Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intracoronary thrombodynamics in acute coronary syndromes was studied with an experimental canine model. An intracoronary thrombus was precipitated at the mock ruptured atheromatous plaque consisting of cholesterol and collagen. In 8 of 10 control models, acute myocardial infarction (AMI) was induced by intracoronary occlusive thrombus 1 h after the start of the experiment. Coronary blood flow decreased continuously (Type A, n = 5) or cyclically (Type B, n = 3) to end in AMI. Effects of pharmacological interventions to prevent AMI were also studied with the model. An intravenous bolus injection of a thromboxane synthetase inhibitor (RS-5186), heparin, a thrombin inhibitor (argatroban), and a thrombolytic agent (urokinase) was performed in 10 models for each drug. The incidence of AMI was significantly decreased to 3 of the 10 models injected with the thromboxane synthetase inhibitor and heparin (p < .05, each drug group vs. control). The preventive effect of argatroban was more potent and AMI occurred in 2 of 10 models (p < 0.01, argatroban vs control).
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PMID:Experimental evaluation of coronary thrombodynamics and effects of pharmacological interventions in acute coronary syndromes. 145 44

A venous thrombosis model was produced by vessel wall damage generated by freezing a small segment of the rat jugular vein. The process of thrombus formation was investigated by electron microscopic study. Ultrastructural studies demonstrated that the initiation of thrombus formation could be deendothelialization caused by freezing of vessel. When blood flow was reestablished, platelets adhered to subendothelium within 1 min. Then platelets aggregated on the adhering platelets, and fibrin net was formed. Finally, thrombi composed predominantly of fibrin and red blood cells with platelet aggregates and leukocytes were generated. An anti-platelet agent, ticlopidine, revealed a potent antithrombotic effect in this model. Because ticlopidine decreased the number of platelet aggregates, reduced the size of aggregates, and inhibited platelet degranulation, it is conceivable that platelet aggregation in early phase of thrombus formation plays a crucial role even in venous thrombosis model. A synthetic thrombin inhibitor, argatroban, also showed a potent antithrombotic effect, but a thrombolytic agent, urokinase, was less effective. In conclusion, this model is both platelet- and coagulation-dependent.
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PMID:Effect of ticlopidine and other antithrombotics on the venous thrombosis induced by endothelial damage of jugular vein in rats. 195 78

Recent studies have suggested important roles for certain proteases and protease inhibitors in the growth and development of the CNS. In the present studies, inhibitors of urokinase or thrombin in cultured neural cells and serum-free medium from the cells were identified by screening for components that formed sodium dodecyl sulfate-stable complexes with 125I-urokinase or 125I-thrombin. Rinsed glioblastoma possessed two components that complexed 125I-urokinase. One was type 1 plasminogen activator inhibitor (PAI-1), because the 125I-urokinase-containing complexes were immunoprecipitated with anti-PAI-1 antibodies. The other component formed complexes with 125I-urokinase that were not recognized by antibodies to PAI-1 or protease nexin-1 (PN-1). Its identity is unknown. In addition to these cell-bound components, the glioblastoma cells also secreted two inhibitors that formed complexes with 125I-urokinase; one was PAI-1, and the other was PN-1. The secreted PN-1 also formed complexes with 125I-thrombin. It was the only thrombin inhibitor detected in these studies. Human neuroblastoma cells did not contain components that formed detectable complexes with either 125I-urokinase or 125I-thrombin. However, human neuroblastoma cells did contain very low levels of PN-1 mRNA and PN-1 protein. Added PN-1 bound to the surface of both glioblastoma and neuroblastoma cells. This interaction accelerated the inhibition of thrombin by PN-1 and blocked the ability of PN-1 to form complexes with 125I-urokinase. Thus, cell-bound PN-1 was a specific thrombin inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibitors of urokinase and thrombin in cultured neural cells. 198 20

Recombinant hirudin (rH, CGP 39393) is a potent thrombin inhibitor. In addition to its anticoagulant effect, we investigated its profibrinolytic activity in vitro and ex vivo. The fibrinolytic activity of the euglobulin fraction of 15 normal plasmas with or without urokinase was tested in a fibrin plate assay both before and after addition of rH. The same cycle was repeated in 8 plasmas with heparin instead of rH. For the ex vivo evaluation 12 healthy volunteers received 0.1-0.3 mg/kg/h rH for 6 h. Blood samples were drawn at 0 h, 6 h, 12 h and 24 h and various fibrinolytic parameters were assayed. In the presence of rH or heparin a slightly stronger fibrinolytic effect was observed, measured as fibrin plate lysis activity, both when rH was added to plasma in vitro and when it was administered intravenously. However, this may be explained by the specific anticoagulant action of rH and heparin in the dynamic equilibrium of fibrinolysis and clotting in the test system. Moreover, under rH treatment the observed changes in the various fibrinolytic parameters could not be differentiated from the normal circadian rhythm of these proteins. There was no convincing evidence to indicate enhancement of plasma fibrinolytic activity by recombinant hirudin.
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PMID:[Profibrinolytic activity of recombinant hirudin?]. 202 37

Increasing attention is being paid to alterations of the hemostatic balance in tumors, in general, and brain tumors, in particular. Apparently divergent results, showing excess fibrinolysis (i.e., increased plasminogen activator activity) or its inhibition (i.e., increased inhibitor activity), have been reported. The 9L rat brain tumor is a gliosarcoma and a model used to study treatment paradigms for human gliomas. To study the roles of fibrin and fibrinolysis in this brain tumor model, we used these features to investigate the nature of the plasminogen activator (PA) and thrombin inhibitors in normal rat brain and in the 9L rat brain tumor, growing both in vitro and in vivo in rat brain. The results indicate that cells cultured from the tumor in vitro express PA inhibitory activity which is both of the protease nexin I and PA inhibitor 1 types. However, the serpin PA inhibitory activity in extracts of both the normal brain and tumor is of the protease nexin I/PA inhibitor 3 type. This activity is higher in the tumor than in the surrounding "normal" tissue. In addition, we present evidence for a novel thrombin inhibitor which (a) is present only in the tumor growing in rat brain and undetectable either in the normal brain tissue or in vitro, (b) is in a latent, but sodium dodecyl sulfate-activatable, state, and (c) does not bind urokinase. In current studies, investigators are exploring the roles of these molecules and the target serine proteases they inhibit in the pathogenesis of gliomas.
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PMID:Serpin inhibitors of urokinase and thrombin in normal rat brain and the 9L brain tumor: evidence for elevated expression of protease nexin I-like inhibitor and a novel sodium dodecyl sulfate-activated tumor antithrombin. 211 23

Protease nexin-1 is a protein proteinase inhibitor that is secreted by a variety of cultured cells and rapidly forms complexes with thrombin, urokinase, and plasmin; the complexes then bind back to the cells and are internalized and degraded. In fibroblast cultures, protease nexin-1 is localized to the extracellular matrix. Here we report that protease nexin-1, which is bound to the surface of fibroblasts, forms complexes with thrombin, but not urokinase or plasmin. Experiments were conducted to determine directly if protease nexin-1 binding to the fibroblast surface alters its proteinase specificity. To do this, cell surface protease nexin-1 was inhibited using anti-protease nexin-1 monoclonal antibodies that stoichiometrically block its ability to form complexes with target proteinases. Then, purified protease nexin-1 was added to these cells; the cell-bound molecule formed complexes with thrombin, but not urokinase or plasmin. Similar experiments showed that protease nexin-1 bound to preparations of fibroblast extracellular matrix also formed complexes with thrombin, but not urokinase or plasmin. Components of the extracellular matrix other than heparin-like glycosaminoglycans are required for this regulation since heparin did not block the formation of complexes between protease nexin-1 and urokinase or plasmin. These results suggest that protease nexin-1 is primarily a thrombin inhibitor in interstitial fluids where much of it would be bound to cell surfaces.
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PMID:Binding of protease nexin-1 to the fibroblast surface alters its target proteinase specificity. 264 83

The effect of a selective thrombin inhibitor, (2R, 4R)-4-methyl-1-[N2-[(3-methyl-1,2,3,4-tetrahydro-8-quinolinyl)sulfonyl]- L-arginyl]-2-piperidinecarboxylic acid (MCI-9038), on the fibrinolysis induced by t-PA and u-PA was studied in vitro and in vivo. MCI-9038 remarkably reduced the lysis time of the plasma clot generated by the addition of calcium chloride to the plasma at the concentration ranging from 0.01 to 0.3 microM. Heparin also reduced the plasma clot lysis time with a lower effect than MCI-9038. The fibrin crosslinkage in the plasma clot was inhibited by MCI-9038 or heparin. MCI-9038 potently inhibited the factor XIIIa generation from factor XIII by thrombin. The effect on the in vivo thrombolysis was studied on the arterial thrombosis generated by the endothelial cell injury of the rabbit carotid artery by acetic acid. t-PA dissolved the thrombi with the infusion at 0.96 mg/kg over 2 h without a significant activation of a systemic fibrinolysis. u-PA dissolved the thrombi with the infusion at 180,000 and 360,000 IU/kg over 2 h. At a dose of 0.48 mg/kg t-PA or 90,000 IU/kg u-PA, the thrombi were not dissolved, but the combined use of MCI-9038 at 1.2 mg/kg over 2 h effectively dissolved the thrombi. Thus, combination of MCI-9038 with plasminogen activators accelerated thrombolysis of an experimental thrombosis in rabbits.
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PMID:Effect of a selective thrombin inhibitor MCI-9038 on fibrinolysis in vitro and in vivo. 287 8

Thrombin inhibitors have recently advanced to the stage of preclinical testing as anticoagulants. However, little is known about the effects of these inhibitors on the enzymes of the fibrinolytic system. In the present study we evaluated the effect of two protein and two synthetic inhibitors of thrombin on tissue plasminogen activator (tPA), urokinase, and plasmin. We found that hirudin inhibited the amidolytic activity of plasmin but had no effect on tPA or urokinase. Antithrombin III inhibited plasmin and urokinase but had no effect on tPA. D-Phe-Pro-Arg-CH2Cl inhibited plasmin and tPA but had no effect on urokinase. Thromstop inhibited all three fibrinolytic enzymes: plasmin, urokinase, and tPA. Thus each thrombin inhibitor tested had different inhibitory effects on the fibrinolytic enzymes. These effects should be carefully considered when thrombin inhibitors are used as antithrombotic drugs.
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PMID:Inhibition of fibrinolytic enzymes by thrombin inhibitors. 297 31

Peptide aldehyde transition state analogue inhibitors of serine and cysteine proteases have been used to selectively inhibit proteases for which prior evidence supports a role in tumor cell metastasis. These enzymes include cathepsin B, urokinase plasminogen activator (PA), and thrombin. The inhibition constants of the peptidyl aldehyde inhibitors show that they are highly selective for a particular targeted serine or cysteine protease. The inhibitors are introduced by i.p. injection or by miniosmotic pumps into syngeneic C57BL/6 mice also given injections of B16-F10 melanoma cells, and the number of metastatic foci in the lung was determined. While the injection protocol gave an initially high but changing in vivo concentration of inhibitor over time, the minipump implant gave a constant steady state concentration of inhibitor over 5-7 days. Minipump infusion of leupeptin (acetylleucylleucylargininal), a strong inhibitor of cathepsin B at a steady state plasma concentration 1000-fold greater than its Ki(cathepsin B), gave no significant decrease in lung colonization by the B16 tumor cells. Ep475, a stoichiometric irreversible peptide inhibitor of cathepsin B-like proteases, also did not significantly inhibit metastatic foci formation. Introduction of selective inhibitors of urokinase PA, tert-butyloxycarbonylglutamylglycyl-argininal and H-glutamylglycylargininal at concentrations near its Ki, produced no significant decrease in mouse lung colonization. The selective thrombin inhibitor D-phenylalanylprolylargininal infused to a steady state concentration 100-fold greater than its Ki dramatically increased B16 melanoma colonization of mouse lung. The results indicate that neither secreted cathepsin B-like nor urokinase PA have roles in B16 colonization of mouse lung, while thrombin may have a role in preventing metastasis. These experiments do not eliminate roles for a cathepsin B-like enzyme or urokinase PA in the initial steps of the metastatic process.
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PMID:Selective inhibition of proteolytic enzymes in an in vivo mouse model for experimental metastasis. 308 87

A fraction of the 125I-thrombin that binds to human platelets is taken into a sodium dodecyl sulfate-resistant 77 kDa complex with a platelet factor (Bennett, W. F., and Glenn, K. C. (1980) Cell 22, 621-627). Here we show that this platelet factor is in several respects similar to protease nexin I (PNI), a fibroblast thrombin inhibitor. The complexes are of the appropriate size, bind to Sepharose that has been derivatized with anti-PNI antibody, do not form when the thrombin active site has been blocked with diisopropylphosphofluoridate, and do not appear on platelets when heparin is present. However, the platelet factor does not bind urokinase, indicating that this "platelet PN" may be distinct from PNI. Following brief incubation with 125I-thrombin, platelet PN X 125I X thrombin complexes are found both associated with the platelets and free in the binding medium. 125I-Thrombin has a higher affinity for platelet PN than for platelet receptors. In 30-s binding incubations carried out with thrombin at concentrations below 0.3 nM, formation of the 77-kDa complex accounts for most of the platelet specific binding of 125I-thrombin. Subtracting this large contribution to 125I-thrombin-specific binding reveals that the reversible binding of 125I-thrombin to platelet receptors exhibits sigmoidal thrombin dose-dependence. Thrombin stimulation of platelet [14C]serotonin release exhibits similar thrombin dose dependence. These results indicate that platelets may possess a mechanism for suppressing their interaction with active thrombin at thrombin doses below 0.3 nM. It is possible that platelet PN carries out this function by capturing thrombin before thrombin binds to its signal-transmitting receptors.
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PMID:Thrombin interaction with platelets. Influence of a platelet protease nexin. 310 83


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