Extracellular Vesicle Tissue Factor Research Articles

Thrombin-mediated activation of PAR1 enhances doxorubicin-induced cardiac injury in mice.

The chemotherapeutic drug doxorubicin is cardiotoxic and can cause irreversible heart failure. In addition to being cardiotoxic, doxorubicin also induces the activation of coagulation. We determined the effect of thrombin-mediated activation of protease-activated receptor 1 (PAR1) on doxorubicin-induced cardiac injury. Administration of doxorubicin to mice resulted in a significant increase in plasma prothrombin fragment 1+2, thrombin-antithrombin complexes, and extracellular vesicle tissue factor activity. Doxorubicin-treated mice expressing low levels of tissue factor, but not factor XII-deficient mice, had reduced plasma thrombin-antithrombin complexes compared to controls. To evaluate the role of thrombin-mediated activation of PAR1, transgenic mice insensitive to thrombin (Par1R41Q) or activated protein C (Par1R46Q) were subjected to acute and chronic models of doxorubicin-induced cardiac injury and compared with Par1 wild-type (Par1+/+) and PAR1 deficient (Par1-/-) mice. Par1R41Q and Par1-/- mice, but not Par1R46Q mice, demonstrated similar reductions in the cardiac injury marker cardiac troponin I, preserved cardiac function, and reduced cardiac fibrosis compared to Par1+/+ controls after administration of doxorubicin. Furthermore, inhibition of Gαq signaling downstream of PAR1 with the small molecule inhibitor Q94 significantly preserved cardiac function in Par1+/+ mice, but not in Par1R41Q mice subjected to the acute model of cardiac injury when compared to vehicle controls. In addition, mice with PAR1 deleted in either cardiomyocytes or cardiac fibroblasts demonstrated reduced cardiac injury compared to controls. Taken together, these data suggest that thrombin-mediated activation of PAR1 contributes to doxorubicin-induced cardiac injury.

Tissue factor release following traumatic brain injury drives thrombin generation

BackgroundTraumatic brain injury (TBI) results in neurovascular damage that initiates intrinsic mechanisms of hypercoagulation, which can contribute to the development of life‐threatening complications, such as coagulopathy and delayed thrombosis. Clinical studies have hypothesized that tissue factor (TF) induces hypercoagulability after TBI; however, none have directly shown this relationship. ObjectivesIn the current study, we took a stepwise approach to understand what factors are driving thrombin generation following experimental TBI. MethodsWe employed the contusion‐producing controlled cortical impact (CCI) model and the diffuse closed head injury (CHI) model to investigate these mechanisms as a function of injury severity and modality. Whole blood was collected at 6 hours and 24 hours after injury, and platelet‐poor plasma was used to measure thrombin generation and extracellular vesicle (EV) TF. ResultsWe found that plasma thrombin generation, dependent on TF present in the plasma, was greater in CCI‐injured animals compared to sham at both 6 hours (120.4 ± 36.9 vs 0.0 ± 0.0 nM*min endogenous thrombin potential) and 24 hours (131.0 ± 34.0 vs 32.1 ± 20.6 nM*min) after injury. This was accompanied by a significant increase in EV TF at 24 hours (328.6 ± 62.1 vs 167.7 ± 20.8 fM) after CCI. Further, EV TF is also increased at 6 hours (126.6 ± 17.1 vs 63.3 ± 14.4 fM) but not 24 hours following CHI. ConclusionTF‐mediated thrombin generation is time‐dependent after injury and TF increases resolve earlier following CHI as compared to CCI. Taken together, these data support a TF‐mediated pathway of thrombin generation after TBI and pinpoint TF as a major player in TBI‐induced coagulopathy. [Display omitted] [Display omitted]

In Covid-19 Infection, Plasma Extracellular Vesicle Tissue Factor Activity Does Not Correlate with D-Dimer Levels

Objective: Identify a plasma-based activity, or biomarker, that defines the mechanism(s) by which Covid-19 disease triggers excessive coagulation.Introduction: While acute respiratory syndrome is the fundamental feature of severe Covid-19 disease, having a high level of the coagulation biomarker D-dimer upon admission is associated with increased thrombosis and mortality. As such, hospitalized patients are often placed on anticoagulant heparins. How Covid-19 triggers excessive coagulation is unresolved. Sars-CoV-2 infection could expose existing tissue factor (TF) to blood or, via cytokines, induce TF expression on cells that are in direct contact with blood. Extracellular vesicles (EV) are lipid bound microparticles released by all types of healthy and damaged cell and Covid-19 patient plasma EV TF activity has been recently reported. Cellular activation and damage due to SARS-CoV-2 could also release polyanionic nucleic acids and polyphosphates and generate neutrophil extracellular traps as contact surfaces for clot formation.Methods:Study 1. We attempted to identify excessive coagulation pathway activities in Covid-19 plasma-based, Ca++-induced thrombin generation assays. Assays were performed in the absence and presence of selective extrinsic (TF) and intrinsic (contact activation) pathway inhibitors (n=296 plasma samples). D-dimer levels were also determined. In a smaller study, Covid-19 patient samples were collected directly into citrate or citrate plus corn trypsin inhibitor, then processed for analysis.Study 2. We conducted studies to evaluate the extent to which EV TF activity contributes to the Covid-19-associated coagulopathies. Plasma EVs were isolated and EV TF activity determined by the difference in FXa activity in the absence vs presence of anti-TF antibody. D-dimer and tissue factor pathway inhibitor a (TFPIa) antigen levels were measured. Data from 232 samples collected from 96 Covid-19 positive patients and 18 samples from 14 healthy controls were analyzed. For each study analysis, patient samples were organized into groups based on the disease severity outcomes as follows: hospitalization (Hospitalization; n=37); intensive care (ICU; n=16); mechanical ventilation (Ventilation; n=22); or fatality (Deceased; n=22).Result:Study 1. Covid-19 samples showed considerable thrombin generation variability with some samples failing to generate thrombin; pathway selective inhibitors reduced thrombin generation while heparinase treatment increased thrombin generation. Upon analysis, thrombin generation parameters showed no significant correlations to either D-dimer levels or disease severity. Instead, plasma prepared from blood collected directly into corn trypsin inhibitor revealed that contact activation that occurred post-sample collection dominates procoagulant activity.Study 2. Figure 1, shows EV TF activities, D-dimer and TFPIα levels obtained for Covid-19 samples, with data segregated based on disease severity outcomes. Statistically significant difference versus the Hospitalized group are shown. TFPIa levels were highest in heparin IV patients (24.4+1.5 nM) vs Heparin-SQ (12.8+0.9 nM) vs enoxaparin (10.8 +0.7 nM) (p value:<0.0001). It is known that heparin treatment increases circulating TFPIα, however an increase in TFPIα might also further increase circulating TF/FVIIa/XaTFPI inhibitory complex, which would dissociate in citrated plasma, and might account for the increase in EV TF in other studies.Conclusions: Contact activation that occurs post-sample collection is sufficient to obscure endogenous triggers of coagulation, if present, in Covid-19 patients' plasma. D-dimer and TFPIα strongly correlate with disease severity although the latter is likely affected by heparin treatment. The most severe Covid-19 patients with high D-dimer did not show detectible plasma EV TF activity. Plasma EV TF activity does not appear to adequately represent the mechanism responsible for elevated D-dimer levels in Covid-19 cases. [Display omitted] DisclosuresDi Paola: CSL Behring: Consultancy, Honoraria.

Comparison of the coagulopathies associated with COVID‐19 and sepsis

BackgroundCoronavirus disease 2019 (COVID‐19) is associated with activation of coagulation that mainly presents as thrombosis. Sepsis is also associated with activation of coagulation that mainly presents as disseminated intravascular coagulation. Many studies have reported increased levels of plasma D‐dimer in patients with COVID‐19 that is associated with severity, thrombosis, and mortality. ObjectivesThe aim of this study was to compare levels of circulating extracellular vesicle tissue factor (EVTF) activity and active plasminogen activator inhibitor 1 (PAI‐1) in plasma from patients with COVID‐19 or sepsis. MethodsWe measured levels of D‐dimer, EVTF activity, and active PAI‐1 in plasma samples from patients with COVID‐19 (intensive care unit [ICU], N = 15; and non‐ICU, N = 20) and patients with sepsis (N = 35). ResultsPatients with COVID‐19 had significantly higher levels of D‐dimer, EVTF activity, and active PAI‐1 compared with healthy controls. Patients with sepsis had significantly higher levels of D‐dimer and EVTF activity compared with healthy controls. Levels of D‐dimer were significantly lower in patients with COVID‐19 compared with patients with sepsis. Levels of EVTF activity were significantly higher in ICU patients with COVID‐19 compared with patients with sepsis. Levels of active PAI‐1 were significantly higher in patients with COVID‐19 compared with patients with sepsis. ConclusionsHigh levels of both EVTF activity and active PAI‐1 may promote thrombosis in patients with COVID‐19 due to simultaneous activation of coagulation and inhibition of fibrinolysis. The high levels of active PAI‐1 in patients with COVID‐19 may limit plasmin degradation of crosslinked fibrin and the release of D‐dimer. This may explain the lower levels of D‐dimer in patients with COVID‐19 compared with patients with sepsis.

Patients With COVID-19 Have Elevated Levels of Circulating Extracellular Vesicle Tissue Factor Activity That Is Associated With Severity and Mortality-Brief Report.

Patients with coronavirus disease 2019 (COVID-19) have a high rate of thrombosis. We hypothesized that severe acute respiratory syndrome coronavirus 2 infection leads to induction of TF (tissue factor) expression and increased levels of circulating TF-positive extracellular vesicles (EV) that may drive thrombosis. Approach and Results: We measured levels of plasma EV TF activity in 100 patients with COVID-19 with moderate and severe disease and 28 healthy controls. Levels of EV TF activity were significantly higher in patients with COVID-19 compared with controls. In addition, levels of EV TF activity were associated with disease severity and mortality. Finally, levels of EV TF activity correlated with several plasma markers, including D-dimer, which has been shown to be associated with thrombosis in patients with COVID-19. Our results indicate that severe acute respiratory syndrome coronavirus 2 infection induces the release of TF-positive EVs into the circulation that are likely to contribute to thrombosis in patients with COVID-19. EV TF activity was also associated with severity and mortality.

Circulating Extracellular Vesicle Tissue Factor Activity in Chuvash Erythrocytosis

Background:Chuvash erythrocytosis (CE), an inherited autosomal recessive disease endemic to Russia's mid-Volga River region, is caused by a germlineVHLC598T mutation (encoding VHLR200W) that alters oxygen sensing (PMID: 12415268). VHLR200W protein displays impaired degradation of hypoxia inducible transcription factor (HIF)-α subunits leading to increased HIF-1 and HIF-2 in normoxia and increased transcription of many HIF-regulated genes including erythropoietin (PMID: 14726398). CE patients have increased risk of venous and arterial thromboses, which are the major cause of morbidity and mortality (PMID:28104701). Thrombosis occurs despite lower blood pressure, body mass index and white blood cells compared to controls and is not related to the elevation in hematocrit but is increased in patients treated with phlebotomy therapy (PMID: 31289208). We have shown by microarray analysis of CE peripheral blood mononuclear cells modestly increased expression of several HIF-regulated pro-thrombotic genes at false discovery rate &amp;lt;0.05, includingIL1B(encoding interleukin-1beta),THBS1(thrombospondin-1),EGR1(early growth response 1),NLRP3,ITGA2B(integrin alpha-IIb),SERPINE1(plasminogen activator inhibitor-1) andF3(tissue factor) (PMID: 23993337). TF is a primary initiator of coagulation that binds factor VII/VIIa. The TF/factor VIIa complex catalyzes the conversion of inactive protease factor X to active protease factor Xa, leading to thrombin and thrombus formation (PMID: 19923557). EV-TF is barely detectable under basal circumstances but in disease states such as cardiovascular disease, sickle cell disease and cancer it derives from monocytes, endothelial cells, vascular smooth muscle cells and tumor cells (PMIDs: 20690821, 12805058, 17166244, 14988149, 26916302). Granulocytes of patients with polycythemia vera and essential thrombocytopenia expressF3as assessed by RT-qPCR (PMID: 32203583). Because of the central role of tissue factor in initiating the extrinsic pathway of coagulation, we set up to determine if extracellular vesicle associated tissue factor activity (EV-TF) could be detected in the plasma of CE patients. Methods:EightVHLC598T homozygotes and 6VHLwild type controls from Cheboksary, Chuvashia, Russia were studied as outpatients under basal circumstances. Blood was collected from these participants by venipuncture into vacutainer tubes containing 0.129 M sodium citrate. Immediately after venipuncture, platelet free plasma (PFP) was prepared by two rounds of centrifugation at 2,500 × g for 15 minutes at room temperature and EVs were isolated from PFP by centrifugation at 20,000 g for 15 minutes at 4 ºC. EV-TF was measured in duplicate by a two-stage Factor Xa generation assay with and without anti-TF antibody using Innovin (Siemens Healthcare Diagnostics) as a standard (PMID: 30656275). We also isolated granulocyte mRNA from 3 of the patients and 2 of the controls at a different time point and measured F3 transcripts by RT-qPCR. Results:We detected EV-TF in 4 of 8 CE patients but in no wild type controls (one-sided P = 0.043). The range of 0.45 to 1.25 pg/ml is similar to the range recently reported in US patients with cancer (PMID: 32548563). MCHC tended to be lower among 4 CE patients with detectable EV-TF than 4 without (one-sided P = 0.12), but this was not the case for serum ferritin. We also detectedF3transcripts in granulocytes, and these levels were higher in the 3 patients than the 2 controls that we analyzed (one-sided P = 0.12). Furthermore,F3mRNA correlated with plasma EV-TF in these five subjects (Spearman rho = 0.71, one-sided P &amp;lt; 0.05). As previously reported, CE patients had higher hemoglobin, hematocrit and red blood cells and lower platelets compared to controls (PMID: 14726398). They also had lower values for serum ferritin and mean corpuscular hemoglobin concentration (MCHC) suggesting iron deficiency, likely induced by phlebotomy therapy or by the presence of gastritis, which is increased in CE. Discussion:The presence of EV-TF in the plasma of 4 out of 8 CE patients and none of six controls, and increasedF3transcripts in CE granulocytes, may point to a potential thrombogenic role, although none of the CE patients in this study had a history of thrombosis. Further studies on larger numbers of patients are warranted to confirm these findings and to clarify the potential role of EV-TF in thrombosis in CE. *NM, JTP &amp; VRG contributed equally Figure Disclosures Gordeuk: CSL Behring:Consultancy, Research Funding;Ironwood:Research Funding;Imara:Research Funding;Global Blood Therapeutics:Consultancy, Research Funding;Novartis:Consultancy.

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

IntroductionWe 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 MethodsWe 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 ConclusionsIn 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.

Circulating Extracellular Vesicle Tissue Factor Activity During Orthohantavirus Infection Is Associated With Intravascular Coagulation.

Background Puumala orthohantavirus (PUUV) causes hemorrhagic fever with renal syndrome (HFRS). Patients with HFRS have an activated coagulation system with increased risk of disseminated intravascular coagulation (DIC) and venous thromboembolism (VTE). The aim of the study was to determine whether circulating extracellular vesicle tissue factor (EVTF) activity levels associates with DIC and VTE (grouped as intravascular coagulation) in HFRS patients.MethodsLongitudinal samples were collected from 88 HFRS patients. Patients were stratified into groups of those with intravascular coagulation (n = 27) and those who did not (n = 61). We measured levels of circulating EVTF activity, fibrinogen, activated partial prothrombin time, D-dimer, tissue plasminogen activator (tPA), plasminogen activator inhibitor 1 (PAI-1), and platelets.ResultsPlasma EVTF activity was transiently increased during HFRS. Levels of EVTF activity were significantly associated with plasma tPA and PAI-1, suggesting that endothelial cells could be a potential source. Patients with intravascular coagulation had significantly higher peak EVTF activity levels compared with those who did not, even after adjustment for sex and age. The peak EVTF activity value predicting intravascular coagulation was 0.51 ng/L with 63% sensitivity and 61% specificity with area under the curve = 0.63 (95% confidence interval, 0.51–0.76) and P = .046.ConclusionsPlasma EVTF activity during HFRS is associated with intravascular coagulation.