Vitamin E reduces monocyte tissue factor expression in cirrhotic patients

Clotting activation may occur in liver cirrhosis, but the pathophysiological mechanism has not been fully elucidated. Because a previous study demonstrated that lipid peroxidation is increased in cirrhosis, we analyzed whether there is a relationship between lipid peroxidation and clotting activation. Thirty cirrhotic patients (19 men and 11 women; age, 34 to 79 years) and 30 controls matched for sex and age were investigated. In all subjects, monocyte expression of tissue factor (TF) antigen and activity; plasma levels of prothrombin fragment 1+2 (F1+2), a marker of thrombin generation; and urinary excretion of Isoprostane-F2alpha-III, a marker of lipid peroxidation, were measured. Furthermore, the above-reported variables were re-evaluated after 30 days of treatment with standard therapy (n = 5) or standard therapy plus 300 mg vitamin E twice daily (n = 9). In addition, we analyzed in vitro if vitamin E (50 micromol/L) influenced monocyte TF expression and F1+2 generation. Cirrhotic patients had higher values of Isoprostane-F2alpha-III (P <. 0001), F1+2 (P <.0001), and monocyte TF antigen (P <.0001) and activity (P <.03) than controls. Isoprostane-F2alpha-III was significantly correlated with F1+2 (Rho = 0.85; P <.0001) and TF antigen (Rho = 0.95; P <.0001) and activity (Rho = 0.94; P <.0001). After vitamin E treatment, Isoprostane-F2alpha-III (P =.008), F1+2 (P <.008), and monocyte TF antigen (P =.012) and activity (P =.008) significantly decreased; no changes of these variables were detected in patients not receiving vitamin E. In vitro, vitamin E significantly reduced the expression of monocyte TF antigen (-52%; P =.001) and activity (-55%; P =.003), as well as F1+2 generation (-51%; P =.025). This study shows that vitamin E reduces both lipid peroxidation and clotting activation and suggests that lipid peroxidation may be an important mediator of clotting activation in liver cirrhosis.

The nucleocapsid protein of murine hepatitis virus type 3 induces transcription of the novel fgl2 prothrombinase gene

Using a set of parental and recombinant murine hepatitis virus strains, we demonstrate that the nucleocapsid protein induces transcription of the novel fgl2 prothrombinase gene and elevated procoagulant activity in those strains that produce fulminant hepatitis. Chinese hamster ovary cells cotransfected with a construct expressing nucleocapsid protein from susceptible strains and with a luciferase reporter construct containing the fgl2 promoter showed a 6-fold increase in luciferase activity compared with nontransfected cells or cells cotransfected with a construct expressing nucleocapsid protein from resistant strains. Two deletions found at coding sites 111-123 and 1143-1145 of structural domains I and III, respectively, of the nucleocapsid gene may account for the differences between pathogenic and nonpathogenic strains. Preliminary mapping of the fgl2 promoter has defined a region from -372 to -306 upstream from the ATG translation initiation site to be responsive to nucleocapsid protein. Hence, mapping of genetic determinants in parental and recombinant strains demonstrates that the nucleocapsid protein of strains that induce fulminant hepatitis is responsible for transcription of the fgl2 prothrombinase gene. These studies provide new insights into the role of the nucleocapsid gene in the pathogenesis of viral hepatitis.

LDL increases inactive tissue factor on vascular smooth muscle cell surfaces: hydrogen peroxide activates latent cell surface tissue factor

BACKGROUND

Tissue factor, which is required for the initiation of the extrinsic coagulation cascade, is known to be upregulated in cells within atherosclerotic lesions, including smooth muscle cells. Tissue factor expression on the smooth muscle cell surface could be of pathological significance as a contributor to plaque growth, thrombus formation, and the acute coronary syndrome after plaque rupture.

METHODS AND RESULTS

In this study, we show that LDL increased tissue factor mRNA and cell surface protein in smooth muscle cells without a marked increase in surface tissue factor activity. Hydrogen peroxide activated tissue factor on the cell surface but did not increase tissue factor mRNA or cell surface protein. Sequentially added LDL and hydrogen peroxide increased mRNA, cell surface protein, and activity; surface activity was greater than that observed with hydrogen peroxide alone. The action of hydrogen peroxide did not involve a regulatory mechanism associated with the cytoplasmic tail of tissue factor because a truncated tissue factor lacking the cytoplasmic tail was activated by hydrogen peroxide.

CONCLUSIONS

These results suggest a novel 2-step pathway for increased tissue factor activity on smooth muscle cell surfaces in which lipoproteins regulate synthesis of a latent tissue factor and oxidants activate the protein complex.

Tissue factor pathway inhibitor expression in human crescentic glomerulonephritis

BACKGROUND

Tissue factor (TF) pathway inhibitor (TFPI), the major endogenous inhibitor of extrinsic coagulation pathway activation, protects renal function in experimental crescentic glomerulonephritis (GN). Its glomerular expression and relationship to TF expression and fibrin deposition in human crescentic GN have not been reported.

METHODS

Glomerular TFPI, TF, and fibrin-related antigen (FRA) expression were correlated in renal biopsies from 11 patients with crescentic GN. Biopsies from 11 patients with thin basement membrane disease and two normal kidneys were used as controls.

RESULTS

TFPI was undetectable in control glomeruli but was detectable in interstitial microvessels. In crescentic biopsies, TFPI was detected in cellular crescents and was more prominent in fibrous/fibrocellular crescents, indicating a correlation with the chronicity of crescentic lesions. TFPI appeared to be associated with macrophages but not endothelial or epithelial cells. TFPI was generally undetectable in regions of the glomerular tuft with minimal damage. In contrast, TF and FRA were strongly expressed in regions of minimal injury, as well as in more advanced proliferative and necrotizing lesions. Despite prominent TF expression, FRA was less prominent in fibrous/fibrocellular crescents in which TFPI expression was maximal.

CONCLUSIONS

These data suggest that TFPI is strongly expressed in the later stages of crescent formation and is inversely correlated with the presence of FRA in human crescentic GN. This late induction of TFPI may inhibit TF activity and favor reduced fibrin deposition in the chronic stages of crescent formation.

Endothelial tissue factor induction by T lymphocytes in systemic sclerosis

We evaluated the ability of circulating T lymphocytes obtained from patients with systemic sclerosis (SSc) to induce the expression of tissue factor (TF) by human umbilical vein endothelial cells (HUVECs), and compared the results with those obtained from healthy controls. Nine patients with SSc and 10 sex- and age-matched healthy subjects were studied. Peripheral T lymphocytes obtained from SSc patients induced TF activity from HUVECs in a dose-dependent manner. A significant induction of endothelial TF was observed when 2 x 10(6) lymphocytes per well (TF values, mean+/-SD: 0.34+0.21U/microg of cell protein vs 0.04+/-0.03; n = 9, p = 0.001) or 1 x 10(6) lymphocytes per well (0.13+/-0.06 vs 0.04+/-0.04; n = 8, p<0.001) were added to HUVEC cultures. Lower concentrations of T lymphocytes were ineffective. Similar results were obtained with control lymphocytes. There were no differences in endothelial TF induction between patients and controls at any lymphocyte concentration tested. Within the SSc group, there were no correlations between TF activity and clinical features or disease duration.

Activation of human vascular endothelial cells by factor Xa: effect of specific inhibitors

Recently, human umbilical vein endothelial cells (HUVEC) have been shown to express functional high-affinity receptors for factor Xa, which may be of importance in the regulation of coagulation and homeostasis of the vascular wall. In this paper, we demonstrate that when added to cultured HUVEC, factor Xa was a potent mitogen, stimulating an increase in cell number at a 0.3 to 100 nM concentration. The same doses of factor Xa also increased intracellular free calcium levels and phosphoinositide turnover. When added to confluent HUVEC, factor Xa induced the expression of tissue factor and the release of tissue-type plasminogen activator and plasminogen activator inhibitor-1 without affecting urokinase expression. Indirect (antithrombin-pentasaccharide) and direct (DX9065) inhibitors of factor Xa affected all these activities of factor Xa in a dose-dependent manner. Taken together, these data show that the activities induced by factor Xa on HUVEC were dependent on its catalytic activity and could be inhibited by both direct and indirect factor Xa inhibitors.

Arterial flow conditions downregulate thrombomodulin on saphenous vein endothelium

BACKGROUND

The antithrombogenic properties of venous endothelium may be attenuated when vein is implanted in the arterial circulation. Such changes may facilitate thrombosis, which is the final common pathway for saphenous vein arterial bypass graft occlusion.

METHODS AND RESULTS

Using human saphenous vein in a validated ex vivo flow circuit, we investigated (1) the possibility that arterial flow conditions (mean pressure, 100 mm Hg, 90 cpm, approximately 200 mL/min) alter the concentration of proteins involved in regulating thrombosis at the vessel wall and (2) the influence of ion channel blockade on such effects. Concentrations of thrombomodulin and tissue factor were quantified by Western blotting (ratio of von Willebrand factor staining) and immunohistochemistry (as a percentage of CD31-staining area). Thrombomodulin concentrations after 90 minutes of venous and arterial flow conditions were quantified by immunostaining (68.9+/-4.8% and 41.0+/-3.0% CD31, respectively; P<0.01) and by Western blotting (1.35+/-0.20 and 0. 15+/-0.03 ratio of von Willebrand factor, respectively; P<0.01). The ability of endothelial cells to generate activated protein C also decreased from 62+/-14 to 19+/-10 ng. min-1. 1000 cells-1 (P=0.01). The significant reduction in thrombomodulin was attenuated if calcium was removed from the perfusate but not by external vein stenting. Inclusion in the vein perfusate of drugs that reduce calcium entry (including Gd3+, to block stretch-activated ion channels, and nifedipine) abolished the reduction in thrombomodulin concentration observed after arterial flow conditions. In freshly excised vein, negligible concentrations of tissue factor were detected on the endothelium and concentrations did not increase after 90 minutes of arterial flow conditions, although the inclusion of nifedipine caused the immunostaining to increase from 3.0+/-0.4% to 8.5+/-0.7% CD31 (P<0.02).

CONCLUSIONS

In saphenous vein endothelium exposed to arterial flow conditions, there is rapid downregulation of thrombomodulin, sufficient to limit protein C activation, by a calcium-dependent mechanism.

Expression of tissue factor in non-small-cell lung cancers and its relationship to metastasis

Tissue factor (TF) is an initiator of the extrinsic cascade of blood coagulation. Although recent studies have revealed a relationship between metastatic properties and TF expression in some neoplastic cells, the significance of TF in lung cancer, especially in non-small-cell lung cancer (NSCLC), is still unclear. In this study, TF was detected in NSCLC cell lines by functional study, Western blot analysis and immunocytochemical staining. TF levels in eight NSCLC cell lines were also quantitated by enzyme-linked immunosorbent assay (ELISA), and TF expression was evaluated in 55 specimens of surgically resected NSCLCs. NSCLC cell lines derived from metastatic lesions produced high levels of TF (48.3+/-23.5 ng 10(-6) cells, mean +/- s.e.m.), whereas those derived from primary lesions produced low levels of TF (0.2+/-0.1 ng 10(-6) cells). Immunohistochemical studies disclosed significantly stronger staining for TF in cells from NSCLC patients with metastasis than in those without metastasis. Among the 28 patients with metastasis, ten were strongly positive, 16 were moderately positive and two were negative for TF. In contrast, among the 27 patients without metastasis, only two were strongly positive, 18 were moderately positive and seven were negative for TF. Therefore, malignant cells from patients with lung cancer produce various levels of TF, and TF may play an important role in the metastatic process.

Aberrations of the tissue factor pathway in patients positive for lupus anticoagulant

To evaluate the relationship between the tissue factor (TF) pathway and lupus anticoagulant (LA), in the present study, we measured the plasma levels of TF antigen and TF pathway inhibitor (TFPI) antigen in patients positive for LA. Plasma TF and TFPI levels in LA-positive patients were significantly higher than levels in healthy volunteers (p < 0.01). In LA-positive patients, there were no significant differences in plasma TF and TFPI levels between patients with and without thrombosis. In patients with thrombosis, there was no significant difference in the plasma TF level between LA-positive and LA-negative patients; however, the plasma TFPI level in LA-positive patients was significantly lower than that in LA-negative patients (p < 0.01). We also examined the TF pathway in human umbilical venous endothelial cells (HUVEC) incubated with plasma of LA-positive patients, LA-negative patients, and healthy volunteers. TF activity was significantly higher (p < .05) in HUVECs incubated with the plasma of LA-positive patients than in cells incubated with the plasma of the other two groups (p < .01). However, there was no significant difference in TFPI antigen levels among the media of HUVECs incubated with the plasma of all groups. The viability of HUVEC incubated with the plasma of LA-positive patients with thromboses, LA-positive patients without thromboses, and LA-negative patients with thromboses were significantly lower than that of HUVECs incubated with the plasma of healthy volunteers (p < .01). These findings suggest that abnormalities of the TF pathway plays an important role in the mechanism of hypercoagulability in LA-positive patients. LA may affect vascular endothelial cells causing thrombogenesis.

The effect of melatonin on cellular activation processes in human blood

The pineal hormone melatonin, due to its lipophilic nature, has access to every cell and every part of a cell in the body, suggesting that it could exert effects on blood immune cells. The regulation of the activation of monocytes may be important in a number of diseases, especially pathophysiological conditions associated with inflammatory reactions. Considering this, a study on the effect of melatonin on monocytes in whole blood was carried out. Melatonin added at a final concentration of 5 ng/mL to whole blood in vitro reduced lipopolysaccharide (LPS)-induced tissue factor (TF) activity in monocytes by 55% in blood from a group of subjects with melatonin-sensitive cells. At even lower concentrations of melatonin (20-50 pg/mL) and in the physiological range, a trend of suppressed LPS-induced TF activity by approximately 20% was seen. A further indication of a downregulation of LPS-stimulated monocytes by melatonin was shown by its reduction of LPS-induced tumor necrosis factor (TNF). Twenty to one hundred pg/mL melatonin caused a significant reduction of LPS-induced TNF production by approximately 25-30%. In contrast, melatonin at a final concentration of 10 pg/mL, added to whole blood incubated with LPS and also the phorbol ester, PMA, caused a significant rise of 25%; whereas 100 pg/mL enhanced LPS + PMA-induced TNF by approximately 80% as compared to LPS + PMA alone. These effects were not detectable during the winter darkness of Tromsø (70 degrees N), probably due to the high content of melatonin in the blood even at daytime. These results show that melatonin may have a beneficial effect by suppressing the expression of TF activity in LPS-stimulated monocytes. Furthermore, the results indicate that LPS-induced TF in monocytes of whole blood is independent of protein kinase C (PKC) activation. Melatonin is probably amplifying cellular activation reactions that are PKC-dependent. This may be physiologically important in upregulation of the immune system.

Lipopolysaccharide induction of tissue factor in THP-1 cells involves Jun protein phosphorylation and nuclear factor kappaB nuclear translocation

Tissue Factor (TF) gene expression is transiently induced in human monocytic THP-1 cells by lipopolysaccharide (LPS). We characterized the transcription factor complexes binding to the TF gene promoter LPS response element (LRE) (-220 to -172), which contains binding sites for nuclear factor kappaB (NFkappaB) and activator protein 1 (AP1) transcription factors, and examined the nature of the activation of these factors during a 24-h time course of LPS stimulation. We found proteolysis of the cytoplasmic inhibitory protein IkappaBalpha and nuclear translocation of the NFkappaB/Rel family proteins p65 and c-Rel, corresponding to the transient binding of a p65/c-Rel heterodimer to the kappaB-like site of the LRE. AP1 binding to the LRE was found to be constitutive, with the majority of the AP1 complexes being JunD/Fra-2 heterodimers. A change in the activation state of the AP1 complexes was, however, found to be transient, as determined by JunD phosphorylation of AP1 bound to the proximal binding site. This directly correlates to the transient activation of Jun N-terminal kinase (SAPK/JNK). These data indicate that LPS induction of TF gene expression in monocytic THP-1 cells is regulated by both the transient phosphorylation of Jun-family proteins and the nuclear translocation and transient binding of NFkappaB/Rel proteins.

Effects of heparin and related sulfated polysaccharides on tissue factor expression induced by mitogenic and non-mitogenic factors in human vascular smooth muscle cells

Smooth muscle cells (SMCs) of the intima are generally quiescent and non proliferative. Their proliferation due to different stimulations occurs in myointimal hyperplasia and is regularly present in atherogenesis or after transluminal angioplasty leading to vascular occlusive stenosis. In the course of these pathologies, the Tissue Factor (TF) synthesis was upregulated and rapidly expressed at the membrane of the SMCs. Heparin is known to inhibit SMCs proliferation induced by FCS. We evaluated the inhibitory effect of heparin on the expression of TF induced by various mitogenic (FCS, PDGF-BB and EGF) and non-mitogenic (bacterial LPS) agents. Inhibition by heparin of SMCs proliferation induced by the same agonists was also determined. Quiescent human vascular SMCs from normal adult arteries were treated for 1 h by heparin and related sulfated polysaccharides before stimulation by the agonists. All the agonists up-regulated the expression of TF antigen and activity. TF expression induced by the growth factors was inhibited by heparin (IC 50: 10-30 microg/ml), and other sulfated polysaccharides (IC 50: 1-5 microg/ml). SMCs proliferation, late activation of the extracellular signal-regulated kinases (ERK1/2), and PKC activity were inhibited by heparin (IC 50: 30-50 microg/ml) in SMCs stimulated by FCS but not in SMCs treated by PDGF or EGF. In contrast, heparin had no effect on LPS-induced TF expression nor on LPS-induced PKC activation. These results indicate that, besides its well known effect on SMC proliferation, heparin displays an inhibitory effect on cell mediated blood clotting processes through regulation of the TF expression.

Tissue factor expression by rat osteosarcoma cells adherent to tissue culture polystyrene and selected orthopedic biomaterials

Tissue factor (TF), a transmembrane glycoprotein expressed by numerous cell types, plays a critical role in the initiation of blood coagulation at sites of vascular injury. Activated products of the coagulation cascade may then enhance the inflammatory responses associated with wound healing. In the present investigation the ability of rat osteosarcoma (ROS) cells to express TF activity was examined following their growth on tissue-culture polystyrene (TCPS) and selected orthopedic biomaterials (titanium and zirconium alloys, and stainless steel). ROS cells exhibited significant TF activity as evidenced by the conversion of Factor X to Factor Xa in the presence of TF, Factor VIIa, and Ca2+. Factor Xa concentrations ranged from 1.0 fM per cell at 10 min to 6.0 fM per cell after 60 min. Additionally, ROS cells stimulated with calcium ionophore (A23187) exhibited approximately twice the activity of non-stimulated cells when grown on TCPS but not on the metallic substrates. ROS cells (stimulated or unstimulated) adherent to the zirconium alloy generated lower amounts of Factor Xa compared to those bound to the other alloys and unstimulated cells grown on TCPS. These results indicate that ROS cells cultured on these synthetic surfaces differentially express procoagulant activity and that cells grown on TCPS, but not the metallic alloys, exhibit increased TF activity in response to stimulation by calcium ionophore. This procoagulant activity may potentiate subsequent inflammatory responses associated with the use of orthopedic biomaterials and thereby influence the tissue compatibility of the implant.

Human allogeneic lymphocytes trigger endothelial cell tissue factor expression by a tumor necrosis factor-dependent pathway

Lymphocyte adhesion to endothelial cells and the extravascular deposition of fibrin are 2 important processes during pathologic situations such as allograft rejection. Tissue factor (TF) expression was therefore measured on human umbilical vein endothelial cells (HUVECs) after coculture with allogeneic lymphocytes (PBLs) by a factor Xa generation assay. When cocultured with PBLs, HUVECs expressed strong procoagulant activity related to the TF/factor VII-dependent pathway, which was enhanced when endothelial cells were treated with interferon-gamma (IFN-gamma). The highest TF activity was measured when 10(5) lymphocytes were incubated with 10(4) HUVECs (ratio 10: 1) for 4 hours, a time-dependent course similar to that obtained with tumor necrosis factor-alpha (TNF-alpha), and direct contact between the 2 cell types was necessary. PBL-induced TF activity was inhibited by cycloheximide or actinomycin D, indicating active protein synthesis that was confirmed by the increase in TF mRNA detected by reverse transcription-polymerase chain reaction. It was then demonstrated that 1 of the primary signaling pathways leading to endothelial cell TF expression was a rapid initial interaction between membrane TNF expressed on PBLs and the 75-kd TNF receptor, with subsequent involvement of platelet-activating factor and P-selectin. Finally, we showed that the transduction of external signals involving the activation of protein kinase C and protein tyrosine kinases also contributed to the regulation of TF expression.

Activated platelets induce tissue factor expression on human umbilical vein endothelial cells by ligation of CD40

CD40 is a type I member of the tumour necrosis factor (TNF) receptor superfamily of proteins, and is present on a wide variety of cells including vascular endothelial cells. Ligation of this receptor on endothelial cells is known to increase expression of inflammatory adhesion molecules. We have recently demonstrated that platelets express the ligand of CD40 (CD154) within seconds of exposure to agonist, and interact with endothelial cells to participate directly in the induction of an inflammatory response. Here we show that activated platelets induce tissue factor (TF) expression on endothelial cells in a CD40/CD154-dependent manner, and that the magnitude of this response can equal that induced by TNFe. Moreover, CD40 ligation on endothelial cells downregulates the expression of thrombomodulin. We also show that CD40-mediated TF expression is less sensitive to inhibition with the oxidative radical scavenger pyrrolidine dithiocarbamate than is that mediated by TNFalpha, indicating that CD40 has a distinct signalling pathway. Tissue factor is a cell membrane protein which functions as the main trigger of the extrinsic pathway of blood coagulation, and its expression on endothelial cells is implicated in wound healing and angiogenesis. Since platelets are among the first cells involved in haemostasis following tissue injury, our data showing that ligation of CD40 by CD154 induces a procoagulant phenotype on vascular endothelial cells suggests that platelets may play an important role in the induction of wound healing.

Murine hepatitis virus strain 3 induces the macrophage prothrombinase fgl-2 through p38 mitogen-activated protein kinase activation

The clinical syndrome of acute liver failure produced by fulminant viral hepatitis can be reproduced in mice by infection with murine hepatitis virus strain 3 (MHV-3). Although it is clear that MHV-3-induced hepatitis depends upon macrophage activation and the expression of a specific prothrombinase, fgl-2, the signaling pathways involved in virally stimulated cell activation are unclear. Since we had previously found that MHV-3 induces the tyrosine phosphorylation of cellular proteins, we investigated the roles of the mitogen-activated protein kinase (MAPK) proteins. In a series of Western blots, immunoprecipitation and in vitro kinase assay studies, we found that both the extracellular signal-related kinase (ERK) and p38 MAPK proteins are tyrosine-phosphorylated and activated following exposure of murine peritoneal exudative macrophages (PEM) to MHV-3. Although p38 phosphorylation and activity are induced soon after MHV-3 exposure, peaking by 1-5 min, ERK phosphorylation and activity increase more gradually, peaking at 20-30 min and gradually fading thereafter. Interestingly, whereas selective p38 inhibition with SB203580 (1-20 microM) abolished the virally stimulated induction of fgl-2 mRNA, protein, and functional activity, selective ERK inhibition with PD98059 (1-50 microM) limited fgl-2 functional activity but had little to no effect on fgl-2 mRNA or protein levels. Moreover, whereas inhibition of ERK had no effect on p38 activity, p38 inhibition consistently increased MHV-3-induced ERK activity. To ensure that these pathways were relevant in vivo, MHV-3 was injected intraperitoneally, and peritoneal exudative macrophages were collected. Again, MHV-3 exposure led to increased p38 and ERK tyrosine phosphorylation. These data argue that MHV-3 induces tightly interconnected ERK and p38 MAPK cascades in the macrophage both in vitro and in vivo. Although the ERK and p38 MAPK proteins have discordant effects at the level of fgl-2 expression, both converge at the level of its activity, suggesting that targeted MAPK inhibition may ultimately be useful in the modulation of viral hepatitis.

Tissue factor activity of SW-480 human colon adenocarcinoma cells is modulated by thrombin and protein kinase C activation

Expression of tissue factor (TF), a cellular initiator of the extrinsic coagulation cascade, is a feature of many malignant tumours and is intimately involved in the process of metastasis. SW-480 human colon adenocarcinoma cells responded to thrombin (1 U ml(-1)) or phorbol 12-myristate 13-acetate (PMA, 0.1 microM) with a 6.0-fold and a 7.7-fold increase in their procoagulant activity (PCA), respectively, after 4-6 h incubation in serum-free medium. The thrombin-enhanced PCA was significantly inhibited by complexing of thrombin with hirudin, or by serine protease inhibition with 3,4-dichloroisocoumarin. Both effects of thrombin and PMA on PCA in SW-480 cells were blocked by pretreatment of cells with cycloheximide or actinomycin D, indicating that the response required de novo protein and RNA synthesis. The thrombin-enhanced PCA depended on the activation of protein kinase C (PKC) as it was diminished by staurosporine and calphostin C. Moreover, stimulation of SW-480 cells by thrombin or PMA led to a significant increase in TF mRNA within 3 h as measured by the reverse-transcription PCR method, which was also dependent on the activation of PKC. The unaltered decay rate of thrombin-enhanced TF mRNA, evaluated after the addition of staurosporine, suggested that its inhibitory effect occurred at a transcription level. Our data suggest that thrombin enhances TF gene expression and protein synthesis in tumour cells in vitro via PKC activation. The induction of TF expression in tumour cells by thrombin indicates that tumour-associated PCA might have a positive-feedback effect on in vivo local propagation of thrombus by thrombin formation.

Expression of the fgl2 and its protein product (prothrombinase) in tissues during murine hepatitis virus strain-3 (MHV-3) infection

Murine Hepatitis Virus Strain 3 (MHV-3) produces fulminant hepatitis with 80-90% mortality in Balb/cJ mice. Previous studies in our laboratory have shown that peritoneal macrophages from MHV-3 infected mice produce a procoagulant (PCA) which has the ability to cleave prothrombin to thrombin (prothrombinase) encoded by the gene fgl2 located on chromosome 5. PCA accounts for sinusoidal thrombosis and hepatic necrosis and the necrosis and mortality can be prevented by treatment of animals with a monoclonal antibody to PCA. These present studies were designed to examine the expression of this gene (mRNA by Northern analysis and in situ hybridization) and the gene product PCA (immunochemistry) in tissues recovered from MHV-3 infected Balb/cJ mice in an attempt to explain the liver specific nature of MHV-3 disease. Fgl2 gene expression was detected as early as 8 hours after MHV-3 infection which persisted to 48 hours in the liver, spleen and lungs whereas no gene expression was seen in the brain or kidneys despite the fact that equivalent viral titers were detected in all tissues at all times. In the liver, fgl2 gene expression was confined to endothelial and Kupffer cells with no expression in hepatocytes. Immunochemistry localized the PCA protein to Kupffer cells and endothelial cells and necrotic foci within the liver. No PCA protein was detected by immunochemistry in any other tissues at any time during the course of MHV-3 infection. These results explain the liver specific nature (fulminant hepatitis) of MHV-3 infection and provides further evidence for the role of PCA in the pathogenesis of fulminant hepatitis. MHV-3 induces selective transcription of the gene fgl2 and only hepatic reticuloendothelial cells produce functional protein (PCA) which is known to account for fulminant hepatic failure produced by MHV-3.

The pattern of induction of apoptosis during infection with MHV-3 correlates with strain variation in resistance and susceptibility to lethal hepatitis

In the present study we have investigated the possibility that strain specific differences in the induction of apoptosis in macrophages could play a role in the resistance of strain A/J mice to MHV-3 induced hepatitis. MHV-3 infected macrophages from Balb/c and A/J mice were analyzed at various time points after infection. Apoptosis in A/J macrophages could be detected at 8 h post infection and increased significantly by 12 h, when almost 50-70% of the infected cells were undergoing apoptosis. In Balb/c macrophages, apoptotic changes were less pronounced and were observed in only 5-10% of the cells. MHV-3 induced apoptosis was inversely correlated with the ability of this virus to induce expression of fgl-2 prothrombinase protein and syncytia formation. Infected macrophages from A/J mice did not express fgl-2 protein and did not form syncytia. In contrast, infection of Balb/c derived macrophages resulted in fgl-2 expression and extensive syncytia formation. These data fit a model in which apoptosis of virally infected cells is a protective response which eliminates cells whose survival might be harmful for the whole organism.

Pentoxifylline inhibits hypoxia-induced upregulation of tumor cell tissue factor and vascular endothelial growth factor

Tissue factor (TF), the membrane glycoprotein that initiates blood coagulation, is constitutively expressed by many tumor cells and is implicated in peri-tumor fibrin deposition and hypercoagulability in cancer. Upregulation of tumor TF correlates with enhanced metastatic potential. Furthermore, TF has been colocalized with VEGF in breast cancer, specially at sites of early angiogenesis. There are no data on the effect of hypoxia on tumor cell TF expression. Since hypoxia is known to stimulate VEGF production, we studied whether this also induces tumor cell TF expression. Confluent monolayers of A375 melanoma, MCF-7 breast carcinoma and A549 lung carcinoma were cultured in either 95% air, 5% CO2 (normoxic) or 95% N2, 5% CO2 (hypoxic; 25-30 mmHg) for 24 h. Procoagulant activity (PCA) was measured by amidolytic and clotting assays, surface TF antigen by flow cytometry, early apoptosis by annexin V binding and VEGF levels in culture supernatants by ELISA. Hypoxia significantly increased tumor cell PCA in all three cell lines tested and TF antigen on A375 cells was increased four-fold (P <0.05). Pentoxifylline (PTX), a methylxanthine derivative, significantly inhibited the hypoxia-induced increase in PCA as well as VEGF release in all three cell lines tested. In A375 cells, PTX significantly inhibited TF antigen expression by both normoxic and hypoxic cells. Hypoxia induced a slight (5%) but not significant, increase in early apoptosis. Intravenous injection of hypoxic A375 cells into nude rats produced more pronounced thrombocytopenia (n = 5, P <0.01) and more lung metastases (n = 3, P <0.05) compared to normoxic cells. We conclude that hypoxia increases TF expression by malignant cells which enhances tumor cell-platelet binding and hematogenous metastasis. Hypoxia-induced upregulation of TF appears to parallel that of VEGF, although the mechanism remains unclear.

Expression of tissue factor in hepatic ischemic-reperfusion injury of the rat

BACKGROUND

Tissue factor (TF) is a membranous protein normally present on the surface of the fibroblasts and smooth muscle cells of vessels. TF is an initiation factor for blood coagulation, and its expression is induced on macrophages and endothelial cells during the inflammatory or immune response. We studied the significance of TF expression in warm ischemic-reperfusion injury of the liver using a rat model.

METHODS

Following laparotomy of Lewis rats, the branches of the hepatic artery and portal vein leading to the median, left, and caudate lobes of the liver were clamped for 2 hr. The liver was reperfused after 120 min of ischemia. Rats were killed at 0, 1, 3, 5, 8, and 12 hr after reperfusion, and liver tissues were harvested. TF activity was measured by the chromophilic substrate S-2222. TF expression was studied by immunohistochemical staining with the monoclonal antibody HTF-K108.

RESULTS

TF activity in the blood showed a peak at 3 hr after reperfusion (8.9+/-0.5 U/L), then decreased and returned to the normal level by 12 hr (0.9+/-0.3 U/L). TF activity in ischemic liver tissue increased gradually over 12 hr after reperfusion (1223+/-275 U/g dry weight before ischemia and 2545+/-284 U/g weight at 12 hr after reperfusion). Histologically spotty necroses were observed in the liver tissue 5 hr after reperfusion. The necrotic area extended and encompassed almost all of the ischemic liver by 12 hr after reperfusion. Histochemically, TF staining was negative on the hepatocytes and slightly positive on sinusoid cells of the normal liver. On the other hand, TF was strongly stained, especially on the hypertrophic monocytic cells accumulating at the site of the necrosis, but staining was not evident on the necrotic hepatocytes. A slight degree of TF staining was observed on the alveolar epithelium of the lung, irrespective of liver ischemia and reperfusion.

CONCLUSION

These results demonstrate that TF plays an important role in the development of the hepatic ischemic-reperfusion injury, and the subsequent microcirculatory incompetence might cause the formation of microthrombus and the development of necrosis.

Expression of functional tissue factor on small vesicles of lipopolysaccharide-stimulated human vascular endothelial cells

We examined tissue factor expression on lipopolysaccharide-stimulated endothelial cells and their small vesicles by using specific antibodies and flow cytometry. Tissue factor functional activity was also assessed by activation of factor X. Endothelial cells were stimulated with 10 microg/ml of lipopolysaccharide in M-199/bovine serum albumin. Flow cytometry showed that expression of tissue factor on endothelial cells reached a maximum at 6 hours after stimulation, whereas that on small vesicles reached a maximum after 12 hours. Factor X activation mediated by factor VIIa and tissue factor was observed over a similar time course and was inhibited by the addition of antitissue factor antibody. Immunoelectron microscopy suggested that small vesicles with expression of some tissue factor were produced from the surface of endothelial cells. Our findings thus showed that tissue factor on endothelial cells produced by lipopolysaccharide stimulation was partly released to small vesicles. This may cause disseminated intravascular coagulation and related coagulation disorders.