Plasma tissue factor pathway inhibitor and tissue factor antigen levels after administration of heparin in patients with angina pectoris

Tissue Factor and Tissue Factor Pathway Inhibitor in the Wound-Healing Process After Neurosurgery

Objectives:

The aim of the study was to assess the concentrations of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in the blood of patients with a postoperative wound after neurosurgery.

Method:

Participants included 20 adult patients who underwent neurosurgery because of degenerative spine changes. The concentration of TF and TFPI in the patients’ blood serum was measured 3 times: before surgery, during the first 24 hr after surgery, and between the 5th and 7th days after surgery. The control group comprised 20 healthy volunteers similar to the patient group with respect to gender and age.

Results:

A statistically significant difference was observed between TF concentration at all three measurement time points in the research group and TF concentration in the control group ( p = .018, p = .010, p = .001). A statistically significant difference was found between TFPI concentration at the second time point in the research group and TFPI concentration in the control group ( p = .041). No statistically significant within-subject difference was found between TF concentrations before and after surgery. A statistically significant within-subject difference was found between TFPI concentrations within 24 hr after surgery and 5–7 days after surgery ( p = .004).

Conclusion:

High perioperative concentrations of TF indicate not only the presence of thrombophilia but also the importance of TF in the wound-healing process. Perioperative changes in TFPI concentrations are related to its compensatory influence on hemostasis in thrombophilic conditions.

The role of tissue factor pathway inhibitor in atherosclerosis and arterial thrombosis

Tissue factor pathway inhibitor (TFPI) is the main inhibitor of tissue factor (TF)-mediated coagulation. In atherosclerotic plaques TFPI co-localizes with TF, where it is believed to play an important role in attenuating TF activity. Findings in animal models such as TFPI knockout models and gene transfer models are consistent on the role of TFPI in arterial thrombosis as they reveal an active role for TFPI in attenuating arterial thrombus formation. In addition, ample experimental evidence exists indicating that TFPI has inhibitory effects on both smooth muscle cell migration and proliferation, both which are recognized as important pathological features in atherosclerosis development. Nonetheless, the clinical relevance of these antithrombotic and atheroprotective effects remains unclear. Paradoxically, the majority of clinical studies find increased instead of decreased TFPI antigen and activity levels in atherothrombotic disease, particularly in atherosclerosis and coronary artery disease (CAD). Increased TFPI levels in cardiovascular disease might result from complex interactions with established cardiovascular risk factors, such as hypercholesterolemia, diabetes and smoking. Moreover, it is postulated that increased TFPI levels reflect either the amount of endothelial perturbation and platelet activation, or a compensatory mechanism for the increased procoagulant state observed in cardiovascular disease. In all, the prognostic value of plasma TFPI in cardiovascular disease remains to be established. The current review focuses on TFPI in clinical studies of asymptomatic and symptomatic atherosclerosis, coronary artery disease and ischemic stroke, and discusses potential atheroprotective actions of TFPI.

Detection of endogenous tissue factor levels in plasma using the calibrated automated thrombogram assay

BACKGROUND

The calibrated automated thrombogram (CAT) assay measures thrombin generation in plasma.

OBJECTIVE

Use the CAT assay to detect endogenous tissue factor (TF) in recalcified platelet-rich plasma (PRP) and platelet-free plasma (PFP).

METHODS

Blood from healthy volunteers was collected into citrate and incubated at 37 degrees C with or without lipopolysaccharide (LPS) for 5 hours. PRP and PFP were prepared and clotting was initiated by recalcification. Thrombin generation was measured using the CAT assay.

RESULTS

The lag time (LT) was significantly shortened in PRP prepared from LPS-treated blood compared with untreated blood (10+/-3 min versus 20+/-6 min), and this change was reversed by the addition of inactivated human factor VIIa. LPS stimulation did not change the peak thrombin. Similar results were observed in PFP (21+/-4 min versus 35+/-5 min). LPS stimulation also significantly reduced the LT of PRP and PFP derived from blood containing citrate and a factor XIIa inhibitor. Finally, a low concentration of exogenous TF shortened the LT of PFP prepared from unstimulated, citrated blood without affecting the peak thrombin.

CONCLUSION

Changes in LT in the CAT assay can be used to monitor levels of endogenous TF in citrated plasma.

The FVIIa-tissue factor complex induces the expression of MMP7 in LOVO cells in vitro

BACKGROUND AND AIMS

The extracellular interactions of plasma clotting factor VIIa (FVIIa) with tissue factor (TF) on the cell surface trigger intracellular signaling events involved in multiple physiological processes. TF expression is related to the metastatic potential of tumor cells and is a significant risk factor in the development of hepatic metastases in patients with colorectal cancer. At present, it is unclear how the interaction between TF and FVIIa influences the development of metastasis in colon cancer.

MATERIALS AND METHODS

We used a stable LOVO cell line derived from colorectal adenocarcinoma for our model Western blot analysis, Northern blot analysis, polymerase chain reaction, and RNA inference (RNAi), and the Dual-Luciferase Reporter Assay System technology were utilized to determine if MMP7 can be up-regulated by the VIIa/TF complex.

RESULTS

Northern blot analysis confirmed that the plasma clotting factor FVIIa/TF complex resulted in a marked increase in MMP7 expression in a time- and dose-dependent manner via the p38 pathway in vitro. The proximal promoter of the human MMP7 gene was cloned into a luciferase reporter construction (MMP7.luc1592). Upon treatment with FVIIa, reporter activity in LOVO cells was increased by 2.5-fold. TF RNAi almost completely abolished FVIIa-mediated MMP7.luc induction. Deletion constructs from MMP7.luc1592 further defined an active promoter region.

INTERPRETATION

Taken together, these data provide evidence that expression of MMP7 in colon cancer may be regulated by FVIIa and TF at the transcriptional level. MMP7 may act as a downstream mediator of FVIIa/TF signal transduction to facilitate the development of metastasis in colon cancer.

Immunologic quantitation of tissue factors

The large number of conflicting reports on the presence and concentration of circulating tissue factor (TF) in blood generates uncertainties regarding its relevance to hemostasis and association with specific diseases. We believe that the source of these controversies lies in part in the assays used for TF quantitation. We have developed a highly sensitive and specific double monoclonal antibody fluorescence-based immunoassay and integrated it into the Luminex Multi-Analyte Platform. This assay, which uses physiologically relevant standard and appropriate specificity controls, measures TF antigen in recombinant products and natural sources including placenta, plasma, cell lysates and cell membranes. Comparisons of reactivity patterns of various full-length and truncated TFs on an equimolar basis revealed quantitative differences in the immune recognition of TFs by our antibodies in the order of TF 1-263 > 1-242 > 1-218 > placental TF. Despite this differential recognition, all TF species are quantifiable at concentrations < or = 2 pM. Using a calibration curve constructed with recombinant TF 1-263 and plasma from healthy individuals (n = 91), we observed the concentration of TF antigen in plasma to be substantially lower than that generally reported in the literature: TF antigen in plasma of 72 individuals (79%) was below 2 pM (quantitative limit of our assay); TF antigen levels between 2.0 and 5.0 pM could be detected in six individuals (7%); and in 14% (13 plasmas), the non-specific signal was higher than the specific signal, and thus TF levels could not be determined. These differential recognition patterns affect TF quantitation in plasma and should be considered when evaluating plasma TF-like antigen concentrations.

Immediate Effects of Fluvastain on Circulating Soluble Endothelial Protein C and Free Tissue Factor Pathway Inhibitor in Acute Coronary Syndromes

BACKGROUND

Statins promptly lower rates of adverse cardiovascular events in patients with acute coronary syndromes (ACS). These therapeutic properties may be mediated by the effects of statins on key hemostatic factors. This study examined the immediate effects of fluvastatin on plasma free tissue factor pathway inhibitor (fTFPI) and soluble endothelial protein C receptor (sEPCR) concentrations in patients with unstable angina or non-ST segment elevation myocardial infarction.

METHODS

We studied 57 patients consecutively admitted to our emergency department and randomly assigned to placebo (n = 29) versus fluvastatin, 80 mg, p.o. (n = 28). All patients were treated with aspirin and metoprolol p.o., nitroglycerin i.v., and subcutaneous enoxaparin. Venous blood was sampled as soon as possible upon admission, before and 6 h after administration of study drug and standard anti-ischemic therapy.

RESULTS

Mean sEPCR concentrations decreased significantly in patients treated with fluvastatin (-8.1 +/- 6.7% from baseline) and was unchanged in the placebo group (-2.3 +/- 14.4%, P = 0.007 vs. fluvastatin). Though fTFPI increased significantly after the administration of both fluvastatin and placebo, the mean increase after fluvastatin (450+/-436%) was significantly greater than after placebo (155+/-141%, P = 0.001).

CONCLUSIONS

Treatment with fluvastatin significantly modified key hemostatic factors toward an antithrombotic effect within 6 h. These properties may, in part, explain the early salutary effects of fluvastatin in patients with ACS.

Pro- and non-coagulant forms of non-cell-bound tissue factor in vivo

BACKGROUND

Concentrations of non-cell-bound (NCB; soluble) tissue factor (TF) are elevated in blood collecting in the pericardial cavity of patients during cardiopulmonary bypass (CPB). Previously, we reported microparticles supporting thrombin generation in such blood samples. In this study we investigated the extent of microparticle association of the NCB form of TF in pericardial and systemic blood, and whether this microparticle-associated form is active in thrombin generation compared with non-microparticle-bound, (fluid-phase) TF.

METHODS

Systemic and pericardial blood samples were collected before and during CPB from six patients undergoing cardiac surgery. Microparticles were isolated by differential centrifugation and their thrombin-generating capacity measured in a chromogenic assay. Microparticle-associated and fluid-phase forms of NCB TF were measured by ELISA. Microparticle-associated TF was visualized by flow cytometry.

RESULTS

In pericardial samples, 45-77% of NCB TF was microparticle-associated, and triggered factor VII (FVII)-mediated thrombin generation in vitro. Microparticles from systemic samples triggered thrombin generation independently of FVII, except at the end of bypass (P = 0.003). The fluid-phase form of TF did not initiate thrombin generation. Both forms of NCB TF were, at least in part, antigenically cryptic.

CONCLUSIONS

We demonstrate the occurrence of two forms of NCB TF. One form, which is microparticle-associated, supports thrombin generation via FVII. The other form, which is fluid-phase, does not stimulate thrombin formation. We hypothesize that the microparticle-associated form of NCB TF may be actively involved in postoperative thromboembolic processes when pericardial blood is returned into the patients.

Parameters of the tissue factor pathway with coumadin/dipyridamole versus ticlopidine as adjunct antithrombotic-drug regimen in coronary artery stenting

A different rate and timing of subacute stent thrombosis after percutaneous coronary intervention was reported with various peri-interventional antithrombotic regimens. Next to platelet activation, coagulation triggered by tissue factor (TF) may play a key role in this process. Thirty-one consecutive patients with stable and unstable angina undergoing coronary stenting were randomly assigned to adjunct oral anticoagulation/anti-platelet therapy (coumadin, dipyridamole, aspirin and heparin; n = 16) or adjunct anti-platelet therapy with thienopyridin (ticlopidine, aspirin and heparin; n = 15). Antigen levels of plasma TF, total tissue factor pathway inhibitor (TFPI) and TFPI/ activated factor X (TFPI/FXa) complex were determined before and for up to 6 days after intervention by immunoassay. At baseline, significantly higher levels of plasma TF and TFPI/FXa were found in patients with unstable angina [TF, 161 pg/ml (126-191 pg/ml); TFPI/FXa, 7.8 ng/ml (6.1-9.6 ng/ml)] compared with stable angina [TF, 62 pg/ml (46-82 pg/ml), P < 0.0001; TFPI/FXa, 4.5 ng/ml (3-7.6 ng/ml), P= 0.003]. One hour after intervention, an increase of plasma TF and TFPI/FXa was seen in both treatment groups. In unstable angina patients, plasma levels of TF, TFPI and TFPI/FXa were more efficiently reduced by adjunct ticlopidine therapy compared with adjunct coumadin/dipyridamole. These data suggest reduced release of circulating TF by combined anti-platelet therapy with ticlopidine and aspirin after coronary artery stenting, which may-contribute to the lower incidence of subacute stent thrombosis previously observed.

Platelets, circulating tissue factor, and fibrin colocalize in ex vivo thrombi: real-time fluorescence images of thrombus formation and propagation under defined flow conditions

Although it is generally accepted that the initial event in coagulation and intravascular thrombus formation is the exposure of tissue factor (TF) to blood, there is still little agreement about the mechanisms of thrombus propagation and the identities of the molecular species participating in this process. In this study, we characterized the thrombotic process in real-time and under defined flow conditions to determine the relative contribution and spatial distribution of 3 components of the thrombi: circulating or blood-borne TF (cTF), fibrin, and platelets. For this purpose, we used high-sensitivity, multicolor immunofluorescence microscopy coupled with a laminar flow chamber. Freshly drawn blood, labeled with mepacrine (marker for platelets and white cells), anti-hTF1(Alexa.568) (marker for tissue factor), and anti-T(2)G(Cy-5)(1) (marker for fibrin) was perfused over collagen-coated glass slides at wall shear rates of 100 and 650 s(-1). A motorized filter cube selector facilitated imaging every 5 seconds at 1 of 3 different wavelengths, corresponding to optimal wavelengths for the 3 markers above. Real-time video recordings obtained during each of 10 discrete experiments show rapid deposition of platelets and fibrin onto collagen-coated glass. Overlay images of fluorescent markers corresponding to platelets, fibrin, and cTF clearly demonstrate colocalization of these 3 components in growing thrombi. These data further support our earlier observations that, in addition to TF present in the vessel wall, there is a pool of TF in circulating blood that contributes to the propagation of thrombosis at a site of vascular injury.

Tissue factor and tissue factor pathway inhibitor levels in unstable angina patients during short-term low-molecular-weight heparin administration

High tissue factor (TF), tissue factor pathway inhibitor (TFPI) levels and a hypercoagulability state have been documented in unstable angina patients. We evaluated whether short-term enoxaparin administration (100 IU/kg b.i.d. for 3 d) reduces the high TF levels and the hypercoagulability state, and whether it influences the fibrinolytic system in 20 unstable angina patients. On d 3, we observed a significant reduction in TF levels both 1 h and 4 h after the morning injection (-25.6% and -21.7%; P < 0.001 respectively) in comparison with the base-line levels. Both 1 and 4 h after the morning injection on the d 3, TFPI levels significantly (P < 0.001) increased (+96.4%, +96.9% respectively) with respect to the base-line values. After enoxaparin administration, at all observation times, thrombin-antithrombin complexes and prothrombin fragment F1 + 2 levels were significantly (P < 0.001) lower with respect to base-line levels. We observed a slight but significant increase in tissue plasminogen activator antigen levels in preinjection samples, as well as 1 h and 4 h after enoxaparin administration, in comparison with the base-line values. This study provides evidence that low-molecular-weight heparin (LMWH) administration, in addition to a reduction of hypercoagulability and a mild fibrinolytic activation, is associated with decreased TF levels, so indicating a novel mechanism of interference of LMWH with the haemostatic system.

Regulation of functions of vascular wall cells by tissue factor pathway inhibitor: basic and clinical aspects

Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor that inhibits the initial reactions of blood coagulation. A major pool of TFPI is the form associated with the surface of endothelial cells, which is speculated to play an important role in regulating the functions of vascular wall cells. TFPI consists of 3 tandem Kunitz inhibitor domains, the first and second of which inhibit the tissue factor-factor VIIa complex and factor Xa, respectively. Recent findings indicate that TFPI has another function, ie, the modulation of cell proliferation. This function is based on the interaction of the C-terminal region of TFPI with these cells. In addition to endothelial cells, it has been shown that many other vascular wall cells can synthesize TFPI, eg, mesangial cells, smooth muscle cells, monocytes, fibroblasts, and cardiomyocytes. TFPI is associated with these cells mainly through heparan sulfate proteoglycans on their surface. However, recent findings suggest that there are several other candidates for TFPI-binding proteins on these cells. On the other hand, studies on plasma levels of TFPI in patients with various diseases suggest that TFPI may be a marker of endothelial cell dysfunction. An increasing number of reports suggest that recombinant TFPI may attenuate thrombosis and prevent restenosis. Clinical trials are needed to explore these possibilities. Recent reports also indicate that the application of recombinant TFPI or TFPI gene transfer prevents restenosis in addition to thrombosis after arterial injury in the animal model; corroboration of these reports awaits clinical investigation.

Effects of a low molecular weight heparin, bemiparin, and unfractionated heparin on hemostatic properties of endothelium

Human endothelial cells synthesize and secrete a variety of molecules involved in fibrinolysis and coagulation. The effects of a low molecular weight heparin, Bemiparin, and unfractionated heparin (UFH) were compared on plasminogen activator inhibitor-1 (PAI-1), tissue-plasminogen activator (t-PA), tissue factor (TF), tissue factor pathway inhibitor (TFPI) release, and PAI-1 gene expression by human umbilical vein endothelial cells (HUVEC). Cell cultures were supplemented with Bemiparin or UFH at 1 or 10 U/mL. Culture media samples were obtained before the addition of the drugs and 2, 6, and 24 hours afterward to measure the antigen levels of TF, TFPI, t-PA, and PAI-1. RNA was obtained to study the endothelial expression of PAI-1 by reverse transcriptase-polymerase chain reaction (RT-PCR). Bemiparin at 1 U/mL resulted in a decreased messenger RNA (mRNA) PAI-1 expression, which remained unaltered when UFH had been added. PAI-1 levels increased after the cultures had been supplemented with either Bemiparin or UFH at both doses. UFH induced an increase in t-PA either at 1 or 10 U/mL. Both doses of UFH, but not Bemiparin, induced an important increase in TF secretion. An increase in the TFPI levels was seen with UFH at 1 U/mL. The decrease in PAI-1 gene expression observed with a therapeutic dose of Bemiparin might confer this drug interesting profibrinolytic properties. The fact that Bemiparin, in contrast with UFH, does not induce an increase in TF could give this drug another positive feature.

Tissue factor pathway inhibitor: an update of potential implications in the treatment of cardiovascular disorders

Tissue factor (TF) plays a crucial role in the pathogenesis of thrombotic, vascular and inflammatory disorders. Thus, the inhibition of this membrane protein provides a unique therapeutic approach for prophylaxis and/or treatment of various diseases. Tissue factor pathway inhibitor (TFPI), the only endogenous inhibitor of the TF/Factor VIIa (FVIIa) complex, has recently been characterised biochemically and pharmacologically. Studies in patients demonstrated that both TF and TFPI may be indicators for the course and the outcome of cardiovascular and other diseases. Based on experimental and clinical data, TFPI might become an important drug for several clinical indications. TFPI is expected to inhibit the development of post-injury intimal hyperplasia and thrombotic occlusion in atherosclerotic vessels as well as to be effective in acute coronary syndromes, such as unstable angina and myocardial infarction. Of special interest is the inhibition of TF-mediated processes in sepsis and disseminated intravascular coagulation (DIC), which are associated with the activation of various inflammatory pathways as well as of the coagulation system. A Phase II trial of the efficacy of TFPI in patients with severe sepsis showed a mortality reduction in TFPI- compared to placebo-treated patients and an improvement of organ dysfunctions. TFPI can be administered exogenously in high doses to suppress TF-mediated effects, alternatively high amounts of TFPI can be released from intravascular stores by other drugs, such as heparin and low molecular weight heparins (LMWH). Using this method high concentrations of the inhibitor are provided at sites of tissue damage and ongoing thrombosis. At present, clinical studies with TFPI are rather limited so that the clinical potential of the drug cannot be assessed properly. However, TFPI and its variants are expected to undergo further development and to find indications in various clinical states.

Inhibition of tissue factor reduces thrombus formation and intimal hyperplasia after porcine coronary angioplasty

OBJECTIVES

We investigated the in vivo effects of tissue factor (TF) inhibition with recombinant tissue factor pathway inhibitor (rTFPI) on acute thrombus formation and intimal hyperplasia and the in vitro effects on smooth muscle cell migration and proliferation.

BACKGROUND

Inhibition of TF with TFPI has been shown to reduce intimal hyperplasia in experimental models. However, its effects after coronary angioplasty and the cellular mechanisms involved have not been investigated.

METHODS

Twenty-three swine underwent multivessel coronary angioplasty. Fifteen (n = 25 arteries) were euthanized at 72 h to assess thrombus formation and eight (n = 24 arteries) at 28 days to assess intimal hyperplasia. Animals in the 72-h time point received: 1) human rTFPI (0.5 mg bolus plus 25 microg/kg/min continuous infusion for 3 days) plus heparin (150 IU/kg intravenous bolus) plus acetyl salicylic acid (ASA) (325 mg/day); 2) rTFPI regimen plus ASA and 3) heparin (150 IU/kg intravenous bolus) plus ASA.

RESULTS

On histology the control group had evidence of mural thrombus (area 0.8+/-0.4 mm2). Treatment with TFPI plus heparin abolished thrombus formation (mean area: 0.0+/-0.0 mm2, p < 0.05) but was associated with prolonged activated partial thromboplastin time and extravascular hemorrhage. Recombinant TFPI alone inhibited thrombosis without bleeding complications (mean area: 0.03+/-0.02 mm2, p < 0.05 vs. control). Animals in the 28-day time point received continuous intravenous infusion of rTFPI or control solution for 14 days. Tissue factor pathway inhibitor reduced neointimal formation with mean intimal area of 1.2+/-0.3 mm2 versus 3.2+/-0.4 mm2 in the control group; p < 0.01. Recombinant TFPI had no effect on human aortic smooth muscle cell growth but inhibited platelet-derived growth factor BB-induced migration.

CONCLUSIONS

Inhibition of TF with rTFPI can prevent acute thrombosis and intimal hyperplasia after injury. Tissue factor plasma inhibitor may prove useful as an adjunct to intracoronary interventions.

The effect of heparin on tissue factor and tissue factor pathway inhibitor in patients with acute myocardial infarction

We examined plasma TF and free TFPI levels in 26 consecutive patients with AMI, 26 patients with stable exertional angina, and 25 patients with chest pain syndrome. In patients with AMI, blood samples were obtained immediately after admission and at 4, 8, 16, 24, and 48 h, and the third, fifth, seventh, and fourteenth day after initiation of reperfusion therapy. Plasma TF levels in patients with AMI on admission were significantly higher than in the chest pain syndrome and stable exertional angina groups (248.0+/-117. 4 vs. 179.5+/-29.2 vs. 189.5+/-29.6 pg/ml, P<0.01). In patients with AMI, the level subsequently decreased after heparin administration and was maintained at significantly lower levels compared to those on admission. Plasma free TFPI levels in patients with AMI on admission were significantly higher than in the chest pain syndrome and stable exertional angina groups [33.5+/-12.4 vs. 26.0+/-7.6 ng/ml (P<0.01) vs. 27.5+/-6.3 ng/ml, P<0.05]. In patients with AMI, it reached the maximum level at 4 h after the administration of heparin, and gradually decreased over the time course. These data indicated that continuous administration of a low dose of heparin was effective in decreasing TF levels without affecting TFPI levels. Our results elucidate one of the mechanisms by which the administration of heparin is beneficial in AMI patients undergoing percutaneous revascularization.