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Çarçak N, Onat F, Sitnikova E. Astrocytes as a target for therapeutic strategies in epilepsy: current insights. Front Mol Neurosci 2023; 16:1183775. [PMID: 37583518 PMCID: PMC10423940 DOI: 10.3389/fnmol.2023.1183775] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 07/12/2023] [Indexed: 08/17/2023] Open
Abstract
Astrocytes are specialized non-neuronal glial cells of the central nervous system, contributing to neuronal excitability and synaptic transmission (gliotransmission). Astrocytes play a key roles in epileptogenesis and seizure generation. Epilepsy, as a chronic disorder characterized by neuronal hyperexcitation and hypersynchronization, is accompanied by substantial disturbances of glial cells and impairment of astrocytic functions and neuronal signaling. Anti-seizure drugs that provide symptomatic control of seizures primarily target neural activity. In epileptic patients with inadequate control of seizures with available anti-seizure drugs, novel therapeutic candidates are needed. These candidates should treat epilepsy with anti-epileptogenic and disease-modifying effects. Evidence from human and animal studies shows that astrocytes have value for developing new anti-seizure and anti-epileptogenic drugs. In this review, we present the key functions of astrocytes contributing to neuronal hyperexcitability and synaptic activity following an etiology-based approach. We analyze the role of astrocytes in both development (epileptogenesis) and generation of seizures (ictogenesis). Several promising new strategies that attempted to modify astroglial functions for treating epilepsy are being developed: (1) selective targeting of glia-related molecular mechanisms of glutamate transport; (2) modulation of tonic GABA release from astrocytes; (3) gliotransmission; (4) targeting the astrocytic Kir4.1-BDNF system; (5) astrocytic Na+/K+/ATPase activity; (6) targeting DNA hypo- or hypermethylation of candidate genes in astrocytes; (7) targeting astrocytic gap junction regulators; (8) targeting astrocytic adenosine kinase (the major adenosine-metabolizing enzyme); and (9) targeting microglia-astrocyte communication and inflammatory pathways. Novel disease-modifying therapeutic strategies have now been developed, such as astroglia-targeted gene therapy with a broad spectrum of genetic constructs to target astroglial cells.
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Affiliation(s)
- Nihan Çarçak
- Department of Pharmacology, Faculty of Pharmacy, Istanbul University, Istanbul, Turkey
- Institute of Health Sciences, Department of Neuroscience, Acibadem Mehmet Ali Aydinlar University, Istanbul, Turkey
| | - Filiz Onat
- Institute of Health Sciences, Department of Neuroscience, Acibadem Mehmet Ali Aydinlar University, Istanbul, Turkey
- Department of Medical Pharmacology, Faculty of Medicine, Acibadem Mehmet Ali Aydinlar University, Istanbul, Turkey
| | - Evgenia Sitnikova
- Institute of Higher Nervous Activity and Neurophysiology of Russian Academy of Sciences, Moscow, Russia
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Li X, Li Q, Xu L, Ma Z, Shi Y, Zhang X, Yang Y, Wang J, Fan L, Wu L. Involvement of Kir4.1 in pain insensitivity of the BTBR mouse model of autism spectrum disorder. Biochim Biophys Acta Mol Basis Dis 2023; 1869:166700. [PMID: 36990129 DOI: 10.1016/j.bbadis.2023.166700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 03/19/2023] [Accepted: 03/21/2023] [Indexed: 03/30/2023]
Abstract
Autism spectrum disorder (ASD) is a severe neurodevelopmental disorder. Abnormal pain sensation is a common clinical symptom of ASD that seriously affects the quality of life of patients with ASD and their families. However, the underlying mechanism is unclear. It is believed to be related to the excitability of neurons and the expression of ion channels. Herein, we confirmed that baseline pain and Complete Freund's adjuvant (CFA)-induced chronic inflammatory pain were impaired in the BTBR T+ Itpr3tf/J (BTBR) mouse model of ASD. RNA sequencing (RNA-seq) analyses of the dorsal root ganglia (DRG), which are closely related to pain in ASD model mice, revealed that high expression of KCNJ10 (encoding Kir4.1) might be an important factor in ASD pain sensation abnormalities. The levels of Kir4.1 were further verified by western blotting, RT-qPCR, and immunofluorescence. By inhibiting Kir4.1, the pain insensitivity of BTBR mice improved, confirming that a high expression level of Kir4.1 was highly correlated with decreased pain sensitivity in ASD. Meanwhile, we found that the anxiety behaviours and the social novelty recognition were changed after CFA induced inflammatory pain. And after inhibiting Kir4.1, the stereotyped behaviours and social novelty recognition of BTBR mice were also improved. Further, we found that the expression levels of glutamate transporters, excitatory amino acid transporter 1 (EAAT1), and excitatory amino acid transporter 2 (EAAT2) were increased in the DRG of BTBR mice but decreased after inhibiting Kir4.1. This suggests that Kir4.1 may play a key role in the improvement of pain insensitivity in ASD by regulating glutamate transporters. In conclusion, our findings revealed the possible mechanism and role of Kir4.1 in the pain insensitivity in ASD, using bioinformatics analyses and animal experiments, and provided a theoretical basis for clinically targeted intervention in ASD.
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Affiliation(s)
- Xiang Li
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Qi Li
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Lisha Xu
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Zhe Ma
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Yaxin Shi
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Xirui Zhang
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Yuan Yang
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Jia Wang
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China
| | - Lili Fan
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China.
| | - Lijie Wu
- Department of Children's and Adolescent Health, Public Health College, Harbin Medical University, Harbin, China.
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Leo M, Schmitt LI, Steffen R, Kutritz A, Kleinschnitz C, Hagenacker T. Modulation of Glutamate Transporter EAAT1 and Inward-Rectifier Potassium Channel K ir4.1 Expression in Cultured Spinal Cord Astrocytes by Platinum-Based Chemotherapeutics. Int J Mol Sci 2021; 22:6300. [PMID: 34208258 PMCID: PMC8230757 DOI: 10.3390/ijms22126300] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/06/2021] [Accepted: 06/09/2021] [Indexed: 12/26/2022] Open
Abstract
Platinum-based chemotherapeutics still play an essential role in cancer treatment. Despite their high effectiveness, severe side effects such as chemotherapy-induced neuropathy (CIPN) occur frequently. The pathophysiology of CIPN by platinum-based chemotherapeutics is not fully understood yet, but primarily the disturbance of dorsal root ganglion cells is discussed. However, there is increasing evidence of central nervous system involvement with activation of spinal cord astrocytes after treatment with chemotherapeutics. We investigated the influence of cis- or oxaliplatin on the functionality of cultured rat spinal cord astrocytes by using immunocytochemistry and patch-clamp electrophysiology. Cis- or oxaliplatin activated spinal astrocytes and led to downregulation of the excitatory amino acid transporter 1 (EAAT1) expression. Furthermore, the expression and function of potassium channel Kir4.1 were modulated. Pre-exposure to a specific Kir4.1 blocker in control astrocytes led to a reduced immune reactivity (IR) of EAAT1 and a nearly complete block of the current density. When spinal astrocytes were pre-exposed to antibiotic minocycline, all effects of cis- or oxaliplatin were abolished. Taken together, the modulation of Kir4.1 and EAAT1 proteins in astrocytes could be linked to the direct impact of cis- or oxaliplatin, identifying spinal astrocytes as a potential target in the prevention and treatment of chemotherapy-induced neuropathy.
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Affiliation(s)
- Markus Leo
- Department of Neurology, Center for Translational Neuro- and Behavioral Sciences (C-TNBS), University Hospital Essen, 45147 Essen, Germany; (L.-I.S.); (R.S.); (A.K.); (C.K.); (T.H.)
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Kong H, Wang H, Zhuo Z, Li Z, Tian P, Wu J, Liu J, Chen Z, Zhang J, Luo Q. Inhibition of miR-181a-5p reduces astrocyte and microglia activation and oxidative stress by activating SIRT1 in immature rats with epilepsy. J Transl Med 2020; 100:1223-1237. [PMID: 32461588 DOI: 10.1038/s41374-020-0444-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 05/07/2020] [Accepted: 05/08/2020] [Indexed: 02/06/2023] Open
Abstract
MicroRNAs regulate gene expression at the posttranscriptional level, and this process has been shown to be implicated in the pathological processes of temporal lobe epilepsy. At present, studies about the impact of microRNA-181a (miR-181a) on epilepsy have focused on hippocampal neurons, and the effect of miR-181a on other cells in the hippocampus remains poorly understood. Herein, we explored the role of miR-181a-5p in a lithium-pilocarpine model of epilepticus in immature rats. We found that the hippocampal expression level of miR-181a-5p was increased. Inhibition of miR-181a-5p protected the hippocampus against epilepsy, including hippocampal insults, neuronal apoptosis, astrocyte and microglia activation, neuroinflammation, oxidative stress, mitochondrial function, and cognitive dysfunction. Moreover, miR-181a-5p inhibition exerted a seizure-suppressing effect via SIRT1 upregulation. Overall, our findings reveal the potential role of the miR-181a-5p/SIRT1 pathway in the development of temporal lobe epilepsy, and this pathway may represent a novel target for ameliorating epilepsy and its sequelae.
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Affiliation(s)
- Huimin Kong
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China.
| | - Huaili Wang
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China
| | - Zhihong Zhuo
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China
| | - Zhenbiao Li
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China
| | - Peichao Tian
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China
| | - Jing Wu
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China
| | - Jian Liu
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China
| | - Zheng Chen
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China
| | - Jiyao Zhang
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China
| | - Qiang Luo
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, PR China.
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Jarero-Basulto JJ, Gasca-Martínez Y, Rivera-Cervantes MC, Ureña-Guerrero ME, Feria-Velasco AI, Beas-Zarate C. Interactions Between Epilepsy and Plasticity. Pharmaceuticals (Basel) 2018; 11:ph11010017. [PMID: 29414852 PMCID: PMC5874713 DOI: 10.3390/ph11010017] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 02/01/2018] [Accepted: 02/06/2018] [Indexed: 02/06/2023] Open
Abstract
Undoubtedly, one of the most interesting topics in the field of neuroscience is the ability of the central nervous system to respond to different stimuli (normal or pathological) by modifying its structure and function, either transiently or permanently, by generating neural cells and new connections in a process known as neuroplasticity. According to the large amount of evidence reported in the literature, many stimuli, such as environmental pressures, changes in the internal dynamic steady state of the organism and even injuries or illnesses (e.g., epilepsy) may induce neuroplasticity. Epilepsy and neuroplasticity seem to be closely related, as the two processes could positively affect one another. Thus, in this review, we analysed some neuroplastic changes triggered in the hippocampus in response to seizure-induced neuronal damage and how these changes could lead to the establishment of temporal lobe epilepsy, the most common type of focal human epilepsy.
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Affiliation(s)
- José J Jarero-Basulto
- Cellular Neurobiology Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, 45220 Zapopan, Jalisco, Mexico.
| | - Yadira Gasca-Martínez
- Cellular Neurobiology Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, 45220 Zapopan, Jalisco, Mexico.
| | - Martha C Rivera-Cervantes
- Cellular Neurobiology Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, 45220 Zapopan, Jalisco, Mexico.
| | - Mónica E Ureña-Guerrero
- Neurotransmission Biology Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, 45220 Zapopan, Jalisco, Mexico.
| | - Alfredo I Feria-Velasco
- Cellular Neurobiology Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, 45220 Zapopan, Jalisco, Mexico.
| | - Carlos Beas-Zarate
- Development and Neural Regeneration Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, 45220 Zapopan, Jalisco, Mexico.
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Hope KA, LeDoux MS, Reiter LT. Glial overexpression of Dube3a causes seizures and synaptic impairments in Drosophila concomitant with down regulation of the Na +/K + pump ATPα. Neurobiol Dis 2017; 108:238-248. [PMID: 28888970 PMCID: PMC5675773 DOI: 10.1016/j.nbd.2017.09.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/25/2017] [Accepted: 09/05/2017] [Indexed: 12/20/2022] Open
Abstract
Duplication 15q syndrome (Dup15q) is an autism-associated disorder co-incident with high rates of pediatric epilepsy. Additional copies of the E3 ubiquitin ligase UBE3A are thought to cause Dup15q phenotypes, yet models overexpressing UBE3A in neurons have not recapitulated the epilepsy phenotype. We show that Drosophila endogenously expresses Dube3a (fly UBE3A homolog) in glial cells and neurons, prompting an investigation into the consequences of glial Dube3a overexpression. Here we expand on previous work showing that the Na+/K+ pump ATPα is a direct ubiquitin ligase substrate of Dube3a. A robust seizure-like phenotype was observed in flies overexpressing Dube3a in glial cells, but not neurons. Glial-specific knockdown of ATPα also produced seizure-like behavior, and this phenotype was rescued by simultaneously overexpressing ATPα and Dube3a in glia. Our data provides the basis of a paradigm shift in Dup15q research given that clinical phenotypes have long been assumed to be due to neuronal UBE3A overexpression.
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Affiliation(s)
- Kevin A Hope
- Department of Neurology, UTHSC, Memphis, TN, United States; Integrated Biomedical Science Program, UTHSC, Memphis, TN, United States; Department of Anatomy and Neurobiology, UTHSC, Memphis, TN, United States
| | - Mark S LeDoux
- Department of Neurology, UTHSC, Memphis, TN, United States; Department of Anatomy and Neurobiology, UTHSC, Memphis, TN, United States
| | - Lawrence T Reiter
- Department of Neurology, UTHSC, Memphis, TN, United States; Department of Anatomy and Neurobiology, UTHSC, Memphis, TN, United States; Department of Pediatrics, UTHSC, Memphis, TN, United States.
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7
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Hattingen E, Enkirch SJ, Jurcoane A, Kruse M, Delev D, Grote A, Becker A. Hippocampal "gliosis only" on MR imaging represents a distinct entity in epilepsy patients. Neuroradiology 2017; 60:161-168. [PMID: 29085967 DOI: 10.1007/s00234-017-1939-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 10/17/2017] [Indexed: 10/18/2022]
Abstract
PURPOSE The purpose of this study is to evaluate whether patients with drug-resistant mesial temporal lobe epilepsy (TLE) due to hippocampal "gliosis only" have different MRI features than those with hippocampal sclerosis (HS). Most TLE patients have HS corresponding to severe neuronal loss and gliosis, but a few have "gliosis only" without significant reduction of neuronal density. METHODS We analyzed the morphology of cerebral 3 T MRIs (T1, T2, and FLAIR) of 103 patients with HS and 20 with "gliosis only" concerning hippocampal and amygdala aspect, volumes, and signal intensity (SI) using Fisher's exact test, Student's t test, and principal component analysis. RESULTS Visually, the ipsilateral hippocampus was hyperintense in both groups, but SI was markedly increased in 74% of HS and in 25% of "gliosis only" patients; the ipsilateral hippocampus was smaller in 92% of HS and in 50% of "gliosis only" patients, and its internal architecture was lost in 57% of HS and 5% of "gliosis only" patients; the contralateral hippocampal SI was altered in 25% of HS and in 70% of "gliosis only" patients (all p < 0.001). Ipsilateral hippocampus of HS patients had lower volume (mean ± SD 2.86 ± 0.87 ml) compared with that of "gliosis only" patients (3.4 ± 1.02 ml) and had higher SI than the contralateral hippocampus of HS patients and then the hippocampus of "gliosis only" patients (all p < 0.01). CONCLUSION "Gliosis only" has different MRI hippocampal characteristics than HS: less volume loss, less increase of the T2-w signal intensity, preservation of internal architecture, and more contralateral affection.
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Affiliation(s)
- Elke Hattingen
- Neuroradiology, Department of Radiology, University Clinics Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany.
| | - Simon Jonas Enkirch
- Neuroradiology, Department of Radiology, University Clinics Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany
| | - Alina Jurcoane
- Neuroradiology, Department of Radiology, University Clinics Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany
| | - Maximilian Kruse
- Neuroradiology, Department of Radiology, University Clinics Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany
| | - Daniel Delev
- Department of Neurosurgery, University Clinics Bonn, Bonn, Germany.,Department of Neurosurgery, University Clinics Freiburg, Freiburg, Germany
| | - Alexander Grote
- Department of Neurosurgery, University Clinics Bonn, Bonn, Germany.,Department of Neurosurgery, Evangelic Hospital of Bethel, Bielefeld, Germany
| | - Albert Becker
- Institute of Neuropathology, University Clinics Bonn, Bonn, Germany
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Setkowicz Z, Kosonowska E, Janeczko K. Inflammation in the developing rat modulates astroglial reactivity to seizures in the mature brain. J Anat 2017; 231:366-379. [PMID: 28597918 DOI: 10.1111/joa.12636] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/07/2017] [Indexed: 11/29/2022] Open
Abstract
Astrocytes participate in neuronal development and excitability, and produce factors enhancing or suppressing inflammatory processes occurring due to neurodegenerative diseases, such as epilepsy. Seizures, in turn, trigger the release of inflammatory mediators, causing structural and functional changes in the brain. Therefore, it appears reasonable to determine whether generalized inflammation at developmental periods can affect astrocyte reactivity to epileptic seizures occurring in the adult brain. Lipopolysaccharide (LPS) was injected in 6- or 30-day-old rats (P6 or P30, respectively). At the age of 2 months, seizures were induced, and pilocarpine and morphological changes of astrocytes located within the hippocampal formation were assessed. Additionally, expression of glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), aquaporin 4 (AQP4), and inwardly rectifying potassium channel Kir 4.1 (Kir4.1) was determined using Western blots. The animal group given LPS on P6 displayed maximal susceptibility to pilocarpine-induced seizures, significantly higher than the group that received LPS on P30. In the immunohistologically examined hippocampal formation, the GFAP-immunoreactive area was not affected by LPS alone. However, it was reduced following seizures in naïve controls but not in LPS-pretreated rats. Increases in the ramification of astrocytic processes were detected only in adult rats given LPS on P30, not on P6. Seizures abolished the effects. Following seizures, the process ramification showed no significant change in the two LPS-treated rat groups, whereas it was significantly reduced in the dentate gyrus of LPS-untreated controls. Glial fibrillary acidic protein (GFAP) expression showed no changes induced with LPS alone and rose slightly after seizures. AQP4 content was lower in rats given LPS on P6 and was seizure-resistant in the two LPS-treated groups, contrary to a decrease in untreated controls. GS expression was not affected by LPS treatments and was reduced after seizures without an intergroup difference. Kir4.1 underwent highly significant increases in all groups experiencing seizures, but LPS alone had no effect. It can be concluded that the generalized inflammatory status led to some important changes in astrocytes reflected, in part at least by permanent modifications of their morphology and molecular profile. Moreover, the previously experienced inflammation prevented the cells from much stronger changes in response to seizures observed in adult untreated controls. The obtained results point to a link between the activation of astrocytes by transient systemic inflammation occurring during the developmental period and their subsequent reactivity to seizures, which may play an important role in the functional features of the brain, including its susceptibility to seizures.
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Affiliation(s)
- Zuzanna Setkowicz
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, Krakow, Poland
| | - Emilia Kosonowska
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, Krakow, Poland
| | - Krzysztof Janeczko
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, Krakow, Poland
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Abstract
High-frequency deep brain stimulation (DBS) is an effective treatment for some movement disorders. Though mechanisms underlying DBS are still unclear, commonly accepted theories include a “functional inhibition” of neuronal cell bodies and the excitation of axonal projections near the electrodes. It is becoming clear, however, that the paradoxical dissociation “local inhibition” and “distant excitation” is far more complex than initially thought. Despite an initial increase in neuronal activity following stimulation, cells are often unable to maintain normal ionic concentrations, particularly those of sodium and potassium. Based on currently available evidence, we proposed an alternative hypothesis. Increased extracellular concentrations of potassium during DBS may change the dynamics of both cells and axons, contributing not only to the intermittent excitation and inhibition of these elements but also to interrupt abnormal pathological activity. In this article, we review mechanisms through which high extracellular potassium may mediate some of the effects of DBS.
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Affiliation(s)
- Gerson Florence
- Division of Functional Neurosurgery, Department of Neurology, Hospital das Clínicas, School of Medicine of the University of São Paulo, São Paulo, SP, Brazil
- Department of Radiology and Oncology, School of Medicine of the University of São Paulo, São Paulo, SP, Brazil
| | - Koichi Sameshima
- Department of Radiology and Oncology, School of Medicine of the University of São Paulo, São Paulo, SP, Brazil
| | - Erich T. Fonoff
- Division of Functional Neurosurgery, Department of Neurology, Hospital das Clínicas, School of Medicine of the University of São Paulo, São Paulo, SP, Brazil
| | - Clement Hamani
- Division of Neurosurgery, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada
- Behavioural Neurobiology Laboratory and the Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
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Lu XCM, Shear DA, Graham PB, Bridson GW, Uttamsingh V, Chen Z, Leung LY, Tortella FC. Dual Therapeutic Effects of C-10068, a Dextromethorphan Derivative, Against Post-Traumatic Nonconvulsive Seizures and Neuroinflammation in a Rat Model of Penetrating Ballistic-Like Brain Injury. J Neurotrauma 2015; 32:1621-32. [PMID: 25794265 DOI: 10.1089/neu.2014.3766] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Post-traumatic seizures can exacerbate injurious outcomes of severe brain trauma, yet effective treatments are limited owing to the complexity of the pathology underlying the concomitant occurrence of both events. In this study, we tested C-10068, a novel deuterium-containing analog of (+)-N-methyl-3-ethoxymorphinan, in a rat model of penetrating ballistic-like brain injury (PBBI) and evaluated the effects of C-10068 on PBBI-induced nonconvulsive seizures (NCS), acute neuroinflammation, and neurofunctional outcomes. NCS were detected by electroencephalographic monitoring. Neuroinflammation was evaluated by immunohistochemical markers, for example, glial fibrillary acidic protein and major histocompatibility complex class I, for activation of astrocytes and microglia, respectively. Neurofunction was tested using rotarod and Morris water maze tasks. Three infusion doses of C-10068 (1.0, 2.5, and 5.0 mg/kg/h × 72 h) were tested in the antiseizure study. Neuroinflammation and neurofunction were evaluated in animals treated with 5.0 mg/kg/h × 72 h C-10068. Compared to vehicle treatment, C-10068 dose dependently reduced PBBI-induced NCS incidence (40-50%), frequency (20-70%), and duration (30-82%). The most effective antiseizure dose of C-10068 (5.0 mg/kg/h × 72 h) also significantly attenuated hippocampal astrocyte activation and perilesional microglial reactivity post-PBBI. Within C-10068-treated animals, a positive correlation was observed in reduction in NCS frequency and reduction in hippocampal astrocyte activation. Further, C-10068 treatment significantly attenuated astrocyte activation in seizure-free animals. However, C-10068 failed to improve PBBI-induced motor and cognitive functions with the dosing regimen used in this study. Overall, the results indicating that C-10068 exerts both potent antiseizure and antiinflammatory effects are promising and warrant further investigation.
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Affiliation(s)
- Xi-Chun May Lu
- 1 Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Deborah A Shear
- 1 Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | | | - Gary W Bridson
- 2 Concert Pharmaceuticals Inc. , Lexington, Massachusetts
| | | | - Zhiyong Chen
- 1 Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Lai Yee Leung
- 1 Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Frank C Tortella
- 1 Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
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Wu XL, Tang YC, Lu QY, Xiao XL, Song TB, Tang FR. Astrocytic Cx 43 and Cx 40 in the mouse hippocampus during and after pilocarpine-induced status epilepticus. Exp Brain Res 2015; 233:1529-39. [PMID: 25690864 DOI: 10.1007/s00221-015-4226-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Accepted: 02/09/2015] [Indexed: 12/15/2022]
Abstract
Astrocytes have now been well accepted to play important roles in epileptogenesis by controlling gliotransmitter release and neuronal excitability, contributing to blood-brain barrier dysfunction and involving in brain inflammation. Recent studies indicate that abnormal expression of gap junction protein connexin (Cx) may also be a contributing factor for seizure generation. To further address this issue, we investigated the progressive changes of Cx 43 and Cx 40 in the mouse hippocampus at 4 h, 1 day, 1 week and 2 months during and after pilocarpine-induced status epilepticus (PISE). The co-localization of Cx 43 and Cx 40 with glial fibrillary acidic protein (GFAP) was also examined. We observed that Cx 43 and Cx 40 protein expression remained unaltered at 4 h during and at 1 day (acute stage) after PISE. However, their expression was significantly increased in CA1 and CA3 areas and in the dentate gyrus at 1 week (latent stage) and 2 months (chronic stage) after PISE. Double immunofluorescence labeling indicated the localization of Cx 43 and Cx 40 in astrocytes. Combined with progressive neuronal loss in the mouse hippocampus, our results suggest that the increase in gap junctions in the neuronoglial syncytium of reactive astrocytes may be implicated in synchronization of hippocampal hyperactivity leading to neuronal loss and epileptogenesis.
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Affiliation(s)
- X L Wu
- Department of Human Anatomy, Histology and Embryology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, People's Republic of China
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Robel S, Buckingham SC, Boni JL, Campbell SL, Danbolt NC, Riedemann T, Sutor B, Sontheimer H. Reactive astrogliosis causes the development of spontaneous seizures. J Neurosci 2015; 35:3330-45. [PMID: 25716834 PMCID: PMC4339349 DOI: 10.1523/jneurosci.1574-14.2015] [Citation(s) in RCA: 195] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 12/16/2014] [Accepted: 01/12/2015] [Indexed: 11/21/2022] Open
Abstract
Epilepsy is one of the most common chronic neurologic diseases, yet approximately one-third of affected patients do not respond to anticonvulsive drugs that target neurons or neuronal circuits. Reactive astrocytes are commonly found in putative epileptic foci and have been hypothesized to be disease contributors because they lose essential homeostatic capabilities. However, since brain pathology induces astrocytes to become reactive, it is difficult to distinguish whether astrogliosis is a cause or a consequence of epileptogenesis. We now present a mouse model of genetically induced, widespread chronic astrogliosis after conditional deletion of β1-integrin (Itgβ1). In these mice, astrogliosis occurs in the absence of other pathologies and without BBB breach or significant inflammation. Electroencephalography with simultaneous video recording revealed that these mice develop spontaneous seizures during the first six postnatal weeks of life and brain slices show neuronal hyperexcitability. This was not observed in mice with neuronal-targeted β1-integrin deletion, supporting the hypothesis that astrogliosis is sufficient to induce epileptic seizures. Whole-cell patch-clamp recordings from astrocytes further suggest that the heightened excitability was associated with impaired astrocytic glutamate uptake. Moreover, the relative expression of the cation-chloride cotransporters (CCC) NKCC1 (Slc12a2) and KCC2 (Slc12a5), which are responsible for establishing the neuronal Cl(-) gradient that governs GABAergic inhibition were altered and the NKCC1 inhibitor bumetanide eliminated seizures in a subgroup of mice. These data suggest that a shift in the relative expression of neuronal NKCC1 and KCC2, similar to that observed in immature neurons during development, may contribute to astrogliosis-associated seizures.
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Affiliation(s)
- Stefanie Robel
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35209,
| | - Susan C Buckingham
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35209
| | - Jessica L Boni
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35209
| | - Susan L Campbell
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35209
| | - Niels C Danbolt
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway, and
| | - Therese Riedemann
- Institute of Physiology, Department of Physiological Genomics, Ludwig-Maximilians-University of Munich, 80336 Munich, Germany
| | - Bernd Sutor
- Institute of Physiology, Department of Physiological Genomics, Ludwig-Maximilians-University of Munich, 80336 Munich, Germany
| | - Harald Sontheimer
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35209
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DiNuzzo M, Mangia S, Maraviglia B, Giove F. Does abnormal glycogen structure contribute to increased susceptibility to seizures in epilepsy? Metab Brain Dis 2015; 30:307-16. [PMID: 24643875 PMCID: PMC4169361 DOI: 10.1007/s11011-014-9524-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 03/05/2014] [Indexed: 12/22/2022]
Abstract
Epilepsy is a family of brain disorders with a largely unknown etiology and high percentage of pharmacoresistance. The clinical manifestations of epilepsy are seizures, which originate from aberrant neuronal synchronization and hyperexcitability. Reactive astrocytosis, a hallmark of the epileptic tissue, develops into loss-of-function of glutamine synthetase, impairment of glutamate-glutamine cycle and increase in extracellular and astrocytic glutamate concentration. Here, we argue that chronically elevated intracellular glutamate level in astrocytes is instrumental to alterations in the metabolism of glycogen and leads to the synthesis of polyglucosans. Unaccessibility of glycogen-degrading enzymes to these insoluble molecules compromises the glycogenolysis-dependent reuptake of extracellular K(+) by astrocytes, thereby leading to increased extracellular K(+) and associated membrane depolarization. Based on current knowledge, we propose that the deterioration in structural homogeneity of glycogen particles is relevant to disruption of brain K(+) homeostasis and increased susceptibility to seizures in epilepsy.
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Affiliation(s)
- Mauro DiNuzzo
- MARBILab, Museo storico della fisica e Centro di studi e ricerche "Enrico Fermi", Rome, Italy,
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14
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Rusan ZM, Kingsford OA, Tanouye MA. Modeling glial contributions to seizures and epileptogenesis: cation-chloride cotransporters in Drosophila melanogaster. PLoS One 2014; 9:e101117. [PMID: 24971529 PMCID: PMC4074161 DOI: 10.1371/journal.pone.0101117] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 06/03/2014] [Indexed: 12/21/2022] Open
Abstract
Flies carrying a kcc loss-of-function mutation are more seizure-susceptible than wild-type flies. The kcc gene is the highly conserved Drosophila melanogaster ortholog of K+/Cl- cotransporter genes thought to be expressed in all animal cell types. Here, we examined the spatial and temporal requirements for kcc loss-of-function to modify seizure-susceptibility in flies. Targeted RNA interference (RNAi) of kcc in various sets of neurons was sufficient to induce severe seizure-sensitivity. Interestingly, kcc RNAi in glia was particularly effective in causing seizure-sensitivity. Knockdown of kcc in glia or neurons during development caused a reduction in seizure induction threshold, cell swelling, and brain volume increase in 24-48 hour old adult flies. Third instar larval peripheral nerves were enlarged when kcc RNAi was expressed in neurons or glia. Results suggest that a threshold of K+/Cl- cotransport dysfunction in the nervous system during development is an important determinant of seizure-susceptibility in Drosophila. The findings presented are the first attributing a causative role for glial cation-chloride cotransporters in seizures and epileptogenesis. The importance of elucidating glial cell contributions to seizure disorders and the utility of Drosophila models is discussed.
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Affiliation(s)
- Zeid M. Rusan
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Olivia A. Kingsford
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California, United States of America
| | - Mark A. Tanouye
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California, United States of America
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
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15
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DiNuzzo M, Mangia S, Maraviglia B, Giove F. Physiological bases of the K+ and the glutamate/GABA hypotheses of epilepsy. Epilepsy Res 2014; 108:995-1012. [PMID: 24818957 DOI: 10.1016/j.eplepsyres.2014.04.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 03/20/2014] [Accepted: 04/01/2014] [Indexed: 01/19/2023]
Abstract
Epilepsy is a heterogeneous family of neurological disorders that manifest as seizures, i.e. the hypersynchronous activity of large population of neurons. About 30% of epileptic patients do not respond to currently available antiepileptic drugs. Decades of intense research have elucidated the involvement of a number of possible signaling pathways, however, at present we do not have a fundamental understanding of epileptogenesis. In this paper, we review the literature on epilepsy under a wide-angle perspective, a mandatory choice that responds to the recurrent and unanswered question about what is epiphenomenal and what is causal to the disease. While focusing on the involvement of K+ and glutamate/GABA in determining neuronal hyperexcitability, emphasis is given to astrocytic contribution to epileptogenesis, and especially to loss-of-function of astrocytic glutamine synthetase following reactive astrogliosis, a hallmark of epileptic syndromes. We finally introduce the potential involvement of abnormal glycogen synthesis induced by excess glutamate in increasing susceptibility to seizures.
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Affiliation(s)
- Mauro DiNuzzo
- MARBILab, Museo storico della fisica e Centro di studi e ricerche "Enrico Fermi", Rome, Italy.
| | - Silvia Mangia
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA
| | - Bruno Maraviglia
- Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy; Fondazione Santa Lucia IRCCS, Rome, Italy
| | - Federico Giove
- MARBILab, Museo storico della fisica e Centro di studi e ricerche "Enrico Fermi", Rome, Italy; Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy
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16
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De Bock M, Kerrebrouck M, Wang N, Leybaert L. Neurological manifestations of oculodentodigital dysplasia: a Cx43 channelopathy of the central nervous system? Front Pharmacol 2013; 4:120. [PMID: 24133447 PMCID: PMC3783840 DOI: 10.3389/fphar.2013.00120] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 09/02/2013] [Indexed: 12/30/2022] Open
Abstract
The coordination of tissue function is mediated by gap junctions (GJs) that enable direct cell–cell transfer of metabolic and electric signals. GJs are formed by connexins of which Cx43 is most widespread in the human body. In the brain, Cx43 GJs are mostly found in astroglia where they coordinate the propagation of Ca2+ waves, spatial K+ buffering, and distribution of glucose. Beyond its role in direct intercellular communication, Cx43 also forms unapposed, non-junctional hemichannels in the plasma membrane of glial cells. These allow the passage of several neuro- and gliotransmitters that may, combined with downstream paracrine signaling, complement direct GJ communication among glial cells and sustain glial-neuronal signaling. Mutations in the GJA1 gene encoding Cx43 have been identified in a rare, mostly autosomal dominant syndrome called oculodentodigital dysplasia (ODDD). ODDD patients display a pleiotropic phenotype reflected by eye, hand, teeth, and foot abnormalities, as well as craniofacial and bone malformations. Remarkably, neurological symptoms such as dysarthria, neurogenic bladder (manifested as urinary incontinence), spasticity or muscle weakness, ataxia, and epilepsy are other prominent features observed in ODDD patients. Over 10 mutations detected in patients diagnosed with neurological disorders are associated with altered functionality of Cx43 GJs/hemichannels, but the link between ODDD-related abnormal channel activities and neurologic phenotype is still elusive. Here, we present an overview on the nature of the mutants conveying structural and functional changes of Cx43 channels and discuss available evidence for aberrant Cx43 GJ and hemichannel function. In a final step, we examine the possibilities of how channel dysfunction may lead to some of the neurological manifestations of ODDD.
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Affiliation(s)
- Marijke De Bock
- Physiology Group, Department of Basic Medical Sciences, Ghent University Ghent, Belgium
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17
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Stobart JL, Anderson CM. Multifunctional role of astrocytes as gatekeepers of neuronal energy supply. Front Cell Neurosci 2013; 7:38. [PMID: 23596393 PMCID: PMC3622037 DOI: 10.3389/fncel.2013.00038] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 03/26/2013] [Indexed: 01/01/2023] Open
Abstract
Dynamic adjustments to neuronal energy supply in response to synaptic activity are critical for neuronal function. Glial cells known as astrocytes have processes that ensheath most central synapses and express G-protein-coupled neurotransmitter receptors and transporters that respond to neuronal activity. Astrocytes also release substrates for neuronal oxidative phosphorylation and have processes that terminate on the surface of brain arterioles and can influence vascular smooth muscle tone and local blood flow. Membrane receptor or transporter-mediated effects of glutamate represent a convergence point of astrocyte influence on neuronal bioenergetics. Astrocytic glutamate uptake drives glycolysis and subsequent shuttling of lactate from astrocytes to neurons for oxidative metabolism. Astrocytes also convert synaptically reclaimed glutamate to glutamine, which is returned to neurons for glutamate salvage or oxidation. Finally, astrocytes store brain energy currency in the form of glycogen, which can be mobilized to produce lactate for neuronal oxidative phosphorylation in response to glutamatergic neurotransmission. These mechanisms couple synaptically driven astrocytic responses to glutamate with release of energy substrates back to neurons to match demand with supply. In addition, astrocytes directly influence the tone of penetrating brain arterioles in response to glutamatergic neurotransmission, coordinating dynamic regulation of local blood flow. We will describe the role of astrocytes in neurometabolic and neurovascular coupling in detail and discuss, in turn, how astrocyte dysfunction may contribute to neuronal bioenergetic deficit and neurodegeneration. Understanding the role of astrocytes as a hub for neurometabolic and neurovascular coupling mechanisms is a critical underpinning for therapeutic development in a broad range of neurodegenerative disorders characterized by chronic generalized brain ischemia and brain microvascular dysfunction.
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Affiliation(s)
- Jillian L Stobart
- Division of Neurodegenerative Disorders, Department of Pharmacology and Therapeutics, St. Boniface Hospital Research, University of Manitoba Winnipeg, MB, Canada ; Department of Nuclear Medicine, Institute of Pharmacology and Toxicology, University of Zürich Zürich, Switzerland
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18
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Abstract
The proposed area of onset for absence epilepsy characteristic of spontaneously occurring spike and slow-wave discharges (SWDs) in the genetic absence rat model is the subgranular layer of the somatosensory cortex. Modulation of the hyperexcitable cortical foci by bilateral transcranial direct current stimulation (tDCS) might change the expression of SWDs. The effects of cathodal and anodal tDCS as well as cumulative effects of different intensities of repeated cathodal stimulation on EEG and behavior were examined. Cathodal tDCS reduced the number of SWDs during stimulation and affected the mean duration after stimulation both in an intensity-dependent manner. Behavior was changed after the highest stimulation intensity. Spectral analyses of the EEG during stimulation revealed an increase in sub-delta and delta frequency ranges, suggesting that cortical cells were hyperpolarized. Cathodal tDCS might be an effective non-invasive tool to decrease cortical excitability, presumably in focal zone in this genetic model.
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Affiliation(s)
- M Zobeiri
- Department of Biological Psychology, Donders Centre for Cognition, Radboud University Nijmegen, The Netherlands.
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19
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Andreasen M, Nedergaard S. Heterogeneous firing behavior during ictal-like epileptiform activity in vitro. J Neurophysiol 2011; 107:1379-92. [PMID: 22157126 DOI: 10.1152/jn.00309.2011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Seizure activity in vivo is caused by populations of neurons displaying a high degree of variability in activity pattern during the attack. The reason for this variability is not well understood. Here we show in an in vitro preparation that hippocampal CA1 pyramidal cells display four types of afterdischarge behavior during stimulus-induced ictal-like events in the presence of Cs(+) (5 mM): type I (43.7%) consisting of high-frequency firing riding on a plateau potential; type II (28.2%) consisting of low-frequency firing with no plateau potential; type III (18.3%) consisting of high-frequency firing with each action potential preceded by a transient hyperpolarization and time-locked to population activity, no plateau potential; "passive" (9.9%) typified by no afterdischarge. Type I behavior was blocked by TTX (0.2 μM) and intracellular injection of QX314 (12.5-25 mM). TTX (0.2 μM) or phenytoin (50 μM) terminated ictal-like events, suggesting that the persistent Na(+) current (I(NaP)) is pivotal for type I behavior. Type I behavior was not correlated to intrinsic bursting capability. Blockade of the M current (I(M)) with linopirdine (10 μM) increased the ratio of type I neurons to 100%, whereas enhancing I(M) with retigabine (50-100 μM) greatly reduced the epileptiform activity. These results suggest an important role of I(M) in determining afterdischarge behavior through control of I(NaP) expression. We propose that type I neurons act as pacemakers, which, through synchronization, leads to recruitment of type III neurons. Together, they provide the "critical mass" necessary for ictogenesis to become regenerative.
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20
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Vázquez-Chona FR, Swan A, Ferrell WD, Jiang L, Baehr W, Chien WM, Fero M, Marc RE, Levine EM. Proliferative reactive gliosis is compatible with glial metabolic support and neuronal function. BMC Neurosci 2011; 12:98. [PMID: 21985191 PMCID: PMC3203081 DOI: 10.1186/1471-2202-12-98] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 10/10/2011] [Indexed: 01/13/2023] Open
Abstract
Background The response of mammalian glial cells to chronic degeneration and trauma is hypothesized to be incompatible with support of neuronal function in the central nervous system (CNS) and retina. To test this hypothesis, we developed an inducible model of proliferative reactive gliosis in the absence of degenerative stimuli by genetically inactivating the cyclin-dependent kinase inhibitor p27Kip1 (p27 or Cdkn1b) in the adult mouse and determined the outcome on retinal structure and function. Results p27-deficient Müller glia reentered the cell cycle, underwent aberrant migration, and enhanced their expression of intermediate filament proteins, all of which are characteristics of Müller glia in a reactive state. Surprisingly, neuroglial interactions, retinal electrophysiology, and visual acuity were normal. Conclusion The benign outcome of proliferative reactive Müller gliosis suggests that reactive glia display context-dependent, graded and dynamic phenotypes and that reactivity in itself is not necessarily detrimental to neuronal function.
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Affiliation(s)
- Félix R Vázquez-Chona
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, 65 Mario Capecchi Dr., Salt Lake City, UT 84132, USA
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21
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Amiri M, Bahrami F, Janahmadi M. Functional contributions of astrocytes in synchronization of a neuronal network model. J Theor Biol 2011; 292:60-70. [PMID: 21978738 DOI: 10.1016/j.jtbi.2011.09.013] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 09/04/2011] [Accepted: 09/06/2011] [Indexed: 01/05/2023]
Abstract
In the present study, a biologically plausible neuronal population model is developed, which considers functional outcome of neuron-astrocyte interactions. Based on established neurophysiologic findings, astrocytes dynamically regulate the synaptic transmission of neuronal networks. The employed structure is based on the main physiological and anatomical features of the CA1 subfield of the hippocampus. Utilizing our model, we demonstrate that healthy astrocytes provide appropriate feedback control in regulating neural activity. In this way, the astrocytes compensate the increase of excitation coupling strength among neurons and stabilize the normal level of synchronized behavior. Next, malfunction of astrocytes in the regulatory feedback loop is investigated. In this way, pathologic astrocytes are no longer able to regulate and/or compensate the excessive increase of the excitation level. Consequently, disruption of astrocyte signaling initiates hypersynchronous firing of neurons. Our results suggest that diminishing of neuron-astrocyte cross-talk leads to an abnormal synchronized neuronal firing, which suggests that astrocytes could be a proximal target for the treatment of related disorders including epilepsy.
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Affiliation(s)
- Mahmood Amiri
- School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran.
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22
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Vargova L, Homola A, Cicanic M, Kuncova K, Krsek P, Marusic P, Sykova E, Zamecnik J. The diffusion parameters of the extracellular space are altered in focal cortical dysplasias. Neurosci Lett 2011; 499:19-23. [PMID: 21620932 DOI: 10.1016/j.neulet.2011.05.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 04/05/2011] [Accepted: 05/12/2011] [Indexed: 11/15/2022]
Abstract
Most hypotheses concerning the mechanisms underlying seizure activity in focal cortical dysplasia (FCD) are based on alterations in synaptic transmission and glial dysfunction. However, neurons may also communicate by extrasynaptic transmission, which was recently found to affect epileptiform activity under experimental conditions and which is mediated by the diffusion of neuroactive substances in the extracellular space (ECS). The ECS diffusion parameters were therefore determined using the real-time iontophoretic method in human neocortical tissue samples obtained from surgically treated epileptic patients. The obtained values of the extracellular space volume fraction and tortuosity were then correlated with the histologicaly assessed type of cortical malformation (FCD type I or II). While the extracellular volume remained unchanged (FCD I) or larger (FCD II) than in normal/control tissue, tortuosity was significantly increased in both types of dysplasia, indicating the presence of additional diffusion barriers and compromised diffusion, which might be another factor contributing to the epileptogenicity of FCD.
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Affiliation(s)
- L Vargova
- Department of Neuroscience and Center for Cell Therapy and Tissue Repair, 2nd Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
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23
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Abstract
Astrocytes dynamically interact with neurons to regulate synaptic transmission. Although the gap junction proteins connexin 30 (Cx30) and connexin 43 (Cx43) mediate the extensive network organization of astrocytes, their role in synaptic physiology is unknown. Here we show, by inactivating Cx30 and Cx43 genes, that astroglial networks tone down hippocampal synaptic transmission in CA1 pyramidal neurons. Gap junctional networking facilitates extracellular glutamate and potassium removal during synaptic activity through modulation of astroglial clearance rate and extracellular space volume. This regulation limits neuronal excitability, release probability, and insertion of postsynaptic AMPA receptors, silencing synapses. By controlling synaptic strength, connexins play an important role in synaptic plasticity. Altogether, these results establish connexins as critical proteins for extracellular homeostasis, important for the formation of functional synapses.
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Yang T, Zhou D, Stefan H. Why mesial temporal lobe epilepsy with hippocampal sclerosis is progressive: uncontrolled inflammation drives disease progression? J Neurol Sci 2010; 296:1-6. [PMID: 20663517 DOI: 10.1016/j.jns.2010.06.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 05/28/2010] [Accepted: 06/02/2010] [Indexed: 02/05/2023]
Abstract
Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is a group of chronic disorders characterized by prominent neuronal loss and gliosis in the hippocampus and amygdala. Newly published data indicate that it may be a progressive disease, but the mechanism underlying the progressive nature remains unknown. Recently, substantial evidence for an inflammatory mechanism in MTLE has been documented. We are therefore presenting a review of literature concerning the effects of uncontrolled inflammation on the disease progression of MTLE-HS. We found that increasing amounts of evidence support the association between uncontrolled inflammation and progression of the disease. Uncontrolled inflammatory processes may be a main mechanism underlying the self-propagating cycle of uncontrolled inflammation, blood-brain barrier damage, and seizures that drive the progressive nature. Thus it is important to unravel the principles of communication between the different factors in this cycle. The dynamic modulation of inflammatory processes aimed at preventing or interrupting this cycle has the potential to emerge as a novel therapeutic strategy. This line of therapy might offer new perspectives on the pharmacologic treatment of seizures, and possibly on delaying disease progression or retarding epileptogenesis as well.
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Affiliation(s)
- Tianhua Yang
- Department of Neurology, West China Hospital, Si Chuan University, Cheng du, Sichuan, China
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25
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Amiri M, Bahrami F, Janahmadi M. Functional modeling of astrocytes in epilepsy: a feedback system perspective. Neural Comput Appl 2010. [DOI: 10.1007/s00521-010-0479-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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26
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Durand DM, Park EH, Jensen AL. Potassium diffusive coupling in neural networks. Philos Trans R Soc Lond B Biol Sci 2010; 365:2347-62. [PMID: 20603356 DOI: 10.1098/rstb.2010.0050] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Conventional neural networks are characterized by many neurons coupled together through synapses. The activity, synchronization, plasticity and excitability of the network are then controlled by its synaptic connectivity. Neurons are surrounded by an extracellular space whereby fluctuations in specific ionic concentration can modulate neuronal excitability. Extracellular concentrations of potassium ([K(+)](o)) can generate neuronal hyperexcitability. Yet, after many years of research, it is still unknown whether an elevation of potassium is the cause or the result of the generation, propagation and synchronization of epileptiform activity. An elevation of potassium in neural tissue can be characterized by dispersion (global elevation of potassium) and lateral diffusion (local spatial gradients). Both experimental and computational studies have shown that lateral diffusion is involved in the generation and the propagation of neural activity in diffusively coupled networks. Therefore, diffusion-based coupling by potassium can play an important role in neural networks and it is reviewed in four sections. Section 2 shows that potassium diffusion is responsible for the synchronization of activity across a mechanical cut in the tissue. A computer model of diffusive coupling shows that potassium diffusion can mediate communication between cells and generate abnormal and/or periodic activity in small (section sign 3) and in large networks of cells (section sign 4). Finally, in section sign 5, a study of the role of extracellular potassium in the propagation of axonal signals shows that elevated potassium concentration can block the propagation of neural activity in axonal pathways. Taken together, these results indicate that potassium accumulation and diffusion can interfere with normal activity and generate abnormal activity in neural networks.
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Affiliation(s)
- Dominique M Durand
- Department of Biomedical Engineering, Neural Engineering Center, Case Western Reserve University, Cleveland, OH 44106, USA.
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27
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Stewart TH, Eastman CL, Groblewski PA, Fender JS, Verley DR, Cook DG, D'Ambrosio R. Chronic dysfunction of astrocytic inwardly rectifying K+ channels specific to the neocortical epileptic focus after fluid percussion injury in the rat. J Neurophysiol 2010; 104:3345-60. [PMID: 20861444 DOI: 10.1152/jn.00398.2010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Astrocytic inwardly rectifying K(+) currents (I(KIR)) have an important role in extracellular K(+) homeostasis, which influences neuronal excitability, and serum extravasation has been linked to impaired K(IR)-mediated K(+) buffering and chronic hyperexcitability. Head injury induces acute impairment in astroglial membrane I(KIR) and impaired K(+) buffering in the rat hippocampus, but chronic spontaneous seizures appear in the perilesional neocortex--not the hippocampus--in the early weeks to months after injury. Thus we examined astrocytic K(IR) channel pathophysiology in both neocortex and hippocampus after rostral parasaggital fluid percussion injury (rpFPI). rpFPI induced greater acute serum extravasation and metabolic impairment in the perilesional neocortex than in the underlying hippocampus, and in situ whole cell recordings showed a greater acute loss of astrocytic I(KIR) in neocortex than hippocampus. I(KIR) loss persisted through 1 mo after injury only in the neocortical epileptic focus, but fully recovered in the hippocampus that did not generate chronic seizures. Neocortical cell-attached recordings showed no loss or an increase of I(KIR) in astrocytic somata. Confocal imaging showed depletion of KIR4.1 immunoreactivity especially in processes--not somata--of neocortical astrocytes, whereas hippocampal astrocytes appeared normal. In naïve animals, intracortical infusion of serum, devoid of coagulation-mediating thrombin activity, reproduces the effects of rpFPI both in vivo and at the cellular level. In vivo serum infusion induces partial seizures similar to those induced by rpFPI, whereas bath-applied serum, but not dialyzed albumin, rapidly silenced astrocytic K(IR) membrane currents in whole cell and cell-attached patch-clamp recordings in situ. Thus both acute impairment in astrocytic I(KIR) and chronic spontaneous seizures typical of rpFPI are reproduced by serum extravasation, whereas the chronic impairment in astroglial I(KIR) is specific to the neocortex that develops the epileptic focus.
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Affiliation(s)
- Tessandra H Stewart
- Department of Neurological Surgery, University of Washington, School of Medicine, Seattle, USA
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28
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D'Ambrosio R. A possible causative role for blood-brain barrier failure and reactive astrocytosis in acquired epilepsy. Epilepsy Curr 2010; 5:244-6. [PMID: 16372063 PMCID: PMC1312745 DOI: 10.1111/j.1535-7511.2005.00077.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Lasting Blood–Brain Barrier Disruption Induces Epileptic Focus in the Rat Somatosensory Cortex Seiffert E, Dreier JP, Ivens S, Bechmann I, Tomkins O, Heinemann U, Friedman A J Neurosci 2004;24:7829–7836 Perturbations in the integrity of the blood–brain barrier have been reported in both humans and animals under numerous pathologic conditions. Although the blood– brain barrier prevents the penetration of many blood constituents into the brain extracellular space, the effect of such perturbations on the brain function and their roles in the pathogenesis of cortical diseases are unknown. In this study, we established a model for focal disruption of the blood–brain barrier in the rat cortex by direct application of bile salts. Exposure of the cerebral cortex in vivo to bile salts resulted in long-lasting extravasation of serum albumin to the brain extracellular space and was associated with a prominent activation of astrocytes with no inflammatory response or marked cell loss. By using electrophysiological recordings in brain slices, we found that a focus of epileptiform discharges developed within 4 to 7 days after treatment and could be recorded up to 49 days postoperatively in more than 60% of slices from treated animals but only rarely (10%) in sham-operated controls. Epileptiform activity involved both glutamatergic and GABAergic neurotransmission. Epileptiform activity also was induced by direct cortical application of native serum, denatured serum, or albumin-containing solution. In contrast, perfusion with serum-adapted electrolyte solution did not induce abnormal activity, thereby suggesting that the exposure of the serum-devoid brain environment to serum proteins underlies epileptogenesis in the blood–brain barrier–disrupted cortex. Although many neuropathologies entail a compromised blood–brain barrier, this is the first direct evidence that it may have a role in the pathogenesis of focal cortical epilepsy, a common neurologic disease.
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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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Choi J, Nordli DR, Alden TD, DiPatri A, Laux L, Kelley K, Rosenow J, Schuele SU, Rajaram V, Koh S. Cellular injury and neuroinflammation in children with chronic intractable epilepsy. J Neuroinflammation 2009; 6:38. [PMID: 20021679 PMCID: PMC2811703 DOI: 10.1186/1742-2094-6-38] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 12/19/2009] [Indexed: 11/25/2022] Open
Abstract
Objective To elucidate the presence and potential involvement of brain inflammation and cell death in neurological morbidity and intractable seizures in childhood epilepsy, we quantified cell death, astrocyte proliferation, microglial activation and cytokine release in brain tissue from patients who underwent epilepsy surgery. Methods Cortical tissue was collected from thirteen patients with intractable epilepsy due to focal cortical dysplasia (6), encephalomalacia (5), Rasmussen's encephalitis (1) or mesial temporal lobe epilepsy (1). Sections were processed for immunohistochemistry using markers for neuron, astrocyte, microglia or cellular injury. Cytokine assay was performed on frozen cortices. Controls were autopsy brains from eight patients without history of neurological diseases. Results Marked activation of microglia and astrocytes and diffuse cell death were observed in epileptogenic tissue. Numerous fibrillary astrocytes and their processes covered the entire cortex and converged on to blood vessels, neurons and microglia. An overwhelming number of neurons and astrocytes showed DNA fragmentation and its magnitude significantly correlated with seizure frequency. Majority of our patients with abundant cell death in the cortex have mental retardation. IL-1beta, IL-8, IL-12p70 and MIP-1beta were significantly increased in the epileptogenic cortex; IL-6 and MCP-1 were significantly higher in patients with family history of epilepsy. Conclusions Our results suggest that active neuroinflammation and marked cellular injury occur in pediatric epilepsy and may play a common pathogenic role or consequences in childhood epilepsy of diverse etiologies. Our findings support the concept that immunomodulation targeting activated microglia and astrocytes may be a novel therapeutic strategy to reduce neurological morbidity and prevent intractable epilepsy.
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Affiliation(s)
- Jieun Choi
- Department of Pediatrics, Northwestern University Children's Memorial Hospital, Chicago, IL, USA.
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Functional and molecular interactions between aquaporins and Na,K-ATPase. Neuroscience 2009; 168:915-25. [PMID: 19962432 DOI: 10.1016/j.neuroscience.2009.11.062] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 11/18/2009] [Accepted: 11/19/2009] [Indexed: 01/11/2023]
Abstract
The water channel aquaporin 4 (AQP4) is abundantly expressed in astrocytes and provides a mechanism by which water permeability of the plasma membrane can be regulated. Astrocytes play a key role in the clearance of both potassium (K(+)) and glutamate released during neuronal activity. Emerging evidence suggests that AQP4 facilitates K(+) clearance by astrocytes and contributes to recovery of neuronal excitability. Here we report that AQP4 can assemble with its regulator metabotropic glutamate receptor 5 (mGluR5) and with Na,K-ATPase; the enzyme responsible for active K(+) transport and for establishing the electrochemical gradient across the cell plasma membrane. We have, by use of pull down assays in rat brain tissue, identified the segment in the AQP4 NH(2)-terminus containing the amino acid residues 23-32 as the site for interaction with Na,K-ATPase catalytic subunit and with mGluR5. Mutagenesis studies revealed that the AQP4 amino acids K27 and W30 are of key importance for interaction with both Na,K-ATPase and mGluR5. To confirm that interaction also occurs within intact cells, we have performed fluorescence resonance energy transfer (FRET) studies in primary astrocytes derived from rat striatum. The results indicate close proximity of wild type AQP4 and Na,K-ATPase in the plasma membrane of rat astrocytes. FRET efficiencies observed with the mutants AQP4 K27A and AQP4 W30A were significantly lower, highlighting the importance of these residues for the interaction between AQP4 and Na,K-ATPase. We conclude that AQP4/Na,K-ATPase/mGluR5 can form a macromolecular complex/transporting microdomain in astrocytes. This complex may be of functional importance for the regulation of water and K(+) homeostasis in the brain, as well as for neuron-astrocyte metabolic crosstalk.
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Zhang S, Wang H, Lu Q, Qing G, Wang N, Wang Y, Li S, Yang D, Yan F. Detection of early neuron degeneration and accompanying glial responses in the visual pathway in a rat model of acute intraocular hypertension. Brain Res 2009; 1303:131-43. [DOI: 10.1016/j.brainres.2009.09.029] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 09/04/2009] [Accepted: 09/05/2009] [Indexed: 12/31/2022]
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Abstract
Seizures are the result of a sudden and temporary synchronization of neuronal activity, the reason for which is not clearly understood. Astrocytes participate in the control of neurotransmitter storage and neurotransmission efficacy. They provide fuel to neurons, which need a high level of energy to sustain normal and pathological neuronal activities, such as during epilepsy. Various genetic or induced animal models have been developed and used to study epileptogenic mechanisms. Methionine sulfoximine induces both seizures and the accumulation of brain glycogen, which might be considered as a putative energy store to neurons in various animals. Animals subjected to methionine sulfoximine develop seizures similar to the most striking form of human epilepsy, with a long pre-convulsive period of several hours, a long convulsive period during up to 48 hours and a post convulsive period during which they recover normal behavior. The accumulation of brain glycogen has been demonstrated in both the cortex and cerebellum as early as the pre-convulsive period, indicating that this accumulation is not a consequence of seizures. The accumulation results from an activation of gluconeogenesis specifically localized to astrocytes, both in vivo and in vitro. Both seizures and brain glycogen accumulation vary when using different inbred strains of mice. C57BL/6J is the most "resistant" strain to methionine sulfoximine, while CBA/J is the most "sensitive" one. The present review describes the data obtained on methionine sulfoximine dependent seizures and brain glycogen in the light of neurotransmission, highlighting the relevance of brain glycogen content in epilepsies.
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Affiliation(s)
- Jean-François Cloix
- Laboratoire de Neurobiologie, Université d'Orléans, BP 6759, 45067 Orléans Cedex 2, France.
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Baby SM, Bogdanovich S, Willmann G, Basu U, Lozynska O, Khurana TS. Differential expression of utrophin-A and -B promoters in the central nervous system (CNS) of normal and dystrophic mdx mice. Brain Pathol 2009; 20:323-42. [PMID: 19486009 DOI: 10.1111/j.1750-3639.2009.00275.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Utrophin (Utrn) is the autosomal homolog of dystrophin, the Duchene Muscular Dystrophy (DMD) locus product and of therapeutic interest, as its overexpression can compensate dystrophin's absence. Utrn is transcribed by Utrn-A and -B promoters with mRNAs differing at their 5' ends. However, previous central nervous system (CNS) studies used C-terminal antibodies recognizing both isoforms. As this distinction may impact upregulation strategies, we generated Utrn-A and -B promoter-specific antibodies, Taqman Polymerase chain reaction (PCR)-based absolute copy number assays, and luciferase-reporter constructs to study CNS of normal and dystrophic mdx mice. Differential expression of Utrn-A and -B was noted in microdissected and capillary-enriched fractions. At the protein level, Utrn-B was predominantly expressed in vasculature and ependymal lining, whereas Utrn-A was expressed in neurons, astrocytes, choroid plexus and pia mater. mRNA quantification demonstrated matching patterns of differential expression; however, transcription-translation mismatch was noted for Utrn-B in caudal brain regions. Utrn-A and Utrn-B proteins were significantly upregulated in olfactory bulb and cerebellum of mdx brain. Differential promoter activity, mRNA and protein expressions were studied in cultured C2C12, bEnd3, neurons and astrocytes. Promoter activity ranking for Utrn-A and -B was neurons > astrocytes > C2C12 > bEnd3 and bEnd3 > astrocytes > neurons > C2C12, respectively. Our results identify promoter usage patterns for therapeutic targeting and define promoter-specific differential distribution of Utrn isoforms in normal and dystrophic CNS.
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Affiliation(s)
- Santhosh M Baby
- Department of Physiology and Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, A-601 Richards Building, 3700 Hamilton Walk, Philadelphia, Pennsylvania 19104-6085, USA
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Cunha AOS, Mortari MR, Liberato JL, dos Santos WF. Neuroprotective effects of diazepam, carbamazepine, phenytoin and ketamine after pilocarpine-induced status epilepticus. Basic Clin Pharmacol Toxicol 2009; 104:470-7. [PMID: 19371260 DOI: 10.1111/j.1742-7843.2009.00403.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cell damage and spatial localization deficits are often reported as long-term consequences of pilocarpine-induced status epilepticus. In this study, we investigated the neuroprotective effects of repeated drug administration after long-lasting status epilepticus. Groups of six to eight Wistar rats received microinjections of pilocarpine (2.4 mg/microl, 1 microl) in the right dorsal hippocampus to induce a status epilepticus, which was attenuated by thiopental injection (35 mg/kg, i.p.) 3 hrs after onset. Treatments consisted of i.p. administration of diazepam, ketamine, carbamazepine, or phenytoin at 4, 28, 52, and 76 hr after the onset of status epilepticus. Two days after the treatments, rats were tested in the Morris water maze and 1 week after the cognitive tests, their brains were submitted to histology to perform haematoxylin and eosin staining and glial fibrillary acidic protein (GFAP) immunofluorescence detection. Post-status epilepticus rats exhibited extensive gliosis and cell loss in the hippocampal CA1, CA3 (70% cell loss for both areas) and dentate gyrus (60%). Administration of all drugs reduced cell loss in the hippocampus, with best effects observed in brains slices of diazepam-treated animals, which showed less than 30% of loss in the three areas and decreased GFAP immunolabelling. Treatments improved spatial navigation during training trials and probe trial, with exception of ketamine. Interestingly, in the probe trial, only diazepam-treated animals showed preference for the goal quadrant. Our data point to significant neuroprotective effects of repeated administration of diazepam against status epilepticus-induced cell damage and cognitive disturbances.
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The role of extracellular potassium dynamics in the different stages of ictal bursting and spreading depression: a computational study. J Theor Biol 2009; 258:219-28. [PMID: 19490858 DOI: 10.1016/j.jtbi.2009.01.032] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Revised: 01/24/2009] [Accepted: 01/30/2009] [Indexed: 11/22/2022]
Abstract
Experimental evidences point out the participation of nonsynaptic mechanisms (e.g., fluctuations in extracellular ions) in epileptiform bursting and spreading depression (SD). During these abnormal oscillatory patterns, it is observed an increase of extracellular potassium concentration [K(+)](o) and a decrease of extracellular calcium concentration [Ca(2+)](o) which raises the neuronal excitability. However, whether the high [K(+)](o) triggers and propagates these abnormal neuronal activities or plays a secondary role into this process is unclear. To better understand the influence of extracellular potassium dynamics in these oscillatory patterns, the experimental conditions of high [K(+)](o) and zero [Ca(2+)](o) were replicated in an extended Golomb model where we added important regulatory mechanisms of ion concentration as Na(+)-K(+) pump, ion diffusion and glial buffering. Within these conditions, simulations of the cell model exhibit seizure-like discharges (ictal bursting). The SD was elicited by the interruption of the Na(+)-K(+) pump activity, mimicking the effect of cellular hypoxia (an experimental protocol to elicit SD, the hypoxia-induced SD). We used the bifurcation theory and the fast-slow method to analyze the interference of K(+) dynamics in the cellular excitability. This analysis indicates that the system loses its stability at a high [K(+)](o), transiting to an elevated state of neuronal excitability. Effects of high [K(+)](o) are observed in different stages of ictal bursting and SD. In the initial stage, the increase of [K(+)](o) creates favorable conditions to trigger both oscillatory patterns. During the neuronal activity, a continuous growth of [K(+)](o) by outward K(+) flow depresses K(+) currents in a positive feedback way. At the last stage, due to the depression of K(+) currents, the Na(+)-K(+) pump is the main mechanism in the end of neuronal activity. Thus, this work suggests that [K(+)](o) dynamics may play a fundamental role in these abnormal oscillatory patterns.
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Zhu L, Polley N, Mathews GC, Delpire E. NKCC1 and KCC2 prevent hyperexcitability in the mouse hippocampus. Epilepsy Res 2008; 79:201-12. [PMID: 18394864 PMCID: PMC2394664 DOI: 10.1016/j.eplepsyres.2008.02.005] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Revised: 02/11/2008] [Accepted: 02/13/2008] [Indexed: 10/22/2022]
Abstract
During postnatal development of the central nervous system (CNS), the response of GABA(A) receptors to its agonist undergoes maturation from depolarizing to hyperpolarizing. This switch in polarity is due to the developmental decrease of the intracellular Cl concentration in neurons. Here we show that absence of NKCC1 in P9-P13 CA3 pyramidal neurons, through genetic manipulation or through bumetanide inhibition, results in a significant increase in cell excitability. Furthermore, the pro-convulsant agent 4-aminopyridine induces seizure-like events in NKCC1-null mice but not in wild-type mice. Measurements of muscimol responses in the presence and absence of NKCC1 shows that the Na-K-2Cl cotransporter only marginally affects intracellular Cl(-) in P9-P13 CA3 principal neurons. However, large increases in intracellular Cl(-) are observed in CA3 pyramidal neurons following increased hyperexcitability, indicating that P9-P13 CA3 pyramidal neurons lack robust mechanisms to regulate intracellular Cl(-) during high synaptic activity. This increase in the Cl(-) concentration is network-driven and activity-dependent, as it is blocked by the non-NMDA glutamate receptor antagonist DNQX. We also show that expression of the outward K-Cl cotransporter, KCC2, prevents the development of hyperexcitability, as a reduction of KCC2 expression by half results in increased susceptibility to seizure under control and 4-AP conditions.
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Affiliation(s)
- Lei Zhu
- Neuroscience Graduate Program, Vanderbilt University Medical Center, Nashville, TN 37232
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Nathan Polley
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Gregory C. Mathews
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232
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Samoilova M, Wentlandt K, Adamchik Y, Velumian AA, Carlen PL. Connexin 43 mimetic peptides inhibit spontaneous epileptiform activity in organotypic hippocampal slice cultures. Exp Neurol 2008; 210:762-75. [DOI: 10.1016/j.expneurol.2008.01.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 01/02/2008] [Accepted: 01/07/2008] [Indexed: 01/12/2023]
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Ragsdale DS. How do mutant Nav1.1 sodium channels cause epilepsy? ACTA ACUST UNITED AC 2008; 58:149-59. [PMID: 18342948 DOI: 10.1016/j.brainresrev.2008.01.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 01/17/2008] [Accepted: 01/21/2008] [Indexed: 11/28/2022]
Abstract
Voltage-gated sodium channels comprise pore-forming alpha subunits and auxiliary beta subunits. Nine different alpha subtypes, designated Nav1.1-Nav1.9 have been identified in excitable cells. Nav1.1, 1.2 and 1.6 are major subtypes in the adult mammalian brain. More than 200 mutations in the Nav1.1 alpha subtype have been linked to inherited epilepsy syndromes, ranging in severity from the comparatively mild disorder Generalized Epilepsy with Febrile Seizures Plus to the epileptic encephalopathy Severe Myoclonic Epilepsy of Infancy. Studies using heterologous expression and functional analysis of recombinant Nav1.1 channels suggest that epilepsy mutations in Nav1.1 may cause either gain-of-function or loss-of-function effects that are consistent with either increased or decreased neuronal excitability. How these diverse effects lead to epilepsy is poorly understood. This review summarizes the data on sodium channel mutations and epilepsy and builds a case for the hypothesis that most Nav1.1 mutations have their ultimate epileptogenic effects by reducing Nav1.1-mediated whole cell sodium currents in GABAergic neurons, resulting in widespread loss of brain inhibition, an ideal background for the genesis of epileptic seizures.
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Affiliation(s)
- David S Ragsdale
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Quebec, Canada H3A 2B4.
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Conditional knock-out of Kir4.1 leads to glial membrane depolarization, inhibition of potassium and glutamate uptake, and enhanced short-term synaptic potentiation. J Neurosci 2007; 27:11354-65. [PMID: 17942730 DOI: 10.1523/jneurosci.0723-07.2007] [Citation(s) in RCA: 458] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
During neuronal activity, extracellular potassium concentration ([K+]out) becomes elevated and, if uncorrected, causes neuronal depolarization, hyperexcitability, and seizures. Clearance of K+ from the extracellular space, termed K+ spatial buffering, is considered to be an important function of astrocytes. Results from a number of studies suggest that maintenance of [K+]out by astrocytes is mediated by K+ uptake through the inward-rectifying Kir4.1 channels. To study the role of this channel in astrocyte physiology and neuronal excitability, we generated a conditional knock-out (cKO) of Kir4.1 directed to astrocytes via the human glial fibrillary acidic protein promoter gfa2. Kir4.1 cKO mice die prematurely and display severe ataxia and stress-induced seizures. Electrophysiological recordings revealed severe depolarization of both passive astrocytes and complex glia in Kir4.1 cKO hippocampal slices. Complex cell depolarization appears to be a direct consequence of Kir4.1 removal, whereas passive astrocyte depolarization seems to arise from an indirect developmental process. Furthermore, we observed a significant loss of complex glia, suggestive of a role for Kir4.1 in astrocyte development. Kir4.1 cKO passive astrocytes displayed a marked impairment of both K+ and glutamate uptake. Surprisingly, membrane and action potential properties of CA1 pyramidal neurons, as well as basal synaptic transmission in the CA1 stratum radiatum appeared unaffected, whereas spontaneous neuronal activity was reduced in the Kir4.1 cKO. However, high-frequency stimulation revealed greatly elevated posttetanic potentiation and short-term potentiation in Kir4.1 cKO hippocampus. Our findings implicate a role for glial Kir4.1 channel subunit in the modulation of synaptic strength.
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Najm IM, Tilelli CQ, Oghlakian R. Pathophysiological mechanisms of focal cortical dysplasia: a critical review of human tissue studies and animal models. Epilepsia 2007; 48 Suppl 2:21-32. [PMID: 17571350 DOI: 10.1111/j.1528-1167.2007.01064.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cortical dysplasia (CD, also known as malformations of cortical development) are the pathological substrates in a large percentage of patients with pharmacoresistant epilepsy who may be amenable to surgical treatment. Therefore, research on the mechanisms of dysplastic lesion formation and epileptogenicity is of paramount importance for the prevention, detection, and treatment of CD-induced epilepsy. The purpose of this review is to discuss and critically evaluate the current state and results of human tissue experimentation (focusing on reported results of studies done on neocortical dysplastic tissue resected from patients with pharmacoresistant epilepsy), and to discuss some of the concerns related to research that uses surgically resected epileptic human tissue. The use of better animal models of CD as a tool toward the better understanding of the mechanisms of pathogenesis, epileptogenesis, and epileptogenicity of dysplastic lesions will be reviewed from the perspective of their usefulness in a model of translational research that should ultimately result in better diagnostic and therapeutic techniques of CD.
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Affiliation(s)
- Imad M Najm
- Cleveland Clinic Epilepsy Center Head, Section of Adult Epilepsy and Clinical Neurophysiology, 9500 Euclid Avenue, S51, Cleveland, OH 44195, USA.
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Lively S, Brown IR. Analysis of the extracellular matrix protein SC1 during reactive gliosis in the rat lithium-pilocarpine seizure model. Brain Res 2007; 1163:1-9. [PMID: 17628511 DOI: 10.1016/j.brainres.2007.05.052] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Revised: 05/11/2007] [Accepted: 05/19/2007] [Indexed: 01/13/2023]
Abstract
When the nervous system is subjected to stressful stimuli, reactive gliosis often ensues. This phenomenon consists of the hypertrophy of astrocyte processes as well as the proliferation of these cells. In this study, the lithium-pilocarpine model of temporal lobe epilepsy was employed to study the effects of status epilepticus (SE) on the localization of SC1 protein in reactive astrocytes. SC1 is an anti-adhesive extracellular matrix protein strongly expressed in the mammalian brain. At 1 day following SE, SC1 transiently localized to hypertrophied astrocyte processes that were closely associated with neurons and blood vessels. SC1 was also detected at 7 days post-SE in proliferating astrocytes labeled with the cell division marker PCNA. These findings indicate that the anti-adhesive protein SC1 is ideally localized to create an environment conducive to process extension and cellular proliferation in reactive astrocytes.
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Affiliation(s)
- Starlee Lively
- Center for Neurobiology of Stress, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4
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Andreasen M, Skov J, Nedergaard S. Inwardly rectifying K+ (Kir) channels antagonize ictal-like epileptiform activity in area CA1 of the rat hippocampus. Hippocampus 2007; 17:1037-48. [PMID: 17604346 DOI: 10.1002/hipo.20335] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Reactive glial cells, for example, from patients with temporal lope epilepsy have a reduced density of inward rectifying K(+) (Kir) channels and thus a reduced K(+) buffering capacity. Evidence is accumulating that this downregulation of Kir channels could be implicated in epileptogenesis. In rat hippocampal brain slices, prolonged exposure to the nonselective Kir channel antagonist, Cs(+) (5 mM), gives rise to an epileptiform field potential (Cs-FP) in area CA1 composed of an initial positive (interictal-like) phase followed by a prolonged negative (ictal-like) phase. We have previously shown that the interictal-like phase depends on synaptic activation. The present study extends these findings by showing that the ictal-like phase of the Cs-FP is (i) sensitive to osmotic expansion of the extracellular space, (ii) reversed very quickly during wash out of Cs(+), and (iii) re-established in the presence of Ba(2+) (30-200 microM) or isosmotic low extracellular concentration of Na(+) ([Na(+)](o), 51.25 mM). The interictal-like phase showed less or no sensitivity to these treatments. In the complete absence of Cs(+), the Cs-FP could be fully reconstructed by the combined application of 4-aminopyridine (0.5 mM), an isosmotic high extracellular concentration of K(+) ([K(+)](o), 7 mM), and low [Na(+)](o) (51.25 mM). These results suggest that the interictal-like phase is initiated through synaptic activation and results from an unspecific increase in neuronal excitability, whereas the ictal-like phase is entirely dependent on blockade of Kir channels in CA1. We propose that glial dysfunction-related loss of Kir channels may not alone be sufficient for starting the induction process, but will likely increase the tendency of an epileptogenic process to proceed into seizure activity.
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Affiliation(s)
- Mogens Andreasen
- Department of Physiology, Institute of Physiology and Biophysics, University of Aarhus, Arhus C, Denmark.
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Dallas S, Miller DS, Bendayan R. Multidrug Resistance-Associated Proteins: Expression and Function in the Central Nervous System. Pharmacol Rev 2006; 58:140-61. [PMID: 16714484 DOI: 10.1124/pr.58.2.3] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Drug delivery to the brain is highly restricted, since compounds must cross a series of structural and metabolic barriers to reach their final destination, often a cellular compartment such as neurons, microglia, or astrocytes. The primary barriers to the central nervous system are the blood-brain and blood-cerebrospinal fluid barriers. Through structural modifications, including the presence of tight junctions that greatly limit paracellular transport, the cells that make up these barriers restrict diffusion of many pharmaceutically active compounds. In addition, the cells that comprise the blood-brain and blood-cerebrospinal fluid barriers express multiple ATP-dependent, membrane-bound, efflux transporters, such as members of the multidrug resistance-associated protein (MRP) family, which contribute to lowered drug accumulation. A relatively new concept in brain drug distribution just beginning to be explored is the possibility that cellular components of the brain parenchyma could act as a "second" barrier to brain permeation of pharmacological agents via expression of many of the same transporters. Indeed, efflux transporters expressed in brain parenchyma may facilitate the overall export of xenobiotics from the central nervous system, essentially handing them off to the barrier tissues. We propose that these primary and secondary barriers work in tandem to limit overall accumulation and distribution of xenobiotics in the central nervous system. The present review summarizes recent knowledge in this area and emphasizes the clinical significance of MRP transporter expression in a variety of neurological disorders.
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Affiliation(s)
- Shannon Dallas
- Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, USA
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Stamatakis M, Mantzaris NV. Modeling of ATP-mediated signal transduction and wave propagation in astrocytic cellular networks. J Theor Biol 2006; 241:649-68. [PMID: 16460762 DOI: 10.1016/j.jtbi.2006.01.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Revised: 11/12/2005] [Accepted: 01/03/2006] [Indexed: 11/17/2022]
Abstract
Astrocytes, a special type of glial cells, were considered to have supporting role in information processing in the brain. However, several recent studies have shown that they can be chemically stimulated by neurotransmitters and use a form of signaling, in which ATP acts as an extracellular messenger. Pathological conditions, such as spreading depression, have been linked to abnormal range of wave propagation in astrocytic cellular networks. Nevertheless, the underlying intra- and inter-cellular signaling mechanisms remain unclear. Motivated by the above, we constructed a model to understand the relationship between single-cell signal transduction mechanisms and wave propagation and blocking in astrocytic networks. The model incorporates ATP-mediated IP3 production, the subsequent Ca2+ release from the ER through IP3R channels and ATP release into the extracellular space. For the latter, two hypotheses were tested: Ca2+- or IP3-dependent ATP release. In the first case, single astrocytes can exhibit excitable behavior and frequency-encoded oscillations. Homogeneous, one-dimensional astrocytic networks can propagate waves with infinite range, while in two dimensions, spiral waves can be generated. However, in the IP3-dependent ATP release case, the specific coupling of the driver ATP-IP3 system with the driven Ca2+ subsystem leads to one- and two-dimensional wave patterns with finite range of propagation.
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Affiliation(s)
- Michail Stamatakis
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX 77005, USA
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Setkowicz Z, Nowak B, Janeczko K. Neocortical injuries at different developmental stages determine different susceptibility to seizures induced in adulthood. Epilepsy Res 2006; 68:255-63. [PMID: 16387474 DOI: 10.1016/j.eplepsyres.2005.11.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Revised: 10/26/2005] [Accepted: 11/27/2005] [Indexed: 11/29/2022]
Abstract
Gliosis, axonal sprouting and remodelling of nerve connections in the injured brain have been regarded as epileptogenic processes dependent on the age when the injury was inflicted. The present study examines whether brains injured at different developmental stages may acquire different susceptibility to experimental status epilepticus induced in adulthood. In 6- and 30-day-old Wistar rats (P6s and P30s, respectively), a mechanical injury was performed in the left cerebral hemisphere. On postnatal day 60, all the animals and controls received single injections of kainic acid to evoke status epilepticus. During a 6-h period following the injection, the animals were observed continuously and motor symptoms of seizure activity were recorded and rated. P6s showed significantly lower intensity of kainic acid-induced epileptic symptoms and significantly longer survival than controls or P30s. In P30s, no significant change was detected. The data provide evidence that the developmental stage when the brain is injured determines epileptogenecity of the lesion. However, a considerable discrepancy between these data and those obtained previously following pilocarpine administration in the same experimental models of brain injury shows that each of the two models of epilepsy may display different aspects of the same age-dependent process triggered by the brain injury.
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Affiliation(s)
- Zuzanna Setkowicz
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, 6 Ingardena St., 30 060 Kraków, Poland
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Kralic JE, Ledergerber DA, Fritschy JM. Disruption of the neurogenic potential of the dentate gyrus in a mouse model of temporal lobe epilepsy with focal seizures. Eur J Neurosci 2005; 22:1916-27. [PMID: 16262631 DOI: 10.1111/j.1460-9568.2005.04386.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Adult hippocampal neurogenesis is enhanced in response to multiple stimuli including seizures. However, the relationship between neurogenesis and the development of temporal lobe epilepsy (TLE) remains unclear. Unilateral intrahippocampal injection of kainate in adult mice models the morphological characteristics (e.g. neuronal loss, gliosis, granule cell dispersion and hypertrophy) and occurrence of chronic, spontaneous recurrent partial seizures observed in human TLE. We investigated the influence of a kainate-induced epileptogenic focus on hippocampal neurogenesis, comparing neural stem cell proliferation following status epilepticus and spontaneous recurrent partial seizures. Cell proliferation in the subgranular zone was transiently increased bilaterally after kainate treatment. As a result, neurogenesis was stimulated in the contralateral dentate gyrus. In contrast, the epileptic hippocampus exhibited a strongly reduced neurogenic potential, even after onset of spontaneous recurrent partial seizures, possibly due to an alteration of the neurogenic niche in the subgranular zone. These results show that neurogenesis does not contribute to the formation of the epileptic focus and may be affected when dispersion of dentate gyrus granule cells occurs. Therefore, in patients with TLE, hippocampal sclerosis and granule cell dispersion may play a significant role in disrupting the potential for hippocampal neurogenesis.
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Affiliation(s)
- Jason E Kralic
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH -8057 Zurich, Switzerland
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Benarroch EE. Neuron-astrocyte interactions: partnership for normal function and disease in the central nervous system. Mayo Clin Proc 2005; 80:1326-38. [PMID: 16212146 DOI: 10.4065/80.10.1326] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Interactions between neurons and astrocytes are critical for signaling, energy metabolism, extracellular ion homeostasis, volume regulation, and neuroprotection in the central nervous system. Astrocytes face the synapses, send end-foot processes that enwrap the brain capillaries, and form an extensive network interconnected by gap junctions. Astrocytes express several membrane proteins and enzymes that are critical for uptake of glutamate at the synapses, ammonia detoxification, buffering of extracellular K+, and volume regulation. They also participate in detection, propagation, and modulation of excitatory synaptic signals, provide metabolic support to the active neurons, and contribute to functional hyperemia in the active brain tissue. Disturbances of these neuron-astrocyte interactions are likely to play an important role in neurologic disorders including cerebral ischemia, neurodegeneration, migraine, cerebral edema, and hepatic encephalopathy.
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Affiliation(s)
- Eduardo E Benarroch
- Department of Neurology, Mayo Clinic College of Medicine, 200 First St SW, Rochester, MN 55905, USA.
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D'Ambrosio R, Fender JS, Fairbanks JP, Simon EA, Born DE, Doyle DL, Miller JW. Progression from frontal-parietal to mesial-temporal epilepsy after fluid percussion injury in the rat. Brain 2005; 128:174-88. [PMID: 15563512 PMCID: PMC2696356 DOI: 10.1093/brain/awh337] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
We recently described an in vivo model of post-traumatic epilepsy (PTE) in the rat where chronic spontaneous recurrent seizures appear following a single episode of fluid percussion injury (FPI). PTE, studied during the first 2 months post-injury, was focal and seizures originated predominantly from the frontal-parietal neocortex at or around the injury site. However, rarer bilateral seizures originating from a different and undefined focus were also observed. To shed light on the Posttraumatic Epileptogenic mechanisms and on the generation of bilateral seizures, we studied rats up to 7 months post-injury. In vivo paired epidural and depth-electrode recordings indicated that the anterior hippocampus evolves into an epileptic focus which initiates bilateral seizures. The rate of frontal-parietal seizures remained constant over time after 2 weeks post-injury, while the rate of hippocampal seizures greatly increased over time, suggesting that different mechanisms mediate neocortical and hippocampal post-traumatic epileptogenesis. Because of different temporal evolution of these foci, the epileptic syndrome was characterized by predominant frontal-parietal seizures early after injury, but by predominant mesio-temporal seizures at later time points. Pathological analysis demonstrated progressive hippocampal and temporal cortex pathology that paralleled the increase in frequency and duration of bilateral seizures. These results demonstrate that FPI-induced frontal-parietal epilepsy (FPE) progresses to mesial-temporal lobe epilepsy (MTLE) with dual pathology. These observations establish numerous similarities between FPI-induced and human PTE and further validate it as a clinically relevant model of PTE.
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Affiliation(s)
- Raimondo D'Ambrosio
- Department of Neurological Surgery, Center on Human Development and Disability, University of Washington, School of Medicine, Harborview Medical Center, Box 359915, 325 Ninth Avenue, Seattle, WA 98104, USA.
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