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Gołaszewska A, Misztal T, Kazberuk A, Rusak T. Study on the Mechanism of the Adrenaline-Evoked Procoagulant Response in Human Platelets. Int J Mol Sci 2024; 25:2997. [PMID: 38474244 DOI: 10.3390/ijms25052997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Revised: 02/23/2024] [Accepted: 03/03/2024] [Indexed: 03/14/2024] Open
Abstract
Adrenaline has recently been found to trigger phosphatidylserine (PS) exposure on blood platelets, resulting in amplification of the coagulation process, but the mechanism is only fragmentarily established. Using a panel of platelet receptors' antagonists and modulators of signaling pathways, we evaluated the importance of these in adrenaline-evoked PS exposure by flow cytometry. Calcium and sodium ion influx into platelet cytosol, after adrenaline treatment, was examined by fluorimetric measurements. We found a strong reduction in PS exposure after blocking of sodium and calcium ion influx via Na+/H+ exchanger (NHE) and Na+/Ca2+ exchanger (NCX), respectively. ADP receptor antagonists produced a moderate inhibitory effect. Substantial limitation of PS exposure was observed in the presence of GPIIb/IIIa antagonist, phosphoinositide-3 kinase (PI3-K) inhibitors, or prostaglandin E1, a cyclic adenosine monophosphate (cAMP)-elevating agent. We demonstrated that adrenaline may develop a procoagulant response in human platelets with the substantial role of ion exchangers (NHE and NCX), secreted ADP, GPIIb/IIIa-dependent outside-in signaling, and PI3-K. Inhibition of the above mechanisms and increasing cytosolic cAMP seem to be the most efficient procedures to control adrenaline-evoked PS exposure in human platelets.
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Affiliation(s)
- Agata Gołaszewska
- Department of General and Experimental Pathology, Medical University of Bialystok, Mickiewicza 2C, 15-230 Bialystok, Poland
| | - Tomasz Misztal
- Department of Physical Chemistry, Medical University of Bialystok, Mickiewicza 2A, 15-369 Bialystok, Poland
| | - Adam Kazberuk
- Department of Medicinal Chemistry, Medical University of Bialystok, Mickiewicza 2D, 15-959 Bialystok, Poland
| | - Tomasz Rusak
- Department of Physical Chemistry, Medical University of Bialystok, Mickiewicza 2A, 15-369 Bialystok, Poland
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Huang N, Qiu Y, Liu Y, Liu T, Xue X, Song P, Xu J, Fu Y, Sun R, Yin Y, Li P. Floralozone protects endothelial function in atherosclerosis by ameliorating NHE1. Acta Biochim Biophys Sin (Shanghai) 2021; 53:1310-1320. [PMID: 34409427 DOI: 10.1093/abbs/gmab109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Indexed: 02/07/2023] Open
Abstract
Endothelial dysfunction is the pathological basis of atherosclerosis. Incomplete understanding of endothelial dysfunction etiology has impeded drug development for this devastating disease despite the currently available therapies. Floralozone, an aroma flavor, specifically exists in rabbit ear grass. Recently, floralozone has been demonstrated to inhibit atherosclerosis, but the underlying mechanisms are undefined. The present study was undertaken to explore whether floralozone pharmacologically targets endothelial dysfunction and therefore exerts therapeutic effects on atherosclerosis. The Na+/H+ exchanger 1 (NHE1), a channel protein, plays a vital role in atherosclerosis. Whether NHE1 is involved in the therapeutic effects of floralozone on endothelial dysfunction has yet to be further answered. By performing oil red staining and hematoxylin-eosin staining, vascular functional study, and oxidative stress monitoring, we found that floralozone not only reduced the size of carotid atherosclerotic plaque but also prevented endothelial dysfunction in atherosclerotic rats. NHE1 expression was upregulated in the inner membrane of carotid arteries and H2O2-induced primary rat aortic endothelial cells. Inspiringly, floralozone prevented the upregulation of NHE1 in vivo and in vitro. Notably, the administration of NHE1 activator LiCl significantly weakened the protective effect of floralozone on endothelial dysfunction in vivo and in vitro. Our study demonstrated that floralozone exerted its protective effect on endothelial dysfunction in atherosclerosis by ameliorating NHE1. NHE1 maybe a drug target for the treatment of atherosclerosis, and floralozone may be an effective drug to meet the urgent needs of atherosclerosis patients by dampening NHE1.
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Affiliation(s)
- Ning Huang
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
| | - Yue Qiu
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
| | - Yanhua Liu
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
| | - Tianheng Liu
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
| | - Xianjun Xue
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
| | - Ping Song
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
| | - Jian Xu
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
| | - Yutian Fu
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
| | - Ruili Sun
- Henan Key Laboratory of Immunology and Targeted Drugs, School of Laboratory Medicine, Xinxiang Medical University, Xinxiang 453003, China
- Henan Collaborative Innovation Center of Molecular Diagnosis and Laboratory Medicine, School of Laboratory Medicine, Xinxiang Medical University, Xinxiang 453003, China
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
| | - Yaling Yin
- School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang 450003, China
| | - Peng Li
- College of Pharmacy, Xinxiang Medical University, Xinxiang 453003, China
- Henan International Joint Laboratory of Cardiovascular Remodeling and Drug Intervention, Xinxiang 453003, China
- Xinxiang Key Laboratory of Vascular Remodeling Intervention and Molecular Targeted Therapy Drug Development, Xinxiang 453003, China
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3
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Affiliation(s)
- Jarred M Whitlock
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
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Abstract
Microparticles are a distinctive group of small vesicles, without nucleus, which are involved as significant modulators in several physiological and pathophysiological mechanisms. Plasma microparticles from various cellular lines have been subject of research. Data suggest that they are key players in development and manifestation of cardiovascular diseases and their presence, in high levels, is associated with chronic inflammation, endothelial damage and thrombosis. The strong correlation of microparticle levels with several outcomes in cardiovascular diseases has led to their utilization as biomarkers. Despite the limited clinical application at present, their significance emerges, mainly because their detection and enumeration methods are improving. This review article summarizes the evidence derived from research, related with the genesis and the function of microparticles in the presence of various cardiovascular risk factors and conditions. The current data provide a substrate for several theories of how microparticles influence various cellular mechanisms by transferring biological information.
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Affiliation(s)
- Christos Voukalis
- a Institute of Cardiovascular Sciences , University of Birmingham , Birmingham , UK
| | - Eduard Shantsila
- a Institute of Cardiovascular Sciences , University of Birmingham , Birmingham , UK
| | - Gregory Y H Lip
- b Liverpool Centre for Cardiovascular Science , University of Liverpool and Liverpool Heart & Chest Hospital , Liverpool , UK.,c Department of Clinical Medicine, Aalborg Thrombosis Research Unit , Aalborg University , Aalborg , Denmark
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Sepúlveda C, Palomo I, Fuentes E. Antiplatelet activity of drugs used in hypertension, dyslipidemia and diabetes: Additional benefit in cardiovascular diseases prevention. Vascul Pharmacol 2017; 91:10-17. [DOI: 10.1016/j.vph.2017.03.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 02/03/2017] [Accepted: 03/21/2017] [Indexed: 02/02/2023]
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Abstract
Neutrophils are essential for killing bacteria and other microorganisms, and they also have a significant role in regulating the inflammatory response. Stimulated neutrophils activate their NADPH oxidase (NOX2) to generate large amounts of superoxide, which acts as a precursor of hydrogen peroxide and other reactive oxygen species that are generated by their heme enzyme myeloperoxidase. When neutrophils engulf bacteria they enclose them in small vesicles (phagosomes) into which superoxide is released by activated NOX2 on the internalized neutrophil membrane. The superoxide dismutates to hydrogen peroxide, which is used by myeloperoxidase to generate other oxidants, including the highly microbicidal species hypochlorous acid. NOX activation occurs at other sites in the cell, where it is considered to have a regulatory function. Neutrophils also release oxidants, which can modify extracellular targets and affect the function of neighboring cells. We discuss the identity and chemical properties of the specific oxidants produced by neutrophils in different situations, and what is known about oxidative mechanisms of microbial killing, inflammatory tissue damage, and signaling.
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Affiliation(s)
- Christine C Winterbourn
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch 8011, New Zealand; , ,
| | - Anthony J Kettle
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch 8011, New Zealand; , ,
| | - Mark B Hampton
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch 8011, New Zealand; , ,
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Chang HB, Gao X, Nepomuceno R, Hu S, Sun D. Na(+)/H(+) exchanger in the regulation of platelet activation and paradoxical effects of cariporide. Exp Neurol 2015; 272:11-6. [PMID: 25595121 DOI: 10.1016/j.expneurol.2014.12.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2014] [Revised: 12/21/2014] [Accepted: 12/25/2014] [Indexed: 01/09/2023]
Abstract
Platelets are anucleated cell fragments derived from mature megakaryocytes and function in hemostasis when the endothelium is injured. Hemostasis involving platelets can be divided into four phases: adhesion, activation, secretion, and aggregation. Platelet activation requires a rise in intracellular Ca(2+) concentrations and results in both a morphological change and the secretion of platelet granule contents. Na(+)/H(+) exchanger isoform 1 (NHE1) regulates the intracellular pH (pHi) and the volume of platelets. In addition, NHE1 plays a large role in platelet activation. Thrombus generation involves NHE1 activation and an increase in [Ca(2+)]i, which results from NHE1-mediated Na(+) overload and the reversal of the Na(+)/Ca(2+) exchanger. Cariporide (HOE-642), a potent NHE1 inhibitor, has inhibitory effects on the degranulation of human platelets, the formation of platelet-leukocyte-aggregates, and the activation of the GPIIb/IIIa receptor (PAC-1). However, despite the demonstrated protection against myocardial infarction as mediated by cariporide in patients undergoing coronary artery bypass graft surgery, the EXPEDITION clinical trial revealed that cariporide treatment increased mortality due to thromboembolic stroke. These findings suggest that a better understanding of NHE1 and its effect on platelet function and procoagulant factor regulation is warranted in order to develop therapies using NHE inhibitors.
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Affiliation(s)
| | - Xin Gao
- Department of Neurology, University of Pittsburgh, USA; Dept. of Neurological Surgery, The Second Affiliated Hospital of the Harbin Medical University, Harbin 150086, China
| | | | - Shaoshan Hu
- Dept. of Neurological Surgery, The Second Affiliated Hospital of the Harbin Medical University, Harbin 150086, China
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, USA; Veterans Affairs Pittsburgh Health Care System, Geriatric Research, Educational and Clinical Center, Pittsburgh, PA 15213, USA.
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Liu G, Liu G, Alzoubi K, Umbach AT, Pelzl L, Borst O, Gawaz M, Lang F. Upregulation of store operated Ca channel Orai1, stimulation of Ca(2+) entry and triggering of cell membrane scrambling in platelets by mineralocorticoid DOCA. Kidney Blood Press Res 2014; 38:21-30. [PMID: 24525794 DOI: 10.1159/000355750] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/20/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Mineralocorticoid excess leads to vascular injury, which is partially due to hypertension but in addition involves increased concentration of cytosolic Ca(2+) concentration in platelets, key players in the pathophysiology of occlusive vascular disease. Mineralocorticoids are in part effective by rapid nongenomic mechanisms including phosphatidylinositide-3-kinase (PI3K) signaling, which involves activation of the serum & glucocorticoid inducible kinase (SGK) isoforms. SGK1 has in turn been shown to participate in the regulation of the pore forming Ca(2+) channel protein Orai1 in platelets. Orai1 accomplishes entry of Ca(2+), which is in turn known to trigger cell membrane scrambling. Platelets lack nuclei but are able to express protein by translation, which is stimulated by PI3K signaling. The present study explored whether the mineralocorticoid desoxycorticosterone acetate (DOCA) influences platelet Orai1 protein abundance, cytosolic Ca(2+)-activity ([Ca(2+)]i), phosphatidylserine abundance at the cell surface and/or cell volume. METHODS Orai1 protein abundance was estimated utilizing CF™488A conjugated antibodies, [Ca(2+)]i utilizing Fluo3-fluorescence, phosphatidylserine abundance utilizing FITC-labelled annexin V, and cell volume utilizing forward scatter in flow cytometry. RESULTS DOCA (10 µg/ml) treatment of murine platelets was followed by a significant increase of Orai1 protein abundance, [Ca(2+)]i, percentage of phosphatidylserine exposing platelets and platelet swelling. The effect on [Ca(2+)]i, phosphatidylserine abundance and cell volume were completely abrogated by addition of the specific SGK inhibitor EMD638683 (50 µM) CONCLUSIONS: The mineralocorticoid DOCA upregulates Orai1 protein abundance in the cell membrane, thus increasing [Ca(2+)]i and triggering phosphatidylserine abundance, effects paralleled by platelet swelling.
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Affiliation(s)
- Guoxing Liu
- Department of Physiology, University of Tübingen, Tübingen, Germany
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9
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Liu F, Gamez G, Myers DR, Clemmons W, Lam WA, Jobe SM. Mitochondrially mediated integrin αIIbβ3 protein inactivation limits thrombus growth. J Biol Chem 2013; 288:30672-30681. [PMID: 24014035 PMCID: PMC3798537 DOI: 10.1074/jbc.m113.472688] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 08/26/2013] [Indexed: 11/06/2022] Open
Abstract
When platelets are strongly stimulated, a procoagulant platelet subpopulation is formed that is characterized by phosphatidylserine (PS) exposure and epitope modulation of integrin αIIbβ3 or a loss of binding of activation-dependent antibodies. Mitochondrial permeability transition pore (mPTP) formation, which is essential for the formation of procoagulant platelets, is impaired in the absence of cyclophilin D (CypD). Here we investigate the mechanisms responsible for these procoagulant platelet-associated changes in integrin αIIbβ3 and the physiologic role of procoagulant platelet formation in the regulation of platelet aggregation. Among strongly stimulated adherent platelets, integrin αIIbβ3 epitope changes, mPTP formation, PS exposure, and platelet rounding were closely associated. Furthermore, platelet mPTP formation resulted in a decreased ability to recruit additional platelets. In the absence of CypD, integrin αIIbβ3 function was accentuated in both static and flow conditions, and, in vivo, a prothrombotic phenotype occurred in mice with a platelet-specific deficiency of CypD. CypD-dependent proteolytic events, including cleavage of the integrin β3 cytoplasmic domain, coincided closely with integrin αIIbβ3 inactivation. Calpain inhibition blocked integrin β3 cleavage and inactivation but not mPTP formation or PS exposure, indicating that integrin inactivation and PS exposure are mediated by distinct pathways subsequent to mPTP formation. mPTP-dependent alkalinization occurred in procoagulant platelets, suggesting a possible alternative mechanism for enhancement of calpain activity in procoagulant platelets. Together, these results indicate that, in strongly stimulated platelets, mPTP formation initiates the calpain-dependent cleavage of integrin β3 and associated regulatory proteins, resulting in integrin αIIbβ3 inactivation, and demonstrate a novel CypD-dependent negative feedback mechanism that limits platelet aggregation and thrombotic occlusion.
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Affiliation(s)
- Fang Liu
- From the Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Graciela Gamez
- From the Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322
| | - David R Myers
- From the Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322,; the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30322, and
| | - Wayne Clemmons
- From the Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Wilbur A Lam
- From the Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322,; the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30322, and; the Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, Georgia 30322
| | - Shawn M Jobe
- From the Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322,; the Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, Georgia 30322.
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10
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Heemskerk JWM, Mattheij NJA, Cosemans JMEM. Platelet-based coagulation: different populations, different functions. J Thromb Haemost 2013; 11:2-16. [PMID: 23106920 DOI: 10.1111/jth.12045] [Citation(s) in RCA: 237] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Platelets in a thrombus interact with (anti)coagulation factors and support blood coagulation. In the concept of cell-based control of coagulation, three different roles of platelets can be distinguished: control of thrombin generation, support of fibrin formation, and regulation of fibrin clot retraction. Here, we postulate that different populations of platelets with distinct surface properties are involved in these coagulant functions. Platelets with elevated Ca(2+) and exposed phosphatidylserine control thrombin and fibrin generation, while platelets with activated α(IIb) β(3) regulate clot retraction. We review how coagulation factor binding depends on the platelet activation state. Furthermore, we discuss the ligands, platelet receptors and downstream intracellular signaling pathways implicated in these coagulant functions. These insights lead to an adapted model of platelet-based coagulation.
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Affiliation(s)
- J W M Heemskerk
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands.
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11
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Megakaryocyte development is normal in mice with targeted disruption of Tescalcin. Exp Cell Res 2012; 318:662-9. [PMID: 22285131 DOI: 10.1016/j.yexcr.2012.01.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 12/30/2011] [Accepted: 01/05/2012] [Indexed: 11/23/2022]
Abstract
BACKGROUND Tescalcin is an EF-hand calcium-binding protein that interacts with the Na+/H+ exchanger 1 (NHE1). Levay and Slepak recently proposed a role for tescalcin in megakaryopoiesis that was independent of NHE1 activity. Their studies using K562 and HEL cell lines, and human CD34+ hematopoietic stem cells suggested an essential role for tescalcin in megakaryocyte differentiation. OBJECTIVE To study the role of tescalcin in megakaryocyte development using a murine model of megakaryopoiesis. METHODS We generated a mouse with targeted disruption of tescalcin and investigated megakaryocyte development. RESULTS Tescalcin-deficient mice had a normal number of megakaryocytes and platelets. The morphology, polyploidization profile, and expression of Fli-1 in bone marrow-derived megakaryocytes were also normal. CONCLUSION Tescalcin does not appear to be necessary for normal megakaryocyte development.
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Morel O, Morel N, Jesel L, Freyssinet JM, Toti F. Microparticles: a critical component in the nexus between inflammation, immunity, and thrombosis. Semin Immunopathol 2011; 33:469-86. [DOI: 10.1007/s00281-010-0239-3] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2010] [Accepted: 12/20/2010] [Indexed: 12/27/2022]
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13
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Morel O, Jesel L, Freyssinet JM, Toti F. Cellular mechanisms underlying the formation of circulating microparticles. Arterioscler Thromb Vasc Biol 2011; 31:15-26. [PMID: 21160064 DOI: 10.1161/atvbaha.109.200956] [Citation(s) in RCA: 388] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Microparticles (MPs) derived from platelets, monocytes, endothelial cells, red blood cells, and granulocytes may be detected in low concentrations in normal plasma and at increased levels in atherothrombotic cardiovascular diseases. The elucidation of the cellular mechanisms underlying the generation of circulating MPs is crucial for improving our understanding of their pathophysiological role in health and disease. The flopping of phosphatidylserine (PS) to the outer leaflet of the plasma membrane is the key event that will ultimately lead to the shedding of procoagulant MPs from activated or apoptotic cells. Research over the last few years has revealed important roles for calcium-, mitochondrial-, and caspase-dependent mechanisms leading to PS exposure. The study of Scott cells has unraveled different molecular mechanisms that may contribute to fine-tuning of PS exposure and MP release in response to a variety of specific stimuli. The pharmacological modulation of MP release may have a substantial therapeutic impact in the management of atherothrombotic vascular disorders. Because PS exposure is a key feature in pathological processes different from hemostasis and thrombosis, the most important obstacle in the field of MP-modulating drugs seems to be carefully targeting MP release to relevant cell types at an optimal level, so as to achieve a beneficial action and limit possible adverse effects.
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Affiliation(s)
- Olivier Morel
- Institut d'Hématologie & Immunologie, Université de Strasbourg, Strasbourg, France
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14
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Abstract
Although long considered to be cellular debris, microparticles (MPs) are more recently considered reflective of cellular stimulation, activation, and degeneration/apoptosis. MPs that arise from the cellular components of blood and the endothelial lining of blood vessels are referred to as blood MPs and by general consensus are small (≤1.5 μm), expose the anionic phospholipid (PL) phosphatidylserine (PS) on the outer leaflet of their membrane, and bear surface membrane antigens reflecting their cellular origin. This brief review summarizes the different approaches used by several groups to study blood MPs. The aim of this article is to review the technical aspects of characterizing the morphological and functional properties of blood MPs with emphasis on the preanalytical and analytical variables involved in these studies.
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Affiliation(s)
- Arun S Shet
- Department of Medicine, St. Johns Medical College and Hospital, St. Johns National Academy of Health Sciences, Bangalore, India.
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15
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Bernhardt I, Weiss E, Robinson HC, Wilkins R, Bennekou P. Differential Effect of HOE642 on Two Separate Monovalent Cation Transporters in the Human Red Cell Membrane. Cell Physiol Biochem 2008; 20:601-6. [PMID: 17762186 DOI: 10.1159/000107543] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2007] [Indexed: 11/19/2022] Open
Abstract
Residual K(+) fluxes in red blood cells can be stimulated in conditions of low ionic strength. Previous studies have identified both the non-selective, voltage-dependent cation (NSVDC) channel and the K(+)(Na(+))/H(+) exchanger as candidate pathways mediating this effect, although it is possible that these pathways represent different modes of operation of a single system. In the present study the effects of HOE642, recently characterised as an inhibitor of the K(+)(Na(+))/H(+) exchanger, on NSVDC has been determined to clarify this question. Radioisotope flux measurements and conductance determinations showed that HOE642 exerted differential effects on the NSVDC channel and the K(+)(Na(+))/H(+) exchanger, confirming that the salt loss observed in low ionic strength solutions represents contributions from at least two independent ion transport pathways. The findings are discussed in the context of red blood cell apoptosis (eryptosis) and disease.
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Affiliation(s)
- Ingolf Bernhardt
- Laboratory of Biophysics, Saarland University, Saarbruecken, Germany.
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16
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Wolfs JL, Wielders SJ, Comfurius P, Lindhout T, Giddings JC, Zwaal RF, Bevers EM. Reversible inhibition of the platelet procoagulant response through manipulation of the Gardos channel. Blood 2006; 108:2223-8. [PMID: 16741254 DOI: 10.1182/blood-2006-01-009613] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
AbstractThe platelet procoagulant response requires a sustained elevation of the intracellular Ca2+ concentration, [Ca2+]i, causing exposure of phosphatidylserine (PS) at the outer surface of the plasma membrane. An increased [Ca2+]i also activates Ca2+-dependent K+ channels. Here, we investigated the contribution of the efflux of K+ ions on the platelet procoagulant response in collagen-thrombin–activated platelets using selective K+ channel blockers. The Gardos channel blockers clotrimazol, charybdotoxin, and quinine caused a similar decrease in prothrombinase activity as well as in the number of PS-exposing platelets detected by fluorescence-conjugated annexin A5. Apamin and iberiotoxin, inhibitors of other K+ channels, were without effect. Only clotrimazol showed a significant inhibition of the collagen-plus-thrombin–induced intracellular calcium response. Clotrimazol and charybdotoxin did not inhibit aggregation and release under the conditions used. Inhibition by Gardos channel blockers was reversed by valinomycin, a selective K+ ionophore. The impaired procoagulant response of platelets from a patient with Scott syndrome was partially restored by pretreatment with valinomycin, suggesting a possible defect of the Gardos channel in this syndrome. Collectively, these results provide evidence for the involvement of efflux of K+ ions through Ca2+-activated K+ channels in the procoagulant response of platelets, opening potential strategies for therapeutic interventions.
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Affiliation(s)
- Jef L Wolfs
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands
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