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

Tissue Factor, Tissue Factor Pathway Inhibitor and Factor VII Activity in Cardiovascular Complicated Type 2 Diabetes Mellitus

OBJECTIVES

Tissue factor (TF) is the main initiator of the extrinsic coagulation pathway through factor VII (FVII) activation, which is physiologically inhibited by tissue factor pathway inhibitor (TFPI). Alteration of this pathway has been described in Type 2 diabetes mellitus (T2DM). The aim of this study is to assess TF and TFPI plasma levels and FVII coagulant activity (FVIIa) in T2DM in relation to cardiothrombotic disease and their correlation to metabolic and clinical behavior of the patients.

METHODS

The study was conducted on 80 T2DM patients divided to accordingly; groupI: 40 patients without a history or clinically detected heart disease, and groupII: 40 patients with a history of myocardial infarction compared to 30 controls. The patients were recruited from Ain Shams University diabetes clinic from September 2007 to February 2009 after informed consent was obtained. Peripheral blood samples were taken for measurement of plasma TF and TFPI levels using ELISA technique and quantitative FVIIa using FVII deficient plasma.

RESULTS

Plasma levels of TF, TFPI and FVIIa were significantly higher in T2DM patients compared to the controls (p<0.001). TF (236.50±79.23)and TFPI (242.33±85.84)were significantly higher in group II, compared to group I (150.33±81.16), (152.8± 82.46), (p<0.001). TF and TFPI were significantly correlated to body mass index and glycemic control. Also, TF and TFPI were significantly higher in hypertensives (p=0.001) and dyslipidemics (p=0.006) but not in smokers (p=0.64), (p=0.11) respectively.

CONCLUSION

There was a correlation between high TF, TFPI plasma levels, FVIIa activity and cardiothrombotic complications in T2DM especially in the presence of high risk factors such as poor glycemic control, dyslipidemia and obesity. Future target therapy against TF may be beneficial for T2DM patients.

Impaired control of the tissue factor pathway of blood coagulation in systemic lupus erythematosus

Thrombosis is a frequent manifestation in patients with systemic lupus erythematosus (SLE), although precise mechanisms remain unclear. This study investigated whether the major physiological trigger of blood coagulation, the tissue factor (TF) pathway, was altered in SLE patients. Furthermore, we investigated potential associations between the TF pathway, the presence of antiphospholipid (APL) antibodies and other abnormalities present in SLE. A total of 101 participants (40 SLE patients and 61 age- and sex-matched controls) were recruited from Tasmania, Australia. Markers of the TF pathway, hypercoagulability, inflammation and endothelial cell damage were measured in plasma. Serum levels of APL antibodies (anti-cardiolipin antibodies [ACL], lupus anticoagulants [LAC], anti-beta2-glycoprotein-1 [anti-β2GP1] and anti-prothrombin antibodies) were also determined. Despite similar TF and TF pathway inhibitor (TFPI) total antigen levels, SLE patients had significantly increased levels of TFPI free antigen (patients vs controls; mean ± SD) (11.6 ± 0.9 ng/mL vs 6.4 ± 0.4 ng/mL; p < 0.001) but significantly reduced TFPI activity (0.66 ± 0.07 U/mL vs 1.22 ± 0.03 U/mL; p < 0.001), compared with healthy controls. Anti-TFPI activity, designated as the ability of isolated IgG fractions to inhibit TFPI activity in normal plasma, was detected in 19/40 (47.5%) of SLE patients and 3/40 (7.5%) of healthy controls. The significant reduction in TFPI activity in SLE patients reflects impaired functional control of the TF pathway. Moreover, SLE patients with a history of thrombosis demonstrated higher levels of TFPI activity compared with patients without a previous thrombotic event (0.97 ± 0.07 U/mL vs 0.53 ± 0.14 U/mL; p = 0.0026). Changes to the TF pathway were not associated with manifestations of SLE such as inflammation or endothelial cell damage. The results from this study suggest hypercoagulability in SLE may (in part) be due to reduced TFPI activity, a mechanism that appears to be independent of other abnormalities in SLE.

Deterioration of glomerular endothelial surface layer and the alteration in the renal function after a growth promoter boldenone injection in rabbits

Boldenone is an anabolic steroid developed for veterinary use. Recently, it is used by bodybuilders in both off-season and precontest, where it is well known for increasing vascularity while preparing for a bodybuilding contest. However, the side effect of this steroid on the human health is still unclear. Therefore, the present study was designed to investigate the possible effect of the growth promoter, boldenone undecylenate, on the function and structure of the rabbit’s kidneys. A total of 36 adult New Zealand rabbits were divided into 4 groups. Control group includes animals that were injected intramuscularly with olive oil and dissected after 3 weeks. Three experimental groups include animals that receive one, two and three intramuscular injections of 5 mg/kg body weight boldenone, and dissected after 3, 6, and 9 weeks, respectively, and the interval of each dose of boldenone was 3 weeks. The biochemical analysis of the blood serum of treated rabbit showed a significant increase in the total protein, urea and creatinine concentrations, with a significant decrease in albumin/globulin (A/G) ratio. At the same time, a significant glomerulus mass reduction that accompanied with the expression of CD34, a marker for endothelial cells deterioration, was also determined. The incidence of the glomerulosclerosis was significantly increased compared with the control group (0.46 ± 0.05, p < 0.05). The glomerulosclerosis scores were 1.32 ± 0.10, 2.14 ± 0.11 and 3.02 ± 0.09 in groups 2, 3 and 4, respectively. These findings suggest that misuse of the boldenone undecylenate may contribute to the occurrence of a chronic renal injury that may lead to a progressive renal failure.

Tissue Factor Pathway Inhibitor

Objective—

To investigate in women older than 60 whether aortic stiffness or pulse pressure (PP) is associated with selected procoagulant or anticoagulant factors and to examine whether pulsatile stretch influences these factors in human vascular smooth muscle cells (VSMCs) in vitro.

Methods and Results—

Aortic pulse wave velocity (PWV) and carotid PP were studied in 123 apparently healthy postmenopausal women. PWV, PP, von Willebrand factor, and free tissue factor pathway inhibitor (TFPI), but not mean arterial pressure, increased with age. Free TFPI and PWV were positively correlated, even after adjustment for age and PP and other confounding parameters. In vitro, 5% or 10% pulsatile stretch (at 1 Hz) enhanced TFPI synthesis and secretion by VSMCs in a time-independent manner (1 to 48 hours) without changes in protein level of smooth muscle myosin heavy chain. Application of 5% static stretch had no effect.

Conclusion—

In postmenopausal women, free TFPI increases as vascular wall function deteriorates and PP increases. These findings are supported by the increase in TFPI synthesized by VSMCs in response to cyclic stress in vitro. They suggest that VSMCs require pulsatility to interfere with the coagulation process and highlight the relevance of plasma free TFPI levels to cardiovascular diseases.

Recent advances in the development of coagulation factors and procoagulants for the treatment of hemophilia

Hemophilia is a family of rare bleeding disorders. The two primary types, hemophilia A and hemophilia B, are caused by recessive X-chromosome linked mutations that result in deficiency of coagulation factor VIII (FVIII) or factor IX (FIX), respectively. Clinically, hemophilia is manifested by spontaneous bleeding, particularly into the joints (haemarthrosis) and soft tissue, and excessive bleeding following trauma or surgery. The total overall number of hemophilia patients worldwide is approximately 400,000, however only about 100,000 of these individuals are treated. The first treatment of hemophilia was initiated when it was determined that the clotting deficiency could be corrected by a plasma fraction taken from normal blood. The discovery of factor VIII enrichment by cryoprecipitation of plasma opened a new era of therapy which eventually led to the production of factor concentrates and the subsequent development of highly purified forms of plasma factors. The most significant improvements have been the availability of recombinant forms of factors VIII and IX. Unfortunately, recombinant factors still retain some of the limitations of plasma concentrates. These limitations include development of antibody responses in patients and the relatively short half-life of the molecules requiring frequent injection to maintain effective concentration. Treatment beyond replacement of native factors has been tried. They include the development of modified factor VIII and IX molecules with improved potency, stability and circulating half-life and enhancement of a prothrombotic responses and/or stabilization of coagulation factors via inhibition of key negative regulatory pathways. These approaches will be reviewed in this commentary.

Association of Asn221Ser mutation in tissue factor pathway inhibitor-beta with plasma total tissue factor pathway inhibitor level

Tissue factor pathway inhibitor (TFPI) is an anticoagulant protease inhibitor that inhibits the tissue factor-initiated blood coagulation cascade reactions. Based on these anticoagulant functions of TFPI, we hypothesized that genetic variations in TFPI may alter the TFPI expression or impair the anticoagulant function and could predispose persons to deep vein thrombosis (DVT). This study was undertaken to examine whether the genetic polymorphisms in TFPI are associated with the plasma TFPI levels and risk for DVT. We sequenced the entire coding regions of TFPI in 175 Japanese DVT patients and identified 12 genetic variants, including one missense mutation, Asn221Ser. The missense mutation occurred at the site presumably attached to the glycosylphosphatidylinositol anchor in the TFPI-beta form. The allele frequency of the mutant Ser-coding allele of the Asn221Ser mutation was 8% in the Japanese general population consisting of 1684 individuals. The Asn221Ser mutation was significantly associated with the total TFPI levels (Asn/Asn, n = 108, total TFPI = 56.57 +/- 0.88 ng/ml (mean +/- SD) vs. Asn/Ser + Ser/Ser, n = 16, total TFPI = 63.44 +/- 2.28 ng/ml, P = 0.0058). The genotype was not associated with the free TFPI level. This Asn221Ser mutation was not associated with DVT. Thus, the Asn221Ser mutation occurring in the TFPI-beta form was associated with the total TFPI level, but not a risk for DVT. The absence of the putative glycosylphosphatidylinositol anchor in TFPI-beta under pathological conditions remains to be studied.

Quantitative cardiovascular magnetic resonance for molecular imaging

Cardiovascular magnetic resonance (CMR) molecular imaging aims to identify and map the expression of important biomarkers on a cellular scale utilizing contrast agents that are specifically targeted to the biochemical signatures of disease and are capable of generating sufficient image contrast. In some cases, the contrast agents may be designed to carry a drug payload or to be sensitive to important physiological factors, such as pH, temperature or oxygenation. In this review, examples will be presented that utilize a number of different molecular imaging quantification techniques, including measuring signal changes, calculating the area of contrast enhancement, mapping relaxation time changes or direct detection of contrast agents through multi-nuclear imaging or spectroscopy. The clinical application of CMR molecular imaging could offer far reaching benefits to patient populations, including early detection of therapeutic response, localizing ruptured atherosclerotic plaques, stratifying patients based on biochemical disease markers, tissue-specific drug delivery, confirmation and quantification of end-organ drug uptake, and noninvasive monitoring of disease recurrence. Eventually, such agents may play a leading role in reducing the human burden of cardiovascular disease, by providing early diagnosis, noninvasive monitoring and effective therapy with reduced side effects.

Deterioration of glomerular endothelial surface layer induced by oxidative stress is implicated in altered permeability of macromolecules in Zucker fatty rats

AIMS/HYPOTHESIS

The glomerular endothelial layer is coated by the endothelial surface layer (ESL), which is suggested to play a role in regulation of the permselectivity of macromolecules. Production of heparanase, a degrading enzyme of the ESL, is induced by reactive oxygen species (ROS). We hypothesised that oxidative stress could cause deterioration of the glomerular ESL by induction of heparanase, resulting in increased glomerular permeability.

METHODS

Male Zucker fatty (ZF) rats with albuminuria and Zucker lean (ZL) rats were used in this study. Some of the ZF rats were treated with the angiotensin II receptor blocker, irbesartan. We determined the amount of ESL by wheat germ agglutinin staining and heparan sulphate proteoglycan production by western blot analysis. Glomerular hyperfiltration of macromolecules was visualised using in vivo microscopy. We used 2',7'-dichlorofluorescein diacetate-derived chemiluminescence staining to assess ROS production, and heparanase production and expression were determined by western blot analysis and quantitative real-time polymerase chain reaction respectively.

RESULTS

By 18 weeks of age, ZF rats had developed albuminuria. The glomerular endothelial cell glycocalyx was significantly decreased in ZF compared with ZL rats. Glomerular filtration and the permeability of macromolecules were increased in ZF, but not in ZL rats. Glomerular ROS and heparanase production were significantly increased in ZF compared with ZL rats. These changes in ZF rats were reversed by irbesartan treatment.

CONCLUSIONS/INTERPRETATION

Increased oxidative stress induces glomerular ESL deterioration in part through increased heparanase levels, resulting in exacerbation of glomerular permselectivity and development of albuminuria.

Heparanase procoagulant effects and inhibition by heparins

Heparanase is an endo-beta-D-glucuronidase capable of cleaving heparan sulfate (HS) side chains of heparan sulfate proteoglycans (HSPG) on cell surfaces and the extracellular matrix, activity that is strongly implicated in tumor metastasis and angiogenesis. Evidence was provided that heparanase over-expression in cancer cells results in a marked increase in tissue factor (TF) levels. Likewise, TF was induced by exogenous addition of recombinant heparanase to tumor cells and primary endothelial cells, induction that was mediated by p38 phosphorylation and correlated with enhanced procoagulant activity. TF induction was further confirmed in heparanase over-expressing transgenic mice and correlated with heparanase expression levels in leukemia patients. Heparanase was also found to be involved in the regulation of tissue factor pathway inhibitor (TFPI). A physical interaction between heparanase and TFPI was demonstrated, suggesting a mechanism by which secreted heparanase interacts with TFPI on the cell surface, leading to dissociation of TFPI from the cell membrane and increased coagulation activity, thus further supporting the local pro-thrombotic function of heparanase. Data indicate a possible involvement of heparanase in early miscarriages and point to a regulatory effect on TFPI and TFPI-2 in trophoblasts. As heparins are strong inhibitor of heparanase, in view of the effect of heparanase on TF, the role of heparins anticoagulant-activity may potentially be expanded. Taking into account the pro-metastatic and pro-angiogenic functions of heparanase, its over-expression in human malignancies and abundance in platelets, its involvement in the coagulation machinery is an intriguing novel arena for further research.

Anti-inflammatory actions of serine protease inhibitors containing the Kunitz domain

INTRODUCTION

Protease inhibitors, including the Kunitz, Kazal, serpin and mucus families, play important roles in inhibiting protease activities during homeostasis, inflammation, tissue injury, and cancer progression. Interestingly, in addition to their anti-protease activity, protease inhibitors also often possess other intrinsic properties that contribute to termination of the inflammatory process, including modulation of cytokine expression, signal transduction and tissue remodeling. In this review we have tried to summarize recent findings on the Kunitz family of serine proteinase inhibitors and their implications in health and disease.

MATERIALS AND METHODS

A systematic search was performed in the electronic databases PubMed and ScienceDirect up to October 2009. We tried to limit the review to anti-inflammatory actions and actions not related to protease inhibition.

RESULTS AND CONCLUSION

Recent studies have demonstrated that the Kunitz inhibitors are not only protease inhibitors, but can also prevent inflammation and tissue injury and subsequently promote tissue remodeling.

Circulating thrombotic and haemostatic components in patients with coronary artery disease

The study aimed to analyze the circulating levels of thrombotic and haemostatic components; tissue factor, tissue factor pathway inhibitor, tissue plasminogen activator and plasminogen activator inhibitor-1 in patients with acute myocardial infarction at presentation (Group 1, n=49), unstable angina and Non-ST elevated MI after treatment (Group 2, n=22), stable angina (Group 3, n=18) and healthy individuals (Group 4, n=31). Significant finding was increase in tissue factor not only in Group 1 (2.0 fold, P=0.001), Group 2 (2.2 fold, P=0.015) but also in Group 3 (1.8 fold, P=0.018) as compared to controls. In Group 1 Plasminogen activator inhibitor-1 increased significantly (35.8%, P=0.02). Tissue factor pathway inhibitor and tissue plasminogen activator demonstrated increase in Group 1 of age<40 years while insignificant changes in elder patients. Increased thrombotic and decreased fibrinolytic conditions in acute myocardial infarction patients were observed. Increase TF in stable angina demonstrates procoagulant status in these patients as well.

Lipoproteins, platelets and atherothrombosis

Atherosclerosis and thrombosis associated with the rupture of vulnerable plaque are the main causes of cardiovascular events, including acute coronary syndrome. Low-density lipoprotein (LDL) plays a key role in the pathogenesis of atherothrombotic processes. LDLs modify the antithrombotic properties of the vascular endothelium and change vessel contractility by reducing the availability of endothelial nitric oxide and activating proinflammatory signaling pathways. In addition, LDLs also influence the functions and interactions of cells present in atherosclerotic lesions, whether they come from the circulation or are resident in vessel walls. In fact, LDLs entering affected vessels undergo modifications (e.g. oxidation, aggregation and glycosylation) that potentiate their atherogenic properties. Once modified, these intravascular LDLs promote the formation of foam cells derived from smooth muscle cells and macrophages, thereby increasing the vulnerability of atherosclerotic plaque. Moreover, they also increase the thrombogenicity of both plaque and blood, in which circulating tissue factor levels are raised and platelet reactivity is enhanced. This review focuses on the importance of native and modified LDL for the pathogenesis of atherothrombosis. It also discusses current studies on LDL and its effects on the actions of vascular cells and blood cells, particularly platelets, and considers novel potential therapeutic targets.

Tissue factor pathway inhibitor relates to fibrin degradation in patients with acute deep venous thrombosis

Reduced concentration of tissue factor pathway inhibitor is a risk factor for development of deep venous thrombosis, whereas elevated concentrations of tissue factor pathway inhibitor are observed in patients with acute myocardial infarction and disseminated intravascular coagulation. Presently, we studied the association between inflammation, endothelial cell perturbation, fibrin degradation and the concentration of tissue factor pathway inhibitor in patients suspected for acute deep venous thrombosis. We determined the tissue factor pathway inhibitor -33T/C polymorphism, free and total tissue factor pathway inhibitor, C-reactive protein, von Willebrand factor and D-Dimer in 160 consecutive patients admitted to hospital with a tentative diagnosis of acute deep venous thrombosis. Deep venous thrombosis was identified in 57 patients (18 distal and 39 proximal). The distribution of the tissue factor pathway inhibitor genotypes between patients with and without deep venous thrombosis showed a trend toward significant deviation (P = 0.08). The concentrations of free and total tissue factor pathway inhibitor, C-reactive protein, von Willebrand factor and D-Dimer were significantly higher in patients with deep venous thrombosis than in patients without deep venous thrombosis (P < 0.001 for all quantities). The significant relationship between free and total tissue factor pathway inhibitor and deep venous thrombosis persisted when adjusted for the tissue factor pathway inhibitor -33T/C polymorphism, C-reactive protein, von Willebrand Factor and potentially confounding clinical conditions (P < or = 0.004), but disappeared when adjusted for D-Dimer (P > or = 0.10). We conclude that patients suffering from acute deep venous thrombosis express significantly higher concentrations of tissue factor pathway inhibitor than patients without deep venous thrombosis. The significant relationship is not associated with the -33T/C polymorphism, inflammation or endothelial cell perturbation, but is most likely related to release of tissue factor pathway inhibitor from fibrin deposits.

Heparanase coagulation and cancer progression

Heparanase is an endo-beta-D-glucuronidase capable of cleaving heparan sulphate (HS) side chains of heparan sulphate proteoglycans on cell surfaces and the extracellular matrix; activity that is strongly implicated in tumour metastasis and angiogenesis. It has been shown that heparanase overexpression in human leukaemia, glioma and breast carcinoma cells results in a marked increase in tissue factor (TF) levels. In addition, TF was induced by exogenous addition of recombinant heparanase to tumour cells and primary endothelial cells; induction that was mediated by p38 phosphorylation and correlated with enhanced procoagulant activity. TF induction was further confirmed in transgenic mice overexpressing heparanase, and correlated with heparanase expression levels in leukaemia patients. Heparanase was also found to be involved in the regulation of tissue factor pathway inhibitor (TFPI). It has been shown that heparanase overexpression or exogenous addition induces a two- to three-fold increase in TFPI expression. Similarly, heparanase stimulated accumulation of TFPI in the cell culture medium. However, extracellular accumulation exceeded the observed increase in TFPI at the protein level, and appeared to be independent of HS and heparanase enzymatic activity. Instead, a physical interaction between heparanase and TFPI was demonstrated, suggesting a mechanism by which secreted heparanase interacts with TFPI on the cell surface, leading to dissociation of TFPI from the cell membrane and increased coagulation activity, thus further supporting the local prothrombotic function of heparanase. As heparins are strong inhibitors of heparanase, in view of the effect of heparanase on the TF/TFPI pathway, the role of anticoagulant activity of heparin may potentially be expanded. Taking into account the prometastatic and pro-angiogenic functions of heparanase, its overexpression in human malignancies and abundance in platelets, its involvement in the coagulation machinery is an intriguing novel arena for further research.

Intracoronary β‐irradiation enhances balloon‐injury‐induced tissue factor expression in the porcine injury model

Intracoronary brachytherapy (ICBT) effectively reduces restenosis but is associated with late thrombosis. Since tissue factor (TF) is an important mediator of arterial thrombosis, we tested the hypothesis that ICBT results in persistently augmented TF expression. Coronary arteries from 12 pigs were randomized to: control (C; no injury), oversized balloon injury (BI), or BI followed by ICBT. Animals were sacrificed at 1, 7, 14, or 60 days postprocedure, and coronary arteries collected for expression analyses and immunostaining. ICBT-treated arteries had higher TF antigen and activity at all time-points compared to BI arteries (Western blot: 16 571 +/- 2090 vs 10 135 +/- 2939 densitometric units, p = 0.001; ELISA: 0.42 +/- 0.13 nM vs 0.25 +/- 0.14 nM, p = 0.001; TF activity assay: 0.303 +/- 0.11 nM vs 0.18 +/- 0.07 nM, p = 0.01; immunohistochemical staining: 30.6 +/- 6.6% vs 11.5% +/- 3.2%, p = 0.01). TF expression increased following BI, increased further following ICBT, and persisted for the duration of the study. We conclude that TF expression increases after BI, but is further increased and persists for a longer duration following ICBT, suggesting that a TF-mediated mechanism may play a role in late thrombosis following ICBT.

In vivo veritas: Thrombosis mechanisms in animal models

Experimental models have enhanced our understanding of atherothrombosis pathophysiology and have played a major role in the search for adequate therapeutic interventions. Various animal models have been developed to simulate thrombosis and to study in vivo parameters related to hemodynamics and rheology that lead to thrombogenesis. Although no model completely mimics the human condition, much can be learned from existing models about specific biologic processes in disease causation and therapeutic intervention. In general, large animals such as pigs and monkeys have been better suited to study atherosclerosis and arterial and venous thrombosis than smaller species such as rats, rabbits, and dogs. On the other hand, mouse models of arterial and venous thrombosis have attracted increasing interest over the past two decades, owing to direct availability of a growing number of genetically modified mice, improved technical feasibility, standardization of new models of local thrombosis, and low maintenance costs. To simulate rupture of an atherosclerotic plaque, models of arterial thrombosis often involve vascular injury, which can be achieved by several means. There is no animal model that is sufficiently tall, that can mimic the ability of humans to walk upright, and that possesses the calf muscle pump that plays an important role in human venous hemodynamics. A number of spontaneous or genetically engineered animals with overexpression or deletion of various elements in the coagulation, platelet, and fibrinolysis pathways are now available. These animal models can replicate important aspects of thrombosis in humans, and provide a valuable resource in the development of novel concepts of disease mechanisms in human patients.

Tissue factor pathway inhibitor, vascular risk factors and subclinical atherosclerosis: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Tissue factor pathway inhibitor (TFPI) is an endothelial membrane-associated anticoagulant protein. Higher circulating levels might reflect endothelial damage.

OBJECTIVE

We hypothesized an association of higher total TFPI with subclinical atherosclerosis.

PATIENTS/METHODS

Total TFPI was measured in 1000 participants of the Multi-Ethnic Study of Atherosclerosis, a cohort of 6814 men and women without clinical vascular disease, aged 45-84, from four ethnic groups. Subclinical atherosclerosis measures were coronary artery calcium (CAC), carotid intima-media thickness (IMT) and ankle-brachial index (ABI).

RESULTS

TFPI was higher with age, male gender, higher LDL-cholesterol, smoking and diabetes, but not ethnicity. Adjusting for risk factors, TFPI in the 4th quartile versus 1st quartile was associated with a 1.2-fold increased risk of detectable CAC (95% CI 1.0-1.4), a 2.1-fold increased risk of CAC >400 Agatston units (95% CI 1.1-4.0) and a 1.6-fold (95% CI 1.1-2.5) increased risk of internal carotid IMT above the 80th percentile, but not with external carotid IMT or low ABI. Findings were consistent across ethnic groups.

CONCLUSIONS

In this diverse population, higher total TFPI was associated with prevalent CAC (limited to levels >400 units), and elevated internal carotid IMT, independent of other factors. Higher TFPI may indicate endothelial dysfunction. Further study is needed of TFPI and progression of atherosclerosis.

Comparison of skin microvascular reactivity with hemostatic markers of endothelial dysfunction and damage in type 2 diabetes

Aim:

Patients with non-insulin-dependent diabetes mellitus (NIDDM) are at increased cardiovascular risk due to an accelerated atherosclerotic process. The present study aimed to compare skin microvascular function, pulse wave velocity (PWV), and a variety of hemostatic markers of endothelium injury [von Willebrand factor (vWF), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (t-PA), tissue factor pathway inhibitor (TFPI), and the soluble form of thrombomodulin (s-TM)] in patients with NIDDM.

Methods:

54 patients with NIDDM and 38 sex- and age-matched controls were studied. 27 diabetics had no overt micro- and/or macrovascular complications, while the remainder had either or both. The forearm skin blood flow was assessed by laser-Doppler imaging, which allowed the measurement of the response to iontophoretically applied acetylcholine (endothelium-dependent vasodilation) and sodium nitroprusside (endothelium-independent vasodilation), as well as the reactive hyperemia triggered by the transient occlusion of the circulation.

Results:

Both endothelial and non-endothelial reactivity were significantly blunted in diabetics, regardless of the presence or the absence of vascular complications. Plasma vWF, TFPI and s-TM levels were significantly increased compared with controls only in patients exhibiting vascular complications. Concentrations of t-PA and PAI-1 were significantly increased in the two groups of diabetics versus controls.

Conclusion:

In NIDDM, both endothelium-dependent and -independent microvascular skin reactivity are impaired, whether or not underlying vascular complications exist. It also appears that microvascular endothelial dysfunction is not necessarily associated in NIDDM with increased circulating levels of hemostatic markers of endothelial damage known to reflect a hypercoagulable state.

Thrombocyte aggregation, endothelial dysfunction and acute myocardial infarction

<zakljucak> Akutni infarkt miokarda u razvijenim i srednje razvijenim zemljama jedan je od najcescih uzroka mortaliteta i morbiditeta, pa poznavanje patofiziologije ateroskleroze i aterotromboze predstavlja najveci izazov savremenoj medicini. Najcesci uzrok AIM je ateroskleroza epikardnih koronarnih arterija sa posledicnom rupturom i/ili erozijom aterosklerotskog plaka, nastajanjem intrakoronarne tromboze i prekida cirkulacije arterijske krvi u predelu irigacije infarktne arterije. Sklonost ka aterosklerozi ne znaci po pravilu i sklonost ka trombozi, i obrnuto. Mnogobrojni faktori rizika od ishemijske bolesti srca modifikuju funkciju hemostaznog sistema, remete ravnotezu izmedju proagregatornih i antiagregatornih, prokoagulantnih i antikoagulantnih, profibrinolitickih i antifibrinolitickih mehanizama. Na taj nacin genetski uslovljena sklonost ka trombozi potencira se faktorima rizika, sto zajedno vodi ka aterotrombozi i akutnom koronarnom sindromu. Fizicko opterecenje je jedan od faktora rizika od ishemijske bolesti srca. Efekat zavisi od vrste opterecenja, duzine trajanja i stepena utreniranosti bolesnika. Umerena fizicka aktivnost kroz duzi vremenski period ima protektivni znacaj kod bolesnika sa ishemijskom bolescu srca, jer poboljsava funkciju endotela, smanjuje oksidativni stres na nivou endotela, smanjuje broj i aktivnost trombocita kao i aktivnost mnogih faktora koagulacije i na taj nacin smanjuje ucestalost ponovnih koronarnih dogadjaja. Nasuprot tome, akutna fizicka aktivnost dovodi do izrazenog prokoagulantnog stanja sto na terenu disfunkcije endotela i specificnosti hemostaznog sistema moze provocirati ponovnu koronarnu trombozu.

Porphyromonas gingivalis infection and prothrombotic effects in human aortic smooth muscle cells

INTRODUCTION

Accumulating evidence has demonstrated an association between periodontal infectious agents, such as Porphyromonas gingivalis, and vascular disease. Tissue factor (TF) and its specific tissue factor pathway inhibitor (TFPI) are produced by vascular cells and are important regulators of the coagulation cascade.

MATERIALS AND METHODS

To assess the role of P. gingivalis in atherothrombosis, we infected primary human aortic smooth muscle cells (HASMC) with either P. gingivalis 381, its non-invasive mutant DPG3, or heat-killed P. gingivalis 381. Levels and activity of TF and TFPI were measured 8 and 24 hours after infection in cell extracts and cell culture supernatants.

RESULTS

P. gingivalis 381 did not affect total TF antigen or TF activity in HASMC, but it significantly suppressed TFPI levels and activity compared to uninfected control cells, and those infected with the non-invasive mutant strain or the heat-killed bacteria. Further, P. gingivalis' LPS (up to a concentration of 5 microg/ml) failed to induce prothrombotic effects in HASMC, suggesting a significant role for the ability of whole viable bacteria to invade this cell type.

CONCLUSION

These data demonstrate for the first time that infection with a periodontal pathogen induces a prothrombotic response in HASMC.

Purification and characterization of a trypsin inhibitor from Putranjiva roxburghii seeds

A highly stable and potent trypsin inhibitor was purified to homogeneity from the seeds of Putranjiva roxburghii belonging to Euphorbiaceae family by acid precipitation, cation-exchange and anion-exchange chromatography. SDS-PAGE analysis, under reducing condition, showed that protein consists of a single polypeptide chain with molecular mass of approximately 34 kDa. The purified inhibitor inhibited bovine trypsin in 1:1 molar ratio. Kinetic studies showed that the protein is a competitive inhibitor with an equilibrium dissociation constant of 1.4x10(-11) M. The inhibitor retained the inhibitory activity over a broad range of pH (pH 2-12), temperature (20-80 degrees C) and in DTT (up to100 mM). The complete loss of inhibitory activity was observed above 90 degrees C. CD studies, at increasing temperatures, demonstrated the structural stability of inhibitor at high temperatures. The polypeptide backbone folding was retained up to 80 degrees C. The CD spectra of inhibitor at room temperature exhibited an alpha, beta pattern. N-terminal amino acid sequence of 10 residues did not show any similarities to known serine proteinase inhibitors, however, two peptides obtained by internal partial sequencing showed significant resemblance to Kunitz-type inhibitors.

Impact of Adenovirus-mediated Local Expression of Human Tissue Factor Pathway Inhibitor on Vascular Smooth Muscular Cell Proliferation and Apoptosis in the Stent-implanted Femoral Artery of the Rabbit

This study examined the effect of gene transfer of local tissue factor pathway inhibitor (TFPI) on vascular smooth muscle cells (VSMCs) in stent-implanted arteries. Rabbit femoral arteries were balloon-injured, stent-implanted and infected with the replication-defective recombinant adenovirus-mediated TFPI gene (Ad-TFPI) or the β-galactosidase gene (Ad- LacZ), or treated with saline solution. Expression of TFPI at the site of the stent was confirmed after 3 days using reverse transcription-polymerase chain reaction (RT-PCR). After 7 days, proliferating cells were visualized by immunostaining with antibodies to proliferating cell nuclear antigen (PCNA) and apoptotic cells were detected using the terminal deoxynucleotidyl mediated nick end labelling (TUNEL) technique. Cell proliferation was significantly decreased and apoptosis significantly increased in the media in the Ad-TFPI group compared with the other two groups. In conclusion, Ad-TFPI gene transfer can significantly suppress VSMC proliferation and induce its apoptosis in the media at the site of an implanted stent and may have potential for the treatment of instent re-stenosis.

The tissue factor pathway in ischemic stroke

To explore the role of the the tissue factor (TF) pathway in ischemic stroke. We measured blood concentrations of markers of the TF pathway [TF antigen, free tissue factor pathway inhibitor antigen (TFPIf) and activity (TFPIac), and activated factor VII (FVIIa)] within 7 days (acute phase) and after 3-6 months (convalescence) in 150 patients with first-ever ischemic stroke and 150 community controls. During the acute phase, TF antigen and TFPIf were not significantly altered but TFPIac was increased (mean 1.27 versus 1.13 U/ml, P = 0.04) and FVIIa was decreased in cases compared with controls (mean 43.3 versus 57.9 mU/ml, P = 0.0004). After adjusting for baseline differences between cases and controls, increasing quartiles of TFPIf were independently associated with reduced odds of stroke, and reducing quartiles of FVIIa and increasing quartiles of TFPIac with increased odds of stroke. During the convalescent phase, FVIIa and TFPIac returned to normal but TF antigen and TFPIf were significantly decreased compared with controls [median TF antigen, 110 (follow-up) versus 155 pg/ml (controls), P = 0.0008; median TFPIf, 15.5 (follow-up) versus 23.3 ng/ml (controls), P = 0.002]. Alterations of blood concentrations of TF pathway markers are common in patients with acute ischemic stroke. The mechanisms are unclear but may relate to enhanced formation of TF-FVIIa complexes and upregulation and release of TFPI during the acute phase, and ongoing consumption of TF antigen and TFPIf during the chronic phase as the atherosclerotic plaque heals.

The haemostatic role of tissue factor pathway inhibitor

Under normal conditions the blood circulates freely within the confines of the vascular system, carrying oxygen, nutrients, and hormonal information around the body and removing metabolic waste. If blood gains access to extravascular sites, or the vasculature becomes pathologically challenged, hemostasis may be activated. This process is finely regulated by positive and negative feedback loops that modulate fibrin clot formation. Blood coagulation revolves around the activation and assembly of the components of the prothrombinase complex, which converts the inactive zymogen, prothrombin, into its active form, thrombin. This serine protease catalyzes the conversion of fibrinogen to fibrin, the structural scaffold that stabilizes platelet aggregates at sites of vascular injury. The extent of the hemostatic response is controlled by the action of inhibitory pathways, which ensure that thrombin activity and the spread of the hemostatic plug is limited to the site of vessel damage. This review article focuses on the major physiological regulator of tissue factor-induced coagulation, tissue factor pathway inhibitor, its expression, anticoagulant function, and its role in normal hemostasis.

Prognostic value of plasma tissue factor and tissue factor pathway inhibitor for cardiovascular death in patients with coronary artery disease: the AtheroGene study

BACKGROUND

Tissue factor (TF) and its specific inhibitor, tissue factor pathway inhibitor (TFPI), are important contributors to the initiation of the coagulation process.

OBJECTIVES

To compare plasma levels of soluble TF (sTF) and free-TFPI (f-TFPI) between patients with stable angina pectoris (SAP) and acute coronary syndrome (ACS) and to assess the impact of the two variables on long-term prognosis.

PATIENTS/METHODS

Patients with SAPs (n = 1146) and acute coronary syndrome (n = 523) from the AtheroGene study were included and followed for 2.3 years. Because of the strong impact of unfractionated heparin (UFH) on f-TFPI levels, but not on sTF levels, patients having received UFH before blood drawing were excluded from the analyses on f-TFPI (n = 226).

RESULTS

On admission, no significant differences in sTF levels were observed between SAP and ACS patients. By comparison to patients with stable angina, f-TFPI levels significantly increased in patients with acute unstable angina and further increased in patients presenting with non-ST-elevation myocardial infarction and ST-elevation myocardial infarction (P < 10(-4)). Among the 1669 individuals with a coronary artery disease, 56 died from a cardiovascular cause. In prospective analyses, high sTF levels were independently associated with an increased risk of cardiovascular death in individuals with ACS (fully adjusted hazard ratio associated with one quartile increase = 2.06; 95% confidence interval 1.24-3.45; P = 0.006) but not in those with SAP (hazard ratio = 1.07; 95% confidence interval 0.78-1.46; P = 0.67). In SAP and ACS patients, high f-TFPI levels were not independently associated with an increased risk of cardiovascular death.

CONCLUSIONS

Plasma sTF levels were predictive of cardiovascular mortality in individuals with ACS, whereas f-TFPI levels were associated with the severity of myocardial damage on admission but were not independently related to outcome.

The endothelial glycocalyx: composition, functions, and visualization

This review aims at presenting state-of-the-art knowledge on the composition and functions of the endothelial glycocalyx. The endothelial glycocalyx is a network of membrane-bound proteoglycans and glycoproteins, covering the endothelium luminally. Both endothelium- and plasma-derived soluble molecules integrate into this mesh. Over the past decade, insight has been gained into the role of the glycocalyx in vascular physiology and pathology, including mechanotransduction, hemostasis, signaling, and blood cell–vessel wall interactions. The contribution of the glycocalyx to diabetes, ischemia/reperfusion, and atherosclerosis is also reviewed. Experimental data from the micro- and macrocirculation alludes at a vasculoprotective role for the glycocalyx. Assessing this possible role of the endothelial glycocalyx requires reliable visualization of this delicate layer, which is a great challenge. An overview is given of the various ways in which the endothelial glycocalyx has been visualized up to now, including first data from two-photon microscopic imaging.

Molecular weight dependent tissue factor pathway inhibitor release by heparin and heparin oligosaccharides

Heparin and low molecular weight heparins exert their vascular effects by mobilizing tissue factor pathway inhibitor (TFPI) from the vascular endothelium into the blood circulation. We compared the influence of molecular weight on the TFPI release by heparin and its fractions in a non-human primate model. Primates were treated with unfractionated heparin, a low molecular weight heparin (gammaparin), or a heparin-derived oligosaccharide mixture (C3). Endothelial TFPI release was determined using both immunologic and functional assays. After intravenous administration, all agents significantly increased TFPI levels (p<0.05) in a dose dependent manner. The increase produced by unfractionated heparin and gammaparin was greater than that by C3 at an equal dosage (p<0.05). With subcutaneous injection, all agents produced less TFPI release. Repeated administration of heparin-derived oligosaccharides gradually increased TFPI release. A 1.89 fold increase in TFPI levels was observed 4 days after C3 treatment (2.5 mg/kg). Our findings indicated that TFPI release is dependent on the molecular weight of heparin and its derivatives. Heparin oligosaccharides exert their vascular effects through increased TFPI release after long-term repeated administration.

Atherothrombosis and high-risk plaque: part I: evolving concepts

Atherothrombosis is a complex disease in which cholesterol deposition, inflammation, and thrombus formation play a major role. Rupture of high-risk, vulnerable plaques is responsible for coronary thrombosis, the main cause of unstable angina, acute myocardial infarction, and sudden cardiac death. In addition to rupture, plaque erosion may also lead to occlusive thrombosis and acute coronary events. Atherothrombosis can be evaluated according to histologic criteria, most commonly categorized by the American Heart Association (AHA) classification. However, this classification does not include the thin cap fibroatheroma, the most common form of high-risk, vulnerable plaque. Furthermore, the AHA classification does not include plaque erosion. As a result, new classifications have emerged and are reviewed in this article. The disease is asymptomatic during a long period and dramatically changes its course when complicated by thrombosis. This is summarized in five phases, from early lesions to plaque rupture, followed by plaque healing and fibrocalcification. For the early phases, the role of endothelial dysfunction, cholesterol transport, high-density lipoprotein, and proteoglycans are discussed. Furthermore, the innate and adaptive immune response to autoantigens, the Toll-like receptors, and the mechanisms of calcification are carefully analyzed. For the advanced phases, the role of eccentric remodeling, vasa vasorum neovascularization, and mechanisms of plaque rupture are systematically evaluated. In the final thrombosis section, focal and circulating tissue factor associated with apoptotic macrophages and circulatory monocytes is examined, closing the link between inflammation, plaque rupture, and blood thrombogenicity.

Hemextin AB Complex, a Unique Anticoagulant Protein Complex from Hemachatus haemachatus (African Ringhals Cobra) Venom That Inhibits Clot Initiation and Factor VIIa Activity

During injury or trauma, blood coagulation is initiated by the interaction of factor VIIa (FVIIa) in the blood with freshly exposed tissue factor (TF) to form the TF.FVIIa complex. However, unwanted clot formation can lead to death and debilitation due to vascular occlusion, and hence, anticoagulants are important for the treatment of thromboembolic disorders. Here, we report the isolation and characterization of two synergistically acting anticoagulant proteins, hemextins A and B, from the venom of Hemachatus haemachatus (African Ringhals cobra). N-terminal sequences and CD spectra of the native proteins indicate that these proteins belong to the three-finger toxin family. Hemextin A (but not hemextin B) exhibits mild anticoagulant activity. However, hemextin B forms a complex (hemextin AB complex) with hemextin A and synergistically enhances its anticoagulant potency. Prothrombin time assay showed that these two proteins form a 1:1 complex. Complex formation was supported by size-exclusion chromatography. Using a "dissection approach," we determined that hemextin A and the hemextin AB complex prolong clotting by inhibiting TF.FVIIa activity. The site of anticoagulant effects was supported by their inhibitory effect on the reconstituted TF.FVIIa complex. Furthermore, we demonstrated their specificity of inhibition by studying their effects on 12 serine proteases; the hemextin AB complex potently inhibited the amidolytic activity of FVIIa in the presence and absence of soluble TF. Kinetic studies showed that the hemextin AB complex is a noncompetitive inhibitor of soluble TF.FVIIa amidolytic activity, with a Ki of 50 nm. Isothermal titration calorimetric studies showed that the hemextin AB complex binds directly to FVIIa with a binding constant of 1.62 x 10(5) m(-1). The hemextin AB complex is the first reported natural inhibitor of FVIIa that does not require a scaffold to mediate its inhibitory activity. Molecular interactions of the hemextin AB complex with FVIIa/TF.FVIIa will provide a new paradigm in the search for anticoagulants that inhibit the initiation of blood coagulation.

Vascular endothelial tissue factor pathway inhibitor kinetics in culture following exposure to DX-9065a--a selective and direct factor Xa inhibitor

BACKGROUND

Tissue factor (TF), a membrane-bound glycoprotein that initiates blood coagulation by allosteric activation of factor (f) VII, is regulated predominantly by tissue factor pathway inhibitor (TFPI). Because vascular endothelial cells synthesize and constitutively secrete TFPI and fXa may directly influence its cellular clearance, we sought to determine the effects of DX-9065a, a direct and selective fXa inhibitor, on TFPI kinetics in culture.

METHODS/RESULTS

Human umbilical vein endothelial cells were grown to confluence and incubated with unfractionated heparin (1.0 U/mL), enoxaparin (1.5 U/mL), or DX-9065a at low (10 ng/ml), moderate (30 ng/ml), or high (90 ng/ml) concentrations. Compared to control, increases in TFPI were seen with both unfractionated heparin (182% higher, p < 0.001) and enoxaparin (194% higher, p < 0.001). Low concentration DX-9065a did not increase TFPI levels above control (0.8% higher, p = 0.91). In contrast, moderate and high concentrations produced 124% higher (p < 0.001) and 198% higher (p < 0.001) TFPI concentrations than control, respectively.

CONCLUSIONS

DX-9065a increases vascular endothelial cell TFPI concentrations in human tissue culture. Although the mechanism has yet to be established, decreased fXa availability may limit fXa-TFPI complex formation and its subsequent cellular uptake. Whether increased surface TFPI contributes to the overall anticoagulant profile of DX-9065a will require further investigation.

Tissue Factor, Tissue Factor Pathway Inhibitor and Vascular Endothelial Growth Factor-A in Carotid Atherosclerotic Plaques

OBJECTIVE

To determine the concentration of tissue factor (TF), tissue factor pathway inhibitor (TFPI) and vascular endothelial growth factor A (VEGF-A) in carotid plaques.

MATERIALS AND METHODS

Thirty-eight consecutive patients (20 symptomatic, 18 asymptomatic) undergoing carotid endarterectomy were enrolled into the current study. The concentration of TF, TFPI and VEGF-A in carotid plaque homogenates and blood plasma was measured using enzyme immunoassay.

RESULTS

The concentration of TF in carotid plaque homogenates was 60 fold higher than in blood plasma. There were no statistically significant differences between the concentration of TF, TFPI and VEGF-A in symptomatic and asymptomatic plaques. Carotid plaques of diabetic patients contained an increased level of TF and VEGF-A ( p = 0.002, p = 0.005). The plaque concentration of VEGF-A was elevated among older patients ( p = 0.02). Carotid plaques of non-smokers contained an increased level of TFPI ( p = 0.03). The concentration of TF, TFPI and VEGF-A in carotid plaques correlated positively with plasma level of these factors ( R = 0.86; p < 0.0001; R = 0.91; p < 0.0001; R = 0.80; p = 0.001, respectively). A highly positive correlation between concentration of VEGF-A and TF, TFPI in carotid plaques was also observed ( R = 0.75; p < 0.001; R = 0.62; p < 0.001, respectively).

CONCLUSIONS

TF, TFPI and VEGF-A concentrations do not differ in atheroma removed from symptomatic and asymptomatic patients but are higher in diabetic patients. There is a highly positive correlation between the level of VEGF-A and TF, TFPI in carotid plaques.

Daily and Circadian Rhythms of Tissue Factor Pathway Inhibitor and Factor VII Activity

Objective— Diurnal variations in levels of factor VII (FVII), FVIII, proteins C and S, antithrombin, plasminogen activator inhibitor-1, prothrombin fragment F 1+2 , and D-dimers in healthy humans point to the existence of circadian rhythms of coagulation factors. We sought for temporal fluctuations of tissue factor pathway inhibitor (TFPI) activity in human and mouse plasma.

Methods and Results— TFPI activity showed significant daily variations with highest levels in the morning in healthy men (+11%) and in mice at the light-to-dark transition (+63%), the beginning of the physically active period. Variations in FVII activity paralleled those in TFPI. In mice, the feeding schedule had a strong impact on these rhythms. Although restricted feeding and fasting shifted the peak of TFPI, the FVII peak disappeared. Investigation of temporal fluctuations in constant darkness indicated the existence of daily rhythms for TFPI and of true circadian rhythms for FVII.

Conclusions— For the first time, we report, both in humans and mice, temporal variations in TFPI activity. The coherent variations in FVII and TFPI activity could interplay to maintain the coagulation equilibrium. The chronobiological patterns should be considered to analyze activity levels of these factors. Moreover, the mouse model could be exploited to investigate modifiers of coagulation rhythms potentially associated to morning peaks of cardiovascular events.

Blood coagulation and its regulation by anticoagulant pathways: genetic pathogenesis of bleeding and thrombotic diseases

Blood coagulation and its regulation by anticoagulant pathways: genetic pathogenesis Platelet-mediated primary haemostasis and blood coagulation have evolved as important defence mechanisms against bleeding. The formation of the platelet plug provides the initial occlusion of the vascular lesion. This is temporally co-ordinated with the activation of the coagulation system, which occurs in response to the rupture of endothelium and the exposure of blood to the extravascular tissue. The reactions of blood coagulation are carefully controlled by several anticoagulant mechanisms and under normal conditions they prevail over the procoagulant forces. Genetic or acquired disturbances of the natural balance between the pro- and anticoagulant systems may result in bleeding or thrombotic diseases.

Detached endothelial cells and microparticles as sources of tissue factor activity

INTRODUCTION

Cytokine activation of endothelial cell monolayers is associated with cell detachment, microparticle shedding from plasma membranes, and phosphatidylserine appearance in the plasma membrane outer leaflets. While tissue factor expression on activated endothelial cells and microparticles is well documented, the contribution of detached endothelial cells to tissue factor activity is less clear. We studied tissue factor expression and the role of tissue factor pathway inhibitor on adherent and detached endothelial cells and on microparticles following endothelial cell activation with TNF-alpha.

MATERIALS AND METHODS

Detached endothelial cells and microparticles were obtained from cultures of human umbilical vein endothelial cells by differential centrifugation of cell culture supernatant. For microparticle capture, an antibody directed against CD146 was used. Functional tissue factor activity was measured by chromogenic assay and tissue factor antigen by ELISA. Endothelial cell and microparticle morphology was examined by light and transmission electron microscopy.

RESULTS

After cell activation for 22 h, functional tissue factor activity was distributed as follows: 60%, adherent endothelial cells; 35%, detached cells; and 5%, microparticles. Tissue factor protein followed a similar distribution. Cell detachment was 47%. Electron microscopy demonstrated shedding of microparticles with a diameter of 0.1-0.6 mum. Cy3-annexin V revealed increased phosphatidylserine on activated adherent endothelial cells and microparticles. Pre-incubation of adherent and detached endothelial cells and microparticles with anti-tissue factor antibody blocked factor Xa production. Pre-incubation with anti-tissue factor pathway inhibitor antibody increased tissue factor activity of adherent endothelial cells 2.8-fold, detached cells 1.4-fold, and microparticles 45-fold.

CONCLUSIONS

Detached endothelial cells as well as microparticles from activated endothelial cell monolayers express tissue factor activity, and this activity on microparticles is markedly inhibited by microparticle-associated tissue factor pathway inhibitor.

Role for the Kunitz-3 domain of tissue factor pathway inhibitor-alpha in cell surface binding

BACKGROUND

Tissue factor pathway inhibitor (TFPI)-alpha, a key regulator of tissue factor-induced coagulation, contains 3 tandem Kunitz-type inhibitory domains. Kunitz-1 binds and inhibits factor VIIa in the factor VIIa/tissue factor complex, and Kunitz-2 binds and inhibits factor Xa. The role of the Kunitz-3 domain of TFPI-alpha, however, has remained an enigma.

METHODS AND RESULTS

To determine the structures within TFPI-alpha involved in its binding to cell surface, altered forms of TFPI-alpha were expressed in C127 (mouse mammary) cells: C-terminal truncated forms TFPI-alpha (252), TFPI-alpha (242), and TFPI-alpha (181), which also lacks the third Kunitz domain (K3); TFPI-alpha (desK3), which lacks only the K3 domain; and TFPI-alpha (R199L), in which the putative P1 site in K3 is changed from arginine to leucine. By flow cytometry (fluorescence-activated cell sorting), the altered forms 252, 242, and R199L showed significantly reduced binding, whereas the forms 181 and desK3 completely failed to bind to the cell surface. Transient expression of WT-, desK3-, and K3/K2-TFPI-alpha (in which K3 is replaced with K2) in another cell line (b-end3, mouse endothelial) produced comparable results. Exogenously added C-terminal truncated and R199L forms of TFPI-alpha bound poorly and desK3 did not bind at all to the surface of ECV304 cells in which TFPI-alpha expression had been "knocked down" by RNA interference.

CONCLUSIONS

Optimal cell binding of endogenously expressed TFPI-alpha requires its K3 and C-terminal domains, and within the K3 domain, the P1 (R199) residue plays an important role. Thus, one role of the K3 domain involves the cell surface localization of TFPI-alpha.

Potential of free-form TFPI and PAI-1 to be useful markers of early atherosclerosis in a Japanese general population (the Suita Study): association with the intimal-medial thickness of carotid arteries

This study assessed markers of vascular endothelial cell dysfunction associated with early atherosclerosis in carotid arteries. We measured the plasma levels of free-form tissue factor pathway inhibitor (free TFPI), plasminogen activator inhibitor-1 (PAI-1), and von Willebrand factor (vWF) in 522 adults without cardiovascular disease enrolled in the Suita Study. For each sex, we analyzed the association of the degree of intimal-medial thickness (IMT) with hemostatic markers using logistic regression analysis considering potential confounding risk factors, including age, body mass index, lifestyle (current smoking and drinking), illness (diabetes mellitus and hyperlipidemia), systolic blood pressure, and antihypertensive drug use. The age-adjusted levels of free TFPI and PAI-1 were positively and independently associated with the degree of IMT for men. Even after adjustment for all confounding factors, the level of PAI-1 was positively associated with the degree of IMT. These results indicate that measurement of the levels of free TFPI and PAI-1 is a potentially useful tool for the detection of early atherosclerosis in men.

Oxidized phospholipids in oxidized low-density lipoprotein reduce the activity of tissue factor pathway inhibitor through association with its carboxy-terminal region

Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor that inhibits the initial reactions of blood coagulation. In this study, we explored the nature of active components that reduce the anticoagulant activity of TFPI in oxidized low-density lipoprotein (ox-LDL). The organic solvent-soluble fraction obtained from ox-LDL was fractionated by normal-phase HPLC. The binding profile of each fraction to TFPI showed a single peak eluting near purified oxidized phospholipid. To explore further the components in oxidized phospholipid that inhibit TFPI activity, we used oxidized phospholipids that mimic the biological activity of ox-LDL. The oxidation products of 1- and/or 2-oleoyl phosphatidylcholine or phosphatidylethanolamine were the most potent inhibitors of TFPI activity, whereas those of arachidonyl phosphatidylcholine possessed only a weak inhibitory effect on the TFPI activity. These oxidized phospholipids mainly associated with the C-terminal basic region of the TFPI molecule. The results indicate that oxidation products of delta-9 unsaturated phospholipids are candidate active components of ox-LDL that impair the function of TFPI through specific association with its C-terminal basic region.

Targeted nanoparticles for quantitative imaging of sparse molecular epitopes with MRI

Before molecular imaging with MRI can be applied clinically, certain problems, such as the potential sparseness of molecular epitopes on targeted cell surfaces, and the relative weakness of conventional targeted MR contrast agents, must be overcome. Accordingly, the conditions for diagnostic conspicuity that apply to any paramagnetic MRI contrast agent with known intrinsic relaxivity were examined in this study. A highly potent paramagnetic liquid perfluorocarbon nanoparticle contrast agent ( approximately 250 nm diameter, >90,000 Gd3+/particle) was imaged at 1.5 T and used to successfully predict a range of sparse concentrations in experimental phantoms with the use of standard MR signal models. Additionally, we cultured and targeted the smooth muscle cell (SMC) monolayers that express "tissue factor," a glycoprotein of crucial significance to hemostasis and response to vascular injury, by conjugating an anti-tissue factor antibody fragment to the nanoparticles to effect specific binding. Quantification of the signal from cell monolayers imaged at 1.5 T demonstrated, as predicted via modeling, that only picomolar concentrations of paramagnetic perfluorocarbon nanoparticles were required for the detection and quantification of tissue factor at clinical field strengths. Thus, for targeted paramagnetic agents carrying high payloads of gadolinium, it is possible to quantify molecular epitopes present in picomolar concentrations in single cells with routine MRI.

Tissue factor and tissue factor pathway inhibitor

The classical 'cascade/waterfall' hypothesis formulated to explain in vitro coagulation organised the amplification processes into the intrinsic and extrinsic pathways. Recent molecular biology and clinical data indicate that tissue factor/factor-VII interaction is the primary cellular initiator of coagulation in vivo. The process of blood coagulation is divided into an initiation phase followed by a propagation phase. The discovery of tissue factor pathway inhibitor further supports the revised theory of coagulation. Tissue factor is also a signalling receptor. Recent evidence has shown that blood-borne tissue factor has an important procoagulant function in sepsis, atherosclerosis and cancer, and other functions beyond haemostasis such as immune function and metastases.

Purification and pH stability characterization of a chymotrypsin inhibitor from Schizolobium parahyba seeds

Schizolobium parahyba chymotrypsin inhibitor (SPCI) was completely purified as a single polypeptide chain with two disulfide bonds, by TCA precipitation and ion exchange chromatography. This purification method is faster and more efficient than that previously reported: SPCI is stable from pH 2 to 12 at 25 degrees C, and is highly specific for chymotrypsin at pH 7-12. It weakly inhibits elastase and has no significant inhibitory effect against trypsin and alpha-amylase. SPCI is a thermostable protein and resists thermolysin digestion up to 70 degrees C.