Differential roles of tissue factor and phosphatidylserine in activation of coagulation

Platelet lipidomics and de novo lipogenesis: impact on health and disease

PURPOSE OF REVIEW

Lipids play vital roles in platelet structure, signaling, and metabolism. In addition to capturing exogenous lipids, platelets possess the capacity for de novo lipogenesis, regulated by acetyl-coA carboxylase 1 (ACC1). This review aims to cover the critical roles of platelet de novo lipogenesis and lipidome in platelet production, function, and diseases.

RECENT FINDINGS

Upon platelet activation, approximately 20% of the platelet lipidome undergoes significant modifications, primarily affecting arachidonic acid-containing species. Multiple studies emphasize the impact of de novo lipogenesis, with ACC1 as key player, on platelet functions. Mouse models suggest the importance of the AMPK-ACC1 axis in regulating platelet membrane arachidonic acid content, associated with TXA 2 secretion, and thrombus formation. In human platelets, ACC1 inhibition leads to reduced platelet reactivity. Remodeling of the platelet lipidome, alongside with de novo lipogenesis, is also crucial for platelet biogenesis. Disruptions in the platelet lipidome are observed in various pathological conditions, including cardiovascular and inflammatory diseases, with associations between these alterations and shifts in platelet reactivity highlighted.

SUMMARY

The platelet lipidome, partially regulated by ACC-driven de novo lipogenesis, is indispensable for platelet production and function. It is implicated in various pathological conditions involving platelets.

Serum Metabolomics Uncovers the Mechanisms of Inulin in Preventing Non-Alcoholic Fatty Liver Disease

Inulin may be a promising therapeutic molecule for treating non-alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms of its therapeutic activity remain unclear. To address this issue, a high-fat-diet-induced NAFLD mouse model was developed and treated with inulin. The NAFLD phenotype was evaluated via histopathological analysis and biochemical parameters, including serum levels of alanine aminotransferase, aspartate aminotransferase, liver triglycerides, etc. A serum metabolomics study was conducted using ultra-performance liquid chromatography coupled with tandem mass spectrometry. The results revealed that inulin mitigated NAFLD symptoms such as histopathological changes and liver cholesterol levels. Through the serum metabolomics study, 347 differential metabolites were identified between the model and control groups, and 139 differential metabolites were identified between the inulin and model groups. Additionally, 48 differential metabolites (such as phosphatidylserine, dihomo-γ-linolenic acid, L-carnitine, and 13-HODE) were identified as candidate targets of inulin and subjected to pathway enrichment analysis. The results revealed that these 48 differential metabolites were enriched in several metabolic pathways such as fatty acid biosynthesis and cardiolipin biosynthesis. Taken together, our results suggest that inulin might attenuate NAFLD partially by modulating 48 differential metabolites and their correlated metabolic pathways, constituting information that might help us find novel therapies for NAFLD.

Whole blood storage duration alters fibrinogen levels and thrombin formation

INTRODUCTION

Whole blood resuscitation for hemorrhagic shock in trauma represents an opportunity to correct coagulopathy in trauma while also supplying red blood cells. The production of microvesicles in stored whole blood and their effect on its hemostatic parameters have not been described in previous literature. We hypothesized that microvesicles in aged stored whole blood are procoagulant and increase thrombin production via phosphatidylserine.

METHODS

Whole blood was obtained from male C57BL/6 male mice and stored in anticoagulant solution for up to 10 days. At intervals, stored whole blood underwent examination with rotational thromboelastography, and platelet-poor plasma was prepared for analysis of thrombin generation. Microvesicles were prepared from 10-day-old whole blood aliquots and added to fresh whole blood or platelet-poor plasma to assess changes in coagulation and thrombin generation. Microvesicles were treated with recombinant mouse lactadherin prior to addition to plasma to inhibit phosphatidylserine's role in thrombin generation.

RESULTS

Aged murine whole blood had decreased fibrin clot formation compared with fresh samples with decreased plasma fibrinogen levels. Thrombin generation in plasma from aged blood increased over time of storage. The addition of microvesicles to fresh plasma resulted in increased thrombin generation compared with controls. When phosphatidylserine on microvesicles was blocked with lactadherin, there was no difference in the endogenous thrombin potential, but the generation of thrombin was blunted with lower peak thrombin levels.

CONCLUSION

Cold storage of murine whole blood results in decreased fibrinogen levels and fibrin clot formation. Aged whole blood demonstrates increased thrombin generation, and this is due in part to microvesicle production in stored whole blood. One mechanism by which microvesicles are procoagulant is by phosphatidylserine expression on their membranes.

Design of Apoptotic Cell-Inspired Particles as a Blood Coagulation Test

The blood coagulation test is an indispensable test for monitoring the blood coagulation and fibrinolysis functions. Currently, activated partial thromboplastin time (APTT) is the most widely used approach to coagulation testing. However, APTT reagents need to be optimized due to the fact that they are unstable, highly variable, and cannot be easily controlled. In this study, we created apoptotic cell-inspired methacryloyloxyethyl phosphorylserine (MPS) particles for blood coagulation as an alternative to conventional APTT reagents. Particle size could be controlled by changing the concentration of the polymer. The blood coagulation ability of particles was stable at different environmental temperatures. Moreover, the procoagulant activity could be enhanced by increasing the concentration to 0.06 mg/mL and reducing the size of the particles to around 900 nm. Fibrin clotted by particles showed no significant difference from that formed by APTT regent Actin FSL. We propose that MPS particles are a potential alternative to Actin FS for the application of blood coagulation tests.

Apoptotic cells promote circulating tumor cell survival and metastasis

During tumor progression and especially following cytotoxic therapy, cell death of both tumor and stromal cells is widespread. Despite clinical observations that high levels of apoptotic cells correlate with poorer patient outcomes, the physiological effects of dying cells on tumor progression remain incompletely understood. Here, we report that circulating apoptotic cells robustly enhance tumor cell metastasis to the lungs. Using intravenous metastasis models, we observed that the presence of apoptotic cells, but not cells dying by other mechanisms, supports circulating tumor cell (CTC) survival following arrest in the lung vasculature. Apoptotic cells promote CTC survival by recruiting platelets to the forming metastatic niche. Apoptotic cells externalize the phospholipid phosphatidylserine to the outer leaflet of the plasma membrane, which we found increased the activity of the coagulation initiator Tissue Factor, thereby triggering the formation of platelet clots that protect proximal CTCs. Inhibiting the ability of apoptotic cells to induce coagulation by knocking out Tissue Factor, blocking phosphatidylserine, or administering the anticoagulant heparin abrogated the pro-metastatic effect of apoptotic cells. This work demonstrates a previously unappreciated role for apoptotic cells in facilitating metastasis by establishing CTC-supportive emboli, and suggests points of intervention that may reduce the pro-metastatic effect of apoptotic cells.

GRAPHICAL ABSTRACT

Extracellular vesicles in plasma and cerebrospinal fluid in patients with COVID-19 and neurological symptoms

INTRODUCTION

Increased levels of extracellular vesicles (EVs) are associated with haemostatic disturbances in various clinical settings. However, their role in COVID-19 patients is still not fully clear. In the present study we investigated EVs in plasma from patients with COVID-19 and neurological symptoms in relation to the activation of coagulation.

METHODS

Nineteen COVID-19 patients with neurological symptoms and twenty-three aged-matched healthy individuals were included. Global coagulation assays were performed and levels of EVs were determined by flow-cytometry in plasma and cerebrospinal fluid (CSF).

RESULTS

A procoagulant state characterized by significantly increased overall coagulation- (OCP) and overall haemostatic potential (OHP), diminished overall fibrinolytic potential (OFP) together with a denser fibrin structure was found in patients with COVID-19. Flow cytometry revealed elevated levels of plasma circulating EVs derived from neutrophils (MPO+) and platelets (CD61+), as well as EVs expressing phosphatidylserine (PS+) and complement component C5b-9 (TCC+) in patients with COVID-19 compared with controls. The concentrations of PS+, CD61+ and TCC+ EVs were positively correlated with OCP and OHP in COVID-19 patients. Moreover, we identified CD61+, MPO+ and endothelial cell-derived EVs, as well as EVs exposing PS and TCC in the CSF of patients suffering from neurological symptoms during COVID-19.

CONCLUSION

The unique finding in this study was the presence of EVs in the CSF of COVID-19 patients with neurologic manifestations as well as higher expression of complement protein on circulating plasma EVs. EVs may indicate blood-brain barrier damage during SARS-COV-2 infection.

Serum Reactive Antibodies against the N-Methyl-D-Aspartate Receptor NR2 Subunit-Could They Act as Potential Biomarkers?

Synaptic dysfunction and disrupted communication between neuronal and glial cells play an essential role in the underlying mechanisms of multiple sclerosis (MS). Earlier studies have revealed the importance of glutamate receptors, particularly the N-methyl-D-aspartate (NMDA) receptor, in excitotoxicity, leading to abnormal synaptic transmission and damage of neurons. Our study aimed to determine whether antibodies to the NR2 subunit of NMDAR are detected in MS patients and evaluate the correlation between antibody presence and clinical outcome. Furthermore, our focus extended to examine a possible link between NR2 reactivity and anti-coagulant antibody levels as pro-inflammatory molecules associated with MS. A cross-sectional study was carried out, including 95 patients with MS and 61 age- and gender-matched healthy controls (HCs). The enzyme-linked immunosorbent assay was used to detect anti-NR2 antibodies in serum samples of participants along with IgG antibodies against factor (F)VIIa, thrombin, prothrombin, FXa, and plasmin. According to our results, significantly elevated levels of anti-NR2 antibodies were detected in MS patients compared to HCs (p < 0.05), and this holds true when we compared the Relapsing-Remitting MS course with HCs (p < 0.05). A monotonically increasing correlation was found between NR2 seropositivity and advanced disability (rs = 0.30; p < 0.01), anti-NR2 antibodies and disease worsening (rs = 0.24; p < 0.05), as well as between antibody activity against NR2 and thrombin (rs = 0.33; p < 0.01). The presence of anti-NR2 antibodies in MS patients was less associated with anti-plasmin IgG antibodies [OR:0.96 (95%CI: 0.92-0.99); p < 0.05]; however, such an association was not demonstrated when analyzing only RRMS patients. In view of our findings, NR2-reactive antibodies may play, paving the way for further research into their potential as biomarkers and therapeutic targets in MS.

Lyophilized apoptotic vesicle-encapsulated adhesive hydrogel sponge as a rapid hemostat for traumatic hemorrhage in coagulopathy

Rapid hemostasis of uncontrolled bleeding following traumatic injuries, especially accompanied by coagulopathies, remains a significant clinical challenge. Extracellular vesicles (EVs) show therapeutic effects for fast clotting. However, low yield, specific storage conditions, and lack of proper carriers have hindered EVs' clinical application. Herein, we establish an optimized procedure method to generate lyophilized mesenchymal stem cell-derived apoptotic vesicles (apoVs) with adhesive hydrogel sponge to show superior procoagulant activity for traumatic hemorrhage. Mechanistically, apoVs' procoagulant ability stems from their high tissue factor (TF) and phosphatidylserine (PS) expression independent of hemocytes and circulating procoagulant microparticles (cMPs). Their stable hemostatic capability was maintained after 2-month room temperature storage. Subsequently, we mixed apoVs with both phenylboronic acid grafted oxidized hyaluronic acid (PBA-HA) and poly(vinyl alcohol) (PVA) simultaneously, followed by lyophilization to construct a novel apoV-encapsulated hydrogel sponge (apoV-HS). Compared to commercial hemostats, apoV-HS exhibits rapid procoagulant ability in liver-laceration and femoral artery hemorrhage in rat and rabbit models of coagulopathies. The combination of high productivity, physiological stability, injectability, plasticity, excellent adhesivity, biocompatibility, and rapid coagulant property indicates that apoV-HS is a promising therapeutic approach for heavy hemorrhage in civilian and military populations.

The roles of P-selectin in cancer cachexia

P-selectin, a cell adhesion molecule of the selectin family, is expressed on the surface of activated endothelial cells (ECs) and platelets. Binding of P-selectin to P-selectin glycoprotein ligand-1 (PSGL-1) supports the leukocytes capture and rolling on stimulated ECs and increases the aggregation of leukocytes and activated platelets. Cancer cachexia is a systemic inflammation disorder characterized by metabolic disturbances, reduced body weight, loss of appetite, fat depletion, and progressive muscle atrophy. Cachexia status is associated with increased pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), which activates ECs to release P-selectin. Single-nucleotide polymorphisms (SNPs) loci of P-selectin encoding gene SELP are associated with higher level of plasma P-selectin and increase the susceptibility to cachexia in cancer patients. Elevated P-selectin expression has been observed in the hypothalamus, liver, and gastrocnemius muscle in animal models with cancer cachexia. Increased P-selectin may cause excessive inflammatory processes, muscle atrophy, and blood hypercoagulation, thus facilitating the development of cancer cachexia. In this review, physiological functions of P-selectin and its potential roles in cancer cachexia have been summarized. We also discuss the therapeutic potential of P-selectin inhibitors for the treatment of cancer cachexia.

Phosphatidylserine in Diabetes Research

Phospholipids are lipids that constitute the basic structure of cell membranes. In-depth research has shown that in addition to supporting cell structures, phospholipids participate in multiple cellular processes, including promoting cell signal transduction, guiding protein translocation, activating enzymatic activity, and eliminating dysfunctional/redundant organelles/cells. Diabetes is a chronic metabolic disease with a complicated etiology and pathology. Studies have shown that the level of certain phospholipids, for example, the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) in liver tissue, is negatively associated with insulin sensitivity. In addition, PS is a phospholipid exhibiting extensive cellular functions in diabetes. For this review, we analyzed many PS studies focusing on diabetes and insulin sensitivity in recent years and found that PS participates in controlling insulin secretion, regulating insulin signaling transduction, and participating in the progression of diabetic complications by mediating coagulation disorders in the microvasculature or targeting mitochondria. Moreover, PS supplements in food and PS-containing liposomes have been shown to protect against type 1 and type 2 diabetes (T1D and T2D, respectively) in animal studies. Therefore, by summarizing the regulatory roles played by PS in diabetes and the potential of successfully using PS or PS-containing liposomes for diabetic therapy, we hope to provide new ideas for further research into the mechanisms of diabetes and for drug development for treating diabetes and its complications.

Role of Mesenchymal Stem/Stromal Cells in Coagulation

Mesenchymal stem/stromal cells (MSCs) are widely used in disease models in order to control several phases in the response to injuries, immune reaction, wound healing, and regeneration. MSCs can act upon both the innate and adaptive immune systems and target a broad number of functions, such as the secretion of cytokines, proteolytic enzymes, angiogenic factors, and the regulating of cell proliferation and survival. The role of MSCs in coagulation has been less studied. This review evaluates the properties and main functions of MSCs in coagulation. MSCs can regulate coagulation in a wide range of pathways. MSCs express and release tissue factors (TF), one of the key regulators of the extrinsic coagulation pathways; MSCs can trigger platelet production and contribute to platelet activation. Altogether, MSCs seem to have a pro-thrombotic role and their superior characterization prior to their administration is necessary in order to prevent adverse coagulation events.

Identification of a broad lipid repertoire associated to the endothelial cell protein C receptor (EPCR)

Evidence is mounting that the nature of the lipid bound to the endothelial cell protein C receptor (EPCR) has an impact on its biological roles, as observed in anticoagulation and more recently, in autoimmune disease. Phosphatidylethanolamine and phosphatidylcholine species dominate the EPCR lipid cargo, yet, the extent of diversity in the EPCR-associated lipid repertoire is still unknown and remains to be uncovered. We undertook mass spectrometry analyses to decipher the EPCR lipidome, and identified species not yet described as EPCR ligands, such as phosphatidylinositols and phosphatidylserines. Remarkably, we found further, more structurally divergent lipids classes, represented by ceramides and sphingomyelins, both in less abundant quantities. In support of our mass spectrometry results and previous studies, high-resolution crystal structures of EPCR in three different space groups point to a prevalent diacyl phospholipid moiety in EPCR’s pocket but a mobile and ambiguous lipid polar head group. In sum, these studies indicate that EPCR can associate with varied lipid classes, which might impact its properties in anticoagulation and the onset of autoimmune disease.

Neurovascular Unit-Derived Extracellular Vesicles: From Their Physiopathological Roles to Their Clinical Applications in Acute Brain Injuries

Extracellular vesicles (EVs) form a heterogeneous group of membrane-enclosed structures secreted by all cell types. EVs export encapsulated materials composed of proteins, lipids, and nucleic acids, making them a key mediator in cell–cell communication. In the context of the neurovascular unit (NVU), a tightly interacting multicellular brain complex, EVs play a role in intercellular communication and in maintaining NVU functionality. In addition, NVU-derived EVs can also impact peripheral tissues by crossing the blood–brain barrier (BBB) to reach the blood stream. As such, EVs have been shown to be involved in the physiopathology of numerous neurological diseases. The presence of NVU-released EVs in the systemic circulation offers an opportunity to discover new diagnostic and prognostic markers for those diseases. This review outlines the most recent studies reporting the role of NVU-derived EVs in physiological and pathological mechanisms of the NVU, focusing on neuroinflammation and neurodegenerative diseases. Then, the clinical application of EVs-containing molecules as biomarkers in acute brain injuries, such as stroke and traumatic brain injuries (TBI), is discussed.

Structural model of tissue factor (TF) and TF-factor VIIa complex in a lipid membrane: A combined experimental and computational study

Tissue factor (TF) is a membrane protein involved in blood coagulation. TF initiates a cascade of proteolytic reactions, ultimately leading to the formation of a blood clot. The first reaction consists of the binding of the coagulation factor VII and its conversion to the activated form, FVIIa. Here, we combined experimental, i.e. quartz crystal microbalance with dissipation monitoring and neutron reflectometry, and computational, i.e. molecular dynamics (MD) simulation, methods to derive a complete structural model of TF and TF/FVIIa complex in a lipid bilayer. This model shows that the TF transmembrane domain (TMD), and the flexible linker connecting the TMD to the extracellular domain (ECD), define the location of the ECD on the membrane surface. The average orientation of the ECD relative to the bilayer surface is slightly tilted towards the lipid headgroups, a conformation that we suggest is promoted by phosphatidylserine lipids, and favours the binding of FVIIa. On the other hand, the formation of the TF/FVIIa complex induces minor changes in the TF structure, and reduces the conformational freedom of both TF and FVIIA. Altogether we describe the protein-protein and protein-lipid interactions favouring blood coagulation, but also instrumental to the development of new drugs.

pH-Responsive Liposomes Loaded with Targeting Procoagulant Proteins as Potential Embolic Agents for Solid Tumor-Targeted Therapy

Selectively inducing tumor thrombosis and subsequent necrosis is a novel and promising antitumor strategy. We have previously designed a targeting procoagulant protein, called tTF-EG3287, which is a fusion of a truncated tissue factor (tTF) with EG3287, a short peptide against the neuropilin-1 (NRP1) binding site of vascular endothelial growth factor-A 165 (VEGF-A 165). However, off-target effects and high-dose requirements limit the further use of tTF-EG3287 in antitumor therapy. Therefore, we encapsulated tTF-EG3287 into poly(2-ethyl-2-oxazoline)-distearoyl phosphatidyl ethanolamine (PEOz-DSPE)-modified liposomes to construct pH-responsive liposomes as a novel vascular embolization agent, called tTF-EG3287@Liposomes. The liposomes had an average particle size of about 100 nm and showed considerable drug-loading capacity, encapsulation efficiency, and biocompatibility. Under the stimulation of acidic microenvironments (pH 6.5), the lipid membrane of tTF-EG3287@Liposomes collapsed, and the cumulative drug release rate within 72 h was 83 ± 1.26%. When administered to a mouse model of hepatocellular carcinoma (HCC), tTF-EG3287@Liposomes showed prolonged retention and enhanced accumulation in the tumor as well as a superior antitumor effec, compared with tTF-EG3287. This study demonstrates the potential of tTF-EG3287@Liposomes as a novel embolic agent for solid tumors and provides a new strategy for tumor-targeted infarction therapy.

Extracellular Vesicles Derived from 3T3-L1 Adipocytes Enhance Procoagulant Activity

Obesity is associated with the risk of venous thromboembolism. Thrombi are constantly formed via the coagulation cascade and degraded by the fibrinolytic system, so they tend to form in obese individuals. Adipocytes are involved in thrombus formation in obesity, but it is not clear whether bioactive factors from adipocytes directly initiate or enhance coagulation and thrombosis. In this study, we confirmed that adipocyte-derived extracellular vesicles (ADEVs) enhance procoagulant activity in vitro. ADEVs prepared from the culture supernatant of mature 3T3-L1 adipocytes shortened plasma clotting times. Moreover, the effect of ADEVs on clotting time was weakened when using plasma lacking factors of the extrinsic pathway, but not the intrinsic pathway. ADEVs contain tissue factors and phosphatidylserine, which are involved in the extrinsic pathway, and blockade of these molecules diminished the effects of ADEVs on plasma clotting time. Additionally, the effect of ADEVs on plasma clotting time was further enhanced when cells were stimulated with the proinflammatory cytokine tumor necrosis factor-α. Thus, ADEVs may be a factor in thrombus formation in obesity.

Phosphatidylserine Exposing Extracellular Vesicles in Pre-eclamptic Patients

Background: Pre-eclampsia (P-EC) is associated with systemic inflammation, endothelial dysfunction and hypercoagulability. The role of extracellular vesicles (EVs) in coagulation disturbances affecting the development and severity of P-EC remains elusive. We aimed to evaluate the concentration of EVs expressing phosphatidylserine (PS) and specific markers in relation to the thrombin and fibrin formation as well as fibrin clot properties, in pregnant women with P-EC in comparison to healthy pregnant women of similar gestational age.

Methods: Blood samples of 30 pregnant women diagnosed with P-EC were collected on the morning following admission to hospital and after delivery (mean duration 5 days). The concentration of the PS-exposing EVs (PS+ EVs) from platelets (CD42a⁺, endothelial cells (CD62E⁺), and PS+ EVs expressing tissue factor (TF) and vascular cell adhesion molecule 1 (VCAM-1) were measured by flow cytometry. Further phenotyping of EVs also included expression of PlGF. Markers of maternal haemostasis were correlated with EVs concentration in plasma.

Results: Preeclamptic pregnancy was associated with significantly higher plasma levels of PS+ CD42a⁺ EVs and PS+ VCAM-1⁺ EVs in comparison with normotensive pregnancy. P-EC patients after delivery had markedly elevated concentration of PS+ CD42a⁺ EVs, CD62E⁺ EVs, TF⁺ EVs, and VCAM-1⁺ EVs compared to those before delivery. Inverse correlation was observed between EVs concentrations (PS+, PS+ TF⁺, and PlGF⁺) and parameters of overall haemostatic potential (OHP) and fibrin formation, while PS+ VCAM-1⁺ EVs directly correlated with FVIII activity in plasma.

Conclusion: Increased levels of PS+ EVs subpopulations in P-EC and their association with global haemostatic parameters, as well as with fibrin clot properties may suggest EVs involvement in intravascular fibrin deposition leading to subsequent microcirculation disorders.

Mesenchymal stromal cell delivery via an ex vivo bioreactor preclinical test system attenuates clot formation for intravascular application

While mesenchymal stromal cells are an appealing therapeutic option for a range of clinical applications, their potential to induce clotting when used systemically remains a safety concern, particularly in hypercoagulable conditions, such as in patients with severe COVID‐19, trauma, or cancers. Here, we tested a novel preclinical approach aimed at improving the safety of mesenchymal stromal cell (MSC) systemic administration by use of a bioreactor. In this system, MSCs are seeded on the exterior of a hollow‐fiber filter, sequestering them behind a hemocompatible semipermeable membrane with defined pore‐size and permeability to allow for a molecularly defined cross talk between the therapeutic cells and the whole blood environment, including blood cells and signaling molecules. The potential for these bioreactor MSCs to induce clots in coagulable plasma was compared against directly injected “free” MSCs, a model of systemic administration. Our results showed that restricting MSCs exposure to plasma via a bioreactor extends the time necessary for clot formation to occur when compared with “free” MSCs. Measurement of cell surface data indicates the presence of known clot inducing factors, namely tissue factor and phosphatidylserine. Results also showed that recovering cells and flushing the bioreactor prior to use further prolonged clot formation time. Furthermore, application of this technology in two in vivo models did not require additional heparin in fully anticoagulated experimental animals to maintain target activated clotting time levels relative to heparin anticoagulated controls. Taken together the clinical use of bioreactor housed MSCs could offer a novel method to control systemic MSC exposure and prolong clot formation time.

Biological mechanisms and therapeutic relevance of the gasdermin family

Innate immunity enables host defense against pathogens and endogenous danger through inflammasomes, which are supramolecular complexes that recognize the threats and activate the immune response. Inflammasome activation often leads to pyroptosis, a highly inflammatory and lytic form of cell death, as a means of killing infected cells and releasing IL-1 family cytokines that communicate with other cells. Dysregulated inflammasome signaling results in a wide range of immune disorders including gout, sepsis, and hepatitis. Discovered as a direct killer molecule in pyroptosis, gasdermin D (GSDMD) is a pore-forming protein that represents a novel family with diverse cellular functions and pathological roles. This review summarizes current opinions in the biological mechanisms and therapeutic values of the GSDM family, particularly of GSDMD. Detailed mechanisms of auto-inhibition and pore formation by the GSDM family are presented, followed by a brief summary of the progress in the development of GSDM-targeting therapeutics.

Inhibition of triggering receptor expressed on myeloid cells-1 impairs thrombin generation

BACKGROUND

New evidence has shown the link between inflammation and thrombosis. Triggering receptor expressed on myeloid cells-1 (TREM-1) is an immunoreceptor expressed mostly on neutrophils and monocytes/macrophages. TREM-1 acts as an amplifier of the inflammatory response, and its pharmacological inhibition displays protective effects in various models of inflammatory disorders, in particular by dampening coagulation abnormalities and thrombocytopenia observed during acute inflammation.

OBJECTIVES

We aimed to decipher the role of TREM-1 in fostering thrombin generation.

METHODS

We measured thrombin generation (TG) by the use of calibrated automated thrombography with whole blood, and isolated primary human neutrophils and monocytes upon stimulation with lipopolysaccharide (LPS). Tissue factor (TF) expression was measured by flow cytometry and its activity by ELISA. Phosphatidylserine (PtdSer) exposure was determined by flow cytometry. A dodecapeptide (LR12) was used as a specific inhibitor of TREM-1.

RESULTS

LPS increased TG, TF expression, and activity, as well as the exposure of PtdSer on the surface of monocytes. LR12 dampened TF activity through the decrease of PtdSer exposure, leading to a reduction of thrombin generation.

CONCLUSIONS

TREM-1 inhibition decreases thrombin generation and could be an interesting target for the development of new inhibitors of leukocyte-associated thrombotic activity.

Vincristine induces procoagulant activity of the human lymphoblastic leukemia cell line Jurkat through the release of extracellular vesicles

Thromboembolic events are frequent and serious complications of acute lymphoblastic leukaemia treatment. The importance of chemotherapy in the pathogenesis of this increased risk is enhanced by the fact that thrombosis rarely occurs at diagnosis. Our study aims at investigating the effect of chemotherapy on pro-coagulant activity (PCA), phosphatidylserine (PS) exposure, tissue factor (TF) activity and derived extracellular vesicles (EV) of Jurkat cells. Jurkat cells were treated with two commonly used chemotherapeutics: Vincristine (VCR) or Daunorubicin (DNR), at relevant concentrations. PCA of cells and derived EV were evaluated using Thrombin generation Assay (TGA). Cells or EV were incubated with annexin V or anti TF antibodies to assess the respective contribution of TF and PS. PS exposure on cells was analysed by flow cytometry. Derived EV were evaluated in fluorescence microscopy and flow cytometry. Untreated Jurkat cells and EV support thrombin generation. Thrombin generation was abolished when PS activity was inhibited by annexin V. VCR treatment resulted in a time dependent increase of thrombin generation. After VCR exposure, TF activity increased as well as PS exposure increased on the cell surface. The increase in TF activity was abolished by annexin V indicating that PS was required. A spontaneous release of EV from Jurkat cells was observed and VCR treatment increased the number of generated EV. Our results indicate that VCR increased the PCA of Jurkat cells predominantly through PS exposure and increased EV generation. Lymphoid blasts derived EV could be biomarkers to determine high thrombotic risk ALL patients.

Tissue factor activity on microvesicles from cancer patients

PURPOSE

The expression of active tissue factor (TF) on the surface of microvesicles (MVs) is essential for the activation of the coagulation system and transduction of the signaling pathways in cancer cells. In its use as a biomarker for cancer-associated venous thromboembolism (VTE), TF has shown high expression variability. As a contribution to this discussion, we present a study investigating plasma samples from patients with various progressive tumors at high risk for VTE.

METHODS

Based on our previous study uncovering microvesicles (MVs), the larger ectosome-like extracellular vesicles (EV), as the major source of TF activity in EV preparations, we now determined TF activity on enriched MVs isolated from plasma of cancer patients and compared it with that on MVs from healthy individuals.

RESULTS

We found considerably higher amounts of MVs as well as higher levels of MV-bound TF activities in the plasma of cancer patients. We also show that preparations from plasma of cancer patients have the potency to induce ERK phosphorylation in a human tumor cell line through proteinase-activated receptor two (PAR2) activation.

CONCLUSION

We suggest that MVs instead of whole EV preparations, and TF activity rather than its antigenic quantification should be used in clinical studies for identifying patients with progressive tumors at high risk for VTE.

Phosphatidylserine's role in Ebola's inflammatory cytokine storm and hemorrhagic consumptive coagulopathy and the therapeutic potential of annexin V

The phosphatidylserine (PS) molecule is present in cell membranes where it is actively kept on their inner leaflets but when cells are damaged it moves to the surface and become a signal for their removal, the platform upon which the coagulation cascade takes place and a ligand that activates a feedback cycle of inflammatory cytokine secretion and initiates the wakeup call for the innate immune response. These are physiologic responses to PS but the Ebola virus displays PS molecules on its membrane’s surface and the huge numbers of viruses cause a pathologic inflammatory cytokine storm and a hemorrhagic consumptive coagulopathy. Annexin V is an innate molecule that can cloak membrane displayed PS and prevents its Th1 cell’s inflammatory cytokine generation and cascade thrombin generation. The hypothesis presented is that its administration will cloak PS and prevent Ebola’s consumptive coagulopathy and its cytokine storm.

Hydroxyurea alters circulating monocyte subsets and dampens its inflammatory potential in sickle cell anemia patients

Sickle cell anemia (SCA) is a hemolytic disease in which vaso-occlusion is an important pathophysiological mechanism. The treatment is based on hydroxyurea (HU), which decreases leukocyte counts and increases fetal hemoglobin synthesis. Different cell types are thought to contribute to vaso-occlusion. Nevertheless, the role of monocytes subsets remains unclear. We investigated frequencies of monocytes subsets in blood and their response to HU therapy, testing their ability to express pro-inflammatory molecules and tissue factor (TF). We identified major changes in monocyte subsets, with classical monocytes (CD14⁺⁺CD16⁻) appearing highly frequent in who were not taking HU, whereas those with patrolling phenotype (CD14^dimCD16⁺) were enriched in individuals undergoing therapy. Additionally, HU decreased the production of TNF-α, IL1-β, IL-6, IL-8 as well as TF by the LPS-activated monocytes. Likewise, frequency of TF-expressing monocytes is increased in patients with previous vaso-occlusion. Moreover, activated monocytes expressing TF produced several pro-inflammatory cytokines simultaneously. Such polyfunctional capacity was dramatically dampened by HU therapy. The frequency of classical monocytes subset was positively correlated with percentage cytokine producing cells upon LPS stimulation. These findings suggest that classical monocytes are the subset responsible for multiple pro-inflammatory cytokine production and possibly drive inflammation and vaso-occlusion in SCA which is damped by HU.

Thrombogenic Risk Induced by Intravascular Mesenchymal Stem Cell Therapy: Current Status and Future Perspectives

Mesenchymal stem cells (MSCs) are currently studied and used in numerous clinical trials. Nevertheless, some concerns have been raised regarding the safety of these infusions and the thrombogenic risk they induce. MSCs express procoagulant activity (PCA) linked to the expression of tissue factor (TF) that, when in contact with blood, initiates coagulation. Some even describe a dual activation of both the coagulation and the complement pathway, called Instant Blood-Mediated Inflammatory Reaction (IBMIR), explaining the disappointing results and low engraftment rates in clinical trials. However, nowadays, different approaches to modulate the PCA of MSCs and thus control the thrombogenic risk after cell infusion are being studied. This review summarizes both in vitro and in vivo studies on the PCA of MSC of various origins. It further emphasizes the crucial role of TF linked to the PCA of MSCs. Furthermore, optimization of MSC therapy protocols using different methods to control the PCA of MSCs are described.

Effect of MSCs and MSC-Derived Extracellular Vesicles on Human Blood Coagulation

Mesenchymal stem cells (MSCs) have emerged as a potent therapeutic tool for the treatment of a number of pathologies, including immune pathologies. However, unwelcome effects of MSCs on blood coagulation have been reported, motivating us to explore the thrombotic properties of human MSCs from the umbilical cord. We revealed strong procoagulant effects of MSCs on human blood and platelet-free plasma using rotational thromboelastometry and thrombodynamic tests. A similar potentiation of clotting was demonstrated for MSC-derived extracellular vesicles (EVs). To offer approaches to avoid unwanted effects, we studied the impact of a heparin supplement on MSC procoagulative properties. However, MSCs still retained procoagulant activity toward blood from children receiving a therapeutic dose of unfractionated heparin. An analysis of the mechanisms responsible for the procoagulant effect of MSCs/EVs revealed the presence of tissue factor and other proteins involved in coagulation-associated pathways. Also, we found that some MSCs and EVs were positive for annexin V, which implies the presence of phosphatidylserine on their surfaces, which can potentiate clot formation. Thus, we revealed procoagulant activity of MSCs/EVs associated with the presence of phosphatidylserine and tissue factor, which requires further analysis to avoid adverse effects of MSC therapy in patients with a risk of thrombosis.

Exercise during hemodialysis does not affect the phenotype or prothrombotic nature of microparticles but alters their proinflammatory function

Hemodialysis patients have dysfunctional immune systems, chronic inflammation and comorbidity-associated risks of cardiovascular disease (CVD) and infection. Microparticles are biologically active nanovesicles shed from activated endothelial cells, immune cells, and platelets; they are elevated in hemodialysis patients and are associated with chronic inflammation and predictive of CVD mortality in this group. Exercise is advocated in hemodialysis to improve cardiovascular health yet acute exercise induces an increase in circulating microparticles in healthy populations. Therefore, this study aimed to assess acute effect of intradialytic exercise (IDE) on microparticle number and phenotype, and their ability to induce endothelial cell reactive oxygen species (ROS) in vitro. Eleven patients were studied during a routine hemodialysis session and one where they exercised in a randomized cross-over design. Microparticle number increased during hemodialysis (2064-7071 microparticles/μL, P < 0.001) as did phosphatidylserine+ (P < 0.05), platelet-derived (P < 0.01) and percentage procoagulant neutrophil-derived microparticles (P < 0.05), but this was not affected by IDE. However, microparticles collected immediately and 60 min after IDE (but not later) induced greater ROS generation from cultured endothelial cells (P < 0.05), suggesting a transient proinflammatory event. In summary IDE does not further increase prothrombotic microparticle numbers that occurs during hemodialysis. However, given acute proinflammatory responses to exercise stimulate an adaptation toward a circulating anti-inflammatory environment, microparticle-induced transient increases of endothelial cell ROS in vitro with IDE may indicate the potential for a longer-term anti-inflammatory adaptive effect. These findings provide a crucial evidence base for future studies of microparticles responses to IDE in view of the exceptionally high risk of CVD in these patients.

Apoptotic vesicles: deathly players in cancer-associated coagulation

Although cancer is associated with coagulation disorders, it is still unclear how the combination of tumor cell and host factors enhance the hypercoagulable state of cancer patients. Emerging evidence points to a central role for tumor endosomal and plasma membrane-derived vesicular components in the pathogenesis of cancer-related thrombosis. In particular, tumor cell membranes and extracellular vesicles (EV) harbor lipids and proteinaceous coagulation factors able to initiate multiple points within the coagulation matrix. The impact of chemotherapy upon a host already burdened with a hypercoagulable state increases the risk of pathological coagulation. We argue that chemotherapy-induced EV harbor the most active components for cancer related thrombosis and discuss how membrane components of the host and tumor act to initiate coagulation to enhance thrombotic risk in cancer patients.

Procoagulant and immunogenic properties of melanoma exosomes, microvesicles and apoptotic vesicles

Extracellular vesicles (EV) are lipid particles released from eukaryotic cells into the extracellular fluid. Depending on the cell type or mechanism of release, vesicles vary in form and function and exert distinct functions in coagulation and immunity. Tumor cells may constitutively shed vesicles known as exosomes or microvesicles (MV). Alternatively, apoptosis induces the release of apoptotic blebs or vesicles (ApoV) from the plasma membrane. EV have been implicated in thrombotic events (the second highest cause of death in cancer patients) and tumor vesicles contribute to the anti-cancer immune response. In this study, we utilized the well characterized B16 melanoma model to determine the molecular composition and procoagulant and immunogenic potential of exosomes, MV and ApoV. Distinct patterns of surface and cytoplasmic molecules (tetraspanins, integrins, heat shock proteins and histones) were expressed between the vesicle types. Moreover, in vitro coagulation assays revealed that membrane-derived vesicles, namely MV and ApoV, were more procoagulant than exosomes–with tissue factor and phosphatidylserine critical for procoagulant activity. Mice immunized with antigen-pulsed ApoV and challenged with B16 tumors were protected out to 60 days, while lower protection rates were afforded by MV and exosomes. Together the results demonstrate distinct phenotypic and functional differences between vesicle types, with important procoagulant and immunogenic functions emerging for membrane-derived MV and ApoV versus endosome-derived exosomes. This study highlights the potential of EV to contribute to the prothrombotic state, as well as to anti-cancer immunity.

Prognostic implications and procoagulant activity of phosphatidylserine exposure of blood cells and microparticles in patients with atrial fibrillation treated with pulmonary vein isolation

The present study aimed to evaluate the procoagulant effects of phosphatidylserine (PS) exposure on blood cells and microparticles (MPs), and examine its role in predicting early recurrence atrial fibrillation (ERAF) in patients with atrial fibrillation (AF) treated with pulmonary vein isolation (PVI). Blood samples were obtained from 40 healthy controls and 56 patients with AF at baseline (prior to PVI), and 0, 1 h, 1 day, 3 days and 7 days following PVI. The exposure of PS (PS⁺) to blood cells (platelets, erythrocytes and leukocytes) and MPs was detected using flow cytometry. The procoagulant activity was evaluated by coagulation time, and the formation of factor Xa (FXa) and thrombin. In addition, independent factors associated with PS⁺ blood cells and MPs, and significant predictors of ERAF following PVI were investigated by statistical analyses. The numbers of PS⁺ blood cells and MPs were significantly increased by PVI (P<0.01). A significant decrease in coagulation time, and increases in FXa and thrombin were exhibited in the PS⁺ blood cells and MPs from patients with AF treated with PVI, whereas these alterations were inhibited by either lactadherin or anti-tissue factor (P<0.01). The maximum power of the PVI was significantly associated with platelet-derived MPs, and high-sensitivity C-reactive protein (hs-CRP) was closely associated with leukocyte-derived MPs and endothelial-derived MPs (EMPs) (P<0.01). In addition, hs-CRP and EMPs >355/µl were identified as independent predictors of ERAF (P<0.05). The increased numbers of PS⁺ platelets, erythrocytes, leukocytes and MPs contributed to the procoagulant state of AF, and hs-CRP and EMPs were able to predict ERAF following PVI.

Different Potential of Extracellular Vesicles to Support Thrombin Generation: Contributions of Phosphatidylserine, Tissue Factor, and Cellular Origin

Cells release diverse types of vesicles constitutively or in response to proliferation, injury, inflammation, or stress. Extracellular vesicles (EVs) are crucial in intercellular communication, and there is emerging evidence for their roles in inflammation, cancer, and thrombosis. We investigated the thrombogenicity of platelet-derived EVs, which constitute the majority of circulating EVs in human blood, and assessed the contributions of phosphatidylserine and tissue factor exposure on thrombin generation. Addition of platelet EVs to vesicle-free human plasma induced thrombin generation in a dose-dependent manner, which was efficiently inhibited by annexin V, but not by anti-tissue factor antibodies, indicating that it was primarily due to the exposure of phosphatidylserine on platelet EVs. Platelet EVs exhibited higher thrombogenicity than EVs from unstimulated monocytic THP-1 cells, but blockade of contact activation significantly reduced thrombin generation by platelet EVs. Stimulation of monocytic cells with lipopolysaccharide enhanced their thrombogenicity both in the presence and in the absence of contact activation, and thrombin generation was efficiently blocked by anti-tissue factor antibodies. Our study provides evidence that irrespective of their cellular origin, EVs support the propagation of coagulation via the exposure of phosphatidylserine, while the expression of functional tissue factor on EVs appears to be limited to pathological conditions.

Eculizumab decreases the procoagulant activity of extracellular vesicles in paroxysmal nocturnal hemoglobinuria: A pilot prospective longitudinal clinical study

INTRODUCTION

Paroxysmal nocturnal hemoglobinuria (PNH) is a disease characterized by the susceptibility of blood cells to attack by the complement system, inducing extracellular vesicle (EV) production. Thromboembolism is the leading cause of death in this condition. Eculizumab, a humanized monoclonal antibody which inhibits the C5 protein of the complement, reduces the thrombotic risk in PNH.

MATERIALS AND METHOD

We conducted a pilot, prospective, open-label, longitudinal clinical study with six PNH patients treated with eculizumab. The aim was to measure, by flow cytometry, the EVs' production in the patients' platelet-free plasma (PFP) before and during the treatment. We also assessed the procoagulant activity in PFP using STA®-Procoag-PPL and thrombin generation assays (TGA). A high-sensitive version of TGA was also used to study the procoagulant profile induced by the EVs using EVs pelleted from PFP.

RESULTS

We observed a decrease in platelet EV count with eculizumab treatment (p<0.05). STA®-Procoag-PPL assay showed a decrease of the procoagulant profile induced by procoagulant phospholipids (PL) during treatment. These results were not confirmed by TGA on PFP, due to a lack of sensitivity. Thus, we used a high-sensitive version of TGA that enabled us to observe variation in the procoagulant profile induced by the EVs with eculizumab (p<0.05).

CONCLUSIONS

Eculizumab has an impact on the extent of EV production and on the procoagulant profile induced by the procoagulant PL and the EVs. One factor in the antithrombotic action of eculizumab is its ability to decrease EV production and the procoagulant profile induced by PL and EVs.

Ultraviolet-A1 irradiation therapy for systemic lupus erythematosus

Systemic lupus erythematosus (lupus, SLE) is a chronic autoimmune disease characterized by the production of autoantibodies, which bind to antigens and are deposited within tissues to fix complement, resulting in widespread systemic inflammation. The studies presented herein are consistent with hyperpolarized, adenosine triphosphate (ATP)-deficient mitochondria being central to the disease process. These hyperpolarized mitochondria resist the depolarization required for activation-induced apoptosis. The mitochondrial ATP deficits add to this resistance to apoptosis and also reduce the macrophage energy that is needed to clear apoptotic bodies. In both cases, necrosis, the alternative pathway of cell death, results. Intracellular constituents spill into the blood and tissues, eliciting inflammatory responses directed at their removal. What results is “autoimmunity.” Ultraviolet (UV)-A1 photons have the capacity to remediate this aberrancy. Exogenous exposure to low-dose, full-body, UV-A1 radiation generates singlet oxygen. Singlet oxygen has two major palliative actions in patients with lupus and the UV-A1 photons themselves have several more. Singlet oxygen depolarizes the hyperpolarized mitochondrion, triggering non-ATP-dependent apoptosis that deters necrosis. Next, singlet oxygen activates the gene encoding heme oxygenase (HO-1), a major governor of systemic homeostasis. HO-1 catalyzes the degradation of the oxidant heme into biliverdin (converted to bilirubin), Fe, and carbon monoxide (CO), the first three of these exerting powerful antioxidant effects, and in conjunction with a fourth, CO, protecting against injury to the coronary arteries, the central nervous system, and the lungs. The UV-A1 photons themselves directly attenuate disease in lupus by reducing B cell activity, preventing the suppression of cell-mediated immunity, slowing an epigenetic progression toward SLE, and ameliorating discoid and subacute cutaneous lupus. Finally, a combination of these mechanisms reduces levels of anticardiolipin antibodies and protects during lupus pregnancy. Capping all of this is that UV-A1 irradiation is an essentially innocuous, highly manageable, and comfortable therapeutic agency.

Evaluation of procoagulant tissue factor expression in canine hemangiosarcoma cell lines

OBJECTIVE To evaluate expression of procoagulant tissue factor (TF) by canine hemangiosarcoma cells in vitro. SAMPLES 4 canine hemangiosarcoma cell lines (SB-HSA [mouse-passaged cutaneous tumor], Emma [primary metastatic brain tumor], and Frog and Dal-1 [primary splenic tumors]) and 1 nonneoplastic canine endothelial cell line (CnAoEC). PROCEDURES TF mRNA and TF antigen expression were evaluated by quantitative real-time PCR assay and flow cytometry, respectively. Thrombin generation was measured in canine plasma and in coagulation factor-replete or specific coagulation factor-deficient human plasma by calibrated automated thrombography. Corn trypsin inhibitor and annexin V were used to examine contributions of contact activation and membrane-bound phosphatidylserine, respectively, to thrombin generation. RESULTS All cell lines expressed TF mRNA and antigen, with significantly greater expression of both products in SB-HSA and Emma cells than in CnAoEC. A greater percentage of SB-HSA cells expressed TF antigen, compared with other hemangiosarcoma cell lines. All hemangiosarcoma cell lines generated significantly more thrombin than did CnAoEC in canine or factor-replete human plasma. Thrombin generation induced by SB-HSA cells was significantly lower in factor VII-deficient plasma than in factor-replete plasma and was abolished in factor X-deficient plasma; residual thrombin generation in factor VII-deficient plasma was abolished by incubation of cells with annexin V. Thrombin generation by SB-HSA cells was unaffected by the addition of corn trypsin inhibitor. CONCLUSIONS AND CLINICAL RELEVANCE Hemangiosarcoma cell lines expressed procoagulant TF in vitro. Further research is needed to determine whether TF can be used as a biomarker for hemostatic dysfunction in dogs with hemangiosarcoma.

Increased blood cell phosphatidylserine exposure and circulating microparticles contribute to procoagulant activity after carotid artery stenting

OBJECTIVE Phosphatidylserine (PS) is a major component of the inner leaflet of membrane bilayers. During cell activation or apoptosis, PS is externalized to the outer membrane, providing an important physiological signal necessary for the release of the microparticles (MPs) that are generated through the budding of cellular membranes. MPs express PS and membrane antigens that reflect their cellular origin. PS exposure on the cell surface and the release of MPs provide binding sites for factor Xa and prothrombinase complexes that promote thrombin formation. Relatively little is known about the role of PS exposure on blood cells and MPs in patients with internal carotid artery (ICA) stenosis who have undergone carotid artery stenting (CAS). The authors aimed to investigate the extent of PS exposure on blood cells and MPs and to define its role in procoagulant activity (PCA) in the 7 days following CAS. METHODS The study included patients with ICA stenosis who had undergone CAS (n = 70), matched patients who had undergone catheter angiography only (n = 30), and healthy controls (n = 30). Blood samples were collected from all patients just before the procedure after an overnight fast and at 2, 6, 24, 48, and 72 hours and 7 days after the CAS procedure. Blood was collected from healthy controls after an overnight fast. Phosphatidylserine-positive (PS+) MPs and blood cells were analyzed by flow cytometry, while PCA was assessed with clotting time analysis, purified coagulation complex assays, and fibrin formation assays. RESULTS The authors found that levels of PS+ blood cells and PS+ blood cell-derived MPs (platelets and platelet-derived MPs [PMPs], neutrophils and neutrophil-derived MPs [NMPs], monocytes and monocyte-derived MPs [MMPs], erythrocytes and erythrocyte-derived MPs [RMPs], and endothelial cells and endothelial cell-derived MPs [EMPs]) were increased in the 7 days following the CAS procedure. Specifically, elevation of PS exposure on platelets/PMPs, neutrophils/NMPs, and monocytes/MMPs was detected within 2 hours of CAS, whereas PS exposure was delayed on erythrocytes/RMPs and EMPs, with an increase detected 24 hours after CAS. In addition, PS+ platelets/PMPs peaked at 2 hours, while PS+ neutrophils/NMPs, monocytes/MMPs, and erythrocytes/RMPs peaked at 48 hours. After their peak, all persisted at levels above baseline for 7 days post-CAS. Moreover, the level of PS+ blood cells/MPs was correlated with shortened coagulation time and significantly increased intrinsic and extrinsic Xase, thrombin generation, and fibrin formation. Pretreatment of blood cells with lactadherin at their peak time point after CAS blocked PS, resulting in prolonged coagulation times, decreased procoagulant enzyme activation, and fibrin production. CONCLUSIONS The results of this study suggest that increased exposure of PS on blood cells and MPs may contribute to enhanced PCA in patients with ICA stenosis who have undergone CAS, explaining the risk of perioperative thromboembolic complications in these patients. PS on blood cells and MPs may serve as an important biomarker for predicting, and as a pivotal target for monitoring and treating, acute postoperative complications after CAS. ■ CLASSIFICATION OF EVIDENCE Type of question: association; study design: prospective cohort trial; evidence: Class I.

Characteristics of erythrocyte-derived microvesicles and its relation with atherosclerosis

Microvesicles are formed under many circumstances, especially in atheromatous plaques. Erythrocyte-derived microvesicles (ErMVs) have been proved to promote atherosclerosis by promoting hypercoagulation, mediating inflammation and inducing cell adhesion. Several clinical studies have reported potential roles of ErMVs in cardiovascular disease diagnosis, but the current understanding of ErMVs remains insufficient. In this paper, we will review current research on the formation and degradation of ErMVs and the possible effects of ErMVs in atherosclerosis, discuss potential clinical applications in cardiovascular disease, and hope to raise awareness of the relation with atherosclerosis.

High intravascular tissue factor-but not extracellular microvesicles-in septic patients is associated with a high SAPS II score

Background

Sepsis is associated with coagulation abnormalities, and a high content of intravascular tissue factor (TF) may contribute to the development of multisystem organ failure. Circulating microvesicles (MVs) are increased during sepsis and characterized by their phosphatidylserine content. It is unclear whether MVs—as a part of the host response to the infection—are beneficial or rather contribute to systemic complications in sepsis. In the present prospective clinical pilot study, we investigated whether plasma TF and MVs are associated with the risk of multiple organ failure and mortality.

Methods

Thirty patients diagnosed with sepsis, severe sepsis, or septic shock were enrolled and classified as 19 survivors and 11 non-survivors. Blood samples were collected on the day of admission and then daily for up to 2 weeks. MVs and TF were quantified in plasma by ELISA.

Results

Non-survivors had significantly higher TF concentrations on day 3 compared to survivors. Logistic regression analysis revealed that patients with high amounts of TF had significantly increased risk for severity of disease, according to high Simplified Acute Physiology Score II (SAPS II) scores (odds ratio 18.7). In contrast, a higher content of phosphatidylserine-rich MVs were apparently associated with a lower risk for mortality and multiple organ failure, although this was only a trend and the odds ratios were not significant.

Conclusions

This study showed that a high amount of TF in septic patients is significantly associated with increased risk for disease severity, according to a high SAPS II score. Quantification of total MVs in plasma, independent from their cell origin, might be indicative for the outcome of patients in sepsis.

Extracellular Vesicles: A New Frontier in Biomarker Discovery for Non-Alcoholic Fatty Liver Disease

In recent years, the global burden of obesity and diabetes has seen a parallel rise in other metabolic complications, such as non-alcoholic fatty liver disease (NAFLD). This condition, once thought to be a benign accumulation of hepatic fat, is now recognized as a serious and prevalent disorder that is conducive to inflammation and fibrosis. Despite the rising incidence of NAFLD, there is currently no reliable method for its diagnosis or staging besides the highly invasive tissue biopsy. This limitation has resulted in the study of novel circulating markers as potential candidates, one of the most popular being extracellular vesicles (EVs). These submicron membrane-bound structures are secreted from stressed and activated cells, or are formed during apoptosis, and are known to be involved in intercellular communication. The cargo of EVs depends upon the parent cell and has been shown to be changed in disease, as is their abundance in the circulation. The role of EVs in immunity and epigenetic regulation is widely attested, and studies showing a correlation with disease severity have made these structures a favorable target for diagnostic as well as therapeutic purposes. This review will highlight the research that is available on EVs in the context of NAFLD, the current limitations, and projections for their future utility in a clinical setting.

Release and cellular origin of extracellular vesicles during circulation of whole blood over adsorbent polymers for lipid apheresis

Whole blood lipid apheresis is clinically applied in patients with familial hypercholesterolemia to reduce low density lipoprotein and other apolipoprotein B 100 containing lipoproteins. Here, the hemocompatibility of two polyacrylate-coated polyacrylamide-based polymers for lipid apheresis by evaluating the adhesion of blood cells to the adsorbent polymers, their respective activation, as well as the release of microvesicles during circulation of whole blood over the polymers was studied. Characterization of the adsorbents by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy revealed differences with respect to their surface morphology and their surface chemical composition. Despite these differences, equivalent amounts of leukocytes and platelets adhered to both polymers during circulation of whole blood over the adsorbent columns. The release of phosphatidylserine-exposing microvesicles, in contrast, increased significantly with increasing surface roughness and with the amount of polyacrylate groups at the adsorbent surface. The majority of microvesicles generated during blood-material contact were platelet-derived, and their release was associated with enhanced thrombin generation. Microvesicles were present in free and in cell-bound form, and 75% of all monocytes, but only 0.2% and 2.3% of red blood cells and platelets, respectively, were associated with microvesicles, pointing to a role of monocytes in the clearance of released microvesicles. Taken together, microvesicles are sensitive indicators for biomaterial-induced activation of blood cells in apheresis. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 636-646, 2017.

Increased phosphatidylserine-exposing microparticles and their originating cells are associated with the coagulation process in patients with IgA nephropathy

BACKGROUND

Relatively little information is available about phosphatidylserine positive (PS(+)) microparticles (MPs) and their originating cells in IgA nephropathy (IgAN) despite well-established intraglomerular coagulation. Our objectives were to detect PS exposure on MP membranes and MP-origin cells and to evaluate its role in procoagulant activity (PCA) and fibrin formation and their association with pathological lesions in the disease.

METHODS

Patients with IgAN and healthy controls were studied. Lactadherin was used to quantify PS exposure on MPs and MP-origin cells. PCA of MPs and MP-origin cells was evaluated by clotting time and purified coagulation complex assays. Fibrin production was determined by turbidity. PS exposure, fibrin strands and FVa/Xa binding were observed on MPs/cells using confocal microscopy.

RESULTS

Using flow cytometry, we found that IgAN patients had high levels of PS(+) MPs derived from lymphocytes, monocytes, neutrophils, platelets, erythrocytes and endothelial cells (ECs). The PS exposure on MP-origin cells also increased in these patients. MPs and MP-origin cells (leukocytes, platelets and erythrocytes) isolated from IgAN patients and ECs cultured with IgAN serum had a significantly shorter median coagulation time (P < 0.001), higher median intrinsic FXa (P < 0.001) and higher thrombin (P < 0.001) generation than controls. These coagulation functional assays were associated with the glomerular lesions. The lesions were also correlated with glomerular fibrin deposition (all P < 0.05). In the presence of patient MPs or their related cells, fibrin formation peaked faster with a higher maximum turbidity when compared with healthy controls. Blocking PS with lactadherin in the IgAN group prolonged coagulation time to control levels, inhibited the PCA up to 80% and markedly reduced fibrin formation. More importantly, we observed that fibrin strands formed on MPs and ECs in the same regions that bound lactadherin, similar to the FVa/Xa costaining.

CONCLUSIONS

We find that high levels of PS(+) MPs and the MP-origin cells are associated with the coagulation process in IgAN, and this may provide a previously unrecognized contribution to intraglomerular coagulation.

Low-Energy Ultrasound Treatment Improves Regional Tumor Vessel Infarction by Retargeted Tissue Factor

OBJECTIVES

To enhance the regional antitumor activity of the vascular-targeting agent truncated tissue factor (tTF)-NGR by combining the therapy with low-energy ultrasound (US) treatment.

METHODS

For the in vitro US exposure of human umbilical vein endothelial cells (HUVECs), cells were put in the focus of a US transducer. For analysis of the US-induced phosphatidylserine (PS) surface concentration on HUVECs, flow cytometry was used. To demonstrate the differences in the procoagulatory efficacy of TF-derivative tTF-NGR on binding to HUVECs with a low versus high surface concentration of PS, we performed factor X activation assays. For low-energy US pretreatment, HT1080 fibrosarcoma xenotransplant-bearing nude mice were treated by tumor-regional US-mediated stimulation (ie, destruction) of microbubbles. The therapy cohorts received the tumor vessel-infarcting tTF-NGR protein with or without US pretreatment (5 minutes after US stimulation via intraperitoneal injection on 3 consecutive days).

RESULTS

Combination therapy experiments with xenotransplant-bearing nude mice significantly increased the antitumor activity of tTF-NGR by regional low-energy US destruction of vascular microbubbles in tumor vessels shortly before application of tTF-NGR (P < .05). Mechanistic studies proved the upregulation of anionic PS on the outer leaflet of the lipid bilayer of endothelial cell membranes by low-energy US and a consecutive higher potential of these preapoptotic endothelial cells to activate coagulation via tTF-NGR and coagulation factor X as being a basis for this synergistic activity.

CONCLUSIONS

Combining retargeted tTF to tumor vessels with proapoptotic stimuli for the tumor vascular endothelium increases the antitumor effects of tumor vascular infarction. Ultrasound treatment may thus be useful in this respect for regional tumor therapy.

Procoagulant phospholipid concentration in canine erythrocyte concentrates stored with or without prestorage leukoreduction

OBJECTIVE

To evaluate canine erythrocyte concentrates (ECs) for the presence of procoagulant phospholipid (PPL), determine whether PPL concentration changes during the course of storage of ECs, and ascertain whether prestorage leukoreduction (removal of leukocytes via gravity filtration) reduces the development of PPL.

SAMPLE

10 whole blood units (420 g each) collected from 10 random-source, clinically normal dogs (1 U/dog).

PROCEDURES

The dogs were randomized to 1 of 2 groups. Of the 10 whole blood units collected, 5 were processed through a standard method, and 5 underwent leukoreduction. Whole blood units were processed to generate ECs, from which aliquots were aseptically collected from each unit weekly for 5 weeks. Supernatants from the concentrates were evaluated for procoagulant activity, which was converted to PPL concentration, by use of an automated assay and by measurement of real-time thrombin generation.

RESULTS

Supernatants from stored canine ECs contained procoagulant activity as measured by both assays. In general, the PPL concentration gradually increased during the storage period, but leukoreduction reduced the development of increased procoagulant activity over time.

CONCLUSIONS AND CLINICAL RELEVANCE

The presence of PPL in canine ECs may be associated with procoagulant and proinflammatory effects in vivo, which could have adverse consequences for dogs treated with ECs.

Elucidating mechanisms of toxicity using phenotypic data from primary human cell systems--a chemical biology approach for thrombosis-related side effects

Here we describe a chemical biology approach for elucidating potential toxicity mechanisms for thrombosis-related side effects. This work takes advantage of a large chemical biology data set comprising the effects of known, well-characterized reference agents on the cell surface levels of tissue factor (TF) in a primary human endothelial cell-based model of vascular inflammation, the BioMAP^® 3C system. In previous work with the Environmental Protection Agency (EPA) for the ToxCast™ program, aryl hydrocarbon receptor (AhR) agonists and estrogen receptor (ER) antagonists were found to share an usual activity, that of increasing TF levels in this system. Since human exposure to compounds in both chemical classes is associated with increased incidence of thrombosis-related side effects, we expanded this analysis with a large number of well-characterized reference compounds in order to better understand the underlying mechanisms. As a result, mechanisms for increasing (AhR, histamine H1 receptor, histone deacetylase or HDAC, hsp90, nuclear factor kappa B or NFκB, MEK, oncostatin M receptor, Jak kinase, and p38 MAPK) and decreasing (vacuolar ATPase or V-ATPase) and mTOR) TF expression levels were uncovered. These data identify the nutrient, lipid, bacterial, and hypoxia sensing functions of autophagy as potential key regulatory points controlling cell surface TF levels in endothelial cells and support the mechanistic hypothesis that these functions are associated with thrombosis-related side effects in vivo.