced apoptosis (18.7% vs. 7.6%, P < 0.0001 at 1 µm liraglutide) and cellular TF activity (-40% at 100 nm liraglutide). Indirect cytoprotection led to 20% reduction in MP generation, thereby lowering MP-mediated apoptosis (6.3% vs. 3.7%, P = 0.022) and NF-κB activation (-50%) in target cells. New cytoprotective effects of liraglutide were evidenced, limiting the expression of TF activity by ß cells and the generation of noxious MPs. Altogether, these data suggest that liraglutide could target pro-apoptotic and pro-inflammatory MPs in transplanted islets.

Exocrine cell-derived microparticles in response to lipopolysaccharide promote endocrine dysfunction in cystic fibrosis.

BACKGROUND: Diabetes in cystic fibrosis (CF) is a result of exocrine pancreas alteration followed by endocrine dysfunction at a later stage. Microparticles (MPs) are plasma membrane fragments shed from stimulated or damaged cells that act as cellular effectors. Our aim was to identify a new form of interaction between exocrine and endocrine pancreatic cells mediated by exocrine MPs, in the context of recurrent infection in CF. METHODS: MPs from either human exocrine CFTRΔF508-mutated (CFPAC-1) cells or exocrine normal pancreatic (PANC-1) cells were collected after treatment by LPS from Pseudomonas aeruginosa and applied to rat endocrine normal insulin-secreting RIN-m5F cells. MP membrane integration in target cells was established by confocal microscopy and flow cytometry using PKH26 lipid probe. Apoptosis, lysosomal activity, insulin secretion were measured after 18 h. MP-mediated NF-κB activation was measured in HEK-Blue reporter cells by SEAP reporter gene system and in RIN-m5F cells by Western blot. In endocrine normal cells, CFTR inhibition was achieved using Inhibitor-172. RESULTS: Compared to PANC-1, MPs from CFPAC-1 significantly reduced insulin secretion and lysosomal activity in RIN-m5F. MPs induced NF-κB activation by increasing the level of IκB phosphorylation. Moreover, the inhibition of NF-κB activation using specific inhibitors was associated with a restored insulin secretion. Interestingly, CFTR inhibition in normal RIN-m5F cells promoted apoptosis and decreased insulin secretion. CONCLUSIONS: During recurrent infections associated with CF, exocrine MPs may contribute to endocrine cell dysfunction via NF-κB pathways. Membrane CFTR dysfunction is associated with decreased insulin secretion.

Pharmacological modulation of procoagulant microparticles improves haemodynamic dysfunction during septic shock in rats.

Circulating microparticles play a pro-inflammatory and procoagulant detrimental role in the vascular dysfunction of septic shock. It was the objective of this study to investigate mechanisms by which a pharmacological modulation of microparticles could affect vascular dysfunction in a rat model of septic shock. Septic or sham rats were treated by activated protein C (aPC) and resuscitated during 4 hours. Their microparticles were harvested and inoculated to another set of healthy recipient rats. Haemodynamic parameters were monitored, circulating total procoagulant microparticles assessed by prothrombinase assay, and their cell origin characterised. Mesenteric resistance arteries, aorta and heart were harvested for western blotting analysis. We found that a) the amount and phenotype of circulating microparticles were altered in septic rats with an enhanced endothelial, leucocyte and platelet contribution; b) aPC treatment significantly reduced the generation of leucocyte microparticles and norepinephrine requirements to reach the mean arterial pressure target in septic rats; c) Microparticles from untreated septic rats, but not from aPC-treated ones, significantly reduced the healthy recipients' mean arterial pressure; d) Microparticle thromboxane content and aPC activity were significantly increased in aPC-treated septic rats. In inoculated naïve recipients, microparticles from aPC-treated septic rats prompted reduced NF-κB and cyclooxygenase-2 arterial activation, blunted the generation of pro-inflammatory iNOS and secondarily increased platelet and endothelial microparticles. In conclusion, in this septic shock model, increased circulating levels of procoagulant microparticles led to negative haemodynamic outcomes. Pharmacological treatment by aPC modified the cell origin and levels of circulating microparticles, thereby limiting vascular inflammation and favouring haemodynamic improvement.

Do atrial differences in endothelial damage, leukocyte and platelet activation, or tissue factor activity contribute to chamber-specific thrombogenic status in patients with atrial fibrillation?

BACKGROUND: Thrombi form mainly in the left rather than the right atria of patients with atrial fibrillation (AF), the reason of this predilection being unknown. OBJECTIVE: The purpose of this study was to investigate whether atrial-specific differences in endothelial damage, leukocyte activation, platelet stimulation, and tissue factor activity occur in patients with AF. METHODS: Twenty-two patients (16 men, 6 women; age 56 ± 8 years; 16 paroxysmal AF, 6 persistent AF) with AF undergoing pulmonary vein isolation were investigated. Blood samples from the left and the right atrium were obtained at the start of the procedure. Microparticles (MPs) released by apoptotic/stimulated cells were measured by capture assays. Their procoagulant abilities were quantified by functional prothrombinase and tissue factor assays and their cellular origin were determined (endothelium, platelet, leukocyte). Platelet reactivity was evaluated by whole blood flow cytometry for expression of platelet P-selectin (CD62P), active glycoprotein IIb/IIIa receptor (PAC-1). Platelet aggregation was evaluated using ADP, TRAP and collagen-induced whole blood aggregometry. RESULTS: There were no atrial-specific differences in the levels of total procoagulant MPs, leukocyte-derived-MPs or platelet-derived MPs. Conversely, endothelial-derived MPs and tissue factor activity and collagen-induced platelet aggregation were slightly elevated in the right atrium (P < 0.05). CONCLUSIONS: Our data show no evidence for increased thrombogenic status in the left atrium that would account for its greater propensity for thrombus formation in patients with AF.

Factors influencing the level of circulating procoagulant microparticles in acute pulmonary embolism.

BACKGROUND: Flow cytometry has shown levels of platelet-derived microparticles (PMPs) and endothelial-derived microparticles (EMPs) to be elevated in deep-vein thrombosis. Cardiovascular risk factors can also contribute to hypercoagulability due to circulating procoagulant microparticles (CPMPs). AIMS: To investigate in a case-control study the respective contribution of pulmonary embolism and cardiovascular risk factors to the level of hypercoagulability due to CPMPs. METHODS: CPMP, PMP and EMP levels were measured in 45 consecutive patients (age 67.9 +/- 11.6 years; 66.7% men) admitted to an intensive care unit for acute pulmonary embolism (APE), 45 healthy control subjects with no history of venous thromboembolism or vascular risk factors (Controls(noCVRFs)), and 45 patients with cardiovascular risk factors (Controls(CVRFs)). APE was diagnosed by spiral computed tomography or scintigraphy. CPMP levels were assessed using a prothrombinase assay on platelet-depleted plasma (results expressed as nmol/L equivalent). RESULTS: CPMP levels were higher in APE patients than in Controls(noCVRFs) (medians 4.7 vs 3.2 nmol/L, interquartile ranges [IQRs] 2.9-11.1 vs 2.3-4.6 nmol/L; p=0.02). Similar results were reported for PMPs (medians 2.2 vs 1.9 nmol/L, IQRs 1.7-5.8 vs 1.4-2.4 nmol/L; p=0.02), whereas EMP levels were not significantly different. However, CPMP procoagulant activity was not significantly different in APE patients and Controls(CVRFs). CONCLUSIONS: CPMPs and PMPs were significantly elevated in APE patients vs Controls(noCVRFs), but this correlation was not significant when APE patients were compared with Controls(CVRFs). Our observations highlight the importance of adjusting for the presence of cardiovascular risk factors in conditions in which microparticle levels are raised.

Circulating procoagulant microparticles in acute pulmonary embolism: a case-control study.

We investigated whether circulating procoagulant microparticles (CPMPs) contributed to hypercoagulability in 45 patients with acute pulmonary embolism (APE) and in 45 controls with and 45 controls without cardiovascular risk factors. Concentrations of CPMPs and platelet-derived microparticles (PMPs) were statistically significantly higher in patients with APE than in controls without cardiovascular risk factors. PMPs appeared to be the main source of procoagulant microparticle release in APE, but this correlation disappeared when APE patients were compared to controls with cardiovascular risk factors. CPMPs may have a role in venous thrombosis as mediators of cardiovascular risk factors.

Microparticle-induced release of B-lymphocyte regulators by rheumatoid synoviocytes.

INTRODUCTION: In the present study, we investigated the ability of microparticles isolated from synovial fluids from patients with rheumatoid arthritis or osteoarthritis to induce the synthesis and release of key cytokines of B-lymphocyte modulation such as B cell-activating factor, thymic stroma lymphopoietin, and secretory leukocyte protease inhibitor by rheumatoid fibroblast-like synoviocytes. METHODS: Microparticles were analyzed in synovial fluids from patients with rheumatoid arthritis, osteoarthritis, microcristalline arthritis, and reactive arthritis. In addition, microparticle release after activation from various cell lines (CEM lymphocyte and THP-1 cells) was assessed. Microparticles were isolated by differential centrifugation, and quantitative determinations were carried out by prothrombinase assay after capture on immobilized annexin V. B cell-activating factor, thymic stroma lymphopoietin, and secretory leukocyte protease inhibitor release was evaluated by enzyme-linked immunosorbent assay. RESULTS: Microparticles isolated from synovial fluids obtained from rheumatoid arthritis and osteoarthritis patients or microparticles derived from activated THP-1 cells were able to induce B cell-activating factor, thymic stroma lymphopoietin, and secretory leukocyte protease inhibitor release by rheumatoid arthritis fibroblast-like synoviocytes. Conversely, CEM-lymphocytes-derived microparticles generated by treatment with a combination of PHA, PMA and Adt-D did not promote the release of B cell-activating factor but favored the secretion of thymic stroma lymphopoietin and secretory leukocyte protease inhibitor by rheumatoid arthritis fibrobast-like synoviocytes. However, microparticles isolated from actinomycin D-treated CEM lymphocytes were not able to induce B cell-activating factor, thymic stroma lymphopoietin, or secretory leukocyte protease inhibitor release, indicating that microparticles derived from apoptotic T cells do not function as effectors in B-cell activation. CONCLUSIONS: These results demonstrate that microparticles are signalling structures that may act as specific conveyors in the triggered induction and amplification of autoimmunity. This study also indicates that microparticles have differential effects in the crosstalk between B lymphocytes and target cells of autoimmunity regarding the parental cells from which they derive.

Membrane microvesicles as actors in the establishment of a favorable prostatic tumoral niche: a role for activated fibroblasts and CX3CL1-CX3CR1 axis.

Tumor microenvironment is enriched in plasma membrane microvesicles (MV) shed from all cell types that constitute the tumor mass, reflecting the antigenic profile of the cells they originate from. Fibroblasts and tumor cells mutually communicate within tumor microenvironment. Recent evidences suggest that tumor-derived MVs (TMV) exert a broad array of biological functions in cell-to-cell communication. To elucidate their role in cancer-to-fibroblast cell communication, TMV obtained from two prostate carcinoma cell lines with high and weak metastatic potential (PC3 and LnCaP, respectively) have been characterized. TMV exhibit matrix metalloproteinases (MMP) and extracellular MMP inducer at their surface, suggesting a role in extracellular matrix degradation. Moreover, TMV not only induce the activation of fibroblasts assessed through extracellular signal-regulated kinase 1/2 phosphorylation and MMP-9 up-regulation, increase motility and resistance to apoptosis but also promote MV shedding from activated fibroblasts able in turn to increase migration and invasion of highly metastatic PC3 cells but not LnCaP cells. PC3 cell chemotaxis seems, at least partially, dependent on membrane-bound CX3CL1/fractalkine ligand for chemokine receptor CX3CR1. The present results highlight a mechanism of mutual communication attributable not only to soluble factors but also to determinants harbored by MV, possibly contributing to the constitution of a favorable niche for cancer development.

Recombinant activated protein C attenuates endothelial injury and inhibits procoagulant microparticles release in baboon heatstroke.

OBJECTIVE: We tested the hypothesis that the antithrombotic and cytoprotective effects of recombinant human activated protein C (rhAPC) protect baboons against the lethal effects of heatstroke. METHODS AND RESULTS: Fourteen anesthetized baboons assigned randomly to rhAPC (n=7) or control group (n=7) were heat-stressed in a prewarmed incubator at 44 to 47 degrees C until systolic blood pressure fell below 90 mm Hg, which signaled severe heatstroke. rhAPC was administered intravenously (24 microg/kg/h) for 12 hours at onset of heatstroke. Heat stress induced coagulation and fibrinolysis activation as evidenced by a significant increase from baseline levels in plasma levels of thrombin-antithrombin (TAT) complexes, tissue plasminogen activator, and D-dimer. Heat stress elicited cell activation/injury as assessed by the release of interleukin (IL)-6, soluble thrombomodulin, and procoagulant microparticles (MPs). rhAPC did not significantly reduce heatstroke-induced thrombin generation, and D-dimer and had no effect on fibrinolytic activity. In contrast, rhAPC infusion attenuated significantly the plasma rise of IL-6 and inhibited the release of soluble thrombomodulin and MPs as compared with control group. No difference in survival was observed between rhAPC-treated and control group. CONCLUSIONS: rhAPC given to heatstroke baboons provided cytoprotection, but had no effect on heatstroke-induced coagulation activation and fibrin formation. Inhibition of MPs by rhAPC suggested a novel mechanism of action for this protein.

Endothelial cell activation contributes to the release of procoagulant microparticles during acute cardiac allograft rejection.

BACKGROUND: Circulating procoagulant microparticles are reliable markers of vascular damage. The microparticle phenotypes provide additional information reflecting the nature of cell injury. This study assessed procoagulant microparticle levels and phenotypes in the diagnosis of acute allograft rejection after heart transplantation. METHODS: Microparticles were prospectively investigated in the venous blood of 64 heart transplant patients, 23 with allograft rejection mainly of low score, and 41 without a rejection episode. Plasma concentrations of cytokines, cytoadhesins, and platelet activation markers were determined. RESULTS: By univariate analysis, the mean time elapsed from heart transplant, cold ischemia time, E-selectin-, Fas- and tissue factor-bearing microparticles were associated with allograft rejection. By multivariate analysis, E-selectin-microparticle levels appeared independently associated with allograft rejection, even when other significant variables were included in the model (odds ratio, 9.8; 95% confidence interval, 1.36-71.4; p = 0.023). CONCLUSION: The pattern of procoagulant microparticles released during acute allograft rejection suggests endothelial cell activation and Fas-mediated apoptosis. E-selectin-bearing microparticles appeared as an independent marker of acute allograft rejection that was still informative after adjustment for graft characteristics.