1
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Ghasemi SH, Ahmadian MT, Assempour A. Computational modeling of blood clot lysis considering the effect of vessel wall and pulsatile blood flow. Phys Rev E 2023; 108:034403. [PMID: 37849169 DOI: 10.1103/physreve.108.034403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 08/01/2023] [Indexed: 10/19/2023]
Abstract
Stroke is one of the major causes of global death, which can occur due to blockage in a blood vessel by a clot. The immediate dissolving of the clot is essential to restore the blood flow and prevent tissue necrosis. Clot dissolution can be achieved via thrombolytic therapy using plasminogen activators. In this study, a clot dissolution model is developed for a three-dimensional patient-specific carotid artery that investigates the effect of different vessel wall models on clot dissolution. The lysis pattern of the clot and hemodynamics of blood flow are evaluated using three different models of the vessel wall, namely, rigid, linear elastic, and Mooney-Rivlin hyperelastic. The effect of flow condition is considered by solving the Navier-Stokes equations for the free flow domain and the Brinkman equation for the clot domain with the same pressure and velocity fields. This will result in continuous pressure and velocity over the interfaces of the free flow and clot domains. The blood inflow is assumed to be pulsatile. In addition, the species transport driven by diffusion and convection is considered to be different in the porous medium and plasma. The obtained results show that in all models, the starting time of clot volume decrease is almost the same and the clot starts dissolving from the inner curvature of the artery. However, in the hyperelastic model, dissolving the clot takes longer compared to the other two models. By monitoring the vessel wall deformation, the exact time of vessel recanalization is determined.
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Affiliation(s)
| | | | - Ahmad Assempour
- School of Mechanical Engineering, Sharif University of Technology, Tehran 14588-89694, Iran
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2
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Lyubenov L, Shi C, Zhao D, Yang L, Lei Y, Mammadova-Bach E, de Chiara L, Semeraro R, Landini S, Romagnani P, Vörg E, Devarapu SK, Welz R, Kiessig ST, Anders HJ. Intravenous Glu-plasminogen attenuates cholesterol crystal embolism-induced thrombotic angiopathy, acute kidney injury and kidney infarction. Nephrol Dial Transplant 2023; 38:93-105. [PMID: 36102665 DOI: 10.1093/ndt/gfac273] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND Cholesterol crystal (CC) embolism causes acute kidney injury (AKI) and ischaemic cortical necrosis associated with high mortality. We speculated that sustaining the fibrinolytic system with Glu-plasminogen (Glu-Plg) could be a safe way to attenuate AKI and prevent ischaemic infarction upon CC embolism. METHODS We induced CC embolism by injecting CC into the left kidney artery of C57BL/6J mice. The primary endpoint was glomerular filtration rate (GFR). RESULTS Starting as early as 2 h after CC embolism, thrombotic angiopathy progressed gradually in the interlobular, arcuate and interlobar arteries. This was associated with a decrease of GFR reaching a peak at 18 h, i.e. AKI, and progressive ischaemic kidney necrosis developing between 12-48 h after CC injection. Human plasma Glu-Plg extracts injected intravenously 4 h after CC embolism attenuated thrombotic angiopathy, GFR loss as well as ischaemic necrosis in a dose-dependent manner. No bleeding complications occurred after Glu-Plg injection. Injection of an intermediate dose (0.6 mg/kg) had only a transient protective effect on microvascular occlusions lasting for a few hours without a sustained protective effect on AKI at 18-48 h or cortical necrosis, while 1.5 mg/kg were fully protective. Importantly, no bleeding complications occurred. CONCLUSIONS These results provide the first experimental evidence that Glu-Plg could be an innovative therapeutic strategy to attenuate thrombotic angiopathy, AKI, kidney necrosis and potentially other clinical manifestations of CC embolism syndrome.
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Affiliation(s)
- Lyuben Lyubenov
- Department of Medicine IV, Hospital of Ludwig-Maximilian-University, Munich, Germany
| | - Chongxu Shi
- Department of Medicine IV, Hospital of Ludwig-Maximilian-University, Munich, Germany
| | - Danyang Zhao
- Department of Medicine IV, Hospital of Ludwig-Maximilian-University, Munich, Germany
| | - Luying Yang
- Department of Medicine IV, Hospital of Ludwig-Maximilian-University, Munich, Germany
| | - Yutian Lei
- Department of Medicine IV, Hospital of Ludwig-Maximilian-University, Munich, Germany
| | - Elmina Mammadova-Bach
- Department of Medicine IV, Hospital of Ludwig-Maximilian-University, Munich, Germany.,Walther-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilian-University, Munich, Germany
| | - Letizia de Chiara
- Department of Experimental and Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy
| | - Roberto Semeraro
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Samuela Landini
- Medical Genetics Unit, Meyer Children's University Hospital, Florence, Italy
| | - Paola Romagnani
- Department of Experimental and Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy.,Nephrology and Dialysis Unit, Meyer Children's University Hospital, Florence, Italy
| | - Elena Vörg
- PreviPharma Consulting GmbH, Mannheim, Germany
| | | | | | | | - Hans-Joachim Anders
- Department of Medicine IV, Hospital of Ludwig-Maximilian-University, Munich, Germany
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3
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Microscale structural changes of individual fibrin fibers during fibrinolysis. Acta Biomater 2022; 141:114-122. [PMID: 35007782 PMCID: PMC8898298 DOI: 10.1016/j.actbio.2022.01.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 12/31/2021] [Accepted: 01/04/2022] [Indexed: 02/06/2023]
Abstract
Fibrinolysis is the enzymatic digestion of fibrin, the primary structural component in blood clots. Mechanisms of fibrin fiber digestion during lysis have long been debated and obtaining detailed structural knowledge of these processes is important for developing effective clinical approaches to treat ischemic stroke and pulmonary embolism. Using dynamic fluorescence microscopy, we studied the time-resolved digestion of individual fibrin fibers by the fibrinolytic enzyme plasmin. We found that plasmin molecules digest fibers along their entire lengths, but that the rates of digestion are non-uniform, resulting in cleavage at a single location along the fiber. Using mathematical modeling we estimated the rate of plasmin arrival at the fiber surface and the number of digestion sites on a fiber. We also investigated correlations between local fiber digestion rates, cleavage sites, and fiber properties such as initial thickness. Finally, we uncovered a previously unknown tension-dependent mechanism that pulls fibers apart during digestion. Taken together these results promote a paradigm shift in understanding mechanisms of fibrinolysis and underscore the need to consider fibrin tension when assessing fibrinolytic approaches. STATEMENT OF SIGNIFICANCE: We developed a method for interrogating lysis of individual fibrin fibers, enabling the time-resolved observation of individual fiber digestion for the first time. Our results resolve longstanding disagreements about fibrinolytic processes and reveal previously unknown mechanisms that also play a role. Also, we developed the first microscale mathematical model of plasmin-fibrin interaction, which predicts the number of plasmin molecules on each fiber and can serve as a framework for investigating novel therapeutics.
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4
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Undas A, Natorska J. Improving fibrinolysis in venous thromboembolism: impact of fibrin structure. Expert Rev Hematol 2019; 12:597-607. [PMID: 31159611 DOI: 10.1080/17474086.2019.1627193] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Introduction. Fibrinolysis is of key importance in maintaining vessel patency. Impaired fibrinolysis associated with more compact fibrin structure has been shown in patients with venous thromboembolism (VTE), including deep-vein thrombosis and pulmonary embolism (PE). Currently, recombinant or modified plasminogen activators are the only commonly available thrombolytic agents. However, they are fraught with side effects and suboptimal effectiveness. Areas covered. Based on the available literature, the current evidence linking fibrinolysis with VTE and potential therapeutic targets among fibrinolysis proteins are presented. Expert opinion. Prolonged clot lysis time has been reported as a new predictor of first-time and recurrent VTE, including PE. Anticoagulant therapy, including non-vitamin K antagonist oral anticoagulants, has a favorable impact on fibrinolysis in VTE patients. Several VTE risk factors are also related to lower efficiency of fibrinolysis and their treatment improve fibrinolysis, in part by alterations to fibrin properties. There is an increasing number of studies aiming at developing novel profibrinolytic therapeutic agents for treatment of VTE patients, mostly targeting the antifibrinolytic proteins, i.e. antiplasmin, plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor.
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Affiliation(s)
- Anetta Undas
- a Institute of Cardiology, Jagiellonian University Medical College , Kraków , Poland
| | - Joanna Natorska
- a Institute of Cardiology, Jagiellonian University Medical College , Kraków , Poland
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5
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Pieters M, Wolberg AS. Fibrinogen and fibrin: An illustrated review. Res Pract Thromb Haemost 2019; 3:161-172. [PMID: 31011700 PMCID: PMC6462751 DOI: 10.1002/rth2.12191] [Citation(s) in RCA: 149] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 01/30/2019] [Indexed: 12/19/2022] Open
Abstract
Since its discovery over 350 years ago, studies of fibrinogen have revealed remarkable characteristics. Its complex structure as a large (340 kDa) hexameric homodimer supports complex roles in hemostasis and homeostasis. Fibrinogen synthesis is regulated at the transcriptional and translational levels, undergoing both constitutive (basal) secretion from liver, and inducible upregulation in response to inflammatory events. In addition, alternative splicing yields fibrinogen variants with unique properties and contributions to coagulation biochemistry. During coagulation, fibrinogen conversion to fibrin occurs via thrombin‐mediated proteolytic cleavage that produces intermediate protofibrils and then mature fibers that provide remarkable biochemical and mechanical stability to clots. Fibrin formation, structure, and stability are regulated by various genetic, biochemical, and environmental factors, allowing for dynamic kinetics of fibrin formation and structure. Interactions between fibrinogen and/or fibrin and plasma proteins and receptors on platelets, leukocytes, endothelial cells, and other cells enable complex functions in hemostasis, thrombosis, pregnancy, inflammation, infection, cancer, and other pathologies. Disorders in fibrinogen concentration and/or function increase risk of bleeding, thrombosis, and infection. This illustrated review covers fundamental aspects of fibrinogen and fibrin biology, biochemistry, biophysics, epidemiology, and clinical applications. Continued efforts to enhance our understanding of fibrinogen and fibrin in these processes are likely to advance treatment and prevention of many human diseases.
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Affiliation(s)
- Marlien Pieters
- Center of Excellence for Nutrition North-West University Potchefstroom South Africa
| | - Alisa S Wolberg
- Department of Pathology and Laboratory Medicine University of North Carolina Chapel Hill North Carolina
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6
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Tutwiler V, Peshkova AD, Le Minh G, Zaitsev S, Litvinov RI, Cines DB, Weisel JW. Blood clot contraction differentially modulates internal and external fibrinolysis. J Thromb Haemost 2019; 17:361-370. [PMID: 30582674 DOI: 10.1111/jth.14370] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Indexed: 01/16/2023]
Abstract
Essentials Clot contraction influences the rate of fibrinolysis in vitro. Internal fibrinolysis is enhanced ∼2-fold in contracted vs. uncontracted blood clots. External fibrinolysis is ∼4-fold slower in contracted vs. uncontracted blood clots. Contraction can modulate lytic resistance and potentially the clinical outcome of thrombosis. SUMMARY: Background Fibrinolysis involves dissolution of polymeric fibrin networks that is required to restore blood flow through vessels obstructed by thrombi. The efficiency of lysis depends in part on the susceptibility of fibrin to enzymatic digestion, which is governed by the structure and spatial organization of fibrin fibers. How platelet-driven clot contraction affects the efficacy of fibrinolysis has received relatively little study. Objective Here, we examined the effects of clot contraction on the rate of internal fibrinolysis emanating from within the clot to simulate (patho)physiological conditions and external fibrinolysis initiated from the clot exterior to simulate therapeutic thrombolysis. Methods Clot contraction was prevented by inhibiting platelet myosin IIa activity, actin polymerization or platelet-fibrin(ogen) binding. Internal fibrinolysis was measured by optical tracking of clot size. External fibrinolysis was determined by the release of radioactive fibrin degradation products. Results and Conclusions Clot contraction enhanced the rate of internal fibrinolysis ∼2-fold. In contrast, external fibrinolysis was ~4-fold slower in contracted clots. This dichotomy in the susceptibility of contracted and uncontracted clots to internal vs. external lysis suggests that the rate of lysis is dependent upon the interplay between accessibility of fibrin fibers to fibrinolytic agents, including clot permeability, and the spatial proximity of the fibrin fibers that modulate the effects of the fibrinolytic enzymes. Understanding how compaction of blood clots influences clot lysis might have important implications for prevention and treatment of thrombotic disorders.
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Affiliation(s)
- Valerie Tutwiler
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Alina D Peshkova
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russian Federation
| | - Giang Le Minh
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russian Federation
| | - Sergei Zaitsev
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Rustem I Litvinov
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russian Federation
| | - Douglas B Cines
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - John W Weisel
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
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7
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Urano T, Castellino FJ, Suzuki Y. Regulation of plasminogen activation on cell surfaces and fibrin. J Thromb Haemost 2018; 16:S1538-7836(22)02204-8. [PMID: 29779246 PMCID: PMC6099326 DOI: 10.1111/jth.14157] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Indexed: 01/27/2023]
Abstract
The fibrinolytic system dissolves fibrin and maintains vascular patency. Recent advances in imaging analyses allowed visualization of the spatiotemporal regulatory mechanism of fibrinolysis, as well as its regulation by other plasma hemostasis cofactors. Vascular endothelial cells (VECs) retain tissue-type plasminogen activator (tPA) after secretion and maintain high plasminogen (plg) activation potential on their surfaces. As in plasma, the serpin, plasminogen activator inhibitor type 1 (PAI-1), regulates fibrinolytic potential via inhibition of the VEC surface-bound plg activator, tPA. Once fibrin is formed, plg activation by tPA is initiated and effectively amplified on the surface of fibrin, and fibrin is rapidly degraded. The specific binding of plg and tPA to lytic edges of partly degraded fibrin via newly generated C-terminal lysine residues, which amplifies fibrin digestion, is a central aspect of this pathophysiological mechanism. Thrombomodulin (TM) plays a role in the attenuation of plg binding on fibrin and the associated fibrinolysis, which is reversed by a carboxypeptidase B inhibitor. This suggests that the plasma procarboxypeptidase B, thrombin-activatable fibrinolysis inhibitor (TAFI), which is activated by thrombin bound to TM on VECs, is a critical aspect of the regulation of plg activation on VECs and subsequent fibrinolysis. Platelets also contain PAI-1, TAFI, TM, and the fibrin cross-linking enzyme, factor (F) XIIIa, and either secrete or expose these agents upon activation in order to regulate fibrinolysis. In this review, the native machinery of plg activation and fibrinolysis, as well as their spatiotemporal regulatory mechanisms, as revealed by imaging analyses, are discussed.
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Affiliation(s)
- T. Urano
- Department of Medical PhysiologyHamamatsu University School of MedicineHamamatsuJapan
| | - F. J. Castellino
- W.M. Keck Center for Transgene ResearchUniversity of Notre DameUniversity of Notre DameNotre DameINUSA
| | - Y. Suzuki
- Department of Medical PhysiologyHamamatsu University School of MedicineHamamatsuJapan
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8
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Pitek AS, Wang Y, Gulati S, Gao H, Stewart PL, Simon DI, Steinmetz NF. Elongated Plant Virus-Based Nanoparticles for Enhanced Delivery of Thrombolytic Therapies. Mol Pharm 2017; 14:3815-3823. [PMID: 28881141 DOI: 10.1021/acs.molpharmaceut.7b00559] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Thrombotic cardiovascular disease, including acute myocardial infarction, ischemic stroke, and venous thromboembolic disease, is the leading cause of morbidity and mortality worldwide. While reperfusion therapy with thrombolytic agents reduces mortality from acute myocardial infarction and disability from stroke, thrombolysis is generally less effective than mechanical reperfusion and is associated with fatal intracerebral hemorrhage in up to 2-5% of patients. To address these limitations, we propose the tobacco mosaic virus (TMV)-based platform technology for targeted delivery of thrombolytic therapies. TMV is a plant virus-based nanoparticle with a high aspect ratio shape measuring 300 × 18 nm. These soft matter nanorods have favorable flow and margination properties allowing the targeting of the diseased vessel wall. We have previously shown that TMV homes to thrombi in a photochemical mouse model of arterial thrombosis. Here we report the synthesis of TMV conjugates loaded with streptokinase (STK). Various TMV-STK formulations were produced through bioconjugation of STK to TMV via intervening PEG linkers. TMV-STK was characterized using SDS-PAGE and Western blot, transmission electron microscopy, cryo-electron microscopy, and cryo-electron tomography. We investigated the thrombolytic activity of TMV-STK in vitro using static phantom clots, and in a physiologically relevant hydrodynamic model of shear-induced thrombosis. Our findings demonstrate that conjugation of STK to the TMV surface does not compromise the activity of STK. Moreover, the nanoparticle conjugate significantly enhances thrombolysis under flow conditions, which can likely be attributed to TMV's shape-mediated flow properties resulting in enhanced thrombus accumulation and dissolution. Together, these data suggest TMV to be a promising platform for the delivery of thrombolytics to enhance clot localization and potentially minimize bleeding risk.
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Affiliation(s)
- Andrzej S Pitek
- Department of Biomedical Engineering, Case Western Reserve University , Cleveland, Ohio 44106, United States
| | - Yunmei Wang
- Harrington Heart and Vascular Institute, Case Cardiovascular Research Institute, Department of Medicine, University Hospitals Case Medical Center and Case Western Reserve University School of Medicine , Cleveland, Ohio 44106, United States
| | - Sahil Gulati
- Department of Pharmacology, Case Western Reserve University , Cleveland, Ohio 44106, United States.,Cleveland Center for Membrane and Structural Biology, Case Western Reserve University , Cleveland, Ohio 44106, United States
| | - Huiyun Gao
- Harrington Heart and Vascular Institute, Case Cardiovascular Research Institute, Department of Medicine, University Hospitals Case Medical Center and Case Western Reserve University School of Medicine , Cleveland, Ohio 44106, United States
| | - Phoebe L Stewart
- Department of Pharmacology, Case Western Reserve University , Cleveland, Ohio 44106, United States.,Cleveland Center for Membrane and Structural Biology, Case Western Reserve University , Cleveland, Ohio 44106, United States
| | - Daniel I Simon
- Harrington Heart and Vascular Institute, Case Cardiovascular Research Institute, Department of Medicine, University Hospitals Case Medical Center and Case Western Reserve University School of Medicine , Cleveland, Ohio 44106, United States
| | - Nicole F Steinmetz
- Department of Biomedical Engineering, Case Western Reserve University , Cleveland, Ohio 44106, United States.,Department of Radiology, Case Western Reserve University , Cleveland, Ohio 44106, United States.,Department of Materials Science and Engineering, Case Western Reserve University , Cleveland, Ohio 44106, United States.,Department of Macromolecular Science and Engineering, Case Western Reserve University , Cleveland, Ohio 44106, United States.,Case Comprehensive Cancer Center, Division of General Medical Sciences-Oncology, Case Western Reserve University , Cleveland, Ohio 44106, United States
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9
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Bannish BE, Chernysh IN, Keener JP, Fogelson AL, Weisel JW. Molecular and Physical Mechanisms of Fibrinolysis and Thrombolysis from Mathematical Modeling and Experiments. Sci Rep 2017; 7:6914. [PMID: 28785035 PMCID: PMC5547096 DOI: 10.1038/s41598-017-06383-w] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 06/12/2017] [Indexed: 11/20/2022] Open
Abstract
Despite the common use of thrombolytic drugs, especially in stroke treatment, there are many conflicting studies on factors affecting fibrinolysis. Because of the complexity of the fibrinolytic system, mathematical models closely tied with experiments can be used to understand relationships within the system. When tPA is introduced at the clot or thrombus edge, lysis proceeds as a front. We developed a multiscale model of fibrinolysis that includes the main chemical reactions: the microscale model represents a single fiber cross-section; the macroscale model represents a three-dimensional fibrin clot. The model successfully simulates the spatial and temporal locations of all components and elucidates how lysis rates are determined by the interplay between the number of tPA molecules in the system and clot structure. We used the model to identify kinetic conditions necessary for fibrinolysis to proceed as a front. We found that plasmin regulates the local concentration of tPA through forced unbinding via degradation of fibrin and tPA release. The mechanism of action of tPA is affected by the number of molecules present with respect to fibrin fibers. The physical mechanism of plasmin action (crawling) and avoidance of inhibition is defined. Many of these new findings have significant implications for thrombolytic treatment.
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Affiliation(s)
- Brittany E Bannish
- University of Central Oklahoma, Department of Mathematics and Statistics, Edmond, OK, 73034, USA.
| | - Irina N Chernysh
- University of Pennsylvania School of Medicine, Department of Cell and Developmental Biology, Philadelphia, PA, 19104, USA
| | - James P Keener
- University of Utah, Departments of Mathematics and Bioengineering, Salt Lake City, UT, 84112-0090, USA
| | - Aaron L Fogelson
- University of Utah, Departments of Mathematics and Bioengineering, Salt Lake City, UT, 84112-0090, USA
| | - John W Weisel
- University of Pennsylvania School of Medicine, Department of Cell and Developmental Biology, Philadelphia, PA, 19104, USA
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10
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Bohorquez H, Seal JB, Cohen AJ, Kressel A, Bugeaud E, Bruce DS, Carmody IC, Reichman TW, Battula N, Alsaggaf M, Therapondos G, Bzowej N, Tyson G, Joshi S, Nicolau-Raducu R, Girgrah N, Loss GE. Safety and Outcomes in 100 Consecutive Donation After Circulatory Death Liver Transplants Using a Protocol That Includes Thrombolytic Therapy. Am J Transplant 2017; 17:2155-2164. [PMID: 28276658 DOI: 10.1111/ajt.14261] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 02/14/2017] [Accepted: 02/22/2017] [Indexed: 02/06/2023]
Abstract
Donation after circulatory death (DCD) liver transplantation (LT) reportedly yields inferior survival and increased complication rates compared with donation after brain death (DBD). We compare 100 consecutive DCD LT using a protocol that includes thrombolytic therapy (late DCD group) to an historical DCD group (early DCD group n = 38) and a cohort of DBD LT recipients (DBD group n = 435). Late DCD LT recipients had better 1- and 3-year graft survival rates than early DCD LT recipients (92% vs. 76.3%, p = 0.03 and 91.4% vs. 73.7%, p = 0.01). Late DCD graft survival rates were comparable to those of the DBD group (92% vs. 93.3%, p = 0.24 and 91.4% vs. 88.2%, p = 0.62). Re-transplantation occurred in 18.4% versus 1% for the early and late DCD groups, respectively (p = 0.001). Patient survival was similar in all three groups. Ischemic-type biliary lesions (ITBL) occurred in 5%, 3%, and 0.2% for early DCD, late DCD, and DBD groups, respectively, but unlike in the early DCD group, in the late DCD group ITBL was endoscopically managed and resolved in each case. Using a protocol that includes a thrombolytic therapy, DCD LT yielded patient and graft survival rates comparable to DBD LT.
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Affiliation(s)
- H Bohorquez
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - J B Seal
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - A J Cohen
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - A Kressel
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA
| | - E Bugeaud
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA
| | - D S Bruce
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA
| | - I C Carmody
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - T W Reichman
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA
| | - N Battula
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA
| | - M Alsaggaf
- School of Medicine, University of Queensland, New Orleans, LA
| | - G Therapondos
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - N Bzowej
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - G Tyson
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - S Joshi
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - R Nicolau-Raducu
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA
| | - N Girgrah
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
| | - G E Loss
- Multi-Organ Transplant Institute, Ochsner Clinic Foundation, New Orleans, LA.,School of Medicine, University of Queensland, New Orleans, LA
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11
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Hudson NE. Biophysical Mechanisms Mediating Fibrin Fiber Lysis. BIOMED RESEARCH INTERNATIONAL 2017; 2017:2748340. [PMID: 28630861 PMCID: PMC5467299 DOI: 10.1155/2017/2748340] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 04/30/2017] [Indexed: 01/19/2023]
Abstract
The formation and dissolution of blood clots is both a biochemical and a biomechanical process. While much of the chemistry has been worked out for both processes, the influence of biophysical properties is less well understood. This review considers the impact of several structural and mechanical parameters on lytic rates of fibrin fibers. The influences of fiber and network architecture, fiber strain, FXIIIa cross-linking, and particle transport phenomena will be assessed. The importance of the mechanical aspects of fibrinolysis is emphasized, and future research avenues are discussed.
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Affiliation(s)
- Nathan E. Hudson
- Department of Physics, East Carolina University, N304 Howell Science Complex, Greenville, NC 27858, USA
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12
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Carlon TA, Sudheendra D. Interventional Therapy for Upper Extremity Deep Vein Thrombosis. Semin Intervent Radiol 2017; 34:54-60. [PMID: 28265130 DOI: 10.1055/s-0036-1597764] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Approximately 10% of all deep vein thromboses occur in the upper extremity, and that number is increasing due to the use of peripherally inserted central catheters. Sequelae of upper extremity deep vein thrombosis (UEDVT) are similar to those for lower extremity deep vein thrombosis (LEDVT) and include postthrombotic syndrome and pulmonary embolism. In addition to systemic anticoagulation, there are multiple interventional treatment options for UEDVT with the potential to reduce the incidence of these sequelae. To date, there have been no randomized trials to define the optimal management strategy for patients presenting with UEDVT, so many conclusions are drawn from smaller, single-center studies or from LEDVT research. In this article, the authors describe the evidence for the currently available treatment options and an approach to a patient with acute UEDVT.
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Affiliation(s)
- Timothy A Carlon
- Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Deepak Sudheendra
- Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania
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13
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Translational initiatives in thrombolytic therapy. Front Med 2017; 11:1-19. [DOI: 10.1007/s11684-017-0497-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 10/10/2016] [Indexed: 01/26/2023]
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14
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Abstract
Fibrinogen and fibrin are essential for hemostasis and are major factors in thrombosis, wound healing, and several other biological functions and pathological conditions. The X-ray crystallographic structure of major parts of fibrin(ogen), together with computational reconstructions of missing portions and numerous biochemical and biophysical studies, have provided a wealth of data to interpret molecular mechanisms of fibrin formation, its organization, and properties. On cleavage of fibrinopeptides by thrombin, fibrinogen is converted to fibrin monomers, which interact via knobs exposed by fibrinopeptide removal in the central region, with holes always exposed at the ends of the molecules. The resulting half-staggered, double-stranded oligomers lengthen into protofibrils, which aggregate laterally to make fibers, which then branch to yield a three-dimensional network. Much is now known about the structural origins of clot mechanical properties, including changes in fiber orientation, stretching and buckling, and forced unfolding of molecular domains. Studies of congenital fibrinogen variants and post-translational modifications have increased our understanding of the structure and functions of fibrin(ogen). The fibrinolytic system, with the zymogen plasminogen binding to fibrin together with tissue-type plasminogen activator to promote activation to the active proteolytic enzyme, plasmin, results in digestion of fibrin at specific lysine residues. In spite of a great increase in our knowledge of all these interconnected processes, much about the molecular mechanisms of the biological functions of fibrin(ogen) remains unknown, including some basic aspects of clotting, fibrinolysis, and molecular origins of fibrin mechanical properties. Even less is known concerning more complex (patho)physiological implications of fibrinogen and fibrin.
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Affiliation(s)
- John W Weisel
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
| | - Rustem I Litvinov
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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Piebalgs A, Xu XY. Towards a multi-physics modelling framework for thrombolysis under the influence of blood flow. J R Soc Interface 2016; 12:20150949. [PMID: 26655469 PMCID: PMC4707866 DOI: 10.1098/rsif.2015.0949] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Thrombolytic therapy is an effective means of treating thromboembolic diseases but can also give rise to life-threatening side effects. The infusion of a high drug concentration can provoke internal bleeding while an insufficient dose can lead to artery reocclusion. It is hoped that mathematical modelling of the process of clot lysis can lead to a better understanding and improvement of thrombolytic therapy. To this end, a multi-physics continuum model has been developed to simulate the dissolution of clot over time upon the addition of tissue plasminogen activator (tPA). The transport of tPA and other lytic proteins is modelled by a set of reaction–diffusion–convection equations, while blood flow is described by volume-averaged continuity and momentum equations. The clot is modelled as a fibrous porous medium with its properties being determined as a function of the fibrin fibre radius and voidage of the clot. A unique feature of the model is that it is capable of simulating the entire lytic process from the initial phase of lysis of an occlusive thrombus (diffusion-limited transport), the process of recanalization, to post-canalization thrombolysis under the influence of convective blood flow. The model has been used to examine the dissolution of a fully occluding clot in a simplified artery at different pressure drops. Our predicted lytic front velocities during the initial stage of lysis agree well with experimental and computational results reported by others. Following canalization, clot lysis patterns are strongly influenced by local flow patterns, which are symmetric at low pressure drops, but asymmetric at higher pressure drops, which give rise to larger recirculation regions and extended areas of intense drug accumulation.
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Affiliation(s)
- Andris Piebalgs
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, UK
| | - X Yun Xu
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, UK
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Amino-Terminal Fusion of Epidermal Growth Factor 4,5,6 Domains of Human Thrombomodulin on Streptokinase Confers Anti-Reocclusion Characteristics along with Plasmin-Mediated Clot Specificity. PLoS One 2016; 11:e0150315. [PMID: 26974970 PMCID: PMC4790962 DOI: 10.1371/journal.pone.0150315] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 02/11/2016] [Indexed: 11/23/2022] Open
Abstract
Streptokinase (SK) is a potent clot dissolver but lacks fibrin clot specificity as it activates human plasminogen (HPG) into human plasmin (HPN) throughout the system leading to increased risk of bleeding. Another major drawback associated with all thrombolytics, including tissue plasminogen activator, is the generation of transient thrombin and release of clot-bound thrombin that promotes reformation of clots. In order to obtain anti-thrombotic as well as clot-specificity properties in SK, cDNAs encoding the EGF 4,5,6 domains of human thrombomodulin were fused with that of streptokinase, either at its N- or C-termini, and expressed these in Pichia pastoris followed by purification and structural-functional characterization, including plasminogen activation, thrombin inhibition, and Protein C activation characteristics. Interestingly, the N-terminal EGF fusion construct (EGF-SK) showed plasmin-mediated plasminogen activation, whereas the C-terminal (SK-EGF) fusion construct exhibited ‘spontaneous’ plasminogen activation which is quite similar to SK i.e. direct activation of systemic HPG in absence of free HPN. Since HPN is normally absent in free circulation due to rapid serpin-based inactivation (such as alpha-2-antiplasmin and alpha-2-Macroglobin), but selectively present in clots, a plasmin-dependent mode of HPG activation is expected to lead to a desirable fibrin clot-specific response by the thrombolytic. Both the N- and C-terminal fusion constructs showed strong thrombin inhibition and Protein C activation properties as well, and significantly prevented re-occlusion in a specially designed assay. The EGF-SK construct exhibited fibrin clot dissolution properties with much-lowered levels of fibrinogenolysis, suggesting unmistakable promise in clot dissolver therapy with reduced hemorrhage and re-occlusion risks.
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Jiang Y, Fan X, Yu Z, Liao Z, Wang XS, van Leyen K, Sun X, Lo EH, Wang X. Combination Low-Dose Tissue-Type Plasminogen Activator Plus Annexin A2 for Improving Thrombolytic Stroke Therapy. Front Cell Neurosci 2015; 9:397. [PMID: 26528130 PMCID: PMC4604305 DOI: 10.3389/fncel.2015.00397] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 09/22/2015] [Indexed: 01/14/2023] Open
Abstract
Risk of hemorrhagic transformation, incomplete reperfusion, neurotoxicity, and a short treatment time window comprises major challenges for tissue plasminogen activator (tPA) thrombolytic stroke therapy. Improving tPA therapy has become one of the highest priorities in the stroke field. This mini review article focuses on our recent efforts aimed at evaluating a novel combination approach of low-dose tPA plus recombinant annexin A2 (rA2, a tPA, and plasminogen co-receptor), which might enhance tPA thrombolytic efficacy, while reducing its associated complications related to intracerebral hemorrhagic transformation. Results of our experimental studies using a focal embolic stroke model in rats support the feasibility of the combination approach and suggest the potential for successful clinical translation.
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Affiliation(s)
- Yinghua Jiang
- Department of Neurosurgery, The First Affiliated Hospital, Chongqing Medical University , Chongqing , China ; Neuroscience Program, Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA
| | - Xiang Fan
- Neuroscience Program, Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA ; Research Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine , Tianjin , China
| | - Zhanyang Yu
- Neuroscience Program, Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA
| | - Zhengbu Liao
- Department of Neurosurgery, The First Affiliated Hospital, Chongqing Medical University , Chongqing , China ; Neuroscience Program, Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA
| | - Xiao-Shu Wang
- Department of Neurosurgery, The First Affiliated Hospital, Chongqing Medical University , Chongqing , China ; Neuroscience Program, Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA
| | - Klaus van Leyen
- Neuroscience Program, Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA
| | - Xiaochuan Sun
- Department of Neurosurgery, The First Affiliated Hospital, Chongqing Medical University , Chongqing , China
| | - Eng H Lo
- Neuroscience Program, Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA
| | - Xiaoying Wang
- Neuroscience Program, Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA
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Rehan M, Sagar A, Sharma V, Mishra S, Ashish, Sahni G. Penta-L-lysine Potentiates Fibrin-Independent Activity of Human Tissue Plasminogen Activator. J Phys Chem B 2015; 119:13271-7. [PMID: 26447340 DOI: 10.1021/acs.jpcb.5b07735] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The therapeutic action of tissue plasminogen activator (t-PA) is a two-step process: (1) binding to lysine-rich fibrin (Km event) and (2) converting local plasminogen into plasmin (Kcat event). Overcoming limitations of other structural biophysics methods, we wanted to employ small-angle X-ray scattering (SAXS) to visualize what shape changes occur/accompany t-PA activation, but the prime hurdle was the polydisperse nature of the fibrin, which occluded scattering information from t-PA. Earlier, larger polylysine peptides have been used to potentiate activation of t-PA, so while screening short polylysine peptides as alternatives to fibrin or larger peptides, we found that penta-polylysine (P5) specifically activates t-PA in a dose-dependent manner, averaging to almost 3-fold more than in the absence of any peptide. SAXS data analysis confirmed that P5 does not induce association of t-PA molecules, and a narrower peak profile of the Kratky plot indicated that P5 binding quenches inherent motion in t-PA. Shape reconstruction of t-PA ∓ P5 revealed that P5 closes the "gap" between the two gross domains of t-PA, viz. fused F/E, K1 and K2 domains, and the P domain. Docking experiments suggested that, while other polylysine peptides preferentially interacted with the surfaces of kringle domains, P5 "slipped into" the gap/groove between K2 and P domains, thereby mediating a substantial increase in the number of long-range interactions between the K2 domain and exosites in the P domain. We report here dissection of shape events involved in between Km/Kcat steps of t-PA activation, which can pave the way toward the search for small molecule function regulator(s) of t-PA.
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Affiliation(s)
- Mohammad Rehan
- CSIR-Institute of Microbial Technology , Sector 39-A, Chandigarh, 160036, India
| | - Amin Sagar
- CSIR-Institute of Microbial Technology , Sector 39-A, Chandigarh, 160036, India
| | - Vandna Sharma
- CSIR-Institute of Microbial Technology , Sector 39-A, Chandigarh, 160036, India
| | - Sanskruti Mishra
- CSIR-Institute of Microbial Technology , Sector 39-A, Chandigarh, 160036, India
| | - Ashish
- CSIR-Institute of Microbial Technology , Sector 39-A, Chandigarh, 160036, India
| | - Girish Sahni
- CSIR-Institute of Microbial Technology , Sector 39-A, Chandigarh, 160036, India
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Abstract
Fibrinolysis appears in many diverse physiological situations, and the components of the system are well established, along with mechanistic details for the individual reactions and some high-resolution structures. Key questions in understanding the regulation of fibrinolysis surround mechanisms of initiation and propagation, the localization of fibrinolysis reactions to the fibrin clot, and the influence of fibrin structure and clot composition on thrombolysis. This review covers these key areas with a focus on recent developments on fibrin structure and binding, the effects of a variety of cell types, the consequences of histones and DNA released by neutrophils, and the influence of flow. A complete understanding of the regulation of fibrinolysis will come from the building of detailed mathematical models. Suitable models are at an early stage of development, but may improve as model clots increase in complexity to incorporate the components and interactions listed above.
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Affiliation(s)
- C Longstaff
- Biotherapeutics, Haemostasis Section, National Institute for Biological Standards and Control, South Mimms, Potters Bar, UK
| | - K Kolev
- Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary
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Zhang Z, Lin L, Zhang J, Zhang Q, Zhao N, Wu L, Chen J, Wu Z, Wu G, Lin J, Chen Y, Xu Y. Thrombolytic and Antiplatelet Effects of a Novel Plasminogen Activator from the Venom of Gloydius Brevicaudus Viper. J Atheroscler Thromb 2015; 22:1080-90. [PMID: 26004931 DOI: 10.5551/jat.27649] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
AIM To investigate the thrombolytic and antiplatelet effects of a novel plasminogen activator from the venom of the Gloydius brevicaudus viper (GBV-PA) in vitro and in vivo. METHODS Thrombolytic experiments were performed in rabbit models of ear vein thrombosis and carotid artery thrombosis and in dog model of acute cerebral infarction. Inhibition of thrombus formation was evaluated in rat inferior vena cava thrombosis model and ferric chloride-induced arterial thrombosis. In vitro, we assayed the antithrombotic effect of GBV-PA on rabbit blood clots, euglobulin lysis time (ELT) of rabbit plasma, and ADP-induced platelet aggregation. RESULTS GBV-PA intravenous administration significantly reduced vascular recanalization times of rabbit ear veins thrombosis and thrombus weight of rabbit carotid artery thrombosis. The arterial recanalization rates were dose- and time-dependently improved after the administration of GBV-PA in canine acute cerebral infarction model. Thrombus length and weight were significantly reduced by GBV-PA both in rat inferior vena cava and ferric chloride-induced arterial thrombosis models. Thrombus formation in the blood of rabbits that were administered of GBV-PA was also inhibited. GBV-PA radically reduced plasma ELT of the rabbit's blood clots. ADP-induced platelet aggregation was inhibited by GBV-PA in a dose-dependent manner with a half-maximal inhibitory concentration of 19.9 μg/mL. CONCLUSION This study demonstrates that GBV-PA is a thrombolytic and antiplatelet agent. It has significant antithrombotic effects on various in vitro and in vivo experimental models of thrombosis. The mechanisms that underline its antithrombotic effects were related to GBV-PA's capabilities of increasing fibrinolytic activity and inhibition of platelet aggregation.
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Seal JB, Bohorquez H, Reichman T, Kressel A, Ghanekar A, Cohen A, McGilvray ID, Cattral MS, Bruce D, Greig P, Carmody I, Grant D, Selzner M, Loss G. Thrombolytic protocol minimizes ischemic-type biliary complications in liver transplantation from donation after circulatory death donors. Liver Transpl 2015; 21:321-8. [PMID: 25545787 DOI: 10.1002/lt.24071] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 11/13/2014] [Accepted: 11/17/2014] [Indexed: 12/31/2022]
Abstract
Liver transplantation (LT) with donation after circulatory death (DCD) donors has been associated with a high rate of ischemic-type biliary strictures (ITBSs) and inferior graft survival. To investigate the impact of an intraoperative tissue plasminogen activator (tPA) on outcomes following DCD LT, we conducted a retrospective analysis of DCD LT at the Toronto General Hospital (TGH) and the Ochsner Medical Center (OMC). Between 2009 and 2013, 85 DCD LTs were performed with an intraoperative tPA injection (n = 30 at TGH, n = 55 at OMC), and they were compared with 33 DCD LTs without a tPA. Donor and recipient characteristics were similar in the 2 groups. There was no significant difference in the intraoperative packed red blood cell transfusion requirement (3.2 ± 3.4 versus 3.1 ± 2.3 U, P = 0.74). Overall, biliary strictures occurred less commonly in the tPA-treated group (16.5% versus 33.3%, P = 0.07) with a much lower rate of diffuse intrahepatic strictures (3.5% versus 21.2%, P = 0.005). After 1 and 3 years, the tPA group versus the non-tPA group had superior patient survival (97.6% versus 87.0% and 92.7% versus 79.7%, P = 0.016) and graft survival (96.4% versus 69.7% and 90.2% versus 63.6%, P < 0.001). In conclusion, a tPA injection into the hepatic artery during DCD LT reduces ITBSs and improves graft and patient survival without increasing the risk for bleeding.
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Affiliation(s)
- John B Seal
- Multi-Organ Transplant Program, Department of Surgery, Toronto General Hospital, University of Toronto, Toronto, Canada
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Howard M, Zern BJ, Anselmo AC, Shuvaev VV, Mitragotri S, Muzykantov V. Vascular targeting of nanocarriers: perplexing aspects of the seemingly straightforward paradigm. ACS NANO 2014; 8:4100-32. [PMID: 24787360 PMCID: PMC4046791 DOI: 10.1021/nn500136z] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 04/30/2014] [Indexed: 05/18/2023]
Abstract
Targeted nanomedicine holds promise to find clinical use in many medical areas. Endothelial cells that line the luminal surface of blood vessels represent a key target for treatment of inflammation, ischemia, thrombosis, stroke, and other neurological, cardiovascular, pulmonary, and oncological conditions. In other cases, the endothelium is a barrier for tissue penetration or a victim of adverse effects. Several endothelial surface markers including peptidases (e.g., ACE, APP, and APN) and adhesion molecules (e.g., ICAM-1 and PECAM) have been identified as key targets. Binding of nanocarriers to these molecules enables drug targeting and subsequent penetration into or across the endothelium, offering therapeutic effects that are unattainable by their nontargeted counterparts. We analyze diverse aspects of endothelial nanomedicine including (i) circulation and targeting of carriers with diverse geometries, (ii) multivalent interactions of carrier with endothelium, (iii) anchoring to multiple determinants, (iv) accessibility of binding sites and cellular response to their engagement, (v) role of cell phenotype and microenvironment in targeting, (vi) optimization of targeting by lowering carrier avidity, (vii) endocytosis of multivalent carriers via molecules not implicated in internalization of their ligands, and (viii) modulation of cellular uptake and trafficking by selection of specific epitopes on the target determinant, carrier geometry, and hydrodynamic factors. Refinement of these aspects and improving our understanding of vascular biology and pathology is likely to enable the clinical translation of vascular endothelial targeting of nanocarriers.
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Affiliation(s)
- Melissa Howard
- Center for Targeted Therapeutics and Translational Nanomedicine, Institute for Translational Medicine & Therapeutics and Department of Pharmacology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, United States
| | - Blaine J. Zern
- Center for Targeted Therapeutics and Translational Nanomedicine, Institute for Translational Medicine & Therapeutics and Department of Pharmacology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, United States
| | - Aaron C. Anselmo
- Department of Chemical Engineering, Center for Bioengineering, University of California, Santa Barbara, California 93106, United States
| | - Vladimir V. Shuvaev
- Center for Targeted Therapeutics and Translational Nanomedicine, Institute for Translational Medicine & Therapeutics and Department of Pharmacology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, United States
| | - Samir Mitragotri
- Department of Chemical Engineering, Center for Bioengineering, University of California, Santa Barbara, California 93106, United States
| | - Vladimir Muzykantov
- Center for Targeted Therapeutics and Translational Nanomedicine, Institute for Translational Medicine & Therapeutics and Department of Pharmacology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, United States
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Bizjak N, Bajd F, Vidmar J, Blinc A, Perme MP, Marder VJ, Novokhatny V, Serša I. Direct microscopic monitoring of initial and dynamic clot lysis using plasmin or rt-PA in an in vitro flow system. Thromb Res 2014; 133:908-13. [PMID: 24613694 DOI: 10.1016/j.thromres.2014.02.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 01/03/2014] [Accepted: 02/13/2014] [Indexed: 10/25/2022]
Abstract
INTRODUCTION Plasmin is a direct-acting thrombolytic agent with a favorable safety profile upon intra-arterial delivery in pre-clinical and phase I studies. However, the thrombolytic efficacy of plasmin, relative to that of rt-PA, remains to be established. We have compared the dynamics of clot lysis with plasmin or rt-PA in an in vitro perfusion system, in which thrombolytic agent is administered locally, allowed to induce lysis for short intervals, then washed with plasma in a re-circulation circuit. MATERIALS AND METHODS Whole blood human clots were prepared in observation chambers, exposed to plasmin or rt-PA at equimolar concentrations (1.2/1.0, 1.8/1.5 and 2.4/2.0 mg/ml) for measured intervals of time, followed by perfusion with human plasma. Clot size was monitored by digital analysis of sequential photographs obtained through an optical microscope. RESULTS Plasma perfusion after incubation with thrombolytic agent rapidly removed superficial clot fragments. This initial decrease in clot size was greater with plasmin than with rt-PA when tested at the highest concentrations of agent (0.63 ± 0.11 vs. 0.30 ± 0.11, p=0.001 for clots with non-cross-linked fibrin and 0.53 ± 0.15 vs. 0.14 ± 0.15, p=0.02, for clots with cross-linked-fibrin). Subsequent clot lysis during plasma flow was greater after prior incubation with rt-PA. Longer incubation times of plasmin resulted in larger portions of the clot being washed free. Repeated plasmin incubations and plasma perfusions of a clot successfully induced stepwise reductions in clot size. CONCLUSIONS Initial clot lysis is greater with direct exposure using plasmin than rt-PA. During washout and circulation with plasma, rt-PA induced continued clot lysis, while plasmin lysis was curtailed, presumably because of plasmin inhibition.
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Affiliation(s)
| | | | - Jernej Vidmar
- Institute of Physiology, Medical Faculty of Ljubljana, Slovenia
| | - Aleš Blinc
- Department of Vascular Diseases, University of Ljubljana Medical Center, Slovenia
| | - Maja Pohar Perme
- Institute of Biomedical Informatics, Medical Faculty of Ljubljana, Slovenia
| | - Victor J Marder
- Division of Hematology/Medical Oncology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | | | - Igor Serša
- Jožef Stefan Institute, Ljubljana, Slovenia; EN-FIST Centre of Excellence, Ljubljana, Slovenia.
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A novel mechanism controlling the growth of hemostatic thrombi. UKRAINIAN BIOCHEMICAL JOURNAL 2013. [DOI: 10.15407/ubj85.06.094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Abstract
Despite continued achievements in antithrombotic pharmacotherapy, difficulties remain in managing patients at high risk for both thrombosis and hemorrhage. Utility of antithrombotic agents (ATAs) in these settings is restricted by inadequate pharmacokinetics and narrow therapeutic indices. Use of advanced drug delivery systems (ADDSs) may help to circumvent these problems. Various nanocarriers, affinity ligands, and polymer coatings provide ADDSs that have the potential to help optimize ATA pharmacokinetics, target drug delivery to sites of thrombosis, and sense pathologic changes in the vascular microenvironment, such as altered hemodynamic forces, expression of inflammatory markers, and structural differences between mature hemostatic and growing pathological clots. Delivery of ATAs using biomimetic synthetic carriers, host blood cells, and recombinant fusion proteins that are activated preferentially at sites of thrombus development has shown promising outcomes in preclinical models. Further development and translation of ADDSs that spare hemostatic fibrin clots hold promise for extending the utility of ATAs in the management of acute thrombotic disorders through rapid, transient, and targeted thromboprophylaxis. If the potential benefit of this technology is to be realized, a systematic and concerted effort is required to develop clinical trials and translate the use of ADDSs to the clinical arena.
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Lishko VK, Yermolenko IS, Owaynat H, Ugarova TP. Fibrinogen counteracts the antiadhesive effect of fibrin-bound plasminogen by preventing its activation by adherent U937 monocytic cells. J Thromb Haemost 2012; 10:1081-90. [PMID: 22507544 PMCID: PMC4532274 DOI: 10.1111/j.1538-7836.2012.04745.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Fibrinogen and plasminogen strongly reduce adhesion of leukocytes and platelets to fibrin clots, highlighting a possible role for these plasma proteins in surface-mediated control of thrombus growth and stability. In particular, adsorption of fibrinogen on fibrin clots renders their surfaces non-adhesive, while the conversion of surface-bound plasminogen to plasmin by transiently adherent blood cells results in degradation of a superficial fibrin layer, leading to cell detachment. Although the mechanisms whereby these proteins exert their antiadhesive effects are different, the outcome is the same: the formation of a mechanically unstable surface that does not allow firm cell attachment. OBJECTIVES Since fibrin clots in circulation are exposed to both fibrinogen and plasminogen, their combined effect on adhesion of monocytic cells was examined. METHODS Fibrin gels were coated with plasminogen and its activation by adherent U937 monocytic cells in the presence of increasing concentrations of fibrinogen was examined by either measuring (125) I-labeled fibrin degradation products or plasmin amidolytic activity. RESULTS Unexpectedly, the antiadhesive effects of two fibrin binding proteins were not additive; in fact, in the presence of fibrinogen, the effect of plasminogen was strongly reduced. An investigation of the underlying mechanism revealed that fibrinogen prevented activation of fibrin-bound plasminogen by cells. Confocal microscopy showed that fibrinogen accumulates in a thin superficial layer of a clot, where it exerts its blocking effect on activation of plasminogen. CONCLUSION The results point to a complex interplay between the fibrinogen- and plasminogen-dependent antiadhesive systems, which may contribute to the mechanisms that control the adhesiveness of a fibrin shell on the surface of hemostatic thrombi.
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Affiliation(s)
- V K Lishko
- School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
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Vidmar J, Blinc A, Kralj E, Balažic J, Bajd F, Serša I. An MRI study of the differences in the rate of thrombolysis between red blood cell-rich and platelet-rich components of venous thrombi ex vivo. J Magn Reson Imaging 2012; 34:1184-91. [PMID: 22006553 DOI: 10.1002/jmri.22731] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To test whether T(1)-weighted MRI can detect the differences in the rate of thrombolysis induced by recombinant tissue plasminogen activator (rt-PA) between platelet-rich regions and red blood cell (RBC)-rich regions of venous thrombi ex vivo. MATERIALS AND METHODS Each of 21 venous thrombi ex vivo (8 pulmonary emboli and 13 in situ thrombi) was dissected along the longitudinal axis. Half of it was analyzed for the presence of platelet, fibrin, and RBC components by immunohistochemistry and the other half was imaged serially by high-resolution T(1)-weighted three-dimensional MRI to assess the progression of thrombolysis. The MR images were analyzed for proportions of the remaining platelet-rich and RBC-rich regions. RESULTS Laminated platelet-rich regions, corresponding to Zahn lines, were confirmed immunohistochemically and by MRI in 18/21 venous thrombi. In T(1)-weighted MR images (TE/TR = 10/105 ms) the mean signal intensity of platelet-rich regions was on average 2.3 higher than that of RBC-rich regions. The rate of thrombolysis in platelet-rich regions was on average 30% lower than in RBC-rich regions. After 120 min of thrombolysis the proportion of lysed platelet-rich regions was 0.27 ± 0.04 versus 0.40 ± 0.08 in RBC regions, which resulted in 1.4% decrease of lysed thrombus volume per 1% increase of platelet-rich content. CONCLUSION Venous thrombi are most often composed of interspersed platelet-rich and RBC-rich regions. T(1) -weighted MRI is capable of noninvasive discrimination between those two components of venous thrombi ex vivo which have a different susceptibility to thrombolysis by rt-PA.
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Affiliation(s)
- Jernej Vidmar
- Institute of Physiology, Medical faculty of Ljubljana, Slovenia
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29
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Swedberg JE, Harris JM. Natural and engineered plasmin inhibitors: applications and design strategies. Chembiochem 2012; 13:336-48. [PMID: 22238174 DOI: 10.1002/cbic.201100673] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Indexed: 12/17/2022]
Abstract
The serine protease plasmin is ubiquitously expressed throughout the human body in the form of the zymogen plasminogen. Conversion to active plasmin occurs through enzymatic cleavage by plasminogen activators. The plasminogen activator/plasmin system has a well-established function in the removal of intravascular fibrin deposition through fibrinolysis and the inhibition of plasmin activity; this has found widespread clinical use in reducing perioperative bleeding. Increasing evidence also suggests diverse, although currently less defined, roles for plasmin in a number of physiological and pathological processes relating to extracellular matrix degradation, cell migration and tissue remodelling. In particular, dysregulation of plasmin has been linked to cancer invasion/metastasis and various chronic inflammatory conditions; this has prompted efforts to develop inhibitors of this protease. Although a number of plasmin inhibitors exist, they commonly suffer from poor potency and/or specificity of inhibition that either results in reduced efficacy or prevents clinical use. Consequently, there is a need for further development of high-affinity plasmin inhibitors that maintain selectivity over other serine proteases. This review summarises clearly defined and potential applications for plasmin inhibition. The properties of naturally occurring and engineered plasmin inhibitors are discussed in the context of current knowledge regarding plasmin structure, specificity and function. This includes design strategies to obtain the potency and specificity of inhibition in addition to controlled temporal and spatial distribution tailored for the intended use.
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Affiliation(s)
- Joakim E Swedberg
- Institute for Molecular Bioscience, The University of Queensland, Brisbane QLD 4072 (Australia)
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Laing ST, Moody MR, Kim H, Smulevitz B, Huang SL, Holland CK, McPherson DD, Klegerman ME. Thrombolytic efficacy of tissue plasminogen activator-loaded echogenic liposomes in a rabbit thrombus model. Thromb Res 2011; 130:629-35. [PMID: 22133272 DOI: 10.1016/j.thromres.2011.11.010] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 11/01/2011] [Accepted: 11/04/2011] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Ultrasound (US)-enhanced thrombolytic treatment protocols currently in clinical trials for stroke applications involve systemic administration of tissue plasminogen activator (tPA; Alteplase), which carries a risk of adverse bleeding events. The present study aimed to compare the thrombolytic efficacy of a tPA-loaded echogenic liposome (ELIP) formulation with insonification protocols causing rapid fragmentation or acoustically-driven diffusion. MATERIALS AND METHODS Thrombi were induced in the abdominal aortas of male New Zealand white rabbits (2-3kg) using thrombin and a sclerosing agent (sodium ricinoleate) after aortic denudation with a balloon catheter. Thrombolytic and cavitation nucleation agents (200μg of tPA alone, tPA mixed with 50μg of a microbubble contrast agent, or tPA-loaded ELIP) were bolus- injected proximal to the clot through a catheter introduced into the abdominal aorta from the carotid artery. Clots were exposed to transabdominal color Doppler US (6MHz) for 30 minutes at a low mechanical index (MI=0.2) to induce sustained bubble activity (acoustically-driven diffusion), or for 2 minutes at an MI of 0.4 to cause ELIP fragmentation. Degree of recanalization was determined by Doppler flow measurements distal to the clots. RESULTS All treatments showed thrombolysis, but tPA-loaded ELIP was the most efficacious regimen. Both US treatment strategies enhanced thrombolytic activity over control conditions. CONCLUSIONS The thrombolytic efficacy of tPA-loaded ELIP is comparable to other clinically described effective treatment protocols, while offering the advantages of US monitoring and enhanced thrombolysis from a site-specific delivery agent.
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Affiliation(s)
- Susan T Laing
- Dept. of Internal Medicine, Division of Cardiology, University of Texas Health Science Center, Houston
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Wolf K, Friedl P. Extracellular matrix determinants of proteolytic and non-proteolytic cell migration. Trends Cell Biol 2011; 21:736-44. [PMID: 22036198 DOI: 10.1016/j.tcb.2011.09.006] [Citation(s) in RCA: 235] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2011] [Revised: 09/20/2011] [Accepted: 09/22/2011] [Indexed: 11/25/2022]
Abstract
Cell invasion into the 3D extracellular matrix (ECM) is a multistep biophysical process involved in inflammation, tissue repair, and metastatic cancer invasion. Migrating cells navigate through tissue structures of complex and often varying physicochemical properties, including molecular composition, porosity, alignment and stiffness, by adopting strategies that involve deformation of the cell and engagement of matrix-degrading proteases. We review how the ECM determines whether or not pericellular proteolysis is required for cell migration, ranging from protease-driven invasion and secondary tissue destruction, to non-proteolytic, non-destructive movement that solely depends on cell deformability and available tissue space. These concepts call for therapeutic targeting of proteases to prevent invasion-associated tissue destruction rather than the migration process per se.
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Affiliation(s)
- Katarina Wolf
- Department of Cell Biology, Nijmegen Center for Molecular Life Science, Radboud University Nijmegen, 6500 HB Nijmegen, The Netherlands.
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32
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Carnemolla R, Muzykantov VR. Vascular targeting of antithrombotic agents. IUBMB Life 2011; 63:632-9. [PMID: 21766410 DOI: 10.1002/iub.474] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 03/27/2011] [Indexed: 11/11/2022]
Abstract
In this review we discuss the limited efficacy for current pharmacological agents used in prophylaxis and treatment of thrombosis and highlight targeted delivery of anti-thrombotic agents to fibrin, platelets, red blood cells and endothelium.
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Affiliation(s)
- Ronald Carnemolla
- Department of Pharmacology, University of Pennsylvania, Philadelphia, USA
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Walvick RP, Bråtane BT, Henninger N, Sicard KM, Bouley J, Yu Z, Lo E, Wang X, Fisher M. Visualization of clot lysis in a rat embolic stroke model: application to comparative lytic efficacy. Stroke 2011; 42:1110-5. [PMID: 21372305 DOI: 10.1161/strokeaha.110.602102] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE The purpose of this study was to develop a novel MRI method for imaging clot lysis in a rat embolic stroke model and to compare tissue plasminogen activator (tPA)-based clot lysis with and without recombinant Annexin-2 (rA2). METHODS In experiment 1 we used in vitro optimization of clot visualization using multiple MRI contrast agents in concentrations ranging from 5 to 50 μL in 250 μL blood. In experiment 2, we used in vivo characterization of the time course of clot lysis using the clot developed in the previous experiment. Diffusion, perfusion, angiography, and T1-weighted MRI for clot imaging were conducted before and during treatment with vehicle (n=6), tPA (n=8), or rA2 plus tPA (n=8) at multiple time points. Brains were removed for ex vivo clot localization. RESULTS Clots created with 25 μL Magnevist were the most stable and provided the highest contrast-to-noise ratio. In the vehicle group, clot length as assessed by T1-weighted imaging correlated with histology (r=0.93). Clot length and cerebral blood flow-derived ischemic lesion volume were significantly smaller than vehicle at 15 minutes after treatment initiation in the rA2 plus tPA group, whereas in the tPA group no significant reduction from vehicle was observed until 30 minutes after treatment initiation. The rA2 plus tPA group had a significantly shorter clot length than the tPA group at 60 and 90 minutes after treatment initiation and significantly smaller cerebral blood flow deficit than the tPA group at 90 minutes after treatment initiation. CONCLUSIONS We introduce a novel MRI-based clot imaging method for in vivo monitoring of clot lysis. Lytic efficacy of tPA was enhanced by rA2.
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Affiliation(s)
- Ronn P Walvick
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
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Fan X, Yu Z, Liu J, Liu N, Hajjar KA, Furie KL, Lo EH, Wang X. Annexin A2: a tissue plasminogen activator amplifier for thrombolytic stroke therapy. Stroke 2010; 41:S54-8. [PMID: 20876506 DOI: 10.1161/strokeaha.110.596106] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hemorrhagic transformation, incomplete reperfusion, neurotoxicity, and the short treatment time window comprise major challenges for thrombolytic therapy. Improving tissue plasminogen activator therapy has become one of the highest priorities in the stroke field. Recent efforts have been aimed at identifying new strategies that might enhance the thrombolytic efficacy of tissue plasminogen activator at the same time as reducing its associated complications related to hemorrhage and neurotoxicity. We believe that the combination of low-dose tissue plasminogen activator with recombinant annexin A2 (a tissue plasminogen activator and plasminogen coreceptor) might constitute a promising approach. Our pilot study using a focal embolic stroke model in rats supports this hypothesis.
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Affiliation(s)
- Xiang Fan
- Neuroprotection Research Laboratory, Department of Neurology and Radiology, Massachusetts General Hospital, Charlestown, MA 02129, USA
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The interplay between tissue plasminogen activator domains and fibrin structures in the regulation of fibrinolysis: kinetic and microscopic studies. Blood 2010; 117:661-8. [PMID: 20966169 PMCID: PMC3031486 DOI: 10.1182/blood-2010-06-290338] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Regulation of tissue-type plasminogen activator (tPA) depends on fibrin binding and fibrin structure. tPA structure/function relationships were investigated in fibrin formed by high or low thrombin concentrations to produce a fine mesh and small pores, or thick fibers and coarse structure, respectively. Kinetics studies were performed to investigate plasminogen activation and fibrinolysis in the 2 types of fibrin, using wild-type tPA (F-G-K1-K2-P, F and K2 binding), K1K1-tPA (F-G-K1-K1-P, F binding), and delF-tPA (G-K1-K2-P, K2 binding). There was a trend of enzyme potency of tPA > K1K1-tPA > delF-tPA, highlighting the importance of the finger domain in regulating activity, but the differences were less apparent in fine fibrin. Fine fibrin was a better surface for plasminogen activation but more resistant to lysis. Scanning electron and confocal microscopy using orange fluorescent fibrin with green fluorescent protein-labeled tPA variants showed that tPA was strongly associated with agglomerates in coarse but not in fine fibrin. In later lytic stages, delF-tPA-green fluorescent protein diffused more rapidly through fibrin in contrast to full-length tPA, highlighting the importance of finger domain-agglomerate interactions. Thus, the regulation of fibrinolysis depends on the starting nature of fibrin fibers and complex dynamic interaction between tPA and fibrin structures that vary over time.
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Mutch NJ, Koikkalainen JS, Fraser SR, Duthie KM, Griffin M, Mitchell J, Watson HG, Booth NA. Model thrombi formed under flow reveal the role of factor XIII-mediated cross-linking in resistance to fibrinolysis. J Thromb Haemost 2010; 8:2017-24. [PMID: 20586921 PMCID: PMC3071935 DOI: 10.1111/j.1538-7836.2010.03963.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 06/07/2010] [Indexed: 12/01/2022]
Abstract
BACKGROUND Activated factor XIII (FXIIIa), a transglutaminase, introduces fibrin-fibrin and fibrin-inhibitor cross-links, resulting in more mechanically stable clots. The impact of cross-linking on resistance to fibrinolysis has proved challenging to evaluate quantitatively. METHODS We used a whole blood model thrombus system to characterize the role of cross-linking in resistance to fibrinolytic degradation. Model thrombi, which mimic arterial thrombi formed in vivo, were prepared with incorporated fluorescently labeled fibrinogen, in order to allow quantification of fibrinolysis as released fluorescence units per minute. RESULTS A site-specific inhibitor of transglutaminases, added to blood from normal donors, yielded model thrombi that lysed more easily, either spontaneously or by plasminogen activators. This was observed both in the cell/platelet-rich head and fibrin-rich tail. Model thrombi from an FXIII-deficient patient lysed more quickly than normal thrombi; replacement therapy with FXIII concentrate normalized lysis. In vitro addition of purified FXIII to the patient's preprophylaxis blood, but not to normal control blood, resulted in more stable thrombi, indicating no further efficacy of supraphysiologic FXIII. However, addition of tissue transglutaminase, which is synthesized by endothelial cells, generated thrombi that were more resistant to fibrinolysis; this may stabilize mural thrombi in vivo. CONCLUSIONS Model thrombi formed under flow, even those prepared as plasma 'thrombi', reveal the effect of FXIII on fibrinolysis. Although very low levels of FXIII are known to produce mechanical clot stability, and to achieve γ-dimerization, they appear to be suboptimal in conferring full resistance to fibrinolysis.
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Affiliation(s)
- N J Mutch
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
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Zhu H, Fan X, Yu Z, Liu J, Murata Y, Lu J, Zhao S, Hajjar KA, Lo EH, Wang X. Annexin A2 combined with low-dose tPA improves thrombolytic therapy in a rat model of focal embolic stroke. J Cereb Blood Flow Metab 2010; 30:1137-46. [PMID: 20068577 PMCID: PMC2949213 DOI: 10.1038/jcbfm.2009.279] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Recent studies showed that soluble annexin A2 dramatically increases tissue plasminogen activator (tPA)-mediated plasmin generation in vitro, and reduces thrombus formation in vivo. Here, we hypothesize that combining annexin A2 with tPA can significantly enhance thrombolysis efficacy, so that lower doses of tPA can be applied in ischemic stroke to avoid neurotoxic and hemorrhagic complications. In vitro activity assays confirmed tPA-specific amplification of plasmin generation by recombinant annexin A2. In a rat focal embolic stroke model, combination therapy with tPA and recombinant annexin A2 protein at 2 h post-ischemia decreased the effective dose required for tPA by four-fold and reduced brain infarction. Combining annexin A2 with tPA also lengthened the time window for thrombolysis. Compared with tPA (10 mg/kg) alone, the combination of annexin A2 (5 mg/kg) plus low-dose tPA (2.5 mg/kg) significantly enhanced fibrinolysis, attenuated mortality, brain infarction, and hemorrhagic transformation, even when administered at 4 h post-ischemia. Combination with recombinant annexin A2, the effective thrombolytic dose of tPA can be decreased. As a result, brain hemorrhage and infarction are reduced, and the time window for stroke reperfusion prolonged. Our present findings provide a promising new approach for enhancing tPA-based thrombolytic stroke therapy.
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Affiliation(s)
- Haihao Zhu
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA
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Sustained thromboprophylaxis mediated by an RBC-targeted pro-urokinase zymogen activated at the site of clot formation. Blood 2010; 115:5241-8. [PMID: 20410503 DOI: 10.1182/blood-2010-01-261610] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Plasminogen activators (PAs) are used to treat life-threatening thrombosis, but not for thromboprophylaxis because of rapid clearance, risk of bleeding, and central nervous system (CNS) toxicity. We describe a novel strategy that may help to overcome these limitations by targeting a thrombin-activated PA pro-drug to circulating red blood cells (RBCs). We fused a single chain antibody (scFv Ter-119) that binds to mouse glycophorin A (GPA) with a variant human single-chain low molecular weight urokinase construct that can be activated selectively by thrombin (scFv/uPA-T). scFv/uPA-T bound specifically to mouse RBCs without altering their biocompatibility and retained its zymogenic properties until converted by thrombin into an active 2-chain molecule. As a result, RBC-bound scFv/uPA-T caused thrombin-induced fibrinolysis. One hour and 48 hours after intravenous (IV) injection in mice, approximately 70% and approximately 35% of scFv/uPA-T was retained in the blood, respectively, and approximately 95% of the circulating scFv/uPA-T remained bound to RBCs. A single IV injection of scFv/uPA-T provided effective prophylaxis against arterial and venous thrombosis for up to 24 hours. Thus, prophylactic delivery of RBC-targeted PA pro-drugs activated selectively at the site of clot formation represents a new approach to prevent thrombosis in clinical settings where the risk of clotting is high.
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Lishko VK, Yermolenko IS, Ugarova TP. Plasminogen on the surfaces of fibrin clots prevents adhesion of leukocytes and platelets. J Thromb Haemost 2010; 8:799-807. [PMID: 20095998 PMCID: PMC4530790 DOI: 10.1111/j.1538-7836.2010.03778.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND OBJECTIVES Although leukocytes and platelets adhere to fibrin with alacrity in vitro, these cells do not readily accumulate on the surfaces of fibrin clots in vivo. The difference in the capacity of blood cell integrins to adhere to fibrin in vivo and in vitro is striking and implies the existence of a physiologic antiadhesive mechanism. The surfaces of fibrin clots in the circulation are continually exposed to plasma proteins, several of which can bind fibrin and influence cell adhesion. Recently, we have demonstrated that adsorption of soluble fibrinogen on the surface of a fibrin clot results in its deposition as a soft multilayer matrix, which prevents attachment of blood cells. In the present study, we demonstrate that another plasma protein, plasminogen, which is known to accumulate in the superficial layer of fibrin, exerts an antiadhesive effect. RESULTS After being coated with plasminogen, the surfaces of fibrin clots became essentially non-adhesive for U937 monocytic cells, blood monocytes, and platelets. The data revealed that activation of fibrin-bound plasminogen by the plasminogen-activating system assembled on adherent cells resulted in the generation of plasmin, which decomposed the superficial fibrin layer, resulting in cell detachment under flow. The surfaces generated after the initial cell adhesion remained non-adhesive for subsequent attachment of leukocytes and platelets. CONCLUSION We propose that the limited degradation of fibrin by plasmin generated by adherent cells loosens the fibers on the clot surface, producing a mechanically unstable substrate that is unable to support firm integrin-mediated cell adhesion.
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Affiliation(s)
- V K Lishko
- Center for Metabolic Biology, School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
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Vidmar J, Blinc A, Sersa I. A comparison of the ADC and T2 mapping in an assessment of blood-clot lysability. NMR IN BIOMEDICINE 2010; 23:34-40. [PMID: 19642088 DOI: 10.1002/nbm.1422] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The structural characteristics of blood clots are associated with their susceptibility to thrombolysis. As their morphology can be characterized by MRI, several attempts have been made to link the lysability of blood clots with their MRI properties; however, so far no study has associated a clot's lysability with the diffusion properties of the water in the clot. The apparent diffusion coefficient (ADC) is highly sensitive to changes in serum mobility and may be used to distinguish between the non-retracted and the fully retracted regions of the blood clot. Therefore, the ADC may be a suitable, or even a better, marker for an assessment of the clot's retraction and consequently for its lysability than the relaxation time T(2). The purpose of this study was to evaluate whether it is possible to predict the outcome of clot thrombolysis by ADC mapping prior to treatment. After two hours of thrombolysis using a recombinant tissue plasminogen activator in plasma, whole-blood clots were efficiently dissolved in regions with ADC >or= 0.8 x 10(-9) m(2)/s or T(2) >or= 130 ms, whereas dissolution was poor and prolonged in regions with ADC < 0.8 x 10(-9) m(2)/s or T(2) < 130 ms. An analysis based on a comparison between the initial and final ADC and T(2) maps after two hours of thrombolysis showed that the ADC can more accurately detect the different grades of clot retraction than T(2) and predict the regions of a clot that are resistant to thrombolysis. Therefore, the ADC could be used as an efficient prognostic marker for the outcome of thrombolysis. However, in vivo studies are needed to test this idea.
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Affiliation(s)
- Jernej Vidmar
- JoZef Stefan Institute, Jamova 39, Ljubljana 1000, Slovenia
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Lessons from the aprotinin saga: current perspective on antifibrinolytic therapy in cardiac surgery. J Anesth 2009; 24:96-106. [DOI: 10.1007/s00540-009-0866-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 06/04/2009] [Indexed: 11/26/2022]
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Zaitsev S, Zaitzev S, Spitzer D, Murciano JC, Ding BS, Tliba S, Kowalska MA, Bdeir K, Kuo A, Stepanova V, Atkinson JP, Poncz M, Cines DB, Muzykantov VR. Targeting of a mutant plasminogen activator to circulating red blood cells for prophylactic fibrinolysis. J Pharmacol Exp Ther 2009; 332:1022-31. [PMID: 19952305 DOI: 10.1124/jpet.109.159194] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chemical coupling to carrier red blood cells (RBCs) converts tissue type plasminogen activator (tPA) from a problematic therapeutic into a safe agent for thromboprophylaxis. The goal of this study was to develop a more clinically relevant recombinant biotherapeutic by fusing a mutant tPA with a single-chain antibody fragment (scFv) with specificity for glycophorin A (GPA) on mouse RBCs. The fusion construct (anti-GPA scFv/PA) bound specifically to mouse but not human RBCs and activated plasminogen; this led to rapid and stable attachment of up to 30,000 copies of anti-GPA scFv/PA per mouse RBC that were thereby endowed with high fibrinolytic activity. Binding of anti-GPA scFv/PA neither caused RBC aggregation, hemolysis, uptake in capillary-rich lungs or in the reticuloendothelial system nor otherwise altered the circulation of RBCs. Over 40% of labeled anti-GPA scFv/PA injected in mice bound to RBC, which markedly prolonged its intravascular circulation and fibrinolytic activity compared with its nontargeted PA counterpart, anti-GPA scFv/PA, but not its nontargeted PA analog, prevented thrombotic occlusion in FeCl(3) models of vascular injury. These results provide proof-of-principle for the development of a recombinant PA variant that binds to circulating RBC and provides thromboprophylaxis by use of a clinically relevant approach.
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Affiliation(s)
- Sergei Zaitsev
- IFEM, University of Pennsylvania School of Medicine, One John Morgan Building, 3620 Hamilton Walk, Philadelphia, PA 19104-6068, USA
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Murciano JC, Higazi AAR, Cines DB, Muzykantov VR. Soluble urokinase receptor conjugated to carrier red blood cells binds latent pro-urokinase and alters its functional profile. J Control Release 2009; 139:190-6. [PMID: 19616049 DOI: 10.1016/j.jconrel.2009.07.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Revised: 06/29/2009] [Accepted: 07/08/2009] [Indexed: 11/24/2022]
Abstract
Coupling plasminogen activators to carrier red blood cells (RBC) prolongs their life-time in the circulation and restricts extravascular side effects, thereby allowing their utility for short-term thromboprophylaxis. Unlike constitutively active plasminogen activators, single chain urokinase plasminogen activator (scuPA) is activated by plasmin proteolysis or binding to its receptor, uPAR. In this study we conjugated recombinant soluble uPAR (suPAR) to rat RBC, forming RBC/suPAR complex. RBC carrying suPAR circulated in rats similarly to naïve RBC and markedly prolonged the circulation time of suPAR. RBC/suPAR carrying approximately 3x10(4) suPAR molecules per RBC specifically bound up to 2x10(4) molecules of scuPA, retained approximately 75% of scuPA-binding capacity after circulation in rats and markedly altered the functional profile of bound scuPA. RBC carrying directly conjugated scuPA adhered to endothelial cells, while showing no appreciable fibrinolytic activity. In contrast, RBC/suPAR loaded with scuPA did not exhibit increased adhesion to endothelium, while effectively dissolving fibrin clots. This molecular design, capitalizing on unique biological features of the interaction of scuPA with its receptor, provides a promising modality to deliver a pro-drug for prevention of thrombosis.
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Shaw GJ, Meunier JM, Lindsell CJ, Holland CK. Tissue plasminogen activator concentration dependence of 120 kHz ultrasound-enhanced thrombolysis. ULTRASOUND IN MEDICINE & BIOLOGY 2008; 34:1783-92. [PMID: 18468773 PMCID: PMC2614894 DOI: 10.1016/j.ultrasmedbio.2008.03.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 03/03/2008] [Accepted: 03/12/2008] [Indexed: 05/11/2023]
Abstract
It has been known for some time that the application of ultrasound can enhance the efficacy of thrombolytic medications such as recombinant tissue plasminogen activator (rt-PA). Potential clinical applications of this ultrasound-enhanced thrombolysis (UET) include the treatment of myocardial infarction, acute ischemic stroke, deep venous thrombosis and other thrombotic disorders. It may be possible to reduce the dose of rt-PA while maintaining lytic efficacy; however there is little data on the rt-PA concentration dependence of UET. In this work, the rt-PA concentration dependence of clot lysis resulting from 120 kHz UET exposure was measured in an in vitro human clot model. Clots were exposed to rt-PA for 30 min, with (UET treated) or without 120 kHz ultrasound (rt-PA treated) at 37 degrees C, and the clot width measured as a function of time. The rt-PA concentration ranged from 0-10 microg/mL. The initial lytic rate for the UET-treated group was greater than that of the rt-PA group at almost all rt-PA concentrations, and exhibited a maximum over concentration values of 1-3 microg/mL.
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Affiliation(s)
- George J Shaw
- Department of Emergency Medicine, University of Cincinnati College ofMedicine, Cincinnati, OH 45267-0769, USA.
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Härdig BM, Carlson J, Roijer A. Changes in clot lysis levels of reteplase and streptokinase following continuous wave ultrasound exposure, at ultrasound intensities following attenuation from the skull bone. BMC Cardiovasc Disord 2008; 8:19. [PMID: 18727834 PMCID: PMC2533283 DOI: 10.1186/1471-2261-8-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Accepted: 08/26/2008] [Indexed: 11/29/2022] Open
Abstract
Background Ultrasound (US) has been used to enhance thrombolytic therapy in the treatment of stroke. Considerable attenuation of US intensity is however noted if US is applied over the temporal bone. The aim of this study was therefore to explore possible changes in the effect of thrombolytic drugs during low-intensity, high-frequency continuous-wave ultrasound (CW-US) exposure. Methods Clots were made from fresh venous blood drawn from healthy volunteers. Each clot was made from 1.4 ml blood and left to coagulate for 1 hour in a plastic test-tube. The thrombolytic drugs used were, 3600 IU streptokinase (SK) or 0.25 U reteplase (r-PA), which were mixed in 160 ml 0.9% NaCl solution. Continuous-wave US exposure was applied at a frequency of 1 MHz and intensities ranging from 0.0125 to 1.2 W/cm2. For each thrombolytic drug (n = 2, SK and r-PA) and each intensity (n = 9) interventional clots (US-exposed, n = 6) were submerged in thrombolytic solution and exposed to CW-US while control clots (also submerged in thrombolytic solution, n = 6) were left unexposed to US. To evaluate the effect on clot lysis, the haemoglobin (Hb) released from each clot was measured every 20 min for 1 hour (20, 40 and 60 min). The Hb content (mg) released was estimated by spectrophotometry at 540 nm. The difference in effect on clot lysis was expressed as the difference in the amount of Hb released between pairs of US-exposed clots and control clots. Statistical analysis was performed using Wilcoxon's signed rank test. Results Continuous-wave ultrasound significantly decreased the effects of SK at intensities of 0.9 and 1.2 W/cm2 at all times (P < 0.05). Continuous-wave ultrasound significantly increased the effects of r-PA on clot lysis following 20 min exposure at 0.9 W/cm2 and at 1.2 W/cm2, following 40 min exposure at 0.3, 0.6, 0.9 and at 1.2 W/cm2, and following 60 min of exposure at 0.05 0.3, 0.6, 0.9 and at 1.2 W/cm2 (all P < 0.05). Conclusion Increasing intensities of CW-US exposure resulted in increased clot lysis of r-PA-treated blood clots, but decreased clot lysis of SK-treated clots.
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Affiliation(s)
- Bjarne Madsen Härdig
- Department of Clinical Sciences, Cardiology, Lund University, Lund University Hospital, Lund, S221 85, Sweden.
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Anand M, Rajagopal K, Rajagopal KR. A model for the formation, growth, and lysis of clots in quiescent plasma. A comparison between the effects of antithrombin III deficiency and protein C deficiency. J Theor Biol 2008; 253:725-38. [PMID: 18539301 DOI: 10.1016/j.jtbi.2008.04.015] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/18/2008] [Accepted: 04/09/2008] [Indexed: 11/15/2022]
Abstract
A mathematical model comprised of 23 reaction-diffusion equations is used to simulate the biochemical changes and transport of various reactants involved in coagulation and fibrinolysis in quiescent plasma. The growth and lysis of a thrombus, as portrayed by the model equations, is governed by boundary conditions that include the surface concentration of TF-VIIa, the generation of XIa by contact activation (in vitro), and the secretion of tPA due to endothelial activation. We apply the model to two clinically relevant hypercoagulable states, caused by deficiency of either antithrombin III or protein C. These predictions are compared with published experimental data which validate the utility of the developed model under the special case of static conditions. The incorporation of varying hemodynamic conditions in to the current fluid static model remains to be performed.
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Affiliation(s)
- M Anand
- Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA
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Prophylactic thrombolysis by thrombin-activated latent prourokinase targeted to PECAM-1 in the pulmonary vasculature. Blood 2007; 111:1999-2006. [PMID: 18045968 DOI: 10.1182/blood-2007-07-103002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A recombinant prodrug, single-chain urokinase-type plasminogen activator (scuPA) fused to an anti-PECAM-1 antibody single-chain variable fragment (anti-PECAM scFv/scuPA) targets endothelium and augments thrombolysis in the pulmonary vasculature.(1) To avoid premature activation and inactivation and to limit systemic toxicity, we replaced the native plasmin activation site in scFv/low-molecular-weight (lmw)-scuPA with a thrombin activation site, generating anti-PECAM scFv/uPA-T that (1) is latent and activated by thrombin instead of plasmin; (2) binds to PECAM-1; (3) does not consume plasma fibrinogen; (4) accumulates in mouse lungs after intravenous injection; and (5) resists PA inhibitor PAI-1 until activated by thrombin. In mouse models of pulmonary thrombosis caused by thromboplastin and ischemia-reperfusion (I/R), scFv/uPA-T provided more potent thromboprophylaxis and greater lung protection than plasmin-sensitive scFv/uPA. Endothelium-targeted thromboprophylaxis triggered by a prothrombotic enzyme illustrates a novel approach to time- and site-specific regulation of proteolytic reactions that can be modulated for therapeutic benefit.
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Walker JB, Bajzar L. Complete inhibition of fibrinolysis by sustained carboxypeptidase B activity: the role and requirement of plasmin inhibitors. J Thromb Haemost 2007; 5:1257-64. [PMID: 17389009 DOI: 10.1111/j.1538-7836.2007.02541.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The antifibrinolytic effect of activated thrombin-activatable fibrinolysis inhibitor (TAFIa) and carboxypeptidase B (CPB) displays threshold behavior. When CPB was used to simulate conditions mimicking continuous TAFIa activity, it affected the lysis of plasma clots differently to clots formed from a minimal fibrinolytic system comprising fibrinogen, plasminogen and alpha(2)-antiplasmin. Whereas CPB saturably prolonged clot lysis in the purified system, the effect of CPB did not appear saturable in plasma clots. METHODS To rationalize this difference, we investigated the effects of alpha(2)-antiplasmin, alpha(2)-macroglobulin, antithrombin and aprotinin on CPB-mediated antifibrinolysis. RESULTS CPB alone prolonged fibrinolysis in a saturable manner and the efficacy of CPB increased with decreasing tissue-type plasminogen activator (t-PA) concentration. The inhibitors by themselves did not halt fibrinolysis and the potency of each inhibitor in the absence of CPB mirrored their solution-phase plasmin inhibitory potentials: alpha(2)-antiplasmin approximately equal to aprotinin >> alpha(2)-macroglobulin >> antithrombin. With both CPB and inhibitor present, a synergistic effect was observed. The antifibrinolytic sensitivity to CPB was related to the plasmin inhibitory potential of the inhibitor. CONCLUSIONS Fibrinolysis could be completely inhibited by alpha(2)-antiplasmin, alpha(2)-macroglobulin and antithrombin, but not aprotinin, in the presence of CPB, and occurred only when the irreversible inhibitor or pool of inhibitors were in excess of plasminogen. Western blot analysis indicated that the CPB-mediated shutdown of fibrinolysis was a result of plasminogen consumption prior to clot lysis. The CPB concentration required for fibrinolytic shutdown was dependent on t-PA concentration and the inhibitory potential of the irreversible inhibitor pool.
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Affiliation(s)
- J B Walker
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
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Houard X, Rouzet F, Touat Z, Philippe M, Dominguez M, Fontaine V, Sarda-Mantel L, Meulemans A, Le Guludec D, Meilhac O, Michel JB. Topology of the fibrinolytic system within the mural thrombus of human abdominal aortic aneurysms. J Pathol 2007; 212:20-8. [PMID: 17352452 DOI: 10.1002/path.2148] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Development and progression of acquired abdominal aortic aneurysms (AAAs) involve proteolytic activity. In the present study, we investigate the distribution of fibrinolytic system components within mural thrombi of human AAAs. 20 mural thrombi and the remaining AAA walls were dissected. The luminal, intermediate and abluminal thrombus layers, and media and adventitia were separately incubated in cell culture medium. Conditioned media were then analysed for plasminogen activators (PAs), plasminogen activator inhibitor-1 (PAI-1), free-plasmin, plasmin alpha(2)-antiplasmin complexes (PAPs) and D-dimers release. In parallel, PA and PAI-1 mRNA expression analysis was performed by RT-PCR. The study was completed by immunohistochemical localization of these components in AAA, ex vivo functional imaging using (99m)Tc-aprotinin as a ligand and measurement of PAP and D-dimer plasma levels. All fibrinolytic system components were present in each aneurysmal layer. However, the mural thrombus was the main source of active serine-protease release. Interestingly, the luminal layer of the thrombus released greater amounts of PAPs and D-dimers. This paralleled the preferential immunolocalization of plasminogen and PAs, and the (99m)Tc-aprotinin scintigraphic signal observed in the luminal pole of the thrombus. In contrast, mRNA expression analysis showed an exclusive synthesis of tPA and PAI-1 within the wall, whereas uPA mRNA was also expressed within the thrombus. Taken together, these results suggest that the increased plasma concentrations of PAPs and D-dimers found in AAA patients are related to mural thrombus proteolytic activity, thus explaining their known link with AAA progression. Components of the fibrinolytic system could also represent a target for functional imaging of thrombus activities in AAA.
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Affiliation(s)
- X Houard
- INSERM U698, Cardiovascular Haematology, Bioengineering and Remodelling, Bichat-Claude Bernard Hospital, 46 Rue Henri Huchard, 75877 Paris Cedex 18, France
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Danielyan K, Ding BS, Gottstein C, Cines DB, Muzykantov VR. Delivery of Anti-Platelet-Endothelial Cell Adhesion Molecule Single-Chain Variable Fragment-Urokinase Fusion Protein to the Cerebral Vasculature Lyses Arterial Clots and Attenuates Postischemic Brain Edema. J Pharmacol Exp Ther 2007; 321:947-52. [PMID: 17389242 DOI: 10.1124/jpet.107.120535] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Efficacy and safety of current means to prevent cerebrovascular thrombosis in patients at high risk of stroke are suboptimal. In theory, anchoring fibrinolytic plasminogen activators to the luminal surface of the cerebral endothelium might arrest formation of occlusive clots in this setting. We tested this approach using the recombinant construct antiplatelet-endothelial cell adhesion molecule (PECAM) single-chain variable fragment (scFv)-urokinase-type plasminogen activator (uPA), fusing low-molecular-weight single-chain urokinase-type plasminogen activator with a scFv of an antibody directed to the stably expressed endothelial surface determinant PECAM-1, implicated in inflammation and thrombosis. Studies in mice showed that scFv-uPA, but not unconjugated uPA 1) accumulates in the brain after intravascular injection, 2) lyses clots lodged in the cerebral arterial vasculature without hemorrhagic complications, 3) provides rapid and stable cerebral reperfusion, and 4) alleviates post-thrombotic brain edema. Effective and safe thromboprophylaxis in the cerebral arterial circulation by anti-PECAM scFv-uPA represents a prototype of a new paradigm to prevent recurrent cerebrovascular thrombosis.
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Affiliation(s)
- Kristina Danielyan
- Department of Pharmacology and Targeted Therapeutics Program, Institute of Translational Medicine and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104-6068, USA
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