Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.68 (tissue plasminogen activator)
 11,311 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

How heparin inhibits vascular smooth muscle cell proliferation and migration has not been established. We have investigated the hypothesis that heparin inhibits vascular smooth muscle cell proliferation and migration by interfering with the expression and activity of proteases such as plasminogen activators. In an in vitro mitogenesis model, tissue-type plasminogen activator (tPA) mRNA and protein increase in baboon smooth muscle cells stimulated with fetal bovine serum or phorbol esters. Heparin inhibits smooth muscle cell proliferation and suppresses the induction of tPA mRNA and protein while it has little effect on the mRNA of urokinase-type plasminogen activator, plasminogen activator inhibitor type I, and a number of genes that are also modulated by serum and phorbol esters. The inhibitory effect on tPA mRNA is specific to heparin-like molecules and does not depend on the anticoagulation activity of heparin. The increase in tPA mRNA is due to increased transcription, which is suppressed by heparin. The induction of tPA by serum and phorbol esters is diminished by protein kinase C inhibitors such as H7 or staurosporine and by protein kinase C depletion. Since heparin suppresses the induction of the tPA gene by phorbol esters, these results suggest that heparin may interfere with the protein kinase C pathway.
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PMID:Heparin selectively inhibits the transcription of tissue-type plasminogen activator in primate arterial smooth muscle cells during mitogenesis. 131 Jun 87

Heparin is a potent inhibitor of arterial smooth muscle cell (SMC) migration and proliferation in vivo and in vitro. We propose that heparin affects these SMC functions by interfering with either the expression or the activity of secreted proteases required for cell movement. We have reported that heparin selectively inhibits the expression of tissue-type plasminogen activator in SMCs during mitogenesis. In this study we show that the gene expression of another kind of protease, interstitial collagenase, is induced by fetal bovine serum and is also suppressed by heparin. The inhibitory effect on the induced collagenase mRNA is specific to heparin-like molecules and does not depend on the anticoagulant activity of heparin. The induction of the collagenase gene depends on the protein kinase C pathway, since it can be induced by phorbol esters such as phorbol 12-myristate 13-acetate and blocked by inhibitors such as H-7 and staurosporine. In transient transfection assays with chloramphenicol acetyltransferase constructs containing the phorbol ester-responsive element introduced into baboon SMCs, heparin inhibits transcription induced by serum or phorbol 12-myristate 13-acetate. These results support the conclusion that, in primate SMCs, interstitial collagenase gene transcription mediated by the phorbol ester-responsive element is blocked by heparin.
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PMID:Heparin inhibits collagenase gene expression mediated by phorbol ester-responsive element in primate arterial smooth muscle cells. 131 15

Heparin is indispensable anticoagulant for cardiopulmonary bypass, but the dose of heparin is even now under discussion. In this study, hemostatic fluctuation was analyzed during and after the bypass using hemostatic molecular markers. The subjects were 16 adult cases of open heart surgery, 12 males, 4 females. The average age was 55.0 year. Operations were aortocoronary bypass in 12, valvular surgery in 3 and ASD patch closure in one with moderate hypothermic cardiopulmonary bypass. At the beginning of cardiopulmonary bypass, 3 mg/kg heparin was administered and the equivalent amount of protamine sulfate was used for neutralization at the end of the bypass. Platelet count, hematocrit, antithrombin III (ATIII), beta-thromboglobulin, platelet factor 4, fibrinopeptide A, thrombin antithrombin III complex, FDP, D dimer FDP, plasmin alpha 2 plasmin inhibitor complex, tissue plasminogen activator (t-PA), and thrombomodulin (TM) were measured through the operation up to two weeks after surgery. ATIII decreased to 50% of control value all through the bypass. Platelet markers increased immediately, and the activated state continued 3 hours after the bypass. Coagulation markers increased markedly after the aortic declamping, and reached at its peak by three times as control value, immediately after the protamine neutralization and continued for 3 hours. During the bypass, fibrinogenolysis caused by t-PA which was stimulated by non-physiological circulation and stimulating substances, was observed. Fibrinolysis occurred following the hypercoagulability after the neutralization. TM was within normal range before the aortic declamping. But increased gradually after the declamp, and reached twice as much as the base line. It could be concluded that hypercoagulability and high platelet activation might play a role of perioperative thrombosis. Hypercoagulability and increase of serum TM would be related to reperfusion of the lung. The increasing of TM would reflect broad injury of vessel walls after the bypass, because plasma TM increased following the generalized injury of endothelial cells.
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PMID:[A clinical study on hemostatic fluctuation during and after cardiopulmonary bypass using hemostatic molecular markers]. 133 89

The chimeric molecule K1K2Pu, comprising the two kringle domains (K1 and K2) of tissue-type plasminogen activator (t-PA) and the COOH-terminal region with the serine protease domain (Pu) of urokinase-type plasminogen activator (u-PA), was previously shown to have a 5- to 10-fold reduced clearance rate with maintained specific thrombolytic activity, resulting in an increased thrombolytic potency in animal models of venous and arterial thrombosis. To document the thrombolytic potential of K1K2Pu, the thrombolytic potency and fibrin specificity were studied in a combined platelet-rich arterial eversion graft thrombosis and venous whole blood clot model in heparinized dogs (100 U/kg bolus and 50 U/kg per h infusion). Dose-response effects of bolus injections of K1K2Pu (0.032 to 0.25 mg/kg) were compared with those of recombinant t-PA (rt-PA) and of recombinant single chain u-PA (rscu-PA) (0.25 to 1.0 mg/kg each) in groups of five or six dogs, each given heparin with or without the thromboxane synthase inhibitor/prostaglandin endoperoxide receptor antagonist ridogrel. Heparin and ridogrel in the absence of a thrombolytic agent did not produce arterial reflow or venous clot lysis in five dogs. Addition of K1K2Pu, rt-PA or rscu-PA resulted in a dose-dependent induction of arterial reflow and of venous clot lysis in the absence of systemic fibrinolytic activation and fibrinogen breakdown. Consistent arterial reflow required 0.063 mg/kg of K1K2Pu and 0.5 mg/kg of rt-PA or of rscu-PA. The thrombolytic potency for venous clot lysis, expressed as percent lysis per mg compound administered per kg body weight, was (mean +/- SEM) 750 +/- 160 for K1K2Pu, 68 +/- 17 for rscu-PA (p less than 0.001 vs. K1K2Pu) and 110 +/- 29 for rt-PA (p less than 0.001 vs. K1K2Pu). The plasma clearance rates were significantly lower for K1K2Pu than for rscu-PA and rt-PA. In the absence of ridogrel, arterial reflow was significantly slower and was followed by cyclic reocclusion and reflow; however, venous clot lysis was unaffected. Template bleeding times were not significantly altered in the absence but were markedly prolonged in the presence of ridogrel. These results confirm and establish that, when given as a bolus injection, K1K2Pu has an approximately 10-fold higher thrombolytic potency for arterial and venous thrombolysis than does rt-PA or rscu-PA. Thrombolysis with K1K2Pu is obtained in the absence of systemic fibrinolytic activation and fibrinogen breakdown. These properties suggest that K1K2Pu offers potential for thrombolytic therapy by bolus administration in patients with thromboembolic disease.
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PMID:Comparative thrombolytic properties of tissue-type plasminogen activator (t-PA), single-chain urokinase-type plasminogen activator (u-PA) and K1K2Pu (a t-PA/u-PA chimera) in a combined arterial and venous thrombosis model in the dog. 134 79

41,299 patients entering 914 hospitals up to 24 h (median 4 h) after the onset of suspected acute myocardial infarction were randomised between streptokinase (SK: 1.5 MU infused over about 1 h), tissue plasminogen activator (tPA, duteplase: 0.60 MU/kg infused over about 4 h), or anisoylated plasminogen-streptokinase activator complex (APSAC), anistreplase: 30 U over about 3 min). All patients were to receive aspirin (162 mg/day enteric-coated), with the first tablet chewed for rapid and full antiplatelet effect. Half of all patients were randomly allocated subcutaneous calcium heparin (12,500 IU starting at 4 h and given twice daily for 7 days or until prior discharge) in addition to aspirin, and the other half were to receive aspirin alone. ASPIRIN PLUS HEPARIN VERSUS ASPIRIN ALONE--The addition of heparin to aspirin was associated with an excess of transfused or other major non-cerebral bleeds (1.0% aspirin plus heparin vs 0.8% aspirin alone; 2p < 0.01) and of definite or probable cerebral haemorrhage (0.56% vs 0.40%; 2p < 0.05), but with no significnat differences in total stroke (1.28% vs 1.18%). Reinfarctions were slightly less common among those allocated aspirin plus heparin (3.16% vs 3.47%; 2p = 0.09). There was no signficant difference in the pre-specified endpoint of 35-day mortality (2132 [10.3%] aspirin plus heparin vs 2189 [10.6%] aspirin alone). During the scheduled heparin treatment period there were slightly fewer deaths in the aspirin plus heparin group (days 0-7 in hospital: 1534 [7.4%] vs 1633 [7.9%]; 2 p = 0.06), with a slight convergence by day 35 (598 further deaths [3.1% of survivors] vs 556 [2.9%]). The pattern was similar to that observed in the GISSI-2 trial, so that in both trials combined there was a significant reduction in mortality during the scheduled treatment period (2071 [6.8%] vs 2239 [7.3%]; 2p < 0.01). This indicates avoidance of 5 deaths (SD 2) per 1000 patients allocated this high-dose subcutaneous heparin regimen in addition to aspirin, but some of any early benefit may be lost after heparin ceases, with no significant mortality advantage in days 0-35 (both trials: 3100 [10.0%] vs 3172 [10.2%]) or during follow-up to 6 months. SK VERSUS APSAC--APSAC was associated with significantly more reports of allergy causing persistent symptoms and of non-cerebral bleeds, but not of transfused bleeds or of reinfarctions. There was a slight excess of strokes with APSAC (1.04% SK vs 1.26% APSAC; 2p = 0.08), much of it appearing soon after treatment started (strokes during days 0-1: 0.50% SK vs 0.73% APSAC; 2p < 0.02) and being attributed to cerebral haemorrhage (0.24% SK vs 0.55% APSAC; 2p < 0.0001). No significant difference was observed in reinfarction (3.47% SK vs 3.55% APSAC). There was no significant mortality difference during days 0-35, either among all randomised patients (1455 [10.6%] SK vs 1448 [10.5%] APSAC) or among the pre-specified subset presenting within 0-6 h of pain onset and with ST elevation on the electrocardiogram in whom fibrinolytic treatment may have most to offer (861 [10.0%] SK vs 855 [9.9%] APSAC). No significant difference in 6-month survival was apparent overall or in the subset.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:ISIS-3: a randomised comparison of streptokinase vs tissue plasminogen activator vs anistreplase and of aspirin plus heparin vs aspirin alone among 41,299 cases of suspected acute myocardial infarction. ISIS-3 (Third International Study of Infarct Survival) Collaborative Group. 1111 34

Smooth muscle cells (SMCs) in balloon-injured rat carotid artery express tissue-type plasminogen activator (t-PA) at a time when they are migrating from the media to the intima. Since heparin inhibits SMC migration and intimal thickening, we have examined the possibility that heparin might also inhibit t-PA expression. Heparin (nonanticoagulant fraction; molecular weight, approximately 6,000) was administered by continuous intravenous infusion (1.0 mg/kg per hour) to Sprague-Dawley rats subjected to balloon injury of the left common carotid artery. At various times up to 14 days after injury, plasminogen activator expression was analyzed by zymography, plasmin generation, enzyme-linked immunosorbent assay, Northern blotting, and in situ hybridization. This dose of heparin inhibited SMC accumulation at 14 days by 60%. Both urokinase plasminogen activator (u-PA) and t-PA activity increased in injured arteries and reached a maximum at 7 days. Heparin treatment decreased t-PA, but not u-PA, activity. Total t-PA protein was decreased by treatment with heparin but not chondroitin sulfate, and the decrease in t-PA protein was associated with decreased t-PA mRNA in the media. These results in the injured rat carotid artery agree with our earlier observations that heparin inhibits t-PA gene expression in cultured baboon aortic SMCs. They also provide support for the hypothesis that heparin interferes with the expression of certain proteases required for SMC migration and proliferation.
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PMID:Heparin inhibits the expression of tissue-type plasminogen activator by smooth muscle cells in injured rat carotid artery. 137 98

Heparin in combination with endothelial cell growth factor (ECGF) affects physiological responses and growth of human umbilical vein endothelial cells (HUVEC). We have examined the effect of heparin, crude ECGF (endothelial cell growth supplement [ECGS]), or both on the basal and thrombin challenged output of metabolites by HUVEC. The supernatant and/or cell lysate was assayed for released prostacyclin, von Willebrand factor, tissue plasminogen activator, plasminogen activator inhibitor and thrombospondin. Heparin modified release of all these metabolites when in combination with ECGS, and in general these responses were the opposite of those generated by inflammatory mediators such as interleukin-1. It has been postulated that heparin acts by potentiating the effect of ECGF, but heparin inhibited thrombospondin release and enhanced that of von Willebrand factor in the absence of ECGS, while ECGS alone inhibited release of plasminogen activator inhibitor. Thus, under our experimental conditions it would appear that heparin and crude ECGF can affect HUVEC independently of one another.
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PMID:Effects of heparin and endothelial cell growth supplement on haemostatic functions of vascular endothelium. 150 15

To evaluate the effect of thrombin on the dynamics of thrombolysis, we infused rabbits with heparin or hirudin alone or in conjunction with tissue-type plasminogen activator (t-PA) and monitored the kinetics of fibrinolysis and changes in ex vivo platelet aggregation responses over time. Both heparin and hirudin enhanced total fibrinolysis in an ex vivo arteriovenous shunt preparation: 82 +/- 2% and 79 +/- 2%, respectively, compared with 51 +/- 8% for t-PA alone (P less than 0.05) and 50 +/- 4% for t-PA plus aspirin (p less than 0.05). Heparin coadministered with t-PA significantly reduced the half-time for clot lysis compared with t-PA alone (p less than 0.05), whereas hirudin coadministered with t-PA significantly reduced the half-time for clot lysis compared with that for t-PA alone, t-PA plus aspirin, and t-PA plus heparin (5.5 +/- 0.6 versus 12.1 +/- 2.0 versus 12.6 +/- 2.2 versus 10.0 +/- 0.8 minutes, respectively; p less than 0.05). Both heparin and hirudin prevented the increase in ADP-induced platelet aggregation normally seen with t-PA alone (p less than 0.01 by t test; p less than 0.05 by two-way analysis of variance). These data demonstrate that selective, antithrombin III-independent thrombin inhibitors can enhance the efficacy of thrombolysis by modulating the dynamics of the process and preventing platelet activation associated with plasminogen activator therapy.
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PMID:Effect of thrombin inhibition on the dynamics of thrombolysis and on platelet function during thrombolytic therapy. 155 Dec 6

Although the benefits of coronary thrombolysis are well established, the optimal therapeutic strategy for ensuring rapid and sustained coronary artery patency remains controversial. The available data suggest that the success of coronary thrombolysis depends not only on the induction of clot lysis, but also on the extent to which procoagulant activity that promotes recurrent thrombosis is inhibited. Procoagulant activity increases almost immediately in patients treated with fibrinolytic agents, and persistent increases in thrombin activity have been associated with recurrent coronary thrombosis. Heparin administered intravenously appears to markedly attenuate the thrombin activity associated with thrombolysis and, in patients treated with tissue plasminogen activator (t-PA), prevents early recurrent coronary thrombosis. The results of clinical trials of coronary thrombolysis indicate that conjunctive treatment of patients with heparin improves survival compared with treatment with fibrinolytic agents alone. Although recent clinical trials in which patients were treated with streptokinase suggested that 12,500 units of heparin administered subcutaneously twice daily decreases mortality, this dosage regimen does not induce therapeutic levels of anticoagulation within the first 24 h in most patients. The failure to achieve early therapeutic anticoagulation may account for the lack of mortality benefit in trials in which patients given t-PA were treated with conjunctive subcutaneous heparin therapy. Thus, the available experimental and clinical data suggest that intravenous heparin should be given to patients treated with fibrinolytic agents for acute myocardial infarction.
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PMID:Role of heparin in coronary thrombolysis. 155 78

Having previously shown in the Heparin Aspirin Reperfusion Trial that the empiric use of early intravenous heparin after recombinant tissue-type plasminogen activator (rt-PA) is an important component in the overall treatment strategy, we examine in this report the specific relation between the degree of prolongation of activated partial thromboplastin time and coronary artery patency. To evaluate the hypothesis that arterial patency after administration of rt-PA for acute myocardial infarction is sustained by effective anticoagulation, activated partial thromboplastin time of heparin recipients was determined 8 and 12 h after the start of thrombolysis. Mean activated partial thromboplastin time was higher among patients with an open infarct-related artery than in those with a closed artery (81 +/- 4 vs. 54 +/- 9 s, p less than 0.02). Only 45% of patients with values less than 45 s at both 8 and 12 h had Thrombolysis in Myocardial Infarction (TIMI) flow grade 2 or 3 in the infarct-related artery at 18 h. In contrast, 88% of patients with activated partial thromboplastin time greater than 45 s and 95% of those with values greater than 60 s had an open infarct-related artery at 18 h (p = 0.003 and 0.0006, respectively). Among patients with an initially patent infarct-related artery who underwent repeat angiography at 7 days, activated partial thromboplastin time was similar in those with a persistently patent artery and those with late reocclusion. Excessive anticoagulation did not appear to increase hemorrhagic risk except that access site-related hemorrhage was more common in patients with activated partial thromboplastin time greater than 100 s at 8 h.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Heparin-induced prolongation of partial thromboplastin time after thrombolysis: relation to coronary artery patency. HART Investigators. 160 35


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