The evolution of recombinant thrombolytics: Current status and future directions

Thrombolytic efficacy and safety of recombinant scu-PA in a rabbit retinal vein occlusion model

Retinal vein occlusion (RVO) has become the second most common retinal vascular disease after diabetic retinopathy. Existing therapeutic approaches, including intravitreal injection of antivascular endothelial growth factors (anti-VEGFs) and/or glucocorticoids and laser therapy, primarily address secondary macular edema and neovascularisation. However, these strategies do not address the underlying cause of the disease and may have harmful side effects. There is an urgent need for therapies that have a better prognosis and include the administration of thrombolytics at an early stage. Therefore, in the present study, we investigated the thrombolytic effect of treatment with recombinant human Single-chain urokinase-type plasminogen activators (scu-PA)and the differences in its efficacy at different doses in a rabbit RVO model. In addition, through a series of ophthalmological examinations, such as optical coherence tomography (OCT) and electrophysiology, conducted to ascertain the effects of treatment with scu-PA on the ocular fibrinolytic system, we noted a definitive safety window for the vitreous administration of scu-PA. Therefore, this study is the first to confirm that an intravenous or vitreous cavity injection of scu-PA has definitive potential for treating RVO; however, additional clinical studies are needed for further validation.

Fibrinolytic uses in the emergency department: a narrative review

INTRODUCTION

Several life-threatening conditions associated with thrombosis include acute ischemic stroke (AIS), acute myocardial infarction (AMI), and acute pulmonary embolism (PE). Fibrinolytics are among the treatment algorithms for these conditions.

OBJECTIVE

This narrative review provides emergency clinicians with an overview of fibrinolytics for AIS, AMI, and PE in the emergency department (ED) setting.

DISCUSSION

Pathologic thrombosis can result in vascular occlusion and embolism, ultimately leading to end-organ injury. Fibrinolytics are medications utilized to lyse a blood clot, improving vascular flow. One of the first agents utilized was streptokinase, though this is not as often used with the availability of fibrin-specific agents including alteplase (tPA), tenecteplase (TNK), and reteplase (rPA). These agents are integral components in the management of several conditions, including AIS, AMI, and PE. Patients with AIS who present within 3-4.5 h of measurable neurologic deficit with no evidence of intracerebral hemorrhage (ICH) or other contraindications may be eligible to receive tPA or TNK. In the absence of percutaneous coronary intervention (PCI), fibrinolytics should be considered in patients with AMI presenting with chest pain for at least 30 min but less than 12 h, though it may be considered up to 24 h. Unlike in AIS and PE, anticoagulation and antiplatelet medications should be administered in those with AMI receiving fibrinolytics. Following fibrinolytics, PCI is typically necessary. Fibrinolytics are recommended in patients with high-risk PE (hemodynamic instability), as they reduce the risk of mortality. The most significant complication following fibrinolytic administration includes major bleeding such as ICH, which occurs most frequently in those with AIS compared to AMI and PE. Thus, close patient monitoring is necessary following fibrinolytic administration.

CONCLUSIONS

An understanding of fibrinolytics in the ED setting is essential, including the indications, contraindications, and dosing.

Proteases, a powerful biochemical tool in the service of medicine, clinical and pharmaceutical

Proteases, enzymes that hydrolyze peptide bonds, have various applications in medicine, clinical applications, and pharmaceutical development. They are used in cancer treatment, wound debridement, contact lens cleaning, prion degradation, biofilm removal, and fibrinolytic agents. Proteases are also crucial in cardiovascular disease treatment, emphasizing the need for safe, affordable, and effective fibrinolytic drugs. Proteolytic enzymes and protease biosensors are increasingly used in diagnostic and therapeutic applications. Advanced technologies, such as nanomaterials-based sensors, are being developed to enhance the sensitivity, specificity, and versatility of protease biosensors. These biosensors are becoming effective tools for disease detection due to their precision and rapidity. They can detect extracellular and intracellular proteases, as well as fluorescence-based methods for real-time and label-free detection of virus-related proteases. The active utilization of proteolytic enzymatic biosensors is expected to expand significantly in biomedical research, in-vitro model systems, and drug development. We focused on journal articles and books published in English between 1982 and 2024 for this study.

Cutting-edge advances in nano/biomedicine: A review on transforming thrombolytic therapy

Thrombotic blockages within blood vessels give rise to critical cardiovascular disorders, including ischemic stroke, venous thromboembolism, and myocardial infarction. The current approach to the therapy of thrombolysis involves administering Plasminogen Activators (PA), but it is hindered by fast drug elimination, narrow treatment window, and the potential for bleeding complications. Leveraging nanomedicine to encapsulate and deliver PA offers a solution by improving the efficacy of therapy, safeguarding the medicine from proteinase biodegradation, and reducing unwanted effects in in vivo trials. In this review, we delve into the underlying venous as well as arterial thrombus pathophysiology and provide an overview of clinically approved PA used to address acute thrombotic conditions. We explore the existing challenges and potential directions within recent pivotal research on a variety of targeted nanocarriers, such as lipid, polymeric, inorganic, and biological carriers, designed for precise delivery of PA to specific sites. We also discuss the promising role of microbubbles and ultrasound-assisted Sono thrombolysis, which have exhibited enhanced thrombolysis in clinical studies. Furthermore, our review delves into approaches for the strategic development of nano-based carriers tailored for targeting thrombolytic action and efficient encapsulation of PA, considering the intricate interaction in biology systems as well as nanomaterials. In conclusion, the field of nanomedicine offers a valuable method for the exact and effective therapy of severe thrombus conditions, presenting a pathway toward improved patient outcomes and reduced complications.

Penicillium citrinum CFAM 521 Isolated From the Amazon Region: A Novel Source of a Fibrinolytic Enzyme

Fibrinolytic agents are essential in treating thrombosis, playing a critical role in improving survival rates in cardiovascular diseases. Microbial fibrinolytic proteases have emerged as promising alternatives due to their affordability, specificity, lower toxicity, and reduced side effects. Consequently, the search for microorganisms capable of producing these enzymes has gained significant economic importance in the pharmaceutical industry. This study reports and characterizes a novel fibrinolytic enzyme produced by Penicillium citrinum CFAM 521, a strain isolated from the Amazon region. The enzyme was purified using a polyethylene glycol (PEG)-phosphate salt aqueous two-phase system (ATPS). The effects of PEG molecular weight, PEG concentration, and phosphate concentration on the protease partition coefficient (K) were evaluated through a 22 full factorial design. The enzyme exhibited both fibrinolytic and fibrinogenolytic activities. After partitioning in a two-phase system with 10% (w/w) PEG and 15% (w/w) sodium phosphate, the fibrinolytic proteases were predominantly retained in the salt-rich bottom phase (K = 0.33). The enzyme has a molecular weight of 34 kDa, with optimal pH and temperature at 9°C and 37°C, respectively. Inhibitory analysis confirmed that it is a serine protease, and its activity was enhanced by the addition of Mn2+. Notably, the enzyme exhibited no hemolytic activity. Therefore, P. citrinum CFAM 521 represents a novel source of fibrinolytic enzymes, highlighting its potential as an alternative for the development of thrombolytic agents.

Engineered Microrobots for Targeted Delivery of Bacterial Outer Membrane Vesicles (OMV) in Thrombus Therapy

In the realm of thrombosis treatment, bioengineered outer membrane vesicles (OMVs) offer a novel and promising approach, as they have rich content of bacterial-derived components. This study centers on OMVs derived from Escherichia coli BL21 cells, innovatively engineered to encapsulate the staphylokinase-hirudin fusion protein (SFH). SFH synergizes the properties of staphylokinase (SAK) and hirudin (HV) to enhance thrombolytic efficiency while reducing the risks associated with re-embolization and bleeding. Building on this foundation, this study introduces two cutting-edge microrobotic platforms: SFH-OMV@H for venous thromboembolism (VTE) treatment, and SFH-OMV@MΦ, designed specifically for cerebral venous sinus thrombosis (CVST) therapy. These platforms have demonstrated significant efficacy in dissolving thrombi, with SFH-OMV@H showcasing precise vascular navigation and SFH-OMV@MΦ effectively targeting cerebral thrombi. The study shows that the integration of these bioengineered OMVs and microrobotic systems marks a significant advancement in thrombosis treatment, underlining their potential to revolutionize personalized medical approaches to complex health conditions.

Heterologous expression of nattokinase in E. coli: Biochemical characterization and functional analysis of fibrin binding residues

Heterologous expression of nattokinase, a potent fibrinolytic enzyme, has been successfully carried out in various microorganisms. However, the successful expression of this enzyme as a soluble protein was not achieved in E. coli. This study delves into the expression of nattokinase in E. coli as a soluble protein followed by its biochemical characterization and functional analysis for fibrinolytic activity. E. coli BL21C41 and pET32a vector host strain with pGro7 protein chaperone induced with IPTG at 16 °C 180 rpm for 16 h enabled the production of recombinant nattokinase in soluble fraction. Enzymatic assays demonstrated its protease activity, while characterization revealed optimal catalytic conditions at 37 °C and pH 8.0, with remarkable stability over a broad pH range (6.0-10.0) and up to 50 °C. The kinetic constants were determined as follows: Km = 25.83 ± 3.43 μM, Vmax = 62.91 ± 1.68 μM/s, kcat = 38.45 ± 1.06 s-1, and kcat/Km = 1.49 × 106 M-1 s-1. In addition, the fibrinolytic activity of NK, quantified by the fibrin plate hydrolysis assay was 1038 ± 156 U/ml, with a corresponding specific activity of 1730 ± 260 U/mg and the assessment of clot lysis time on an artificial clot (1 mg) was found to be 51.5 ± 2.5 min unveiling nattokinase's fibrinolytic potential. Through molecular docking, a substantial binding energy of -6.46 kcal/mol was observed between nattokinase and fibrin, indicative of a high binding affinity. Key fibrin binding residues, including Ser300, Leu302, and Asp303, were identified and confirmed. These mutants affected specifically the fibrin binding and not the proteolytic activity of NK. This comprehensive study provides crucial conditions for the expression of protein in soluble form in E. coli and biochemical properties paving the way for future research and potential applications in medicine and biotechnology.

Advances in Nano-Functional Materials in Targeted Thrombolytic Drug Delivery

Thrombotic disease has been listed as the third most fatal vascular disease in the world. After decades of development, clinical thrombolytic drugs still cannot avoid the occurrence of adverse reactions such as bleeding. A number of studies have shown that the application of various nano-functional materials in thrombus-targeted drug delivery, combined with external stimuli, such as magnetic, near-infrared light, ultrasound, etc., enrich the drugs in the thrombus site and use the properties of nano-functional materials for collaborative thrombolysis, which can effectively reduce adverse reactions such as bleeding and improve thrombolysis efficiency. In this paper, the research progress of organic nanomaterials, inorganic nanomaterials, and biomimetic nanomaterials for drug delivery is briefly reviewed.

Diverse origins of fibrinolytic enzymes: A comprehensive review

Fibrinolytic enzymes cleave fibrin which plays a crucial role in thrombus formation which otherwise leads to cardiovascular diseases. While different fibrinolytic enzymes have been purified, only a few have been utilized as clinical and therapeutic agents; hence, the search continues for a fibrinolytic enzyme with high specificity, fewer side effects, and one that can be mass-produced at a lower cost with a higher yield. In this context, this review discusses the physiological mechanism of thrombus formation and fibrinolysis, and current thrombolytic drugs in use. Additionally, an overview of the optimization, production, and purification of fibrinolytic enzymes and the role of Artificial Intelligence (AI) in optimization and the patents granted is provided. This review classifies microbial as well as non-microbial fibrinolytic enzymes isolated from food sources, including fermented foods and non-food sources, highlighting their advantages and disadvantages. Despite holding immense potential for the discovery of novel fibrinolytic enzymes, only a few fermented food sources limited to Asian countries have been studied, necessitating the research on fibrinolytic enzymes from fermented foods of other regions. This review will aid researchers in selecting optimal sources for screening fibrinolytic enzymes and is the first one to provide insights and draw a link between the implication of source selection and in vivo application.

The effect of plasmin-mediated degradation on fibrinolysis and tissue plasminogen activator diffusion

We modify a three-dimensional multiscale model of fibrinolysis to study the effect of plasmin-mediated degradation of fibrin on tissue plasminogen activator (tPA) diffusion and fibrinolysis. We propose that tPA is released from a fibrin fiber by simple kinetic unbinding, as well as by "forced unbinding," which occurs when plasmin degrades fibrin to which tPA is bound. We show that, if tPA is bound to a small-enough piece of fibrin that it can diffuse into the clot, then plasmin can increase the effective diffusion of tPA. If tPA is bound to larger fibrin degradation products (FDPs) that can only diffuse along the clot, then plasmin can decrease the effective diffusion of tPA. We find that lysis rates are fastest when tPA is bound to fibrin that can diffuse into the clot, and slowest when tPA is bound to FDPs that can only diffuse along the clot. Laboratory experiments confirm that FDPs can diffuse into a clot, and they support the model hypothesis that forced unbinding of tPA results in a mix of FDPs, such that tPA bound to FDPs can diffuse both into and along the clot. Regardless of how tPA is released from a fiber, a tPA mutant with a smaller dissociation constant results in slower lysis (because tPA binds strongly to fibrin), and a tPA mutant with a larger dissociation constant results in faster lysis.

The effect of mutation on neurotoxicity reduction of new chimeric reteplase, a computational study

Background and purpose

Excitotoxicity in nerve cells is a type of neurotoxicity in which excessive stimulation of receptors (such as N-methyl-d-aspartate glutamate receptors (NMDAR)) leads to the influx of high-level calcium ions into cells and finally cell damage or death. This complication can occur after taking some of the plasminogen activators like tissue plasminogen activator and reteplase. The interaction of the kringle2 domain in such plasminogen activator with the amino-terminal domain (ATD) of the NR1 subunit of NMDAR finally leads to excitotoxicity. In this study, we assessed the interaction of two new chimeric reteplase, mutated in the kringle2 domain, with ATD and compared the interaction of wild-type reteplase with ATD, computationally.

Experimental approach

Homology modeling, protein docking, molecular dynamic simulation, and molecular dynamics trajectory analysis were used for the assessment of this interaction.

Findings/Results

The results of the free energy analysis between reteplase and ATD (wild reteplase: -2127.516 ± 0.0, M1-chr: -1761.510 ± 0.0, M2-chr: -521.908 ± 0.0) showed lower interaction of this chimeric reteplase with ATD compared to the wild type.

Conclusion and implications

The decreased interaction between two chimeric reteplase and ATD of NR1 subunit in NMDAR which leads to lower neurotoxicity related to these drugs, can be the start of a way to conduct more tests and if the results confirm this feature, they can be considered potential drugs in acute ischemic stroke treatment.

Identification, characterization, and engineering of glycosylation in thrombolyticsa

Cardiovascular diseases, such as myocardial infarction, ischemic stroke, and pulmonary embolism, are the most common causes of disability and death worldwide. Blood clot hydrolysis by thrombolytic enzymes and thrombectomy are key clinical interventions. The most widely used thrombolytic enzyme is alteplase, which has been used in clinical practice since 1986. Another clinically used thrombolytic protein is tenecteplase, which has modified epitopes and engineered glycosylation sites, suggesting that carbohydrate modification in thrombolytic enzymes is a viable strategy for their improvement. This comprehensive review summarizes current knowledge on computational and experimental identification of glycosylation sites and glycan identity, together with methods used for their reengineering. Practical examples from previous studies focus on modification of glycosylations in thrombolytics, e.g., alteplase, tenecteplase, reteplase, urokinase, saruplase, and desmoteplase. Collected clinical data on these glycoproteins demonstrate the great potential of this engineering strategy. Outstanding combinatorics originating from multiple glycosylation sites and the vast variety of covalently attached glycan species can be addressed by directed evolution or rational design. Directed evolution pipelines would benefit from more efficient cell-free expression and high-throughput screening assays, while rational design must employ structure prediction by machine learning and in silico characterization by supercomputing. Perspectives on challenges and opportunities for improvement of thrombolytic enzymes by engineering and evolution of protein glycosylation are provided.

Population Pharmacokinetics of Tenecteplase in Patients With Acute Myocardial Infarction and Application to Patients With Acute Ischemic Stroke

The pharmacokinetics (PK) of tenecteplase in patients with acute ischemic stroke has not been extensively studied. This study aimed to describe PK characteristics of tenecteplase in patients with acute myocardial infarction (AMI) using a population PK approach and to assess applicability of the findings to patients with acute ischemic stroke by means of external validation. A population PK model was developed using nonlinear mixed-effects modeling based on the phase II TIMI 10B study in patients with AMI (785 PK observations from 103 patients). The statistical and clinical impact of selected covariates on PK parameters were evaluated by a stepwise covariate modeling procedure and simulations, respectively. The performance of the final model was evaluated for patients with acute ischemic stroke using summary statistics of tenecteplase concentrations of 75 patients from investigator-initiated study N1811s. Tenecteplase PK was well described by a 2-compartment linear model, incorporating allometric scaling of clearance and volume parameters and weight-normalized creatinine clearance on clearance. Simulations showed that the identified covariates (weight and creatinine clearance) were of limited influence on exposure at the intended dosing regimen for patients with acute ischemic stroke. The model overpredicted mean tenecteplase plasma concentrations from N1811s by 39%, but 72% of the distribution from N1811s was within the 90% prediction interval of the model predictions. The PK characteristics of tenecteplase in patients with AMI were well described by the final model. Simulations from the model indicated that no specific dose recommendations based on covariates are warranted for patients with AMI.

Safety and efficacy of low-cost alternative urokinase in acute ischemic stroke: A systematic review and meta-analysis

INTRODUCTION

Use of intravenous thrombolysis (IVT) for treatment of acute ischemic stroke (AIS) varies greatly between countries, ranging from 10% to 15% in high-income countries to less than 2% in low- and middle income countries (LMICs). This is because alteplase is expensive and has been cited as one of the most common barriers to IVT in LMICs. Urokinase (UK) is a thrombolytic agent which is almost 50 times cheaper with easier production and purification than alteplase. UK may become a cost-effective option for IVT in LMICs if it is found to be safe and effective. We conducted this study to assess the existing evidence on the safety and efficacy of UK vs alteplase for IVT in AIS.

METHODS

The study was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and meta-Analyses) guideline. Systematic literature search was done in PubMed, EMBASE, and Google Scholar for English literature published from 2010 to 2021.

RESULTS

A total of 4061 participants in the alteplase and 2062 participants in the UK group were included in the final statistical analysis. After IVT, a good functional outcome at last follow-up was found among 80.57 % of patients in the alteplase group compared to 73.79 % of patients in the UK group (OR: 1.11; 95 % CI: 0.95- 1.31; I2 = 0 %; P = 0.18). Symptomatic Intracerebral Hemorrhage (sICH) was found among 1.77 % of patients in the alteplase group compared to 2.83 % of patients in the UK group (OR: 0.84; 95 % CI: 0.56- 1.26; I2 = 0 %; P = 0.41). Similarly, mortality was found among 5.03 % of patients in the alteplase group compared to 5.42 % of patients in the UK group (OR: 0.87; 95 % CI: 0.66-1.14; I2 = 0 %; P = 0.30).

CONCLUSION

Our meta-analysis found that intravenous UK is not inferior to alteplase in terms of safety and efficacy and can be a viable alternative for IVT in AIS patients in LMICs.

A Brief Review of Thrombolytics for Venous Interventions

Anticoagulation continues to be the mainstay of therapy for the management of venous thromboembolism. However, anticoagulation does not lead to the breakdown or dissolving of the thrombus. In an acute pulmonary embolism, extensive thrombus burden can be associated with a high risk for early decompensation, and in acute deep venous thrombosis, it can be associated with an increased risk for phlegmasia. In addition, residual thrombosis can be associated with chronic thromboembolic pulmonary hypertension and postthrombotic syndrome in a chronic setting. Thrombolytic therapy is a crucial therapeutic choice in treating venous thromboembolism for thrombus resolution. Historically, it was administered systemically and was associated with high bleeding rates, particularly major bleeding, including intracranial bleeding. In the last two decades, there has been a significant increase in catheter-based therapies with and without ultrasound, where lower doses of thrombolytic agents are utilized, potentially reducing the risk for major bleeding events and improving the odds of reducing the thrombus burden. In this article, we provide an overview of several thrombolytic therapies, including delivery methods, doses, and outcomes.

2022 Update of the Consensus on the Rational Use of Antithrombotics and Thrombolytics in Veterinary Critical Care (CURATIVE) Domain 6: Defining rational use of thrombolytics

OBJECTIVES

To systematically review available evidence and establish guidelines related to the use of thrombolytics for the management of small animals with suspected or confirmed thrombosis.

DESIGN

PICO (Population, Intervention, Control, and Outcome) questions were formulated, and worksheets completed as part of a standardized and systematic literature evaluation. The population of interest included dogs and cats (considered separately) and arterial and venous thrombosis. The interventions assessed were the use of thrombolytics, compared to no thrombolytics, with or without anticoagulants or antiplatelet agents. Specific protocols for recombinant tissue plasminogen activator were also evaluated. Outcomes assessed included efficacy and safety. Relevant articles were categorized according to level of evidence, quality, and as to whether they supported, were neutral to, or opposed the PICO questions. Conclusions from the PICO worksheets were used to draft guidelines, which were subsequently refined via Delphi surveys undertaken by the Consensus on the Rational Use of Antithrombotics and Thrombolytics in Veterinary Critical Care (CURATIVE) working group.

RESULTS

Fourteen PICO questions were developed, generating 14 guidelines. The majority of the literature addressing the PICO questions in dogs is experimental studies (level of evidence 3), thus providing insufficient evidence to determine if thrombolysis improves patient-centered outcomes. In cats, literature was more limited and often neutral to the PICO questions, precluding strong evidence-based recommendations for thrombolytic use. Rather, for both species, suggestions are made regarding considerations for when thrombolytic drugs may be considered, the combination of thrombolytics with anticoagulant or antiplatelet drugs, and the choice of thrombolytic agent.

CONCLUSIONS

Substantial additional research is needed to address the role of thrombolytics for the treatment of arterial and venous thrombosis in dogs and cats. Clinical trials with patient-centered outcomes will be most valuable for addressing knowledge gaps in the field.

Use of thrombolytic agents to treat neonatal thrombosis in clinical practice

Among children, neonates have the highest incidence of thrombosis. Thrombolytic agents are used for the management of life and/or organ-threatening thrombosis. Literature on the efficacy and safety of thrombolytic agents in neonates is limited. We reviewed the evidence on dosing, administration, monitoring and treatment duration of tissue plasminogen activator (tPA), streptokinase and urokinase (URK) in neonates (≤ 28days). A systematic literature search was conducted of current databases from inception until 31 March 2021. The initial search yielded 6881 articles and 18 were retained for review. tPA, streptokinase and URK was utilized in 12, seven and four studies on 115, 51 and 16 patients, respectively. The dose range for tPA, streptokinase and URK was 0.01 -0.6 mg/kg/h, 50-2000 and 1000-0 000 units/kg/h, respectively, and treatment duration ranged from 30 min to 30 days. This is the first study to objectively summarize the efficacy and safety of thrombolytic agents in neonates. Overall, thrombolysis was associated with 87.9% complete or partial thrombus resolution and 7.4% recurrence risk. The bleeding risk associated with thrombolytic agents was 23.1% on pooled analysis, which is higher than other anticoagulants. Larger prospective studies are required to determine effective dosing regimens of these therapeutic drugs and further clarify their efficacy and safety. Blood Coagul Fibrinolysis 33:000-000 Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.

Effects of MaiLiuPian on carotid thrombosis in rats and acute pulmonary embolism in mice and its antithrombotic mechanism

Mailiupian (MLP) is a new patent functional food that consists of Crataegi Fructus, Notoginseng Radix, and Ginkgo Folium, which was reported to be active in improving the microcirculation based on formulation screening. However, whether it is effective in inhibiting thrombus and its mechanism has not been evaluated. Therefore, in the present study, the models of arterial thrombosis induced by FeCl₃ and the models of APE by ADP were established to evaluate the antithrombosis effect of MLP. Results showed that MLP markedly reduced the weight and size of wet thrombosis in FeCl₃ -induced rats and decreased the recovery time from symptoms of APE mice. MLP was proved to prolong APTT, PT, TT and improve the levels of t-PA and 6-keto-PGF_1α significantly, meanwhile, PAI-1 and TXB₂ were reduced apparently. By comparing tail bleeding time, MLP showed antithrombotic effects, but without the risk of bleeding, taking aspirin as a control. PRACTICAL APPLICATIONS: Our experiments proved that MLP, a new patent health food, acted on both coagulation and fibrinolytic systems and the platelet aggregation to play antithrombosis roles, providing a theoretical basis for applications of MLP in preventing or curing thrombosis diseases.

Comparative genomic analyses of Bacillus subtilis strains to study the biochemical and molecular attributes of nattokinases

The present research work explores the Nattokinase (NK) producing capacity of five Bacillus subtilis strains (MTCC 2616, MTCC 2756, MTCC 2451, MTCC 1427, and MTCC 7164) using soybean varieties as substrate under solid-state fermentation conditions. Subsequently, the biochemical attributes of NKs were analyzed. Soybean variety didn't affect the production of NK to a significant extent; however, the five strains differed substantially for their NK producing capacity. NK produced by MTCC 2451 (R3) showed a low Kmvalue implying its higher specificity for fibrin but this strain (MTCC 2451) didn't produce NK in sufficient quantity. The low Km of MTCC 2451 NK implicates its potential candidature for treating blood clots in cardiovascular patients. The NK produced by MTCC 2616 (R1) was produced in sufficient quantity and showed good fibrin dissolving potential. The aprN of MTCC 2616 substantially varied from the other four strains. The aprN of MTCC 2756 (R2), MTCC 2451 (R3), MTCC 1427 (R4), and MTCC 7164 (R5) shared > 99% sequence identity, but the encoded NKs had significant variations in their Km values. The biochemical-molecular analyses indicate the co-presence of three critical residues (Thr130, Asp140, and Tyr217) as a quintessential attribute in determining the low Km of NK enzymes, and the absence of any one of the three critical residues may affect (highly increase) the Km.

Rational design of a new variant of Reteplase with optimized physicochemical profile and large-scale production in Escherichia coli

Structural engineering of the recombinant thrombolytic drug, Reteplase, and its cost-effective production are important goals in the pharmaceutical industry. In this study, a single-point mutant of the protein was rationally designed and evaluated in terms of physicochemical characteristics, enzymatic activity, as well as large-scale production settings. An accurate homology model of Reteplase was used as the input to appropriate tools to identify the aggregation-prone sites, while considering the structural stability. Selected variants underwent extensive molecular dynamic simulations (total 540 ns) to assess their solvation profile and their thermal stability. The Reteplase-fibrin interaction was investigated by docking. The best variant was expressed in E. coli, and Box-Behnken design was used through response surface methodology to optimize its expression conditions. M72R mutant demonstrated appropriate stability, enhanced enzymatic activity (p < 0.05), and strengthened binding to fibrin, compared to the wild type. The optimal conditions for the variant's production in a bioreactor was shown to be 37 ºC, induction with 0.5 mM IPTG, for 2 h of incubation. Under these conditions, the final amount of the produced enzyme was increased by about 23 mg/L compared to the wild type, with an increase in the enzymatic activity by about 2 IU/mL. This study thus offered a new Reteplase variant with nearly all favorable properties, except solubility. The impact of temperature and incubation time on its large-scale production were underlined as well.

Reteplase Fc-fusions produced in N. benthamiana are able to dissolve blood clots ex vivo

Thrombolytic and fibrinolytic therapies are effective treatments to dissolve blood clots in stroke therapy. Thrombolytic drugs activate plasminogen to its cleaved form plasmin, a proteolytic enzyme that breaks the crosslinks between fibrin molecules. The FDA-approved human tissue plasminogen activator Reteplase (rPA) is a non-glycosylated protein produced in E. coli. rPA is a deletion mutant of the wild-type Alteplase that benefits from an extended plasma half-life, reduced fibrin specificity and the ability to better penetrate into blood clots. Different methods have been proposed to improve the production of rPA. Here we show for the first time the transient expression in Nicotiana benthamiana of rPA fused to the immunoglobulin fragment crystallizable (Fc) domain on an IgG1, a strategy commonly used to improve the stability of therapeutic proteins. Despite our success on the expression and purification of dimeric rPA-Fc fusions, protein instability results in high amounts of Fc-derived degradation products. We hypothesize that the "Y"- shape of dimeric Fc fusions cause steric hindrance between protein domains and leads to physical instability. Indeed, mutations of critical residues in the Fc dimerization interface allowed the expression of fully stable rPA monomeric Fc-fusions. The ability of rPA-Fc to convert plasminogen into plasmin was demonstrated by plasminogen zymography and clot lysis assay shows that rPA-Fc is able to dissolve blood clots ex vivo. Finally, we addressed concerns with the plant-specific glycosylation by modulating rPA-Fc glycosylation towards serum-like structures including α2,6-sialylated and α1,6-core fucosylated N-glycans completely devoid of plant core fucose and xylose residues.

Crocetin attenuating Urinary tract Infection and adherence of uropathogenic E. coli in NRK-52E cells via an inflammatory pathway

BACKGROUND AND OBJECTIVE

Urinary tract infections (UTI) are commonly treated with broad-spectrum antibiotics, but treatment has limitation due to causes of nephrotoxicity in uroepithelial cells. Recently, the researcher focuses their research on alternative therapy for the treatment of UTI. This study evaluated the anti-infectious effect of crocetin against adherence of pathogenic [2-¹⁴ C]-acetate labeled Escherichia coli (MTCC-729) to rat proximal renal tubular cells (NRK-52E cells) and explores the possible mechanism of action.

MATERIALS AND METHODS

In vitro cytotoxicity and radio acetate labeled tests were performed on NRK-52E cells. The rats were divided into five different groups as follows: normal control (NC), disease control (DC), and various doses of crocetin (1.25, 2.5, and 5 mg/kg) treated group rats. White blood cells in blood, urine, and bacterial colony counts were estimated at regular intervals. Pro-inflammatory cytokines, such as interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), interleukin-10 (IL-10), and interleukin-8 (IL-8), were also estimated. In the current study, we estimated the mRNA expression of toll-like receptor-4 (TLR-4) and toll-like receptor-2 (TLR-2) in the renal and bladder tissues.

RESULTS

Crocetin significantly (p < .05) inhibited the adherence of E. Coli in NRK-52E cells. Crocetin suppresses the lipid peroxidation (LPO) 42% in cells treated with H₂ O₂ cells without crocetin. The white blood cells (WBC) count in blood and urine were augmented and crocetin treatment significantly (p < .05) reduced the WBC in urine and blood. The pro-inflammatory cytokines, such as IL-6, MCP-1, IL-10, and IL-8, significantly (p < .05) increased in the DC group and crocetin significantly (p < .05) reduced the pro-inflammatory cytokines. Dose-dependent treatment of crocetin significantly reduced the mRNA expression of TLR2 and TLR4 in the renal and bladder tissues.

CONCLUSION

Crocetin considerably reduced the bacterial adherence to NRK-52E cells, attenuated the H₂ O₂ induced toxicity in NRK-52E cells and also improved the renal tubular function, and reduced the inflammatory response via altering the inflammatory and antioxidant markers.

PRACTICAL APPLICATION

As we all know that urinary tract infection is the most common disease worldwide. In this study, we scrutinized the protective effect of crocetin against urinary tract infection. Crocetin treatment considerably reduced the zone of inhibition and improved radioactivity. Crocetin significantly reduced the levels of cytokines and inflammatory mediators. Crocetin can be used as a protective drug in the treatment of urinary tract infections.

Mannose-binding lectin-associated serine protease-1 cleaves plasminogen and plasma fibronectin: prefers plasminogen over known fibrinogen substrate

Mannose-binding lectin-associated serine protease-1 (MASP-1) is known to interact with complement and coagulation pathways. Recently it was reported that MASP-1 interacts with the fibrinolytic system but details remain unclear. The objective of the study is to find MASP-1 substrates that participate in the fibrinolytic system. Commercially available fibrinogen might contain some impurities. Fibrinogen was treated with MASP-1 followed by analysis on SDS-PAGE and the obtained cleaved fragments were identified by matrix-assisted laser desorption/ionization-time of flight/time of flight. Functional analysis of identified substrate was confirmed by fluorogenic and turbidimetric assay. Statistical analysis was done by using the Student t test. This study reports that plasminogen and plasma fibronectin are two hitherto unknown substrates of MASP-1. Conversion of plasminogen to plasmin like molecule by MASP-1 was confirmed by cleavage of plasmin specific substrate and digestion of fibrin clot. The role of MASP-1 in clot dissolution was confirmed by turbidity assay. Our study shows that MASP-1 selects plasminogen over fibrinogen to be a preferable substrate. MASP-1 promotes the fibrinolytic activity by the generation of plasmin like molecule from plasminogen and further destabilizes the clot by digestion of plasma fibronectin.

Thrombolytic Enzymes of Microbial Origin: A Review

Enzyme therapies are attracting significant attention as thrombolytic drugs during the current scenario owing to their great affinity, specificity, catalytic activity, and stability. Among various sources, the application of microbial-derived thrombolytic and fibrinolytic enzymes to prevent and treat vascular occlusion is promising due to their advantageous cost-benefit ratio and large-scale production. Thrombotic complications such as stroke, myocardial infarction, pulmonary embolism, deep venous thrombosis, and peripheral occlusive diseases resulting from blood vessel blockage are the major cause of poor prognosis and mortality. Given the ability of microbial thrombolytic enzymes to dissolve blood clots and prevent any adverse effects, their use as a potential thrombolytic therapy has attracted great interest. A better understanding of the hemostasis and fibrinolytic system may aid in improving the efficacy and safety of this treatment approach over classical thrombolytic agents. Here, we concisely discuss the physiological mechanism of thrombus formation, thrombo-, and fibrinolysis, thrombolytic and fibrinolytic agents isolated from bacteria, fungi, and algae along with their mode of action and the potential application of microbial enzymes in thrombosis therapy.

Fucoidan-functionalized polysaccharide submicroparticles loaded with alteplase for efficient targeted thrombolytic therapy

Intravenous administration of fibrinolytic drugs is the standard treatment of acute thrombotic diseases. However, current fibrinolytics exhibit limited clinical efficacy because of their short plasma half-lives and might trigger hemorrhagic transformations. Therefore, it is mandatory to develop innovative nanomedicine-based solutions for more efficient and safer thrombolysis with biocompatible and biodegradable thrombus-targeted nanocarrier. Herein, fucoidan-functionalized hydrogel polysaccharide submicroparticles with high biocompatibility are elaborated by the inverse miniemulsion/crosslinking method. They are loaded with the gold standard fibrinolytic - alteplase - to direct site-specific fibrinolysis due to nanomolar interactions between fucoidan and P-selectin overexpressed on activated platelets and endothelial cells in the thrombus area. The thrombus targeting properties of these particles are validated in a microfluidic assay containing recombinant P-selectin and activated platelets under arterial and venous blood shear rates as well as in vivo. The experiments on the murine model of acute thromboembolic ischemic stroke support this product's therapeutic efficacy, revealing a faster recanalization rate in the middle cerebral artery than with free alteplase, which reduces post-ischemic cerebral infarct lesions and blood-brain barrier permeability. Altogether, this proof-of-concept study demonstrates the potential of a biomaterial-based targeted nanomedicine for the precise treatment of acute thrombotic events, such as ischemic stroke.

Biopharmaceutical quality control with mass spectrometry

Mass spectrometry (MS) is a powerful technique for protein identification, quantification and characterization that is widely applied in biochemical studies, and which can provide data on the quantity, structural integrity and post-translational modifications of proteins. It is therefore a versatile and widely used analytic tool for quality control of biopharmaceuticals, especially in quantifying host-cell protein impurities, identifying post-translation modifications and structural characterization of biopharmaceutical proteins. Here, we summarize recent advances in MS-based analyses of these key quality attributes of the biopharmaceutical development and manufacturing processes.

Use of Exogenous Enzymes in Human Therapy: Approved Drugs and Potential Applications

The development of safe and efficacious enzyme-based human therapies has increased greatly in the last decades, thanks to remarkable advances in the understanding of the molecular mechanisms responsible for different diseases, and the characterization of the catalytic activity of relevant exogenous enzymes that may play a remedial effect in the treatment of such pathologies. Several enzyme-based biotherapeutics have been approved by FDA (the U.S. Food and Drug Administration) and EMA (the European Medicines Agency) and many are undergoing clinical trials. Apart from enzyme replacement therapy in human genetic diseases, which is not discussed in this review, approved enzymes for human therapy find applications in several fields, from cancer therapy to thrombolysis and the treatment, e.g., of clotting disorders, cystic fibrosis, lactose intolerance and collagen-based disorders. The majority of therapeutic enzymes are of microbial origin, the most convenient source due to fast, simple and cost-effective production and manipulation. The use of microbial recombinant enzymes has broadened prospects for human therapy but some hurdles such as high immunogenicity, protein instability, short half-life and low substrate affinity, still need to be tackled. Alternative sources of enzymes, with reduced side effects and improved activity, as well as genetic modification of the enzymes and novel delivery systems are constantly searched. Chemical modification strategies, targeted- and/or nanocarrier-mediated delivery, directed evolution and site-specific mutagenesis, fusion proteins generated by genetic manipulation are the most explored tools to reduce toxicity and improve bioavailability and cellular targeting. This review provides a description of exogenous enzymes that are presently employed for the therapeutic management of human diseases with their current FDA/EMA-approved status, along with those already experimented at the clinical level and potential promising candidates.

The promising shadow of microbubble over medical sciences: from fighting wide scope of prevalence disease to cancer eradication

Microbubbles are typically 0.5-10 μm in size. Their size tends to make it easier for medication delivery mechanisms to navigate the body by allowing them to be swallowed more easily. The gas included in the microbubble is surrounded by a membrane that may consist of biocompatible biopolymers, polymers, surfactants, proteins, lipids, or a combination thereof. One of the most effective implementation techniques for tiny bubbles is to apply them as a drug carrier that has the potential to activate ultrasound (US); this allows the drug to be released by US. Microbubbles are often designed to preserve and secure medicines or substances before they have reached a certain area of concern and, finally, US is used to disintegrate microbubbles, triggering site-specific leakage/release of biologically active drugs. They have excellent therapeutic potential in a wide range of common diseases. In this article, we discussed microbubbles and their advantageous medicinal uses in the treatment of certain prevalent disorders, including Parkinson's disease, Alzheimer's disease, cardiovascular disease, diabetic condition, renal defects, and finally, their use in the treatment of various forms of cancer as well as their incorporation with nanoparticles. Using microbubble technology as a novel carrier, the ability to prevent and eradicate prevalent diseases has strengthened the promise of effective care to improve patient well-being and life expectancy.

Hemorrhagic Transformation in Ischemic Stroke and the Role of Inflammation

Hemorrhagic transformation (HT) is a common complication in patients with acute ischemic stroke. It occurs when peripheral blood extravasates across a disrupted blood brain barrier (BBB) into the brain following ischemic stroke. Preventing HT is important as it worsens stroke outcome and increases mortality. Factors associated with increased risk of HT include stroke severity, reperfusion therapy (thrombolysis and thrombectomy), hypertension, hyperglycemia, and age. Inflammation and the immune system are important contributors to BBB disruption and HT and are associated with many of the risk factors for HT. In this review, we present the relationship of inflammation and immune activation to HT in the context of reperfusion therapy, hypertension, hyperglycemia, and age. Differences in inflammatory pathways relating to HT are discussed. The role of inflammation to stratify the risk of HT and therapies targeting the immune system to reduce the risk of HT are presented.

Systematic Analysis of Combined Thrombolysis Using Ultrasound and Different Fibrinolytic Drugs in an in Vitro Clot Model of Intracerebral Hemorrhage

Adequate removal of blood clots by minimally invasive surgery seems to correlate with a better clinical outcome in patients with intracerebral hemorrhages (ICHs). Moreover, neurotoxic effects of recombinant tissue plasminogen activator have been reported. The aim of this study was to improve fibrinolysis using an intra-clot ultrasound application with tenecteplase and urokinase in our established ICH clot model. One hundred thirty clots were produced from 25 or 50 mL of human blood, incubated for different periods and equipped with drainage, through which an ultrasound catheter was placed in 65 treatment clots for 1 h, randomly allocated into three groups: administration of ultrasound, administration of 60 IU of tenecteplase or administration of 30,000 IU urokinase. Relative end weights were compared. This study found a significant increase in thrombolysis caused by a combination of ultrasound and fibrinolytic drugs, whereas ultrasound and tenecteplase are significantly more effective in the treatment of larger and aged clots.

Study on the activity of recombinant mutant tissue-type plasminogen activator fused with the C-terminal fragment of hirudin

In the present study, bifunctional fusion proteins were designed by fusing the kringle 2 and protease domains of tissue-type plasminogen activator (tPA) to the C-terminal fragment of hirudin. The thrombolytic and anticoagulant activities of these recombinant proteins from mammalian cells were investigated using in vitro coagulation models and chromogenic assays. The results showed that all assayed tPA mutants retained catalytic activity. The C-terminal fragment of hirudin may have weak affinity to thrombin and thus was insufficient to suppress thrombin-mediated fibrin agglutination. The strength of the thrombolytic activity only relied on the selected tPA sequences, and the fibrinolytic efficiency of single-chain protein significantly decreased. Our data indicate that truncated tPA combined with a hirudin peptide may provide a framework for the further development of a new antithrombotic agent.

Fibrinolytic-Facilitated Chronic Subdural Hematoma Drainage-A Systematic Review

BACKGROUND

The current treatment options for chronic subdural hematoma (CSDH) include burr hole drainage, twist drill drainage, and craniotomy with or without postoperative catheter drainage. Although generally effective, these treatments have continued to be complicated by recurrence, especially in partially hemolyzed or septated hematomas. Recently, interest in the use of fibrinolytic agents as an adjunct to surgical treatment to address this limitation has been increasing. We conducted a systematic review, focusing on the efficacy and safety profile of fibrinolytic agents and compared the different fibrinolytic agents.

METHODS

The PubMed, EMBASE, CINAHL Plus, and Cochrane Library databases were searched for trials relevant to fibrinolytic administration in the treatment of CSDH. The findings are reported in accordance with the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. The data from 1702 subjects from 6 retrospective observational studies were qualitatively analyzed. In addition, we included 11 case series and reports for discussion.

RESULTS

For 1449 patients, the use of urokinase or tissue plasminogen activator improved hematoma drainage and shortened the hospital stay (7.04 days), with an overall hematoma recurrence rate of 1.59%. The incidence of infection, seizure, and intracranial bleeding was 3.18%, 0.80%, and 0.41%, respectively, which compared favorably with previously reported findings for surgical drainage without the use of fibrinolytic agents.

CONCLUSIONS

The routine use of intrathecal urokinase and tissue plasminogen activator could be a new direction in the management of CSDH. Conclusive clinical evidence is lacking, however, and further prospective controlled studies are warranted to confirm the benefit and safety of this treatment strategy and to identify the optimal agent and dosing regimen.

Effects of Arteriovenous Thrombolysis Combined with Mechanical Thrombectomy on Efficacy and Neurological Function of Acute Cerebral Infarct Patients

Objective

To investigate the effects of arteriovenous thrombolysis combined with mechanical thrombectomy on clinical efficacy, neurological function, and the changes of nerve injury markers of acute cerebral infarct (ACI) patients.

Methods

A total of 143 cases with ACI admitted to our hospital from June 2017 to June 2019 were elected as research subjects. Among them, 69 cases of patients who received treatment of arteriovenous thrombolysis were considered as group A, and 74 cases of patients who received treatment of arteriovenous thrombolysis combined with mechanical thrombectomy were considered as group B. NIHSS score, clinical efficacy, vascular recanalization, adverse reactions, hemodynamics, neurological injury indexes, duration of coma, length of hospital stay, and prognosis of patients in the two groups were compared.

Results

After treatment, the NIHSS score of group A was higher than that of group B (P < 0.05), the clinical efficacy of group B was better than that of group A, and the incidence of adverse reactions was lower than that of group A (P < 0.05). There was no difference in vascular recanalization rate, duration of coma, and prognosis between the two groups (P > 0.05). Length of hospital stay, maximum peak velocity after treatment (Vs), and mean flow rate (Vm) of group A were lower than those of group B, while vascular resistance index (RI), pulsatility index (PI), serum glutamic acid (Glu), neuron-specific enolase (NES), and S100β protein detected by enzyme-linked immunosorbent assay (ELISA) of group A were higher than those of group B (P < 0.05).

Conclusion

Arteriovenous thrombolysis combined with mechanical thrombectomy has a significant effect on ACI, with high safety and quick effect. In addition, it has a stronger effect on improving and protecting the neurological function of patients, which is worth promoting in clinical practice.

Microbial Modulation of Coagulation Disorders in Venous Thromboembolism

Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is the third leading cause of cardiovascular death in the world. Important risk factors of thrombosis include bed restraint, surgery, major trauma, long journeys, inflammation, pregnancy, and oral contraceptives, previous venous thromboembolism, cancer, and bacterial infections. Sepsis increases the risk of blood clot formation 2–20 times. In this review, we discussed various mechanisms related to the role of bacteria in venous thrombosis also taking into consideration the role of the human microbiome. Many known bacteria, such as Helicobacter pylori, Chlamydia pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, and Escherichia coli, causing infections may increase the risk of thrombotic complications through platelet activation or may lead to an inflammatory reaction involving the fibrinolytic system. Additionally, the bacteria participate in the production of factors causing or increasing the risk of cardiovascular diseases. An example can be trimethylamine N-oxide (TMAO) but also uremic toxins (indoxyl sulfate), short-chain fatty acids (SCFA) phytoestrogens, and bile acids. Finally, we presented the involvement of many bacteria in the development of venous thromboembolism and other cardiovascular diseases.

Fibrinolytic protease from Bacillus cereus S46: Purification, characterization, and evaluation of its in vitro thrombolytic potential

Intravascular thrombosis is a prime cause of cardiac complications worldwide. Microbial fibrinolytic proteases are of clinical significance in thrombosis treatment. The present study discusses the purification and characterization of a protease from Bacillus cereus S46, ascertaining its in vitro thrombolytic activity against a blood clot. By the three-step purification involving precipitation, dialysis, and diethylaminoethyl-cellulose ion-exchange chromatography, a 12.37-fold purification of the enzyme to homogeneity was achieved. The apparent molecular mass of the protease was 30 kDa, as found by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The optimum activity of the enzyme was observed at pH 8.0 and 40°C. The enzyme retained an 82.19% residual activity at pH 8.0 and 40°C for 1 h. The K_m and V_max values of the protease with casein were 0.0027 mM and 9.712 µmol/min, respectively. In an in vitro assay, the purified protease resulted in 97.02% lysis of the blood clot. The fibrinolytic potential of the enzyme, together with its characteristics of being active and stable under near-physiological conditions, may suggest its application as a therapeutic agent.

Erythrocytes as Carriers of Therapeutic Enzymes

Therapeutic enzymes are administered for the treatment of a wide variety of diseases. They exert their effects through binding with a high affinity and specificity to disease-causing substrates to catalyze their conversion to a non-noxious product, to induce an advantageous physiological change. However, the metabolic and clinical efficacies of parenterally or intramuscularly administered therapeutic enzymes are very often limited by short circulatory half-lives and hypersensitive and immunogenic reactions. Over the past five decades, the erythrocyte carrier has been extensively studied as a strategy for overcoming these limitations and increasing therapeutic efficacy. This review examines the rationale for the different therapeutic strategies that have been applied to erythrocyte-mediated enzyme therapy. These strategies include their application as circulating bioreactors, targeting the monocyte-macrophage system, the coupling of enzymes to the surface of the erythrocyte and the engineering of CD34+ hematopoietic precursor cells for the expression of therapeutic enzymes. An overview of the diverse biomedical applications for which they have been investigated is also provided, including the detoxification of exogenous chemicals, thrombolytic therapy, enzyme replacement therapy for metabolic diseases and antitumor therapy.

Urokinase Plasminogen Activator: A Potential Thrombolytic Agent for Ischaemic Stroke

Stroke continues to be one of the leading causes of mortality and morbidity worldwide. Restoration of cerebral blood flow by recombinant plasminogen activator (rtPA) with or without mechanical thrombectomy is considered the most effective therapy for rescuing brain tissue from ischaemic damage, but this requires advanced facilities and highly skilled professionals, entailing high costs, thus in resource-limited contexts urokinase plasminogen activator (uPA) is commonly used as an alternative. This literature review summarises the existing studies relating to the potential clinical application of uPA in ischaemic stroke patients. In translational studies of ischaemic stroke, uPA has been shown to promote nerve regeneration and reduce infarct volume and neurological deficits. Clinical trials employing uPA as a thrombolytic agent have replicated these favourable outcomes and reported consistent increases in recanalisation, functional improvement and cerebral haemorrhage rates, similar to those observed with rtPA. Single-chain zymogen pro-urokinase (pro-uPA) and rtPA appear to be complementary and synergistic in their action, suggesting that their co-administration may improve the efficacy of thrombolysis without affecting the overall risk of haemorrhage. Large clinical trials examining the efficacy of uPA or the combination of pro-uPA and rtPA are desperately required to unravel whether either therapeutic approach may be a safe first-line treatment option for patients with ischaemic stroke. In light of the existing limited data, thrombolysis with uPA appears to be a potential alternative to rtPA-mediated reperfusive treatment due to its beneficial effects on the promotion of revascularisation and nerve regeneration.

Design and production of new chimeric reteplase with enhanced fibrin affinity: a theoretical and experimental study

Plasminogen activators (PAs) are widely used for treatment of disorders caused by clot formation. Fibrin specific PAs are safe drugs from this group because of reducing the incidence of hemorrhage. The newer generation of PAs like tenecteplase, reteplase and desmoteplase were designed with the aim of achieving desirable properties such as improving specificity and affinity to fibrin and increasing half-life. Protein engineering and using of theoretical methods can help to rational and reliable design of new PAs with a set of favorable properties. In the present study, two new chimeric reteplase named M1-chr and M2-chr were designed with the aim of enhancing fibrin affinity also some potential properties include of increasing resistance to plasminogen activator inhibitor-1 and decreasing neurotoxicity. So, finger domain of desmoteplase was added to reteplase as a high fibrin specific domain. Some other point mutations were considering to achieve other mentioned properties. Three dimensional structure of wild-type reteplase and mutants were created by homology modeling and were evaluated by molecular dynamic simulation. Then, mutants docked to fibrin by HADDOCK web tools. Result of theoretical section verified the stability of mutants' structures. Also showed better interaction between M1-chr with fibrin than M2-chr. Wild-type and mutants were produced in bacterial expression system. Experimental assessment showed both mutants have appropriate enzymatic activity also 1.9-fold fibrin binding ability compared to wild-type. Therefore, this study offers new thrombolytic drugs with desirable properties specially enhanced fibrin affinity so they can represent a promising future in cost-effective production of favorable thrombolytic drugs.Communicated by Ramaswamy H. Sarma.

Intracameral tenecteplase during phacoemulsification in rabbits: clinical assessment of the anterior segment and biochemical analysis of the aqueous humor

Abstract To evaluate the use of tenecteplase in transoperative phacoemulsification in healthy rabbits, the study was carried out with fifteen New Zealand rabbits, divided into three groups: control group (CG), untreated group (UG) and treated group (TG). UG and TG were operated by phacoemulsification and TG received 50 µg / 0.3 mL of intracameral tenecteplase. The postoperative evaluations were 24 h, 72 h, 7 days, 15 days and 21 days. In TP21 the animals were submitted to euthanasia and aqueous humor samples were collected. No significant differences were observed in the clinical evaluations between CG and TG in relation to incidence rates of intraocular pressure (IOP), corneal edema, fibrin deposits, hyphema, aqueous flare and synechia. In the physicochemical evaluation of the aqueous humor, there were no significant differences between the three groups in relation to pH values and concentrations of chloride ions. The aqueous humor density values were statistically different between CG and the other groups. In the histological evaluation, there were no significant differences between the groups. The use of tenecteplase in transoperative phacoemulsification in rabbits did not present significant differences in terms of clinical, physicochemical and histological parameters.

Comparison of urokinase and reteplase thrombolytic treatment in patients with high-risk pulmonary embolism

Thrombolytic treatment is recommended for patients with high-risk pulmonary embolism. The present study compared thrombolytic therapy with urokinase and reteplase. A total of 37 patients presenting with acute high-risk pulmonary embolism at the Intensive Care Unit of Weinan Central Hospital of Shaanxi Province (Weinan, China) between June 2013 and January 2017 were retrospectively analyzed. According to their treatment, these subjects were assigned to the reteplase group (n=16) or the urokinase group (n=21). Systolic blood pressure (SBP), heart rate (HR) and respiratory rate (RR) were recorded prior to, and at 2, 4, 24 and 48 h after thrombolytic therapy. Complications, including bleeding, were closely monitored. Changes in blood gas analysis, troponin-T (TNT), pro-B-type natriuretic peptide (pro-BNP) and D-dimer (D-D) were observed. In the reteplase and urokinase group, 11 and 13 cases exhibited marked improvement, treatment was rated as effective in 4 and 6 cases, and 1 and 2 mortalities occurred, resulting in an overall effective rate of 93.8 and 90.5%, respectively (P>0.05). In the reteplase group, one patient was unsuccessfully resuscitated and died. In the urokinase group, one patient died of gastric hemorrhage after 22 h of thrombolysis, while another patient died of brain failure resuscitation. The treatment improved the SBP in each of the two groups (P<0.05), and this outcome was similar between these two groups (P>0.05). HR and RR were similar prior to and after thrombolytic therapy (P>0.05). In contrast to the urokinase group, TNT was significantly decreased after thrombolyis compared with the baseline in the reteplase group. Complications in the reteplase group were higher, but in contrast to the urokinase group, no life-threatening bleeding occurred. Although reteplase is as effective as urokinase in treating high-risk pulmonary embolism, reteplase may reduce myocardial damage.

Bacterial staphylokinase as a promising third-generation drug in the treatment for vascular occlusion

Vascular occlusion is one of the major causes of mortality and morbidity. Blood vessel blockage can lead to thrombotic complications such as myocardial infarction, stroke, deep venous thrombosis, peripheral occlusive disease, and pulmonary embolism. Thrombolytic therapy currently aims to rectify this through the administration of recombinant tissue plasminogen activator. Research is underway to design an ideal thrombolytic drug with the lowest risk. Despite the potent clot lysis achievable using approved thrombolytic drugs such as alteplase, reteplase, streptokinase, tenecteplase, and some other fibrinolytic agents, there are some drawbacks, such as high production cost, systemic bleeding, intracranial hemorrhage, vessel re-occlusion by platelet-rich and retracted secondary clots, and non-fibrin specificity. In comparison, bacterial staphylokinase, is a new, small-size plasminogen activator, unlike bacterial streptokinase, it hinders the systemic degradation of fibrinogen and reduces the risk of severe hemorrhage. A fibrin-bound plasmin-staphylokinase complex shows high resistance to a₂-antiplasmin-related inhibition. Staphylokinase has the potential to be considered as a promising thrombolytic agent with properties of cost-effective production and the least side effects.

Structural Biology and Protein Engineering of Thrombolytics

Myocardial infarction and ischemic stroke are the most frequent causes of death or disability worldwide. Due to their ability to dissolve blood clots, the thrombolytics are frequently used for their treatment. Improving the effectiveness of thrombolytics for clinical uses is of great interest. The knowledge of the multiple roles of the endogenous thrombolytics and the fibrinolytic system grows continuously. The effects of thrombolytics on the alteration of the nervous system and the regulation of the cell migration offer promising novel uses for treating neurodegenerative disorders or targeting cancer metastasis. However, secondary activities of thrombolytics may lead to life-threatening side-effects such as intracranial bleeding and neurotoxicity. Here we provide a structural biology perspective on various thrombolytic enzymes and their key properties: (i) effectiveness of clot lysis, (ii) affinity and specificity towards fibrin, (iii) biological half-life, (iv) mechanisms of activation/inhibition, and (v) risks of side effects. This information needs to be carefully considered while establishing protein engineering strategies aiming at the development of novel thrombolytics. Current trends and perspectives are discussed, including the screening for novel enzymes and small molecules, the enhancement of fibrin specificity by protein engineering, the suppression of interactions with native receptors, liposomal encapsulation and targeted release, the application of adjuvants, and the development of improved production systems.

Site-specific PEGylation of micro-plasmin for improved thrombolytic therapy through engineering enhanced resistance against serpin mediated inhibition

The relatively rapid inhibition of microplasmin by α₂-AP leads to short functional half-life of the molecule in vivo, causing inefficient clot dissolution, even after site-specific, local catheter-based delivery. Here, we describe a PEGylation approach for improving the therapeutic potential via improving the survival of microplasmin in presence of its cognate inhibitor, α₂-AP, wherein a series of strategically designed cysteine analogs of micro-plasminogen were prepared and expressed in E. coli, and further modified by covalent grafting in vitro with PEG groups of different molecular sizes so as to select single or double PEG chains that increase the molecular weight and hydrodynamic radii of the conjugates, but with a minimal discernible effect on intrinsic plasmin activity and structural framework, as explored by amidolytic activity and CD-spectroscopy, respectively. Interestingly, some of the purified PEG-coupled proteins after conversion to their corresponding proteolytically active forms were found to exhibit significantly reduced inhibition rates (up to 2-fold) by α₂-AP relative to that observed with wild-type microplasmin. These results indicate an interesting, and not often observed, effect of PEG groups through reduced/altered dynamics between protease and inhibitor, likely through a steric hindrance mechanism. Thus, the present study successfully identifies single- and double-site PEGylated muteins of microplasmin with significantly enhanced functional half-life through enhanced resistance to inactivation by its in vivo plasma inhibitor. Such an increased survival of bioactivity in situ, holds unmistakable potential for therapeutic exploitation, especially in ischemic strokes where a direct, catheter-based deposition within the cranium has been shown to be promising, but is currently limited by the very short in vivo bioactive half-life of the fibrin dissolving agent/s.