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Gan Y, Wei Z, Liu C, Li G, Feng Y, Deng Y. Solute carrier transporter disease and developmental and epileptic encephalopathy. Front Neurol 2022; 13:1013903. [PMID: 36419532 PMCID: PMC9676364 DOI: 10.3389/fneur.2022.1013903] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 09/07/2022] [Indexed: 09/14/2023] Open
Abstract
The International League Against Epilepsy officially revised its classification in 2017, which amended "epileptic encephalopathy" to "developmental and epileptic encephalopathy". With the development of genetic testing technology, an increasing number of genes that cause developmental and epileptic encephalopathies are being identified. Among these, solute transporter dysfunction is part of the etiology of developmental and epileptic encephalopathies. Solute carrier transporters play an essential physiological function in the human body, and their dysfunction is associated with various human diseases. Therefore, in-depth studies of developmental and epileptic encephalopathies caused by solute carrier transporter dysfunction can help develop new therapeutic modalities to facilitate the treatment of refractory epilepsy and improve patient prognosis. In this article, the concept of transporter protein disorders is first proposed, and nine developmental and epileptic encephalopathies caused by solute carrier transporter dysfunction are described in detail in terms of pathogenesis, clinical manifestations, ancillary tests, and precise treatment to provide ideas for the precise treatment of epilepsy.
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Affiliation(s)
- Yajing Gan
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Zihan Wei
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Chao Liu
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Guoyan Li
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Yan Feng
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Yanchun Deng
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
- Xijing Institute of Epilepsy and Encephalopathy, Xi'an, China
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2
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André MV, Cacciagli P, Cano A, Vaugier L, Roussel M, Girard N, Chabrol B, Villard L, Milh M. The phenotype caused by recessive variations in SLC25A22: Report of a new case and literature review. Arch Pediatr 2020; 28:87-92. [PMID: 33342683 DOI: 10.1016/j.arcped.2020.10.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 07/20/2020] [Accepted: 10/31/2020] [Indexed: 10/22/2022]
Abstract
We describe the clinical, electroencephalography (EEG), and developmental features of a patient with developmental and epileptic encephalopathy due to a homozygous pathogenic variation of mitochondrial glutamate/H+ symporter SLC25A22. Epilepsy began during the first week of life with focal onset seizures. Interictal EEG revealed a suppression-burst pattern with extensive periods of non-activity. The prospective follow-up confirmed developmental encephalopathy as well as ongoing active epilepsy and almost no sign of development at 8 years of age. We confirm in the following paper that SLC25A22 recessive variations may cause a severe developmental and epileptic encephalopathy characterized by a suppression-burst pattern. On the basis of an in-depth literature review, we also provide an overview of this rare genetic cause of neonatal onset epilepsy.
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Affiliation(s)
- M-V André
- Department of pediatric neurology, hôpital de la Timone, AP-HM, 13085 Marseille, France.
| | - P Cacciagli
- Inserm, GMGF, UMR_S 910, faculté de médecine, Aix-Marseille university, 13085 Marseille, France; Department of medical genetics, hôpital de La Timone, AP-HM, 13085 Marseille, France
| | - A Cano
- Department of pediatric neurology, hôpital de la Timone, AP-HM, 13085 Marseille, France
| | - L Vaugier
- Department of clinical neurophysiology, hôpital de la Timone, AP-HM, 13085 Marseille, France
| | - M Roussel
- Department of clinical neurophysiologie, hôpital Nord, AP-HM, 13015 Marseille, France
| | - N Girard
- Department of Neuroradiology, Aix-Marseille University, AP-HM, 13085 Marseille, France
| | - B Chabrol
- Department of pediatric neurology, hôpital de la Timone, AP-HM, 13085 Marseille, France
| | - L Villard
- Inserm, GMGF, UMR_S 910, faculté de médecine, Aix-Marseille university, 13085 Marseille, France; Department of medical genetics, hôpital de La Timone, AP-HM, 13085 Marseille, France
| | - M Milh
- Department of pediatric neurology, hôpital de la Timone, AP-HM, 13085 Marseille, France; Inserm, GMGF, UMR_S 910, faculté de médecine, Aix-Marseille university, 13085 Marseille, France
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3
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Goubert E, Mircheva Y, Lasorsa FM, Melon C, Profilo E, Sutera J, Becq H, Palmieri F, Palmieri L, Aniksztejn L, Molinari F. Inhibition of the Mitochondrial Glutamate Carrier SLC25A22 in Astrocytes Leads to Intracellular Glutamate Accumulation. Front Cell Neurosci 2017; 11:149. [PMID: 28620281 PMCID: PMC5449474 DOI: 10.3389/fncel.2017.00149] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 05/09/2017] [Indexed: 12/16/2022] Open
Abstract
The solute carrier family 25 (SLC25) drives the import of a large diversity of metabolites into mitochondria, a key cellular structure involved in many metabolic functions. Mutations of the mitochondrial glutamate carrier SLC25A22 (also named GC1) have been identified in early epileptic encephalopathy (EEE) and migrating partial seizures in infancy (MPSI) but the pathophysiological mechanism of GC1 deficiency is still unknown, hampered by the absence of an in vivo model. This carrier is mainly expressed in astrocytes and is the principal gate for glutamate entry into mitochondria. A sufficient supply of energy is essential for the proper function of the brain and mitochondria have a pivotal role in maintaining energy homeostasis. In this work, we wanted to study the consequences of GC1 absence in an in vitro model in order to understand if glutamate catabolism and/or mitochondrial function could be affected. First, short hairpin RNA (shRNA) designed to specifically silence GC1 were validated in rat C6 glioma cells. Silencing GC1 in C6 resulted in a reduction of the GC1 mRNA combined with a decrease of the mitochondrial glutamate carrier activity. Then, primary astrocyte cultures were prepared and transfected with shRNA-GC1 or mismatch-RNA (mmRNA) constructs using the Neon® Transfection System in order to target a high number of primary astrocytes, more than 64%. Silencing GC1 in primary astrocytes resulted in a reduced nicotinamide adenine dinucleotide (Phosphate) (NAD(P)H) formation upon glutamate stimulation. We also observed that the mitochondrial respiratory chain (MRC) was functional after glucose stimulation but not activated by glutamate, resulting in a lower level of cellular adenosine triphosphate (ATP) in silenced astrocytes compared to control cells. Moreover, GC1 inactivation resulted in an intracellular glutamate accumulation. Our results show that mitochondrial glutamate transport via GC1 is important in sustaining glutamate homeostasis in astrocytes. Main Points:The mitochondrial respiratory chain is functional in absence of GC1 Lack of glutamate oxidation results in a lower global ATP level Lack of mitochondrial glutamate transport results in intracellular glutamate accumulation
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Affiliation(s)
| | - Yanina Mircheva
- INMED, INSERM, Aix-Marseille UniversitéMarseille, France.,Centre De Recherche De L'Institut Universitaire En Santé Mentale de QuébecQuebec City, QC, Canada
| | - Francesco M Lasorsa
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, and CNR Institute of Biomembranes, Bioenergetics and Molecular BiotechnologiesBari, Italy
| | | | - Emanuela Profilo
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, and CNR Institute of Biomembranes, Bioenergetics and Molecular BiotechnologiesBari, Italy
| | - Julie Sutera
- INMED, INSERM, Aix-Marseille UniversitéMarseille, France
| | - Hélène Becq
- INMED, INSERM, Aix-Marseille UniversitéMarseille, France
| | - Ferdinando Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, and CNR Institute of Biomembranes, Bioenergetics and Molecular BiotechnologiesBari, Italy
| | - Luigi Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, and CNR Institute of Biomembranes, Bioenergetics and Molecular BiotechnologiesBari, Italy
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Trabelsi Y, Amri M, Becq H, Molinari F, Aniksztejn L. The conversion of glutamate by glutamine synthase in neocortical astrocytes from juvenile rat is important to limit glutamate spillover and peri/extrasynaptic activation of NMDA receptors. Glia 2016; 65:401-415. [PMID: 27862359 DOI: 10.1002/glia.23099] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 12/31/2022]
Abstract
Glutamate transporters (EAATs) are important to maintain spatial and temporal specificity of synaptic transmission. Their efficiency to uptake and transport glutamate into the intracellular space depends on several parameters including the intracellular concentrations of Na+ and glutamate, the elevations of which may slow down the cycling rate of EAATs. In astrocytes, glutamate is maintained at low concentration due to the presence of specific enzymes such as glutamine synthase (GS). GS inhibition results in cytosolic accumulation of glutamate suggesting that the conversion of glutamate by GS is important for EAATs operation. Here we recorded astrocytes from juvenile rat neocortical slices and analyzed the consequences of elevated intracellular glutamate concentrations and of GS inhibition on the time course of synaptically evoked transporter current (STC). In slices from rats treated with methionine sulfoximine (MSO), a GS inhibitor, STC evoked by short burst of high frequency stimulation (HFS; 100 Hz for 100 ms) but not by low frequency stimulation (LFS; 0.1 Hz) was twice slower than STC evoked from saline injected rats. Same results were obtained for astrocytes recorded with pipette containing 3-10 mM glutamate and compared with cells recorded with 0 or1 mM glutamate in the patch pipette. We also showed that HFS elicited significantly larger NMDAR-excitatory postsynaptic currents (EPSCs) with a stronger peri/extrasynaptic component in pyramidal cells from MSO-treated compared with saline treated rats. Taken together our data demonstrate that the conversion of glutamate by GS is fundamental to ensure an efficient clearance of glutamate by EAATs and to prevent glutamate spillover. GLIA 2017;65:401-415.
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Affiliation(s)
- Yosra Trabelsi
- Institut de Neurobiologie de la Méditerranée (INMED), Aix-Marseille Université, Marseille, 13009, France.,INSERM, UMR_S 901, Marseille, 13009, France
| | - Mohamed Amri
- Laboratoire de Neurophysiologie Fonctionnelle et Pathologies, Tunis, UR11ES09, Tunisie
| | - Hélène Becq
- Institut de Neurobiologie de la Méditerranée (INMED), Aix-Marseille Université, Marseille, 13009, France.,INSERM, UMR_S 901, Marseille, 13009, France
| | - Florence Molinari
- Institut de Neurobiologie de la Méditerranée (INMED), Aix-Marseille Université, Marseille, 13009, France.,INSERM, UMR_S 901, Marseille, 13009, France
| | - Laurent Aniksztejn
- Institut de Neurobiologie de la Méditerranée (INMED), Aix-Marseille Université, Marseille, 13009, France.,INSERM, UMR_S 901, Marseille, 13009, France
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5
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Current understanding and neurobiology of epileptic encephalopathies. Neurobiol Dis 2016; 92:72-89. [DOI: 10.1016/j.nbd.2016.03.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 03/01/2016] [Accepted: 03/09/2016] [Indexed: 12/25/2022] Open
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6
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Lei M, Xu H, Li Z, Wang Z, O'Malley TT, Zhang D, Walsh DM, Xu P, Selkoe DJ, Li S. Soluble Aβ oligomers impair hippocampal LTP by disrupting glutamatergic/GABAergic balance. Neurobiol Dis 2015; 85:111-121. [PMID: 26525100 DOI: 10.1016/j.nbd.2015.10.019] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 09/01/2015] [Accepted: 10/21/2015] [Indexed: 02/06/2023] Open
Abstract
Epileptic activity may be more prevalent in early stage Alzheimer's disease (AD) than previously believed. Several studies report spontaneous seizures and interictal discharges in mouse models of AD undergoing age-related Aβ accumulation. The mechanism by which Aβ-induced neuronal excitability can trigger epileptiform activity remains unknown. Here, we systematically examined field excitatory postsynaptic potentials (fEPSP) in stratum radiatum and population spikes (PSs) in the adjacent stratum pyramidale of CA1 in wild-type mouse hippocampal slices. Soluble Aβ oligomers (oAβ) blocked hippocampal LTP and EPSP-spike (E-S) potentiation, and these effects were occluded by prior treatment with the glutamate uptake inhibitor TBOA. In accord, oAβ elevated glutamate levels in the hippocampal slice medium. Recording the PS revealed that oAβ increased PS frequency and reduced LTP, and this LTP deficit was occluded by pretreatment with the GABAA antagonist picrotoxin. Whole-cell recordings showed that oAβ significantly increased spontaneous EPSC frequency. Decreasing neuronal activity by increasing GABA tone or partially blocking NMDAR activity prevented oAβ impairment of hippocampal LTP. Finally, treating slices with two antiepileptic drugs rescued the LTP inhibition induced by oAβ. We conclude that soluble Aβ oligomers at the low nanomolar levels present in AD brain increase neuronal excitability by disrupting glutamatergic/GABAergic balance, thereby impairing synaptic plasticity.
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Affiliation(s)
- Ming Lei
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA; Department of Neurology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080, China
| | - Huixin Xu
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Zhangyuan Li
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Zemin Wang
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Tiernan T O'Malley
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Dainan Zhang
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Dominic M Walsh
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Pingyi Xu
- Department of Neurology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080, China; Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangdong 510120, China.
| | - Dennis J Selkoe
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Shaomin Li
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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7
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Dulac O, Plecko B, Gataullina S, Wolf NI. Occasional seizures, epilepsy, and inborn errors of metabolism. Lancet Neurol 2014; 13:727-39. [PMID: 24943345 DOI: 10.1016/s1474-4422(14)70110-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Seizures are a common paediatric problem, with inborn errors of metabolism being a rare underlying aetiology. The clinical presentation of inborn errors of metabolism is often associated with other neurological symptoms, such as hypotonia, movement disorders, and cognitive disturbances. However, the occurrence of epilepsy associated with inborn errors of metabolism represents a major challenge that needs to be identified quickly; for some cases, specific treatments are available, metabolic decompensation might be avoided, and accurate counselling can be given about recurrence risk. Some clinical presentations are more likely than others to point to an inborn error of metabolism as the cause of seizures. Knowledge of important findings at examination, and appropriate biochemical investigation of children with seizures of uncertain cause, can aid the diagnosis of an inborn error of metabolism and ascertain whether or not the seizures are amenable to specific metabolic treatment.
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Affiliation(s)
- Olivier Dulac
- Paris Descartes University, Inserm U1129, Paris, France; CEA, Gif-sur-Yvette, France; Department of Paediatric Neurology, Hôpital Necker-Enfants Malades, AP-HP, Paris, France.
| | - Barbara Plecko
- Department of Child Neurology, University Children's Hospital, University of Zurich, Switzerland
| | | | - Nicole I Wolf
- Department of Child Neurology, VU University Medical Center, Amsterdam, Netherlands; Neuroscience Campus Amsterdam, Amsterdam, Netherlands
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Andreae LC, Burrone J. The role of neuronal activity and transmitter release on synapse formation. Curr Opin Neurobiol 2014; 27:47-52. [PMID: 24632375 PMCID: PMC4127784 DOI: 10.1016/j.conb.2014.02.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 01/16/2014] [Accepted: 02/06/2014] [Indexed: 01/08/2023]
Abstract
The long history of probing the role of neuronal activity in the development of nervous system circuitry has recently taken an interesting turn. Although undoubtedly activity plays a critical part in the maintenance and refinement of synaptic connections, often via competitive mechanisms, evidence is building that it also drives the process of synapse formation itself. Perhaps predictably, this turns out not to be a uniform process. It seems that different circuits, indeed specific synaptic connections, are differentially sensitive to the effects of activity. We examine possible ways in which neurotransmitter may drive synapse formation, and speculate on how the environment of the developing brain may allow a different spatiotemporal range for neuronal activity to operate in the generation of connectivity.
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Affiliation(s)
- Laura C Andreae
- MRC Centre for Developmental Neurobiology, King's College London, New Hunt's House, 4th Floor, Guy's Hospital Campus, London SE1 1UL, UK.
| | - Juan Burrone
- MRC Centre for Developmental Neurobiology, King's College London, New Hunt's House, 4th Floor, Guy's Hospital Campus, London SE1 1UL, UK.
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9
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Dulac O, Milh M, Holmes GL. Brain maturation and epilepsy. HANDBOOK OF CLINICAL NEUROLOGY 2014; 111:441-6. [PMID: 23622192 DOI: 10.1016/b978-0-444-52891-9.00047-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
At full term, both glutamate and gamma-amino-butyric acid (GABA) are excitatory; cortical synapses are beginning to appear, there is little myelin in the cerebral hemispheres, and long tracts hardly start to develop. Neonatal myoclonic encephalopathy can result from premature activation of N-methyl-D-aspartate (NMDA) transmission. Benign neonatal seizures and migrating partial seizures in infancy could involve excessive or premature excitability of deep cortical layers. Benign rolandic epilepsy and continuous spike waves in slow sleep are consistent with an excess of both excitatory and inhibitory cortical synapses. West and Lennox-Gastaut syndromes express age-related diffuse cortical hyperexcitability, the pattern depending on the age of occurrence; synchronization of spikes is becoming possible with maturation of the myelin. Idiopathic generalized epilepsy is itself modulated by maturation that causes frontal hyperexcitability generating myoclonic-astatic seizures, between the ages of infantile and juvenile myoclonic epilepsies. Physiological delay of hippocampo-neocortical pathways maturation could account for the delayed occurrence of mesial temporal epilepsy following infantile damage, whereas premature maturation could contribute to fronto-temporal damage characteristic of fever-induced epileptic encephalopathy in school-age children, a dramatic school-age epileptic encephalopathy.
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Affiliation(s)
- Olivier Dulac
- Department of Pediatric Neurology, Hôpital Necker-Enfants Malades, UMR663, Paris, France.
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Abstract
Epilepsies associated with inborn errors of metabolism (IEM) represent a major challenge. Seizures rarely dominate the clinical presentation, which is more frequently associated with other neurological symptoms, such as hypotonia and/or cognitive disturbances. Although epilepsy in IEM can be classified in various ways according to pathogenesis, age of onset, or electroclinical presentation, the most pragmatic approach is determined by whether they are accessible to specific treatment or not. The main potentially treatable causes comprise vitamin B6 (pyridoxine deficiency), biotine, and GLUT1 deficiency (GLUT1DS) syndromes. Folinic acid-dependent seizures are allelic with pyridoxine dependency. Incompletely treatable IEMs include pyridoxal phosphate, serine, and creatine deficiencies. The main IEMs that present with epilepsy but offer no specific treatment are nonketotic hyperglycinemia, mitochondrial disorders, sulfite oxidase deficiency, ceroid-lipofuscinosis, Menkes disease, and peroxisomal disorders.
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Affiliation(s)
- Nadia Bahi-Buisson
- Department of Pediatric Neurology, Université Paris Descartes; Imaging Institute; INSERM U781, Paris, France.
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Molinari F, Cattani A, Mdzomba J, Aniksztejn L. Glutamate transporters control metabotropic glutamate receptors activation to prevent the genesis of paroxysmal burst in the developing hippocampus. Neuroscience 2012; 207:25-36. [DOI: 10.1016/j.neuroscience.2012.01.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 12/23/2011] [Accepted: 01/19/2012] [Indexed: 12/26/2022]
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Abstract
When mimicking epileptic processes in a laboratory setting, it is important to understand the differences between experimental models of seizures and epilepsy. Because human epilepsy is defined by the appearance of multiple spontaneous recurrent seizures, the induction of a single acute seizure without recurrence does not constitute an adequate epilepsy model. Animal models of epilepsy might be useful for various tasks. They allow for the investigation of pathophysiological mechanisms of the disease, the evaluation, or the development of new antiepileptic treatments, and the study of the consequences of recurrent seizures and neurological and psychiatric comorbidities. Although clinical relevance is always an issue, the development of models of pediatric epilepsies is particularly challenging due to the existence of several key differences in the dynamics of human and rodent brain maturation. Another important consideration in modeling pediatric epilepsy is that "children are not little adults," and therefore a mere application of models of adult epilepsies to the immature specimens is irrelevant. Herein, we review the models of pediatric epilepsy. First, we illustrate the differences between models of pediatric epilepsy and models of the adulthood consequences of a precipitating insult in early life. Next, we focus on new animal models of specific forms of epilepsies that occur in the developing brain. We conclude by emphasizing the deficiencies in the existing animal models and the need for several new models.
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Cortical cultures coupled to micro-electrode arrays: a novel approach to perform in vitro excitotoxicity testing. Neurotoxicol Teratol 2011; 34:116-27. [PMID: 21856414 DOI: 10.1016/j.ntt.2011.08.001] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 07/03/2011] [Accepted: 08/04/2011] [Indexed: 01/08/2023]
Abstract
In vitro neuronal cultures exhibit spontaneous electrophysiological activity that can be modulated by chemical stimulation and can be monitored over time by using Micro-Electrode Arrays (MEAs), devices composed by a glass substrate and metal electrodes. Dissociated networks respond to transmitters, their blockers and many other pharmacological substances, including neurotoxic compounds. In this paper we present results related to the effects, both acute (i.e. 1 hour after the treatment) and chronic (3 days after the treatment), of increasing glutamatergic transmission induced by the application of rising concentrations of glutamate and its agonists (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid - AMPA, N-methyl-D-aspartate - NMDA and AMPA together with cyclothiazide - CTZ). Increase of available glutamate was obtained in two ways: 1) by direct application of exogenous glutamate and 2) by inhibiting the clearance of the endogenously released glutamate through DL-threo-β-benzyloxyaspartate (TBOA). Our findings show that fine modulations (i.e. low concentrations of drug) of the excitatory synaptic transmission are reflected in the electrophysiological activation of the network, while intervention leading to excessive direct stimulation of glutamatergic pathways (i.e. medium and high concentrations of drug) results in the abolishment of the electrophysiological activity and eventually cell death. The results obtained by means of the MEA recordings have been compared to the analysis of cell viability to confirm the excitotoxic effect of the applied drug. In conclusion, our study demonstrates that MEA-coupled cortical networks are very sensitive to pharmacological manipulation of the excitatory ionotropic glutamatergic transmission and might provide sensitive endpoints to detect acute and chronic neurotoxic effects of chemicals and drugs for predictive toxicity testing.
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González-Martínez JA, Ying Z, Prayson R, Bingaman W, Najm I. Glutamate clearance mechanisms in resected cortical dysplasia. J Neurosurg 2011; 114:1195-202. [DOI: 10.3171/2010.10.jns10715] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Object
Changes in the expression of glutamate transporters (GLTs) may play a role in the expression of epileptogenicity. Previous studies have shown an increased number of neuronal GLTs in human dysplastic neurons. The expression of glial and neuronal GLTs and glutamine synthetase (GS) in balloon cells (BCs) and BC-containing cortical dysplasia has not been studied.
Methods
The authors analyzed neocortical samples that were resected in 5 patients who had cortical dysplasia–induced medically intractable focal epilepsy and who underwent extraoperative prolonged electrocorticographic (ECoG) recordings. The expressions of glial (GLT1/EAAT2) and neuronal (EAAT3, EAAC1) GLTs and GS proteins were immunohistochemically studied in all 5 resected samples. The authors also assessed in situ colocalization of GLTs and GS with neuronal and glial markers.
Results
Balloon cell–containing cortical dysplasia lesions did not exhibit ictal patterns on prolonged extraoperative ECoG recordings. There was a differential expression of glial and neuronal GLTs in BCs and dysplastic neurons: the majority of BCs highly expressed glial but not neuronal GLTs. Dysplastic neurons showed increased immunohistochemical staining with neuronal EAAT3 but not with EAAT2/GLT1. Moreover, only glial fibrillary acidic protein–positive BCs also expressed GS.
Conclusions
There is a differential GLT expression in dysplastic and balloon cells. The presence of glial GLTs and GS in balloon cell cortical dysplasia suggests a possible antiepileptic role for BCs and is consistent with the reported increased epileptogenicity in GLT1-deficient animals.
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Affiliation(s)
| | | | - Richard Prayson
- 2Department of Surgical Pathology, Cleveland Clinic, Cleveland, Ohio
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Bertsche A, Bruehl C, Pietz J, Draguhn A. Region- and pattern-specific effects of glutamate uptake blockers on epileptiform activity in rat brain slices. Epilepsy Res 2010; 88:118-26. [DOI: 10.1016/j.eplepsyres.2009.10.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 10/09/2009] [Accepted: 10/14/2009] [Indexed: 11/16/2022]
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16
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Modulation of astrocyte glutamate transporters decreases seizures in a mouse model of Tuberous Sclerosis Complex. Neurobiol Dis 2010; 37:764-71. [PMID: 20045054 DOI: 10.1016/j.nbd.2009.12.020] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 12/13/2009] [Accepted: 12/17/2009] [Indexed: 11/21/2022] Open
Abstract
Astrocyte dysfunction may contribute to epileptogenesis and other neurological deficits in Tuberous Sclerosis Complex (TSC). In particular, decreased expression and function of astrocyte glutamate transporters have been implicated in causing elevated extracellular glutamate levels, neuronal death, and epilepsy in a mouse model of TSC (Tsc1(GFAP)CKO mice), involving inactivation of the Tsc1 gene primarily in astrocytes. Here, we tested whether pharmacological induction of astrocyte glutamate transporter expression can prevent the neurological phenotype of Tsc1(GFAP)CKO mice. Early treatment with ceftriaxone prior to the onset of epilepsy increased expression of astrocyte glutamate transporters, decreased extracellular glutamate levels, neuronal death, and seizure frequency, and improved survival in Tsc1(GFAP)CKO mice. In contrast, late treatment with ceftriaxone after onset of epilepsy increased glutamate transporter expression, but had no effect on seizures. These results indicate that astrocyte glutamate transporters contribute to epileptogenesis in Tsc1(GFAP)CKO mice and suggest novel therapeutic strategies for epilepsy in TSC directed at astrocytes.
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17
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Waldbaum S, Patel M. Mitochondria, oxidative stress, and temporal lobe epilepsy. Epilepsy Res 2010; 88:23-45. [PMID: 19850449 PMCID: PMC3236664 DOI: 10.1016/j.eplepsyres.2009.09.020] [Citation(s) in RCA: 207] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 09/18/2009] [Accepted: 09/22/2009] [Indexed: 10/20/2022]
Abstract
Mitochondrial oxidative stress and dysfunction are contributing factors to various neurological disorders. Recently, there has been increasing evidence supporting the association between mitochondrial oxidative stress and epilepsy. Although certain inherited epilepsies are associated with mitochondrial dysfunction, little is known about its role in acquired epilepsies such as temporal lobe epilepsy (TLE). Mitochondrial oxidative stress and dysfunction are emerging as key factors that not only result from seizures, but may also contribute to epileptogenesis. The occurrence of epilepsy increases with age, and mitochondrial oxidative stress is a leading mechanism of aging and age-related degenerative disease, suggesting a further involvement of mitochondrial dysfunction in seizure generation. Mitochondria have critical cellular functions that influence neuronal excitability including production of adenosine triphosphate (ATP), fatty acid oxidation, control of apoptosis and necrosis, regulation of amino acid cycling, neurotransmitter biosynthesis, and regulation of cytosolic Ca(2+) homeostasis. Mitochondria are the primary site of reactive oxygen species (ROS) production making them uniquely vulnerable to oxidative stress and damage which can further affect cellular macromolecule function, the ability of the electron transport chain to produce ATP, antioxidant defenses, mitochondrial DNA stability, and synaptic glutamate homeostasis. Oxidative damage to one or more of these cellular targets may affect neuronal excitability and increase seizure susceptibility. The specific targeting of mitochondrial oxidative stress, dysfunction, and bioenergetics with pharmacological and non-pharmacological treatments may be a novel avenue for attenuating epileptogenesis.
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Affiliation(s)
- Simon Waldbaum
- Department of Pharmaceutical Sciences University of Colorado Denver School of Pharmacy Aurora, CO 80045 U.S.A
| | - Manisha Patel
- Department of Pharmaceutical Sciences University of Colorado Denver School of Pharmacy Aurora, CO 80045 U.S.A
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18
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Molinari F, Kaminska A, Fiermonte G, Boddaert N, Raas-Rothschild A, Plouin P, Palmieri L, Brunelle F, Palmieri F, Dulac O, Munnich A, Colleaux L. Mutations in the mitochondrial glutamate carrier SLC25A22 in neonatal epileptic encephalopathy with suppression bursts. Clin Genet 2009; 76:188-94. [PMID: 19780765 DOI: 10.1111/j.1399-0004.2009.01236.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Neonatal epileptic encephalopathies with suppression bursts (SBs) are very severe and relatively rare diseases characterized by neonatal onset of seizures, interictal electroencephalogram (EEG) with SB pattern and very poor neurological outcome or death. Their etiology remains elusive but they are occasionally caused by metabolic diseases or malformations. Studying an Arab Muslim Israeli consanguineous family, with four affected children presenting a severe neonatal epileptic encephalopathy, we have previously identified a mutation in the SLC25A22 gene encoding a mitochondrial glutamate transporter. In this report, we describe a novel SLC25A22 mutation in an unrelated patient born from first cousin Algerian parents and presenting severe epileptic encephalopathy characterized by an EEG with SB, hypotonia, microcephaly and abnormal electroretinogram. We showed that this patient carried a homozygous p.G236W SLC25A22 mutation which alters a highly conserved amino acid and completely abolishes the glutamate carrier's activity in vitro. Comparison of the clinical features of patients from both families suggests that SLC25A22 mutations are responsible for a novel clinically recognizable epileptic encephalopathy with SB.
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Affiliation(s)
- F Molinari
- Laboratoire de génétique et épigénétique des maladies métaboliques, neurosensorielles et du développement (INSERM U781), Hôpital Necker-Enfants Malades, Université Paris Descartes, Paris, France.
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19
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Blankenship AG, Feller MB. Mechanisms underlying spontaneous patterned activity in developing neural circuits. Nat Rev Neurosci 2009; 11:18-29. [PMID: 19953103 DOI: 10.1038/nrn2759] [Citation(s) in RCA: 518] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Patterned, spontaneous activity occurs in many developing neural circuits, including the retina, the cochlea, the spinal cord, the cerebellum and the hippocampus, where it provides signals that are important for the development of neurons and their connections. Despite there being differences in adult architecture and output across these various circuits, the patterns of spontaneous network activity and the mechanisms that generate it are remarkably similar. The mechanisms can include a depolarizing action of GABA (gamma-aminobutyric acid), transient synaptic connections, extrasynaptic transmission, gap junction coupling and the presence of pacemaker-like neurons. Interestingly, spontaneous activity is robust; if one element of a circuit is disrupted another will generate similar activity. This research suggests that developing neural circuits exhibit transient and tunable features that maintain a source of correlated activity during crucial stages of development.
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Affiliation(s)
- Aaron G Blankenship
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, California 92093, USA
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20
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Allene C, Cossart R. Early NMDA receptor-driven waves of activity in the developing neocortex: physiological or pathological network oscillations? J Physiol 2009; 588:83-91. [PMID: 19917570 DOI: 10.1113/jphysiol.2009.178798] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Several patterns of coherent activity have been described in developing cortical structures, thus providing a general framework for network maturation. A detailed timely description of network patterns at circuit and cell levels is essential for the understanding of pathogenic processes occurring during brain development. Disturbances in the expression timetable of this pattern sequence are very likely to affect network maturation. This review focuses on the maturation of coherent activity patterns in developing neocortical structures. It emphasizes the intrinsic and synaptic cellular properties that are unique to the immature neocortex and, in particular, the critical role played by extracellular glutamate in controlling network excitability and triggering synchronous network waves of activity.
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Affiliation(s)
- Camille Allene
- INSERM u901, Institut de Neurobiologie de la Méditerranée, Unité 01 Parc Scientifique de Luminy, Boîte Postale 13, Marseille 13273, France
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21
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Blankenship AG, Ford KJ, Johnson J, Seal RP, Edwards RH, Copenhagen DR, Feller MB. Synaptic and extrasynaptic factors governing glutamatergic retinal waves. Neuron 2009; 62:230-41. [PMID: 19409268 PMCID: PMC2807181 DOI: 10.1016/j.neuron.2009.03.015] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Revised: 01/28/2009] [Accepted: 03/17/2009] [Indexed: 11/28/2022]
Abstract
In the few days prior to eye-opening in mice, the excitatory drive underlying waves switches from cholinergic to glutamatergic. Here, we describe the unique synaptic and spatiotemporal properties of waves generated by the retina's glutamatergic circuits. First, knockout mice lacking vesicular glutamate transporter type 1 do not have glutamatergic waves, but continue to exhibit cholinergic waves, demonstrating that the two wave-generating circuits are linked. Second, simultaneous outside-out patch and whole-cell recordings reveal that retinal waves are accompanied by transient increases in extrasynaptic glutamate, directly demonstrating the existence of glutamate spillover during waves. Third, the initiation rate and propagation speed of retinal waves, as assayed by calcium imaging, are sensitive to pharmacological manipulations of spillover and inhibition, demonstrating a role for both signaling pathways in shaping the spatiotemporal properties of glutamatergic retinal waves.
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Affiliation(s)
- Aaron G Blankenship
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
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22
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Sequential generation of two distinct synapse-driven network patterns in developing neocortex. J Neurosci 2009; 28:12851-63. [PMID: 19036979 DOI: 10.1523/jneurosci.3733-08.2008] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Developing cortical networks generate a variety of coherent activity patterns that participate in circuit refinement. Early network oscillations (ENOs) are the dominant network pattern in the rodent neocortex for a short period after birth. These large-scale calcium waves were shown to be largely driven by glutamatergic synapses albeit GABA is a major excitatory neurotransmitter in the cortex at such early stages, mediating synapse-driven giant depolarizing potentials (GDPs) in the hippocampus. Using functional multineuron calcium imaging together with single-cell and field potential recordings to clarify distinct network dynamics in rat cortical slices, we now report that the developing somatosensory cortex generates first ENOs then GDPs, both patterns coexisting for a restricted time period. These patterns markedly differ by their developmental profile, dynamics, and mechanisms: ENOs are generated before cortical GDPs (cGDPs) by the activation of glutamatergic synapses mostly through NMDARs; cENOs are low-frequency oscillations (approximately 0.01 Hz) displaying slow kinetics and gradually involving the entire network. At the end of the first postnatal week, GABA-driven cortical GDPs can be reliably monitored; cGDPs are recurrent oscillations (approximately 0.1 Hz) that repetitively synchronize localized neuronal assemblies. Contrary to cGDPs, cENOs were unexpectedly facilitated by short anoxic conditions suggesting a contribution of glutamate accumulation to their generation. In keeping with this, alterations of extracellular glutamate levels significantly affected cENOs, which are blocked by an enzymatic glutamate scavenger. Moreover, we show that a tonic glutamate current contributes to the neuronal membrane excitability when cENOs dominate network patterns. Therefore, cENOs and cGDPs are two separate aspects of neocortical network maturation that may be differentially engaged in physiological and pathological processes.
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23
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Jelenkovic AV, Jovanovic MD, Stanimirovic DD, Bokonjic DD, Ocic GG, Boskovic BS. Beneficial effects of ceftriaxone against pentylenetetrazole-evoked convulsions. Exp Biol Med (Maywood) 2008; 233:1389-94. [PMID: 18703755 DOI: 10.3181/0803-rm-83] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Although considered to be generally safe, a number of beta-lactam antibiotics have been associated with epileptic seizures in humans. Furthermore, some beta-lactam antibiotics, including ceftriaxone, are used to evoke convulsions under experimental conditions. Recently it was demonstrated that ceftriaxone increased expression of the glutamate transporter (GLT1) and its biochemical and functional activity in the brain of rodents. GLT1 regulates extracellular concentrations of glutamate, an excitatory amino acid involved in the pathogenesis of seizures and epilepsy. Because of its rapid transfer of glutamate into neurons and adjacent glial cells, GLT1 diminishes glutamate toxicity. We investigated whether ceftriaxone (200 mg/kg body wt) administered intraperitoneally (ip) for 6 days could modify the convulsant effects of pentylenetetrazole (PTZ, 100 mg/kg ip) in inbred male BALBcAnNCR and C57 black (BL)/6 mice aged 4 and 12 weeks. Ceftriaxone pretreatment provided significant protective effects against PTZ-evoked generalized clonic convulsions (GCCs), generalized clonic-tonic convulsions (GCTCs), and convulsion-induced mortality during a period of 30 mins after PTZ administration. The incidence of GCCs, GCTCs, and death was statistically significantly lower for BALBcAnNCR mice of both ages, particularly younger mice. The latency time for each of the three parameters was significantly greater, with the exception of GCCs in adult mice. Protective effects of ceftriaxone were also noticed in adult C57BL/6 mice but not in prepubertal C57BL/6 mice. This is the first demonstration of anticonvulsant effects of ceftriaxone or any other beta-lactam antibiotic, which are not uniform across the mouse population. Our results provide new insight into the effects of ceftriaxone, which need further investigation.
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Affiliation(s)
- Ankica V Jelenkovic
- Institute for Biological Research Sinisa Stankovic, University of Belgrade, Bulevar Despota Stefana, 142, 11000 Belgrade, Serbia.
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24
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Corner MA. Spontaneous neuronal burst discharges as dependent and independent variables in the maturation of cerebral cortex tissue cultured in vitro: a review of activity-dependent studies in live 'model' systems for the development of intrinsically generated bioelectric slow-wave sleep patterns. ACTA ACUST UNITED AC 2008; 59:221-44. [PMID: 18722470 DOI: 10.1016/j.brainresrev.2008.08.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Revised: 08/01/2008] [Accepted: 08/05/2008] [Indexed: 10/21/2022]
Abstract
A survey is presented of recent experiments which utilize spontaneous neuronal spike trains as dependent and/or independent variables in developing cerebral cortex cultures when synaptic transmission is interfered with for varying periods of time. Special attention is given to current difficulties in selecting suitable preparations for carrying out biologically relevant developmental studies, and in applying spike-train analysis methods with sufficient resolution to detect activity-dependent age and treatment effects. A hierarchy of synchronized nested burst discharges which approximate early slow-wave sleep patterns in the intact organism is established as a stable basis for isolated cortex function. The complexity of reported long- and short-term homeostatic responses to experimental interference with synaptic transmission is reviewed, and the crucial role played by intrinsically generated bioelectric activity in the maturation of cortical networks is emphasized.
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Affiliation(s)
- Michael A Corner
- Netherlands Institute for Brain Research, Amsterdam, The Netherlands.
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25
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Glutamate transporters regulate lesion-induced plasticity in the developing somatosensory cortex. J Neurosci 2008; 28:4995-5006. [PMID: 18463253 DOI: 10.1523/jneurosci.0861-08.2008] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Glutamate transporters are involved in neural differentiation, neuronal survival, and synaptic transmission. In the present study, we examined glutamate transporter 1 (GLT1) expression in the neonatal somatosensory cortex of C57BL/6 mice, and pursued its role in somatosensory development by comparing barrel development between GLT1 knock-out and control mice. During the first few neonatal days, a critical period for barrels, GLT1 expression is strikingly upregulated in cortical astrocytes, whereas it was downregulated in neuronal elements to below the detection threshold. GLT1 knock-out neonates developed normally in terms of body growth, cortical histoarchitecture, barrel formation, and critical period termination. However, when row C whiskers were lesioned during the critical period, reduction of lesioned row C barrels and reciprocal expansion of intact row B/D barrels were both milder in GLT1 knock-out mice than in control littermates. Accordingly, the map plasticity index, calculated as (B + D)/2C, was significantly lowered in GLT1 knock-out mice. We also found that extracellular glutamate levels in the neonatal somatosensory cortex were significantly elevated in GLT1 knock-out mice. Diminished lesion-induced plasticity was further found in mutant mice lacking glutamate-aspartate transporter (GLAST), an astrocyte-specific glutamate transporter throughout development. Therefore, glutamate transporters regulate critical period plasticity by enhancing expansion of active barrels and shrinkage of inactive barrels. Because cortical contents of glutamate receptors and GLAST were unaltered in GLT1 knock-out mice, this action appears to be mediated, at least partly, by keeping the ambient glutamate level low. Considering an essential role of glutamate receptors in the formation of whisker-related thalamocortical synapse patterning, glutamate transporters thus facilitate their activity-dependent remodeling.
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26
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Stafstrom CE. Neurobiological mechanisms of developmental epilepsy: translating experimental findings into clinical application. Semin Pediatr Neurol 2007; 14:164-72. [PMID: 18070672 DOI: 10.1016/j.spen.2007.08.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although seizures are very common during early brain development, consequences of seizures during this age period are less severe than in the mature brain. Reasons for this discrepancy relate to both the sequential development of neural elements (ion channels, neurotransmitters, synapses, and circuits) and the effects of seizures on these ongoing processes at different ages. In this review, I critically discuss 2 recent experimental trends in developmental neurobiology that impact seizures and their consequences. First, the paradoxic excitatory effects of gamma-aminobutyric acid early in life are related to seizure susceptibility in this developmental period. Second, the plasticity of immature neuronal circuits and the effects of seizures on subsequent cognition and behavior as a function of age are considered. These topics are relevant to the pediatric neurologist when evaluating and treating a young child with seizures.
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Affiliation(s)
- Carl E Stafstrom
- Department of Neurology, Section of Pediatric Neurology, University of Wisconsin, Madison 53792, USA
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27
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Ben-Ari Y, Gaiarsa JL, Tyzio R, Khazipov R. GABA: a pioneer transmitter that excites immature neurons and generates primitive oscillations. Physiol Rev 2007; 87:1215-84. [PMID: 17928584 DOI: 10.1152/physrev.00017.2006] [Citation(s) in RCA: 892] [Impact Index Per Article: 52.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Developing networks follow common rules to shift from silent cells to coactive networks that operate via thousands of synapses. This review deals with some of these rules and in particular those concerning the crucial role of the neurotransmitter gamma-aminobuytric acid (GABA), which operates primarily via chloride-permeable GABA(A) receptor channels. In all developing animal species and brain structures investigated, neurons have a higher intracellular chloride concentration at an early stage leading to an efflux of chloride and excitatory actions of GABA in immature neurons. This triggers sodium spikes, activates voltage-gated calcium channels, and acts in synergy with NMDA channels by removing the voltage-dependent magnesium block. GABA signaling is also established before glutamatergic transmission, suggesting that GABA is the principal excitatory transmitter during early development. In fact, even before synapse formation, GABA signaling can modulate the cell cycle and migration. The consequence of these rules is that developing networks generate primitive patterns of network activity, notably the giant depolarizing potentials (GDPs), largely through the excitatory actions of GABA and its synergistic interactions with glutamate signaling. These early types of network activity are likely required for neurons to fire together and thus to "wire together" so that functional units within cortical networks are formed. In addition, depolarizing GABA has a strong impact on synaptic plasticity and pathological insults, notably seizures of the immature brain. In conclusion, it is suggested that an evolutionary preserved role for excitatory GABA in immature cells provides an important mechanism in the formation of synapses and activity in neuronal networks.
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Affiliation(s)
- Yehezkel Ben-Ari
- Insititut de Neurobiologie de la Méditerranée, Institut National de la Santé et de la Recherche Médicale U. 29, Marseille, France.
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28
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Sheldon AL, Robinson MB. The role of glutamate transporters in neurodegenerative diseases and potential opportunities for intervention. Neurochem Int 2007; 51:333-55. [PMID: 17517448 PMCID: PMC2075474 DOI: 10.1016/j.neuint.2007.03.012] [Citation(s) in RCA: 434] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Revised: 03/28/2007] [Accepted: 03/30/2007] [Indexed: 12/20/2022]
Abstract
Extracellular concentrations of the predominant excitatory neurotransmitter, glutamate, and related excitatory amino acids are maintained at relatively low levels to ensure an appropriate signal-to-noise ratio and to prevent excessive activation of glutamate receptors that can result in cell death. The latter phenomenon is known as 'excitotoxicity' and has been associated with a wide range of acute and chronic neurodegenerative disorders, as well as disorders that result in the loss of non-neural cells such as oligodendroglia in multiple sclerosis. Unfortunately clinical trials with glutamate receptor antagonists that would logically seem to prevent the effects of excessive receptor activation have been associated with untoward side effects or little clinical benefit. In the mammalian CNS, the extracellular concentrations of glutamate are controlled by two types of transporters; these include a family of Na(+)-dependent transporters and a cystine-glutamate exchange process, referred to as system X(c)(-). In this review, we will focus primarily on the Na(+)-dependent transporters. A brief introduction to glutamate as a neurotransmitter will be followed by an overview of the properties of these transporters, including a summary of the presumed physiologic mechanisms that regulate these transporters. Many studies have provided compelling evidence that impairing the function of these transporters can increase the sensitivity of tissue to deleterious effects of aberrant activation of glutamate receptors. Over the last decade, it has become clear that many neurodegenerative disorders are associated with a change in localization and/or expression of some of the subtypes of these transporters. This would suggest that therapies directed toward enhancing transporter expression might be beneficial. However, there is also evidence that glutamate transporters might increase the susceptibility of tissue to the consequences of insults that result in a collapse of the electrochemical gradients required for normal function such as stroke. In spite of the potential adverse effects of upregulation of glutamate transporters, there is recent evidence that upregulation of one of the glutamate transporters, GLT-1 (also called EAAT2), with beta-lactam antibiotics attenuates the damage observed in models of both acute and chronic neurodegenerative disorders. While it seems somewhat unlikely that antibiotics specifically target GLT-1 expression, these studies identify a potential strategy to limit excitotoxicity. If successful, this type of approach could have widespread utility given the large number of neurodegenerative diseases associated with decreases in transporter expression and excitotoxicity. However, given the massive effort directed at developing glutamate receptor agents during the 1990s and the relatively modest advances to date, one wonders if we will maintain the patience needed to carefully understand the glutamatergic system so that it will be successfully targeted in the future.
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Affiliation(s)
- Amanda L. Sheldon
- Department of Neuroscience, University of Pennsylvania, Philadelphia, PA. 19104-4318
- Departments of Pediatrics and Pharmacology, Children’s Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA. 19104-4318
| | - Michael B. Robinson
- Departments of Pediatrics and Pharmacology, Children’s Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA. 19104-4318
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29
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Magni DV, Oliveira MS, Furian AF, Fiorenza NG, Fighera MR, Ferreira J, Mello CF, Royes LFF. Creatine decreases convulsions and neurochemical alterations induced by glutaric acid in rats. Brain Res 2007; 1185:336-45. [PMID: 17950259 DOI: 10.1016/j.brainres.2007.09.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2007] [Revised: 09/11/2007] [Accepted: 09/12/2007] [Indexed: 10/22/2022]
Abstract
Glutaric acidemia type I (GA-I) is an inherited metabolic disease characterized by striatal degeneration, seizures, and accumulation of glutaric acid (GA). Considering that GA impairs energy metabolism and induces reactive species generation, we investigated whether the acute administration of creatine, an amino acid with antioxidant and ergogenic properties, protects against the seizures and neurochemical alterations (inhibition of Na(+),K(+)-ATPase and increased protein carbonylation) induced by the intrastriatal injection of GA (4 micromol/striatum). We also investigated whether creatine protected against the GA-induced inhibition of glutamate uptake in vitro. Creatine administration (300 mg/kg, p.o.) decreased seizures (evidenced by electrographic changes), protein carbonylation and Na(+),K(+)-ATPase inhibition induced by GA. However, creatine, at a dose capable of fully preventing GA-induced protein carbonylation (50 and 150 mg/kg, p.o.), did not prevent convulsions and Na(+),K(+)-ATPase inhibition, suggesting that the anticonvulsant activity of creatine in this experimental model is not related to its antioxidant action. Creatine also protected against the GA-induced inhibition of l-[(3)H]glutamate uptake in synaptosomes, suggesting that creatine may reduce the deleterious effects of GA by maintaining glutamate uptake in the synaptic cleft. Therefore, considering that creatine significantly attenuates the deleterious effects of GA assessed by behavioral and neurochemical measures, it is plausible to propose the use of this amino acid as an adjuvant therapy in the management of glutaric acidemia.
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Affiliation(s)
- Danieli Valnes Magni
- Centro de Ciências da Saúde, Laboratório de Psicofarmacologia e Neurotoxicidade, Departamento de Fisiologia, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil
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30
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Cattani AA, Bonfardin VD, Represa A, Ben-Ari Y, Aniksztejn L. Generation of slow network oscillations in the developing rat hippocampus after blockade of glutamate uptake. J Neurophysiol 2007; 98:2324-36. [PMID: 17634340 DOI: 10.1152/jn.00378.2007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cell-surface glutamate transporters are essential for the proper function of early cortical networks because their dysfunction induces seizures in the newborn rat in vivo. We have now analyzed the consequences of their inhibition by DL-TBOA on the activity of the developing CA1 rat hippocampal network in vitro. DL-TBOA generated a pattern of recurrent depolarization with an onset and decay of several seconds' duration in interneurons and pyramidal cells. These slow network oscillations (SNOs) were mostly mediated by gamma-aminobutyric acid (GABA) in pyramidal cells and by GABA and N-methyl-D-aspartate (NMDA) receptors in interneurons. However, in both cell types SNOs were blocked by NMDA receptor antagonists, suggesting that their generation requires a glutamatergic drive. Moreover, in interneurons, SNOs were still generated after the blockade of NMDA-mediated synaptic currents with MK-801, suggesting that SNOs are expressed by the activation of extrasynaptic NMDA receptors. Long-lasting bath application of glutamate or NMDA failed to induce SNOs, indicating that they are generated by periodic but not sustained activation of NMDA receptors. In addition, SNOs were observed in interneurons recorded in slices with or without the strata pyramidale and oriens, suggesting that the glutamatergic drive may originate from the radiatum and pyramidale strata. We propose that in the absence of an efficient transport of glutamate, the transmitter diffuses in the extracellular space to activate extrasynaptic NMDA receptors preferentially present on interneurons that in turn activate other interneurons and pyramidal cells. This periodic neuronal coactivation may contribute to the generation of seizures when glutamate transport dysfunction is present.
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Affiliation(s)
- Adriano Augusto Cattani
- Institut de Neurobiologie de la Méditerranée (INMED), Institut National de la Santé et de la Recherche Médicale U29 (INSERMU29), Université de la Méditerranée, Marseille, France
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