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Mundrucz L, Kecskés A, Henn-Mike N, Kóbor P, Buzás P, Vennekens R, Kecskés M. TRPM4 regulates hilar mossy cell loss in temporal lobe epilepsy. BMC Biol 2023; 21:96. [PMID: 37101159 PMCID: PMC10134545 DOI: 10.1186/s12915-023-01604-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 04/18/2023] [Indexed: 04/28/2023] Open
Abstract
BACKGROUND Mossy cells comprise a large fraction of excitatory neurons in the hippocampal dentate gyrus, and their loss is one of the major hallmarks of temporal lobe epilepsy (TLE). The vulnerability of mossy cells in TLE is well known in animal models as well as in patients; however, the mechanisms leading to cellular death is unclear. RESULTS Transient receptor potential melastatin 4 (TRPM4) is a Ca2+-activated non-selective cation channel regulating diverse physiological functions of excitable cells. Here, we identified that TRPM4 is present in hilar mossy cells and regulates their intrinsic electrophysiological properties including spontaneous activity and action potential dynamics. Furthermore, we showed that TRPM4 contributes to mossy cells death following status epilepticus and therefore modulates seizure susceptibility and epilepsy-related memory deficits. CONCLUSIONS Our results provide evidence for the role of TRPM4 in MC excitability both in physiological and pathological conditions.
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Affiliation(s)
- Laura Mundrucz
- Institute of Physiology, Medical School, University of Pécs, Pécs, 7624, Hungary
| | - Angéla Kecskés
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, 7624, Hungary
- Szentagothai Research Centre, Centre for Neuroscience, University of Pécs, Pécs, 7624, Hungary
| | - Nóra Henn-Mike
- Institute of Physiology, Medical School, University of Pécs, Pécs, 7624, Hungary
- Szentagothai Research Centre, Centre for Neuroscience, University of Pécs, Pécs, 7624, Hungary
| | - Péter Kóbor
- Institute of Physiology, Medical School, University of Pécs, Pécs, 7624, Hungary
| | - Péter Buzás
- Institute of Physiology, Medical School, University of Pécs, Pécs, 7624, Hungary
| | - Rudi Vennekens
- Laboratory of Ion Channel Research, Biomedical Sciences Group, Department of Cellular and Molecular Medicine, VIB-KU Leuven Center for Brain & Disease Research, KU Leuven, Louvain, 3000, Belgium
| | - Miklós Kecskés
- Institute of Physiology, Medical School, University of Pécs, Pécs, 7624, Hungary.
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Metodiev D, Minkin K, Ruseva M, Ganeva R, Parvanov D, Nachev S. Pathomorphological Diagnostic Criteria for Focal Cortical Dysplasias and Other Common Epileptogenic Lesions—Review of the Literature. Diagnostics (Basel) 2023; 13:diagnostics13071311. [PMID: 37046529 PMCID: PMC10092959 DOI: 10.3390/diagnostics13071311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/20/2023] [Accepted: 03/28/2023] [Indexed: 04/03/2023] Open
Abstract
Focal cortical dysplasia (FCD) represents a heterogeneous group of morphological changes in the brain tissue that can predispose the development of pharmacoresistant epilepsy (recurring, unprovoked seizures which cannot be managed with medications). This group of neurological disorders affects not only the cerebral cortex but also the subjacent white matter. This work reviews the literature describing the morphological substrate of pharmacoresistant epilepsy. All illustrations presented in this study are obtained from brain biopsies from refractory epilepsy patients investigated by the authors. Regarding classification, there are three main FCD types, all of which involve cortical dyslamination. The 2022 revision of the International League Against Epilepsy (ILAE) FCD classification includes new histologically defined pathological entities: mild malformation of cortical development (mMCD), mild malformation of cortical development with oligodendroglial hyperplasia in frontal lobe epilepsy (MOGHE), and “no FCD on histopathology”. Although the pathomorphological characteristics of the various forms of focal cortical dysplasias are well known, their aetiologic and pathogenetic features remain elusive. The identification of genetic variants in FCD opens an avenue for novel treatment strategies, which are of particular utility in cases where total resection of the epileptogenic area is impossible.
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Cabrera OH, Useinovic N, Maksimovic S, Near M, Quillinan N, Todorovic SM, Jevtovic-Todorovic V. Neonatal ketamine exposure impairs infrapyramidal bundle pruning and causes lasting increase in excitatory synaptic transmission in hippocampal CA3 neurons. Neurobiol Dis 2022; 175:105923. [PMID: 36371060 PMCID: PMC9831613 DOI: 10.1016/j.nbd.2022.105923] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 10/27/2022] [Accepted: 11/07/2022] [Indexed: 11/11/2022] Open
Abstract
Preclinical models demonstrate that nearly all anesthetics cause widespread neuroapoptosis in the developing brains of infant rodents and non-human primates. Anesthesia-induced developmental apoptosis is succeeded by prolonged neuropathology in the surviving neurons and lasting cognitive impairments, suggesting that anesthetics interfere with the normal developmental trajectory of the brain. However, little is known about effects of anesthetics on stereotyped axonal pruning, an important developmental algorithm that sculpts neural circuits for proper function. Here, we proposed that neonatal ketamine exposure may interfere with stereotyped axonal pruning of the infrapyramidal bundle (IPB) of the hippocampal mossy fiber system and that impaired pruning may be associated with alterations in the synaptic transmission of CA3 neurons. To test this hypothesis, we injected postnatal day 7 (PND7) mouse pups with ketamine or vehicle over 6 h and then studied them at different developmental stages corresponding to IPB pruning (PND20-40). Immunohistochemistry with synaptoporin (a marker of mossy fibers) revealed that in juvenile mice treated with ketamine at PND7, but not in vehicle-treated controls, positive IPB fibers extended farther into the stratum pyramidale of CA3 region. Furthermore, immunofluorescent double labeling for synaptoporin and PSD-95 strongly suggested that the unpruned IPB caused by neonatal ketamine exposure makes functional synapses. Importantly, patch-clamp electrophysiology for miniature excitatory postsynaptic currents (mEPSCs) in acute brain slices ex vivo revealed increased frequency and amplitudes of mEPSCs in hippocampal CA3 neurons in ketamine-treated groups when compared to vehicle controls. We conclude that neonatal ketamine exposure interferes with normal neural circuit development and that this interference leads to lasting increase in excitatory synaptic transmission in hippocampus.
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Affiliation(s)
- Omar Hoseá Cabrera
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA
| | - Nemanja Useinovic
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA
| | - Stefan Maksimovic
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA
| | - Michelle Near
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA
| | - Nidia Quillinan
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA,University of Colorado School of Medicine at Anschutz Medical Campus, Neuroscience Graduate Program, Aurora, CO, USA
| | - Slobodan M. Todorovic
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA,University of Colorado School of Medicine at Anschutz Medical Campus, Neuroscience Graduate Program, Aurora, CO, USA
| | - Vesna Jevtovic-Todorovic
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA,University of Colorado School of Medicine at Anschutz Medical Campus, Department of Pharmacology, Aurora, CO, USA,Corresponding author. (V. Jevtovic-Todorovic)
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4
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Steiner A, Owen BM, Bauer JP, Seanez L, Kwon S, Biddinger JE, Huffman R, Ayala JE, Nobis WP, Lewis AS. Glucagon-like peptide-1 receptor differentially controls mossy cell activity across the dentate gyrus longitudinal axis. Hippocampus 2022; 32:797-807. [PMID: 36063105 PMCID: PMC9675713 DOI: 10.1002/hipo.23469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 07/27/2022] [Accepted: 08/18/2022] [Indexed: 01/07/2023]
Abstract
Understanding the role of dentate gyrus (DG) mossy cells (MCs) in learning and memory has rapidly evolved due to increasingly precise methods for targeting MCs and for in vivo recording and activity manipulation in rodents. These studies have shown MCs are highly active in vivo, strongly remap to contextual manipulation, and that their inhibition or hyperactivation impairs pattern separation and location or context discrimination. Less well understood is how MC activity is modulated by neurohormonal mechanisms, which might differentially control the participation of MCs in cognitive functions during discrete states, such as hunger or satiety. In this study, we demonstrate that glucagon-like peptide-1 (GLP-1), a neuropeptide produced in the gut and the brain that regulates food consumption and hippocampal-dependent mnemonic function, might regulate MC function through expression of its receptor, GLP-1R. RNA-seq demonstrated that most, though not all, Glp1r in hippocampal principal neurons is expressed in MCs, and in situ hybridization revealed strong expression of Glp1r in hilar neurons. Glp1r-ires-Cre mice crossed with Ai14D reporter mice followed by co-labeling for the MC marker GluR2/3 revealed that almost all MCs in the ventral DG expressed Glp1r and that almost all Glp1r-expressing hilar neurons were MCs. However, only ~60% of dorsal DG MCs expressed Glp1r, and Glp1r was also expressed in small hilar neurons that were not MCs. Consistent with this expression pattern, peripheral administration of the GLP-1R agonist exendin-4 (5 μg/kg) increased cFos expression in ventral but not dorsal DG hilar neurons. Finally, whole-cell patch-clamp recordings from ventral MCs showed that bath application of exendin-4 (200 nM) depolarized MCs and increased action potential firing. Taken together, this study adds to known MC activity modulators a neurohormonal mechanism that may preferentially affect ventral DG physiology and may potentially be targetable by several GLP-1R pharmacotherapies already in clinical use.
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Affiliation(s)
- Alex Steiner
- Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Benjamin M. Owen
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - James P. Bauer
- Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Leann Seanez
- Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Sam Kwon
- Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jessica E. Biddinger
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ragan Huffman
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Julio E. Ayala
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA
- Vanderbilt Center for Addiction Research, Vanderbilt University, Nashville, TN, USA
| | - William P. Nobis
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Alan S. Lewis
- Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
- Vanderbilt Center for Addiction Research, Vanderbilt University, Nashville, TN, USA
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Kecskés A, Czéh B, Kecskés M. Mossy cells of the dentate gyrus: Drivers or inhibitors of epileptic seizures? BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119279. [PMID: 35526721 DOI: 10.1016/j.bbamcr.2022.119279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 04/22/2022] [Accepted: 04/25/2022] [Indexed: 05/12/2023]
Abstract
Mossy cells (MCs) are glutamatergic cells of the dentate gyrus with an important role in temporal lobe epilepsy. Under physiological conditions MCs can control both network excitations via direct synapses to granule cells and inhibition via connections to GABAergic interneurons innervating granule cells. In temporal lobe epilepsy mossy cell loss is one of the major hallmarks, but whether the surviving MCs drive or inhibit seizure initiation and generalization is still a debate. The aim of the present review is to summarize the latest findings on the role of mossy cells in healthy and overexcited hippocampus.
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Affiliation(s)
- Angéla Kecskés
- Department of Pharmacology and Pharmacotherapy, Medical School & Szentagothai Research Centre, Molecular Pharmacology Research Group, Centre for Neuroscience, University of Pécs, H-7624 Pécs, Hungary
| | - Boldizsár Czéh
- Department of Laboratory Medicine, Medical School & Szentagothai Research Centre, Histology and Light Microscopy Core Facility, Centre for Neuroscience, University of Pécs, H-7624 Pécs, Hungary
| | - Miklós Kecskés
- Institute of Physiology, Medical School & Szentagothai Research Centre, Molecular Neuroendocrinology Research Group, Centre for Neuroscience, University of Pécs, H-7624 Pécs, Hungary.
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Dynamics of neurodegeneration in the hippocampus of Krushinsky-Molodkina rats correlates with the progression of limbic seizures. Epilepsy Behav 2022; 134:108846. [PMID: 35849865 DOI: 10.1016/j.yebeh.2022.108846] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 06/17/2022] [Accepted: 07/04/2022] [Indexed: 11/21/2022]
Abstract
Audiogenic seizures (AGS) (audiogenic kindling) in genetically selected audiogenic rodents are a reliable model of temporal lobe epilepsy (TLE). Temporal lobe epilepsy is accompanied with neurodegeneration in the hippocampus, but how the cells die is not fully understood. We analyzed the dynamics and mechanisms of cell loss in the hippocampus of audiogenic Krushinsky-Molodkina (KM) rats during the development of TLE. Audiogenic kindling of different durations was carried out to reproduce TLE progression in KM rats. Behavioral analysis showed the development of post-tonic clonus, the main indicator of TLE, by the 14th AGS. The severity and duration of post-tonic clonus positively correlated with the increase in the number of AGS. Temporal lobe epilepsy development was accompanied with two peaks of cell loss. The first peak was detected after 7 AGS in the dentate gyrus (DG) granular layer and associated with activation of p53- and mitochondria-dependent apoptosis. After a 7-day rest period, activation of autophagy and restoration of cell number were revealed. The second peak occurred after 14 AGS, affected both granular and hilar mossy cells and persisted further after 21 AGS, but no compensation was observed. Thus, activation of autophagy probably plays a neuroprotective role and supports survival of hippocampal cells at the beginning of epileptogenesis, but exacerbation of limbic seizures during TLE development causes irreversible neurodegeneration.
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7
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Seizure-induced strengthening of a recurrent excitatory circuit in the dentate gyrus is proconvulsant. Proc Natl Acad Sci U S A 2022; 119:e2201151119. [PMID: 35930664 PMCID: PMC9371717 DOI: 10.1073/pnas.2201151119] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Epilepsy is a devastating brain disorder for which effective treatments are very limited. There is growing interest in early intervention, which requires a better mechanistic understanding of the early stages of this disorder. While diverse brain insults can lead to epileptic activity, a common cellular mechanism relies on uncontrolled recurrent excitatory activity. In the dentate gyrus, excitatory mossy cells (MCs) project extensively onto granule cells (GCs) throughout the hippocampus, thus establishing a recurrent MC-GC-MC excitatory loop. MCs are implicated in temporal lobe epilepsy, a common form of epilepsy, but their role during initial seizures (i.e., before the characteristic MC loss that occurs in late stages) is unclear. Here, we show that initial seizures acutely induced with an intraperitoneal kainic acid (KA) injection in adult mice, a well-established model that leads to experimental epilepsy, not only increased MC and GC activity in vivo but also triggered a brain-derived neurotrophic factor (BDNF)-dependent long-term potentiation (LTP) at MC-GC excitatory synapses. Moreover, in vivo induction of MC-GC LTP using MC-selective optogenetic stimulation worsened KA-induced seizures. Conversely, Bdnf genetic removal from GCs, which abolishes LTP, and selective MC silencing were both anticonvulsant. Thus, initial seizures are associated with MC-GC synaptic strengthening, which may promote later epileptic activity. Our findings reveal a potential mechanism of epileptogenesis that may help in developing therapeutic strategies for early intervention.
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8
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Blackstad JS, Osen KK, Leergaard TB. The fibro- and cyto-architecture demarcating the border between the dentate gyrus and CA3 in sheep (Ovis aries) and domestic pig (Sus scrofa domesticus). Hippocampus 2022; 32:639-659. [PMID: 35913094 PMCID: PMC9546232 DOI: 10.1002/hipo.23457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 05/28/2022] [Accepted: 07/07/2022] [Indexed: 11/05/2022]
Abstract
The hippocampal formation is essential for spatial navigation and episodic memory. The anatomical structure is largely similar across mammalian species, apart from the deep polymorphic layer of the dentate gyrus and the adjacent part of cornu ammonis 3 (CA3) which feature substantial variations. In rodents, the polymorphic layer has a triangular cross‐section abutting on the end of the CA3 pyramidal layer, while in primates it is long and band‐shaped capping the expanded CA3 end, which here lacks a distinct pyramidal layer. This structural variation has resulted in a confusing nomenclature and unclear anatomical criteria for the definition of the dentate‐ammonic border. Seeking to clarify the border, we present here a light microscopic investigation based on Golgi‐impregnated and Timm–thionin‐stained sections of the Artiodactyla sheep and domestic pig, in which the dentate gyrus and CA3 end have some topographical features in common with primates. In short, the band‐shaped polymorphic layer coincides with the Timm‐positive mossy fiber collateral plexus and the Timm‐negative subgranular zone. While the soma and excrescence‐covered proximal dendrites of the mossy cells are localized within the plexus, the peripheral mossy cell dendrites extend outside the plexus, both into the granular and molecular layers, and the CA3. The main mossy fibers leave the collateral plexus in a scattered formation to converge gradually through the CA3 end in between the dispersed pyramidal cells, which are of three subtypes, as in monkey, with the classical apical subtype dominating near the hidden blade, the nonapical subtype near the exposed blade, and the dentate subtype being the only pyramidal cells that extend dendrites into the dentate gyrus. In agreement with our previous study in mink, the findings show that the border between the dentate gyrus and the CA3 end can be more accurately localized by the mossy fiber system than by cyto‐architecture alone.
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Affiliation(s)
- Jan Sigurd Blackstad
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Kavli Institute for Systems Neuroscience and Center for Biology of Memory, Norwegian University of Science and Technology, Trondheim, Norway
| | - Kirsten K Osen
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Trygve B Leergaard
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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Puhahn-Schmeiser B, Kleemann T, Jabbarli R, Bock HH, Beck J, Freiman TM. Granule cell dispersion in two mouse models of temporal lobe epilepsy and reeler mice is associated with changes in dendritic orientation and spine distribution. Hippocampus 2022; 32:517-528. [PMID: 35621370 DOI: 10.1002/hipo.23447] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 04/05/2022] [Accepted: 04/11/2022] [Indexed: 11/06/2022]
Abstract
Temporal lobe epilepsy is characterized by hippocampal neuronal death in CA1 and hilus. Dentate gyrus granule cells survive but show dispersion of the compact granule cell layer. This is associated with decrease of the glycoprotein Reelin, which regulates neuron migration and dendrite outgrow. Reelin-deficient (reeler) mice show no layering, their granule cells are dispersed throughout the dentate gyrus. We studied granule cell dendritic orientation and distribution of postsynaptic spines in reeler mice and two mouse models of temporal lobe epilepsy, namely the p35 knockout mice, which show Reelin-independent neuronal migration defects, and mice with unilateral intrahippocampal kainate injection. Granule cells were Golgi-stained and analyzed, using a computerized camera lucida system. Granule cells in naive controls exhibited a vertically oriented dendritic arbor with a small bifurcation angle if positioned proximal to the hilus and a wider dendritic bifurcation angle, if positioned distally. P35 knockout- and kainate-injected mice showed a dispersed granule cell layer, granule cells showed basal dendrites with wider bifurcation angles, which lost position-specific differences. Reeler mice lacked dendritic orientation. P35 knockout- and kainate-injected mice showed increased dendritic spine density in the granule cell layer. Molecular layer dendrites showed a reduced spine density in kainate-injected mice only, whereas in p35 knockouts no reduced spine density was seen. Reeler mice showed a homogenous high spine density. We hypothesize that granule cells migrate in temporal lobe epilepsy, develop new dendrites which show a spread of the dendritic tree, create new spines in areas proximal to mossy fiber sprouting, which is present in p35 knockout- and kainate-injected mice and loose spines on distal dendrites if mossy cell death is present, as it was in kainate-injected mice only. These results are in accordance with findings in epilepsy patients.
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Affiliation(s)
- Barbara Puhahn-Schmeiser
- Faculty of Medicine, Department of Neurosurgery, Medical Center, University of Freiburg, Freiburg, Germany
| | - Tobias Kleemann
- Department of Gastroenterology and Rheumatology, Carl-Thiem-Hospital, Cottbus, Germany
| | - Ramazan Jabbarli
- Faculty of Medicine, Department of Neurosurgery, Medical Center, University of Duisburg-Essen, Essen, Germany
| | - Hans H Bock
- Faculty of Medicine, Department of Gastroenterology, Hepatology and Infectiology, Medical Center, University of Duesseldorf, Duesseldorf, Germany
| | - Jürgen Beck
- Faculty of Medicine, Department of Neurosurgery, Medical Center, University of Freiburg, Freiburg, Germany
| | - Thomas M Freiman
- Department of Neurosurgery, University Medical Center Rostock, Rostock, Germany
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Puhahn-Schmeiser B, Leicht K, Gessler F, Freiman TM. Aberrant hippocampal mossy fibers in temporal lobe epilepsy target excitatory and inhibitory neurons. Epilepsia 2021; 62:2539-2550. [PMID: 34453315 DOI: 10.1111/epi.17035] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 07/26/2021] [Accepted: 07/30/2021] [Indexed: 11/30/2022]
Abstract
OBJECTIVE The pathoanatomical correlate of temporal lobe epilepsy is hippocampal sclerosis, characterized by selective neuronal death of mossy cells in the hilus and of pyramidal cells in cornu ammonis 1. Although granule cells survive, they lose mossy cells as a target and redirect their axons (mossy fibers) backward into the molecular cell layer. It has been assumed that this process results in excitatory circuits. We therefore examined whether sprouted mossy fibers form synaptic connection not only with excitatory granule cells but also with inhibitory interneurons, such as basket cells. METHODS Resected hippocampal specimens of patients with hippocampal sclerosis were compared to controls of patients with extrahippocampal lesions with only mild sclerosis. Mossy fibers were traced with Neurobiotin or labeled against synaptoporin; inhibitory interneurons were labeled against parvalbumin. Synapses were examined with electron microscopy, labeled with γ-aminobutyric acid immunogold. RESULTS Sprouted mossy fibers of epileptic hippocampi innervate not only excitatory granule cells but also inhibitory parvalbuminergic interneurons. Despite neuronal death in hippocampal sclerosis, the axonal plexus of inhibitory parvalbuminergic interneurons surrounding the granule cells is preserved. Connections of sprouted mossy fibers and inhibitory axon terminals were quantified, showing that the number of inhibitory axon terminals significantly exceeds the number of sprouted excitatory mossy fiber terminals (.03 boutons/µm vs. .11 boutons/µm; p < .001). SIGNIFICANCE Although no definite conclusions regarding the function of our findings may be derived from this anatomical study, the observed aberrant connectivity might lead to an increased inhibition and synchronization of granule cells, because the preserved inhibitory interneurons show an additional innervation through sprouted mossy fibers. This might result in the instability of a previously balanced network.
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Affiliation(s)
- Barbara Puhahn-Schmeiser
- Department of Neurosurgery, Faculty of Medicine, Medical Center, University of Freiburg, Freiburg, Germany
| | - Kathrin Leicht
- Department of Neurosurgery, Faculty of Medicine, Medical Center, University of Freiburg, Freiburg, Germany
| | - Florian Gessler
- Department of Neurosurgery, Faculty of Medicine, University of Rostock, Rostock, Germany
| | - Thomas M Freiman
- Department of Neurosurgery, Faculty of Medicine, University of Rostock, Rostock, Germany
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11
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Zaitsev АV, Amakhin DV, Dyomina AV, Zakharova MV, Ergina JL, Postnikova TY, Diespirov GP, Magazanik LG. Synaptic Dysfunction in Epilepsy. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s002209302103008x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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12
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An inventory of basic research in temporal lobe epilepsy. Rev Neurol (Paris) 2021; 177:1069-1081. [PMID: 34176659 DOI: 10.1016/j.neurol.2021.02.390] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/26/2021] [Accepted: 02/05/2021] [Indexed: 12/25/2022]
Abstract
Temporal lobe epilepsy is a severe neurological disease, characterized by seizure occurrence and invalidating cognitive co-morbidities, which affects up to 1% of the adults. Roughly one third of the patients are resistant to any conventional pharmacological treatments. The last option in that case is the surgical removal of the epileptic focus, with no guarantee for clinical symptom alleviation. This state of affairs requests the identification of cellular or molecular targets for novel therapeutic approaches with limited side effects. Here we review some generalities about the disease as well as some of the most recent discoveries about the cellular and molecular mechanisms of TLE, and the latest perspectives for novel treatments.
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13
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Freiman TM, Häussler U, Zentner J, Doostkam S, Beck J, Scheiwe C, Brandt A, Haas CA, Puhahn-Schmeiser B. Mossy fiber sprouting into the hippocampal region CA2 in patients with temporal lobe epilepsy. Hippocampus 2021; 31:580-592. [PMID: 33720466 DOI: 10.1002/hipo.23323] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 02/23/2021] [Accepted: 02/27/2021] [Indexed: 01/28/2023]
Abstract
Hippocampal sclerosis (HS) in Temporal Lobe Epilepsy (TLE) shows neuronal death in cornu ammonis (CA)1, CA3, and CA4. It is known that granule cells and CA2 neurons survive and their axons, the mossy fibers (MF), lose their target cells in CA3 and CA4 and sprout to the granule cell layer and molecular layer. We examined in TLE patients and in a mouse epilepsy model, whether MF sprouting is directed to the dentate gyrus or extends to distant CA regions and whether sprouting is associated with death of target neurons in CA3 and CA4. In 319 TLE patients, HS was evaluated by Wyler grade and International League against Epilepsy (ILAE) types using immunohistochemistry against neuronal nuclei (NeuN). Synaptoporin was used to colocalize MF. In addition, transgenic Thy1-eGFP mice were intrahippocampally injected with kainate and sprouting of eGFP-positive MFs was analyzed together with immunocytochemistry for regulator of G-protein signaling 14 (RGS14). In human HS Wyler III and IV as well as in ILAE 1, 2, and 3 specimens, we found synaptoporin-positive axon terminals in CA2 and even in CA1, associated with the extent of granule cell dispersion. Sprouting was seen in cases with cell death of target neurons in CA3 and CA4 (classical severe HS ILAE type 1) but also without this cell death (atypical HS ILAE type 2). Similarly, in epileptic mice eGFP-positive MFs sprouted to CA2 and beyond. The presence of MF terminals in the CA2 pyramidal cell layer and in CA1 was also correlated with the extent of granule cell dispersion. The similarity of our findings in human specimens and in the mouse model highlights the importance and opens up new chances of using translational approaches to determine mechanisms underlying TLE.
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Affiliation(s)
- Thomas M Freiman
- Department of Neurosurgery, Rostock University Medical Center, Rostock, Germany
| | - Ute Häussler
- Department of Neurosurgery, Experimental Epilepsy Research, Medical Center-University of Freiburg, Faculty of Medicine, Freiburg, Germany.,Faculty of Medicine, Center for Basics in NeuroModulation, University of Freiburg, Freiburg, Germany.,BrainLinks-BrainTools Center, University of Freiburg, Freiburg, Germany
| | - Josef Zentner
- Faculty of Medicine, Department of Neurosurgery, Medical Center-University of Freiburg, Freiburg, Germany
| | - Soroush Doostkam
- Faculty of Medicine, Institute of Neuropathology, Medical Center-University of Freiburg, Freiburg, Germany
| | - Jürgen Beck
- Faculty of Medicine, Department of Neurosurgery, Medical Center-University of Freiburg, Freiburg, Germany
| | - Christian Scheiwe
- Faculty of Medicine, Department of Neurosurgery, Medical Center-University of Freiburg, Freiburg, Germany
| | - Armin Brandt
- Epilepsy Center, University Medical Center, Albert-Ludwigs-University, Freiburg, Germany
| | - Carola A Haas
- Department of Neurosurgery, Experimental Epilepsy Research, Medical Center-University of Freiburg, Faculty of Medicine, Freiburg, Germany.,Faculty of Medicine, Center for Basics in NeuroModulation, University of Freiburg, Freiburg, Germany.,BrainLinks-BrainTools Center, University of Freiburg, Freiburg, Germany
| | - Barbara Puhahn-Schmeiser
- Faculty of Medicine, Department of Neurosurgery, Medical Center-University of Freiburg, Freiburg, Germany
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14
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Lenck-Santini PP, Sakkaki S. Alterations of Neuronal Dynamics as a Mechanism for Cognitive Impairment in Epilepsy. Curr Top Behav Neurosci 2021; 55:65-106. [PMID: 33454922 DOI: 10.1007/7854_2020_193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Epilepsy is commonly associated with cognitive and behavioral deficits that dramatically affect the quality of life of patients. In order to identify novel therapeutic strategies aimed at reducing these deficits, it is critical first to understand the mechanisms leading to cognitive impairments in epilepsy. Traditionally, seizures and epileptiform activity in addition to neuronal injury have been considered to be the most significant contributors to cognitive dysfunction. In this review we however highlight the role of a new mechanism: alterations of neuronal dynamics, i.e. the timing at which neurons and networks receive and process neural information. These alterations, caused by the underlying etiologies of epilepsy syndromes, are observed in both animal models and patients in the form of abnormal oscillation patterns in unit firing, local field potentials, and electroencephalogram (EEG). Evidence suggests that such mechanisms significantly contribute to cognitive impairment in epilepsy, independently of seizures and interictal epileptiform activity. Therefore, therapeutic strategies directly targeting neuronal dynamics rather than seizure reduction may significantly benefit the quality of life of patients.
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Affiliation(s)
- Pierre-Pascal Lenck-Santini
- Aix-Marseille Université, INSERM, INMED, Marseille, France. .,Department of Neurological sciences, University of Vermont, Burlington, VT, USA.
| | - Sophie Sakkaki
- Department of Neurological sciences, University of Vermont, Burlington, VT, USA.,Université de. Montpellier, CNRS, INSERM, IGF, Montpellier, France
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15
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Ábrahám H, Molnár JE, Sóki N, Gyimesi C, Horváth Z, Janszky J, Dóczi T, Seress L. Etiology-related Degree of Sprouting of Parvalbumin-immunoreactive Axons in the Human Dentate Gyrus in Temporal Lobe Epilepsy. Neuroscience 2020; 448:55-70. [PMID: 32931846 DOI: 10.1016/j.neuroscience.2020.09.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 08/22/2020] [Accepted: 09/05/2020] [Indexed: 11/16/2022]
Abstract
In the present study, we examined parvalbumin-immunoreactive cells and axons in the dentate gyrus of surgically resected tissues of therapy-resistant temporal lobe epilepsy (TLE) patients with different etiologies. Based on MRI results, five groups of patients were formed: (1) hippocampal sclerosis (HS), (2) malformation of cortical development, (3) malformation of cortical development + HS, (4) tumor-induced TLE, (5) patients with negative MRI result. Four control samples were also included in the study. Parvalbumin-immunoreactive cells were observed mostly in subgranular location in the dentate hilus in controls, in tumor-induced TLE, in malformation of cortical development and in MR-negative cases. In patients with HS, significant decrease in the number of hilar parvalbumin-immunoreactive cells and large numbers of ectopic parvalbumin-containing neurons were detected in the dentate gyrus' molecular layer. The ratio of ectopic/normally-located cells was significantly higher in HS than in other TLE groups. In patients with HS, robust sprouting of parvalbumin-immunoreactive axons were frequently visible in the molecular layer. The extent of sprouting was significantly higher in TLE patients with HS than in other groups. Strong sprouting of parvalbumin-immunoreactive axons were frequently observed in patients who had childhood febrile seizure. Significant correlation was found between the level of sprouting of axons and the ratio of ectopic/normally-located parvalbumin-containing cells. Electron microscopy demonstrated that sprouted parvalbumin-immunoreactive axons terminate on proximal and distal dendritic shafts as well as on dendritic spines of granule cells. Our results indicate alteration of target profile of parvalbumin-immunoreactive neurons in HS that contributes to the known synaptic remodeling in TLE.
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Affiliation(s)
- Hajnalka Ábrahám
- Department of Medical Biology and Central Electron Microscopic Laboratory, University of Pécs Medical School, Szigeti u 12., Pécs 7624, Hungary.
| | - Judit E Molnár
- Department of Medical Biology and Central Electron Microscopic Laboratory, University of Pécs Medical School, Szigeti u 12., Pécs 7624, Hungary
| | - Noémi Sóki
- Department of Medical Biology and Central Electron Microscopic Laboratory, University of Pécs Medical School, Szigeti u 12., Pécs 7624, Hungary
| | - Csilla Gyimesi
- Department of Neurology, University of Pécs Medical School, Rét u. 2., Pécs 7623, Hungary
| | - Zsolt Horváth
- Department of Neurosurgery, University of Pécs Medical School, Rét u. 2., Pécs 7623, Hungary
| | - József Janszky
- Department of Neurology, University of Pécs Medical School, Rét u. 2., Pécs 7623, Hungary
| | - Tamás Dóczi
- Department of Neurosurgery, University of Pécs Medical School, Rét u. 2., Pécs 7623, Hungary
| | - László Seress
- Department of Medical Biology and Central Electron Microscopic Laboratory, University of Pécs Medical School, Szigeti u 12., Pécs 7624, Hungary
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16
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Grovola MR, Paleologos N, Wofford KL, Harris JP, Browne KD, Johnson V, Duda JE, Wolf JA, Cullen DK. Mossy cell hypertrophy and synaptic changes in the hilus following mild diffuse traumatic brain injury in pigs. J Neuroinflammation 2020; 17:44. [PMID: 32005260 PMCID: PMC6993507 DOI: 10.1186/s12974-020-1720-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 01/19/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Each year in the USA, over 2.4 million people experience mild traumatic brain injury (TBI), which can induce long-term neurological deficits. The dentate gyrus of the hippocampus is notably susceptible to damage following TBI, as hilar mossy cell changes in particular may contribute to post-TBI dysfunction. Moreover, microglial activation after TBI may play a role in hippocampal circuit and/or synaptic remodeling; however, the potential effects of chronic microglial changes are currently unknown. The objective of the current study was to assess neuropathological and neuroinflammatory changes in subregions of the dentate gyrus at acute to chronic time points following mild TBI using an established model of closed-head rotational acceleration induced TBI in pigs. METHODS This study utilized archival tissue of pigs which were subjected to sham conditions or rapid head rotation in the coronal plane to generate mild TBI. A quantitative assessment of neuropathological changes in the hippocampus was performed via immunohistochemical labeling of whole coronal tissue sections at 3 days post-injury (DPI), 7 DPI, 30 DPI, and 1 year post-injury (YPI), with a focus on mossy cell atrophy and synaptic reorganization, in context with microglial alterations (e.g., density, proximity to mossy cells) in the dentate gyrus. RESULTS There were no changes in mossy cell density between sham and injured animals, indicating no frank loss of mossy cells at the mild injury level evaluated. However, we found significant mossy cell hypertrophy at 7 DPI and 30 DPI in anterior (> 16% increase in mean cell area at each time; p = < 0.001 each) and 30 DPI in posterior (8.3% increase; p = < 0.0001) hippocampus. We also found dramatic increases in synapsin staining around mossy cells at 7 DPI in both anterior (74.7% increase in synapsin labeling; p = < 0.0001) and posterior (82.7% increase; p = < 0.0001) hippocampus. Interestingly, these morphological and synaptic alterations correlated with a significant change in microglia in proximity to mossy cells at 7 DPI in anterior and at 30 DPI in the posterior hippocampus. For broader context, while we found that there were significant increases in microglia density in the granule cell layer at 30 DPI (anterior and posterior) and 1 YPI (posterior only) and in the molecular layer at 1 YPI (anterior only), we found no significant changes in overall microglial density in the hilus at any of the time points evaluated post-injury. CONCLUSIONS The alterations of mossy cell size and synaptic inputs paired with changes in microglia density around the cells demonstrate the susceptibility of hilar mossy cells after even mild TBI. This subtle hilar mossy cell pathology may play a role in aberrant hippocampal function post-TBI, although additional studies are needed to characterize potential physiological and cognitive alterations.
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Affiliation(s)
- Michael R Grovola
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA
- Center for Brain Injury & Repair, Department of Neurosurgery, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA
| | - Nicholas Paleologos
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA
- Center for Brain Injury & Repair, Department of Neurosurgery, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA
| | - Kathryn L Wofford
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA
- Center for Brain Injury & Repair, Department of Neurosurgery, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA
| | - James P Harris
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA
- Center for Brain Injury & Repair, Department of Neurosurgery, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA
| | - Kevin D Browne
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA
- Center for Brain Injury & Repair, Department of Neurosurgery, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA
| | - Victoria Johnson
- Center for Brain Injury & Repair, Department of Neurosurgery, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA
| | - John E Duda
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA
- Parkinson's Disease Research, Education and Clinical Center, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - John A Wolf
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA
- Center for Brain Injury & Repair, Department of Neurosurgery, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA
| | - D Kacy Cullen
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA.
- Center for Brain Injury & Repair, Department of Neurosurgery, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA.
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, 105E Hayden Hall/3320 Smith Walk, Philadelphia, PA, 19104, USA.
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17
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Gonzalez-Reyes LE, Chiang CC, Zhang M, Johnson J, Arrillaga-Tamez M, Couturier NH, Reddy N, Starikov L, Capadona JR, Kottmann AH, Durand DM. Sonic Hedgehog is expressed by hilar mossy cells and regulates cellular survival and neurogenesis in the adult hippocampus. Sci Rep 2019; 9:17402. [PMID: 31758070 PMCID: PMC6874678 DOI: 10.1038/s41598-019-53192-4] [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: 08/28/2018] [Accepted: 10/29/2019] [Indexed: 12/12/2022] Open
Abstract
Sonic hedgehog (Shh) is a multifunctional signaling protein governing pattern formation, proliferation and cell survival during embryogenesis. In the adult brain, Shh has neurotrophic function and is implicated in hippocampal neurogenesis but the cellular source of Shh in the hippocampus remains ill defined. Here, we utilize a gene expression tracer allele of Shh (Shh-nlacZ) which allowed the identification of a subpopulation of hilar neurons known as mossy cells (MCs) as a prominent and dynamic source of Shh within the dentate gyrus. AAV-Cre mediated ablation of Shh in the adult dentate gyrus led to a marked degeneration of MCs. Conversely, chemical stimulation of hippocampal neurons using the epileptogenic agent kainic acid (KA) increased the number of Shh+ MCs indicating that the expression of Shh by MCs confers a survival advantage during the response to excitotoxic insults. In addition, ablation of Shh in the adult dentate gyrus led to increased neural precursor cell proliferation and their migration into the subgranular cell layer demonstrating that MCs-generated Shh is a key modulator of hippocampal neurogenesis.
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Affiliation(s)
- Luis E Gonzalez-Reyes
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA.
- Advanced Platform Technology Center, L. Stokes Cleveland VA Medical Center, Rehab. R&D, 10701 East Blvd. Mail Stop 151 AW/APT, Cleveland, OH, 44106, USA.
| | - Chia-Chu Chiang
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Mingming Zhang
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Joshua Johnson
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Manuel Arrillaga-Tamez
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Nicholas H Couturier
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Neha Reddy
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Lev Starikov
- Department of Molecular, Cellular and Biomedical Sciences, CUNY School of Medicine at City College of New York and Graduate Center, City University of New York, New York, NY, 10031, USA
| | - Jeffrey R Capadona
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA
- Advanced Platform Technology Center, L. Stokes Cleveland VA Medical Center, Rehab. R&D, 10701 East Blvd. Mail Stop 151 AW/APT, Cleveland, OH, 44106, USA
| | - Andreas H Kottmann
- Department of Molecular, Cellular and Biomedical Sciences, CUNY School of Medicine at City College of New York and Graduate Center, City University of New York, New York, NY, 10031, USA
| | - Dominique M Durand
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, 44106, USA
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18
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Kahn JB, Port RG, Yue C, Takano H, Coulter DA. Circuit-based interventions in the dentate gyrus rescue epilepsy-associated cognitive dysfunction. Brain 2019; 142:2705-2721. [PMID: 31363737 PMCID: PMC6736326 DOI: 10.1093/brain/awz209] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 04/26/2019] [Accepted: 05/22/2019] [Indexed: 12/15/2022] Open
Abstract
Temporal lobe epilepsy is associated with significant structural pathology in the hippocampus. In the dentate gyrus, the summative effect of these pathologies is massive hyperexcitability in the granule cells, generating both increased seizure susceptibility and cognitive deficits. To date, therapeutic approaches have failed to improve the cognitive symptoms in fully developed, chronic epilepsy. As the dentate's principal signalling population, the granule cells' aggregate excitability has the potential to provide a mechanistically-independent downstream target. We examined whether normalizing epilepsy-associated granule cell hyperexcitability-without correcting the underlying structural circuit disruptions-would constitute an effective therapeutic approach for cognitive dysfunction. In the systemic pilocarpine mouse model of temporal lobe epilepsy, the epileptic dentate gyrus excessively recruits granule cells in behavioural contexts, not just during seizure events, and these mice fail to perform on a dentate-mediated spatial discrimination task. Acutely reducing dorsal granule cell hyperactivity in chronically epileptic mice via either of two distinct inhibitory chemogenetic receptors rescued behavioural performance such that they responded comparably to wild type mice. Furthermore, recreating granule cell hyperexcitability in control mice via excitatory chemogenetic receptors, without altering normal circuit anatomy, recapitulated spatial memory deficits observed in epileptic mice. However, making the granule cells overly quiescent in both epileptic and control mice again disrupted behavioural performance. These bidirectional manipulations reveal that there is a permissive excitability window for granule cells that is necessary to support successful behavioural performance. Chemogenetic effects were specific to the targeted dorsal hippocampus, as hippocampal-independent and ventral hippocampal-dependent behaviours remained unaffected. Fos expression demonstrated that chemogenetics can modulate granule cell recruitment via behaviourally relevant inputs. Rather than driving cell activity deterministically or spontaneously, chemogenetic intervention merely modulates the behaviourally permissive activity window in which the circuit operates. We conclude that restoring appropriate principal cell tuning via circuit-based therapies, irrespective of the mechanisms generating the disease-related hyperactivity, is a promising translational approach.
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Affiliation(s)
- Julia B Kahn
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Russell G Port
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- The Research Institute of the Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Cuiyong Yue
- The Research Institute of the Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Hajime Takano
- The Research Institute of the Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Douglas A Coulter
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- The Research Institute of the Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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19
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Farrell JS, Nguyen QA, Soltesz I. Resolving the Micro-Macro Disconnect to Address Core Features of Seizure Networks. Neuron 2019; 101:1016-1028. [PMID: 30897354 PMCID: PMC6430140 DOI: 10.1016/j.neuron.2019.01.043] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 12/14/2018] [Accepted: 01/18/2019] [Indexed: 02/07/2023]
Abstract
Current drug treatments for epilepsy attempt to broadly restrict excitability to mask a symptom, seizures, with little regard for the heterogeneous mechanisms that underlie disease manifestation across individuals. Here, we discuss the need for a more complete view of epilepsy, outlining how key features at the cellular and microcircuit level can significantly impact disease mechanisms that are not captured by the most common methodology to study epilepsy, electroencephalography (EEG). We highlight how major advances in neuroscience tool development now enable multi-scale investigation of fundamental questions to resolve the currently controversial understanding of seizure networks. These findings will provide essential insight into what has emerged as a disconnect between the different levels of investigation and identify new targets and treatment options.
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Affiliation(s)
- Jordan S Farrell
- Department of Neurosurgery, Stanford University, Stanford, CA, USA.
| | - Quynh-Anh Nguyen
- Department of Neurosurgery, Stanford University, Stanford, CA, USA
| | - Ivan Soltesz
- Department of Neurosurgery, Stanford University, Stanford, CA, USA.
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20
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Irritable No More: Activating Mossy Cells for the Treatment of Epilepsy. Epilepsy Curr 2018; 18:251-252. [PMID: 30254523 DOI: 10.5698/1535-7597.18.4.251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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21
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Bui AD, Nguyen TM, Limouse C, Kim HK, Szabo GG, Felong S, Maroso M, Soltesz I. Dentate gyrus mossy cells control spontaneous convulsive seizures and spatial memory. Science 2018; 359:787-790. [PMID: 29449490 DOI: 10.1126/science.aan4074] [Citation(s) in RCA: 159] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2017] [Accepted: 12/21/2017] [Indexed: 01/06/2023]
Abstract
Temporal lobe epilepsy (TLE) is characterized by debilitating, recurring seizures and an increased risk for cognitive deficits. Mossy cells (MCs) are key neurons in the hippocampal excitatory circuit, and the partial loss of MCs is a major hallmark of TLE. We investigated how MCs contribute to spontaneous ictal activity and to spatial contextual memory in a mouse model of TLE with hippocampal sclerosis, using a combination of optogenetic, electrophysiological, and behavioral approaches. In chronically epileptic mice, real-time optogenetic modulation of MCs during spontaneous hippocampal seizures controlled the progression of activity from an electrographic to convulsive seizure. Decreased MC activity is sufficient to impede encoding of spatial context, recapitulating observed cognitive deficits in chronically epileptic mice.
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Affiliation(s)
- Anh D Bui
- Department of Neurosurgery, Stanford University, Stanford, CA 94305, USA. .,Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697, USA
| | - Theresa M Nguyen
- Department of Neurosurgery, Stanford University, Stanford, CA 94305, USA
| | - Charles Limouse
- Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
| | - Hannah K Kim
- Department of Neurosurgery, Stanford University, Stanford, CA 94305, USA
| | - Gergely G Szabo
- Department of Neurosurgery, Stanford University, Stanford, CA 94305, USA
| | - Sylwia Felong
- Department of Neurosurgery, Stanford University, Stanford, CA 94305, USA
| | - Mattia Maroso
- Department of Neurosurgery, Stanford University, Stanford, CA 94305, USA
| | - Ivan Soltesz
- Department of Neurosurgery, Stanford University, Stanford, CA 94305, USA
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22
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Excitatory Synaptic Input to Hilar Mossy Cells under Basal and Hyperexcitable Conditions. eNeuro 2017; 4:eN-NWR-0364-17. [PMID: 29214210 PMCID: PMC5714709 DOI: 10.1523/eneuro.0364-17.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 11/06/2017] [Accepted: 11/10/2017] [Indexed: 11/21/2022] Open
Abstract
Hilar mossy cells (HMCs) in the hippocampus receive glutamatergic input from dentate granule cells (DGCs) via mossy fibers (MFs) and back-projections from CA3 pyramidal neuron collateral axons. Many fundamental features of these excitatory synapses have not been characterized in detail despite their potential relevance to hippocampal cognitive processing and epilepsy-induced adaptations in circuit excitability. In this study, we compared pre- and postsynaptic parameters between MF and CA3 inputs to HMCs in young and adult mice of either sex and determined the relative contributions of the respective excitatory inputs during in vitro and in vivo models of hippocampal hyperexcitability. The two types of excitatory synapses both exhibited a modest degree of short-term plasticity, with MF inputs to HMCs exhibiting lower paired-pulse (PP) and frequency facilitation than was described previously for MF–CA3 pyramidal cell synapses. MF–HMC synapses exhibited unitary excitatory synaptic currents (EPSCs) of larger amplitude, contained postsynaptic kainate receptors, and had a lower NMDA/AMPA receptor ratio compared to CA3–HMC synapses. Pharmacological induction of hippocampal hyperexcitability in vitro transformed the abundant but relatively weak CA3–HMC connections to very large amplitude spontaneous bursts of compound EPSCs (cEPSCs) in young mice (∼P20) and, to a lesser degree, in adult mice (∼P70). CA3–HMC cEPSCs were also observed in slices prepared from mice with spontaneous seizures several weeks after intrahippocampal kainate injection. Strong excitation of HMCs during synchronous CA3 activity represents an avenue of significant excitatory network generation back to DGCs and might be important in generating epileptic networks.
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23
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Schmeiser B, Li J, Brandt A, Zentner J, Doostkam S, Freiman TM. Different mossy fiber sprouting patterns in ILAE hippocampal sclerosis types. Epilepsy Res 2017; 136:115-122. [DOI: 10.1016/j.eplepsyres.2017.08.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 07/07/2017] [Accepted: 08/05/2017] [Indexed: 12/28/2022]
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24
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Extent of mossy fiber sprouting in patients with mesiotemporal lobe epilepsy correlates with neuronal cell loss and granule cell dispersion. Epilepsy Res 2017; 129:51-58. [DOI: 10.1016/j.eplepsyres.2016.11.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 11/20/2016] [Indexed: 11/21/2022]
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25
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Schaefermeier P, Heinze S. Hippocampal Characteristics and Invariant Sequence Elements Distribution of GLRA2 and GLRA3 C-to-U Editing. Mol Syndromol 2016; 8:85-92. [PMID: 28611548 DOI: 10.1159/000453300] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/25/2016] [Indexed: 11/19/2022] Open
Abstract
Glycine receptor α2 and α3 subunit (GLRA2/GLRA3) high-affinity variants, of which the subjacent amino acid substitutions issue from C-to-U RNA editing, are thought to influence tonic inhibition and pathophysiology. In light of the detection of GLRA3 NM_006529:r.1157C>U and GLRA2 NM_002063:r.1416C>U exchanges in hippocampus explants of temporal lobe epilepsy patients, we now examine the healthy situation and relate it to the epileptic situation by ascertaining controls in a legitimate reanalysis. The GLRA2 and GLRA3 editing events that would ultimately result in a glycine receptor with increased affinity occur in the postmortem nonepileptic hippocampus. Most notably, their relative amounts do not significantly differ from those in increased damaged hippocampus explants, whereas curbed relative amounts in epileptic explants without cell loss come out statistically significant. Local sequence alignment reveals invariant sequence stretches consistent in GLRA2/ GLRA3 and other edited transcripts that coincide with known APOB sequence elements. Concerning the essential mooring element, GLRA2/GLRA3 comply strictly only with the motif's 5' part. While this lack of canonical mooring elements and uncertain action of the famous deaminase APOBEC1 suggest a specific regulation of GLRA2/GLRA3 editing, its reduction in the less-damaged epileptic hippocampus could be attributed to anomalous epileptic neurogenesis.
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Affiliation(s)
- Philipp Schaefermeier
- Charité University Medicine Berlin, Germany,Helmholtz Group RNA Editing and Hyperexcitability Disorders, Max-Delbrück-Centre for Molecular Medicine, Berlin, Germany
| | - Sarah Heinze
- Institute of Forensic Sciences and Legal Medicine, Charité Berlin, Berlin, Germany,Klinikum Oldenburg gGmbH, Oldenburg, Germany,Institute of Forensic Medicine, Johannes Gutenberg University of Mainz, Mainz, Germany
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26
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Alexander A, Maroso M, Soltesz I. Organization and control of epileptic circuits in temporal lobe epilepsy. PROGRESS IN BRAIN RESEARCH 2016; 226:127-54. [PMID: 27323941 PMCID: PMC5140277 DOI: 10.1016/bs.pbr.2016.04.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
When studying the pathological mechanisms of epilepsy, there are a seemingly endless number of approaches from the ultrastructural level-receptor expression by EM-to the behavioral level-comorbid depression in behaving animals. Epilepsy is characterized as a disorder of recurrent seizures, which are defined as "a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain" (Fisher et al., 2005). Such abnormal activity typically does not occur in a single isolated neuron; rather, it results from pathological activity in large groups-or circuits-of neurons. Here we choose to focus on two aspects of aberrant circuits in temporal lobe epilepsy: their organization and potential mechanisms to control these pathological circuits. We also look at two scales: microcircuits, ie, the relationship between individual neurons or small groups of similar neurons, and macrocircuits, ie, the organization of large-scale brain regions. We begin by summarizing the large body of literature that describes the stereotypical anatomical changes in the temporal lobe-ie, the anatomical basis of alterations in microcircuitry. We then offer a brief introduction to graph theory and describe how this type of mathematical analysis, in combination with computational neuroscience techniques and using parameters obtained from experimental data, can be used to postulate how microcircuit alterations may lead to seizures. We then zoom out and look at the changes which are seen over large whole-brain networks in patients and animal models, and finally we look to the future.
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Affiliation(s)
- A Alexander
- Stanford University, Stanford, CA, United States
| | - M Maroso
- Stanford University, Stanford, CA, United States
| | - I Soltesz
- Stanford University, Stanford, CA, United States.
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Bungenberg J, Surano N, Grote A, Surges R, Pernhorst K, Hofmann A, Schoch S, Helmstaedter C, Becker AJ. Gene expression variance in hippocampal tissue of temporal lobe epilepsy patients corresponds to differential memory performance. Neurobiol Dis 2015; 86:121-30. [PMID: 26631617 DOI: 10.1016/j.nbd.2015.11.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 10/27/2015] [Accepted: 11/13/2015] [Indexed: 01/05/2023] Open
Abstract
Temporal lobe epilepsy (TLE) is a severe brain disorder affecting particularly young adults. TLE is frequently associated with memory deterioration and neuronal damage of the hippocampal formation. It thereby reveals striking parallels to neurodegenerative disorders including Alzheimer's disease (AD). TLE patients differ with respect to their cognitive performance, but currently little is known about relevant molecular-genetic factors. Here, we correlated differential memory performance of pharmacoresistant TLE patients undergoing neurosurgery for seizure control with in-vitro findings of their hippocampal tissues. We analyzed mRNA transcripts and subsequently promoter variants specifically altered in brain tissue of individuals with 'very severe' memory impairment. TLE patients (n=79) were stratified according to preoperative memory impairment using an established four-tiered grading system ranging from 'average' to 'very severely'. Multimodal cluster analyses revealed molecules specifically associated with synaptic function and abundantly expressed in TLE patients with very impaired memory performance. In a subsequent promoter analysis, we found the single nucleotide polymorphism rs744373 C-allele to be associated with high mRNA levels of bridging integrator 1 (BIN1)/Amphiphysin 2, i.e. a major component of the endocytotic machinery and located in a crucial genetic AD risk locus. Using in vitro luciferase transfection assays, we found that BIN1 promoter activation is genotype dependent and strongly increased by reduced binding of the transcriptional repressor TGIF. Our data indicate that poor memory performance in patients with TLE strongly corresponds to distinctly altered neuronal transcript signatures, which - as demonstrated for BIN1 - can correlate with a particular allelic promoter variant. Our data suggest aberrant transcriptional signaling to significantly impact synaptic dynamics in TLE resulting in impaired memory performance and may serve as basis for future therapy development of this severe comorbidity.
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Affiliation(s)
- Julia Bungenberg
- Dept. of Neuropathology, University of Bonn Medical Center, Germany
| | - Natascha Surano
- Dept. of Neuropathology, University of Bonn Medical Center, Germany
| | - Alexander Grote
- Dept. of Neurosurgery, University of Bonn Medical Center, Germany
| | - Rainer Surges
- Dept. of Epileptology, University of Bonn Medical Center, Germany
| | | | - Andrea Hofmann
- Institute of Human Genetics, Department of Genomics, Life & Brain Center, University of Bonn, Bonn, Germany
| | - Susanne Schoch
- Dept. of Neuropathology, University of Bonn Medical Center, Germany
| | | | - Albert J Becker
- Dept. of Neuropathology, University of Bonn Medical Center, Germany.
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Li J, Xing H, Jiang G, Su Z, Wu Y, Zhang Y, Guo S. Increased Expression of Rac1 in Epilepsy Patients and Animal Models. Neurochem Res 2015; 41:836-43. [PMID: 26603293 DOI: 10.1007/s11064-015-1759-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 10/14/2015] [Accepted: 11/04/2015] [Indexed: 12/11/2022]
Abstract
The mechanisms of epilepsy remain incompletely understood. Rac1 (ras-related C3 botulinum toxin substrate 1) belongs to the Rho family of small GTPases. Rac1 play important roles in cytoskeleton rearrangement and neuronal synaptic plasticity, which had also been implicated in epilepsy. However, little is known regarding the expression of Rac1 in the epileptic brain or whether Rac1-targeted interventions affect the progression of epilepsy. The aim of this study was to investigate the expression profile of Rac1 in brain tissues from patients suffering from temporal lobe epilepsy (TLE) and experimental epileptic rats and determine the possible role of Rac1 in epilepsy. We demonstrated that the expression of Rac1 is significantly increased in TLE patients and in lithium-pilocarpine epilepsy model animals compared to the corresponding controls. Rac1 inhibitor NSC23766 reduced the severity of status epilepticus during the acute stage in a lithium-pilocarpine animal model. Consistent with these results, the latent period of a PTZ kindling animal model also increased. Our results demonstrated that the increased expression of Rac1 may contribute to pathophysiology of epilepsy.
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Affiliation(s)
- Jie Li
- Department of Neurology, The First Affiliated Hospital of Xinxiang Medical University, Weihui, 453100, Henan Province, China.
| | - Hongxia Xing
- Department of Neurology, The First Affiliated Hospital of Xinxiang Medical University, Weihui, 453100, Henan Province, China
| | - Guohui Jiang
- Department of Neurology, Affiliated Hospital of North Sichuan Medical University, Nanchong, 637000, Sichuan Province, China
| | - Zhou Su
- Department of Neurology, The First Affiliated Hospital of Xinxiang Medical University, Weihui, 453100, Henan Province, China
| | - Yuqing Wu
- Department of Neurology, The First Affiliated Hospital of Xinxiang Medical University, Weihui, 453100, Henan Province, China
| | - Yi Zhang
- Department of Neurology, The First Affiliated Hospital of Xinxiang Medical University, Weihui, 453100, Henan Province, China
| | - Shuangxi Guo
- Department of Neurology, The First Affiliated Hospital of Xinxiang Medical University, Weihui, 453100, Henan Province, China
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Bui A, Kim HK, Maroso M, Soltesz I. Microcircuits in Epilepsy: Heterogeneity and Hub Cells in Network Synchronization. Cold Spring Harb Perspect Med 2015; 5:5/11/a022855. [PMID: 26525454 DOI: 10.1101/cshperspect.a022855] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Epilepsy is a complex disorder involving neurological alterations that lead to the pathological development of spontaneous, recurrent seizures. For decades, seizures were thought to be largely repetitive, and had been examined at the macrocircuit level using electrophysiological recordings. However, research mapping the dynamics of large neuronal populations has revealed that seizures are not simply recurrent bursts of hypersynchrony. Instead, it is becoming clear that seizures involve a complex interplay of different neurons and circuits. Herein, we will review studies examining microcircuit changes that may underlie network hyperexcitability, discussing observations from network theory, computational modeling, and optogenetics. We will delve into the idea of hub cells as pathological centers for seizure activity, and will explore optogenetics as a novel avenue to target and treat pathological circuits. Finally, we will conclude with a discussion on future directions in the field.
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Affiliation(s)
- Anh Bui
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697
| | - Hannah K Kim
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697
| | - Mattia Maroso
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697
| | - Ivan Soltesz
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697
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Coras R, Blümcke I. Clinico-pathological subtypes of hippocampal sclerosis in temporal lobe epilepsy and their differential impact on memory impairment. Neuroscience 2015; 309:153-61. [DOI: 10.1016/j.neuroscience.2015.08.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 07/30/2015] [Accepted: 08/02/2015] [Indexed: 12/26/2022]
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Van Liefferinge J, Jensen CJ, Albertini G, Bentea E, Demuyser T, Merckx E, Aronica E, Smolders I, Massie A. Altered vesicular glutamate transporter expression in human temporal lobe epilepsy with hippocampal sclerosis. Neurosci Lett 2015; 590:184-8. [PMID: 25668490 DOI: 10.1016/j.neulet.2015.01.080] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 01/20/2015] [Accepted: 01/29/2015] [Indexed: 11/27/2022]
Abstract
Vesicular glutamate transporters (VGLUTs) are responsible for loading glutamate into synaptic vesicles. Altered VGLUT protein expression has been suggested to affect quantal size and glutamate release under both physiological and pathological conditions. In this study, we investigated mRNA and protein expression levels of the three VGLUT subtypes in hippocampal tissue of patients suffering from temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS), International League Against Epilepsy type 1 (ILAE type 1) compared to autopsy controls, using quantitative polymerase chain reaction and semi-quantitative western blotting. mRNA expression levels of the VGLUTs are unaffected in hippocampal epileptic tissue compared to autopsy controls. At the protein level, VGLUT1 expression remains unaltered, while VGLUT2 is significantly decreased and VGLUT3 protein is significantly increased in hippocampal biopsies from TLE patients compared to controls. Our findings at the protein level can be explained by previously described histopathological changes observed in HS. Although VGLUTs have been repeatedly investigated in distinct rodent epilepsy models, their expression levels were hitherto not fully unraveled in the most difficult-to-treat form of epilepsy: TLE with HS ILAE type 1. We here, demonstrate for the first time that VGLUT2 protein expression is significantly decreased and VGLUT3 protein is significantly increased in the hippocampus of patients suffering from TLE with HS ILAE type 1 compared to autopsy controls.
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Affiliation(s)
- Joeri Van Liefferinge
- Department of Pharmaceutical Chemistry and Drug Analysis, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Cathy J Jensen
- Department of Pharmaceutical Biotechnology and Molecular Biology, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Giulia Albertini
- Department of Pharmaceutical Chemistry and Drug Analysis, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Eduard Bentea
- Department of Pharmaceutical Biotechnology and Molecular Biology, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Thomas Demuyser
- Department of Pharmaceutical Chemistry and Drug Analysis, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Ellen Merckx
- Department of Pharmaceutical Biotechnology and Molecular Biology, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Eleonora Aronica
- Departments of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, The Netherlands; SEIN-Stichting Epilepsie Instellingen Nederland, Heemstede, The Netherlands; Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, The Netherlands
| | - Ilse Smolders
- Department of Pharmaceutical Chemistry and Drug Analysis, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium.
| | - Ann Massie
- Department of Pharmaceutical Biotechnology and Molecular Biology, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
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Zhang W, Thamattoor AK, LeRoy C, Buckmaster PS. Surviving mossy cells enlarge and receive more excitatory synaptic input in a mouse model of temporal lobe epilepsy. Hippocampus 2014; 25:594-604. [PMID: 25488607 DOI: 10.1002/hipo.22396] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/24/2014] [Indexed: 11/07/2022]
Abstract
Numerous hypotheses of temporal lobe epileptogenesis have been proposed, and several involve hippocampal mossy cells. Building on previous hypotheses we sought to test the possibility that after epileptogenic injuries surviving mossy cells develop into super-connected seizure-generating hub cells. If so, they might require more cellular machinery and consequently have larger somata, elongate their dendrites to receive more synaptic input, and display higher frequencies of miniature excitatory synaptic currents (mEPSCs). To test these possibilities pilocarpine-treated mice were evaluated using GluR2-immunocytochemistry, whole-cell recording, and biocytin-labeling. Epileptic pilocarpine-treated mice displayed substantial loss of GluR2-positive hilar neurons. Somata of surviving neurons were 1.4-times larger than in controls. Biocytin-labeled mossy cells also were larger in epileptic mice, but dendritic length per cell was not significantly different. The average frequency of mEPSCs of mossy cells recorded in the presence of tetrodotoxin and bicuculline was 3.2-times higher in epileptic pilocarpine-treated mice as compared to controls. Other parameters of mEPSCs were similar in both groups. Average input resistance of mossy cells in epileptic mice was reduced to 63% of controls, which is consistent with larger somata and would tend to make surviving mossy cells less excitable. Other intrinsic physiological characteristics examined were similar in both groups. Increased excitatory synaptic input is consistent with the hypothesis that surviving mossy cells develop into aberrantly super-connected seizure-generating hub cells, and soma hypertrophy is indirectly consistent with the possibility of axon sprouting. However, no obvious evidence of hyperexcitable intrinsic physiology was found. Furthermore, similar hypertrophy and hyper-connectivity has been reported for other neuron types in the dentate gyrus, suggesting mossy cells are not unique in this regard. Thus, findings of the present study reveal epilepsy-related changes in mossy cell anatomy and synaptic input but do not strongly support the hypothesis that mossy cells develop into seizure-generating hub cells.
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Affiliation(s)
- Wei Zhang
- Department of Comparative Medicine, Stanford University, Stanford, California
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33
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Hernández-González S, Ballestín R, López-Hidalgo R, Gilabert-Juan J, Blasco-Ibáñez JM, Crespo C, Nácher J, Varea E. Altered distribution of hippocampal interneurons in the murine Down Syndrome model Ts65Dn. Neurochem Res 2014; 40:151-64. [PMID: 25399236 DOI: 10.1007/s11064-014-1479-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 11/10/2014] [Accepted: 11/12/2014] [Indexed: 12/30/2022]
Abstract
Down Syndrome, with an incidence of one in 800 live births, is the most common genetic alteration producing intellectual disability. We have used the Ts65Dn model, that mimics some of the alterations observed in Down Syndrome. This genetic alteration induces an imbalance between excitation and inhibition that has been suggested as responsible for the cognitive impairment present in this syndrome. The hippocampus has a crucial role in memory processing and is an important area to analyze this imbalance. In this report we have analysed, in the hippocampus of Ts65Dn mice, the expression of synaptic markers: synaptophysin, vesicular glutamate transporter-1 and isoform 67 of the glutamic acid decarboxylase; and of different subtypes of inhibitory neurons (Calbindin D-28k, parvalbumin, calretinin, NPY, CCK, VIP and somatostatin). We have observed alterations in the inhibitory neuropil in the hippocampus of Ts65Dn mice. There was an excess of inhibitory puncta and a reduction of the excitatory ones. In agreement with this observation, we have observed an increase in the number of inhibitory neurons in CA1 and CA3, mainly interneurons expressing calbindin, calretinin, NPY and VIP, whereas parvalbumin cell numbers were not affected. These alterations in the number of interneurons, but especially the alterations in the proportion of the different types, may influence the normal function of inhibitory circuits and underlie the cognitive deficits observed in DS.
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Affiliation(s)
- Samuel Hernández-González
- Neurobiology Unit, Program in Basic and Applied Neurosciences, Cell Biology Department, Universitat de València, Dr. Moliner, 50, 46100, Burjassot, Spain
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34
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Yamawaki R, Thind K, Buckmaster PS. Blockade of excitatory synaptogenesis with proximal dendrites of dentate granule cells following rapamycin treatment in a mouse model of temporal lobe epilepsy. J Comp Neurol 2014; 523:281-97. [PMID: 25234294 DOI: 10.1002/cne.23681] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 09/09/2014] [Accepted: 09/16/2014] [Indexed: 12/13/2022]
Abstract
Inhibiting the mammalian target of rapamycin (mTOR) signaling pathway with rapamycin blocks granule cell axon (mossy fiber) sprouting after epileptogenic injuries, including pilocarpine-induced status epilepticus. However, it remains unclear whether axons from other types of neurons sprout into the inner molecular layer and synapse with granule cell dendrites despite rapamycin treatment. If so, other aberrant positive-feedback networks might develop. To test this possibility stereological electron microscopy was used to estimate the numbers of excitatory synapses in the inner molecular layer per hippocampus in pilocarpine-treated control mice, in mice 5 days after pilocarpine-induced status epilepticus, and after status epilepticus and daily treatment beginning 24 hours later with rapamycin or vehicle for 2 months. The optical fractionator method was used to estimate numbers of granule cells in Nissl-stained sections so that numbers of excitatory synapses in the inner molecular layer per granule cell could be calculated. Control mice had an average of 2,280 asymmetric synapses in the inner molecular layer per granule cell, which was reduced to 63% of controls 5 days after status epilepticus, recovered to 93% of controls in vehicle-treated mice 2 months after status epilepticus, but remained at only 63% of controls in rapamycin-treated mice. These findings reveal that rapamycin prevented excitatory axons from synapsing with proximal dendrites of granule cells and raise questions about the recurrent excitation hypothesis of temporal lobe epilepsy.
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Affiliation(s)
- Ruth Yamawaki
- Department of Comparative Medicine, Stanford University, Stanford, CA, 94305
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35
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Soussi R, Boulland JL, Bassot E, Bras H, Coulon P, Chaudhry FA, Storm-Mathisen J, Ferhat L, Esclapez M. Reorganization of supramammillary-hippocampal pathways in the rat pilocarpine model of temporal lobe epilepsy: evidence for axon terminal sprouting. Brain Struct Funct 2014; 220:2449-68. [PMID: 24889162 PMCID: PMC4481331 DOI: 10.1007/s00429-014-0800-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 05/14/2014] [Indexed: 01/11/2023]
Abstract
In mesial temporal lobe epilepsy (MTLE), spontaneous seizures likely originate from a multi-structural epileptogenic zone, including several regions of the limbic system connected to the hippocampal formation. In this study, we investigate the structural connectivity between the supramammillary nucleus (SuM) and the dentate gyrus (DG) in the model of MTLE induced by pilocarpine in the rat. This hypothalamic nucleus, which provides major extracortical projections to the hippocampal formation, plays a key role in the regulation of several hippocampus-dependent activities, including theta rhythms, memory function and emotional behavior, such as stress and anxiety, functions that are known to be altered in MTLE. Our findings demonstrate a marked reorganization of DG afferents originating from the SuM in pilocarpine-treated rats. This reorganization, which starts during the latent period, is massive when animals become epileptic and continue to evolve during epilepsy. It is characterized by an aberrant distribution and an increased number of axon terminals from neurons of both lateral and medial regions of the SuM, invading the entire inner molecular layer of the DG. This reorganization, which reflects an axon terminal sprouting from SuM neurons, could contribute to trigger spontaneous seizures within an altered hippocampal intrinsic circuitry.
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Affiliation(s)
- Rabia Soussi
- INSERM, UMR 1106, Institut de Neurosciences des Systèmes - INS, 13385, Marseille, France
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36
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Jinde S, Zsiros V, Jiang Z, Nakao K, Pickel J, Kohno K, Belforte JE, Nakazawa K. Hilar mossy cell degeneration causes transient dentate granule cell hyperexcitability and impaired pattern separation. Neuron 2013; 76:1189-200. [PMID: 23259953 DOI: 10.1016/j.neuron.2012.10.036] [Citation(s) in RCA: 138] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2012] [Indexed: 02/08/2023]
Abstract
Although excitatory mossy cells of the hippocampal hilar region are known to project both to dentate granule cells and to interneurons, it is as yet unclear whether mossy cell activity's net effect on granule cells is excitatory or inhibitory. To explore their influence on dentate excitability and hippocampal function, we generated a conditional transgenic mouse line, using the Cre/loxP system, in which diphtheria toxin receptor was selectively expressed in mossy cells. One week after injecting toxin into this line, mossy cells throughout the longitudinal axis were degenerated extensively, theta wave power of dentate local field potentials increased during exploration, and deficits occurred in contextual discrimination. By contrast, we detected no epileptiform activity, spontaneous behavioral seizures, or mossy-fiber sprouting 5-6 weeks after mossy cell degeneration. These results indicate that the net effect of mossy cell excitation is to inhibit granule cell activity and enable dentate pattern separation.
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Affiliation(s)
- Seiichiro Jinde
- Unit on Genetics of Cognition and Behavior, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
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Schneider CJ, Bezaire M, Soltesz I. Toward a full-scale computational model of the rat dentate gyrus. Front Neural Circuits 2012; 6:83. [PMID: 23162433 PMCID: PMC3499761 DOI: 10.3389/fncir.2012.00083] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Accepted: 10/27/2012] [Indexed: 11/13/2022] Open
Abstract
Recent advances in parallel computing, including the creation of the parallel version of the NEURON simulation environment, have allowed for a previously unattainable level of complexity and detail in neural network models. Previously, we published a functional NEURON model of the rat dentate gyrus with over 50,000 biophysically realistic, multicompartmental neurons, but network simulations could only utilize a single processor. By converting the model to take advantage of parallel NEURON, we are now able to utilize greater computational resources and are able to simulate the full-scale dentate gyrus, containing over a million neurons. This has eliminated the previous necessity for scaling adjustments and allowed for a more direct comparison to experimental techniques and results. The translation to parallel computing has provided a superlinear speedup of computation time and dramatically increased the overall computer memory available to the model. The incorporation of additional computational resources has allowed for more detail and elements to be included in the model, bringing the model closer to a more complete and accurate representation of the biological dentate gyrus. As an example of a major step toward an increasingly accurate representation of the biological dentate gyrus, we discuss the incorporation of realistic granule cell dendrites into the model. Our previous model contained simplified, two-dimensional dendritic morphologies that were identical for neurons of the same class. Using the software tools L-Neuron and L-Measure, we are able to introduce cell-to-cell variability by generating detailed, three-dimensional granule cell morphologies that are based on biological reconstructions. Through these and other improvements, we aim to construct a more complete full-scale model of the rat dentate gyrus, to provide a better tool to delineate the functional role of cell types within the dentate gyrus and their pathological changes observed in epilepsy.
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Affiliation(s)
- Calvin J Schneider
- Department of Anatomy and Neurobiology, University of California Irvine Irvine, CA, USA
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38
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Karádi K, Janszky J, Gyimesi C, Horváth Z, Lucza T, Dóczi T, Kállai J, Abrahám H. Correlation between calbindin expression in granule cells of the resected hippocampal dentate gyrus and verbal memory in temporal lobe epilepsy. Epilepsy Behav 2012; 25:110-9. [PMID: 22796338 DOI: 10.1016/j.yebeh.2012.06.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 06/05/2012] [Accepted: 06/07/2012] [Indexed: 01/06/2023]
Abstract
Calbindin expression of granule cells of the dentate gyrus is decreased in temporal lobe epilepsy (TLE) regardless of its etiology. In this study, we examined the relation between reduction of calbindin immunoreactivity and the verbal and visuo-spatial memory function of patients with TLE of different etiologies. Significant linear correlation was shown between calbindin expression and short-term and long-term percent retention and retroactive interference in auditory verbal learning test (AVLT) of patients including those with hippocampal sclerosis. In addition, we found significant linear regression between calbindin expression and short-term and long-term percent retention of AVLT in patients whose epilepsy was caused by malformation of cortical development or tumor and when no hippocampal sclerosis and substantial neuronal loss were detected. Together with the role of calbindin in memory established in previous studies on calbindin knock-out mice, our results suggest that reduction of calbindin expression may contribute to memory impairments of patients with TLE, particularly, when neuronal loss is not significant.
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Affiliation(s)
- Kázmér Karádi
- Department of Behavioral Sciences, Faculty of Medicine, University of Pécs, Szigeti u. 12., Pécs 7624, Hungary
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Buckmaster PS. Mossy cell dendritic structure quantified and compared with other hippocampal neurons labeled in rats in vivo. Epilepsia 2012; 53 Suppl 1:9-17. [PMID: 22612804 DOI: 10.1111/j.1528-1167.2012.03470.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mossy cells are likely to contribute to normal hippocampal function and to the pathogenesis of neurologic disorders that involve the hippocampus, including epilepsy. Mossy cells are the least well-characterized excitatory neurons in the hippocampus. Their somatic and dendritic morphology has been described qualitatively but not quantitatively. In the present study rat mossy cells were labeled intracellularly with biocytin in vivo. Somatic and dendritic structure was reconstructed three-dimensionally. For comparison, granule cells, CA3 pyramidal cells, and CA1 pyramidal cells were labeled and analyzed using the same approach. Among the four types of hippocampal neurons, granule cells had the smallest somata, fewest primary dendrites and dendritic branches, and shortest total dendritic length. CA1 pyramidal cells had the most dendritic branches and longest total dendritic length. Mossy cells and CA3 pyramidal cells both had large somata and similar total dendritic lengths. However, mossy cell dendrites branched less than CA3 pyramidal cells, especially close to the soma. These findings suggest that mossy cells have dendritic features that are not identical to any other type of hippocampal neuron. Therefore, electrotonic properties that depend on soma-dendritic structure are likely to be distinct in mossy cells compared to other neurons.
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Affiliation(s)
- Paul S Buckmaster
- Department of Comparative Medicine, Stanford University,300 Pasteur Drive, Stanford, CA 94305-5342, U.S.A.
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40
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Increased excitatory synaptic input to granule cells from hilar and CA3 regions in a rat model of temporal lobe epilepsy. J Neurosci 2012; 32:1183-96. [PMID: 22279204 DOI: 10.1523/jneurosci.5342-11.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
One potential mechanism of temporal lobe epilepsy is recurrent excitation of dentate granule cells through aberrant sprouting of their axons (mossy fibers), which is found in many patients and animal models. However, correlations between the extent of mossy fiber sprouting and seizure frequency are weak. Additional potential sources of granule cell recurrent excitation that would not have been detected by markers of mossy fiber sprouting in previous studies include surviving mossy cells and proximal CA3 pyramidal cells. To test those possibilities in hippocampal slices from epileptic pilocarpine-treated rats, laser-scanning glutamate uncaging was used to randomly and focally activate neurons in the granule cell layer, hilus, and proximal CA3 pyramidal cell layer while measuring evoked EPSCs in normotopic granule cells. Consistent with mossy fiber sprouting, a higher proportion of glutamate-uncaging spots in the granule cell layer evoked EPSCs in epileptic rats compared with controls. In addition, stimulation spots in the hilus and proximal CA3 pyramidal cell layer were more likely to evoke EPSCs in epileptic rats, despite significant neuron loss in those regions. Furthermore, synaptic strength of recurrent excitatory inputs to granule cells from CA3 pyramidal cells and other granule cells was increased in epileptic rats. These findings reveal substantial levels of excessive, recurrent, excitatory synaptic input to granule cells from neurons in the hilus and proximal CA3 field. The aberrant development of these additional positive-feedback circuits might contribute to epileptogenesis in temporal lobe epilepsy.
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Pennucci R, Tavano S, Tonoli D, Gualdoni S, de Curtis I. Rac1 and Rac3 GTPases regulate the development of hilar mossy cells by affecting the migration of their precursors to the hilus. PLoS One 2011; 6:e24819. [PMID: 21949760 PMCID: PMC3176786 DOI: 10.1371/journal.pone.0024819] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 08/18/2011] [Indexed: 11/21/2022] Open
Abstract
We have previously shown that double deletion of the genes for Rac1 and Rac3 GTPases during neuronal development affects late developmental events that perturb the circuitry of the hippocampus, with ensuing epileptic phenotype. These effects include a defect in mossy cells, the major class of excitatory neurons of the hilus. Here, we have addressed the mechanisms that affect the loss of hilar mossy cells in the dorsal hippocampus of mice depleted of the two Rac GTPases. Quantification showed that the loss of mossy cells was evident already at postnatal day 8, soon after these cells become identifiable by a specific marker in the dorsal hilus. Comparative analysis of the hilar region from control and double mutant mice revealed that synaptogenesis was affected in the double mutants, with strongly reduced presynaptic input from dentate granule cells. We found that apoptosis was equally low in the hippocampus of both control and double knockout mice. Labelling with bromodeoxyuridine at embryonic day 12.5 showed no evident difference in the proliferation of neuronal precursors in the hippocampal primordium, while differences in the number of bromodeoxyuridine-labelled cells in the developing hilus revealed a defect in the migration of immature, developing mossy cells in the brain of double knockout mice. Overall, our data show that Rac1 and Rac3 GTPases participate in the normal development of hilar mossy cells, and indicate that they are involved in the regulation of the migration of the mossy cell precursor by preventing their arrival to the dorsal hilus.
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Affiliation(s)
- Roberta Pennucci
- Cell Adhesion Unit, Division of Neuroscience, San Raffaele Scientific Institute and San Raffaele University, Milano, Italy
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Volz F, Bock HH, Gierthmuehlen M, Zentner J, Haas CA, Freiman TM. Stereologic estimation of hippocampal GluR2/3- and calretinin-immunoreactive hilar neurons (presumptive mossy cells) in two mouse models of temporal lobe epilepsy. Epilepsia 2011; 52:1579-89. [PMID: 21635231 DOI: 10.1111/j.1528-1167.2011.03086.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE Hippocampal mossy cells receive dense innervation from dentate granule cells and, in turn, mossy cells innervate both granule cells and interneurons. Mossy cell loss is thought to trigger granule cell mossy fiber sprouting, which may affect granule cell excitability. The aim of this study was to quantify mossy cell loss in two animal models of temporal lobe epilepsy, and determine whether there exists a relationship between mossy cell loss, mossy fiber sprouting, and granule cell dispersion. METHODS Representative hippocampal sections from p35 knockout mice and mice with unilateral intrahippocampal kainate injection were immunolabeled for GluR2/3, two subunits of the amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor and calretinin to identify mossy cells. Mossy fibers were immunostained against synaptoporin. KEY FINDINGS p35 Knockout mice showed no hilar cell death, but moderate mossy fiber sprouting and granule cell dispersion. In the kainate-injected hippocampus, there was an 80% and 85% reduction of GluR2/3- and GluR2/3/calretinin-positive hilar neurons, respectively, and dense mossy fiber sprouting and significant granule cell dispersion. In the contralateral hippocampus there was a 52% loss of GluR2/3-, but only a 20% loss of GluR2/3-calretinin-immunoreactive presumptive mossy cells, and granule cell dispersion; no mossy fiber sprouting was observed. SIGNIFICANCE These results indicate a probable lack of causality between mossy cell death and mossy fiber sprouting.
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Affiliation(s)
- Florian Volz
- Department of Neurosurgery, University Medical Center, Albert-Ludwigs-University, Freiburg, Germany
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Freiman TM, Eismann-Schweimler J, Frotscher M. Granule cell dispersion in temporal lobe epilepsy is associated with changes in dendritic orientation and spine distribution. Exp Neurol 2011; 229:332-8. [DOI: 10.1016/j.expneurol.2011.02.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 02/16/2011] [Accepted: 02/20/2011] [Indexed: 01/16/2023]
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Abrahám H, Richter Z, Gyimesi C, Horváth Z, Janszky J, Dóczi T, Seress L. Degree and pattern of calbindin immunoreactivity in granule cells of the dentate gyrus differ in mesial temporal sclerosis, cortical malformation- and tumor-related epilepsies. Brain Res 2011; 1399:66-78. [PMID: 21621747 DOI: 10.1016/j.brainres.2011.05.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 05/04/2011] [Accepted: 05/04/2011] [Indexed: 11/17/2022]
Abstract
A loss of calbindin immunoreactivity in granule cells of the hippocampal dentate gyrus is a characteristic feature of temporal lobe epilepsy with hippocampal sclerosis. Whether decreased calbindin expression is unique to the hippocampal sclerosis associated with cryptogenic temporal lobe epilepsy, or also occurs in tumor- or malformation-related epilepsy, is unknown. We show that calbindin immunoreactivity in granule cells has been decreased in epilepsy regardless of its etiology. In cases of cortical malformations or hippocampal sclerosis, calbindin immunoreactivity was undetectable in most granule cells. In tumor-related resections, in patients who had a long history of epileptic seizures, calbindin was detected only in one-third of granule cells. Regardless of etiology, calbindin expression correlated with age of onset and with duration of the epilepsy. In contrast to tumor-induced epilepsy, where calbindin-immunoreactive granule cells were equally distributed in the granule cell layer, in hippocampal sclerosis and malformation-related epilepsy, two-thirds of calbindin-immunoreactive granule cells were located in the outer half and only one-third in the inner half of the layer. Developmentally, granule cells at the border of the molecular layer are ontogenetically the oldest, and those at the border of the hilus are the youngest. The reduction of calbindin immunoreactivity in ontogenetically younger granule cells highlights the deleterious effect of early occurring epilepsy and initial early precipitating injury, including febrile seizures that may substantially affect developing immature granule cells, but less the earlier born matured ones.
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Affiliation(s)
- Hajnalka Abrahám
- Central Electron Microscopic Laboratory, Faculty of Medicine, University of Pécs, Szigeti u 12., Pécs, 7624, Hungary.
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Löscher W, Brandt C. Prevention or modification of epileptogenesis after brain insults: experimental approaches and translational research. Pharmacol Rev 2011; 62:668-700. [PMID: 21079040 DOI: 10.1124/pr.110.003046] [Citation(s) in RCA: 288] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Diverse brain insults, including traumatic brain injury, stroke, infections, tumors, neurodegenerative diseases, and prolonged acute symptomatic seizures, such as complex febrile seizures or status epilepticus (SE), can induce "epileptogenesis," a process by which normal brain tissue is transformed into tissue capable of generating spontaneous recurrent seizures. Furthermore, epileptogenesis operates in cryptogenic causes of epilepsy. In view of the accumulating information about cellular and molecular mechanisms of epileptogenesis, it should be possible to intervene in this process before the onset of seizures and thereby either prevent the development of epilepsy in patients at risk or increase the potential for better long-term outcome, which constitutes a major clinical need. For identifying pharmacological interventions that prevent, interrupt or reverse the epileptogenic process in people at risk, two groups of animal models, kindling and SE-induced recurrent seizures, have been recommended as potentially useful tools. Furthermore, genetic rodent models of epileptogenesis are increasingly used in assessing antiepileptogenic treatments. Two approaches have been used in these different model categories: screening of clinically established antiepileptic drugs (AEDs) for antiepileptogenic or disease-modifying potential, and targeting the key causal mechanisms that underlie epileptogenesis. The first approach indicated that among various AEDs, topiramate, levetiracetam, carisbamate, and valproate may be the most promising. On the basis of these experimental findings, two ongoing clinical trials will address the antiepileptogenic potential of topiramate and levetiracetam in patients with traumatic brain injury, hopefully translating laboratory discoveries into successful therapies. The second approach has highlighted neurodegeneration, inflammation and up-regulation of immune responses, and neuronal hyperexcitability as potential targets for antiepileptogenesis or disease modification. This article reviews these areas of progress and discusses the challenges associated with discovery of antiepileptogenic therapies.
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Affiliation(s)
- Wolfgang Löscher
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine, Bünteweg 17, Hannover, Germany.
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Schauwecker PE. Galanin receptor 1 deletion exacerbates hippocampal neuronal loss after systemic kainate administration in mice. PLoS One 2010; 5:e15657. [PMID: 21179451 PMCID: PMC3001489 DOI: 10.1371/journal.pone.0015657] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 11/19/2010] [Indexed: 11/30/2022] Open
Abstract
Background Galanin is a neuropeptide with a wide distribution in the central and peripheral nervous systems and whose physiological effects are mediated through three G protein-coupled receptor subtypes, GalR1, GalR2, and GalR3. Several lines of evidence indicate that galanin, as well as activation of the GalR1 receptor, is a potent and effective modulator of neuronal excitability in the hippocampus. Methodology/Principal Findings In order to test more formally the potential influence of GalR1 on seizure-induced excitotoxic cell death, we conducted functional complementation tests in which transgenic mice that exhibit decreased expression of the GalR1 candidate mRNA underwent kainate-induced status epilepticus to determine if the quantitative trait of susceptibility to seizure-induced cell death is determined by the activity of GalR1. In the present study, we report that reduction of GalR1 mRNA via null mutation or injection of the GalR1 antagonist, galantide, prior to kainate-induced status epilepticus induces hippocampal damage in a mouse strain known to be highly resistant to kainate-induced neuronal injury. Wild-type and GalR1 knockout mice were subjected to systemic kainate administration. Seven days later, Nissl and NeuN immune- staining demonstrated that hippocampal cell death was significantly increased in GalR1 knockout strains and in animals injected with the GalR1 antagonist. Compared to GalR1-expressing mice, GalR1-deficient mice had significantly larger hippocampal lesions after status epilepticus. Conclusions/Significance Our results suggest that a reduction of GalR1 expression in the C57BL/6J mouse strain renders them susceptible to excitotoxic injury following systemic kainate administration. From these results, GalR1 protein emerges as a new molecular target that may have a potential therapeutic value in modulating seizure-induced cell death.
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Affiliation(s)
- P Elyse Schauwecker
- Department of Cell and Neurobiology, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America.
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Seress L, Abrahám H, Horváth Z, Dóczi T, Janszky J, Klemm J, Byrne R, Bakay RAE. Survival of mossy cells of the hippocampal dentate gyrus in humans with mesial temporal lobe epilepsy. J Neurosurg 2010; 111:1237-47. [PMID: 19392605 DOI: 10.3171/2008.11.jns08779] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Hippocampal sclerosis can be identified in most patients with mesial temporal lobe epilepsy (TLE). Surgical removal of the sclerotic hippocampus is widely performed to treat patients with drug-resistant mesial TLE. In general, both epilepsy-prone and epilepsy-resistant neurons are believed to be in the hippocampal formation. The hilar mossy cells of the hippocampal dentate gyrus are usually considered one of the most vulnerable types of neurons. The aim of this study was to clarify the fate of mossy cells in the hippocampus in epileptic humans. METHODS Of the 19 patients included in this study, 15 underwent temporal lobe resection because of drug-resistant TLE. Four patients were used as controls because they harbored tumors that had not invaded the hippocampus and they had experienced no seizures. Histological evaluation of resected hippocampal tissues was performed using immunohistochemistry. RESULTS Mossy cells were identified in the control as well as the epileptic hippocampi by using cocaine- and amphetamine-regulated transcript peptide immunohistochemistry. In most cases the number of mossy cells was reduced and thorny excrescences were smaller in the epileptic hippocampi than in controls; however, there was a significant loss of pyramidal cells and a partial loss of granule cells in the same epileptic hippocampi in which mossy cell loss was apparent. The loss of mossy cells could be correlated with the extent of hippocampal sclerosis, patient age at seizure onset, duration of epilepsy, and frequency of seizures. CONCLUSIONS In many cases large numbers of mossy cells were present in the hilus of the dentate gyrus when most pyramidal neurons of the CA1 and CA3 areas of the Ammon's horn were lost, suggesting that mossy cells may not be more vulnerable to epileptic seizures than the hippocampal pyramidal neurons.
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Affiliation(s)
- László Seress
- Central Electron Microscopic Laboratory University of Pécs, Hungary
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Expression of urokinase-type plasminogen activator receptor is increased during epileptogenesis in the rat hippocampus. Neuroscience 2009; 163:316-28. [DOI: 10.1016/j.neuroscience.2009.06.019] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 05/24/2009] [Accepted: 06/09/2009] [Indexed: 12/30/2022]
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Kienzler F, Norwood BA, Sloviter RS. Hippocampal injury, atrophy, synaptic reorganization, and epileptogenesis after perforant pathway stimulation-induced status epilepticus in the mouse. J Comp Neurol 2009; 515:181-96. [PMID: 19412934 DOI: 10.1002/cne.22059] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Prolonged dentate granule cell discharges produce hippocampal injury and chronic epilepsy in rats. In preparing to study this epileptogenic process in genetically altered mice, we determined whether the background strain used to generate most genetically altered mice, the C57BL/6 mouse, is vulnerable to stimulation-induced seizure-induced injury. This was necessary because C57BL/6 mice are reportedly resistant to the neurotoxic effects of kainate-induced seizures, which we hypothesized to be related to strain differences in kainate's effects, rather than genetic differences in intrinsic neuronal vulnerability. Bilateral perforant pathway stimulation-induced granule cell discharge for 4 hours under urethane anesthesia produced degeneration of glutamate receptor subunit 2 (GluR2)-positive hilar mossy cells and peptide-containing interneurons in both FVB/N (kainate-vulnerable) and C57BL/6 (kainate-resistant) mice, indicating no strain differences in neuronal vulnerability to seizure activity. Granule cell discharge for 2 hours in C57BL/6 mice destroyed most GluR2-positive dentate hilar mossy cells, but not peptide-containing hilar interneurons, indicating that mossy cells are the neurons most vulnerable to this insult. Stimulation for 24 hours caused extensive hippocampal neuron loss and injury to the septum and entorhinal cortex, but no other detectable damage. Mice stimulated for 24 hours developed hippocampal sclerosis, granule cell mossy fiber sprouting, and chronic epilepsy, but not the granule cell layer hypertrophy (granule cell dispersion) produced by intrahippocampal kainate. These results demonstrate that perforant pathway stimulation in mice reliably reproduces the defining features of human mesial temporal lobe epilepsy with hippocampal sclerosis. Experimental studies in transgenic or knockout mice are feasible if electrical stimulation is used to produce controlled epileptogenic insults.
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Affiliation(s)
- Friederike Kienzler
- Departments of Pharmacology and Neurology, University of Arizona College of Medicine, Tucson, Arizona 85724, USA
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