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Kang SK, Markowitz GJ, Kim ST, Johnston MV, Kadam SD. Age- and sex-dependent susceptibility to phenobarbital-resistant neonatal seizures: role of chloride co-transporters. Front Cell Neurosci 2015; 9:173. [PMID: 26029047 PMCID: PMC4429249 DOI: 10.3389/fncel.2015.00173] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 04/18/2015] [Indexed: 11/13/2022] Open
Abstract
Ischemia in the immature brain is an important cause of neonatal seizures. Temporal evolution of acquired neonatal seizures and their response to anticonvulsants are of great interest, given the unreliability of the clinical correlates and poor efficacy of first-line anti-seizure drugs. The expression and function of the electroneutral chloride co-transporters KCC2 and NKCC1 influence the anti-seizure efficacy of GABAA-agonists. To investigate ischemia-induced seizure susceptibility and efficacy of the GABAA-agonist phenobarbital (PB), with NKCC1 antagonist bumetanide (BTN) as an adjunct treatment, we utilized permanent unilateral carotid-ligation to produce acute ischemic-seizures in post-natal day 7, 10, and 12 CD1 mice. Immediate post-ligation video-electroencephalograms (EEGs) quantitatively evaluated baseline and post-treatment seizure burdens. Brains were examined for stroke-injury and western blot analyses to evaluate the expression of KCC2 and NKCC1. Severity of acute ischemic seizures post-ligation was highest at P7. PB was an efficacious anti-seizure agent at P10 and P12, but not at P7. BTN failed as an adjunct, at all ages tested and significantly blunted PB-efficacy at P10. Significant acute post-ischemic downregulation of KCC2 was detected at all ages. At P7, males displayed higher age-dependent seizure susceptibility, associated with a significant developmental lag in their KCC2 expression. This study established a novel neonatal mouse model of PB-resistant seizures that demonstrates age/sex-dependent susceptibility. The age-dependent profile of KCC2 expression and its post-insult downregulation may underlie the PB-resistance reported in this model. Blocking NKCC1 with low-dose BTN following PB treatment failed to improve PB-efficacy.
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Affiliation(s)
- Seok Kyu Kang
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger Baltimore, MD, USA
| | - Geoffrey J Markowitz
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger Baltimore, MD, USA
| | - Shin Tae Kim
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger Baltimore, MD, USA
| | - Michael V Johnston
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger Baltimore, MD, USA ; Department of Neurology, Johns Hopkins University School of Medicine Baltimore, MD, USA ; Department of Pediatrics, Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Shilpa D Kadam
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger Baltimore, MD, USA ; Department of Neurology, Johns Hopkins University School of Medicine Baltimore, MD, USA
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152
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Fu P, Tang R, Yu Z, Huang S, Xie M, Luo X, Wang W. Bumetanide-induced NKCC1 inhibition attenuates oxygen-glucose deprivation-induced decrease in proliferative activity and cell cycle progression arrest in cultured OPCs via p-38 MAPKs. Brain Res 2015; 1613:110-9. [PMID: 25881895 DOI: 10.1016/j.brainres.2015.04.006] [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] [Received: 02/23/2015] [Revised: 03/23/2015] [Accepted: 04/04/2015] [Indexed: 11/28/2022]
Abstract
The Na-K-Cl co-transporter 1 (NKCC1; a member of the cation-chloride co-transporter family) mediates the coupled movement of Na(+) and/or K(+) with Cl(-) across the plasma membrane of cells (Haas and Forbush, 2000, Annu. Rev. Physiol., 62, 515-534; Russell, 2000, Physiol. Rev., 80, 211-276). Although it acts as an important regulator of cell volume, secretion, and modulator of cell apoptosis and proliferation (Chen et al., 2005, J. Cereb. Blood Flow Metab., 25, 54-66; Kahle et al., 2008, Nat. Clin. Pract. Neurol., 4, 490-503; Kidokoro et al., 2014, Am. J. Physiol. Ren. Physiol., 306, F1155-F1160; Wang et al., 2011, Cell. Physiol. Biochem., 28, 703-714), NKCC1׳s effects on oligodendrocyte precursor cells (OPCs) have not been characterized. The aim of this study was to investigate whether and to what extent inhibition of NKCC1 alters oxygen glucose deprivation (OGD)-induced cell cycle progression. In the present study, we demonstrated that inhibition of NKCC1 with bumetanide attenuates the decrease in OGD-induced DNA synthesis in cultured OPCs. Western blots showed that NKCC1 inhibition led to an increased expression of cyclin D1, CDK 4, and cyclin E in OGD-treated cells. Furthermore, our results showed bumetanide attenuated the decrease in OGD-induced proliferation and arrest of cell cycle progression via the P-38 MAPK signaling cascade. Thus, NKCC1 plays important roles in the proliferation of OPCs under OGD-induced stress.
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Affiliation(s)
- Peicai Fu
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
| | - Ronghua Tang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
| | - Zhiyuan Yu
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China; Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan 430030, PR China
| | - Shanshan Huang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
| | - Minjie Xie
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China; Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan 430030, PR China
| | - Xiang Luo
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
| | - Wei Wang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China; Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan 430030, PR China.
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153
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Blaesse P, Schmidt T. K-Cl cotransporter KCC2--a moonlighting protein in excitatory and inhibitory synapse development and function. Pflugers Arch 2015; 467:615-24. [PMID: 24909111 DOI: 10.1007/s00424-014-1547-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 05/23/2014] [Accepted: 05/26/2014] [Indexed: 01/28/2023]
Abstract
The K-Cl cotransporter KCC2 has two entirely independent biological actions as either an ion transporter or a structural protein orchestrating the organization of the cytoskeleton in neuronal structures. The K-Cl cotransport by KCC2 is central for hyperpolarizing inhibitory signaling, which is based on chloride currents mediated by γ-aminobutyric acid (GABA)- or glycine-gated receptor channels. In contrast, the structural role of KCC2 seems to be crucially involved in the maturation and regulation of excitatory glutamatergic synapses. This dual role at GABAergic/glycinergic and glutamatergic synapses makes KCC2 a key molecule in the regulation of inhibitory and excitatory signaling. Therefore, KCC2 is most likely involved in the synchronization of the two types of activity during network formation in the immature system and a similar synchronizing role might also be important under physiological and pathological conditions in mature neuronal networks. In this review, we explore new findings on the regulation of KCC2 by protease-mediated cleavage and on the structural role of KCC2 in spine morphogenesis and glutamate receptor clustering. We then discuss the implications of the putative interaction between the independent functions of the transporter and overlapping regulatory mechanisms in a neurophysiological context. In addition, we look at the multifunctional properties of KCC2 in the light of evolution and propose that KCC2 belongs to the group of moonlighting (multifunctional) proteins.
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Affiliation(s)
- Peter Blaesse
- Institute of Physiology I (Neurophysiology), Westfälische Wilhelms-University Münster, Robert-Koch-Strasse 27a, 48149, Münster, Germany,
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154
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Jiang H, Jiang W, Zou J, Wang B, Yu M, Pan Y, Lin Y, Mao Y, Wang Y. The GluN2B subunit of N-methy-D-asparate receptor regulates the radial migration of cortical neurons in vivo. Brain Res 2015; 1610:20-32. [PMID: 25838242 DOI: 10.1016/j.brainres.2015.03.031] [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] [Received: 10/05/2014] [Revised: 02/01/2015] [Accepted: 03/09/2015] [Indexed: 10/23/2022]
Abstract
The formation of layered structure of the mammalian neocortex requires a fine organized migration of post-mitotic neurons during early development. However, whether the radial migration is regulated by NMDA receptor and specific subunits remains contradictory and unknown. Here, we reported that in the developing rat cortex, migration of presumptive layer II/III neurons to their deserved destination was regulated by NMDA receptors with GluN2B but not GluN2A subunit. Using in utero electroporation of small interference RNA (siRNA) of distinct NMDA receptor subunits, we found that knockdown GluN1 and GluN2B subunits dramatically delayed the neuronal migration to proper layer II/III, while improperly stayed at lower layers or even the germinal regions, without changing the cell fate. In contrast, knockdown of GluN2A subunit did not impair the neuronal migration. Additionally, the ecotopic neurons by GluN2B RNAi developed to well dendritic differentiation, while the ones by GluN1 RNAi still kept morphology of migrating neurons. Therefore, GluN2B subunit of NMDA receptor plays an essential role in regulating proper neuronal migration and cortical lamination.
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Affiliation(s)
- Huayu Jiang
- Neurology Department, Shanghai Tenth People׳s Hospital, Tongji University, School of Medicine, Shanghai 200072, China
| | - Weiqing Jiang
- Department of Neurology, School of Medicine, Renji Hospital, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Jing Zou
- Department of Neurology, School of Medicine, Renji Hospital, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Baoxiang Wang
- Department of Neurology, School of Medicine, Renji Hospital, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Mingrong Yu
- Neurology Department, Qiqihar Hospital, Heilongjiang Agriculture Reclamation Bureau, Qiqihar 161005, China
| | - Yuanmei Pan
- Department of Neurology, School of Medicine, Renji Hospital, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Yan Lin
- Department of Neurology, School of Medicine, Renji Hospital, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Yingwei Mao
- Department of Biology, 214 Life Sciences Building Penn State University, University Park, PA 16802, USA
| | - Yonggang Wang
- Neurology Department, Shanghai Tenth People׳s Hospital, Tongji University, School of Medicine, Shanghai 200072, China.
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155
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Deidda G, Parrini M, Naskar S, Bozarth IF, Contestabile A, Cancedda L. Reversing excitatory GABAAR signaling restores synaptic plasticity and memory in a mouse model of Down syndrome. Nat Med 2015; 21:318-26. [PMID: 25774849 DOI: 10.1038/nm.3827] [Citation(s) in RCA: 185] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 02/19/2015] [Indexed: 12/12/2022]
Abstract
Down syndrome (DS) is the most frequent genetic cause of intellectual disability, and altered GABAergic transmission through Cl(-)-permeable GABAA receptors (GABAARs) contributes considerably to learning and memory deficits in DS mouse models. However, the efficacy of GABAergic transmission has never been directly assessed in DS. Here GABAAR signaling was found to be excitatory rather than inhibitory, and the reversal potential for GABAAR-driven Cl(-) currents (ECl) was shifted toward more positive potentials in the hippocampi of adult DS mice. Accordingly, hippocampal expression of the cation Cl(-) cotransporter NKCC1 was increased in both trisomic mice and individuals with DS. Notably, NKCC1 inhibition by the FDA-approved drug bumetanide restored ECl, synaptic plasticity and hippocampus-dependent memory in adult DS mice. Our findings demonstrate that GABA is excitatory in adult DS mice and identify a new therapeutic approach for the potential rescue of cognitive disabilities in individuals with DS.
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Affiliation(s)
- Gabriele Deidda
- Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Martina Parrini
- Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Shovan Naskar
- Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Ignacio F Bozarth
- Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Andrea Contestabile
- Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Laura Cancedda
- Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
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156
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Pressler RM, Boylan GB, Marlow N, Blennow M, Chiron C, Cross JH, de Vries LS, Hallberg B, Hellström-Westas L, Jullien V, Livingstone V, Mangum B, Murphy B, Murray D, Pons G, Rennie J, Swarte R, Toet MC, Vanhatalo S, Zohar S. Bumetanide for the treatment of seizures in newborn babies with hypoxic ischaemic encephalopathy (NEMO): an open-label, dose finding, and feasibility phase 1/2 trial. Lancet Neurol 2015; 14:469-77. [PMID: 25765333 DOI: 10.1016/s1474-4422(14)70303-5] [Citation(s) in RCA: 178] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND Preclinical data suggest that the loop-diuretic bumetanide might be an effective treatment for neonatal seizures. We aimed to assess dose and feasibility of intravenous bumetanide as an add-on to phenobarbital for treatment of neonatal seizures. METHODS In this open-label, dose finding, and feasibility phase 1/2 trial, we recruited full-term infants younger than 48 h who had hypoxic ischaemic encephalopathy and electrographic seizures not responding to a loading-dose of phenobarbital from eight neonatal intensive care units across Europe. Newborn babies were allocated to receive an additional dose of phenobarbital and one of four bumetanide dose levels by use of a bivariate Bayesian sequential dose-escalation design to assess safety and efficacy. We assessed adverse events, pharmacokinetics, and seizure burden during 48 h continuous electroencephalogram (EEG) monitoring. The primary efficacy endpoint was a reduction in electrographic seizure burden of more than 80% without the need for rescue antiepileptic drugs in more than 50% of infants. The trial is registered with ClinicalTrials.gov, number NCT01434225. FINDINGS Between Sept 1, 2011, and Sept 28, 2013, we screened 30 infants who had electrographic seizures due to hypoxic ischaemic encephalopathy. 14 of these infants (10 boys) were included in the study (dose allocation: 0·05 mg/kg, n=4; 0·1 mg/kg, n=3; 0·2 mg/kg, n=6; 0·3 mg/kg, n=1). All babies received at least one dose of bumetanide with the second dose of phenobarbital; three were withdrawn for reasons unrelated to bumetanide, and one because of dehydration. All but one infant also received aminoglycosides. Five infants met EEG criteria for seizure reduction (one on 0·05 mg/kg, one on 0·1 mg/kg and three on 0·2 mg/kg), and only two did not need rescue antiepileptic drugs (ie, met rescue criteria; one on 0·05 mg/kg and one on 0·3 mg/kg). We recorded no short-term dose-limiting toxic effects, but three of 11 surviving infants had hearing impairment confirmed on auditory testing between 17 and 108 days of age. The most common non-serious adverse reactions were moderate dehydration in one, mild hypotension in seven, and mild to moderate electrolyte disturbances in 12 infants. The trial was stopped early because of serious adverse reactions and limited evidence for seizure reduction. INTERPRETATION Our findings suggest that bumetanide as an add-on to phenobarbital does not improve seizure control in newborn infants who have hypoxic ischaemic encephalopathy and might increase the risk of hearing loss, highlighting the risks associated with the off-label use of drugs in newborn infants before safety assessment in controlled trials. FUNDING European Community's Seventh Framework Programme.
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Affiliation(s)
- Ronit M Pressler
- Section of Clinical Neurosciences and Neonatal Unit, University College London, London, UK.
| | - Geraldine B Boylan
- Irish Centre for Fetal and Neonatal Translational Research, University College Cork, Cork, Ireland
| | - Neil Marlow
- Section of Clinical Neurosciences and Neonatal Unit, University College London, London, UK
| | - Mats Blennow
- Neonatology, Karolinska University Hospital, Stockholm, Sweden
| | - Catherine Chiron
- Inserm U1129, Paris, France; University Paris Descartes, Paris, France
| | - J Helen Cross
- Section of Clinical Neurosciences and Neonatal Unit, University College London, London, UK
| | - Linda S de Vries
- Neonatology, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Boubou Hallberg
- Neonatology, Karolinska University Hospital, Stockholm, Sweden
| | | | - Vincent Jullien
- Inserm U1129, Paris, France; University Paris Descartes, Paris, France
| | - Vicki Livingstone
- Irish Centre for Fetal and Neonatal Translational Research, University College Cork, Cork, Ireland
| | - Barry Mangum
- Duke Clinical Research Institute, Duke University, NC, USA
| | - Brendan Murphy
- Irish Centre for Fetal and Neonatal Translational Research, University College Cork, Cork, Ireland
| | - Deirdre Murray
- Irish Centre for Fetal and Neonatal Translational Research, University College Cork, Cork, Ireland
| | - Gerard Pons
- Inserm U1129, Paris, France; University Paris Descartes, Paris, France
| | - Janet Rennie
- Section of Clinical Neurosciences and Neonatal Unit, University College London, London, UK
| | - Renate Swarte
- Neonatology, Erasmus University Medical Centre Rotterdam, Rotterdam, Netherlands
| | - Mona C Toet
- Neonatology, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Sampsa Vanhatalo
- Children's Clinical Neurophysiology, Children's Hospital, Helsinki University Central Hospital, Helsinki, Finland
| | - Sarah Zohar
- Department for Statistics, Inserm, Inserm U1138, Paris, France
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157
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Bialer M, Johannessen SI, Levy RH, Perucca E, Tomson T, White HS. Progress report on new antiepileptic drugs: A summary of the Twelfth Eilat Conference (EILAT XII). Epilepsy Res 2015; 111:85-141. [PMID: 25769377 DOI: 10.1016/j.eplepsyres.2015.01.001] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/09/2015] [Indexed: 10/24/2022]
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158
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Coates TA, Woolnough O, Masters JM, Asadova G, Chandrakumar C, Baker MD. Acute temperature sensitivity in optic nerve axons explained by an electrogenic membrane potential. Pflugers Arch 2015; 467:2337-49. [DOI: 10.1007/s00424-015-1696-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 02/17/2015] [Accepted: 02/17/2015] [Indexed: 02/05/2023]
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159
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Silbert BI, Heaton AE, Cash RFH, James I, Dunne JW, Lawn ND, Silbert PL, Mastaglia FL, Thickbroom GW. Evidence for an excitatory GABAA response in human motor cortex in idiopathic generalised epilepsy. Seizure 2015; 26:36-42. [PMID: 25799900 DOI: 10.1016/j.seizure.2015.01.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/28/2014] [Accepted: 01/23/2015] [Indexed: 12/24/2022] Open
Abstract
PURPOSE Impaired GABAergic inhibition has been implicated in the pathophysiology of epilepsy. The possibility of a paradoxical excitatory effect of GABA in epilepsy has been suggested, but has not been investigated in vivo. We investigated pre- and post-synaptic GABAergic mechanisms in patients with idiopathic generalised epilepsy (IGE). METHOD In 10 patients and 12 control subjects we explored short- and long-interval intracortical inhibition (SICI, LICI; post-synaptic GABAA and GABAB-mediated respectively) and long-interval intracortical facilitation (LICF; pre-synaptic disinhibition) using transcranial magnetic stimulation. RESULTS While post-synaptic GABAB-mediated inhibition was unchanged in IGE (p=0.09), LICF was reduced compared to controls (controls: 141±17% of baseline; untreated patients: 107±12%, p=0.2; treated patients: 79±10%, p=0.003). GABAA-mediated inhibition was reduced in untreated patients (response amplitude 56±4% of baseline vs. 26±6% in controls, p=0.004) and normalised with treatment (37±12%, p=0.5 vs. controls). When measured during LICI, GABAA-mediated inhibition became excitatory in untreated IGE (response amplitude 120±10% of baseline, p=0.017), but not in treated patients. CONCLUSION Pre- and post-synaptic GABA-mediated inhibitory mechanisms are altered in IGE. The findings lend in vivo support to evidence from experimental models and in vitro studies of human epileptic brain tissue that GABA may have a paradoxical excitatory role in ictogenesis.
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Affiliation(s)
- Benjamin I Silbert
- Western Australian Neuroscience Research Institute, University of Western Australia, 4th Floor, A Block, QEII Medical Centre, Verdun Street, Nedlands, Perth, Western Australia 6009, Australia
| | - Alexandra E Heaton
- Western Australian Neuroscience Research Institute, University of Western Australia, 4th Floor, A Block, QEII Medical Centre, Verdun Street, Nedlands, Perth, Western Australia 6009, Australia
| | - Robin F H Cash
- Western Australian Neuroscience Research Institute, University of Western Australia, 4th Floor, A Block, QEII Medical Centre, Verdun Street, Nedlands, Perth, Western Australia 6009, Australia; Division of Brain, Imaging and Behaviour - Systems Neuroscience, Toronto Western Research Institute, University Health Network, 339 Bathurst Street, MP14-324, Toronto, Ontario M5T 2S8, Canada
| | - Ian James
- Centre for Clinical Immunology and Biomedical Statistics, Institute for Immunology and Infectious Diseases, Murdoch University, Building 390, Discovery Way, Murdoch, Perth, Western Australia 6150, Australia
| | - John W Dunne
- Department of Neurology, Royal Perth Hospital, Level 8, A Block, GPO Box X2213, Perth, Western Australia 6001, Australia
| | - Nicholas D Lawn
- Department of Neurology, Royal Perth Hospital, Level 8, A Block, GPO Box X2213, Perth, Western Australia 6001, Australia
| | - Peter L Silbert
- Department of Neurology, Royal Perth Hospital, Level 8, A Block, GPO Box X2213, Perth, Western Australia 6001, Australia
| | - Frank L Mastaglia
- Western Australian Neuroscience Research Institute, University of Western Australia, 4th Floor, A Block, QEII Medical Centre, Verdun Street, Nedlands, Perth, Western Australia 6009, Australia
| | - Gary W Thickbroom
- Western Australian Neuroscience Research Institute, University of Western Australia, 4th Floor, A Block, QEII Medical Centre, Verdun Street, Nedlands, Perth, Western Australia 6009, Australia.
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160
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Orlov SN, Koltsova SV, Kapilevich LV, Dulin NO, Gusakova SV. Cation-chloride cotransporters: Regulation, physiological significance, and role in pathogenesis of arterial hypertension. BIOCHEMISTRY (MOSCOW) 2015; 79:1546-61. [DOI: 10.1134/s0006297914130070] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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161
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Puskarjov M, Ahmad F, Khirug S, Sivakumaran S, Kaila K, Blaesse P. BDNF is required for seizure-induced but not developmental up-regulation of KCC2 in the neonatal hippocampus. Neuropharmacology 2015; 88:103-9. [PMID: 25229715 DOI: 10.1016/j.neuropharm.2014.09.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 09/01/2014] [Accepted: 09/04/2014] [Indexed: 01/21/2023]
Abstract
A robust increase in the functional expression of the neuronal K-Cl cotransporter KCC2 during CNS development is necessary for the emergence of hyperpolarizing ionotropic GABAergic transmission. BDNF-TrkB signaling has been implicated in the developmental up-regulation of KCC2 and, in mature animals, in fast activity-dependent down-regulation of KCC2 function following seizures and trauma. In contrast to the decrease in KCC2 expression observed in the adult hippocampus following trauma, seizures in the neonate trigger a TrkB-dependent up-regulation of neuronal Cl(-) extrusion capacity associated with enhanced surface expression of KCC2. Here, we show that this effect is transient, and impaired in the hippocampus of Bdnf(-/-) mice. Notably, however, a complete absence of BDNF does not compromise the increase in KCC2 protein or K-Cl transport functionality during neuronal development. Furthermore, we present data indicating that the functional up-regulation of KCC2 by neonatal seizures is temporally limited by calpain activity.
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Affiliation(s)
- Martin Puskarjov
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Faraz Ahmad
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Stanislav Khirug
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Sudhir Sivakumaran
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Kai Kaila
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Peter Blaesse
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland.
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162
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MacKenzie G, Maguire J. Chronic stress shifts the GABA reversal potential in the hippocampus and increases seizure susceptibility. Epilepsy Res 2015; 109:13-27. [PMID: 25524838 PMCID: PMC4272449 DOI: 10.1016/j.eplepsyres.2014.10.003] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 09/16/2014] [Accepted: 10/01/2014] [Indexed: 10/24/2022]
Abstract
The most commonly reported precipitating factor for seizures is stress. However, the underlying mechanisms whereby stress triggers seizures are not yet fully understood. Here we demonstrate a potential mechanism underlying changes in neuronal excitability in the hippocampus following chronic stress, involving a shift in the reversal potential for GABA (EGABA) associated with a dephosphorylation of the potassium chloride co-transporter, KCC2. Mice subjected to chronic restraint stress (30min/day for 14 consecutive days) exhibit an increase in serum corticosterone levels which is associated with increased susceptibility to seizures induced with kainic acid (20mg/kg). Following chronic stress, but not acute stress, we observe a dephosphorylation of KCC2 residue S940, which regulates KCC2 cell surface expression and function, in the hippocampus. To determine the impact of alterations in KCC2 expression following chronic stress, we performed gramicidin perforated patch recordings to measure changes in EGABA and neuronal excitability of principal hippocampal neurons. We observe a depolarizing shift in EGABA in hippocampal CA1 pyramidal neurons after chronic stress. In addition, there is an increase in the intrinsic excitability of CA1 pyramidal neurons, evident by a shift in the input-output curve which could be reversed with the NKCC1 inhibitor, bumetanide. These data uncover a potential mechanism involving chronic stress-induced plasticity in chloride homeostasis which may contribute to stress-induced seizure susceptibility.
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Affiliation(s)
- Georgina MacKenzie
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Jamie Maguire
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA.
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163
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Fritschy JM. Significance of GABAA Receptor Heterogeneity. DIVERSITY AND FUNCTIONS OF GABA RECEPTORS: A TRIBUTE TO HANNS MÖHLER, PART B 2015; 73:13-39. [DOI: 10.1016/bs.apha.2014.11.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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164
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Endocrine and neurobehavioral abnormalities induced by propofol administered to neonatal rats. Anesthesiology 2014; 121:1010-7. [PMID: 24992523 DOI: 10.1097/aln.0000000000000366] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND The authors studied whether neonatal propofol anesthesia affects development of the endocrine and neural systems. METHODS Sprague-Dawley rats were anesthetized using intraperitoneal propofol for 5 h on postnatal days (P) 4, 5, or 6. Pups that received either saline or intralipid, but not those in the negative control groups, were also maternally separated for 5 h. Serum levels of corticosterone were measured immediately after anesthesia and in adulthood after prepulse inhibition of acoustic startle testing (≥P80), followed by measurement of hippocampal neuronal activity. RESULTS Propofol acutely increased corticosterone levels to 146.6 ± 23.5 ng/ml (n = 6) versus 16.4 ± 3.5 ng/ml (n = 6) and 18.4 ± 3.2 ng/ml (n = 6) in saline- and intralipd-treated pups, respectively. In adulthood, the propofol group exhibited exacerbated endocrine responses to stress in a form of increased corticosterone levels (1,171.58 ± 149.17 ng/ml [n = 15] vs. 370.02 ± 36.01 ng/ml [n = 10] in the saline group). The propofol group had increased the frequency of miniature inhibitory postsynaptic currents in CA1 neurons of male and female rats, but reduced prepulse inhibition of startle was detected only in males. The Na-K-2Cl cotransporter inhibitor bumetanide, administered to pups before propofol injection, alleviated long-term endocrine and prepulse inhibition abnormalities. Exogenous corticosterone, administered to naive pups, induced synaptic and endocrine but not prepulse inhibition effects, similar to those of propofol. CONCLUSION Propofol-caused acute increases in corticosterone levels and γ-aminobutyric acid type A receptor-mediated excitation at the time of anesthesia may play mechanistic roles in development of exacerbated endocrine responses to stress and neurobehavioral abnormalities.
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165
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Donovan MD, O'Brien FE, Boylan GB, Cryan JF, Griffin BT. The effect of organic anion transporter 3 inhibitor probenecid on bumetanide levels in the brain: an integrated in vivo microdialysis study in the rat. J Pharm Pharmacol 2014; 67:501-10. [DOI: 10.1111/jphp.12341] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Accepted: 09/28/2014] [Indexed: 01/29/2023]
Abstract
Abstract
Objectives
Recent data highlight the potential of bumetanide as a treatment for neonatal seizures and autism, as it facilitates the excitatory to inhibitory switch in gamma-aminobutyric acid signalling. This study examines the extent of blood-brain barrier (BBB) permeation of bumetanide, a key determinant of the efficacy of centrally acting drugs. Furthermore, the impact of efflux transporter organic anion transporter 3 (oat3) inhibition on bumetanide pharmacokinetics was investigated.
Methods
Bumetanide levels in extracellular fluid (ECF) and plasma in the presence and absence of oat3 inhibitor probenecid were monitored using integrated microdialysis.
Key findings
Following a bumetanide bolus/continuous infusion of 10 mg/kg and 6 mg/kg/h, bumetanide was detected in hippocampal ECF at the estimated concentration of 131 ± 55 ng/ml. Plasma bumetanide levels were ∼20 mg/l at steady state. Coadministration of probenecid resulted in an increase in bumetanide levels in both ECF and plasma, indicating that oat3 inhibition influences the pharmacokinetics of bumetanide primarily in the periphery.
Conclusion
Although bumetanide reached detectable levels in hippocampal ECF, bumetanide concentration in ECF was low relative to systemic concentration. Oat3 inhibition by probenecid resulted in increased bumetanide concentrations in brain and plasma. As an acute treatment in neonatal seizures, the bumetanide/probenecid combination may hold therapeutic potential.
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Affiliation(s)
- Maria D Donovan
- Pharmacodelivery Group, University College Cork, Cork, Ireland
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Fionn E O'Brien
- Pharmacodelivery Group, University College Cork, Cork, Ireland
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Geraldine B Boylan
- Department of Paediatrics and Child Health, University College Cork, Cork, Ireland
- Irish Centre for Fetal and Neonatal Translational Research, University College Cork, Cork, Ireland
| | - John F Cryan
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
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166
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Khazipov R, Valeeva G, Khalilov I. Depolarizing GABA and developmental epilepsies. CNS Neurosci Ther 2014; 21:83-91. [PMID: 25438879 DOI: 10.1111/cns.12353] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 10/14/2014] [Accepted: 10/20/2014] [Indexed: 12/22/2022] Open
Abstract
Early in development, GABA, which is the main inhibitory neurotransmitter in adult brain, depolarizes immature neurons and exerts dual--excitatory and shunting/inhibitory--effects in the developing neuronal networks. The present review discusses some general questions, including the properties of excitation at depolarizing GABAergic synapse and shunting inhibition by depolarizing GABA; technical issues in exploration of depolarizing GABA using various techniques and preparations, including the developmental aspects of traumatic injury and what is known (or rather unknown) on the actions of GABA in vivo; complex roles of depolarizing GABA in developmental epilepsies, including a contribution of depolarizing GABA to enhanced excitability in the immature networks, caused by repetitive seizures accumulation of intracellular chloride concentration that increases excitatory GABA power and its synchronizing proconvulsive effects, and correction of chloride homeostasis as a potential strategy to treat neonatal seizures.
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Affiliation(s)
- Roustem Khazipov
- INMED-INSERM U901, Marseille, France; Aix-Marseille University, Marseille, France; Laboratory of Neurobiology, Kazan Federal University, Kazan, Russia
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167
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In vivo effects of bumetanide at brain concentrations incompatible with NKCC1 inhibition on newborn DGC structure and spontaneous EEG seizures following hypoxia-induced neonatal seizures. Neuroscience 2014; 286:203-15. [PMID: 25463517 DOI: 10.1016/j.neuroscience.2014.11.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 11/17/2014] [Accepted: 11/18/2014] [Indexed: 12/21/2022]
Abstract
Neonatal seizures caused by perinatal asphyxia and hypoxic-ischemic encephalopathy can be refractory to conventional anticonvulsants. This may be due to the depolarizing effects of gamma-aminobutyric acid (GABA) achieved by the activity of the Na(+)-K(+)-2Cl(-) cotransporter (NKCC1). The aim of this study is to evaluate the long-term effects of bumetanide, a NKCC1 inhibitor, on hippocampal neurogenesis and seizure susceptibility in hypoxia-induced neonatal seizure model. Wistar rats were subjected to hypoxia-induced neonatal seizures at postnatal day 10 (P10). Following acute seizures, the rats were treated with intraperitoneal injection (i.p.) of bumetanide at a dose of 0.5mg/kg for 3 weeks. In later adulthood, hypoxia-induced seizures increased the number of newborn dentate gyrus cells (DGCs), promoted mossy fiber sprouting (MFS) and reduced the apical dendritic complexity of newborn DGCs 1 month after the insults. In addition, these seizures resulted in long-lasting consequences, such as spontaneous electroencephalography (EEG) seizures, though spatial learning impairments were not seen. Bumetanide treatments significantly enhanced cell proliferation and dendritic development of newborn DGCs after neonatal seizures, accompanied by the decreased seizure activity. However, systemic administration of bumetanide resulted in much lower brain concentrations, and was incompatible with NKCC1 inhibition in blood-brain barrier (BBB)-protected brain tissue. Our results suggested that bumetanide might have long-term effects in suppressing seizure activity, and altering the neurogenesis after neonatal seizures. These effects of bumetanide may be mediated by the targets outside the BBB-protected central nerve system (CNS) or CNS-located target(s) other than NKCC1.
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168
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Töllner K, Brandt C, Römermann K, Löscher W. The organic anion transport inhibitor probenecid increases brain concentrations of the NKCC1 inhibitor bumetanide. Eur J Pharmacol 2014; 746:167-73. [PMID: 25449033 DOI: 10.1016/j.ejphar.2014.11.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 10/22/2014] [Accepted: 11/09/2014] [Indexed: 12/14/2022]
Abstract
Bumetanide is increasingly being used for experimental treatment of brain disorders, including neonatal seizures, epilepsy, and autism, because the neuronal Na-K-Cl cotransporter NKCC1, which is inhibited by bumetanide, is implicated in the pathophysiology of such disorders. However, use of bumetanide for treatment of brain disorders is associated with problems, including poor brain penetration and systemic adverse effects such as diuresis, hypokalemic alkalosis, and hearing loss. The poor brain penetration is thought to be related to its high ionization rate and plasma protein binding, which restrict brain entry by passive diffusion, but more recently brain efflux transporters have been involved, too. Multidrug resistance protein 4 (MRP4), organic anion transporter 3 (OAT3) and organic anion transporting polypeptide 2 (OATP2) were suggested to mediate bumetanide brain efflux, but direct proof is lacking. Because MRP4, OAT3, and OATP2 can be inhibited by probenecid, we studied whether this drug alters brain levels of bumetanide in mice. Probenecid (50 mg/kg) significantly increased brain levels of bumetanide up to 3-fold; however, it also increased its plasma levels, so that the brain:plasma ratio (~0.015-0.02) was not altered. Probenecid markedly increased the plasma half-life of bumetanide, indicating reduced elimination of bumetanide most likely by inhibition of OAT-mediated transport of bumetanide in the kidney. However, the diuretic activity of bumetanide was not reduced by probenecid. In conclusion, our study demonstrates that the clinically available drug probenecid can be used to increase brain levels of bumetanide and decrease its elimination, which could have therapeutic potential in the treatment of brain disorders.
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Affiliation(s)
- Kathrin Töllner
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany
| | - Claudia Brandt
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany
| | - Kerstin Römermann
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany
| | - Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany.
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169
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Töllner K, Brandt C, Erker T, Löscher W. Bumetanide is not capable of terminating status epilepticus but enhances phenobarbital efficacy in different rat models. Eur J Pharmacol 2014; 746:78-88. [PMID: 25445051 DOI: 10.1016/j.ejphar.2014.10.056] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 10/21/2014] [Accepted: 10/27/2014] [Indexed: 12/27/2022]
Abstract
In about 20-40% of patients, status epilepticus (SE) is refractory to standard treatment with benzodiazepines, necessitating second- and third-line treatments that are not always successful, resulting in increased mortality. Rat models of refractory SE are instrumental in studying the changes underlying refractoriness and to develop more effective treatments for this severe medical emergency. Failure of GABAergic inhibition is a likely cause of the development of benzodiazepine resistance during SE. In addition to changes in GABAA receptor expression, trafficking, and function, alterations in Cl(-) homeostasis with increased intraneuronal Cl(-) levels may be involved. Bumetanide, which reduces intraneuronal Cl(-) by inhibiting the Cl(-) intruding Na(+), K(+), Cl(-) cotransporter NKCC1, has been reported to interrupt SE induced by kainate in urethane-anesthetized rats, indicating that this diuretic drug may be an interesting candidate for treatment of refractory SE. In this study, we evaluated the effects of bumetanide in the kainate and lithium-pilocarpine models of SE as well as a model in which SE is induced by sustained electrical stimulation of the basolateral amygdala. Unexpectedly, bumetanide alone was ineffective to terminate SE in both conscious and anesthetized adult rats. However, it potentiated the anticonvulsant effect of low doses of phenobarbital, although this was only seen in part of the animals; higher doses of phenobarbital, particularly in combination with diazepam, were more effective to terminate SE than bumetanide/phenobarbital combinations. These data do not suggest that bumetanide, alone or in combination with phenobarbital, is a valuable option in the treatment of refractory SE in adult patients.
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Affiliation(s)
- Kathrin Töllner
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany
| | - Claudia Brandt
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany
| | - Thomas Erker
- Department of Medicinal Chemistry, University of Vienna, Austria
| | - Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany.
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170
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Kaila K, Price TJ, Payne JA, Puskarjov M, Voipio J. Cation-chloride cotransporters in neuronal development, plasticity and disease. Nat Rev Neurosci 2014; 15:637-54. [PMID: 25234263 DOI: 10.1038/nrn3819] [Citation(s) in RCA: 504] [Impact Index Per Article: 50.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Electrical activity in neurons requires a seamless functional coupling between plasmalemmal ion channels and ion transporters. Although ion channels have been studied intensively for several decades, research on ion transporters is in its infancy. In recent years, it has become evident that one family of ion transporters, cation-chloride cotransporters (CCCs), and in particular K(+)-Cl(-) cotransporter 2 (KCC2), have seminal roles in shaping GABAergic signalling and neuronal connectivity. Studying the functions of these transporters may lead to major paradigm shifts in our understanding of the mechanisms underlying brain development and plasticity in health and disease.
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Affiliation(s)
- Kai Kaila
- 1] Department of Biosciences, University of Helsinki, 00014 Helsinki, Finland. [2] Neuroscience Center, University of Helsinki, 00014 Helsinki, Finland
| | - Theodore J Price
- University of Texas at Dallas, School of Behavior and Brain Sciences, Dallas, Texas 75093, USA
| | - John A Payne
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California 95616, USA
| | - Martin Puskarjov
- 1] Department of Biosciences, University of Helsinki, 00014 Helsinki, Finland. [2] Neuroscience Center, University of Helsinki, 00014 Helsinki, Finland
| | - Juha Voipio
- Department of Biosciences, University of Helsinki, 00014 Helsinki, Finland
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171
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Arosio D, Ratto GM. Twenty years of fluorescence imaging of intracellular chloride. Front Cell Neurosci 2014; 8:258. [PMID: 25221475 PMCID: PMC4148895 DOI: 10.3389/fncel.2014.00258] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 08/12/2014] [Indexed: 11/23/2022] Open
Abstract
Chloride homeostasis has a pivotal role in controlling neuronal excitability in the adult brain and during development. The intracellular concentration of chloride is regulated by the dynamic equilibrium between passive fluxes through membrane conductances and the active transport mediated by importers and exporters. In cortical neurons, chloride fluxes are coupled to network activity by the opening of the ionotropic GABAA receptors that provides a direct link between the activity of interneurons and chloride fluxes. These molecular mechanisms are not evenly distributed and regulated over the neuron surface and this fact can lead to a compartmentalized control of the intracellular concentration of chloride. The inhibitory drive provided by the activity of the GABAA receptors depends on the direction and strength of the associated currents, which are ultimately dictated by the gradient of chloride, the main charge carrier flowing through the GABAA channel. Thus, the intracellular distribution of chloride determines the local strength of ionotropic inhibition and influences the interaction between converging excitation and inhibition. The importance of chloride regulation is also underlined by its involvement in several brain pathologies, including epilepsy and disorders of the autistic spectra. The full comprehension of the physiological meaning of GABAergic activity on neurons requires the measurement of the spatiotemporal dynamics of chloride fluxes across the membrane. Nowadays, there are several available tools for the task, and both synthetic and genetically encoded indicators have been successfully used for chloride imaging. Here, we will review the available sensors analyzing their properties and outlining desirable future developments.
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Affiliation(s)
- Daniele Arosio
- Institute of Biophysics, National Research Council and Bruno Kessler Foundation Trento, Italy ; Centre for Integrative Biology, University of Trento Trento, Italy
| | - Gian Michele Ratto
- Nanoscience Institute, National Research Council of Italy Pisa, Italy ; NEST, Scuola Normale Superiore Pisa, Italy
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172
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The GABA excitatory/inhibitory developmental sequence: a personal journey. Neuroscience 2014; 279:187-219. [PMID: 25168736 DOI: 10.1016/j.neuroscience.2014.08.001] [Citation(s) in RCA: 194] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 07/17/2014] [Accepted: 08/01/2014] [Indexed: 12/11/2022]
Abstract
The developing brain is talkative but its language is not that of the adult. Most if not all voltage and transmitter-gated ionic currents follow a developmental sequence and network-driven patterns differ in immature and adult brains. This is best illustrated in studies engaged almost three decades ago in which we observed elevated intracellular chloride (Cl(-))i levels and excitatory GABA early during development and a perinatal excitatory/inhibitory shift. This sequence is observed in a wide range of brain structures and animal species suggesting that it has been conserved throughout evolution. It is mediated primarily by a developmentally regulated expression of the NKCC1 and KCC2 chloride importer and exporter respectively. The GABAergic depolarization acts in synergy with N-methyl-d-aspartate (NMDA) receptor-mediated and voltage-gated calcium currents to enhance intracellular calcium exerting trophic effects on neuritic growth, migration and synapse formation. These sequences can be deviated in utero by genetic or environmental insults leading to a persistence of immature features in the adult brain. This "neuroarcheology" concept paves the way to novel therapeutic perspectives based on the use of drugs that block immature but not adult currents. This is illustrated notably with the return to immature high levels of chloride and excitatory actions of GABA observed in many pathological conditions. This is due to the fact that in the immature brain a down regulation of KCC2 and an up regulation of NKCC1 are seen. Here, I present a personal history of how an unexpected observation led to novel concepts in developmental neurobiology and putative treatments of autism and other developmental disorders. Being a personal account, this review is neither exhaustive nor provides an update of this topic with all the studies that have contributed to this evolution. We all rely on previous inventors to allow science to advance. Here, I present a personal summary of this topic primarily to illustrate why we often fail to comprehend the implications of our own observations. They remind us - and policy deciders - why Science cannot be programed, requiring time, and risky investigations that raise interesting questions before being translated from bench to bed. Discoveries are always on sideways, never on highways.
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173
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Mòdol L, Cobianchi S, Navarro X. Prevention of NKCC1 phosphorylation avoids downregulation of KCC2 in central sensory pathways and reduces neuropathic pain after peripheral nerve injury. Pain 2014; 155:1577-1590. [PMID: 24813295 DOI: 10.1016/j.pain.2014.05.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 04/24/2014] [Accepted: 05/02/2014] [Indexed: 12/24/2022]
Abstract
Neuropathic pain after peripheral nerve injury is characterized by loss of inhibition in both peripheral and central pain pathways. In the adult nervous system, the Na(+)-K(+)-2Cl(-) (NKCC1) and neuron-specific K(+)-Cl(-) (KCC2) cotransporters are involved in setting the strength and polarity of GABAergic/glycinergic transmission. After nerve injury, the balance between these cotransporters changes, leading to a decrease in the inhibitory tone. However, the role that NKCC1 and KCC2 play in pain-processing brain areas is unknown. Our goal was to study the effects of peripheral nerve injury on NKCC1 and KCC2 expression in dorsal root ganglia (DRG), spinal cord, ventral posterolateral (VPL) nucleus of the thalamus, and primary somatosensory (S1) cortex. After sciatic nerve section and suture in adult rats, assessment of mechanical and thermal pain thresholds showed evidence of hyperalgesia during the following 2 months. We also found an increase in NKCC1 expression in the DRG and a downregulation of KCC2 in spinal cord after injury, accompanied by later decrease of KCC2 levels in higher projection areas (VPL and S1) from 2 weeks postinjury, correlating with neuropathic pain signs. Administration of bumetanide (30 mg/kg) during 2 weeks following sciatic nerve lesion prevented the previously observed changes in the spinothalamic tract projecting areas and the appearance of hyperalgesia. In conclusion, the present results indicate that changes in NKCC1 and KCC2 in DRG, spinal cord, and central pain areas may contribute to development of neuropathic pain.
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Affiliation(s)
- Laura Mòdol
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain
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174
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Kahle KT, Merner ND, Friedel P, Silayeva L, Liang B, Khanna A, Shang Y, Lachance-Touchette P, Bourassa C, Levert A, Dion PA, Walcott B, Spiegelman D, Dionne-Laporte A, Hodgkinson A, Awadalla P, Nikbakht H, Majewski J, Cossette P, Deeb TZ, Moss SJ, Medina I, Rouleau GA. Genetically encoded impairment of neuronal KCC2 cotransporter function in human idiopathic generalized epilepsy. EMBO Rep 2014; 15:766-74. [PMID: 24928908 PMCID: PMC4196980 DOI: 10.15252/embr.201438840] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 04/18/2014] [Accepted: 04/23/2014] [Indexed: 12/28/2022] Open
Abstract
The KCC2 cotransporter establishes the low neuronal Cl(-) levels required for GABAA and glycine (Gly) receptor-mediated inhibition, and KCC2 deficiency in model organisms results in network hyperexcitability. However, no mutations in KCC2 have been documented in human disease. Here, we report two non-synonymous functional variants in human KCC2, R952H and R1049C, exhibiting clear statistical association with idiopathic generalized epilepsy (IGE). These variants reside in conserved residues in the KCC2 cytoplasmic C-terminus, exhibit significantly impaired Cl(-)-extrusion capacities resulting in less hyperpolarized Gly equilibrium potentials (EG ly), and impair KCC2 stimulatory phosphorylation at serine 940, a key regulatory site. These data describe a novel KCC2 variant significantly associated with a human disease and suggest genetically encoded impairment of KCC2 functional regulation may be a risk factor for the development of human IGE.
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Affiliation(s)
- Kristopher T Kahle
- Department of Cardiology, Manton Center for Orphan Disease Research, Howard Hughes Medical Institute Boston Children's Hospital, Boston, MA, USA Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, USA
| | - Nancy D Merner
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, USA Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute McGill Université, Montréal, QC, Canada
| | - Perrine Friedel
- INMED, INSERM Unité 901, Marseille, France Aix-Marseille Université UMR 901, Marseille, France
| | - Liliya Silayeva
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Bo Liang
- Department of Biological Chemistry and Molecular Pharmacology (BCMP), Harvard Medical School, Boston, MA, USA
| | - Arjun Khanna
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, USA
| | - Yuze Shang
- Department of Cardiology, Manton Center for Orphan Disease Research, Howard Hughes Medical Institute Boston Children's Hospital, Boston, MA, USA Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, USA
| | - Pamela Lachance-Touchette
- Center of Research of the Université de Montréal and the Department of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Cynthia Bourassa
- Center of Research of the Université de Montréal and the Department of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Annie Levert
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute McGill Université, Montréal, QC, Canada
| | - Patrick A Dion
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, USA Department of Pathology and Cell Biology, Université de Montréal, Montréal, QC, Canada
| | - Brian Walcott
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, USA
| | - Dan Spiegelman
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute McGill Université, Montréal, QC, Canada
| | - Alexandre Dionne-Laporte
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute McGill Université, Montréal, QC, Canada
| | - Alan Hodgkinson
- CHU Sainte Justine Research Centre, Department of Pediatrics, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Philip Awadalla
- CHU Sainte Justine Research Centre, Department of Pediatrics, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada CARTaGENE, Montréal, QC, Canada
| | - Hamid Nikbakht
- Department of Human Genetics, McGill University and Genome Quebec Innovation Centre, Montréal, QC, Canada
| | - Jacek Majewski
- Department of Human Genetics, McGill University and Genome Quebec Innovation Centre, Montréal, QC, Canada
| | - Patrick Cossette
- Center of Research of the Université de Montréal and the Department of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Tarek Z Deeb
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Igor Medina
- INMED, INSERM Unité 901, Marseille, France Aix-Marseille Université UMR 901, Marseille, France
| | - Guy A Rouleau
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute McGill Université, Montréal, QC, Canada
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175
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Gómez CD, Buijs RM, Sitges M. The anti-seizure drugs vinpocetine and carbamazepine, but not valproic acid, reduce inflammatory IL-1β and TNF-α expression in rat hippocampus. J Neurochem 2014; 130:770-9. [PMID: 24903676 DOI: 10.1111/jnc.12784] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 05/26/2014] [Accepted: 05/30/2014] [Indexed: 12/25/2022]
Abstract
In the present study, the effects of the two classical anti-epileptic drugs, carbamazepine and valproic acid, and the non-classical anti-seizure drug vinpocetine were investigated on the expression of the pro-inflammatory cytokines IL-1β and TNF-α in the hippocampus of rats by PCR or western blot after the administration of one or seven doses. Next, the effects of the anti-seizure drugs were investigated on the rise in cytokine expression induced by lipopolysaccharides (LPS) inoculation in vivo. To validate our methods, the changes induced by the pro-convulsive agents 4-aminopyridine, pentylenetetrazole and pilocarpine were also tested. Finally, the effect of the anti-seizure drugs on seizures and on the concomitant rise in pro-inflammatory cytokine expression induced by 4-aminopyridine was explored. Results show that vinpocetine and carbamazepine reduced the expression of IL-1β and TNF-α from basal conditions, and the increase in both pro-inflammatory cytokines induced by LPS. In contrast, valproic acid failed to reduce both the expression of the cytokines from basal conditions and the rise in IL-1β and TNF-α expression induced by LPS. Tonic-clonic seizures induced either by 4-aminopyridine, pentylenetetrazole or pilocarpine increased the expression of IL-1β and TNF-α markedly. 4-aminopyridine-induced changes were reduced by all the tested anti-seizure drugs, although valproic acid was less effective. We conclude that the anti-seizure drugs, vinpocetine and carbamazepine, whose mechanisms of action involve a decrease in ion channels permeability, also reduce cerebral inflammation. The mechanism of action of anti-seizure drugs like vinpocetine and carbamazepine involves a decrease in Na(+) channels permeability. We here propose that this mechanism of action also involves a decrease in cerebral inflammation.
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Affiliation(s)
- Carlos D Gómez
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, DF, México
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176
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Puskarjov M, Kahle KT, Ruusuvuori E, Kaila K. Pharmacotherapeutic targeting of cation-chloride cotransporters in neonatal seizures. Epilepsia 2014; 55:806-18. [PMID: 24802699 PMCID: PMC4284054 DOI: 10.1111/epi.12620] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2014] [Indexed: 12/15/2022]
Abstract
Seizures are a common manifestation of acute neurologic insults in neonates and are often resistant to the standard antiepileptic drugs that are efficacious in children and adults. The paucity of evidence-based treatment guidelines, coupled with a rudimentary understanding of disease pathogenesis, has made the current treatment of neonatal seizures empiric and often ineffective, highlighting the need for novel therapies. Key developmental differences in γ-aminobutyric acid (GABA)ergic neurotransmission between the immature and mature brain, and trauma-induced alterations in the function of the cation-chloride cotransporters (CCCs) NKCC1 and KCC2, probably contribute to the poor efficacy of standard antiepileptic drugs used in the treatment of neonatal seizures. Although CCCs are attractive drug targets, bumetanide and other existing CCC inhibitors are suboptimal because of pharmacokinetic constraints and lack of target specificity. Newer approaches including isoform-specific NKCC1 inhibitors with increased central nervous system penetration, and direct and indirect strategies to enhance KCC2-mediated neuronal chloride extrusion, might allow therapeutic modulation of the GABAergic system for neonatal seizure treatment. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.
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Affiliation(s)
- Martin Puskarjov
- Department of Biosciences and Neuroscience Center, University of HelsinkiHelsinki, Finland
| | - Kristopher T Kahle
- Department of Neurosurgery, Harvard Medical School, Massachusetts General HospitalBoston, Massachusetts, U.S.A
| | - Eva Ruusuvuori
- Department of Biosciences and Neuroscience Center, University of HelsinkiHelsinki, Finland
| | - Kai Kaila
- Department of Biosciences and Neuroscience Center, University of HelsinkiHelsinki, Finland
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177
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Kaila K, Ruusuvuori E, Seja P, Voipio J, Puskarjov M. GABA actions and ionic plasticity in epilepsy. Curr Opin Neurobiol 2014; 26:34-41. [PMID: 24650502 DOI: 10.1016/j.conb.2013.11.004] [Citation(s) in RCA: 167] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 10/23/2013] [Accepted: 11/06/2013] [Indexed: 11/18/2022]
Abstract
Concepts of epilepsy, based on a simple change in neuronal excitation/inhibition balance, have subsided in face of recent insights into the large diversity and context-dependence of signaling mechanisms at the molecular, cellular and neuronal network level. GABAergic transmission exerts both seizure-suppressing and seizure-promoting actions. These two roles are prone to short-term and long-term alterations, evident both during epileptogenesis and during individual epileptiform events. The driving force of GABAergic currents is controlled by ion-regulatory molecules such as the neuronal K-Cl cotransporter KCC2 and cytosolic carbonic anhydrases. Accumulating evidence suggests that neuronal ion regulation is highly plastic, thereby contributing to the multiple roles ascribed to GABAergic signaling during epileptogenesis and epilepsy.
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Affiliation(s)
- Kai Kaila
- Department of Biosciences, University of Helsinki, FI-00014 Helsinki, Finland; Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland.
| | - Eva Ruusuvuori
- Department of Biosciences, University of Helsinki, FI-00014 Helsinki, Finland; Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Patricia Seja
- Department of Biosciences, University of Helsinki, FI-00014 Helsinki, Finland; Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Juha Voipio
- Department of Biosciences, University of Helsinki, FI-00014 Helsinki, Finland
| | - Martin Puskarjov
- Department of Biosciences, University of Helsinki, FI-00014 Helsinki, Finland; Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
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178
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Deidda G, Bozarth IF, Cancedda L. Modulation of GABAergic transmission in development and neurodevelopmental disorders: investigating physiology and pathology to gain therapeutic perspectives. Front Cell Neurosci 2014; 8:119. [PMID: 24904277 PMCID: PMC4033255 DOI: 10.3389/fncel.2014.00119] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 04/14/2014] [Indexed: 01/30/2023] Open
Abstract
During mammalian ontogenesis, the neurotransmitter GABA is a fundamental regulator of neuronal networks. In neuronal development, GABAergic signaling regulates neural proliferation, migration, differentiation, and neuronal-network wiring. In the adult, GABA orchestrates the activity of different neuronal cell-types largely interconnected, by powerfully modulating synaptic activity. GABA exerts these functions by binding to chloride-permeable ionotropic GABAA receptors and metabotropic GABAB receptors. According to its functional importance during development, GABA is implicated in a number of neurodevelopmental disorders such as autism, Fragile X, Rett syndrome, Down syndrome, schizophrenia, Tourette's syndrome and neurofibromatosis. The strength and polarity of GABAergic transmission is continuously modulated during physiological, but also pathological conditions. For GABAergic transmission through GABAA receptors, strength regulation is achieved by different mechanisms such as modulation of GABAA receptors themselves, variation of intracellular chloride concentration, and alteration in GABA metabolism. In the never-ending effort to find possible treatments for GABA-related neurological diseases, of great importance would be modulating GABAergic transmission in a safe and possibly physiological way, without the dangers of either silencing network activity or causing epileptic seizures. In this review, we will discuss the different ways to modulate GABAergic transmission normally at work both during physiological and pathological conditions. Our aim is to highlight new research perspectives for therapeutic treatments that reinstate natural and physiological brain functions in neuro-pathological conditions.
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Affiliation(s)
- Gabriele Deidda
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
| | - Ignacio F Bozarth
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
| | - Laura Cancedda
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
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179
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Töllner K, Brandt C, Töpfer M, Brunhofer G, Erker T, Gabriel M, Feit PW, Lindfors J, Kaila K, Löscher W. A novel prodrug-based strategy to increase effects of bumetanide in epilepsy. Ann Neurol 2014; 75:550-62. [PMID: 24615913 DOI: 10.1002/ana.24124] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 10/21/2013] [Accepted: 12/21/2013] [Indexed: 11/07/2022]
Abstract
OBJECTIVE There is considerable interest in using bumetanide, a chloride importer Na-K-Cl cotransporter antagonist, for treatment of neurological diseases, such as epilepsy or ischemic and traumatic brain injury, that may involve deranged cellular chloride homeostasis. However, bumetanide is heavily bound to plasma proteins (~98%) and highly ionized at physiological pH, so that it only poorly penetrates into the brain, and chronic treatment with bumetanide is compromised by its potent diuretic effect. METHODS To overcome these problems, we designed lipophilic and uncharged prodrugs of bumetanide that should penetrate the blood-brain barrier more easily than the parent drug and are converted into bumetanide in the brain. The feasibility of this strategy was evaluated in mice and rats. RESULTS Analysis of bumetanide levels in plasma and brain showed that administration of 2 ester prodrugs of bumetanide, the pivaloyloxymethyl (BUM1) and N,N-dimethylaminoethylester (BUM5), resulted in significantly higher brain levels of bumetanide than administration of the parent drug. BUM5, but not BUM1, was less diuretic than bumetanide, so that BUM5 was further evaluated in chronic models of epilepsy in mice and rats. In the pilocarpine model in mice, BUM5, but not bumetanide, counteracted the alteration in seizure threshold during the latent period. In the kindling model in rats, BUM5 was more efficacious than bumetanide in potentiating the anticonvulsant effect of phenobarbital. INTERPRETATION Our data demonstrate that the goal of designing bumetanide prodrugs that specifically target the brain is feasible and that such drugs may resolve the problems associated with using bumetanide for treatment of neurological disorders.
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Affiliation(s)
- Kathrin Töllner
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany
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180
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Kaminski RM, Rogawski MA, Klitgaard H. The potential of antiseizure drugs and agents that act on novel molecular targets as antiepileptogenic treatments. Neurotherapeutics 2014; 11:385-400. [PMID: 24671870 PMCID: PMC3996125 DOI: 10.1007/s13311-014-0266-1] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
A major goal of contemporary epilepsy research is the identification of therapies to prevent the development of recurrent seizures in individuals at risk, including those with brain injuries, infections, or neoplasms; status epilepticus; cortical dysplasias; or genetic epilepsy susceptibility. In this review we consider the evidence largely from preclinical models for the antiepileptogenic activity of a diverse range of potential therapies, including some marketed antiseizure drugs, as well as agents that act by immune and inflammatory mechanisms; reduction of oxidative stress; activation of the mammalian target of rapamycin or peroxisome proliferator-activated receptors γ pathways; effects on factors related to thrombolysis, hematopoesis, and angiogenesis; inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reducatase; brain-derived neurotrophic factor signaling; and blockade of α2 adrenergic and cannabinoid receptors. Antiepileptogenesis refers to a therapy of which the beneficial action is to reduce seizure frequency or severity outlasting the treatment period. To date, clinical trials have failed to demonstrate that antiseizure drugs have such disease-modifying activity. However, studies in animal models with levetiracetam and ethosuximide are encouraging, and clinical trials with these agents are warranted. Other promising strategies are inhibition of interleukin 1β signaling by drugs such as VX-765; modulation of sphingosine 1-phosphate signaling by drugs such as fingolimod; activation of the mammalian target of rapamycin by drugs such as rapamycin; the hormone erythropoietin; and, paradoxically, drugs such as the α2 adrenergic receptor antagonist atipamezole and the CB1 cannabinoid antagonist SR141716A (rimonabant) with proexcitatory activity. These approaches could lead to a new paradigm in epilepsy drug therapy where treatment for a limited period prevents the occurrence of spontaneous seizures, thus avoiding lifelong commitment to symptomatic treatment.
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Affiliation(s)
| | - Michael A. Rogawski
- />Department of Neurology, University of California, Davis School of Medicine, Sacramento, CA USA
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181
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White HS, Löscher W. Searching for the ideal antiepileptogenic agent in experimental models: single treatment versus combinatorial treatment strategies. Neurotherapeutics 2014; 11:373-84. [PMID: 24425186 PMCID: PMC3996126 DOI: 10.1007/s13311-013-0250-1] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
A major unmet medical need is the lack of treatments to prevent (or modify) epilepsy in patients at risk, for example, after epileptogenic brain insults such as traumatic brain injury, stroke, or prolonged acute symptomatic seizures like complex febrile seizures or status epilepticus. Typically, following such brain insults there is a seizure-free interval ("latent period"), lasting months to years before the onset of spontaneous recurrent epileptic seizures. The latent period after a brain insult offers a window of opportunity in which an appropriate treatment may prevent or modify the epileptogenic process induced by a brain insult. A similar latent period occurs in patients with epileptogenic gene mutations. Studies using animal models of epilepsy have led to a greater understanding of the factors underlying epileptogenesis and have provided significant insight into potential targets by which the development of epilepsy may be prevented or modified. This review focuses largely on some of the most common animal models of epileptogenesis and their potential utility for evaluating proposed antiepileptogenic therapies and identifying useful biomarkers. The authors also describe some of the limitations of using animal models in the search for therapies that move beyond the symptomatic treatment of epilepsy. Promising results of previous studies designed to evaluate antiepileptogenesis and the role of monotherapy versus polytherapy approaches are also discussed. Recent data from both models of genetic and acquired epilepsies strongly indicate that it is possible to prevent or modify epileptogenesis, and, hopefully, such promising results can ultimately be translated into the clinic.
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Affiliation(s)
- H. Steve White
- />Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT USA
| | - Wolfgang Löscher
- />Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
- />Center for Systems Neuroscience, Hannover, Germany
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182
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Lang M, Moradi-Chameh H, Zahid T, Gane J, Wu C, Valiante T, Zhang L. Regulating hippocampal hyperexcitability through GABAB Receptors. Physiol Rep 2014. [PMID: 24771688 PMCID: PMC4001873 DOI: 10.1002/phy2.278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Disturbances of GABAergic inhibition are a major cause of epileptic seizures. GABA exerts its actions via ionotropic GABAA receptors and metabotropic G protein‐coupled GABAB receptors. Malfunction of GABAA inhibition has long been recognized in seizure genesis but the role of GABAB receptors in controlling seizure activity is still not well understood. Here, we examined the anticonvulsive, or inhibitory effects, of GABAB receptors in a mouse model of hippocampal kindling as well as mouse hippocampal slices through the use of GS 39783, a positive allosteric GABAB receptor modulator, and CGP 55845, a selective GABAB receptor antagonist. When administered via intraperitoneal injections in kindled mice, GS 39783 (5 mg/kg) did not attenuate hippocampal EEG discharges, but did reduce aberrant hippocampal spikes, whereas CGP 55845 (10 mg/kg) prolonged hippocampal discharges and increased spike incidences. When examined in hippocampal slices, neither GS 39783 at 5 μmol/L nor the GABAB receptor agonist baclofen at 0.1 μmol/L alone significantly altered repetitive excitatory field potentials, but GS 39783 and baclofen together reversibly abolished these field potentials. In contrast, CGP 55845 at 1 μmol/L facilitated induction and incidence of these field potentials. In addition, CGP 55845 attenuated the paired pulse depression of CA3 population spikes and increased the frequency of EPSCs in individual CA3 pyramidal neurons. Collectively, these data suggest that GABABB receptors regulate hippocampal hyperexcitability by inhibiting CA3 glutamatergic synapses. We postulate that positive allosteric modulation of GABAB receptors may be effective in reducing seizure‐related hyperexcitability. GABAB positive modulator GS 39783 attenuated, whereas GABAB antagonist CGP55845 facilitated hippocampal EEG spikes in kindled mice and excitatory field potentials in hippocampal slices. We postulate that GABAB receptors may inhibit CA3 glutamate synapses and hence regulate hippocampal hyperexcitability.
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Affiliation(s)
- Min Lang
- Toronto Western Research Institute; University Health Network; Toronto Ontario Canada
| | - Homeira Moradi-Chameh
- Toronto Western Research Institute; University Health Network; Toronto Ontario Canada
- Department of Physiology; University of Tarbiat Modares; Tehran Iran
| | - Tariq Zahid
- Toronto Western Research Institute; University Health Network; Toronto Ontario Canada
| | - Jonathan Gane
- Toronto Western Research Institute; University Health Network; Toronto Ontario Canada
| | - Chiping Wu
- Toronto Western Research Institute; University Health Network; Toronto Ontario Canada
| | - Taufik Valiante
- Department of Surgery (Division of Neurosurgery); University of Toronto; Toronto Ontario Canada
| | - Liang Zhang
- Toronto Western Research Institute; University Health Network; Toronto Ontario Canada
- Department of Medicine (Division of Neurology); University of Toronto; Toronto Ontario Canada
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183
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Medina I, Friedel P, Rivera C, Kahle KT, Kourdougli N, Uvarov P, Pellegrino C. Current view on the functional regulation of the neuronal K(+)-Cl(-) cotransporter KCC2. Front Cell Neurosci 2014; 8:27. [PMID: 24567703 PMCID: PMC3915100 DOI: 10.3389/fncel.2014.00027] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Accepted: 01/18/2014] [Indexed: 12/22/2022] Open
Abstract
In the mammalian central nervous system (CNS), the inhibitory strength of chloride (Cl(-))-permeable GABAA and glycine receptors (GABAAR and GlyR) depends on the intracellular Cl(-) concentration ([Cl(-)]i). Lowering [Cl(-)]i enhances inhibition, whereas raising [Cl(-)]i facilitates neuronal activity. A neuron's basal level of [Cl(-)]i, as well as its Cl(-) extrusion capacity, is critically dependent on the activity of the electroneutral K(+)-Cl(-) cotransporter KCC2, a member of the SLC12 cation-Cl(-) cotransporter (CCC) family. KCC2 deficiency compromises neuronal migration, formation and the maturation of GABAergic and glutamatergic synaptic connections, and results in network hyperexcitability and seizure activity. Several neurological disorders including multiple epilepsy subtypes, neuropathic pain, and schizophrenia, as well as various insults such as trauma and ischemia, are associated with significant decreases in the Cl(-) extrusion capacity of KCC2 that result in increases of [Cl(-)]i and the subsequent hyperexcitability of neuronal networks. Accordingly, identifying the key upstream molecular mediators governing the functional regulation of KCC2, and modifying these signaling pathways with small molecules, might constitute a novel neurotherapeutic strategy for multiple diseases. Here, we discuss recent advances in the understanding of the mechanisms regulating KCC2 activity, and of the role these mechanisms play in neuronal Cl(-) homeostasis and GABAergic neurotransmission. As KCC2 mediates electroneutral transport, the experimental recording of its activity constitutes an important research challenge; we therefore also, provide an overview of the different methodological approaches utilized to monitor function of KCC2 in both physiological and pathological conditions.
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Affiliation(s)
- Igor Medina
- INSERM, Institut de Neurobiologie de la Méditerranée (INMED)Marseille, France
- Aix-Marseille Université, UMR901Marseille, France
| | - Perrine Friedel
- INSERM, Institut de Neurobiologie de la Méditerranée (INMED)Marseille, France
- Aix-Marseille Université, UMR901Marseille, France
| | - Claudio Rivera
- INSERM, Institut de Neurobiologie de la Méditerranée (INMED)Marseille, France
- Aix-Marseille Université, UMR901Marseille, France
- Neuroscience Center, University of HelsinkiHelsinki, Finland
| | - Kristopher T. Kahle
- Department of Cardiology, Manton Center for Orphan Disease Research, Howard Hughes Medical Institute, Boston Children's HospitalBoston, MA, USA
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical SchoolBoston, MA, USA
| | - Nazim Kourdougli
- INSERM, Institut de Neurobiologie de la Méditerranée (INMED)Marseille, France
- Aix-Marseille Université, UMR901Marseille, France
| | - Pavel Uvarov
- Institute of Biomedicine, Anatomy, University of HelsinkiHelsinki, Finland
| | - Christophe Pellegrino
- INSERM, Institut de Neurobiologie de la Méditerranée (INMED)Marseille, France
- Aix-Marseille Université, UMR901Marseille, France
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184
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Luhmann HJ, Kilb W, Clusmann H. Malformations of cortical development and neocortical focus. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 114:35-61. [PMID: 25078498 DOI: 10.1016/b978-0-12-418693-4.00003-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Developmental neocortical malformations resulting from abnormal neurogenesis, disturbances in programmed cell death, or neuronal migration disorders may cause a long-term hyperexcitability. Early generated Cajal-Retzius and subplate neurons play important roles in transient cortical circuits, and structural/functional disorders in early cortical development may induce persistent network disturbances and epileptic disorders. In particular, depolarizing GABAergic responses are important for the regulation of neurodevelopmental events, like neurogenesis or migration, while pathophysiological alterations in chloride homeostasis may cause epileptic activity. Although modern imaging techniques may provide an estimate of the structural lesion, the site and extent of the cortical malformation may not correlate with the epileptogenic zone. The neocortical focus may be surrounded by widespread molecular, structural, and functional disturbances, which are difficult to recognize with imaging technologies. However, modern imaging and electrophysiological techniques enable focused hypotheses of the neocortical epileptogenic zone, thus allowing more specific epilepsy surgery. Focal cortical malformation can be successfully removed with minimal rim, close to or even within eloquent cortex with a promising risk-benefit ratio.
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Affiliation(s)
- Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
| | - Werner Kilb
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Hans Clusmann
- Department of Neurosurgery, RWTH Aachen University, Aachen, Germany
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185
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Baraban SC, Löscher W. What new modeling approaches will help us identify promising drug treatments? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:283-94. [PMID: 25012385 DOI: 10.1007/978-94-017-8914-1_23] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Despite the development of numerous novel antiepileptic drugs (AEDs) in recent years, several unmet clinical needs remain, including resistance to AEDs in about 30 % of patients with epilepsy, adverse effects of AEDs that can reduce quality of life, and the lack of treatments that can prevent development of epilepsy in patients at risk. Animal models of seizures and epilepsy have been instrumental in the discovery and preclinical development of novel AEDs, but obviously the previously used models have failed to identify drugs that address unmet medical needs. Thus, we urgently need fresh ideas for improving preclinical AED development. In this review, a number of promising models will be described, including the use of simple vertebrates such as zebrafish (Danio rerio), large animal models such as the dog and newly characterized rodent models of pharmacoresistant epilepsy. While these strategies, like any animal model approach also have their limitations, they offer hope that new more effective AEDs will be identified in the coming years.
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Affiliation(s)
- Scott C Baraban
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco, CA, 94143, USA,
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186
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Kahle KT, Deeb TZ, Puskarjov M, Silayeva L, Liang B, Kaila K, Moss SJ. Modulation of neuronal activity by phosphorylation of the K-Cl cotransporter KCC2. Trends Neurosci 2013; 36:726-737. [PMID: 24139641 PMCID: PMC4381966 DOI: 10.1016/j.tins.2013.08.006] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 08/19/2013] [Accepted: 08/26/2013] [Indexed: 12/29/2022]
Abstract
The K-Cl cotransporter KCC2 establishes the low intraneuronal Cl- levels required for the hyperpolarizing inhibitory postsynaptic potentials mediated by ionotropic γ-aminobutyric acid receptors (GABAARs) and glycine receptors (GlyRs). Decreased KCC2-mediated Cl- extrusion and impaired hyperpolarizing GABAAR- and/or GlyR-mediated currents have been implicated in epilepsy, neuropathic pain, and spasticity. Recent evidence suggests that the intrinsic ion transport rate, cell surface stability, and plasmalemmal trafficking of KCC2 are rapidly and reversibly modulated by the (de)phosphorylation of critical serine, threonine, and tyrosine residues in the C terminus of this protein. Alterations in KCC2 phosphorylation have been associated with impaired KCC2 function in several neurological diseases. Targeting KCC2 phosphorylation directly or indirectly via upstream regulatory kinases might be a novel strategy to modulate GABA- and/or glycinergic signaling for therapeutic benefit.
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Affiliation(s)
- Kristopher T Kahle
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
- Howard Hughes Medical Institute, Department of Cardiology, Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA
| | - Tarek Z Deeb
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Martin Puskarjov
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Liliya Silayeva
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Bo Liang
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Kai Kaila
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
- Department of Neuroscience, Physiology and Pharmacology, University College, London, WC1E 6BT, UK
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187
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Sharopov S, Chen R, Sun H, Kolbaev SN, Kirischuk S, Luhmann HJ, Kilb W. Inhibition of different GABA transporter systems is required to attenuate epileptiform activity in the CA3 region of the immature rat hippocampus. Epilepsy Res 2013; 108:182-9. [PMID: 24359690 DOI: 10.1016/j.eplepsyres.2013.11.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 09/30/2013] [Accepted: 11/21/2013] [Indexed: 11/27/2022]
Abstract
GABA transporters (GATs) are an essential element of the GABAergic system, which regulate excitability in the central nervous system and are thus used as targets for anticonvulsive therapy. However, in the immature nervous system the functions of the GABAergic system and the expression profile of GATs are distinct from the adult situation, obscuring to predict how different GAT isoforms influence epileptiform activity. Therefore we analyzed the effects of subtype specific GAT inhibitors on repetitive epileptiform discharges using field potential and whole-cell patch-clamp recordings in the CA3 region of hippocampal slices of immature (postnatal days 4-7) rats. These experiments revealed that inhibition of GAT-1 with either tiagabine (30 μM) or NO-711 (10 μM) exhibited only a minor anticonvulsive effect on repetitive epileptiform discharges. Blockade of GAT-2/3 with SNAP-5114 (40 μM) had no anticonvulsive effect, but significantly prolonged the decay of spontaneous GABAergic postsynaptic currents. In contrast, the combined application of 10 μM NO-711 and 40 μM SNAP-5114 blocked epileptiform activity in 33% of all slices and reduced the occurrence of epileptiform discharges by 54% in the remaining slices. In addition, the input resistance decreased by 10.5 ± 1.0% under this condition. These results indicate that both GAT-1 and GAT-2/3 are functional in the immature hippocampus and that only the combined inhibition of GAT 1-3 is sufficient to promote a considerable anticonvulsive effect. We conclude from these results that both GAT-1 and GAT-2/3 act synergistically to regulate the excitability in the immature hippocampus.
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Affiliation(s)
- Salim Sharopov
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany
| | - Rongqing Chen
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany
| | - Haiyan Sun
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany
| | - Sergei N Kolbaev
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany
| | - Sergei Kirischuk
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany.
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188
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Ding Y, Wang S, Jiang Y, Yang Y, Zhang M, Guo Y, Wang S, Ding MP. Fructose-1,6-diphosphate protects against epileptogenesis by modifying cation-chloride co-transporters in a model of amygdaloid-kindling temporal epilepticus. Brain Res 2013; 1539:87-94. [PMID: 24095797 DOI: 10.1016/j.brainres.2013.09.042] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Revised: 09/23/2013] [Accepted: 09/25/2013] [Indexed: 11/27/2022]
Abstract
Fructose-1,6-diphosphate (FDP) shifts the metabolism of glucose from glycolysis to the pentose phosphate pathway and has anticonvulsant activity in several acute seizure animal models. In the present study, we investigated the anti-epileptogenic effects of FDP in an amygdaloid-kindling seizure model, which is an animal model of the most common form of human temporal lobe epilepsy. We found that 1.0 g/kg FDP slowed seizure progression and shortened the corresponding after-discharge duration (ADD). FDP increased the number of stimulations needed to reach seizure stages 2-5 and prolonged the cumulative ADD prior to reaching stages 3-5. It also shortened staying days and cumulative ADD in stages 4-5. However, it demonstrated no significant protective effect when administered after the animals were fully kindled. In hippocampal neurons, cation-chloride co-transporters (CCCs) are suggested to play interesting roles in epilepsy by modulating γ-aminobutyric acid (GABA)ergic activity through controlling GABAA receptor-mediated reversal potential. We examined the potential link between FDP and the hippocampal expression of two main members of the CCCs: the neuron-specific K(+)-Cl(-)co-transporter 2 (KCC2) and Na(+)-K(+)-Cl(-)co-transporter 1 (NKCC1). FDP inhibited the kindling-induced downregulation of KCC2 expression and decreased NKCC1 expression during the kindling session. Taken together, our data reveal that FDP may have protective activity against epileptogenesis, from partial to generalized tonic-clonic seizures. Furthermore, our findings suggest that the FDP-induced imbalance between KCC2 and NKCC1 expression may be involved in the neuroprotective effect.
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Affiliation(s)
- Yao Ding
- Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China
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189
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Töpfer M, Töllner K, Brandt C, Twele F, Bröer S, Löscher W. Consequences of inhibition of bumetanide metabolism in rodents on brain penetration and effects of bumetanide in chronic models of epilepsy. Eur J Neurosci 2013; 39:673-87. [PMID: 24251546 DOI: 10.1111/ejn.12424] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 09/24/2013] [Accepted: 10/14/2013] [Indexed: 11/28/2022]
Abstract
The diuretic bumetanide, which acts by blocking the Na-K-Cl cotransporter (NKCC), is widely used to inhibit neuronal NKCC1, particularly when NKCC1 expression is abnormally increased in brain diseases such as epilepsy. However, bumetanide poorly penetrates into the brain and, in rodents, is rapidly eliminated because of extensive oxidation of its N-butyl sidechain, reducing the translational value of rodent experiments. Inhibition of oxidation by piperonyl butoxide (PBO) has previously been reported to increase the half-life and diuretic activity of bumetanide in rats. Here we studied whether inhibition of bumetanide metabolism by PBO also increases brain levels of bumetanide in rats, and whether this alters pharmacodynamic effects in the kindling model of epilepsy. Furthermore, we studied the effects of PBO in mice. Mice eliminated bumetanide less rapidly than rats (elimination half-life 47 min vs. 13 min). Pretreatment with PBO increased the half-life in mice to average values (70 min) previously determined in humans, and markedly elevated brain levels of bumetanide. In rats, the increase in plasma and brain levels of bumetanide by PBO was less marked than in mice. PBO significantly increased the diuretic activity of bumetanide in rats and, less effectively, in mice. In epileptic mice, bumetanide (with PBO) did not suppress spontaneous seizures. In the rat kindling model, bumetanide (with or without PBO) did not exert anticonvulsant effects on fully kindled seizures, but dose-dependently altered kindling development. These data indicate that PBO offers a simple means to enhance the translational properties of rodent experiments with bumetanide, particularly when using mice.
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Affiliation(s)
- Manuel Töpfer
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine, Bünteweg 17, Hannover, D-30559, Germany; Center for Systems Neuroscience, Hannover, Germany
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190
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Löscher W, Klitgaard H, Twyman RE, Schmidt D. New avenues for anti-epileptic drug discovery and development. Nat Rev Drug Discov 2013; 12:757-76. [DOI: 10.1038/nrd4126] [Citation(s) in RCA: 424] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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191
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Deeb TZ, Nakamura Y, Frost GD, Davies PA, Moss SJ. Disrupted Cl(-) homeostasis contributes to reductions in the inhibitory efficacy of diazepam during hyperexcited states. Eur J Neurosci 2013; 38:2453-67. [PMID: 23627375 PMCID: PMC3735799 DOI: 10.1111/ejn.12241] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 03/29/2013] [Accepted: 03/31/2013] [Indexed: 11/28/2022]
Abstract
The K(+) -Cl(-) cotransporter type 2 is the major Cl(-) extrusion mechanism in most adult neurons. This process in turn leads to Cl(-) influx upon activation of γ-aminobutyric acid type A (GABAA ) receptors and the canonical hyperpolarising inhibitory postsynaptic potential. Several neurological disorders are treated with drugs that target and enhance GABAA receptor signaling, including the commonly used benzodiazepine diazepam and the anesthetic propofol. Some of these disorders are also associated with deficits in GABAA signaling and become less sensitive to therapeutic drugs that target GABAA receptors. To date, it is unknown if alterations in the neuronal Cl(-) gradient affect the efficacies of diazepam and propofol. We therefore used the in vitro model of glutamate-induced hyperexcitability to test if alterations in the Cl(-) gradient affect the efficacy of GABAA modulators. We exclusively utilised the gramicidin perforated-patch-clamp configuration to preserve the endogenous Cl(-) gradient in rat neurons. Brief exposure to glutamate reduced the inhibitory efficacy of diazepam within 5 min, which was caused by the collapse of the Cl(-) gradient, and not due to reductions in GABAA receptor number. Unlike diazepam, propofol retained its efficacy by shunting the membrane conductance despite the glutamate-induced appearance of depolarising GABAA -mediated currents. Similarly, pharmacological inhibition of K(+) -Cl(-) cotransporter type 2 by furosemide disrupted Cl(-) homeostasis and reduced the efficacy of diazepam but not propofol. Collectively our results suggest that pathological hyperexcitable conditions could cause the rapid accumulation of intracellular Cl(-) and the appearance of depolarising GABAA -mediated currents that would decrease the efficacy of diazepam.
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Affiliation(s)
- Tarek Z Deeb
- Department of Neuroscience, Tufts University, Boston, MA, USA
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192
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Khanna A, Walcott BP, Kahle KT. Limitations of Current GABA Agonists in Neonatal Seizures: Toward GABA Modulation Via the Targeting of Neuronal Cl(-) Transport. Front Neurol 2013; 4:78. [PMID: 23805124 PMCID: PMC3691543 DOI: 10.3389/fneur.2013.00078] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 06/09/2013] [Indexed: 01/18/2023] Open
Abstract
Neonatal intensive care has advanced rapidly in the last 40 years, with dramatic decreases in mortality and morbidity; however, for neonatal seizures, neither therapies nor outcomes have changed significantly. Basic and clinical studies indicate that seizures in neonates have long-term neurodevelopmental and psychiatric consequences, highlighting the need for novel pharmacotherapeutics. First-line treatments targeting GABAA receptors, like barbiturates and benzodiazepines, are limited in their efficacy and carry significant risks to the developing brain. Here, we review the use of current GABA agonist therapies for neonatal seizures and suggest other treatment strategies given recent developments in the understanding of disease pathogenesis. One promising avenue is the indirect manipulation of the GABAergic system, via the modulation of neuronal Cl− gradients, by targeting the cation-Cl− cotransporters (NKCC1 and KCC2) or their regulatory signaling molecules. This strategy might yield a novel class of more efficacious anti-epileptics with fewer side effects by specifically addressing disease pathophysiology. Moreover, this strategy may have ramifications for other adult seizure syndromes in which GABA receptor-mediated depolarizations play a pathogenic role, such as temporal lobe epilepsy.
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Affiliation(s)
- Arjun Khanna
- Division of Neurosurgery, Department of Surgery, Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA
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193
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Hertz L. The Glutamate-Glutamine (GABA) Cycle: Importance of Late Postnatal Development and Potential Reciprocal Interactions between Biosynthesis and Degradation. Front Endocrinol (Lausanne) 2013; 4:59. [PMID: 23750153 PMCID: PMC3664331 DOI: 10.3389/fendo.2013.00059] [Citation(s) in RCA: 160] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/02/2013] [Indexed: 01/28/2023] Open
Abstract
The gold standard for studies of glutamate-glutamine (GABA) cycling and its connections to brain biosynthesis from glucose of glutamate and GABA and their subsequent metabolism are the elegant in vivo studies by (13)C magnetic resonance spectroscopy (NMR), showing the large fluxes in the cycle. However, simpler experiments in intact brain tissue (e.g., immunohistochemistry), brain slices, cultured brain cells, and mitochondria have also made important contributions to the understanding of details, mechanisms, and functional consequences of glutamate/GABA biosynthesis and degradation. The purpose of this review is to attempt to integrate evidence from different sources regarding (i) the enzyme(s) responsible for the initial conversion of α-ketoglutarate to glutamate; (ii) the possibility that especially glutamate oxidation is essentially confined to astrocytes; and (iii) the ontogenetically very late onset and maturation of glutamine-glutamate (GABA) cycle function. Pathway models based on the functional importance of aspartate for glutamate synthesis suggest the possibility of interacting pathways for biosynthesis and degradation of glutamate and GABA and the use of transamination as the default mechanism for initiation of glutamate oxidation. The late development and maturation are related to the late cortical gliogenesis and convert brain cortical function from being purely neuronal to becoming neuronal-astrocytic. This conversion is associated with huge increases in energy demand and production, and the character of potentially incurred gains of function are discussed. These may include alterations in learning mechanisms, in mice indicated by lack of pairing of odor learning with aversive stimuli in newborn animals but the development of such an association 10-12 days later. The possibility is suggested that analogous maturational changes may contribute to differences in the way learning is accomplished in the newborn human brain and during later development.
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Affiliation(s)
- Leif Hertz
- Clinical Pharmacology, Medical University of ChinaShenyang, China
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194
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Sergeeva OA. GABAergic transmission in hepatic encephalopathy. Arch Biochem Biophys 2013; 536:122-30. [PMID: 23624382 DOI: 10.1016/j.abb.2013.04.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 04/08/2013] [Accepted: 04/09/2013] [Indexed: 01/05/2023]
Abstract
Hepatic encephalopathy (HE)(1) is a neuropsychiatric disorder caused by chronic or acute liver failure. Nearly thirty years ago a hypothesis was formulated explaining the neuropathology of HE by increased GABAergic tone. Recent progress in the GABAA-receptor (GABAAR) molecular pharmacology and biochemistry as well as the physiology of GABAergic transmission provided better understanding of GABA's role in health and disease. A detailed analysis of neuronal populations and their GABAergic afferents affected in HE is still missing. The slow progress in understanding the pathology of GABAergic transmission in HE is due to the high complexity of brain circuitries controlled by multiple types of GABAergic interneurons and the large variety of GABAAR, which are differently affected by pathological conditions and not yet fully identified. The mechanisms of action of the GABAAR agonist taurine, allosteric positive modulators (inhibitory neurosteroids, anaesthetics, benzodiazepines and histamine) and inhibitors of the GABAAR (excitatory neurosteroids, Ro15-4513) are discussed with respect to HE pathophysiology. Perspectives for GABAergic drugs in the symptomatic treatment of HE are suggested.
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Affiliation(s)
- Olga A Sergeeva
- Department of Neurophysiology, Medical Faculty, Heinrich-Heine-University, D-40225 Düsseldorf, Germany.
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195
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Cleary RT, Sun H, Huynh T, Manning SM, Li Y, Rotenberg A, Talos DM, Kahle KT, Jackson M, Rakhade SN, Berry G, Jensen FE. Bumetanide enhances phenobarbital efficacy in a rat model of hypoxic neonatal seizures. PLoS One 2013; 8:e57148. [PMID: 23536761 PMCID: PMC3594228 DOI: 10.1371/journal.pone.0057148] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Accepted: 01/17/2013] [Indexed: 01/30/2023] Open
Abstract
Neonatal seizures can be refractory to conventional anticonvulsants, and this may in part be due to a developmental increase in expression of the neuronal Na(+)-K(+)-2 Cl(-) cotransporter, NKCC1, and consequent paradoxical excitatory actions of GABAA receptors in the perinatal period. The most common cause of neonatal seizures is hypoxic encephalopathy, and here we show in an established model of neonatal hypoxia-induced seizures that the NKCC1 inhibitor, bumetanide, in combination with phenobarbital is significantly more effective than phenobarbital alone. A sensitive mass spectrometry assay revealed that bumetanide concentrations in serum and brain were dose-dependent, and the expression of NKCC1 protein transiently increased in cortex and hippocampus after hypoxic seizures. Importantly, the low doses of phenobarbital and bumetanide used in the study did not increase constitutive apoptosis, alone or in combination. Perforated patch clamp recordings from ex vivo hippocampal slices removed following seizures revealed that phenobarbital and bumetanide largely reversed seizure-induced changes in EGABA. Taken together, these data provide preclinical support for clinical trials of bumetanide in human neonates at risk for hypoxic encephalopathy and seizures.
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Affiliation(s)
- Ryan T. Cleary
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Hongyu Sun
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Thanhthao Huynh
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Simon M. Manning
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
- Division of Newborn Medicine, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
| | - Yijun Li
- Division of Genetics and Metabolism, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Alexander Rotenberg
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Delia M. Talos
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Kristopher T. Kahle
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michele Jackson
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Sanjay N. Rakhade
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Gerard Berry
- Division of Genetics and Metabolism, Children’s Hospital Boston, Boston, Massachusetts, United States of America
| | - Frances E. Jensen
- Department of Neurology, Children’s Hospital Boston, Boston, Massachusetts, United States of America
- Program in Neurobiology, Harvard Medical School, Boston, Massachusetts, United States of America
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196
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Pavlov I, Kaila K, Kullmann DM, Miles R. Cortical inhibition, pH and cell excitability in epilepsy: what are optimal targets for antiepileptic interventions? J Physiol 2013; 591:765-74. [PMID: 22890709 PMCID: PMC3591695 DOI: 10.1113/jphysiol.2012.237958] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 08/10/2012] [Indexed: 12/14/2022] Open
Abstract
Epilepsy is characterised by the propensity of the brain to generate spontaneous recurrent bursts of excessive neuronal activity, seizures. GABA-mediated inhibition is critical for restraining neuronal excitation in the brain, and therefore potentiation of GABAergic neurotransmission is commonly used to prevent seizures. However, data obtained in animal models of epilepsy and from human epileptic tissue suggest that GABA-mediated signalling contributes to interictal and ictal activity. Prolonged activation of GABA(A) receptors during epileptiform bursts may even initiate a shift in GABAergic neurotransmission from inhibitory to excitatory and so have a proconvulsant action. Direct targeting of the membrane mechanisms that reduce spiking in glutamatergic neurons may better control neuronal excitability in epileptic tissue. Manipulation of brain pH may be a promising approach and recent advances in gene therapy and optogenetics seem likely to provide further routes to effective therapeutic intervention.
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Affiliation(s)
- Ivan Pavlov
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London WC1N 3BG, UK.
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197
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Löscher W, Rogawski MA. How theories evolved concerning the mechanism of action of barbiturates. Epilepsia 2013. [PMID: 23205959 DOI: 10.1111/epi.12025] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The barbiturate phenobarbital has been in use in the treatment of epilepsy for 100 years. It has long been recognized that barbiturates act by prolonging and potentiating the action of γ-aminobutyric acid (GABA) on GABA(A) receptors and at higher concentrations directly activating the receptors. A large body of data supports the concept that GABA(A) receptors are the primary central nervous system target for barbiturates, including the finding that transgenic mice with a point mutation in the β3 GABA(A) -receptor subunit exhibit diminished sensitivity to the sedative and immobilizing actions of the anesthetic barbiturate pentobarbital. Although phenobarbital is only modestly less potent as a GABA(A) -receptor modulator than pentobarbital, phenobarbital is minimally sedating at effective anticonvulsant doses. Possible explanations for the reduced sedative effect of phenobarbital include more regionally restricted action; partial agonist activity; reduced propensity to directly activate GABA(A) receptors (possibly including extrasynaptic receptors containing δ subunits); and reduced activity at other ion channel targets, including voltage-gated calcium channels. In recent years, substantial progress has been made in defining the structural features of GABA(A) receptors responsible for gating and allosteric modulation by drugs. Although the precise sites of action of barbiturates have not yet been defined, the second and third transmembrane domains of the β subunit appear to be critical; binding may involve a pocket formed by β-subunit methionine 286 as well as α-subunit methionine 236. In addition to effects on GABA(A) receptors, barbiturates block AMPA/kainate receptors, and they inhibit glutamate release through an effect on P/Q-type high-voltage activated calcium channels. The combination of these various actions likely accounts for their diverse clinical activities. Despite the remarkable progress of the last century, there is still much to learn about the actions of barbiturates that can be applied to the discovery of new, more therapeutically useful agents.
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Affiliation(s)
- Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, Hannover, Germany.
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198
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Recent progress in GABAergic excitation from mature brain. Arch Pharm Res 2012; 35:2035-44. [PMID: 23263799 DOI: 10.1007/s12272-012-1202-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 11/23/2012] [Accepted: 11/27/2012] [Indexed: 01/15/2023]
Abstract
The excitatory effect of γ-Aminobutyric acid (GABA) has been recognized in very young animals and in seizure generation, but not so much in animals after weaning age or in adults. The existence of this phenomenon in mature brain is still controversial. In the course of debate, creative studies have identified and characterized the phenomenon in suprachiasmatic nucleus, cortex, hippocampus and basolateral amygdala, albeit mostly in single neurons. In neural circuit activity, presumed GABAergic excitation was observed in basolateral amygdala during the study of a neuropeptide, cholecystokinin. Though the functional meaning of this phenomenon in vivo remains to be uncovered, it may be implicated in epilepsy or anxiety in the adult brain.
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199
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Jourdain P, Boss D, Rappaz B, Moratal C, Hernandez MC, Depeursinge C, Magistretti PJ, Marquet P. Simultaneous optical recording in multiple cells by digital holographic microscopy of chloride current associated to activation of the ligand-gated chloride channel GABA(A) receptor. PLoS One 2012; 7:e51041. [PMID: 23236427 PMCID: PMC3517575 DOI: 10.1371/journal.pone.0051041] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 10/31/2012] [Indexed: 11/17/2022] Open
Abstract
Chloride channels represent a group of targets for major clinical indications. However, molecular screening for chloride channel modulators has proven to be difficult and time-consuming as approaches essentially rely on the use of fluorescent dyes or invasive patch-clamp techniques which do not lend themselves to the screening of large sets of compounds. To address this problem, we have developed a non-invasive optical method, based on digital holographic microcopy (DHM), allowing monitoring of ion channel activity without using any electrode or fluorescent dye. To illustrate this approach, GABA(A) mediated chloride currents have been monitored with DHM. Practically, we show that DHM can non-invasively provide the quantitative determination of transmembrane chloride fluxes mediated by the activation of chloride channels associated with GABA(A) receptors. Indeed through an original algorithm, chloride currents elicited by application of appropriate agonists of the GABA(A) receptor can be derived from the quantitative phase signal recorded with DHM. Finally, chloride currents can be determined and pharmacologically characterized non-invasively simultaneously on a large cellular sampling by DHM.
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Affiliation(s)
- Pascal Jourdain
- Brain and Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Daniel Boss
- Brain and Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Benjamin Rappaz
- Brain and Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Corinne Moratal
- Brain and Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | | | - Christian Depeursinge
- Institute of Applied Optics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Pierre Julius Magistretti
- Brain and Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- Center for Psychiatric Neuroscience Department, Lausanne University Hospital, Prilly, Switzerland
| | - Pierre Marquet
- Brain and Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- Center for Psychiatric Neuroscience Department, Lausanne University Hospital, Prilly, Switzerland
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200
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Deeb TZ, Maguire J, Moss SJ. Possible alterations in GABAA receptor signaling that underlie benzodiazepine-resistant seizures. Epilepsia 2012; 53 Suppl 9:79-88. [PMID: 23216581 PMCID: PMC4402207 DOI: 10.1111/epi.12037] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Benzodiazepines have been used for decades as first-line treatment for status epilepticus (SE). For reasons that are not fully understood, the efficacy of benzodiazepines decreases with increasing duration of seizure activity. This often forces clinicians to resort to more drastic second- and third-line treatments that are not always successful. The antiseizure properties of benzodiazepines are mediated by γ-aminobutyric acid type A (GABA(A) ) receptors. Decades of research have focused on the failure of GABAergic inhibition after seizure onset as the likely cause of the development benzodiazepine resistance during SE. However, the details of the deficits in GABA(A) signaling are still largely unknown. Therefore, it is necessary to improve our understanding of the mechanisms of benzodiazepine resistance so that more effective strategies can be formulated. In this review we discuss evidence supporting the role of altered GABA(A) receptor function as the major underlying cause of benzodiazepine-resistant SE in both humans and animal models. We specifically address the prevailing hypothesis, which is based on changes in the number and subtypes of GABA(A) receptors, as well as the potential influence of perturbed chloride homeostasis in the mature brain.
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Affiliation(s)
- Tarek Z Deeb
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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