Tissue Factor Pathway Inhibitor Concentration Research Articles

Plasma tissue factor pathway inhibitor levels in coronavirus disease 2019 patients: a systematic review and meta-analysis.

PROSPERO CRD42023437353.

Longitudinal observations of TFPI levels in paediatric Haemophilia A patients.

Inhibition of tissue factor pathway inhibitor (TFPI) is a potential new mode of action to achieve haemostasis in haemophilia A and B patients. Knowledge about potential developmental changes of TFPI levels during childhood are a prerequisite to translate adult doses of TFPI inhibitors to doses in paediatric patients. In this study we present longitudinal data for total TFPI concentrations (TFPI-T) and TFPI activity (TFPI-A) from 48 paediatric Haemophilia A patients in the age range from 3 to 18 years (2-12 observations per patient). TFPI-T and TFPI-A tend to decrease over age during childhood. Lowest values were observed between 12 and<18 years. On average, TFPI-T and TFPI-A were lower in adolescent haemophilia patients than in adult haemophilia patients. In summary, the presented information on TFPI levels in children adds to the current knowledge of developmental haemostasis and it can be helpful in evaluating how children respond to haemophilia treatment including the new class of anti-TFPI compounds.

Considerations for the Bioanalytical Part of Equivalence Studies of Biosimilar Nadroparin Calcium

According to current regulatory views, a comparative study of the pharmacodynamics (PD) of low molecular weight heparin (LMWH) products and confirmation of their equivalence require comparing three PD markers: the anti-Xa activity, the anti-IIa activity, and the tissue factor pathway inhibitor (TFPI) concentration. The aim of this study was to analyse the features specific to the bioanalytical part of an equivalence study of a nadroparin calcium biosimilar after single subcutaneous administration. Material and methods: the anti-Xa and anti-IIa activity values and TFPI content were determined in human plasma samples obtained after single subcutaneous administration of the test and the reference product in the same dose, using commercially available reagent kits and pre-validated assays. The authors calculated the main PD parameters (surrogate pharmacokinetic markers), namely the maximum activity or concentration (Amax or Cmax), time to maximum activity or concentration (Tmax), area under the activity–time (or concentration–time) curve (AUC ), and half-life period (T1/2), by means of model-independent statistical moment analysis and carried out further statistical testing of the parameters. Results: the anti-Xa activity and TFPI concentration results provided for the possibility of calculating and comparing the PD parameters (Amax or Cmax, AUC0-24, AUC0-∞, Tmax, T1/2) and estimating the confidence intervals that are necessary to confirm the bioequivalence of the studied products. The anti-IIa activity data had a characteristic pattern of slight fluctuations around one level, which prevented the calculation and comparison of PD parameters. Conclusion: the study identified specific features to consider when planning comparative PD studies of nadroparin calcium products. Firstly, it is feasible to divide samples into two test aliquots (one for anti-Xa and anti-IIa activity determination, the other for TFPI analysis) at the moment of collection in order to perform the analytical step correctly. Secondly, there is no need in full validation for the bioanalytical assays of the anti-Xa and anti-II activity and TFPI content in human plasma validated in the concentration ranges of 0.024–0.182 IU/mL, 0.0069–0.052 IU/mL and 1.56–100 ng/mL, respectively; a confirmation that the active ingredient does not interfere with the analytical procedure is adequate for the purpose. Finally, the data obtained may not allow for calculating PD parameters and comparing confidence intervals for all three markers. The listed considerations may be relevant for other LMWH products as well.

Tissue factor pathway inhibitor is a potential modifier of bleeding risk in factor XI deficiency

BackgroundFactor (F) XI deficiency is associated with increased bleeding risk in some individuals. Neither FXI levels nor clinical clotting assays predict the bleeding risk. Compared with controls, FXI-deficient bleeders have reduced clot formation, decreased fibrin network density, and increased susceptibility to fibrinolysis. Tissue factor pathway inhibitor (TFPI) was recently implicated as a modifying factor in individuals with bleeding of unknown cause. ObjectivesTo determine the potential of TFPI in modifying the bleeding risk in FXI-deficient individuals. MethodsThe effects of TFPI on thrombin generation and clot formation, structure, and fibrinolysis in FXI-deficient plasma were measured in vitro in the absence or presence of inhibitory anti-TFPI antibody or exogenous recombinant TFPIα. Total plasma TFPI concentration was measured in 2 independent cohorts of controls and FXI-deficient individuals classified as bleeders or nonbleeders (cohort 1: 10 controls and 16 FXI-deficient individuals; cohort 2: 48 controls and 57 FXI-deficient individuals) and correlated with ex vivo plasma clot formation and fibrinolysis parameters associated with bleeding risk. ResultsIn an in vitro FXI deficiency model, inhibition of TFPI enhanced thrombin generation and clot formation, increased the network density, and decreased fibrinolysis, whereas an increase in TFPI had the opposite effects. Compared with controls, plasma from FXI-deficient bleeders had higher TFPI concentration. Total plasma TFPI concentrations correlated with parameters from ex vivo clotting and fibrinolysis assays that differentiate FXI-deficient bleeders and nonbleeders. ConclusionCoagulation and fibrinolysis parameters that differentiate FXI-deficient nonbleeders and bleeders were altered by plasma TFPIα. Total plasma TFPI was increased in FXI-deficient bleeders. TFPI may modify the bleeding risk in FXI-deficient individuals.

Target‐mediated drug disposition modeling of an anti‐TFPI antibody (MG1113) in cynomolgus monkeys to predict human pharmacokinetics and pharmacodynamics

BackgroundMG1113 is a human monoclonal antibody of tissue factor pathway inhibitor (TFPI) under development for prophylaxis for hemophilia patients with or without inhibitors against factor VIII products, which have been used for the treatment of hemophilia. Because TFPI is a negative regulator in the extrinsic coagulation pathway, neutralization of TFPI function by MG1113 can potentially increase coagulation activity by bypassing the intrinsic coagulation pathway, which factor VIII activates. ObjectivesThis study aims to determine the correlation between pharmacokinetics (PK) and pharmacodynamics (PD) after administering MG1113 to monkeys and to predict the PK and PD of MG1113 in humans by the Target‐Mediated Drug Disposition (TMDD) model using the results from monkeys. MethodsThe PK profile of MG1113 and the PD effect on the free TFPI level were evaluated after intravenous (IV) and subcutaneous (SC) administrations of MG1113 (2.5, 5, and 10 mg/kg) to male cynomolgus monkeys. After setting up the PK/PD model on monkeys, PK parameters on humans were calculated using allometric scaling, and then clinically effective doses were predicted applying the TMDD model. Results and ConclusionsMG1113 showed nonlinear PK after both IV and SC administrations at the dosing range from 2.5 to10 mg/kg. The concentrations of MG1113 versus TFPI could be characterized a dose‐response relationship using a TMDD model. The TMDD modeling and simulation built in this study were used to simulate various dosage regimens of MG1113 to apply to the first‐in‐human study design, and moreover expected to be referred to establish the dose for further clinical trials.

Tissue factor pathway inhibitor upregulates CXCR7 expression and enhances CXCL12-mediated migration in chronic lymphocytic leukemia

The infiltration of chronic lymphocytic leukemia (CLL) cells into lymphoid organs correlates with disease severity. CXCL12 is a key chemotactic factor for the trafficking of CLL. Tissue factor pathway inhibitor (TFPI) is a serine protease inhibitor and plays a role in CXCL12-mediated hematopoietic stem cell homing. We aim to explore the role of TFPI in CXCL12-mediated migration of CLL cells. In this study, plasma TFPI concentrations were measured by ELISA. CLL cells were isolated from patients and used for trans-endothelial migration (TEM) assays. Quantitative RT-PCR and Western blotting were used to detect the expression of CXCR7, CXCR4 and β-catenin. Immunofluorescence and co-immunoprecipitation was used to detect the binding of TFPI and glypican-3 (GPC3). We found that plasma TFPI levels in CLL patients were higher than in healthy controls, particularly in the patients with advanced disease. TFPI enhanced CXCL12-mediated TEM of CLL cells by increasing the expression of the CXCL12 receptor CXCR7, but not of the CXCL12 receptor CXCR4. The effect of TFPI on TEM was abolished by the CXCR7 inhibitor, CCX771, while the CXCR4 inhibitor AMD3100 strongly increased TEM. TFPI co-localized with GPC3 on the cell surface. An antibody to GPC3, HS20, decreased CXCR7 expression and abolished the effect of TFPI on TEM. TFPI activated β-catenin and the Wnt/β-catenin inhibitor IWP4 repressed the effect of TFPI on CXCR7 expression and TEM. We conclude that TFPI may contribute to organ infiltration in CLL patients.

Tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in the peritoneal fluid in patients with peritonitis – is the key towards intraperitoneal adhesions and complications?

Abstract Introduction The concentrations of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in the peritoneal fluid and blood plasma in patients with peritonitis were examined. The fibrinogenesis of the peritoneal cavity is not well-known although it is regarded as the main cause of intraperitoneal adhesions and the complications that arise from this. Materials and methods The study enrolled a group of 77 consecutive patients with peritonitis, 28 women and 49 men aged 18–79 years (with an average age of 45 ±18 years). The patients were divided into 2 subgroups: those with complications (n = 64) and those without (n = 13). Concentrations of TF and TFPI in the peritoneal fluid and blood plasma of patients were examined. Results In the peritoneal fluid, patients with complications had a higher concentration of TF (p &lt; 0.007), but a lower concentration of TFPI (p &lt; 0.0006). In blood plasma, TF was higher but TFPI was lower (p &lt; 0.00001 in both). The area under curve (AUC) for TF and TFPI was 0.763 and 0.93 respectively, the cut-off point was 809.08 pg/mL and 21.6 pg/mL, respectively. The positive predictive value (PPV) and negative predictive value (NPV) for TF was 68% and 75% and for TFPI, 80% and 85%, respectively. Conclusions The data can be taken as an example of cross-linking between extravascular coagulation and intraperitoneal adhesions. On the basis of TF and TFPI, it is clearly illustrated that there is some connection between coagulation and peritoneal fibrinogenesis, which could be involved in the pathogenesis of many complications in abdominal surgery and also indicate therapeutic targets.

Levels of TAFI, TFPI and ADAMTS-13 in inflammatory bowel disease.

There is an increased tendency for thrombosis and thromboembolic complications in patients with inflammatory bowel disease (IBD). The aim of the present study was to determine the serum concentrations of thrombin-activatable fibrinolysis inhibitor (TAFI), tissue factor pathway inhibitor (TFPI) and a disintegrin and metalloproteinase with thrombospondin motif-13 (ADAMTS-13) in patients with IBD and to assess their possible role in the etiopathogenesis of the disease. Thirty-four patients with IBD (23 ulcerative colitis and 11 Crohn's disease) and 20 healthy controls were included in the present study. TAFI, TFPI, and ADAMTS-13 concentrations were determined by enzyme-linked immunosorbent assay. Mean TAFI, TFPI, and ADAMTS-13 concentrations in the patient group were 17.75 ng/ml, 72.10 ng/ml, and 14.90 U/l, respectively. In the control group, these values were 117.10 ng/ml, 300 ng/ml, and 191.55 U/l, respectively. TAFI, TFPI, and ADAMTS-13 values were significantly lower in the patient group than in the control group (all p<0.01). TAFI, TFPI, and ADAMTS-13 levels were significantly lower in the patient group. These findings indicate the presence of a clear, multifactorial imbalance in the coagulation-fibrinolytic system in the patient group. It is also possible that this imbalance in the coagulation and fibrinolytic system may play a role in the still unclear etiopathogenesis of the disease.

Is Neovascularization a Leading Mechanism of Intra-plaque Hemorrhage and Carotid Plaque Destabilization?

Introduction: The accelerating carotid plaque growth can cause fibrous cap rupture followed by embolization to brain vessels. Important role in this process is ascribed to thrombotic factors and their inhibitors although another mechanism based on rupture of deficient vessels formed inside the plaque within the neovascularization process is also proposed. Interestingly, the second sequence of events provoke intra-plaque hemorrhage without a fibrous cap rupture. To determine whether the neovascularization is a main process responsible for carotid plaque destabilization the current study was conducted in asymptomatic and symptomatic patients with carotid stenosis. Methods: There were 121 individuals included to the study. Among them, study group consisted of 86 consecutive patients undergoing carotid endarterectomy (23 symptomatic, 63 asymptomatic, mean age 68±7,4 years) and 35 individuals without any symptoms and signs of atherosclerosis served as a control group. The concentration of vascular endothelial growth factor (VEGF) and its receptors, sVEGFR1, sVEGFR2, and tissue factor (TF) and tissue factor pathway inhibitor (TFPI) (ELISA immunoassay) in plaque homogenates and blood plasma was measured. In addition, activity of TF and TFPI (actichrome assay) were also measured. Concentration and activity results of all tested parameters were recounted for the milligram of protein contained in the plasma and plaques homogenates. Results: Analyzing patients with symptomatic and asymptomatic carotid stenosis the only statistically significant difference was found in the concentration of VEGF in plaque homogenates which was significantly higher in symptomatic plaques (302,9 vs 182,1 pg/ml; p=0,005 and 88,0 vs 67,9 pg/mg protein; p=0,05). The plaques homogenate’s TF level recounted for the milligram of protein was nearly 300-fold higher and TF activity was 5-fold higher in comparison with their plasma concertation and activity in the study group. The concentration and activity of TFPI was also higher in the plaque homogenates then in the plasma. The activity of TFPI in plaque homogenates recounted for the milligram of protein was 25-fold higher than in the plasma of the study patients. The VEGF concentration in plaque homogenates was significantly higher than in the plasma of study patients. There was no difference in VEGF concentration in the plasma of the study group and the control group. The lowest concentration of VEGF-R1 recounted for the milligram of protein was observed in the plasma of the control group. Higher concentration of VEGF-R1 recounted for the milligram protein was found in the plasma of the study group, but the distinctly highest concentration of VEGF-R1 (more than 10-fold higher) was observed in the study group plaque homogenates. Reverse characteristic showed the concentration of VEGF-R2, the lowest level was observed in the plaque homogenates and the highest in the plasma of the control group. Conclusion: The neovascularization process might be a leading mechanism of intra-plaque hemorrhage and carotid plaque destabilization. The plaque homogenates and blood plasma of patients with severe carotid stenosis have a strong prothrombotic profile. The plaque homogenates of patients with carotid stenosis in contrary to plasma possess signs of outspread angiogenetic activity.

Diurnal variations in tissue factor and tissue factor pathway inhibitor concentrations in relation to on-treatment platelet reactivity: an analysis of patients with acute myocardial infarction

The aim of the study was to evaluate diurnal changes of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) concentrations in relation to on-treatment platelet reactivity. The study group included 51 patients with acute myocardial infarction (AMI) treated with primary percutaneous coronary intervention and dual antiplatelet therapy. TF and TFPI concentrations were assessed using enzyme-linked immunosorbent assay kits. We found a significant increase of TF concentration in clopidogrel-resistant, but not clopidogrel-sensitive, patients at 10.00 a.m. (410.66 pg/mL) in comparison with 6.00 a.m. (250.99 pg/mL), 14.00 p.m. (255.12 pg/mL) and 19.00 p.m. (267.58 pg/mL). Moreover, TF concentration at 10.00 a.m. was 30% higher in clopidogrel-resistant than clopidogrel-sensitive patients (p = .043). We failed to demonstrate diurnal variation in TFPI concentration in clopidogrel-resistant patients. However, TFPI concentration in clopidogrel-sensitive patients was significantly higher at 10.00 a.m. as compared with other sampling points (p < .05). We observed a marked elevation in TF concentration at 10.00 a.m. only in aspirin-resistant patients and a significant increase in TFPI concentration at 10 a.m. only in aspirin-sensitive patients. Our findings suggest the presence of diurnal variations in TF and TFPI concentrations in AMI patients, with the highest thrombotic risk in patients with high on-treatment platelet reactivity in the midmorning.

Measurement of plasma and platelet tissue factor pathway inhibitor, factor V and Protein S in people with haemophilia.

Tissue factor pathway inhibitor (TFPI) is a naturally occurring anticoagulant found in plasma, where it circulates bound to lipoproteins, factor V (FV) or Protein S (PS), and in platelets. Therapeutic agents targeting TFPI are under development for the treatment of haemophilia A and haemophilia B. To begin to understand how TFPI, FV and PS interact to modulate haemophilia bleeding. Plasma and platelet antigen concentrations of these factors were determined in 73 people with haemophilia A and 18 with haemophilia B. Using multiple regression models, these were compared to the same analytes measured in 224 male blood donors. There were no differences in plasma or platelet TFPI, FV or PS concentrations between haemophilia types or severities. However, compared to blood donors, people with haemophilia had approximately one-third lower plasma PS, 9% lower plasma TFPIα, 50% higher platelet FV and 26% lower platelet Protein S. Together, the presented data suggest that individuals with haemophilia may have a compensatory procoagulant response of both plasma and platelet proteins to the decreased concentrations of FVIII or FIX.

Oxygenation impairment in patients with acute aortic dissection is associated with disorders of coagulation and fibrinolysis: a prospective observational study.

Stanford type-A acute aortic dissection (AAD) is typically accompanied by oxygenation impairment before surgery. In addition, inflammation, coagulation and fibrinolysis also impair blood oxygenation. However, our understanding of the concentration of these factors in bronchoalveolar lavage fluid (BALF) has not been reported. The objective of the study was to investigate the impact of preoperative acute lung injury (ALI) on postoperative oxygenation impairment and to explore the effect of coagulation and fibrinolysis in blood and BALF. This investigation utilized a prospective observational study design, which was registered at www.clinicaltrials.gov (identifier NCT01894334). The study included 53 patients undergoing surgery for Stanford type-A AAD at an academic hospital in China between October 2013 and July 2014. Preoperative ALI was identified according to the oxygenation index calculated by the PaO2/FiO2 ratio. The subjects were divided into the ALI group (oxygenation index ≤300 mmHg) or the control group (oxygenation index >300 mmHg). The primary outcome was patient oxygenation index, while secondary outcomes were concentrations of tissue factor (TF), tissue factor pathway inhibitor (TFPI), and plasminogen activator inhibitor-1 (PAI-1) in serum and BALF. The incidence of preoperative ALI for Stanford type-A AAD patients was 41.5%. Stanford type-A AAD patients with preoperative ALI had a lower postoperative oxygenation index (104.6±31.7 vs. 248.7±48.0 mmHg, P<0.001), higher concentrations of TF in serum and BALF (F=133.67, P<0.001; F=68.14, P<0.001), higher concentrations of TFPI in serum and BALF (F=31.98, P<0.001; F=45.58, P<0.001), and higher concentrations of PAI-1 in serum and BALF (F=213.88, P<0.001; F=107.95, P<0.001) when compared with those without preoperative ALI. Type-A AAD patients also showed a greater loss of blood (1,524±458 vs. 1,175±327 mL, P=0.040), longer mechanical ventilation time in the ICU (27.24±8.37 vs. 17.33±7.36 h, P<0.001), longer total stay in the ICU (42.27±10.85 vs. 33.45±9.05 h, P=0.002), and longer total hospital stay (17.77±5.00 vs. 13.48±3.97 days, P=0.001). Multivariate linear regression analysis indicated that preoperative PAI-1 in BALF, and TF in both serum and BALF were significantly associated with preoperative oxygenation impairment in patients with Stanford type-A AAD. Preoperative ALI caused more serious postoperative oxygenation impairment for Stanford type-A AAD, and coagulation and fibrinolysis appear to play critical roles in this process. Preoperative PAI-1 in BALF and TF in both serum and BALF were significant factors related to the occurrence of preoperative oxygenation impairment for Stanford type-A AAD.

Activation of TF-Dependent Blood Coagulation Pathway and VEGF-A in Patients with Essential Thrombocythemia

Background and objectives: Recent studies suggest that a vascular endothelial growth factor (VEGF-A) may be involved in the thrombotic process by stimulating the expression of tissue factor in vascular endothelial cells. Tissue factor (TF) can also stimulate the transcription of the gene encoding VEGF-A. The relationship between coagulation and angiogenesis in myeloproliferative neoplasms is not fully understood. The aim of this study was to evaluate the concentration of TF in relation to VEGF-A in the blood of patients with essential thrombocythemia (ET). Patients and methods: The study group consisted of 130, newly diagnosed patients with ET (mean age 61 years). The control group consisted of 35 healthy volunteers (mean age 51 years). Concentrations of VEGF-A, TF, and tissue factor pathway inhibitor (TFPI) were analysed using immunoenzymatic methods. TF and TFPI activities were performed using chromogenic assays. Results: The median concentration of TF Ag was 3-fold higher and the TF activity was more than 15-fold higher in ET patients than in normal individuals. There were no statistically significant differences in the TFPI concentration and activity between groups. VEGF-A was significantly increased in patients with ET (p < 0.000001). Analysis of correlations revealed a positive correlation between VEGF-A and TF Ag as well as a positive correlation between VEGF-A and TFPI activity. Conclusions: The simultaneous increase of TF concentration and activity, VEGF-A in the blood of patients with ET, as well as a positive correlation between the concentration of TF and VEGF-A demonstrates the coexistence of TF-dependent coagulation and activation of angiogenesis.

Evaluation of plasma levels of tissue factor and tissue factor pathway inhibitor in patients with psoriasis.

IntroductionPsoriasis is a chronic, recurrent, inflammatory skin disorder with systemic involvement. It has recently been established that psoriasis is associated with an increased cardiovascular risk. Chronic skin-specific inflammation may promote atherosclerosis. Myocardial infarction or stroke can also be a result of underlying haemostasis disorders. Disorders in fibrinolysis and thrombosis in patients with psoriasis have been observed by many authors.AimThis study points to the key role played by the tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in the extrinsic pathway of blood coagulation and the potential influence of microvascular disorders in inflamed psoriatic skin on TF and TFPI activity.Material and methodsThe study included 47 patients with active psoriasis vulgaris, hospitalized in the Dermatological Ward of the Regional Specialist Hospital, Research and Development Centre in Wroclaw, as well as 18 people from the control group.ResultsThere were significant differences in the blood concentrations of TF and TFPI in patients with psoriasis when compared to the control group. A low TFPI concentration in psoriatic patients may indicate an increased risk of atherosclerosis. Interpretation of a decreased level of TF in patients with psoriasis is difficult because it seems to be at odds with observations among patients with other atherosclerosis risk factors such as hypertension, hyperlipidaemia, diabetes or smoking.ConclusionsIt appears that further studies are necessary to explain this problem, perhaps to include an evaluation of TF levels in psoriatic skin.

Longer procoagulant phospholipid-dependent clotting time, lower endogenous thrombin potential and higher tissue factor pathway inhibitor concentrations are associated with increased VTE occurrence in patients with newly diagnosed multiple myeloma: results of the prospective ROADMAP-MM-CAT study

Venous thromboembolism (VTE) is a common complication in newly diagnosed symptomatic multiple myeloma (NDMM) patients. We explored cellular and plasma hypercoagulability in NDMM patients to identify relevant biomarkers that can be used in combination with clinical factors in the development of a risk assessment model (RAM) for VTE. Untreated patients (n = 144) with NDMM were prospectively enrolled, baseline biomarkers prior to anti-myeloma treatment and thromboprophylaxis initiation were obtained. These were compared against values in a group of healthy individuals with similar age and sex distribution. The primary study end point was symptomatic VTE occurrence. At 12-month follow-up cumulative VTE rate was 10.4%. NDMM patients showed biological signs of cellular and plasma hypercoagulability and endothelial cell activation. Procoagulant phospholipid clotting time (Procoagulant-PPL) was shorter, P-selectin levels lower and thrombin generation attenuated overall compared to healthy subjects. Longer Procoag-PPL®, lower endogenous thrombin potential (ETP), and higher levels of tissue factor pathway inhibitor (TFPI) were associated with VTE occurrence. Multivariate analysis showed that Procoag-PPL® and ETP were independent risk factors for VTE. We conclude that Procoag-PPL® and ETP can be prospectively incorporated into a RAM for VTE in MM in combination with clinical and disease risk factors.

Plasma Proteolytic Cascade Activation during Neonatal Cardiopulmonary Bypass Surgery.

Neonates undergoing cardiopulmonary bypass (CPB) surgery to correct congenital heart defects often experience excessive bleeding. Exposure of blood to artificial materials during CPB may activate coagulation, complement and inflammatory pathways. In addition, the surgical stress placed on the haemostatic system may result in cross-activation of other plasma proteolytic cascades, which could further complicate physiological responses to the surgical procedure and post-operative recovery. Plasma protease inhibitors undergo distinct conformational changes upon interaction with proteases, and, thereby, can serve as endogenous biosensors to identify activation of the different proteolytic cascades. We tested the hypothesis that changes in the concentration and conformation of protease inhibitors regulating plasma proteolytic cascades during neonatal CPB are associated with post-operative bleeding. Plasma samples from 44 neonates were obtained at four time points across the surgical procedure. Anti-thrombin, antitrypsin, anti-chymotrypsin, anti-plasmin, C1-inhibitor and tissue factor pathway inhibitor (TFPI) concentrations and conformations were evaluated by enzyme-linked immunosorbent assay, transverse urea gradient gel electrophoresis and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The most striking changes were observed following heparin administration and were associated with the appearance of inactive forms of anti-thrombin and an increase in the plasma concentration of TFPI. Changes in anti-thrombin and TFPI remained evident throughout surgery and into the post-operative period but were not different between patients with or without post-operative bleeding. The concentration of antitrypsin decreased across surgery, but there was no significant accumulation of inactive conformations of any inhibitor besides anti-thrombin, indicating that widespread cross-activation of other plasma proteolytic cascades by coagulation proteases did not occur.

Procoagulant State in Current and Former Anabolic Androgenic Steroid Abusers.

Anabolic androgenic steroid (AAS) abusers are considered at increased risk of cardiovascular morbidity and mortality. We hypothesized that current and former AAS abuse would induce a procoagulant shift in the haemostatic balance. Men 18 to 50 years of age were included as current AAS abusers, former AAS abusers or controls. Morning blood samples were collected after overnight fasting. Thrombin generation (lag time, time to peak, peak height, and endogenous thrombin potential [ETP]) and coagulation factor II (prothrombin), VII and X, antithrombin, protein C, free protein S and tissue factor pathway inhibitor (TFPI) were assessed. Groups were compared by ANOVA or Kruskal-Wallis test and probabilities were corrected for multiple comparisons. Associations were evaluated using linear regression models. ETP was increased around 15% in current (n = 37) and former (n = 33) AAS abusers compared with controls (n = 30; p < 0.001). Prothrombin and factor X were increased ≥10% in AAS abusers and prothrombin was a predictor of ETP (p < 0.0005). Lag time and time to peak were increased 10 to 30% in current AAS abusers (p < 0.001) and associated with higher concentrations of TFPI, antithrombin, protein C and protein S (p < 0.0005; = 0.005). Multivariate linear regression, with all coagulation inhibitors as covariates, identified TFPI to be independently associated with lag time and time to peak (p < 0.0005). Thrombin generation is augmented in current and former AAS abusers, reflecting a procoagulant state, with altered concentrations of coagulation proteins. Prospective studies are needed to clarify whether these findings translate into an increased thrombotic risk in AAS abusers potentially even after cessation.

Time of day and short-duration high-intensity exercise influences on coagulation and fibrinolysis

Exercise has been demonstrated to have considerable effects upon haemostasis, with activation dependent upon the duration and intensity of the exercise bout. In addition, markers of coagulation and fibrinolysis have been shown to possess circadian rhythms, peaking within the morning (0600–1200 h). Therefore, the time of day in which exercise is performed may influence the activation of the coagulation and fibrinolytic systems. This study aimed to examine coagulation and fibrinolytic responses to short-duration high-intensity exercise when completed at different times of the day. Fifteen male cyclists (VO2max: 60.3 ± 8.1 ml kg−1 min−1) completed a 4-km cycling time trial (TT) on five separate occasions at 0830, 1130, 1430, 1730 and 2030. Venous blood samples were obtained pre- and immediately post-exercise, and analysed for tissue factor (TF), tissue factor pathway inhibitor (TFPI), thrombin–anti-thrombin complexes (TAT) and D-Dimer. Exercise significantly increased plasma concentrations of TF (p < .0005), TFPI (p < .0006), TAT complexes (p < .0012) and D-Dimer (p < .0003). There was a time-of-day effect in pre-exercise TF (p = .004) and TFPI (p = .031), with 0830 greater than 1730 (p .001), while 1730 was less than 2030 h (p = .008), respectively. There was no significant effect of time of day for TAT (p = .364) and D-Dimer (p = .228). Power output, TT time and heart rate were not significantly different between TTs (p > .05); however, percentage VO2max was greater at 1730 when compared to 2030 (p = .04). Due to a time-of-day effect present within TF, peaking at 0830, caution should be applied when prescribing short-duration high-intensity exercise bout within the morning in populations predisposed to hypercoagulability.

Correlates of plasma and platelet tissue factor pathway inhibitor, factor V, and Protein S

Summary Essentials Tissue Factor Pathway Inhibitor, Protein S, and Factor V circulate in plasma and platelet pools.These proteins were measured in plasma and platelets from 435 healthy subjects and correlated.Plasma and platelet pools differ in their demographic correlates and alterations by estrogen.Plasma and platelet pools may differentially modulate thrombotic and hemostatic responses BackgroundPlasma Tissue Factor Pathway Inhibitor (TFPI) circulates bound to factor V (fV) and Protein S (PS). Estrogen therapy decreases plasma TFPI and PS. TFPI, fV, and PS circulate within platelets, and are released upon activation to modulate thrombus formation.ObjectiveIdentify factors affecting the concentrations of plasma and platelet TFPI, fV, and PS.MethodsBlood samples were obtained from 435 healthy individuals. Plasma total TFPI, TFPIɑ, fV, and PS, and platelet TFPI, fV, and PS were quantified. Correlations between these protein concentrations and age, gender, race, and estrogen use were established.ResultsIn males, only plasma fV increased with age, while in females, all plasma analytes increased with age. Males had higher plasma total TFPI, TFPIα, and PS than females. The platelet proteins in either sex remained relatively stable with increasing age. Platelet TFPI and PS were comparable in both sexes, while platelet fV was higher in females. Estrogen use was associated with decreased plasma total TFPI and TFPIα, and platelet PS, but not with platelet TFPI concentration. Racial differences in plasma and platelet proteins were observed, some of which were larger than inter‐individual differences observed within racial groups. TFPI, fV and PS concentrations correlated in plasma, while only fV and PS correlated in platelets.ConclusionsPlasma and platelet TFPI, fV and PS differ in their: (i) in vivo association; (ii) demographic correlates; and (iii) alteration by estrogen therapies. Therefore, the plasma and platelet pools of these proteins may modulate hemostasis and thrombosis via different biochemical pathways.

A preliminary estimation of tissue factor pathway inhibitor (TFPI) and protein C in patients with intracranial tumors.

In patients with intracranial tumors, hypercoagulability is observed due to brain tissue and tumor cells being the source of tissue factor. The aim of the study was to assess tissue factor (TF), tissue factor pathway inhibitor (TFPI) and protein C in the plasma and tumor tissue homogenate in patients with intracranial tumors. The study included 77 patients; 24 patients were diagnosed with glioma, 20 patients with meningioma and 33 patients with metastatic tumors; mean age - 54 years. The material for the study was the plasma and tumor tissue homogenate sampled during surgery. The control group consisted of 30 controls; mean age - 51 years. In the plasma of all the participants and in tumor tissue homogenate, the concentrations of TF-Ag, TFPI-Ag and protein C activity, and the concentration of total protein were measured. The results were converted per mg of protein. In patients with intracranial tumors, elevated concentrations of TF-Ag, TFPI-Ag and protein C activity were noted, also after the conversion per mg of protein. A 100-fold higher concentration of TF per 1 mg of protein was found in tumor tissue compared to the patients' plasma. In tumor tissue homogenate, a lower TFPI concentration and a lower protein C activity were recorded. The study confirmed the essential prothrombotic properties in patients with intracranial tumors, expressed with an elevated TF level, as well as a tremendous amount of TF in tumor tissue homogenate derived from tumors. The elevated concentration of TFPI and protein C activity converted per mg of total protein should be analyzed in terms of their pleiotropic function, along with the participation in hemostasis control. It seems that the reduced protein C activity and low TFPI level are associated with the enormous TF value in tumor tissue homogenates.