Isolated CD39 expression on CD4+ T cells denotes both regulatory and memory populations

Foxp3(+) regulatory T cells (Tregs) express both ectoenzymes CD39 and CD73, which in tandem hydrolyze pericellular ATP into adenosine, an immunoinhibitory molecule that contributes to Treg suppressive function. Using Foxp3GFP knockin mice, we noted that the mouse CD4(+)CD39(+) T-cell pool contains two roughly equal size Foxp3(+) and Foxp3(-) populations. While Foxp3(+)CD39(+) cells are CD73(bright) and are the bone fide Tregs, Foxp3(-)CD39(+) cells do not have suppressive activity and are CD44(+)CD62L(-)CD25(-)CD73(dim/-), exhibiting memory cell phenotype. Functionally, CD39 expression on memory and Treg cells confers protection against ATP-induced apoptosis. Compared with Foxp3(-)CD39(-) naïve T cells, Foxp3(-)CD39(+) cells freshly isolated from non-immunized mice express at rest significantly higher levels of mRNA for T-helper lineage-specific cytokines IFN-gamma (Th1), IL-4/IL-10 (Th2), IL-17A/F (Th17), as well as pro-inflammatory cytokines, and rapidly secrete these cytokines upon stimulation. Moreover, the presence of Foxp3(-)CD39(+) cells inhibits TGF-beta induction of Foxp3 in Foxp3(-)CD39(-) cells. Furthermore, when transferred in vivo, Foxp3(-)CD39(+) cells rejected MHC-mismatched skin allografts in a much faster tempo than Foxp3(-)CD39(-) cells. Thus, besides Tregs, CD39 is also expressed on pre-existing memory T cells of Th1-, Th2- and Th17-types with heightened alloreactivity.

Isolated CD39 Expression On CD4+ T Cells Denotes Both Regulatory and Memory Populations (47.26)

Foxp3+ regulatory T cells (Tregs) express both ectoenzymes CD39 and CD73, which in tandem hydrolyze pericellular ATP into adenosine, an immunoinhibitory molecule that contributes to Treg suppressive function. Using Foxp3GFP knockin mice, we noted that the mouse CD4+CD39+ T cell pool contains two roughly equal size Foxp3+ and Foxp3- populations. While Foxp3+CD39+ cells are CD73bright and are the bone fide Tregs, Foxp3-CD39+ cells are CD44+CD62L-CD25-CD73dim/-, exhibiting memory cell phenotype. Compared with Foxp3-CD39- naïve T cells, Foxp3-CD39+ cells freshly isolated from non-immunized mice express strikingly higher levels of mRNA for T helper lineage specific cytokines IFN-γ (Th1), IL-4/IL-10 (Th2), IL-17A/F (Th17), as well as pro-inflammatory cytokines IL-1, IL-6, TNF-α, and MCP-1. Upon stimulation, Foxp3-CD39+ but not Foxp3-CD39- cells rapidly secrete these cytokines. Moreover, the presence of Foxp3-CD39+ cells inhibits TGF-β-induced conversion of Foxp3-CD39- cells into iTregs. Thus, CD39 denotes both Treg and pre-existing memory T cells of Th1-, Th2-, and Th17-types.

Adenosine generation catalyzed by CD39 and CD73 expressed on regulatory T cells mediates immune suppression

The study of T regulatory cells (T reg cells) has been limited by the lack of specific surface markers and an inability to define mechanisms of suppression. We show that the expression of CD39/ENTPD1 in concert with CD73/ecto-5′-nucleotidase distinguishes CD4⁺/CD25⁺/Foxp3⁺ T reg cells from other T cells. These ectoenzymes generate pericellular adenosine from extracellular nucleotides. The coordinated expression of CD39/CD73 on T reg cells and the adenosine A2A receptor on activated T effector cells generates immunosuppressive loops, indicating roles in the inhibitory function of T reg cells. Consequently, T reg cells from Cd39-null mice show impaired suppressive properties in vitro and fail to block allograft rejection in vivo. We conclude that CD39 and CD73 are surface markers of T reg cells that impart a specific biochemical signature characterized by adenosine generation that has functional relevance for cellular immunoregulation.

Disordered cellular migration and angiogenesis in cd39-null mice

BACKGROUND

Nucleoside triphosphate diphosphohydrolase-1 (NTPDase1)/CD39 is the major ectonucleotidase of endothelial cells and monocytes and catalyzes phosphohydrolysis of extracellular nucleoside diphosphates (NDP) and triphosphates (NTP, eg, ATP and UTP). Deletion of cd39 causes perturbations in the hydrolysis of NTP and NDP in the vasculature. Activation of P2 receptors appears to influence endothelial cell chemotactic and mitogenic responses in vitro. Therefore, aberrant regulation of nucleotide P2 receptors may influence angiogenesis in cd39-null mice. Methods and Results- In control mice, implanted Matrigel plugs containing growth factors were rapidly populated by monocyte/macrophages, endothelial cells, and pericytes, with the development of new vessels over days. In cd39-null mice, migrating cells were completely confined to the tissue-Matrigel interface in a clearly stratified manner. Absolute failure of new vessel ingrowth was consistently observed in the mutant mice. Linked to these findings, chemotaxis of cd39-null monocyte/macrophages to nucleotides was impaired in vitro. This abnormality was associated with desensitization of nucleotide receptor P2Y-mediated signaling pathways.

CONCLUSIONS

Our findings demonstrate a role for NTPDase1 and phosphohydrolysis of extracellular nucleotides in the regulation of the cellular infiltration and new vessel growth in a model of angiogenesis.

Production of tissue factor pathway inhibitor in cardiomyocytes and its upregulation by interleukin-1

Tissue factor pathway inhibitor (TFPI) is a protease inhibitor that regulates tissue factor (TF)--initiated coagulation. We report here that cardiomyocytes express TFPI and the expression could be increased by Interleukin-1(IL-1beta). The TFPI expression in cardiomyocytes was confirmed by Northern blotting with rat cardiomyocytes and also by immunostaining with anti-TFPI antibody on human heart specimens from patients either with sarcoidosis, myocarditis or myocardial infarction. The regulation of TFPI expression in cardiomyocytes differs from that in endothelial cells because TFPI expression is not induced in human endothelial cells by IL-1beta.

Assignment of ecto-nucleoside triphosphate diphosphohydrolase-1/cd39 expression to microglia and vasculature of the brain

Extracellular nucleotides are ubiquitous extracellular mediators that interact with and activate nucleotide type 2 (P2) receptors. These receptors initiate a wide variety of signalling pathways that appear important for functional associations between neurons and glial cells and for the regulation of blood flow, haemostatic and inflammatory reactions in the brain. Ectonucleotidases are extracellular nucleotide-metabolizing enzymes that modulate P2 receptor-mediated signalling by the regulated hydrolysis of these agonists. A considerable number of ectoenzyme species with partially overlapping substrate and tissue distributions have been described. Major candidates for expression in the brain are members of the ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase or CD39) family. The production of cd39-/- mice and specific reagents have enabled us to analyse the specific cellular distribution of NTPDase1 (CD39), the prototype member of the enzyme family, in the mouse brain. Using monospecific antibodies and enzyme histochemical staining, we have identified NTPDase1 as a major ectonucleotidase associated with both microglia and the endothelial and smooth muscle cells of the vasculature. NTPDase1 is not expressed by neurons and astrocytes. Additional unidentified ectonucleotidase functional activity is observed at lower levels throughout the brain parenchyma. NTPDase1 may regulate P2 receptor-mediated functions of microglia as well as influence nucleotide signalling between neurons or astrocytes that are associated with multiple microglial ramifications. The expression of NTPDase1 by cerebrovascular endothelial and smooth muscle cells also suggests involvement in the regulation of blood flow and thrombogenesis.

Does hypertension confer a hypercoagulable state in stroke-prone spontaneously hypertensive rats?

OBJECTIVE

To verify whether hypertension confers a hypercoagulable state in a hypertensive animal model.

DESIGN

The parameters of blood coagulation were compared between stroke-prone spontaneously hypertensive rats (SHR-SP) and Wistar-Kyoto (WKY) rats. Each rat group consisted of a younger subgroup at 8-12 weeks old (n = 12) and an older subgroup at 16-20 weeks old (n = 12).

METHODS

Prothrombin time (PT), activated partial thromboplastin time (APTT), fluorogenic PT, fibrinogen, fibrin/fibrinogen degradation products (FDP), thrombin-anti-thrombin III complex (TAT), factor Xa activity, anti-thrombin III (AT-III), tissue factor pathway inhibitor (TFPI), protein C and C1 inhibitor were measured in both rat groups.

RESULTS

There was no significant difference in FDP and TAT levels between SHR-SP and WKY rats even at 16-20 weeks when SHR-SP developed severe hypertensive vascular lesions. Contrary to expectations, fluorogenic PT and factor Xa activity were significantly lower in SHR-SP than in WKY rats. While there was no significant difference in AT-III, TFPI and protein C activities between SHR-SP and WKY rats, C1 inhibitor activity was significantly higher in SHR-SP than in WKY rats. The elevated C1 inhibitor activity was inversely correlated with the reduced factor Xa activity. Gel-filtered fractionated plasma with C1 inhibitor activity had an inhibitory effect on the purified rat factor Xa, and immunodepletion of C1 inhibitor from the fractionated plasma attenuated the inhibitory effect

CONCLUSION

These results suggest that SHR-SP get into a hypocoagulable state rather than a hypercoagulable state, and that the reduction of factor Xa activity in SHR-SP may be related to the elevation of C1 inhibitor activity.

Modulation of nucleoside [correction of nucleotide] triphosphate diphosphohydrolase-1 (NTPDase-1)cd39 in xenograft rejection

BACKGROUND

There is increasing evidence showing that extracellular nucleosides [corrected] may be important mediators of vascular inflammation. Nucleoside [corrected] triphosphate diphosphohydrolase-1 (NTPDase-1, identical to CD39), the major vascular endothelial ectonucleotidase, is responsible for the hydrolysis of both extracellular ATP and ADP in the blood plasma to AMP. Studies were therefore conducted to evaluate the role of vascular NTPDase-1/cd39 in modulating platelet activation and vascular injury in cardiac xenografts.

MATERIALS AND METHODS

Cardiac xenografts from both wild-type and cd39 knockout mice (C57BL/6 x 129 Svj) were transplanted into Lewis rats. Alterations in cd39 mRNA transcripts and NTPDase activity expression were evaluated in wild-type grafts in untreated rats and then following complement depletion and immunosuppression. Rejection responses were studied with both mutant and wild-type grafts in the following models: presensitization with or without complement depletion, complement depletion alone, and with chronic immunosuppression to induce long-term graft survival.

RESULTS

NTPDase biochemical activity in wild-type xenografts rapidly decreased after transplantation but soon rebounded with graft survival. Elevated levels of cd39 mRNA with associated increases in NTPDase activity were observed in all long-term surviving wild-type grafts. Hyperacute xenograft rejection times were comparable in wild-type and mutant grafts but cd39-deficient grafts were subject to more rapid rejection and exhibited pronounced vascular injury in complement-depleted, presensitized rats. The cd39-deficient grafts in immunosuppressed recipients were subject to increased intravascular platelet sequestration and fibrin deposition; this resulted in focal myocardial infarction in long-term surviving mutant xenografts.

CONCLUSIONS

Augmentation of NTPDase-1 activity may be an important adaptive response for graft survival. Our results suggest that NTPDase-1/cd39 influences pathways of vascular injury in cardiac xenografts.

Targeted disruption of cd39/ATP diphosphohydrolase results in disordered hemostasis and thromboregulation

CD39, or vascular adenosine triphosphate diphosphohydrolase, has been considered an important inhibitor of platelet activation. Unexpectedly, cd39-deficient mice had prolonged bleeding times with minimally perturbed coagulation parameters. Platelet interactions with injured mesenteric vasculature were considerably reduced in vivo and purified mutant platelets failed to aggregate to standard agonists in vitro. This platelet hypofunction was reversible and associated with purinergic type P2Y1 receptor desensitization. In keeping with deficient vascular protective mechanisms, fibrin deposition was found at multiple organ sites in cd39-deficient mice and in transplanted cardiac grafts. Our data indicate a dual role for adenosine triphosphate diphosphohydrolase in modulating hemostasis and thrombotic reactions.

A novel degradation pathway of tissue factor pathway inhibitor: incorporation into fibrin clot and degradation by thrombin

Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor with three tandem inhibitory domains (K1, K2, and K3) that regulates the initial reactions of the extrinsic blood coagulation pathway through K1 and K2. In the present study, the effect of thrombin on TFPI in a purified system was first examined using recombinant TFPI from Chinese hamster ovary (CHO) cells. TFPI was inactivated by thrombin with cleavage of three peptide bonds, Lys 254-Thr 255 in the C-terminal basic region, Arg 107-Gly 108 (reactive site toward factor Xa in K2), and Lys 86-Thr 87 between K1 and K2. Then, degradation of radiolabeled TFPI by thrombin was examined in two systems: (1) mixed with plasma and then tissue factor (TF) and calcium ion, and (2) mixed with fibrinogen and then thrombin. TFPI degradation was detected in serum from normal plasma and more extensively from anti-thrombin (AT)-depleted plasma by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Significant radioactivity was found in the clot after coagulation of the plasma, which decreased after 20 hours' incubation. These changes were more prominent in AT-depleted plasma than in normal plasma. When TFPI lacking the C-terminal basic region was used instead of full-length TFPI, most of the radioactivity was found in serum rather than in fibrin clots. Incorporation of TFPI into the fibrin clot was prevented by a synthetic C-terminal peptide of TFPI. Similar results were obtained after mixing radiolabeled TFPI with fibrinogen and then thrombin in the presence of calcium ion or EDTA. These results demonstrate a novel degradation pathway of TFPI, ie, incorporation into fibrin via the C-terminal basic region and degradation by thrombin (possibly fibrin-bound thrombin).

Effect of depolymerized holothurian glycosaminoglycan (DHG) on tissue factor pathway inhibitor: in vitro and in vivo studies

Depolymerized holothurian glycosaminoglycan (DHG) is a glycosaminoglycan extracted from the sea cucumber Stichopus japonicus Selenka. In previous studies, we demonstrated that DHG has antithrombotic and anticoagulant activities that are distinguishable from those of heparin and dermatan sulfate. In the present study, we examined the effect of DHG on the tissue factor pathway inhibitor (TFPI), which inhibits the initial reaction of the tissue factor (TF)-mediated coagulation pathway. We first examined the effect of DHG on factor Xa inhibition by TFPI and the inhibition of TF-factor VIIa by TFPI-factor Xa in in vitro experiments using human purified proteins. DHG increased the rate of factor Xa inhibition by TFPI, which was abolished either with a synthetic C-terminal peptide or with a synthetic K3 domain peptide of TFPI. In contrast, DHG reduced the rate of TF-factor VIIa inhibition by TFPI-factor Xa. Therefore, the effect of DHG on in vitro activity of TFPI appears to be contradictory. We then examined the effect of DHG on TFPI in cynomolgus monkeys and compared it with that of unfractionated heparin. DHG induced an increase in the circulating level of free-form TFPI in plasma about 20-fold when administered i.v. at 1 mg/kg. The prothrombin time (PT) in monkey plasma after DHG administration was longer than that estimated from the plasma concentrations of DHG. Therefore, free-form TFPI released by DHG seems to play an additive role in the anticoagulant mechanisms of DHG through the extrinsic pathway in vivo. From the results shown in the present work and in previous studies, we conclude that DHG shows anticoagulant activity at various stages of coagulation reactions, i.e., by inhibiting the initial reaction of the extrinsic pathway, by inhibiting the intrinsic Xase, and by inhibiting thrombin.

Structure and function of the recombinant fifth domain of human beta 2-glycoprotein I: effects of specific cleavage between Lys77 and Thr78

In order to elucidate the mechanism of binding of beta 2-glycoprotein I (beta 2-GPI) to cardiolipin (CL), we constructed a high-level expression system for the C-terminal domain (Domain V) of beta 2-GPI using Pichia pastoris and studied its conformation and liposome-binding activity. Purified Domain V was found to have the native disulfide bonds. It had a compactly folded conformation, judging from the circular dichroism spectrum, and exhibited a cooperative unfolding transition induced by pH or urea. Also, it bound liposomes containing CL. Commercially available human beta 2-GPI is known to be selectively cleaved between Lys 317 and Thr 318. We found that bovine factor Xa weakly but specifically cleaves the corresponding site of recombinant Domain V, i.e., the peptide bond between Lys 77 and Thr 78. The conformation of the "nicked" Domain V, which was cleaved at this site, was examined by circular dichroism and fluorescence measurements, and concluded to be similar to that of the intact protein. The stability of the nicked Domain V to urea was slightly lower than that of the intact protein. Although both Domains V bound to liposomes containing CL, the affinity of the nicked Domain V was greatly reduced in comparison with the intact protein, indicating that the cleavage of the peptide bond between Lys 77 and Thr 78 controls the binding to CL. In addition, analysis of the fluorescence spectra in the presence and absence of CL liposomes indicated that Trp 76 is involved in the binding site. These results suggest that the region including Trp 76, Lys 77, and Thr 78 has a critical role in binding to CL.

Measurement of the free form of TFPI antigen in hyperlipidemia. Relationship between free and endothelial cell-associated forms of TFPI

Tissue factor pathway inhibitor (TFPI), a protease with three tandem Kunitz-type (K1, K2, and K3) domains, inhibits the initial reaction of the TF-mediated coagulation pathway. TFPI occurs in a free and a lipoprotein-associated form in plasma as well as an endothelial cell-associated form on vascular walls. In a previous study we had demonstrated that free-form TFPI activity was lower in hyperlipidemic patients. In the present study we established a new enzyme immunoassay method for measuring free-form TFPI antigen; this new method uses a monoclonal antibody that recognizes the K3 domain of free-form TFPI but not lipoprotein-associated TFPI. Free-form TFPI antigen was significantly lower in hyperlipidemic patients compared with those in normolipidemic individuals. We applied this new method to measure the amount of endothelial cell-associated TFPI, which can be released by heparin injection, as "free-form TFPI." We found that free-form TFPI antigen in plasma was positively correlated with the endothelial cell-associated form. These results indicate that both of these forms of TFPI are in equilibrium in vivo and that our new method can be used for assessing changes in the levels of endothelial cell-associated TFPI antigen and, hence, for assessing thrombotic tendencies in various disease states.

Effect of depolymerized holothurian glycosaminoglycan (DHG) on the activation of factor VIII and factor V by thrombin

Our previous study has shown that depolymerized holothurian glycosaminoglycan (DHG) has two different inhibitory activities in the blood coagulation cascade: heparin cofactor II-dependent thrombin inhibition; and antithrombin III- and heparin cofactor II-independent inhibition of the intrinsic factor Xase complex [Nagase et al. (1995) Blood 85, 1527-1534]. In the present study, the effect of DHG on the activation of factor VIII and factor V by thrombin was examined with purified human components. DHG inhibited the activation of factor VIII by thrombin at concentrations exceeding 80 nM, but not the activation of factor V by thrombin at concentrations of up to 8 mu M. On Western blot analysis, DHG inhibited the cleavage of factor VIII light chain at concentrations exceeding 0.8 mu M. The interaction between DHG and factors VIII and V and thrombin was examined with a DHG-cellulofine column. DHG had strong affinity for factor V and thrombin, but slight affinity for factor VIII. The interaction of DHG with thrombin was analyzed, using fluorescein isothiocyanate-labeled DHG. One mole of DHG bound 2 mol of thrombin, with a dissociation constant (Kd) of 3.04 x 10(-6) M. These results suggest that DHG interferes with the interaction between thrombin and factor VIII, probably by making a binary complex through the anionic binding exosite II of thrombin.

An anti-tissue factor pathway inhibitor (TFPI) monoclonal antibody recognized the third Kunitz domain (K3) of free-form TFPI but not lipoprotein-associated forms in plasma

Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor with three tandem inhibitory domains, which inhibits the initial reactions of the extrinsic blood coagulation pathway through the first and second Kunitz domains. We prepared a monoclonal antibody against recombinant human TFPI (rTFPI) and determined the epitope as the third Kunitz domain, using fragments derived from rTFPI (K1-K2 fragment and K3 fragment) and synthetic peptides. We then developed an enzyme immunoassay (EIA) method using a combination of the monoclonal antibody and a polyclonal antibody. Although TFPI activity is distributed among LDL/VLDL-associated, HDL-associated, and free forms of TFPI after gel-filtration of human plasma, only the free form was detected by the EIA method. After incubation with LDL, the antigenicity of rTFPI was reduced, but that of K3 fragment was not. Gel-filtration analysis of the mixture of radiolabeled rTFPI or K3 with LDL demonstrated that rTFPI, but not K3, bound LDL. From these results, we concluded that the monoclonal antibody against TFPI recognized only a free form of TFPI in plasma, since the epitope of lipoprotein-associated TFPI had been masked by the interaction with lipoproteins.

Effect of heparin on the inhibition of factor Xa by tissue factor pathway inhibitor: a segment, Gly212-Phe243, of the third Kunitz domain is a heparin-binding site

Tissue factor pathway inhibitor (TFPI) inhibits the tissue factor--factor VIIa complex and factor Xa with its first and second Kunitz domains (K1 and K2), respectively. The inhibitory activity is enhanced by heparin, and the C-terminal basic part has been shown to be a heparin-binding site (HBS-1). To characterize and localize a second heparin-binding site (HBS-2), we studied the effect of heparin on the inhibitory activity of two forms of recombinant human TFPI, the full-length TFPI (rTFPI), and TFPI lacking the C-terminal basic part (rTFPI-C), by assaying the inhibition of human factor Xa. rTFPI-C inhibited factor Xa with an initial Ki of 6.79 nM in the absence of Ca2+ and 22.3 nM in the presence of 5 mM CaCl2. Heparin decreased the initial Ki to 1.79 nM in the absence of Ca2+ and 2.68 nM in the presence of 5 mM CaCl2, indicating the presence of HBS-2 in rTFPI-C. The dissociation constant for the binding of HBS-2 with heparin was determined to be 830 nM using fluorescein-labeled heparin and rTFPI-C. Heparin enhanced the inhibitory activity of a fragment consisting of the K2 and K3 domains, but it did not stimulate the inhibitory activity of the K2 domain. A synthetic peptide mimicking from Gly212 to Phe243 in the K3 domain reduced the effect of heparin on the inhibition by rTFPI-C and rTFPI. These results defined the location of HBS-2 in the basic region of the K3 domain between Gly212 and Phe243.

Depolymerized holothurian glycosaminoglycan with novel anticoagulant actions: antithrombin III- and heparin cofactor II-independent inhibition of factor X activation by factor IXa-factor VIIIa complex and heparin cofactor II-dependent inhibition of thrombin

The inhibition mechanism of a polysaccharide anticoagulant, depolymerized holothurian glycosaminoglycan (DHG), was examined by analyzing its effects on the clotting time of human plasma depleted of antithrombin III (ATIII), of heparin cofactor II (HCII), or of both heparin cofactors. The effect exerted by this agent on the activation of prothrombin and factor X in purified human components were also examined and all effects were compared with those of other glycosaminoglycans (GAGs). The capacity of DHG to prolong activated partial thromboplastin time was not reduced in ATIII-depleted, HCII-depleted, HCII-depleted, or ATIII- and HCII-depleted plasma, whereas its capacity to prolong prothrombin time and thrombin clotting time was reduced in HCII-depleted plasma. DHG inhibited the amidolytic activity of thrombin in the presence of HCII with a second order rate constant of 1.2 x 10(8) (mol/L)-1 min-1. These results indicated that DHG has two different inhibitory activities, one being an HCII-dependent thrombin inhibition and the other an ATIII- and HCII-independent inhibition of the coagulation cascade. The heparin cofactors-independent inhibitory activity of DHG was investigated in the activation of prothrombin by factor Xa and in the activation of factor X by tissue factor-factor VIIa complex or by factor IXa. DHG significantly inhibited the activation of factor X by factor IXa in the presence of factor VIIIa, but not in the absence of factor VIIIa. The interaction between DHG and factors IXa, VIIIa, and X was investigated with a DHG-cellulofine column, on which DHG had strong affinity for factors IXa and VIIIa. These findings show that the heparin cofactors-independent inhibition exhibited by DHG was caused by inhibition of the interaction of factor X with the intrinsic factor Xase complex, probably by binding to the factor IXa-factor VIIIa complex.

Amino acid sequence and inhibitory activity of rhesus monkey tissue factor pathway inhibitor (TFPI): comparison with human TFPI

Rhesus monkey cDNA for tissue factor pathway inhibitor (TFPI) was cloned by means of the reverse transcriptase-polymerase chain reaction, using liver mRNA, and its nucleotide sequence was determined by sequencing five independent clones. Monkey TFPI was found to have a signal peptide of 28 amino acid residues and to be a mature protein of 276 amino acid residues, in which three and seventeen amino acid residue substitutions compared to human TFPI were found, respectively. All the cysteine residues, three putative carbohydrate-linked asparagine residues, and the P1 amino acid residues of each of the three Kunitz inhibitor domains were conserved in the two species. Recombinant monkey TFPI (rTFPI) was isolated from the culture medium of transformed Chinese hamster ovary cells. Amino acid sequence analysis and immunoblotting analysis, using polyclonal and monoclonal antibodies, showed that the carboxyl-terminal basic part of Rhesus monkey rTFPI had been truncated. The inhibitory activity of monkey rTFPI was compared with that of human rTFPI without the carboxyl-terminal basic part. The prothrombin time of human plasma was slightly more prolonged by the addition of monkey rTFPI than by that of human rTFPI. However, no significant differences were found between the potencies of human and monkey rTFPI as to the inhibition of factor Xa and tissue factor-factor VIIa complex.

Response of plasma tissue factor pathway inhibitor to diet-induced hypercholesterolemia in crab-eating monkeys

Tissue factor pathway inhibitor (TFPI), a protease inhibitor associated with lipoproteins in plasma and endothelial cells, can inhibit the initial reactions of the tissue factor-mediated coagulation pathway. A positive relationship between TFPI and cholesterol has been demonstrated in human plasma. To investigate this relation in more detail, in the present study we measured TFPI in the plasma of monkeys on a high-cholesterol diet. After diet treatment, cholesterol levels and TFPI activity were increased 3- and 1.5-fold, respectively. Three forms of TFPI, low-density lipoprotein (LDL)/very-low-density lipoprotein (VLDL)-associated TFPI, high-density lipoprotein (HDL)-associated TFPI, and free TFPI, were measured after gel filtration of plasma. In hypercholesterolemic monkeys, levels of TFPI activity and antigen in the LDL/VLDL fraction were increased to about three times those of normal monkeys. Changes in HDL-associated TFPI and free TFPI were not significant compared with the change in LDL/VLDL-associated TFPI. After the monkeys received heparin infusions TFPI was increased about fivefold, but there was no significant difference in these increases between normal and hypercholesterolemic monkeys. The increase in TFPI after heparin infusion is discussed in terms of the relationship between lipoprotein-associated TFPI in plasma and endothelial cell-associated TFPI.

Human tissue factor pathway inhibitor (TFPI) gene: complete genomic structure and localization on the genetic map of chromosome 2q

Tissue factor pathway inhibitor (TFPI), a protease inhibitor that circulates in association with plasma lipoproteins (VLDL, LDL and HDL), helps to regulate the extrinsic blood coagulation cascade. We have cloned a 125-kb genomic region containing the entire human TFPI gene on six overlapping cosmids and prepared a restriction map of this contig to clarify gene structure. More than half (45 kb) of the 85-kb gene is occupied with 5' noncoding elements: coding begins at exon 3. A HindIII RFLP identified with one cosmid was genotyped in the CEPH panel of 59 reference families. Linkage analysis using markers on human chromosome 2 located the TFPI gene on 2q, 36 cM proximal to D2S43(pYNZ15) and 13 cM distal to the crystalline gamma-polypeptide locus CRYGP1(p5G1).

Purification and characterization of two isoforms of T-kininogens from rat liver microsomes

T-Kininogen is one of the acute phase proteins, and is a precursor of T-kinin and a cysteine protease inhibitor. Two homologous T-kininogens (TI- and TII-kininogens) were isolated from microsomal fraction of inflamed rat liver, by chromatographies on columns of DEAE-Sepharose CL-6B and DEAE-5PW and by affinity chromatography on a column of anti T-kininogen monoclonal antibody. The amino terminal amino acid sequences of the two microsomal pyridylethylated T-kininogens after pyroglutamyl aminopeptidase treatment were identical with those of TI- and TII-kininogens from inflamed rat plasma. Microsomal T-kininogens moved faster on SDS-PAGE after treatment with endoglycosidase H. The amounts of microsomal TI- and TII-kininogens in inflamed and non-inflamed rat liver were quantitated by immunoblotting of homogenates of liver microsomes using anti T-kininogen rabbit antiserum. The amounts of microsomal T-kininogens were increased in inflamed rat liver, but the ratio of the amounts of TI-kininogen to TII-kininogen was not different in the inflamed and non-inflamed rat liver. On the other hand, TII-kininogen was not significantly detected in non-inflamed rat plasma. These results indicate that the secretion of one of the T-kininogens, TII-kininogen, into plasma may be prevented by some unknown mechanism.

cDNA cloning and expression of rat tissue factor pathway inhibitor (TFPI)

Tissue factor pathway inhibitor (TFPI) is a factor Xa-dependent inhibitor for the factor VIIa-tissue factor complex. We isolated cDNA for rat TFPI by screening a lambda gt10 rat liver cDNA library. We determined the 1,228 bp nucleotide sequence, comprising a 88 bp 5' non-coding region, a 906 bp open reading frame, and a 234 bp 3' non-coding region, which encodes a protein of 302 amino acid residues. On Northern blot analysis of rat TFPI mRNA, rat TFPI mRNA was detected as two forms with different molecular sizes, 4.0 and 1.4 kb, which were expressed abundantly in heart, lung, kidney, and aortic endothelial cells. The homology of the amino acid sequence of rat TFPI with those of human and rabbit TFPI was found to be 60.7 and 57.4%, respectively. The lengths of the three tandem Kunitz-type inhibitor domains were strictly conserved not only among TFPI from the three species, but also among other proteins containing Kunitz-type inhibitor domains. The homology of the Kunitz-type domains in TFPI among the three species was 57, 86, and 69% in the 1st, 2nd, and 3rd domains, respectively. There was no significant difference in hydropathy profiles of TFPI from man, rabbit, and rat.

Hydroxylated kininogens and kinins

Hydroxyprolyl-3-bradykinin was identified in the digest of purified human high molecular weight (H) kininogen with plasma kallikrein. Hydroxyproline was not detected in the heavy and light chains portions of H kininogen, although they include three possible sites for hydroxylation of proline by proline hydroxylase. The content of hydroxyprolyl-3-bradykinin in H kininogen from individual plasmas varied from 14% to 64% of total kinin. The present results and our previous results indicate that only kinin moity in H kininogen from human and monkey plasmas has been partially hydroxylated post-translationally by proline-4-hydroxylase.

Amino acid sequence and location of the disulfide bonds in bovine beta 2 glycoprotein I: the presence of five Sushi domains

beta 2 glycoprotein I is a plasma protein with the ability to bind with various kinds of negatively charged substances. The complete amino acid sequence and the location of all the disulfide bonds of bovine beta 2 glycoprotein I were determined. Bovine beta 2 glycoprotein I consists of 326 amino acid residues with five asparagine-linked carbohydrate chains. Homology with the human protein was calculated to be 83%. Eleven disulfide bonds in bovine beta 2 glycoprotein I constitute four characteristic domains, Sushi domains, and one modified form of a Sushi domain.

Characterization of rat factors X and Xa: demonstration of factor Xa in rat plasma

We have found that rat plasma corrected the non-activated PT of human normal or factor-X deficient plasma, and the factor Xa-like activity being constantly detected in every 1 ml of blood collected via the cannulated carotid artery of rats. The present study was undertaken to characterize the factor Xa-like activity in rat plasma by preparing rat factor X and a monoclonal antibody against it. Factor X was purified from a BaCl2 eluate of rat plasma by chromatographies on columns of DEAE-Sepharose CL-6B and Sulfate Cellulofine or on a column of Affi-Gel 10 conjugated with a monoclonal antibody against rat factor X. Factor Xa-like activity in rat plasma was eliminated by the treatment of rat plasma with a monoclonal antibody which recognized the heavy chain portions of rat factors X and Xa. A kinetical study demonstrated that rat factor Xa was strongly inhibited by rat antithrombin III, with a Ki of 2.2 x 10(-11) M, in the presence of heparin. However, in the absence of heparin, the second order rate constant for the inhibition of rat factor Xa by rat antithrombin III was 2.6 x 10(4) M-1.min-1, which was one forty-third that for the inhibition of human factor Xa by human antithrombin III. Furthermore, rat factor Xa was resistant to the inhibition by rat alpha-1-antitrypsin and alpha-2-macroglobulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydroxyprolyl3-bradykinin in high molecular mass kininogen. Presence in human and monkey kininogens, but not in kininogens from bovine, rat, rabbit, guinea pig and mouse plasmas

The contents of hydroxyprolyl3-bradykinin in high molecular mass (HMM) kininogens from human and animal plasmas were examined by reversed-phase HPLC following their proteolytic scission by bovine plasma kallikrein. The relative contents of hydroxyprolyl3-bradykinin in kinins from HMM kininogens from pooled plasmas of human and monkey origin were 33 and 73%, respectively. On the other hand, hydroxyprolyl3-bradykinin could not be detected in HMM kininogen preparations from bovine, rat, guinea pig, rabbit and mouse plasmas. Hydroxyproline in hydroxyprolyl3-bradykinin was assigned as trans-4-hydroxyproline by comparison of the retention times on reversed-phase HPLC with isomers of hydroxyproline after derivatization with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole chloride.

Purification and characterization of rat T-kininogens isolated from plasma of adjuvant-treated rats. Identification of three kinds of T-kininogens

Two T-kininogens (TI- and TII-kininogens) found in plasma of Freund's adjuvant-treated rats were purified by several chromatographic procedures. The isolated TI- and TII-kininogens showed different mobilities on polyacrylamide gel electrophoresis in the absence of sodium dodecyl sulfate, but were indistinguishable in the presence of sodium dodecyl sulfate. They were also indistinguishable in amino acid composition and antigenicity, but differed in sialic acid content. The NH2- and COOH-terminal sequences were determined. In the 30 NH2-terminal residues, 2 were different. The kinin regions in the COOH-terminal portions of the two kininogens have sequences that demonstrate TI-kininogen contains a mixture of two kinin-containing regions, with substitution of 4 amino acid residues, one of which is identical to the COOH-terminal portion of alpha 1-major acute phase protein (Cole, T., Inglis, A. S., Roxburgh, C. M., Howlett, G. J., and Schreiber, G. (1985) FEBS Lett. 182, 57-61) and the other to the COOH-terminal portion of TI-kininogen (Furuto-Kato, S., Matsumoto, A., Kitamura, N., and Nakanishi, S. (1985) J. Biol. Chem. 260, 12054-12059), both predicted from cDNA sequences. The amino acid sequence of the kinin-containing region from TII-kininogen is the same as the COOH-terminal portion of TII-kininogen predicted from the cDNA. These results indicate that T-kininogens from the plasma of adjuvant-treated rats consist of a family of kininogens, that is, TI- and TII-kininogens (separable on DEAE-Sephadex A-50), and that TI-kininogen consists of at least two variants (TI alpha and TI beta) which correspond to the alpha 1-major acute phase protein reported by Cole et al. and TI-kininogen reported by Furuto-Kato et al., respectively. Immunoblotting studies with plasmas from non-inflamed and adjuvant-treated rats also indicate that T-kininogen which was previously isolated from non-inflamed rat plasma corresponds to TI-kininogen and that TII-kininogen is newly generated after treatment of rats with adjuvants.

Purification and characterization of two kinds of low molecular weight kininogens from rat (non-inflamed) plasma. One resistant and the second sensitive to rat glandular kallikreins

Two kinds of low molecular weight kininogens (identified as A and B) were isolated from pooled plasma of Sprague-Dawley rats. They show a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence and absence of 2-mercaptoethanol, and the molecular weights are 68,000 for low Mr kininogen A and 73,000 for low Mr kininogen B. Although the molecular weights and amino acid compositions of the low Mr kininogens are similar, rat submaxillary and urinary kallikreins released bradykinin from low Mr kininogen B, whereas low Mr kininogen A was resistant to these enzymes. The COOH-terminal portion of low Mr kininogen A was isolated after cyanogen bromide treatment, and the amino acid sequence of the COOH-terminal 55 residues including the T-kinin (Ile-Ser-bradykinin) was determined. The COOH-terminal portion consists of two sequences with substitution of 4 residues. One peptide corresponds to alpha 1-major acute phase protein (Cole, T., Inglis, A. S., Roxburgh, C. M., Howlett, G. J., and Schreiber, G. (1985) FEBS Lett. 182, 57-61) and the other to the TI-kininogen predicted from a cDNA study (Furuto-Kato, S., Matsumoto, A., Kitamura, N., and Nakanishi, S. (1985) J. Biol. Chem. 260, 12054-12059). The results demonstrate that there exist at least two kinds of low Mr kininogens with clearly different function in rat plasma: one of them, low Mr kininogen A, is a precursor of T-kinin and is resistant to kallikreins, and the second, low Mr kininogen B, is sensitive to tissue kallikreins and shares properties with bovine and human low Mr kininogens. The results also demonstrate that T-kininogen is a mixture of two isoproteins which correspond to alpha 1-major acute phase protein or TI-kininogen, respectively. We could not detect the low Mr kininogen corresponding to the TII-kininogen predicted from the cDNA study of Furuto-Kato et al.

Characterization of serine proteinases isolated from rat submaxillary gland: with special reference to the degradation of rat kininogens by these enzymes

From the homogenate of rat submaxillary gland, two kinds of serine proteinases, named tentatively proteinases A and B, were isolated and their chemical properties and activities toward rat kininogens were examined, in comparison with those of submaxillary kallikrein. Proteinase A with Mr of 28,200 rapidly cleaved high-molecular-weight (HMW) kininogen into a protein of 67 kDa, which retained thiol-proteinase inhibitory activity, but had lost the correcting activity of HMW kininogen on the prolonged clotting time of Fitzgerald trait plasma. It liberated bradykinin from HMW kininogen but did not liberate kinin from T-kininogen and did not degrade T-kininogen. On the other hand, proteinase B with Mr of 30,400 showed a very weak activity for the liberation of kinin from T-kininogen and the cleavage of T-kininogen at pH 8.0. However, the enzyme extensively degraded T-kininogen at pH 4.5. Proteinase B also degraded HMW kininogen at pH 4.5 and pH 8.0, but liberated bradykinin only at pH 8.0. Thiol-proteinase inhibitory activities of HMW kininogen and T-kininogen were inactivated after the incubation with proteinase B at pH 4.5 but not at pH 8.0, while the correcting activity of HMW kininogen on the Fitzgerald trait plasma was inactivated at pH 4.5 and 8.0. The NH2-terminal amino acid sequences of proteinases A and B were different from each other, and distinguishable with those of serine proteinases in rat submaxillary gland so far reported. These results provide evidence that in addition to the known kallikrein, there exist at least two kinds of serine proteinases in rat submaxillary gland, both of which liberate bradykinin from rat HMW kininogen at pH 8.0 and modulate the functional activities of HMW kininogen and T-kininogen, degrading these proteins at pH 8.0 or 4.5.

Identification of T-kininogen in high and low molecular weight kininogens deficient rat (brown Norway Katholiek strain)

Kinin release in Brown Norway Katholiek (B/N-Ka) rat plasma was compared with those of Brown Norway Kitasato and Sprague-Dawley rats by treating with rat plasma kallikrein, rat urinary kallikrein, snake venom kininogenase and trypsin. B/N-Ka rat plasma yielded no detectable amount of kinin by either plasma kallikrein, urinary kallikrein or snake venom kininogenase, but yielded variable amount of kinin by trypsin. The released kinin was proved to be isoleucylseryl-bradykinin by high performance liquid chromatography and bioassay profiles. B/N-Ka rat plasma formed a precipitation line against antiserum to T-kininogen, but no line against antiserum to HMW kininogen-light chain.

A new function of kininogens as thiol-proteinase inhibitors: inhibition of papain and cathepsins B, H and L by bovine, rat and human plasma kininogens

The amidolytic activities of papain and rat liver cathepsins B, H and L were strongly inhibited by high (HMM) and low (LMM) molecular mass kininogens from bovine, human and rat plasmas, and their Ki values were estimated to be in the order of 10(-10) - 10(-11)M for papain and 10(-8) - 10(-9)M for cathepsins. The derivatives of bovine kininogens, HMM kinin-free protein, HMM kinin- and fragment 1 X 2-free protein, and LMM kinin-free protein also showed strong inhibitory activity toward these thiol-proteinases. These results suggest that a reactive site which interacts with thiol-proteinases is contained in the heavy chain portion in kininogens.

Demonstration of arginyl-bradykinin moiety in rat HMW kininogen: direct evidence for liberation of bradykinin by rat glandular kallikreins

The amino acid sequence around kinin moiety in rat High-Molecular-Weight (HMW) kininogen was determined by isolating a peptide containing bradykinin after cyanogen bromide treatment of the purified kininogen as follows; NH2-Thr-Ser-Val-Ile-Arg-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg-Ala-Pro-Arg- Val-Lys-Lys-. The data indicated that rat HMW kininogen contains the arginyl-bradykinin moiety, instead of lysyl-bradykinin. Kinins liberated from rat HMW kininogen by rat urinary and submaxillary kallikreins were identified to be bradykinin, not arginyl-bradykinin.