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Dos Santos RR, Bernardino TC, da Silva MCM, de Oliveira ACP, Drumond LE, Rosa DV, Massensini AR, Moraes MFD, Doretto MC, Romano-Silva MA, Reis HJ. Neurochemical abnormalities in the hippocampus of male rats displaying audiogenic seizures, a genetic model of epilepsy. Neurosci Lett 2021; 761:136123. [PMID: 34293418 DOI: 10.1016/j.neulet.2021.136123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 07/11/2021] [Accepted: 07/16/2021] [Indexed: 11/17/2022]
Abstract
BACKGROUND Epilepsy is a disorder characterized by recurrent seizures that affects 1% of the population. However, the neurochemical alterations observed in epilepsy are not fully understood. There are different animal models of epilepsy, such as genetic or drug induced. In the present study, we utilize Wistar Audiogenic Rats (WAR), a murine strain that develops seizures in response to high intensity audio stimulation, in order to investigate abnormalities in glutamatergic and GABAergic systems. METHODS Synaptosomes and glial plasmalemmal vesicles were prepared from hippocampus and cortex, respectively. Glutamate and GABA release and uptake were assayed by monitoring the fluorescence and using L-[3H]-radiolabeled compounds. Glutamate and calcium concentration in the synaptosomes were also measured. The expression of neuronal calcium sensor 1 (NCS-1) was determined by western blot. RESULTS Glutamate and GABA release evoked by KCl was decreased in WAR compared to control Wistar rats. Calcium independent release was not considerably different in both groups. The total amount of glutamate of synaptosomes, as well as glutamate uptake by synaptosomes and GPV were also decreased in WAR in comparison with the controls. In addition, [Ca2+]i of hippocampal synaptosomes, as well as NCS-1 expression in the hippocampus, were increased in WAR in comparison with controls. CONCLUSION In conclusion, our results suggest that WAR have important alterations in the glutamatergic and GABAergic pathways, as well as an increased expression of NCS-1 in the hippocampus and inferior colliculus. These alterations may be linked to the spreading of hyperexcitability and recruitment of various brain regions.
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Affiliation(s)
- Rodrigo Ribeiro Dos Santos
- Departamento de Saúde Mental, Faculdade de Medicina, Universidade Federal de Minas Gerais. Av Alfredo Balena 190, CEP 30130-100 Belo Horizonte, MG, Brazil; Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Túlio C Bernardino
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Maria Carolina Machado da Silva
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Antônio C P de Oliveira
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Luciana E Drumond
- Núcleo de Neurociências, Departamento de Biofísica e Fisiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Daniela V Rosa
- Departamento de Saúde Mental, Faculdade de Medicina, Universidade Federal de Minas Gerais. Av Alfredo Balena 190, CEP 30130-100 Belo Horizonte, MG, Brazil
| | - André R Massensini
- Núcleo de Neurociências, Departamento de Biofísica e Fisiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Márcio F D Moraes
- Núcleo de Neurociências, Departamento de Biofísica e Fisiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Maria C Doretto
- Núcleo de Neurociências, Departamento de Biofísica e Fisiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Marco A Romano-Silva
- Departamento de Saúde Mental, Faculdade de Medicina, Universidade Federal de Minas Gerais. Av Alfredo Balena 190, CEP 30130-100 Belo Horizonte, MG, Brazil
| | - Helton J Reis
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil.
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2
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Nakajima T, Kawabata-Iwakawa R, Kaneko Y, Hamano SI, Sano R, Tamura S, Hasegawa H, Kobari T, Kominato Y, Nishiyama M, Kurabayashi M. Novel Cardiocerebral Channelopathy Associated with a KCND3 V392I Mutation. Int Heart J 2020; 61:1049-1055. [PMID: 32921676 DOI: 10.1536/ihj.20-203] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
While a KCND3 V392I mutation uniquely displays a mixed electrophysiological phenotype of Kv4.3, only limited clinical information on the mutation carriers is available. We report two teenage siblings exhibiting both cardiac (early repolarization syndrome and paroxysmal atrial fibrillation) and cerebral phenotypes (epilepsy and intellectual disability), in whom we identified the KCND3 V392I mutation. We propose a link between the KCND3 mutation with a mixed electrophysiological phenotype and cardiocerebral phenotypes, which may be defined as a novel cardiocerebral channelopathy.
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Affiliation(s)
- Tadashi Nakajima
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine
| | - Reika Kawabata-Iwakawa
- Division of Integrated Oncology Research, Gunma University Initiative for Advanced Research
| | - Yoshiaki Kaneko
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine
| | | | - Rie Sano
- Department of Legal Medicine, Gunma University Graduate School of Medicine
| | - Shuntaro Tamura
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine
| | - Hiroshi Hasegawa
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine
| | - Takashi Kobari
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine
| | - Yoshihiko Kominato
- Department of Legal Medicine, Gunma University Graduate School of Medicine
| | - Masahiko Nishiyama
- Division of Integrated Oncology Research, Gunma University Initiative for Advanced Research.,Department of Molecular Pharmacology and Oncology, Gunma University Graduate School of Medicine
| | - Masahiko Kurabayashi
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine
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3
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Zhao L, Luo F, Wang A, Zhang J, Wang Y, Zhao L, Wang Z, Pu Q. Quick stabilization of capillary for rapid determination of potassium ions in the blood of epilepsy patients by capillary electrophoresis without sample pretreatment. Electrophoresis 2020; 41:1273-1279. [PMID: 32358896 DOI: 10.1002/elps.202000022] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 04/21/2020] [Accepted: 04/23/2020] [Indexed: 11/07/2022]
Abstract
Mutations in the potassium channel genes may be linked to the development of epilepsy and affect the blood potassium levels. Therefore, accurate determination of potassium in the blood will be critical to diagnose the cause of epilepsy. CE is a competent technique for the fast detection of multiple ions, but complicated matrices of a blood sample may cause significant variation of migration times and the peak shape. In this work, a procedure for rapid stabilization of the capillary inner surface through preflushing of a blood sample was employed. The process takes only 40 min for a capillary and then it can be used for more than 2 weeks. No pretreatment of the blood sample or other surface modification of the capillary is needed for the analysis. The RSDs of the migration time and peak area were reduced to 1.5 and 5.1% from 12.6 and 14.5%, respectively. The proposed method has been successfully applied to the determination of the potassium contents in the blood sample of patients with epilepsy at different stages. The recoveries of potassium ions in these blood samples are in a range from 86.5 to 104.5%.
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Affiliation(s)
- Litao Zhao
- School of Pharmacy, Lanzhou University, Lanzhou, P. R. China
| | - Fanghong Luo
- School of Pharmacy, Lanzhou University, Lanzhou, P. R. China
| | - Anting Wang
- School of Pharmacy, Lanzhou University, Lanzhou, P. R. China
| | - Jing Zhang
- School of Pharmacy, Lanzhou University, Lanzhou, P. R. China
| | - Yuanhang Wang
- College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, P. R. China
| | - Liangtao Zhao
- TSing Biomedical Research Center, The Second Hospital of Lanzhou University, Lanzhou, P. R. China
| | - Zhaoyan Wang
- School of Pharmacy, Lanzhou University, Lanzhou, P. R. China
| | - Qiaosheng Pu
- College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, P. R. China
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4
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Noh W, Pak S, Choi G, Yang S, Yang S. Transient Potassium Channels: Therapeutic Targets for Brain Disorders. Front Cell Neurosci 2019; 13:265. [PMID: 31263403 PMCID: PMC6585177 DOI: 10.3389/fncel.2019.00265] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 05/28/2019] [Indexed: 01/04/2023] Open
Abstract
Transient potassium current channels (IA channels), which are expressed in most brain areas, have a central role in modulating feedforward and feedback inhibition along the dendroaxonic axis. Loss of the modulatory channels is tightly associated with a number of brain diseases such as Alzheimer’s disease, epilepsy, fragile X syndrome (FXS), Parkinson’s disease, chronic pain, tinnitus, and ataxia. However, the functional significance of IA channels in these diseases has so far been underestimated. In this review, we discuss the distribution and function of IA channels. Particularly, we posit that downregulation of IA channels results in neuronal (mostly dendritic) hyperexcitability accompanied by the imbalanced excitation and inhibition ratio in the brain’s networks, eventually causing the brain diseases. Finally, we propose a potential therapeutic target: the enhanced action of IA channels to counteract Ca2+-permeable channels including NMDA receptors could be harnessed to restore dendritic excitability, leading to a balanced neuronal state.
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Affiliation(s)
- Wonjun Noh
- Department of Nano-Bioengineering, Incheon National University, Incheon, South Korea
| | - Sojeong Pak
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - Geunho Choi
- Department of Computer Science and Engineering, Incheon National University, Incheon, South Korea
| | - Sungchil Yang
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - Sunggu Yang
- Department of Nano-Bioengineering, Incheon National University, Incheon, South Korea
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5
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Arnold EC, McMurray C, Gray R, Johnston D. Epilepsy-Induced Reduction in HCN Channel Expression Contributes to an Increased Excitability in Dorsal, But Not Ventral, Hippocampal CA1 Neurons. eNeuro 2019; 6:ENEURO.0036-19.2019. [PMID: 30957013 PMCID: PMC6449163 DOI: 10.1523/eneuro.0036-19.2019] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Accepted: 03/05/2019] [Indexed: 12/31/2022] Open
Abstract
CA1 neurons in epileptic animals are vulnerable to selective changes in ion channel expression, called acquired channelopathies, which can increase the excitability of a neuron. Under normal conditions there is a gradient of ion channel expression and intrinsic excitability along the longitudinal, dorsoventral axis of hippocampal area CA1 of the rodent. Many of these channels, including M-channels, GIRK channels and HCN channels, all have dorsoventral expression gradients that might be altered in rodent models of epilepsy. Here, we show that the excitability of dorsal, but not ventral CA1 neurons, had an increased firing rate, reduced interspike interval (ISI) and increased input resistance in a status epilepticus (SE) model of temporal lobe epilepsy (TLE). As a result, the excitability of CA1 neurons became uniform across the dorsoventral axis of the rat hippocampus post-SE. Using current clamp recordings with pharmacology and immunohistochemistry, we demonstrate that the expression of HCN channels was downregulated in the dorsal CA1 region post-SE, while the expression of M and GIRK channels were unchanged. We did not find this acquired channelopathy in ventral CA1 neurons post-SE. Our results suggest that the excitability of dorsal CA1 neurons post-SE increase to resemble the intrinsic properties of ventral CA1 neurons, which likely makes the hippocampal circuit more permissible to seizures, and contributes to the cognitive impairments associated with chronic epilepsy.
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Affiliation(s)
- Elizabeth C. Arnold
- Institute for Neuroscience, University of Texas at Austin, Austin, TX 78712
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712
| | - Calli McMurray
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712
| | - Richard Gray
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712
| | - Daniel Johnston
- Institute for Neuroscience, University of Texas at Austin, Austin, TX 78712
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712
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6
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Rubboli G, Plazzi G, Picard F, Nobili L, Hirsch E, Chelly J, Prayson RA, Boutonnat J, Bramerio M, Kahane P, Dibbens LM, Gardella E, Baulac S, Møller RS. Mild malformations of cortical development in sleep-related hypermotor epilepsy due to KCNT1 mutations. Ann Clin Transl Neurol 2018; 6:386-391. [PMID: 30847371 PMCID: PMC6389734 DOI: 10.1002/acn3.708] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 11/02/2018] [Accepted: 11/18/2018] [Indexed: 11/18/2022] Open
Abstract
Mutations in the sodium‐activated potassium channel gene KCNT1 have been associated with nonlesional sleep‐related hypermotor epilepsy (SHE). We report the co‐occurrence of mild malformation of cortical development (mMCD) and KCNT1 mutations in four patients with SHE. Focal cortical dysplasia type I was neuropathologically diagnosed after epilepsy surgery in three unrelated MRI‐negative patients, periventricular nodular heterotopia was detected in one patient by MRI. Our findings suggest that KCNT1 epileptogenicity may result not only from dysregulated excitability by controlling Na+K+ transport, but also from mMCD. Therefore, pathogenic variants in KCNT1 may encompass both lesional and nonlesional epilepsies.
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Affiliation(s)
- Guido Rubboli
- Danish Epilepsy Centre, Filadelfia Dianalund Denmark.,University of Copenhagen Copenhagen Denmark
| | - Giuseppe Plazzi
- Department of Biomedical and Neuromotor Sciences University of Bologna Bologna Italy.,IRCCS Institute of Neurological Sciences Bologna Italy
| | - Fabienne Picard
- Department of Clinical Neurosciences University Hospitals and Medical School of Geneva Geneva Switzerland
| | - Lino Nobili
- Epilepsy Surgery Center Niguarda Hospital Milan Italy
| | - Edouard Hirsch
- INSERM Unité 964: Génétique et Physiopathologie des Maladies Neuro Dévelopmentales Epileptogènes Epilepsy Unit « Francis Rohmer » Hautepierre Hospital University Hospital Strasbourg France
| | - Jamel Chelly
- Service de Diagnostic Génétique Hôpital Civil de Strasbourg Hôpitaux Universitaires de Strasbourg Strasbourg France
| | | | - Jean Boutonnat
- Département d'Anatomie et de Cytologie Pathologiques Institut de Biologie et de Pathologie CHU de Grenoble Grenoble France
| | | | - Philippe Kahane
- Neurology Department Grenoble-Alpes University and Hospital Grenoble France
| | - Leanne M Dibbens
- Epilepsy Research Group School of Pharmacy and Medical Sciences University of South Australia and Sansom Institute for Health Research Adelaide Australia
| | - Elena Gardella
- Danish Epilepsy Centre, Filadelfia Dianalund Denmark.,Institute for Regional Health Services University of Southern Denmark Odense Denmark
| | - Stéphanie Baulac
- Institut du Cerveau et de la Moelle, ICM Inserm U1127 F-7501 Paris France.,CNRS UMR 7225 F-75013 Paris France.,Sorbonne Université F-75013 Paris France
| | - Rikke S Møller
- Danish Epilepsy Centre, Filadelfia Dianalund Denmark.,Institute for Regional Health Services University of Southern Denmark Odense Denmark
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7
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BRAF somatic mutation contributes to intrinsic epileptogenicity in pediatric brain tumors. Nat Med 2018; 24:1662-1668. [PMID: 30224756 DOI: 10.1038/s41591-018-0172-x] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 07/27/2018] [Indexed: 12/21/2022]
Abstract
Pediatric brain tumors are highly associated with epileptic seizures1. However, their epileptogenic mechanisms remain unclear. Here, we show that the oncogenic BRAF somatic mutation p.Val600Glu (V600E) in developing neurons underlies intrinsic epileptogenicity in ganglioglioma, one of the leading causes of intractable epilepsy2. To do so, we developed a mouse model harboring the BRAFV600E somatic mutation during early brain development to reflect the most frequent mutation, as well as the origin and timing thereof. Therein, the BRAFV600E mutation arising in progenitor cells during brain development led to the acquisition of intrinsic epileptogenic properties in neuronal lineage cells, whereas tumorigenic properties were attributed to high proliferation of glial lineage cells. RNA sequencing analysis of patient brain tissues with the mutation revealed that BRAFV600E-induced epileptogenesis is mediated by RE1-silencing transcription factor (REST), which is a regulator of ion channels and neurotransmitter receptors associated with epilepsy. Moreover, we found that seizures in mice were significantly alleviated by an FDA-approved BRAFV600E inhibitor, vemurafenib, as well as various genetic inhibitions of Rest. Accordingly, this study provides direct evidence of a BRAF somatic mutation contributing to the intrinsic epileptogenicity in pediatric brain tumors and suggests that BRAF and REST could be treatment targets for intractable epilepsy.
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8
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Hong Y, Deng N, Jin HN, Xuan ZZ, Qian YX, Wu ZY, Xie W. Saikosaponin A modulates remodeling of Kv4.2-mediated A-type voltage-gated potassium currents in rat chronic temporal lobe epilepsy. DRUG DESIGN DEVELOPMENT AND THERAPY 2018; 12:2945-2958. [PMID: 30254424 PMCID: PMC6141107 DOI: 10.2147/dddt.s166408] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Background Chronic temporal lobe epilepsy (cTLE) is the most common intractable epilepsy. Recent studies have shown that saikosaponin A (SSa) could inhibit epileptiform discharges induced by 4 action potentials and selectively increase the transient inactivating K+ currents (IA). However, the mechanisms of SSa on IA remain unclear. In this study, we comprehensively evaluated the anticonvulsant activities of SSa and explored whether or not it plays an anti-epileptic role in a Li-pilocarpine induced epilepsy rat model via remodeling Kv4.2-mediated A-type voltage-gated potassium currents (Kv4.2-mediated IA). Materials and methods All in vitro spontaneous recurrent seizures (SRS) were recorded with continuous video monitoring. Nissl’s staining was used to evaluate the SSa protection of neurons and immunohistochemistry, Western blot, and quantitative reverse transcription PCR were used to quantify the expression of Kchip1 and Kv4.2 in the hippocampal CA1 field and the adjacent cortex following Li-pilocarpine induced status epilepticus. We used whole-cell current-clamp recordings to evaluate the anticonvulsant activities of SSa in a hippocampal neuronal culture model of cTLE, while whole-cell voltage-clamp recordings were used to evaluate the modulatory effects of SSa on Kv4.2-mediated IA. Results SSa treatment significantly reduced the frequency and duration of SRS over the course of eight weeks and increased the production of Kchip1 and Kv4.2. In addition, SSa attenuated spontaneous recurrent epileptiform discharges (SREDs) in the hippocampal neuronal model and up-regulated Kv4.2-mediated IA. Conclusions SSa exerted a disease-modifying effect in our cTLE rat model both in vivo and in vitro; the increase in Kv4.2-mediated IA may contribute to the anticonvulsant mechanisms of SSa.
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Affiliation(s)
- Yu Hong
- Department of Traditional Chinese Medicine, School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China, .,Department of Traditional Chinese Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, China,
| | - Ning Deng
- Department of Traditional Chinese Medicine, School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China,
| | - Han-Na Jin
- Department of Internal Neurology, People's Hospital of Huizhou Zhongkai Hi-tech Industrial Development Zone, Huizhou, China
| | - Zheng-Zheng Xuan
- Neuroelectrophysiological Examination Room, Traditional Chinese Medicine Hospital of Guangdong Province, Guangzhou, China
| | - Yi-Xiao Qian
- Department of Traditional Chinese Medicine, School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China,
| | - Zhi-Yong Wu
- Department of Traditional Chinese Medicine, School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China, .,Department of Traditional Chinese Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, China,
| | - Wei Xie
- Department of Traditional Chinese Medicine, School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China, .,Department of Traditional Chinese Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, China,
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Iffland PH, Crino PB. Focal Cortical Dysplasia: Gene Mutations, Cell Signaling, and Therapeutic Implications. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2017; 12:547-571. [PMID: 28135561 DOI: 10.1146/annurev-pathol-052016-100138] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Focal cortical dysplasias (FCDs) are malformations of cortical development (MCDs) that are highly associated with medication-resistant epilepsy and are the most common cause of neocortical epilepsy in children. FCDs are a heterogeneous group of developmental disorders caused by germline or somatic mutations that occur in genes regulating the PI3K/Akt/mTOR pathway-a key pathway in neuronal growth and migration. Accordingly, FCDs are characterized by abnormal cortical lamination, cell morphology (e.g., cytomegaly), and cellular polarity. In some FCD subtypes, balloon cells express proteins typically seen in neuroglial progenitor cells. Because recurrent intractable seizures are a common feature of FCDs, epileptogenic electrophysiological properties are also observed in addition to local inflammation. Here, we will summarize the current literature regarding FCDs, addressing the current classification system, histopathology, molecular genetics, electrophysiology, and transcriptome and cell signaling changes.
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Affiliation(s)
- Philip H Iffland
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania 19140;
| | - Peter B Crino
- Department of Neurology, University of Maryland School of Medicine, Baltimore, Maryland 21201;
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Siedlecka M, Grajkowska W, Galus R, Dembowska-Bagińska B, Jóźwiak J. Focal cortical dysplasia: Molecular disturbances and clinicopathological classification (Review). Int J Mol Med 2016; 38:1327-1337. [DOI: 10.3892/ijmm.2016.2760] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 06/23/2016] [Indexed: 11/05/2022] Open
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Abstract
This review attempts to give a concise and up-to-date overview on the role of potassium channels in epilepsies. Their role can be defined from a genetic perspective, focusing on variants and de novo mutations identified in genetic studies or animal models with targeted, specific mutations in genes coding for a member of the large potassium channel family. In these genetic studies, a demonstrated functional link to hyperexcitability often remains elusive. However, their role can also be defined from a functional perspective, based on dynamic, aggravating, or adaptive transcriptional and posttranslational alterations. In these cases, it often remains elusive whether the alteration is causal or merely incidental. With ∼80 potassium channel types, of which ∼10% are known to be associated with epilepsies (in humans) or a seizure phenotype (in animals), if genetically mutated, a comprehensive review is a challenging endeavor. This goal may seem all the more ambitious once the data on posttranslational alterations, found both in human tissue from epilepsy patients and in chronic or acute animal models, are included. We therefore summarize the literature, and expand only on key findings, particularly regarding functional alterations found in patient brain tissue and chronic animal models.
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Affiliation(s)
- Rüdiger Köhling
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany
| | - Jakob Wolfart
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany
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12
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Aging-Related Hyperexcitability in CA3 Pyramidal Neurons Is Mediated by Enhanced A-Type K+ Channel Function and Expression. J Neurosci 2015; 35:13206-18. [PMID: 26400949 DOI: 10.1523/jneurosci.0193-15.2015] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aging-related impairments in hippocampus-dependent cognition have been attributed to maladaptive changes in the functional properties of pyramidal neurons within the hippocampal subregions. Much evidence has come from work on CA1 pyramidal neurons, with CA3 pyramidal neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing in the hippocampal circuit. Here, we use whole-cell current-clamp to demonstrate that aged rat (29-32 months) CA3 pyramidal neurons fire significantly more action potentials (APs) during theta-burst frequency stimulation and that this is associated with faster AP repolarization (i.e., narrower AP half-widths and enlarged fast afterhyperpolarization). Using a combination of patch-clamp physiology, pharmacology, Western blot analyses, immunohistochemistry, and array tomography, we demonstrate that these faster AP kinetics are mediated by enhanced function and expression of Kv4.2/Kv4.3 A-type K(+) channels, particularly within the perisomatic compartment, of CA3 pyramidal neurons. Thus, our study indicates that inhibition of these A-type K(+) channels can restore the intrinsic excitability properties of aged CA3 pyramidal neurons to a young-like state. Significance statement: Age-related learning deficits have been attributed, in part, to altered hippocampal pyramidal neuronal function with normal aging. Much evidence has come from work on CA1 neurons, with CA3 neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing. Hence, we conducted a series of experiments to identify the cellular mechanisms that underlie the hyperexcitability reported in the CA3 region. Contrary to CA1 neurons, we demonstrate that postburst afterhyperpolarization is not altered with aging and that aged CA3 pyramidal neurons are able to fire significantly more action potentials and that this is associated with faster action potential repolarization through enhanced expression of Kv4.2/Kv4.3 A-type K(+) channels, particularly within the cell bodies of CA3 pyramidal neurons.
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13
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Yang S, Tang CM, Yang S. The Shaping of Two Distinct Dendritic Spikes by A-Type Voltage-Gated K(+) Channels. Front Cell Neurosci 2015; 9:469. [PMID: 26696828 PMCID: PMC4673864 DOI: 10.3389/fncel.2015.00469] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 11/17/2015] [Indexed: 12/03/2022] Open
Abstract
Dendritic ion channels have been a subject of intense research in neuroscience because active ion channels in dendrites shape input signals. Ca2+-permeable channels including NMDA receptors (NMDARs) have been implicated in supralinear dendritic integration, and the IA conductance in sublinear integration. Despite their essential roles in dendritic integration, it has remained uncertain whether these conductance coordinate with, or counteract, each other in the process of dendritic integration. To address this question, experiments were designed in hippocampal CA1 neurons with a recent 3D digital holography system that has shown excellent performance for spatial photoactivation. The results demonstrated a role of IA as a key modulator for two distinct dendritic spikes, low- and high-threshold Ca2+ spikes, through a preferential action of IA on Ca2+-permeable channel-mediated currents, over fast AMPAR-mediated currents. It is likely that the rapid kinetics of IA provides feed-forward inhibition to counteract the regenerative Ca2+ channel-mediated dendritic excitability. This research reveals one dynamic ionic mechanism of dendritic integration, and may contribute to a new understanding of neuronal hyperexcitability embedded in several neural diseases such as epilepsy, fragile X syndrome and Alzheimer’s disease.
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Affiliation(s)
- Sungchil Yang
- Department of Biomedical Sciences, City University of Hong Kong Kowloon, Hong Kong
| | - Cha-Min Tang
- Department of Neurology and Department of Physiology, University of Maryland School of Medicine Baltimore VAMC, MD, USA
| | - Sunggu Yang
- Department of Nano-Bioengineering, Incheon National University Incheon, South Korea
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Tau-dependent Kv4.2 depletion and dendritic hyperexcitability in a mouse model of Alzheimer's disease. J Neurosci 2015; 35:6221-30. [PMID: 25878292 DOI: 10.1523/jneurosci.2552-14.2015] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuronal hyperexcitability occurs early in the pathogenesis of Alzheimer's disease (AD) and contributes to network dysfunction in AD patients. In other disorders with neuronal hyperexcitability, dysfunction in the dendrites often contributes, but dendritic excitability has not been directly examined in AD models. We used dendritic patch-clamp recordings to measure dendritic excitability in the CA1 region of the hippocampus. We found that dendrites, more so than somata, of hippocampal neurons were hyperexcitable in mice overexpressing Aβ. This dendritic hyperexcitability was associated with depletion of Kv4.2, a dendritic potassium channel important for regulating dendritic excitability and synaptic plasticity. The antiepileptic drug, levetiracetam, blocked Kv4.2 depletion. Tau was required, as crossing with tau knock-out mice also prevented both Kv4.2 depletion and dendritic hyperexcitability. Dendritic hyperexcitability induced by Kv4.2 deficiency exacerbated behavioral deficits and increased epileptiform activity in hAPP mice. We conclude that increased dendritic excitability, associated with changes in dendritic ion channels including Kv4.2, may contribute to neuronal dysfunction in early stages AD.
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15
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Wolfart J, Laker D. Homeostasis or channelopathy? Acquired cell type-specific ion channel changes in temporal lobe epilepsy and their antiepileptic potential. Front Physiol 2015; 6:168. [PMID: 26124723 PMCID: PMC4467176 DOI: 10.3389/fphys.2015.00168] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 05/19/2015] [Indexed: 01/16/2023] Open
Abstract
Neurons continuously adapt the expression and functionality of their ion channels. For example, exposed to chronic excitotoxicity, neurons homeostatically downscale their intrinsic excitability. In contrast, the “acquired channelopathy” hypothesis suggests that proepileptic channel characteristics develop during epilepsy. We review cell type-specific channel alterations under different epileptic conditions and discuss the potential of channels that undergo homeostatic adaptations, as targets for antiepileptic drugs (AEDs). Most of the relevant studies have been performed on temporal lobe epilepsy (TLE), a widespread AED-refractory, focal epilepsy. The TLE patients, who undergo epilepsy surgery, frequently display hippocampal sclerosis (HS), which is associated with degeneration of cornu ammonis subfield 1 pyramidal cells (CA1 PCs). Although the resected human tissue offers insights, controlled data largely stem from animal models simulating different aspects of TLE and other epilepsies. Most of the cell type-specific information is available for CA1 PCs and dentate gyrus granule cells (DG GCs). Between these two cell types, a dichotomy can be observed: while DG GCs acquire properties decreasing the intrinsic excitability (in TLE models and patients with HS), CA1 PCs develop channel characteristics increasing intrinsic excitability (in TLE models without HS only). However, thorough examination of data on these and other cell types reveals the coexistence of protective and permissive intrinsic plasticity within neurons. These mechanisms appear differentially regulated, depending on the cell type and seizure condition. Interestingly, the same channel molecules that are upregulated in DG GCs during HS-related TLE, appear as promising targets for future AEDs and gene therapies. Hence, GCs provide an example of homeostatic ion channel adaptation which can serve as a primer when designing novel anti-epileptic strategies.
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Affiliation(s)
- Jakob Wolfart
- Oscar Langendorff Institute of Physiology, University of Rostock Rostock, Germany
| | - Debora Laker
- Oscar Langendorff Institute of Physiology, University of Rostock Rostock, Germany
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16
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Thom M. Review: Hippocampal sclerosis in epilepsy: a neuropathology review. Neuropathol Appl Neurobiol 2015; 40:520-43. [PMID: 24762203 PMCID: PMC4265206 DOI: 10.1111/nan.12150] [Citation(s) in RCA: 328] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 04/23/2014] [Indexed: 12/12/2022]
Abstract
Hippocampal sclerosis (HS) is a common pathology encountered in mesial temporal lobe epilepsy (MTLE) as well as other epilepsy syndromes and in both surgical and post-mortem practice. The 2013 International League Against Epilepsy (ILAE) classification segregates HS into typical (type 1) and atypical (type 2 and 3) groups, based on the histological patterns of subfield neuronal loss and gliosis. In addition, granule cell reorganization and alterations of interneuronal populations, neuropeptide fibre networks and mossy fibre sprouting are distinctive features of HS associated with epilepsies; they can be useful diagnostic aids to discriminate from other causes of HS, as well as highlighting potential mechanisms of hippocampal epileptogenesis. The cause of HS remains elusive and may be multifactorial; the contribution of febrile seizures, genetic susceptibility, inflammatory and neurodevelopmental factors are discussed. Post-mortem based research in HS, as an addition to studies on surgical samples, has the added advantage of enabling the study of the wider network changes associated with HS, the long-term effects of epilepsy on the pathology and associated comorbidities. It is likely that HS is heterogeneous in aspects of its cause, epileptogenetic mechanisms, network alterations and response to medical and surgical treatments. Future neuropathological studies will contribute to better recognition and understanding of these clinical and patho-aetiological subtypes of HS.
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Affiliation(s)
- Maria Thom
- Departments of Neuropathology and Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, UK
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17
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Expression of astrocyte-related receptors in cortical dysplasia with intractable epilepsy. J Neuropathol Exp Neurol 2014; 73:798-806. [PMID: 25003238 DOI: 10.1097/nen.0000000000000099] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Epilepsy is one of the major neurologic diseases, and astrocytes play important roles in epileptogenesis. To investigate possible roles of astrocyte-related receptors in patients with intractable epilepsy associated with focal cortical dysplasia (FCD) and other conditions, we examined resected epileptic foci from 31 patients, including 23 with FCD type I, IIa, or IIb, 5 with tuberous sclerosis complex, and 3 with low-grade astrocytoma. Control samples were from 21 autopsied brains of patients without epilepsy or neurologic deficits and 5 patients with pathologic gliosis without epilepsy. Immunohistochemical and immunoblot analyses with antibodies against purinergic receptor subtypes P2RY1, P2RY2, P2RY4, potassium channels Kv4.2 and Kir4.1, and metabotropic receptor subtypes mGluR1 and mGluR5 were performed. Anti-glial fibrillary acidic protein, anti-NeuN, and anti-CD68 immunostaining was used to identify astrocytes, neurons, and microglia, respectively. Most glial fibrillary acidic protein-immunopositive astrocyte cells in the brain samples from patients with epilepsy were P2RY1-, P2RY2-, P2RY4-, Kv4.2-, Kir4.1-, mGluR1-, and mGluR5-positive, whereas samples from controls and pathologic gliosis showed lower expression levels of these astrocyte-related receptors. Our findings suggest that, although these receptors are necessary for astrocyte transmission, formation of the neuron-glia network, and other physiologic functions, overexpression in the brains of patients with intractable epilepsy may be associated with activation of intracellular and glio-neuronal signaling pathways that contribute to epileptogenesis.
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18
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Aronica E, Crino PB. Epilepsy related to developmental tumors and malformations of cortical development. Neurotherapeutics 2014; 11:251-68. [PMID: 24481729 PMCID: PMC3996119 DOI: 10.1007/s13311-013-0251-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Structural abnormalities of the brain are increasingly recognized in patients with neurodevelopmental delay and intractable focal epilepsies. The access to clinically well-characterized neurosurgical material has provided a unique opportunity to better define the neuropathological, neurochemical, and molecular features of epilepsy-associated focal developmental lesions. These studies help to further understand the epileptogenic mechanisms of these lesions. Neuropathological evaluation of surgical specimens from patients with epilepsy-associated developmental lesions reveals two major pathologies: focal cortical dysplasia and low-grade developmental tumors (glioneuronal tumors). In the last few years there have been major advances in the recognition of a wide spectrum of developmental lesions associated with a intractable epilepsy, including cortical tubers in patients with tuberous sclerosis complex and hemimegalencephaly. As an increasing number of entities are identified, the development of a unified and comprehensive classification represents a great challenge and requires continuous updates. The present article reviews current knowledge of molecular pathogenesis and the pathophysiological mechanisms of epileptogenesis in this group of developmental disorders. Both emerging neuropathological and basic science evidence will be analyzed, highlighting the involvement of different, but often converging, pathogenetic and epileptogenic mechanisms, which may create the basis for new therapeutic strategies in these disorders.
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Affiliation(s)
- Eleonora Aronica
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands,
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Are alterations in transmitter receptor and ion channel expression responsible for epilepsies? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:211-29. [PMID: 25012379 DOI: 10.1007/978-94-017-8914-1_17] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Neuronal voltage-gated ion channels and ligand-gated synaptic receptors play a critical role in maintaining the delicate balance between neuronal excitation and inhibition within neuronal networks in the brain. Changes in expression of voltage-gated ion channels, in particular sodium, hyperpolarization-activated cyclic nucleotide-gated (HCN) and calcium channels, and ligand-gated synaptic receptors, in particular GABA and glutamate receptors, have been reported in many types of both genetic and acquired epilepsies, in animal models and in humans. In this chapter we review these and discuss the potential pathogenic role they may play in the epilepsies.
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20
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Shah NH, Aizenman E. Voltage-gated potassium channels at the crossroads of neuronal function, ischemic tolerance, and neurodegeneration. Transl Stroke Res 2013; 5:38-58. [PMID: 24323720 DOI: 10.1007/s12975-013-0297-7] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/14/2013] [Accepted: 10/14/2013] [Indexed: 11/29/2022]
Abstract
Voltage-gated potassium (Kv) channels are widely expressed in the central and peripheral nervous system and are crucial mediators of neuronal excitability. Importantly, these channels also actively participate in cellular and molecular signaling pathways that regulate the life and death of neurons. Injury-mediated increased K(+) efflux through Kv2.1 channels promotes neuronal apoptosis, contributing to widespread neuronal loss in neurodegenerative disorders such as Alzheimer's disease and stroke. In contrast, some forms of neuronal activity can dramatically alter Kv2.1 channel phosphorylation levels and influence their localization. These changes are normally accompanied by modifications in channel voltage dependence, which may be neuroprotective within the context of ischemic injury. Kv1 and Kv7 channel dysfunction leads to neuronal hyperexcitability that critically contributes to the pathophysiology of human clinical disorders such as episodic ataxia and epilepsy. This review summarizes the neurotoxic, neuroprotective, and neuroregulatory roles of Kv channels and highlights the consequences of Kv channel dysfunction on neuronal physiology. The studies described in this review thus underscore the importance of normal Kv channel function in neurons and emphasize the therapeutic potential of targeting Kv channels in the treatment of a wide range of neurological diseases.
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Affiliation(s)
- Niyathi Hegde Shah
- Department of Neurobiology, University of Pittsburgh School of Medicine, 3500 Terrace Street, E1456 BST, Pittsburgh, PA, 15261, USA,
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21
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22
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Saikosaponin a Enhances Transient Inactivating Potassium Current in Rat Hippocampal CA1 Neurons. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:413092. [PMID: 23554830 PMCID: PMC3608310 DOI: 10.1155/2013/413092] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 01/01/2013] [Indexed: 11/18/2022]
Abstract
Saikosaponin a (SSa), a main constituent of the Chinese herb Bupleurum chinense DC., has been demonstrated to have antiepileptic activity. Recent studies have shown that SSa could inhibit NMDA receptor current and persistent sodium current. However, the effects of SSa on potassium (K+) currents remain unclear. In this study, we tested the effect of SSa on 4AP-induced epileptiform discharges and K+ currents in CA1 neurons of rat hippocampal slices. We found that SSa significantly inhibited epileptiform discharges frequency and duration in hippocampal CA1 neurons in the 4AP seizure model in a dose-dependent manner with an IC50
of 0.7 μM. SSa effectively increased the amplitude of ITotal
and IA, significantly negative-shifted the activation curve, and positive-shifted steady-state curve of IA. However, SSa induced no significant changes in the amplitude and activation curve of IK. In addition, SSa significantly increased the amplitude of 4AP-sensitive K+ current, while there was no significant change in the amplitude of TEA-sensitive K+ current. Together, our data indicate that SSa inhibits epileptiform discharges induced by 4AP in a dose-dependent manner and that SSa exerts selectively enhancing effects on IA. These increases in IA may contribute to the anticonvulsant mechanisms of SSa.
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23
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Cotella D, Radicke S, Cipriani V, Cavaletto M, Merlin S, Follenzi A, Ravens U, Wettwer E, Santoro C, Sblattero D. N-glycosylation of the mammalian dipeptidyl aminopeptidase-like protein 10 (DPP10) regulates trafficking and interaction with Kv4 channels. Int J Biochem Cell Biol 2012; 44:876-85. [PMID: 22387313 DOI: 10.1016/j.biocel.2012.02.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/09/2012] [Accepted: 02/14/2012] [Indexed: 02/01/2023]
Abstract
The dipeptidyl aminopeptidase-like protein 10 (DPP10) is a type II transmembrane protein homologue to the serine protease DPPIV/CD26 but enzymatically inactive. In the mammalian brain, DPP10 forms a complex with voltage-gated potassium channels of the Kv4 family, regulating their cell surface expression and biophysical properties. DPP10 is a glycoprotein containing eight predicted N-glycosylation sites in the extracellular domain. In this study we investigated the role of N-glycosylation on DPP10 trafficking and functional activity. Using site-directed mutagenesis (N to Q) we showed that N-glycosylation occured at six positions. Glycosylation at these specific residues was necessary for DPP10 trafficking to the plasma membrane as observed by flow cytometry. The surface expression levels of the substitutions N90Q, N119Q, N257Q and N342Q were reduced by more than 60%. Hence the interaction with the Kv4.3/KChIP2a channel complex was disrupted preventing the hastening effect of wild type DPP10 on current kinetics. Interestingly, N257 was crucial for this function and its substitution to glutamine completely blocked DPP10 sorting to the cell surface and prevented DPP10 dimerization. In summary, we demonstrated that glycosylation was necessary for both DPP10 trafficking to the cell surface and functional interaction with Kv4 channels.
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Affiliation(s)
- Diego Cotella
- Department of Health Sciences and Interdisciplinary Research Centre on Autoimmune Diseases (IRCAD), Università del Piemonte Orientale A. Avogadro, Via Solaroli 17, 28100 Novara, Italy.
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24
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Guo Y, Baum LW, Sham PC, Wong V, Ng PW, Lui CHT, Sin NC, Tsoi TH, Tang CS, Kwan JS, Yip BH, Xiao SM, Thomas GN, Lau YL, Yang W, Cherny SS, Kwan P. Two-stage genome-wide association study identifies variants in CAMSAP1L1 as susceptibility loci for epilepsy in Chinese. Hum Mol Genet 2011; 21:1184-9. [DOI: 10.1093/hmg/ddr550] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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25
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Woll MP, De Cotiis DA, Bewley MC, Tacelosky DM, Levenson R, Flanagan JM. Interaction between the D2 dopamine receptor and neuronal calcium sensor-1 analyzed by fluorescence anisotropy. Biochemistry 2011; 50:8780-91. [PMID: 21875085 DOI: 10.1021/bi200637e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Neuronal calcium sensor-1 (NCS-1) is a small calcium binding protein that plays a key role in the internalization and desensitization of activated D2 dopamine receptors (D2Rs). Here, we have used fluorescence anisotropy (FA) and a panel of NCS-1 EF-hand variants to interrogate the interaction between the D2R and NCS-1. Our data are consistent with the following conclusions. (1) FA titration experiments indicate that at low D2R peptide concentrations calcium-loaded NCS-1 binds to the D2R peptide in a monomeric form. At high D2R peptide concentrations, the FA titration data are best fit by a model in which the D2R peptide binds two NCS-1 monomers sequentially in a cooperative fashion. (2) Competition FA experiments in which unlabeled D2R peptide was used to compete with labeled peptide for binding to NCS-1 shifted titration curves to higher NCS-1 concentrations, suggesting that the binding of NCS-1 to the D2R is highly specific and that binding occurs in a cooperative fashion. (3) N-Terminally myristoylated NCS-1 dimerizes in a calcium-dependent manner. (4) Co-immunoprecipitation experiments in HEK-293 confirm that NCS-1 can oligomerize in cell lysates and that oligomerization is dependent on calcium binding and requires functionally intact EF-hand domains. (5) Ca(2+)/Mg(2+) FA titration experiments revealed that NCS-1 EF-hands 2-4 (EF2-4) contributed to binding with the D2R peptide. EF2 appears to have the highest affinity for Ca(2+), and occupancy of this site is sufficient to promote high-affinity binding of the NCS-1 monomer to the D2R peptide. Magnesium ions may serve as a physiological cofactor with calcium for NCS-1-D2R binding. Finally, we propose a structural model that predicts that the D2R peptide binds to the first 60 residues of NCS-1. Together, our results support the possibility of using FA to screen for small molecule drugs that can specifically block the interaction between the D2R and NCS-1.
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Affiliation(s)
- Matthew P Woll
- Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
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26
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Masino SA, Li T, Theofilas P, Sandau US, Ruskin DN, Fredholm BB, Geiger JD, Aronica E, Boison D. A ketogenic diet suppresses seizures in mice through adenosine A₁ receptors. J Clin Invest 2011; 121:2679-83. [PMID: 21701065 DOI: 10.1172/jci57813] [Citation(s) in RCA: 195] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 04/20/2011] [Indexed: 12/15/2022] Open
Abstract
A ketogenic diet (KD) is a high-fat, low-carbohydrate metabolic regimen; its effectiveness in the treatment of refractory epilepsy suggests that the mechanisms underlying its anticonvulsive effects differ from those targeted by conventional antiepileptic drugs. Recently, KD and analogous metabolic strategies have shown therapeutic promise in other neurologic disorders, such as reducing brain injury, pain, and inflammation. Here, we have shown that KD can reduce seizures in mice by increasing activation of adenosine A1 receptors (A1Rs). When transgenic mice with spontaneous seizures caused by deficiency in adenosine metabolism or signaling were fed KD, seizures were nearly abolished if mice had intact A1Rs, were reduced if mice expressed reduced A1Rs, and were unaltered if mice lacked A1Rs. Seizures were restored by injecting either glucose (metabolic reversal) or an A1R antagonist (pharmacologic reversal). Western blot analysis demonstrated that the KD reduced adenosine kinase, the major adenosine-metabolizing enzyme. Importantly, hippocampal tissue resected from patients with medically intractable epilepsy demonstrated increased adenosine kinase. We therefore conclude that adenosine deficiency may be relevant to human epilepsy and that KD can reduce seizures by increasing A1R-mediated inhibition.
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Affiliation(s)
- Susan A Masino
- Department of Psychology and Neuroscience Program, Trinity College, Hartford, Connecticut, USA
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27
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Kanyshkova T, Broicher T, Meuth SG, Pape HC, Budde T. A-type K+ currents in intralaminar thalamocortical relay neurons. Pflugers Arch 2011; 461:545-56. [PMID: 21437601 DOI: 10.1007/s00424-011-0953-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 02/22/2011] [Indexed: 10/18/2022]
Abstract
Transient A-type K+ currents (I(A)) are known to influence the firing pattern of a number of thalamic cell types, but have not been investigated in intralaminar thalamocortical (TC) relay neurons yet. We therefore combined whole-cell patch-clamp techniques, PCR analysis, and immunohistochemistry to investigate the voltage-dependent and pharmacological properties of I(A) and to determine its molecular basis in TC neurons from the centrolateral, paracentral, and centromedial thalamic nuclei. I(A) revealed half-maximal (V (h)) activation and inactivation at about -17 and -67 mV, respectively. At a concentration of 5-10 mM 4-aminopyridine (4-AP) completely blocked I(A). Furthermore, I(A) was nearly unaffected by two sea anemone toxins (blood depressing substances 1 and 2, BDS1 and BDS2; 6-8% block at a concentration of 1 μM) but strongly sensitive to the K(V)4 channel blocker Heteropoda venatoria toxin 2 (HpTx2; about 45% block at a concentration of 5 μM). PCR screening revealed the expression of K(V)4.1-4.3, with strongest expression for K(V)4.2 and weak expression for K(V)4.1. Accordingly K(V)4.1 was not detected in immunohistochemical staining. Furthermore, K(V)4.2 and K(V)4.3 revealed mainly dendritic and somatic staining, respectively. Together with current clamp recordings, these findings point to a scenario where the fast transient I(A) in intralaminar TC neurons has a depolarized threshold at potentials negative to -50 mV, is substantially generated by K(V)4.2 and K(V)4.3 channels, allows prominent burst firing at hyperpolarized potentials, prevents the generation of high-threshold potentials, generates a delayed onset of firing at more depolarized potentials, and allows fast tonic firing.
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Affiliation(s)
- Tatyana Kanyshkova
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, 48149, Münster, Germany
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28
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Handley MTW, Lian LY, Haynes LP, Burgoyne RD. Structural and functional deficits in a neuronal calcium sensor-1 mutant identified in a case of autistic spectrum disorder. PLoS One 2010; 5:e10534. [PMID: 20479890 PMCID: PMC2866544 DOI: 10.1371/journal.pone.0010534] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Accepted: 04/15/2010] [Indexed: 11/18/2022] Open
Abstract
Neuronal calcium sensor-1 (NCS-1) is a Ca(2+) sensor protein that has been implicated in the regulation of various aspects of neuronal development and neurotransmission. It exerts its effects through interactions with a range of target proteins one of which is interleukin receptor accessory protein like-1 (IL1RAPL1) protein. Mutations in IL1RAPL1 have recently been associated with autism spectrum disorders and a missense mutation (R102Q) on NCS-1 has been found in one individual with autism. We have examined the effect of this mutation on the structure and function of NCS-1. From use of NMR spectroscopy, it appeared that the R102Q affected the structure of the protein particularly with an increase in the extent of conformational exchange in the C-terminus of the protein. Despite this change NCS-1(R102Q) did not show changes in its affinity for Ca(2+) or binding to IL1RAPL1 and its intracellular localisation was unaffected. Assessment of NCS-1 dynamics indicated that it could rapidly cycle between cytosolic and membrane pools and that the cycling onto the plasma membrane was specifically changed in NCS-1(R102Q) with the loss of a Ca(2+) -dependent component. From these data we speculate that impairment of the normal cycling of NCS-1 by the R102Q mutation could have subtle effects on neuronal signalling and physiology in the developing and adult brain.
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Affiliation(s)
- Mark T. W. Handley
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Lu-Yun Lian
- School of Biological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Lee P. Haynes
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Robert D. Burgoyne
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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