Evaluation of clinical efficacy of streptokinase by comparison with the thrombolytic agent on animal model.

Cardiovascular disorders, including acute myocardial infarction (AMI), often lead to blood clot formation, impacting blood circulation. Streptokinase, a cost-effective and widely available thrombolytic agent, is crucial in treating thrombosis. This study aimed to produce streptokinase from Streptococcus pyogenes EBL-48 and compare its efficacy with heparin in an animal model. We evaluated the clot-lysing effectiveness of streptokinase produced from Streptococcus pyogenes EBL-48, emphasizing its low cost and ease of production. Streptokinase was produced using pre-optimized fermentation media and purified through ion exchange and gel-filtration chromatography. In vivo analysis involved inducing clots in a trial animal model using ferric chloride, comparing streptokinase with heparin. Ultrasonography assessed the clot-lysing activity of streptokinase. Streptokinase (47 kDa) effectively lysed clots, proving its low cost, easy production, and minimal adverse effects. Ultrasonography confirmed its fibrinolytic efficacy. These findings highlight potential as an affordable and easily produced thrombolytic agent, particularly relevant in resource-limited settings. Streptokinase efficacy and minimal adverse effects make it a promising option for thrombolytic therapy, especially in economically constrained regions. Future studies could optimize production techniques, explore different strains, and conduct clinical trials for human validation. Comparative studies with other thrombolytic agents would enhance understanding of their advantages and limitations.

Decrease of prothrombin level during thrombolysis in acute myocardium infarction.

Previously, the direct interactions of Bß26-42 fibrin residues with prothrombin were demonstrated. It was also shown that forming prothrombin complexes with E- or DDE-fragments causes non-enzymatic prothrombin activation. The direct measuring of the prothrombin level in the blood plasma of patients with acute myocardial infarction (AMI) allowed us to find a situation where such an activation can occur in vivo. Blood coagulation parameters in the blood plasma of patients with AMI were measured at 2 hours, three days, and seven days after the thrombolysis by streptokinase accompanied with intravenous administration of anticoagulants: unfractionated high molecular weight heparin (HMWH) and low-molecular-weight heparin (LMWH). The prothrombin level in the blood plasma of patients with AMI was normal before thrombolytic therapy and substantially decreased after streptokinase administration. This effect was prominent in the case of concomitant anticoagulant therapy with LMWH and was not observed when HMWH was applied. It can be explained by the fact that LMWH preferentially inhibits factor Xa, while the HMWH is an effective inhibitor of both factor Xa and thrombin. This observation suggested that the prothrombin level decrease was caused by the thrombin-like activity and possible autolysis of prothrombin by thrombin. Also, thrombolytic therapy with streptokinase caused the accumulation of fibrin degradation products (FDPs), some of which were able to bind prothrombin. The dramatic decrease of prothrombin level in the blood plasma of patients with AMI during thrombolysis allowed us to conclude the non-enzymatic prothrombin activation with the following autolysis of prothrombin that contributes to the pathology.

Efficiency of targeted delivery of streptokinase based on fibrin-specific liposomes in the in vivo experiment.

Acute thrombosis has a narrow therapeutic window and remains the leading cause of morbidity and mortality, while thrombolytic therapy has limited efficacy and risk of side effects. We have developed and investigated new fibrin-specific systems for local drug delivery to increase efficiency while minimizing the side effects of streptokinase. The experiment was carried out on dogs with 2-h thrombi in the femoral artery received intravenous injections of streptokinase, liposome-bound and free streptokinase at 40/60% ratio, and immunoliposomes. The completeness of the vessel lumen restoration affected by the thrombus, and the risks of side effects were assessed. Fibrinolytic parameters (plasminogen, fibrinogen, alpha2-antiplasmin, and D-dimers levels) were measured at several time points after thrombus induction and the administration of the drug. There was a strong activation of fibrinolysis and consumption of fibrinolysis inhibitors after therapy with all liposomal forms of streptokinase. According to the ultrasound data, immunoliposomal form of streptokinase significantly reduces the degree of residual stenosis to 32% [30.5; 33.7] in 180 min after injection. The high fibrinolytic effect of liposomal forms of streptokinase is not accompanied by a sharp drop in the fibrinogen concentration in the blood compared to the native streptokinase by 60 min. The morphometric evaluation of the artery samples showed that immunoliposomal form of streptokinase induces a significant increase in the degree of free vascular lumen compared to the native streptokinase (71.3% (62.7; 77.5) vs. 47.7% (39.6; 55.7), p < 0.001). Thus, the study shows the efficacy of streptokinase-induced thrombolysis using immunoliposomal form of drug delivery system. Mechanism of action of the immunoliposomal delivery system.

Cloning and purification of an anti-thrombotic, chimeric Staphylokinase in Pichia pastoris.

There has been an increasing prevalence of cardiovascular diseases such as myocardial infarction and stroke in modern societies because of multiple lifestyle related issues like sedentariness and obesity, alcohol consumption and many more "life-style"factors. The FDA-approved thrombolytics such as Tissue Plasminogen Activator, Streptokinase etc. are used to lyse the clots in thrombotic disorders such as myocardial infarction, stroke etc. but re-occlusion and bleeding that are co-incident to their clinical usage are not addressed. Hence, there is need to develop thrombolytics having properties like increased fibrin clot specificity and thrombin inhibition capability to prevent re-occlusion. In the present work, a fusion protein construct containing two components i.e. Staphylokinase (SAK) and Epidermal Growth Factor (EGF) 4, 5, 6-like domains of human thrombomodulin (THBD) was expressed in Pichia pastoris after genetic optimization. SAK isolated from Staphylococcus aureus is a fibrin-specific plasminogen activator while EGF 4, 5, 6-like domains are reported to be responsible for imparting thrombin inhibition to human thrombomodulin, and therefore, expected could help prevent re-occlusion in the novel construct - SAK_EGF, which is a 43 kDa protein. After expression, it was purified (approx. 13-fold) using two-step purification protocol involving ion-exchange followed by Gel Filtration Chromatography (GFC). The functional characterization including plasminogen activation and thrombin inhibition showed that both the fusion partners viz. SAK and 4,5,6 EGF-like domains retained their respective activities after fusion, confirming it to be a bio-active construct. Thus, this engineered protein could be clinically promising due to the combinatorial effect of fibrin-specific thrombus lysis and prevention of re-occulusion.

A systematic review of the efficacy and safety of intrapericardial fibrinolysis in patients with pericardial effusion.

Pericardial effusion is the abnormal accumulation of fluid in the pericardial space. The complications of pericardial effusion can either be acute (e.g., cardiac tamponade) or chronic (e.g., constrictive pericarditis). We have conducted a systematic review of the scientific literature to evaluate the efficacy and safety of intrapericardial fibrinolysis in preventing complications of pericardial effusion. We searched for both published and unpublished studies. 29 studies, with a total of 109 patients were included in this review; 17 case reports, 11 case series, and one randomised controlled trial (RCT). All included studies had a high risk of bias. The most common causes of pericardial effusion were Staphylococcus aureus (12 studies with 23 cases) and Mycobacterium tuberculosis (2 studies with 19 cases). The most common fibrinolytic agents used were streptokinase (15 studies) and urokinase (5 studies). Intrapericardial fibrinolysis prevented complications in 94 (86.2%) patients. Non-fatal procedure-related complications were reported 21 (19.2%) patients. No patient died following intrapericardial fibrinolysis. There is very low certainty of the efficiency and safety of intrapericardial fibrinolysis in preventing the complications of pericardial effusion. High quality RCTs are required to address this question.

Potential application of immobilized streptokinase extracted from Streptococcus equinus VIT_VB2.

Streptokinase purified from Streptococcus equinus VIT_VB2 isolated from bovine milk sample was immobilized in various solid supports namely entrapment in agarose gel, calcium alginate beads and gelatin gel by cross-linking with formaldehyde. Immobilization of streptokinase in calcium alginate beads showed maximum efficiency (81.8 ± 1.06%) when compared with entrapment with agarose gel (55.6 ± 2.17%) and cross-linked gelatin formaldehyde gel (71.0 ± 1.54%). The purified SK activity was expressed maximum in calcium alginate (1%) and gelatin gel (0.25%) with 1292.68 ± 1.33 and 1121.9 ± 1.2 U mL-1, respectively. Similarly, SK entrapped in gelatin gel and calcium alginate showed maximum in vitro blood clot lysis activity with 77.67 ± 2.64% and 76.16 ± 2.72%, respectively. The immobilized SK in gelatin gel showed complete clot lysis within 15 min; hence, this application of the study could be used in the treatment of superficial thrombophlebitis, phlebitis, and venous thrombosis. These beads were used for three repeated cycles to check the conversion of substrates into their products, and we concluded that SK can be immobilized in the suitable matrices. Therefore, this helps in the drug-delivery strategies in highly efficient way, moreover, economically competent process in the pharmaceutics.

Current Controversies in Thrombolytic Use in Acute Pulmonary Embolism.

BACKGROUND: Acute pulmonary embolism (PE) has an annual incidence of 100,000 cases in the United States and is divided into three categories: nonmassive, submassive, and massive. Several studies have evaluated the use of thrombolytics in submassive and massive PE. OBJECTIVE: Our aim was to provide emergency physicians with an updated review of the controversy about the use of thrombolytics in submassive and massive PE. DISCUSSION: Nonmassive PE is defined as PE in the setting of no signs of right ventricular strain (echocardiogram or biomarker) and hemodynamic stability. Submassive PE is defined as evidence of right ventricular strain with lack of hemodynamic instability. Massive PE occurs with occlusive thromboembolism that causes hemodynamic instability. Thrombolysis is warranted in patients with massive PE. Thrombolytic use in submassive PE with signs of right ventricular strain or damage presents a quandary for physicians. Several recent studies have evaluated the use of thrombolytics in patients with submassive PE. These studies have inconsistent definitions of submassive PE, evaluate differing primary outcomes, and use different treatment protocols with thrombolytics and anticoagulation agents. Although significant study heterogeneity exists, thrombolytics can improve long-term outcomes, with decreased bleeding risk with half-dose thrombolytics and catheter-directed treatments. Major bleeding significantly increases in patients over age 65 years. The risks and benefits of thrombolytic treatment-primarily improved long-term outcomes-should be considered on a case-by-case basis. Shared decision-making with the patient discussing the risks and benefits of treatment is advised. CONCLUSIONS: Thrombolytic use in massive PE is warranted, but patients with submassive PE require case-by-case analysis with shared decision making. The risks, including major hemorrhage, and benefits, primarily improved long-term outcomes, should be considered. Half-dose thrombolytics and catheter-directed treatment demonstrate advantages with decreased risk of bleeding and improved long-term functional outcomes. Further studies that assess risk stratification, functional outcomes, and treatment protocols are needed.

An In Vitro Thrombolysis Study Using a Mixture of Fast-Acting and Slower Release Microspheres.

PURPOSE: To test the hypothesis that a mixture combining fast and slower release rate microspheres can restore blood flow rapidly and prevent formation of another blockage in thrombolysis. METHODS: We used polyethylene glycol (PEG) microspheres which provide the release of the encapsulated streptokinase (SK) on the scale of minutes, and Eudragit FS30D (Eud), a polymethacrylate polymer, for development of delayed release microspheres which were desirable to prevent a putative second thrombus. Eud microspheres were coated with chitosan (CS) to further extend half-life. Experiments included the development, characterization of Eud/SK and CS-Eud/SK microspheres, and in vitro thrombolytic studies of the mixtures of PEG/SK and Eud /SK microspheres and of PEG/SK and CS-Eud/SK microspheres. RESULTS: CS-Eud/SK microspheres have slightly lower encapsulation efficiency, reduced activity of SK, and a much slower release of SK when compared with microspheres of Eud/SK microspheres. Counter-intuitively, slower release leads to faster thrombolysis after reocclusion as a result of greater retention of agent and the mechanism of distributed intraclot thrombolysis. CONCLUSIONS: A mixture of PEG/SK and CS-Eud/SK microspheres could break up the blood clot rapidly while providing clot-lytic efficacy in prevention of a second blockage up to 4 h.

Optimization of Self-Assembled Chitosan/Streptokinase Nanoparticles and Evaluation of Their Cytotoxicity and Thrombolytic Activity.

In this study, the enzyme streptokinase (thrombolysis agent) and chitosan (Cs) nanoparticles were prepared by self-assembly. Using experimental design, chitosan concentration, solution pH and stirring time were studied as independent variables to identify their effects on size, polydispersity index (PDI) and loading efficiency of nanoparticles. Results showed that pH and concentration have a direct effect on size. Additionally, minimum PDI was observed at lowest values of concentration and highest values of stirring time. pH-5.6 was also necessary to obtain the smallest PDI and highest loading efficiency values. The model predicted that to obtain maximum loading efficiency and minimum size along with low PDI, optimum values are 0.5 mg/mL, 5.18 and 30 min for the Cs concentration, solution pH and stirring time, respectively. The corresponding mean ± SD values for experimentally prepared nanoparticles were 43 ± 10%, 526 ± 121 nm, 0.3 ± 0.2, respectively. MTT and euglobulin clot lysis assays on the optimized nanoparticles showed that chitosan/streptokinase nanoparticles have slightly toxic effect on human fetal lung fibroblast cells (Mrc-5), compared with chitosan and streptokinase alone as a control. Also, thrombolytic activity of encapsulated streptokinase in nanoparticles is decreased slightly in comparison with free streptokinase. However, the preparation keeps a good potency for use as a thrombolytic agent in vivo.

Delivery of tissue plasminogen activator and streptokinase magnetic nanoparticles to target vascular diseases.

Thrombolytic therapy for acute myocardial infarction standardly makes use of the medications streptokinase (SK) and tissue plasminogen activator (tPA). In this study, the potential of silica-coated magnetic nanoparticles (SiO2-MNPs) as nanocarriers clinical thrombolytic therapy was investigated. SiO2-MNPs for use in targeted therapeutic delivery of tPA and SK were prepared using a combined technique incorporating controlled precipitation and hydrothermal methods. Response surface methodology (RSM) was employed to evaluate the efficiency of the SiO2-MNPs. The production of SK secreted from Streptococcus equi was enhanced using random mutagenesis. The tPA and SK A were encapsulated by means of a silanizing agent with a surface rich in 3-aminopropyltrimethoxysilane layered around the SiO2-MNPs. Blood clot lysis assays and fibrin-containing agarose plates were used to carry out in vitro thrombolysis testing. The optimum conditions for producing MNPs were found to be at pH=13 and at a temperature of 75°C for 45 min. Culture conditions of 2.75% NaCl concentration at initial pH=7.5 for 90 s under UV resulted in maximum SK activity. The tPA/SK-conjugated SiO2-MNPs (SiO2-MNP-tPA-SK) increased operating stability in whole blood and storage stability in a buffer by 92%. More effective thrombolysis using magnetic targeting was indicated by a 38% reduction in blood clot lysis time achieved with SiO2-MNP-tPA-SK compared to administering the SiO2-MNPs without guidance. The silica-coated magnetic nanocarriers developed in this study show potential for improved clinical thrombolytic therapy.

Effects of organic extracts and their different fractions of five Bangladeshi plants on in vitro thrombolysis.

BACKGROUND: The increasingly high incidence of ischemic stroke caused by thrombosis of the arterial vessels is one of the major factors that threaten people's health and lives in the world. The present treatments for thrombosis are still unsatisfactory. Herbal preparations have been used since ancient times for the treatment of several diseases. The aim of this study was to investigate whether herbal preparations possess thrombolytic activity or not. METHODS: An in vitro thrombolytic model was used to check the clot lysis effect of the crude extracts and fractions of five Bangladeshi plant viz., Trema orientalis L., Bacopa monnieri L., Capsicum frutescens L., Brassica oleracea L. and Urena sinuata L. using streptokinase as a positive control and water as a negative control. Briefly, venous blood drawn from twenty healthy volunteers was allowed to form clots which were weighed and treated with the test plant materials to disrupt the clots. Weight of clot after and before treatment provided a percentage of clot lysis. RESULTS: Using an in vitro thrombolytic model, different fractions of five Bangladeshi medicinal plants namely T. orientalis, B. monnieri, C. frutescens, B. oleracea and U. sinuata showed various range of clot lysis activity. Chloroform fractions of T. orientalis, B. monnieri, C. frutescens, B. oleracea and U. sinuata showed highest significant (P < 0.05 and P < 0.001) clot lysis activity viz., 46.44 ± 2.44%, 48.39 ± 10.12%, 36.87 ± .27%, 30.24 ± 0.95% and 47.89 ± 6.83% respectively compared with positive control standard streptokinase (80.77 ± 1.12%) and negative control sterile distilled water (5.69 ± 3.09%). Other fractions showed moderate to low clot lysis activity. Order of clot lysis activity was found to be: Streptokinase > Chloroform fractions > Methanol (crude) extract > Hydro-methanol fractions > Ethyl acetate fractions > n-hexane fractions > Water. CONCLUSIONS: Our study suggests that thrombolytic activity of T. orientalis, B. monnieri and U. sinuata could be considered as very promising and beneficial for the Bangladeshi traditional medicine. Lower effects of other extracts might suggest the lack of bio-active components and/or insufficient quantities in the extract. In vivo clot dissolving property and active component(s) of T. orientalis and B. monnieri for clot lysis could lead the plants for their therapeutic uses. However, further work will establish whether or not, chloroform soluble phytochemicals from these plants could be incorporated as a thrombolytic agent for the improvement of the patients suffering from atherothrombotic diseases.

In vitro thrombolytic activity of purified streptokinase extracted from Streptococcus equinus VIT_VB2 isolated from bovine milk.

Streptokinase (SK) is an extracellular enzyme secreted by various strains of ß-hemolytic Streptococci. The main focus of the current study is to evaluate the in vitro thrombolytic activity of purified SK extracted from Streptococcus equinus VIT_VB2 (Accession no. JX406835) isolated from milk sample. The growth rate of S. equinus VIT_VB2 strain was studied with pH and biomass content which has positive significant effect on enzyme yield. A temperature of 10 °C and pH of 6 was found to be optimum for maximum SK activity. The specific activity of the purified SK produced by VIT_VB2 strain was found to be 6,585 IU mg(-1). The molecular mass of the enzyme was determined as 47 kDa by SDS-PAGE. In vitro thrombolytic activity of purified SK was determined using synthetic chromogenic substrate S-2251, the activity of the purified enzyme was found to be 6,330 ± 2.2 IU. The purity of SK was compared with standard SK by HPLC. This is the first report which reveals the SK activity of S. equinus isolated from milk sample.

Production of recombinant streptokinase from Streptococcus pyogenes isolate and its potential for thrombolytic therapy.

OBJECTIVES: To produce an effective recombinant streptokinase (rSK) from pathogenic Streptococcus pyogenes isolate in yeast, and evaluate its potential for thrombolytic therapy. METHODS: This study was conducted from November 2012 to December 2013 at King Khalid University, Abha, Kingdom of Saudi Arabia (KSA). Throat swabs collected from 45 pharyngitis patients in Asser Central Hospital, Abha, KSA were used to isolate Streptococcus pyogenes. The bacterial DNA was used for amplification of the streptokinase gene (1200 bp). The gene was cloned and in vitro transcribed in an eukaryotic expression vector that was transformed into yeast Pichia pastoris SMD1168, and the rSK protein was purified and tested for its thrombolytic activity. RESULTS: The Streptococcus pyogenes strain was isolated and its DNA nucleotide sequence revealed similarity to other Streptococcus pyogenes in the Gene bank. Sequencing of the amplified gene based on DNA nucleotide sequence revealed a SK gene closely related to other SK genes in the Gene bank. However, based on deduced amino acids sequence, the gene formed a separate cluster different from clusters formed by other examined genes, suggesting a new bacterial isolate and accordingly a new gene. The purified protein showed 82% clot lysis compared to a commercial SK (81%) at an enzyme concentration of 2000 U/ml. CONCLUSION: The present yeast rSK showed similar thrombolytic activity in vitro as that of a commercial SK, suggesting its potential for thrombolytic therapy and large scale production. 

Evaluation on clot buster activity of staphylokinase from Staphylococcus sp.

Thrombolytic agents play a major role in the treatment of cardiovascular diseases. Streptokinase is the prominently commercialized thrombolytic drug used for the treatment of cardiovascular diseases. The later studies on staphylokinase (SaK) showed promising results as an alternative fibrinolytic drug. The present study explores the isolation, production and purification of SaK producing Staphylococcus sp. from milk samples. The potent isolate MSA4 of Staphylococcus sp. was selected for production and purification of SaK. The total activity and specific activity of purified staphylokinase was found to be 1266 IU mL(-1) and 815.5 IU mg(-1), respectively. The partially purified enzyme was lysed the euglobulin clot completely within 18 h of incubation and the purified enzyme showed 79% of blood clot lysis activity.

Plasmin cleavage of von Willebrand factor as an emergency bypass for ADAMTS13 deficiency in thrombotic microangiopathy.

BACKGROUND: Von Willebrand factor (VWF) multimer size is controlled through continuous proteolysis by ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type I motif, member 13). This prevents spontaneous platelet agglutination and microvascular obstructions. ADAMTS13 deficiency is associated with thrombotic thrombocytopenic purpura, in which life-threatening episodes of microangiopathy damage kidneys, heart, and brain. Enigmatically, a complete ADAMTS13 deficiency does not lead to continuous microangiopathy. We hypothesized that plasmin, the key enzyme of the fibrinolytic system, serves as a physiological backup enzyme for ADAMTS13 in the degradation of pathological platelet-VWF complexes. METHODS AND RESULTS: Using real-time microscopy, we determined that plasmin rapidly degrades platelet-VWF complexes on endothelial cells in absence of ADAMTS13, after activation by urokinase-type plasminogen activator or the thrombolytic agent streptokinase. Similarly, plasmin degrades platelet-VWF complexes in platelet agglutination studies. Plasminogen directly binds to VWF and its A1 domain in a lysine-dependent manner, as determined by enzyme-linked immunosorbent assay. Plasma levels of plasmin-α2-antiplasmin complexes increase with the extent of thrombocytopenia in patients with acute episodes of thrombotic thrombocytopenic purpura, independent of ADAMTS13 activity. This indicates that plasminogen activation takes place during microangiopathy. Finally, we show that the thrombolytic agent streptokinase has therapeutic value for Adamts13(-/-) mice in a model of thrombotic thrombocytopenic purpura. CONCLUSIONS: We propose that plasminogen activation on endothelial cells acts as a natural backup for ADAMTS13 to degrade obstructive platelet-VWF complexes. Our findings indicate that thrombolytic agents may have therapeutic value in the treatment of microangiopathies and may be useful to bypass inhibitory antibodies against ADAMTS13 that cause thrombotic thrombocytopenic purpura.

Purification and characterization of a novel C-type hemolytic lectin for clot lysis from the fresh water clam Villorita cyprinoides: a possible natural thrombolytic agent against myocardial infarction.

Villorita cyprinoides (black clam) is a fresh water clam that belongs as a bivalve to the group of mollusc. The saline extracts from the muscle reveal high titers of agglutination potency on trypsin-treated rabbit erythrocytes. With the help of affinity chromatography a hemolytic protein with lectin activity which could all be inhibited by D-galactose were isolated. The lectins were separated on DEAE-cellulose and the main component was purified after an additional step of gel filtration on sephadex G-75. The main component is a non-glycosylated protein with a molecular weight of 96,560 Da determined by MALDI-ToF, consisting of a single protein chain and characterized by the lack of polymers and intermediate disulfide bonds. The pure main lectin with clot lytic feature shows two bands at molecular weights 36,360 and 26, 520 Da. Optimal inhibition of the pure lectin is achieved by D-galactose containing oligo- and polysaccharides. The lectin activity decreased above 40 °C and was lost at 62 °C, the stability over the pH range between 7.0 and 8.0 and requires divalent cations for their activity. The novel C-type hemolytic lectin for clot lysis from the clam Villorita cyprinoides was identified and evaluated, the purified hemolytic lectin (0.35 mg/ml and 0.175 mg/ml) enhanced clot lysis activity when compared to the different concentration (5 mg/ml and 1 mg/ml) of commercial streptokinase. In the present study identified hemolytic lectin was a rapid and effective clot lytic molecule and could be developed as new drug molecule in future.

Ultrasound-assisted thrombolysis with streptokinase improves thrombus resolution with minimal distal embolisation.

Catheter-directed ultrasound (US) has a synergistic effect on thrombus with streptokinase (SK). We aimed to assess whether a new method of arterial thrombolysis based on a combination of short-term US and intravenous SK administration can improve efficacy and minimize distal embolisation as compared to these two interventions applied separately. Experiments have been done on 23 mongrel dogs with ligature-induced femoral thrombosis divided into groups treated with (i) enzymatic thrombolysis (intravenous SK, n = 6), (ii) 36 kHz US-assisted thrombolysis (n = 6), (iii) US+SK applied together (n = 6), and (iv) control group with no treatment (n = 5). US intensity at the distal end of the waveguide was 10-15 W/cm(2). Selective angiography, plethysmography and sphygmography have been used to assess thrombus resolution and distal embolisation. US-assisted thrombolysis alone was associated with good thrombus resolution, but substantial distal embolisation. SK-induced fibrinolysis alone did not provoke distal embolization but showed delayed thrombus resolution compared to US-treated group. Dual US+SK therapy resulted in high rate of US destruction without significant Under the combined US+SK action, nearly additive summation of US cavitation and SK effects as well as synergistic effects of both these factors on hemostasis parameters (activated partial thromboplastin, prothrombin, and thrombin time; fibrinogen, FDP, D-dimers, antithrombin III, plasminogen, and α2-antiplasmin) have been observed. Combination of CK and US-induced thrombolysis shows high efficacy with minimal distal embolisation. Arterial thrombus destruction by the combination of gradual (40 min) SK intravenous administration followed by short-time (1.5 min) intense US exposure improves shows positive effect of parameters of haemostasis. The magnitude and clinical significance of possible adverse effects of the dual fibrinolytic intervention related to endothelial injury and risk of bleeding needs to be further assessed in longer-term experiments and appropriately designed clinical trials.

Thrombolytic therapy for submassive pulmonary embolism.

Approximately 10% of all patients with acute pulmonary embolism (PE) die within the first three months after diagnosis. However, PE is not universally life-threatening, but covers a wide spectrum of clinical severity and death risk. Thrombolytic treatment is indicated patients with acute massive PE who are at high risk for early death, i.e. those patients who present with arterial hypotension and shock. On the other hand, low molecular-weight heparin or fondaparinux is adequate treatment for most normotensive patients with PE. Recombinant tissue plasminogen activator, given as 100 mg infusion over 2 h, is the treatment of choice for patients with PE, although older regimens using urokinase or streptokinase are also efficacious. Beyond the relatively small numbers of patients with massive, high-risk PE as a target population for thrombolysis, there is increasing awareness of the need for risk stratification of normotensive patients and the search for an intermediate-risk group (also called submassive PE). Recent meta-analyses of cohort studies suggest that imaging of the right ventricle or biomarkers of myocardial injury alone may be insufficient for guiding therapeutic decisions. Instead, accumulating evidence appears to support strategies which combine the information provided by an imaging procedure with a biomarker test. These data provide the rationale for a large multinational randomized trial which has set out to determine whether normotensive patients with right ventricular dysfunction, detected by echocardiography or computed tomography, plus evidence of myocardial injury as indicated by a positive troponin test, may benefit from early thrombolytic treatment. This study, which is underway in 13 European countries, will enroll a total of 1000 patients and will be completed in 2012. Together with a parallel trial currently being conducted in the United States, it will hopefully answer the question whether thrombolysis is indicated in submassive PE, thus terminating a 40-year-old debate and filling an important gap in our management concept for acute pulmonary embolism.

Homocysteine and its thiolactone impair plasmin activity induced by urokinase or streptokinase in vitro.

Mechanisms of homocysteine (Hcy) contribution to thrombosis are complex and only partly recognized. The available data suggest that the prothrombotic activity of homocysteine may be not only a result of the changes in coagulation process and endothelial dysfunction, but also the dysfunction of fibrinolysis. The aim of the present work was to assess the effects of homocysteine (10-100 µM mM) and its thiolactone (HTL, 0.1-1 µM) on plasminogen and plasmin functions in vitro. The amidolytic activity of generated plasmin in Hcy or HTL-treated plasminogen and plasma samples was measured by the hydrolysis of chromogenic substrate. Effects of Hcy and HTL on proteolytic activity of plasmin were monitored electrophoretically, by using of fibrinogen as a substrate. The exposure of human plasma and purified plasminogen to Hcy or HTL resulted in the decrease of urokinase-induced plasmin activity. In plasminogen samples treated with the highest concentration of homocysteine (100 µM) or thiolactone (1 µM), the activity of plasmin was inhibited by about 50%. In plasma samples, a reduction of amidolytic activity by about 30% (for 100 µM Hcy) and 40% (for 1 µM HTL), was observed. Both Hcy and HTL were also able to diminish the streptokinase-induced proteolytic activity of plasmin. In conclusion, the results obtained in this study demonstrate that Hcy and HTL may affect fibrinolytic properties of plasminogen and plasma, leading to the decrease of plasmin activity.