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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Monocyte-derived macrophages, focal to initiation and progression of atherosclerosis, have been implicated in thrombotic complication of this disease. In the present study we demonstrated tissue factor based procoagulant activity in cultured macrophages from the White Carneau pigeon following endotoxin (1-2 micrograms/ml) stimulation. This macrophage procoagulant activity paralleled activity obtained with pigeon brain homogenate. We used Enzyme-Linked Coagulation Assay (ELCA), an ultrasensitive microtiter plate assay, to measure procoagulant activity in these cells. Through the use of clotting factors purified from pigeon plasma, procoagulant activity could be detected with as few as 1-3 cells. Tissue factor antigen, detected through the use of immunogold labelling in conjunction with a polyclonal antibody which was highly specific to human tissue factor, was distributed uniformly over the plasma membrane of the endotoxin-stimulated cells. These studies suggest that this procoagulant activity might play an important role in the pathobiology of atherosclerosis in White Carneau pigeons by initiating fibrin polymerization and thus leading to thrombotic complications of the disease.
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PMID:Expression and localization of tissue factor-based procoagulant activity (PCA) in pigeon monocyte-derived macrophages. 816 19

Oxidized low-density lipoprotein (oxLDL) has been characterized as an atherogenic molecule responsible for the induction of a variety of gene products. One such gene, tissue factor (TF), the cellular initiator of the coagulation cascade, is not expressed in normal vascular tissue but is expressed by monocytes and foam cells in atherosclerotic lesions. Therefore, we examined the effect of oxLDL on TF expression in cultured human adherent monocytes. Endotoxin-free oxLDL alone did not induce TF expression in adherent monocytes. However, oxLDL significantly enhanced TF expression induced by the inflammatory mediator, bacterial lipopolysaccharide (LPS), in a time- and dose-dependent manner. In contrast, oxLDL did not alter LPS-mediated production of interleukin-8 and actually inhibited LPS-induced secretion of tumor necrosis factor-alpha, suggesting that some aspects of the signaling pathways for TF induction differ from those of other LPS-responsive monocyte/macrophage gene products. Thus, this study documents specific modulation of the expression of LPS-inducible genes in monocytic cells by oxLDL. Factors that enhance TF expression in monocyte/macrophage cells present in atheroma may contribute to the severity of thrombotic episodes and complications observed in atherosclerosis.
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PMID:Oxidized LDL enhances lipopolysaccharide-induced tissue factor expression in human adherent monocytes. 817 55

Recent advances in determining anti-thrombogenic functions of vascular endothelial cells are reviewed. The following anticoagulant and fibrinolytic systems of endothelial cells are physiologically important; (1) Endothelial cell-derived metabolites including prostacyclin and nitric oxide (NO) support platelet inactivity. (2) Antithrombin III and tissue factor pathway inhibitor (TFPI) bound to heparin-like proteoglycans on endothelial cell membrane inhibit activated serine protease coagulation factors such as thrombin, factor Xa and factor VIIa-tissue factor complex. (3) Thrombomodulin converts thrombin from procoagulant into anticoagulant. Thrombin associated to thrombomodulin on endothelial cells activates protein C. Activated protein C in concert with protein S bound to endothelial cell membrane inactivates factors Va and VIIIa. (4) A receptor for both tissue plasminogen activator and plasminogen on endothelial cells provides an efficient plasmin generating system. Perturbation of these anti-thrombogenic systems of endothelial cells is caused by endotoxin (LPS), cytokines such as interleukin-1 and tumor necrosis factor (TNF), and risk factors for atherogenesis including lipoprotein(a) and homocysteine may result in arterial or venous thrombosis with subsequent development of atherosclerosis.
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PMID:[Anticoagulant and fibrinolytic systems of the injured vascular endothelial cells]. 817 40

Tissue factor (TF) is the predominant physiological initiator of coagulation, and its regulation is a critical aspect of endothelial cell hemostatic function. This report describes the regulation of TF mRNA expression by two physiological agonists: minimally oxidized low-density lipoprotein (MM-LDL), which may modulate endothelial hemostatic function in atherosclerosis, and lipopolysaccharide (LPS), which is a mediator of septic shock. Northern blot analysis of total RNA from human endothelial cells exposed to either MM-LDL or LPS for varying times showed that TF mRNA increased sharply at 1 hour, peaked at 2 to 3 hours, and declined to basal levels by 6 to 8 hours after treatment. The half-life of TF mRNA in MM-LDL- and LPS-exposed endothelial cells was approximately 45 minutes and 40 minutes, respectively. The rate of TF mRNA degradation was similar at 1 and 4 hours after exposure in either MM-LDL- or LPS-stimulated endothelial cells. Nuclear runoff transcription assays showed a significantly increased rate of TF gene transcription in both MM-LDL- and LPS-exposed endothelial cells. Cycloheximide inhibited the induction of TF protein activity, but it enhanced the accumulation of TF mRNA in MM-LDL- and LPS-induced endothelial cells. These results indicated that regulation of TF expression by MM-LDL and LPS in human endothelial cells occurs principally at the level of gene transcription.
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PMID:Regulation of endothelial cell tissue factor expression by minimally oxidized LDL and lipopolysaccharide. 821 12

In response to vascular injury, such as occurs in acute or chronic atherosclerosis, vascular smooth muscle cells (VSMCs) proliferate and migrate, ultimately contributing to vessel narrowing. Several growth agonists, including platelet-derived growth factor and fibroblast growth factor, are known to cause VSMCs to proliferate and are believed to be present at sites of vessel injury. Targets for inhibiting VSMC growth or migration in the presence of multiple growth agonists include genes that are induced in common by VSMC growth factors. This article summarizes the in vivo and in vitro findings of experiments designed to investigate the regulation of tissue factor in VSMCs in 2 animal models. The findings demonstrate that tissue factor is rapidly induced by growth factors in VSMC culture and by balloon injury in aortic media, and they suggest that VSMCs may play a major role in mediating the early thrombotic response. Strategies designed to inhibit the response of VSMCs to growth agonists may therefore have important implications for the treatment of intravascular thrombosis.
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PMID:Tissue factor regulation in vascular smooth muscle: a summary of studies performed using in vivo and in vitro models. 837 2

The role of monocytes as initiators of coagulation through the expression of tissue factor has been well documented in vitro, and the relationship of monocyte tissue factor to the thrombotic complications of atherosclerosis has been suggested. Tissue factor antigen has been identified in the plasma membranes of monocytes adherent to the vascular endothelium overlying atherosclerotic plaques and the presence of tissue factor in adherent mononuclear cells correlates with the polymerization of fibrin at these same sites. To further understand the relationship of cellular adhesion to tissue factor expression, human monocytes were cocultured for periods ranging from 30 min to 24 hr with endothelial cells isolated from human umbilical veins (HUVEC). Tissue factor antigen, as assayed by both ELISA and immunogold electron microscopy, was minimal on either monocytes or HUVEC maintained in homogeneous cultures or on the cells when cocultured for 1 hr or less. This was true whether the HUVEC were in a native state or if they had been stimulated with interleukin-1 (IL-1 beta) or lipopolysaccharide (LPS) prior to monocyte adhesion. Typically, less than 13% of the cells in short-term cocultures were positively labeled through anti-tissue factor immunogold microscopy. The level of tissue factor, however, was increased 3-fold above baseline when monocytes were cocultured with unstimulated HUVEC for 4 hr, and it was more than double this if the HUVEC had been exposed to IL-1 beta or LPS (7-fold increase). By 24 hr, the expression of tissue factor antigen was nearly 50-fold higher in cocultures involving stimulated HUVEC, and at later times greater than 70% of the cells were labeled with immunogold. Through the use of quantitative immunogold electron microscopy, the increase in tissue factor was most pronounced on monocytes which had three times greater increase in tissue factor than HUVEC in the same cultures. These studies document the stimulation of tissue factor expression by monocytes upon coculture with endothelial cells, and the data document an enhancement of this coculture effect upon HUVEC stimulation with cytokines. These observations have relevance to atherosclerotic disease by suggesting that interaction of monocytes with dysfunctional endothelial cells overlying atherosclerotic plaques would be sufficient to induce tissue factor and by so doing predispose to localized thrombotic events.
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PMID:Tissue factor expression during coculture of endothelial cells and monocytes. 861 25

Growing evidence suggests that moderately elevated levels of homocysteine are associated not only with arterial thrombosis and atherosclerosis but also with venous thrombosis as well. We have reviewed recent studies that indicate that homocysteine inhibits several different anticoagulant mechanisms that are mediated by the vascular endothelium. The protein C enzyme system appears to be one of the most important anticoagulant pathways in the blood. Homocysteine inhibits the expression and activity of endothelial cell surface thrombomodulin, the thrombin cofactor responsible for protein C activation. Homocysteine inhibits the antithrombin III binding activity of endothelial heparan sulfate proteoglycan, thereby suppressing the anticoagulant effect of antithrombin III. Homocysteine also inhibits the ecto-ADPase activity of human umbilical vein endothelial cells (HUVECS). Because ADP is a potent platelet aggregatory agent, this action of homocysteine is prothrombotic. Homocysteine also interferes with the fibrinolytic properties of the endothelial surface because it inhibits the binding of tissue plasminogen activator. Homocysteine stimulates HUVEC tissue factor activity. We have found that lipoprotein(a) [Lp(a)] also stimulates HUVEC tissue factor activity. The combination of Lp(a) plus homocysteine induced more tissue factor activity than either agent alone. These disruptions in several different vessel wall-related anticoagulant functions provide plausable mechanisms for the occurrence of thrombosis in hyperhomocysteinemia.
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PMID:Homocysteine and hemostasis: pathogenic mechanisms predisposing to thrombosis. 864 72

Tissue factor, a member of the cytokine-receptor superfamily and high-affinity receptor and cofactor for plasma factor VII/VIIa (ref. 1), is the primary cellular initiator of blood coagulation. It is involved in thrombosis and inflammation associated with sepsis, atherosclerosis and cancer, and can participate in other cellular processes including intracellular signalling, metastasis, tumor-associated angiogenesis, and embryogenesis. Here we report that inactivation of the tissue factor gene (TF) results in abnormal circulation from yolk sac to embryo beyond embryonic day 8.5, leading to embryo wasting and death. Vitelline vessels from null mice were deficient in smooth-muscle alpha-actin-expressing mesenchymal cells, which participate in organization of the vessel wall. This implies that tissue factor has a role in blood vessel development.
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PMID:Role of tissue factor in embryonic blood vessel development. 877 17

Monocytes induced to express tissue factor (TF), the initiator of the clotting cascade, might play an important role in the pathogenesis of atherosclerosis. We have investigated the TF-inducing capacity of two factors thought to be involved in atherogenesis, i.e. the platelet derived growth factor-BB (PDGF-BB) and monocyte chemotactic protein-1 (MCP-1), a member of the chemokine superfamily. PDGF-BB and MCP-1 are potent chemotactic and activating factors for human blood monocytes. alpha-thrombin which is known to induce TF in endothelial cells and that recently has been shown to induce secretion of MCP-1 from endothelial cells and monocytes was also studied. PDGF-BB induced a dose-dependent expression of TF-antigen in monocytes with maximal response at 20-50 ng/mL. At higher concentrations the expression was reduced. No synergistic effect between PDGF-BB and LPS was seen. MCP-1 also induced a dose-dependent TF-expression with maximal response at 50 ng/mL. In contrast to these results thrombin did not. MCP-1 had a slight, but not significant, priming effect on LPS-induced TF expression. These data show that PDGF-BB and MCP-1 are potent inducers of TF in human peripheral blood monocytes. We suggest that this TF-induction might be an important link between hemostasis and inflammation.
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PMID:Platelet-derived growth factor-BB and monocyte chemotactic protein-1 induce human peripheral blood monocytes to express tissue factor. 887 Jan 75

Accelerated coronary atherosclerosis in cardiac allografts is the major limiting factor for long-term survival after heart transplantation. There is growing evidence that activation of the coagulation mechanism is involved in the development of transplant atherosclerosis. Tissue factor (TF) expression by cells of the monocyte/macrophage system may represent an important mechanism underlying the fibrin deposition in the affected vessels. In the present study, we investigated the effect of cyclosporine A (CsA) on the lipopolysaccharide (LPS)-induced procoagulant activity (PCA) in human monocytes/macrophages. CsA exerted a dose-dependent inhibitory effect on LPS-induced monocyte/macrophage PCA, which was identified as TF activity based on functional and immunologic characterization. As shown by reverse transcriptase-polymerase chain reaction, CsA reduced the transcription of the TF gene in LPS-stimulated monocytes/macrophages. Electrophoretic mobility shift assay showed that CsA inhibited the LPS-induced activation of the nuclear factor kappa B (NF-kappa B). As shown by Western blot analysis, CsA treatment decreased the nuclear translocation of NF-kappa B, thereby suggesting the mechanism for the inhibitory effect of CsA on TF induction. Hence, a nonimmunologic effect of CsA may contribute to its successful use in transplant medicine.
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PMID:Cyclosporine a inhibits tissue factor expression in monocytes/macrophages. 891 48


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