A kinetic analysis of the interaction of human recombinant tissue factor pathway inhibitor with factor Xa utilizing and immunoassay and the effect of antithrombin III/heparin on the complex formation

We have recently shown that a complex formation of tissue factor pathway inhibitor (TFPI) and factor Xa (Xa) promotes a clearance of proteoglycans-associated TFPI. In the current studies, the interaction between human recombinant TFPI (h-rTFPI) and Xa were kinetically analyzed by utilizing both a protease inhibitor, p-(amidophenyl) methanesulfonyl fluoride hydrochloride, and a specific enzyme-linked immunosorbent assay for the complex of h-rTFPI with Xa. We further investigated the effect of antithrombin III on the complex formation between h-rTFPI and Xa. We found that the h-rTFPI/Xa complex formed in a time-dependent manner: the second-order rate constant (K1) for the complex formation was calculated to be 0.86x10(6) M(-1)s(-1). The addition of antithrombin III to the h-rTFPI solution modestly reduced the rate of the complex formation between h-rTFPI and Xa. Heparin strikingly enhanced antithrombin III's inhibition of Xa and resulted in complete abrogation of the complex formation between h-rTFPI and Xa in the absence or presence of acidic phospholipids. Furthermore, antithrombin III induced dissociation of the preformed h-rTFPI/Xa complex in the presence of heparin. These results suggest that in the presence of heparin, antithrombin III interferes with the catabolism of TFPI mediated via Xa.

Human recombinant tissue factor pathway inhibitor induces apoptosis in cultured human endothelial cells

Tissue factor pathway inhibitor (TFPI) is mainly synthesized in vascular endothelial cells and exhibits a strong and specific inhibitory activity against tissue factor-mediated blood coagulation. In the present study, we demonstrate that human recombinant TFPI (h-rTFPI) inhibits the growth of cultured human umbilical vein endothelial cells (HUVECs) by inducing apoptosis. In a growth-rate assay of HUVECs, the growth of the cultured HUVECs is completely abolished by the addition of 1 microM h-rTFPI to the culture medium containing fetal bovine serum (FBS), basic fibroblast growth factor, and epidermal growth factor. In addition, h-rTFPI and h-rTFPI-C which lacks the carboxyl-terminal basic region prevent the survival of growth-arrested HUVECs which are starved in a medium containing 2%, FBS alone, suggesting that h-rTFPI directly induces the death of these HUVECs. This hypothesis is supported by the finding that h-rTFPI does not inhibit the synthesis of DNA in HUVECs during proliferation, as shown by a 5-bromo-2'-deoxyuridine (BrdU) incorporation assay. Furthermore, Giemsa staining and a gel electrophoretic analysis of DNA fragmentation show that the HUVEC death mediated by h-rTFPI has the typical characteristics of apoptosis. However, the apoptosis in HUVECs is considerably inhibited in the presence of 1 microg/ml of the protein synthesis inhibitor, cycloheximide. Therefore, the process of apoptosis triggered by h-rTFPI is, at least in part, actively conducted by the cells.

[Surgical results of postinfarction ventricular septal perforation: operative planning using "endocardial patch repair with infarct exclusion"]

Between 1983 and 1996, twenty-two consecutive patients underwent surgical repair for postinfarction ventricular perforation (VSP). Overall hospital mortality was 31.8% in the reviewed group. 15 patients were operated upon within two weeks of onset of VSP and hospital mortality was 27.3% in this group. The earlier operation might provide more favorable results in the surgery of VSP. When the preoperative coronary angiography revealed multivessel disease, concomitant myocardial revascularization was performed. In recent 2 cases, we employed the new technique introduced by Komeda and David for the reconstruction of the left ventricule using a single pericardial patch. We found this new technique had many advantages over traditional "Daggett's method". Better operative results could be expected with this technique.

Tissue factor expression on macrophages in coronary plaques in patients with unstable angina

Tissue factor is a membrane-bound glycoprotein that functions in the extrinsic pathway of blood coagulation by acting as a cofactor for factor VII, and the resulting complex leads to thrombin production in vivo. The purpose of the present study is to determine whether macrophages express tissue factor in human coronary atherosclerotic plaques. We examined directional coronary atherectomy specimens from 24 patients with unstable angina and 23 with stable exertional angina. In these specimens, macrophages were detected in 22 (92%) of 24 patients with unstable angina versus 12 (52%) of 23 with stable exertional angina (P = .003). The percentage of macrophage infiltration area was significantly larger in patients with unstable angina than in those with stable exertional angina (17 +/- 3% versus 6 +/- 2%, P = .008). The immunohistochemical double staining revealed the expression of tissue factor on macrophages in 18 (75%) of 24 patients with unstable angina versus 3 (13%) of 23 with stable exertional angina (P < .0001). Thrombus was identified in 20 (83%) of 24 patients with unstable angina versus 12 (52%) of 23 with stable exertional angina (P = .02). Fibrin deposition was mainly observed around macrophages expressing tissue factor in the patients with unstable angina. We have shown that tissue factor expression on macrophages was more frequent in coronary atherosclerotic plaques in patients with unstable angina. Tissue factor expressed on macrophages may play an important role in the thrombogenicity in coronary atherosclerotic plaques of these patients.

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).

Localization and activity of tissue factor in human aortic atherosclerotic lesions

Tissue factor (TF) is a transmembrane protein that serves as the major initiator of the blood coagulation cascade. The overexpression of TF antigen and mRNA has previously been reported in advanced atherosclerotic lesions. Recently TF procoagulant activity has also been identified in these lesions. However, localization and activity of TF in various stages of atherosclerosis have not yet been reported. We studied TF localization and its activity in three stages of the human atherosclerotic lesions (diffuse intimal thickening, fatty streak, and atheromatous plaque). The thoracic aortas were obtained from 23 autopsy cases and were examined immunohistochemically using an anti-human TF polyclonal antibody and biotinylated factor VIIa (FVIIa) as a probe to test the FVIIa-binding ability of TF. In addition, the TF-mediated activation of factor X (FX) was quantitatively assessed using a chromogenic assay. In lesions of the diffuse intimal thickening and the fatty streak, almost all of intimal smooth muscle cells (SMCs), macrophages, and endothelial cells were positive for TF. In the atheromatous plaques, TF antigen was detected extensively in the extracellular matrix as well as in the intimal cells. TF in all stages of atherosclerotic lesions had the ability to bind biotinylated FVIIa. TF activity was detected in each lesion and was more prominent in fatty streaks and atheromatous plaques than in the diffuse intimal thickening. These results indicate that active TF is expressed in the early stage of atherosclerotic lesions as well as in the advanced stage, and it contributes to the thrombotic property of human atherosclerotic lesions.

Tissue factor pathway inhibitor inhibits aortic smooth muscle cell migration induced by tissue factor/factor VIIa complex

Tissue factor (TF), a transmembrane glycoprotein, forms a high affinity complex with factor VII/VIIa (FVIIa) and thereby initiates blood coagulation. Tissue factor pathway inhibitor (TFPI) is an endogenous protease inhibitor of TF/FVIIa-initiated coagulation. We previously reported that TF was a strong chemotactic factor for cultured vascular smooth muscle cells (SMCs). In this study, we examined the contribution of FVIIa and the effect of TFPI to TF-induced cultured SMC migration. TF/FVIIa complex showed a strong migration ability, however, neither TF alone nor FVIIa induced SMC migration. TF/FVIIa treated by a serine protease inhibitor and the complex of TF and inactivated FVIIa (DEGR-FVIIa) did not stimulate SMC migration. Pretreatment with hirudin and the antibodies to alpha-thrombin and factor X had no effect on TF/FVIIa-induced SMC migration, although alpha-thrombin and factor Xa also induced SMC migration respectively. TFPI markedly inhibited TF/FVIIa-induced SMC migration in a concentration-dependent manner, but did not affect the SMC migration induced by platelet-derived growth factor (PDGF)-BB, basic fibroblast-growth factor (bFGF), or alpha-thrombin. These results indicate that the catalytic activity of TF/FVIIa complex is important on SMC migration, and TFPI can reduce SMC migration as well as thrombosis.

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.

Increased plasma tissue factor levels in acute myocardial infarction

BACKGROUND

Tissue factor (TF) is a low molecular weight glycoprotein that initiates the clotting cascade and is considered to be a major regulator of coagulation, hemostasis, and thrombosis.

METHODS AND RESULTS

We examined plasma TF levels in 31 consecutive patients with acute myocardial infarction (AMI) (within 6 hours after the onset of symptoms), 27 patients with stable exertional angina, and 27 control subjects. Ten patients with AMI had a history of unstable angina before infarction, and 21 had a sudden onset of infarction. The plasma TF level was higher in the AMI group than in the stable exertional angina and control groups (240 +/- 112 vs 184 +/- 46 pg/ml [p < 0.05] vs 177 +/- 37 pg/ml, p < 0.01, respectively). TF levels were decreased in the chronic phase (2 weeks after admission) compared with the acute phase of infarction (from 240 +/- 112 pg/ml to 222 +/- 97 pg/ml, p < 0.05). In addition, plasma TF levels were higher in patients with AMI with prodromal unstable angina than in patients with a sudden onset of infarction (300 +/- 169 pg/ml vs 212 +/- 57 pg/ml, p < 0.05). TF levels were similar in the acute and chronic phases in the patients with AMI with prodromal unstable angina (300 +/- 169 pg/ml vs 290 +/- 136 pg/ml, p = not significant) but were decreased in the chronic phase in the patients with AMI with sudden onset (from 212 +/- 57 pg/ml to 190 +/- 49 pg/ml, p < 0.05).

CONCLUSION

Increased plasma TF levels in patients with AMI may reflect enhanced intravascular procoagulant activity. The higher TF levels in patients with AMI with prodramol unstable angina may be associated with repeated episodes of myocardial ischemia and reperfusion.

Human recombinant tissue-factor pathway inhibitor prevents the proliferation of cultured human neonatal aortic smooth muscle cells

Tissue-factor pathway inhibitor (TFPI) inhibits the procoagulant activity of the tissue-factor/factor VIIa complex. It was recently reported that TFPI prevented restenosis following tissue injury in a rabbit atherosclerotic model. In order to clarify the mechanism behind this successful prevention of restenosis, we investigated the direct effect of human recombinant TFPI (h-rTFPI) on the proliferation of cultured human neonatal aortic smooth muscle cells (hSMC). We found that h-rTFPI exhibits inhibitory activity toward hSMC proliferation, while h-rTFPI-C which lacks the carboxyl (C)-terminal region does not. Furthermore, we found that h-rTFPI binds to hSMCs with K(d) = 526 nM but that this binding is inhibited by the addition of the synthetic C-terminal peptide, Lys254-Met276, to h-rTFPI. Thus, the interaction of h-rTFPI with hSMCs mediated via the C-terminal region is responsible for the anti-proliferative action of h-rTFPI. On the basis of these results, we presume that the anti-proliferative effect of h-rTFPI in addition to its anticoagulant function plays a significant role in preventing restenosis following tissue injury.

Antithrombotic effect of human recombinant tissue factor pathway inhibitor on endotoxin-induced intravascular coagulation in rats: concerted effect with antithrombin

In our current study, we examined the antithrombotic effect of Chinese hamster ovary cell-derived human recombinant tissue factor pathway inhibitor (h-rTFPI) by intravenous injection of h-rTFPI with or without antithrombin into endotoxin-treated rats. An injection of h-rTFPI at a high dose (4 mg/kg of h-rTFPI or three doses of 1 mg/kg) significantly prevented the decrease of fibrinogen and factor VIII and the increase of fibrin/fibrinogen degradation products and glutamic-pyruvic transaminase in rats, while a single injection of 1 mg/kg of h-rTFPI or 250 U/kg of antithrombin did not significantly prevent intravascular coagulation. However, a simultaneous injection of 1 mg/kg of h-rTFPI and 250 U/kg of antithrombin did significantly prevent intravascular coagulation. From the studies on the clearance rate and immunohistochemical staining of injected h-rTFPI into normal rats, we found that most of the intravenously-injected h-rTFPI was localized on the central vein and sinusoids in the liver and catabolized via the proteoglycan-mediated pathway with a half-life of 48 min. These results suggest that h-rTFPI and antithrombin prevented endotoxin-induced intravascular coagulation in concert by binding to the vascular walls of the liver and by inhibiting fibrin formation on Kupffer cells in hepatic sinusoids.

[PT-INR as a parameter for anticoagulant therapy after valve replacement surgery]

We retrospectively analyzed the intensity of anticoagulant therapy in the 195 patients who underwent valve replacement surgery with mechanical valves. An optimal level or target range of prothrombin time-international normalized ratio (PT-INR) was sought. Previously, we employed a range of 10 to 25% of thrombotest value, which corresponded to the range of 1.5 to 3.5 of PT-INR value. In one patient who underwent mitral valve replacement, PT-INR valve was 1.72 when he developed an episode of cerebral thromboembolism. There was no tendency in PT-INR value in 51 patients who developed non-critical bleeding. As a while, PT-INR value was over 4.0 in 2 patients who required a in-hospital treatment for major bleeding complications. Based on our experience, we recommend a range of 2.0 to 3.0 of PT-INR value after valve replacement surgery with mechanical valves.

The clearance of proteoglycan-associated human recombinant tissue factor pathway inhibitor (h-rTFPI) in rabbits: a complex formation of h-rTFPI with factor Xa promotes a clearance rate of h-rTFPI

The very rapid clearance of human recombinant tissue factor pathway inhibitor (h-rTFPI) may result from its binding to vascular proteogly can and LDL receptor-related protein (LRP). To investigate the effect of factor Xa on the clearance of h-rTFPI, we developed a specific ELISA for h-rTFPI/factor Xa complex, and compared the pharmacokinetic parameters of h-rTFPI/factor Xa complex and the clearance rate of the cellular proteogly can-associated h-rTFPI/factor Xa complex with those of h-rTFPI by itself in rabbits. We found that the h-rTFPI/factor Xa complex disappeared from circulation at a rapid rate of clearance, having pharmacokinetic parameters similar to those of non-complexed h-rTFPI. After the rapid disappearance of the h-rTFPI complex from plasma, an intravenous injection of heparin resulted in a release of h-rTFPI/factor Xa complex into plasma. However, the recovery of heparin-releasable h-rTFPI/factor Xa decreased significantly in a time-dependent manner. Therefore, we examined the half-life of proteogly can-associated h-rTFPI/factor Xa and determined it to be 51 min, which was significantly shorter than that of h-rTFPI by itself (107 min). These results suggest that a complex formation of h-rTFPI with factor Xa promotes a clearance of proteogly can-associated h-rTFPI existing in the liver and kidney.

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.

Role of tissue factor in disseminated intravascular coagulation

We examined plasma antigen levels of tissue factor (TF) in 95 cases of disseminated intravascular coagulation (DIC), to investigate the role of TF in DIC. A significant elevation of plasma antigen levels of TF was observed in cases of DIC associated with cancer. However, no such significant elevation was observed in cases of DIC associated with acute promyelocytic leukemia (APL), acute leukemia except APL, blastic crisis of chronic myelogenous leukemia, non-Hodgkin lymphoma (NHL), sepsis or fulminant hepatitis. No significant elevation of TF was observed in patients without DIC, except 4 cases of cancer who developed DIC thereafter. Plasma antigen levels of TF were higher in both cases of DIC with renal failure and chronic renal failure without DIC than its levels in those without renal failure. Therefore, plasma antigen levels of TF in DIC patients with renal failure were considered to be carefully estimated. The levels of TF were decreased with the clinical improvement in some cases of DIC but were further increased or remained at high levels in patients who showed no improvement of DIC. Thus, plasma antigen levels of TF is an important marker to predict the development and/or prognosis of DIC, especially in patients with cancer.

Resection of hepatoblastoma with right atrial extension using cardiopulmonary bypass

A 3-year-old boy underwent a successful combined resection of a hepatoblastoma and its intracaval right atrial extension using a cardiopulmonary bypass. This type of extension is extremely rare in hepatoblastoma. The cardiopulmonary bypass enabled complete resection of the intracardiac mass of the hepatoblastoma. In addition, dissection and ligation of the right hepatic vein under cardiopulmonary bypass made the following right hepatectomy easy and safe.

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.

Neutrophil-independent myocardial dysfunction during an early stage of global ischemia and reperfusion of isolated hearts

The effect of global ischemia and reperfusion on the expression of cytokine genes and cell adhesion molecules by myocardial tissues and neutrophils was studied by using the Langendorff model. Although cardiac function deteriorated after reperfusion of ischemic hearts, there was no evidence of inflammation and myocardial degeneration, which is in contrast to previous findings that neutrophil-mediated inflammation is a critical step in post-ischemic reperfusion injury in regional ischemia. Flow cytometry analysis demonstrated that the global ischemia and reperfusion did not affect the expression of adhesion molecules on neutrophils. We also examined the expression of various cytokines which are involved in inflammatory responses. Only interleukin 1 alpha was induced after the reperfusion of the ischemic hearts. These results suggest that neutrophils barely contribute to the myocardial dysfunction and IL-1 alpha may play a role in post-ischemic myocardial dysfunction during the early stage of reperfusion.

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.

[Cardiac dysfunction and endogenous cytokines in global ischemia and reperfusion injury]

The myocardial ischemia and reperfusion injury is caused by the re-introduction of coronary circulation in ischemic myocardial tissues. A number of experiments demonstrate that immunological response such as adherence of neutrophils to endothelial cells play a critical role in reperfusion injury. In this paper, the effect of global ischemia and reperfusion on the expression of cytokine genes by myocardial tissues as well as cell adhesion molecules by neutrophils were studied by using Langendorff model. Cardiac dysfunction and immunological response in 25 min global ischemia at 37.5 degrees C followed by 60 min reperfusion were studied in isolated rat heart perfused with blood supplied from support rat (Langendorff model). Cardiac functions were measured with a left intraventricular balloon. The mean post-experimental reduction of the left ventricular end-systolic pressure were 87.5 +/- 1.6% of pre-experimental level in the control perfusion group and 55.5 +/- 5.8% in the reperfusion group. Immunofluorescence flow cytometry showed that ischemia and reperfusion injury did not affect the expression of adhesion molecules on neutrophils which were isolated from perfused blood samples. Cytokine gene expression was analyzed by direct analysis of mRNA obtained from the blood-perfused, isolated rat heart. The level of expression of the cytokine genes was assessed using semiquantitative reverse transcriptase-polymerase chain reaction (semiquantitative RT-PCR). IL-6, IL-8, IFN-gamma, TNF-alpha were expressed in normal heart tissue at low level and were upregulated following ischemia and reperfusion. IL-1 beta, MCP-1 and IL-1 receptor antagonist were not expressed at detectable level in normal heart but were induced following global ischemia. IL-1 alpha was not expressed at detectable level in normal heart but was induced following reperfusion of the ischemic heart. Histological examination of myocardial tissue from the reperfusion group revealed no evidence of myocardial necrosis. Only a mild interstitial edema as well as weak focal hemorrhage was detected after reperfusion of ischemic hearts. These results suggest that there is a process which causes early stage of post-ischemic myocardial dysfunction without involving myocardial necrosis nor infiltration of inflammatory cells.

Anti-human factor IX monoclonal antibodies specific for calcium ion-induced conformations

Four monoclonal antibodies have been produced, which are specific for the Ca2+ or Sr2(+)-induced conformation of human factor IX. Certain, but not all, gamma-carboxy-glutamic acid residues in factor IX are involved in the epitope expression together with the conformation stabilized by the adjacent region of Gla-domain and a disulfide bridge. All the antibodies interfered with the binding of factor IX to phospholipids and inhibited the procoagulant activity of factors IX and IXa beta.