| 1. |
- Cheng, X F, et al.
(författare)
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Binding of tissue plasminogen activator to endothelial cells. The effect on functional properties. Localization of a ligand in the B-chain of tPA.
- 1995
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Ingår i: Thrombosis Research. - 0049-3848 .- 1879-2472. ; 77:2, s. 149-64
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Tidskriftsartikel (refereegranskat)abstract
- The binding of 125I-labelled tissue plasminogen activator (tPA), the tPA A- or B-chain to endothelial cells (EC) were studied in suspensions of cultured human umbilical vein EC (HUVEC) or immortalized microvascular EC (HMEC). By determinations of the concentration-dependent binding it was shown that both the A-chain and the B-chain, which were isolated after partial reduction of two-chain tPA, contain ligands for binding to EC. The affinity for the B-chain was much higher than for the A-chain according to Scatchard analysis (Kd 24 and 515 nM, respectively), whereas the number of binding sites was higher for the A-chain than for the B-chain (Bmax 8 x 10(5) and 1.2 x 10(5), respectively). There were no cross interactions between the A- and B-chains and their binding sites. The binding of tPA to EC induced an almost 100-fold increase of the activation rate when compared to the same amount of enzyme in free solution, which in contrast to the fibrin-induced stimulation was not inhibited by antibodies against fibrin. The enzymatic activity of the B-chain was much less affected by the association to the cells. Both tPA and the tPA B-chain were largely protected against inhibition by an excess plasminogen activator type-1 (PAI-1) when bound to EC, whereas the same amount of free tPA was totally inactivated. The competition studies strongly indicated that an N-terminal segment in the B-chain, AKHRRSPGER, may be the ligand part of the B-chain. It is interesting to note that this polypeptide segment also participates in a binding site for PAI-1, necessary for effective inhibition. This implies a possible competition between PAI-1 and a tPA-receptor for binding of tPA. High molecular weight urokinase had no quenching effect on the binding of the B-chain to EC.
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| 2. |
- Ernofsson, Mats, et al.
(författare)
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Platelet-derived growth factor-BB and monocyte chemotactic protein-1 induce human peripheral blood monocytes to express tissue factor
- 1996
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Ingår i: Thrombosis Research. - : Elsevier BV. - 0049-3848 .- 1879-2472. ; 83:4, s. 307-320
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 3. |
- Henriksson, Anders E., et al.
(författare)
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Experimental haemorrhage and blood component transfusion in humans : no change in plasma concentration of thrombin-antithrombin complex and plasmin-antiplasmin complex.
- 1996
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Ingår i: Thrombosis Research. - : Elsevier BV. - 0049-3848 .- 1879-2472. ; 82:5, s. 409-15
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Tidskriftsartikel (refereegranskat)abstract
- The influence of haemorrhage and blood transfusion on primary haemostasis, coagulation and fibrinolysis was investigated in ten healthy male volunteers. Acute loss of 10% of the blood volume did not give any significant alteration in thrombin- antithrombin III (TAT) complex and plasmin-alpha 2-antiplasmin (PAP) complex levels compared with a control series. The skin bleeding time with the Simplate II device was not altered after the 10% blood loss. Acute loss of 10% of blood volume followed by transfusion of packed red cells or stored plasma did not resulted in any significant change in bleeding time, TAT and PAP complex levels. It could be concluded that a controlled haemorrhage does not give any detectable changes of the platelet dependent primary haemostasis, blood coagulation and fibrinolysis. Transfusion of one unit of packed red cells or stored plasma does not seem to adversely affect the haemostasis.
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| 4. |
- Holm, Johan, et al.
(författare)
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Changes in levels of factor VII and protein S after acute myocardial infarction: effects of low-dose warfarin
- 1999
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Ingår i: Thrombosis Research. - 1879-2472. ; 96:3, s. 205-212
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Tidskriftsartikel (refereegranskat)abstract
- Persistent coagulation activity after an acute myocardial infarction may increase the risk of reinfarction. We prospectively investigated the effects on plasma coagulation of a low, fixed dose of warfarin in combination with aspirin after myocardial infarction. We also evaluated the influence of coagulation activity on clinical outcome. Plasma samples from 97 patients, randomised to 1.25 mg of warfarin daily in combination with 75 mg of aspirin or aspirin alone were drawn 4 days, 1 month, and 6 months after myocardial infarction. Patients receiving warfarin had a greater reduction in factor VII coagulation activity (FVII:C) after 6 months: 0.18 vs. 0.06 U/mL,(95% CI, 0.02-0.22), whereas no differences were seen in levels of protein C, protein S, or prothrombin fragment 1+2. In the acute phase, the level of free protein S was lower than after 6 months in both groups: 25.6 vs. 28.8% (95% CI, 4.19--2.35). Cardiovascular mortality, reinfarction, and stroke were evaluated after 4 years (median). In a survival analysis, every 0.1 U/mL increase in the level of FVII:C1 month after myocardial infarction was associated with an 15% increase in risk of cardiovascular events (95% C1, 1.01-1.30). Warfarin at 1.25 mg daily reduces FVII:C but not systemic thrombin generation measured as prothrombin fragment 1 +2. Low levels of the anticoagulant protein S may contribute to a procoagulant state.
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| 5. |
- Holst, Jan, et al.
(författare)
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The effect of protamine sulphate on plasma tissue factor pathway inhibitorreleased by intravenous and subcutaneous unfractionated and low molecularweight heparin in man
- 1997
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Ingår i: Thrombosis Research. - 0049-3848 .- 1879-2472. ; 86:4, s. 343-348
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Tidskriftsartikel (refereegranskat)abstract
- Heparin, a negatively charged sulphated glycosaminoglycan, is clinically the most important antithrombotic drug. Heparin augments the inhibitory activity of antithrombin (AT) towards thrombin, factor Xa (FXa) and other activated clotting enzymes. Tissue factor pathway inhibitor (TFPI) is an endogenous heparin releasable three domain Kunitz-type coagulation inhibitor which inhibits the crucial tissue factor-factor VIIa (TF-FVIIa) dependent coagulation pathway in the presence of FXa. The importance of the TF-FVIIa pathway and TFPI has recently been reviewed (1). TFPI is located to different vascular pools, the largest being the vascular endothelium from where TFPI can be released dose-dependently to the blood by heparins (2). TFPI is speculated to contribute to the anticoagulant properties of heparins, but to which degree is not yet fully understood. In recent years low molecular weight heparins (LMWH) have proven to be effective and safe both for prophylactic (3) and therapeutic treatment (4) of deep vein thrombosis (DVT). Protamine is the least toxic and clinically most commonly used antidote to heparin. However, in vitro and in vivo LMW heparinized blood is not fully neutralized by protamine, as substantial anti-Xa activity remains following neutralization (5). This post-protamine effect has been shown to be partly TFPI dependent when measured in a dilute TF-dependent assay (6,7). We undertook this in vivo study on healthy volunteers in order to investigate whether TFPI released by UH or LMWH (intravenous (iv) or subcutaneous (sc)) remains in the circulation following neutralization of the heparin activity with protamine sulphate (PS). We measured TFPI by three different methods-chromogenic activity, anticlotting activity and a new antigen assay specific for full-length and three-domain TFPI.
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| 6. |
- Tenno, Taavo, et al.
(författare)
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Tissue factor expression in human monocytic cell lines
- 1997
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Ingår i: Thrombosis Research. - 0049-3848 .- 1879-2472. ; 88:2, s. 215-28
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Tidskriftsartikel (refereegranskat)abstract
- Tissue factor (TF) is a main initiator of the coagulation protease cascade. Control of the expression of this protein in monocytes is essential, since these cells are the only circulating blood cells responsible for TF expression. In this report we have used two human cell lines, arrested at different stages of monocytic differentiation, to study TF expression. The monoblastic cell line U-937 had a constitutive expression of TF surface protein and low TF mRNA levels detected by immunofluorescence or quantitative reverse transcriptase polymerase chain reaction respectively. The phorbol-12-myristate-13-acetate (PMA) was a potent enhancer of TF expression in U-937. Lipopolysaccharide (LPS) and tumor necrosis factor (TNF) had no effect on TF expression in U-937. The Mono Mac 6 cell line, with phenotypic features similar to that of mature monocytes, expressed lower basal levels of TF mRNA and surface TF antigen. However, in Mono Mac 6 cells TF expression was induced in response to LPS and TNF. These results indicate differences in basal and induced TF expression between U-937 and Mono Mac 6 cell lines.
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