Increased plasma tissue-type plasminogen activator levels in patients with chronic thrombocytopenia

Plasma fibrinolytic factors were measured in 14 patients with chronic idiopathic thrombocytopenic purpura (ITP), in 5 patients with chronic central thrombocytopenia and in 16 healthy volunteers. The von Willebrand factor (vWF), tissue-type plasminogen activator (t-PA) and D-dimer (DD) antigens were found to be significantly higher in both patient groups than in the control group. No difference appeared in euglobulin fibrinolytic activity and plasminogen activator inhibitor activity. The increases in both t-PA and vWF suggest the occurrence of an endothelial cell stimulation, associated with the reduction of circulating platelet number. The correlation of increased DD and t-PA levels during ITP can be the proof of a fibrinolysis activation and suggest an antifibrinolytic role of platelets at physiological concentrations. These results can justify antifibrinolytic therapy in bleeding thrombocytopenic patients.     

Fibrinolytic properties of a human endothelial hybrid cell line (Ea.hy 926)

The fibrinolytic characteristics of the endothelial hybrid cell line EA.hy 926, established by fusing a human umbilical vein endothelial cell with a human carcinoma cell line, were studied. The hybrid cell line produced large amounts of tissue-type plasminogen activator (t- PA), plasminogen activator inhibitor type 1, and a small amount of urokinase. All plasminogen activator present in conditioned medium was complexed with inhibitor because the cells secreted plasminogen activator inhibitor in excess over plasminogen activator and no activator activity was detectable in conditioned media by direct activity assays. t-PA activator activity was, however, demonstrable in conditioned media after treatment with sodium dodecyl sulfate, in agreement with t-PA antigen determinations. Increased plasminogen activator inhibitor activity could be induced by incubating the cells in the presence of endotoxin or microtubule inhibitors, whereas increased t-PA activity could be induced by microtubule inhibitors. Interleukin-1 had no effect. The fibrinolytic characteristics of the hybrid cell line were stable for at least 30 passages. The perpetual human hybrid cell line EA.hy 926 therefore may be a useful tool for the study of fibrinolysis in cultured endothelial cells.     

Increased concentration of the fast-acting plasminogen activator inhibitor in plasma associated with familial venous thrombosis

We have earlier demonstrated that in a family with a tendency to recurrent venous thrombosis the release of tissue plasminogen activator (t-PA) activity in blood after stimulation was abnormally low. This observation could be related either to an impaired release of t-PA into the blood stream or to a masking of the released t-PA by a high concentration of PA inhibitor(s). In order to distinguish between these two possibilities the family was reinvestigated using various newer techniques, including an ELISA for t-PA, an assay for quantitation of the fast-acting PA inhibitor and SDS polyacrylamide gel electrophoresis followed by fibrin-enzymography. Hereby the family members were demonstrated to have a high concentration in plasma of the PA inhibitor. After stimulation the release of t-PA into the blood was normal, the t-PA activity, however, was immediately inactivated by complex formation with the fast-acting PA inhibitor.     

Residual plasminogen activator inhibitor activity after venous stasis as a criterion for hypofibrinolysis: a study in 83 patients with confirmed deep vein thrombosis

In eighty-three patients with confirmed deep vein thrombosis, the fibrinolytic system was studied before and after a 10-minute venous occlusion. Blood was collected at least 3 months after the last acute episode, and PAI-1 antigen and activity, as well as tissue-type plasminogen activator (t-PA) antigen, urokinase-type plasminogen activator (u-PA) antigen, and fibrinolytic activity were measured in these samples. During venous stasis, plasminogen activator inhibitor (PAI) activity decreased in almost all patients (81 of 83), from a median value of 8.2 to 2.9 U/mL (P less than .001, Wilcoxon signed-rank test). Because PAI-1 antigen augmented from a median value of 16 to 19.2 ng/mL (P less than .001), the decline in PAI activity was attributed to an increase in t-PA antigen from a median value of 10 to 21.7 ng/mL (P less than .001). Neutralization of PAI activity thus reflects the patient's capacity to overcome basal inhibitory potential through t-PA release. Based on residual PAI activity after 10-minute stasis, patients were classified as good or bad responders (PAI activity below detection limit, ie, less than or equal to 1.0 and greater than 1.0 U/ml, respectively). Good responders had a significantly higher fibrinolytic response after stasis than bad responders (median euglobulin clot lysis time 60 v 180 minutes; dilute whole blood clot lysis time 60 v 120 minutes; fibrinolytic activity on fibrin plates 7.7 v 0 U/mL). Furthermore, good responders, as compared with bad responders, had higher t-PA release (median 16.5 v 11.5 ng/mL), lower basal PAI activity (median 4.8 v 11.2 U/mL), and lower basal PAI-1 (median 11 v 21 ng/mL) and u-PA antigen (median 7.9 v 9.0 ng/mL, P less than .02). Hypofibrinolysis, as defined by the inability of released t-PA to overcome PAI-1 basal inhibitory potential, was observed in 45 of 83 patients (54%) and resulted either from an insufficient release of t-PA or from an increased basal PAI activity.     

Intra- and postoperative fibrinolysis in patients undergoing cardiopulmonary bypass surgery

The influence of cardiopulmonary bypass (CPB) on fibrinolytic activity was assessed in 100 patients with valvular heart disease or atrial septal defects. Euglobulin fibrinolytic activity (EFA), tissue type plasminogen activator (t-PA) activity, plasminogen activator inhibitor 1 (PAI-1) activity, plasminogen, alpha 2-antiplasmin (alpha 2-AP), fibrinogen degradation products (FDP), and D-dimer were measured pre-, intra-, and postoperatively. There were significant increases in EFA and t-PA activity (p less than 0.002), and decreases in plasminogen and alpha 2-AP (p less than 0.0001) intraoperatively with respect to baseline values. t-PA activity decreased significantly after surgery (p less than 0.002), whereas PAI-1 activity showed a marked increase shortly after operation and on postoperative day 1 (p less than 0.0001). FDP and D-dimer levels were significantly increased both intra- and postoperatively, the latter showing higher values (p less than 0.01 and p less than 0.0001, respectively). This study shows that there is an activation of the fibrinolytic system, as a result of the increased activation of plasminogen and decreased levels of plasmin inhibitors, during CPB surgery followed by a postoperative fibrinolytic shutdown.     

Changes in the fibrinolytic components of cultured human umbilical vein endothelial cells induced by endotoxin, tumor necrosis factor-alpha and interleukin-1alpha

BACKGROUND AND OBJECTIVE: Vascular fibrinolysis, a major natural defense mechanism against thrombosis, is a highly regulated process. The aim of this study was to evaluate the effect of endotoxin, tumor necrosis factor-alpha (TNFalpha) and interleukin-1alpha (IL-1alpha), on the fibrinolytic potential of cultured human umbilical vein endothelial cells (HUVEC). DESIGN AND METHODS: Samples of stimulated conditioned media were collected over a period of 24 hours to determine: plasminogen activator (PA) and plasminogen activator inhibitor (PAI) activity, PAI-1 mRNA, tissue-type plasminogen activator (t-PA) antigen and urokinase-type plasminogen activator (u-PA) antigen. RESULTS: Similar changes were observed after endotoxin and cytokine stimulation: there was a significant increase of PAI activity (p<0.01), starting at 6 hours, which remained 24 hours after stimulation. PAI-1 mRNA also showed an important rise with these agents, although cytokines induced an earlier and more intense inhibitor response (up to 6-fold increase). PA activity increased significantly at 6 hours (p<0.01) to drop at 24 hours and was mainly related to the presence of u-PA. INTERPRETATION AND CONCLUSIONS: We conclude that endotoxin,+TNFalpha and IL-1alpha induce profound alterations in the fibrinolytic potential of HUVEC, characterized by an initial rise of activators (u-PA) followed by a strong increase of PAI-1. These changes may be of pathophysiologic significance for thrombosis and inflammatory reactions.     

Characterization and fibrinolytic properties of human omental tissue mesothelial cells. Comparison with endothelial cells

It has been reported that omental fat tissue is a good source of human microvascular endothelial cells. By characterization we demonstrate that the epitheloid cells isolated from omental tissue are not endothelial cells, but mesothelial cells. They contain abundant cytokeratins 8 and 18, which are absent in endothelial cells, and vimentin. No staining with the endothelial-specific antibodies EN-4 and PAL-E is observed. A faint and diffuse staining of von Willebrand factor (vWF) is seen in mesothelial cells, whereas microvascular endothelial cells from subcutaneous fat display vWF in distinct granular structures. Human peritoneal mesothelium produces plasminogen activator-dependent fibrinolytic activity, which is essential in the resolution of fibrous exudates and may therefore be important in preventing the formation of fibrous peritoneal adhesions. This fibrinolytic activity is plasminogen activator-dependent, but has not been fully characterized. We report here that human omental tissue mesothelial cells in vitro produce large amounts of tissue-type plasminogen activator (t-PA), together with type 1 and 2 plasminogen activator inhibitor (PAI-1 and PAI-2). PAI-1 is predominantly secreted into the culture medium, whereas the major part of PAI-2 is found in the cells. No urokinase-type plasminogen activator is detected. On stimulation with the inflammatory mediator tumor necrosis factor (TNF), at least a threefold decrease in t-PA antigen is observed, together with an increase in both PAI-1 and PAI-2. TNF also induces a marked change in cell shape. Whereas TNF and bacterial lipopolysaccharide (LPS) have similar effects on the production of PA inhibitor by human endothelial cells, LPS has no or only a relatively small effect on the fibrinolytic properties of mesothelial cells. The decreased fibrinolytic activity induced by the cytokine TNF may impair the natural dissolution of fibrin deposits at the peritoneum in the presence of an inflammatory reaction.     

Absence of functional activity of tissue plasminogen activator in patients with severe forms of von Willebrand''s disease

Some patients with von Willebrand's disease do not respond to stimuli such as venous occlusion and infusion of a vasopressin analogue DDAVP. In these patients, fibrinolytic activity is not enhanced and von Willebrand's factor is not released into the blood. Skin biopsies and cryostat sections were used to study the fibrinolytic activity of skin vessels and localization of tissue plasminogen activator (t-PA) in three patients with severe form of von Willebrand's disease. On fibrin films, no fibrinolysis developed around the skin vessels of the patients; however, using specific polyclonal and monoclonal antibodies to t-PA, and peroxidase coupled specific IgG, presence of t-PA antigen was demonstrated in endothelial cells (EC) of all of them. In plasma no t-PA activity was detected either before or after venous occlusion although t-PA inhibitor activity was in a normal range. Small amounts of t-PA antigen was measured in blood by ELISA. From these results, it is concluded that in patients with severe forms of von Willebrand's disease, t-PA present in EC is not functional and can not transform plasminogen into plasmin.     

Defective fibrinolysis in Beh?et's syndrome: significance and possible mechanisms.

Reduced fibrinolytic activity has frequently been reported in Behcet''s syndrome, but both the underlying mechanism and its relation to the development of thrombosis are unclear. The fibrinolytic activity was studied in seven patients with Behçet''s syndrome and 12 patients with idiopathic oral ulceration. The patients with Behçet''s disease had significantly reduced resting tissue plasminogen activator(t-PA) both by euglobulin fibrin plate lysis and enzyme linked immunosorbent assay (ELISA), but the tissue plasminogen activator inhibitor(t-PAI) was not significantly different from the control value. After stimulation by venous occlusion the euglobulin fibrin plate lysis results showed three good responders and four poor responders, but neither t-PA antigen nor t-PAI concentrations showed any clear difference between the two groups. Interestingly, three out of the four patients with a history of thrombosis were good responders. The group with oral ulceration showed no significant difference from the controls for any of these measurements. These findings suggest that the reduced resting fibrinolytic activity is usually due to decreased production of t-PA, but that the defective response to stimulation may be multifactorial in origin. The fibrinolytic abnormalities appear unrelated to the development of thrombosis.     

凝血及纤溶系统变化在急性心肌梗塞溶栓治疗中的作用

本文通过对急性心肌梗塞(AMI)早期溶栓治疗的43例患者进行凝血及纤溶系统功能的测定,分别在溶栓前、溶栓后4h、12h、24h、48h及1周测定凝血酶原时间(PT)、活化的部分凝血活酶时间(APTT)、纤溶酶原(PLG)、α_2抗纤溶酶(α_2AP)、纤维蛋白原(Fg)、D二聚体含量(D=Dimer)、组织型纤维溶酶原活化物(t-PA)、组织型纤溶酶原活化物抑制物(PAI),其结果显示,溶栓组冠脉再通26例(60.5%),溶栓前与溶栓后4h相比冠脉再通组t-PA活性明显高于未通组(P<0.01),PLG活性及Fg含量的降低幅度再通组明显高于未通组,建议溶栓中应把测定t-PA、PAI、PLG及Fg作为判断溶栓治疗效果的指标.     

The pathogenesis of accelerated fibrinolysis in hepatosplenic schistosomiasis.

Seventy patients with different stages of hepatosplenic schistosomiasis and 18 non-bilharzial normal controls were studied. Plasminogen, plasminogen activators (PA), tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), alpha 2-antiplasmin (alpha 2-AP), plasminogen activator inhibitor (PAI), fibrinogen/fibrin degradation products (FDP) and D-dimer were determined to elucidate the role of plasminogen activators and inhibitors in the pathogenesis of accelerated fibrinolysis in schistosomiasis. There was a progressive increase in the levels of PA, t-PA, u-PA, FDP and D-dimer indicating enhanced fibrinolytic activity with advancing disease. In addition, there was progressive decrease of plasminogen, alpha 2-AP and PAI levels which might be due to decreased hepatic synthesis and/or increased peripheral consumption. These findings suggest that the pathogenesis of accelerated fibrinolysis in schistosomiasis is multifactorial, but may be due to the progressive increase in the levels of plasminogen activators. In addition, the increase of FDP and D-dimer levels are evidence of secondary fibrinolysis following thrombin generation.     

Antithrombotic regulation in human endothelial cells by fibrinolytic factors

Vascular endothelial cells (ECs) modulate the blood fibrinolytic system by secreting tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), and their inhibitor, type-1 plasminogen activator inhibitor (PAI-1). ECs also express t-PA receptors (t-PAR) and u-PA receptors (u-PAR) on their cell surfaces, assembling both enzymes to regulate the cellular fibrinolytic activity. In addition, ECs modulate these factors in response to several stimuli. Fibrin clots on ECs induce the up- and downregulation of t-PA and PAI-1 production, respectively, thus causing an effective lysis of the fibrin clot. Heat shock (43 degrees C) increases the expression of u-PA, t-PA, PAI-1, and u-PAR by which ECs become more fibrinolytic around the cells. Furthermore, because ECs possess t-PAR and u-PAR on their cell surfaces, the binding of t-PA and u-PA is a critical event, which affords ECs the localized and condensed fibrinolytic potential. Therefore, ECs play a central role in antithrombotic activity by regulating the levels of these fibrinolytic factors.     

Hemodynamic forces modulate the effects of cytokines on fibrinolytic activity of endothelial cells

We investigated the effects of hemodynamic force on fibrinolytic activity of cultured human umbilical vein endothelial cells stimulated by cytokines, using a modified cone-plate viscometer in which well- controlled and -defined shear forces were generated. Treatment of the cells with interleukin (IL)-beta or tumor necrosis factor alpha (TNFalpha) under static conditions had no effect on tissue plasminogen activator (t-PA) secretion, while release of plasminogen activator inhibitor 1 (PAI-1) increased. When cells were exposed to increasing shear stress up to 24 dynes/cm2, levels of t-PA and t-PA/PAI-1 complex significantly increased relative to shear stress, while total PAI-1 and active PAI-1 secretion decreased gradually. In the presence of IL-1beta or TNFalpha, the increase in production of t-PA and the t-PA/PAI-1 complex was further augmented. Dot blot hybridization analysis of cultured cells in similar experimental conditions using t-PA and PAI-1 cDNA probes revealed no t-PA mRNA in 3 microg total RNA from static endothelial cells under resting or cytokine-stimulated conditions, but abundant t-PA mRNA was detected in cells subjected to a shear force of 18 dynes/cm2, and the increase was further augmented by addition of cytokines. In contrast, PAI-1 mRNA was detected in resting and cytokine- stimulated, nonsheared endothelial cells, but levels decreased after exposure to shear stress, even in the presence of cytokines. These results indicate a role for hemodynamic forces in regulating fibrinolytic activity with or without cytokine stimulation.     

The renin angiotensin system and endothelial dysfunction in chronic heart failure: role of endogenous fibrinolysis

Regulation of vascular tone by the endothelium is abnormal in patients with heart failure and contributes to the characteristic peripheral vasoconstriction and increased afterload. This endothelial dysfunction is mediated through several endothelium-derived factors, including nitric oxide; there is an important interplay between the endothelium and the renin angiotensin system. The benefits of ACE inhibition in heart failure relate, in part, to a reduction in ischemic events which may be mediated by improvements in endothelial function and the endothelium derived fibrinolytic parameters: tissue plasminogen activator (t-PA) and its inhibitor, plasminogen activator inhibitor type 1 (PAI-1). In addition to potential improvements in the regulation of vasomotion, ACE inhibitor therapy may increase bradykinin induced t-PA release and/or reduce angiotensin II mediated PAI-1 release. Recent evidence suggests that both angiotensin II type 1 receptor (AT(1)) antagonism and ACE inhibition improve basal fibrinolytic parameters in patients with heart failure which may facilitate the acute endogenous fibrinolytic response. 1999 by CHF, Inc.     

An increase of C-reactive protein is associated with enhanced activation of endogenous fibrinolysis at baseline but an impaired endothelial fibrinolytic response after venous occlusion

OBJECTIVES: The goal of this study was to determine whether chronic inflammation of the vascular wall may be associated with an impaired activation of the fibrinolytic system. BACKGROUND: Inflammation plays an important role in the initiation and progression of atherosclerosis, and the fibrinolytic system may prevent local thrombus formation. METHODS: We included 50 patients six months after their first myocardial infarction. Plasma levels of the inflammatory marker C-reactive protein (CRP) were determined at basal conditions, and the fibrinolytic parameters tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1) were measured at basal conditions and after a standardized venous occlusion (VO) of the forearm. RESULTS: Patients with high CRP levels (> or =3 mg/l) showed a significantly higher t-PA activity at baseline compared with patients with medium (1 to 2.9 mg/l) and low (<1 mg/l) CRP levels (p <0.005). In contrast, patients with low CRP levels showed a higher increase of t-PA activity (p <0.05) and a higher reduction of PAI-1 activity during VO (p <0.05) compared with patients with medium and high CRP levels. A multivariate analysis that included cardiovascular risk factors and medical treatment showed that CRP is an independent predictor of the t-PA response after a standardized VO. CONCLUSIONS: Chronic low-grade inflammation is associated with enhanced activation of endogenous fibrinolysis at baseline but a reduced fibrinolytic response to VO. This impaired endogenous fibrinolytic capacity might be an important contributor to the increased coronary event rate associated with elevated CRP levels.     

复方丹参滴丸对冠心病患者纤溶系统t-PA、PAI-1含量与活性的调控

目的观察复方丹参滴丸对冠心病患者内源性纤溶活性及血管内皮功能的影响，探讨其作用机制。方法冠心病患者78例，随机分为对照组和复方丹参滴丸组。对照组采用常规治疗；复方丹参滴丸组在常规治疗基础上加用复方丹参滴丸每次10粒，每日3次。两组用药时间均为4周。比较治疗前后血浆组织型纤溶酶原激活剂（t-PA）、纤溶酶原激活剂抑制因子-1（PAI-1）活性及浓度。结果复方丹参滴丸治疗4周后，患者血浆PAI-1活性及浓度下降（P〈0．05），t—PA活性及浓度含量升高（P〈0．05），与治疗前比较差异有统计学意义；常规治疗组治疗前后t-PA和PAI-1活性差异无统计学意义。结论复方丹参滴丸可有效地调控改善冠心病患者内源性纤溶活性及血管内皮功能。     

Endothelial Tissue-Type Plasminogen Activator Release in Coronary Heart Disease: Transient Reduction in Endothelial Fibrinolytic Reserve in Patients With Unstable Angina Pectoris or Acute Myocardial Infarction

Objectives. We sought to examine whether the disturbed fibrinolytic system in patients with an acute coronary syndrome is associated with a reduced endothelial fibrinolytic capacity.Background. Intracoronary thrombus formation is a frequent finding in acute coronary syndromes. Systemic alterations of coagulation and fibrinolysis are known to occur, but possible disturbances of endothelial fibrinolytic function have not been investigated.Methods. We compared 42 patients with an acute coronary syndrome (acute myocardial infarction in 11 and unstable angina pectoris in 31) with 25 patients with stable angina. Venous blood was sampled serially for determination of markers of the fibrinolytic system and of hypercoagulability from admission to day 10. An occlusion test to determine the maximal endothelial tissue-type plasminogen activator (t-PA) release was also performed.Results. Both on day 0 and day 10, patients with an acute coronary syndrome had a marked elevation of t-PA mass concentration (mean value ± SEM 14.4 ± 1.6 [day 0], 18.9 ± 2.5 ng/ml [day 10]) and of plasminogen activator inhibitor (PAI) (9.4 ± 2.2 [day 0], 11.3 ± 2.6 AU/liter [day 10], p < 0.05 vs. patients with stable angina). There was also a hypercoagulative state with elevated thrombin activity and increased D-dimers (p < 0.05 vs. patients with stable angina). Maximal endothelial t-PA release was initially reduced (p < 0.05 vs. patients with stable angina) to 2.3 ± 0.9 ng/ml, but levels recovered during follow-up to 4.4 ± 1.4 ng/ml (vs. 5.7 ± 1.5 ng/ml in patients with stable angina).Conclusions. Despite the known prolonged systemic alteration of fibrinolysis in acute coronary syndromes, endothelial fibrinolytic capacity is reduced only during the acute phase and becomes normalized during follow-up, and thus is linked more to intravascular thrombus formation than to steady state levels of markers of the fibrinolytic system.     

ABNORMAL FIBRINOLYTIC ACTIVITY IN SYSTEMIC LUPUS ERYTHEMATOSUS AND POSSIBLE MECHANISMS

Plasma fibrinolytic activity was measured in 34 patients withsystemic lupus erythematosus (SLE) and 12 normal subjects. Patientswith SLE showed a significantly reduced resting level of plasmatissue plasminogcn activator (t-PA) compared to normal. Thereduction in t-PA was demonstrated both by a functional assay(fibrin-plate lysis, FP) and an immunochemical assay (ELISA).Measurement of the fibrinolytic response following venous occlusionallowed division of the patients into two groups. In the first(24 patients), there was a normal increase in t-PA response,demonstrated both by the functional and immunochemical assays.In the second (10 patients), there was a significantly reducedplasma t-PA response measured by FP. Seven of the patients inthis second group, which included four patients with histologicalevidence of vasculitis, showed a similar failure of t-PA response(ELISA) after venous occlusion. These results suggest that theirimpaired fibrinolytic response may be related to defective t-PArelease secondary to endothelial cell damage. The remainingthree patients in the latter group had a normal t-PA (ELISA)response despite a reduced FP response, suggesting the presenceof an inhibitor. KEY WORDS: Fibrinolysis, Tissue plasminogcn activator, Vasculitis.