1
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Eitelmann S, Stephan J, Everaerts K, Durry S, Pape N, Gerkau NJ, Rose CR. Changes in Astroglial K + upon Brief Periods of Energy Deprivation in the Mouse Neocortex. Int J Mol Sci 2022; 23:ijms23094836. [PMID: 35563238 PMCID: PMC9102782 DOI: 10.3390/ijms23094836] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/21/2022] [Accepted: 04/24/2022] [Indexed: 11/16/2022] Open
Abstract
Malfunction of astrocytic K+ regulation contributes to the breakdown of extracellular K+ homeostasis during ischemia and spreading depolarization events. Studying astroglial K+ changes is, however, hampered by a lack of suitable techniques. Here, we combined results from fluorescence imaging, ion-selective microelectrodes, and patch-clamp recordings in murine neocortical slices with the calculation of astrocytic [K+]. Brief chemical ischemia caused a reversible ATP reduction and a transient depolarization of astrocytes. Moreover, astrocytic [Na+] increased by 24 mM and extracellular [Na+] decreased. Extracellular [K+] increased, followed by an undershoot during recovery. Feeding these data into the Goldman-Hodgkin-Katz equation revealed a baseline astroglial [K+] of 146 mM, an initial K+ loss by 43 mM upon chemical ischemia, and a transient K+ overshoot of 16 mM during recovery. It also disclosed a biphasic mismatch in astrocytic Na+/K+ balance, which was initially ameliorated, but later aggravated by accompanying changes in pH and bicarbonate, respectively. Altogether, our study predicts a loss of K+ from astrocytes upon chemical ischemia followed by a net gain. The overshooting K+ uptake will promote low extracellular K+ during recovery, likely exerting a neuroprotective effect. The resulting late cation/anion imbalance requires additional efflux of cations and/or influx of anions, the latter eventually driving delayed astrocyte swelling.
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2
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Ransom BR, Goldberg MP, Arai K, Baltan S. White Matter Pathophysiology. Stroke 2022. [DOI: 10.1016/b978-0-323-69424-7.00009-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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3
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Shen XY, Gao ZK, Han Y, Yuan M, Guo YS, Bi X. Activation and Role of Astrocytes in Ischemic Stroke. Front Cell Neurosci 2021; 15:755955. [PMID: 34867201 PMCID: PMC8635513 DOI: 10.3389/fncel.2021.755955] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 10/22/2021] [Indexed: 12/21/2022] Open
Abstract
Ischemic stroke refers to the disorder of blood supply of local brain tissue caused by various reasons. It has high morbidity and mortality worldwide. Astrocytes are the most abundant glial cells in the central nervous system (CNS). They are responsible for the homeostasis, nutrition, and protection of the CNS and play an essential role in many nervous system diseases’ physiological and pathological processes. After stroke injury, astrocytes are activated and play a protective role through the heterogeneous and gradual changes of their gene expression, morphology, proliferation, and function, that is, reactive astrocytes. However, the position of reactive astrocytes has always been a controversial topic. Many studies have shown that reactive astrocytes are a double-edged sword with both beneficial and harmful effects. It is worth noting that their different spatial and temporal expression determines astrocytes’ various functions. Here, we comprehensively review the different roles and mechanisms of astrocytes after ischemic stroke. In addition, the intracellular mechanism of astrocyte activation has also been involved. More importantly, due to the complex cascade reaction and action mechanism after ischemic stroke, the role of astrocytes is still difficult to define. Still, there is no doubt that astrocytes are one of the critical factors mediating the deterioration or improvement of ischemic stroke.
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Affiliation(s)
- Xin-Ya Shen
- Graduate School of Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Zhen-Kun Gao
- Graduate School of Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yu Han
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai, China
| | - Mei Yuan
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai, China
| | - Yi-Sha Guo
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai, China
| | - Xia Bi
- Department of Rehabilitation Medicine, Shanghai University of Medicine and Health Sciences Affiliated Zhoupu Hospital, Shanghai, China
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4
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Intermittent Hypoxia and Effects on Early Learning/Memory: Exploring the Hippocampal Cellular Effects of Pediatric Obstructive Sleep Apnea. Anesth Analg 2021; 133:93-103. [PMID: 33234943 DOI: 10.1213/ane.0000000000005273] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
This review provides an update on the neurocognitive phenotype of pediatric obstructive sleep apnea (OSA). Pediatric OSA is associated with neurocognitive deficits involving memory, learning, and executive functioning. Adenotonsillectomy (AT) is presently accepted as the first-line surgical treatment for pediatric OSA, but the executive function deficits do not resolve postsurgery, and the timeline for recovery remains unknown. This finding suggests that pediatric OSA potentially causes irreversible damage to multiple areas of the brain. The focus of this review is the hippocampus, 1 of the 2 major sites of postnatal neurogenesis, where new neurons are formed and integrated into existing circuitry and the mammalian center of learning/memory functions. Here, we review the clinical phenotype of pediatric OSA, and then discuss existing studies of OSA on different cell types in the hippocampus during critical periods of development. This will set the stage for future study using preclinical models to understand the pathogenesis of persistent neurocognitive dysfunction in pediatric OSA.
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5
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van Putten MJ, Fahlke C, Kafitz KW, Hofmeijer J, Rose CR. Dysregulation of Astrocyte Ion Homeostasis and Its Relevance for Stroke-Induced Brain Damage. Int J Mol Sci 2021; 22:5679. [PMID: 34073593 PMCID: PMC8198632 DOI: 10.3390/ijms22115679] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/21/2021] [Accepted: 05/22/2021] [Indexed: 12/14/2022] Open
Abstract
Ischemic stroke is a leading cause of mortality and chronic disability. Either recovery or progression towards irreversible failure of neurons and astrocytes occurs within minutes to days, depending on remaining perfusion levels. Initial damage arises from energy depletion resulting in a failure to maintain homeostasis and ion gradients between extra- and intracellular spaces. Astrocytes play a key role in these processes and are thus central players in the dynamics towards recovery or progression of stroke-induced brain damage. Here, we present a synopsis of the pivotal functions of astrocytes at the tripartite synapse, which form the basis of physiological brain functioning. We summarize the evidence of astrocytic failure and its consequences under ischemic conditions. Special emphasis is put on the homeostasis and stroke-induced dysregulation of the major monovalent ions, namely Na+, K+, H+, and Cl-, and their involvement in maintenance of cellular volume and generation of cerebral edema.
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Affiliation(s)
- Michel J.A.M. van Putten
- Department of Clinical Neurophysiology, University of Twente, 7522 NB Enschede, The Netherlands; (M.J.A.M.v.P.); (J.H.)
| | - Christoph Fahlke
- Institut für Biologische Informationsprozesse, Molekular-und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52425 Jülich, Germany;
| | - Karl W. Kafitz
- Institute of Neurobiology, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany;
| | - Jeannette Hofmeijer
- Department of Clinical Neurophysiology, University of Twente, 7522 NB Enschede, The Netherlands; (M.J.A.M.v.P.); (J.H.)
| | - Christine R. Rose
- Institute of Neurobiology, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany;
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6
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Gerkau NJ, Rakers C, Durry S, Petzold GC, Rose CR. Reverse NCX Attenuates Cellular Sodium Loading in Metabolically Compromised Cortex. Cereb Cortex 2019; 28:4264-4280. [PMID: 29136153 DOI: 10.1093/cercor/bhx280] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 10/04/2017] [Indexed: 01/05/2023] Open
Abstract
In core regions of ischemic stroke, disruption of blood flow causes breakdown of ionic gradients and, ultimately, calcium overload and cell death. In the surrounding penumbra, cells may recover upon reperfusion, but recovery is hampered by additional metabolic demands imposed by peri-infarct depolarizations (PIDs). There is evidence that sodium influx drives PIDs, but no data exist on PID-related sodium accumulations in vivo. Here, we found that PIDs in mouse neocortex are associated with propagating sodium elevations in neurons and astrocytes. Similar transient sodium elevations were induced in acute tissue slices by brief chemical ischemia. Blocking NMDA-receptors dampened sodium and accompanying calcium loads of neurons in tissue slices, while inhibiting glutamate transport diminished sodium influx into astrocytes, but amplified neuronal sodium loads. In both cell types, inhibition of sodium/calcium exchange (NCX) increased sodium transients. Blocking NCX also significantly reduced calcium transients, a result confirmed in vivo. Our study provides the first quantitative data on sodium elevations in peri-infarct regions in vivo. They suggest that sodium influx drives reversal of NCX, triggering a massive secondary calcium elevation while promoting export of sodium. Reported neuroprotective effects of NCX activity in stroke models might thus be related to its dampening of ischemia-induced sodium loading.
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Affiliation(s)
- Niklas J Gerkau
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, Duesseldorf, Germany
| | - Cordula Rakers
- German Center for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Str. 27, Bonn, Germany
| | - Simone Durry
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, Duesseldorf, Germany
| | - Gabor C Petzold
- German Center for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Str. 27, Bonn, Germany.,Department of Neurology, University Hospital Bonn, Sigmund-Freud-Str. 25, Bonn, Germany
| | - Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, Duesseldorf, Germany
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7
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Mahmoud S, Gharagozloo M, Simard C, Gris D. Astrocytes Maintain Glutamate Homeostasis in the CNS by Controlling the Balance between Glutamate Uptake and Release. Cells 2019; 8:E184. [PMID: 30791579 PMCID: PMC6406900 DOI: 10.3390/cells8020184] [Citation(s) in RCA: 340] [Impact Index Per Article: 68.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 02/15/2019] [Accepted: 02/19/2019] [Indexed: 01/26/2023] Open
Abstract
Glutamate is one of the most prevalent neurotransmitters released by excitatory neurons in the central nervous system (CNS); however, residual glutamate in the extracellular space is, potentially, neurotoxic. It is now well-established that one of the fundamental functions of astrocytes is to uptake most of the synaptically-released glutamate, which optimizes neuronal functions and prevents glutamate excitotoxicity. In the CNS, glutamate clearance is mediated by glutamate uptake transporters expressed, principally, by astrocytes. Interestingly, recent studies demonstrate that extracellular glutamate stimulates Ca2+ release from the astrocytes' intracellular stores, which triggers glutamate release from astrocytes to the adjacent neurons, mostly by an exocytotic mechanism. This released glutamate is believed to coordinate neuronal firing and mediate their excitatory or inhibitory activity. Therefore, astrocytes contribute to glutamate homeostasis in the CNS, by maintaining the balance between their opposing functions of glutamate uptake and release. This dual function of astrocytes represents a potential therapeutic target for CNS diseases associated with glutamate excitotoxicity. In this regard, we summarize the molecular mechanisms of glutamate uptake and release, their regulation, and the significance of both processes in the CNS. Also, we review the main features of glutamate metabolism and glutamate excitotoxicity and its implication in CNS diseases.
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Affiliation(s)
- Shaimaa Mahmoud
- Program of Immunology, Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
| | - Marjan Gharagozloo
- Program of Immunology, Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
| | - Camille Simard
- Program of Immunology, Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
| | - Denis Gris
- Program of Immunology, Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
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8
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Cozzolino O, Marchese M, Trovato F, Pracucci E, Ratto GM, Buzzi MG, Sicca F, Santorelli FM. Understanding Spreading Depression from Headache to Sudden Unexpected Death. Front Neurol 2018; 9:19. [PMID: 29449828 PMCID: PMC5799941 DOI: 10.3389/fneur.2018.00019] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 01/11/2018] [Indexed: 01/03/2023] Open
Abstract
Spreading depression (SD) is a neurophysiological phenomenon characterized by abrupt changes in intracellular ion gradients and sustained depolarization of neurons. It leads to loss of electrical activity, changes in the synaptic architecture, and an altered vascular response. Although SD is often described as a unique phenomenon with homogeneous characteristics, it may be strongly affected by the particular triggering event and by genetic background. Furthermore, SD may contribute differently to the pathogenesis of widely heterogeneous clinical conditions. Indeed, clinical disorders related to SD vary in their presentation and severity, ranging from benign headache conditions (migraine syndromes) to severely disabling events, such as cerebral ischemia, or even death in people with epilepsy. Although the characteristics and mechanisms of SD have been dissected using a variety of approaches, ranging from cells to human models, this phenomenon remains only partially understood because of its complexity and the difficulty of obtaining direct experimental data. Currently, clinical monitoring of SD is limited to patients who require neurosurgical interventions and the placement of subdural electrode strips. Significantly, SD events recorded in humans display electrophysiological features that are essentially the same as those observed in animal models. Further research using existing and new experimental models of SD may allow a better understanding of its core mechanisms, and of their differences in different clinical conditions, fostering opportunities to identify and develop targeted therapies for SD-related disorders and their worst consequences.
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Affiliation(s)
- Olga Cozzolino
- NEST, Istituto Nanoscienze CNR and Scuola Normale Superiore, Pisa, Italy
| | - Maria Marchese
- Molecular Medicine and Clinical Neurophysiology Laboratories, Department of Developmental Neuroscience, IRCCS Fondazione Stella Maris, Pisa, Italy
| | - Francesco Trovato
- NEST, Istituto Nanoscienze CNR and Scuola Normale Superiore, Pisa, Italy
| | - Enrico Pracucci
- NEST, Istituto Nanoscienze CNR and Scuola Normale Superiore, Pisa, Italy
| | - Gian Michele Ratto
- NEST, Istituto Nanoscienze CNR and Scuola Normale Superiore, Pisa, Italy
| | | | - Federico Sicca
- Molecular Medicine and Clinical Neurophysiology Laboratories, Department of Developmental Neuroscience, IRCCS Fondazione Stella Maris, Pisa, Italy
| | - Filippo M Santorelli
- Molecular Medicine and Clinical Neurophysiology Laboratories, Department of Developmental Neuroscience, IRCCS Fondazione Stella Maris, Pisa, Italy
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9
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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10
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 942] [Impact Index Per Article: 157.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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11
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Dreier JP, Lemale CL, Kola V, Friedman A, Schoknecht K. Spreading depolarization is not an epiphenomenon but the principal mechanism of the cytotoxic edema in various gray matter structures of the brain during stroke. Neuropharmacology 2017; 134:189-207. [PMID: 28941738 DOI: 10.1016/j.neuropharm.2017.09.027] [Citation(s) in RCA: 128] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 09/16/2017] [Accepted: 09/19/2017] [Indexed: 12/15/2022]
Abstract
Spreading depolarization (SD) is a phenomenon of various cerebral gray matter structures that only occurs under pathological conditions. In the present paper, we summarize the evidence from several decades of research that SD and cytotoxic edema in these structures are largely overlapping terms. SD/cytotoxic edema is a toxic state that - albeit initially reversible - leads eventually to cellular death when it is persistent. Both hemorrhagic and ischemic stroke are among the most prominent causes of SD/cytotoxic edema. SD/cytotoxic edema is the principal mechanism that mediates neuronal death in these conditions. This applies to gray matter structures in both the ischemic core and the penumbra. SD/cytotoxic edema is often a single terminal event in the core whereas, in the penumbra, a cluster of repetitive prolonged SDs is typical. SD/cytotoxic edema also propagates widely into healthy surrounding tissue as short-lasting, relatively harmless events so that regional electrocorticographic monitoring affords even remote detection of ischemic zones. Ischemia cannot only cause SD/cytotoxic edema but it can also be its consequence through inverse neurovascular coupling. Under this condition, ischemia does not start simultaneously in different regions but spreads in the tissue driven by SD/cytotoxic edema-induced microvascular constriction (= spreading ischemia). Spreading ischemia prolongs SD/cytotoxic edema. Thus, it increases the likelihood for the transition from SD/cytotoxic edema into cellular death. Vasogenic edema is the other major type of cerebral edema with relevance to ischemic stroke. It results from opening of the blood-brain barrier. SD/cytotoxic edema and vasogenic edema are distinct processes with important mutual interactions. This article is part of the Special Issue entitled 'Cerebral Ischemia'.
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Affiliation(s)
- Jens P Dreier
- Center for Stroke Research Berlin, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany; Departments of Neurology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany; Experimental Neurology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany.
| | - Coline L Lemale
- Center for Stroke Research Berlin, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany
| | - Vasilis Kola
- Center for Stroke Research Berlin, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany
| | - Alon Friedman
- Department of Physiology and Cell Biology, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel; Department of Medical Neuroscience, Faculty of Medicine, Dalhousie University, Halifax, Canada
| | - Karl Schoknecht
- Center for Stroke Research Berlin, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany; Experimental Neurology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany
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12
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Begum G, Song S, Wang S, Zhao H, Bhuiyan MIH, Li E, Nepomuceno R, Ye Q, Sun M, Calderon MJ, Stolz DB, St Croix C, Watkins SC, Chen Y, He P, Shull GE, Sun D. Selective knockout of astrocytic Na + /H + exchanger isoform 1 reduces astrogliosis, BBB damage, infarction, and improves neurological function after ischemic stroke. Glia 2017; 66:126-144. [PMID: 28925083 DOI: 10.1002/glia.23232] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 08/25/2017] [Accepted: 08/29/2017] [Indexed: 01/25/2023]
Abstract
Stimulation of Na+ /H+ exchanger isoform 1 (NHE1) in astrocytes causes ionic dysregulation under ischemic conditions. In this study, we created a Nhe1flox/flox (Nhe1f/f ) mouse line with exon 5 of Nhe1 flanked with two loxP sites and selective ablation of Nhe1 in astrocytes was achieved by crossing Nhe1f/f mice with Gfap-CreERT2 Cre-recombinase mice. Gfap-CreERT2+/- ;Nhe1f/f mice at postnatal day 60-90 were treated with either corn oil or tamoxifen (Tam, 75 mg/kg/day, i.p.) for 5 days. After 30 days post-injection, mice underwent transient middle cerebral artery occlusion (tMCAO) to induce ischemic stroke. Compared with the oil-vehicle group (control), Tam-treated Gfap-CreERT2+/- ;Nhe1f/f (Nhe1 KO) mice developed significantly smaller ischemic infarction, less edema, and less neurological function deficits at 1-5 days after tMCAO. Immunocytochemical analysis revealed less astrocytic proliferation, less cellular hypertrophy, and less peri-lesion gliosis in Nhe1 KO mouse brains. Selective deletion of Nhe1 in astrocytes also reduced cerebral microvessel damage and blood-brain barrier (BBB) injury in ischemic brains. The BBB microvessels of the control brains show swollen endothelial cells, opened tight junctions, increased expression of proinflammatory protease MMP-9, and significant loss of tight junction protein occludin. In contrast, the Nhe1 KO mice exhibited reduced BBB breakdown and normal tight junction structure, with increased expression of occludin and reduced MMP-9. Most importantly, deletion of astrocytic Nhe1 gene significantly increased regional cerebral blood flow in the ischemic hemisphere at 24 hr post-MCAO. Taken together, our study provides the first line of evidence for a causative role of astrocytic NHE1 protein in reactive astrogliosis and ischemic neurovascular damage.
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Affiliation(s)
- Gulnaz Begum
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shanshan Song
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shaoxia Wang
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Hanshu Zhao
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | | | - Eric Li
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Rachel Nepomuceno
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Qing Ye
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ming Sun
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | | | - Donna B Stolz
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Claudette St Croix
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Yinhuai Chen
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio
| | - Pingnian He
- Department of Cellular and Molecular Physiology, Penn State Hershey College of Medicine, Hershey, Pennsylvania
| | - Gary E Shull
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania.,Veterans Affairs Pittsburgh Health Care System, Geriatric Research, Educational and Clinical Center, Pittsburgh, Pennsylvania
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13
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Yang DM, Huettner JE, Bretthorst GL, Neil JJ, Garbow JR, Ackerman JJH. Intracellular water preexchange lifetime in neurons and astrocytes. Magn Reson Med 2017; 79:1616-1627. [PMID: 28675497 DOI: 10.1002/mrm.26781] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 04/20/2017] [Accepted: 05/17/2017] [Indexed: 01/06/2023]
Abstract
PURPOSE To determine the intracellular water preexchange lifetime, τi , the "average residence time" of water, in the intracellular milieu of neurons and astrocytes. The preexchange lifetime is important for modeling a variety of MR data sets, including relaxation, diffusion-sensitive, and dynamic contrast-enhanced data sets. METHODS Herein, τi in neurons and astrocytes is determined in a microbead-adherent, cultured cell system. In concert with thin-slice selection, rapid flow of extracellular media suppresses extracellular signal, allowing determination of the transcytolemmal-exchange-dominated, intracellular T1 . With this knowledge, and that of the intracellular T1 in the absence of exchange, τi can be derived. RESULTS Under normal culture conditions, τi for neurons is 0.75 ± 0.05 s versus 0.57 ± 0.03 s for astrocytes. Both neuronal and astrocytic τi s decrease within 30 min after the onset of oxygen-glucose deprivation, with the astrocytic τi showing a substantially greater decrease than the neuronal τi . CONCLUSIONS Given an approximate intra- to extracellular volume ratio of 4:1 in the brain, these data imply that, under normal physiological conditions, an MR experimental characteristic time of less than 0.012 s is required for a nonexchanging, two-compartment (intra- and extracellular) model to be valid for MR studies. This characteristic time shortens significantly (i.e., 0.004 s) under injury conditions. Magn Reson Med 79:1616-1627, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Donghan M Yang
- Department of Chemistry, Washington University, St. Louis, Missouri, USA.,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - James E Huettner
- Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri, USA
| | - G Larry Bretthorst
- Department of Radiology, Washington University, St. Louis, Missouri, USA
| | - Jeffrey J Neil
- Department of Neurology, Washington University, St. Louis, Missouri, USA.,Department of Pediatrics, Washington University, St. Louis, Missouri, USA.,Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Joel R Garbow
- Department of Radiology, Washington University, St. Louis, Missouri, USA.,Alvin J. Siteman Cancer Center, Washington University, St. Louis, Missouri, USA
| | - Joseph J H Ackerman
- Department of Chemistry, Washington University, St. Louis, Missouri, USA.,Department of Radiology, Washington University, St. Louis, Missouri, USA.,Alvin J. Siteman Cancer Center, Washington University, St. Louis, Missouri, USA.,Department of Internal Medicine, Washington University, St. Louis, Missouri, USA
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14
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Gerkau NJ, Rakers C, Petzold GC, Rose CR. Differential effects of energy deprivation on intracellular sodium homeostasis in neurons and astrocytes. J Neurosci Res 2017; 95:2275-2285. [PMID: 28150887 DOI: 10.1002/jnr.23995] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 11/10/2016] [Accepted: 11/10/2016] [Indexed: 12/11/2022]
Abstract
The maintenance of a low intracellular sodium concentration by the Na+ /K+ -ATPase (NKA) is critical for brain function. In both neurons and glial cells, NKA activity is required to counteract changes in the sodium gradient due to opening of voltage- and ligand-gated channels and/or activation of sodium-dependent secondary active transporters. Because NKA consumes about 50% of cellular ATP, sodium homeostasis is strictly dependent on an intact cellular energy metabolism. Despite the high energetic costs of electrical signaling, neurons do not contain significant energy stores themselves, but rely on a close metabolic interaction with surrounding astrocytes. A disruption of energy supply as observed during focal ischemia causes a rapid drop in ATP in both neurons and astrocytes. There is accumulating evidence that dysregulation of intracellular sodium is an inherent consequence of a reduction in cellular ATP, triggering secondary failure of extra- and intracellular homeostasis of other ions -in particular potassium, calcium, and protons- and thereby promoting excitotoxicity. The characteristics, cellular mechanisms and direct consequences of harmful sodium influx, however, differ between neurons and astrocytes. Moreover, recent work has shown that an intact astrocyte metabolism and sodium homeostasis are critical to maintain the sodium homeostasis of surrounding neurons as well as their capacity to recover from imposed sodium influx. Understanding the mechanisms of sodium increases upon metabolic failure and the differential responses of neurons and glial cells as well as their metabolic interactions will be critical to fully unravel the events causing cellular malfunction, failure and cell death following energy depletion. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Niklas J Gerkau
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstrasse 1, D-40225, Düsseldorf, Germany
| | - Cordula Rakers
- German Center for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Strasse 27, 53127, Bonn, Germany
| | - Gabor C Petzold
- German Center for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Strasse 27, 53127, Bonn, Germany
| | - Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstrasse 1, D-40225, Düsseldorf, Germany
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15
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Gutiérrez Aguilar GF, Alquisiras-Burgos I, Espinoza-Rojo M, Aguilera P. Glial Excitatory Amino Acid Transporters and Glucose Incorporation. ADVANCES IN NEUROBIOLOGY 2017; 16:269-282. [PMID: 28828615 DOI: 10.1007/978-3-319-55769-4_13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Excitatory amino acid transporters (EAATs) expressed in astrocytes remove the glutamate released by neurons in and around the synaptic cleft. In this manner, astrocytes preserve the signaling functions mediated by glutamate on synapses and prevent excitotoxicity. Additionally, EAAT activation stimulates glucose utilization in astrocytes, linking neuronal activity with astrocyte metabolism. In this chapter, we briefly review the characteristics of the EAATs and the glucose transporters (GLUTs) expressed in the brain. Thereafter, we focus on the effect of EAATs activation and its association with glucose utilization in astrocytes, specifically addressing the role played by Na+ and Ca2+ ions. Next, we analyze evidence that proposes mechanisms by which the activity of GLUTs could be modulated after EAAT activation (e.g., kinases altering GLUTs traffic to cell membrane). Finally, we analyzed the current knowledge on EAAT function during energy deficiency as a possible inducer of GLUT expression to prevent neuronal damage.
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Affiliation(s)
- Germán Fernando Gutiérrez Aguilar
- Laboratorio de Patología Vascular Cerebral, Instituto Nacional de Neurología y Neurocirugía "Manuel Velasco Suárez", Insurgentes Sur #3877, Col. La Fama, Tlalpan, Ciudad de México, 14269, México
| | - Ivan Alquisiras-Burgos
- Laboratorio de Patología Vascular Cerebral, Instituto Nacional de Neurología y Neurocirugía "Manuel Velasco Suárez", Insurgentes Sur #3877, Col. La Fama, Tlalpan, Ciudad de México, 14269, México
| | - Mónica Espinoza-Rojo
- Laboratorio de Biología Molecular y Genómica, Universidad Autónoma de Guerrero, Chilpancingo, Guerrero, 39087, México
| | - Penélope Aguilera
- Laboratorio de Patología Vascular Cerebral, Instituto Nacional de Neurología y Neurocirugía "Manuel Velasco Suárez", Insurgentes Sur #3877, Col. La Fama, Tlalpan, Ciudad de México, 14269, México.
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16
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Yalamanchili N, Kriete A, Alfego D, Danowski KM, Kari C, Rodeck U. Distinct Cell Stress Responses Induced by ATP Restriction in Quiescent Human Fibroblasts. Front Genet 2016; 7:171. [PMID: 27757122 PMCID: PMC5047886 DOI: 10.3389/fgene.2016.00171] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 09/09/2016] [Indexed: 12/22/2022] Open
Abstract
Quiescence is the prevailing state of many cell types under homeostatic conditions. Yet, surprisingly little is known about how quiescent cells respond to energetic and metabolic challenges. To better understand compensatory responses of quiescent cells to metabolic stress, we established, in human primary dermal fibroblasts, an experimental ‘energy restriction’ model. Quiescence was achieved by short-term culture in serum-deprived media and ATP supply restricted using a combination of glucose transport inhibitors and mitochondrial uncouplers. In aggregate, these measures led to markedly reduced intracellular ATP levels while not compromising cell viability over the observation period of 48 h. Analysis of the transcription factor (TF) landscape induced by this treatment revealed alterations in several signal transduction nodes beyond the expected biosynthetic adaptations. These included increased abundance of NF-κB regulated TFs and altered TF subsets regulated by Akt and p53. The observed changes in gene regulation and corresponding alterations in key signaling nodes are likely to contribute to cell survival at intracellular ATP concentrations substantially below those achieved by growth factor deprivation alone. This experimental model provides a benchmark for the investigation of cell survival pathways and related molecular targets that are associated with restricted energy supply associated with biological aging and metabolic diseases.
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Affiliation(s)
- Nirupama Yalamanchili
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia PA, USA
| | - Andres Kriete
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia PA, USA
| | - David Alfego
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia PA, USA
| | - Kelli M Danowski
- Department of Dermatology, St. Joseph Mercy Health System, Michigan State University, East Lansing MI, USA
| | - Csaba Kari
- Department of Dermatology and Cutaneous Biology, Thomas Jefferson University, Philadelphia PA, USA
| | - Ulrich Rodeck
- Department of Dermatology and Cutaneous Biology, Thomas Jefferson University, Philadelphia PA, USA
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17
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Chatton JY, Magistretti PJ, Barros LF. Sodium signaling and astrocyte energy metabolism. Glia 2016; 64:1667-76. [PMID: 27027636 DOI: 10.1002/glia.22971] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 01/10/2016] [Accepted: 01/13/2016] [Indexed: 12/21/2022]
Abstract
The Na(+) gradient across the plasma membrane is constantly exploited by astrocytes as a secondary energy source to regulate the intracellular and extracellular milieu, and discard waste products. One of the most prominent roles of astrocytes in the brain is the Na(+) -dependent clearance of glutamate released by neurons during synaptic transmission. The intracellular Na(+) load collectively generated by these processes converges at the Na,K-ATPase pump, responsible for Na(+) extrusion from the cell, which is achieved at the expense of cellular ATP. These processes represent pivotal mechanisms enabling astrocytes to increase the local availability of metabolic substrates in response to neuronal activity. This review presents basic principles linking the intracellular handling of Na(+) following activity-related transmembrane fluxes in astrocytes and the energy metabolic pathways involved. We propose a role of Na(+) as an energy currency and as a mediator of metabolic signals in the context of neuron-glia interactions. We further discuss the possible impact of the astrocytic syncytium for the distribution and coordination of the metabolic response, and the compartmentation of these processes in cellular microdomains and subcellular organelles. Finally, we illustrate future avenues of investigation into signaling mechanisms aimed at bridging the gap between Na(+) and the metabolic machinery. GLIA 2016;64:1667-1676.
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Affiliation(s)
- Jean-Yves Chatton
- Department of Fundamental Neurosciences, University of Lausanne, Rue Du Bugnon 9, Lausanne, Switzerland
| | - Pierre J Magistretti
- King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia.,Brain Mind Institute, Ecole Polytechnique Fédérale De Lausanne (EPFL), Lausanne, Switzerland
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18
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Weller J, Steinhäuser C, Seifert G. pH-Sensitive K+ Currents and Properties of K2P Channels in Murine Hippocampal Astrocytes. ION CHANNELS AS THERAPEUTIC TARGETS, PART A 2016; 103:263-94. [DOI: 10.1016/bs.apcsb.2015.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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19
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Ransom BR, Goldberg MP, Arai K, Baltan S. White Matter Pathophysiology. Stroke 2016. [DOI: 10.1016/b978-0-323-29544-4.00009-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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20
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de Lavor MSL, Binda NS, Fukushima FB, Caldeira FMC, da Silva JF, Silva CMO, de Oliveira KM, Martins BDC, Torres BBJ, Rosado IR, Gomez RS, Gomez MV, de Melo EG. Ischemia-reperfusion model in rat spinal cord: cell viability and apoptosis signaling study. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2015; 8:9941-9949. [PMID: 26617703 PMCID: PMC4637788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 08/25/2015] [Indexed: 06/05/2023]
Abstract
This work aimed at determining the ideal ischemia time in an in vitro ischemia-reperfusion model of spinal cord injury. Rat spinal cord slices were prepared and then exposed or not to oxygen deprivation and low glucose (ODLG) for 30, 45, 60, 75 and 90 minutes. Cell viability was assessed by triphenyltetrazolium (TTC), lactate dehydrogenase (LDH) release, and fluorochrome dyes specific for cell dead (ethidium homodimer) using the apotome system. Glutamate release was enzymatically measured by a fluorescent method. Gene expression of apoptotic factors was assessed by real time RT-PCR. Whereas spinal cord slices exposed to ODLG exhibited mild increase in fluorescence for 30 minutes after the insult, the 45, 60, 75 and 90 minutes caused a 2-fold increase. ODLG exposure for 45, 60, 75 or 90 minutes, glutamate and LDH release were significantly elevated. nNOS mRNA expression was overexpressed for 45 minutes and moderately increased for 60 minutes in ODLG groups. Bax/bcl-xl ratio, caspase 9 and caspase 3 mRNA expressions were significantly increased for 45 minutes of ODLG, but not for 30, 60, 75 and 90 minutes. Results showed that cell viability reduction in the spinal cord was dependent on ischemic time, resulting in glutamate and LDH release. ODLG for 45 minutes was adequate for gene expression evaluation of proteins and proteases involved in apoptosis pathways.
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Affiliation(s)
- Mário Sérgio Lima de Lavor
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
- Departamento de Ciências Agrárias e Ambientais, Universidade Estadual de Santa CruzIlhéus, Bahia, Brasil
| | - Nancy Scardua Binda
- INCT, Laboratório de Neurociências, Faculdade de Medicina, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais
| | - Fabíola Bono Fukushima
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
| | - Fátima Maria Caetano Caldeira
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
| | - Juliana Figueira da Silva
- INCT, Laboratório de Neurociências, Faculdade de Medicina, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais
| | - Carla Maria Osório Silva
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
| | - Karen Maciel de Oliveira
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
| | - Bernardo de Caro Martins
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
| | - Bruno Benetti Junta Torres
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
| | - Isabel Rodrigues Rosado
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
| | - Renato Santiago Gomez
- INCT, Laboratório de Neurociências, Faculdade de Medicina, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais
| | - Marcus Vinícius Gomez
- INCT, Laboratório de Neurociências, Faculdade de Medicina, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais
| | - Eliane Gonçalves de Melo
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas GeraisBelo Horizonte, Minas Gerais, Brasil
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21
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Abstract
The term spreading depolarization (SD) refers to waves of abrupt, sustained mass depolarization in gray matter of the CNS. SD, which spreads from neuron to neuron in affected tissue, is characterized by a rapid near-breakdown of the neuronal transmembrane ion gradients. SD can be induced by hypoxic conditions--such as from ischemia--and facilitates neuronal death in energy-compromised tissue. SD has also been implicated in migraine aura, where SD is assumed to ascend in well-nourished tissue and is typically benign. In addition to these two ends of the "SD continuum," an SD wave can propagate from an energy-depleted tissue into surrounding, well-nourished tissue, as is often the case in stroke and brain trauma. This review presents the neurobiology of SD--its triggers and propagation mechanisms--as well as clinical manifestations of SD, including overlaps and differences between migraine aura and stroke, and recent developments in neuromonitoring aimed at better diagnosis and more targeted treatments.
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Affiliation(s)
- Jens P Dreier
- Department of Neurology, Charité University Medicine Berlin, 10117 Berlin, Germany; Department of Experimental Neurology, Charité University Medicine Berlin, 10117 Berlin, Germany; Center for Stroke Research, Charité University Medicine Berlin, 10117 Berlin, Germany.
| | - Clemens Reiffurth
- Department of Experimental Neurology, Charité University Medicine Berlin, 10117 Berlin, Germany; Center for Stroke Research, Charité University Medicine Berlin, 10117 Berlin, Germany
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22
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Karus C, Ziemens D, Rose CR. Lactate rescues neuronal sodium homeostasis during impaired energy metabolism. Channels (Austin) 2015; 9:200-8. [PMID: 26039160 PMCID: PMC4594511 DOI: 10.1080/19336950.2015.1050163] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Recently, we established that recurrent activity evokes network sodium oscillations in neurons and astrocytes in hippocampal tissue slices. Interestingly, metabolic integrity of astrocytes was essential for the neurons' capacity to maintain low sodium and to recover from sodium loads, indicating an intimate metabolic coupling between the 2 cell types. Here, we studied if lactate can support neuronal sodium homeostasis during impaired energy metabolism by analyzing whether glucose removal, pharmacological inhibition of glycolysis and/or addition of lactate affect cellular sodium regulation. Furthermore, we studied the effect of lactate on sodium regulation during recurrent network activity and upon inhibition of the glial Krebs cycle by sodium-fluoroacetate. Our results indicate that lactate is preferentially used by neurons. They demonstrate that lactate supports neuronal sodium homeostasis and rescues the effects of glial poisoning by sodium-fluoroacetate. Altogether, they are in line with the proposed transfer of lactate from astrocytes to neurons, the so-called astrocyte-neuron-lactate shuttle.
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Affiliation(s)
- Claudia Karus
- a Institute of Neurobiology; Faculty of Mathematics and Natural Sciences; Heinrich Heine University Düsseldorf ; Düsseldorf , Germany
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23
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Minieri L, Pivonkova H, Harantova L, Anderova M, Ferroni S. Intracellular Na+
inhibits volume-regulated anion channel in rat cortical astrocytes. J Neurochem 2015; 132:286-300. [DOI: 10.1111/jnc.12962] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 09/04/2014] [Accepted: 09/25/2014] [Indexed: 01/08/2023]
Affiliation(s)
- Laura Minieri
- Department of Pharmacy and Biotechnology; University of Bologna; Bologna Italy
| | - Helena Pivonkova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine; Academy of Sciences of the Czech Republic; Prague Czech Republic
| | - Lenka Harantova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine; Academy of Sciences of the Czech Republic; Prague Czech Republic
| | - Miroslava Anderova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine; Academy of Sciences of the Czech Republic; Prague Czech Republic
| | - Stefano Ferroni
- Department of Pharmacy and Biotechnology; University of Bologna; Bologna Italy
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24
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Abstract
There is abundant evidence that glycolysis and the Na(+)/K(+)-ATPase pump are functionally coupled, and it is thought that the nature of the coupling is energetic, with glycolysis providing the ATP that fuels the pump. This notion has been instrumental to current models of brain energy metabolism. However, structural and biophysical considerations suggest that the pump should also have access to mitochondrial ATP, which is much more abundant. In the present study, we have investigated the source of ATP that fuels the Na(+) pump in astrocytes, taking advantage of the high temporal resolution of recently available FRET nanosensors for glucose, lactate and ATP. The activity of the Na(+) pump was assessed in parallel with the Na(+)-sensitive dye SBFI AM (Na(+)-binding benzofuran isophthalate acetoxymethyl ester). OXPHOS (oxidative phosphorylation) inhibition resulted in bulk ATP depletion and a 5-fold stimulation of glycolytic flux, in spite of which Na(+) pumping was inhibited by 90%. Mathematical modelling of ATP dynamics showed that the observed pump failure is inconsistent with preferential fuelling of the Na(+) pump by glycolytic ATP. We conclude that the nature of the functional coupling between the Na(+) pump and the glycolytic machinery is not energetic and that the pump is mainly fuelled by mitochondrial ATP.
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25
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Ionic transporter activity in astrocytes, microglia, and oligodendrocytes during brain ischemia. J Cereb Blood Flow Metab 2013; 33:969-82. [PMID: 23549380 PMCID: PMC3705429 DOI: 10.1038/jcbfm.2013.44] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 02/27/2013] [Accepted: 02/28/2013] [Indexed: 01/09/2023]
Abstract
Glial cells constitute a large percentage of cells in the nervous system. During recent years, a large number of studies have critically attributed to glia a new role which no longer reflects the long-held view that glia constitute solely a silent and passive supportive scaffolding for brain cells. Indeed, it has been hypothesized that glia, partnering neurons, have a much more actively participating role in brain function. Alteration of intraglial ionic homeostasis in response to ischemic injury has a crucial role in inducing and maintaining glial responses in the ischemic brain. Therefore, glial transporters as potential candidates in stroke intervention are becoming promising targets to enhance an effective and additional therapy for brain ischemia. In this review, we will describe in detail the role played by ionic transporters in influencing astrocyte, microglia, and oligodendrocyte activity and the implications that these transporters have in the progression of ischemic lesion.
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26
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Regional Characteristics of Histamine Uptake into Neonatal Rat Astrocytes. Neurochem Res 2013; 38:1348-59. [DOI: 10.1007/s11064-013-1028-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/20/2013] [Accepted: 03/23/2013] [Indexed: 01/06/2023]
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27
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Rose CR, Karus C. Two sides of the same coin: sodium homeostasis and signaling in astrocytes under physiological and pathophysiological conditions. Glia 2013; 61:1191-205. [PMID: 23553639 DOI: 10.1002/glia.22492] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 02/06/2013] [Indexed: 11/07/2022]
Abstract
The intracellular sodium concentration of astrocytes is classically viewed as being kept under tight homeostatic control and at a relatively stable level under physiological conditions. Indeed, the steep inwardly directed electrochemical gradient for sodium, generated by the Na⁺/K⁺-ATPase, contributes to maintain the electrochemical gradient of K⁺ and the highly K⁺-based negative membrane potential, and is a central element in energizing membrane transport. As such it is tightly coupled to the homeostasis of extra- and intracellular potassium, calcium or pH and to the reuptake of transmitters such as glutamate. Recent studies, however, have demonstrated that this picture is far too simplistic. It is now firmly established that transmitters, most notably glutamate, and excitatory neuronal activity evoke long-lasting sodium transients in astrocytes, the properties of which are distinctly different from those of activity-related glial calcium signals. From these studies, it emerges that sodium homeostasis and signaling are two sides of the same coin: sodium-dependent transporters, primarily known for their role in ion regulation and homeostasis, also generate relevant ion signals during neuronal activity. The functional consequences of activity-related sodium transients are manifold and are just coming into view, enabling surprising and important new insights into astrocyte function and neuron-glia interaction in the brain. The present review will highlight current knowledge about the mechanisms that contribute to sodium homeostasis in astrocytes, present recent data on the spatial and temporal properties of activity-related glial sodium signals and discuss their functional consequences with a special emphasis on pathophysiological conditions.
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Affiliation(s)
- Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
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28
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Lange SC, Bak LK, Waagepetersen HS, Schousboe A, Norenberg MD. Primary cultures of astrocytes: their value in understanding astrocytes in health and disease. Neurochem Res 2012; 37:2569-88. [PMID: 22926576 DOI: 10.1007/s11064-012-0868-0] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 08/01/2012] [Accepted: 08/01/2012] [Indexed: 12/26/2022]
Abstract
During the past few decades of astrocyte research it has become increasingly clear that astrocytes have taken a central position in all central nervous system activities. Much of our new understanding of astrocytes has been derived from studies conducted with primary cultures of astrocytes. Such cultures have been an invaluable tool for studying roles of astrocytes in physiological and pathological states. Many central astrocytic functions in metabolism, amino acid neurotransmission and calcium signaling were discovered using this tissue culture preparation and most of these observations were subsequently found in vivo. Nevertheless, primary cultures of astrocytes are an in vitro model that does not fully mimic the complex events occurring in vivo. Here we present an overview of the numerous contributions generated by the use of primary astrocyte cultures to uncover the diverse functions of astrocytes. Many of these discoveries would not have been possible to achieve without the use of astrocyte cultures. Additionally, we address and discuss the concerns that have been raised regarding the use of primary cultures of astrocytes as an experimental model system.
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Affiliation(s)
- Sofie C Lange
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
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29
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Sohn Y, Yoo KY, Park OK, Kwon SH, Lee CH, Choi JH, Hwang IK, Seo JY, Cho JH, Won MH. Na+/HCO3 − Cotransporter Immunoreactivity Changes in Neurons and Expresses in Astrocytes in the Gerbil Hippocampal CA1 Region After Ischemia/Reperfusion. Neurochem Res 2011; 36:2459-69. [DOI: 10.1007/s11064-011-0572-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 07/28/2011] [Accepted: 08/02/2011] [Indexed: 10/17/2022]
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30
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Tse KH, Kingham PJ, Novikov LN, Wiberg M. Adipose tissue and bone marrow-derived stem cells react similarly in an ischaemia-like microenvironment. J Tissue Eng Regen Med 2011; 6:473-85. [PMID: 21751425 DOI: 10.1002/term.452] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Accepted: 05/23/2011] [Indexed: 12/22/2022]
Abstract
Mesenchymal stem cells (MSCs) from adipose tissue and bone marrow are promising cell sources for autologous cell therapy of nerve injuries, as demonstrated by their intrinsic neurotrophic potential. However, extensive death of transplanted cells limits their full benefits. This study investigated the effects of ischaemia (metabolically induced by sodium azide and 2-deoxyglucose) and serum-derived mitogens on the viability and functional profile of MSCs in vitro. MSCs were more susceptible to combined, rather than individual, blockade of glycolysis and oxidative phosphorylation. Apoptosis and autophagy were involved in ischaemia-induced cell death. Chemical ischaemia alone and serum withdrawal alone induced a similar amount of cell death, with significantly different intracellular ATP maintenance. Combined ischaemia and serum deprivation had additive effects on cell death. Expression of the extracellular matrix (ECM) molecules laminin and fibronectin was attenuated under ischaemia and independent of serum level; however, BDNF and NGF levels remained relatively constant. Strong upregulation of VEGF and to a lesser extent angiopoietin-1 was observed under ischaemia but not in serum withdrawal conditions. Importantly, this study demonstrated similar reactions of MSCs derived from adipose and bone marrow tissue, in ischaemia-like and mitogen-deprived microenvironments in terms of viability, cellular energetics, cell death mechanisms and expression levels of various growth-promoting molecules. Also, the results suggest that ischaemia has a larger impact on the ability of MSCs to survive transplantation than withdrawal of mitogens.
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Affiliation(s)
- Kai-Hei Tse
- Department of Integrative Medical Biology, Section of Anatomy, Umeå University, Sweden
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31
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Reactive oxygen species hydrogen peroxide mediates Kaposi's sarcoma-associated herpesvirus reactivation from latency. PLoS Pathog 2011; 7:e1002054. [PMID: 21625536 PMCID: PMC3098240 DOI: 10.1371/journal.ppat.1002054] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 03/16/2011] [Indexed: 01/17/2023] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) establishes a latent
infection in the host following an acute infection. Reactivation from latency
contributes to the development of KSHV-induced malignancies, which include
Kaposi's sarcoma (KS), the most common cancer in untreated AIDS patients,
primary effusion lymphoma and multicentric Castleman's disease. However,
the physiological cues that trigger KSHV reactivation remain unclear. Here, we
show that the reactive oxygen species (ROS) hydrogen peroxide
(H2O2) induces KSHV reactivation from latency through
both autocrine and paracrine signaling. Furthermore, KSHV spontaneous lytic
replication, and KSHV reactivation from latency induced by oxidative stress,
hypoxia, and proinflammatory and proangiogenic cytokines are mediated by
H2O2. Mechanistically, H2O2
induction of KSHV reactivation depends on the activation of mitogen-activated
protein kinase ERK1/2, JNK, and p38 pathways. Significantly,
H2O2 scavengers N-acetyl-L-cysteine (NAC), catalase
and glutathione inhibit KSHV lytic replication in culture. In a mouse model of
KSHV-induced lymphoma, NAC effectively inhibits KSHV lytic replication and
significantly prolongs the lifespan of the mice. These results directly relate
KSHV reactivation to oxidative stress and inflammation, which are physiological
hallmarks of KS patients. The discovery of this novel mechanism of KSHV
reactivation indicates that antioxidants and anti-inflammation drugs could be
promising preventive and therapeutic agents for effectively targeting KSHV
replication and KSHV-related malignancies. Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of all
clinical forms of Kaposi's sarcoma (KS) and several other malignancies. The
life cycle of KSHV consists of latent and lytic phases. While establishment of
viral latency is essential for KSHV to evade host immune surveillances, viral
lytic replication promotes KSHV-induced malignancies. In this study, we show
that the reactive oxygen species (ROS) hydrogen peroxide
(H2O2) induces KSHV reactivation from latency.
Furthermore, induction of KSHV reactivation by oxidative stress, hypoxia, and
proinflammatory and proangiogenic cytokines, which are physiological hallmarks
in all clinical forms of KS patients, is mediated by H2O2.
Significantly, antioxidants inhibit H2O2-induced KSHV
lytic replication in culture and in a mouse model of KSHV-induced lymphoma.
These results show that ROS is likely an important physiological cue that
triggers KSHV replication. The discovery of this novel mechanism of KSHV
reactivation indicates that antioxidants and anti-inflammation drugs might be
promising preventive and therapeutic agents for effectively targeting KSHV
replication and KSHV-related malignancies.
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Molecular Pathophysiology of White Matter Anoxic-Ischemic Injury. Stroke 2011. [DOI: 10.1016/b978-1-4160-5478-8.10008-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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33
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Inducers of Chemical Hypoxia Act in a Gender- and Brain Region-Specific Manner on Primary Astrocyte Viability and Cytochrome c Oxidase. Neurotox Res 2010; 20:1-14. [DOI: 10.1007/s12640-010-9213-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 05/11/2010] [Accepted: 08/02/2010] [Indexed: 12/19/2022]
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Beckner ME, Fellows-Mayle W, Zhang Z, Agostino NR, Kant JA, Day BW, Pollack IF. Identification of ATP citrate lyase as a positive regulator of glycolytic function in glioblastomas. Int J Cancer 2010; 126:2282-95. [PMID: 19795461 DOI: 10.1002/ijc.24918] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Glioblastomas, the most malignant type of glioma, are more glycolytic than normal brain tissue. Robust migration of glioblastoma cells has been previously demonstrated under glycolytic conditions and their pseudopodia contain increased glycolytic and decreased mitochondrial enzymes. Glycolysis is suppressed by metabolic acids, including citric acid which is excluded from mitochondria during hypoxia. We postulated that glioma cells maintain glycolysis by regulating metabolic acids, especially in their pseudopodia. The enzyme that breaks down cytosolic citric acid is ATP citrate lyase (ACLY). Our identification of increased ACLY in pseudopodia of U87 glioblastoma cells on 1D gels and immunoblots prompted investigation of ACLY gene expression in gliomas for survival data and correlation with expression of ENO1, that encodes enolase 1. Queries of the NIH's REMBRANDT brain tumor database based on Affymetrix data indicated that decreased survival correlated with increased gene expression of ACLY in gliomas. Queries of gliomas and glioblastomas found an association of upregulated ACLY and ENO1 expression by chi square for all probe sets (reporters) combined and correlation for numbers of probe sets indicating shared upregulation of these genes. Real-time quantitative PCR confirmed correlation between ACLY and ENO1 in 21 glioblastomas (p < 0.001). Inhibition of ACLY with hydroxycitrate suppressed (p < 0.05) in vitro glioblastoma cell migration, clonogenicity and brain invasion under glycolytic conditions and enhanced the suppressive effects of a Met inhibitor on cell migration. In summary, gene expression data, proteomics and functional assays support ACLY as a positive regulator of glycolysis in glioblastomas.
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Affiliation(s)
- Marie E Beckner
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA, USA.
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Xu G, Wang W, Kimelberg HK, Zhou M. Electrical coupling of astrocytes in rat hippocampal slices under physiological and simulated ischemic conditions. Glia 2010; 58:481-93. [PMID: 19795502 DOI: 10.1002/glia.20939] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mammalian protoplasmic astrocytes are extensively coupled through gap junction channels but the biophysical properties of these channels under physiological and ischemic conditions in situ are not well defined. Using confocal morphometric analysis of biocytin-filled astrocytic syncytia in rat hippocampal CA1 stratum radiatum we found that each astrocyte directly couples, on average, to 11 other astrocytes with a mean interastrocytic distance of 45 microm. Voltage-independent and bidirectional transjunctional currents were always measured between directly coupled astrocyte pairs in dual voltage-clamp recordings, but never from astrocyte-NG2 glia or astrocyte-interneuron pairs. The electrical coupling ratio varied considerably among astrocytes in developing postnatal day 14 rats (P14, 0.5-12.4%, mean = 3.6%), but became more constant in young adult P21 rats (0.18-3.9%, mean = 1.6%), and the coupling ratio declined exponentially with increasing pair distance. Electrical coupling was not affected by short-term oxygen-glucose deprivation (OGD) treatment, but showed delayed inhibition in an acidic extracellular pH of 6.4. Combination of acidic pH (6.4) and OGD, a condition that better represents cerebral ischemia in vivo, accelerated the inhibition of electrical coupling. Our results show that, under physiological conditions, 20.7-24.2% of K(+) induced currents can travel from any astrocytic soma in CA1 stratum radiatum to the gap junctions of the nearest neighbor astrocytes, but this should be severely inhibited as a consequence of the OGD and acidosis seen in the ischemic brain.
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Affiliation(s)
- Guangjin Xu
- Department of Neurology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China
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Jayakumar AR, Norenberg MD. The Na-K-Cl Co-transporter in astrocyte swelling. Metab Brain Dis 2010; 25:31-8. [PMID: 20336356 DOI: 10.1007/s11011-010-9180-3] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Accepted: 01/28/2010] [Indexed: 10/19/2022]
Abstract
Ion channels, exchangers and transporters are known to be involved in cell volume regulation. A disturbance in one or more of these systems may result in loss of ion homeostasis and cell swelling. In particular, activation of the Na(+)-K(+)-Cl(-) cotransporters has been shown to regulate cell volume in many conditions. The Na(+)-K(+)-Cl- cotransporters (NKCC) are a class of membrane proteins that transport Na, K, and Cl ions into and out of a wide variety of epithelial and nonepithelial cells. Studies have established the role of NKCC1 in astrocyte swelling/brain edema in ischemia and trauma. Our recent studies suggest that NKCC1 activation is also involved in astrocyte swelling induced by ammonia and in the brain edema in the thioacetamide model of acute liver failure. This review will focus on mechanisms of NKCC1 activation and its contribution to astrocyte swelling/brain edema in neurological disorders, with particular emphasis on ammonia neurotoxicity and acute liver failure.
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Affiliation(s)
- Arumugam R Jayakumar
- Department of Pathology (D-33), University of Miami Miller School of Medicine, P.O. Box 016960, Miami, FL 33125, USA.
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The vacuolar-type H-ATPase in ovine rumen epithelium is regulated by metabolic signals. J Biomed Biotechnol 2010; 2010:525034. [PMID: 20069127 PMCID: PMC2804115 DOI: 10.1155/2010/525034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Accepted: 10/13/2009] [Indexed: 12/21/2022] Open
Abstract
In this study, the effect of metabolic inhibition (MI) by glucose substitution with 2-deoxyglucose (2-DOG) and/or application of antimycin A on ovine rumen epithelial cells (REC) vacuolar-type H+-ATPase (vH+-ATPase) activity was investigated. Using fluorescent spectroscopy, basal pHi of REC was measured to be 7.3 ± 0.1 in HCO3−-free, glucose-containing NaCl medium. MI induced a strong pHi reduction (−0.44 ± 0.04 pH units) with a more pronounced effect of 2-DOG compared to antimycin A (−0.30 ± 0.03 versus −0.21 ± 0.03 pH units). Treatment with foliomycin, a specific vH+-ATPase inhibitor, decreased REC pHi by 0.21 ± 0.05 pH units. After MI induction, this effect was nearly abolished (−0.03 ± 0.02 pH units). In addition, membrane-associated localization of vH+-ATPase B subunit disappeared. Metabolic control of vH+-ATPase involving regulation of its assembly state by elements of the glycolytic pathway could provide a means to adapt REC ATP consumption according to energy availability.
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Chao D, Xia Y. Ionic storm in hypoxic/ischemic stress: can opioid receptors subside it? Prog Neurobiol 2009; 90:439-70. [PMID: 20036308 DOI: 10.1016/j.pneurobio.2009.12.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2009] [Revised: 09/10/2009] [Accepted: 12/17/2009] [Indexed: 12/17/2022]
Abstract
Neurons in the mammalian central nervous system are extremely vulnerable to oxygen deprivation and blood supply insufficiency. Indeed, hypoxic/ischemic stress triggers multiple pathophysiological changes in the brain, forming the basis of hypoxic/ischemic encephalopathy. One of the initial and crucial events induced by hypoxia/ischemia is the disruption of ionic homeostasis characterized by enhanced K(+) efflux and Na(+)-, Ca(2+)- and Cl(-)-influx, which causes neuronal injury or even death. Recent data from our laboratory and those of others have shown that activation of opioid receptors, particularly delta-opioid receptors (DOR), is neuroprotective against hypoxic/ischemic insult. This protective mechanism may be one of the key factors that determine neuronal survival under hypoxic/ischemic condition. An important aspect of the DOR-mediated neuroprotection is its action against hypoxic/ischemic disruption of ionic homeostasis. Specially, DOR signal inhibits Na(+) influx through the membrane and reduces the increase in intracellular Ca(2+), thus decreasing the excessive leakage of intracellular K(+). Such protection is dependent on a PKC-dependent and PKA-independent signaling pathway. Furthermore, our novel exploration shows that DOR attenuates hypoxic/ischemic disruption of ionic homeostasis through the inhibitory regulation of Na(+) channels. In this review, we will first update current information regarding the process and features of hypoxic/ischemic disruption of ionic homeostasis and then discuss the opioid-mediated regulation of ionic homeostasis, especially in hypoxic/ischemic condition, and the underlying mechanisms.
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Affiliation(s)
- Dongman Chao
- Yale University School of Medicine, Department of Pediatrics, New Haven, CT 06520, USA
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39
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Tong XP, Li XY, Zhou B, Shen W, Zhang ZJ, Xu TL, Duan S. Ca(2+) signaling evoked by activation of Na(+) channels and Na(+)/Ca(2+) exchangers is required for GABA-induced NG2 cell migration. ACTA ACUST UNITED AC 2009; 186:113-28. [PMID: 19596850 PMCID: PMC2712990 DOI: 10.1083/jcb.200811071] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
NG2 cells originate from various brain regions and migrate to their destinations during early development. These cells express voltage-gated Na(+) channels but fail to produce typical action potentials. The physiological role of Na(+) channels in these cells is unclear. We found that GABA induces membrane depolarization and Ca(2+) elevation in NG2 cells, a process requiring activation of GABA(A) receptors, Na(+) channels, and Na(+)/Ca(2+) exchangers (NCXs), but not Ca(2+) channels. We have identified a persistent Na(+) current in these cells that may underlie the GABA-induced pathway of prolonged Na(+) elevation, which in turn triggers Ca(2+) influx via NCXs. This unique Ca(2+) signaling pathway is further shown to be involved in the migration of NG2 cells. Thus, GABAergic signaling mediated by sequential activation of GABA(A) receptors, noninactivating Na(+) channels, and NCXs may play an important role in the development and function of NG2 glial cells in the brain.
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Affiliation(s)
- Xiao-ping Tong
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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40
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Sickmann HM, Walls AB, Schousboe A, Bouman SD, Waagepetersen HS. Functional significance of brain glycogen in sustaining glutamatergic neurotransmission. J Neurochem 2009; 109 Suppl 1:80-6. [DOI: 10.1111/j.1471-4159.2009.05915.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Liu Y, Liu XJ, Sun D. Ion transporters and ischemic mitochondrial dysfunction. Cell Adh Migr 2009; 3:94-8. [PMID: 19276659 PMCID: PMC2675155 DOI: 10.4161/cam.3.1.7516] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Accepted: 12/02/2008] [Indexed: 11/19/2022] Open
Abstract
Ischemia-induced ionic imbalance leads to the activation of numerous events including mitochondrial dysfunction and eventual cell death. Dysregulation of mitochondrial Ca(2+) (Ca(2+)(m)) plays a critical role in cell damage under pathological conditions including traumatic brain injury and stroke. High Ca(2+)(m) levels can induce the persistent opening of the mitochondrial permeability transition pore and trigger mitochondrial membrane depolarization, Ca(2+) release, cessation of oxidative phosphorylation, matrix swelling and eventually outer membrane rupture with release of cytochrome c and other apoptogenic proteins. Thus, the dysregulation of mitochondrial Ca(2+) homeostasis is now recognized to play a crucial role in triggering mitochondrial dysfunction and subsequent apoptosis. Recent studies show that some secondary active transport proteins, such as Na(+)-dependent chloride transporter and Na(+)/Ca(2+) exchanger, contribute to ischemia-induced dissipation of ion homeostasis including Ca(2+)(m).
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Affiliation(s)
- Yan Liu
- Department of Neurological Surgery; University of Wisconsin School of Medicine and Public Health; Madison, WI USA
- Department of Biological Sciences and Biotechnology; Institute of Biomedical Informatics; School of Medicine; Tsinghua University; Beijing, China
| | - Xiang-jun Liu
- Department of Biological Sciences and Biotechnology; Institute of Biomedical Informatics; School of Medicine; Tsinghua University; Beijing, China
| | - Dandan Sun
- Department of Neurological Surgery; University of Wisconsin School of Medicine and Public Health; Madison, WI USA
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Jayakumar AR, Liu M, Moriyama M, Ramakrishnan R, Forbush B, Reddy PVB, Norenberg MD. Na-K-Cl Cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling. J Biol Chem 2008; 283:33874-82. [PMID: 18849345 PMCID: PMC2590687 DOI: 10.1074/jbc.m804016200] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Revised: 10/08/2008] [Indexed: 11/06/2022] Open
Abstract
Brain edema and the consequent increase in intracranial pressure and brain herniation are major complications of acute liver failure (fulminant hepatic failure) and a major cause of death in this condition. Ammonia has been strongly implicated as an important factor, and astrocyte swelling appears to be primarily responsible for the edema. Ammonia is known to cause cell swelling in cultured astrocytes, although the means by which this occurs has not been fully elucidated. A disturbance in one or more of these systems may result in loss of ion homeostasis and cell swelling. In particular, activation of the Na-K-Cl cotransporter (NKCC1) has been shown to be involved in cell swelling in several neurological disorders. We therefore examined the effect of ammonia on NKCC activity and its potential role in the swelling of astrocytes. Cultured astrocytes were exposed to ammonia (NH(4)Cl; 5 mm), and NKCC activity was measured. Ammonia increased NKCC activity at 24 h. Inhibition of this activity by bumetanide diminished ammonia-induced astrocyte swelling. Ammonia also increased total as well as phosphorylated NKCC1. Treatment with cyclohexamide, a potent inhibitor of protein synthesis, diminished NKCC1 protein expression and NKCC activity. Since ammonia is known to induce oxidative/nitrosative stress, and antioxidants and nitric-oxide synthase inhibition diminish astrocyte swelling, we also examined whether ammonia caused oxidation and/or nitration of NKCC1. Cultures exposed to ammonia increased the state of oxidation and nitration of NKCC1, whereas the antioxidants N-nitro-l-arginine methyl ester and uric acid all significantly diminished NKCC activity. These agents also reduced phosphorylated NKCC1 expression. These results suggest that activation of NKCC1 is an important factor in the mediation of astrocyte swelling by ammonia and that such activation appears to be mediated by NKCC1 abundance as well as by its oxidation/nitration and phosphorylation.
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Affiliation(s)
- Arumugam R Jayakumar
- Department of Pathology and Biochemistry, University of Miami School of Medicine and Veterans Affairs Medical Center, Miami, Florida 33101, USA
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43
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Lo JC, Huang WC, Chou YC, Tseng CH, Lee WL, Sun SH. Activation of P2X(7) receptors decreases glutamate uptake and glutamine synthetase activity in RBA-2 astrocytes via distinct mechanisms. J Neurochem 2007; 105:151-64. [PMID: 18067549 DOI: 10.1111/j.1471-4159.2007.05119.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glutamate clearance by astrocytes is critical for controlling excitatory neurotransmission and ATP is an important mediator for neuron-astrocyte interaction. However, the effect of ATP on glutamate clearance has never been examined. Here we report that treatment of RBA-2 cells, a type-2-like astrocyte cell line, with ATP and the P2X(7) receptor selective agonist 3'-O-(4-benzoylbenzoyl) adenosine 5'-triphosphate (BzATP) decreased the Na+-dependent [3H]glutamate uptake within minutes. Mechanistic studies revealed that the decreases were augmented by removal of extracellular Mg2+ or Ca2+, and was restored by P2X7 selective antagonist , periodate-oxidized 2',3'-dialdehyde ATP (oATP), indicating that the decreases were mediated through P2X(7) receptors. Furthermore, stimulation of P2X7 receptors for 2 h inhibited both activity and protein expression of glutamine synthetase (GS), and oATP abolished the inhibition. In addition, removal of extracellular Ca(2+) and inhibition of protein kinase C (PKC) restored the ATP-decreased GS expression but failed to restore the P2X(7)-decreased [3H]glutamate uptake. Therefore, P2X7-mediated intracellular signals play a role in the down-regulation of GS activity/expression. Activation of P2X7 receptors stimulated increases in intracellular Na+ concentration ([Na+](i)) suggesting that the P2X(7)-induced increases in [Na+](i) may affect the local Na+ gradient and decrease the Na+-dependent [3H]glutamate uptake. These findings demonstrate that the P2X7-mediated decreases in glutamate uptake and glutamine synthesis were mediated through distinct mechanisms in these cells.
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Affiliation(s)
- Jun-Chih Lo
- Institute of Neuroscience, National Yang Ming University, Taipei, Taiwan, Republic of China
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44
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Kintner DB, Luo J, Gerdts J, Ballard AJ, Shull GE, Sun D. Role of Na+-K+-Cl−cotransport and Na+/Ca2+exchange in mitochondrial dysfunction in astrocytes following in vitro ischemia. Am J Physiol Cell Physiol 2007; 292:C1113-22. [PMID: 17035299 DOI: 10.1152/ajpcell.00412.2006] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Na+-K+-Cl−cotransporter isoform 1 (NKCC1) and reverse mode operation of the Na+/Ca2+exchanger (NCX) contribute to intracellular Na+and Ca2+overload in astrocytes following oxygen-glucose deprivation (OGD) and reoxygenation (REOX). Here, we further investigated whether NKCC1 and NCX play a role in mitochondrial Ca2+(Cam2+) overload and dysfunction. OGD/REOX caused a doubling of mitochondrial-releasable Ca2+( P < 0.05). When NKCC1 was inhibited with bumetanide, the mitochondrial-releasable Ca2+was reduced by ∼42% ( P < 0.05). Genetic ablation of NKCC1 also reduced Cam2+accumulation. Moreover, OGD/REOX in NKCC1+/+astrocytes caused dissipation of the mitochondrial membrane potential (Ψm) to 42 ± 3% of controls. In contrast, when NKCC1 was inhibited with bumetanide, depolarization of Ψmwas attenuated significantly (66 ± 10% of controls, P < 0.05). Cells were also subjected to severe in vitro hypoxia by superfusion with a hypoxic, acidic, ion-shifted Ringer buffer (HAIR). HAIR/REOX triggered a secondary, sustained rise in intracellular Ca2+that was attenuated by reversal NCX inhibitor KB-R7943. The hypoxia-mediated increase in Cam2+was accompanied by loss of Ψmand cytochrome c release in NKCC1+/+astrocytes. Bumetanide or genetic ablation of NKCC1 attenuated mitochondrial dysfunction and astrocyte death following ischemia. Our study suggests that NKCC1 acting in concert with NCX causes a perturbation of Cam2+homeostasis and mitochondrial dysfunction and cell death following in vitro ischemia.
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Affiliation(s)
- Douglas B Kintner
- Dept. of Neurological Surgery, University of Wisconsin School of Medicine, Madison, WI 53792, USA
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Kosugi T, Kawahara K. Reversed Actrocytic GLT-1 during Ischemia is Crucial to Excitotoxic Death of Neurons, but Contributes to the Survival of Astrocytes themselves. Neurochem Res 2006; 31:933-43. [PMID: 16830212 DOI: 10.1007/s11064-006-9099-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/05/2006] [Indexed: 10/24/2022]
Abstract
During ischemia, the operation of astrocytic/neuronal glutamate transporters is reversed and glutamate and Na(+) are co-transported to the extracellular space. This study aims to investigate whether this reversed operation of glutamate transporters has any functional meanings for astrocytes themselves. Oxygen/glucose deprivation (OGD) of neuron/astrocyte co-cultures resulted in the massive death of neurons, and the cell death was significantly reduced by treatment with either AP5 or DHK. In cultured astrocytes with little GLT-1 expression, OGD produced Na(+) overload, resulting in the reversal of astrocytic Na(+)/Ca(2+)-exchanger (NCX). The reversed NCX then caused Ca(2+) overload leading to the damage of astrocytes. In contrast, the OGD-induced Na(+) overload and astrocytic damage were significantly attenuated in PACAP-treated astrocytes with increased GLT-1 expression, and the attenuation was antagonized by treatment with DHK. These results suggested that the OGD-induced reversal of GLT-1 contributed to the survival of astrocytes themselves by releasing Na(+) with glutamate via reversed GLT-1.
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Affiliation(s)
- Tatsuro Kosugi
- Laboratory of Cellular Cybernetics, Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814, Japan
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Gao F, Okunieff P, Han Z, Ding I, Wang L, Liu W, Zhang J, Yang S, Chen J, Underhill CB, Kim S, Zhang L. Hypoxia-induced alterations in hyaluronan and hyaluronidase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 566:249-56. [PMID: 16594159 DOI: 10.1007/0-387-26206-7_33] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Hyaluronan (HA), a large negatively-charged polysaccharide, is a major component of vessel basal membrane. HA is expressed by a variety of cells, including tumor and endothelial cells. We hypothesized that HA could be up-regulated by hypoxia to enhance vessel formation. To determine the effect of hypoxia on the production of HA, tumor cells were treated with either media alone (control) or a hypoxia inducer (CoCl or NaN3) for 24 h. The level of HA in the media was then measured by ELISA. The results showed that both CoCl and NaN3 induced the production of HA. Since the low molecular weight form of HA (SMW) possesses pro-angiogenic properties, we investigated whether hypoxia-induced HA can be processed into SMW. Under hypoxic conditions, the activity of hyaluronidase, the enzyme responsible for degrading HA, was measured by an ELISA-like assay. The activity of hyaluronidase was shown to be up-regulated by hypoxia and, further, could carry out the function of processing HA into SMW. In addition, the hypoxic areas of tumor tissues were stained strongly with biotinylated HA-binding proteins, indicating that the level of HA was high compared to the oxic areas. This study demonstrates that hypoxia can stimulate the production of HA and the activity of hyaluronidase, which may promote angiogenesis as a compensation mechanism for hypoxia.
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Beckner ME, Gobbel GT, Abounader R, Burovic F, Agostino NR, Laterra J, Pollack IF. Glycolytic glioma cells with active glycogen synthase are sensitive to PTEN and inhibitors of PI3K and gluconeogenesis. J Transl Med 2005; 85:1457-70. [PMID: 16170333 DOI: 10.1038/labinvest.3700355] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Increased glycolysis is characteristic of malignancy. Previously, with a mitochondrial inhibitor, we demonstrated that glycolytic ATP production was sufficient to support migration of melanoma cells. Recently, we found that glycolytic enzymes were abundant and some were increased in pseudopodia formed by U87 glioma (astrocytoma) cells. In this study, we examined cell migration, adhesion (a step in migration), and Matrigel invasion of U87 and LN229 glioma cells when their mitochondria were inhibited with sodium azide or limited by 1% O(2). Cell migration, adhesion, and invasion were comparable, with and without mitochondrial inhibition. Upon discovering that glycolysis alone can support glioma cell migration, unique features of glucose metabolism in astrocytic cells were investigated. The ability of astrocytic cells to remove lactate, the inhibitor of glycolysis, via gluconeogenesis and incorporation into glycogen led to consideration of supportive genetic mutations. Loss of phosphatase and tensin homolog (PTEN) releases glycogenesis from constitutive inhibition by glycogen synthase kinase-3 (GSK3). We hypothesize that glycolysis in gliomas can support invasive migration, especially when aided by loss of PTEN's regulation on the phosphatidylinositol-3 kinase (PI3K)/Akt pathway leading to inhibition of GSK3. Migration of PTEN-mutated U87 cells was studied for release of extracellular lactic acid and support by gluconeogenesis, loss of PTEN, and active PI3K. Lactic acid levels plateaued and phosphorylation changes confirmed activation of the PI3K/Akt pathway and glycogen synthase when cells relied only on glycolysis. Glycolytic U87 cell migration and phosphorylation of GSK3 were inhibited by PTEN transfection. Glycolytic migration was also suppressed by inhibiting PI3K and gluconeogenesis with wortmannin and metformin, respectively. These findings confirm that glycolytic glioma cells can migrate invasively and that the loss of PTEN is supportive, with activated glycogenic potential included among the relevant downstream effects.
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Affiliation(s)
- Marie E Beckner
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
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FLOYD CANDACEL, GORIN FREDRICA, LYETH BRUCEG. Mechanical strain injury increases intracellular sodium and reverses Na+/Ca2+ exchange in cortical astrocytes. Glia 2005; 51:35-46. [PMID: 15779085 PMCID: PMC2996279 DOI: 10.1002/glia.20183] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Traditionally, astrocytes have been considered less susceptible to injury than neurons. Yet, we have recently shown that astrocyte death precedes neuronal death in a rat model of traumatic brain injury (TBI) (Zhao et al.: Glia 44:140-152, 2003). A main mechanism hypothesized to contribute to cellular injury and death after TBI is elevated intracellular calcium ([Ca2+]i). Since calcium regulation is also influenced by regulation of intracellular sodium ([Na+]i), we used an in vitro model of strain-induced traumatic injury and live-cell fluorescent digital imaging to investigate alterations in [Na+]i in cortical astrocytes after injury. Changes in [Na+]i, or [Ca2+]i were monitored after mechanical injury or L-glutamate exposure by ratiometric imaging of sodium-binding benzofuran isophthalate (SBFI-AM), or Fura-2-AM, respectively. Mechanical strain injury or exogenous glutamate application produced increases in [Na+]i that were dependent on the severity of injury or concentration. Injury-induced increases in [Na+]i were significantly reduced, but not completely eliminated, by inhibition of glutamate uptake by DL-threo-beta-benzyloxyaspartate (TBOA). Blockade of sodium-dependent calcium influx through the sodium-calcium exchanger with 2-[2-[4-(4-Nitrobenzyloxy)phenyl]ethyl]isothiourea mesylate (KB-R7943) reduced [Ca2+]i after injury. KB-R7943 also reduced astrocyte death after injury. These findings suggest that in astrocytes subjected to mechanical injury or glutamate excitotoxicity, increases in intracellular Na+ may be a critical component in the injury cascade and a therapeutic target for reduction of lasting deficits after traumatic brain injury.
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Affiliation(s)
- CANDACE L. FLOYD
- Department of Neurological Surgery, Center for Neuroscience, University of California, Davis, California
| | - FREDRIC A. GORIN
- Department of Neurology, Center for Neuroscience, University of California, Davis, California
| | - BRUCE G. LYETH
- Department of Neurological Surgery, Center for Neuroscience, University of California, Davis, California
- Correspondence to: Bruce G. Lyeth, Department of Neurological Surgery, University of California at Davis, 1515 Newton Court, One Shields Avenue, Davis, CA 95616-8797.
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Chesler M. Failure and function of intracellular pH regulation in acute hypoxic-ischemic injury of astrocytes. Glia 2005; 50:398-406. [PMID: 15846798 DOI: 10.1002/glia.20141] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Astrocytes can die rapidly following ischemic and traumatic injury to the CNS. Brain acid-base status has featured prominently in theories of acute astrocyte injury. Failure of astrocyte pH regulation can lead to cell loss under conditions of severe acidosis. By contrast, the function of astrocyte pH regulatory mechanisms appears to be necessary for acute cell death following the simulation of transient ischemia and reperfusion. Severe lactic acidosis, and the failure of astrocytes to regulate intracellular pH (pH(i)) have been emphasized in brain ischemia under hyperglycemic conditions. Direct measurements of astrocyte pH(i) after cardiac arrest demonstrated a mean pH(i) of 5.3 in hyperglycemic rats. In addition, both in vivo and in vitro studies of astrocytes have shown similar pH levels to be cytotoxic. Whereas astrocytes exposed to hypoxia alone may require 12-24 h to die, acidosis has been found to exacerbate and speed hypoxic loss of these cells. Recently, astrocyte cultures were exposed to hypoxic, acidic media in which the large ionic perturbations characteristic of brain ischemia were simulated. Upon return to normal saline ("reperfusion"), the majority of cells died. This injury was dependent on external Ca2+ and was prevented by inhibition of reversed Na(+)-Ca2+ exchange, blockade of Na(+)-H+ exchange, or by low pH of the reperfusion saline. These data suggested that cytotoxic elevation of [Ca2+]i occurred during reperfusion due to a sequence of activated Na(+)-H+ exchange, cytosolic Na+ loading, and resultant reversal of Na(+)-Ca2+ exchange. The significance of this reperfusion model to ischemic astrocyte injury in vivo is discussed.
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Affiliation(s)
- Mitchell Chesler
- Department of Neurosurgery and Department of Physiology and Neuroscience, New York University School of Medicine, New York, New York
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Abstract
Despite intense efforts at the bench and at the bedside, few therapeutic strategies exist to combat the consequences of cerebral ischemia. Traditionally, a "neurocentric" view has dominated research in this field. Evidence is now accumulating that glial cells, in particular astrocytes, play an active and important role in the pathophysiology of cerebral ischemia. Brain energetics, water and ion homeostasis, inflammation, trophic factor production, vascular regulation, neuroneogenesis, and vasculogenesis, among others, are all under the control of glial cells. As a consequence, glial cells have been identified as promising targets for novel therapeutic approaches in brain protection. This review aims at dissecting possible protective as well as destructive roles of astrocytes (and other glial cells) in cerebral ischemia. By emphasizing open issues in this field, we hope to stimulate further research into this relatively unexplored aspect of brain pathophysiology.
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Affiliation(s)
- Maiken Nedergaard
- Department of Neurosurgery, Center for Aging and Developmental Biology, University of Rochester Medical Center, Rochester, New York
| | - Ulrich Dirnagl
- Department of Neurosurgery, Center for Aging and Developmental Biology, University of Rochester Medical Center, Rochester, New York
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