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Howard MA. New complex physiological findings evolve hypothesized mechanisms of Dravet syndrome. Neural Regen Res 2024; 19:1867-1868. [PMID: 38227502 DOI: 10.4103/1673-5374.390967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 11/09/2023] [Indexed: 01/17/2024] Open
Affiliation(s)
- MacKenzie A Howard
- Department of Neurology, Dell Medical School, Austin, TX, USA Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, USA
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Guo J, Min D, Farrell EK, Zhou Y, Faingold CL, Cotten JF, Feng HJ. Enhancing the action of serotonin by three different mechanisms prevents spontaneous seizure-induced mortality in Dravet mice. Epilepsia 2024; 65:1791-1800. [PMID: 38593237 PMCID: PMC11166528 DOI: 10.1111/epi.17966] [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: 08/17/2023] [Revised: 03/12/2024] [Accepted: 03/13/2024] [Indexed: 04/11/2024]
Abstract
OBJECTIVE Sudden unexpected death in epilepsy (SUDEP) is an underestimated complication of epilepsy. Previous studies have demonstrated that enhancement of serotonergic neurotransmission suppresses seizure-induced sudden death in evoked seizure models. However, it is unclear whether elevated serotonin (5-HT) function will prevent spontaneous seizure-induced mortality (SSIM), which is characteristic of human SUDEP. We examined the effects of 5-HT-enhancing agents that act by three different pharmacological mechanisms on SSIM in Dravet mice, which exhibit a high incidence of SUDEP, modeling human Dravet syndrome. METHODS Dravet mice of both sexes were evaluated for spontaneous seizure characterization and changes in SSIM incidence induced by agents that enhance 5-HT-mediated neurotransmission. Fluoxetine (a selective 5-HT reuptake inhibitor), fenfluramine (a 5-HT releaser and agonist), SR 57227 (a specific 5-HT3 receptor agonist), or saline (vehicle) was intraperitoneally administered over an 8-day period in Dravet mice, and the effect of these treatments on SSIM was examined. RESULTS Spontaneous seizures in Dravet mice generally progressed from wild running to tonic seizures with or without SSIM. Fluoxetine at 30 mg/kg, but not at 20 or 5 mg/kg, significantly reduced SSIM compared with the vehicle control. Fenfluramine at 1-10 mg/kg, but not .2 mg/kg, fully protected Dravet mice from SSIM, with all mice surviving. Compared with the vehicle control, SR 57227 at 20 mg/kg, but not at 10 or 5 mg/kg, significantly lowered SSIM. The effect of these drugs on SSIM was independent of sex. SIGNIFICANCE Our data demonstrate that elevating serotonergic function by fluoxetine, fenfluramine, or SR 57227 significantly reduces or eliminates SSIM in Dravet mice in a sex-independent manner. These findings suggest that deficits in serotonergic neurotransmission likely play an important role in the pathogenesis of SSIM, and fluoxetine and fenfluramine, which are US Food and Drug Administration-approved medications, may potentially prevent SUDEP in at-risk patients.
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Affiliation(s)
- Jialing Guo
- National Health Commission Key Laboratory of Birth Defect Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Anesthesia, Harvard Medical School, Boston, MA, USA
| | - Daniel Min
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Emory K. Farrell
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Yupeng Zhou
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Carl L. Faingold
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA
| | - Joseph F. Cotten
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Anesthesia, Harvard Medical School, Boston, MA, USA
| | - Hua-Jun Feng
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Anesthesia, Harvard Medical School, Boston, MA, USA
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Chancey JH, Ahmed AA, Guillén FI, Ghatpande V, Howard MA. Complex Synaptic and Intrinsic Interactions Disrupt Input/Output Functions in the Hippocampus of Scn1b Knock-Out Mice. J Neurosci 2023; 43:8562-8577. [PMID: 37845033 PMCID: PMC10711733 DOI: 10.1523/jneurosci.0786-23.2023] [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: 05/01/2023] [Revised: 09/21/2023] [Accepted: 10/03/2023] [Indexed: 10/18/2023] Open
Abstract
Pathogenic variants in SCN1B have been linked to severe developmental epileptic encephalopathies including Dravet syndrome. Scn1b knock-out (KO) mice model SCN1B loss-of-function (LOF) disorders, demonstrating seizures, developmental delays, and early death. SCN1B encodes the protein β1, an ion channel auxiliary subunit that also has roles in cell adhesion, neurite outgrowth, and gene expression. The goal of this project is to better understand of how loss of Scn1b alters information processing in the brain, resulting in seizures and associated cognitive dysfunction. Using slice electrophysiology in the CA1 region of the hippocampus from male and female Scn1b KO mice and wild-type (WT) littermates, we found that processing of physiologically relevant patterned Schaffer collateral (SC) stimulation produces larger, prolonged depolarizations and increased spiking in KO neurons compared with WTs. KO neurons exhibit enhanced intrinsic excitability, firing more action potentials with current injection. Interestingly, SC stimulation produces smaller, more facilitating excitatory and IPSCs in KO pyramidal neurons, but larger postsynaptic potentials (PSPs) with the same stimulation. We also found reduced intrinsic firing of parvalbumin (PV)-expressing interneurons and disrupted recruitment of both parvalbumin-expressing and somatostatin (SST)-expressing interneurons in response to patterned synaptic stimulation. Neuronal information processing relies on the interplay between synaptic properties, intrinsic properties that amplify or suppress incoming synaptic signals, and firing properties that produce cellular output. We found changes at each of these levels in Scn1b KO pyramidal neurons, resulting in fundamentally altered cellular information processing in the hippocampus that likely contributes to the complex phenotypes of SCN1B-linked epileptic encephalopathies.SIGNIFICANCE STATEMENT Genetic developmental epileptic encephalopathies have limited treatment options, in part because of our lack of understanding of how genetic changes result in dysfunction at the cellular and circuit levels. SCN1B is a gene linked to Dravet syndrome and other developmental epileptic encephalopathies, and Scn1b knock-out (KO) mice phenocopy the human disease, allowing us to study underlying neurophysiological changes. Here, we found changes at all levels of neuronal information processing in brains lacking Scn1b, including intrinsic excitability, synaptic properties, and synaptic integration, resulting in greatly enhanced input/output functions of the hippocampus. Our study shows that loss of Scn1b results in a complex array of cellular and network changes that fundamentally alters information processing in the hippocampus.
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Affiliation(s)
- Jessica Hotard Chancey
- Departments of Neurology and Neuroscience, Center for Learning and Memory, Dell Medical School, University of Texas at Austin, Austin, Texas 78712
| | - Alisha A Ahmed
- Departments of Neurology and Neuroscience, Center for Learning and Memory, Dell Medical School, University of Texas at Austin, Austin, Texas 78712
| | - Fernando Isaac Guillén
- Departments of Neurology and Neuroscience, Center for Learning and Memory, Dell Medical School, University of Texas at Austin, Austin, Texas 78712
| | - Vighnesh Ghatpande
- Departments of Neurology and Neuroscience, Center for Learning and Memory, Dell Medical School, University of Texas at Austin, Austin, Texas 78712
| | - MacKenzie A Howard
- Departments of Neurology and Neuroscience, Center for Learning and Memory, Dell Medical School, University of Texas at Austin, Austin, Texas 78712
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Stöber TM, Batulin D, Triesch J, Narayanan R, Jedlicka P. Degeneracy in epilepsy: multiple routes to hyperexcitable brain circuits and their repair. Commun Biol 2023; 6:479. [PMID: 37137938 PMCID: PMC10156698 DOI: 10.1038/s42003-023-04823-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 04/06/2023] [Indexed: 05/05/2023] Open
Abstract
Due to its complex and multifaceted nature, developing effective treatments for epilepsy is still a major challenge. To deal with this complexity we introduce the concept of degeneracy to the field of epilepsy research: the ability of disparate elements to cause an analogous function or malfunction. Here, we review examples of epilepsy-related degeneracy at multiple levels of brain organisation, ranging from the cellular to the network and systems level. Based on these insights, we outline new multiscale and population modelling approaches to disentangle the complex web of interactions underlying epilepsy and to design personalised multitarget therapies.
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Affiliation(s)
- Tristan Manfred Stöber
- Frankfurt Institute for Advanced Studies, 60438, Frankfurt am Main, Germany
- Institute for Neural Computation, Faculty of Computer Science, Ruhr University Bochum, 44801, Bochum, Germany
- Epilepsy Center Frankfurt Rhine-Main, Department of Neurology, Goethe University, 60590, Frankfurt, Germany
| | - Danylo Batulin
- Frankfurt Institute for Advanced Studies, 60438, Frankfurt am Main, Germany
- CePTER - Center for Personalized Translational Epilepsy Research, Goethe University, 60590, Frankfurt, Germany
- Faculty of Computer Science and Mathematics, Goethe University, 60486, Frankfurt, Germany
| | - Jochen Triesch
- Frankfurt Institute for Advanced Studies, 60438, Frankfurt am Main, Germany
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India
| | - Peter Jedlicka
- ICAR3R - Interdisciplinary Centre for 3Rs in Animal Research, Faculty of Medicine, Justus Liebig University Giessen, 35390, Giessen, Germany.
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University, 60590, Frankfurt am Main, Germany.
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Chancey JH, Ahmed AA, Guillén FI, Howard MA. Complex synaptic and intrinsic interactions disrupt input/output functions in the hippocampus of Scn1b knockout mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.29.538823. [PMID: 37163033 PMCID: PMC10168369 DOI: 10.1101/2023.04.29.538823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Mutations in the SCN1B gene have been linked to severe developmental epileptic encephalopathies including Dravet syndrome. Scn1b k nock o ut (KO) mice model SCN1B loss of function disorders, demonstrating seizures, developmental delays, and early death. SCN1B encodes the protein β1, an ion channel auxiliary subunit that also has roles in cell adhesion, neurite outgrowth, and gene expression. The goal of this project is to better understand of how loss of β1 alters information processing in the brain, resulting in seizures and associated cognitive dysfunction. Using slice electrophysiology in the CA1 region of the hippocampus from male and female Scn1b KO mice and w ild-type (WT) littermates, we found that processing of physiologically relevant patterned S chaffer c ollateral (SC) stimulation produces larger, prolonged depolarizations and increased spiking in KO neurons compared to WTs. KO neurons exhibit enhanced intrinsic excitability, firing more action potentials with current injection. Interestingly, SC stimulation produces smaller, more facilitating excitatory and inhibitory postsynaptic currents in KO pyramidal neurons, but larger postsynaptic potentials with the same stimulation. We also found reduced intrinsic firing of parvalbumin-expressing interneurons and disrupted recruitment of both parvalbumin- and somatostatin-expressing interneurons in response to patterned synaptic stimulation. Neuronal information processing relies on the interplay between synaptic properties, intrinsic properties that amplify or suppress incoming synaptic signals, and firing properties that produce cellular output. We found changes at each of these levels in Scn1b KO pyramidal neurons, resulting in fundamentally altered information processing in the hippocampus that likely contributes to the complex phenotypes of SCN1B -linked epileptic encephalopathies. Significance statement Genetic developmental epileptic encephalopathies have limited treatment options, in part due to our lack of understanding of how genetic changes result in dysfunction at the cellular and circuit levels. SCN1B is a gene linked to Dravet syndrome and other epileptic encephalopathies, and Scn1b knockout mice phenocopy the human disease, allowing us to study underlying neurophysiological changes. Here we found changes at all levels of neuronal information processing in brains lacking β1, including intrinsic excitability, synaptic properties, and synaptic integration, resulting in greatly enhanced input/output functions of the hippocampus. Our study shows that loss of β1 results in a complex array of cellular and network changes that fundamentally alters information processing in the hippocampus.
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Catron MA, Howe RK, Besing GLK, St. John EK, Potesta CV, Gallagher MJ, Macdonald RL, Zhou C. Sleep slow-wave oscillations trigger seizures in a genetic epilepsy model of Dravet syndrome. Brain Commun 2022; 5:fcac332. [PMID: 36632186 PMCID: PMC9830548 DOI: 10.1093/braincomms/fcac332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 10/09/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022] Open
Abstract
Sleep is the preferential period when epileptic spike-wave discharges appear in human epileptic patients, including genetic epileptic seizures such as Dravet syndrome with multiple mutations including SCN1A mutation and GABAA receptor γ2 subunit Gabrg2Q390X mutation in patients, which presents more severe epileptic symptoms in female patients than male patients. However, the seizure onset mechanism during sleep still remains unknown. Our previous work has shown that the sleep-like state-dependent homeostatic synaptic potentiation can trigger epileptic spike-wave discharges in one transgenic heterozygous Gabrg2+/Q390X knock-in mouse model.1 Here, using this heterozygous knock-in mouse model, we hypothesized that slow-wave oscillations themselves in vivo could trigger epileptic seizures. We found that epileptic spike-wave discharges in heterozygous Gabrg2+/Q390X knock-in mice exhibited preferential incidence during non-rapid eye movement sleep period, accompanied by motor immobility/facial myoclonus/vibrissal twitching and more frequent spike-wave discharge incidence appeared in female heterozygous knock-in mice than male heterozygous knock-in mice. Optogenetically induced slow-wave oscillations in vivo significantly increased epileptic spike-wave discharge incidence in heterozygous Gabrg2+/Q390X knock-in mice with longer duration of non-rapid eye movement sleep or quiet-wakeful states. Furthermore, suppression of slow-wave oscillation-related homeostatic synaptic potentiation by 4-(diethylamino)-benzaldehyde injection (i.p.) greatly attenuated spike-wave discharge incidence in heterozygous knock-in mice, suggesting that slow-wave oscillations in vivo did trigger seizure activity in heterozygous knock-in mice. Meanwhile, sleep spindle generation in wild-type littermates and heterozygous Gabrg2+/Q390X knock-in mice involved the slow-wave oscillation-related homeostatic synaptic potentiation that also contributed to epileptic spike-wave discharge generation in heterozygous Gabrg2+/Q390X knock-in mice. In addition, EEG spectral power of delta frequency (0.1-4 Hz) during non-rapid eye movement sleep was significantly larger in female heterozygous Gabrg2+/Q390X knock-in mice than that in male heterozygous Gabrg2+/Q390X knock-in mice, which likely contributes to the gender difference in seizure incidence during non-rapid eye movement sleep/quiet-wake states of human patients. Overall, all these results indicate that slow-wave oscillations in vivo trigger the seizure onset in heterozygous Gabrg2+/Q390X knock-in mice, preferentially during non-rapid eye movement sleep period and likely generate the sex difference in seizure incidence between male and female heterozygous Gabrg2+/Q390X knock-in mice.
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Affiliation(s)
- Mackenzie A Catron
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Neuroscience Graduate Program, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Rachel K Howe
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Gai-Linn K Besing
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Emily K St. John
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | | | - Martin J Gallagher
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Neuroscience Graduate Program, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Neuroscience Graduate Program, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Chengwen Zhou
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Neuroscience Graduate Program, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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Song C, Wei W, Wang T, Zhou M, Li Y, Xiao B, Huang D, Gu J, Shi L, Peng J, Jin D. Microglial infiltration mediates cognitive dysfunction in rat models of hypothalamic obesity via a hypothalamic-hippocampal circuit involving the lateral hypothalamic area. Front Cell Neurosci 2022; 16:971100. [PMID: 36072565 PMCID: PMC9443213 DOI: 10.3389/fncel.2022.971100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 07/29/2022] [Indexed: 11/13/2022] Open
Abstract
This study aimed to explore the mechanism underlying cognitive dysfunction mediated by the lateral hypothalamic area (LHA) in a hypothalamic-hippocampal circuit in rats with lesion-induced hypothalamic obesity (HO). The HO model was established by electrically lesioning the hypothalamic nuclei. The open field (OP) test, Morris water maze (MWM), novel object recognition (NOR), and novel object location memory (NLM) tests were used to evaluate changes in cognition due to alterations in the hypothalamic-hippocampal circuit. Western blotting, immunohistochemical staining, and cholera toxin subunit B conjugated with Alexa Fluor 488 (CTB488) reverse tracer technology were used to determine synaptophysin (SYN), postsynaptic density protein 95 (PSD95), ionized calcium binding adaptor molecule 1 (Iba1), neuronal nuclear protein (NeuN), and Caspase3 expression levels and the hypothalamic-hippocampal circuit. In HO rats, severe obesity was associated with cognitive dysfunction after the lesion of the hypothalamus. Furthermore, neuronal apoptosis and activated microglia in the downstream of the lesion area (the LHA) induced microglial infiltration into the intact hippocampus via the LHA-hippocampal circuit, and the synapses engulfment in the hippocampus may be the underlying mechanism by which the remodeled microglial mediates memory impairments in HO rats. The HO rats exhibited microglial infiltration and synapse loss into the hippocampus from the lesioned LHA via the hypothalamic-hippocampal circuit. The underlying mechanisms of memory function may be related to the circuit.
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Affiliation(s)
- Chong Song
- Department of Neurosurgery, The Central Hospital of Dalian University of Technology, Dalian, China
- Department of Neurosurgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
- *Correspondence: Chong Song,
| | - Wei Wei
- Department of Neurosurgery, The Central Hospital of Dalian University of Technology, Dalian, China
| | - Tong Wang
- Department of Neurosurgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
- Department of Neurosurgery, The Third Hospital of Mianyang (Sichuan Mental Health Center), Mianyang, China
| | - Min Zhou
- Department of Neurosurgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Yunshi Li
- The First School of Clinical Medicine, Southern Medical University, Guangzhou, China
| | - Bing Xiao
- The First School of Clinical Medicine, Southern Medical University, Guangzhou, China
| | - Dongyi Huang
- The First School of Clinical Medicine, Southern Medical University, Guangzhou, China
| | - Junwei Gu
- Department of Neurosurgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Linyong Shi
- Department of Neurosurgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Junjie Peng
- Department of Neurosurgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
- *Correspondence: Chong Song,
| | - Dianshi Jin
- Department of Neurosurgery, The Central Hospital of Dalian University of Technology, Dalian, China
- *Correspondence: Chong Song,
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