Les microparticules circulantes : rôles physiologiques et implications dans les maladies inflammatoires et thrombotiques

Transcriptomic Analysis of Liver Tissue of Black Sea Bass (Centropristis striata) Exposed to High Nitrogen Environment

The black sea bass, Centropristis striata, is a potential candidate for commercial aquaculture. Due to inadequate removal of nitrogen in its breeding environment, C. striata exhibits increased nitrate concentration, which can cause acute toxicity, including energy metabolism damage and tissue damage. Therefore, RNA-seq technology was applied to characterize genes associated with toxicity tolerance under nitrate stress. The nitrate treatment caused significant changes in a total of 8920 genes, of which 2949 genes were up-regulated and 5971 genes were down-regulated. It was found that significantly enriched GO terms and KEGG were associated with blood microparticles, inhibitors of enzyme activity, and complement and coagulation cascade pathways. Furthermore, through bioinformatics analysis, it was found that these different pathways obtained in GO and KEGG enrichment analysis were mostly related to the immune and inflammatory response of fish. This study expands our understanding of the mechanism of nitrate stress affecting the liver function of C. striata.

Protein Compositions Changes of Circulating Microparticles in Patients With Valvular Heart Disease Subjected to Cardiac Surgery Contribute to Systemic Inflammatory Response and Disorder of Coagulation

We recently demonstrated that circulating microparticles (MPs) from patients with valvular heart diseases (VHD) subjected to cardiac surgery impaired endothelial function and vasodilation. However, it is unknown whether or not the protein composition of these circulating MPs actually changes in response to the disease and the surgery. Circulating MPs were isolated from age-matched control subjects (n = 50) and patients (n = 50) with VHD before and 72 h after cardiac surgery. Proteomics study was performed by liquid chromatography and mass spectrometry combined with isobaric tags for relative and absolute quantification technique. The differential proteins were identified by ProteinPilot, some of which were validated by Western blotting. Bio-informatic analysis of differential proteins was carried out. A total of 849 proteins were identified and 453 proteins were found in all three groups. Meanwhile, 165, 39, and 80 proteins were unique in the control, pre-operation, and postoperation groups respectively. The unique proteins were different in localization, molecular function, and biological process. The pro-inflammatory proteins were increased in VHD patients and more so postoperatively. Proteins related to coagulation were dramatically changed before and after surgery. The protein composition of circulating MPs was changed in patients with VHD undergoing cardiac surgery, which may lead to activation of the systemic inflammatory response and disorders of coagulation.

Cancer microvesicles induce tissue factor-related procoagulant activity in endothelial cells in vitro

: Microvesicles associated with tissue factor (TF) may play a role in cancer-related venous thromboembolism; however, not much is known about their interaction with the tumour stroma, especially the endothelium or any procoagulant changes seen because of this interaction. Using a head and neck squamous cell carcinoma line (UMSCC81B) and human umbilical vein endothelial cells (HUVECs), this study explored the interaction of cancer microvesicles released into cell culture media with endothelial cells in vitro, and assessed the procoagulant activity resulting from this interaction. Cell-free media containing UMSCC81B cancer microvesicles supported coagulation in a concentration-dependent manner, suggesting TF and microvesicle presence, this media was then added to HUVECs and flow cytometry analysis showed a subpopulation of HUVECs that had acquired a significantly high expression of TF, which was dependent upon the concentration of UMSCC81B media containing microvesicles present and confocal microscopy confirmed HUVECs associated with labelled microvesicles. The range of TF-positive HUVECs was determined to be 0, 4.2(±1.4), 12.5(±3.72), and 45.9(±18.7)% for microvesicle-positive media concentration of 0, 25, 50, and 100%, respectively, which resulted in decreasing prothrombin values of more than 600 (no clot), 126.4, 65.8, and 47.8 s. Our results demonstrate that procoagulant microvesicles shed by UMSCC81B induced a procoagulant effect in HUVECs through increased clotting activity and cell membrane surface expression of TF.

Changes in the pattern of plasma extracellular vesicles after severe trauma

Background

Extracellular vesicles (EV) released into the circulation after traumatic injury may influence complications. We thus evaluated the numbers of EV in plasma over 28 days after trauma and evaluated their pro-coagulant and inflammatory effects.

Methods and findings

37 patients suffering trauma with an injury severity score >15 were studied along with 24 healthy controls. Plasma samples were isolated by double centrifugation (2000g 20min; 13000g 2min) from blood collected from within an hour up to 28 days after injury. Plasma EV were counted and sized using nanoparticle tracking analysis (NTA); counts and cellular origins were also determined by flow cytometry (FC) using cell-specific markers. Functional effects were tested in a procoagulant phospholipid assay and in flow-based, leukocyte adhesion assay after endothelial cells (EC) were treated with EV.

We found that EV concentrations measured by NTA were significantly increased in trauma patients compared to healthy controls, and remained elevated over days. In addition, or FC showed that patients with trauma had higher numbers of EV derived from platelets (CD41+), leukocytes (CD45+) and endothelial EC (CD144+). The increases were evident throughout the 28-day follow-up. However, the FC count represented <1% of the count detected by NTA, and only 1–2% of EV identified using NTA had a diameter >400nm. The procoagulant phospholipid activity assay showed that patient plasma accelerated coagulation on day 1 and day 3 after trauma, with coagulation times correlated with EV counts. Furthermore, treatment of EC for 24 hours with plasma containing EV tended to increase the recruitment of peripheral flowing blood mononuclear cells.

Conclusions

EV counted by FC represent a small sub-population of the total load detected by NTA. Both methods however indicate a significant increase in plasma EV after severe traumatic injury that have pro-coagulant and pro-inflammatory effects that may influence outcomes.

Cerebral malaria--clinical manifestations and pathogenesis

One of the most common central nervous system diseases in tropical countries is cerebral malaria (CM). Malaria is a common protozoan infection that is responsible for enormous worldwide mortality and economic burden on the society. Episodes of Plasmodium falciparum (Pf) caused CM may be lethal, while survivors are likely to suffer from persistent debilitating neurological deficits, especially common in children. In this review article, we have summarized the various symptoms and manifestations of CM in children and adults, and entailed the molecular basis of the disease. We have also emphasized how pathogenesis of the disease is effected by the parasite and host responses including blood brain barrier (BBB) disruption, endothelial cell activation and apoptosis, nitric oxide bioavailability, platelet activation and apoptosis, and neuroinflammation. Based on a few recent studies carried out in experimental mouse malaria models, we propose a basis for the neurological deficits and sequelae observed in human cerebral malaria, and summarize how existing drugs may improve prognosis in affected individuals.

Circulating Endothelial Microparticles: A Key Hallmark of Atherosclerosis Progression

The levels of circulating microparticles (MPs) are raised in various cardiovascular diseases. Their increased level in plasma is regarded as a biomarker of alteration in vascular function. The prominent MPs present in blood are endothelial microparticles (EMPs) described as complex submicron (0.1 to 1.0 μm) vesicles like structure, released in response to endothelium cell activation or apoptosis. EMPs possess both physiological and pathological effects and may promote oxidative stress and vascular inflammation. EMPs release is triggered by inducer like angiotensin II, lipopolysaccharide, and hydrogen peroxide leading to the progression of atherosclerosis. However, there are multiple physiological pathways for EMPs generation like NADPH oxidase derived endothelial ROS formation, Rho kinase pathway, and mitogen-activated protein kinases. Endothelial dysfunction is a key initiating event in atherosclerotic plaque formation. Atheroemboli, resulting from ruptured carotid plaques, is a major cause of stroke. Increasing evidence suggests that EMPs play an important role in the pathogenesis of cardiovascular disease, acting as a marker of damage, either exacerbating disease progression or triggering a repair response. In this regard, it has been suggested that EMPs have the potential to act as biomarkers of disease status. This review aims to provide updated information of EMPs in relation to atherosclerosis pathogenesis.

Disease dynamics in patients with acute myeloid leukemia: new biomarkers

Acute myeloid leukemia (AML) is characterized by rapid growth of leukemic blast cells. Extracellular vesicles (EVs), shedding from various cells, express antigens, reflecting their cellular origin. The current study was designed to explore the role of circulating EVs as potential biomarkers of AML activity and predictors of thrombogenicity in patients with this malignancy. Blood samples were collected from healthy controls and patients with newly diagnosed AML at three time points: diagnosis, nadir, and remission. EV concentration, cell origin, and expression of coagulation proteins were characterized using fluorescence-activated cell sorting. EV cytokine contents were evaluated by protein array. Procoagulant activity was assessed using Factor Xa chromogenic assay. Forty-two AML patients were enrolled in the study. Total EV numbers were higher in patients in first remission compared with controls, whereas blast EV counts were higher in patients at diagnosis compared with controls and patients in remission. Blast EV levels were significantly lower in patients who achieved remission and were alive at 3-year follow up compared with their succumbed counterparts. At all three time points, percentage of endothelial EVs was higher in patients compared with controls. EV procoagulant activity was elevated at diagnosis and in remission, and, unlike controls' EVs, patients' EVs increased endothelial cell thrombogenicity. EVs of AML patients express membrane proteins of blast cells and might serve as biomarkers of leukemia dynamics and presence of minimal residual disease. Increased levels of endothelial EVs and their procoagulant activity may indicate a vascular injury associated with a hypercoagulable state in AML.

Potential avoidance of adverse analgesic effects using a biologically "smart" hydrogel capable of controlled bupivacaine release

Acute pain remains a tremendous clinical and economic burden, as its prevalence and common narcotic-based treatments are associated with poorer outcomes and higher costs. Multimodal analgesia portends great therapeutic promise, but rarely allows opioid sparing, and new alternatives are necessary. Microparticles (MPs) composed of biodegradable polymers [e.g., poly(lactic-co-glycolic acid) or PLGA] have been applied for controlled drug release and acute pain treatment research. However, foreign particles' presence within inflamed tissue may affect the drug release or targeting, and/or cause a secondary inflammatory reaction. We examined how small alterations in the particulate nature of MPs affect both their uptake into and subsequent activation of macrophages. MPs composed of PLGA and chitosan (PLGA-Chi) loaded with bupivacaine (BP) were engineered at different sizes and their opsonization by J774 macrophages was assessed. Uptake of PLGA-Chi by macrophages was found to be size dependent, but they were not cytotoxic or proinflammatory in effect. Moreover, encapsulation of MPs in a thermoresponsive loading gel (pluronic F-127) effectively prevented opsonization. Finally, MPs displayed sustained, tunable release of BP up to 7 days. These results demonstrate our ability to develop a drug delivery system capable of controlled release of local anesthetics to treat acute/subacute pain while concurrently avoiding enhanced inflammation.

Extracellular vesicle protein levels are related to brain atrophy and cerebral white matter lesions in patients with manifest vascular disease: the SMART-MR study

OBJECTIVES

Extracellular vesicles (EVs) and their protein levels have been identified as a potential risk marker for the development of vascular disease. In the present study, we assessed whether levels of four previously identified EV proteins (cystatin C, serpin G1, serpin F2 and CD14) are associated with cerebral white matter lesions (WMLs) and brain atrophy.

DESIGN

Cohort study; cross-sectional and prospective.

SETTING

Single centre, secondary and tertiary setting.

PARTICIPANTS

1309 patients with manifest vascular disease from the Second Manifestations of ARTerial disease-MR (SMART-MR) study, of which 994 had successful brain MRI and EV protein level measurements.

OUTCOMES

WML and brain parenchymal fraction (BPF), as parameter for brain atrophy, at baseline and follow-up.

STATISTICAL METHODS

The relationship between EV protein levels and WML volume (expressed as log transformed percentage of intracranial volume) and BPF (expressed percentage of intracranial volume) on 1.5 T brain MRI was assessed with multivariable linear regression modelling. Subsequently, the relationship between baseline EV protein levels and progression of atrophy and WML was analysed in 534 patients, in whom a follow-up MRI was obtained after 4 years.

RESULTS

Higher EV-cystatin C and EV-CD14 were significantly associated with larger WML volume (linear regression coefficient (95% CI) 0.10 log %/SD (0.04 to 0.17) and 0.14 log %/SD (0.07 to 0.20), respectively. Higher EV-CD14 was associated with more brain atrophy (-0.14%/SD; -0.27 to -0.01). Baseline EV-CD14 was significantly associated with increase of WMLs (0.11 log %/SD (0.04 to 0.18)). No relationship with EV-serpins was observed at baseline or at follow-up.

CONCLUSIONS

EV proteins cystatin C and CD14 are related to cerebral WMLs and the progression of brain atrophy in patients with manifest vascular disease, potentially identifying EVs in the aetiology of structural brain changes.

Placenta-derived microparticles

Microparticles (MPs), sub-micron membrane vesicles, participate in the placental and maternal crosstalk in normal pregnancies as well as in gestational vascular complications (GVC). The article will review the effects of MPs on placental physiological processes, including hemostasis, trophoblast migration, invasion, placental vasculature and their involvement in pathologic states such as thrombosis, inflammation and endothelial dysfunction, resulting in GVC.

Phospholipidomics of human blood microparticles

The phospholipidome of blood microparticles (MPs) obtained from platelet-rich plasma of healthy individuals was characterized by hydrophilic interaction liquid chromatography (HILIC) coupled to electrospray ionization tandem mass spectrometry (ESI-MS/MS). The HILIC separation, performed on a silica stationary phase using an acetonitrile/methanol gradient, enabled the separation of several phospholipids (PL) classes, viz., phosphatidyl-cholines (PCs), -ethanolamines (PEs), -serines (PSs), -inositoles (PIs), sphyngomielins (SMs), and lyso forms of PCs and PEs. Structural characterization of species belonging to each class was performed by MS/MS measurements, in either positive or negative ion mode. The set of 131 phospholipids (including regioisomers) here identified represents the most comprehensive phospholipidomic characterization reported for human MPs. Although the phospholipidome composition of MPs and platelets, collected from the same donors, was found to be qualitatively the same, quantitative differences were evidenced for lyso-PCs, which appear to be significantly more abundant in MPs.

Microvesicle protein levels are associated with increased risk for future vascular events and mortality in patients with clinically manifest vascular disease

BACKGROUND AND OBJECTIVES

Microvesicles (MVs) are small membrane vesicles that are involved in atherotrombotic processes. In the present study, we evaluated the risk of MV protein levels on the occurrence of new vascular events in patients with clinically manifest vascular disease.

METHODS

In this cohort study 1060 patients were prospectively followed for the occurrence of a new vascular event or death (median follow up 6.4 years, interquartile range 5.2-7.3 years). MVs were isolated from plasma and MV protein levels of Cystatin C, Serpin G1, Serpin F2 and CD14 were measured. Multivariable Cox proportional hazards models were used to estimate the risk for new vascular events, vascular mortality and all-cause mortality. During follow up 136 vascular events occurred, 65 vascular mortality and 114 all-cause mortality.

RESULTS

An increase in 1 standard deviation (SD) of Cystatin C MV level was related to an increased risk for myocardial infarction (HR 1.49; 95%CI 1.20-1.86), vascular mortality (HR 1.48; 95%CI 1.17-1.86), vascular events (HR 1.27; 1.07-1.52) and all-cause mortality (HR 1.41; 95%CI 1.18-1.69). Serpin F2 MV levels were related to an increased risk for myocardial infarction (HR 1.22; 95%CI 1.00-1.51), vascular mortality (HR 1.25; 95%CI 1.00-1.56), and all-cause mortality (HR 1.22; 95% CI 1.03-1.45). CD14 MV levels were related to an increased risk for myocardial infarction (HR 1.55; 95%CI 1.27-1.91), vascular mortality (HR 1.37; 95%CI 1.10-1.70), vascular events (HR 1.32; 95%CI 1.12-1.55), all-cause mortality (HR 1.36; 95%CI 1.15-1.62) and occurrence of ischemic stroke (HR 1.32; 95%CI 1.00-1.74).

CONCLUSIONS

Cystatin C, Serpin F2 and CD14 MV levels are related to an elevated risk for future vascular events and mortality in patients with clinically manifest vascular disease.

Leukocyte-derived microparticles in vascular homeostasis

Leukocyte-derived microparticles (LMPs) may originate from neutrophils, monocytes/macrophages, and lymphocytes. They express markers from their parental cells and harbor membrane and cytoplasmic proteins as well as bioactive lipids implicated in a variety of mechanisms, maintaining or disrupting vascular homeostasis. When they carry tissue factor or coagulation inhibitors, they participate in hemostasis and pathological thrombosis. Both proinflammatory and anti-inflammatory processes can be affected by LMPs, thus ensuring an appropriate inflammatory response. LMPs also play a dual role in the endothelium by either improving the endothelial function or inducing an endothelial dysfunction. LMPs are implicated in all stages of atherosclerosis. They circulate at a high level in the bloodstream of patients with high atherothrombotic risk, such as smokers, diabetics, and subjects with obstructive sleep apnea, where their prolonged contact with the vessel wall may contribute to its overall deterioration. Numbering microparticles, including LMPs, might be useful in predicting cardiovascular events. LMPs modify the endothelial function and promote the recruitment of inflammatory cells in the vascular wall, necessary processes for the progression of the atherosclerotic lesion. In addition, LMPs favor the neovascularization within the vulnerable plaque and, in the ruptured plaque, they take part in coagulation and platelet activation. Finally, LMPs participate in angiogenesis. They might represent a novel therapeutic tool to reset the angiogenic switch in pathologies with altered angiogenesis. Additional studies are needed to further investigate the role of LMPs in cardiovascular diseases. However, large-scale studies are currently difficult to set up because microparticle measurement still requires elaborate techniques which lack standardization.

Calpastatin controls polymicrobial sepsis by limiting procoagulant microparticle release

RATIONALE

Sepsis, a leading cause of death worldwide, involves widespread activation of inflammation, massive activation of coagulation, and lymphocyte apoptosis. Calpains, calcium-activated cysteine proteases, have been shown to increase inflammatory reactions and lymphocyte apoptosis. Moreover, calpain plays an essential role in microparticle release.

OBJECTIVES

We investigated the contribution of calpain in eliciting tissue damage during sepsis.

METHODS

To test our hypothesis, we induced polymicrobial sepsis by cecal ligation and puncture in wild-type (WT) mice and transgenic mice expressing high levels of calpastatin, a calpain-specific inhibitor.

MEASUREMENTS AND MAIN RESULTS

In WT mice, calpain activity increased transiently peaking at 6 hours after cecal ligation and puncture surgery. Calpastatin overexpression improved survival, organ dysfunction (including lung, kidney, and liver damage), and lymphocyte apoptosis. It decreased the sepsis-induced systemic proinflammatory response and disseminated intravascular coagulation, by reducing the number of procoagulant circulating microparticles and therefore delaying thrombin generation. The deleterious effect of microparticles in this model was confirmed by transferring microparticles from septic WT to septic transgenic mice, worsening their survival and coagulopathy.

CONCLUSIONS

These results demonstrate an important role of the calpain/calpastatin system in coagulation/inflammation pathways during sepsis, because calpain inhibition is associated with less severe disseminated intravascular coagulation and better overall outcomes in sepsis.

Association between vascular access failure and microparticles in hemodialysis patients

Background

Vascular access failure, a major cause of morbidity in hemodialysis (HD) patients, occurs mainly at stenotic endothelium following an acute thrombotic event. Microparticles (MPs) are fragments derived from injured cell membrane and are closely associated with coagulation and vascular inflammatory responses.

Methods

We investigated the relationship between levels of circulating MPs and vascular access patency in HD patients. A total of 82 HD patients and 28 healthy patients were enrolled. We used flow cytometry to measure endothelial MPs (EMPs) identified by CD31+CD42− or CD51+ and platelet-derived MPs (PMPs) identified by CD31+CD42+ in plasma samples of participants. Vascular access patency was defined as an interval from the time of access formation to the time of first access stenosis in each patient. MP counts were compared according to access patent duration.

Results

The levels of EMP (both CD31+CD42− and CD51+) and CD31+CD42+PMP were significantly higher in patients than in healthy participants. Levels of CD31+CD42−EMP and CD31+CD42+PMP showed a positive correlation. In non-diabetic HD patients, CD31+CD42−EMPs and CD31+CD42+PMPs were more elevated in the shorter access survival group (access survival <1 year) than in the longer survival group (access survival ≥ 4 years).

Conclusion

Elevated circulating EMP or PMP counts are influenced by end-stage renal disease and increased levels of EMP and PMP may be associated with vascular access failure in HD patients.

Clopidogrel effectively suppresses endothelial microparticle generation induced by indoxyl sulfate via inhibition of the p38 mitogen-activated protein kinase pathway

BACKGROUND/AIMS

Endothelial microparticles (EMPs) are closely associated with vascular dysfunction. We investigated the effects of several drugs on EMP generation in human umbilical vein endothelial cells (HUVECs), and the involvement of the mitogen-activated protein kinase (MAPK) in EMP generation.

METHODS

CD31+CD42-EMP counts were measured by flow cytometry in supernatants of HUVECs incubated with indoxyl sulfate. The EMP responses to losartan, lovastatin, clopidogrel, and mesoglycan were examined. We then measured the effects of MAPK inhibitors on EMPs.

RESULTS

(1) Indoxyl sulfate induced EMP release in HUVECs in a dose-dependent fashion; (2) all drugs (10-50 μM) inhibited EMP generation induced by indoxyl sulfate, with clopidogrel being the most effective; (3) the p38 MAPK inhibitor suppressed EMP generation induced by indoxyl sulfate, and (4) clopidogrel significantly suppressed MAPK signaling activated by indoxyl sulfate, with the most potency on p38.

CONCLUSION

The p38 signaling involves EMP generation induced by indoxyl sulfate and is effectively suppressed by clopidogrel.

Microparticles and pregnancy complications

Microparticles (MPs) are shed from cell membranes of a variety of cells, promote thrombus formation, mediate pro-inflammatory effects and may cause endothelial dysfunction. Normal pregnancy is characterized by increased levels of MPs compared to non-pregnant healthy women but the prevalence, cell origin and the role of MPs in pregnancy-related complications remain controversial. Normal pregnancy is an acquired hyper-coagulable state due to an increase in procoagulants and decrease in natural anticoagulants. Pregnancy-related complications such as preeclampsia, intrauterine fetal growth restriction (IUGR) and fetal loss are associated with placental dysfunction and may cause significant maternal and fetal morbidity and mortality. This article highlights the role of microparticles in maternal placental crosstalk and the interplay between microparticles, thrombosis and pregnancy complications.

Chronic venous insufficiency is associated with elevated level of circulating microparticles

BACKGROUND

Chronic venous insufficiency (CVI) results when the veins in the legs no longer pump blood back to the heart effectively. Microparticles (MPs) are small membrane vesicles released by several circulating and vascular cells upon activation or apoptosis.

OBJECTIVES

The purpose of this study was to assess the subpopulations of circulating endothelial (EMPs) and platelet microparticles (PMPs) in CVI, and to disclose their contribution in mediating dysfunction of human peripheral venules.

PATIENTS AND METHODS

Human peripheral venules were explanted during leg surgery on patients with CVI and on control subjects (C); concurrently, blood samples were collected and circulating MPs isolated. The techniques used were: flow cytometry, fluorescence and electron microscopy, myograph technique and western-blotting technique.

RESULTS

The results showed that compared with controls, patients with CVI had: (i) a marked elevation of circulating EMPs and PMPs; (ii) a structural modification of the venous wall consisting of activation of endothelial and smooth muscle cells, an abundance of intermediary filaments and synthesis of hyperplasic-multilayered basal lamina; (iii) a significantly altered reactivity of the venous wall, closely associated with EMPs and PMPs adherence; (iv) altered contractile response to noradrenaline, acetylcholine, 5-hydroxytryptamine and KCl, and an impeded relaxation in response to sodium nitroprusside; and (iv) a substantially increased protein expression of tissue factor (TF) and of P-Selectin both in the venular vascular wall and on the surface of EMPs and PMPs.

CONCLUSIONS

The findings indicate that CVI is accompanied by an enhanced release of EMPs and PMPs that contribute to altered dysfunctional response of the venous wall.

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.

Characterizing blood microparticles: technical aspects and challenges

Although long considered to be cellular debris, microparticles (MPs) are more recently considered reflective of cellular stimulation, activation, and degeneration/apoptosis. MPs that arise from the cellular components of blood and the endothelial lining of blood vessels are referred to as blood MPs and by general consensus are small (≤1.5 μm), expose the anionic phospholipid (PL) phosphatidylserine (PS) on the outer leaflet of their membrane, and bear surface membrane antigens reflecting their cellular origin. This brief review summarizes the different approaches used by several groups to study blood MPs. The aim of this article is to review the technical aspects of characterizing the morphological and functional properties of blood MPs with emphasis on the preanalytical and analytical variables involved in these studies.

Impact of neutrophil apoptosis on haemostatic activation in chronic liver disease patients

Recent studies suggest the impact of apoptosis on the mechanisms leading to hypercoagulability. We aimed to clarify the potential role of neutrophil apoptosis in neutropenia and hypercoagulable state encountered in chronic liver disease patients. This study was conducted on 15 normal controls and 45 patients with chronic liver disease classified according to modified Child Pugh classification into, Child A, B and C groups (15 cases each). Haemostatic parameters studied include, prothrombin time, partial thromboplastin time, tissue factor, protein C antigen, protein S antigen, and markers of haemostatic activation [prothrombin fragment 1+2 (F1+2), thrombus precursor protein (TpP) and D-dimer]. Flowcytometric study was done for quantitative assay of neutrophil apoptotic subpopulations to detect the percentage of early and late apoptotic, and necrotic neutrophils using Annexin V-FITC/propidium iodide dye. Semiquantitative assay of apoptotic neutrophils showing DNA fragmentation was performed on neutrophil culture using terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labelling test. In addition to enzyme-linked immunosorbent assay for soluble Fas (APO-1/CD95) in culture supernatant. The results revealed a rise in the neutrophil apoptotic and necrotic markers with progression of the disease, and they were inversely correlated with the absolute neutrophil count. The apoptotic neutrophil cells showed a significant positive correlation with several haemostatic parameters (tissue factor, prothrombin fragment 1+2, thrombus precursor protein and D-dimer). Regression analysis proved that apoptotic parameters are independent determinants of prothrombotic markers, which further incriminate the apoptotic mechanisms in the hypercoagulable state encountered in this clinical setting.

Platelet microparticles are heterogeneous and highly dependent on the activation mechanism: Studies using a new digital flow cytometer

BACKGROUND

Platelet-derived microparticles (MPs) are believed to play an important role in coagulation and inflammatory disorders. Unfortunately, MP size renders them difficult to study and analyze by conventional flow cytometry.

METHODS

We analyzed and characterized platelet-derived MPs, using antibodies against the major surface glycoproteins (GP), the platelet activation antigen P-selectin (CD62P), and a marker of procoagulant activity (phosphatidylserine exposure). MPs were generated by exposure of platelets to thrombin receptor activating peptide (TRAP) or ionophore. Both agonists induced significant microvesiculation of platelets, and the resulting MPs were analyzed by a new digital flow cytometer: Becton-Dickinson FACSAria.

RESULTS

Membrane GPs were equally well represented in MPs generated by either reagent. In contrast, P-selectin was more intensely expressed in TRAP-MPs, while phosphatidylserine (PS) expression was markedly increased in ionophore-MPs. Two distinct populations of TRAP-MPs (one PS-positive and another PS-negative) were apparent. The latter characteristic facilitated sorting of MPs according to their PS exposure.

CONCLUSIONS

The data presented herein show a significant improvement in the methodology applied until now to the characterization of MPs. The ability to characterize and sort MP subpopulations may help to resolve their contributions to normal and pathological functions.