1
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Lee CSM, Kaur A, Montague SJ, Hicks SM, Andrews RK, Gardiner EE. Tissue inhibitors of metalloproteinases (TIMPs) modulate platelet ADAM10 activity. Platelets 2023; 34:2288213. [PMID: 38031964 DOI: 10.1080/09537104.2023.2288213] [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: 08/21/2023] [Accepted: 11/21/2023] [Indexed: 12/01/2023]
Abstract
Platelet-specific collagen receptor glycoprotein (GP)VI is stable on the surface of circulating platelets but undergoes ectodomain cleavage on activated platelets. Activation-dependent GPVI metalloproteolysis is primarily mediated by A Disintegrin And Metalloproteinase (ADAM) 10. Regulation of platelet ADAMs activity is not well-defined however Tissue Inhibitors of Metalloproteinases (TIMPs) may play a role. As levels of TIMPs on platelets and the control of ADAMs-mediated shedding by TIMPs has not been evaluated, we quantified the levels of TIMPs on the surface of resting and activated platelets from healthy donors by flow cytometry and multiplex ELISA. Variable levels of all TIMPs could be detected on platelets. Plasma contained significant quantities of TIMP1 and TIMP2, but only trace amounts of TIMP3 and TIMP4. Recombinant TIMP3 strongly ablated resting and activated platelet ADAM10 activity, when monitored using a quenched fluorogenic peptide substrate with ADAM10 specificity. Whilst ADAM10-specific inhibitor GI254023X or ethylenediamine tetraacetic acid (EDTA) could modulate ligand-initiated shedding of GPVI, only recombinant TIMP2 achieved a modest (~20%) inhibition. We conclude that some platelet TIMPs are able to modulate platelet ADAM10 activity but none strongly regulate ligand-dependent shedding of GPVI. Our findings provide new insights into the regulation of platelet receptor sheddase activity.
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Affiliation(s)
- Christine Shu Mei Lee
- Division of Genome Science and Cancer, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Amandeep Kaur
- Division of Genome Science and Cancer, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Samantha J Montague
- Division of Genome Science and Cancer, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Sarah M Hicks
- Division of Genome Science and Cancer, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Robert K Andrews
- Division of Genome Science and Cancer, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Elizabeth E Gardiner
- Division of Genome Science and Cancer, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
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2
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Hearn JI, Gardiner EE. Research and Clinical Approaches to Assess Platelet Function in Flowing Blood. Arterioscler Thromb Vasc Biol 2023; 43:1775-1783. [PMID: 37615110 DOI: 10.1161/atvbaha.123.317048] [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] [Indexed: 08/25/2023]
Abstract
Platelet adhesion and activation is fundamental to the formation of a hemostatic response to limit loss of blood and instigate wound repair to seal a site of vascular injury. The process of platelet aggregate formation is supported by the coagulation system driving injury-proximal formation of thrombin, which converts fibrinogen to insoluble fibrin. This highly coordinated series of molecular and membranous events must be routinely achieved in flowing blood, at vascular fluid shear rates that place significant strain on molecular and cellular interactions. Platelets have long been recognized to be able to slow down and adhere to sites of vascular injury and then activate and recruit more platelets that forge and strengthen adhesive ties with the vascular wall under these conditions. It has been a major challenge for the Platelet Research Community to construct experimental conditions that allow precise definition of the molecular steps occurring under flow. This brief review will discuss work to date from our group, as well as others that has furthered our understanding of platelet function in flowing blood.
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Affiliation(s)
- James I Hearn
- Division of Genome Science and Cancer, John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Elizabeth E Gardiner
- Division of Genome Science and Cancer, John Curtin School of Medical Research, The Australian National University, Canberra, Australia
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3
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Mangin PH, Gardiner EE, Ariëns RAS, Jandrot-Perrus M. Glycoprotein VI interplay with fibrin(ogen) in thrombosis. J Thromb Haemost 2023; 21:1703-1713. [PMID: 36990158 DOI: 10.1016/j.jtha.2023.03.022] [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: 08/23/2022] [Revised: 03/17/2023] [Accepted: 03/21/2023] [Indexed: 03/30/2023]
Abstract
Platelets play a central role in the arrest of bleeding. The ability of platelets to engage with extracellular matrix proteins of the subendothelium has long been recognized as a pivotal platelet attribute, underpinning adequate hemostasis. The propensity of platelets to rapidly bind and functionally respond to collagen was one of the earliest documented events in platelet biology. The receptor primarily responsible for mediating platelet/collagen responses was identified as glycoprotein (GP) VI and successfully cloned in 1999. Since that time, this receptor has held the attention of many research groups, and through these efforts, we now have an excellent understanding of the roles of GPVI as a platelet- and megakaryocyte-specific adheso-signaling receptor in platelet biology. GPVI is considered a viable antithrombotic target, as data obtained from groups across the world is consistent with GPVI being less involved in physiological hemostatic processes but participating in arterial thrombosis. This review will highlight the key aspects of GPVI contributions to platelet biology and concentrate on the interaction with recently identified ligands, with a focus on fibrin and fibrinogen, discussing the role of these interactions in the growth and stability of thrombi. We will also discuss important therapeutic developments that target GPVI to modulate platelet function while minimizing bleeding outcomes.
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Affiliation(s)
- Pierre H Mangin
- Université de Strasbourg, Institut National de la Santé et de la Recherche Médicale, Etablissement Français du Sang Grand-Est, Unité Mixte de Recherche-S1255, Fédération de Médecine Translationnelle de Strasbourg F-67065 Strasbourg, France.
| | - Elizabeth E Gardiner
- The John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - Robert A S Ariëns
- Discovery and Translational Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom
| | - Martine Jandrot-Perrus
- Université de Paris Institut National de la Santé et de la Recherche Médicale, UMR-S1148, Hôpital Bichat, Paris, France
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4
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Tantawy AAG, Elsherif NHK, Ebeid FS, El-Gamal RAER, Ismail EAR, Kenny MA, Morcos MBE. Evaluation of the effect of eltrombopag therapy on the platelet collagen receptor glycoprotein VI (GPVI) expression and soluble GPVI levels in young patients with immune thrombocytopenia. J Thromb Thrombolysis 2023; 55:243-251. [PMID: 36479670 PMCID: PMC10011314 DOI: 10.1007/s11239-022-02734-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/17/2022] [Indexed: 12/12/2022]
Abstract
BACKGROUND Platelet glycoprotein VI (GPVI) receptor is essential for platelet adhesion and aggregation. Eltrombopag is as an effective treatment for chronic immune thrombocytopenia (ITP); yet, its effect on platelet function is not fully characterized. AIM This prospective study investigated the effect of eltrombopag therapy on platelet function through assessment of GPVI receptor expression and soluble GPVI levels among pediatric patients with persistent or chronic ITP. METHODS Thirty-six children and adolescents with persistent or chronic ITP were divided equally into two groups either to receive eltrombopag therapy or the standard of care. All patients were followed-up for 12 months with assessment of bleeding score and complete blood count (CBC). Evaluation of GPVI expression using flow cytometry and measurement of its soluble form by ELISA was done at baseline and at 6 months. RESULTS ITP patients on eltrombopag had significantly lower bleeding score after 6 months of therapy while the quality of life has significantly improved. Platelet count was significantly increased throughout the study. GPVI expression by flow cytometry and soluble GPVI levels were significantly increased after eltrombopag therapy. After 12 months, ITP patients on eltrombopag were able to maintain a good quality of life and low bleeding score. CONCLUSION Our data suggest that eltrombopag, through its effect on the GPVI receptor expression and its soluble form, might reduce bleeding manifestations and improve the quality of life of chronic and persistent ITP children independent of its effect on the platelet count.
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Affiliation(s)
| | - Nayera Hazaa Khalil Elsherif
- Pediatrics Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt. .,Abbaseya square, Eldemerdash Hospital, cairo, Egypt.
| | - Fatma Soliman Ebeid
- Pediatrics Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt
| | | | | | - Mahmoud A Kenny
- Pediatrics Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt
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5
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The molecular basis of immune-based platelet disorders. Clin Sci (Lond) 2021; 134:2807-2822. [PMID: 33140828 DOI: 10.1042/cs20191101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 10/12/2020] [Accepted: 10/23/2020] [Indexed: 12/17/2022]
Abstract
Platelets have a predominant role in haemostasis, the maintenance of blood volume and emerging roles as innate immune cells, in wound healing and in inflammatory responses. Platelets express receptors that are important for platelet adhesion, aggregation, participation in inflammatory responses, and for triggering degranulation and enhancing thrombin generation. They carry a cargo of granules bearing enzymes, adhesion molecules, growth factors and cytokines, and have the ability to generate reactive oxygen species. The platelet is at the frontline of a host of cellular responses to invading pathogens, injury, and infection. Perhaps because of this intrinsic responsibility of a platelet to rapidly respond to thrombotic, pathological and immunological factors as part of their infantry role; platelets are susceptible to targeted attack by the adaptive immune system. Such attacks are often transitory but result in aberrant platelet activation as well as significant loss of platelet numbers and platelet function, paradoxically leading to elevated risks of both thrombosis and bleeding. Here, we discuss the main molecular events underlying immune-based platelet disorders with specific focus on events occurring at the platelet surface leading to activation and clearance.
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6
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Borst O, Gawaz M. Glycoprotein VI - novel target in antiplatelet medication. Pharmacol Ther 2021; 217:107630. [DOI: 10.1016/j.pharmthera.2020.107630] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 07/11/2020] [Indexed: 02/07/2023]
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7
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Harbi MH, Smith CW, Nicolson PLR, Watson SP, Thomas MR. Novel antiplatelet strategies targeting GPVI, CLEC-2 and tyrosine kinases. Platelets 2020; 32:29-41. [PMID: 33307909 DOI: 10.1080/09537104.2020.1849600] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Antiplatelet medications comprise the cornerstone of treatment for diseases that involve arterial thrombosis, including acute coronary syndromes (ACS), stroke and peripheral arterial disease. However, antiplatelet medications may cause bleeding and, furthermore, thrombotic events may still recur despite treatment. The interaction of collagen with GPVI receptors on the surface of platelets has been identified as one of the major players in the pathophysiology of arterial thrombosis that occurs following atherosclerotic plaque rupture. Promisingly, GPVI deficiency in humans appears to have a minimal impact on bleeding. These findings together suggest that targeting platelet GPVI may provide a novel treatment strategy that provides additional antithrombotic efficacy with minimal disruption of normal hemostasis compared to conventional antiplatelet medications. CLEC-2 is gaining interest as a therapeutic target for a variety of thrombo-inflammatory disorders including deep vein thrombosis (DVT) with treatment also predicted to cause minimal disruption to hemostasis. GPVI and CLEC-2 signal through Src, Syk and Tec family tyrosine kinases, providing additional strategies for inhibiting both receptors. In this review, we summarize the evidence regarding GPVI and CLEC-2 and strategies for inhibiting these receptors to inhibit platelet recruitment and activation in thrombotic diseases.
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Affiliation(s)
- Maan H Harbi
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham , Birmingham, UK
| | - Christopher W Smith
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham , Birmingham, UK
| | - Phillip L R Nicolson
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham , Birmingham, UK.,University Hospitals Birmingham NHS Foundation Trust , Birmingham, UK
| | - Steve P Watson
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham , Birmingham, UK
| | - Mark R Thomas
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham , Birmingham, UK.,University Hospitals Birmingham NHS Foundation Trust , Birmingham, UK.,Sandwell and West Birmingham NHS Trust , Birmingham, UK
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8
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Loyau Inserm S, Faille D, Gautier P, Nurden P, Jandrot-Perrus M, Ajzenberg N. Absence of bleeding upon dual antiplatelet therapy in a patient with a immune GPVI deficiency. Platelets 2020; 32:705-709. [PMID: 32627625 DOI: 10.1080/09537104.2020.1787974] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Acquired deficiencies in platelet glycoprotein VI are rare and have not been found associated with other defects. Here we report the case of a 64-year old male patient presenting an immune GPVI deficiency associated to a mutation in the alpha-actinin gene and who has been treated with dual anti platelet therapy without bleeding.Introduction: Glycoprotein (GP) VI, a pluripotent receptor interacting with collagen and fibrin(ogen) is responsible for thrombus formation, growth and stability (1-4). It is co-expressed with the Fc receptor γ (FcRγ) chain (5). GPVI is not critical for haemostasis since subjects with a GPVI deficiency usually present low or even no bleeding tendency (6, 7). Acquired GPVI deficiency due to antibody-induced GPVI depletion is the most frequent finding. At least 10 patients have been described with an acquired GPVI deficiency, most often associated to immune thrombocytopenia, moderate bleeding and impaired collagen-induced platelet aggregation (7). Several mechanisms leading to the GPVI deficiency are proposed including antibody-triggered GPVI internalization and/or shedding of the extracellular domain (8, 9). We report the case of a patient presenting an acquired GPVI deficiency different from those previously described: (i) he is male whereas all previous cases were female, (ii) he is heterozygous for a mutation in α (alpha)-actinin-1 gene and (iii) he was treated with dual antiplatelet therapy with no haemorrhagic manifestation.
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Affiliation(s)
| | - Dorothée Faille
- Inserm UMR_S1148, Université de Paris, Paris, France.,Laboratoire d'Hématologie, AP-HP, Hôpital Bichat, Paris, France
| | - Philippe Gautier
- Hemophilia Center, Laboratory of Hematology, University Hospital, Caen, France
| | - Paquita Nurden
- Institut Hospitalo-Universitaire LIRYC, Hôpital Xavier Arnozan, Pessac, France
| | | | - Nadine Ajzenberg
- Inserm UMR_S1148, Université de Paris, Paris, France.,Laboratoire d'Hématologie, AP-HP, Hôpital Bichat, Paris, France
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9
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Shedding of soluble glycoprotein VI is neither affected by animal-derived antibeta-2-glycoprotein 1 antibodies nor IgG fractions from patients with systemic lupus erythematosus. Blood Coagul Fibrinolysis 2020; 31:258-263. [DOI: 10.1097/mbc.0000000000000909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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10
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Zhou P, Yin JX, Tao HL, Zhang HW. Pathogenesis and management of heparin-induced thrombocytopenia and thrombosis. Clin Chim Acta 2020; 504:73-80. [DOI: 10.1016/j.cca.2020.02.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 01/30/2020] [Accepted: 02/03/2020] [Indexed: 01/19/2023]
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11
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Hicks SM, Coupland LA, Jahangiri A, Choi PY, Gardiner EE. Novel scientific approaches and future research directions in understanding ITP. Platelets 2020; 31:315-321. [PMID: 32054377 DOI: 10.1080/09537104.2020.1727871] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Diagnosis of immune thrombocytopenia (ITP) and prediction of response to therapy remain significant and constant challenges in hematology. In patients who present with ITP, the platelet count is frequently used as a surrogate marker for disease severity, and so often determines the need for therapy. Although there is a clear link between thrombocytopenia and hemostasis, a direct correlation between the extent of thrombocytopenia and bleeding symptoms, especially at lower platelet counts is lacking. Thus, bleeding in ITP is heterogeneous, unpredictable, and nearly always based on a multitude of risk factors, beyond the platelet count. The development of an evidence-based, validated risk stratification model for ITP treatment is a major goal in the ITP community and this review discusses new laboratory approaches to evaluate the various pathobiologies of ITP that may inform such a model.
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Affiliation(s)
- Sarah M Hicks
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Lucy A Coupland
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia.,The National Platelet Research and Referral Centre (NPRC), Canberra, Australia
| | - Anila Jahangiri
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Philip Y Choi
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia.,The National Platelet Research and Referral Centre (NPRC), Canberra, Australia.,Haematology Department, The Canberra Hospital, Canberra, Australia
| | - Elizabeth E Gardiner
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia.,The National Platelet Research and Referral Centre (NPRC), Canberra, Australia
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12
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Qiao J, Dunne E, Wines B, Kenny D, McCarthy GM, Hogarth PM, Xu K, Andrews RK, Gardiner EE. Plasma levels of the soluble form of the FcγRIIa receptor vary with receptor polymorphisms and are elevated in rheumatoid arthritis. Platelets 2019; 31:392-398. [DOI: 10.1080/09537104.2019.1647527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Jianlin Qiao
- Australian Centre for Blood Diseases, Monash University, Melbourne, Australia
- Blood Disease Institute, Xuzhou Medical University, Xuzhou, China
- Department of Hematology, the Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Eimear Dunne
- Molecular & Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Bruce Wines
- Centre for Biomedical Research, Burnet Institute, Melbourne, Australia
| | - Dermot Kenny
- Molecular & Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | | | - P. Mark Hogarth
- Centre for Biomedical Research, Burnet Institute, Melbourne, Australia
| | - Kailin Xu
- Blood Disease Institute, Xuzhou Medical University, Xuzhou, China
- Department of Hematology, the Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Robert K. Andrews
- Australian Centre for Blood Diseases, Monash University, Melbourne, Australia
| | - Elizabeth E. Gardiner
- ACRF Department of Cancer Biology and Therapeutics, John Curtin School of Medical Research, The Australian National University, Canberra, Australia
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13
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Nurden AT. Clinical significance of altered collagen-receptor functioning in platelets with emphasis on glycoprotein VI. Blood Rev 2019; 38:100592. [PMID: 31351674 DOI: 10.1016/j.blre.2019.100592] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 07/05/2019] [Accepted: 07/19/2019] [Indexed: 01/01/2023]
Abstract
Much interest surrounds the receptors α2β1 and glycoprotein VI (GPVI) whose synchronized action mediates the attachment and activation of platelets on collagen, essential for preventing blood loss but also the most thrombogenic component of the vessel wall. Subject to density variations on platelets through natural polymorphisms, the absence of α2β1 or GPVI uniquely leads to a substantial block of hemostasis without causing major bleeding. Specific to the megakaryocyte lineage, GPVI and its signaling pathways are most promising targets for anti-thrombotic therapy. This review looks at the clinical consequences of the loss of collagen receptor function with emphasis on both the inherited and acquired loss of GPVI with brief mention of mouse models when necessary. A detailed survey of rare case reports of patients with inherited disease-causing variants of the GP6 gene is followed by an assessment of the causes and clinical consequences of acquired GPVI deficiency, a more frequent finding most often due to antibody-induced platelet GPVI shedding. Release of soluble GPVI is brought about by platelet metalloproteinases; a process induced by ligand or antibody binding to GPVI or even high shear forces. Also included is an assessment of the clinical importance of GPVI-mediated platelet interactions with fibrin and of the promise shown by the pharmacological inhibition of GPVI in a cardiovascular context. The role for GPVI in platelet function in inflammation and in the evolution and treatment of major illnesses such as rheumatoid arthritis, cancer and sepsis is also discussed.
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Affiliation(s)
- Alan T Nurden
- Institut de Rhythmologie et de Modélisation Cardiaque, PTIB, Hôpital Xavier Arnozan, 33600 Pessac, France.
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14
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Jandrot-Perrus M, Hermans C, Mezzano D. Platelet glycoprotein VI genetic quantitative and qualitative defects. Platelets 2019; 30:708-713. [PMID: 31068042 DOI: 10.1080/09537104.2019.1610166] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Platelet membrane glycoprotein VI (GPVI) is increasingly recognized as an important receptor for thrombus formation and growth. Numerous arguments have been published indicating that GPVI plays a major role in thrombosis without being essential for physiological hemostasis. In humans, GPVI deficiencies are rarely reported. These are most often deficiencies occurring in the context of autoimmunity and, more rarely, genetic deficits. The purpose of this review is to compile data on the quantitative and qualitative genetic abnormalities of GPVI.
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Affiliation(s)
- Martine Jandrot-Perrus
- a UMR_S1148, Laboratory for Vascular Translational Science , INSERM, University Paris Diderot , Paris , France
| | - Cedric Hermans
- b Haemostasis and Thrombosis Unit, Haemophilia Clinic, Division of Adult Haematology , St-Luc University Hospital , Brussels , Belgium
| | - Diego Mezzano
- c Department of Hematology-Oncology , School of Medicine, Pontificia Universidad Católica de Chile , Santiago , Chile
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15
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Mechanisms of receptor shedding in platelets. Blood 2018; 132:2535-2545. [DOI: 10.1182/blood-2018-03-742668] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 10/12/2018] [Indexed: 02/07/2023] Open
Abstract
Abstract
The ability to upregulate and downregulate surface-exposed proteins and receptors is a powerful process that allows a cell to instantly respond to its microenvironment. In particular, mobile cells in the bloodstream must rapidly react to conditions where infection or inflammation are detected, and become proadhesive, phagocytic, and/or procoagulant. Platelets are one such blood cell that must rapidly acquire and manage proadhesive and procoagulant properties in order to execute their primary function in hemostasis. The regulation of platelet membrane properties is achieved via several mechanisms, one of which involves the controlled metalloproteolytic release of adhesion receptors and other proteins from the platelet surface. Proteolysis effectively lowers receptor density and reduces the reactivity of platelets, and is a mechanism to control robust platelet activation. Recent research has also established clear links between levels of platelet receptors and platelet lifespan. In this review, we will discuss the current knowledge of metalloproteolytic receptor regulation in the vasculature with emphasis on the platelet receptor system to highlight how receptor density can influence both platelet function and platelet survival.
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16
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Slater A, Perrella G, Onselaer MB, Martin EM, Gauer JS, Xu RG, Heemskerk JWM, Ariëns RAS, Watson SP. Does fibrin(ogen) bind to monomeric or dimeric GPVI, or not at all? Platelets 2018; 30:281-289. [DOI: 10.1080/09537104.2018.1508649] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Alexandre Slater
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Gina Perrella
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, Maastricht, The Netherlands
| | - Marie-Blanche Onselaer
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Eleyna M Martin
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Julia S Gauer
- Thrombosis and Tissue Repair Group, Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
| | - Rui-Gang Xu
- Thrombosis and Tissue Repair Group, Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
| | - Johan WM Heemskerk
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, Maastricht, The Netherlands
| | - Robert A S Ariëns
- Thrombosis and Tissue Repair Group, Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
| | - Steve P Watson
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
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17
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Luu S, Gardiner EE, Andrews RK. Bone Marrow Defects and Platelet Function: A Focus on MDS and CLL. Cancers (Basel) 2018; 10:E147. [PMID: 29783667 PMCID: PMC5977120 DOI: 10.3390/cancers10050147] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 05/11/2018] [Accepted: 05/16/2018] [Indexed: 12/16/2022] Open
Abstract
The bloodstream typically contains >500 billion anucleate circulating platelets, derived from megakaryocytes in the bone marrow. This review will focus on two interesting aspects of bone marrow dysfunction and how this impacts on the quality of circulating platelets. In this regard, although megakaryocytes are from the myeloid lineage leading to granulocytes (including neutrophils), erythrocytes, and megakaryocytes/platelets, recent evidence has shown that defects in the lymphoid lineage leading to B cells, T cells, and natural killer (NK) cells also result in abnormal circulating platelets. Current evidence is limited regarding whether this latter phenomenon might potentially arise from (a) some form of as-yet-undetected defect common to both lineages; (b) adverse interactions occurring between cells of different lineages within the bone marrow environment; and/or (c) unknown disease-related factor(s) affecting circulating platelet receptor expression/function after their release from megakaryocytes. Understanding the mechanisms underlying how both myeloid and lymphoid lineage bone marrow defects lead to dysfunction of circulating platelets is significant because of the potential diagnostic and predictive value of peripheral platelet analysis for bone marrow disease progression, the additional potential effects of new anti-cancer drugs on platelet function, and the critical role platelets play in regulation of bleeding risk, inflammation, and innate immunity.
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Affiliation(s)
- Sarah Luu
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia.
| | - Elizabeth E Gardiner
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT 2600, Australia.
| | - Robert K Andrews
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia.
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18
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Gardiner EE. Proteolytic processing of platelet receptors. Res Pract Thromb Haemost 2018; 2:240-250. [PMID: 30046726 PMCID: PMC6055504 DOI: 10.1002/rth2.12096] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 03/01/2018] [Indexed: 12/17/2022] Open
Abstract
Platelets have a major role in hemostasis and an emerging role in biological processes including inflammation and immunity. Many of these processes require platelet adhesion and localization at sites of tissue damage or infection and regulated platelet activation, mediated by platelet adheso-signalling receptors, glycoprotein (GP) Ib-IX-V and GPVI. Work from a number of laboratories has demonstrated that levels of these receptors are closely regulated by metalloproteinases of the A Disintegrin And Metalloproteinase (ADAM) family, primarily ADAM17 and ADAM10. It is becoming increasingly evident that platelets have important roles in innate immunity, inflammation, and in combating infection that extends beyond processes of hemostasis. This overview will examine the molecular events that regulate levels of platelet receptors and then assess ramifications for these events in settings where hemostasis, inflammation, and infection processes are triggered.
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Affiliation(s)
- Elizabeth E. Gardiner
- ACRF Department of Cancer Biology and TherapeuticsJohn Curtin School of Medical ResearchThe Australian National UniversityCanberraACTAustralia
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19
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Arthur JF, Gardiner EE, Andrews RK, Al-Tamimi M. Focusing on plasma glycoprotein VI. Thromb Haemost 2017; 107:648-55. [DOI: 10.1160/th11-10-0745] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Accepted: 12/10/2011] [Indexed: 12/18/2022]
Abstract
SummaryNew methods for analysing both platelet and plasma forms of the platelet-specific collagen receptor, glycoprotein VI (GPVI) in experimental models or human clinical samples, and the development of the first therapeutic compounds based on dimeric soluble GPVI-Fc or anti-GPVI antibody-based constructs, coincide with increased understanding of the potential pathophysiological role of GPVI ligand binding and shedding. Platelet GPVI not only mediates platelet activation at the site of vascular injury where collagen is exposed, but is also implicated in the pathogenesis of other diseases, such as atherosclerosis and coagulopathy, rheumatoid arthritis and tumour metastasis. Here, we describe some of the critical mechanisms for generating soluble GPVI from platelets, and future avenues for exploiting this unique platelet-specific receptor for diagnosis and/or disease prevention.
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20
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Soluble glycoprotein VI, a specific marker of platelet activation is increased in the plasma of subjects with seropositive rheumatoid arthritis. PLoS One 2017; 12:e0188027. [PMID: 29141000 PMCID: PMC5687752 DOI: 10.1371/journal.pone.0188027] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 10/29/2017] [Indexed: 11/29/2022] Open
Abstract
Objectives Anti-citrullinated protein antibodies (ACPA) have been shown to cause platelet activation in vitro, through the low-affinity immunoglobulin G (IgG) receptor (FcγRIIa) on platelets. Platelet activation via engagement of FcγRIIa results in proteolytic cleavage and shedding of platelet specific glycoprotein VI (GPVI) which can be detected in the plasma as soluble GPVI (sGPVI). We hypothesized that plasma levels of sGPVI would be increased among patients with seropositive RA as a consequence of antibody-induced platelet activation and GPVI shedding. Methods Samples from 84 patients with RA (65 seropositive and 19 seronegative) and 67 healthy controls were collected prospectively and analysed for sGPVI using a standardised ELISA. Results Patients with seropositive RA had significantly higher levels of sGPVI compared to seronegative RA and controls. Median (IQR) sGPVI levels were 4.2 ng/ml (3.2, 8.0) in seropositve RA, 2.2 ng/ml (1.5, 3.5) in seronegative RA and 2.2 ng/ml (1.6, 3.4) in controls (p<0.0001). sGPVI levels correlated with ACPA titres (r = 0.32, p = 0.0026) and with RF titres (r = 0.48, p<0.0001). Conclusion Plasma sGPVI, a specific marker of platelet activation is increased among patients with seropositive RA.
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21
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Rabbolini DJ, Gardiner EE, Morel‐Kopp M, Dunkley S, Jahangiri A, Lee CS, Stevenson WS, Ward CM. Anti-glycoprotein VI mediated immune thrombocytopenia: An under-recognized and significant entity? Res Pract Thromb Haemost 2017; 1:291-295. [PMID: 30046699 PMCID: PMC6058269 DOI: 10.1002/rth2.12033] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 06/27/2017] [Indexed: 11/05/2022] Open
Abstract
Idiopathic immune thrombocytopenia (ITP) is an autoimmune disorder characterized by relapsing/ remitting thrombocytopenia. Bleeding complications are infrequent with platelet counts above 30×109/L, and this level is commonly used as a threshold for treatment. The question of another/ co-existent diagnosis or an alternate mechanism of platelet destruction arises when bleeding is experienced with platelet counts above this threshold. We report a case of anti-GPVI mediated ITP that was diagnosed following investigations performed to address this key clinical question. A patient with ITP experienced exaggerated bruising symptoms despite a platelet count of 91×109/L. Platelet functional testing showed an isolated platelet defect of collagen-induced aggregation. Next generation sequencing excluded a pathogenic variant of GP6, and anti-GPVI antibodies that curtailed GPVI function were confirmed by extended platelet phenotyping. We propose that anti-GPVI mediated ITP may be under-recognized, and that inclusion of GPVI in antibody detection assays may improve their diagnostic utility and in turn, facilitate a better understanding of ITP pathophysiology and aid individualized treatment approaches.
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Affiliation(s)
- David J. Rabbolini
- Department of Haematology and Transfusion MedicineRoyal North Shore HospitalSydneyNSWAustralia
- Northern Blood Research CentreKolling Institute of Medical ResearchUniversity of SydneySydneyNSWAustralia
| | - Elizabeth E. Gardiner
- ACRF Department of Cancer Biology and TherapeuticsJohn Curtin School of Medical ResearchAustralian National UniversityCanberraACTAustralia
| | - Marie‐Christine Morel‐Kopp
- Department of Haematology and Transfusion MedicineRoyal North Shore HospitalSydneyNSWAustralia
- Northern Blood Research CentreKolling Institute of Medical ResearchUniversity of SydneySydneyNSWAustralia
| | | | - Anila Jahangiri
- ACRF Department of Cancer Biology and TherapeuticsJohn Curtin School of Medical ResearchAustralian National UniversityCanberraACTAustralia
| | - Christine S‐M. Lee
- ACRF Department of Cancer Biology and TherapeuticsJohn Curtin School of Medical ResearchAustralian National UniversityCanberraACTAustralia
| | - William S. Stevenson
- Department of Haematology and Transfusion MedicineRoyal North Shore HospitalSydneyNSWAustralia
- Northern Blood Research CentreKolling Institute of Medical ResearchUniversity of SydneySydneyNSWAustralia
| | - Christopher M. Ward
- Department of Haematology and Transfusion MedicineRoyal North Shore HospitalSydneyNSWAustralia
- Northern Blood Research CentreKolling Institute of Medical ResearchUniversity of SydneySydneyNSWAustralia
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22
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Minet V, Dogné JM, Mullier F. Functional Assays in the Diagnosis of Heparin-Induced Thrombocytopenia: A Review. Molecules 2017; 22:molecules22040617. [PMID: 28398258 PMCID: PMC6153750 DOI: 10.3390/molecules22040617] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 04/05/2017] [Accepted: 04/08/2017] [Indexed: 01/09/2023] Open
Abstract
A rapid and accurate diagnosis in patients with suspected heparin-induced thrombocytopenia (HIT) is essential for patient management but remains challenging. Current HIT diagnosis ideally relies on a combination of clinical information, immunoassay and functional assay results. Platelet activation assays or functional assays detect HIT antibodies that are more clinically significant. Several functional assays have been developed and evaluated in the literature. They differ in the activation endpoint studied; the technique or technology used; the platelet donor selection; the platelet suspension (washed platelets, platelet rich plasma or whole blood); the patient sample (serum or plasma); and the heparin used (type and concentrations). Inconsistencies in controls performed and associated results interpretation are common. Thresholds and performances are determined differently among papers. Functional assays suffer from interlaboratory variability. This lack of standardization limits the evaluation and the accessibility of functional assays in laboratories. In the present article, we review all the current activation endpoints, techniques and methodologies of functional assays developed for HIT diagnosis.
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Affiliation(s)
- Valentine Minet
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), Namur Research Institute for LIfe Sciences (NARILIS), University of Namur, Namur 5000, Belgium.
| | - Jean-Michel Dogné
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), Namur Research Institute for LIfe Sciences (NARILIS), University of Namur, Namur 5000, Belgium.
| | - François Mullier
- CHU UCL Namur, Namur Thrombosis and Hemostasis Center (NTHC), Hematology Laboratory, Université catholique de Louvain, Yvoir 5530, Belgium.
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23
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Lukito P, Wong A, Jing J, Arthur JF, Marasco SF, Murphy DA, Bergin PJ, Shaw JA, Collecutt M, Andrews RK, Gardiner EE, Davis AK. Mechanical circulatory support is associated with loss of platelet receptors glycoprotein Ibα and glycoprotein VI. J Thromb Haemost 2016; 14:2253-2260. [PMID: 27601054 DOI: 10.1111/jth.13497] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 08/22/2016] [Indexed: 11/25/2022]
Abstract
Essentials Relationship of acquired von Willebrand disease (VWD) and platelet dysfunction is explored. Patients with ventricular assist devices and on extracorporeal membrane oxygenation are investigated. Acquired VWD and platelet receptor shedding is demonstrated in the majority of patients. Loss of platelet adhesion receptors glycoprotein (GP) Ibα and GPVI may increase bleeding risk. SUMMARY Background Ventricular assist devices (VADs) and extracorporeal membrane oxygenation (ECMO) are associated with bleeding that is not fully explained by anticoagulant or antiplatelet use. Exposure of platelets to elevated shear in vitro leads to increased shedding. Objectives To investigate whether loss of platelet receptors occurs in vivo, and the relationship with acquired von Willebrand syndrome (AVWS). Methods Platelet counts, coagulation tests and von Willebrand factor (VWF) analyses were performed on samples from 21 continuous flow VAD (CF-VAD), 20 ECMO, 12 heart failure and seven aortic stenosis patients. Levels of platelet receptors were measured by flow cytometry or ELISA. Results The loss of high molecular weight VWF multimers was observed in 18 of 19 CF-VAD and 14 of 20 ECMO patients, consistent with AVWS. Platelet receptor shedding was demonstrated by elevated soluble glycoprotein (GP) VI levels in plasma and significantly reduced surface GPIbα and GPVI levels in CF-VAD and ECMO patients as compared with healthy donors. Platelet receptor levels were also significantly reduced in heart failure patients. Conclusions These data link AVWS and increased platelet receptor shedding in patients with CF-VADs or ECMO for the first time. Loss of the platelet surface receptors GPIbα and GPVI in heart failure, CF-VAD and ECMO patients may contribute to ablated platelet adhesion/activation, and limit thrombus formation under high/pathologic shear conditions.
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Affiliation(s)
- P Lukito
- Haematology Unit, Alfred Hospital, Melbourne, Australia
| | - A Wong
- Haematology Unit, Alfred Hospital, Melbourne, Australia
| | - J Jing
- Australian Centre for Blood Diseases, Monash University, Melbourne, Australia
| | - J F Arthur
- Australian Centre for Blood Diseases, Monash University, Melbourne, Australia
| | - S F Marasco
- Cardiothoracic Unit, Alfred Hospital, Melbourne, Australia
| | - D A Murphy
- Intensive Care Unit, Alfred Hospital, Melbourne, Australia
| | - P J Bergin
- Cardiology Unit, Alfred Hospital, Melbourne, Australia
| | - J A Shaw
- Cardiology Unit, Alfred Hospital, Melbourne, Australia
| | - M Collecutt
- Haematology Laboratory, Alfred Hospital, Melbourne, Australia
| | - R K Andrews
- Australian Centre for Blood Diseases, Monash University, Melbourne, Australia
| | - E E Gardiner
- Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - A K Davis
- Haematology Unit, Alfred Hospital, Melbourne, Australia
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24
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Abstract
Proteolytic shedding of the extracellular ectodomain of platelet receptors provides a key mechanism for irreversible loss of ligand-binding capacity, and for regulating platelet function in health and disease. Platelets derived from megakaryocytes are small anucleate cells in peripheral blood, with the ability to rapidly adhere, become activated, and secrete an array of procoagulant and proinflammatory factors at sites of vascular injury or disease, and to form a platelet aggregate (thrombus) which is not only critical in normal hemostasis and wound healing, but in atherothrombotic diseases including myocardial infarction and ischemic stroke. Basic mechanisms of receptor shedding on platelets have important distinctions from how receptors on other cell types might be shed, in that shedding is rapidly initiated (within seconds to minutes) and occurs under altered shear conditions encountered in flowing blood or experimentally ex vivo. This review will consider the key components of platelet receptor shedding, that is, the receptor with relevant cleavage site, the (metallo)proteinase or sheddase and how its activity is regulated, and the range of known regulatory factors that control platelet receptor shedding including receptor-associated molecules such as calmodulin, factors controlling sheddase surface expression and activity, and other elements such as shear stress, plasma membrane properties, cellular activation status or age. Understanding these basic mechanisms of platelet receptor shedding is significant in terms of utilizing receptor surface expression or soluble proteolytic fragments as platelet-specific biomarkers and/or ultimately therapeutic targeting of these mechanisms to control platelet reactivity and function.
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Affiliation(s)
- Robert K Andrews
- a Australian Centre for Blood Diseases , Monash University , Melbourne , Australia 3004.,b Department of Cancer Biology and Therapeutics, the John Curtin School of Medical Research , Australian National University , Canberra , Australia 2600
| | - Elizabeth E Gardiner
- a Australian Centre for Blood Diseases , Monash University , Melbourne , Australia 3004.,b Department of Cancer Biology and Therapeutics, the John Curtin School of Medical Research , Australian National University , Canberra , Australia 2600
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25
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Chatterjee M, Gawaz M. Clinical significance of receptor shedding-platelet GPVI as an emerging diagnostic and therapeutic tool. Platelets 2016; 28:362-371. [PMID: 27753514 DOI: 10.1080/09537104.2016.1227062] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Platelet membrane bedecked with a wide array of receptors offers a platform to regulate platelet responsiveness, thrombotic propensity, inflammatory disposition, and immune reactivity under diverse pathophysiological conditions. Ectopic proteolytic cleavage of such receptors irreversibly inactivates receptor-mediated intracellular signaling governing cellular functions, further releases soluble fragments into circulation which might modulate functions of target cells. Glycoprotein VI-(GPVI) is a membrane glycoprotein expressed in platelets and megakaryocytes. Platelet GPVI surface expression is enhanced following acute ischemic events like myocardial infarction and cerebral stroke, serves as an imminent diagnostic tool independent of markers of tissue necrosis, and is associated with poor prognosis. Platelets undergo GPVI shedding and thereby contribute to soluble plasma levels of sGPVI, with distinct diagnostic and prognostic attributes. This review summarizes the functional significance and mechanistic basis whereby GPVI surface availability is up- or downregulated on platelets and the impact of GPVI in diagnostic, prognostic, and therapeutic strategies in diseases where platelets play a regulatory role. Further, we also highlight how novel non-invasive platelet-based diagnostic and therapeutic strategies have evolved utilizing GPVI for lesion-directed antithrombotic therapy or to counteract atherosclerotic disposition to ameliorate care of patients particularly in the context of cardio-cerebro-vascular medicine.
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Affiliation(s)
- Madhumita Chatterjee
- a Innere Medizin III, Kardiologie und Kreislauferkrankungen , Eberhard Karls Universität , Tübingen , Germany
| | - Meinrad Gawaz
- a Innere Medizin III, Kardiologie und Kreislauferkrankungen , Eberhard Karls Universität , Tübingen , Germany
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26
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Qiao J, Al-Tamimi M, Baker RI, Andrews RK, Gardiner EE. The platelet Fc receptor, FcγRIIa. Immunol Rev 2016; 268:241-52. [PMID: 26497525 DOI: 10.1111/imr.12370] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Human platelets express FcγRIIa, the low-affinity receptor for the constant fragment (Fc) of immunoglobulin (Ig) G that is also found on neutrophils, monocytes, and macrophages. Engagement of this receptor on platelets by immune complexes triggers intracellular signaling events that lead to platelet activation and aggregation. Importantly these events occur in vivo, particularly in response to pathological immune complexes, and engagement of this receptor on platelets has been causally linked to disease pathology. In this review, we will highlight some of the key features of this receptor in the context of the platelet surface, and examine the functions of platelet FcγRIIa in normal hemostasis and in response to injury and infection. This review will also highlight pathological consequences of engagement of this receptor in platelet-based autoimmune disorders. Finally, we present some new data investigating whether levels of the extracellular ligand-binding region of platelet glycoprotein VI which is rapidly shed upon engagement of platelet FcγRIIa by autoantibodies, can report on the presence of pathological anti-heparin/platelet factor 4 immune complexes and thus identify patients with pathological autoantibodies who are at the greatest risk of developing life-threatening thrombosis in the setting of heparin-induced thrombocytopenia.
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Affiliation(s)
- Jianlin Qiao
- The Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | - Mohammad Al-Tamimi
- Department of Basic Medical Sciences, Hashemite University, Zarqa, Jordan
| | - Ross I Baker
- Western Australian Centre for Thrombosis and Haemostasis, Murdoch University, Perth, WA, Australia
| | - Robert K Andrews
- The Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | - Elizabeth E Gardiner
- The Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
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27
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Lee RH, Bergmeier W. Platelet immunoreceptor tyrosine-based activation motif (ITAM) and hemITAM signaling and vascular integrity in inflammation and development. J Thromb Haemost 2016; 14:645-54. [PMID: 26749528 DOI: 10.1111/jth.13250] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 12/24/2015] [Indexed: 01/13/2023]
Abstract
Platelets are essential for maintaining hemostasis following mechanical injury to the vasculature. Besides this established function, novel roles of platelets are becoming increasingly recognized, which are critical in non-injury settings to maintain vascular barrier integrity. For example, during embryogenesis platelets act to support the proper separation of blood and lymphatic vessels. This role continues beyond birth, where platelets prevent leakage of blood into the lymphatic vessel network. During the course of inflammation, platelets are necessary to prevent local hemorrhage due to neutrophil diapedesis and disruption of endothelial cell-cell junctions. Surprisingly, platelets also work to secure tumor-associated blood vessels, inhibiting excessive vessel permeability and intra-tumor hemorrhaging. Interestingly, many of these novel platelet functions depend on immunoreceptor tyrosine-based activation motif (ITAM) signaling but not on signaling via G protein-coupled receptors, which plays a crucial role in platelet plug formation at sites of mechanical injury. Murine platelets express two ITAM-containing receptors: the Fc receptor γ-chain (FcRγ), which functionally associates with the collagen receptor GPVI, and the C-type lectin-like 2 (CLEC-2) receptor, a hemITAM receptor for the mucin-type glycoprotein podoplanin. Human platelets express an additional ITAM receptor, FcγRIIA. These receptors share common downstream effectors, including Syk, SLP-76 and PLCγ2. Here we will review the recent literature that highlights a critical role for platelet GPVI/FcRγ and CLEC-2 in vascular integrity during development and inflammation in mice and discuss the relevance to human disease.
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Affiliation(s)
- R H Lee
- McAllister Heart Institute, University of North Carolina, Chapel Hill, NC, USA
| | - W Bergmeier
- McAllister Heart Institute, University of North Carolina, Chapel Hill, NC, USA
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, USA
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28
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Sánchez Guiu IM, Martínez-Martinez I, Martínez C, Navarro-Fernandez J, García-Candel F, Ferrer-Marín F, Vicente V, Watson SP, Andrews RK, Gardiner EE, Lozano ML, Rivera J. An atypical IgM class platelet cold agglutinin induces GPVI-dependent aggregation of human platelets. Thromb Haemost 2015; 114:313-24. [PMID: 25994029 DOI: 10.1160/th14-11-0945] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 03/15/2015] [Indexed: 12/12/2022]
Abstract
Platelet cold agglutinins (PCA) cause pseudothrombocytopenia, spurious thrombocytopenia due to ex vivo platelet clumping, complicating clinical diagnosis, but mechanisms and consequences of PCA are not well defined. Here, we characterised an atypical immunoglobulin (Ig)M PCA in a 37-year-old woman with lifelong bleeding and chronic moderate thrombocytopenia, that induces activation and aggregation of autologous or allogeneic platelets via interaction with platelet glycoprotein (GP)VI. Patient temperature-dependent pseudothrombocytopenia was EDTA-independent, but was prevented by integrin αIIbβ3 blockade. Unstimulated patient platelets revealed elevated levels of bound IgM, increased expression of activation markers (P-selectin and CD63), low GPVI levels and abnormally high thromboxane (TX)A2 production. Patient serum induced temperature- and αIIbβ3-dependent decrease of platelet count in allogeneic donor citrated platelet-rich plasma (PRP), but not in PRP from Glanzmann's thrombasthenia or afibrinogenaemia patients. In allogeneic platelets, patient plasma induced shape change, P-selectin and CD63 expression, (14)C-serotonin release, and TXA2 production. Activation was not inhibited by aspirin, cangrelor or blocking anti-Fc receptor (FcγRIIA) antibody, but was abrogated by inhibitors of Src and Syk, and by a soluble GPVI-Fc fusion protein. GPVI-deficient platelets were not activated by patient plasma. These data provide the first evidence for an IgM PCA causing platelet activation/aggregation via GPVI. The PCA activity persisted over a five-year follow-up period, supporting a causative role in patient chronic thrombocytopenia and bleeding.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - M L Lozano
- María Luisa Lozano, MD, PhD, Centro Regional de Hemodonación, C/ Ronda de Garay s/n, Murcia, 30003, Spain, Tel.: +34 968341990, Fax: +34 96826191, E-mail:
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29
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Establishment of immunoassay for platelet-derived soluble glycoprotein VI, a novel platelet marker. J Immunol Methods 2015; 418:52-60. [PMID: 25655782 DOI: 10.1016/j.jim.2015.01.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 12/31/2014] [Accepted: 01/26/2015] [Indexed: 11/24/2022]
Abstract
Soluble Glycoprotein VI (GPVI) is an attractive marker for disorders marked by platelet activation, such as thrombotic microangiopathy, myocardial infarction, and stroke. Several groups have already developed an immunoassay for soluble GPVI; however, there are several discrepancies between the groups' assays. In this study, we prepared the two types of recombinant soluble GPVI, the monomeric form GPVI (GPVI-His) and the dimeric form of GPVI (GPVI-Fc), moreover, we generated four anti-GPVI antibodies, F1232-7-1 (7S1), F1232-10-2 (10S2), F1232-19-1 (19D1), and F1232-21-1 (21D1). The former 2 antibodies (7S1 and 10S2) had a high affinity for both GPVI-His and GPVI-Fc, while the latter 2 antibodies (19D1 and 21D1) showed a high affinity for GPVI-Fc but low affinity for GPVI-His. All of the antibodies comparably recognized surface GPVI on resting platelets. Furthermore, we established two immunoassays for soluble GPVI, 7S1/10S2-HRP and 19D1/21D1-HRP (capture antibody/detection antibody). 7S1/10S2-HRP showed equivalent reactivity with GPVI-His and GPVI-Fc, whereas 19D1/21D1-HRP had high affinity for GPVI-Fc but low reactivity with GPVI-His. In terms of reactivity with platelet-derived soluble GPVI, 7S1/10S2-HRP demonstrated sensitive detection whereas 19D1/21D1-HRP was nonreactive. Taken together, 7S1/10S2-HRP is a suitable candidate for a reliable soluble GPVI immunoassay as it has a high affinity for monomeric GPVI.
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30
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Naitoh K, Hosaka Y, Honda M, Ogawa K, Shirakawa K, Furusako S. Properties of soluble glycoprotein VI, a potential platelet activation biomarker. Platelets 2014; 26:745-50. [PMID: 25549161 DOI: 10.3109/09537104.2014.991707] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glycoprotein VI (GPVI) plays a critical role in the platelet response to collagen. Clinical studies suggest that the plasma level of soluble GPVI (sGPVI) is a highly specific and useful platelet activation marker. However, many properties of sGPVI have not been fully characterized, such as its sensitivity in detecting platelet activation and its elimination rate from the blood. In this study we established a sandwich enzyme-linked immunosorbent assay for human sGPVI, which cross-reacts to cynomolgus monkey sGPVI, and evaluated the time course of sGPVI production in a cynomolgus monkey model of lipopolysaccharide (LPS)-induced thrombocytopenia. The sGPVI levels in this model were dramatically elevated and returned to baseline by 24 hours after LPS injection, the change was more pronounced than the existing platelet activation biomarker, soluble P-selectin (sP-selectin) levels. The elimination half-life of recombinant human sGPVI was about 2.5 hours following intravenous administration to monkeys. These results suggest that plasma sGPVI closely reflects platelet activation in the bloodstream and has a short half-life. sGPVI would be a useful biomarker for disorders marked by platelet activation and for monitoring anti-platelet therapy.
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Affiliation(s)
- Katsuki Naitoh
- a Biology Laboratory, Discovery Research, Mochida Pharmaceutical Co., LTD. , Jimba , Gotemba , Shizuoka , Japan
| | - Yoshitaka Hosaka
- a Biology Laboratory, Discovery Research, Mochida Pharmaceutical Co., LTD. , Jimba , Gotemba , Shizuoka , Japan
| | - Motoyasu Honda
- a Biology Laboratory, Discovery Research, Mochida Pharmaceutical Co., LTD. , Jimba , Gotemba , Shizuoka , Japan
| | - Kumiko Ogawa
- a Biology Laboratory, Discovery Research, Mochida Pharmaceutical Co., LTD. , Jimba , Gotemba , Shizuoka , Japan
| | - Kamon Shirakawa
- a Biology Laboratory, Discovery Research, Mochida Pharmaceutical Co., LTD. , Jimba , Gotemba , Shizuoka , Japan
| | - Shoji Furusako
- a Biology Laboratory, Discovery Research, Mochida Pharmaceutical Co., LTD. , Jimba , Gotemba , Shizuoka , Japan
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31
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Abstract
While platelet activation is essential to maintain blood vessel patency and minimize loss of blood upon injury, untimely or excessive activity can lead to unwanted platelet activation and aggregation. Resultant thrombosis has the potential to block blood vessels, causing myocardial infarction or stroke. To tackle this major cause of mortality, clinical therapies that target platelet responsiveness (antiplatelet therapy) can successfully reduce cardiovascular events, especially in people at higher risk; however, all current antiplatelet therapies carry an increased probability of bleeding. This review will evaluate new and emerging targets for antithrombotics, focusing particularly on platelet glycoprotein VI, as blockade or depletion of this platelet-specific receptor conveys benefits in experimental models of thrombosis and thromboinflammation without causing major bleeding complications.
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Affiliation(s)
- Robert K Andrews
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | - Jane F Arthur
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | - Elizabeth E Gardiner
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
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32
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Platelet receptor expression and shedding: glycoprotein Ib-IX-V and glycoprotein VI. Transfus Med Rev 2014; 28:56-60. [PMID: 24674813 DOI: 10.1016/j.tmrv.2014.03.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 03/04/2014] [Accepted: 03/04/2014] [Indexed: 01/13/2023]
Abstract
Quantity, quality, and lifespan are 3 important factors in the physiology, pathology, and transfusion of human blood platelets. The aim of this review is to discuss the proteolytic regulation of key platelet-specific receptors, glycoprotein(GP)Ib and GPVI, involved in the function of platelets in hemostasis and thrombosis, and nonimmune or immune thrombocytopenia. The scope of the review encompasses the basic science of platelet receptor shedding, practical aspects related to laboratory analysis of platelet receptor expression/shedding, and clinical implications of using the proteolytic fragments as platelet-specific biomarkers in vivo in terms of platelet function and clearance. These topics can be relevant to platelet transfusion regarding both changes in platelet receptor expression occurring ex vivo during platelet storage and/or clinical use of platelets for transfusion. In this regard, quantitative analysis of platelet receptor profiles on blood samples from individuals could ultimately enable stratification of bleeding risk, discrimination between causes of thrombocytopenia due to impaired production vs enhanced clearance, and monitoring of response to treatment prior to change in platelet count.
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Gawaz M, Vogel S, Pfannenberg C, Pichler B, Langer H, Bigalke B. Implications of glycoprotein VI for theranostics. Thromb Haemost 2014; 112:26-31. [PMID: 24553806 DOI: 10.1160/th13-09-0756] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 01/31/2014] [Indexed: 01/03/2023]
Abstract
Glycoprotein VI (GPVI), a membrane glycoprotein solely expressed in platelets and megakaryocytes, plays a critical role in thrombus formation due to collagen/GPVI-mediated platelet activation and adhesion. Recent studies have shown that surface expression of GPVI on circulating platelets is enhanced in acute cardiovascular diseases such as myocardial infarction and ischaemic stroke. Increased GPVI levels are associated with poor clinical outcome and are an early indicator for imminent myocardial infarction in patients with chest pain. The soluble form of the dimeric GPVI fusion protein (sGPVI-Fc) binds with high affinity to collagen and atherosclerotic plaque tissue. Non-invasive imaging studies with radiolabelled sGPVI-Fc show specific binding activity to vascular lesions in vivo. Further, sGPVI-Fc has been developed as a new therapeutic platelet-based strategy for lesion-directed antithrombotic therapy. This review summarises the potential of GPVI for diagnostic and therapeutic options based on novel non-invasive molecular imaging modalities to ameliorate care of patients with cardiovascular diseases.
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Affiliation(s)
- M Gawaz
- Meinrad Gawaz, MD, Department of Cardiology, University of Tübingen, Otfried-Müller-Straße 10, 72076 Tübingen, Germany, Tel.: +49 7071 29 83688, Fax: +49 7071 29 5749, E-mail:
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Gardiner EE, Andrews RK. Structure and function of platelet receptors initiating blood clotting. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 844:263-75. [PMID: 25480646 DOI: 10.1007/978-1-4939-2095-2_13] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
At the clinical level, recent studies reveal the link between coagulation and other pathophysiological processes, including platelet activation, inflammation, cancer, the immune response, and/or infectious diseases. These links are likely to underpin the coagulopathy associated with risk factors for venous thromboembolic (VTE) and deep vein thrombosis (DVT). At the molecular level, the interactions between platelet-specific receptors and coagulation factors could help explain coagulopathy associated with aberrant platelet function, as well as revealing new approaches targeting platelet receptors in diagnosis or treatment of VTE or DVT. Glycoprotein (GP)Ibα, the major ligand-binding subunit of the platelet GPIb-IX-V complex, that binds the adhesive ligand, von Willebrand factor (VWF), is co-associated with the platelet-specific collagen receptor, GPVI. The GPIb-IX-V/GPVI adheso-signaling complex not only initiates platelet activation and aggregation (thrombus formation) in response to vascular injury or disease but GPIbα also regulates coagulation through a specific interaction with thrombin and other coagulation factors. Here, we discuss the structure and function of key platelet receptors involved in thrombus formation and coagulation in health and disease, with a particular focus on platelet GPIbα.
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Affiliation(s)
- Elizabeth E Gardiner
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
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Gardiner EE, Andrews RK. Plasma sGPVI: Changing levels in human disease. Thromb Res 2013; 133:306-7. [PMID: 24411101 DOI: 10.1016/j.thromres.2013.12.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 12/18/2013] [Accepted: 12/19/2013] [Indexed: 01/20/2023]
Affiliation(s)
- Elizabeth E Gardiner
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research & Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, 3004.
| | - Robert K Andrews
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research & Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, 3004.
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Nazi I, Arnold DM, Smith JW, Horsewood P, Moore JC, Warkentin TE, Crowther MA, Kelton JG. FcγRIIa proteolysis as a diagnostic biomarker for heparin-induced thrombocytopenia. J Thromb Haemost 2013; 11:1146-53. [PMID: 23551961 DOI: 10.1111/jth.12208] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Indexed: 11/28/2022]
Abstract
BACKGROUND A significant challenge in the management of heparin-induced thrombocytopenia (HIT) patients is making a timely and accurate diagnosis. The readily available enzyme immunoassays (EIAs) have low specificities. In contrast, platelet activation assays have higher specificities, but they are technically demanding and not widely available. In addition, ~ 10% of samples referred for HIT testing are initially classified as indeterminate by the serotonin release assay (SRA), which further delays accurate diagnosis. HIT is characterized by platelet activation, which leads to FcγRIIa proteolysis. This raises the possibility that identification of the proteolytic fragment of FcγRIIa could serve as a surrogate marker for HIT. OBJECTIVES To determine the specificity of platelet FcγRIIa proteolysis induced by sera from patients with HIT, and to correlate the results with those of the SRA. METHODS/PATIENTS Sera from HIT patients and control patients with other thrombocytopenic/prothrombotic disorders were tested for their ability to proteolyse FcγRIIa. The results were correlated with anti-platelet factor 4 (PF4)/heparin antibodies (EIA), and heparin-dependent platelet activation (SRA). RESULTS Only HIT patient samples (20/20) caused heparin-dependent FcγRIIa proteolysis, similar to what was shown by the SRA. None of the samples from the other patient groups or hospital controls caused FcγRIIa proteolysis. Among nine additional samples that tested indeterminate in the SRA, FcγRIIa proteolysis resolved five samples that had a positive anti-PF4/heparin EIA result; three had no FcγRIIa proteolysis, and two were shown to have heparin-dependent FcγRIIa proteolysis CONCLUSIONS This study suggests that heparin-dependent FcγRIIa proteolysis is at least as specific as the SRA for the diagnosis of HIT.
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Affiliation(s)
- I Nazi
- Department of Medicine, Michael G DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.
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Bender M, May F, Lorenz V, Thielmann I, Hagedorn I, Finney BA, Vögtle T, Remer K, Braun A, Bösl M, Watson SP, Nieswandt B. Combined in vivo depletion of glycoprotein VI and C-type lectin-like receptor 2 severely compromises hemostasis and abrogates arterial thrombosis in mice. Arterioscler Thromb Vasc Biol 2013; 33:926-34. [PMID: 23448972 DOI: 10.1161/atvbaha.112.300672] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Platelet inhibition is a major strategy to prevent acute ischemic cardiovascular and cerebrovascular events, which may, however, be associated with an increased bleeding risk. The (hem)immunoreceptor tyrosine activation motif-bearing platelet receptors, glycoprotein VI (GPVI) and C-type lectin-like receptor 2 (CLEC-2), might be promising antithrombotic targets because they can be depleted from circulating platelets by antibody treatment, leading to sustained antithrombotic protection, but only moderately increased bleeding times in mice. APPROACH AND RESULTS We investigated whether both (hem)immunoreceptor tyrosine activation motif-bearing receptors can be targeted simultaneously and what the in vivo consequences of such a combined therapeutic GPVI/CLEC-2 deficiency are. We demonstrate that isolated targeting of either GPVI or CLEC-2 in vivo does not affect expression or function of the respective other receptor. Moreover, simultaneous treatment with both antibodies resulted in the sustained loss of both GPVI and CLEC-2, while leaving other activation pathways intact. However, GPVI/CLEC-2-depleted mice displayed a dramatic hemostatic defect and profound impairment of arterial thrombus formation. Furthermore, a strongly diminished hemostatic response could also be reproduced in mice genetically lacking GPVI and CLEC-2. CONCLUSIONS These results demonstrate that GPVI and CLEC-2 can be simultaneously downregulated in platelets in vivo and reveal an unexpected functional redundancy of the 2 receptors in hemostasis and thrombosis. These findings may have important implications of the potential use of anti-GPVI and anti-CLEC-2-based agents in the prevention of thrombotic diseases.
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Affiliation(s)
- Markus Bender
- University Hospital Würzburg and Rudolf Virchow Center, DFG Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
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Zahid M, Mangin P, Loyau S, Hechler B, Billiald P, Gachet C, Jandrot-Perrus M. The future of glycoprotein VI as an antithrombotic target. J Thromb Haemost 2012; 10:2418-27. [PMID: 23020554 DOI: 10.1111/jth.12009] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The treatment of acute coronary syndromes has been considerably improved in recent years with the introduction of highly efficient antiplatelet drugs. However, there are still significant limitations: the recurrence of adverse vascular events remains a problem, and the improvement in efficacy is counterbalanced by an increased risk of bleeding, which is of particular importance in patients at risk of stroke. One of the most attractive targets for the development of new molecules with potential antithrombotic activity is platelet glycoprotein (GP)VI, because its blockade appears to ideally combine efficacy and safety. This review summarizes current knowledge on GPVI regarding its structure, its function, and its role in physiologic hemostasis and thrombosis. Strategies for inhibiting GPVI are presented, and evidence of the antithrombotic efficacy and safety of GPVI antagonists is provided.
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Affiliation(s)
- M Zahid
- Inserm, UMRS_698, Paris, France
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Arthur JF, Qiao J, Shen Y, Davis AK, Dunne E, Berndt MC, Gardiner EE, Andrews RK. ITAM receptor-mediated generation of reactive oxygen species in human platelets occurs via Syk-dependent and Syk-independent pathways. J Thromb Haemost 2012; 10:1133-41. [PMID: 22489915 DOI: 10.1111/j.1538-7836.2012.04734.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND Ligation of the platelet-specific collagen receptor, GPVI/FcRγ, causes rapid, transient disulfide-dependent homodimerization, and the production of intracellular reactive oxygen species (ROS) generated by the NADPH oxidase, linked to GPVI via TRAF4. OBJECTIVES The aim of this study was to evaluate the role of early signaling events in ROS generation following engagement of either GPVI/FcRγ or a second immunoreceptor tyrosine-based activation motif (ITAM)-containing receptor on platelets, FcγRIIa. METHODS AND RESULTS Using an H(2) DCF-DA-based flow cytometric assay to measure intracellular ROS, we show that treatment of platelets with either the GPVI agonists, collagen-related peptide (CRP) or convulxin (Cvx), or the FcγRIIa agonist 14A2, increased intraplatelet ROS; other platelet agonists such as ADP and TRAP did not. Basal ROS in platelet-rich plasma from 14 healthy donors displayed little inter-individual variability. CRP, Cvx or 14A2 induced an initial burst of ROS within 2 min followed by additional ROS reaching a plateau after 15-20 min. The Syk inhibitor BAY61-3606, which blocks ITAM-dependent signaling, had no effect on the initial ROS burst, but completely inhibited the second phase. CONCLUSIONS Together, these results show for the first time that ROS generation downstream of GPVI or FcγRIIa consists of two distinct phases: an initial Syk-independent burst followed by additional Syk-dependent generation.
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Affiliation(s)
- J F Arthur
- Australian Centre for Blood Diseases, Monash University, Melbourne, Victoria, Australia.
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Abstract
Receptor shedding is a mechanism for irreversible removal of transmembrane cell surface receptors by proteolysis of the receptor at a position near the extracellular surface of the plasma membrane. This process generates a soluble ectodomain fragment and a membrane-associated remnant fragment, and is distinct from loss of receptor surface expression by internalization or microparticle release or secretion of alternatively spliced soluble forms of receptors lacking a transmembrane domain. There has been an increased focus on new methods for analyzing shedding of platelet glycoprotein (GP)Ib-IX-V and GPVI because these receptors are platelet specific and are critical for the initiation of platelet adhesion and activation in thrombus formation at arterial shear rates. Platelet receptor shedding provides a mechanism for downregulating surface expression resulting in loss of ligand binding, decreasing the surface density affecting receptor cross linking and signalling and generation of proteolytic fragments that may be functional and/or provide platelet-specific biomarkers.
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Affiliation(s)
- Elizabeth E Gardiner
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
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Qiao J, Arthur JF, Collecutt M, Shen Y, Mu FT, Berndt MC, Davis AK, Andrews RK, Gardiner EE. An acquired defect associated with abnormal signaling of the platelet collagen receptor glycoprotein VI. Acta Haematol 2012; 128:233-41. [PMID: 22922528 DOI: 10.1159/000340048] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 05/28/2012] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Ligands acting at the platelet collagen receptor, glycoprotein (GP)VI, induce intracellular FcRγ/Syk-dependent signaling pathways and Syk-dependent or Syk-independent generation of intracellular reactive oxygen species (ROS). Additional signaling-dependent or signaling-independent pathways lead to metalloproteinase-mediated shedding of GPVI. AIM Analysis of platelet GPVI expression and signaling in a patient with a collagen-selective defect associated with myelodysplastic syndrome (MDS) uniquely demonstrates divergent pathways leading to ROS generation and Syk phosphorylation in human platelets. METHODS Surface expression of GPVI and ligand-induced ROS generation was quantitated by flow cytometry. GPVI shedding and Syk phosphorylation were analyzed by Western blot. RESULTS Despite platelet count/size and GPVI surface expression within normal ranges, platelet-rich plasma showed no aggregation in response to collagen or GPVI-selective agonist collagen-related peptide, but aggregated in response to other agonists, consistent with dysfunctional GPVI signaling. We observed rapid GPVI-dependent Syk-independent ROS generation and disulfide-dependent GPVI homodimerization, but not Syk-dependent ROS or ligand-induced shedding. Temporal analysis showed a gradual decline in platelet count and the appearance of ligand-induced phosphorylation of an ∼40-kDa Syk fragment. CONCLUSIONS These studies show that GPVI ligation in platelets induces intracellular ROS production independent of either Syk activation or divergent pathways leading to platelet aggregation or ectodomain shedding.
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Affiliation(s)
- Jianlin Qiao
- Australian Centre for Blood Diseases, Monash University, Melbourne, Vic., Australia
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Nazi I, Smith JW, Arnold DM, Horsewood P, Moore JC, Warkentin TE, Kelton JG. The association between platelet activation and FcγRIIa proteolysis. J Thromb Haemost 2011; 9:885-7. [PMID: 21320287 DOI: 10.1111/j.1538-7836.2011.04239.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
This study evaluated shedding of the platelet collagen receptor, glycoprotein VI (GPVI) in human plasma. Collagen or other ligands induce metalloproteinase-mediated GPVI ectodomain shedding, generating approximately 55-kDa soluble GPVI (sGPVI) and approximately 10-kDa platelet-associated fragments. In the absence of GPVI ligands, coagulation of platelet-rich plasma from healthy persons induced GPVI shedding, independent of added tissue factor, but inhibitable by metalloproteinase inhibitor, GM6001. Factor Xa (FXa) common to intrinsic and tissue factor-mediated coagulation pathways was critical for sGPVI release because (1) shedding was strongly blocked by the FXa-selective inhibitor rivaroxaban but not FIIa (thrombin) inhibitors dabigatran or hirudin; (2) Russell viper venom that directly activates FX generated sGPVI, with complete inhibition by enoxaparin (inhibits FXa and FIIa) but not hirudin; (3) impaired GPVI shedding during coagulation of washed platelets resuspended in FX-depleted plasma was restored by adding purified FX; and (4) purified FXa induced GM6001-inhibitable GPVI shedding from washed platelets. In 29 patients with disseminated intravascular coagulation, mean plasma sGPVI was 53.9 ng/mL (95% confidence interval, 39.9-72.8 ng/mL) compared with 12.5 ng/mL (95% confidence interval, 9.0-17.3 ng/mL) in thrombocytopenic controls (n = 36, P < .0001), and 14.6 ng/mL (95% confidence interval, 7.9-27.1 ng/mL) in healthy subjects (n = 25, P = .002). In conclusion, coagulation-induced GPVI shedding via FXa down-regulates GPVI under procoagulant conditions. FXa inhibitors have an unexpected role in preventing GPVI down-regulation.
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Qiao JL, Shen Y, Gardiner EE, Andrews RK. Proteolysis of platelet receptors in humans and other species. Biol Chem 2011; 391:893-900. [PMID: 20482312 DOI: 10.1515/bc.2010.081] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In the past 5 years, metalloproteinase-mediated ectodomain shedding of platelet receptors has emerged as a new mechanism for modulating platelet function. By regulating surface expression of the platelet-specific receptors, glycoprotein (GP)VI that binds collagen, and GPIbalpha (the major ligand-binding subunit of the GPIb-IX-V complex) that binds von Willebrand factor (VWF) and other procoagulant and proinflammatory ligands, shedding not only irreversibly downregulates GPVI/GPIbalpha function, but generates proteolytic fragments that might be unique biomarkers or modulators in plasma. This is potentially significant because GPVI and GPIbalpha are involved in initiating thrombotic diseases such as heart attack and stroke, as well as autoimmune diseases where anti-platelet antibodies result in thrombocytopenia. Altered expression levels of GPIbalpha/GPVI are associated with both thrombotic propensity and platelet aging, suggesting an additional role in platelet clearance. Although emerging data are elucidating molecular mechanisms underlying GPIbalpha/GPVI shedding, evidence for the functional consequences of shedding in vivo, either clinically or in animal models, is far more limited. Here we consider recent published evidence for GPVI or GPIbalpha shedding in humans, nonhuman primates and mice, and whether conservation of sheddase cleavage sites across species points to a functional role for metalloproteolytic shedding in vivo.
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Affiliation(s)
- Jian L Qiao
- Australian Centre for Blood Diseases, Monash University, Melbourne, Victoria, Australia
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Arthur JF, Shen Y, Gardiner EE, Coleman L, Murphy D, Kenny D, Andrews RK, Berndt MC. TNF receptor-associated factor 4 (TRAF4) is a novel binding partner of glycoprotein Ib and glycoprotein VI in human platelets. J Thromb Haemost 2011; 9:163-72. [PMID: 20946164 DOI: 10.1111/j.1538-7836.2010.04091.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
BACKGROUND Reactive oxygen species generation is one consequence of ligand engagement of platelet glycoprotein (GP) receptors GPIb-IX-V and GPVI, which bind VWF/collagen and initiate thrombosis at arterial shear; however, the precise molecular mechanism coupling redox pathway activation to engagement of these receptors is unknown. OBJECTIVE The objective of this study was to identify novel binding partners for GPIb-IX-V and GPVI that could provide a potential link between redox pathways and early platelet signaling events. METHODS AND RESULTS Using protein array analysis and affinity-binding assays, we demonstrated that the orphan TNF receptor-associated factor (TRAF) family member, TRAF4, selectively binds cytoplasmic sequences of GPIbβ and GPVI. TRAF4, p47(phox) [of the NADPH oxidase (Nox2) enzyme complex] and other redox relevant signaling proteins such as Hic-5, co-immunoprecipitate with GPIb/GPVI from human platelet lysates whilst MBP-TRAF4 or MBP-p47(phox) fusion proteins specifically pull-down GPIb/GPVI. GPIb- or GPVI-selective agonists induce phosphorylation of the TRAF4-associated proteins, Hic-5 and Pyk2, with phosphorylation attenuated by Nox2 inhibition. CONCLUSION These results describe the first direct association of TRAF4 with a receptor, and identify a novel binding partner for GPIb-IX-V and GPVI, providing a potential link between these platelet receptors and downstream TRAF4/Nox2-dependent redox pathways.
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Affiliation(s)
- J F Arthur
- Australian Centre for Blood Diseases, Monash University, Melbourne, Australia.
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Gardiner EE, Thom JY, Al-Tamimi M, Hughes A, Berndt MC, Andrews RK, Baker RI. Restored platelet function after romiplostim treatment in a patient with immune thrombocytopenic purpura. Br J Haematol 2010; 149:625-8. [DOI: 10.1111/j.1365-2141.2010.08092.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Al-Tamimi M, Mu FT, Moroi M, Gardiner EE, Berndt MC, Andrews RK. Measuring soluble platelet glycoprotein VI in human plasma by ELISA. Platelets 2009; 20:143-9. [PMID: 19437330 DOI: 10.1080/09537100802710286] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Recent experimental evidence demonstrates that the platelet-specific collagen receptor, glycoprotein (GP)VI is essentially all uncleaved on normal circulating platelets, but is shed from the platelet surface in a metalloproteinase-dependent manner in response to GPVI ligands (including collagen), anti-GPVI antibodies or activation at the platelet Fc receptor, FcgammaRIIa. This raises the question of whether shed ectodomain fragment in plasma could be a useful biomarker of thrombotic risk and/or autoimmune thrombocytopenia. In this study, we developed a sandwich enzyme-linked immunosorbent assay (ELISA) for measuring soluble GPVI in human plasma, using rabbit anti-GPVI polyclonal antibody in the solid-phase, murine anti-GPVI monoclonal antibody (1A12) in the fluid-phase and horseradish peroxidase (HRP)-coupled anti-mouse antibody and enhanced chemiluminescence (ECL) for detection. The ELISA was optimized for sensitivity, reproducibility, inter- and intra-assay precision, addition and recovery and detected GPVI in plasma with a lower detection limit of approximately 1 ng/mL. Effects of different anti-coagulants (trisodium citrate, acid-citrate-dextrose or EDTA) were negligible. In ten healthy donors, soluble plasma GPVI levels were 18.9 +/- 4.1 ng/mL. Treating normal platelet-rich plasma with a GPVI ligand (collagen-related peptide, CRP), calmodulin inhibitor W7 (that induces GPVI shedding without platelet activation) or N-ethylmaleimide (that directly activates platelet sheddases), under conditions previously shown to induce GPVI shedding, also increased plasma GPVI levels by up to approximately 7-fold, compared to previously reported autoimmune (anti-GPVI) patient plasma where soluble GPVI was approximately 10-fold higher than normal. Characterization of this sensitive ELISA should facilitate analysis of functional/diagnostic role(s) for soluble GPVI in human plasma associated with thrombotic/immune dysfunction.
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Affiliation(s)
- Mohammad Al-Tamimi
- Department of Immunology, Monash University, Alfred Medical Research & Education Precinct, Melbourne, Australia
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Nurden P, Tandon N, Takizawa H, Couzi L, Morel D, Fiore M, Pillois X, Loyau S, Jandrot-Perrus M, Nurden AT. An acquired inhibitor to the GPVI platelet collagen receptor in a patient with lupus nephritis. J Thromb Haemost 2009; 7:1541-9. [PMID: 19583823 DOI: 10.1111/j.1538-7836.2009.03537.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND GPVI is a major platelet collagen signaling receptor. In rare cases of immune thrombocytopenic purpura (ITP), autoantibodies to GPVI result in receptor shedding. OBJECTIVES To investigate a possible pathogenic role of plasma anti-GPVI antibody located in a woman with lupus nephritis. METHODS Measured were (i) platelet aggregation to collagen and convulxin, (ii) platelet GPVI expression (flow cytometry and western blotting), (iii) plasma soluble GPVI (sGPVI, dual antibody ELISA), and (iv) plasma anti-GPVI antibody (ELISA using recombinant sGPVI). RESULTS In 2006 and early 2007, the patient had a normal platelet count but a virtual absence of platelet aggregation to collagen and convulxin. Her platelets responded normally to other agonists including cross-linking ITAM-dependent FcgammaRIIA by monoclonal antibody, IV.3. Flow cytometry and western blotting showed a platelet deficiency of GPVI. Plasma sGPVI levels were undetectable whereas ELISA confirmed the presence of anti-GPVI antibody. Sequencing revealed a normal GPVI cDNA structure. The patient's plasma and the isolated IgG3 fraction activated and induced GPVI shedding from normal platelets. A deteriorating clinical condition led to increasingly strict immunosuppressive therapy. This was globally associated with a fall in plasma anti-GPVI titres, the restoration of platelet GPVI and the convulxin response, and the loss of her nephrotic syndrome. CONCLUSIONS Our results show that this patient acquired a potent anti-GPVI IgG3 antibody with loss of GPVI and collagen-related platelet function. Further studies are required to determine whether anti-GPVI antibodies occur in other lupus patients with nephritis.
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Affiliation(s)
- P Nurden
- CRPP/PTIB, Hôpital Xavier Arnozan, Pessac, France
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Akiyama M, Kashiwagi H, Todo K, Moroi M, Berndt MC, Kojima H, Kanakura Y, Tomiyama Y. Presence of platelet-associated anti-glycoprotein (GP)VI autoantibodies and restoration of GPVI expression in patients with GPVI deficiency. J Thromb Haemost 2009; 7:1373-83. [PMID: 19522742 DOI: 10.1111/j.1538-7836.2009.03510.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Glycoprotein (GP)VI deficiency is a rare platelet disorder with a mild bleeding tendency. However, its pathophysiology remains unclear. OBJECTIVES We characterized a novel GPVI-deficient patient with immune thrombocytopenic purpura and searched for the presence of anti-GPVI autoantibodies in this and another patient with GPVI deficiency. METHODS AND RESULTS A 12-year-old Japanese girl (case 1) with moderate thrombocytopenia and mild bleeding showed selectively impaired collagen-induced platelet aggregation. Flow cytometric analysis indicated that the patient had a defect in the expression of GPVI-FcRgamma. An eluate of her platelet-associated IgG contained anti-alpha(IIb)beta3 autoantibodies. Moreover, using GPVI-FcRgamma-transfected cells, we unexpectedly identified anti-GPVI antibodies against the soluble ectodomain of GPVI in the eluate, despite the patient's GPVI deficiency. In contrast, anti-GPVI antibodies were not detectable in her plasma. In another case of GPVI deficiency (case 2) without detectable plasma anti-GPVI antibodies, we again detected platelet-associated anti-GPVI antibodies. In a 2-year follow-up of case 1, the platelet count increased to within the normal range and the bleeding tendency improved. Interestingly, GPVI was again expressed on her platelets, in association with a decrease in the relative amount of anti-GPVI antibodies. CONCLUSIONS This is the first demonstration of platelet-associated anti-GPVI antibodies in GPVI-deficient subjects, in one case with spontaneous restoration of GPVI expression. These results strongly suggest an autoimmune mechanism in GPVI deficiency.
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Affiliation(s)
- M Akiyama
- Department of Haematology and Oncology, Graduate School of Medicine C9, Osaka University, Osaka, Japan
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Al-Tamimi M, Mu FT, Arthur JF, Shen Y, Moroi M, Berndt MC, Andrews RK, Gardiner EE. Anti-glycoprotein VI monoclonal antibodies directly aggregate platelets independently of FcγRIIa and induce GPVI ectodomain shedding. Platelets 2009; 20:75-82. [DOI: 10.1080/09537100802645029] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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