Disease relevance of TFPI

• Our data suggest that protein S deficiency not only increases the risk of thrombosis by impairing the protein C system but also by reducing the ability of TFPI to down-regulate the extrinsic coagulation pathway [1].
• The ischaemic leukoaraiosis group had a different endothelial marker profile, with lower levels of TFPI (P = 0.01) and a higher TF/TFPI ratio (P = 0.01) compared with the isolated lacunar infarction group [2].
• Amino acid residues 93 to 154 of the mature TFPI protein, corresponding to the second Kunitz domain (TFPI-kII), were expressed in Escherichia coli [3].
• Low TFPI is a risk factor for a first venous thrombosis [4].
• We measured plasma levels of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in patients with thrombotic thrombocytopenic purpura (TTP) and disseminated intravascular coagulation (DIC) to examine the relationship between TFPI and vascular endothelial cell injury [5].
• Lung-associated TFPI antigen and mRNA decreased during sepsis, and TFPI activity diminished abruptly at 2 hours [6].

Psychiatry related information on TFPI

• These clotting time studies suggested that much of the anticoagulant effect caused by injection of heparin depended on EPI [7].
• Immunohistochemical localization of tissue factor pathway inhibitor-1 (TFPI-1), a Kunitz proteinase inhibitor, in Alzheimer's disease [8].

High impact information on TFPI

• To investigate the relationship between these Kunitz structures and LACI function, we have used site-directed mutagenesis to produce altered forms of LACI in which the residue at the active-site cleft of each Kunitz domain has been individually changed [9].
• Sequence analysis of complementary DNA clones has shown that LACI contains three tandemly repeated Kunitz-type serine protease inhibitory domains [9].
• In contrast, the decrease in TF activity coincided in time with maximal expression of tissue factor pathway inhibitor (TFPI) mRNA, which was determined using reverse transcriptase polymerase chain reaction (RT-PCR), and with maximal TFPI protein levels measured by immunoassay [10].
• Together with functional and antigenic analyses, they also imply that the initiation of blood clotting by extravascular monocyte/macrophages can be modulated locally by TFPI independently of plasma sources of the inhibitor [10].
• Immobilized heparin, a mimic for extracellular matrix-associated proteoglycans, binds physiological concentrations of TFPI-1 in a conformation that supports TF-VIIa-dependent cell adhesion [11].

Chemical compound and disease context of TFPI

• In this study, we investigated whether r-TFPI could ameliorate hypotension by inhibiting excessive production of NO in rats given lipopolysaccharide (LPS) [12].
• Thus, modulation of tissue factor/VIIa non-coagulant activities by LMWH, warfarin, anti-VIIa, or TFPI might be a useful therapeutic method for the inhibition of angiogenesis associated with human tumour growth and metastasis [13].
• Treatment with TFPI plus heparin abolished thrombus formation (mean area: 0.0+/-0.0 mm2, p < 0.05) but was associated with prolonged activated partial thromboplastin time and extravascular hemorrhage [14].
• Activation of tissue factor-dependent coagulation pathway not adequately balanced by TFPI has important roles in sustaining DIC and systemic inflammatory response syndrome, and it contributes to multiple organ dysfunction syndrome and death [15].
• Secondly, we found a correlation between PF4 and TFPI and between TFPI and thrombosis, suggesting that erythromelalgia may be caused by platelet-mediated endothelial activation [16].

Biological context of TFPI

• Tissue factor pathway inhibitor (TFPI) is a Kunitz-type serine proteinase inhibitor that down-regulates tissue factor-initiated blood coagulation [17].
• Proposed cellular binding sites for TFPI include nonspecific association with cell surface glycosaminoglycans and binding to glycosyl phosphatidylinositol-anchored proteins [17].
• We investigated the localisation, gene expression, and activity of tissue factor pathway inhibitor (TFPI) in endothelial cells (EC) grown in static conditions or under shear stress, in the presence of unfractionated heparin (UFH) and two low-molecular-weight heparins (LMWHs). dalteparin and bemiparin (a second generation of LMWHs) [18].
• In parallel we could document EC expression of TF, downregulation of TM and depletion of tissue factor pathway inhibitor (TFPI) in inflamed areas [19].
• In 171 controls and 49 cases in whom blood was taken at least three months after the thrombotic event, the CC genotype was associated with significantly higher total TFPI levels than the TT genotype [20].

Anatomical context of TFPI

• The most biologically active pool of TFPI is associated with the vascular endothelium, however, the biochemical mechanisms responsible for its cellular binding are not entirely defined [17].
• Co-localization of MMPs, TF, and TFPI in atherosclerotic tissues suggests that release of MMPs from inflammatory cell leukocytes may effect TF-mediated coagulation [21].
• We recently reported that recombinant tissue factor pathway inhibitor (r-TFPI), an important inhibitor of the extrinsic pathway of the coagulation system, inhibits TNF-alpha production by monocytes [12].
• TF and TFPI mRNA expression, protein levels and activity were determined and compared to human umbilical vein endothelial cells (HUVEC) [22].
• To evaluate the effects of LMWH, tinzaparin, and TFPI in a model of angiogenesis-mediated processes, we compared the effects of tinzaparin, and recombinant TFPI in inhibiting either basic fibroblast growth factor-2 (FGF2)- or TF/fVIIa-induced endothelial cell tube formation in human umbilical vein endothelial cells (HUVEC) [23].

Associations of TFPI with chemical compounds

• Binding experiments done in the presence of heparin and with altered forms of TFPI suggest that the basic C-terminal region of TFPI is required for TSP-1 binding [17].
• The patients had lower preheparin free TFPI and lower HDL cholesterol (HDL-C) levels than the healthy subjects with equivalent Lp-bound forms (free TFPI, 15. 9+/-6.5 versus 19.2+/-8.1 ng/mL) [24].
• Tissue Factor Pathway Inhibitor (TFPI) is a 36 kDa glycoprotein that helps maintain haemostasis by inhibiting Factor Xa and the Factor VIIa/Tissue Factor (TF) complex [3].
• It is possible that negatively charged n-butyric acid is sequestered by the positively charged peptide or the basic region of recombinant full length TFPI [25].
• When rTFPI was incubated with purified oxononanoyl PC (9CHO-PC) and its carboxylic form (9COOH-PC), the catalytic activity was specifically impaired, though neither oxovaleroyl PC (5CHO-PC) nor lyso-phospholipids reduced the TFPI activity [26].

Physical interactions of TFPI

• Here, we report that TFPI binds specifically and saturably to thrombospondin-1 (TSP-1) purified from platelet alpha-granules with an apparent K(D) of approximately 7.5 nm [17].
• (125)I-factor Xa ligand blots of TFPI fragments generated following MMP-8 degradation were used for probing binding interactions between factor Xa and regions of TFPI, other than the second Kunitz domain [27].
• The activation of factor X by VIIa/TF and the Xa-dependent inhibition of the enzyme complex by tissue factor pathway inhibitor (TFPI) are considered primary steps in the initiation of coagulation [28].
• The masking of the mutational effect by the presence of phospholipid shows a critical importance of Xa Gla-domain interactions in stabilizing the quaternary TF-VIIa-Xa-TFPI complex [29].
• Here, we studied whether the three GATA motifs flanking the transcription initiation sites regulate TFPI gene expression in HepG2 and ECV304 cells by binding to the GATA-2 transcription factor [30].

Enzymatic interactions of TFPI

• MMP-7 (matrilysin) rapidly cleaved TFPI to a major 35-kDa product [21].
• NH(2)-terminal amino acid sequencing revealed that MMP-12 cleaved TFPI at Lys(20)-Leu(21)(close to Kunitz I domain and producing a 35-kDa band), Arg(83)-Ile(84) (between Kunitz I and II domains), and Ser(174)-Thr(175) (between Kunitz II and III domains) [21].
• MMP-7 and MMP-9 cleaved TFPI at Lys(20)-Leu(21) with additional COOH-terminal processing [21].
• MMP-8 cleaves TFPI following Ser(174) within the connecting region between the second and third Kunitz domains ( k (cat)/ K (m) approximately 75 M(-1).s(-1)) as well as following Lys(20) within the NH(2)-terminal region [27].
• Neutrophil elastase rapidly cleaved TFPI at the Thr87-Thr88 bond situated at the link between Kunitz domains I and II [31].

Co-localisations of TFPI

• In atherosclerotic vessels, TFPI protein and mRNA frequently colocalized with TF in ECs overlying the plaque and in microvessels, as well as in the medial and neointimal SMCs, and in macrophages and T cells in areas surrounding the necrotic core [32].
• TFPI also colocalized with antibodies to the human transferrin receptor, a marker for early endocytic, recycling compartment [33].

Regulatory relationships of TFPI

• Binding is inhibited by polyclonal antibodies against TFPI and partially inhibited by the B-7 monoclonal anti-TSP-1 antibody [17].
• HLE treatment not only affects the ability of TFPI to inhibit factor VIIa/TF, but also dramatically reduces its inhibition of factor Xa [34].
• Our results show that tinzaparin and recombinant TFPI both blocked endothelial tube formation induced by either FGF2 or TF/fVIIa, in a concentration-dependent manner [23].
• LPL-induced hydrolysis of VLDL in vitro was not influenced by TFPI neither in suspension nor at the endothelial surface [35].
• Conversely, formation of a factor Xa/TFPI complex may reduce or modulate the proteolytic potential of stimulated leukocytes by temporary inhibition of cathepsin G [31].

Other interactions of TFPI

• Recombinant full-length tissue factor pathway inhibitor (RTFPI) was included in the system because of a previously observed synergistic inhibitory effect of TFPI and the protein C pathway on TF-initiated thrombin generation [36].
• ICAM1, TM and TFPI were elevated in cerebral SVD subjects compared with controls (P <or= 0.006) [2].
• We conclude that the imbalances of PAI-I/tPA and TF/TFPI are significantly associated with MI at a young age, perhaps mediated via impaired fibrinolytic activity [37].
• We have investigated the effect of MMP-8 degradation on the anticoagulant function of tissue factor pathway inhibitor (TFPI) as a potential pathological mechanism contributing to coagulation disorders [27].
• However, we speculate that the anticoagulant efficacy of rhAPC is impaired in neonates and in clinical situations associated with consumption and/or inhibition of PS, AT, and TFPI, such as severe sepsis [38].

Analytical, diagnostic and therapeutic context of TFPI

• TFPI antigen levels in seminal plasma were measured in a total of 176 subjects using an Enzyme-linked immunosorbent assay (ELISA) [39].
• The expression of TFPI mRNA, determined by Northern blotting, was specifically modulated by heparins [18].
• Immunogold electron microscopy revealed that EC exhibited strong cellular labelling for TFPI when grown under arterial flow in the presence of bemiparin [18].
• As plasma TFPI/TF ratio was significantly increased after treatment, the hypercoagulable state was therefore improved after treatment [5].
• In the present study, it was found, by means of agarose gel electrophoresis, that the pre-incubation of full-length rTFPI with heparin or the carboxy (C)-terminal part (peptide 240-265) of TFPI prevented the association with ox-LDL in a dose-dependent manner [40].

References