链霉菌产生的新型纤溶酶的纤溶性质和溶栓作用

目的旨在进一步确证纤溶活性的蛋白酶SW-1的溶栓作用和性质。用体外加热平板法、试管凝块法和在体内对大鼠静脉血栓溶解及对纤溶因子的作用等实验,发现SW-1在体外可直接降解纤维蛋白,而无激活纤溶酶原的作用。在体内,SW-1对大鼠静脉血栓有显著的溶解效果,与同剂量尿激酶的溶栓作用相当。给药(iv)30min后,SW-1引起大鼠血浆中纤溶酶、纤溶酶原水平提高,纤维蛋白原水平下降,而对组织型纤溶酶原激活剂(t-PA)、α₂-纤溶酶抑制剂无显著影响。提示SW-1是一种具有纤溶活性的蛋白酶,而不是纤溶原激活剂。     

Vasoactive intestinal polypeptide (VIP) stimulates fibrinolytic system in the rat

We have studied the fibrinolytic effect of VIP in rats. Intravenous injection of VIP enhanced blood fibrinolytic activity in a dose-related manner. The euglobulin fraction obtained from intact rat plasma incubated with VIP did not produce an increase in fibrinolytic activity, while dextran sulfate (DS) and urokinase (UK) showed the activity. VIP solution placed on a plasminogen-rich fibrin plate did not show fibrinolysis. VIP had neither a plasminogen activator nor plasmin activity. VIP may release plasminogen activators into the blood.     

The effect of dexamethasone on tissue fibrinolytic system in male and female rats.

BACKGROUND: Dexamethasone in low and high doses affects blood fibrinolytic activity both in animals and humans. In this study the effect of a high dose of dexamethasone on plasminogen activator activity (PAA), t-PA antigen level, plasminogen activator inhibition (PAI) and plasmin inhibition (Pl) in rat heart, brain, liver, lungs and kidneys was investigated in both sexes. MATERIALS AND METHODS: Twenty male and twenty female adult Wistar rats were used. Dexamethasone was administered as a single intraperitoneal injection (3mg/kg/day) in rats, once daily, for a period of 5 consecutive days. t-PA antigen level was assayed by an enzyme-linked immunoabsorbant assay method. PAA, PAI and Pl were determined by spectrophotometric methods. The plasminogen used was isolated from rat plasma. RESULTS: Dexamethasone induced variable changes in the fibrinolytic parameters in rat heart, brain and liver of both sexes; in lungs and kidneys dexamethasone had no effect. CONCLUSION: These changes of PAA, PAI and t-PA antigen level in heart, brain and liver induced by dexamethasone might be of importance regarding the involvement of glucocorticoids and plasminogen activators/plasmin in many pathophysiological conditions.     

Activation of Factor XII in Plasma from Rats Pretreated with Tranexamic Acid. Inhibition of a Plasmin-induced Loss of the Functional Activity of High Molecular Weight Kininogen

Abstract: Incubation of plasma from rats pretreated with tranexamic acid (40 mg/l 00 g) with acetone (23 % v/v) yielded enzyme preparations in which all the plasminogen present was recovered as plasmin and a plasmin-like substance without affinity for lysine-Sepharose. This substance, designated “plasmin”, was separated from plasmin and kallikrein in a three-step procedure using columns of lysine-Sepharose, DEAE-Sephadex A-50, and arginine-Sepharose. The ratios of fibrinolytic, caseinolytic, LEe esterase, BAEe esterase and kininogenase activities of “plasmin” corresponded well with those of rat plasmin and human plasmin. Both rat plasmin and “plasmin” destroyed the capacity of high molecular weight kininogen (HMWK) to function as a cofactor in the activation of factor XII in rat plasma, without causing a corresponding release of the kinin part of the molecule. Rat plasma kallikrein induced full release of kinin from HMWK, but the functional capacity was retained. It is suggested that the reduced extent of activation of factor XII observed in plasma from rats injected intravenously with dextran, or rat plasma that has been passed through a column with lysine-Sepharose, is due to the loss of functional HMWK caused by plasmin activated in vivo or on the column.     

Inhibition of plasminogen activator inhibitor-1 by 11-keto-9(E),12(E)-octadecadienoic acid, a novel fatty acid produced by Trichoderma sp

We have recently found a novel fatty acid, 11-keto-9(E),12(E)-octadecadienoic acid (KOD), that enhances fibrinolytic activity of endothelial cells. The mechanism of action of KOD has been investigated. KOD increased 2-fold the plasmin activity of bovine aortic endothelial cells at 250 microM. The stimulation was dependent on plasminogen and was inhibited by anti-urokinase, whereas KOD did not enhance the urokinase-catalyzed plasminogen activation and the resulting plasmin activity in a cell-free system. Neither the production of urokinase nor the conversion of pro-urokinase to the active, two-chain form was elevated by KOD, but it decreased plasminogen activator inhibitor-1 (PAI-1) activity of cells and inactivated PAI-1 irreversibly in a purified system. These results demonstrated that the KOD enhancement of endothelial fibrinolytic activity was mediated, at least in part, by inactivation of PAI-1.     

Hemorrhagic Syndrome Induced by Contact with Caterpillars of the Genus Lonomia (Saturniidae,Hemileucinae)

Abstract

A bleeding syndrome induced by contact with Lonomia achelous caterpillars was first described in Venezuela in 1967. It was reported in the early eighties in North Brazil among rubber latex collectors. From 1989 a very high incidence has been observed in South Brazil due to contact with L. obliqua. Symptoms are similar in all accidents, starting with a burning pain after contact followed by erythema, edema and heat; blisters, headache, nausea, and vomit may also appear. The onset of a hemorrhagic syndrome one to twelve hours later manifests as hematoma throughout the body, epistaxis, bleeding from mucosa and from healing scars, with low plasma fibrinogen concentrations. An intense fibrinolytic activity has been detected in the blood of the patients.

Contact of Swiss rats with Lonomia obliqua caterpillars or intradermal injections of Lonomia hair extracts into rats induced blood incoagulability within one to two hours. Studies with these extracts demonstrated a dose-dependent procoagulant activity, higher on rat than on human plasma and potentiated by calcium. On purified fibrinogen, the extracts are weakly active only when calcium is present. The procoagulant activity of the extract was slightly inhibited by heparin and better inhibited by hirudin.

The mechanism of the overwhelming fibrinolytic state observed in patients has still to be elucidated since it is not explained by in vitro tests with Lonomia obliqua hair extracts on a chromogenic substrate specific for plasmin and there is hardly any plasminogen activator-like activity in these extracts.     

Changes in plasma kininogen levels induced by cellulose sulphate during pregnancy in the rat

1 Cellulose sulphate (1 mg/kg) produced a 30-40% depletion of plasma kininogen in rats.2 The time course of repletion of kininogen in the plasma was compared in rats in the oestrous and dioestrous stages of the cycle and in 22 day pregnant animals. A partial repletion occurred, 3 h after the cellulose sulphate injection, which was followed by a secondary fall in plasma kininogen. Plasma kininogen values were back to control levels 10 h after the treatment in all groups.3 Treatment of rats from days 19-22 of pregnancy with cellulose sulphate resulted in 40% depletion of plasma kininogen and in prolongation of pre-parturition behaviour.4 It is suggested that the increase which normally occurs in plasma kininogen levels towards the end of pregnancy in the rat may play a role in the process of parturition.     

Enhancement of fibrinolytic activity of U937 cells by malformin A1

We have found that malformin A1, a cyclopentapeptide metabolite of Aspergillus niger, enhanced 2.0- to 3.2-fold the 125I-fibrin clot lysis when incubated at 1 to approximately 10 microM with both U937 cells and blood plasma, both of which were essential to the malformin A1 action. The effect was inhibited by epsilon-aminocaproic acid and anti-urokinase serum, but not by anti-tissue-type plasminogen activator IgG, showing that the enhancement was mediated by urokinase-catalyzed plasminogen activation. However, malformin A1 affected neither cellular urokinase activity nor cell-free reactions involved in the fibrinolytic pathway. Malformin-treated, washed cell had an increased capacity to degrade fibrin in the presence of plasma. These results suggest that malformin A1 enhances fibrinolytic activity by affecting cell-mediated response to initiate and/or propagate fibrinolytic activity.     

Effect of aspirin on the fibrinolytic response in perfused rat hindquarters.

The role of aspirin on tissue plasminogen activator (t-PA) release was studied in rats after experimental venous occlusion. For this purpose, we developed a new experimental model which combines a vascular perfusion system (isolated rat hindquarters) with vascular stimulation, namely the application of venous stasis. Application of venous stasis for 30 min induced the release of t-PA from the vascular endothelium into the perfusate (from 0.19 +/- 0.05 to 0.39 +/- 0.05 UI/ml), reaching a peak 90 s after reperfusion. Aspirin administered to rats 60 min before the experiments (100 mg/kg i.v.), or dissolved in Tyrode solution (100 microM), suppressed 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) synthesis (0.38 +/- 0.09 in control and < 0.01 and 0.15 +/- 0.09 ng/ml, respectively, in aspirin-treated groups) but did not prevent the increase in fibrinolytic activity after venous occlusion (from 0.20 +/- 0.04 to 0.38 +/- 0.06 and from 0.07 +/- 0.03 to 0.27 +/- 0.03 IU/ml, respectively, in the aspirin-treated group). Our results suggest that the increase in fibrinolytic activity after experimental venous occlusion in isolated rat hindlegs is modulated by mechanism(s) other than the cyclooxygenase pathway in the vascular wall.     

Effects of doxazosin and atenolol on the fibrinolytic system in patients with hypertension and elevated serum cholesterol

Summary Disturbances in the fibrinolytic system have been associated with cardiovascular disease and its risk factors. In the present study the effects of an alpha₁-adrenoceptor inhibitor (doxazosin) and a selective beta-adrenoceptor blocker (atenolol) on the fibrinolytic system have been evaluated.Eighty four subjects with previously untreated mild to moderate hypertension and elevated serum cholesterol were randomized to receive atenolol or doxazosin in a double-blind study over 6 months. Tissue plasminogen activator(tPA) and plasminogen activator inhibitor (PAI-1) were measured in citrated plasma samples before and after venous occlusion before and at the end of the study period.tPA activity after venous occlusion and tPA capacity were significantly increased after doxazosin as compared to pretreatment values. The fibrinolytic variables did not change in the atenolol group.Thus, doxazosin but not atenolol, improved the activity of the fibrinolytic system in patients with hypertension and an elevated serum cholesterol level. This effect of doxazosin warrants consideration when selecting a first-line antihypertensive drug.Part of this study was presented at the 13th Scientific Meeting of the International Society of Hypertension, Montreal, in June 1990.     

甘糖酯抗血栓作用及其机理研究

家兔iv甘糖酯6.25mg·kg~(-1)和25m g·kg~(-1)观察其对实验性血栓形成的影响.并与等抗凝效价藻酸双酯钠及肝素做比较,提示甘糖酯具有较好的抗血栓作用、为探讨其作用机理。本实验观察了甘糖酯对家兔抗凝血酶Ⅲ(AT—Ⅲ)及纤溶酶原活性的影响。发现甘糖酯可明显提高AT一Ⅲ功能活性,并使纤溶酶原活性升高;提示甘糖酯可通过抑制凝血系统和激活纤维蛋白溶解系统发挥其抗血栓作用。     

Enhancement of plasma fibrinolysis in vitro by jararhagin, the main haemorrhagic metalloproteinase in Bothrops jararaca venom

Jararhagin, a haemorrhagic metalloproteinase from Bothrops jararaca venom, plays an important role in systemic as well as local haemorrhage. In this study, the effect of jararhagin on the fibrinolytic system was investigated. The fibrinolytic activity of various kinds of animal plasmas was measured by the fibrin plate method. No activity was detected in plasma alone. However, after mixing plasma with jararhagin, strong fibrinolytic activity was recorded in guinea-pig, horse, dog, rabbit and human plasmas. The mechanism of the increase of fibrinolytic activity by jararhagin was studied further in guinea-pig plasma. Fibrin-zymographic studies indicated that jararhagin increased tissue-type plasminogen activator (tPA) activity by the dissociation of a complex of tPA with type 1 plasminogen activator inhibitor (PAI-1). ₂-Plasmin inhibitor (₂-PI) activity in the plasma was measured using a synthetic chromogenic substrate method after incubation with jararhagin. The ₂-PI activity in the plasma decreased in both time-dependent and dose-dependent manners. These in vitro results suggest that, in some animal plasmas, jararhagin increases plasma fibrinolytic activity by causing dissociation of the tPA/PAI-1 complex and by the inactivation of ₂-PI. It is possible that this direct action of jararhagin on the enhancement of plasma fibrinolytic activity may contribute to the aetiology of systemic haemorrhage frequently observed in human victims of B. jararaca envenoming.     

Enhanced mucosal fibrinolytic activity in gastroduodenal ulcer haemorrhage and the beneficial effect of acid suppression

BACKGROUND: The high mortality rate in patients with upper gastrointestinal bleeding appears to be particularly related to re-bleeding. The haemostatic mechanisms that may influence the re-bleeding of ulcers are largely unknown. AIM: We studied and analysed fibrinolytic activity in bleeding ulcer patients and the effect of acid suppression on this activity. METHODS: Fibrinolytic activity was analysed in mucosal biopsies from 29 bleeding gastroduodenal ulcer patients and six controls. We analysed levels of D-Dimer, fibrin plate lysis area, plasminogen activator activity, plasminogen activator inhibitor activity, and plasmin antiplasmin complexes. RESULTS: Significantly more fibrinolytic activity was detected in biopsies from patients with bleeding ulcers compared to controls. Moreover, in patients with endoscopic stigmata of recent haemorrhage, mucosal fibrinolytic activity was higher compared to patients without stigmata of recent haemorrhage. In mucosal biopsies of patients that had used acid suppression before admission, a decreased fibrinolytic activity was found compared to patients without such therapy. This effect of acid suppression on fibrinolytic activity was confirmed in nine patients before and after a 24-h ranitidine infusion. CONCLUSIONS: Fibrinolytic activity is enhanced in patients with bleeding gastroduodenal ulcers. Acid suppressive therapy decreases this increased activity, which may be one of the mechanisms explaining the potential beneficial effect of this therapy.     

Enhancement of fibrinolytic activity of vascular endothelial cells by chaetoglobosin A, crinipellin B, geodin and triticone B

Four fungal metabolites, chaetoglobosin A (CGA), crinipellin B (CPB), geodin (GE) and triticone B (TTB), were found to enhance fibrinolytic activity of bovine aortic endothelial cells. Plasmin generation on the cells was elevated 2- to 4-fold when treated with these agents at a concentration of 3 approximately 100 microM. These effects were dependent on plasminogen and inhibited by anti-urokinase antibody. The effect of CGA, but not of CPB, GE and TTB, was abolished by cycloheximide. In a cell-free system, plasmin and urokinase activities as well as urokinase-catalyzed plasminogen activation were not enhanced by these agents. CGA, but not others, induced the production of urokinase in endothelial cells. CPB and GE accelerated plasminogen activator inhibitor- 1 (PAI-1) inactivation, and TTB caused direct, reversible inhibition of PAI-1. Thus, induction of urokinase by CGA and inhibition of PAI-1 by CPB, GE and TTB may, at least partly, account for the elevation of fibrinolytic activity of endothelial cells.     

Fibrinolysis: the key to new pathogenetic mechanisms

The fibrinolytic system includes a broad spectrum of proteolytic enzymes with physiological and pathophysiological functions in several processes, such as haemostatic balance, tissue remodeling, tumor invasion, angiogenesis and reproduction. The main enzyme of the plasminogen activator system is plasmin, which is responsible for the degradation of fibrin into soluble degradation products. The activation of plasminogen into plasmin is mediated by two types of activators, urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA). The activity of both is regulated by specific plasminogen activator inhibitors (PAIs). There are 3 types of PAIs described so far but the most important fibrinolytic inhibitor in vivo is PAI type 1 (PAI-1). Among others, the presence of metabolic syndrome and the -675 4G/5G promoter polymorphism are known to be modulators of PAI-1 levels. Besides their fibrinolytic profile, plasmin and plasminogen activators are implicated in tissue proliferation and cellular adhesion, as they can proteolytically degrade the extracellular matrix and regulate the activation of both growth factors and matrix metalloproteinases. By all these means, the fibrinolytic system is also involved in physiological processes, and in pathological situations such as thrombosis, arteriosclerosis, endometriosis and cancer. PAI 1 has been studied in different settings with thrombotic pathophysiology, such as coronary artery disease and ischaemic stroke. Controversial results have been published and concerns about study designs or presence of confounders have been claimed to be responsible of them. Recently, its involvement in adverse thrombotic events related to the modern drug-eluting coronary stents has renewed the interest of its study. PAI-1 also plays an important role in signal transduction, cell adherence, and migration. Indeed, studies of several types of cancers, including breast cancer, have shown that increased uPA and PAI-1 levels are associated with aggressive tumor behavior and poor prognosis. Endometriosis is defined by the presence of endometrial glands and stroma outside the uterus with marked ability to attach and invade the peritoneum. It is one of the most frequent benign gynecological diseases that affect women with pelvic pain or infertility during their reproductive age. Immune system disorders, genetic predisposition, altered peritoneal environment and endometrial alterations are believed to increase the susceptibility to endometriosis. The plasminogen activator system may be involved in this process, where local extracellular proteolysis plays a crucial role. Altered expression of several components of the fibrinolytic system in both eutopic and ectopic endometrium and peritoneal fluid of women with the disease has been implicated not only in the onset, but also in the progression of the endometriotic lesions.     

In vivo effects of cellulose sulphate on plasma kininogen, complement and inflammation

1. The in vivo action of cellulose sulphate was studied in an attempt to clarify the role of complement and kinin formation in inflammation.2. Inflammatory oedema was produced in the rat paw by heat (45.5 degrees C), and on the ear by xylene. The oedema was assessed by comparing the ratio of fresh wet weight to dry weight of corresponding injured and non-injured parts.3. Following cellulose sulphate (6.5 mg/kg i.v.), plasma kininogen concentrations were promptly reduced by 90% or more. The reduction in complement titres was statistically significant and ranged from 17 to 65%. No toxic effects were observed. The oedema caused by heat or xylene was not reduced in these rats.4. Cellulose sulphate (80 mg/kg i.p.) given over 3 days depleted plasma kininogen by about 90%, but reduced complement titres only slightly. These rats gained less weight and their condition was poor. Blood clotting was impaired and widespread haemorrhages were found. Heat and xylene produced significantly less oedema than in control rats. This diminished response is attributed to toxic side effects of cellulose sulphate, rather than depleted plasma kininogen and reduced plasma complement.5. The results suggest that the inflammatory reactions to thermal and chemical injury can fully develop when plasma kininogen and complement are lowered.     

Dose dependency of earthworm powder on antithrombotic and fibrinolytic effects

The freeze-dried powder ofLumbricus rubellus earthworm was administered orally to rats and its fibrinolytic and antithrombotic effects were investigated. The fibrinolytic activity of plasma was determined by measuring the plasmin activity of the euglobulin fraction and was increased to two-folds of the control at a dose of 0.5g/kg/day and five times with 1 g/kg/day after 4-day administration. The antithrombotic effect was studied in an arterio-venous shunt model of rats. The thrombus weight decreased significantly from 43.2 mg to 32.4 mg at a dose of 0.5g/kg/day after 8-day treatment. The level of fibrinogen/fibrin degradation product (FDP) in serum was elevated in a dose-dependent manner during the treatment period. On the 8th day after administration, the FDP value was increased to 7.7 μg/ml compared with the control value of 3.3 μg/ml. These results support that earthworm powder is valuable for the prevention and/or treatment of thrombotic conditions.     

Some pharmacodynamic properties of carrageenin in the rat

1. Carrageenin oedema is suppressed by pre-treating the rats with cellulose sulphate, a kininogen depleting agent. This inhibition is closely related to the dose of cellulose sulphate and to the time course of kininogen depletion.2. Oedema induced by egg white or by dextran, in which the mediators are histamine and 5-hydroxytryptamine, is quite unaffected by cellulose sulphate treatment.3. Carrageenin injected intravenously lowers the arterial blood pressure of rats. This hypotensive effect is unaffected by histamine antagonists and is abolished by protease inhibitors and thus seems to be due to kinin release from plasma substrates.4. Like cellulose sulphate, carrageenin enhances the esterolytic activity of the blood from treated rats when incubated with benzoyl-arginine ethyl ester.5. The ability of carrageenin to activate the kinin-forming system could account for both its inflammatory and hypotensive effects.     

Coagulation and fibrinolysis in rats poisoned with mercuric chloride

The effect of mercuric chloride on blood coagulation and fibrinolysis in rats was studied. The mercurial was administered to the animals intragastrically in a single dose of 17.9 mg Hg/kg and the effects were tested on the 1st, 3rd and 7th day. The symptoms of hypercoagulability accompanied by decreased fibrinolytic activity of the plasma were observed in the poisoned rats. The main reason of the lowered fibrinolytic activity seemed to be the inhibition of plasma plasminogen activator or the inhibition of plasminogen activation reaction catalyzed by this enzyme.     

中分子质量岩藻聚糖硫酸酯的抗血栓活性及作用机制

目的观察中分子质量岩藻聚糖硫酸酯(MMWF)的抗血栓作用并探讨其作用机制。方法 50只大鼠随机分为正常对照组、模型组、阿司匹林组、MMWF0.25 mg·kg~(-1)组和0.1mg·kg~(-1)组,采用下腔静脉血栓模型,考察血栓湿重和血栓抑制率。酶联免疫吸附测试法(ELISA)测定动物血浆抗凝血酶-Ⅲ(AT-Ⅲ)、蛋白质C(PC)、纤溶酶原(PLG)、组织型纤溶酶原激活物(t-PA)和纤溶酶原激活物抑制物-1(PAI-1)指标。另外50只大鼠按前述分组,通过大鼠血瘀模型考察血液流变学改变。结果在静脉血栓模型中,与正常对照组比较,模型组的AT-Ⅲ和PC活性、t-PA含量及t-PA/PAI-1比值均显著降低,PAI-1和PLG含量显著增加(均P<0.01)。与模型组和阿司匹林组比较,MMWF 0.25 mg·kg~(-1)组和0.1 mg·kg~(-1)组血栓湿重均显著减轻(均P<0.01),AT-Ⅲ和PC无显著改变(P>0.05),t-PA含量和t-PA/PAI-1比值显著升高,PAI-1和PLG含量显著降低(均P<0.01)。在血瘀模型中,与正常对照组比较,模型组的全血黏度、血浆黏度、血细胞比容、红细胞沉降率及红细胞沉降率方程K值等血液流变学指标均有明显升高(均P<0.01)。与模型组比较,MMWF 0.25 mg·kg~(-1)和0.1 mg·kg~(-1)组上述指标均显著改善(P<0.05或P<0.01)。结论 MMWF具有明显的抗血栓作用,其机制可能与增加纤溶作用和改善血液流变学性质有关。