Basic Science of Epilepsy
Basic research using animal models
The April 2013 issue of Epilepsia contains a number of basic research papers using animal models. The following two papers reflect the power and opportunity for applying "bench work" to the real problems of clinical epileptology.
Ligia A. Papale, Christopher D. Makinson, J. Christopher Ehlen, Sergio Tufik, Michael J. Decker, Ketema N. Paul, Andrew Escayg
Gabi Dezsi, Ezgi Ozturk, Davor Stanic, Kim L. Powell, Hal Blumenfeld, Terence J. O'Brien, Nigel C. Jones
Canine epilepsy as a translational model?
Heidrun Potschka, Andrea Fischer, Eva-Lotta von Rüden, Velia Hülsmeyer, Wolfgang Baumgärtne
Dogs with spontaneous diseases can exhibit a striking similarity in etiology, clinical manifestation, and disease course when compared to human patients. Therefore, dogs are intensely discussed as a translational model of human disease. In particular, genetic studies in selected dog breeds serve as an excellent tool to identify epilepsy disease genes. The review gives an overview on the current state of knowledge regarding the etiology, clinical manifestation, pathology, and drug response of canine epilepsy, also pointing out the urgent need for further research on specific aspects. Moreover, the putative advantages, the disadvantages, and limitations of antiepileptic drug testing in canine epilepsy are critically discussed.
Detection of human papillomavirus in human focal cortical dysplasia type IIB
Annals of Neurology Vol 72, Issue 6, pp. 881-892. December 2012. Article first published online: 31 Dec 2012. DOI: 10.1002/ana.23795
Objective: Focal cortical dysplasia type IIB (FCDIIB) is a sporadic developmental malformation of the cerebral cortex highly associated with pediatric epilepsy. Balloon cells (BCs) in FCDIIB exhibit constitutive activation of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway. Recently, the high-risk human papillomavirus type 16 oncoprotein E6 was identified as a potent activator of mTORC1 signaling. Here, we test the hypothesis that HPV16 E6 is present in human FCDIIB specimens.
Interpretation: Our results indicate a new association between HPV16 E6 and FCDIIB and demonstrate for the first time HPV16 E6 in the human brain. We propose a novel etiology for FCDIIB based on HPV16 E6 expression during fetal brain development. ANN NEUROL 2012;72:881-892
Eva M Jimenez-Mateos, Tobias Engel, Paula Merino-Serrais, Ross C McKiernan, Katsuhiro Tanaka, Genshin Mouri, Takanori Sano, Colm O'Tuathaigh, John L Waddington, Suzanne Prenter, Norman Delanty, Michael A Farrell, Donncha F O'Brien, RonÃ¡n M Conroy, Raymond L Stallings, Javier DeFelipe, David C Henshall
Abstract: Temporal lobe epilepsy is a common, chronic neurological disorder characterized by recurrent spontaneous seizures. MicroRNAs (miRNAs) are small, noncoding RNAs that regulate post-transcriptional expression of protein-coding mRNAs, which may have key roles in the pathogenesis of neurological disorders. In experimental models of prolonged, injurious seizures (status epilepticus) and in human epilepsy, we found upregulation of miR-134, a brain-specific, activity-regulated miRNA that has been implicated in the control of dendritic spine morphology. Silencing of miR-134 expression in vivo using antagomirs reduced hippocampal CA3 pyramidal neuron dendrite spine density by 21% and rendered mice refractory to seizures and hippocampal injury caused by status epilepticus. Depletion of miR-134 after status epilepticus in mice reduced the later occurrence of spontaneous seizures by over 90% and mitigated the attendant pathological features of temporal lobe epilepsy. Thus, silencing miR-134 exerts prolonged seizure-suppressant and neuroprotective actions; determining whether these are anticonvulsant effects or are truly antiepileptogenic effects requires additional experimentation. Read article
The editors of the historic textbook Jasper's Basic Mechanisms of Epilepsy announce the publication of the 4th edition by Oxford University Press. The book contains chapters from 90 international research groups summarizing the latest experimental advances in epilepsy for basic and clinical researchers.
This edition considers the role of interactions between neurons, synapses, and glia in the initiation, spread, and arrest of seizures. It examines mechanisms of excitability synchronization, and epileptogenesis and provides a framework for expanding the epilepsy genome and understanding complex heredity. It considers the mechanism of ion channelopathy, developmental epilepsy genes, and epilepsy comorbidities. And for the first time, it describes the current translation of epilepsy mechanisms into new therapeutic strategies.
Long considered the "bible" of basic epilepsy research, the volume provides encyclopedia coverage of current understanding and maps out new research directions for the coming decade.
Bianca Jupp, John Williams, David Binns, Rodney J. Hicks, Lisa Cardamone, Nigel Jones, Sandra Rees, Terence J. O'Brien
These findings demonstrate that hypometabolism occurs early in the processes of limbic epileptogenesis and is not merely a consequence of pyramidal cell loss or the progressive atrophy of limbic brain structures that follow. The hypometabolism may reflect cellular mechanisms occurring early during epileptogenesis in addition to any effects of the subsequent recurrent spontaneous seizures.
György Buzsáki, Costas A. Anastassiou, & Christof Koch
Neuronal activity in the brain gives rise to transmembrane currents that can be measured in the extracellular medium. Although the major contributor of the extracellular signal is the synaptic transmembrane current, other sources â€” including Na+ and Ca2+ spikes, ionic fluxes through voltage- and ligand-gated channels, and intrinsic membrane oscillations â€” can substantially shape the extracellular field. High-density recordings of field activity in animals and subdural grid recordings in humans, combined with recently developed data processing tools and computational modelling, can provide insight into the cooperative behaviour of neurons, their average synaptic input and their spiking output, and can increase our understanding of how these processes contribute to the extracellular signal.
Hierarchical clustering of brain activity during human nonrapid eye movement sleep
Mélanie Boly, Vincent Perlbarg, Guillaume Marrelec, Manuel Schabus, Steven Laureys, Julien Doyon, Mélanie Pélégrini-Issac, Pierre Maquet, and Habib Benali
Consciousness is reduced during nonrapid eye movement (NREM) sleep due to changes in brain function that are still poorly understood. Here, we tested the hypothesis that impaired consciousness during NREM sleep is associated with an increased modularity of brain activity.
Seizure-induced brain-born inflammation sustains seizure recurrence and blood-brain barrier damage
Laura Librizzi PhD, Francesco NoÃ¨ PhD, Annamaria Vezzani PhD, Marco de Curtis MD1, Teresa Ravizza PhD
Epilepsy is a common neurological disorder characterized by recurrent seizures often unresponsive to pharmacological treatment. Brain inflammation is considered a crucial etiopathogenetic mechanism of epilepsy that could be targeted to control seizures. Specific inflammatory mediators overexpressed in human epileptogenic foci are known to promote seizures in animal models. We investigate if seizures induce brain inflammation independently on extra-cerebral factors. We also verify whether brain-born inflammation is required and sufficient to maintain seizure activity and it supports blood-brain barrier (BBB) impairment. We addressed these questions by studying the relationship between seizures, inflammation and BBB permeability in a brain preparation isolated from extracerebral compartments.
Neuron-restrictive silencer factor-mediated hyperpolarization-activated cyclic nucleotide gated channelopathy in experimental temporal lobe epilepsy
McClelland S, Flynn C, Dubé C, Richichi C, Zha Q, Ghestem A, Esclapez M, Bernard C, Baram TZ. (2011)
Acquired HCN1 channelopathy derives from NRSF-mediated transcriptional repression that endures via chromatin modification and may provide insight into the mechanisms of a number of channelopathies that coexist with, and may contribute to, the conversion of a normal brain into an epileptic one.
Glutamatergic pre-ictal discharges emerge at the transition to seizure in human epilepsy
Gilles Huberfeld, Liset Menendez de la Prida, Johan Pallud, Ivan Cohen, Michel Le Van Quyen, Claude Adam, Stephane Clemenceau, Michel Baulac and Richard Miles
Brief and synchronous inter-ictal events can occur between seizures. Using human tissue samples and electroencephalography, this study shows that the transition from pre-ictal discharge to ictal discharge involves distinct temporal and spatial characteristics as well as glutamatergic mechanisms.
Single-neuron dynamics in human focal epilepsy
Wilson Truccolo, Jacob A Donoghue, Leigh R Hochberg, Emad N Eskandar, Joseph R Madsen, William S Anderson, Emery N Brown, Eric Halgren and Sydney S Cash
Epileptic seizures are traditionally considered to reflect hypersynchronous neuronal activity arising from runaway excitation. Here the authors analyze spike train patterns of single neurons during seizures in human epilepsy patients, finding that spiking activity during seizure initiation was highly heterogeneous in small cortical patches and across the network.
A Novel Positron Emission Tomography Imaging Protocol Identifies Seizure-Induced Regional Overactivity of P-Glycoprotein at the Blood-Brain Barrier.
Bankstahl JP, Bankstahl M, Kuntner C, Stanek J, Wanek T, Meier M, Ding XQ, MÃ¼ller M, Langer O, LÃ¶scher W.Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, and Center for Systems Neuroscience, 30559 Hannover, Germany, Health and Environment Department, Molecular Medicine, AIT Austrian Institute of Technology, 2444 Seibersdorf, Austria, Department of Clinical Pharmacology, Medical University of Vienna, 1090 Vienna, Austria, and Department of Cardiology and Angiology and Institute of Diagnostic and Interventional Neuroradiology, Hannover Medical School, 30625 Hannover, Germany.
Exome sequencing of ion channel genes reveals complex profiles confounding personal risk assessment in epilepsy.
Klassen T, Davis C, Goldman A, Burgess D, Chen T, Wheeler D, McPherson J, Bourquin T, Lewis L, Villasana D, Morgan M, Muzny D, Gibbs R, Noebels J.