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Sex-specific differences in KCC2 localisation and inhibitory synaptic transmission in the rat hippocampus. Sci Rep 2022; 12:3186. [PMID: 35210456 PMCID: PMC8873453 DOI: 10.1038/s41598-022-06769-5] [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: 09/17/2021] [Accepted: 02/03/2022] [Indexed: 11/09/2022] Open
Abstract
Sexual differentiation of the brain is influenced by testosterone and its metabolites during the perinatal period, when many aspects of brain development, including the maturation of GABAergic transmission, occur. Whether and how testosterone signaling during the perinatal period affects GABAergic transmission is unclear. Here, we analyzed GABAergic circuit functional markers in male, female, testosterone-treated female, and testosterone-insensitive male rats after the first postnatal week and in young adults. In the hippocampus, mRNA levels of proteins associated with GABA signaling were not significantly affected at postnatal day (P) 7 or P40. Conversely, membrane protein levels of KCC2, which are critical for determining inhibition strength, were significantly higher in females compared to males and testosterone-treated females at P7. Further, female and testosterone-insensitive male rats at P7 showed higher levels of the neurotrophin BDNF, which is a powerful regulator of neuronal function, including GABAergic transmission. Finally, spontaneous GABAergic currents in hippocampal CA1 pyramidal cells were more frequent in females and testosterone-insensitive males at P40. Overall, these results show that perinatal testosterone levels modulate GABAergic circuit function, suggesting a critical role of perinatal sex hormones in regulating network excitability in the adult hippocampus.
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Wolf DC, Desgent S, Sanon NT, Chen JS, Elkaim LM, Bosoi CM, Awad PN, Simard A, Salam MT, Bilodeau GA, Duss S, Sawan M, Lewis EC, Weil AG. Sex differences in the developing brain impact stress-induced epileptogenicity following hyperthermia-induced seizures. Neurobiol Dis 2021; 161:105546. [PMID: 34742878 DOI: 10.1016/j.nbd.2021.105546] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 10/19/2021] [Accepted: 11/02/2021] [Indexed: 12/24/2022] Open
Abstract
Febrile seizures (FS) are common, affecting 2-5% of children between the ages of 3 months and 6 years. Complex FS occur in 10% of patients with FS and are strongly associated with mesial temporal lobe epilepsy. Current research suggests that predisposing factors, such as genetic and anatomic abnormalities, may be necessary for complex FS to translate to mesial temporal lobe epilepsy. Sex hormones are known to influence seizure susceptibility and epileptogenesis, but whether sex-specific effects of early life stress play a role in epileptogenesis is unclear. Here, we investigate sex differences in the activity of the hypothalamic-pituitary-adrenal (HPA) axis following chronic stress and the underlying contributions of gonadal hormones to the susceptibility of hyperthermia-induced seizures (HS) in rat pups. Chronic stress consisted of daily injections of 40 mg/kg of corticosterone (CORT) subcutaneously from postnatal day (P) 1 to P9 in male and female rat pups followed by HS at P10. Body mass, plasma CORT levels, temperature threshold to HS, seizure characteristics, and electroencephalographic in vivo recordings were compared between CORT- and vehicle (VEH)-injected littermates during and after HS at P10. In juvenile rats (P18-P22), in vitro CA1 pyramidal cell recordings were recorded in males to investigate excitatory and inhibitory neuronal circuits. Results show that daily CORT injections increased basal plasma CORT levels before HS and significantly reduced weight gain and body temperature threshold of HS in both males and females. CORT also significantly lowered the generalized convulsions (GC) latency while increasing recovery time and the number of electrographic seizures (>10s), which had longer duration. Furthermore, sex-specific differences were found in response to chronic CORT injections. Compared to females, male pups had increased basal plasma CORT levels after HS, longer recovery time and a higher number of electrographic seizures (>10s), which also had longer duration. Sex-specific differences were also found at baseline conditions with lower latency to generalized convulsions and longer duration of electrographic seizures in males but not in females. In juvenile male rats, the amplitude of evoked excitatory postsynaptic potentials, as well as the amplitude of inhibitory postsynaptic currents, were significantly greater in CORT rats when compared to VEH littermates. These findings not only validate CORT injections as a stress model, but also show a sex difference in baseline conditions as well as a response to chronic CORT and an impact on seizure susceptibility, supporting a potential link between sustained early-life stress and complex FS. Overall, these effects also indicate a putatively less severe phenotype in female than male pups. Ultimately, studies investigating the biological underpinnings of sex differences as a determining factor in mental and neurologic problems are necessary to develop better diagnostic, preventative, and therapeutic approaches for all patients regardless of their sex.
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Affiliation(s)
- Daniele C Wolf
- Centre de Recherche, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Département de Pédiatrie, Université de Montréal, Québec, Canada; Département de Neurosciences, Université de Montréal, Québec, Canada.
| | - Sébastien Desgent
- Centre de Recherche, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Département de Pédiatrie, Université de Montréal, Québec, Canada; Département de Neurosciences, Université de Montréal, Québec, Canada
| | - Nathalie T Sanon
- Centre de Recherche, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Département de Pédiatrie, Université de Montréal, Québec, Canada
| | - Jia-Shu Chen
- The Warren Alpert Medical School of Brown University, Providence, RI, USA
| | - Lior M Elkaim
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
| | - Ciprian M Bosoi
- Centre de Recherche, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Département de Pédiatrie, Université de Montréal, Québec, Canada
| | - Patricia N Awad
- Centre de Recherche, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Département de Pédiatrie, Université de Montréal, Québec, Canada
| | - Alexe Simard
- Centre de Recherche, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Département de Pédiatrie, Université de Montréal, Québec, Canada
| | - Muhammad T Salam
- Laboratoire Polystim, Département de génie électrique, Polytechnique Montréal, Montréal, Québec, Canada
| | - Guillaume-Alexandre Bilodeau
- LITIV Lab., Département de génie informatique et génie logiciel, Polytechnique Montréal, Montréal, Québec, Canada
| | - Sandra Duss
- Centre de Recherche, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Département de Pédiatrie, Université de Montréal, Québec, Canada
| | - Mohamad Sawan
- Laboratoire Polystim, Département de génie électrique, Polytechnique Montréal, Montréal, Québec, Canada
| | | | - Alexander G Weil
- Centre de Recherche, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Département de Pédiatrie, Université de Montréal, Québec, Canada; Département de Neurosciences, Université de Montréal, Québec, Canada; Neurosurgery Service, Department of Surgery, Université de Montréal, Québec, Canada
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Larson EA, Accardi MV, Zhong Y, Paquette D, Authier S. Drug-Induced Seizures: Considerations for Underlying Molecular Mechanisms. Int J Toxicol 2021; 40:403-412. [PMID: 34514888 DOI: 10.1177/10915818211040483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A broad spectrum of chemical entities have been associated with drug-induced seizure (DIS), emphasizing the importance of this potential liability across various drug classes (e.g., antidepressants, antipsychotics, antibiotics, and analgesics among others). Despite its importance within drug safety testing, an understanding of the molecular mechanisms associated with DIS is often lacking. The etiology of DIS is understood to be a result of either a deficit in inhibitory (e.g., gamma aminobutyric acid) or an elevated excitatory (e.g., glutamate) signaling, leading to synchronous neuronal depolarization affecting various brain regions and impairing normal neurological functions. How this altered neuronal signaling occurs and how these changes interact with other non-brain receptor driven DIS-associated changes such as metabolic disturbances, electrolyte imbalances, altered drug metabolism, and withdrawal effects are poorly understood. Herein, we discuss important molecular mechanisms identified in DIS for several drugs and/or drug classes. With a better understanding of the molecular mechanisms associated with DIS, in vivo or in vitro models may be applied to characterize and mitigate DIS risk during drug development. Susceptibility stratification for DIS presents species differences in the following order beagle dogs > rodents and cynomolgus monkeys > Göttingen minipigs with a more than 2-fold difference between canines and minipigs, which is important to consider during non-clinical species selection. While clinical signs such as myoclonus, severe muscle jerks, or convulsions are often associated with abnormal epileptiform EEG activity, tremors are most of the time physiological and rarely observed with concurrent epileptiform EEG activity which need to be considered during DIS risk evaluation.
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Affiliation(s)
| | | | - Yifei Zhong
- Charles River Laboratories, Laval, Quebec, Canada
| | | | - Simon Authier
- Charles River Laboratories, Laval, Quebec, Canada.,Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Quebec, Canada
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Awad PN, Amegandjin CA, Szczurkowska J, Carriço JN, Fernandes do Nascimento AS, Baho E, Chattopadhyaya B, Cancedda L, Carmant L, Di Cristo G. KCC2 Regulates Dendritic Spine Formation in a Brain-Region Specific and BDNF Dependent Manner. Cereb Cortex 2018; 28:4049-4062. [PMID: 30169756 PMCID: PMC6188549 DOI: 10.1093/cercor/bhy198] [Citation(s) in RCA: 29] [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: 10/17/2017] [Revised: 07/17/2018] [Accepted: 07/27/2018] [Indexed: 01/17/2023] Open
Abstract
KCC2 is the major chloride extruder in neurons. The spatiotemporal regulation of KCC2 expression orchestrates the developmental shift towards inhibitory GABAergic drive and the formation of glutamatergic synapses. Whether KCC2's role in synapse formation is similar in different brain regions is unknown. First, we found that KCC2 subcellular localization, but not overall KCC2 expression levels, differed between cortex and hippocampus during the first postnatal week. We performed site-specific in utero electroporation of KCC2 cDNA to target either hippocampal CA1 or somatosensory cortical pyramidal neurons. We found that a premature expression of KCC2 significantly decreased spine density in CA1 neurons, while it had the opposite effect in cortical neurons. These effects were cell autonomous, because single-cell biolistic overexpression of KCC2 in hippocampal and cortical organotypic cultures also induced a reduction and an increase of dendritic spine density, respectively. In addition, we found that the effects of its premature expression on spine density were dependent on BDNF levels. Finally, we showed that the effects of KCC2 on dendritic spine were dependent on its chloride transporter function in the hippocampus, contrary to what was observed in cortex. Altogether, these results demonstrate that KCC2 regulation of dendritic spine development, and its underlying mechanisms, are brain-region specific.
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Affiliation(s)
- Patricia Nora Awad
- Department of Neurosciences, Université de Montréal, Montréal, Québec, Canada
- CHU Sainte-Justine Research Center, Montréal, Québec, Canada
| | - Clara Akofa Amegandjin
- Department of Neurosciences, Université de Montréal, Montréal, Québec, Canada
- CHU Sainte-Justine Research Center, Montréal, Québec, Canada
| | - Joanna Szczurkowska
- Neuroscience and Brain Technologies, Instituto Italiano di Tecnologia, Genova, Italy
| | | | | | - Elie Baho
- Department of Neurosciences, Université de Montréal, Montréal, Québec, Canada
- CHU Sainte-Justine Research Center, Montréal, Québec, Canada
| | - Bidisha Chattopadhyaya
- Department of Neurosciences, Université de Montréal, Montréal, Québec, Canada
- CHU Sainte-Justine Research Center, Montréal, Québec, Canada
| | - Laura Cancedda
- Neuroscience and Brain Technologies, Instituto Italiano di Tecnologia, Genova, Italy
- Telethon Dulbecco Institute, Italy
| | - Lionel Carmant
- Department of Neurosciences, Université de Montréal, Montréal, Québec, Canada
- CHU Sainte-Justine Research Center, Montréal, Québec, Canada
| | - Graziella Di Cristo
- Department of Neurosciences, Université de Montréal, Montréal, Québec, Canada
- CHU Sainte-Justine Research Center, Montréal, Québec, Canada
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van Campen JS, Hessel EVS, Bohmbach K, Rizzi G, Lucassen PJ, Lakshmi Turimella S, Umeoka EHL, Meerhoff GF, Braun KPJ, de Graan PNE, Joëls M. Stress and Corticosteroids Aggravate Morphological Changes in the Dentate Gyrus after Early-Life Experimental Febrile Seizures in Mice. Front Endocrinol (Lausanne) 2018; 9:3. [PMID: 29434572 PMCID: PMC5790804 DOI: 10.3389/fendo.2018.00003] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 01/05/2018] [Indexed: 12/17/2022] Open
Abstract
Stress is the most frequently self-reported seizure precipitant in patients with epilepsy. Moreover, a relation between ear stress and epilepsy has been suggested. Although ear stress and stress hormones are known to influence seizure threshold in rodents, effects on the development of epilepsy (epileptogenesis) are still unclear. Therefore, we studied the consequences of ear corticosteroid exposure for epileptogenesis, under highly controlled conditions in an animal model. Experimental febrile seizures (eFS) were elicited in 10-day-old mice by warm-air induced hyperthermia, while a control group was exposed to a normothermic condition. In the following 2 weeks, mice received either seven corticosterone or vehicle injections or were left undisturbed. Specific measures indicative for epileptogenesis were examined at 25 days of age and compared with vehicle injected or untreated mice. We examined structural [neurogenesis, dendritic morphology, and mossy fiber sprouting (MFS)] and functional (glutamatergic postsynaptic currents and long-term potentiation) plasticity in the dentate gyrus (DG). We found that differences in DG morphology induced by eFS were aggravated by repetitive (mildly stressful) vehicle injections and corticosterone exposure. In the injected groups, eFS were associated with decreases in neurogenesis, and increases in cell proliferation, dendritic length, and spine density. No group differences were found in MFS. Despite these changes in DG morphology, no effects of eFS were found on functional plasticity. We conclude that corticosterone exposure during early epileptogenesis elicited by eFS aggravates morphological, but not functional, changes in the DG, which partly supports the hypothesis that ear stress stimulates epileptogenesis.
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Affiliation(s)
- Jolien S. van Campen
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
- Department of Child Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
| | - Ellen V. S. Hessel
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
| | - Kirsten Bohmbach
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
| | - Giorgio Rizzi
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
| | - Paul J. Lucassen
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, Netherlands
| | - Sada Lakshmi Turimella
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
| | - Eduardo H. L. Umeoka
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
- Neursocience and Behavioral Sciences Department, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, Brazil
| | - Gideon F. Meerhoff
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, Netherlands
| | - Kees P. J. Braun
- Department of Child Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
| | - Pierre N. E. de Graan
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
| | - Marian Joëls
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands
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Feng B, Chen Z. Generation of Febrile Seizures and Subsequent Epileptogenesis. Neurosci Bull 2016; 32:481-92. [PMID: 27562688 DOI: 10.1007/s12264-016-0054-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 07/13/2016] [Indexed: 11/24/2022] Open
Abstract
Febrile seizures (FSs) occur commonly in children aged from 6 months to 5 years. Complex (repetitive or prolonged) FSs, but not simple FSs, can lead to permanent brain modification. Human infants and immature rodents that have experienced complex FSs have a high risk of subsequent temporal lobe epilepsy. However, the causes of FSs and the mechanisms underlying the subsequent epileptogenesis remain unknown. Here, we mainly focus on two major questions concerning FSs: how fever triggers seizures, and how epileptogenesis occurs after FSs. The risk factors responsible for the occurrence of FSs and the epileptogenesis after prolonged FSs are thoroughly summarized and discussed. An understanding of these factors can provide potential therapeutic targets for the prevention of FSs and also yield biomarkers for identifying patients at risk of epileptogenesis following FSs.
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Affiliation(s)
- Bo Feng
- Department of Pharmacology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, School of Medicine, Zhejiang University, Hangzhou, 310058, China
| | - Zhong Chen
- Department of Pharmacology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, School of Medicine, Zhejiang University, Hangzhou, 310058, China.
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7
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Awad PN, Sanon NT, Chattopadhyaya B, Carriço JN, Ouardouz M, Gagné J, Duss S, Wolf D, Desgent S, Cancedda L, Carmant L, Di Cristo G. Reducing premature KCC2 expression rescues seizure susceptibility and spine morphology in atypical febrile seizures. Neurobiol Dis 2016; 91:10-20. [PMID: 26875662 DOI: 10.1016/j.nbd.2016.02.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/26/2016] [Accepted: 02/09/2016] [Indexed: 11/23/2022] Open
Abstract
Atypical febrile seizures are considered a risk factor for epilepsy onset and cognitive impairments later in life. Patients with temporal lobe epilepsy and a history of atypical febrile seizures often carry a cortical malformation. This association has led to the hypothesis that the presence of a cortical dysplasia exacerbates febrile seizures in infancy, in turn increasing the risk for neurological sequelae. The mechanisms linking these events are currently poorly understood. Potassium-chloride cotransporter KCC2 affects several aspects of neuronal circuit development and function, by modulating GABAergic transmission and excitatory synapse formation. Recent data suggest that KCC2 downregulation contributes to seizure generation in the epileptic adult brain, but its role in the developing brain is still controversial. In a rodent model of atypical febrile seizures, combining a cortical dysplasia and hyperthermia-induced seizures (LHS rats), we found a premature and sustained increase in KCC2 protein levels, accompanied by a negative shift of the reversal potential of GABA. In parallel, we observed a significant reduction in dendritic spine size and mEPSC amplitude in CA1 pyramidal neurons, accompanied by spatial memory deficits. To investigate whether KCC2 premature overexpression plays a role in seizure susceptibility and synaptic alterations, we reduced KCC2 expression selectively in hippocampal pyramidal neurons by in utero electroporation of shRNA. Remarkably, KCC2 shRNA-electroporated LHS rats show reduced hyperthermia-induced seizure susceptibility, while dendritic spine size deficits were rescued. Our findings demonstrate that KCC2 overexpression in a compromised developing brain increases febrile seizure susceptibility and contribute to dendritic spine alterations.
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Affiliation(s)
- Patricia N Awad
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Nathalie T Sanon
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Bidisha Chattopadhyaya
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Josianne Nunes Carriço
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Mohamed Ouardouz
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Jonathan Gagné
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Sandra Duss
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Daniele Wolf
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Sébastien Desgent
- CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada
| | - Laura Cancedda
- Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, via Morego, 30, 16163 Genova, Italy
| | - Lionel Carmant
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada.
| | - Graziella Di Cristo
- Neurosciences Department, Université de Montréal, 2960 Chemin de la Tour, Montréal, Québec H3T 1N8, Canada; CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada.
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Abstract
Focal cortical dysplasia is a common cause of medication resistant epilepsy. A better understanding of its presentation, pathophysiology and consequences have helped us improved its treatment and outcome. This paper reviews the most recent classification, pathophysiology and imaging findings in clinical research as well as the knowledge gained from studying genetic and lesional animal models of focal cortical dysplasia. This review of this recently gained knowledge will most likely help develop new research models and new therapeutic targets for patients with epilepsy associated with focal cortical dysplasia.
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9
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Heinemann SD, Posimo JM, Mason DM, Hutchison DF, Leak RK. Synergistic stress exacerbation in hippocampal neurons: Evidence favoring the dual-hit hypothesis of neurodegeneration. Hippocampus 2016; 26:980-94. [PMID: 26934478 DOI: 10.1002/hipo.22580] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2016] [Indexed: 12/21/2022]
Abstract
The dual-hit hypothesis of neurodegeneration states that severe stress sensitizes vulnerable cells to subsequent challenges so that the two hits are synergistic in their toxic effects. Although the hippocampus is vulnerable to a number of neurodegenerative disorders, there are no models of synergistic cell death in hippocampal neurons in response to combined proteotoxic and oxidative stressors, the two major characteristics of these diseases. Therefore, a relatively high-throughput dual-hit model of stress synergy was developed in primary hippocampal neurons. In order to increase the rigor of the study and strengthen the interpretations, three independent, unbiased viability assays were employed at multiple timepoints. Stress synergy was elicited when hippocampal neurons were treated with the proteasome inhibitor MG132 followed by exposure to the oxidative toxicant paraquat, but only after 48 h. MG132 and paraquat only elicited additive effects 24 h after the final hit and even loss of heat shock protein 70 activity and glutathione did not promote stress synergy at this early timepoint. Dual hits of MG132 elicited modest glutathione loss and slightly synergistic toxic effects 48 h after the second hit, but only at some concentrations and only according to two viability assays (metabolic fitness and cytoskeletal integrity). The thiol N-acetyl cysteine protected hippocampal neurons against dual MG132/MG132 hits but not dual MG132/paraquat hits. These findings support the view that proteotoxic and oxidative stress propel and propagate each other in hippocampal neurons, leading to synergistically toxic effects, but not as the default response and only after a delay. The neuronal stress synergy observed here lies in contrast to astrocytic responses to dual hits, because astrocytes that survive severe proteotoxic stress resist additional cell loss following second hits. In conclusion, a new model of hippocampal vulnerability was developed for the testing of therapies, because neuroprotective treatments that are effective against severe, synergistic stress are more likely to succeed in the clinic. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Scott D Heinemann
- Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania
| | - Jessica M Posimo
- Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania
| | - Daniel M Mason
- Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania
| | - Daniel F Hutchison
- Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania
| | - Rehana K Leak
- Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania
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10
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Bowyer JF, Hanig JP. Amphetamine- and methamphetamine-induced hyperthermia: Implications of the effects produced in brain vasculature and peripheral organs to forebrain neurotoxicity. Temperature (Austin) 2014; 1:172-82. [PMID: 27626044 PMCID: PMC5008711 DOI: 10.4161/23328940.2014.982049] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 10/22/2014] [Accepted: 10/27/2014] [Indexed: 12/20/2022] Open
Abstract
The adverse effects of amphetamine- (AMPH) and methamphetamine- (METH) induced hyperthermia on vasculature, peripheral organs and peripheral immune system are discussed. Hyperthermia alone does not produce amphetamine-like neurotoxicity but AMPH and METH exposures that do not produce hyperthermia (≥40°C) are minimally neurotoxic. Hyperthermia likely enhances AMPH and METH neurotoxicity directly through disruption of protein function, ion channels and enhanced ROS production. Forebrain neurotoxicity can also be indirectly influenced through the effects of AMPH- and METH- induced hyperthermia on vasculature. The hyperthermia and the hypertension produced by high doses amphetamines are a primary cause of transient breakdowns in the blood-brain barrier (BBB) resulting in concomitant regional neurodegeneration and neuroinflammation in laboratory animals. This BBB breakdown can occur in the amygdala, thalamus, striatum, sensory and motor cortex and hippocampus. Under these conditions, repetitive seizures greatly enhance neurodegeneration in hippocampus, thalamus and amygdala. Even when the BBB is less disrupted, AMPH- or METH- induced hyperthermia effects on brain vasculature may play a role in neurotoxicity. In this case, striatal and cortical vascular function are adversely affected, and even greater ROS, immune and damage responses are seen in the meninges and cortical surface vasculature. Finally, muscle and liver damage and elevated cytokines in blood can result when amphetamines produce hyperthermia. Proteins, from damaged muscle may activate the peripheral immune system and exacerbate liver damage. Liver damage can further increase cytokine levels, immune system activation and increase ammonia levels. These effects could potentially enhance vascular damage and neurotoxicity.
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11
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Stoenica L, Wilkars W, Battefeld A, Stadler K, Bender R, Strauss U. HCN1 subunits contribute to the kinetics of I(h) in neonatal cortical plate neurons. Dev Neurobiol 2013; 73:785-97. [PMID: 23821600 DOI: 10.1002/dneu.22104] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 06/13/2013] [Accepted: 06/21/2013] [Indexed: 01/03/2023]
Abstract
The distribution of ion channels in neurons regulates neuronal activity and proper formation of neuronal networks during neuronal development. One of the channels is the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel constituting the molecular substrate of hyperpolarization-activated current (I(h)). Our previous study implied a role for the fastest activating subunit HCN1 in the generation of Ih in rat neonatal cortical plate neurons. To better understand the impact of HCN1 in early neocortical development, we here performed biochemical analysis and whole-cell recordings in neonatal cortical plate and juvenile layer 5 somatosensory neurons of HCN1(-/-) and control HCN1(+/+) mice. Western Blot analysis revealed that HCN1 protein expression in neonatal cortical plate tissue of HCN(+/+) mice amounted to only 3% of the HCN1 in young adult cortex and suggested that in HCN1(-/-) mice other isoforms (particularly HCN4) might be compensatory up-regulated. At the first day after birth, functional ablation of the HCN1 subunit did not affect the proportion of Ih expressing pyramidal cortical plate neurons. Although the contribution of individual subunit proteins remains open, the lack of HCN1 markedly slowed the current activation and deactivation in individual I(h) expressing neurons. However, it did not impair maximal amplitude/density, voltage dependence of activation, and cAMP sensitivity. In conclusion, our data imply that, although expression is relatively low, HCN1 contributes substantially to I(h) properties in individual cortical plate neurons. These properties are significantly changed in HCN1(-/-), either due to the lack of HCN1 itself or due to compensatory mechanisms.
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Affiliation(s)
- Luminita Stoenica
- Institute of Cell Biology & Neurobiology, Charité-Universitätsmedizin, Berlin, Germany
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Ih channels prevent overexcitability of early developmental CA1 neurons showing high input resistance in rats. Brain Res Bull 2013; 91:14-20. [DOI: 10.1016/j.brainresbull.2012.11.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 11/23/2012] [Accepted: 11/24/2012] [Indexed: 11/21/2022]
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13
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Desgent S, Duss S, Sanon NT, Lema P, Lévesque M, Hébert D, Rébillard RM, Bibeau K, Brochu M, Carmant L. Early-life stress is associated with gender-based vulnerability to epileptogenesis in rat pups. PLoS One 2012; 7:e42622. [PMID: 22880055 PMCID: PMC3411822 DOI: 10.1371/journal.pone.0042622] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 07/10/2012] [Indexed: 11/19/2022] Open
Abstract
During development, the risk of developing mesial temporal lobe epilepsy (MTLE) increases when the developing brain is exposed to more than one insult in early life. Early life insults include abnormalities of cortical development, hypoxic-ischemic injury and prolonged febrile seizures. To study epileptogenesis, we have developed a two-hit model of MTLE characterized by two early-life insults: a freeze lesion-induced cortical malformation at post-natal day 1 (P1), and a prolonged hyperthermic seizure (HS) at P10. As early life stressors lead to sexual dimorphism in both acute response and long-term outcome, we hypothesized that our model could lead to gender-based differences in acute stress response and long-term risk of developing MTLE. Male and female pups underwent a freeze-lesion induced cortical microgyrus at P1 and were exposed to HS at P10. Animals were monitored by video-EEG from P90 to P120. Pre and post-procedure plasma corticosterone levels were used to measure stress response at P1 and P10. To confirm the role of sex steroids, androgenized female pups received daily testosterone injections to the mother pre-natally and post-natally for nine days while undergoing both insults. We demonstrated that after both insults females did not develop MTLE while all males did. This correlated with a rise in corticosterone levels at P1 following the lesion in males only. Interestingly, all androgenized females showed a similar rise in corticosterone at P1, and also developed MTLE. Moreover, we found that the cortical lesion significantly decreased the latency to generalized convulsion during hyperthermia at P10 in both genders. The cortical dysplasia volumes at adulthood were also similar between male and female individuals. Our data demonstrate sexual dimorphism in long-term vulnerability to develop epilepsy in the lesion + hyperthermia animal model of MTLE and suggest that the response to early-life stress at P1 contributes significantly to epileptogenesis in a gender-specific manner.
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Affiliation(s)
- Sébastien Desgent
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
- Département de Physiologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
- * E-mail: (S. Desgent); (LC)
| | - Sandra Duss
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
| | - Nathalie T. Sanon
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
| | - Pablo Lema
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
| | - Maxime Lévesque
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
| | - David Hébert
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
| | - Rose-Marie Rébillard
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
| | - Karine Bibeau
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
| | - Michèle Brochu
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
- Département de Physiologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
| | - Lionel Carmant
- Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, Québec, Canada
- Département de Physiologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
- * E-mail: (S. Desgent); (LC)
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Atypical febrile seizures, mesial temporal lobe epilepsy, and dual pathology. EPILEPSY RESEARCH AND TREATMENT 2012; 2012:342928. [PMID: 22957226 PMCID: PMC3420631 DOI: 10.1155/2012/342928] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/25/2011] [Revised: 02/02/2012] [Accepted: 02/07/2012] [Indexed: 12/02/2022]
Abstract
Febrile seizures occurring in the neonatal period, especially when prolonged, are thought to be involved in the later development of mesial temporal lobe epilepsy (mTLE) in children. The presence of an often undetected, underlying cortical malformation has also been reported to be implicated in the epileptogenesis process following febrile seizures. This paper highlights some of the various animal models of febrile seizures and of cortical malformation and portrays a two-hit model that efficiently mimics these two insults and leads to spontaneous recurrent seizures in adult rats. Potential mechanisms are further proposed to explain how these two insults may each, or together, contribute to network hyperexcitability and epileptogenesis. Finally the clinical relevance of the two-hit model is briefly discussed in light of a therapeutic and preventive approach to mTLE.
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Ouardouz M, Carmant L. Changes in inhibitory CA1 network in dual pathology model of epilepsy. Channels (Austin) 2012; 6:18-25. [PMID: 22373560 DOI: 10.4161/chan.18615] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The combination of two precipitating factors appears to be more and more recognized in patients with temporal lobe epilepsy. Using a two-hit rat model, with a neonatal freeze lesion mimicking a focal cortical malformation combined with hyperthermia-induced seizures mimicking febrile seizures, we have previously reported an increase of inhibition in CA1 pyramidal cells at P20. Here, we investigated the changes affecting excitatory and inhibitory drive onto CA1 interneurons to better define the changes in CA1 inhibitory networks and their paradoxical role in epileptogenesis, using electrophysiological recordings in CA1 hippocampus from rat pups (16-20 d old). We investigated interneurons in CA1 hippocampal area located in stratum oriens (Or) and at the border of strata lacunosum and moleculare (L-M). Our results revealed an increase of the excitatory drive to both types of interneurons with no change in the inhibitory drive. The mechanisms underlying the increase of excitatory synaptic currents (EPSCs) in both types of interneurons are different. In Or interneurons, the amplitude of spontaneous and miniature EPSCs increased, while their frequency was not affected suggesting changes at the post-synaptic level. In L-M interneurons, the frequency of spontaneous EPSCs increases, but the amplitude is not affected. Analyses of miniature EPSCs showed no changes in both their frequency and amplitude. We concluded that L-M interneurons increase in excitatory drive is due to a change in Shaffer collateral axon excitability. The changes described here in CA1 inhibitory network may actually contribute to the epileptogenicity observed in this dual pathology model by increasing pyramidal cell synchronization.
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Affiliation(s)
- Mohamed Ouardouz
- Sainte-Justine Hospital Research Center, Université de Montréal, Montreal, QC, Canada.
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Hyperthermia induces epileptiform discharges in cultured rat cortical neurons. Brain Res 2011; 1417:87-102. [DOI: 10.1016/j.brainres.2011.08.027] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Revised: 08/08/2011] [Accepted: 08/11/2011] [Indexed: 01/28/2023]
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17
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Long-term consequences of a prolonged febrile seizure in a dual pathology model. Neurobiol Dis 2011; 43:312-21. [PMID: 21406232 DOI: 10.1016/j.nbd.2011.02.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 01/26/2011] [Accepted: 02/27/2011] [Indexed: 12/14/2022] Open
Abstract
Clinical evidence suggests that febrile status epilepticus (SE) in children can lead to acute hippocampal injury and subsequent temporal lobe epilepsy. The contribution of febrile SE to the mechanisms underlying temporal lobe epilepsy are however poorly understood. A rat model of temporal lobe epilepsy following hyperthermic SE was previously established in our laboratory, wherein a focal cortical lesion induced at postnatal day 1 (P1), followed by a hyperthermic SE (more than 30 min) at P10, leads to hippocampal atrophy at P22 (dual pathology model) and spontaneous recurrent seizures (SRS) with mild visuospatial memory deficits in adult rats. The goal of this study was to identify the long term electrophysiological, anatomical and molecular changes in this model. Following hyperthermic SE, all cortically lesioned pups developed progressive SRS as adults, characterized by the onset of highly rhythmic activity in the hippocampus. A reduction of hippocampal volume on the side of the lesion preceded the SRS and was associated with a loss of hippocampal neurons, a marked decrease in pyramidal cell spine density, an increase in the hippocampal levels of NMDA receptor NR2A subunit, but no significant change in GABA receptors. These findings suggest that febrile SE in the abnormal brain leads to hippocampal injury that is followed by progressive network reorganization and molecular changes that contribute to the epileptogenesis as well as the observed memory deficits.
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