Expression of factor V by resident macrophages boosts host defense in the peritoneal cavity.

Macrophages resident in different organs express distinct genes, but understanding how this diversity fits into tissue-specific features is limited. Here, we show that selective expression of coagulation factor V (FV) by resident peritoneal macrophages in mice promotes bacterial clearance in the peritoneal cavity and serves to facilitate the well-known but poorly understood "macrophage disappearance reaction." Intravital imaging revealed that resident macrophages were nonadherent in peritoneal fluid during homeostasis.

Dysfunctional endogenous FIX impairs prophylaxis in a mouse hemophilia B model.

Factor IX (FIX) binds to collagen IV (Col4) in the subendothelial basement membrane. In hemophilia B, this FIX-Col4 interaction reduces the plasma recovery of infused FIX and plays a role in hemostasis. Studies examining the recovery of infused BeneFix (FIX) in null (cross-reactive material negative, CRM) hemophilia B mice suggest the concentration of Col4 readily available for binding FIX is ∼405 nM with a 95% confidence interval of 374 to 436 nM.

Endogenous tissue factor pathway inhibitor has a limited effect on host defence in murine pneumococcal pneumonia.

Streptococcus (S.) pneumoniae is the most common causative pathogen in community-acquired pneumonia. Coagulation and inflammation interact in the host response to infection.

An acquired, calcium-dependent, factor X inhibitor.

Acquired factor X (FX) deficiency unrelated to amyloidosis is a rare disorder in which an anti-FX antibody is infrequently detected. A patient with severe bleeding due to a calcium ion-dependent anti-FX IgG antibody is described. The FX affinity purified IgG bound the light chain of FX, but not FX lacking its γ-carboxyglutamic acid domain, and binding was enhanced >1000-fold in the presence of calcium ions.

Factor V, tissue factor pathway inhibitor, and east Texas bleeding disorder.

In a report reading like a fascinating detective story, Vincent and colleagues crack the mysterious case of east Texas bleeding disorder. They show that affected individuals have a mutation in exon 13 of the coagulation F5 gene that causes increased expression of an alternatively spliced transcript, which encodes a previously unrecognized factor V (FV) isoform they call FV-short. This FV isoform lacks a large portion of the B domain of FV, which is normally released upon the proteolytic activation of FV by thrombin and binds tightly to the coagulation regulator tissue factor pathway inhibitor-α (TFPIα).

Contribution of protein Z and protein Z-dependent protease inhibitor in generalized Shwartzman reaction.

Objective: Sepsis, a leading cause of mortality in critically ill patients, is closely linked to the excessive activation of coagulation and inflammation. Protein Z, a cofactor for the protein Z-dependent protease inhibitor, enhances the inhibition of coagulation factor Xa, and protein Z-dependent protease inhibitor inhibits factor XIa in a protein Z-independent fashion. The functions of protein Z and protein Z-dependent protease inhibitor in the inflammatory and coagulant responses to septic illness have not been evaluated.

Structural basis for catalytic activation of protein Z-dependent protease inhibitor (ZPI) by protein Z.

The anticoagulant serpin, protein Z-dependent protease inhibitor (ZPI), is catalytically activated by its cofactor, protein Z (PZ), to regulate the function of blood coagulation factor Xa on membrane surfaces. The X-ray structure of the ZPI-PZ complex has shown that PZ binds to a unique site on ZPI centered on helix G. In the present study, we show by Ala-scanning mutagenesis of the ZPI-binding interface, together with native PAGE and kinetic analyses of PZ binding to ZPI, that Tyr240 and Asp293 of ZPI are crucial hot spots for PZ binding.

Tissue factor pathway inhibitor: structure-function.

TFPI is a multivalent, Kunitz-type proteinase inhibitor, which, due to alternative mRNA splicing, is transcribed in three isoforms: TFPIalpha, TFPIdelta, and glycosyl phosphatidyl inositol (GPI)-anchored TFPIbeta. The microvascular endothelium is thought to be the principal source of TFPI and TFPIalpha is the predominant isoform expressed in humans. TFPIalpha, apparently attached to the surface of the endothelium in an indirect GPI-anchor-dependent fashion, represents the greatest in vivo reservoir of TFPI.

TFPIβ is the GPI-anchored TFPI isoform on human endothelial cells and placental microsomes.

Tissue factor pathway inhibitor (TFPI) produces factor Xa-dependent feedback inhibition of factor VIIa/tissue factor-induced coagulation. Messages for 2 isoforms of TFPI have been identified. TFPIα mRNA encodes a protein with an acidic N-terminus, 3 Kunitz-type protease inhibitor domains and a basic C-terminus that has been purified from plasma and culture media.

Factor VII-activating protease promotes the proteolysis and inhibition of tissue factor pathway inhibitor.

Objective: Factor VII-activating protease (FSAP) activates both factor VII and pro-urokinase and inhibits platelet-derived growth factor-BB, thus regulating hemostasis- and remodeling-associated processes in the vasculature. A genetic variant of FSAP (Marburg I polymorphism) results in low enzymatic activity and is associated with an enhanced risk of carotid stenosis and stroke. We postulate that there are additional substrates for FSAP that will help to explain its role in vascular biology and have searched for such a substrate.

Inhibition of antithrombin by Plasmodium falciparum histidine-rich protein II.

Histidine-rich protein II (HRPII) is an abundant protein released into the bloodstream by Plasmodium falciparum, the parasite that causes the most severe form of human malaria. Here, we report that HRPII binds tightly and selectively to coagulation-active glycosaminoglycans (dermatan sulfate, heparan sulfate, and heparin) and inhibits antithrombin (AT). In purified systems, recombinant HRPII neutralized the heparin-catalyzed inhibition of factor Xa and thrombin by AT in a Zn(2+)-dependent manner.

Heparin is a major activator of the anticoagulant serpin, protein Z-dependent protease inhibitor.

Protein Z-dependent protease inhibitor (ZPI) is a recently identified member of the serpin superfamily that functions as a cofactor-dependent regulator of blood coagulation factors Xa and XIa. Here we provide evidence that, in addition to the established cofactors, protein Z, lipid, and calcium, heparin is an important cofactor of ZPI anticoagulant function. Heparin produced 20-100-fold accelerations of ZPI reactions with factor Xa and factor XIa to yield second order rate constants approaching the physiologically significant diffusion limit (k(a) = 10(6) to 10(7) M(-1) s(-1)).

The Kunitz-3 domain of TFPI-alpha is required for protein S-dependent enhancement of factor Xa inhibition.

Protein S (PS) enhances the inhibition of factor Xa (FXa) by tissue factor pathway inhibitor-alpha (TFPI-alpha) in the presence of Ca(2+) and phospholipids. Altered forms of recombinant TFPI-alpha were used to determine the structures within TFPI-alpha that may be involved in this PS-dependent effect. Wild-type TFPI-alpha (TFPI(WT)), TFPI-alpha lacking the K3 domain (TFPI-(DeltaK3)), and TFPI-alpha containing a single amino acid change at the putative P1 residue of K3 (R199L, TFPI(K3P1)) produced equivalent FXa inhibition in the absence of PS, whereas the response in FXa inhibition produced by PS was reduced with TFPI(K3P1) (EC(50) 61.

A meta-analysis of potential risks of low levels of protein Z for diseases related to vascular thrombosis.

The relationship between protein Z levels and thrombosis is controversial. We performed a systematic review and meta-analysis of the available studies to assess the association between protein Z and vascular thrombotic diseases. We conducted an electronic literature search through MedLine, Embase, Google Scholar, Web of Science, The Cochrane Library, bibliographies of retrieved articles and abstracts of congresses up to October, 2009.

Contribution of host-derived tissue factor to tumor neovascularization.

Objective: The role of host-derived tissue factor (TF) in tumor growth, angiogenesis, and metastasis has hitherto been unclear and was investigated in this study.

Methods And Results: We compared tumor growth, vascularity, and responses to cyclophosphamide (CTX) of tumors in wild-type (wt) mice, or in animals with TF levels reduced by 99% (low-TF mice). Global growth rate of 3 different types of transplantable tumors (LLC, B16F1, and ES teratoma) or metastasis were unchanged in low-TF mice.

Kinetic characterization of the protein Z-dependent protease inhibitor reaction with blood coagulation factor Xa.

Protein Z-dependent protease inhibitor (ZPI) is a recently identified member of the serpin superfamily that functions as a cofactor-dependent regulator of blood coagulation factors Xa (FXa) and XIa. Here we show that ZPI and its cofactor, protein Z (PZ), inhibit procoagulant membrane-bound factor Xa by the branched pathway acyl-intermediate trapping mechanism used by other serpins, but with significant variations of this mechanism that are unique to ZPI. Rapid kinetic analyses showed that the reaction proceeded by the initial assembly of a membrane-associated PZ-ZPI-FXa Michaelis complex (K(M) 53+/-5 nM) followed by conversion to a stable ZPI-FXa complex (k(lim) 1.

Protein Z-dependent protease inhibitor deficiency produces a more severe murine phenotype than protein Z deficiency.

Protein Z (PZ) is a plasma vitamin K-dependent protein that functions as a cofactor to dramatically enhance the inhibition of coagulation factor Xa by the serpin, protein Z-dependent protease inhibitor (ZPI). In vitro, ZPI not only inhibits factor Xa in a calcium ion-, phospholipid-, and PZ-dependent fashion, but also directly inhibits coagulation factor XIa. In murine gene-deletion models, PZ and ZPI deficiency enhances thrombosis following arterial injury and increases mortality from pulmonary thromboembolism following collagen/epinephrine infusion.

The role of tumor-and host-related tissue factor pools in oncogene-driven tumor progression.

Oncogenic events play an important role in cancer-related coagulopathy (Trousseau syndrome), angiogenesis and disease progression. This can, in part, be attributed to the up-regulation of tissue factor (TF) and release of TF-containing microvesicles into the pericellular milieu and the circulation. In addition, certain types of host cells (stromal cells, inflammatory cells, activated endothelium) may also express TF.

Substitution of the Gla domain in factor X with that of protein C impairs its interaction with factor VIIa/tissue factor: lack of comparable effect by similar substitution in factor IX.

We previously reported that the first epidermal growth factor-like (EGF1) domain in factor X (FX) or factor IX (FIX) plays an important role in the factor VIIa/tissue factor (FVIIa/TF)-induced coagulation. To assess the role of gamma-carboxyglutamic acid (Gla) domains of FX and FIX in FVIIa/TF induced coagulation, we studied four new and two previously described replacement mutants: FX(PCGla) and FIX(PCGla) (Gla domain replaced with that of protein C), FX(PCEGF1) and FIX(PCEGF1) (EGF1 domain replaced with that of protein C), as well as FX(PCGla/EGF1) and FIX(PCGla/EGF1) (both Gla and EGF1 domains replaced with those of protein C). FVIIa/TF activation of each FX mutant and the corresponding reciprocal activation of FVII/TF by each FXa mutant were impaired.

Thrombin-activatable fibrinolysis inhibitor deficiency attenuates bleomycin-induced lung fibrosis.

Decreased fibrinolytic function favors the development of pulmonary fibrosis. Thrombin-activatable fibrinolysis inhibitor (TAFI) is a strong suppressor of fibrinolysis, but its role in lung fibrosis is unknown. Therefore, we compared bleomycin-induced lung fibrosis in TAFI-deficient, heterozygous, and wild-type mice.

Improved coagulation in bleeding disorders by Non-Anticoagulant Sulfated Polysaccharides (NASP).

Additional therapeutic options are needed for patients with bleeding disorders such as hemophilia A, hemophilia B, severe von Willebrand disease, and other rare factor deficiencies. A novel approach to improve coagulation in such clotting disorders has been identified that, parodoxically, involves heparinlike sulfated polysaccharides. Select molecules of this broad class are largely devoid of anticoagulant activity and are here denoted Non-Anticoagulant Sulfated Polysaccharides (NASPs).

Protein Z and protein Z-dependent protease inhibitor. Determinants of levels and risk of venous thrombosis.

To assess the potential roles of protein Z (PZ) and protein Z-dependent protease inhibitor (ZPI) in venous thrombosis, their plasma levels were measured in 426 individuals with venous thrombosis and 471 control individuals participating in the Leiden Thrombophilia Study. A relationship between the level of PZ or ZPI and venous thrombosis was not detected in the overall case-control study. PZ and ZPI circulate as a complex and their plasma levels are interdependent.

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.

Formation of factors IXa and Xa by the extrinsic pathway: differential regulation by tissue factor pathway inhibitor and antithrombin III.

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. IX activation by VIIa/TF is considered to contribute catalyst necessary for further Xa production in the ensuing amplification phase. We have investigated Xa and IXabeta production by VIIa-TF in a system reconstituted with both X and IX and the principal physiologic inhibitors of this pathway TFPI and antithrombin III (AT).