Tissue plasminogen activator release and plasminogen activator inhibitor levels in coronary artery disease

Unstable angina and Q wave myocardial infarction are associated with intraluminal coronary thrombosis, a process to which impaired fibrinolysis may contribute. The authors examined the extrinsic fibrinolytic system, including tissue plasminogen activator antigen, plasminogen activator inhibitor activity and antigen, and euglobulin clot lysis time before and after venous occlusion in 56 patients undergoing coronary angiography for chest pain syndromes and in 16 healthy controls. Fibrinolysis variables were similar (with greater than 95% confidence) in the patients with thrombus-associated coronary syndromes as compared with those with chest pain syndromes not due to coronary thrombosis. These fibrinolytic variables were also similar to those in patients without coronary artery disease and in healthy controls. Their data suggest that defective fibrinolysis is not involved, at least systemically, in the pathogenesis of thrombus-associated coronary artery syndromes.     

Molecular advances in plasminogen activator inhibitor 1 interaction with thrombin and tissue-type plasminogen activator

Plasminogen activator inhibitor 1 (PAI-1) is a glycoprotein that controls the activity of the key enzymes of the fibrinolytic system, the serine proteases tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA). Inhibition is accomplished by rapid formation of inactive, equimolar PAI-1/PA complexes. The physiological importance of PAI-1 for the fibrinolytic system has been underscored by the observation that in humans, a homozygous defect results in hemorrhagic episodes. In addition to its function in surveillance of the integrity of clots, PAI-1 efficiently inhibits the serine protease thrombin in vitro, provided that either the high molecular weight glycosaminoglycan heparin or the glycoprotein vitronectin is present. These cofactors accelerate the rate of thrombin inhibition by PAI-1 by more than two orders of magnitude. Inhibition of thrombin by PAI-1 proceeds according to a "suicide substrate mechanism," typified by a branched reaction pathway, leading either to stable PAI-1/thrombin complexes or to degradation of the inhibitor and recycling of enzyme. The cofactors heparin and vitronectin, although increasing inhibition through different mechanisms, essentially promote PAI-1 degradation by thrombin. In view of the multitude of functions attributed to thrombin, the authors propose that the relevance of thrombin inhibition by PAI-1 is to restrict its mitogenic activity, rather than to affect its coagulation function in plasma. (Trends Cardiovasc Med 1997;7:47-51). ? 1997, Elsevier Science Inc.     

纤溶酶原激活物抑制剂-1在冠状动脉疾病时表达的变化

目的：研究纤溶酶原激活物抑制剂（PAI）-1分子在吸烟患者中的表达以及与冠状动脉粥样硬化病变的关系。方法：入选冠心病患者98例,根据吸烟时间和吸烟支数分为：强吸烟组（45例）和弱吸烟组（53例）;又根据冠脉造影分为：单支病变组（56例）和多支病变组（42例）,比较各组血清PAI-1分子含量。结果：强吸烟组患者血清PAI-1含量明显高于弱吸烟组[（41．17±8．5）mol／L比（34．26±7．8）,mol／L,P〈0．055;多支病变组PAI-1含量明显高于单支病变组[（43．21±8．3）mol／L比（31.16±6．4）mol／L,P〈0．05]。结论：冠状动脉病变严重程度与纤溶酶原激活物抑制剂-1含量有关,吸烟可破坏机体的内环境平衡,对纤溶起到明显的抑制作用。     

Platelet and vascular function during coronary thrombolysis with tissue-type plasminogen activator

Platelet activation may limit the response to tissue-type plasminogen activator (t-PA) during coronary thrombolysis in humans. As an index of platelet activation, we assessed thromboxane A2 biosynthesis during coronary thrombolysis with intravenous t-PA in patients with acute myocardial infarction. Urinary 2,3-dinor-thromboxane B2, a metabolite of thromboxane A2, was increased to a peak of 3,327 +/- 511 pg/mg creatinine (n = 12) following administration of intravenous t-PA and remained elevated for 48 hours. This increase was abolished by pretreatment with aspirin 325 mg orally (n = 6), indicating de novo biosynthesis of thromboxane A2 rather than washout of preformed metabolites during reperfusion. Prostacyclin (PGI2) biosynthesis, determined by excretion of 2,3-dinor-6-keto-PGF1 alpha, also increased after t-PA administration. However, this increase was less pronounced in patients who reperfused (28 +/- 3.3 ng.hr/mg creatinine) than in patients who failed to reperfuse (118 +/- 30 ng.hr/mg creatinine, p less than 0.05). These data provide evidence of platelet activation during coronary thrombolysis with t-PA. In patients who reperfuse, the reduction in PGI2 biosynthesis may be a marker of reperfusion injury to the vasculature and may further amplify platelet activation.     

Evidence for increased levels of plasminogen activator inhibitor and tissue plasminogen activator in plasma of patients with angiographically verified coronary artery disease

We studied 234 consecutive patients who underwent coronary angiography because of severe angina pectoris. Tissue plasminogen activator (tPA), plasminogen activator inhibitor (PAI), and lipoprotein Lp(a) were measured in citrated plasma samples. The 214 patients showing significant coronary artery stenosis (greater than 50% reduction of luminal area in any of the great coronary arteries) had higher mean levels of tPA (P less than 0.001) and PAI (P less than 0.01) than a random population sample of similar age. PAI and tPA levels were higher in smokers than in either non-smokers or ex-smokers, and in patients with hypertension tPA was increased. Subjects with blood group A had a higher mean Lp(a) level than subjects with blood group O. There were positive correlations of PAI and tPA levels with serum triglycerides and with body mass index; Lp(a) correlated weakly with plasma fibrinogen concentrations. The findings suggest an impairment of the fibrinolytic system in patients with coronary artery disease, which offers a link between established risk factors and a plausible pathophysiological mechanism, namely thrombus turnover.     

Amino acid residues that affect interaction of tissue-type plasminogen activator with plasminogen activator inhibitor 1.

Fibrinolysis is regulated in part by the interaction between tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1, a serine protease inhibitor of the serpin family). It is known from our earlier work that deletion of a loop of amino acids (residues 296-302) from the serine protease domain of t-PA suppresses the interaction between the two proteins without altering the reactivity of t-PA towards its substrate, plasminogen. To define more precisely the role of individual residues within this loop, we have used site-directed mutagenesis to replace Lys-296, Arg-298, and Arg-299 with negatively charged glutamic residues. Replacement of all three positively charged amino acids generates a variant of t-PA that associates inefficiently with PAI-1 and is highly resistant to inhibition by the serpin. Two t-PAs with point mutations (Arg-298----Glu and Arg-299----Glu) are partially resistant to inhibition by PAI-1 and associate with the serpin at intermediate rates. Other point mutations (Lys-296----Glu, His-297----Glu, and Pro-301----Gly) do not detectably affect the interaction of t-PA with PAI-1. None of these substitutions has a significant effect on the rate of catalysis by t-PA or on the affinity of the enzyme for its substrate, plasminogen. On the basis of these results, we propose a model in which positively charged residues located in a surface loop near the active site of t-PA form ionic bonds with complementary negatively charged residues C-terminal to the reactive center of PAI-1.     

老年冠心病患者纤溶酶原激活抑制剂的变化

目的探讨老年人冠心病与纤溶酶原激活抑制剂（PAI）的关系。方法测定了93例老年冠心病患者的PAI和组织型纤溶酶原激活剂（t-PA）活性、胆固醇和甘油三酯的血浆水平,并与健康对照组比较。结果冠心病组的PAI活性〔（810±360）AU/L〕明显高于健康对照组〔（640±300）AU/L,P＜0.01〕;冠心病组的t-PA活性〔（390±140）IU/L〕明显低于对照组的水平〔（490±240）IU/L,P＜0.05〕。结论老年人PAI活性的增高和t-PA活性的降低可能参与了冠心病的发病机制。     

Circulating tissue-type plasminogen activator and plasminogen activator inhibitor type 1 in proliferative diabetic retinopathy: a pilot study

Several haemostatic abnormalities are associated with proliferative diabetic retinopathy. While abnormalities in plasma fibrinolytic activity have been described in diabetic retinopathy, platelets (a rich source of plasminogen activator inhibitor type 1, PAI-1) have received little attention. As a result, little is known about the fibrinolytic potential of circulating whole blood in diabetic retinopathy. The concentrations of tissue-type plasminogen activator (t-PA) and of its fast-acting inhibitor. PAI-1 were measured in plasma from eight patients with type 1 diabetes complicated by proliferative retinopathy, and from eight patients with type 1 diabetes and background or no retinopathy, matched for age, sex and duration of diabetes. The concentration of PAI-1 in platelets was also measured. The ratio of t-PTA to PAI-1 in plasma was significantly higher in patients with proliverative retinopathy than in those without (0.66 vs. 0.37, p < 0.02). The average quantitiy of PAI-1 per patelet was significantly lower in the group with proliferative retinopathy (0.33 vs. 0.50 ng/10⁶ platelets, p < 0.02). These data suggest that among patients with type 1 diabetes, total circulating fibrinolytic potential is higher in those with proliferative retinopathy. Received: 14 October 1998 / Accepted in revised form: 30 September 1999     

尿激酶型纤溶酶原激活物与冠心病临床类型的关系

目的 探讨冠状动脉粥样硬化性心脏病（冠心病）患者血清尿激酶型纤溶酶原激活物（urokinase-type plasminogen activator,uPA）浓度变化及临床意义.方法 根据临床表现和冠状动脉造影结果,173例患者分为ST段抬高性心肌梗死（ST-segment elevation myocardial infarction,STEMI）组（n=61）、非ST段抬高急性冠脉综合征（non-ST-segment elevation acute coronary syndrome,NSTE-ACS）组（n=29）、稳定型心绞痛（stable angina pectoris,SAP）组（n=41）、冠状动脉造影正常组（正常对照组,n=42）.酶联免疫吸附试验（ELISA）法测定血清uPA的质量浓度;免疫速率法检测血清高敏C反应蛋白（high-sensitivity Creaction protein,hs-CRP）的质量浓度.结果 （1）STEMI组、NSTE-ACS组、SAP组血清uPA质量浓度均高于正常对照组,差异有统计学意义（P＜0.05或P＜0.01）;STEMI组和NSTE-ACS组血清uPA质量浓度高于SAP组,差异有统计学意义（P＜0.05或P＜0.01）.（2）各组uPA表达特征与hs-CRP的表达特征一致.（3）相关性分析显示,STEMI组、NSTE-ACS组和SAP组血清uPA质量浓度与血清hs-CRP浓度呈正相关（r=0.347,P＜0.01;r=0.452,P＜0.01;r=0.172,P＜0.05）.结论 冠心病患者uPA活性增高,是严重冠状动脉病变的相关危险因素,在冠心病发生、发展中可能起着重要作用.     

Increased plasma fibrinolysis and tissue-type plasminogen activator/tissue-type plasminogen activator inhibitor ratios after ethanol withdrawal in chronic alcoholics.

The effects of alcohol withdrawal on fibrinolysis were studied in 10 middle-aged male chronic alcoholics institutionalized for withdrawal therapy. All patients were sampled on admission [day 1 (D1)] and 21 days after alcohol withdrawal [day 22 (D22)]. The overall plasma fibrinolytic capacity (OFC) was assayed by measuring the ability of patient plasma to generate D-dimers from a standardized fibrin clot, and tissue-type plasminogen activator (t-PA) and t-PA inhibitor (PAI-1) levels were assayed together with serum cholesterol, triglyceride and cholesterol fractions. At D22, the OFC significantly increased in seven patients [D1 = 10 +/- 0.7 microg/h (mean +/- SD), D22 = 17 +/- 7.4 microg/h; P < 0.01], while t-PA and PAI-1 levels decreased in all patients but two (t-PA: D1 = 16.6 +/- 5 ng/ml, D22 = 10.2 +/- 3.8 ng/ml; P < 0.001; and PAI-1: D1 = 46 +/- 39 ng/ml, D22 = 21 +/- 28 ng/ml; P < 0.01). This study clearly demonstrates an increase in overall fibrinolytic activity after alcohol withdrawal, which is mainly due to a decrease in PAI-1 levels. These changes induced by alcohol abstinence might provide clear benefit by reducing the risk of thromboembolic events and particularly of stroke associated with elevated PAI-1 levels described in heavy drinkers.     

Endothelial release of tissue-type plasminogen activator and ischemia-induced vasodilatation are linked in patients with coronary heart disease.

Dysfunction in the vascular endothelium disturbs blood flow and predisposes individuals to atherosclerosis. Deteriorated fibrinolysis may further enhance the risk for atherothrombosis. We investigated 14 healthy volunteers and 24 patients with coronary heart disease. Endothelium-dependent (acetylcholine- and ischemia-induced) and endothelium-independent (nitroprusside-induced) vasodilatation in the forearm vasculature were studied using strain-gauge plethysmography, and the fibrinolytic system measured as the response of tissue plasminogen activator (t-PA) to provocation testing (20 min venous occlusion; VOT). When acetylcholine-induced vasodilatation was measured, endothelium-dependent vasodilatation differed between groups: those with coronary heart disease had a median value of 8.5 ml/min per 100 g tissue (25th to 75th percentile 4.8-10.3), compared with 11.6 ml/min per 100 g tissue (7.3-15.5) among healthy volunteers (P = 0.03). However, ischemia-induced vasodilatation showed no difference between the groups [26.8 (22.7-35.0) versus 29.1 (25.6-30.7) ml/min per 100 g tissue, respectively, NS]. Levels of t-PA after VOT also showed no difference between the groups [21.5 (16.5-31.9) versus 20.4 (11.8-31.5) ng/ml, respectively, NS]. Results of ischemia tests and levels of t-PA after VOT correlated only in patients with coronary heart disease (r = 0.5, P = 0.015), and not in healthy volunteers. We observed a positive correlation between endothelium-dependent vasodilatation function and endothelial release of t-PA. This indicates that the same mechanism that results in defective ischemia-induced endothelial relaxation in patients with coronary heart disease may also result in suppressed fibrinolytic capacity, thus making such patients more prone to atherothrombosis.     

Increased plasminogen activator inhibitor-1 levels in patients with isolated coronary artery ectasia

Isolated coronary artery ectasia (ICAE) is defined as the ectasia of the coronary arteries without concomitant coronary artery stenosis. The etiology and the clinical course of ICAE are still not clear. Increased levels of plasminogen activator inhibitor-1 (PAI-1) inhibit vasa vasorum, leading to diminished vessel wall supply and thus contributes to aortic aneurysm expansion. Whether the same process has role in coronary artery ectasia is not known. The aim of this study is to investigate the association between PAI-1 and coronary artery ectasia in patients without concomitant obstructive coronary artery disease. Among 2830 patients who underwent coronary angiography between March 2010 and 2011, 55 patients (40 male, 15 female, mean age 60?±?8?years) with ICAE, formed our study group. 27 patients with similar patient characteristics, with angiographically proven normal coronary arteries, were enrolled as the control group. The basal characteristics were similar between two groups. PAI-1 levels were statistically higher in the ICAE group compared to the control group (104.13?±?56.65 and 63.39?±?35.01?ng/dl, respectively) (P?=?0.008). A significant positive correlation between CAE and PAI-1 (r?=?0.358, P?=?0.007) was also demonstrated. Serum high sensitive C reactive protein (hsCRP) levels did not differ between two groups (P?>?0.05). The plasma PAI-1 levels were significantly higher in ICAE patients compared to normal coronary artery group. Increased PAI-1 levels may diminish vasa vasorum by antiangiogenic activity leading to coronary ectasia.     

Renal artery embolism: thrombolysis with recombinant tissue-type plasminogen activator

The case of a patient with acute occlusion of the right renal artery due to an embolus is described. Using transoesophageal echocardiography, the left atrial appendage could be identified as the source of embolism. Twenty hours after the onset of symptoms, the embolus could be successfully dissolved with an intra-arterial low-dose infusion of recombinant tissue-type plasminogen activator (10 mg loading dose, 20 mg continuous infusion within 12 h).     

Time dependent release of tissue-type plasminogen activator and plasminogen activator inhibitor into the circulation of pigs during shock.

To investigate short-term activation and inhibition of fibrinolysis during shock, we studied plasma levels of tissue-type plasminogen activator (t-PA) and t-PA inhibition capacity (PAI) in anaesthetized pigs. t-PA in euglobulin fractions of plasma was measured by the conversion of plasminogen to plasmin in the presence of fibrin split products. Plasmin thus generated was measured in a chromogenic substrate assay. PAI was measured as plasma inhibition capacity for human melanoma t-PA. Controls (n = 8) had constant t-PA and PAI for 6 h. Lipopolysaccharide from Salmonella abortus equi in four different doses (n = 9 - 11), or live Escherichia coli (n = 3) induced a transient t-PA increase with peak values at 2 h. PAI decreased to 50% at 2 h and increased to 250% at 6 h. Phorbol myristate acetate (n = 7) induced no change of t-PA or PAI. Dextran sulphate (n = 4) produced a t-PA rise at 30 min, followed by a rapid decline. Endotoxin was an appropriate stimulus for activation and inhibition of fibrinolysis whereas phorbol ester failed to elicit this response.     

The dynamic changes of plasma tissue-type plasminogen activator level and the activity of its inhibitor during coronary vasospasm

This study aimed to examine the dynamic changes of the fibrinolytic system during coronary vasospasm. Tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor (PAI) and fibrinopeptide A (FPA) levels were measured in the great cardiac venous and arterial blood of 9 patients with clinically and angiographically proven vasospastic angina and 11 controls. Before ergonovine provocation, although there was no difference between the above 2 groups in t-PA levels in the aorta or the great cardiac vein, the PAI level in patients with variant angina was lower than in the controls both in the aorta (4.2 +/- 3.5 IU/ml vs 10.9 +/- 5.2 IU/ml) and in the great cardiac vein (2.3 +/- 2.9 IU/ml vs. 11.9 +/- 4.9 IU/ml). During ergonovine-induced coronary vasospasm in patients with variant angina, the t-PA level in the great cardiac vein significantly increased from 3.4 +/- 0.7 ng/ml to 4.4 +/- 0.5 ng/ml (p less than 0.05), but it did not change in the aorta. The maximal dose of ergonovine (0.4 mg) induced mild diffuse coronary vasoconstriction in the controls, and this diffuse coronary vasoconstriction induced a reduction of PAI levels in the great cardiac vein from 11.9 +/- 4.9 IU/ml to 9.5 +/- 4.8 IU/ml (p less than 0.05). FPA levels in the great cardiac vein did not change during ergonovine-induced coronary vasospasm in either group. Thus, the coronary vasospasm induced the release of t-PA from endothelial cells of coronary vessels and resulted in the reduction in the PAI activity in the great cardiac vein.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intramural plasminogen activator inhibitor type-1 and coronary atherosclerosis

Altered expression of plasminogen activator inhibitor type-1 in vessel walls, reviewed here, might affect coronary atherogenesis. Upregulation might exacerbate vasculopathy by potentiating thrombosis and by inhibiting vascular smooth muscle cell migration, resulting in attenuation of thickness of elaborated fibrous caps implicated in the vulnerability of atheroma to rupture.