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Assessing Plasmin Generation in Health and Disease. Int J Mol Sci 2021; 22:ijms22052758. [PMID: 33803235 PMCID: PMC7963172 DOI: 10.3390/ijms22052758] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/20/2021] [Accepted: 03/05/2021] [Indexed: 12/13/2022] Open
Abstract
Fibrinolysis is an important process in hemostasis responsible for dissolving the clot during wound healing. Plasmin is a central enzyme in this process via its capacity to cleave fibrin. The kinetics of plasmin generation (PG) and inhibition during fibrinolysis have been poorly understood until the recent development of assays to quantify these metrics. The assessment of plasmin kinetics allows for the identification of fibrinolytic dysfunction and better understanding of the relationships between abnormal fibrin dissolution and disease pathogenesis. Additionally, direct measurement of the inhibition of PG by antifibrinolytic medications, such as tranexamic acid, can be a useful tool to assess the risks and effectiveness of antifibrinolytic therapy in hemorrhagic diseases. This review provides an overview of available PG assays to directly measure the kinetics of plasmin formation and inhibition in human and mouse plasmas and focuses on their applications in defining the role of plasmin in diseases, including angioedema, hemophilia, rare bleeding disorders, COVID-19, or diet-induced obesity. Moreover, this review introduces the PG assay as a promising clinical and research method to monitor antifibrinolytic medications and screen for genetic or acquired fibrinolytic disorders.
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Macrae FL, Peacock‐Young B, Bowman P, Baker SR, Quested S, Linton E, Hillmen P, Griffin M, Munir T, Payne D, McKinley C, Clarke D, Newton DJ, Hill A, Ariëns RAS. Patients with paroxysmal nocturnal hemoglobinuria demonstrate a prothrombotic clotting phenotype which is improved by complement inhibition with eculizumab. Am J Hematol 2020; 95:944-952. [PMID: 32311169 DOI: 10.1002/ajh.25841] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 04/10/2020] [Accepted: 04/15/2020] [Indexed: 12/26/2022]
Abstract
Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disorder, characterized by complement-mediated intravascular hemolysis and thrombosis. The increased incidence of PNH-driven thrombosis is still poorly understood, but unlike other thrombotic disorders, is thought to largely occur through complement-mediated mechanisms. Treatment with a C5 inhibitor, eculizumab, has been shown to significantly reduce the number of thromboembolic events in these patients. Based on previously described links between changes in fibrin clot structure and thrombosis in other disorders, our aim was to investigate clot structure as a possible mechanism of thrombosis in patients with PNH and the anti-thrombotic effects of eculizumab treatment on clot structure. Clot structure, fibrinogen levels and thrombin generation were examined in plasma samples from 82 patients from the National PNH Service in Leeds, UK. Untreated PNH patients were found to have increased levels of fibrinogen and thrombin generation, with subsequent prothrombotic changes in clot structure. No link was found between increasing disease severity and fibrinogen levels, thrombin generation, clot formation or structure. However, eculizumab treated patients showed decreased fibrinogen levels, thrombin generation and clot density, with increasing time spent on treatment augmenting these antithrombotic effects. These data suggest that PNH patients have a prothrombotic clot phenotype due to increased fibrinogen levels and thrombin generation, and that the antithrombotic effects of eculizumab are, in-part, due to reductions in fibrinogen and thrombin generation with downstream effects on clot structure.
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Affiliation(s)
- Fraser L. Macrae
- Discovery and Translational Science DepartmentLeeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
| | - Barnaby Peacock‐Young
- Discovery and Translational Science DepartmentLeeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
| | - Polly Bowman
- Discovery and Translational Science DepartmentLeeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
| | - Stephen R. Baker
- Discovery and Translational Science DepartmentLeeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
- Department of PhysicsWake Forest University Winston Salem North Carolina USA
| | - Sam Quested
- Discovery and Translational Science DepartmentLeeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
| | - Emma Linton
- Discovery and Translational Science DepartmentLeeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
| | - Peter Hillmen
- Department of HaematologyLeeds Teaching Hospitals NHS Trust Leeds UK
| | - Morag Griffin
- Department of HaematologyLeeds Teaching Hospitals NHS Trust Leeds UK
| | - Talha Munir
- Department of HaematologyLeeds Teaching Hospitals NHS Trust Leeds UK
| | - Daniel Payne
- Department of HaematologyLeeds Teaching Hospitals NHS Trust Leeds UK
| | - Claire McKinley
- Division of Haematology and ImmunologyLeeds Institute of Medical Research at St James's, University of Leeds Leeds UK
| | - Deborah Clarke
- Division of Haematology and ImmunologyLeeds Institute of Medical Research at St James's, University of Leeds Leeds UK
| | - Darren J Newton
- Division of Haematology and ImmunologyLeeds Institute of Medical Research at St James's, University of Leeds Leeds UK
| | - Anita Hill
- Department of HaematologyLeeds Teaching Hospitals NHS Trust Leeds UK
| | - Robert A. S. Ariëns
- Discovery and Translational Science DepartmentLeeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
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Devalet B, Wannez A, Bailly N, Alpan L, Gheldof D, Douxfils J, Bihin B, Chatelain B, Dogné JM, Chatelain C, Mullier F. Prospective and comparative study of paroxysmal nocturnal hemoglobinuria patients treated or not by eculizumab: Focus on platelet extracellular vesicles. Medicine (Baltimore) 2019; 98:e16164. [PMID: 31277120 PMCID: PMC6635286 DOI: 10.1097/md.0000000000016164] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Thrombosis are severe complications of paroxysmal nocturnal hemoglobinuria (PNH), effectively reduced by eculizumab. Extracellular vesicles (EVs) may play a central role. The objective of this study was to assess the procoagulant activity of plasma isolated from PNH patients (treated or not by eculizumab) and to quantify their circulating EVs.We iteratively collected the platelet-free-plasma of 17 PNH patients and 16 matched healthy volunteers, quantified their circulating EVs by flow cytometry and evaluated their procoagulant activity by thrombin generation and STA-Procoag-procoagulant phospholipid (PPL) assays.A significant decrease of EVs from platelets (P = .024) and an increase of the STA-Procoag-PPL clotting time (P = .049) was observed after initiation of eculizumab and up to 11 weeks after. This reduction of prothrombotic biomarkers was not observed with the thrombin generation test due to a lack of sensitivity of this assay. Active hemolysis was observed in 90% of patients and elevated D-dimers in 41% of them. However, no significant difference was observed between patients and control subjects regarding the procoagulant activity, the EVs quantity, or the cellular origin. Lactate dehydrogenase (LDH) levels were lower in eculizumab-treated patients compared to nontreated patients (441 vs 2448 IU/L). D-dimers and LDH decreased after administration of eculizumab (mean decrease of 1307 ng/mL and 4159 IU/L, respectively).These observations suggest a decrease of the phospholipid-dependent procoagulant potential of EVs after eculizumab therapy in PNH patients. TRIAL REGISTRATION:: NUB: B039201214365.
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Affiliation(s)
- Bérangère Devalet
- Department of Hematology, Namur Thrombosis and Hemostasis Center (NTHC), CHU UCL Namur, Université Catholique de Louvain, Yvoir
| | - Adeline Wannez
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur, Namur
| | - Nicolas Bailly
- Hematology Laboratory, Namur Thrombosis and Hemostasis Center (NTHC), CHU UCL Namur, Université Catholique de Louvain, Yvoir
| | - Lutfiye Alpan
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur, Namur
| | - Damien Gheldof
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur, Namur
- Qualiblood s.a., Namur
| | - Jonathan Douxfils
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur, Namur
- Qualiblood s.a., Namur
| | - Benoît Bihin
- Scientific Support Unit, CHU UCL Namur, Université Catholique de Louvain, Yvoir, Belgium
| | - Bernard Chatelain
- Hematology Laboratory, Namur Thrombosis and Hemostasis Center (NTHC), CHU UCL Namur, Université Catholique de Louvain, Yvoir
| | - Jean-Michel Dogné
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur, Namur
| | - Christian Chatelain
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur, Namur
| | - François Mullier
- Hematology Laboratory, Namur Thrombosis and Hemostasis Center (NTHC), CHU UCL Namur, Université Catholique de Louvain, Yvoir
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Dragoni F, Chiarotti F, Iori AP, La Rocca U, Cafolla A. Antithrombotic therapy with rivaroxaban in five patients with paroxysmal nocturnal haemoglobinuria and thrombotic events. Thromb J 2018; 16:26. [PMID: 30377413 PMCID: PMC6196560 DOI: 10.1186/s12959-018-0181-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 08/19/2018] [Indexed: 11/10/2022] Open
Abstract
Five patients with paroxysmal nocturnal haemoglobinuria and thrombotic complications under oral antithrombotic treatment with vitamin K antagonist were switched to receive the direct oral anticoagulant rivaroxaban an factor Xa inhibitor. In all five patients haematological and biochemical parameters and adverse events were evaluated for a period of twelve months. Therapy with rivaroxaban was well tolerated in all cases and one patient showed a significant reduction of bleeding and transfusion requirement. All patients obtained a significant reduction in days of hospitalization with a consequent improvement in their quality of life after rivaroxaban treatment.
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Affiliation(s)
- Francesco Dragoni
- 1Thrombosis Center, "Department of Cellular Biotechnologies and Hematology", "Sapienza" University, Via Benevento 6, 00161 Rome, Italy
| | - Flavia Chiarotti
- 2Reference Center for Behavioral Sciences and Mental Health, National Institute of Health, Rome, Italy
| | - Anna Paola Iori
- 1Thrombosis Center, "Department of Cellular Biotechnologies and Hematology", "Sapienza" University, Via Benevento 6, 00161 Rome, Italy
| | - Ursula La Rocca
- 1Thrombosis Center, "Department of Cellular Biotechnologies and Hematology", "Sapienza" University, Via Benevento 6, 00161 Rome, Italy
| | - Arturo Cafolla
- 1Thrombosis Center, "Department of Cellular Biotechnologies and Hematology", "Sapienza" University, Via Benevento 6, 00161 Rome, Italy
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Devos T, Meers S, Boeckx N, Gothot A, Deeren D, Chatelain B, Chatelain C, Devalet B. Diagnosis and management of PNH: Review and recommendations from a Belgian expert panel. Eur J Haematol 2018; 101:737-749. [PMID: 30171728 DOI: 10.1111/ejh.13166] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 05/21/2018] [Accepted: 05/22/2018] [Indexed: 12/17/2022]
Abstract
Despite its considerable morbidity and mortality, paroxysmal nocturnal haemoglobinuria (PNH) is still underdiagnosed. Patients with PNH can suffer from cardiovascular, gastrointestinal, neurological or haematological symptoms and refer to several specialists. The aim of this paper is to review the diagnosis and the management of PNH patients, with the primary focus on identifying high-risk groups. Additionally, the implementation and prognostic value of the defined high-risk groups will be commented on and the management of PNH patients is discussed from a Belgian perspective. Finally, based on the available data, recommendations are provided. Eculizumab is a potent C5 complement inhibitor and reduces intravascular haemolysis and thrombosis in PNH patients and improves their quality of life. As thrombosis is the main cause of death in PNH patients, identifying high-risk PNH patients in need of therapy is essential. Currently, novel complement inhibitors are in development and the first data seem promising. Another challenge in PNH is to identify new markers to assess the thrombotic risk to achieve a better risk-based prophylactic anti-thrombotic management. Finally, because of the low prevalence of the disease, PNH patients should be included in the prospective PNH registry, which will offer new insights on the natural course of the disease and the impact of treatment of PNH.
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Affiliation(s)
- Timothy Devos
- Department of Haematology, University Hospitals Leuven, Leuven, Belgium.,Laboratory of Experimental Transplantation, Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium
| | - Stef Meers
- Department of Haematology, AZ KLINA, Brasschaat, Belgium
| | - Nancy Boeckx
- Department of Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium.,Department of Oncology, KU Leuven, Leuven, Belgium
| | - Andre Gothot
- Department of Laboratory Haematology and Immuno-Haematology, CHU Liège, Liège, Belgium
| | - Dries Deeren
- Department of Haematology, AZ Delta Roeselare-Menen, Roeselare, Belgium
| | - Bernard Chatelain
- Laboratory of Haematology, CHU UCL Namur, Université catholique de Louvain, Yvoir, Belgium
| | - Christian Chatelain
- Department of Haematology, CHU UCL Namur, Université catholique de Louvain, Yvoir, Belgium
| | - Bérangère Devalet
- Department of Haematology, CHU UCL Namur, Université catholique de Louvain, Yvoir, Belgium
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Tabib A, Hindi I, Karbian N, Zelig O, Falach B, Mevorach D. Prothrombotic mechanisms in patients with congenital p.Cys89Tyr mutation in CD59. Thromb Res 2018; 168:67-77. [PMID: 29929138 DOI: 10.1016/j.thromres.2018.06.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 06/03/2018] [Accepted: 06/08/2018] [Indexed: 01/18/2023]
Abstract
BACKGROUND Thrombosis is the prognostic factor with the greatest effect on survival in patients with paroxysmal nocturnal hemoglobinuria (PNH), who lack dozens of membrane surface proteins. We recently described a primary homozygous Cys89Tyr congenital nonfunctioning CD59 in humans with clinical manifestation in infancy, associated with chronic hemolysis, recurrent strokes, and relapsing peripheral demyelinating neuropathy. Here we investigated hypercoagulability mechanisms characterizing the syndrome. METHODS Membrane attack complex (MAC) deposition (anti-SC5b-9) and free hemoglobin (colorimetric assay) were assessed. Platelet activation was identified (anti-CD61, anti-CD62P), and microparticles (MPs) of 0.5-0.9 μm, were characterized (Annexin V, anti-human GlyA, anti-CD15, anti-CD14, anti-CD61). Platelet-monocyte aggregation was assessed with FlowSight. FINDINGS 2/7 patients (29%) with homozygosity for Cys89Tyr and 6/12 (50%) with any of four described CD59 mutations had recurrent strokes. In plasma samples from four patients carrying identical mutations, MAC deposition was increased on RBCs (p < 0.0003), neutrophils (p < 0.009), and platelets (p < 0.0003). Free-plasma hemoglobin levels were abnormally high, up to 100 mg/dl. Patients with CD59 mutation had RBC-derived MP levels 9-fold higher than those in healthy controls (p < 0.01), and 2-2.5 fold higher than PNH patients (p < 0.09). Leukocyte-activated platelet aggregation was increased (p < 0.0062). Loss of CD59 was shown in the endothelium of these patients. INTERPRETATION Nonfunctioning CD59 is a major risk factor for stroke and hypercoagulability. Uncontrolled hemolysis causes massive MP release and endothelial heme damage. MAC attack on unprotected endothelium and platelet activation and aggregation with leukocytes mediate additional mechanisms leading to vascular occlusion. It is suggested that CD59 loss represents a major arterial prothrombotic factor in PNH and additional diseases.
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Affiliation(s)
- Adi Tabib
- Rheumatology Research Center and Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Issam Hindi
- Rheumatology Research Center and Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Netanel Karbian
- Rheumatology Research Center and Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Orly Zelig
- Department of Hematology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Batla Falach
- Rheumatology Research Center and Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Dror Mevorach
- Rheumatology Research Center and Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
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Wannez A, Devalet B, Bouvy C, Laloy J, Bihin B, Chatelain B, Chatelain C, Dogné JM, Mullier F. Eculizumab decreases the procoagulant activity of extracellular vesicles in paroxysmal nocturnal hemoglobinuria: A pilot prospective longitudinal clinical study. Thromb Res 2017. [PMID: 28646725 DOI: 10.1016/j.thromres.2017.06.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
INTRODUCTION Paroxysmal nocturnal hemoglobinuria (PNH) is a disease characterized by the susceptibility of blood cells to attack by the complement system, inducing extracellular vesicle (EV) production. Thromboembolism is the leading cause of death in this condition. Eculizumab, a humanized monoclonal antibody which inhibits the C5 protein of the complement, reduces the thrombotic risk in PNH. MATERIALS AND METHOD We conducted a pilot, prospective, open-label, longitudinal clinical study with six PNH patients treated with eculizumab. The aim was to measure, by flow cytometry, the EVs' production in the patients' platelet-free plasma (PFP) before and during the treatment. We also assessed the procoagulant activity in PFP using STA®-Procoag-PPL and thrombin generation assays (TGA). A high-sensitive version of TGA was also used to study the procoagulant profile induced by the EVs using EVs pelleted from PFP. RESULTS We observed a decrease in platelet EV count with eculizumab treatment (p<0.05). STA®-Procoag-PPL assay showed a decrease of the procoagulant profile induced by procoagulant phospholipids (PL) during treatment. These results were not confirmed by TGA on PFP, due to a lack of sensitivity. Thus, we used a high-sensitive version of TGA that enabled us to observe variation in the procoagulant profile induced by the EVs with eculizumab (p<0.05). CONCLUSIONS Eculizumab has an impact on the extent of EV production and on the procoagulant profile induced by the procoagulant PL and the EVs. One factor in the antithrombotic action of eculizumab is its ability to decrease EV production and the procoagulant profile induced by PL and EVs.
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Affiliation(s)
- Adeline Wannez
- Université catholique de Louvain, CHU UCL Namur, Namur Thrombosis and Hemostasis Center, Hematology Laboratory, Yvoir, Belgium; University of Namur, Namur Research Institute for Life Sciences, Namur Thrombosis and Hemostasis Center, Department of Pharmacy, Namur, Belgium.
| | - Bérangère Devalet
- Université catholique de Louvain, CHU UCL Namur, Namur Thrombosis and Hemostasis Center, Department of Hematology, Yvoir, Belgium
| | - Céline Bouvy
- University of Namur, Namur Research Institute for Life Sciences, Namur Thrombosis and Hemostasis Center, Department of Pharmacy, Namur, Belgium
| | - Julie Laloy
- University of Namur, Namur Research Institute for Life Sciences, Namur Nanosafety Center, Department of Pharmacy, Namur, Belgium
| | - Benoit Bihin
- CHU UCL Namur, Scientific Support Unit, Yvoir, Belgium
| | - Bernard Chatelain
- Université catholique de Louvain, CHU UCL Namur, Namur Thrombosis and Hemostasis Center, Hematology Laboratory, Yvoir, Belgium
| | - Christian Chatelain
- University of Namur, Namur Research Institute for Life Sciences, Namur Thrombosis and Hemostasis Center, Department of Pharmacy, Namur, Belgium
| | - Jean-Michel Dogné
- University of Namur, Namur Research Institute for Life Sciences, Namur Thrombosis and Hemostasis Center, Department of Pharmacy, Namur, Belgium
| | - François Mullier
- Université catholique de Louvain, CHU UCL Namur, Namur Thrombosis and Hemostasis Center, Hematology Laboratory, Yvoir, Belgium
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Extracellular vesicles and blood diseases. Int J Hematol 2017; 105:392-405. [PMID: 28130731 DOI: 10.1007/s12185-017-2180-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/09/2017] [Accepted: 01/09/2017] [Indexed: 01/19/2023]
Abstract
Extracellular vesicles (EVs) are small membrane vesicles released from many different cell types by the exocytic budding of the plasma membrane in response to cellular activation or apoptosis. EVs disseminate various bioactive effectors originating from the parent cells and transfer functional RNA and protein between cells, enabling them to alter vascular function and induce biological responses involved in vascular homeostasis. Although most EVs in human blood originate from platelets, EVs are also released from leukocytes, erythrocytes, endothelial cells, smooth muscle cells, and cancer cells. EVs were initially thought to be small particles with procoagulant activity; however, they can also evoke cellular responses in the immediate microenvironments and transport microRNAs (miRNA) into target cells. In this review, we summarize the recent literature relevant to EVs, including a growing list of clinical disorders that are associated with elevated EV levels. These studies suggest that EVs play roles in various blood diseases.
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The dysfunction of platelets in paroxysmal nocturnal hemoglobinuria. Thromb Res 2016; 148:50-55. [PMID: 27780113 DOI: 10.1016/j.thromres.2016.07.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 06/06/2016] [Accepted: 07/21/2016] [Indexed: 01/14/2023]
Abstract
INTRODUCTION Thrombosis is a dangerous complication of paroxysmal nocturnal hemoglobinuria (PNH) and has a high mortality rate. However, the mechanism underlying the development of thrombosis in PNH remains unclear. To explore this, platelet function and serum complement activity were investigated in 14 patients with classical PNH, 11 with PNH aplastic anemia (AA) and 30 healthy controls. MATERIAL AND METHODS Serum concentrations of the terminal complement complex (sC5b-9) were determined by enzyme-linked immunofluorescence assay (ELISA), and the levels of C5b-9, CD61 and CD62p on platelet membranes were determined by flow cytometry. Clinical parameters were assessed, including D-dimer and platelet aggregation induced by adenosine diphosphate (ADP) and arachidonic acid (ARA). RESULTS Serum sC5b-9 concentrations were significantly lower in the PNH/PNH-AA than in the control group (P<0.01). C5b-9 deposition was significantly higher on CD59- platelets than on CD59+ platelets in PNH/PNH-AA patients and healthy controls (P<0.01 for each). D-dimer concentration was significantly higher in PNH/PNH-AA patients - especially those with lactate dehydrogenase (LDH) concentrations>1000U/L - than in controls (P<0.05). CD61 (P<0.05) expression was lower on CD59+ platelets in PNH than in controls and CD5- platelets in PNH. Expression of CD62p (P<0.01) was lower on CD59- and CD59+ platelets (P<0.01) in PNH cases than in controls. Platelet aggregation stimulated by the agonists ADP and ARA in the PNH/PNH-AA patients was significantly lower than that in controls (P<0.05). CONCLUSIONS The adhesion and aggregation of platelets, especially of CD59+ platelets, were compensatively decreased in PNH/PNH-AA patients without active thrombosis.
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