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Wang H, Zhao Y, Zhang D, Li J, Yang K, Yang J, Li B. Neuroprotective effects of quinpirole on lithium chloride pilocarpine-induced epilepsy in rats and its underlying mechanisms. Eur J Med Res 2024; 29:121. [PMID: 38355613 PMCID: PMC10865707 DOI: 10.1186/s40001-024-01694-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 01/24/2024] [Indexed: 02/16/2024] Open
Abstract
INTRODUCTION Epilepsy is a common neurological disorder that presents with challenging mechanisms and treatment strategies. This study investigated the neuroprotective effects of quinpirole on lithium chloride pilocarpine-induced epileptic rats and explored its potential mechanisms. METHODS Lithium chloride pilocarpine was used to induce an epileptic model in rats, and the effects of quinpirole on seizure symptoms and cognitive function were evaluated. The Racine scoring method, electroencephalography, and Morris water maze test were used to assess seizure severity and learning and memory functions in rats in the epileptic group. Additionally, immunohistochemistry and Western blot techniques were used to analyze the protein expression levels and morphological changes in glutamate receptor 2 (GluR2; GRIA2), BAX, and BCL2 in the hippocampi of rats in the epileptic group. RESULTS First, it was confirmed that the symptoms in rats in the epileptic group were consistent with features of epilepsy. Furthermore, these rats demonstrated decreased learning and memory function in the Morris water maze test. Additionally, gene and protein levels of GluR2 in the hippocampi of rats in the epileptic group were significantly reduced. Quinpirole treatment significantly delayed seizure onset and decreased the mortality rate after the induction of a seizure. Furthermore, electroencephalography showed a significant decrease in the frequency of the spike waves. In the Morris water maze test, rats from the quinpirole treatment group demonstrated a shorter latency period to reach the platform and an increased number of crossings through the target quadrant. Network pharmacology analysis revealed a close association between quinpirole and GluR2 as well as its involvement in the cAMP signaling pathway, cocaine addiction, and dopaminergic synapses. Furthermore, immunohistochemistry and Western blot analysis showed that quinpirole treatment resulted in a denser arrangement and a more regular morphology of the granule cells in the hippocampi of rats in the epileptic group. Additionally, quinpirole treatment decreased the protein expression of BAX and increased the protein expression of BCL2. CONCLUSION The current study demonstrated that quinpirole exerted neuroprotective effects in the epileptic rat model induced by lithium chloride pilocarpine. Additionally, it was found that the treatment not only alleviated the rats' seizure symptoms, but also improved their learning and memory abilities. This improvement was linked to the modulation of protein expression levels of GLUR2, BAX, and BCL2. These findings provided clues that would be important for further investigation of the therapeutic potential of quinpirole and its underlying mechanisms for epilepsy treatment.
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Affiliation(s)
- Hui Wang
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, Shandong, China
- Department of Pediatrics, The Affiliated Taian City Central Hospital of Qingdao University, Taian, Shandong, China
| | - Yongheng Zhao
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Dongqing Zhang
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Jun Li
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Kun Yang
- Department of Pediatrics, The Affiliated Taian City Central Hospital of Qingdao University, Taian, Shandong, China
| | - Junli Yang
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, Shandong, China.
| | - Baomin Li
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, Shandong, China.
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Konen LM, Wright AL, Royle GA, Morris GP, Lau BK, Seow PW, Zinn R, Milham LT, Vaughan CW, Vissel B. A new mouse line with reduced GluA2 Q/R site RNA editing exhibits loss of dendritic spines, hippocampal CA1-neuron loss, learning and memory impairments and NMDA receptor-independent seizure vulnerability. Mol Brain 2020; 13:27. [PMID: 32102661 PMCID: PMC7045468 DOI: 10.1186/s13041-020-0545-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 01/05/2020] [Indexed: 11/18/2022] Open
Abstract
Calcium (Ca2+)-permeable AMPA receptors may, in certain circumstances, contribute to normal synaptic plasticity or to neurodegeneration. AMPA receptors are Ca2+-permeable if they lack the GluA2 subunit or if GluA2 is unedited at a single nucleic acid, known as the Q/R site. In this study, we examined mice engineered with a point mutation in the intronic editing complementary sequence (ECS) of the GluA2 gene, Gria2. Mice heterozygous for the ECS mutation (named GluA2+/ECS(G)) had a ~ 20% reduction in GluA2 RNA editing at the Q/R site. We conducted an initial phenotypic analysis of these mice, finding altered current-voltage relations (confirming expression of Ca2+-permeable AMPA receptors at the synapse). Anatomically, we observed a loss of hippocampal CA1 neurons, altered dendritic morphology and reductions in CA1 pyramidal cell spine density. Behaviourally, GluA2+/ECS(G) mice exhibited reduced motor coordination, and learning and memory impairments. Notably, the mice also exhibited both NMDA receptor-independent long-term potentiation (LTP) and vulnerability to NMDA receptor-independent seizures. These NMDA receptor-independent seizures were rescued by the Ca2+-permeable AMPA receptor antagonist IEM-1460. In summary, unedited GluA2(Q) may have the potential to drive NMDA receptor-independent processes in brain function and disease. Our study provides an initial characterisation of a new mouse model for studying the role of unedited GluA2(Q) in synaptic and dendritic spine plasticity in disorders where unedited GluA2(Q), synapse loss, neurodegeneration, behavioural impairments and/or seizures are observed, such as ischemia, seizures and epilepsy, Huntington’s disease, amyotrophic lateral sclerosis, astrocytoma, cocaine seeking behaviour and Alzheimer’s disease.
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Affiliation(s)
- Lyndsey M Konen
- Centre for Neuroscience and Regenerative Medicine (CNRM), Faculty of Science, University of Technology Sydney, PO Box 123 Broadway, Sydney, NSW, 2007, Australia.,St Vincent's Centre for Applied Medical Research, Sydney, 2011, Australia
| | - Amanda L Wright
- Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia
| | - Gordon A Royle
- Middlemore Hospital, Counties Manukau DHB, Otahuhu, Auckland, 1062, New Zealand.,The University of Auckland, Faculty of Medical and Health Sciences, School of Medicine, Grafton, Auckland, 1023, New Zealand
| | - Gary P Morris
- Centre for Neuroscience and Regenerative Medicine (CNRM), Faculty of Science, University of Technology Sydney, PO Box 123 Broadway, Sydney, NSW, 2007, Australia.,St Vincent's Centre for Applied Medical Research, Sydney, 2011, Australia
| | - Benjamin K Lau
- Kolling Institute of Medical Research, Royal North Shore Hospital, The University of Sydney, Sydney, 2065, Australia
| | - Patrick W Seow
- Kolling Institute of Medical Research, Royal North Shore Hospital, The University of Sydney, Sydney, 2065, Australia
| | - Raphael Zinn
- Centre for Neuroscience and Regenerative Medicine (CNRM), Faculty of Science, University of Technology Sydney, PO Box 123 Broadway, Sydney, NSW, 2007, Australia.,St Vincent's Centre for Applied Medical Research, Sydney, 2011, Australia
| | - Luke T Milham
- Centre for Neuroscience and Regenerative Medicine (CNRM), Faculty of Science, University of Technology Sydney, PO Box 123 Broadway, Sydney, NSW, 2007, Australia.,St Vincent's Centre for Applied Medical Research, Sydney, 2011, Australia
| | - Christopher W Vaughan
- Kolling Institute of Medical Research, Royal North Shore Hospital, The University of Sydney, Sydney, 2065, Australia
| | - Bryce Vissel
- Centre for Neuroscience and Regenerative Medicine (CNRM), Faculty of Science, University of Technology Sydney, PO Box 123 Broadway, Sydney, NSW, 2007, Australia. .,St Vincent's Centre for Applied Medical Research, Sydney, 2011, Australia.
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O'Leary H, Vanderlinden L, Southard L, Castano A, Saba LM, Benke TA. Transcriptome analysis of rat dorsal hippocampal CA1 after an early life seizure induced by kainic acid. Epilepsy Res 2020; 161:106283. [PMID: 32062370 DOI: 10.1016/j.eplepsyres.2020.106283] [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: 09/09/2019] [Revised: 01/17/2020] [Accepted: 01/29/2020] [Indexed: 12/13/2022]
Abstract
Seizures that occur during early development are associated with adverse neurodevelopmental outcomes. Causation and mechanisms are currently under investigation. Induction of an early life seizure by kainic acid (KA) in immature rats on post-natal day (P) 7 results in behavioral changes in the adult rat that reflect social and intellectual deficits without overt cellular damage. Our previous work also demonstrated increased expression of CA1 hippocampal long-term potentiation (LTP) and reduced desensitization of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type ionotropic glutamate receptors (AMPA-R) one week following a kainic acid induced seizure (KA-ELS). Here we used RNA sequencing (RNAseq) of mRNA from dorsal hippocampal CA1 to probe changes in mRNA levels one week following KA-ELS as a means to investigate the mechanisms for these functional changes. Ingenuity pathway analysis (IPA) confirmed our previous results by predicting an up-regulation of the synaptic LTP pathway. Differential gene expression results revealed significant differences in 7 gene isoforms. Additional assessments included AMPA-R splice variants and adenosine deaminase acting on RNA 2 (ADAR2) editing sites as a means to determine the mechanism for reduced AMPA-R desensitization. Splice variant analysis demonstrated that KA-ELS result in a small, but significant decrease in the "flop" isoform of Gria3, and editing site analysis revealed significant changes in the editing of a kainate receptor subunit, Grik2, and a serotonin receptor, Htr2c. While these specific changes may not account for altered AMPA-R desensitization, the differences indicate that KA-ELS alters gene expression in the hippocampal CA1 one week after the insult.
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Affiliation(s)
- Heather O'Leary
- Department of Pediatrics, University of Colorado, School of Medicine, 80045, United States.
| | - Lauren Vanderlinden
- Department of Biostatistics and Informatics, Colorado School of Public Health, 80045, United States.
| | - Lara Southard
- Department of Psychology, Colorado State University, Fort Collins, 80523, United States.
| | - Anna Castano
- Department of Pediatrics, University of Colorado, School of Medicine, 80045, United States.
| | - Laura M Saba
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, 80045, United States.
| | - Tim A Benke
- Department of Pediatrics, University of Colorado, School of Medicine, 80045, United States; Department of Neurology, University of Colorado, School of Medicine, 80045, United States; Department of Pharmacology, University of Colorado, School of Medicine, 80045, United States; Department of Otolaryngology, University of Colorado, School of Medicine, 80045, United States; Neuroscience Graduate Program, University of Colorado, School of Medicine, 80045, United States.
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4
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Bu W, Zhao WQ, Li WL, Dong CZ, Zhang Z, Li QJ. Neuropeptide Y suppresses epileptiform discharges by regulating AMPA receptor GluR2 subunit in rat hippocampal neurons. Mol Med Rep 2017; 16:387-395. [DOI: 10.3892/mmr.2017.6567] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 02/09/2017] [Indexed: 11/06/2022] Open
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Sharma AK, Reams RY, Jordan WH, Miller MA, Thacker HL, Snyder PW. Mesial Temporal Lobe Epilepsy: Pathogenesis, Induced Rodent Models and Lesions. Toxicol Pathol 2016; 35:984-99. [PMID: 18098044 DOI: 10.1080/01926230701748305] [Citation(s) in RCA: 195] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Mesial temporal lobe epilepsy (MTLE), the most common epilepsy in adults, is generally intractable and is suspected to be the result of recurrent excitation or inhibition circuitry. Recurrent excitation and the development of seizures have been associated with aberrant mossy fiber sprouting in the hippocampus. Of the animal models developed to investigate the pathogenesis of MTLE, post-status epilepticus models have received the greatest acceptance because they are characterized by a latency period, the development of spontaneous motor seizures, and a spectrum of lesions like those of MTLE. Among post-status epilepticus models, induction of systemic kainic acid or pilocarpine-induced epilepsy is less labor-intensive than electrical-stimulation models and these models mirror the clinicopathologic features of MTLE more closely than do kindling, tetanus toxin, hyperthermia, post-traumatic, and perinatal hypoxia/ischemia models. Unfortunately, spontaneous motor seizures do not develop in kindling or adult hyperthermia models and are not a consistent finding in tetanus toxin-induced or perinatal hypoxia/ischemia models. This review presents the mechanistic hypotheses for seizure induction, means of model induction, and associated pathology, especially as compared to MTLE patients. Animal models are valuable tools not only to study the pathogenesis of MTLE, but also to evaluate potential antiepileptogenic drugs.
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Affiliation(s)
- Alok K. Sharma
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
- Department of Pathology, Covance Laboratories Inc., Madison, WI, 53704, USA
| | - Rachel Y. Reams
- Department of Pathology, Lilly Research Laboratories, Division of Eli Lilly and Co., Greenfield, IN, 46140, USA
| | - William H. Jordan
- Department of Pathology, Lilly Research Laboratories, Division of Eli Lilly and Co., Greenfield, IN, 46140, USA
| | - Margaret A. Miller
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
| | - H. Leon Thacker
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
| | - Paul W. Snyder
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
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Status epilepticus induces a TrkB to p75 neurotrophin receptor switch and increases brain-derived neurotrophic factor interaction with p75 neurotrophin receptor: An initial event in neuronal injury induction. Neuroscience 2008; 154:978-93. [DOI: 10.1016/j.neuroscience.2008.04.038] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 04/03/2008] [Accepted: 04/04/2008] [Indexed: 01/12/2023]
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Deshpande LS, Lou JK, Mian A, Blair RE, Sombati S, Attkisson E, DeLorenzo RJ. Time course and mechanism of hippocampal neuronal death in an in vitro model of status epilepticus: role of NMDA receptor activation and NMDA dependent calcium entry. Eur J Pharmacol 2008; 583:73-83. [PMID: 18289526 PMCID: PMC2323609 DOI: 10.1016/j.ejphar.2008.01.025] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 01/02/2008] [Accepted: 01/22/2008] [Indexed: 10/22/2022]
Abstract
The hippocampus is especially vulnerable to seizure-induced damage and excitotoxic neuronal injury. This study examined the time course of neuronal death in relationship to seizure duration and the pharmacological mechanisms underlying seizure-induced cell death using low magnesium (Mg2+) induced continuous high frequency epileptiform discharges (in vitro status epilepticus) in hippocampal neuronal cultures. Neuronal death was assessed using cell morphology and fluorescein diacetate-propidium iodide staining. Effects of low Mg2+ and various receptor antagonists on spike frequency were assessed using patch clamp electrophysiology. We observed a linear and time-dependent increase in neuronal death with increasing durations of status epilepticus. This cell death was dependent upon extracellular calcium (Ca2+) that entered primarily through the N-methyl-d-aspartate (NMDA) glutamate receptor channel subtype. Neuronal death was significantly decreased by co-incubation with the NMDA receptor antagonists and was also inhibited by reduction of extracellular (Ca2+) during status epilepticus. In contrast, neuronal death from in vitro status epilepticus was not significantly prevented by inhibition of other glutamate receptor subtypes or voltage-gated Ca2+ channels. Interestingly this NMDA-Ca2+ dependent neuronal death was much more gradual in onset compared to cell death from excitotoxic glutamate exposure. The results provide evidence that in vitro status epilepticus results in increased activation of the NMDA-Ca2+ transduction pathway leading to neuronal death in a time-dependent fashion. The results also indicate that there is a significant window of opportunity during the initial time of continuous seizure activity to be able to intervene, protect neurons and decrease the high morbidity and mortality associated with status epilepticus.
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Affiliation(s)
- Laxmikant S. Deshpande
- Department of Neurology: LSD, JKL, AM, REB, SS, EA and RJD, Department of Pharmacology and Toxicology: RJD, Department of Molecular Biophysics and Biochemistry: RJD, Virginia Commonwealth University, Richmond, Virginia 23298, USA
| | - Jeffrey K. Lou
- Department of Neurology: LSD, JKL, AM, REB, SS, EA and RJD, Department of Pharmacology and Toxicology: RJD, Department of Molecular Biophysics and Biochemistry: RJD, Virginia Commonwealth University, Richmond, Virginia 23298, USA
| | - Ali Mian
- Department of Neurology: LSD, JKL, AM, REB, SS, EA and RJD, Department of Pharmacology and Toxicology: RJD, Department of Molecular Biophysics and Biochemistry: RJD, Virginia Commonwealth University, Richmond, Virginia 23298, USA
| | - Robert E. Blair
- Department of Neurology: LSD, JKL, AM, REB, SS, EA and RJD, Department of Pharmacology and Toxicology: RJD, Department of Molecular Biophysics and Biochemistry: RJD, Virginia Commonwealth University, Richmond, Virginia 23298, USA
| | - Sompong Sombati
- Department of Neurology: LSD, JKL, AM, REB, SS, EA and RJD, Department of Pharmacology and Toxicology: RJD, Department of Molecular Biophysics and Biochemistry: RJD, Virginia Commonwealth University, Richmond, Virginia 23298, USA
| | - Elisa Attkisson
- Department of Neurology: LSD, JKL, AM, REB, SS, EA and RJD, Department of Pharmacology and Toxicology: RJD, Department of Molecular Biophysics and Biochemistry: RJD, Virginia Commonwealth University, Richmond, Virginia 23298, USA
| | - Robert J. DeLorenzo
- Department of Neurology: LSD, JKL, AM, REB, SS, EA and RJD, Department of Pharmacology and Toxicology: RJD, Department of Molecular Biophysics and Biochemistry: RJD, Virginia Commonwealth University, Richmond, Virginia 23298, USA
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Mukherjee P, Thomas S, Pasinetti GM. Complement anaphylatoxin C5a neuroprotects through regulation of glutamate receptor subunit 2 in vitro and in vivo. J Neuroinflammation 2008; 5:5. [PMID: 18230183 PMCID: PMC2246107 DOI: 10.1186/1742-2094-5-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Accepted: 01/29/2008] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND The complement system is thought to be involved in the pathogenesis of numerous neurological diseases. We previously reported that pre-treatment of murine cortico-hippocampal neuronal cultures with the complement derived anaphylatoxin C5a, protects against glutamate mediated apoptosis. Our present study with C5a receptor knock out (C5aRKO) mice corroborates that the deficiency of C5a renders C5aRKO mouse more susceptible to apoptotic injury in vivo. In this study we explored potential upstream mechanisms involved in C5a mediated neuroprotection in vivo and in vitro. METHODS Based on evidence suggesting that reduced expression of glutamate receptor subunit 2 (GluR2) may influence apoptosis in neurons, we studied the effect of human recombinant C5a on GluR2 expression in response to glutamate neurotoxicity. Glutamate analogs were injected into C5aRKO mice or used to treat in vitro neuronal culture and GluR2 expression were assessed in respect with cell death. RESULTS In C5aRKO mice we found that the neurons are more susceptible to excitotoxicity resulting in apoptotic injury in the absence of the C5a receptor compared to WT control mice. Our results suggest that C5a protects against apoptotic pathways in neurons in vitro and in vivo through regulation of GluR2 receptor expression. CONCLUSION Complement C5a neuroprotects through regulation of GluR2 receptor subunit.
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Affiliation(s)
- Piali Mukherjee
- Department of Psychiatry, Mount Sinai School of Medicine, 1 Gustav L,, Levy Place, New York, NY 10029, USA.
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Friedman LK, Avallone JM, Magrys B. Maturational Effects of Single and Multiple Early-Life Seizures on AMPA Receptors in Prepubescent Hippocampus. Dev Neurosci 2007; 29:427-37. [PMID: 17314473 DOI: 10.1159/000100078] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Accepted: 07/22/2006] [Indexed: 11/19/2022] Open
Abstract
The effects of single versus multiple episodes of status epilepticus on the expression of AMPA receptors during a critical growth spurt are unknown. To determine whether the pattern of hippocampal AMPA receptor subunit expression depends upon the age of the animal, timing and number of perinatal seizures, we characterized maturational changes in AMPA receptor protein levels of the hippocampus with immunohistochemistry and Western blotting in rats of juvenile ages with and without a history of neonatal seizures. Kainic acid (KA) was used to induce a single episode of status epilepticus (1 x KA) in rats on P20 or P30. Animals with a history of multiple seizures (3 x KA) were given KA on P6, P9, and then on P20 or P30. After 1 x KA, in P20 and P30 rats that are preferentially sensitive to CA1 damage, GluR1 immunoreactivity was depleted remarkably in CA1 stratum pyramidale and stratum lucidum and only morphologically healthy cells were faintly labeled. At P30, GluR2 subunit expression was nearly absent in the healthy cells and increased within the injured CA1 neuronal population. Western blot analysis confirmed that the GluR1/GluR2 ratio was decreased at P20 and further decreased at P30. A history of perinatal seizures (3 x KA) prevented the age-dependent alterations in the CA1. Except for areas of cell loss, NR1 and NR2A/B antibody labeling was relatively stable throughout the hippocampus at both ages and conditions examined. Data suggest that (i) Ca2+ permeable AMPA receptors may not be responsible for neuronal injury or irreversible cell loss and that (ii) the expression of AMPA receptors after status epilepticus depends upon the age of the animal, the timing of the first insult and subsequent formation of AMPA receptor subunit compositions within specific populations of hippocampal neurons.
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Affiliation(s)
- L K Friedman
- New York College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA.
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Jia YH, Zhu X, Li SY, Ni JH, Jia HT. Kainate exposure suppresses activation of GluR2 subunit promoter in primary cultured cerebral cortical neurons through induction of RE1-silencing transcription factor. Neurosci Lett 2006; 403:103-8. [PMID: 16701950 DOI: 10.1016/j.neulet.2006.04.027] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 04/18/2006] [Accepted: 04/19/2006] [Indexed: 11/24/2022]
Abstract
The AMPA receptor subunit GluR2 is downregulated in neurons following a wide range of neurological insults. Here we report that suppression of GluR2 gene promoter activity is associated with kainate (KA)-induced downregulation of GluR2 subunit levels in primary cultured cortical neurons. RT-PCR and Northern blotting showed a significant decrease in GluR2 mRNA in cultured neurons after KA exposure. Transfection of cultured neurons with an expression vector pGL3-GluR2(-298/+283), where the reporter gene firefly luciferase was driven by the GluR2 promoter, revealed that KA exposure suppressed the transcriptional activation of the GluR2 promoter. Furthermore, the expression of the RE1-silencing transcription factor (REST) was increased in KA-exposed cortical neurons; enhanced binding of REST to RE1-like silencer element in the proximal promoter of the GluR2 subunit gene was evidenced by electrophoresis mobility shift assay. Chromatin immunoprecipitation showed that suppressed activity of the GluR2 promoter in cultured neurons after KA exposure was related to deacetylation of histone H4. These results indicate that REST as a crucial factor binds to RE1-like silencer element in the GluR2 promoter, suppressing transcription of the GluR2 subunit gene during KA exposure. Our data suggest that transcriptional suppression of the GluR2 subunit gene may contribute at least in part to downregulation of GluR2 subunit protein in neurons during KA exposure. Because our experiments showed a reduction of glutamate release in KA-exposed cortical neurons, REST may play a latent role in delayed neuronal death or in seizure-induced tolerance.
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MESH Headings
- Acetylation
- Animals
- Blotting, Northern
- Cells, Cultured
- Cerebral Cortex/cytology
- Cerebral Cortex/metabolism
- Chromatin Immunoprecipitation
- Down-Regulation
- Electrophoretic Mobility Shift Assay
- Genes, Reporter
- Histones/metabolism
- Kainic Acid/metabolism
- Kainic Acid/toxicity
- Luciferases, Firefly/antagonists & inhibitors
- Luciferases, Firefly/genetics
- Neurons/drug effects
- Neurons/metabolism
- Promoter Regions, Genetic
- Protein Subunits/antagonists & inhibitors
- Protein Subunits/genetics
- RNA, Messenger/antagonists & inhibitors
- Rats
- Rats, Sprague-Dawley
- Receptors, AMPA/antagonists & inhibitors
- Receptors, AMPA/genetics
- Repressor Proteins/biosynthesis
- Reverse Transcriptase Polymerase Chain Reaction
- Silencer Elements, Transcriptional
- Transcription Factors/biosynthesis
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Affiliation(s)
- Yu-Hong Jia
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Xue Yuan Road 38, Beijing 100083, PR China
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Eybalin M, Caicedo A, Renard N, Ruel J, Puel JL. Transient Ca2+-permeable AMPA receptors in postnatal rat primary auditory neurons. Eur J Neurosci 2004; 20:2981-9. [PMID: 15579152 DOI: 10.1111/j.1460-9568.2004.03772.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Fast excitatory transmission in the nervous system is mostly mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors whose subunit composition governs physiological characteristics such as ligand affinity and ion conductance properties. Here, we report that AMPA receptors at inner hair cell (IHC) synapses lack the GluR2 subunit and are transiently Ca2+-permeable before hearing onset as evidenced using agonist-induced Co2+ accumulation, Western blots and GluR2 confocal microscopy in the rat cochlea. AMPA (100 microM) induced Co2+ accumulation in primary auditory neurons until postnatal day (PND) 10. This accumulation was concentration-dependent, strengthened by cyclothiazide (50 microM) and blocked by GYKI 52466 (80 microM) and Joro spider toxin (1 microM). It was unaffected by D-AP5 (50 microM), and it could not be elicited by 56 mM K+ or 1 mM NMDA + 10 microM glycine. Western blots showed that GluR1 immunoreactivity, present in homogenates of immature cochleas, had disappeared by PND12. GluR2 immunoreactivity was not detected until PND10 and GluR3 and GluR4 immunoreactivities were detected at all the ages examined. Confocal microscopy confirmed that the GluR2 immunofluorescence was not located postsynaptically to IHCs before PND10. In conclusion, AMPA receptors on maturing primary auditory neurons differ from those on adult neurons. They are probably composed of GluR1, GluR3 and GluR4 subunits and have a high Ca2+ permeability. The postsynaptic expression of GluR2 subunits may be continuously regulated by the presynaptic activity allowing for variations in the Ca2+ permeability and physiological properties of the receptor.
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Affiliation(s)
- Michel Eybalin
- INSERM U583, Institut des Neurosciences, Hôpital St. Eloi, 80, Avenue Augustin Fliche, BP 74103, 34091 Montpellier cedex 5, France.
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