Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endothelial cells are highly sensitive to changes in the extracellular milieu. Sepsis results in activation of inflammatory and coagulation pathways. We hypothesized that sepsis-associated mediators may alter the response capacity (so-called "set point") of endothelial cells. Human umbilical vein endothelial cells (HUVEC) were preincubated in the presence or absence of tumor necrosis factor (TNF)-alpha, lipopolysaccharide (LPS), hypoxia, hyperthermia, and/or high glucose; treated with or without thrombin for 4 h; and then processed for RNase protection assays of selected activation markers. Priming with TNF-alpha and LPS significantly inhibited thrombin-mediated induction of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, tissue factor, and E-selectin, but not platelet-derived growth factor-A or CD44. In electrophoretic mobility shift assays, thrombin-treated HUVEC demonstrated inducible binding of p65 NF-kappaB, an effect that was significantly blunted by pretreatment of cells with TNF-alpha and LPS. Consistent with these results, TNF-alpha and LPS attenuated the effect of thrombin on IkappaB phosphorylation, total cytoplasmic IkappaB, and nuclear translocation of p65 NF-kappaB. The inhibitory effect of TNF-alpha on thrombin signaling persisted for up to 24 h following removal of the cytokine. Taken together, these data suggest that inflammatory mediators prime endothelial cells to modulate subsequent thrombin response.
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PMID:Preconditioning of primary human endothelial cells with inflammatory mediators alters the "set point" of the cell. 1617 86

Using thapsigargin (Tg), an agent that mobilizes calcium by directly emptying intracellular stores, we previously showed that intracellular calcium may play an important role in the regulation of intercellular adhesion molecule (ICAM)-1 gene expression induced by cytokines in human airway smooth muscle (ASM) cells. In the present study, we extended this previous observation by comparing the effect of Tg and other calcium-mobilizing G-protein-coupled receptor (GPCR) agonists on the expression of different pro-inflammatory genes in response to tumor necrosis factor (TNF)-alpha in ASM cells. We found that in resting cells, Tg (10-100 nM) or the bradykinin (BK) (1-10 muM) and thrombin (Thr) (1 U/ml) stimulated interleukin (IL)-6 secretion but had no effect on regulated on activation, normal T cells expressed and secreted (RANTES) levels. More importantly, such calcium-mobilizing agents significantly enhanced TNF-alpha-induced IL-6 secretion while RANTES secretion was abrogated. The use of luciferase-tagged IL-6 and RANTES promoter constructs demonstrated similar effects of Tg on IL-6 and RANTES genes in basal and TNF-alpha-stimulated conditions. The cyclic adenosine monophosphate (cAMP)-dependent pathway plays a minor role in this differential regulation of IL-6 and RANTES genes expression. 2-Aminoethoxydiphenyl borate (APB), a blocker of store-operated calcium channels (SOCs), and bisindolylmaleimide I (Bis I), a broad-spectrum protein kinase C (PKC) inhibitor, inhibited the basal and synergic effects of IL-6 secretion in response to calcium-mobilizing agents and TNF-alpha, but did not prevent the abrogated effect of RANTES secretion. We also found that Go-6976, a selective calcium-dependent PKC isozyme inhibitor, did not inhibit IL-6 secretion in response to GPCR agonist and TNF-alpha; whereas Rottlerlin, a PKC-delta inhibitor, inhibited both Thr- and TNF-alpha-induced expression of IL-6, while BK-induced IL-6 secretion was not affected. Interestingly, TNF-alpha-induced interferon regulatory factor (IRF)-1 activation was significantly inhibited by all calcium-mobilizing agents, BK, Thr and Tg. These results show that calcium-mobilizing GPCR agonists functionally interact with TNF-alpha to differentially regulate pro-inflammatory genes expression in human ASM cells, possibly by involving Tg-sensitive intracellular calcium stores, SOC and PKC.
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PMID:G-protein-coupled receptor agonists differentially regulate basal or tumor necrosis factor-alpha-stimulated activation of interleukin-6 and RANTES in human airway smooth muscle cells. 1622 99

We have previously shown that the thrombin inhibiting agent melagatran markedly prolongs aPTT and counteracts creatinine increase in endotoxemic pigs. Against this background the effects of the platelet-inhibiting agent, clopidogrel on basic haemostatic, inflammatory and physiological variables were evaluated during porcine endotoxemia. Clopidogrel (10 mg/kg) or saline was randomly injected i.v. 30 min before start of a 6-h continuous infusion of endotoxin in 12 anaesthetised pigs. Another three pigs were given clopidogrel but not endotoxin. Clopidogrel did not affect physiological variables, formation of activated platelet microparticles, PK, aPTT, platelet count, plasma fibrinogen, TNF-alpha, or IL-6 during porcine endotoxemia. Although renal function, as evaluated by creatinine clearance (CLcr) deteriorated significantly (P = 0.01) in the saline-endotoxin, but not in the clopidogrel-endotoxin group, there was no significant difference between the saline-endotoxin and the clopidogrel-endotoxin groups. Renal biopsies were marked with a FITC-labelled chicken anti-fibrinogen antibody detecting fibrinogen and platelet bound fibrinogen, as a marker of porcine platelet activation, and examined by light microscopy. Evaluation of these immunohistochemical slides did not indicate that clopidogrel, significantly reduced the amount of intrarenal fibrin or fibrinogen depositions. Besides a trend to preserve renal function, clopidogrel did not affect haemodynamics or the coagulatory and inflammatory responses in porcine endotoxemia.
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PMID:Early endotoxin-mediated haemostatic and inflammatory responses in the clopidogrel-treated pig. 1623 2

Atherosclerosis is a dynamic disease involving lipid metabolism, inflammation and thrombosis. A key factor in thrombosis is tissue factor, a small transmembrane glycoprotein. Tissue factor binds FactorVIIa, and this complex converts Factor X to Factor Xa, leading to thrombin generation and fibrin formation. Inhibition of this pathway is by tissue factor pathway inhibitor (TFPI). Tissue factor is found sequestered within atherosclerotic plaques, and plaque rupture allows tissue factor exposure to the circulation, leading to formation of a thrombus. Tissue factor is also associated with membrane microparticles in the circulation, most likely released from monocytes activated by an inflammatory event. We hypothesize that consumption of a typical western diet that is moderate in fat content leads to elevated levels of circulating tissue factor that may act as a marker of a prothrombotic state. Healthy volunteers, aged 18-55, consumed a moderate (40%) fat meal, with blood taken before and 3.5 and 6 h after the meal. Plasma was isolated and assayed for plasma triglycerides, tissue factor, thrombin antithrombin (TAT) complexes, TFPI and TNFalpha. The levels of circulating tissue factor increased 56% (from 78 pg/ml to 120 pg/ml) 3.5 h after the meal. Levels decreased, but had not returned to baseline 6 h postprandially. No significant differences in TAT, TFPI and TNFa levels were observed postprandially. These results demonstrate increased tissue factor levels in individuals who consumed a moderate fat diet. This suggests that the typical western diet may play a larger role in cardiovascular disease than merely altering lipid profiles.
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PMID:Postprandial elevation of tissue factor antigen in the blood of healthy adults. 1626 63

Thrombin-activatable fibrinolysis inhibitor (TAFI), also known as carboxypeptidase R, has been implicated as an important negative regulator of the fibrinolytic system. In addition, TAFI is able to inactivate inflammatory peptides such as complement factors C3a and C5a. To determine the role of TAFI in the hemostatic and innate immune response to abdominal sepsis, TAFI gene-deficient (TAFI-/-) and normal wild-type mice received an i.p. injection with Escherichia coli. Liver TAFI mRNA and TAFI protein concentrations increased during sepsis. In contrast to the presumptive role of TAFI as a natural inhibitor of fibrinolysis, TAFI-/- mice did not show any difference in E. coli-induced activation of coagulation or fibrinolysis, as measured by plasma levels of thrombin-anti-thrombin complexes and D-dimer and the extent of fibrin depositions in lung and liver tissues. However, TAFI-/- mice were protected from liver necrosis as indicated by histopathology and clinical chemistry. Furthermore, TAFI-/- mice displayed an altered immune response to sepsis, as indicated by an increased neutrophil recruitment to the peritoneal cavity and a transiently increased bacterial outgrowth together with higher plasma TNF-alpha and IL-6 levels. These data argue against an important part for TAFI in the regulation of the procoagulant-fibrinolytic balance in sepsis and reveals a thus far unknown role of TAFI in the occurrence of hepatic necrosis.
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PMID:Absence of thrombin-activatable fibrinolysis inhibitor protects against sepsis-induced liver injury in mice. 1627 33

Changes in astrocyte shape and function are known to occur in association with human immunodeficiency virus (HIV) dementia (HIVD). However, the causes and consequences of such changes are not completely understood. In vitro data suggest that changes in the expression of aquaporin 4 (AQP4), the aquaporin subtype expressed by astrocytes, can significantly influence cell shape and physiology. In the present study, the authors therefore investigated the possibility that AQP4 levels may be altered in HIVD. Using Western blot, the authors show that immunoreactivity for AQP4 is elevated in brain homogenates from the mid frontal gyrus of patients who died with HIVD (P < .005 HIV seronegative versus HIVD). Of interest, a significant increase was also observed in homogenates from HIV-infected individuals without dementia (P < .05 HIV seronegative versus neurologically normal HIV seropositive). In the present study the authors also examined the stimulated expression of AQP4 in cultured cells. Previous in vitro studies have shown that AQP4 expression may be increased by stimuli that induce cytoskeletal changes and/or the activation of p38 mitogen-activated protein (MAP) kinase. The authors therefore focused on tumor necrosis factor (TNF)-alpha, which has been linked to p38 MAP kinase activation, and thrombin, which may also induce changes in the actin cytoskeleton. Both may be elevated with HIVD. Again using Western blot, the authors show an increase in both AQP4 and phosphorylated p38 MAP kinase in homogenates from TNF-alpha- and thrombin-stimulated organotypic cerebellar and spinal cord cultures. Together, these studies suggest that AQP4 expression may be altered in HIVD and/or in response to exogenous proteinases. Additional studies may be warranted to determine whether altered AQP4 expression represents a protective and/or maladaptive response to central nervous system (CNS) inflammation.
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PMID:Aquaporin 4 is increased in association with human immunodeficiency virus dementia: implications for disease pathogenesis. 1633 47

Factor VIIa/tissue factor (FVIIa/TF) interaction has been reported to induce intracellular signalling in cells constitutively expressing TF, independently of downstream activation of the coagulation cascade. It is unknown, however, whether binding of FVII to its cofactor TF alters the gene expression profile in cells which inducible express TF under inflammatory conditions. To address this issue, gene expression patterns in cultured LPS-stimulated monocyte-derived macrophages with or without exposure to FVIIa were compared by cDNA macro-array analysis. Of the 1176 genes examined on the array, a small set of six genes (IL-6, IL-8,TNF-a, GRO-beta alpha-thymosin, cathepsin H) were consistently up-regulated and one gene suppressed (alpha-antitrypsin) in response to FVIIa in activated monocyte-derived macrophages. Among the seven genes identified by array analysis, five genes were finally confirmed by real-time RT-PCR. Interestingly, all of these genes differentially regulated in response to FVIIa (GRO-beta, IL-6, IL-8, TNF-alpha and alpha-antitrypsin) are critical in inflammation. The changes in gene expression were reflected by corresponding changes in the protein concentrations of IL-6 and IL-8 as demonstrated by ELISA. Active site-inhibited FVIIa had no effect on gene expression indicating that FVIIa-induced gene alteration is dependent on the proteolytic activity of FVIIa. The FVIIa-induced alterations in gene expression were found to be TF-dependent but independent of downstream coagulation proteins like thrombin and FXa. In summary, this study demonstrates that binding of FVIIa to its cofactor TF enhances restricted pro-inflammatory genes in activated monocyte-derived macrophages. By up-regulation of chemokines critical for leukocyte recruitment, FVIIa/TF interaction on activated monocyte-derived macrophages could be relevant to prepare monocytes/macrophages for extravasation and may represent a novel amplification loop of leukocyte recruitment.
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PMID:Differential gene expression in activated monocyte-derived macrophages following binding of factor VIIa to tissue factor. 1636 46

The protein C pathway serves as a modulating system with both anti-inflammatory and anticoagulant properties and is intimately involved in the pathophysiology of inflammation and sepsis. Treatment with recombinant human activated protein C (rhAPC) can reduce the mortality of severe sepsis. We investigated whether an elevation of plasma protein C levels to supra-normal levels by infusion of a protein C zymogen concentrate has an effect on coagulation, protein C activation or inflammation in a human endotoxemia model. Eleven healthy male volunteers were enrolled in a double-blind, placebo-controlled two-way cross-over trial. Ten minutes after infusion of 2ng/kg endotoxin each volunteer received either placebo or a plasma-derived protein C zymogen concentrate (Ceprotin, Baxter) (150 U/kg as a slow bolus infusion followed by 30 U/kg/h continuous infusion until 4 hours after LPS-infusion). Protein C antigen and activity increased 4- to 5-fold after infusion of the concentrate. APC was generated during endotoxin-induced inflammation in the placebo (1.6 fold increase) and the protein C period (4.0-fold increase). The increase of APC levels correlated with the TNF-alpha and IL-6 release in both periods (r = 0.65-0.68; p < 0.05) and paralleled the protein C antigen and activity levels in the period with supranormal protein C levels. Supra normal protein C levels resulted in slightly, although non-significant, lower tissue factor mRNA expression and thrombin generation (TAT, F1+2). Systemic inflammation (TNF-alpha, IL-6) was not influenced by protein C zymogen concentrate administration. Infusion of protein C zymogen was safe and no adverse effects occurred. The increase of protein C levels several fold above the normal range resulted in a proportional increase of the APC levels, but had no major anticoagulant, anti-inflammatory or profibrinolytic effects. Low grade endotoxemia itself induces significant protein C activation, which correlates with the TNF release.
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PMID:The effects of supra-normal protein C levels on markers of coagulation, fibrinolysis and inflammation in a human model of endotoxemia. 1673 92

The flow-responsive transcription factor KLF2 is acquiring a leading role in the regulation of endothelial cell gene expression. A genome-wide microarray expression profiling is described employing lentivirus-mediated, 7-day overexpression of human KLF2 at levels observed under prolonged flow. KLF2 is not involved in lineage typing, as 42 endothelial-specific markers were unaffected. Rather, KLF2 generates a gene transcription profile (> 1000 genes) affecting key functional pathways such as cell migration, vasomotor function, inflammation, and hemostasis and induces a morphology change typical for shear exposure including stress fiber formation. Protein levels for thrombomodulin, endothelial nitric oxide synthase, and plasminogen activator inhibitor type-1 are altered to atheroprotective levels, even in the presence of the inflammatory cytokine TNF-alpha. KLF2 attenuates cell migration by affecting multiple genes including VEGFR2 and the potent antimigratory SEMA3F. The distribution of Weibel-Palade bodies in cultured cell populations is normalized at the single-cell level without interfering with their regulated, RalA-dependent release. In contrast, thrombin-induced release of Weibel-Palade bodies is significantly attenuated, consistent with the proposed role of VWF release at low-shear stress regions of the vasculature in atherosclerosis. These results establish that KLF2 acts as a central transcriptional switch point between the quiescent and activated states of the adult endothelial cell.
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PMID:KLF2 provokes a gene expression pattern that establishes functional quiescent differentiation of the endothelium. 1645 54

Sphingosine kinase 1 (SK1) is one of the two known kinases, which generates sphingosine-1-phosphate (S1P), a potent endogenous lipid mediator involved in cell survival, proliferation, and cell-cell interactions. Activation of SK1 and intracellular generation of S1P were suggested to be part of the growth and survival factor-induced signaling, and overexpression of SK1 provoked cell tumorigenic transformation. Using a highly selective and sensitive LC-MS/MS approach, here we show that SK1 overexpression, but not SK2, in different primary cells and cultured cell lines results in predominant upregulation of the synthesis of dihydrosphingosine-1-phosphate (DHS1P) compared to S1P. Stable isotope pulse-labeling experiments in conjunction with LC-MS/MS quantitation of different sphingolipids demonstrated strong interference of overexpressed SK1 with the de novo sphingolipid biosynthesis by deviating metabolic flow of newly formed sphingoid bases from ceramide formation toward the synthesis of DHS1P. On the contrary, S1P biosynthesis was not directly linked to the de novo sphingoid bases transformations and was dependent on catabolic generation of sphingosine from complex sphingolipids. As a result of SK1 overexpression, migration and Ca2+-response of human pulmonary artery endothelial cells (HPAEC) to stimulation with external S1P, but not thrombin, was strongly impaired. In contrast, selective increase in intracellular content of DHS1P or S1P through the uptake and phosphorylation of corresponding sphingoid bases had no effect on S1P-induced signaling or facilitation of wound healing. Furthermore, infection of human bronchial epithelial cells (HBEpC) with RSV A-2 virus increased SK1-mediated synthesis of DHS1P and S1P, whereas TNF-alpha enhanced only S1P production in HPAEC. These findings uncover a new functional role for SK1, which can control survival/death (DHS1P-S1P/ceramides) balance by targeting sphingolipid de novo biosynthesis and selectively generating DHS1P at a metabolic step preceding ceramide formation.
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PMID:De novo biosynthesis of dihydrosphingosine-1-phosphate by sphingosine kinase 1 in mammalian cells. 1652 9


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