Presence of tissue factor pathway inhibitor in human atherosclerotic plaques is associated with reduced tissue factor activity

Prediction of Peripheral Artery Disease Prognosis Using Clinical and Inflammatory Biomarker Data

Purpose

Inflammatory biomarkers associated with peripheral artery disease (PAD) have been examined separately; however, an algorithm that includes a panel of inflammatory proteins to inform prognosis of PAD could improve predictive accuracy. We developed predictive models for 2-year PAD-related major adverse limb events (MALE) using clinical/inflammatory biomarker data.

Methods

We conducted a prognostic study using 2 phases (discovery/validation models). The discovery cohort included 100 PAD patients that were propensity-score matched to 100 non-PAD patients. The validation cohort included 365 patients with PAD and 144 patients without PAD (non-matched). Plasma concentrations of 29 inflammatory proteins were determined at recruitment and the cohorts were followed for 2 years. The outcome of interest was 2-year MALE (composite of major amputation, vascular intervention, or acute limb ischemia). A random forest model was trained with 10-fold cross-validation to predict 2-year MALE using the following input features: 1) clinical characteristics, 2) inflammatory biomarkers that were expressed differentially in PAD vs non-PAD patients, and 3) clinical characteristics and inflammatory biomarkers.

Results

The model discovery cohort was well-matched on age, sex, and comorbidities. Of the 29 proteins tested, 5 were elevated in PAD vs non-PAD patients (MMP-7, MMP-10, IL-6, CCL2/MCP-1, and TFPI). For prognosis of 2-year MALE on the validation cohort, our model achieved AUROC 0.63 using clinical features alone and adding inflammatory biomarker levels improved performance to AUROC 0.84.

Conclusion

Using clinical characteristics and inflammatory biomarker data, we developed an accurate predictive model for PAD prognosis.

The Role of the Coagulation System in Peripheral Arterial Disease: Interactions with the Arterial Wall and Its Vascular Microenvironment and Implications for Rational Therapies

Peripheral artery disease (PAD) is a clinical manifestation of atherosclerotic disease with a large-scale impact on the economy and global health. Despite the role played by platelets in the process of atherogenesis being well recognized, evidence has been increasing on the contribution of the coagulation system to the atherosclerosis formation and PAD development, with important repercussions for the therapeutic approach. Histopathological analysis and some clinical studies conducted on atherosclerotic plaques testify to the existence of different types of plaques. Likely, the role of coagulation in each specific type of plaque can be an important determinant in the histopathological composition of atherosclerosis and in its future stability. In this review, we analyze the molecular contribution of inflammation and the coagulation system on PAD pathogenesis, focusing on molecular similarities and differences between atherogenesis in PAD and coronary artery disease (CAD) and discussing the possible implications for current therapeutic strategies and future perspectives accounting for molecular inflammatory and coagulation targets. Understanding the role of cross-talking between coagulation and inflammation in atherosclerosis genesis and progression could help in choosing the right patients for future dual pathway inhibition strategies, where an antiplatelet agent is combined with an anticoagulant, whose role, despite pathophysiological premises and trials' results, is still under debate.

Knockdown screening of chromatin binding and regulatory proteins in zebrafish identified Suz12b as a regulator of tfpia and an antithrombotic drug target

Tissue factor pathway inhibitor (TFPI) is an anticoagulant protein that inhibits factor VIIa and Xa in the coagulation cascade. It has been shown that forkhead box P3 protein is a TFPI transcriptional repressor. However, there are no studies on chromatin remodeling that control TFPI expression. We hypothesized that the genome-wide knockdowns of the chromatin binding and regulatory proteins (CBRPs) in zebrafish could identify novel tfpia gene regulators. As an initial step, we selected 69 CBRP genes from the list of zebrafish thrombocyte-expressed genes. We then performed a 3-gene piggyback knockdown screen of these 69 genes, followed by quantification of tfpia mRNA levels. The results revealed that knockdown of brd7, ing2, ing3, ing4, and suz12b increased tfpia mRNA levels. The simultaneous knockdown of these 5 genes also increased tfpia mRNA levels. We also performed individual gene and simultaneous 5-gene knockdowns on the 5 genes in zebrafish larvae. We found that after laser injury, it took a longer time for the formation of the thrombus to occlude the caudal vessel compared to the control larvae. We then treated the larvae and adults with a chemical UNC6852 known to proteolytically degrade polycomb repressor complex 2, where SUZ12 is a member, and observed prolongation of time to occlude (TTO) the caudal vein after laser injury and increased tfpia mRNA levels in larvae and adults, respectively. In summary, our results have identified novel epigenetic regulators for tfpia and exploited this information to discover a drug that enhances tfpia mRNA levels and prolongation of TTO. This discovery provides the basis for testing whether UNC6852 could be used as an antithrombotic drug. This approach could be used to study the regulation of other plasma proteins, including coagulant and anticoagulant factors.

Tissue factor in atherosclerosis and atherothrombosis

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

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

Introduction

Psoriasis 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.

Aim

This 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 methods

The 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.

Results

There 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.

Conclusions

It appears that further studies are necessary to explain this problem, perhaps to include an evaluation of TF levels in psoriatic skin.

Increased expression of TFPI in human carotid stenosis

INTRODUCTION

Tissue factor (TF) pathway inhibitor (TFPI) is the physiological inhibitor of TF induced blood coagulation and two isoforms exists, TFPIα and TFPIβ. In atherosclerotic plaques, TFPI may inhibit TF activity and thrombus formation, which is the main cause of ischemic stroke in carotid artery disease. We aimed to identify the isoforms of TFPI present in human carotid plaques and potential sources of TFPI.

MATERIALS AND METHODS

Human atherosclerotic plaques from carotid endarterectomies were used for mRNA and immunohistochemistry analyses. hPBMCs isolated from buffy coats and THP-1 cells were differentiated and polarized into M1 or M2 macrophages, and subsequently cultured with or without cholesterol crystals (CC). mRNA and protein expression were measured with qRT-PCR and ELISA, respectively, and procoagulant activity was assessed using a two-stage chromogenic assay.

RESULTS

TFPIα and TFPIβ mRNA levels were significantly increased in carotid plaques, whereas TF levels were unchanged as compared to healthy arteries. Antibodies against total TFPI showed elevated levels compared to antibodies against free TFPIα, both by immunohistochemical and ELISA detection in plaques. The antibody against total TFPI also co-localized with CD68 and the M1 and M2 markers CD80 and CD163, respectively. The TFPI mRNA expression was elevated and the procoagulant activity was decreased in M2 compared to M1 polarized human macrophages. TFPI was present in early foam cell formation and CC treatment increased the TFPI mRNA expression even further in M2 macrophages.

CONCLUSIONS

Our data indicate that both isoforms of TFPI are present in advanced plaques and that anti-inflammatory M2 macrophages may be a potential source of TFPI.

Conditional knockout of TFPI-1 in VSMCs of mice accelerates atherosclerosis by enhancing AMOT/YAP pathway

BACKGROUND

Tissue factor pathway inhibitor-1 (TFPI-1) has multiple functions and its precise role and molecular mechanism during the development of atherosclerosis are not clear.

OBJECTIVES

To determine the effect and molecular mechanism of TFPI-1 deficiency in vascular smooth muscle cells (VSMCs) in atherosclerosis in the apolipoprotein E knockout (ApoE^-/-) mouse.

METHODS AND RESULTS

A mouse model with a conditional knockout of TFPI-1 in VSMCs in an atherosclerosis-prone background (ApoE^-/-) was generated. Mice were fed a high fat diet for 18weeks and were then euthanized. Arterial trees and aortas were stained with Sudan IV and were labeled via immunohistochemistry. Cell proliferation and migration of VSMCs in atherosclerotic plaques were assessed. More atherosclerotic lesions and higher levels of proliferation and migration of VSMCs were observed in TFPI-1^fl/fl/Sma-Cre⁺ApoE^-/-mice. An interaction between TFPI-1 and angiomotin (AMOT) was identified in human VSMCs by mass spectrometry, immunoprecipitation and co-localization analyses. Signal pathway changes were detected by Western blot analysis, and the expression levels of target genes were determined by real-time PCR. Decreased phosphorylation of AMOT and Yes-associated protein 1 (YAP) in TFPI-1^fl/fl/Sma-Cre⁺ApoE^-/- mice resulted in increased expression levels of snail family zinc finger 2 (SLUG) and connective tissue growth factor (CTGF), which are target genes of the Hippo signaling pathway that have been verified as atherosclerosis candidate genes.

CONCLUSION

Deficiency in TFPI-1 in the VSMCs of ApoE^-/- mice accelerated the development of atherosclerosis by promoting the proliferation and migration of VSMCs which may be caused by the decreased phosphorylation of AMOT and YAP.

SIGNIFICANCE

TFPI-1 has been found to has an anticoagulant activity, induce cell apoptosis and prevent cell proliferation. For the first time, we constructed a line of conditional knockout mice in which the TPFI-1 gene is deleted in VSMCs. We found that TFPI-1 deficiency clearly promoted the development of atherosclerosis when these mice were crossed into an ApoE^-/-background. One notable feature of atherosclerosis is the proliferation and migration of smooth muscle cells. Previous reports involved TFPI-1 do not completely explain the proliferation and migration of VSMCs because heterozygous TF deficient (TF^±) mice bred in an ApoE^-/- background did not show diminished atherosclerosis compared to TF^+/+ mice bred in the same background. Our results first confirmed that TFPI-1 interacts with AMOT, which led to a decrease in the phosphorylation of YAP and further increased the genes expression of the proliferation and migration involved. Our results further confirmed that atherosclerosis was a localized disease.

M1 and M2 macrophage proteolytic and angiogenic profile analysis in atherosclerotic patients reveals a distinctive profile in type 2 diabetes

This study aimed to investigate atherosclerotic mediators' expression levels in M1 and M2 macrophages and to focus on the influence of diabetes on M1/M2 profiles. Macrophages from 36 atherosclerotic patients (19 diabetics and 17 non-diabetics) were cultured with interleukin-1β (IL-1β) or IL-4 to induce M1 or M2 phenotype, respectively. The atherosclerotic mediators' expression was evaluated by quantitative reverse transcription-polymerase chain reaction (RT-PCR). The results showed that M1 and M2 macrophages differentially expressed mediators involved in proteolysis and angiogenesis processes. The proteolytic balance (matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinase-1 (TIMP-1), MMP-9/plasminogen activator inhibitor-1 (PAI-1) and MMP-9/tissue factor pathway inhibitor-2 (TFPI-2) ratios) was higher in M1 versus M2, whereas M2 macrophages presented higher angiogenesis properties (increased vascular endothelial growth factor/TFPI-2 and tissue factor/TFPI-2 ratios). Moreover, M1 macrophages from diabetics displayed more important proangiogenic and proteolytic activities than non-diabetics. This study reveals that M1 and M2 macrophages could differentially modulate major atherosclerosis-related pathological processes. Moreover, M1 macrophages from diabetics display a deleterious phenotype that could explain the higher plaque vulnerability observed in these subjects.

Biology of tissue factor pathway inhibitor

Recent studies of the anticoagulant activities of the tissue factor (TF) pathway inhibitor (TFPI) isoforms, TFPIα and TFPIβ, have provided new insight into the biochemical and physiological mechanisms that underlie bleeding and clotting disorders. TFPIα and TFPIβ have tissue-specific expression patterns and anticoagulant activities. An alternative splicing event in the 5' untranslated region allows for translational regulation of TFPIβ expression. TFPIα has 3 Kunitz-type inhibitor domains (K1, K2, K3) and a basic C terminus, whereas TFPIβ has the K1 and K2 domains attached to a glycosylphosphatidyl inositol-anchored C terminus. TFPIα is the only isoform present in platelets, whereas endothelial cells produce both isoforms, secreting TFPIα and expressing TFPIβ on the cell surface. TFPIα and TFPIβ inhibit both TF-factor VIIa-dependent factor Xa (FXa) generation and free FXa. Protein S enhances FXa inhibition by TFPIα. TFPIα produces isoform-specific inhibition of prothrombinase during the initiation of coagulation, an anticoagulant activity that requires an exosite interaction between its basic C terminus and an acidic region in the factor Va B domain. Platelet TFPIα may be optimally localized to dampen initial thrombin generation. Similarly, endothelial TFPIβ may be optimally localized to inhibit processes that occur when endothelial TF is present, such as during the inflammatory response.

Plasma tissue factor pathway inhibitor levels in angiographically defined coronary artery disease among saudis

OBJECTIVES

This study was aimed to determine plasma levels of total (TFPI-T) and free (TFPI-F) tissue factor pathway inhibitor, plasminogen activator inhibitor-1 (PAI-1), and tissue plasminogen activator (t-PA) in a cohort of Saudi patients with chronic stable angiographically defined coronary artery disease (CAD) and to determine its correlation with its severity.

METHODS

This cross sectional study was conducted in the department of physiology and department of cardiology, College of Medicine, and King Khalid University Hospital and King Saud University, Riyadh. Sixty known cases of CAD who had undergone angiography (35 males and 25 females) were selected. A control group included 39 (20 males and 19 females) healthy subjects. Fasting venous blood samples were analyzed for total (TFPI-T) and free (TFPI-F) tissue factor pathway inhibitor, plasminogen activator inhibitor-1 (PAI-1), and tissue plasminogen activator (t-PA). Gensini scores and vessel scores were determined for assessing CAD severity.

RESULTS

There were non-significant differences between age, body mass index (BMI) and Blood pressure between the controls and CAD subjects. A comparison of hemostatic markers between control and CAD patients showed significantly higher levels of Fibrinogen, PAI-1, TFPI-T and TFPI-F in CAD patients compared to control subjects. But there was no difference in plasma t-PA levels. TFPI-T had a significant positive correlation with severity of disease determined by Gensini Scores (r=0.344; p=0.006) and vessel scores (r=0.338; p=0.015).

CONCLUSION

Plasma levels of total tissue factor pathway inhibitor are significantly related with the presence and severity of CAD. Elevated levels of TFPI-T may be considered as useful diagnostic and prognostic markers in patients with CAD.

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.

Role of tissue factor in atherothrombosis

Tissue factor (TF) is abundantly present in atherosclerotic plaques and it is the primary source of TF that triggers the rapid activation of the coagulation cascade after plaque rupture. While much of this TF is associated with monocyte/macrophages and vascular smooth muscle cells, recent studies suggests TF-positive microparticles (MPs) are the most abundant source in plaques. Further, while intravascular TF is largely absent in healthy patients, cardiovascular disease patients have increased TF expression in circulating monocytes, which can result in increased levels of TF-positive MPs. This brief review describes how TF is the primary initiator of atherothrombosis and how TF-positive MPs may serve as a biomarker to identify patients at greater risk of forming an occlusive thrombus. In addition, currently used therapeutics, such as statins and inhibitors of the renin angiotensin system, may have additional benefits by reducing TF expression and subsequent thrombosis.

Circulating monocytes mirror the imbalance in TF and TFPI expression in carotid atherosclerotic plaques with lipid-rich and calcified morphology

BACKGROUND

Thrombogenicity of atherosclerotic plaque largely depends on plaque morphology and their content of tissue factor (TF) and tissue factor pathway inhibitor (TFPI). The relationship between morphological composition of plaque (lipid-rich or calcified) and expression of TF and TFPI in circulating blood monocytes and within the plaques is not characterized.

OBJECTIVE

To investigate whether lipid-rich (echolucent) or calcified (echogenic) morphology of carotid atherosclerotic plaques is associated with differences in TF and TFPI expression in circulating blood monocytes and within carotid atherosclerotic plaques.

METHODS

We studied levels of monocyte TF and TFPI mRNA and protein expression and association with traditional risk factors for atherosclerosis in asymptomatic subjects with echolucent (n=20) or echogenic (n=20) carotid plaques, or controls without carotid atherosclerosis (n=20) determined by ultrasonography. Sections of calcified or lipid-rich carotid plaques obtained from symptomatic patients were assessed for TF and TFPI antigen expression.

RESULTS

TF and TFPI surface presentation, surface TF/TFPI ratio, and TF activity were higher in monocytes obtained from subjects with echolucent than with echogenic plaques or controls without carotid atherosclerosis. Multiple regression analyses revealed inverse association between serum apoA1 and monocyte surface TF antigen expression (p=0.007), and positive association between serum apoB and monocyte surface TFPI expression (p=0.028). Sections from lipid-rich carotid plaques contained 2.5-fold more TF and 1.5-fold more TFPI antigens relative to calcified lesions, also yielding a higher TF/TFPI ratio.

CONCLUSIONS

Our findings indicate that circulating monocytes of asymptomatic individuals with echolucent lipid-rich carotid atherosclerosis express an imbalance between TF and TFPI expression cohering with changes found within advanced carotid atherosclerotic plaques obtained from symptomatic patients.

Tissue factor, blood coagulation, and beyond: an overview

Emerging evidence shows a broad spectrum of biological functions of tissue factor (TF). TF classical role in initiating the extrinsic blood coagulation and its direct thrombotic action in close relation to cardiovascular risks have long been established. TF overexpression/hypercoagulability often observed in many clinical conditions certainly expands its role in proinflammation, diabetes, obesity, cardiovascular diseases, angiogenesis, tumor metastasis, wound repairs, embryonic development, cell adhesion/migration, innate immunity, infection, pregnancy loss, and many others. This paper broadly covers seminal observations to discuss TF pathogenic roles in relation to diverse disease development or manifestation. Biochemically, extracellular TF signaling interfaced through protease-activated receptors (PARs) elicits cellular activation and inflammatory responses. TF diverse biological roles are associated with either coagulation-dependent or noncoagulation-mediated actions. Apparently, TF hypercoagulability refuels a coagulation-inflammation-thrombosis circuit in “autocrine” or “paracrine” fashions, which triggers a wide spectrum of pathophysiology. Accordingly, TF suppression, anticoagulation, PAR blockade, or general anti-inflammation offers an array of therapeutical benefits for easing diverse pathological conditions.

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.

Vascular-directed tissue factor pathway inhibitor overexpression regulates plasma cholesterol and reduces atherosclerotic plaque development

RATIONALE

Tissue factor pathway inhibitor (TFPI) is a potent regulator of the tissue factor pathway and is found in plasma in association with lipoproteins.

OBJECTIVE

To determine the role of TFPI in the development of atherosclerosis, we bred mice which overexpress TFPI into the apolipoprotein E-deficient (apoE(-/-)) background.

METHODS AND RESULTS

On a high-fat diet, smooth muscle 22alpha (SM22alpha)-TFPI/apoE(-/-) mice were shown to have less aortic plaque burden compared to apoE(-/-) mice. Unexpectedly, SM22alpha-TFPI/apoE(-/-) had lower plasma cholesterol levels compared to apoE(-/-) mice. Furthermore, SM22alpha-TFPI mice fed a high-fat diet had lower cholesterol levels than did wild-type mice. Because TFPI is associated with lipoproteins and its carboxyl terminus (TFPIct) has been shown to be a ligand for the very-low-density lipoprotein (VLDL) receptor, we hypothesized that TFPI overexpression may regulate lipoprotein distribution. We quantified VLDL binding and uptake in vitro in mouse aortic smooth muscle cells from SM22alpha-TFPI and wild-type mice. Mouse aortic smooth muscle cells from SM22alpha-TFPI mice demonstrated higher VLDL binding and internalization compared to those from wild-type mice. Because SM22alpha-TFPI mice have increased circulating levels of TFPI antigen, we examined whether TFPIct may act to alter lipoprotein distribution. In vitro, TFPIct increased VLDL binding, uptake, and degradation in murine embryonic fibroblasts. Furthermore, this effect was blocked by heparinase treatment. In vivo, systemic administration of TFPIct reduced plasma cholesterol levels in apoE(-/-) mice.

CONCLUSIONS

These studies suggest that overexpression of TFPI lowers plasma cholesterol through the interaction of its carboxyl terminus with lipoproteins and heparan sulfate proteoglycans.

Tissue factor expression in the symptomatic carotid plaque

Background

The aims of this study were to identify that the differences in the natural history of patients with symptomatic and asymptomatic carotid stenosis may be reflected in differences in the expression of procoagulant protein factors.

Methods

Carotid artery plaques were obtained from 33 symptomatic and 4 asymptomatic patients with internal carotid artery stenosis of greater than 70%. These plaques were stained with monoclonal antibody against human tissue factor. Areas of staining for the cap and core were analysed using the analySIS computer programme.

Results

There were 37 patients, of whom 27 were male with a mean age 69.3 years and a range of 53 to 83 years. Statistical analysis using non-parametric tests revealed a significant increase in the area of positive staining for tissue factor in plaques taken from symptomatic patients when compared to those who were asymptomatic (P = 0001). Within the symptomatic patients group there was significantly increased tissue factor in the plaque core of those who were the most recently symptomatic (P = 0.003).

Conclusions

The unstable carotid artery plaque is associated with significantly increased tissue factor expression in the cap and core. Plaques from the most recently symptomatic patients have significantly more tissue factor in the core and this may represent part of the mechanism responsible for plaque destabilisation. More research is needed in this important area.

Keywords

Tissue Factor; Carotid stenosis; Stroke; Plaque stability

Murine strain differences in hemostasis and thrombosis and tissue factor pathway inhibitor

INTRODUCTION

Differences among murine strains often lead to differential responses in models of human disease. The aim of the current study was to investigate whether differences exist among strains in models of hemostasis and thrombosis and whether these differences are reflected in differences in the tissue factor (TF) pathway.

METHODS

We examined baseline hemostatic parameters and the response to FeCl3-induced arterial thrombosis and a tail vein bleeding model in C57BL/6J (C57), 129S1/SvImJ (129S), and Balb/cJ (BalbC) mice. Finally, we examined TF and tissue factor pathway inhibitor (TFPI) activities in blood and expression in vascular tissue to determine whether these factors covary with a thrombotic phenotype.

RESULTS

No differences were observed in PT or aPTT among strains. 129S mice had lower platelet counts (p<0.001). BalbC had an increased rate of occlusion (mean occlusion time of 330+/-45 sec) in a FeCl(3)-induced model of thrombosis when compared to C57 (1182+/-349 sec) or 129 S (1442+/-281 sec) (p<0.05). Similarly, BalbC demonstrated reduced blood loss in tail bleeding experiments when compared to C57 and 129S. Vascular expression of TF and TFPI content did not correlate with the thrombotic phenotype of BalbC. However, circulating TFPI activities were lower in BalbC compared to both C57 and 129S mice. When normalized to circulating TF activities, BalbC had lower circulating TFPI activity than C57 and 129S, and there was a significant correlation between tail bleeding and normalized TFPI activity (r=0.67).

CONCLUSIONS

These data suggest that there are significant differences among strains in thrombosis and hemostasis and that circulating TFPI activity correlates with these differences.

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.

Elevated tissue expression of thrombomodulatory factors correlates with acute symptomatic carotid plaque phenotype

OBJECTIVES

Thrombomodulatory factors have been implicated in plaque instability. The aim was to examine the relationship between thrombomodulatory gene expression, timing of clinical events and plaque histology.

DESIGN OF STUDY

Plaques were obtained from 40 consecutive patients undergoing carotid endarterectomy and divided into three groups (group 1, early symptomatic, within 1 month; group 2, late symptomatic, 1-6 months and group 3, asymptomatic). Total RNA was isolated to determine the expression of tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA), plasminogen activator inhibitor-1 (PAI-1), tissue factor (TF), tissue factor pathway inhibitor (TFPI), thrombomodulin (TM), CD68 and vascular endothelial-cadherin (VE-Cadherin).

RESULTS

Expression of t-PA, PAI-1, TF, TFPI, TM, CD68 and VE-cadherin were significantly increased in the early symptomatic group (p=0.019, 0.028, 0.018, 0.025, 0.038, 0.016 and 0.027 respectively), but the level of gene expression in the late symptomatic group was indistinguishable from the asymptomatic group. The incidence of plaque rupture and intraplaque haemorrhage was significantly increased in the early symptomatic groups (58% versus 18%/18% group 2/3, and 55% versus 6%/9% respectively, p<0.05 for both).

CONCLUSIONS

Expression of thrombomodulatory genes is increased in unstable plaques, though levels after 1 month are comparable to asymptomatic plaques. This transient rise may influence plaque instability, and rapid resolution mirrors the clinical reduction in risk of further thrombo-embolic events.

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.

Dyslipidemia shifts the tissue factor/tissue factor pathway inhibitor balance toward increased thrombogenicity in atherosclerotic plaques: evidence for a corrective effect of statins

BACKGROUND

Tissue factor (TF) is a key mediator of atherosclerotic plaque thrombogenicity and may be regulated by plaque TF pathway inhibitor (TFPI). High atherogenic lipoproteins are a well-known arterial risk factor, but their effects on the TF/TFPI balance in atherosclerotic plaques, as well as those of widely used lipid-lowering agents such as statins, are incompletely understood.

OBJECTIVES

We analyzed the TF/TFPI balance in carotid plaques from 86 patients, according to the presence of dyslipidemia and statin therapy.

RESULTS

In patients with untreated dyslipidemia (ApoB/ApoA1 ratio >0.7) (D+) (n=44), TF antigen (TF) tended to be higher than in those without dyslipidemia (D-) (n=16). In patients with statins (S+) (n=26), TF was lower than in D+ (p=0.02) and similar to that of D- patients. TFPI antigen was higher in D- than in D+ and S+ patients (p<or=0.02). As a result, the TF/TFPI (mol/mol) ratio was higher in D+ than in D- or S+ patients (p<or=0.005). TF activity correlated to TF/TFPI ratio (p<0.0001), and was higher in the D+ than in the D- and in the S+ patients (p=0.02). Among analyzed clinical risk factors and biological parameters, including CRP, dyslipidemia was the only independent predictor for low plaque TFPI and high TF/TFPI ratio. Histochemistry showed that TF and TFPI were mainly expressed in macrophage-rich regions surrounding the lipid-rich core in the three groups.

CONCLUSIONS

These results indicate that dyslipidemia is associated with a shift of the TF/TFPI balance and of TF activity toward higher plaque thrombotic potential. Statins correct this equilibrium mainly by decreasing plaque TF together with blood atherogenic lipoproteins.

Tissue factor upregulation drives a thrombosis-inflammation circuit in relation to cardiovascular complications

The extrinsic coagulation is recognized as an 'inducible' signalling cascade resulting from tissue factor (TF) upregulation by exposure to clotting zymogen FVII upon inflammation or tissue injury. Following the substantial initiation, an array of proteolytic activation generates mediating signals (active serine proteases: FVIIa, FXa and FIIa) that lead to hypercoagulation with fibrin overproduction manifesting thrombosis. In addition, TF upregulation plays a central role in driving a thrombosis-inflammation circuit. Coagulant mediators (FVIIa, FXa and FIIa) and endproduct (fibrin) are proinflammatory, eliciting tissue necrosis factor, interleukins, adhesion molecules and many other intracellular signals in different cell types. Such resulting inflammation could ensure 'fibrin' thrombosis via feedback upregulation of TF. Alternatively, the resulting inflammation triggers platelet/leukocyte/polymononuclear cell activation thus contributing to 'cellular' thrombosis. TF is very vulnerable to upregulation resulting in hypercoagulability and subsequent thrombosis and inflammation, either of which presents cardiovascular risks. The prevention and intervention of TF hypercoagulability are of importance in cardioprotection. Blockade of inflammation reception and its intracellular signalling prevents TF expression from upregulation. Natural (activated protein C, tissue factor pathway inhibitor, or antithrombin III) or pharmacological anticoagulants readily offset the extrinsic hypercoagulation mainly through FVIIa, FXa or FIIa inhibition. Therefore, anticoagulants turn off the thrombosis-inflammation circuit, offering not only antithrombotic but anti-inflammatory significance in the prevention of cardiovascular complications.

Tissue factor mediates inflammation

The role of tissue factor (TF) in inflammation is mediated by blood coagulation. TF initiates the extrinsic blood coagulation that proceeds as an extracellular signaling cascade by a series of active serine proteases: FVIIa, FXa, and thrombin (FIIa) for fibrin clot production in the presence of phospholipids and Ca2+. TF upregulation resulting from its enhanced exposure to clotting factor FVII/FVIIa often manifests not only hypercoagulable but also inflammatory state. Coagulant mediators (FVIIa, FXa, and FIIa) are proinflammatory, which are largely transmitted by protease-activated receptors (PAR) to elicit inflammation including the expression of tissue necrosis factor, interleukins, adhesion molecules (MCP-1, ICAM-1, VCAM-1, selectins, etc.), and growth factors (VEGF, PDGF, bFGF, etc.). In addition, fibrin, and its fragments are also able to promote inflammation. In the event of TF hypercoagulability accompanied by the elevations in clotting signals including fibrin overproduction, the inflammatory consequence could be enormous. Antagonism to coagulation-dependent inflammation includes (1) TF downregulation, (2) anti-coagulation, and (3) PAR blockade. TF downregulation and anti-coagulation prevent and limit the proceeding of coagulation cascade in the generation of proinflammatory coagulant signals, while PAR antagonists block the transmission of such signals. These approaches are of significance in interrupting the coagulation-inflammation cycle in contribution to not only anti-inflammation but also anti-thrombosis for cardioprotection.

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.

Estrogenic regulation of tissue factor and tissue factor pathway inhibitor in platelets

Oral estrogen treatment increases thrombotic risk. Tissue factor (TF), tissue factor pathway inhibitor (TFPI), and platelet interaction with leukocytes are important determinants of thrombogenesis. Therefore, the present study was designed to define and compare platelet TF and TFPI mRNA and adhesion protein expression in platelets derived from animals treated with different types of oral estrogens. Ovariectomized pigs were treated with 17beta-estradiol (2 mg/day), conjugated equine estrogen (CEE; 0.625 mg/day), or raloxifene (60 mg/day) for 4 wk. Compared with intact animals, ovariectomy and treatment differentially affected populations of leukocytes: neutrophils decreased whereas lymphocytes increased significantly 4 wk after ovariectomy and with 17beta-estradiol and CEE treatments; eosinophils increased only with 17beta-estradiol treatment. Content of TF protein increased in platelets from 17beta-estradiol- and raloxifene-treated pigs, whereas TF mRNA was detected only in platelets from 17beta-estradiol- and CEE treated pigs. TFPI mRNA increased in platelets after ovariectomy and estrogen treatment. Only a trace of TFPI protein was detected, but a higher-molecular-mass protein was observed in all treatment groups. Expression of CD40 and CD40 ligand increased with ovariectomy and decreased with 17beta-estradiol and CEE treatments more than with raloxifene. The ratio of activated to basal P-selectin expression decreased with ovariectomy and increased with raloxifene treatments. These results suggest that estrogenic formulations may affect individual thrombotic risk by different mechanisms that regulate TF and platelet-leukocytic interactions. These studies provide the rationale for evaluation of interactions among platelets and TF and TFPI expression on thrombin generation during estrogen treatment in humans.

Lipoprotein(a): new insights into mechanisms of atherogenesis and thrombosis

Lipoprotein(a) (Lp[a]) continues to be a controversial molecule regarding its role in human vascular disease. Although the physiologic role of this molecule is still unclear, novel discoveries within the last few years have suggested numerous mechanisms whereby Lp(a) may contribute to atherosclerosis and its complications in human subjects. These effects may differentially occur in vascular tissue and circulating blood compartments. A complex interplay between tissue-specific effects is probably more relevant to the pathogenicity of this molecule than one single effect alone. This review briefly describes the structure of Lp(a) in relation to its biochemical function, summarizing the current literature on various pathophysiologic mechanisms of Lp(a)-induced vascular disease and the role of cell and tissue-specific effects in promoting atherogenesis and thrombosis.

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.

Tissue factor expression in atrial endothelia associated with nonvalvular atrial fibrillation: possible involvement in intracardiac thrombogenesis

INTRODUCTION

Tissue factor plays a key role in the extrinsic coagulation pathway and is induced by inflammatory cytokines. Atrial myocarditis has been detected recently in some patients with lone atrial fibrillation. Virchow's triad of low blood flow, hypercoagulability, and endothelial dysfunction, enhances thrombus formation. The present study was designed to elucidate the role of endothelial dysfunction in thrombogenesis associated with nonvalvular atrial fibrillation.

MATERIAL AND METHODS

We investigated tissue factor expression in the endothelia of left atrial appendages obtained from seven patients with nonvalvular atrial fibrillation and cardiogenic thromboembolism. Tissues were divided into 7-13 sections and compared with control specimens from four patients who died of noncardiac events. Expression of tissue factor, von Willebrand factor and tissue factor pathway inhibitor was evaluated by immunohistochemistry.

RESULTS

Histopathologically, inflammatory cells infiltrated the endocardium and all seven patients showed features of persistent myocarditis. Activated T cells [15.3+/-9.4 cells/high power field (HPF, mean+/-S.D.) vs. control 2.2+/-4.4/HPF (P=0.0294)] and a few macrophages [5.1+/-8.4 cells/HPF vs. control 2.4+/-3.5 cells/HPF (P=NS)] infiltrated the endocardium. Tissue factor was overexpressed in the endothelia particularly in tissues containing inflammatory cells and denuded matrix of the endocardium, compared with the control group. Von Willebrand factor, but not tissue factor pathway inhibitor, was also overexpressed in these tissues.

CONCLUSION

Tissue factor expression induced by local inflammation is involved in the pathogenesis of thrombosis in patients with nonvalvular atrial fibrillation.

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.

Inhibition of restenosis by tissue factor pathway inhibitor: in vivo and in vitro evidence for suppressed monocyte chemoattraction and reduced gelatinolytic activity

Activation of inflammatory and procoagulant mechanisms is thought to contribute significantly to the initiation of restenosis, a common complication after balloon angioplasty of obstructed arteries. During this process, expression of tissue factor (TF) represents one of the major physiologic triggers of coagulation that results in thrombus formation and the generation of additional signals leading to vascular smooth muscle cell (VSMC) proliferation and migration. In this study, we have investigated the mechanisms by which inhibition of coagulation at an early stage through overexpression of tissue factor pathway inhibitor (TFPI), an endogenous inhibitor of TF, might reduce restenosis. In a rabbit femoral artery model, percutaneous delivery of TFPI using a recombinant adenoviral vector resulted in a significant reduction of the intimamedia ratio 21 days after injury. Investigating several markers of inflammation and coagulation, we found reduced neointimal expression of monocyte chemoattractant protein-1 (MCP-1), lesional monocyte infiltration, and expression of vascular TF, matrix metalloproteinase-2 (MMP-2), and MMP-9. Moreover, overexpression of TFPI suppressed the autocrine release of platelet-derived growth factor BB (PDGF-BB), MCP-1, and MMP-2 in response to factors VIIa and Xa from VSMCs in vitro and inhibited monocyte TF activity. These results suggest that TFPI exerts its action in vivo through not only thrombotic, but also nonthrombotic mechanisms.

The impact on coagulation of an intravenous loading dose in addition to a subcutaneous regimen of low-molecular-weight heparin in the initial treatment of acute coronary syndromes

OBJECTIVES

We sought to quantify the impact of adding an intravenous loading dose to a subcutaneous regimen of enoxaparin in patients with an acute coronary syndrome (ACS).

BACKGROUND

It is unclear whether an intravenous (i.v.) loading dose of enoxaparin should be added to a subcutaneous (s.c.) regimen in patients with ACS.

METHODS

Patients admitted with ACS were randomized to i.v.+s.c.(n = 14) or s.c. alone (n = 11) enoxaparin treatment. Coagulation markers were measured at nine time points during the first 24 h of treatment.

RESULTS

The i.v.+s.c. therapy immediately resulted in therapeutic anti-Xa levels, which remained significantly higher for 6 h compared with s.c. alone, without reaching excessively high levels. A rapid decrease of plasma prothrombin fragments 1+2 (F(1+2)) levels was observed as soon as 5 min after the i.v. injection (33% lower; p = 0.007), and these levels remained lower up to 2 h after the start of treatment compared with SQ alone. The ex vivo thrombin generation time was maximally prolonged at 5 min post-injection in the i.v.+s.c. group and remained significantly prolonged up to 6 h post-injection compared with s.c. alone. The tissue factor pathway inhibitor plasma activity was immediately increased by 194% with i.v.+s.c., whereas the maximum increase with s.c. alone was 47% at 3 h.

CONCLUSIONS

Therapeutic plasma levels of enoxaparin are achieved significantly earlier by an i.v.+s.c. regimen compared with s.c. alone, without leading to unacceptably high levels. As the risk of thrombotic complications is greatest early after admission, the observed differences in antithrombotic effects may translate into a clinical benefit. However, this remains to be established.

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.

Smooth muscle cells in human coronary atherosclerosis can originate from cells administered at marrow transplantation

Atherosclerosis is the major cause of adult mortality in the developed world, and a significant contributor to atherosclerotic plaque progression involves smooth muscle cell recruitment to the intima of the vessel wall. Controversy currently exists on the exact origin of these recruited cells. Here we use sex-mismatched bone marrow transplant subjects to show that smooth muscle cells throughout the atherosclerotic vessel wall can derive from donor bone marrow. We demonstrate extensive recruitment of these cells in diseased compared with undiseased segments and exclude cell-cell fusion events as a cause for this enrichment. These data have broad implications for our understanding of the cellular components of human atherosclerotic plaque and provide a potentially novel target for future diagnostic and therapeutic strategies.

Molecular biology and gene transfer in atherosclerosis in the stenting era

Atherosclerosis is the major cause of death in the developed world. Understanding the pathogenesis of atherosclerosis has been a major challenge to cardiovascular research over the past several decades. During this period a number of advances in various scientific disciplines has increased our understanding of this disease. These include improved understanding of the structural and functional components of normal vessel wall and more recently the use of cell biology and molecular biology techniques to elucidate the pathogenesis of atherosclerosis. None of these advances has been more dramatic nor has potentially more far reaching consequences as the application of molecular biology and gene technology to the practice of cardiovascular medicine. These developments have already opened new and exciting areas of vascular research and may in the future provide for earlier identification of genetic predisposition to atherosclerosis, strategic planning of preventive therapy and more tailored pharmacologic approaches for established disease.

Role of tissue factor pathway inhibitor in the regulation of tissue factor-dependent blood coagulation

Tissue factor pathway inhibitor (TFPI) is a multivalent, Kunitz-type plasma proteinase inhibitor that modulates tissue factor-dependent coagulation in vivo. TFPI possesses a peculiar two-step mechanism of action; it directly inhibits activated factor X and subsequently produces feedback inhibition of the factor VIIa/tissue factor catalytic complex in a factor Xa-dependent fashion. TFPI biochemistry and physiology have been extensively studied during the last decade. Its pathophysiologic role in thrombotic disorders has, however, only recently started to be unraveled. In particular, circulating plasma TFPI levels have been found to modulate the activity of the tissue factor-dependent coagulation cascade. In animal models, neutralization of circulating TFPI activity results in restoration of intravascular thrombus formation previously abolished by aspirin. In patients with acute myocardial infarction, TFPI plasma levels measured in blood samples obtained from the coronary sinus were significantly lower than those measured in blood obtained from the ascending aorta, indicating acute consumption of TFPI within the coronary circulation of patients with intracoronary thrombosis. Finally, recent data indicate that transfection of the arterial wall with the gene coding for TFPI is an effective therapeutic intervention to prevent intravascular thrombus formation. Taken together, these observations underline the pathophysiologic importance of TFPI in regulating the procoagulant activity of tissue factor and open new potential therapeutic approaches for the treatment of thrombotic disorders.

Evolving role of tissue factor and its pathway inhibitor

OBJECTIVE

To review the experimental and clinical evidence of the emerging role of tissue factor in intravascular thrombosis and to examine evidence supporting the potential use of tissue factor pathway inhibitor as an antithrombotic therapeutic agent.

DATA SOURCES AND STUDY SELECTION

A PubMed search was conducted encompassing articles in the English language relating to tissue factor and tissue factor pathway inhibitor in intravascular coagulation.

CONCLUSIONS

Tissue factor, a membrane-bound procoagulant glycoprotein, is the initiator of the extrinsic clotting cascade, which is the predominant coagulation pathway in vivo. The traditional view localizes tissue factor to extravascular sites, where it remains sequestered from circulating factor VII until vascular integrity is disrupted or until tissue factor expression is induced in endothelial cells or monocytes. This perspective has been challenged since the discovery of tissue factor antigen in plasma, on circulating microparticles, and on leukocytes in whole blood. Recently, the apparent role of tissue factor has expanded with the demonstration that this molecule also functions as a signaling receptor. Recombinant tissue factor pathway inhibitor, an analogue of the physiologic inhibitor of tissue factor, is a potent inhibitor of thrombus formation in experimental models. In summary, the tissue factor pathway initiates thrombosis in vivo. In addition to its classic tissue-bound distribution, recently discovered blood-borne tissue factor may have an important procoagulant function. Despite showing promise in early human studies, a recently completed phase 3 trial of recombinant tissue factor pathway inhibitor in severe sepsis failed to show a reduction in the primary end point of 28-day all-cause mortality. Tissue factor pathway inhibitor, however, remains a plausible therapeutic agent in other conditions of increased thrombogenicity, such as acute coronary syndromes, and further studies to examine this potential are warranted.

Demonstration of inducible TFPI-2 mRNA synthesis in BeWo and JEG-3 trophoblast cells using a competitive RT-PCR

Tissue factor pathway inhibitor-2 (TFPI-2) displays structural similarities with TFPI-1, the major inhibitor of tissue factor (TF)/, factor VIIa. It is synthesized mostly by syncytiotrophoblast in the placenta, but its physiological functions are not fully understood. We studied the synthesis of TFPI-2 mRNA and that of TFPI-1 and TF in three human trophoblast cell lines, JAR, BeWo, and JEG-3. We first developed specific competitive reverse transcription-polymerase chain reaction (RT-PCR) assays for each gene studied using human umbilical vein endothelial cells (HUVEC). The three trophoblast cell lines strongly synthesized TF mRNA whereas the synthesis of TFPI-1 mRNA was very low. TFPI-2 mRNA was not detected in unstimulated or stimulated JAR cells. In contrast, JEG-3 and, to a lesser extent, BeWo produced significant amounts of TFPI-2 mRNA, which were significantly increased after stimulation with phorbol 12-myristate 13-acetate (PMA). However, tumor necrosis factor-alpha (TNF-alpha) had no effect on this synthesis. JEG-3 and BeWo are thus two cell lines that could be used to study TFPI-2 gene regulation and to investigate the role of TF, TFPI-1, and TFPI-2 during trophoblast differentiation.

Lipoprotein (a) binds and inactivates tissue factor pathway inhibitor: a novel link between lipoproteins and thrombosis

Lipoprotein (a) [Lp(a)] has been associated with both anti-fibrinolytic and atherogenic effects. However, no direct link currently exists between this atherogenic lipoprotein and intravascular coagulation. The current study examined the binding and functional effects of Lp(a), its lipoprotein constituents, apoliprotein (a) [apo(a)] and low-density lipoprotein (LDL), and lysine-plasminogen (L-PLG), which shares significant homology with apo(a), on tissue factor pathway inhibitor (TFPI), a major regulator of tissue factor-mediated coagulation. Results indicate that Lp(a), apo(a), and PLG but not LDL bound recombinant TFPI (rTFPI) in vitro and that apo(a) bound to a region spanning the last 37 amino acid residues of the c-terminus of TFPI. The apparent binding affinity for TFPI was much higher for Lp(a) (KD approximately 150 nM) compared to PLG (KD approximately 800 nM) and nanomolar concentrations of apo(a) (500 nM) inhibited PLG binding to TFPI. Lp(a) also inhibited in a concentration-dependent manner rTFPI activity and endothelial cell surface TFPI activity in vitro, whereas PLG had no such effect. Moreover physiologic concentrations of PLG (2 microM) had no effect on the concentration-dependent inhibition of TFPI activity induced by Lp(a). In human atherosclerotic plaque, apo(a) and TFPI immunostaining were shown to coexist in smooth muscle cell-rich areas of the intima. These data suggest a novel mechanism whereby Lp(a) through its apo(a) moiety may promote thrombosis by binding and inactivating TFPI.

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.

Tissue factor/tissue factor pathway inhibitor system and long-term prognosis after acute myocardial infarction

The tissue factor and tissue factor pathway inhibitor (TFPI) system has been studied in the acute phase of coronary disease but its prognostic importance has been less well assessed. We evaluated its association with recurrent coronary events during long-term follow-up after a myocardial infarction.

METHODS

We studied 55 consecutive patients with the following criteria for inclusion: (1) first myocardial infarct; (2) aged < 70 years; (3) non-complicated infarct; (4) low risk effort-test. Blood samples were taken 60-80 days after infarction. Tissue factor, total and free-TFPI were measured. A 4-year follow-up was carried out. Death, unstable angina and new myocardial infarction were considered as poor prognosis.

RESULTS

There were no statistical differences in tissue factor/TFPI levels between patients and controls. Total-TFPI showed statistical correlation with total cholesterol (r = 0.59), triglycerides (r = 0.34), LDL-cholesterol (r = 40) and Lipoprotein(a) (r = 0.48). Patients with high levels of cholesterol, LDL-cholesterol and triglycerides showed elevated levels of total-TFPI with no differences in free-TFPI. During follow-up, 8 patients showed poor prognosis. There were no statistical associations between tissue factor/TFPI levels and prognosis.

CONCLUSIONS

After acute myocardial infarction, we did not find any differences in the tissue factor/TFPI system between controls and patients. The tissue factor/TFPI system showed little value as a prognostic factor.

Effects of HMG-CoA reductase inhibitor on hemostasis

Clinical trials of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) therapy have demonstrated improvement in coronary atherosclerosis progression and reduction in risk of cardiovascular events. However, improvement in cardiovascular end-points is incompletely explained by the baseline or treated LDL cholesterol level. The beneficial effects of statins on clinical events may involve nonlipid mechanisms that modify hemostasis. Local activation of platelets and thrombus formation adjacent to atheromatous plaques, especially where ruptured or eroded, are now recognized to be of pathophysiological importance in the acute and chronic clinical expression of coronary heart disease. Thus, favorable effects of statins on hemostasis may be relevant to decreasing or delaying the progression and clinical manifestations of atherosclerosis.

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.

Differences in free and total tissue factor pathway inhibitor, and tissue factor in peripheral artery disease compared to healthy controls

Tissue factor (TF) is one of the major initiators of coagulation and raised plasma levels have been found in various cardiovascular diseases. TF activity is, however, regulated by tissue factor pathway inhibitor (TFPI), and alteration in levels of TF and/or TFPI may thus relate to thrombogenesis and atherogenesis. To investigate possible abnormalities in TF and free TFPI (i.e. unbound to TF) and total TFPI among patients with peripheral artery disease (PAD), we studied 42 patients (mean age 57, 35 men) with objectively proven (by ABPI/Doppler) disease and 42 age- and sex- matched healthy controls. TF, free TFPI and total TFPI were measured in citrated plasma by ELISA. TF was higher in the patients with PAD compared to controls (275+/-122 pg/ml versus 158+/-60, P<0.0001) but levels of total TFPI were lower in the patients (43+/-10 ng/ml versus 50+/-15, P=0.021). There was no significant difference in levels of free TFPI between patients and controls (7.2+/-1.5 ng/ml in controls, 7.5+/-1. 6 among patients, P=0.39). Within the control patients, levels of free and total TFPI were significantly correlated (Spearman r=0.51, P=0.001) but in the patients with PAD this correlation was poor (r=0. 21, P=0.178). We suggest that reduced levels of total TFPI and raised levels of TF may contribute to the process of atherogenesis and the increased risk of thrombosis among patients with cardiovascular disease.