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Keragala CB, McFadyen JD, Ho H, McCutcheon FM, Liu Z, Stevens H, Monagle P, Chunilal S, Medcalf RL, Tran H. Plasma from patients with vaccine-induced immune thrombotic thrombocytopenia displays increased fibrinolytic potential and enhances tissue-type plasminogen activator but not urokinase-mediated plasminogen activation. J Thromb Haemost 2024; 22:785-793. [PMID: 37944898 DOI: 10.1016/j.jtha.2023.10.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 10/24/2023] [Accepted: 10/28/2023] [Indexed: 11/12/2023]
Abstract
BACKGROUND Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare complication of adenovirus vector-based COVID-19 vaccines. VITT is associated with markedly raised levels of D-dimer; yet, how VITT modulates the fibrinolytic system is unknown. OBJECTIVES We aimed to compare changes in fibrinolytic activity in plasma from patients with VITT, patients diagnosed with venous thromboembolism (VTE) after vaccination but without VITT (VTE-no VITT), and healthy vaccinated controls. METHODS Plasma levels of plasmin-antiplasmin (PAP) complexes, plasminogen, and alpha-2-antiplasmin (α2AP) from 10 patients with VITT, 10 patients with VTE-no VITT, and 14 healthy vaccinated controls were evaluated by enzyme-linked immunosorbent assay and/or Western blotting. Fibrinolytic capacity was evaluated by quantitating PAP levels at baseline and after ex vivo plasma stimulation with 50-nM tissue-type plasminogen activator (tPA) or urokinase for 5 minutes. RESULTS Baseline PAP complex levels in control and VTE-no VITT individuals were similar but were ∼7-fold higher in plasma from patients with VITT (P < .0001). VITT samples also revealed consumption of α2AP and fibrinogenolysis consistent with a hyperfibrinolytic state. Of interest, VITT plasma produced significantly higher PAP levels after ex vivo treatment with tPA, but not urokinase, compared to the other groups, indicative of increased fibrinolytic potential. This was not due to D-dimer as addition of D-dimer to VTE-no VITT plasma failed to potentiate tPA-induced PAP levels. CONCLUSION A marked hyperfibrinolytic state occurs in patients with VITT, evidenced by marked elevations in PAP, α2AP consumption, and fibrinogenolysis. An unidentified plasma cofactor that selectively potentiates tPA-mediated plasminogen activation also appears to exist in the plasma of patients with VITT.
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Affiliation(s)
- Charithani B Keragala
- Australian Centre for Blood Diseases, the Central Clinical School, Monash University, Melbourne, Victoria, Australia; Department of Hematology, Monash Health, Clayton, Victoria, Australia; School of Clinical Sciences, Monash Health, Monash University, Clayton, Victoria, Australia
| | - James D McFadyen
- Australian Centre for Blood Diseases, the Central Clinical School, Monash University, Melbourne, Victoria, Australia; Atherothrombosis and Vascular Biology Program, Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia; Department of Hematology, Alfred Hospital, Melbourne, Victoria, Australia; Baker Department of Cardiometabolic Health, the University of Melbourne, Parkville, Victoria, Australia
| | - Heidi Ho
- Australian Centre for Blood Diseases, the Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - Fiona M McCutcheon
- Australian Centre for Blood Diseases, the Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - Zikou Liu
- Australian Centre for Blood Diseases, the Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - Hannah Stevens
- Australian Centre for Blood Diseases, the Central Clinical School, Monash University, Melbourne, Victoria, Australia; Atherothrombosis and Vascular Biology Program, Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia; Department of Hematology, Alfred Hospital, Melbourne, Victoria, Australia
| | - Paul Monagle
- Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia; Hematology Research, Murdoch Children's Research Institute, Melbourne, Victoria, Australia; Clinical Hematology, Royal Children's Hospital, Parkville, Victoria, Australia; Kids Cancer Centre, Sydney Children's Hospital, Randwick, New South Wales, Australia
| | - Sanjeev Chunilal
- Department of Hematology, Monash Health, Clayton, Victoria, Australia; School of Clinical Sciences, Monash Health, Monash University, Clayton, Victoria, Australia
| | - Robert L Medcalf
- Australian Centre for Blood Diseases, the Central Clinical School, Monash University, Melbourne, Victoria, Australia.
| | - Huyen Tran
- Australian Centre for Blood Diseases, the Central Clinical School, Monash University, Melbourne, Victoria, Australia; Department of Hematology, Alfred Hospital, Melbourne, Victoria, Australia.
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Platelet-targeted thrombolysis for treatment of acute ischemic stroke. Blood Adv 2022; 7:561-574. [PMID: 35482909 PMCID: PMC9984306 DOI: 10.1182/bloodadvances.2021006691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 03/28/2022] [Accepted: 04/09/2022] [Indexed: 11/20/2022] Open
Abstract
Thrombolysis with tissue-type plasminogen activator (tPA) remains the main treatment for acute ischemic stroke. Nevertheless, tPA intervention is limited by a short therapeutic window, low recanalization rates, and a risk of intracranial hemorrhage (ICH), highlighting the clinical demand for improved thrombolytic drugs. We examined a novel thrombolytic agent termed "SCE5-scuPA," comprising a single-chain urokinase plasminogen activator (scuPA) fused with a single-chain antibody (SCE5) that targets the activated glycoprotein IIb/IIIa platelet receptor, for its effects in experimental stroke. SCE5-scuPA was first tested in a whole blood clot degradation assay to show the benefit of platelet-targeted thrombolysis. The tail bleeding time, blood clearance, and biodistribution were then determined to inform the use of SCE5-scuPA in mouse models of photothrombotic stroke and middle cerebral artery occlusion against tenecteplase. The impacts of SCE5-scuPA on motor function, ICH, blood-brain barrier (BBB) integrity, and immunosuppression were evaluated. Infarct size was measured by computed tomography imaging and magnetic resonance imaging. SCE5-scuPA enhanced clot degradation ex vivo compared with its nonplatelet-targeting control. The maximal SCE5-scuPA dose that maintained hemostasis and a rapid blood clearance was determined. SCE5-scuPA administration both before and 2 hours after photothrombotic stroke reduced the infarct volume. SCE5-scuPA also improved neurologic deficit, decreased intracerebral blood deposits, preserved the BBB, and alleviated immunosuppression poststroke. In middle cerebral artery occlusion, SCE5-scuPA did not worsen stroke outcomes or cause ICH, and it protected the BBB. Our findings support the ongoing development of platelet-targeted thrombolysis with SCE5-scuPA as a novel emergency treatment for acute ischemic stroke with a promising safety profile.
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Medcalf RL, Keragala CB. The Fibrinolytic System: Mysteries and Opportunities. Hemasphere 2021; 5:e570. [PMID: 34095754 PMCID: PMC8171360 DOI: 10.1097/hs9.0000000000000570] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 04/07/2021] [Indexed: 02/07/2023] Open
Abstract
The deposition and removal of fibrin has been the primary role of coagulation and fibrinolysis, respectively. There is also little doubt that these 2 enzyme cascades influence each other given they share the same serine protease family ancestry and changes to 1 arm of the hemostatic pathway would influence the other. The fibrinolytic system in particular has also been known for its capacity to clear various non-fibrin proteins and to activate other enzyme systems, including complement and the contact pathway. Furthermore, it can also convert a number of growth factors into their mature, active forms. More recent findings have extended the reach of this system even further. Here we will review some of these developments and also provide an account of the influence of individual players of the fibrinolytic (plasminogen activating) pathway in relation to physiological and pathophysiological events, including aging and metabolism.
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Affiliation(s)
- Robert L. Medcalf
- Molecular Neurotrauma and Haemostasis, Australian Centre for Blood Diseases, Central Clinical School, Monash University, Victoria, Australia
| | - Charithani B. Keragala
- Molecular Neurotrauma and Haemostasis, Australian Centre for Blood Diseases, Central Clinical School, Monash University, Victoria, Australia
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Abstract
Plasminogen is an abundant plasma protein that exists in various zymogenic forms. Plasmin, the proteolytically active form of plasminogen, is known for its essential role in fibrinolysis. To date, therapeutic targeting of the fibrinolytic system has been for 2 purposes: to promote plasmin generation for thromboembolic conditions or to stop plasmin to reduce bleeding. However, plasmin and plasminogen serve other important functions, some of which are unrelated to fibrin removal. Indeed, for >40 years, the antifibrinolytic agent tranexamic acid has been administered for its serendipitously discovered skin-whitening properties. Plasmin also plays an important role in the removal of misfolded/aggregated proteins and can trigger other enzymatic cascades, including complement. In addition, plasminogen, via binding to one of its dozen cell surface receptors, can modulate cell behavior and further influence immune and inflammatory processes. Plasminogen administration itself has been reported to improve thrombolysis and to accelerate wound repair. Although many of these more recent findings have been derived from in vitro or animal studies, the use of antifibrinolytic agents to reduce bleeding in humans has revealed additional clinically relevant consequences, particularly in relation to reducing infection risk that is independent of its hemostatic effects. The finding that many viruses harness the host plasminogen to aid infectivity has suggested that antifibrinolytic agents may have antiviral benefits. Here, we review the broadening role of the plasminogen-activating system in physiology and pathophysiology and how manipulation of this system may be harnessed for benefits unrelated to its conventional application in thrombosis and hemostasis.
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