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)

Because fibrin is commonly observed within arthritic joints, studies were undertaken to determine whether purified coagulation and fibrinolytic proteases degrade cartilage in vitro and to seek evidence for the activation of coagulation in arthritic joints through measurements of the levels of inhibitor-enzyme complexes and several other proteins associated with coagulation and fibrinolysis. The concentrations of 13 plasma proteins and complexes of thrombin and Factor Xa with antithrombin III were measured in synovial fluids recovered at the time of knee replacement surgery. All zymogens necessary to constitute the coagulation cascade were present. Thrombin and the combination of prothrombin plus prothrombinase induced proteoglycan release from both normal and arthritic cartilages. Factor Xa and plasmin induced release from diseased cartilage only, and urokinase, tissue plasminogen activator, and activated protein C were without effect at the levels used. At saturating levels of thrombin (> or = 2.0 microM) 80% of the proteoglycan content of normal cartilage was released within 24 h. Thrombin, which is cationic, reversibly binds cartilage with Kd = 7.0 +/- 1.0 microM and Bmax = 820 +/- 70 ng/mg of human cartilage. Levels of thrombin-antithrombin III complexes in synovial fluids and arthritis were 4-fold higher in osteo (OA) and 43-fold higher in rheumatoid (RA) than in controls (0.98 nM). Factor Xa-antithrombin III complex levels were threefold lower in OA and fivefold higher in RA than in controls (0.24 nM). These elevated levels of enzyme-inhibitor complexes imply a history of activation of coagulation within the joint, especially in RA. Since thrombin degrades cartilage in vitro and had been generated in vivo, as inferred by the existence of thrombin-antithrombin III complexes, intraarticular activation of coagulation may both contribute to the pathology of arthritis and comprise a target for therapy and diagnosis.
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PMID:Studies of thrombin-induced proteoglycan release in the degradation of human and bovine cartilage. 804 Mar

The effects of coronary thrombolytic therapy with urokinase on the intrinsic hemostatic and fibrinolytic states were investigated by determining several markers for hemostatic and fibrinolytic activities in 6 patients with acute myocardial infarction who underwent coronary thrombolysis with urokinase. The markers for hemostasis and fibrinolysis were: markers for plasmin generation [alpha 2-plasmin inhibitor (alpha 2-PI), plasminogen, plasmin alpha 2-PI complex (PIC)]; markers for fibrinolysis [fibrin/fibrinogen degradation products-E fragment (FDP-E), FDP D-D dimer (D dimer), fibrinogen]; markers for hemostatic activity (prothrombin time (PT), antithrombin III (AT-III), protein C); markers for thrombin generation [thrombin antithrombin III complex (TAT)]; markers for intrinsic fibrinolytic activity [tissue plasminogen activator plasminogen activator inhibitor complex (TPA PAI complex)]. These markers were measured before, at 1 to 2 hours intervals during first 6 hours, daily during the next 3 days, and subsequently on the 7th and the 14th day after urokinase therapy. Fibrinolysis (determined by increased D dimer) occurred only when alpha 2-PI became unmeasurable with 96 x 10(4) or more units of urokinase administration, then persisted for more than 2 hours. TAT increased from 13.1 +/- 15.4 to 70.8 +/- 65.8 ng/ml soon after fibrinolysis occurred, indicating that thrombin generation occurred at the same time as fibrinolysis. The TPA PAI complex level before urokinase administration (26.4 +/- 6.4 ng/ml) was greater than the normal upper limit, indicating increased intrinsic fibrinolytic activity, then decreased after urokinase administration. These findings suggested that urokinase administration might affect the intrinsic fibrinolytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Serial changes in hemostatic and fibrinolytic states induced by coronary thrombolytic therapy]. 806 82

Phlegmasia cerulea dolens is a rare form of deep vein thrombosis. A patient with recurrent episodes of such thrombosis caused by protein C deficiency who developed phlegmasia cerulea dolens is reported. Limb perfusion with urokinase successfully restored venous outflow after unsuccessful attempts at thrombectomy.
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PMID:Thrombectomy and isolated limb perfusion with urokinase in the treatment of phlegmasia cerulea dolens. 807 98

Protein C inhibitor (PCI) is a heparin-binding plasma serine proteinase inhibitor (serpin) which is thought to be a physiological regulator of activated protein C. We are using recombinant PCI (rPCI) to study structural determinants of target proteinase specificity. A cDNA encoding full-length PCI has been expressed as a fully active proteinase inhibitor using Autographa californica nuclear polyhedrosis virus (baculovirus). rPCI was expressed maximally 4 days after infection and could be expressed either in Sf9 or High-Five cells. rPCI bound heparin and was conveniently purified with heparin-Sepharose (eluting > 0.5 M NaCl). The rPCI formed sodium dodecyl sulfate-polyacrylamide gel electrophoresis-stable complexes with thrombin and activated protein C (APC). The inhibitory properties of wild-type rPCI and plasma-derived PCI are essentially the same either in the absence or presence of heparin with thrombin, APC, trypsin, and urokinase. The residues Phe353-Arg354-Ser355 (P2-P1-P1') constitute part of the reactive site loop of PCI with the Arg-Ser peptide bond being cleaved by the proteinase. Using site-directed mutagenesis we studied the contribution of the reactive site FRS for proteinase inhibition in rPCI. Changing the P1 residue Arg354-->Met generated a reactive site similar to alpha 1-proteinase inhibitor which was a much poorer inhibitor of thrombin, APC, trypsin, and urokinase. Changing the P2 residue Phe353-->Gly generated a mutant with a reactive site like antithrombin which was better at inhibiting thrombin or urokinase, but was much less active with APC or trypsin. Changing the P1' residue Ser355-->Met generated a reactive site like plasminogen activator inhibitor-1 and this protein inhibits all the proteinases essentially like wild-type rPCI. These results show the importance of PCI's Phe353 (P2) and Arg354 (P1) in target proteinase specificity, and they further support the concept of reactive site sequences determining serpin function.
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PMID:Mutagenesis of recombinant protein C inhibitor reactive site residues alters target proteinase specificity. 820 90

The plasminogen activator systems in the blood, the coagulation system, and the complement pathways are reviewed. The review describes the role of the vascular intima in activation of coagulation and fibrinolysis and the interrelations between the complement system and haemostatic mechanisms. Physiological activation of fibrinolysis may be triggered by and limited to fibrin because of a special affinity of plasminogen and plasminogen activators. The binding of plasminogen to fibrin is regulated by histidine-rich glycoprotein, and the primary physiological inhibitor of generated plasmin is alpha 2-antiplasmin and especially the plasminogen-binding form of this immediate plasmin inhibitor. Plasminogen activator inhibitors in the blood, that is, notably plasminogen activator inhibitor type 1 (PAI-1), bind circulating tissue-type plasminogen activator (t-PA). However, local fibrinolysis in vivo mediated by t-PA may be independent of complex formation between plasminogen activator inhibitors and t-PA in the fluid phase. Circulating plasminogen activator inhibitors might regulate fibrinolysis by increasing the clearance of t-PA from the blood. The urokinase-type and factor XII-dependent fibrinolytic proactivator system can be activated following t-PA-mediated generation of plasmin, and could thus serve as an amplification system of t-PA-induced fibrinolysis. It is claimed that the as yet uncharacterized proactivator is essential for optimal generation of plasminogen activator activity by the factor XII-dependent fibrinolytic system. The normal antithrombotic condition of the vascular intima probably results from lack of tissue factor activity and the presence of significant antithrombotic components comprising, among others, antithrombin III and the protein C-protein S system. A number of pathophysiologic stimuli, notably mediators of the acute phase response such as the cytokines interleukin-1 and tumour necrosis factor-alpha (cachectin), have the potential to induce the vascular endothelium to express procoagulant activity. Vascular endothelium promoting coagulant activity releases increased amounts of t-PA antigen and PAI-1 antigen into the circulation, and elevated levels in the blood of both may be regarded as a marker of a generalized procoagulant condition involving the vascular endothelium. In a prospective study in patients with unstable angina pectoris, patients in whom disease progresses and acute myocardial infarction develops, have increased amounts of t-PA antigen and PAI-1 antigen in the blood. This suggests that the procoagulant potential and atherosclerotic process of the vascular intima is more pronounced in the risk group.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Fibrinolysis in patients with acute ischaemic heart disease. With particular reference to systemic effects of tissue-type plasminogen activator treatment on fibrinolysis, coagulation and complement pathways. 822 63

The prevalence of abnormalities of fibrinolysis in patients with venous thromboembolism is as yet unknown. Defined abnormalities include congenital dysfunction and deficiency of plasminogen, and probably impaired plasminogen activation secondary to elevated levels of plasminogen activator inhibitor type 1 (PAI-1) or to impaired release of tissue plasminogen activator (tPA). In this preliminary study, we analyzed plasma samples from 21 patients for whom an investigation for possible thrombophilia was requested. Twenty of the patients had venous thromboembolism, and one had arterial thrombosis at an early age. Two patients had deficiency of protein C or protein S, but no other recognized biochemical disturbances related to thrombophilia were identified. Patient samples and plasma from 25 normal controls were assayed for tPA activity, PAI-1 activity, and urokinase (uPA) activity and antigen. tPA activity and antigen were not significantly different in patients than in controls. PAI-1 activity was significantly greater in patients (P < 0.0001). uPA activity was not different in the two groups. However, uPA antigen was significantly reduced in patients compared to controls (P = 0.001). These data suggest that hypofibrinolysis leading to a risk of thrombosis may be caused not only by elevated PAI-1 activity but also by reduced total uPA concentration.
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PMID:Hypofibrinolysis in patients with hypercoagulability: the roles of urokinase and of plasminogen activator inhibitor. 823 97

The present study was undertaken to investigate the role of plasminogen activator inhibitor type 1 (PAI-1) and activated protein C (APC) in the regulation of tumor cell invasion. PAI-1 was purified in active form from conditioned medium of human umbilical vein endothelial cells under denaturing conditions (4 M guanidine-HCl). The purified inhibitor reacts with urokinase-type plasminogen activator (uPA) and APC. Two selected human lines, HOC-I (ovarian cancer cells) and SMT-ccl (choriocarcinoma cells), preferentially invaded through reconstituted basement membranes in an in vitro invasion assay using a modified Boyden chamber. The present study determined the efficacy of these two agents (PAI-1 and APC) used alone or in combination in inhibiting or facilitating tumor cell invasion. Active PAI-1 inhibited the tumor cell surface receptor-bound uPA activity. In an in vitro invasion assay, active PAI-1 reduced tumor cell invasive potential in a dose-dependent manner. When SMT-ccl cells saturated with uPA-PAI-1 complexes were treated with a 50-fold molar excess of APC, PAI-1-APC complex was demonstrated in conditioned medium, indicating that PAI-1 was dissociated from receptor-bound uPA on tumor cells and that tumor cell-associated uPA restored its enzymatic activity. Although APC alone had no effect on tumor cell invasion, the addition of APC to the cells saturated with uPA-PAI-1 complexes showed regeneration of tumor cell surface receptor-bound uPA activity and produced substantial and efficient invading effects. These data suggest that PAI-1 activity may be neutralized by APC or that APC may promote tumor cell invasion via inactivation of PAI-1 by formation of a stable PAI-1-APC complex. These observations suggest that APC may play a critical role in the initiation of a hematogenous metastatic process (extravasation step).
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PMID:Role of activated protein C in facilitating basement membrane invasion by tumor cells. 826 50

Endothelial cell regulation of protein C activation and fibrinolysis are important components of the hemostatic response to vascular injury or perturbation. Procoagulant albumin (P-A1), a constituent of normal human plasma has been purified and identified as an inducer of endothelial cell tissue factor activity. The purpose of the studies reported herein was to investigate the effects of P-A1 on human endothelial cell protein C activation and fibrinolysis. P-A1 suppressed protein C activation, enhanced release of plasminogen activator inhibitor-1, but had no effect on tissue-plasminogen activator release. Plasminogen activator inhibitor-1 released by P-A1 was functional as evidenced by the capacity to form a covalent complex with 125I-urokinase. Inactive albumin (isolated during the same purification procedure as P-A1, but without tissue factor-inducing activity) did not suppress protein C activation or increase plasminogen activator inhibitor-1 release. These results indicate that P-A1, a component of human plasma, can modulate multiple vascular hemostatic properties, and support the hypothesis that P-A1 is involved in normal or pathologic hemostasis.
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PMID:Regulation of endothelial cell protein C activation and fibrinolysis by procoagulant albumin. 836 71

Thrombomodulin (TM), a membrane proteoglycan on endothelial cells, binds thrombin in a 1:1 complex, accelerates the protein C activation by thrombin, promotes the thrombin inactivation by antithrombin III and inhibits the procoagulant properties of thrombin. The inactivation of single-chain urokinase-type plasminogen activator (scu-PA) by thrombin is accelerated about 70-fold by TM [De Munk, Groeneveld and Rijken (1991) J. Clin. Invest. 88, 1680-1684]. The present study investigates the role of the O-linked glycosaminoglycan moiety of TM in the latter reaction. In the presence of an excess of a fully-glycosylated soluble recombinant human TM mutant (high-Mr rec-TM), 0.11 nM thrombin inactivated 50% of 4.4 nM scu-PA in 45 min at 37 degrees C. In the presence of a soluble recombinant TM mutant lacking the glycosaminoglycans (low-Mr rec-TM), 1.9 nM thrombin was needed to inactivate 50% scu-PA, as compared with 4.7 nM thrombin in the absence of TM. Using the scu-PA inactivation assay the dissociation constant for the thrombin-TM interaction was found to be 0.4 nM for high-Mr rec-TM and 14 nM for low-Mr rec-TM. Treatment of high-Mr rec-TM with chondroitinase ABC to digest the glycosaminoglycans decreased the accelerating effect to the level of low-Mr rec-TM. A similar decrease was observed after treatment of solubilized rabbit TM with chondroitinase ABC. As expected, chondroitinase ABC had no influence on the accelerating effect of low-Mr rec-TM. The free glycosaminoglycans obtained by alkaline treatment of TM or chondroitin sulphate A also accelerated the inactivation of scu-PA by thrombin, but about 1000-fold higher concentrations than with TM were needed to obtain the same acceleration. It is concluded that the major glycosaminoglycan of TM plays a pivotal role in the inactivation of scu-PA by the TM-thrombin complex, both in the formation and in the activity of the complex.
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PMID:Role of the glycosaminoglycan component of thrombomodulin in its acceleration of the inactivation of single-chain urokinase-type plasminogen activator by thrombin. 838 42

The effect of human activated protein C (APC) on t-PA dependent fibrinolysis was studied in vitro using plasma (and whole blood) clot lysis techniques. Clot lysis was monitored by measuring the release of soluble 125I-labelled fibrin degradation products from the clot over time. It was demonstrated that the stimulatory effect of APC on plasma and blood clot lysis was specific for APC and depended on the presence of its active site and Ca2+ ions. Furthermore, the effect depended on the presence of phospholipids in plasma or cells in blood. The presence of pro-urokinase, factor XIII or alpha 2-antiplasmin was not required for the expression of the profibrinolytic effect of APC. Subsequent experiments revealed that the profibrinolytic effect of APC was only observed when thrombin was formed through the coagulation pathway during the initial phase of the clot lysis experiment. It was also shown that the addition of increasing concentrations of thrombin itself could delay the t-PA dependent lysis of clots prepared from Al(OH)3 adsorbed plasma via a mechanism not yet understood. Based on these findings we propose that (a) t-PA dependent lysis of clots prepared from pooled normal plasma is delayed by thrombin generated through the coagulation system, and (b) that by its anticoagulant properties APC blocks this thrombin generation and thereby prevents the delay in clot lysis. Because in this model the profibrinolytic effect of APC is directly related to its anticoagulant properties we predicted and confirmed that other anticoagulants--like heparin--also have profibrinolytic activity. Conversely, procoagulants such as phospholipids can be antifibrinolytic.
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PMID:Activated protein C accelerates clot lysis by virtue of its anticoagulant activity. 838 39


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