The significance of shed membrane particles during programmed cell death in vitro, and in vivo, in HIV-1 infection

The potential applications of microparticles in the diagnosis, treatment, and prognosis of lung cancer

Microparticles (MPs) are 100–1000 nm heterogeneous submicron membranous vesicles derived from various cell types that express surface proteins and antigenic profiles suggestive of their cellular origin. MPs contain a diverse array of bioactive chemicals and surface receptors, including lipids, nucleic acids, and proteins, which are essential for cell-to-cell communication. The tumour microenvironment (TME) is enriched with MPs that can directly affect tumour progression through their interactions with receptors. Liquid biopsy, a minimally invasive test, is a promising alternative to tissue biopsy for the early screening of lung cancer (LC). The diverse biomolecular information from MPs provides a number of potential biomarkers for LC risk assessment, early detection, diagnosis, prognosis, and surveillance. Remodelling the TME, which profoundly influences immunotherapy and clinical outcomes, is an emerging strategy to improve immunotherapy. Tumour-derived MPs can reverse drug resistance and are ideal candidates for the creation of innovative and effective cancer vaccines. This review described the biogenesis and components of MPs and further summarised their main isolation and quantification methods. More importantly, the review presented the clinical application of MPs as predictive biomarkers in cancer diagnosis and prognosis, their role as therapeutic drug carriers, particularly in anti-tumour drug resistance, and their utility as cancer vaccines. Finally, we discussed current challenges that could impede the clinical use of MPs and determined that further studies on the functional roles of MPs in LC are required.

Blood Cell-Derived Microvesicles in Hematological Diseases and beyond

Microvesicles or ectosomes represent a major type of extracellular vesicles that are formed by outward budding of the plasma membrane. Typically, they are bigger than exosomes but smaller than apoptotic vesicles, although they may overlap with both in size and content. Their release by cells is a means to dispose redundant, damaged, or dangerous material; to repair membrane lesions; and, primarily, to mediate intercellular communication. By participating in these vital activities, microvesicles may impact a wide array of cell processes and, consequently, changes in their concentration or components have been associated with several pathologies. Of note, microvesicles released by leukocytes, red blood cells, and platelets, which constitute the vast majority of plasma microvesicles, change under a plethora of diseases affecting not only the hematological, but also the nervous, cardiovascular, and urinary systems, among others. In fact, there is evidence that microvesicles released by blood cells are significant contributors towards pathophysiological states, having inflammatory and/or coagulation and/or immunomodulatory arms, by either promoting or inhibiting the relative disease phenotypes. Consequently, even though microvesicles are typically considered to have adverse links with disease prognosis, progression, or outcomes, not infrequently, they exert protective roles in the affected cells. Based on these functional relations, microvesicles might represent promising disease biomarkers with diagnostic, monitoring, and therapeutic applications, equally to the more thoroughly studied exosomes. In the current review, we provide a summary of the features of microvesicles released by blood cells and their potential implication in hematological and non-hematological diseases.

Vitreous microparticles contain apoptotic signals suggesting a diabetic vitreopathy

AIM

To evaluate differences in microparticle profiles in vitreous samples between diabetic and non-diabetic eyes undergoing vitrectomy.

METHODS

Un-masked cross-sectional series of 34 eyes undergoing vitrectomy. Vitreous specimens were collected and processed to evaluate for membrane integrity (DAPI), apoptosis (Annexin-V), and endothelial-cell origin (V-Cadherin). A BD LSR II flow cytometer was used for analysis and standardized sub-micron-sized beads were used for size comparison.

RESULTS

Thirty-four specimens underwent analysis. Greater levels of Annexin-V were found on microparticles from specimens in which blood had entered the vitreous (n=12) compared to those without blood (n=22; 52.3%±30.7% vs 19.6%±27.2%, P=0.002). Patients with diabetes having surgery with hemorrhage (n=7) had greater expression of Annexin-V than those without hemorrhage (n=8; 62.1%±31.7% vs 18.9%±20.9%, P=0.009). However, in patients with non-diabetic vitreous hemorrhage, the level of Annexin-V expression was not significantly different compared to other disease processes (38.6%±25.7%, n=5 vs 20.0%±30.9%, n=14, P=0.087).

CONCLUSION

Increased expression of the apoptotic marker, Annexin-V is detected on vitreous microparticles in diabetes-related vitreous hemorrhage. When evaluating vitreous hemorrhage in patients without diabetes, the apoptotic signal is not significantly different. Vitrectomy in patients with diabetes, and improvement in visual outcomes, may be related to the removal of a serum-derived, pro-apoptotic vitreous. Further investigation is warranted in order to identify the molecular characteristics of microparticles that regulate disease.

Therapeutic Role of Sirtuins Targeting Unfolded Protein Response, Coagulation, and Inflammation in Hypoxia-Induced Thrombosis

Thrombosis remains one of the leading causes of morbidity and mortality across the world. Many pathological milieus in the body resulting from multiple risk factors escort thrombosis. Hypoxic condition is one such risk factor that disturbs the integrity of endothelial cells to cause an imbalance between anticoagulant and procoagulant proteins. Hypoxia generates reactive oxygen species (ROS) and triggers inflammatory pathways to augment the coagulation cascade. Hypoxia in cells also activates unfolded protein response (UPR) signaling pathways in the endoplasmic reticulum (ER), which tries to restore ER homeostasis and function. But the sustained UPR linked with inflammation, generation of ROS and apoptosis stimulates the severity of thrombosis in the body. Sirtuins, a group of seven proteins, play a vast role in bringing down inflammation, oxidative and ER stress and apoptosis. As a result, sirtuins might provide a therapeutic approach towards the treatment or prevention of hypoxia-induced thrombosis. Sirtuins modulate hypoxia-inducible factors (HIFs) and counteract ER stress-induced apoptosis by attenuating protein kinase RNA-like endoplasmic reticulum kinase (PERK)/Eukaryotic translation initiation factor 2α (eIF2α) pathway activation. It prevents ER-stress mediated inflammation by targeting X-Box Binding Protein 1 (XBP1) and inhibiting nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κβ) signaling through deacetylation. Sirtuins also obstruct nucleotide-binding domain, leucine-rich-containing family, pyrin domain containing 3 (NLRP3) inflammasome activation to reduce the expression of several pro-inflammatory molecules. It protects cells against oxidative stress by targeting nuclear factor erythroid 2-related factor 2 (Nrf2), glutathione (GSH), forkhead box O3 (FOXO3), superoxide dismutase (SOD), catalase (CAT), peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α), glucose-6-phosphate dehydrogenase (G6PD), phosphoglucomutase-2 (PGAM2), and NF-κB, to name few. This review, thus, discusses the potential role of sirtuins as a new treatment for hypoxia-induced thrombosis that involves an intersection of UPR and inflammatory pathways in its pathological manifestation.

Lipid Transporters Beam Signals from Cell Membranes

Lipid composition in cellular membranes plays an important role in maintaining the structural integrity of cells and in regulating cellular signaling that controls functions of both membrane-anchored and cytoplasmic proteins. ATP-dependent ABC and P4-ATPase lipid transporters, two integral membrane proteins, are known to contribute to lipid translocation across the lipid bilayers on the cellular membranes. In this review, we will highlight current knowledge about the role of cholesterol and phospholipids of cellular membranes in regulating cell signaling and how lipid transporters participate this process.

Microparticles in COVID-19 as a link between lung injury extension and thrombosis

Among the distinctive features of coronavirus disease 2019 (COVID-19), numerous reports have stressed the importance of vascular damage associated with coagulopathy onset [1]. Histological analysis of pulmonary vessels in patients with COVID-19 revealed severe endothelial injury associated with intracellular severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and disrupted endothelial cell membranes together with widespread thrombosis and occlusion of alveolar capillaries. Microparticles (MPs) shed by apoptotic/stimulated cells of various cellular lineages, including platelets, leukocytes, macrophages or endothelial cells, are reliable markers of vascular damage [2] released upon pro-inflammatory conditions and behave as active participants in the early steps of clot formation [3]. Circulating MPs promote procoagulant responses due to the exposure of tissue factor, the physiological activator of the coagulation cascade, and of negatively charged phospholipids, such as phosphatidylserine, required for the assembly of the tenase and prothrombinase coagulation complexes ultimately leading to thrombin generation, through which they can precisely be quantified [4]. MPs carry angiotensin-converting enzyme (ACE)1 and upregulate ACE1 expression in neighbouring endothelial cells [5]. By contrast, exosomes were recently reported to convey ACE2, the cell-entry receptor for SARS-CoV-2 [4], in the vasculature [6]. ACE2 converts angiotensin II (Ang II) into angiotensin 1–7 (Ang 1–7), which by virtue of its actions on the Mas receptor, limits the noxious effects of Ang II. Pioneering data have demonstrated that the renin–angiotensin system has a crucial role in severe acute injury and that ACE2 has a protective role in acute lung injury mediated by SARS-CoV [7]. According to this paradigm, the loss of ACE2 function following binding by SARS-CoV-2 may contribute to unopposed Ang II accumulation that further exacerbates tissue injury and promotes inflammation, MPs release and thrombosis. During SARS-CoV-2 infection, we hypothesised that various factors including inflammatory burden, Ang II, altered shear stress and hypoxic vasoconstriction, could enhance MPs shedding by various cell lineages including the alveolar vascular endothelium and contribute to clot formation.

Procoagulant microparticles are associated with the extent of lung injuries in #COVID19 and pulmonary thrombosishttps://bit.ly/3eX2LPc

Expedition into Exosome Biology: A Perspective of Progress from Discovery to Therapeutic Development

Exosomes are membrane-enclosed distinct cellular entities of endocytic origin that shuttle proteins and RNA molecules intercellularly for communication purposes. Their surface is embossed by a huge variety of proteins, some of which are used as diagnostic markers. Exosomes are being explored for potential drug delivery, although their therapeutic utilities are impeded by gaps in knowledge regarding their formation and function under physiological condition and by lack of methods capable of shedding light on intraluminal vesicle release at the target site. Nonetheless, exosomes offer a promising means of developing systems that enable the specific delivery of therapeutics in diseases like cancer. This review summarizes information on donor cell types, cargoes, cargo loading, routes of administration, and the engineering of exosomal surfaces for specific peptides that increase target specificity and as such, therapeutic delivery.

Thrombocytopathies: Not Just Aggregation Defects-The Clinical Relevance of Procoagulant Platelets

Platelets are active key players in haemostasis. Qualitative platelet dysfunctions result in thrombocytopathies variously characterized by defects of their adhesive and procoagulant activation endpoints. In this review, we summarize the traditional platelet defects in adhesion, secretion, and aggregation. In addition, we review the current knowledge about procoagulant platelets, focusing on their role in bleeding or thrombotic pathologies and their pharmaceutical modulation. Procoagulant activity is an important feature of platelet activation, which should be specifically evaluated during the investigation of a suspected thrombocytopathy.

Phosphatidylserine is an overlooked mediator of COVID-19 thromboinflammation

A ubiquitous component of cell membrane, phosphatidylserine (PS), is likely to play a major, but as yet unrecognized, role in the thromboinflammation of COVID-19 and other critical illnesses. PS is present in all plasma membranes but is "hidden" on the inner surface by the action of an ATP-requiring enzyme. Failure of PS to be sequestered on the inner surface of cell membranes, release of PS-containing microparticles from cells, or shedding of enveloped viruses allows it to interact with extracellular proteins, including those of the coagulation and complement systems. Detection and quantification of circulating PS is not standardized, and current methodologies have either focused on circulating cellular elements or subcellular plasma components, but not both. PS may also promote thromboinflammation without circulating if expressed on the surface of endothelial cells, a condition that might only be documented if novel imaging techniques are developed. Research into the role of PS in inflammation and coagulation, called here a "procoagulant phospholipidopathy" may provide novel insights and therapeutic approaches for patients with a variety of illnesses.

Increased airway T lymphocyte microparticles in chronic obstructive pulmonary disease induces airway epithelial injury

In our previous study, T lymphocyte microparticles (TLMPs) originated from CEM T lymphoblast-like cell line induced enhanced production of inflammation-associated cytokines and apoptosis in human bronchial epithelial cells (HBEs). To measure TLMP subpopulations in bronchoalveolar lavage fluids (BALF) from patients with chronic obstructive pulmonary disease (COPD), and to explore the effects of MPs derived from different T cell subpopulations on airway epithelium, this study was conducted. A hospital-based case-control study including 47 COPD patients and 28 healthy volunteers was performed. The cellular origins of MPs from airway in COPD and controls were evaluated using flow cytometry. CD4⁺ or CD8⁺ TLMPs were isolated by MACS to investigate their effects on HBEs in vitro. The numbers of MPs derived from T lymphocytes in BALF as well as these subpopulations (CD4⁺ and CD8⁺ T lymphocytes) were significantly upregulated in COPD patients compared with healthy volunteers. However, there was no significant difference between stable COPD and patients with acute exacerbation. Additionally, significant correlation between CD4⁺ and CD8⁺ TLMPs was observed, however neither type nor total level of TLMPs was correlated with any base parameter. Furthermore, isolated CD4⁺ and CD8⁺ TLMPs reduced cell viability and induced significant production of inflammatory cytokines including interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1, MCP-2, matrix metallopeptidase (MMP)-9 and tumor necrosis factor-alpha (TNF-α) in HBEs, while the levels of anti-inflammatory cytokine IL-10 were decreased. TLMPs in the airways, as putative biomarkers, may lead to airway epithelial injury and inflammation and serve essential roles in the pathophysiology of COPD.

The microvesicle/CD36 complex triggers a prothrombotic phenotype in patients with non-valvular atrial fibrillation

The mechanisms responsible for platelet activation, the prothrombotic state, in non-valvular atrial fibrillation (NVAF) are still obscure. Microvesicles (MVs) can transfer various messages to target cells and may be helpful for exploring the detailed mechanisms. We aimed to investigate the possible mechanisms by which proatherogenic factors of NVAF contribute to platelet activation. Two hundred and ten patients with NVAF were stratified as being at 'low to moderate risk' or 'high risk' for stroke according to the CHADS2 score. Levels of platelet-derived MVs (PMVs) and platelet activation were examined. CD36-positive or CD36-deficient human platelets were stimulated by MVs isolated from NVAF patients with or without various inhibitors in vitro. Levels of PMVs and platelet activation markers enhanced significantly in high-risk patients. The MVs isolated from plasma of NVAF patients bound to platelet CD36 and activated platelets by phosphorylating the mitogen-activated protein kinase 4/Jun N-terminal kinase 2 (MKK4/JNK2) pathways. However, CD36 deficiency protected against MV-induced activation of platelets. We reveal a possible mechanism of platelet activation in NVAF and suggest that the platelet CD36 might be an effective target in preventing the prothrombotic state in NVAF.

Epithelial-mesenchymal transition and membrane microparticles: Potential implications for bronchiolitis obliterans syndrome after lung transplantation

Long term survival post lung transplantation (LTx) is limited by the occurrence of bronchiolitis obliterans syndrome (BOS). One mechanism involved is the epithelial-mesenchymal transition (EMT). Membrane microparticles (MPs) are known to be involved in some respiratory diseases and in other organs allograft rejection episodes. We hypothesized that leukocyte-derived MPs likely contribute to EMT. To emphasize this physiological concept, our objectives were to: (1) confirm the presence of EMT on explanted lungs from patients who underwent a second LTx for BOS; 2) characterize circulating MPs in transplanted patients, with or without BOS; (3) evaluate in vitro the effect of monocyte-derived MPs in EMT of human bronchial epithelial cells. Our IHC analysis on explanted graft lungs revealed significant pathological signs of EMT with an inhomogeneous destruction of the bronchial epithelium, with decreased expression of the epithelial protein E-cadherin and increased expression of the mesenchymal protein Vimentin. The immunophenotyping of MPs demonstrated that the concentration of MPs carrying E-cadherin was lower in patients affected by BOS (p = .007). In vitro, monocyte-derived MPs produced with LPS were associated with decreased E-cadherin expression (p < .05) along with significant morphological and functional cell modifications. MPs may play a role in EMT onset in bronchial epithelium following LTx.

Dendron-Functionalized Surface: Efficient Strategy for Enhancing the Capture of Microvesicles

Microvesicles (MVs) are used by various types of cells in the human body for intercellular communication, making them biomarkers of great potential for the early and non-evasive diagnosis of a spectrum of diseases. An integrated analysis including morphological, quantitative, and compositional studies is most desirable for the clinical application of MV detection; however, such integration is limited by the currently available analysis techniques. In this context, exploiting the phosphatidylserine (PS) exposure of MVs, we synthesized a series of dendritic molecules with PS-binding sites at the periphery. PS-dendron binding was studied at the molecular level using NMR approaches, whereas PS-containing membrane-dendron interaction was investigated in an aqueous environment using plasmon waveguide resonance spectroscopy. As a proof of concept, polyethylene terephthalate surface was functionalized with the synthetic dendrons, forming devices that can capture MVs to facilitate their subsequent analyses.

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Phosphatidylserine-dendron interaction studies with NMR techniques

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Lipid membrane binding enhancement using dendritic molecules

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Dendron-grafted material for effective MV capture

Extracellular vesicles and coagulation in blood from healthy humans revisited

Background: In 2001, we studied the presence and coagulant properties of “microparticles” in the blood of healthy humans. Since then, multiple improvements in detection, isolation and functional characterization of the now called “extracellular vesicles” (EVs) have been made, and shortcomings were identified. Aim: To revisit the presence and function of EVs in blood from healthy humans. Methods: Blood was collected from 20 healthy donors. EV-containing plasma was prepared according to new guidelines, and plasma was diluted to prevent swarm detection. Single EVs were measured by flow cytometry with known sensitivity of fluorescence and light scatter. The haemostatic properties of EVs were measured by thrombin-, fibrin-, and plasmin generation. Plasma concentrations of thrombin-antithrombin complexes and prothrombin fragment 1 + 2 were measured to assess the coagulation status in vivo. Results: Compared to 2001, the total concentrations of detected EVs increased from 190- to 264-fold. In contrast to 2001, however, EVs are non-coagulant which we show can be attributed to improvements in blood collection and plasma preparation. No relation is present between the plasma concentrations of EVs and either TAT or F1 + 2. Finally, we show that EVs support plasmin generation. Discussion: Improvements in blood collection, plasma preparation and detection of EVs reveal that results from earlier studies have to be interpreted with care. Compared to 2001, higher concentrations of EVs are detected in blood of healthy humans which promote fibrinolysis rather than coagulation.

Procoagulant tumor microvesicles attach to endothelial cells on biochips under microfluidic flow

Tumor patients are at a high risk of venous thromboembolism (VTE), and the mechanism by which this occurs may involve tumor-derived microvesicles (MVs). Previously, it has been shown that tumor MVs become attached to endothelial cells in static conditions. To investigate whether this process occurs under physiologically relevant flow rates, tumor MVs were perfused across a microfluidic device coated with growing human umbilical vein endothelial cells (HUVECs). Cell lines were screened for their ability to form tumor spheroids, and two cell lines, ES-2 and U87, were selected; spheroids formed were transferred to a microfluidic chip, and a second endothelial cell biochip was coated with HUVECs and the two chips were linked. Media flowed through the spheroid chip to the endothelial chip, and procoagulant activity (PCA) of the tumor media was determined by a one-stage prothrombin time assay. Tumor MVs were also quantified by flow cytometry before and after interaction with HUVECs. Confocal images showed that HUVECs acquired fluorescence from MV attachment. Labeled MVs were proportionally lost from MV rich media with time when flowed over HUVECs and were not observed on a control chip. The loss of MV was accompanied by a proportional reduction in PCA. Flow cytometry, confocal microscopy, and live flow imagery captured under pulsatile flow confirmed an association between tumor MVs and HUVECs. Tumor MVs attached to endothelial cells under physiological flow rates, which may be relevant to the VTE pathways in cancer patients.

Promising biomarkers for the prediction of catheter-related venous thromboembolism in hospitalized children: An exploratory study

BACKGROUND

Pediatric venous thromboembolism (VTE) has increased over the past 10 years, with central venous catheters (CVC) being the strongest risk factor. Current tools are not sufficient to predict VTE risk. The utility of biomarkers in predicting CVC-related VTE has been minimally explored. Our objective is to determine the utility of microparticles (MPs), factor VIII (FVIII) activity, and thrombin generation (TG) in prospectively predicting VTE occurrence in hospitalized children with CVCs.

PROCEDURE

In this nested case-control pilot study, consecutive hospitalized children needing CVC placement (1 month to 21 years) were enrolled. Venous samples were collected prior to or within 24 h of CVC placement. MPs were measured using factor Xa initiated clot-based assay. FVIII was measured using a one-stage clot-based assay. TG was measured using calibrated automated thrombogram.

RESULTS

There were three CVC-related VTE events (7%) in our cohort of 42 subjects. Xa clotting time (XaCT) ratio was lower (0.68 ± 0.07 vs 0.95 ± 0.21, P = .4), while FVIII (461 ± 120 vs 267 ± 130, P = .02), peak thrombin (418 ± 89 vs 211 ± 101, P = .001), endogenous thrombin potential (ETP) (1828 ± 485 vs 1282 ± 394, P = .03), and velocity index (VI) (182 ± 28 vs 75 ± 53, P = .001) were higher in subjects with CVC-related VTE compared to those without CVC-related VTE. Sensitivity/specificity analysis revealed optimal cutoff values for XaCT ratio (0.75), FVIII (370), ETP (1680), peak (315), and VI (130), with receiver operating characteristic area under the curve values >0.9.

CONCLUSION

MPs, FVIII, and TG can potentially predict pediatric CVC-related VTE in a prospective fashion. Stratification according to VTE risk may aid in guiding preventative efforts in future studies.

Microparticles and cardiovascular diseases

Microparticles are a distinctive group of small vesicles, without nucleus, which are involved as significant modulators in several physiological and pathophysiological mechanisms. Plasma microparticles from various cellular lines have been subject of research. Data suggest that they are key players in development and manifestation of cardiovascular diseases and their presence, in high levels, is associated with chronic inflammation, endothelial damage and thrombosis. The strong correlation of microparticle levels with several outcomes in cardiovascular diseases has led to their utilization as biomarkers. Despite the limited clinical application at present, their significance emerges, mainly because their detection and enumeration methods are improving. This review article summarizes the evidence derived from research, related with the genesis and the function of microparticles in the presence of various cardiovascular risk factors and conditions. The current data provide a substrate for several theories of how microparticles influence various cellular mechanisms by transferring biological information.

The endothelial tumor suppressor p53 is essential for venous thrombus formation in aged mice

Venous thromboembolism (VTE) is a leading cause of morbidity and mortality in elderly people. Increased expression of tumor suppressor protein 53 (p53) has been implicated in vascular senescence. Here, we examined the importance of endothelial p53 for venous thrombosis and whether endothelial senescence and p53 overexpression are involved in the exponential increase of VTE with age. Mice with conditional, endothelial-specific deletion of p53 (End.p53-KO) and their wild-type littermates (End.p53-WT) underwent subtotal inferior vena cava (IVC) ligation to induce venous thrombosis. IVC ligation in aged (12-month-old) End.p53-WT mice resulted in higher rates of thrombus formation and greater mean thrombus size vs adult (12-week-old) End.p53-WT mice, whereas aged End.p53-KO mice were protected from vein thrombosis. Analysis of primary endothelial cells from aged mice or human vein endothelial cells after induction of replicative senescence revealed significantly increased early growth response gene-1 (Egr1) and heparanase expression, and plasma factor Xa levels were elevated in aged End.p53-WT, but not in End.p53-KO mice. Increased endothelial Egr1 and heparanase expression also was observed after doxorubicin-induced p53 overexpression, whereas p53 inhibition using pifithrin-α reduced tissue factor (TF) expression. Importantly, inhibition of heparanase activity using TF pathway inhibitor-2 (TFPI2) peptides prevented the enhanced venous thrombus formation in aged mice and restored it to the thrombotic phenotype of adult mice. Our findings suggest that p53 accumulation and heparanase overexpression in senescent endothelial cells are critically involved in mediating the increased risk of venous thrombosis with age and that heparanase antagonization may be explored as strategy to ameliorate the prothrombotic endothelial phenotype with age.

Short Communication: Apoptotic Membrane Microparticles Quantified by Fluorescent Bead-Based Assay Are Elevated in HIV and SIV Infections

Apoptotic membrane microparticles (MMPs) derived from dying cells of multiple cell origins are highly immunostimulatory and are indicative of global immune activation and cell death in a variety of diseases. In this study, we developed a flow cytometric bead assay to quantify annexin-V⁺ apoptotic (MMPs) in plasma from humans and rhesus macaques. With a combination of flow cytometry and pan-fluorescent beads, MMPs were enumerated in plasma specimens by adding a constant ratio of beads to initial fluid volumes and then calculating MMP/mL based on MMP-to-bead ratios. Using this straightforward assay, we found that circulating MMP quantifications were highly reproducible and similar in number between normal rhesus macaques and humans subjects. However, MMPs increased two- to threefold during HIV and simian immunodeficiency virus (SIV) infections and were positively associated with T cell immune activation. Collectively, we present a rapid bead-based assay for both humans and macaque models to quantify MMPs that could be an instigator and predictor of immune activation, which is a primary source of HIV/SIV disease.

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.

Endothelial cell-derived microvesicles: potential mediators and biomarkers of pathologic processes

This review focuses on the formation, composition and function of endothelial microvesicles (MV), often called microparticles (MP). MV release is a controlled event and is considered a hallmark of cellular activation or alteration. MV may affect the function of target cells through surface interaction and receptor activation, cellular fusion and the delivery of intravesicular cargo. Endothelial MV are released as a consequence of endothelial activation during inflammation and have been described to affect hemostasis, various aspects of inflammatory reaction, vessel formation, apoptosis and cell survival, endothelial cell differentiation and function. Recent data suggest the potential use of MV in diagnostics, assessment of severity and prediction of outcomes in inflammatory diseases and their utilization as targets, mediators and vectors in therapy.

Clinical significance of circulating microparticles for venous thrombo - embolism in cancer patients

Cancer patients have a four-to seven-fold increased risk to develop a venous thromboembolic event. Accumulating evidence from experimental and clinical studies indicates that microparticles (MPs), small procoagulant membrane vesicles that are defined by size and a negatively charged phosphatidylserine rich surface, play an important role in the pathogenesis of cancer-related venous thromboembolism (VTE). However, the clinical significance of MPs as a predictive biomarker for VTE in cancer patients has not been fully elucidated yet. This might be due to unresolved methodological problems and a lack of data from large prospective clinical studies that investigate the role of MPs in cancer-related VTE.

It is the aim of this review to give an overview on the most important characteristics of MPs and studies dealing with the role of MPs in cancer-related VTE. Also recent progresses, unresolved problems and future perspectives in this research field will be discussed. In the conclusion we will assess the clinical significance of MPs in cancer-related VTE.

[Membranous microparticles and respiratory disease]

Microparticles (MP) are plasmic membrane fragments released from cells after physiological stimulation or stress conditions like inflammation or infection. Their production is correlated to the rate of cell apoptosis. All types of cells can produce MP but they are produced mainly by platelets, endothelial cells, and leukocytes. They carry many bio-active molecules on their surface, specific to the parental cell, giving them the ability to be biomarkers and bio-effectors. MP are present in circulating blood, tissues and many biological fluids. Circulating MP levels can change during the course of many diseases. They have been the subject of many studies in the fields of cardiovascular disease and oncology. In the lungs, they are present in circulating blood and in the airways. They seem to have a role in pulmonary homeostasis in physiological situations and also in the expression of several disease processes. In this review of the literature, we were interested in the quantitative and qualitative variations in MP and their impact in airway diseases like chronic obstructive pulmonary disease (COPD) and asthma, pulmonary fibrosis and pulmonary hypertension.

Insights into the Diagnostic Potential of Extracellular Vesicles and Their miRNA Signature from Liquid Biopsy as Early Biomarkers of Diabetic Micro/Macrovascular Complications

Extracellular vesicles (EVs) represent a heterogeneous population of small vesicles, consisting of a phospholipidic bilayer surrounding a soluble interior cargo. Almost all cell types release EVs, thus they are naturally present in all body fluids. Among the several potential applications, EVs could be used as drug delivery vehicles in disease treatment, in immune therapy because of their immunomodulatory properties and in regenerative medicine. In addition to general markers, EVs are characterized by the presence of specific biomarkers (proteins and miRNAs) that allow the identification of their cell or tissue origin. For these features, they represent a potential powerful diagnostic tool to monitor state and progression of specific diseases. A large body of studies supports the idea that endothelial derived (EMPs) together with platelet-derived microparticles (PMPs) are deeply involved in the pathogenesis of diseases characterized by micro- and macrovascular damages, including diabetes. Existing literature suggests that the detection of circulating EMPs and PMPs and their specific miRNA profile may represent a very useful non-invasive signature to achieve information on the onset of peculiar disease manifestations. In this review, we discuss the possible utility of EVs in the early diagnosis of diabetes-associated microvascular complications, specifically related to kidney.

HIV-1 envelope glycoprotein stimulates viral transcription and increases the infectivity of the progeny virus through the manipulation of cellular machinery

During HIV infection, large amounts of progeny viral particles, including infectious virus and a large proportion of defective viral particles, are produced. Despite of the critical role of the infectious viruses in infection and pathogenesis in vivo, whether and how those defective viral particles, especially the virus-associated envelope glycoprotein (vEnv), would impact viral infection remains elusive. In this study, we investigated the effect of vEnv on HIV-infected T cells and demonstrated that the vEnv was able to stimulate HIV transcription in HIV-infected cells, including peripheral blood mononuclear cells (PBMCs) isolated from HIV patients. This vEnv-mediated HIV transcription activation is mediated primarily through the interaction between vEnv and CD4/coreceptors (CCR5 or CXCR4). Through transcriptome analysis, we found that numerous cellular gene products involved in various signaling pathways were modulated by vEnv. Among them, we have further identified a cellular microRNA miR181A2, which is downregulated upon vEnv treatment, resulting in increased HIV LTR histone H3 acetylation and HIV transcription. Furthermore, we also found a vEnv-modulated cellular histone deacetylase, HDAC10, whose downregulation is associated with the increased infectivity of progeny viruses. Altogether, these findings provide evidence of the important role vEnv plays in modulating cellular environments and facilitating HIV expression and infection.

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.

Cell-derived microparticles and the lung

Cell-derived microparticles are small (0.1-1 μm) vesicles shed by most eukaryotic cells upon activation or during apoptosis. Microparticles carry on their surface, and enclose within their cytoplasm, molecules derived from the parental cell, including proteins, DNA, RNA, microRNA and phospholipids. Microparticles are now considered functional units that represent a disseminated storage pool of bioactive effectors and participate both in the maintenance of homeostasis and in the pathogenesis of diseases. The mechanisms involved in microparticle generation include intracellular calcium mobilisation, cytoskeleton rearrangement, kinase phosphorylation and activation of the nuclear factor-κB. The role of microparticles in blood coagulation and inflammation, including airway inflammation, is well established in in vitro and animal models. The role of microparticles in human pulmonary diseases, both as pathogenic determinants and biomarkers, is being actively investigated. Microparticles of endothelial origin, suggestive of apoptosis, have been demonstrated in the peripheral blood of patients with emphysema, lending support to the hypothesis that endothelial dysfunction and apoptosis are involved in the pathogenesis of the disease and represent a link with cardiovascular comorbidities. Microparticles also have potential roles in patients with asthma, diffuse parenchymal lung disease, thromboembolism, lung cancer and pulmonary arterial hypertension.

Dissimilarity of increased phosphatidylserine-positive microparticles and associated coagulation activation in acute coronary syndromes

OBJECTIVE

We evaluated cellular origin, numbers, and procoagulant activity of phosphatidylserine-positive microparticles (MPs) among subgroups in acute coronary syndromes (ACS).

MATERIALS AND METHODS

Parameters were measured on admission, days 1 (within 24 h of admission), 2, 3, and 7. All ST-elevated myocardial infarction (STEMI) patients presented more than 3 h from symptom onset and received fibrinolysis treatment; controls included unstable angina and non-STEMI patients as well as healthy controls. Phosphatidylserine-positive MPs were detected by flow cytometry, whereas procoagulant activity was assessed by coagulation time, purified coagulation complex assays, and fibrin formation. MP-induced fibrins were visualized by confocal microscopy.

RESULTS

On admission, the total MP count was ∼2.5-fold higher in the ACS groups compared with the healthy controls (P<0.05), primarily originating from platelets and endothelial cells, and there were no significant differences among ACS subgroups. Specifically, leukocyte-derived and erythrocyte-derived MPs were higher in the STEMI group compared with unstable angina and non-STEMI groups (both P<0.05). Further, MPs from the ACS groups reduced coagulation time by 27.5% and induced intrinsic and extrinsic FXase, prothrombinase, and fibrin formation by 2.8-, 2.3-, 2.5-, and 1.7-fold, respectively (P<0.05 for all), whereas blocking phosphatidylserine with lactadherin inhibited ∼70% of procoagulant activity. MP number and concomitant coagulation decreased significantly by day 2 and continued to decrease gradually during the recovery period.

CONCLUSION

This study shows that MP characteristics from circulating blood may be used as prognostic indicators to reflect the origin cell of activation and thrombophilic states found in ACS subgroups.

Update on functional and genetic laboratory assays for the detection of platelet microvesicles

Functional and genetic assays for measuring platelet microvesicles (PMVs) are presented and discussed. Functional assays concern two groups of methods: a) homogeneous assays using the cofactor activity of phospholipids (PPLs) contained in PMVs and present in assayed plasmas, and a coagulation or a thrombin generation assay (TGA) as "end points"; b) capture-based assays, in which PMVs bind to an immobilized ligand, such as Annexin V in the presence of calcium, or monoclonal antibodies (MoAbs) specific for membrane proteins. Genetic assays aim to detect micro-RNA (miRNA) present in PMVs: miRNA must be extracted from plasma, and the expression pattern can be determined by various methods such as quantitative real-time PCR, microarray or sequencing. All these technical approaches introduce new exploration tools for measuring or quantitating PMVs or their associated activities, as biomarkers for disease evolution, their diagnosis or prognosis, and for monitoring of some antithrombotic or anti-inflammatory therapies. They offer invaluable analytical tools for research, drug discovery and epidemiological studies and have a strong potential as diagnostic tests.

Glucose and angiotensin II-derived endothelial extracellular vesicles regulate endothelial dysfunction via ERK1/2 activation

In various diseases, including diabetes, extracellular vesicles (EVs) have been detected in circulation and tissues. EVs are small membrane vesicles released from various cell types under varying conditions. Recently, endothelial cell-derived EVs (EEVs) were identified as a marker of endothelial dysfunction in diabetes, but the ensuing mechanisms remain poorly understood. In this study, we dissected the ensuing pathways with respect to nitric oxide (NO) production under the condition of type 2 diabetes. Human umbilical vein endothelial cells (HUVECs) were stimulated with glucose alone and with glucose in combination with angiotensin II (Ang II) for 48 h. In supernatants from glucose + Ang II-stimulated HUVECs, release of EEVs was assessed using Western blotting with an anti-CD144 antibody. EEV release was significantly increased after stimulation of HUVECs, and high glucose + Ang II-derived EEVs impaired ACh-induced vascular relaxation responses and NO production in mice aortic rings. Furthermore, high glucose + Ang II-derived EEVs induced ERK1/2 signalling and decreased endothelial NO synthase (eNOS) protein expression in mice aortas. Furthermore, in the presence of the MEK/ERK1/2 inhibitor PD98059, high glucose plus Ang II treatment stimulated EEVs in HUVECs and those EEVs prevented the impairments of ACh-induced relaxation and NO production in mice aortas. These data strongly indicate that high glucose and Ang II directly affect endothelial cells and the production of EEVs; the resultant EEVs aggravate endothelial dysfunction by regulating eNOS protein levels and ERK1/2 signalling in mice aortas.

Measurement of extracellular vesicles as biomarkers of consequences or cause complications of pathological states, and prognosis of both evolution and therapeutic safety/efficacy

Utility of EVs, as biomarkers of cause or consequence of various pathological complications, and prognosis of blood components' therapy in terms of safety/efficacy and their potential associated hazards, primed by EVs involvements in pro-inflammatory, immunomodulatory and activations of both pro/anti-coagulatory and others associated pathways, as well as various cellular cross talks, are highlighted as the fundamental. Today EVs are becoming the "buzz" words of the current diagnosis, development and research [DDR] strategies, with the aim of ensuring safer therapeutic approaches in the current clinical practices, also incorporating their potential in long term cost effectiveness in health care systems. The main focus of this manuscript is to review the current opinions in some fundamental areas of EVs involvements in health and diseases. Firstly, our goal is highlighting what are EVs/MVs/MPs and how are they generated in physiology, pathology or blood products; classification and significance of EVs generated in vivo; followed by consequences and physiological/pathological induced effects of EVs generation in vivo. Secondly, specific cell origin EVs and association with malignancy; focus on EVs carrying TF and annexin V as a protective protein for harmful effects of EVs, and associations with LA; and incidence of anti-annexin V antibodies are also discussed. Thirdly, utility of EVs is presented: as diagnostic tools of disease markers; prognosis and follow-up of clinical states; evaluation of therapy efficacy; quality and risk assessment of blood products; followed by the laboratory tools for exploring, characterizing and measuring EVs, and/or their associated activity, using our own experiences of capture based assays. Finally, in perspective, the upcoming low volume sampling, fast, reliable and reproducibility and friendly use laboratory tools and the standardization of measurement methods are highlighted with the beneficial effects that we are witnessing in both wound healing and tissue remodeling, with an expected blockbuster status EVs as future therapeutic directions.

Getting to the Outer Leaflet: Physiology of Phosphatidylserine Exposure at the Plasma Membrane

Phosphatidylserine (PS) is a major component of membrane bilayers whose change in distribution between inner and outer leaflets is an important physiological signal. Normally, members of the type IV P-type ATPases spend metabolic energy to create an asymmetric distribution of phospholipids between the two leaflets, with PS confined to the cytoplasmic membrane leaflet. On occasion, membrane enzymes, known as scramblases, are activated to facilitate transbilayer migration of lipids, including PS. Recently, two proteins required for such randomization have been identified: TMEM16F, a scramblase regulated by elevated intracellular Ca(2+), and XKR8, a caspase-sensitive protein required for PS exposure in apoptotic cells. Once exposed at the cell surface, PS regulates biochemical reactions involved in blood coagulation, and bone mineralization, and also regulates a variety of cell-cell interactions. Exposed on the surface of apoptotic cells, PS controls their recognition and engulfment by other cells. This process is exploited by parasites to invade their host, and in specialized form is used to maintain photoreceptors in the eye and modify synaptic connections in the brain. This review discusses what is known about the mechanism of PS exposure at the surface of the plasma membrane of cells, how actors in the extracellular milieu sense surface exposed PS, and how this recognition is translated to downstream consequences of PS exposure.

β 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 β-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 β-cell function, TF activity mediated by MPs and their modulation by 1 μM liraglutide were examined in a cell cross-talk model. Methyl-β-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 β-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.

The diagnostic usefulness of capture assays for measuring global/specific extracellular micro-particles in plasma

Capture assays were developed and validated for measuring the global pro-coagulant activity of micro-particles (MPs, mainly originated from platelets), or specific extravascular cellular MPs (released from erythrocytes, leukocytes, monocytes, endothelial cells) as those exposing TF (MP-TF, mainly observed in patients with some cancers). Conversely to Flow Cytometry methods, these capture assays measure all coagulant activity associated with MPs, through thrombin generation (MP-Activity) or Factor Xa generation (MP-TF), and therefore they bring a complementary information, as they are more specific for the pro-coagulant activity associated with MPs. Small particles (<0.40 µ) exposing Phosphatidyl Serine (PS) exhibit a greater pro-coagulant surface than larger MPs (0.40 to >1.00 µ), those preferentially measured with flow cytometry. Activity associated with MPs is a consequence of disease but can also be a cause contributing to pathological processes and development of thrombo-embolic events. In many diseases, flow cytometry and capture assays do not totally correlate, and have different associations with disease evolution. Optimized capture based assays are presented and discussed, along with their performance characteristics and some applications. They can be performed in any technically skillful hemostasis laboratory, using a thermostated ELISA equipment, or an incubator. Dynamic ranges for MP-Activity assay is from <0.1 nM to >2.5 nM Phospholipids, expressed as Phosphatidyl Serine (PS) equivalent, in the tested dilution. For MP-TF the very sensitive bio-immunoassay reported allows measuring concentrations from <0.10 pg/ml (TF equivalent) to >5.00 pg/ml, in the assayed dilution. No measurable MP-TF was found in normals, although an important concentration was generated from whole blood treated with Lipo-Poly-Saccharides. Capture based assays are then highly useful in the laboratory setting for measuring the activities associated with pro-coagulant, or specific cellular MPs.

Understanding the biosynthesis of platelets-derived extracellular vesicles

Platelet-derived extracellular vesicles (PEVs) are described as sub-cellular vesicles released into circulation upon platelets shear stress, activation, injury, or apoptosis. They are considered as universal biomarkers in a wide range of physiological and pathological processes. They are of tremendous significance for the prediction, diagnosis, and observation of the therapeutic success of many diseases. Understanding their biosynthesis and therefore functional properties would contribute to a better understanding of the pathological mechanisms leading to various diseases in which their levels are raised and they are implicated. The review takes a critical look at the historical background of PEVs, their structural components, the mechanism of their formation, physiological, and exogenous stimuli inducing their release and their detection. It concludes by highlighting on the importance of undertaking in-depth studies into PEVs biosynthesis and subsequently gaining a better understanding of their biological role in general.

Microparticles provide a novel biomarker to predict severe clinical outcomes of dengue virus infection

Shedding of microparticles (MPs) is a consequence of apoptotic cell death and cellular activation. Low levels of circulating MPs in blood help maintain homeostasis, whereas increased MP generation is linked to many pathological conditions. Herein, we investigated the role of MPs in dengue virus (DENV) infection. Infection of various susceptible cells by DENV led to apoptotic death and MP release. These MPs harbored a viral envelope protein and a nonstructural protein 1 (NS1) on their surfaces. Ex vivo analysis of clinical specimens from patients with infections of different degrees of severity at multiple time points revealed that MPs generated from erythrocytes and platelets are two major MP populations in the circulation of DENV-infected patients. Elevated levels of red blood cell-derived MPs (RMPs) directly correlated with DENV disease severity, whereas a significant decrease in platelet-derived MPs was associated with a bleeding tendency. Removal by mononuclear cells of complement-opsonized NS1-anti-NS1 immune complexes bound to erythrocytes via complement receptor type 1 triggered MP shedding in vitro, a process that could explain the increased levels of RMPs in severe dengue. These findings point to the multiple roles of MPs in dengue pathogenesis. They offer a potential novel biomarker candidate capable of differentiating dengue fever from the more serious dengue hemorrhagic fever.

IMPORTANCE

Dengue is the most important mosquito-transmitted viral disease in the world. No vaccines or specific treatments are available. Rapid diagnosis and immediate treatment are the keys to achieve a positive outcome. Dengue virus (DENV) infection, like some other medical conditions, changes the level and composition of microparticles (MPs), tiny bag-like structures which are normally present at low levels in the blood of healthy individuals. This study investigated how MPs in culture and patients' blood are changed in response to DENV infection. Infection of cells led to programmed cell death and MP release. In patients' blood, the majority of MPs originated from red blood cells and platelets. Decreased platelet-derived MPs were associated with a bleeding tendency, while increased levels of red blood cell-derived MPs (RMPs) correlated with more severe disease. Importantly, the level of RMPs during the early acute phase could serve as a biomarker to identify patients with potentially severe disease who require immediate care.

Levels of procoagulant microvesicles are elevated after traumatic injury and platelet microvesicles are negatively correlated with mortality

BACKGROUND

Microvesicles (MV) have been implicated in the development of thrombotic disease, such as acute respiratory distress syndrome (ARDS) and multiple organ failure (MOF). Trauma patients are at increased risk of late thrombotic events, particularly those who receive a major transfusion. The aims of this study were: (a) to determine whether there were increased numbers of pro-coagulant MV following injury; (b) to determine their cellular origin; and (c) to explore the effects of MV with clinical outcomes; in particular red cell transfusion requirements and death.

METHODS

Trauma patients were recruited at a Level 1 trauma centre. The presence of MV procoagulant phospholipid (PPL) was assessed using 2 activity assays (PPL and thrombin generation). Enumeration and MV cellular origin was assessed using 2 colour flow cytometry.

RESULTS

Fifty consecutive patients were recruited; median age 38 (IQR: 24-55), median ISS 18 (IQR: 9-27). Circulating procoagulant MV, rich in phospholipid, were significantly elevated following traumatic injury relative to controls and remained elevated at 72 h post-injury. Red cell/AnnV+ and platelet/AnnV+ MV numbers were 6-fold and 2-fold higher than controls, respectively. Patients who died (n=9, 18%) had significantly fewer CD41/AnnV+ MV and lower endogenous thrombin potential relative to patients who survived.

CONCLUSIONS

MV are elevated following traumatic injury and may be implicated in the increased risk of trauma patients to pro-thrombotic states such as MOF and ARDS. Lower levels of procoagulant MV are associated with mortality and further investigation of this association is warranted.

Studies of circulating microparticle release in peripheral blood after pancreatic islet transplantation

The loss of graft function after intraportal islet transplantation is likely multifactorial involving allogeneic rejection, recurrent autoimmunity, graft exhaustion due to a marginally implanted islet mass, immunosuppressant toxicity, and impaired β-cell regeneration. Because early markers of the loss of β-cell mass or function are lacking, monitoring of islet function remains a challenging issue. We have reported herein monitoring of membrane procoagulant microparticles (MPs) as markers of cell stress in the plasma of three recipients with various clinical histories. Early kinetics of C-peptide and MPs followed identical patterns during the first weeks after transplantation; a major increase probably reflected processes related to cell infusion and islet engraftment. Importantly in the case of rejection, MPs and C-peptide showed opposite patterns. A fall in C-peptide was associated with enhanced insulin needs. Our results suggested that a peak in MP levels might indicate rejection with prognotic value. Treatment of the loss of islet function by a new islet infusion or steroid therapy returned MP and C-peptide levels to their baselines with concomitant restoration of islet function. In the patient with suspected acute cellular rejection, MPs also appeared to be sensors of immunosuppressive steroid therapy.

Rapid shedding of proinflammatory microparticles by human mononuclear cells exposed to cigarette smoke is dependent on Ca2+ mobilization

OBJECTIVES

Microparticles are membrane vesicles shed by cells upon activation and apoptosis. Agonists capable of inducing microparticle generation include cytokines, bacterial products, P-selectin, histamine. Cigarette smoke extract has also been recognized as an agonist involved in microparticle generation with an apoptosis-dependent mechanism. We investigated the possibility that cigarette smoke extract induces the rapid generation of proinflammatory microparticles by human mononuclear cells with a calcium-dependent mechanism.

MATERIALS AND METHODS

Human mononuclear cells were exposed to cigarette smoke extract. [Ca(2+)]i mobilization was assessed with the fluorescent probe Fluo-4 NW. Microparticles were quantified with a prothrombinase assay and by flow cytometry. Normal human bronchial epithelial cells and A549 alveolar cells were incubated with cigarette smoke extract-induced microparticles and the generation of ICAM-1, IL-8, and MCP-1 was assessed by ELISA.

RESULTS

Exposure to cigarette smoke extract induced a rapid increase in [Ca(2+)]i mobilization. Microparticle generation was also increased. EGTA, verapamil and the calmodulin inhibitor, W-7, inhibited microparticle generation. Incubation of lung epithelial cells with cigarette smoke extract-induced microparticles increased the expression of proinflammatory mediators.

CONCLUSIONS

Exposure of mononuclear cells to cigarette smoke extract causes a rapid shedding of microparticles with a proinflammatory potential that might add to the mechanisms of disease from tobacco use.

Role of exosomes in myocardial remodeling

Exosomes are nanovesicles released from cells through exocytosis and are known to be mediators of proximal as well as distant cell-to-cell signaling. They are surrounded by a classical bilayered membrane with an exceptionally high cholesterol/phospholipid ratio. Exosomes were first described in 1977, then named prostasomes, and in 1987 the name exosome was coined. Exosomes contain surface proteins, some of which can act as labels in order to find their target cells. Exosomes also contain messages in the form of proteins and nucleic acids (RNA and DNA) that are transferable to target cells. Little is known and written about cardiac exosomes, although Gupta and Knowlton described exosomes containing HSP60 in 2007. It is now known that exosomes from cardiomyocytes can transfect other cells and that the metabolic milieu of the parental cell decides the quality of exosomes released such that they induce differential gene expression in transfected cells. Future clinical use of exosomes in diagnosis, monitoring disease progress, and treatment is promising.

Microparticle-associated tissue factor activity in patients with metastatic pancreatic cancer and its effect on fibrin clot formation

Highly elevated microparticle (MP)-associated tissue factor (TF) activity was found in patients with pancreatic cancer, one of the most prothrombotic malignancies. It remains to be elucidated whether MP-TF activity reflects the prothrombotic state in these patients. MP-TF activity levels and the TF-dependent and -independent effect of MPs on fibrin clot formation were determined in patients with metastatic pancreatic cancer (n = 27), in healthy individuals (n = 10) and in plasma samples from lipopolysaccharide (LPS)-stimulated blood (LPS-plasma), which is rich in monocyte-derived TF-bearing MPs. The median MP-TF activity was 1.06 pg/mL (range, from 0.19 to 10.34 pg/mL) in patients with pancreatic cancer, 0.61 pg/mL (range, from 0.36 to 0.79 pg/mL) in LPS-plasma, and 0.18 pg/mL (range, from 0.04 to 0.39 pg/mL) in healthy individuals. MPs derived from LPS-plasma had the strongest impact on fibrin clot formation time (median, 157.6 seconds; range, from 149.5 to 170.4 seconds). Fibrin clot formation occurred significantly later in MPs derived from patients with pancreatic cancer (median, 273.4 seconds; range, from 146.6 to 354.4 seconds; P < 0.001) and in healthy individuals (median, 299.0 seconds; range, from 261.1 to 417.9 seconds; P < 0.001). Only in MPs derived from LPS-plasma the fibrin clot formation time dependent strongly on TF (median prolongation after TF blockade: 68% in LPS-plasma, 10% in patients with pancreatic cancer, and 4% in healthy individuals). In conclusion, highly elevated MP-TF activity was found in patients with metastatic pancreatic cancer, but TF-bearing MPs had a small effect on fibrin clot formation. TF-bearing MPs might not be the main mediators of the prothrombotic state associated with pancreatic cancer. However, the small but significant increase in coagulation potential by TF-bearing MPs might contribute to the multifactorial pathogenesis of venous thromboembolism in pancreatic cancer.

Using annexin V-coated magnetic beads to capture active tissue factor-bearing microparticles from body fluids

Microparticles, found in all body fluids including peripheral blood, are important elements that regulate cellular interactions under both physiological and pathological conditions. They play an important role in blood clot formation and increased cell aggregation. However, little is known about the components of the microparticles and their mechanism of action. A method to quantify and assess the underlying mechanism of action of microparticles in pathologies is therefore desirable. We present a specific method to isolate cell-derived microparticles from malignant effusions using annexin V-coated magnetic microbeads. The microparticles can be detected by flow cytometry. Our results show that the microparticles can be isolated with >80% specificity when bound to annexin V-coated magnetic beads, which was originally developed for the detection of apoptotic cells. We also show that the isolated microparticles were still functionally active and can be used for further analysis. Thus, our method enables isolation as well as structural and functional characterisation of the microparticles which are produced in numerous patho-physiological situations. This should help gain a deeper insight into various disease situations, which in turn should pave the way for the development of novel drugs and specific therapy strategies.

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.

Blood/plasma secretome and microvesicles

A major but hitherto overseen component of the blood/plasma secretome is that of extracellular vesicles (EVs) which are shed from all blood cell types. These EVs are made up of microvesicles (MVs) and exosomes. MVs, 100nm-1μm in diameter, are released from the cell surface, and are a rich source of non-conventionally secreted proteins lacking a conventional signal peptide, and thus not secreted by the classical secretory pathways. Exosomes are smaller vesicles (≤100nm) having an endocytic origin and released upon multivesicular body fusion with the plasma membrane. Both vesicle types play major roles in intercellular cross talk and constitute an important component of the secretome especially in the area of biomarkers for cancer. The release of EVs, which are found in all the bodily fluids, is enhanced in cancer and a major focus of cancer proteomics is therefore targeted at EVs. The blood/plasma secretome is also a source of EVs, potentially diagnostic of infectious disease, whether from EVs released from infected cells or from the pathogens themselves. Despite the great excitement in this field, as is stated here and in other parts of this Special issue entitled: An Updated Secretome, much of the EV research, whether proteomic or functional in nature, urgently needs standardisation both in terms of nomenclature and isolation protocols. This article is part of a Special Issue entitled: An Updated Secretome.