Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Vein graft failure is a major limitation of coronary artery and peripheral vascular surgery. Tissue factor (TF), a transmembrane glycoprotein, generates thrombin by initiating the extrinsic coagulation cascade and plays a major role in the response to arterial injury. This study was designed to examine changes in TF protein expression in response to venous bypass grafting. New Zealand White rabbits underwent interposition bypass grafting of the common carotid artery via the ipsilateral external jugular vein. The contralateral control jugular veins (n = 6), early vein grafts (1 or 3 days after grafting, n = 18), and late vein grafts (14 or 28 days after grafting, n = 8) were examined by immunohistochemistry. The presence or absence of TF immunostaining in the intima was assessed in each vessel quadrant. In control veins, intimal TF staining was present in 5 of 24 vessel quadrants. In early vein grafts, TF staining was markedly increased in the intima (72 of 72 quadrants, P < .001 vs control veins), and TF immunostaining colocalized with CD18-positive leukocytes but not with endothelial cells, vascular smooth muscle cells, or RAM11-positive macrophages. In late vein grafts with intimal hyperplasia, TF expression was low or absent in the intima (6 of 32 quadrants, P < .001 vs early vein grafts; P = NS vs control veins), although medial smooth muscle cells expressed TF. Marked changes in TF expression occur in vein grafts. In early vein grafts, TF protein was greatly increased in the intima for at least 3 days and was associated with CD18-positive leukocytes. In late vein grafts with intimal hyperplasia, however, TF protein was not seen in the intima. These findings may have important implications for the development of therapeutic strategies to limit vein graft failure.
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PMID:Modulation of tissue factor protein expression in experimental venous bypass grafts. 926 Dec 61

Binding of Ulex europaeus lectin to microvessels was used to isolate endothelial cells from cycling human endometrium. Cultured human endometrial endothelial cells (HEECs) exhibited endothelial cell-specific characteristics such as tube formation on a basement membrane matrix and sequestration of acetylated low-density lipoprotein. Markers for potentially contaminating epithelial, stromal, smooth muscle, and bone marrow-derived cells were not detected in the HEEC cultures. Basal and proinflammatory-stimulated immunostaining profiles for endothelial cell-specific adhesion markers, as exemplified by Von Willebrand's factor and E-selectin, were similar for cultured HEECs and human umbilical venous cord endothelial cells (HUVECs). However, HUVECs expressed several extracellular matrix proteins that were absent from cultured HEECs. In the latter, the protein kinase C agonist phorbol myristate acetate transiently enhanced tissue factor (TF) mRNA levels and elicited a more prolonged elevation in TF protein levels, but did not affect plasminogen activator inhibitor-1 (PAI-1) mRNA and protein levels. Inappropriate expression of TF, which initiates hemostasis by generating thrombin, and of PAI-1, which regulates hemostasis by acting as the primary inhibitor of fibrinolysis, can each lead to thrombosis. The differential regulation of TF and PAI-1 expression revealed in the current study emphasizes the importance of using HEECs to evaluate mechanisms regulating the hemostatic/thrombotic balance in human endometrium.
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PMID:Human endometrial endothelial cells: isolation, characterization, and inflammatory-mediated expression of tissue factor and type 1 plasminogen activator inhibitor. 1068 11

BACKGROUND-Intravascular clotting has been implicated in the pathogenesis of cardiac allograft vasculopathy (CAV). We previously identified the expression of tissue factor (TF), the primary cellular initiator of blood coagulation, within the coronary intima, which was associated with neointimal thickening. In the present study, the effect of recombinant hirudin on CAV was assessed in Lewis to Fisher rat heterotopic cardiac allografts. METHODS AND RESULTS-Transplant recipients were randomized to a control group (n=10) and a hirudin-treated group (n=12; 2 mg. kg(-1). d(-1) SC). Histological evaluations of rejection, CAV, and TF staining were performed 120 days after transplantation. No significant differences were observed between the 2 groups with respect to the degree of rejection. Hirudin significantly (P<0.05) suppressed the development of CAV in the graft microvessels, but it was less effective in large coronary arteries. Graft intimal cells, isolated by laser-assisted cell picking, showed a marked upregulation of TF gene transcription, which was prevented by hirudin (P<0.01). As demonstrated by immunohistochemistry and quantitative analyses of TF mRNA levels by real-time polymerase chain reaction, hirudin treatment resulted in a significant reduction of TF protein and mRNA expression (P<0.001). CONCLUSIONS-Treatment with hirudin in this rat cardiac transplant model inhibited TF expression and decreased neointimal hyperplasia. These results suggest that TF inhibition by hirudin, in addition to its direct effect on thrombin, may attenuate the hypercoagulable state and prevent the development of CAV at least in restricted sites of the graft coronary vasculature.
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PMID:Hirudin reduces tissue factor expression and attenuates graft arteriosclerosis in rat cardiac allografts. 1089 2

Thromboembolic disorders are common in cancer patients. Two major contributing factors are central venous catheters for drug delivery and the use of l-aparaginase, which decreases the plasma antithrombin level, but the causes of the hypercoagulable state in these patients are not fully understood. In this study, the T24/83 cell line was used as a model to investigate the effects of chemotherapeutic agents on cell surface thrombin regulation. Plasma thrombin generation and prothrombin consumption was increased in most of the treated cells, particularly vincristine- and adriamycin-treated cells (P < 0.05), compared with controls. However, no free thrombin generation or prothrombin consumption was observed in factor VII (FVII)-depleted plasma. No significant differences in the levels of thrombin-alpha2-macroglobulin (IIa-alpha2M) and thrombin-anti-thrombin (TAT) were observed between controls and any of the treatments, except for vincristine- and adriamycin-treated cells, which showed a significant difference in TAT production (P < 0.05). Also, there was an upregulation in tissue factor (TF) mRNA expression in etoposide-, methotrexate- and vincristine-treated monolayers compared with controls, as well as an upregulation in TF protein production in vincristine-treated cells. The data suggests that thrombin generation occurs via the extrinsic (TF-dependent) coagulation pathway on cell surfaces and that some chemotherapeutic agents are able to upregulate TF mRNA and protein expression in T24/83 cells.
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PMID:The effects of chemotherapeutic agents on the regulation of thrombin on cell surfaces. 1254 93

Endothelial cells express negligible amounts of tissue factor (TF) that can be induced by thrombin, which is important for acute coronary syndromes. Recent research suggests that endothelial TF expression is positively regulated by RhoA and p38mapk, but negatively by Akt/endothelial nitric oxide synthase (eNOS) pathway. High-density lipoprotein (HDL) is atheroprotective and exerts antiatherothrombotic effect. This study investigated the effect of a reconstituted HDL (rHDL) on endothelial TF expression induced by thrombin and the underlying mechanisms. In cultured human umbilical vein and aortic endothelial cells, thrombin (4 U/mL, 4 hours) increased TF protein level, which was reduced by rHDL (0.1 mg/mL, 43% inhibition, n=3 to 7, P<0.01). Activation of RhoA but not p38mapk by thrombin was prevented by rHDL. rHDL stimulated Akt/eNOS pathway. The phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin or LY294002 abolished the activation of Akt/eNOS and reversed the inhibitory effect of rHDL on TF expression. Adenoviral expression of the active PI3K mutant (p110) reduced TF expression stimulated by thrombin without inhibiting RhoA activation, whereas expression of the active Akt mutant (m/p) further facilitated TF upregulation by thrombin. Moreover, a dominant-negative Akt mutant (KA) reduced thrombin's effect and did not reverse the rHDL's inhibitory effect on TF expression. Inhibition of eNOS by N(omega)-nitro-L-arginine methyl ester (100 micromol/L) did not affect the rHDL's effect. In conclusion, rHDL inhibits thrombin-induced human endothelial TF expression through inhibition of RhoA and activation of PI3K but not Akt/eNOS. These findings implicate a novel mechanism of antiatherothrombotic effects of HDL.
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PMID:Reconstituted high-density lipoprotein inhibits thrombin-induced endothelial tissue factor expression through inhibition of RhoA and stimulation of phosphatidylinositol 3-kinase but not Akt/endothelial nitric oxide synthase. 1498 29

Oral estrogen treatment increases thrombotic risk. Tissue factor (TF), tissue factor pathway inhibitor (TFPI), and platelet interaction with leukocytes are important determinants of thrombogenesis. Therefore, the present study was designed to define and compare platelet TF and TFPI mRNA and adhesion protein expression in platelets derived from animals treated with different types of oral estrogens. Ovariectomized pigs were treated with 17beta-estradiol (2 mg/day), conjugated equine estrogen (CEE; 0.625 mg/day), or raloxifene (60 mg/day) for 4 wk. Compared with intact animals, ovariectomy and treatment differentially affected populations of leukocytes: neutrophils decreased whereas lymphocytes increased significantly 4 wk after ovariectomy and with 17beta-estradiol and CEE treatments; eosinophils increased only with 17beta-estradiol treatment. Content of TF protein increased in platelets from 17beta-estradiol- and raloxifene-treated pigs, whereas TF mRNA was detected only in platelets from 17beta-estradiol- and CEE treated pigs. TFPI mRNA increased in platelets after ovariectomy and estrogen treatment. Only a trace of TFPI protein was detected, but a higher-molecular-mass protein was observed in all treatment groups. Expression of CD40 and CD40 ligand increased with ovariectomy and decreased with 17beta-estradiol and CEE treatments more than with raloxifene. The ratio of activated to basal P-selectin expression decreased with ovariectomy and increased with raloxifene treatments. These results suggest that estrogenic formulations may affect individual thrombotic risk by different mechanisms that regulate TF and platelet-leukocytic interactions. These studies provide the rationale for evaluation of interactions among platelets and TF and TFPI expression on thrombin generation during estrogen treatment in humans.
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PMID:Estrogenic regulation of tissue factor and tissue factor pathway inhibitor in platelets. 1596 15

Cysteinyl leukotrienes (cysLT), i.e., LTC4, LTD4, and LTE4, are lipid mediators derived from the 5-lipoxygenase pathway, and the cysLT receptors cysLT1-R/cysLT2-R mediate inflammatory tissue reactions. Although endothelial cells (ECs) predominantly express cysLT2-Rs, their role in vascular biology remains to be fully understood. To delineate cysLT2-R actions, we stimulated human umbilical vein EC with LTD4 and determined early induced genes. We also compared LTD4 effects with those induced by thrombin that binds to protease-activated receptor (PAR)-1. Stringent filters yielded 37 cysLT2-R- and 34 PAR-1-up-regulated genes (>2.5-fold stimulation). Most LTD4-regulated genes were also induced by thrombin. Moreover, LTD4 plus thrombin augmented gene expression when compared with each agonist alone. Strongly induced genes were studied in detail: Early growth response (EGR) and nuclear receptor subfamily 4 group A transcription factors; E-selectin; CXC ligand 2; IL-8; a disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif 1 (ADAMTS1); Down syndrome critical region gene 1 (DSCR1); tissue factor (TF); and cyclooxygenase 2. Transcripts peaked at approximately 60 min, were unaffected by a cysLT1-R antagonist, and were superinduced by cycloheximide. The EC phenotype was markedly altered: LTD4 induced de novo synthesis of EGR1 protein and EGR1 localized in the nucleus; LTD4 up-regulated IL-8 formation and secretion; and LTD4 raised TF protein and TF-dependent EC procoagulant activity. These data show that cysLT2-R activation results in a proinflammatory EC phenotype. Because LTD4 and thrombin are likely to be formed concomitantly in vivo, cysLT2-R and PAR-1 may cooperate to augment vascular injury.
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PMID:Cysteinyl leukotriene 2 receptor and protease-activated receptor 1 activate strongly correlated early genes in human endothelial cells. 1660 35

Paclitaxel is used on drug-eluting stents because it inhibits proliferation of vascular cells. Stent thrombosis remains a concern with this compound, particularly with higher dosages. This study investigates the effect of paclitaxel on tissue factor (TF) expression in human endothelial cells. Paclitaxel enhanced thrombin-induced endothelial TF protein expression in a concentration- and time-dependent manner. A concentration of 10(-5) mol/L elicited a 2.1-fold increase in TF protein and a 1.6-fold increase in TF surface activity. The effect was similar after a 1 hour as compared with a 25-hour pretreatment period. Real-time polymerase chain reaction revealed that paclitaxel increased thrombin-induced TF mRNA expression. Paclitaxel potently activated c-Jun terminal NH2 kinase (JNK) as compared with thrombin alone, whereas the thrombin-mediated phosphorylation of p38 and extracellular signal-regulated kinase remained unaffected. Similar to paclitaxel, docetaxel enhanced both TF expression and JNK activation as compared with thrombin alone. The JNK inhibitor SP600125 reduced thrombin-induced TF expression by 35%. Moreover, SP600125 blunted the effect of paclitaxel and docetaxel on thrombin-induced TF expression. Paclitaxel increases endothelial TF expression via its stabilizing effect on microtubules and selective activation of JNK. This observation provides novel insights into the pathogenesis of thrombus formation after paclitaxel-eluting stent deployment and may have an impact on drug-eluting stent design.
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PMID:Paclitaxel enhances thrombin-induced endothelial tissue factor expression via c-Jun terminal NH2 kinase activation. 1679 85

Preeclampsia (PE), intrauterine growth restriction (IUGR) and abruption with or without fetal loss are associated with reduced uteroplacental blood flow, decidual vasculopathy, endothelial cell dysfunction, thrombosis, inflammation and hemorrhage. Our hypothesis is that reduced uteroplacental blood flow causes focal decidual hypoxia that generates vascular endothelial growth factor (VEGF). The latter acts directly on decidual endothelial cells to induce aberrant expression of tissue factor (TF), the primary initiator of coagulation. This in turn generates thrombin that induces: i) further TF expression; and ii) inflammatory cytokines. Both VEGF and TF induce aberrant angiogenesis-vessel maintenance reflected by endothelial cell fenestrations and induction of a prothrombotic surface causing both the decidual hemorrhage (i.e. abruption) and thrombosis (i.e. uteroplacental vascular insufficiency) observed in these adverse pregnancy outcomes. This novel hypothesis is supported by our finding of TF expression in decidual endothelium of pregnancies complicated by IUGR and/or fetal loss. Moreover, treatment of cultured endometrial endothelial cells with VEGF or thrombin induces TF protein and mRNA expression. Quantitative RT-PCR analysis indicates that thrombin enhances (>10-fold) the output of diverse inflammatory cytokines in these cultures. The greatest effect (>2-log) was seen on macrophage inflammatory protein 3alpha (MIP3alpha). In vitro, thrombin results in endometrial endothelial cell aggregations and changes in the apoptotic pathway. Thus, we postulate that reductions in uteroplacental flow initiate a cascade of molecular effects leading to hypoxia, thrombosis, inflammation, and endothelial cell dysfunction resulting in untoward pregnancy outcomes.
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PMID:Thrombin activation of endometrial endothelial cells: a possible role in intrauterine growth restriction. 1726 54

The source and significance of bloodborne tissue factor (TF) are controversial. TF mRNA, protein, and TF-dependent procoagulant activity (PCA) have been detected in human platelets, but direct evidence of TF synthesis is missing. Nonstimulated monocyte-free platelets from most patients expressed TF mRNA, which was enhanced or induced in all of them after platelet activation. Immunoprecipitation assays revealed TF protein (mainly of a molecular weight [Mr] of approximately 47 kDa, with other bands of approximately 35 and approximately 60 kDa) in nonstimulated platelet membranes, which also increased after activation. This enhancement was concomitant with TF translocation to the plasma membrane, as demonstrated by immunofluorescence-confocal microscopy and biotinylation of membrane proteins. Platelet PCA, assessed by factor Xa (FXa) generation, was induced after activation and was inhibited by 48% and 76% with anti-TF and anti-FVIIa, respectively, but not by intrinsic pathway inhibitors. Platelets incorporated [(35)S]-methionine into TF proteins with Mr of approximately 47 kDa, approximately 35 kDa, and approximately 60 kDa, more intensely after activation. Puromycin but not actinomycin D or DRB (5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole) inhibited TF neosynthesis. Thus, human platelets not only assemble the clotting reactions on their membrane, but also supply their own TF for thrombin generation in a timely and spatially circumscribed process. These observations simplify, unify, and provide a more coherent formulation of the current cell-based model of hemostasis.
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PMID:Human platelets synthesize and express functional tissue factor. 1734 8


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