Tissue Factor: An Essential Mediator of Hemostasis and Trigger of Thrombosis

Vitamin D inhibits Tissue Factor and CAMs expression in oxidized low-density lipoproteins-treated human endothelial cells by modulating NF-κB pathway

Epidemiologic studies have clearly demonstrated the correlation existing between Vitamin D (Vit. D) deficiency and increased risk of developing cardiovascular disease, suggesting that it might have a protective role in this clinical setting. Although many experimental studies have investigated the molecular mechanisms by which Vit. D might exert these effects, its potential role in protecting against athero-thrombosis is still partially unknown. We have investigated whether Vit. D might exert anti athero-thombotic effects by preventing expression of adhesion molecules (CAMs) and Tissue Factor (TF), molecules involved in atherothrombotic pathophysiology, in oxLDL stimulated endothelial cells (HUVEC). Moreover, we have investigated whether Vit. D effects might be due to the NF-kB modulation. HUVEC cultivated in medium enriched with Vit. D (10 nM) were stimulated with oxLDL (50 μg/ml). TF gene (RT-PCR), protein (Western blot), surface expression (FACS) and procoagulant activity (FXa generation assay) were measured. Similarly, CAMs gene (RT-PCR), surface expression (FACS) and soluble values (ELISA) were measured. NF-kB translocation was also investigated. Vit. D significantly reduced TF gene as well protein expression and procoagulant activity in oxLDL-treated HUVEC. Similar effects were observed for CAMs. These effects were associated with Vit. D modulation of NF-κB pathway. This study, although in vitro, indicate that Vit. D has protective effect on endothelial cells by inhibiting expression of TF and CAMs, proteins involved in atherothrombotic pathophysiology. Further studies will be necessary to translate these findings to a clinical scenario to better define the potential therapeutical role of Vit. D supplementation in the management of cardiovascular disease in patients with Vit. D deficiency.

Evaluation of different commercial antibodies for their ability to detect human and mouse tissue factor by western blotting

BACKGROUND

Western blotting is used to measure protein expression in cells and tissues. Appropriate interpretation of resulting data is contingent upon antibody validation.

OBJECTIVES

We assessed several commercial anti-human and anti-mouse tissue factor (TF) antibodies for their ability to detect TF by western blotting.

MATERIAL AND METHODS

We used human pancreatic cancer cell lines expressing different levels of TF and a mouse pancreatic cancer cell line expressing TF with a matched knockout derivative.

RESULTS

Human and mouse TF protein detected by western blotting correlated with levels of TF mRNA in these cell lines. The apparent molecular weight of TF is increased by N-linked glycosylation and, as expected, deglycosylation decreased the size of TF based on western blotting. We found that four commercial anti-human TF antibodies detected TF in a TF-positive cell line HPAF-II whereas no signal was observed in a TF-negative cell line MIA PaCa-2. More variability was observed in detecting mouse TF. Two anti-mouse TF antibodies detected mouse TF in a TF-positive cell line and no signal was observed in a TF knockout cell line. However, a third anti-mouse TF antibody detected a nonspecific protein in both the mouse TF-positive and TF-negative cell lines. Two anti-human TF antibodies that are claimed to cross react with mouse TF either recognized a nonspecific band or did not detect mouse TF.

DISCUSSION

Our results indicate that there is a range in quality of commercial anti-TF antibodies.

CONCLUSION

We recommend that all commercial antibodies should be validated to ensure that they detect TF.

Neutrophil Extracellular Traps: Signaling Properties and Disease Relevance

Neutrophil extracellular traps (NETs) are characterized as extracellular DNA fibers comprised of histone and cytoplasmic granule proteins. NETs were first described as a form of innate response against pathogen invasion, which can capture pathogens, degrade bacterial toxic factors, and kill bacteria. Additionally, NETs also provide a scaffold for protein and cell binding. Protein binding to NETs further activate the coagulation system which participates in thrombosis. In addition, NETs also can damage the tissues due to the proteins they carry. Many studies have suggested that the excessive formation of NETs may contribute to a range of diseases, including thrombosis, atherosclerosis, autoimmune diseases, and sepsis. In this review, we describe the structure and components of NETs, models of NET formation, and detection methods. We also discuss the molecular mechanism of NET formation and their disease relevance. Modulation of NET formation may provide a new route for the prevention and treatment of releated human diseases.

Sickle Cell Disease: A Paradigm for Venous Thrombosis Pathophysiology

Venous thromboembolism (VTE) is an important cause of vascular morbidity and mortality. Many risk factors have been identified for venous thrombosis that lead to alterations in blood flow, activate the vascular endothelium, and increase the propensity for blood coagulation. However, the precise molecular and cellular mechanisms that cause blood clots in the venous vasculature have not been fully elucidated. Patients with sickle cell disease (SCD) demonstrate all the risk factors for venous stasis, activated endothelium, and blood hypercoagulability, making them particularly vulnerable to VTE. In this review, we will discuss how mouse models have elucidated the complex vascular pathobiology of SCD. We review the dysregulated pathways of inflammation and coagulation in SCD and how the resultant hypercoagulable state can potentiate thrombosis through down-regulation of vascular anticoagulants. Studies of VTE pathogenesis using SCD mouse models may provide insight into the intersection between the cellular and molecular processes involving inflammation and coagulation and help to identify novel mechanistic pathways.

The Lymphatic Vasculature in the 21st Century: Novel Functional Roles in Homeostasis and Disease

Mammals have two specialized vascular circulatory systems: the blood vasculature and the lymphatic vasculature. The lymphatic vasculature is a unidirectional conduit that returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays major roles in immune cell trafficking and lipid absorption. As we discuss in this review, the molecular characterization of lymphatic vascular development and our understanding of this vasculature's role in pathophysiological conditions has greatly improved in recent years, changing conventional views about the roles of the lymphatic vasculature in health and disease. Morphological or functional defects in the lymphatic vasculature have now been uncovered in several pathological conditions. We propose that subtle asymptomatic alterations in lymphatic vascular function could underlie the variability seen in the body's response to a wide range of human diseases.

Unique transcriptional changes in coagulation cascade genes in SARS-CoV-2-infected lung epithelial cells: A potential factor in COVID-19 coagulopathies

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly become a global pandemic. In addition to the acute pulmonary symptoms of COVID-19 (the disease associated with SARS-CoV-2 infection), pulmonary and distal coagulopathies have caused morbidity and mortality in many patients. Currently, the molecular pathogenesis underlying COVID-19 associated coagulopathies are unknown. While there are many theories for the cause of this pathology, including hyper inflammation and excess tissue damage, the cellular and molecular underpinnings are not yet clear. By analyzing transcriptomic data sets from experimental and clinical research teams, we determined that changes in the gene expression of genes important in the extrinsic coagulation cascade in the lung epithelium may be important triggers for COVID-19 coagulopathy. This regulation of the extrinsic blood coagulation cascade is not seen with influenza A virus (IAV)-infected NHBEs suggesting that the lung epithelial derived coagulopathies are specific to SARS-Cov-2 infection. This study is the first to identify potential lung epithelial cell derived factors contributing to COVID-19 associated coagulopathy.

Expression of tissue factor mRNA in thrombosis associated with antiphospholipid syndrome

Tissue factor (TF) is a procoagulant protein associated with increased risk of thrombotic events in antiphospholipid syndrome (t-APS). The mechanisms by which TF levels are increased in APS have not yet been established. The aim of this study was to investigate whether TF mRNA expression is associated with TF levels and thrombosis in APS. We compared levels of circulating TF and high sensitivity C-reactive protein (hs-CRP) between t-APS and controls (individuals without thrombosis). The association between TF mRNA expression, quantified by real time quantitative polymerase chain reaction, and t-APS was accessed using regression analysis. We included 41 controls and 42 t-APS patients, mean age was 41 years old (SD 14) in both groups. Hs-CRP and TF levels were higher in t-APS patients (mean hs-CRP levels 0.81 mg/dL [SD 1.88] and median TF levels 249.0 pg/mL [IQR 138.77-447.61]) as compared to controls (mean hs-CRP levels 0.24 mg/dL [SD 0.26] and median TF levels 113.0 pg/mL [IQR 81.17-161.53]; P = 0.02 and P < 0.0001, respectively). There was no correlation between TF mRNA expression and TF levels in t-APS (r - 0.209, P = 0.19). TF mRNA expression was not associated with t-APS (adjusted OR 1.16; 95%CI 0.72-1.87). Despite circulating TF levels being higher in patients with t-APS than in controls, TF mRNA expression was similar between groups. The results demonstrate that TF mRNA expression is not associated with levels of circulating TF and hypercoagulability in t-APS.

Tissue factor in atherosclerosis and atherothrombosis

Atherosclerosis is a chronic inflammatory disease that is characterized by the formation of lipid rich plaques in the wall of medium to large sized arteries. Atherothrombosis represents the terminal manifestation of this pathology in which atherosclerotic plaque rupture or erosion triggers the formation of occlusive thrombi. Occlusion of arteries and resultant tissue ischemia in the heart and brain causes myocardial infarction and stroke, respectively. Tissue factor (TF) is the receptor for the coagulation protease factor VIIa, and formation of the TF:factor VIIa complex triggers blood coagulation. TF is expressed at high levels in atherosclerotic plaques by both macrophage-derived foam cells and vascular smooth muscle cells, as well as extracellular vesicles derived from these cells. Importantly, TF mediated activation of coagulation is critically important for arterial thrombosis in the setting of atherosclerotic disease. The major endogenous inhibitor of the TF:factor VIIa complex is TF pathway inhibitor 1 (TFPI-1), which is also present in atherosclerotic plaques. In mouse models, increased or decreased expression of TFPI-1 has been found to alter atherosclerosis. This review highlights the contribution of TF-dependent activation of coagulation to atherthrombotic disease.

Antiviral anticoagulation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel envelope virus that causes coronavirus disease 2019 (COVID-19). Hallmarks of COVID-19 are a puzzling form of thrombophilia that has elevated D-dimer but only modest effects on other parameters of coagulopathy. This is combined with severe inflammation, often leading to acute respiratory distress and possible lethality. Coagulopathy and inflammation are interconnected by the transmembrane receptor, tissue factor (TF), which initiates blood clotting as a cofactor for factor VIIa (FVIIa)-mediated factor Xa (FXa) generation. TF also functions from within the nascent TF/FVIIa/FXa complex to trigger profound changes via protease-activated receptors (PARs) in many cell types, including SARS-CoV-2-trophic cells. Therefore, aberrant expression of TF may be the underlying basis of COVID-19 symptoms. Evidence suggests a correlation between infection with many virus types and development of clotting-related symptoms, ranging from heart disease to bleeding, depending on the virus. Since numerous cell types express TF and can act as sites for virus replication, a model envelope virus, herpes simplex virus type 1 (HSV1), has been used to investigate the uptake of TF into the envelope. Indeed, HSV1 and other viruses harbor surface TF antigen, which retains clotting and PAR signaling function. Strikingly, envelope TF is essential for HSV1 infection in mice, and the FXa-directed oral anticoagulant apixaban had remarkable antiviral efficacy. SARS-CoV-2 replicates in TF-bearing epithelial and endothelial cells and may stimulate and integrate host cell TF, like HSV1 and other known coagulopathic viruses. Combined with this possibility, the features of COVID-19 suggest that it is a TFopathy, and the TF/FVIIa/FXa complex is a feasible therapeutic target.

Structural Integrity of the Alveolar-Capillary Barrier in Cynomolgus Monkeys Challenged with Fully Virulent and Toxin-Deficient Strains of Bacillus anthracis

Inhalational anthrax, a disease caused by inhaling Bacillus anthracis spores, leads to respiratory distress, vascular leakage, high-level bacteremia, and often death within days. Anthrax lethal toxin and edema toxin, which are composed of protective antigen (PA) plus either lethal factor (LF) or edema factor (EF), respectively, play an important yet incompletely defined role in the pulmonary pathophysiology. To better understand their contribution, we examined the structural integrity of the alveolar-capillary barrier in archival formalin-fixed lungs of cynomolgus monkeys challenged with the fully virulent B. anthracis Ames wild-type strain or the isogenic toxin-deficient mutants ΔEF, ΔLF, and ΔPA. Pulmonary spore challenge with the wild-type strain caused high mortality, intra-alveolar hemorrhages, extensive alveolar septal sequestration of bacteria and neutrophils, diffuse destabilization of epithelial and endothelial junctions, increased markers of coagulation and complement activation (including tissue factor and C5a), and multifocal intra-alveolar fibrin deposition. ΔEF challenge was lethal and showed similar alveolar-capillary alterations; however, intra-alveolar hemorrhages, bacterial deposition, and markers of coagulation or complement were absent or markedly lower. In contrast, ΔLF or ΔPA challenges were nonlethal and showed no signs of alveolar bacterial deposition or alveolar-capillary changes. These findings provide evidence that lethal toxin plays a determinative role in bacterial dissemination and alveolar-capillary barrier dysfunction, and edema toxin may significantly exacerbate pulmonary pathologies in a systemic infection.

How do Uremic Toxins Affect the Endothelium?

Uremic toxins can induce endothelial dysfunction in patients with chronic kidney disease (CKD). Indeed, the structure of the endothelial monolayer is damaged in CKD, and studies have shown that the uremic toxins contribute to the loss of cell–cell junctions, increasing permeability. Membrane proteins, such as transporters and receptors, can mediate the interaction between uremic toxins and endothelial cells. In these cells, uremic toxins induce oxidative stress and activation of signaling pathways, including the aryl hydrocarbon receptor (AhR), nuclear factor kappa B (NF-κB), and mitogen-activated protein kinase (MAPK) pathways. The activation of these pathways leads to overexpression of proinflammatory (e.g., monocyte chemoattractant protein-1, E-selectin) and prothrombotic (e.g., tissue factor) proteins. Uremic toxins also induce the formation of endothelial microparticles (EMPs), which can lead to the activation and dysfunction of other cells, and modulate the expression of microRNAs that have an important role in the regulation of cellular processes. The resulting endothelial dysfunction contributes to the pathogenesis of cardiovascular diseases, such as atherosclerosis and thrombotic events. Therefore, uremic toxins as well as the pathways they modulated may be potential targets for therapies in order to improve treatment for patients with CKD.

The clinical management of factor XI deficiency in pregnant women

INTRODUCTION

Factor XI (FXI) deficiency is associated with highly variable bleeding, including excessive gynecologic and obstetrical bleeding. Since approximately 20% of FXI-deficient women will experience pregnancy-related bleeding, careful planning and knowledge of appropriate hemostatic management is pivotal for their care.

AREAS COVERED

In this manuscript, authors present our current understanding of the role of FXI in hemostasis, the nature of the bleeding phenotype caused by its deficiency, and the impact of deficiency on obstetrical care. The authors searched PubMed with the terms, 'factor XI', 'factor XI deficiency', 'women', 'pregnancy', and 'obstetrics' to identify literature on these topics. Expectations of pregnancy-related complications in women with FXI deficiency, including antepartum, abortion-related, and postpartum bleeding, as well as bleeding associated with regional anesthesia are discussed. Recommendations for the care of these women are considered, including guidance for management of prophylactic care and acute bleeding.

EXPERT COMMENTARY

FXI deficiency results in a bleeding diathesis in some, but not all, patients, making treatment decisions and clinical management challenging. Currently available laboratory assays are not particularly useful for distinguishing patients with FXI deficiency who are prone to bleeding from those who are not. There is a need for alternative testing strategies to address this limitation.

Liver gene regulation of hemostasis-related factors is altered by experimental snake envenomation in mice

Few studies have addressed gene expression of hemostasis-related factors during acute thrombo-hemorrhagic diseases. Bites by the lanced-headed viper Bothrops jaracaca induce rapid hemostatic disturbances in victims, leading to systemic bleedings, thrombocytopenia and consumption coagulopathy. Although circulating levels of coagulation factors recover rapidly after administration of specific antivenom therapy, it is unclear if B. jararaca venom (BjV) upregulates the mRNA synthesis of hepatic hemostasis-related factors, or if the recovery occurs under basal conditions after the neutralization of venom components by antivenom. Thus, we aimed to investigate if BjV regulates gene expression of important hemostasis-related factors synthetized by the liver. On that account, Swiss mice were injected with saline or BjV (1.6 mg/kg b.w, s.c.), and after 3, 6 and 24 h blood samples and liver fragments were collected to analyze mRNA expression by real-time qPCR. Increased gene expression of fibrinogen chains, haptoglobin and STAT3 was observed during envenomation, particularly at 3 and 6 h. At 24h, mRNA levels of F10 were raised, while those of Serpinc1, Proc and Adamts13 were diminished. Surprisingly, F3 mRNA levels were steadily decreased at 3 h. Gene expression of Thpo, F7, F5 Tfpi, Mug1 was unaltered. mRNA levels of Vwf, P4hb, F8, F2, Plg, and Serpinf2 were minimally altered, but showed important associations with Nfkb1 gene expression. In conclusion, snakebite envenomation upregulates hepatic mRNA synthesis particularly of fibrinogen chains, and acute-phase markers. This response explains the fast recovery of fibrinogen levels after antivenom administration to patients bitten by B. jararaca snakes.

LPS-induced expression and release of monocyte tissue factor in patients with haemophilia

In haemophilia, thrombin generation and fibrin deposition upon vascular injury critically depend on the tissue factor (TF)-driven coagulation pathway. TF expression by monocytes/macrophages and circulating microvesicles contributes to haemostasis, thrombosis and inflammation. Inflammation is a hallmark of blood-induced joint disease. The aim of this study is to correlate TF production by whole-blood monocytes with inflammatory markers and clinical parameters in patients with moderate-to-severe haemophilia A or B (n = 43) in comparison to healthy males (n = 23). Monocyte TF antigen and microvesicle-associated TF procoagulant activity (MV TF PCA) were measured immediately after blood draw (baseline) and following incubation of whole blood with buffer or lipopolysaccharide (LPS) using two-colour flow cytometry and chromogenic FXa generation assay, respectively. Patients with HIV or uncontrolled HBV/HCV infections were excluded. TF was hardly detectable and not different in baseline and buffer-treaded samples from both groups. Stimulation with LPS, however, induced monocyte TF production, with increased TF-specific mean fluorescence intensity (P = 0.08) and MV TF PCA (P < 0.05) in patients compared to controls. Patients also had elevated hs-CRP and IL-6 serum levels (P < 0.001), which correlated with LPS-induced TF parameters. Further exploratory analyses revealed that the presence of systemic (low-grade) inflammation and boosted LPS-induced monocyte TF production were mainly restricted to patients with clinically controlled HBV and/or HCV infection (n = 16), who were older and also had a significantly worse orthopaedic joint score than patients with no history of viral hepatitis (P < 0.01). Our study delineates a previously unrecognised link between systemic inflammation and inducible monocyte TF production in patients with haemophilia A or B.

Mouse models of hemostasis

Hemostasis is the normal process that produces a blood clot at a site of vascular injury. Mice are widely used to study hemostasis and abnormalities of blood coagulation because their hemostatic system is similar in most respects to that of humans, and their genomes can be easily manipulated to create models of inherited human coagulation disorders. Two of the most widely used techniques for assessing hemostasis in mice are the tail bleeding time (TBT) and saphenous vein bleeding (SVB) models. Here we discuss the use of these methods in the evaluation of hemostasis, and the advantages and limits of using mice as surrogates for studying hemostasis in humans.

Extracellular Vesicles Derived From Platelets, Red Blood Cells, and Monocyte-Like Cells Differ Regarding Their Ability to Induce Factor XII-Dependent Thrombin Generation

As transmitters of biological information, extracellular vesicles (EVs) are crucial for the maintenance of physiological homeostasis, but also contribute to pathological conditions, such as thrombotic disorders. The ability of EVs to support thrombin generation has been linked to their exposure of phosphatidylserine, an anionic phospholipid that is normally restricted to the inner leaflet of the plasma membrane but exposed on the outer leaflet during EV biogenesis. Here, we investigated whether EVs of different cellular origin and from different settings, namely platelets and red blood cells from blood bank units and a monocyte-like cell line (THP-1), differ regarding their potential to support factor XII-dependent thrombin generation. EVs were isolated from blood products or THP-1 cell culture supernatants using differential centrifugation and characterized by a combination of flow cytometry, nanoparticle tracking analysis, and Western blotting. Soluble factors co-enriched during the isolation of EVs were depleted from blood-cell derived EV fractions using size exclusion chromatography, while proteins bound to the surface of EVs were degraded by mild protease treatment. We found that platelet-derived and red blood cell-derived EVs supported factor XII-dependent thrombin generation to comparable extents, while monocytic EVs failed to support thrombin generation when added to EV-depleted human plasma. We excluded a major contribution of co-enriched soluble proteins or of proteins bound to the EV surface to the thrombogenicity of blood cell-derived EVs. Our data suggest that the enhanced potential of blood cell-derived EVs to support thrombin generation is rather due to enhanced exposure of phosphatidylserine on the surface of blood cell-derived EVs. Extending these investigations to EVs from other cell types, such as mesenchymal stromal cells, will be crucial for their future therapeutic applications.

Effect of chemotherapy and longitudinal analysis of circulating extracellular vesicle tissue factor activity in patients with pancreatic and colorectal cancer

INTRODUCTION

We conducted a longitudinal study in patients with pancreatic and colorectal cancer. We determined the effect of chemotherapy on extracellular vesicle tissue factor (EVTF) activity and the association of plasma EVTF activity with venous thromboembolism (VTE) and survival.

MATERIAL AND METHODS

We enrolled 13 patients with pancreatic and 22 patients with colorectal cancer. Plasma samples were collected during the 85-day study period. Patients were followed for 3 months after the study period. We recorded symptomatic VTE during the study period (3 months) or asymptomatic deep vein thrombosis detected by ultrasound at day 85. We measured EVTF activity before and after chemotherapy.

RESULTS AND CONCLUSIONS

In the pancreatic cancer group, 2 patients had elevated levels of EVTF activity. One of these patients developed symptomatic VTE and died, and the second patient did not have a VTE but died. Chemotherapy decreased EVTF activity in 2 pancreatic patients with high levels. In the colorectal cancer group, 4 patients developed VTE, but EVTF activity was not elevated in any patient and no patient died. We observed a borderline significant correlation between EVTF activity and D-dimer in the patients with pancreatic but not colorectal cancer. In this small descriptive study, 2 patients with pancreatic cancer had an elevated level of EVTF activity. Both patients died during the study period, and one had a VTE. Chemotherapy decreased EVTF activity in these patients. In contrast, elevated levels of EVTF activity were not observed in patients with colorectal cancer with or without VTE.

Procoagulant activity in children and adolescents on intensive insulin therapy

BACKGROUND

Type 1 diabetes is associated with atherothrombosis, but limited data exist on procoagulant activity in the young. We investigated procoagulant activity in children/adolescents with type 1 diabetes using intensified insulin treatment compared with controls in a 5-year follow-up study, and further any associations with cardiovascular risk factors.

METHODS

The study included 314 diabetes children/adolescents and 120 healthy controls. Prothrombin fragment 1+2 (F1+2), D-dimer, tissue-factor-procoagulant-activity (TF-PCA), and tissue-factor-pathway-inhibitor (TFPI) were analyzed with ELISAs.

RESULTS

F1+2, D-dimer, and TF-PCA did not differ between the groups or correlate to HbA_1c in the diabetes group at either time points. TFPI was significantly higher in the diabetes group compared with controls both at inclusion and follow-up (both P < .001). In the diabetes group, TFPI correlated significantly to HbA_1c at both time points (r = 0.221 and 0.304, both P < .001). At follow-up, females using oral contraceptives had significantly elevated F1+2, D-dimer, and TF-PCA and lower TFPI compared to no-users (all P < .005), and females had lower TFPI (P = .017) and higher F1+2 compared with males (P = .052), also after adjusting for the use of oral contraceptives.

CONCLUSIONS

The current results show similar procoagulant activity in children/adolescents with type 1 diabetes compared with controls over a 5-year period, indicating that these children using modern intensified insulin treatment are not at high thrombotic risk at younger age. The elevated levels of TFPI in the diabetes group, related to hyperglycaemia, are probably reflecting increased endothelial activation. These findings highlight the significance of optimal blood glucose control in children/adolescents with type 1 diabetes, to maintain a healthy endothelium.

Donepezil Prevents ox-LDL-Induced Attachment of THP-1 Monocytes to Human Aortic Endothelial Cells (HAECs)

Oxidized low-density lipoprotein (ox-LDL)- induced endothelial insults plays an important role in the pathogenesis of atherosclerosis. Donepezil is a well-known acetylcholinesterase inhibitor with its primary application being the treatment of Alzheimer's disease. More recently, there has been increased interest in donepezil as an antiatherosclerosis treatment as it possesses a host of relevant and potentially beneficial properties. In the present study, we found that donepezil could reduce the expression of lectin-type oxidized low-density lipoprotein receptor-1 (LOX-1) in human aortic endothelial cells (HAECs). We found that donepezil could suppress the expression of intercellular adhesion molecule-1 (ICAM-1), which recruits monocytes to adhere to the endothelium, by more than half. Another key finding of our study is that donepezil could reduce the expression of tumor necrosis factor receptor-α (TNF-α) and interleukin-6 (IL-6) by more than half at both the mRNA and protein transcriptional levels. Donepezil also reduced the expression of tissue factor (TF), which is considerably upregulated in atherosclerotic lesions, by more than half. Finally, we turned our attention to the early growth response protein-1 (Egr-1) for its potential role in mediating the effects of donepezil. Through our Egr-1 overexpression experiment, we found that overexpression of Egr-1 almost completely abolished the effects of donepezil described above. Thus, the effects of donepezil are likely mediated through downregulation of Egr-1. These findings provide evidence that donepezil may exert protective effects against atherosclerosis.

Indoxyl Sulfate, a Uremic Endotheliotoxin

Chronic kidney disease (CKD) is associated with a high prevalence of cardiovascular diseases. During CKD, the uremic toxin indoxyl sulfate (IS)—derived from tryptophan metabolism—accumulates. IS is involved in the pathophysiology of cardiovascular complications. IS can be described as an endotheliotoxin: IS induces endothelial dysfunction implicated in cardiovascular morbidity and mortality during CKD. In this review, we describe clinical and experimental evidence for IS endothelial toxicity and focus on the various molecular pathways implicated. In patients with CKD, plasma concentrations of IS correlate with cardiovascular events and mortality, with vascular calcification and atherosclerotic markers. Moreover, IS induces a prothrombotic state and impaired neovascularization. IS reduction by AST-120 reverse these abnormalities. In vitro, IS induces endothelial aryl hydrocarbon receptor (AhR) activation and proinflammatory transcription factors as NF-κB or AP-1. IS has a prooxidant effect with reduction of nitric oxide (NO) bioavailability. Finally, IS alters endothelial cell and endothelial progenitor cell migration, regeneration and control vascular smooth muscle cells proliferation. Reducing IS endothelial toxicity appears to be necessary to improve cardiovascular health in CKD patients.

Evaluation of the Antihemostatic and Antithrombotic Effects of Lowering Coagulation Factor VII Levels in a Non-human Primate

Introduction

Tissue factor (TF) and factor (F) VII, components of the extrinsic pathway of blood coagulation, are essential for hemostatic plug formation in response to injury; less clear are their roles in propagating thrombosis, as observational data in humans with congenital FVII deficiency suggests persistent thrombotic and bleeding risk even at significantly decreased FVII levels. We aimed to define the contribution of FVII to thrombus formation and hemostasis using a non-human primate model.

Methods

We treated baboons with a FVII antisense oligonucleotide (ASO) and measured platelet and fibrin deposition inside and distal to collagen- or TF-coated vascular grafts. We assessed hemostasis by measuring bleeding time (BT) and prothrombin time (PT). Enoxaparin and vehicle treatments served as controls.

Results

FVII-ASO treatment reduced FVII levels by 95% and significantly increased both the PT and BT. Lowering FVII levels did not decrease platelet deposition in collagen- or TF-coated grafts, in thrombi distal to the grafts, or fibrin content of either collagen- and TF-coated grafts. Lowering FVII levels were associated with a modest 25% reduction in platelet deposition at 60 min in the distal thrombus tail of TF-coated grafts only.

Conclusions

FVII inhibition by way of ASO is feasible yet significantly impairs hemostasis while only exhibiting antithrombotic effects when thrombosis is initiated by vessel wall surface-associated TF exposure.

The gut microbiome and thromboembolism

The gut microbiome plays a critical role in various inflammatory conditions, and its modulation is a potential treatment option for these conditions. The role of the gut microbiome in the pathogenesis of thromboembolism has not been fully elucidated. In this review, we summarize the evidence linking the gut microbiome to the pathogenesis of arterial and venous thrombosis. In a human host, potentially pathogenic bacteria are normal residents of the human gut microbiome, but significantly outnumbered by commensal anaerobic bacteria. Several disease states with an increased risk of venous thromboembolism (VTE) are associated with an imbalance in the gut microbiome characterized by a decrease in commensal anaerobic bacteria and an increase in the abundance of pathogenic bacteria of which the most common is the gram-negative Enterobacteriaceae (ENTERO) family. Bacterial lipopolysaccharides (LPS), the glycolipids found on the outer membrane of gram-negative bacteria, is one of the links between the microbiome and hypercoagulability. LPS binds to toll-like receptors to activate endothelial cells and platelets, leading to activation of the coagulation cascade. Bacteria in the microbiome can also metabolite compounds in the diet to produce important metabolites like trimethylamine-N-oxide (TMAO). TMAO causes platelet hyperreactivity, promotes thrombus formation and is associated with cardiovascular disease. Modulating the gut microbiome to target LPS and TMAO levels may be an innovative approach for decreasing the risk of thrombosis.

TMEM173 Drives Lethal Coagulation in Sepsis

The discovery of TMEM173/STING-dependent innate immunity has recently provided guidance for the prevention and management of inflammatory disorders. Here, we show that myeloid TMEM173 occupies an essential role in regulating coagulation in bacterial infections through a mechanism independent of type I interferon response. Mechanistically, TMEM173 binding to ITPR1 controls calcium release from the endoplasmic reticulum in macrophages and monocytes. The TMEM173-dependent increase in cytosolic calcium drives Gasdermin D (GSDMD) cleavage and activation, which triggers the release of F3, the key initiator of blood coagulation. Genetic or pharmacological inhibition of the TMEM173-GSDMD-F3 pathway blocks systemic coagulation and improves animal survival in three models of sepsis (cecal ligation and puncture or bacteremia with Escherichia coli or Streptococcus pneumoniae infection). The upregulation of the TMEM173 pathway correlates with the severity of disseminated intravascular coagulation and mortality in patients with sepsis. Thus, TMEM173 is a key regulator of blood clotting during lethal bacterial infections.

Therapeutic strategies for thrombosis: new targets and approaches

Antiplatelet agents and anticoagulants are a mainstay for the prevention and treatment of thrombosis. However, despite advances in antithrombotic therapy, a fundamental challenge is the side effect of bleeding. Improved understanding of the mechanisms of haemostasis and thrombosis has revealed new targets for attenuating thrombosis with the potential for less bleeding, including glycoprotein VI on platelets and factor XIa of the coagulation system. The efficacy and safety of new agents are currently being evaluated in phase III trials. This Review provides an overview of haemostasis and thrombosis, details the current landscape of antithrombotic agents, addresses challenges with preventing thromboembolic events in patients at high risk and describes the emerging therapeutic strategies that may break the inexorable link between antithrombotic therapy and bleeding risk.

Ten Representative Saponins on Tissue Factor Expression in Human Monocytes: Structure–Activity Relationships and Molecular Docking

Saponins have significant bioactivities in treating cardiovascular disease. Whereas there is a lack of in-depth knowledge about how saponins prevent cardiovascular disease. Tissue factor (TF) is the major initiator of the coagulation cascade and plays an important role in hemostasis and thrombosis. However structure–activity relationships (SARs) of saponins inhibiting TF activity have not been discussed in detail at present. To further clarify the relationships between saponins and TF, in this study, 10 representative saponins were selected to study the inhibitory effect on TF procoagulant activity of monocytes by an improved chromogenic substrate method, and the possible SARs were preliminarily analyzed. Furthermore, molecular docking analysis suggested that 4 representative saponins had a good affinity with TF/FVIIa. In addition, a representative saponin, ruscogenin, decreased both messenger ribonucleic acid and protein levels of TF in human monocytes partly due to its downregulation of nuclear factor kappa-light-chain-enhancer of activated B cells and c-Jun N-terminal kinase pathways. In conclusion, this study provides further explanation for the cardiovascular protection of saponins, and the analysis of SARs between inhibiting TF activity and saponins will be helpful to explore the therapeutic TF inhibitors.

Thrombosis: Risk Factors Among Pediatric Patients With Cancer

BACKGROUND

Thrombosis is the formation of a blood clot, or thrombus, inside of a blood vessel. Pediatric patients with cancer are at a higher risk of developing a thrombus because of their underlying disease, as well as their treatment and supportive care. Thrombosis can lead to significant morbidity, such as pulmonary embolism, in pediatric patients with cancer.

OBJECTIVES

The purpose of this study is to identify risk factors for developing a thrombus among pediatric patients with cancer, along with treatment and prevention protocols. This study also examines the clinical nurse's role in preventing thrombosis and caring for pediatric patients who present with thrombosis.

METHODS

The thrombosis literature was reviewed to identify risk factors, treatment regimens, and strategies for prevention.

FINDINGS

Thrombosis in pediatric patients with cancer requires management of potential complications so that cancer treatment may continue.

Effect of blood flow on platelets, leukocytes, and extracellular vesicles in thrombosis of simulated neonatal extracorporeal circulation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) has frequent and sometimes lethal thrombotic complications. The role that activated platelets, leukocytes, and small (0.3-micron to 1-micron) extracellular vesicles (EVs) play in ECMO thrombosis is not well understood.

OBJECTIVES

To test the effect of blood flow rate on the generation of activated platelets, leukocytes, and EVs in a simulated neonatal ECMO circuit using heparinized human whole blood.

METHODS

Simulated neonatal roller pump circuits circulated whole blood at low, nominal, and high flow rates (0.3, 0.5, and 0.7 L/min) for 6 h. Coagulopathy was defined by thromboelastography (TEG), STA® -procoagulant phospholipid clot time (STA®- Procoag-PPL), and calibrated automated thrombogram. High-resolution flow cytometry measured the cellular expression of prothrombotic phospholipids and proteins on platelets, leukocytes, and EV.

RESULTS

Despite heparinization, occlusive thrombosis halted flow in two of five circuits at 0.3 L/min and three of five circuits at 0.7 L/min. None of the five circuits at 0.5 L/min exhibited occlusive thrombosis. Phosphatidylserine (PS)-positive platelets and EVs increased at all flow rates more than blood under static conditions (P < .0002). Tissue factor (TF)-positive leukocytes and EVs increased only in low-flow and high-flow circuits (P < .0001). Tissue factor pathway inhibitor (TFPI), at 50 times more than the concentration in healthy adults, failed to suppress thrombin initiation in low-flow and high-flow circuits.

CONCLUSIONS

This in vitro study informs ECMO specialists to avoid low and high blood flow that increases TF expression on leukocytes and EVs, which likely initiate clot formation. Interventions to decrease TF generated by ECMO may be an effective approach to decrease thrombosis.

Intrinsic Pathway of Coagulation and Thrombosis

Activation of the intrinsic pathway of coagulation contributes to the pathogenesis of arterial and venous thrombosis. Critical insights into the involvement of intrinsic pathway factors have been derived from the study of gene-specific knockout animals and targeted inhibitors. Importantly, preclinical studies have indicated that targeting components of this pathway, including FXI (factor XI), FXII, and PKK (prekallikrein), reduces thrombosis with no significant effect on protective hemostatic pathways. This review highlights the advances made from studying the intrinsic pathway using gene-specific knockout animals and inhibitors in models of arterial and venous thrombosis. Development of inhibitors of activated FXI and FXII may reduce thrombosis with minimal increases in bleeding compared with current anticoagulant drugs.

Tuning the Thromboinflammatory Response to Venous Flow Interruption by the Ectonucleotidase CD39

Objective- Leukocyte flux contributes to thrombus formation in deep veins under pathological conditions, but mechanisms that inhibit venous thrombosis are incompletely understood. Ectonucleotide di(tri)phosphohydrolase 1 ( ENTPD1 or Cd39), an ectoenzyme that catabolizes extracellular adenine nucleotides, is embedded on the surface of endothelial cells and leukocytes. We hypothesized that under venous stasis conditions, CD39 regulates inflammation at the vein:blood interface in a murine model of deep vein thrombosis. Approach and Results- CD39-null mice developed significantly larger venous thrombi under venous stasis, with more leukocyte recruitment compared with wild-type mice. Gene expression profiling of wild-type and Cd39-null mice revealed 76 differentially expressed inflammatory genes that were significantly upregulated in Cd39-deleted mice after venous thrombosis, and validation experiments confirmed high expression of several key inflammatory mediators. P-selectin, known to have proximal involvement in venous inflammatory and thrombotic events, was upregulated in Cd39-null mice. Inferior vena caval ligation resulted in thrombosis and a corresponding increase in both P-selectin and VWF (von Willebrand Factor) levels which were strikingly higher in mice lacking the Cd39 gene. These mice also manifest an increase in circulating platelet-leukocyte heteroaggregates suggesting heterotypic crosstalk between coagulation and inflammatory systems, which is amplified in the absence of CD39. Conclusions- These data suggest that CD39 mitigates the venous thromboinflammatory response to flow interruption.

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.

Fondaparinux pentasaccharide reduces sepsis coagulopathy and promotes survival in the baboon model of Escherichia coli sepsis

BACKGROUND

Sepsis triggers dysfunction of coagulation and fibrinolytic systems leading to disseminated intravascular coagulation (DIC) that contributes to organ failure and death. Fondaparinux (FPX) is a synthetic pentasaccharide that binds to antithrombin (AT) and selectively inhibits factor (F) Xa and other upstream coagulation proteases but not thrombin (T).

OBJECTIVES

We used a baboon model of lethal Escherichia coli sepsis to investigate the effects of FPX treatment on DIC, organ function, and outcome.

METHODS

Two experimental groups were studied: (a) E. coli challenge (n = 4); and (b) E coli plus FPX (n = 4). Bacteremia was modeled by intravenous infusion of pathogen (1-2 × 1010  CFU/kg). Fondaparinux (0.08 mg/kg) was administered subcutaneously, 3 h prior to and 8 h after bacteria infusion.

RESULTS

Bacteremia rapidly increased plasma levels of inhibitory complexes of AT with coagulation proteases. Activation markers of both intrinsic (FXIa-AT), and extrinsic (FVIIa-AT) pathways were significantly reduced in FPX-treated animals. Factor Xa-AT and TAT complexes were maximal at 4 to 8 h post challenge and reduced >50% in FPX-treated animals. Fibrinogen consumption, fibrin generation and degradation, neutrophil and complement activation, and cytokine production were strongly induced by sepsis. All parameters were significantly reduced, while platelet count was unchanged by the treatment. Fondaparinux infusion attenuated organ dysfunction, prolonged survival, and saved two of four challenged animals (log-rank Mantel-Cox test, P = .0067).

CONCLUSION

Our data indicate that FPX-mediated inhibition of coagulation prevents sepsis coagulopathy; protects against excessive complement activation, inflammation, and organ dysfunction; and provides survival benefit in E. coli sepsis.

Antithrombotic Therapy: Prevention and Treatment of Atherosclerosis and Atherothrombosis

Atherosclerosis is a multifactorial vascular disease that develops in the course of a lifetime. Numerous risk factors for atherosclerosis have been identified, mostly inflicting pro-inflammatory effects. Vessel injury, such as occurring during erosion or rupture of atherosclerotic lesions triggers blood coagulation, in attempt to maintain hemostasis (protect against bleeding). However, thrombo-inflammatory mechanisms may drive blood coagulation such that thrombosis develops, the key process underlying myocardial infarction and ischemic stroke (not due to embolization from the heart). In the blood coagulation system, platelets and coagulation proteins are both essential elements. Hyperreactivity of blood coagulation aggravates atherosclerosis in preclinical models. Pharmacologic inhibition of blood coagulation, either with platelet inhibitors, or better documented with anticoagulants, or both, limits the risk of thrombosis and may potentially reverse atherosclerosis burden, although the latter evidence is still based on animal experimentation.Patients at risk of atherothrombotic complications should receive a single antiplatelet agent (acetylsalicylic acid, ASA, or clopidogrel); those who survived an atherothrombotic event will be prescribed temporary dual antiplatelet therapy (ASA plus a P2Y12 inhibitor) in case of myocardial infarction (6-12 months), or stroke (<6 weeks), followed by a single antiplatelet agent indefinitely. High risk for thrombosis patients (such as those with peripheral artery disease) benefit from a combination of an anticoagulant and ASA. The price of gained efficacy is always increased risk of (major) bleeding; while tailoring therapy to individual needs may limit the risks to some extent, new generations of agents that target less critical elements of hemostasis and coagulation mechanisms are needed to maintain efficacy while reducing bleeding risks.

Inhibition of Platelet Adhesion from Surface Modified Polyurethane Membranes

Coronary thrombosis is one of the leading causes of mortality and morbidity in cardiovascular diseases, and patients who received vascular stent treatments are likely to suffer from restenosis due to tissue damage from stenting procedures (extrinsic pathway) and/or presence of unregulated factor XII (intrinsic pathway). Regardless of the pathway, coagulation factors and exposed collagen activate the G-protein-coupled receptors located at the plasma membrane of the resting platelets resulting in the change of their shapes with protrusions of filopodia and lamellipodia for surface adhesion. In this mini review, we discussed the mechanisms involved in platelet activation, adhesion, and aggregation. More importantly, we reviewed the use of polyurethane membranes with modified surface functional groups to down-regulate platelet adhesion and aggregation activities. Polyurethane membranes with hydrophilic and negatively charged surface properties showed a reduced αIIb-β3 signaling from the activated platelets, resulting in the decrease of platelet adhesion and aggregation. The use of polyurethane membranes with modified surface properties as coatings on vascular stents provides an engineering approach to mitigate blood clotting associated with restenosis.

Bacterial Endotoxin Activates the Coagulation Cascade through Gasdermin D-Dependent Phosphatidylserine Exposure

Excessive activation of the coagulation system leads to life-threatening disseminated intravascular coagulation (DIC). Here, we examined the mechanisms underlying the activation of coagulation by lipopolysaccharide (LPS), the major cell-wall component of Gram-negative bacteria. We found that caspase-11, a cytosolic LPS receptor, activated the coagulation cascade. Caspase-11 enhanced the activation of tissue factor (TF), an initiator of coagulation, through triggering the formation of gasdermin D (GSDMD) pores and subsequent phosphatidylserine exposure, in a manner independent of cell death. GSDMD pores mediated calcium influx, which induced phosphatidylserine exposure through transmembrane protein 16F, a calcium-dependent phospholipid scramblase. Deletion of Casp11, ablation of Gsdmd, or neutralization of phosphatidylserine or TF prevented LPS-induced DIC. In septic patients, plasma concentrations of interleukin (IL)-1α and IL-1β, biomarkers of GSDMD activation, correlated with phosphatidylserine exposure in peripheral leukocytes and DIC scores. Our findings mechanistically link immune recognition of LPS to coagulation, with implications for the treatment of DIC.

Ageing enhances the shedding of splenocyte microvesicles with endothelial pro-senescent effect that is prevented by a short-term intake of omega-3 PUFA EPA:DHA 6:1

BACKGROUND

Ageing is associated with progressive endothelial senescence and dysfunction, and cardiovascular risk. Circulating endothelial microvesicles (MVs) are pro-senescent and pro-inflammatory endothelial effectors in acute coronary syndrome. Omega-3 PUFA intake was claimed beneficial in cardiovascular prevention.

PURPOSE

To investigate whether the intake of the omega-3 formulation EPA:DHA 6:1 by middle-aged and old rats reduces the shedding of pro-senescent microvesicles from cultured spleen leukocytes (SMVs) and clarify the underlying mechanisms in target coronary primary endothelial cells (ECs).

METHODS

Middle-aged male Wistar rats (M, 48-week old) received 500 mg/kg/d of either EPA:DHA 6:1, EPA:DHA 1:1, or vehicle (CTL) for 7 days, old rats (72-week old) for 14 days. Spleen-derived leukocytes were prepared and cultured for 24 h and MVs collected from supernatants (SMVs). Cultured ECs were prepared from freshly isolated porcine coronary arteries. Senescence-associated β-galactosidase activity (SA-β-gal) was assessed by C12FDG, protein expression by Western blot analysis, oxidative stress by dihydroethidium using confocal microscopy, and procoagulant MVs by prothrombinase assay. The pro-senescent potential of SMVs from middle-aged rats (M-SMVs) was analyzed by comparison with young (Y, 12-week) and old (O) rats.

RESULTS

The shedding of SMVs significantly increased with age and was inhibited by EPA:DHA 6:1 intake that also prevented ROS accumulation in spleen. Incubation of ECs with 10 nM SMVs from middle-aged and old but not those from young rats induced premature senescence after 48 h. The pro-senescent effect of M-SMVs was prevented by Losartan and associated with endothelial oxidative stress. M-SMVs induced an up-regulation of senescence markers (p16, p21, p53), pro-atherothrombotic (VCAM-1, ICAM-1, tissue factor) and pro-inflammatory markers (pNF-κB, COX-2) and proteins of the angiotensin system (ACE, AT1-R). Conversely, endothelial NO synthase was down-regulated. Intake of EPA:DHA 1:1 and 6:1 by middle-aged rats decreased SMV shedding by 14% and 24%, respectively. Only EPA:DHA 6:1 intake abolished the M-SMVs-induced endothelial senescence and reduced the pro-senescent action of O-SMVs by 45%. Protection of ECs was not observed in response to SMVs from EPA:DHA 1:1 treated rats.

CONCLUSION

Ingestion of EPA:DHA 6:1 by middle-aged or old rats, respectively abolished or limited both the shedding of SMVs and their pro-senescent, pro-thrombotic and pro-inflammatory effects in ECs, most likely by triggering the local angiotensin system. EPA:DHA 6:1 may help to delay ageing-related endothelial dysfunction.

Electrochemical sandwich-type thrombin aptasensor based on dual signal amplification strategy of silver nanowires and hollow Au-CeO2

Signal amplification is crucial in electrochemical biosensor to obtain low detection limits. In this work, a highly sensitive sandwich-type thrombin aptasensor is constructed, based on dual signal amplification of uniform silver nanowires (AgNWs) and hollow Au-CeO₂ nanocomposites. AgNWs are decorated on the ITO surface to immobilize amino functionalized thrombin capture apemeter 1 (Apt1). And Au nanoparticles (AuNPs) grown directly on the surface of hollow CeO₂ microstructure are used to immobilize sulfydryl functionalized thrombin reporter apemeter 2 (Apt2). Thus, sandwich-type apatasensor has been successfully designed, due to the specific recognition between thrombin and the two kinds of aptamers. One of the signal amplifications is from the good conductivity of uniform AgNWs. Moreover, uniform AgNWs together with hollow Au-CeO₂ exhibit the good catalytic performance for the reduction of H₂O₂, further resulting in significant electrochemical signal amplification. Because the electrochemical signal amplification is closely related to the thrombin concentration, differential pulse voltammetry is used to specifically detect thrombin. Under the optimized conditions, the proposed method has a good linear response ranged from 0.5 pM to 30 nM with a low detection limit of 0.25 pM (S/N = 3) for thrombin. The proposed thrombin aptasensor displays good selectivity, reproducibility and stability, providing a good platform for the ultrasensitive detection of thrombin.

Toll-like receptors 2 and 7 mediate coagulation activation and coagulopathy in murine sepsis

BACKGROUND

Sepsis is a life-threatening condition often manifested as marked inflammation and severe coagulopathy. Toll-like receptors (TLRs) play a pivotal role in inflammation, organ dysfunction and mortality in animal sepsis.

OBJECTIVES

To investigate the role of TLR signaling in mediating sepsis-induced coagulopathy (SIC) in a mouse model.

METHODS

Polymicrobial sepsis was created by cecal ligation and puncture (CLP) or fecal slurry peritoneal injection. To quantify global clotting function, two viscoelastic assays were performed with rotational thromboelastometry, and the results were presented as maximum clot firmness (MCF): (a) EXTEM to test tissue factor (TF)-initiated clot formation; and (b) FIBTEM to test EXTEM in the presence of a platelet inhibitor, cytochalasin D. Plasma coagulation factors were quantified with ELISA. TF gene expression and protein expression were determined with real-time quantitative reverse transcription PCR and flow cytometry, respectively.

RESULTS

Between 4 and 24 hours after CLP surgery, wild-type mice showed significant MCF reduction in both EXTEM and FIBTEM tests. This was accompanied by marked thrombocytopenia and a significant increase in the levels of plasminogen activator inhibitor-1, plasma TF, and D-dimer. In comparison, TLR2-/- and TLR7-/- CLP mice showed preserved MCF and platelet counts, and near-normal plasma TF levels. Bone marrow-derived macrophages treated with a TLR2 agonist Pam3cys-Ser-(Lys)4 (Pam3cys) or a TLR7 agonist (R837) showed marked increases in TF gene expression and protein expression. MicroRNA-146a, a newly identified proinflammatory mediator that is upregulated during sepsis, induced TF production via a TLR7-dependent mechanism.

CONCLUSIONS

Murine sepsis leads to an increased procoagulant response, thrombocytopenia, and global coagulopathy. TLR2 and TLR7 play an important role in procoagulant production and in SIC.

Role of tissue factor in the procoagulant and antibacterial effects of human adipose-derived mesenchymal stem cells during pneumosepsis in mice

Background

Adult mesenchymal stem cells (MSCs) improve the host response during experimental sepsis in animals. MSCs from various sources express a procoagulant activity that has been linked to the expression of tissue factor. This study sought to determine the role of tissue factor associated with adipose-derived MSCs (ASCs) in their procoagulant and antibacterial effects during pneumonia-derived sepsis.

Methods

Mice were infused intravenously with ASCs or vehicle after infection with the common human pathogen Klebsiella pneumoniae via the airways.

Results

Infusion of freshly cultured or cryopreserved ASCs induced the expression of many genes associated with tissue factor signaling and coagulation activation in the lungs. Freshly cultured and cryopreserved ASCs, as well as ASC lysates, exerted procoagulant activity in vitro as determined by a fibrin generation assay, which was almost completely inhibited by an anti-tissue factor antibody. Infusion of cryopreserved ASCs was associated with a rise in plasma thrombin-antithrombin complexes (indicative of coagulation activation) and formation of multiple thrombi in the lungs 4 h post-infusion. Preincubation of ASCs with anti-tissue factor antibody prior to infusion prevented the rise in plasma thrombin-antithrombin complex concentrations but did not influence thrombus formation in the lungs. ASCs reduced bacterial loads in the lungs and liver at 48 h after infection, which was not influenced by preincubation with anti-tissue factor antibody. At this late time point, microthrombi in the lungs were not detected anymore.

Conclusion

These data indicate that ASC-associated tissue factor is responsible for systemic activation of coagulation after infusion of ASCs but not for the formation of microthrombi in the lungs or antibacterial effects.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1391-x) contains supplementary material, which is available to authorized users.

Platelet P-selectin triggers rapid surface exposure of tissue factor in monocytes

Tissue factor (TF) plays a central role in haemostasis and thrombosis. Following vascular damage, vessel wall TF initiates the extrinsic coagulation cascade. TF can also be exposed by monocytes. Inflammatory or infectious stimuli trigger synthesis of new TF protein by monocytes over the course of hours. It has also been suggested that monocytes can expose TF within minutes when stimulated by activated platelets. Here, we have confirmed that monocytes rapidly expose TF in whole blood and further demonstrate that platelet P-selectin exposure is necessary and sufficient. Monocyte TF exposure increased within five minutes in response to platelet activation by PAR1-AP, PAR4-AP or CRP-XL. PAR1-AP did not trigger TF exposure on isolated monocytes unless platelets were also present. In whole blood, PAR1-AP-triggered TF exposure required P-selectin and PGSL-1. In isolated monocytes, although soluble recombinant P-selectin had no effect, P-selectin coupled to 2 µm beads triggered TF exposure. Cycloheximide did not affect rapid TF exposure, indicating that de novo protein synthesis was not required. These data show that P-selectin on activated platelets rapidly triggers TF exposure on monocytes. This may represent a mechanism by which platelets and monocytes rapidly contribute to intravascular coagulation.

Assessment of PON1 activity and circulating TF levels in relation to BMI, testosterone, HOMA-IR, HDL-C, LDL-C, CHO, SOD activity and TAC in women with PCOS: An observational study

BACKGROUND

Polycystic Ovary Syndrome (PCOS) is the most common female endocrinopathy among premenopausal women associated with hyperandrogenism, obesity, dyslipidemia, insulin resistance and inflammation. Oxidative stress is an important component of cardio-metabolic risk seen in PCOS.

MATERIAL AND METHODS

A total of 95 women with PCOS and 95 healthy controls were included in this observational study. Serum PON1 activity and stress markers were measured by spectrophotometric methods. Circulating TF level was measured by ELISA.

RESULTS

We found decreased PON1 activity and increased TF levels in women with PCOS compared to healthy controls. Fasting insulin, HOMA-IR, testosterone, LDL-C, MDA, PC and SOD activity were significantly increased whereas FGIR, QUICKI, HDLC, CAT and TAC were significantly decreased in PCOS women than controls. We observed a positive association of PON1 activity with FGIR, QUICKI, HDL-C and TAC, and its negative association was observed with LH, testosterone, fasting insulin and HOMA-IR in PCOS women. We further observed a positive association of TF with waist, waist to hip ratio, BMI, glucose 1hr, cholesterol, LDL-C, SGPT, uric acid and SOD activity in PCOS women.

CONCLUSIONS

Decreased PON1 activity and raised circulating TF levels are respective indicators of pro-inflammatory and procoagulant status in PCOS women. The imbalanced oxidant/antioxidant status further supports the evidences that PCOS is an oxidant state. Further, the association of PON1 activity and TF levels with the clinical, laboratory findings and stress marker levels suggest that these factors taken together are involved in aggravating the pro-inflammatory status in PCOS women.

Tissue factor pathway inhibitor primes monocytes for antiphospholipid antibody-induced thrombosis

Antiphospholipid antibodies (aPLs) with complex lipid and/or protein reactivities cause complement-dependent thrombosis and pregnancy complications. Although cross-reactivities with coagulation regulatory proteins contribute to the risk for developing thrombosis in patients with antiphospholipid syndrome, the majority of pathogenic aPLs retain reactivity with membrane lipid components and rapidly induce reactive oxygen species-dependent proinflammatory signaling and tissue factor (TF) procoagulant activation. Here, we show that lipid-reactive aPLs activate a common species-conserved TF signaling pathway. aPLs dissociate an inhibited TF coagulation initiation complex on the cell surface of monocytes, thereby liberating factor Xa for thrombin generation and protease activated receptor 1/2 heterodimer signaling. In addition to proteolytic signaling, aPLs promote complement- and protein disulfide isomerase-dependent TF-integrin β1 trafficking that translocates aPLs and NADPH oxidase to the endosome. Cell surface TF pathway inhibitor (TFPI) synthesized by monocytes is required for TF inhibition, and disabling TFPI prevents aPL signaling, indicating a paradoxical prothrombotic role for TFPI. Myeloid cell-specific TFPI inactivation has no effect on models of arterial or venous thrombus development, but remarkably prevents experimental aPL-induced thrombosis in mice. Thus, the physiological control of TF primes monocytes for rapid aPL pathogenic signaling and thrombosis amplification in an unexpected crosstalk between complement activation and coagulation signaling.

Direct Amplification of Tissue Factor:Factor VIIa Procoagulant Activity by Bile Acids Drives Intrahepatic Coagulation

OBJECTIVE

Regulation of TF (tissue factor):FVIIa (coagulation factor VIIa) complex procoagulant activity is especially critical in tissues where plasma can contact TF-expressing cells. One example is the liver, where hepatocytes are routinely exposed to plasma because of the fenestrated sinusoidal endothelium. Although liver-associated TF contributes to coagulation, the mechanisms controlling the TF:FVIIa complex activity in this tissue are not known. Approach and Results: Common bile duct ligation in mice triggered rapid hepatocyte TF-dependent intrahepatic coagulation coincident with increased plasma bile acids, which occurred at a time before observable liver damage. Similarly, plasma TAT (thrombin-antithrombin) levels increased in cholestatic patients without concurrent hepatocellular injury. Pathologically relevant concentrations of the bile acid glycochenodeoxycholic acid rapidly increased hepatocyte TF-dependent procoagulant activity in vitro, independent of de novo TF synthesis and necrotic or apoptotic cell death. Glycochenodeoxycholic acid increased hepatocyte TF activity even in the presence of the phosphatidylserine-blocking protein lactadherin. Interestingly, glycochenodeoxycholic acid and taurochenodeoxycholic acid increased the procoagulant activity of the TF:FVIIa complex relipidated in unilamellar phosphatidylcholine vesicles, which was linked to an apparent decrease in the K_m for FX (coagulation factor X). Notably, the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, a bile acid structural analog, did not increase relipidated TF:FVIIa activity. Bile acids directly enhanced factor X activation by recombinant soluble TF:FVIIa complex but had no effect on FVIIa alone.

CONCLUSIONS

The results indicate that bile acids directly accelerate TF:FVIIa-driven coagulation reactions, suggesting a novel mechanism whereby elevation in a physiological mediator can directly increase TF:FVIIa procoagulant activity.

Platelets and Immune Responses During Thromboinflammation

Besides mediating hemostatic functions, platelets are increasingly recognized as important players of inflammation. Data from experiments in mice and men revealed various intersection points between thrombosis, hemostasis, and inflammation, which are addressed and discussed in this review in detail. One such example is the intrinsic coagulation cascade that is initiated after platelet activation thereby further propagating and re-enforcing wound healing or thrombus formation but also contributing to the pathophysiology of severe diseases. FXII of the intrinsic pathway connects platelet activation with the coagulation cascade during immune reactions. It can activate the contact system thereby either creating an inflammatory state or accelerating inflammation. Recent insights into platelet biology could show that platelets are equipped with complement receptors. Platelets are important for tissue remodeling after injury has been inflicted to the endothelial barrier and to the subendothelial tissue. Thus, platelets are increasingly recognized as more than just cells relevant for bleeding arrest. Future insights into platelet biology are to be expected. This research will potentially offer novel opportunities for therapeutic intervention in diseases featuring platelet abundance.

Neutrophil extracellular traps and fibrocytes in ST-segment elevation myocardial infarction

Leukocyte-mediated inflammation is central in atherothrombosis and ST-segment elevation myocardial infarction (STEMI). Neutrophil extracellular traps (NETs) have been shown to enhance atherothrombosis and stimulate fibroblast function. We analyzed the effects of NETs on cardiac remodeling after STEMI. We measured double-stranded (ds)DNA and citrullinated histone H3 (citH3) as NET surrogate markers in human culprit site and femoral blood collected during primary percutaneous coronary intervention (n = 50). Fibrocytes were characterized in whole blood by flow cytometry, and in culprit site thrombi and myocardium by immunofluorescence. To investigate mechanisms of fibrocyte activation, isolated NETs were used to induce fibrocyte responses in vitro. Enzymatic infarct size was assessed using creatine-phosphokinase isoform MB area under the curve. Left ventricular function was measured by transthoracic echocardiography. NET surrogate markers were increased at the culprit site compared to the femoral site and were positively correlated with infarct size and left ventricular dysfunction at follow-up. In vitro, NETs promoted fibrocyte differentiation from monocytes and induced fibrocyte activation. Highly activated fibrocytes accumulated at the culprit site and in the infarct transition zone. Our data suggest that NETs might be important mediators of fibrotic remodeling after STEMI, possibly by stimulating fibrocytes.

Anticoagulant effect of wogonin against tissue factor expression

Tissue factor (TF) is the primary cause of atherothrombosis, the rupture of atherosclerotic plaques with subsequent thrombosis, leading to acute cardiovascular events, such as myocardial infarction and stroke. Wogonin (Wog) is an active component of Scutellaria baicalensis, used for inflammatory diseases, atherosclerosis, and hyperlipidemia. The anticoagulant effect of Wog on TF expression remains unexplored. In this study, we have investigated the effects of Wog on TF gene expression and its underlying molecular mechanism in human vascular endothelial cells (ECs). We found that Wog dose-dependently inhibited PMA-enhanced TF mRNA, protein, and activity in ECs. This inhibition was attributed to its decreasing nuclear accumulations of transcription factors, phospho-c-Jun and early growth response-1(Egr-1), not nuclear factor-κB (NF-κB), through blocking extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling pathways. Reduction by Wog of Egr-1 nuclear level and Egr-1/DNA binding activity was associated with its inhibition of Egr-1 de novo synthesis. Wog as well as inhibitors to ERK and JNK suppressed TF promoter activity and protein expression in reporter gene and Western blot analyses. Furthermore, it also exhibited anticoagulant function by inhibiting TF expression and activity in tumor necrosis factor-alpha (TNF-α)- and lipopolysaccharide (LPS)-treated ECs and THP-1 cells. These results suggest that Wog inhibits ERK/Egr-1- and JNK/AP-1-mediated transactivation of TF promoter activity, leading to downregulation of TF expression and activity induced by inflammatory mediators. Wog targeting pathological TF expression without affecting its basal level may be a safer templet in the development of anticoagulant agent for cardiovascular thrombotic diseases related to atherothrombosis.