Differential Effects of Antiepileptic Drugs on Focal Seizures in the Intrahippocampal Kainate Mouse Model of Mesial Temporal Lobe Epilepsy

Enhancement of Glutamate Uptake as Novel Antiseizure Approach: Preclinical Proof of Concept

OBJECTIVE

Excitotoxicity is a common hallmark of epilepsy and other neurological diseases associated with elevated extracellular glutamate levels. Thus, here, we studied the protective effects of (R)-AS-1, a positive allosteric modulator (PAM) of glutamate uptake in epilepsy models.

METHODS

(R)-AS-1 was evaluated in a range of acute and chronic seizure models, while its adverse effect profile was assessed in a panel of standard tests in rodents. The effect of (R)-AS-1 on glutamate uptake was assessed in COS-7 cells expressing the transporter. WAY 213613, a selective competitive EAAT2 inhibitor, was used to probe the reversal of the enhanced glutamate uptake in the same transporter expression system. Confocal microscopy and Western blotting analyses were used to study a potential influence of (R)-AS-1 on GLT-1 expression in mice.

RESULTS

(R)-AS-1 showed robust protection in a panel of animal models of seizures and epilepsy, including the maximal electroshock- and 6 Hz-induced seizures, corneal kindling, mesial temporal lobe epilepsy, lamotrigine-resistant amygdala kindling, as well as seizures induced by pilocarpine or Theiler's murine encephalomyelitis virus. Importantly, (R)-AS-1 displayed a favorable adverse effect profile in the rotarod, the minimal motor impairment, and the Irwin tests. (R)-AS-1 enhanced glutamate uptake in vitro and this effect was abolished by WAY 213613, while no influence on GLT-1 expression in vivo was observed after repeated treatment.

INTERPRETATION

Collectively, our results show that (R)-AS-1 has favorable tolerability and provides robust preclinical efficacy against seizures. Thus, allosteric enhancement of EAAT2 function could offer a novel therapeutic strategy for treatment of epilepsy and potentially other neurological disorders associated with glutamate excitotoxicity. ANN NEUROL 2025;97:344-357.

Focal brain administration of antiseizure medications improves outcomes and reduces side effects

This scientific commentary refers to ‘Intracerebral delivery of antiseizure medications by microinvasive neural implants’ by Jackson et al. (https://doi.org/10.1093/brain/awae282).

Chemogenetics with PSAM4-GlyR decreases excitability and epileptiform activity in epileptic hippocampus

Despite the availability of new drugs on the clinics in recent years, drug-resistant epilepsy remains an unresolved challenge for healthcare, and one-third of epilepsy patients remain refractory to anti-seizure medications. Gene therapy in experimental models has emerged as effective treatment targeting specific neuronal populations in the epileptogenic focus. When combined with an external chemical activator using chemogenetics, it also becomes an "on-demand" treatment. Here, we evaluate a targeted and specific chemogenetic therapy, the PSAM/PSEM system, which holds promise as a potential candidate for clinical application in treating drug-resistant epilepsy. We show that the inert ligand uPSEM817, which selectively activates the chloride-permeable channel PSAM4-GlyR, effectively reduces the number of depolarization-induced action potentials in vitro. This effect is likely due to the shunting of depolarizing currents, as evidenced by decreased membrane resistance in these cells. In organotypic slices, uPSEM817 decreased the number of bursts and peak amplitude of events of spontaneous epileptiform activity. Although administration of uPSEM817 in vivo did not significantly alter electrographic seizures in a male mouse model of temporal lobe epilepsy, it did demonstrate a strong trend toward reducing the frequency of interictal epileptiform discharges. These findings indicate that PSAM4-GlyR-based chemogenetics holds potential as an anti-seizure strategy, although further refinement is necessary to enhance its efficacy.

On-Demand Seizures Facilitate Rapid Screening of Therapeutics for Epilepsy

Animal models of epilepsy are critical in drug development and therapeutic testing, but dominant methods for pharmaceutical evaluation face a tradeoff between higher throughput and etiological relevance. For example, in temporal lobe epilepsy, a type of epilepsy where seizures originate from limbic structures like the hippocampus, the main screening models are either based on acutely induced seizures in wild type, naïve animals or spontaneous seizures in chronically epileptic animals. Both types have their disadvantages - the acute convulsant or kindling induced seizures do not account for the myriad neuropathological changes in the diseased, epileptic brains, and spontaneous behavioral seizures are sparse in the chronically epileptic models, making it time-intensive to sufficiently power experiments. In this study, we took a mechanistic approach to precipitate seizures "on demand" in chronically epileptic mice. We briefly synchronized principal cells in the CA1 region of the diseased hippocampus to reliably induce stereotyped on-demand behavioral seizures. These induced seizures resembled naturally occurring spontaneous seizures in the epileptic animals and could be stopped by commonly prescribed anti-seizure medications such as levetiracetam and diazepam. Furthermore, we showed that seizures induced in chronically epileptic animals differed from those in naïve animals, highlighting the importance of evaluating therapeutics in the diseased circuit. Taken together, we envision our model to advance the speed at which both pharmacological and closed loop interventions for temporal lobe epilepsy are evaluated.

Dose-Dependent Induction of Differential Seizure Phenotypes by Pilocarpine in Rats: Considerations for Translational Potential

Background and Objectives: Pilocarpine is used in experimental studies for testing antiepileptic drugs, but further characterization of this model is essential for its usage in testing novel drugs. The aim of our study was to study the behavioral and EEG characteristics of acute seizures caused by different doses of pilocarpine in rats. Materials and Methods: Male Wistar rats were treated with a single intraperitoneal dose of 100 mg/kg (P100), 200 mg/kg (P200), or 300 mg/kg (P300) of pilocarpine, and epileptiform behavior and EEG changes followed within 4 h. Results: The intensity and the duration of seizures were significantly higher in P300 vs. the P200 and P100 groups, with status epilepticus dominating in P300 and self-limiting tonic-clonic seizures in the P200 group. The seizure grade was significantly higher in P200 vs. the P100 group only during the first hour after pilocarpine application. The latency of seizures was significantly shorter in P300 and P200 compared with P100 group. Conclusions: Pilocarpine (200 mg/kg) can be used as a suitable model for the initial screening of potential anti-seizure medications, while at a dose of 300 mg/kg, it can be used for study of the mechanisms of epileptogenesis.

Subthreshold Cannabidiol Potentiates Levetiracetam in the Kainic Acid Model of Temporal Lobe Epilepsy: A Pilot Study

Refractoriness to antiseizure medications is still a major concern in the pharmacotherapy of epilepsy. For this reason, we decided to evaluate the combination of levetiracetam and cannabidiol, administered at a subthreshold dose, to limit the possible adverse effects of this phytocannabinoid. We administered levetiracetam (300 mg/kg/day, via osmotic minipumps), cannabidiol (120 mg/kg/day, injected once a day subcutaneously), or their combination for one week in epileptic rats. Saline-treated epileptic rats were the control group. Animals were monitored with video electroencephalography the week before and after the treatment. No changes were found in the controls. Levetiracetam did not significantly reduce the total seizure number or the overall seizure duration. Still, the overall number of seizures (p < 0.001, Duncan's new multiple range test) and their total duration (p < 0.01) increased in the week following treatment withdrawal. Cannabidiol did not change seizures when administered as a single drug. Instead, levetiracetam combined with cannabidiol resulted in a significant reduction in the overall number and duration of seizures (p < 0.05), when comparing values measured during treatment with both pre- and post-treatment values. These findings depended on changes in convulsive seizures, while non-convulsive seizures were stable. These results suggest that cannabidiol determined a remarkable potentiation of levetiracetam antiseizure effects at a subthreshold dose.

Innovative minimally invasive options to treat drug-resistant epilepsies

Despite the regular discovery of new molecules, one-third of epileptic patients are resistant to antiepileptic drugs. Only a few can benefit from resective surgery, the current gold standard. Although effective in 50-70% of cases, this therapy remains risky, costly, and can be associated with long-term cognitive or neurological side effects. In addition, patients are increasingly reluctant to have a craniotomy, emphasizing the need for new less invasive therapies for focal drug-resistant epilepsies. Here, we review different minimally invasive approaches already in use in the clinic or under preclinical development to treat drug-resistant epilepsies. Localized thermolesion of the epileptogenic zone has been developed in the clinic using high-frequency thermo-coagulations or magnetic resonance imaging-guided laser or ultrasounds. Although less invasive, they have not yet significantly improved the outcomes when compared with resective surgery. Radiosurgery techniques have been used in the clinic for the last 20years and have proven efficiency. However, their efficacy is not better than resective surgery, and various side effects have been reported as well as the potential risk of sudden unexpected death associated with epilepsy. Recently, a new strategy of radiosurgery has emerged using synchrotron-generated X-ray microbeams: microbeam radiation therapy (MRT). The low divergence and high-flux of the synchrotron beams and the unique tolerance to MRT by healthy brain tissues, allows a precise targeting of specific brain regions with minimal invasiveness and limited behavioral or functional consequences in animals. Antiepileptic effects over several months have been recorded in animal models, and histological and synaptic tracing analysis suggest a reduction of neuronal connectivity as a mechanism of action. The possibility of transferring this approach to epileptic patients is discussed in this review.

Preclinical efficacy profiles of the sigma-1 modulator E1R and of fenfluramine in two chronic mouse epilepsy models

OBJECTIVE

Given its key homeostatic role affecting mitochondria, ionotropic and metabotropic receptors, and voltage-gated ion channels, sigma-1 receptor (Sig1R) represents an interesting target for epilepsy management. Antiseizure effects of the positive allosteric modulator E1R have already been reported in acute seizure models. Although modulation of serotonergic neurotransmission is considered the main mechanism of action of fenfluramine, its interaction with Sig1R may be of additional relevance.

METHODS

To further explore the potential of Sig1R as a target, we assessed the efficacy and tolerability of E1R and fenfluramine in two chronic mouse models, including an amygdala kindling paradigm and the intrahippocampal kainate model. The relative contribution of the interaction with Sig1R was analyzed using combination experiments with the Sig1R antagonist NE-100.

RESULTS

Whereas E1R exerted pronounced dose-dependent antiseizure effects at well-tolerated doses in fully kindled mice, only limited effects were observed in response to fenfluramine, without a clear dose dependency. In the intrahippocampal kainate model, E1R failed to influence electrographic seizure activity. In contrast, fenfluramine significantly reduced the frequency of electrographic seizure events and their cumulative duration. Pretreatment with NE-100 reduced the effects of E1R and fenfluramine in the kindling model. Surprisingly, pre-exposure to NE-100 in the intrahippocampal kainate model rather enhanced and prolonged fenfluramine's antiseizure effects.

SIGNIFICANCE

In conclusion, the kindling data further support Sig1R as an interesting target for novel antiseizure medications. However, it is necessary to further explore the preclinical profile of E1R in chronic epilepsy models with spontaneous seizures. Despite the rather limited effects in the kindling paradigm, the findings from the intrahippocampal kainate model suggest that it is of interest to further assess a possible broad-spectrum potential of fenfluramine.

Characterization of the intrahippocampal kainic acid model in female mice with a special focus on seizure suppression by antiseizure medications

Despite special challenges in the medical treatment of women with epilepsy, in particular preclinical animal studies were focused on males for decades and females have only recently moved into the focus of scientific interest. The intrahippocampal kainic acid (IHKA) mouse model of temporal lobe epilepsy (TLE) is one of the most studied models in males reproducing electroencephalographic (EEG) and histopathological features of human TLE. Hippocampal paroxysmal discharges (HPDs) were described as drug resistant focal seizures in males. Here, we investigated the IHKA model in female mice, in particular drug-resistance of HPDs and the influence of antiseizure medications (ASMs) on the power spectrum. After injecting kainic acid (KA) unilaterally into the hippocampus of female mice, we monitored the development of epileptiform activity by local field potential (LFP) recordings. Subsequently, we evaluated the effect of the commonly prescribed ASMs lamotrigine (LTG), oxcarbazepine (OXC) and levetiracetam (LEV), as well as the benzodiazepine diazepam (DZP) with a focus on HPDs and power spectral analysis and assessed neuropathological alterations of the hippocampus. In the IHKA model, female mice replicated key features of human TLE as previously described in males. Importantly, HPDs in female mice did not respond to commonly prescribed ASMs in line with the drug-resistance in males, thus representing a suitable model of drug-resistant seizures. Intriguingly, we observed an increased occurrence of generalized seizures after LTG. Power spectral analysis revealed a pronounced increase in the delta frequency range after the higher dose of 30 mg/kg LTG. DZP abolished HPDs and caused a marked reduction over a wide frequency range (delta, theta, and alpha) of the power spectrum. By characterizing the IHKA model of TLE in female mice we address an important gap in basic research. Considering the special challenges complicating the therapeutic management of epilepsy in women, inclusion of females in preclinical studies is imperative. A well-characterized female model is a prerequisite for the development of novel therapeutic strategies tailored to sex-specific needs and for studies on the effect of epilepsy and ASMs during pregnancy.

Challenges and directions in epilepsy diagnostics and therapeutics: Proceedings of the 17th Epilepsy Therapies and Diagnostics Development conference

Substantial efforts are underway toward optimizing the diagnosis, monitoring, and treatment of seizures and epilepsy. We describe preclinical programs in place for screening investigational therapeutic candidates in animal models, with particular attention to identifying and eliminating drugs that might paradoxically aggravate seizure burden. After preclinical development, we discuss challenges and solutions in the design and regulatory logistics of clinical trial execution, and efforts to develop disease biomarkers and interventions that may be not only seizure-suppressing, but also disease-modifying. As disease-modifying treatments are designed, there is clear recognition that, although seizures represent one critical therapeutic target, targeting nonseizure outcomes like cognitive development or functional outcomes requires changes to traditional designs. This reflects our increasing understanding that epilepsy is a disease with profound impact on quality of life for the patient and caregivers due to both seizures themselves and other nonseizure factors. This review examines selected key challenges and future directions in epilepsy diagnostics and therapeutics, from drug discovery to translational application.

Current advances in rodent drug-resistant temporal lobe epilepsy models: Hints from laboratory studies

Anti-seizure drugs (ASDs) are the first choice for the treatment of epilepsy, but there is still one-third of patients with epilepsy (PWEs) who are resistant to two or more appropriately chosen ASDs, named drug-resistant epilepsy (DRE). Temporal lobe epilepsy (TLE), a common type of epilepsy usually associated with hippocampal sclerosis (HS), shares the highest proportion of drug resistance (approximately 70%). In view of the key role of the temporal lobe in memory, emotion, and other physiological functions, patients with drug-resistant temporal lobe epilepsy (DR-TLE) are often accompanied by serious complications, and surgical procedures also yield extra considerations. The exact mechanisms for the genesis of DR-TLE remain unillustrated, which makes it hard to manage patients with DR-TLE in clinical practice. Animal models of DR-TLE play an irreplaceable role in both understanding the mechanism and searching for new therapeutic strategies or drugs. In this review article, we systematically summarized different types of current DR-TLE models, and then recent advances in mechanism investigations obtained in these models were presented, especially with the development of advanced experimental techniques and tools. We are deeply encouraged that novel strategies show great therapeutic potential in those DR-TLE models. Based on the big steps reached from the bench, a new light has been shed on the precise management of DR-TLE.

Increased Dentate Gyrus Excitability in the Intrahippocampal Kainic Acid Mouse Model for Temporal Lobe Epilepsy

The intrahippocampal kainic acid (IHKA) mouse model is an extensively used in vivo model to investigate the pathophysiology of mesial temporal lobe epilepsy (mTLE) and to develop novel therapies for drug-resistant epilepsy. It is characterized by profound hippocampal sclerosis and spontaneously occurring seizures with a major role for the injected damaged hippocampus, but little is known about the excitability of specific subregions. The purpose of this study was to electrophysiologically characterize the excitability of hippocampal subregions in the chronic phase of the induced epilepsy in the IHKA mouse model. We recorded field postsynaptic potentials (fPSPs) after electrical stimulation in the CA1 region and in the dentate gyrus (DG) of hippocampal slices of IHKA and healthy mice using a multielectrode array (MEA). In the DG, a significantly steeper fPSP slope was found, reflecting higher synaptic strength. Population spikes were more prevalent with a larger spatial distribution in the IHKA group, reflecting a higher degree of granule cell output. Only minor differences were found in the CA1 region. These results point to increased neuronal excitability in the DG but not in the CA1 region of the hippocampus of IHKA mice. This method, in which the excitability of hippocampal slices from IHKA mice is investigated using a MEA, can now be further explored as a potential new model to screen for new interventions that can restore DG function and potentially lead to novel therapies for mTLE.

MiR-324-5p inhibition after intrahippocampal kainic acid-induced status epilepticus does not prevent epileptogenesis in mice

Background

Acquired epilepsies are caused by an initial brain insult that is followed by epileptogenesis and finally the development of spontaneous recurrent seizures. The mechanisms underlying epileptogenesis are not fully understood. MicroRNAs regulate mRNA translation and stability and are frequently implicated in epilepsy. For example, antagonism of a specific microRNA, miR-324-5p, before brain insult and in a model of chronic epilepsy decreases seizure susceptibility and frequency, respectively. Here, we tested whether antagonism of miR-324-5p during epileptogenesis inhibits the development of epilepsy.

Methods

We used the intrahippocampal kainic acid (IHpKa) model to initiate epileptogenesis in male wild type C57BL/6 J mice aged 6-8 weeks. Twenty-four hours after IHpKa, we administered a miR-324-5p or scrambled control antagomir intracerebroventricularly and implanted cortical surface electrodes for EEG monitoring. EEG data was collected for 28 days and analyzed for seizure frequency and duration, interictal spike activity, and EEG power. Brains were collected for histological analysis.

Results

Histological analysis of brain tissue showed that IHpKa caused characteristic hippocampal damage in most mice regardless of treatment. Antagomir treatment did not affect latency to, frequency, or duration of spontaneous recurrent seizures or interictal spike activity but did alter the temporal development of frequency band-specific EEG power.

Conclusion

These results suggest that miR-324-5p inhibition during epileptogenesis induced by status epilepticus does not convey anti-epileptogenic effects despite having subtle effects on EEG frequency bands. Our results highlight the importance of timing of intervention across epilepsy development and suggest that miR-324-5p may act primarily as a proconvulsant rather than a pro-epileptogenic regulator.

NCBP1 Improves Cognitive Function in Mice by Reducing Oxidative Stress, Neuronal Loss, and Glial Activation After Status Epilepticus

Status epilepticus (SE) is a severe manifestation of epilepsy which can cause neurologic injury and death. This study aimed to identify key proteins involved in the pathogenesis of epilepsy and find a potential drug target for SE treatment. Tandem mass tag (TMT)-based quantitative proteomic analysis was applied to screen differentially expressed proteins (DEPs) in epilepsy. The adeno-associated virus was employed to overexpress candidate DEP in mice, and kainic acid (KA) was used to generate a mouse model of epilepsy. Then histopathological examination of the hippocampal tissue was performed, and the inflammatory factors levels in serum and hippocampus were measured. The IP-MS analysis was carried out to identify the interacting protein of nuclear cap-binding protein 1 (NCBP1). The results were that NCBP1 was downregulated in the epileptic hippocampus. NCBP1 overexpression alleviated KA-induced cognitive impairment in mice and reduced the apoptosis and damage of hippocampal neurons. Additionally, overexpressed NCBP1 increased the expression of NeuN and reduced the expression of GFAP and IBA-1 in the hippocampus of the mice. Further study indicated that NCBP1 overexpression inhibited the expression of IL-6, IL-1β, and IFN-γ in serum and hippocampus as well as MDA and LDH in the hippocampus, whereas it increased the SOD levels, suggesting that overexpression of NCBP1 could diminish KA-induced inflammatory responses and oxidative stress. The IP-MS analysis identified that ELAVL4 was the NCBP1-interacting protein. In conclusion, this finding suggests that NCBP1 may potentially serve as a drug target for the treatment of epilepsy.

Human pallial MGE-type GABAergic interneuron cell therapy for chronic focal epilepsy

Mesial temporal lobe epilepsy (MTLE) is the most common focal epilepsy. One-third of patients have drug-refractory seizures and are left with suboptimal therapeutic options such as brain tissue-destructive surgery. Here, we report the development and characterization of a cell therapy alternative for drug-resistant MTLE, which is derived from a human embryonic stem cell line and comprises cryopreserved, post-mitotic, medial ganglionic eminence (MGE) pallial-type GABAergic interneurons. Single-dose intrahippocampal delivery of the interneurons in a mouse model of chronic MTLE resulted in consistent mesiotemporal seizure suppression, with most animals becoming seizure-free and surviving longer. The grafted interneurons dispersed locally, functionally integrated, persisted long term, and significantly reduced dentate granule cell dispersion, a pathological hallmark of MTLE. These disease-modifying effects were dose-dependent, with a broad therapeutic range. No adverse effects were observed. These findings support an ongoing phase 1/2 clinical trial (NCT05135091) for drug-resistant MTLE.

Lestaurtinib (CEP-701) reduces the duration of limbic status epilepticus in periadolescent rats

BACKGROUND

The timely abortion of status epilepticus (SE) is essential to avoid brain damage and long-term neurodevelopmental sequalae. However, available anti-seizure treatments fail to abort SE in 30% of children. Given the role of the tropomyosin-related kinase B (TrkB) receptor in hyperexcitability, we investigated if TrkB blockade with lestaurtinib (CEP-701) enhances the response of SE to a standard treatment protocol and reduces SE-related brain injury.

METHODS

SE was induced with intra-amygdalar kainic acid in postnatal day 45 rats under continuous electroencephalogram (EEG). Fifteen min post-SE onset, rats received intraperitoneal (i.p.) CEP-701 (KCEP group) or its vehicle (KV group). Controls received CEP-701 or its vehicle following intra-amygdalar saline. All groups received two i.p. doses of diazepam, followed by i.p. levetiracetam at 15 min intervals post-SE onset. Hippocampal TrkB dimer to monomer ratios were assessed by immunoblot 24 hr post-SE, along with neuronal densities and glial fibrillary acid protein (GFAP) levels.

RESULTS

SE duration was 50% shorter in the KCEP group compared to KV (p < 0.05). Compared to controls, SE induced a 1.5-fold increase in TrkB dimerization in KV rats (p < 0.05), but not in KCEP rats which were comparable to controls (p > 0.05). The KCEP group had lower GFAP levels than KV (p < 0.05), and both were higher than controls (p < 0.05). KCEP and KV rats had comparable hippocampal neuronal densities (p > 0.05), and both were lower than controls (p < 0.05).

CONCLUSIONS

Given its established human safety, CEP-701 is a promising adjuvant drug for the timely abortion of SE and the attenuation of SE-related brain injury.

Toward the use of novel alternative methods in epilepsy modeling and drug discovery

Epilepsy is a chronic brain disease and, considering the amount of people affected of all ages worldwide, one of the most common neurological disorders. Over 20 novel antiseizure medications (ASMs) have been released since 1993, yet despite substantial advancements in our understanding of the molecular mechanisms behind epileptogenesis, over one-third of patients continue to be resistant to available therapies. This is partially explained by the fact that the majority of existing medicines only address seizure suppression rather than underlying processes. Understanding the origin of this neurological illness requires conducting human neurological and genetic studies. However, the limitation of sample sizes, ethical concerns, and the requirement for appropriate controls (many patients have already had anti-epileptic medication exposure) in human clinical trials underscore the requirement for supplemental models. So far, mammalian models of epilepsy have helped to shed light on the underlying causes of the condition, but the high costs related to breeding of the animals, low throughput, and regulatory restrictions on their research limit their usefulness in drug screening. Here, we present an overview of the state of art in epilepsy modeling describing gold standard animal models used up to date and review the possible alternatives for this research field. Our focus will be mainly on ex vivo, in vitro, and in vivo larval zebrafish models contributing to the 3R in epilepsy modeling and drug screening. We provide a description of pharmacological and genetic methods currently available but also on the possibilities offered by the continued development in gene editing methodologies, especially CRISPR/Cas9-based, for high-throughput disease modeling and anti-epileptic drugs testing.

Animal Models of Drug-Resistant Epilepsy as Tools for Deciphering the Cellular and Molecular Mechanisms of Pharmacoresistance and Discovering More Effective Treatments

In the last 30 years, over 20 new anti-seizure medicines (ASMs) have been introduced into the market for the treatment of epilepsy using well-established preclinical seizure and epilepsy models. Despite this success, approximately 20-30% of patients with epilepsy have drug-resistant epilepsy (DRE). The current approach to ASM discovery for DRE relies largely on drug testing in various preclinical model systems that display varying degrees of ASM drug resistance. In recent years, attempts have been made to include more etiologically relevant models in the preclinical evaluation of a new investigational drug. Such models have played an important role in advancing a greater understanding of DRE at a mechanistic level and for hypothesis testing as new experimental evidence becomes available. This review provides a critical discussion of the pharmacology of models of adult focal epilepsy that allow for the selection of ASM responders and nonresponders and those models that display a pharmacoresistance per se to two or more ASMs. In addition, the pharmacology of animal models of major genetic epilepsies is discussed. Importantly, in addition to testing chemical compounds, several of the models discussed here can be used to evaluate other potential therapies for epilepsy such as neurostimulation, dietary treatments, gene therapy, or cell transplantation. This review also discusses the challenges associated with identifying novel therapies in the absence of a greater understanding of the mechanisms that contribute to DRE. Finally, this review discusses the lessons learned from the profile of the recently approved highly efficacious and broad-spectrum ASM cenobamate.

Long-term outcomes of classic and novel anti-seizure medication in a kainate-induced model of chronic epilepsy

OBJECTIVE

Intrahippocampal injection of kainate (KA) is a reliable model of temporal lobe epilepsy (TLE) that replicates spontaneous recurrent seizures. Both electrographic seizures and electroclinical seizure (most generalized seizure) can be detected in KA model. Electrographic seizures such as high-voltage sharp waves (HVSWs) and hippocampal paroxysmal discharges (HPDs) are far more common and attracting much attention. A comprehensive study on the anticonvulsant effects of classic and novel antiseizure medications (ASMs) on spontaneous electroclinical seizures, especially during long-term treatment, is still lacking. Here, we evaluated the effects of six ASMs in this model on electroclinical seizures over eight weeks.

METHODS

Using 24-hour continuous electroencephalographical (EEG) monitoring in free-moving mice, we tested the effectiveness of six ASMs (valproic acid, VPA; carbamazepine, CBZ; lamotrigine, LTG; perampanel, PER; brivaracetam, BRV; and everolimus, EVL) on the electroclinical seizures over eight weeks in the intrahippocampal kainate mouse model.

RESULTS

VPA, CBZ, LTG, PER and BRV significantly suppressed electroclinical seizures in the early stages of treatment, but the mice gradually developed resistance to these drugs. Overall, the mean frequency of electroclinical seizures was not significantly lower during the 8-week treatment than that at baseline in any ASM-treated group. The individual responses to ASMs varied widely.

CONCLUSION

Long-term treatment with VPA, LTG, CBZ, PER, BRV and EVL did not relieve electroclinical seizures in this TLE model. Additionally, the window for screening new ASMs in this model should be set to at least 3 weeks to account for drug resistance.

The Glycolysis Inhibitor 2-Deoxy-D-Glucose Exerts Different Neuronal Effects at Circuit and Cellular Levels, Partially Reverses Behavioral Alterations and does not Prevent NADPH Diaphorase Activity Reduction in the Intrahippocampal Kainic Acid Model of Temporal Lobe Epilepsy

Temporal lobe epilepsy is the most drug-resistant type with the highest incidence among the other focal epilepsies. Metabolic manipulations are of great interest among others, glycolysis inhibitors like 2-deoxy D-glucose (2-DG) being the most promising intervention. Here, we sought to investigate the effects of 2-DG treatment on cellular and circuit level electrophysiological properties using patch-clamp and local field potentials recordings and behavioral alterations such as depression and anxiety behaviors, and changes in nitric oxide signaling in the intrahippocampal kainic acid model. We found that epileptic animals were less anxious, more depressed, with more locomotion activity. Interestingly, by masking the effect of increased locomotor activity on the parameters of the zero-maze test, no altered anxiety behavior was noted in epileptic animals. However, 2-DG could partially reverse the behavioral changes induced by kainic acid. The findings also showed that 2-DG treatment partially suppresses cellular level alterations while failing to reverse circuit-level changes resulting from kainic acid injection. Analysis of NADPH-diaphorase positive neurons in the CA1 area of the hippocampus revealed that the number of positive neurons was significantly reduced in dorsal CA1 of the epileptic animals and 2-DG treatment did not affect the diminishing effect of kainic acid on NADPH-d+ neurons in the CA1 area. In the control group receiving 2-DG, however, an augmented NADPH-d+ cell number was noted. These data suggest that 2-DG cannot suppress epileptiform activity at the circuit-level in this model of epilepsy and therefore, may fail to control the seizures in temporal lobe epilepsy cases.

Sleep-deprived electroencephalography, a forgotten investigation in psychiatry; a case series

OBJECTIVES

Many patients with psychiatric disorders may have epileptic disorders; however, clinical diagnosis without imaging investigation may result in misdiagnosis and thus resistance to treatment. We investigated electroencephalography (EEG) abnormalities in the patients with psychiatric disorders referred to us with treatment resistance.

METHODS

In this case series study, nine patients with mood and psychotic symptoms who were referred to us at Belmont Private Hospital, Australia, from August 2018 to July 2020, were evaluated.

RESULTS

Complete examination showed the presence of undiagnosed temporal lobe epilepsy. Notably, the seizure symptoms had been assumed as part of other psychiatric co-morbidities.

CONCLUSIONS

This study suggests the necessity of paying attention to the biological etiologies of mental illnesses in the initial assessments in psychiatric and neurological practice. Performing electroencephalogram and treating such patients with mood stabilizers, which have antiepileptic properties, can change the course of the mental illness decisively.

Pronounced antiseizure activity of the subtype-selective GABAA positive allosteric modulator darigabat in a mouse model of drug-resistant focal epilepsy

Aim

Darigabat is an α2/3/5 subunit‐selective positive allosteric modulator of GABA_A receptors that has demonstrated broad‐spectrum activity in several preclinical models of epilepsy as well as in a clinical photoepilepsy trial. The objective here was to assess the acute antiseizure effect of darigabat in the mesial temporal lobe epilepsy (MTLE) mouse model of drug‐resistant focal seizures.

Methods

The MTLE model is generated by single unilateral intrahippocampal injection of low dose (1 nmole) kainic acid in adult mice, and subsequent epileptiform activity is recorded following implantation of a bipolar electrode under general anesthesia. After a period of epileptogenesis (~4 weeks), spontaneous and recurrent hippocampal paroxysmal discharges (HPD; focal seizures) are recorded using intracerebral electroencephalography. The number and cumulated duration of HPDs were recorded following administration of vehicle (PO), darigabat (0.3–10 mg kg⁻¹, PO), and positive control diazepam (2 mg kg⁻¹, IP).

RESULTS

Darigabat dose‐dependently reduced the expression of HPDs, demonstrating comparable efficacy profile to diazepam at doses of 3 and 10 mg kg⁻¹.

CONCLUSIONS

Darigabat exhibited a robust efficacy profile in the MTLE model, a preclinical model of drug‐resistant focal epilepsy. A Phase II proof‐of‐concept placebo‐controlled, adjunctive‐therapy trial (NCT04244175) is ongoing to evaluate efficacy and safety of darigabat in patients with drug‐resistant focal seizures.

Progress report on new antiepileptic drugs: A summary of the Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI): II. Drugs in more advanced clinical development

The Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI) was held in Madrid, Spain on May 22-25, 2022 and was attended by 157 delegates from 26 countries representing basic and clinical science, regulatory agencies, and pharmaceutical industries. One day of the conference was dedicated to sessions presenting and discussing investigational compounds under development for the treatment of seizures and epilepsy. The current progress report summarizes recent findings and current knowledge for seven of these compounds in more advanced clinical development for which either novel preclinical or patient data are available. These compounds include bumetanide and its derivatives, darigabat, ganaxolone, lorcaserin, soticlestat, STK-001, and XEN1101. Of these, ganaxolone was approved by the US Food and Drug Administration in March 2022 for the treatment of seizures associated with cyclin-dependent kinase-like 5 deficiency disorder in patients 2 years of age and older.

Miconazole exerts disease-modifying effects during epilepsy by suppressing neuroinflammation via NF-κB pathway and iNOS production

Neuroinflammation contributes to the generation of epilepsy and has been proposed as an effective therapeutic target. Recent studies have uncovered the potential effects of the anti-fungal drug miconazole for treating various brain diseases by suppressing neuroinflammation but have not yet been studied in epilepsy. Here, we investigated the effects of different doses of miconazole (5, 20, 80 mg/kg) on seizure threshold, inflammatory cytokines release, and glial cells activation in the pilocarpine (PILO) pentylenetetrazole (PTZ), and intrahippocampal kainic acid (IHKA) models. We demonstrated that 5 and 20 mg/kg miconazole increased seizure threshold, but only 20 mg/kg miconazole reduced inflammatory cytokines release, glial cells activation, and morphological alteration during the early post-induction period (24 h, 3 days). We further investigated the effects of 20 mg/kg miconazole on epilepsy (4 weeks after KA injection). We found that miconazole significantly attenuated cytokines production, glial cells activation, microglial morphological changes, frequency and duration of recurrent hippocampal paroxysmal discharges (HPDs), and neuronal and synaptic damage in the hippocampus during epilepsy. In addition, miconazole suppressed the KA-induced activation of the NF-κB pathway and iNOS production. Our results indicated miconazole to be an effective drug for disease-modifying effects during epilepsy, which may act by attenuating neuroinflammation through the suppression of NF-κB activation and iNOS production. At appropriate doses, miconazole may be a safe and effective approved drug that can easily be repositioned for clinical practice.

Spontaneous recurrent seizures in an intra-amygdala kainate microinjection model of temporal lobe epilepsy are differentially sensitive to antiseizure drugs

The discovery and development of novel antiseizure drugs (ASDs) that are effective in controlling pharmacoresistant spontaneous recurrent seizures (SRSs) continues to represent a significant unmet clinical need. The Epilepsy Therapy Screening Program (ETSP) has undertaken efforts to address this need by adopting animal models that represent the salient features of human pharmacoresistant epilepsy and employing these models for preclinical testing of investigational ASDs. One such model that has garnered increased interest in recent years is the mouse variant of the Intra-Amygdala Kainate (IAK) microinjection model of mesial temporal lobe epilepsy (MTLE). In establishing a version of this model, several methodological variables were evaluated for their effect(s) on pertinent quantitative endpoints. Although administration of a benzodiazepine 40 min after kainate (KA) induced status epilepticus (SE) is commonly used to improve survival, data presented here demonstrates similar outcomes (mortality, hippocampal damage, latency periods, and 90-day SRS natural history) between mice given midazolam and those that were not. Using a version of this model that did not interrupt SE with a benzodiazepine, a 90-day natural history study was performed and survival, latency periods, SRS frequencies and durations, and SRS clustering data were quantified. Finally, an important step towards model adoption is to assess the sensitivities or resistances of SRSs to a panel of approved and clinically used ASDs. Accordingly, the following ASDs were evaluated for their effects on SRSs in these mice: phenytoin (20 mg/kg, b.i.d.), carbamazepine (30 mg/kg, t.i.d.), valproate (240 mg/kg, t.i.d.), diazepam (4 mg/kg, b.i.d.), and phenobarbital (25 and 50 mg/kg, b.i.d.). Valproate, diazepam, and phenobarbital significantly attenuated SRS frequency relative to vehicle controls at doses devoid of observable adverse behavioral effects. Only diazepam significantly increased seizure freedom. Neither phenytoin nor carbamazepine significantly altered SRS frequency or freedom under these experimental conditions. These data demonstrate that SRSs in this IAK model of MTLE are pharmacoresistant to two representative sodium channel-inhibiting ASDs (phenytoin and carbamazepine) and partially sensitive to GABA receptor modulating ASDs (diazepam and phenobarbital) or a mixed-mechanism ASD (valproate). Accordingly, this model is being incorporated into the NINDS-funded ETSP testing platform for treatment resistant epilepsy.

Chemogenetic Seizure Control with Clozapine and the Novel Ligand JHU37160 Outperforms the Effects of Levetiracetam in the Intrahippocampal Kainic Acid Mouse Model

Expression of inhibitory designer receptors exclusively activated by designer drugs (DREADDs) on excitatory hippocampal neurons in the hippocampus represents a potential new therapeutic strategy for drug-resistant epilepsy. To overcome the limitations of the commonly used DREADD agonist clozapine, we investigated the efficacy of the novel DREADD ligand JHU37160 in chemogenetic seizure suppression in the intrahippocampal kainic acid (IHKA) mouse model for temporal lobe epilepsy (TLE). In addition, seizure-suppressing effects of chemogenetics were compared to the commonly used anti-epileptic drug (AED), levetiracetam (LEV). Therefore, an adeno-associated viral vector was injected in the sclerotic hippocampus of IHKA mice to induce expression of a tagged inhibitory DREADD hM4Di or only a tag (control) specifically in excitatory neurons using the CamKIIα promoter. Subsequently, animals were treated with LEV (800 mg/kg), clozapine (0.1 mg/kg), and DREADD ligand JHU37160 (0.1 mg/kg) and the effect on spontaneous seizures was investigated. Clozapine and JHU37160-mediated chemogenetic treatment both suppressed seizures in DREADD-expressing IHKA mice. Clozapine treatment suppressed seizures up to 34 h after treatment, and JHU37160 effects lasted for 26 h after injection. Moreover, both compounds reduced the length of seizures that did occur after treatment up to 28 h and 18 h after clozapine and JHU37160, respectively. No seizure-suppressing effects were found in control animals using these ligands. Chemogenetic seizure treatment suppressed seizures during the first 30 min after injection, and seizures remained suppressed during 8 h following treatment. Chemogenetics thus outperformed effects of levetiracetam (p < 0.001), which suppressed seizure frequency with a maximum of 55 ± 9% for up to 1.5 h (p < 0.05). Only chemogenetic and not levetiracetam treatment affected the length of seizures after treatment (p < 0.001). These results show that the chemogenetic therapeutic strategy with either clozapine or JHU37160 effectively suppresses spontaneous seizures in the IHKA mouse model, confirming JHU37160 as an effective DREADD ligand. Moreover, chemogenetic therapy outperforms the effects of levetiracetam, indicating its potential to suppress drug-resistant seizures.

Pharmacoresponsiveness of spontaneous recurrent seizures and the comorbid sleep disorder of epileptic Kcna1-null mice

Drug resistant epilepsy affects ∼30% of people with epilepsy and is associated with epilepsy syndromes with frequent and multiple types of seizures, lesions or cytoarchitectural abnormalities, increased risk of mortality and comorbidities such as cognitive impairment and sleep disorders. A limitation of current preclinical models is that spontaneous seizures with comorbidities take time to induce and test, thus making them low-throughput. Kcna1-null mice exhibit all the characteristics of drug resistant epilepsy with spontaneous seizures and comorbidities occurring naturally; thus, we aimed to determine whether they also demonstrate pharmacoresistanct seizures and the impact of medications on their sleep disorder comorbidity. In this exploratory study, Kcna1-null mice were treated with one of four conventional antiseizure medications, carbamazepine, levetiracetam, phenytoin, and phenobarbital using a moderate throughput protocol (vehicle for 2 days followed by 2 days of treatment with high therapeutic doses selected based on published data in the 6 Hz model of pharmacoresistant seizures). Spontaneous recurrent seizures and vigilance states were recorded with video-EEG/EMG. Carbamazepine, levetiracetam and phenytoin had partial efficacy (67%, 75% and 33% were seizure free, respectively), whereas phenobarbital was fully efficacious and conferred seizure freedom to all mice. Thus, seizures of Kcna1-null mice appear to be resistant to three of the drugs tested. Levetiracetam failed to affect sleep architecture, carbamazepine and phenytoin had moderate effects, and phenobarbital, as predicted, restored sleep architecture. Data suggest Kcna1-null mice may be a moderate throughput model of drug resistant epilepsy useful in determining mechanisms of pharmacoresistance and testing novel therapeutic strategies.

Single-Target Versus Multi-Target Drugs Versus Combinations of Drugs With Multiple Targets: Preclinical and Clinical Evidence for the Treatment or Prevention of Epilepsy

Rationally designed multi-target drugs (also termed multimodal drugs, network therapeutics, or designed multiple ligands) have emerged as an attractive drug discovery paradigm in the last 10-20 years, as potential therapeutic solutions for diseases of complex etiology and diseases with significant drug-resistance problems. Such agents that modulate multiple targets simultaneously are developed with the aim of enhancing efficacy or improving safety relative to drugs that address only a single target or to combinations of single-target drugs. Although this strategy has been proposed for epilepsy therapy >25 years ago, to my knowledge, only one antiseizure medication (ASM), padsevonil, has been intentionally developed as a single molecular entity that could target two different mechanisms. This novel drug exhibited promising effects in numerous preclinical models of difficult-to-treat seizures. However, in a recent randomized placebo-controlled phase IIb add-on trial in treatment-resistant focal epilepsy patients, padsevonil did not separate from placebo in its primary endpoints. At about the same time, a novel ASM, cenobamate, exhibited efficacy in several randomized controlled trials in such patients that far surpassed the efficacy of any other of the newer ASMs. Yet, cenobamate was discovered purely by phenotype-based screening and its presumed dual mechanism of action was only described recently. In this review, I will survey the efficacy of single-target vs. multi-target drugs vs. combinations of drugs with multiple targets in the treatment and prevention of epilepsy. Most clinically approved ASMs already act at multiple targets, but it will be important to identify and validate new target combinations that are more effective in drug-resistant epilepsy and eventually may prevent the development or progression of epilepsy.

Reprogramming reactive glia into interneurons reduces chronic seizure activity in a mouse model of mesial temporal lobe epilepsy

Reprogramming brain-resident glial cells into clinically relevant induced neurons (iNs) is an emerging strategy toward replacing lost neurons and restoring lost brain functions. A fundamental question is now whether iNs can promote functional recovery in pathological contexts. We addressed this question in the context of therapy-resistant mesial temporal lobe epilepsy (MTLE), which is associated with hippocampal seizures and degeneration of hippocampal GABAergic interneurons. Using a MTLE mouse model, we show that retrovirus-driven expression of Ascl1 and Dlx2 in reactive hippocampal glia in situ, or in cortical astroglia grafted in the epileptic hippocampus, causes efficient reprogramming into iNs exhibiting hallmarks of interneurons. These induced interneurons functionally integrate into epileptic networks and establish GABAergic synapses onto dentate granule cells. MTLE mice with GABAergic iNs show a significant reduction in both the number and cumulative duration of spontaneous recurrent hippocampal seizures. Thus glia-to-neuron reprogramming is a potential disease-modifying strategy to reduce seizures in therapy-resistant epilepsy.

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Retroviruses target reactive hippocampal glia proliferating in a mouse model of mesial temporal lobe epilepsy

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Ascl1 and Dlx2 reprogram reactive glia into GABAergic interneurons in the epileptic hippocampus

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Induced interneurons establish GABAergic synapses onto dentate granule cells

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Induced interneurons reduce chronic epileptic activity in the hippocampus

Translational potential of the ghrelin receptor agonist macimorelin for seizure suppression in pharmacoresistant epilepsy

BACKGROUND

Current drugs for epilepsy affect seizures, but no antiepileptogenic or disease-modifying drugs are available that prevent or slow down epileptogenesis, which is characterized by neuronal cell loss, inflammation and aberrant network formation. Ghrelin and ghrelin receptor (ghrelin-R) agonists were previously found to exert anticonvulsant, neuroprotective and anti-inflammatory effects in seizure models and immediately after status epilepticus (SE). Therefore, the aim of this study was to assess whether the ghrelin-R agonist macimorelin is antiepileptogenic in the pharmacoresistant intrahippocampal kainic acid (IHKA) mouse model.

METHODS

SE was induced in C57BL/6 mice by unilateral IHKA injection. Starting 24 h after SE, mice were treated intraperitoneally with macimorelin (5 mg/kg) or saline twice daily for 2 weeks, followed by a 2-week wash-out. Mice were continuously electroencephalogram-monitored, and at the end of the experiment neuroprotection and gliosis were assessed.

RESULTS

Macimorelin significantly decreased the number and duration of seizures during the treatment period, but had no antiepileptogenic or disease-modifying effect in this dose regimen. While macimorelin did not significantly affect food intake or body weight over a 2-week treatment period, its acute orexigenic effect was preserved in epileptic mice but not in sham mice.

CONCLUSIONS

While the full ghrelin-R agonist macimorelin was not significantly antiepileptogenic nor disease-modifying, this is the first study to demonstrate its anticonvulsant effects in the IHKA model of drug-refractory temporal lobe epilepsy. These findings highlight the potential use of macimorelin as a novel treatment option for seizure suppression in pharmacoresistant epilepsy.

Medial septal GABAergic neurons reduce seizure duration upon optogenetic closed-loop stimulation

Seizures can emerge from multiple or large foci in temporal lobe epilepsy, complicating focally targeted strategies such as surgical resection or the modulation of the activity of specific hippocampal neuronal populations through genetic or optogenetic techniques. Here, we evaluate a strategy in which optogenetic activation of medial septal GABAergic neurons, which provide extensive projections throughout the hippocampus, is used to control seizures. We utilized the chronic intrahippocampal kainate mouse model of temporal lobe epilepsy, which results in spontaneous seizures and as is often the case in human patients, presents with hippocampal sclerosis. Medial septal GABAergic neuron populations were immunohistochemically labelled and were not reduced in epileptic conditions. Genetic labelling with mRuby of medial septal GABAergic neuron synaptic puncta and imaging across the rostral to caudal extent of the hippocampus, also indicated an unchanged number of putative synapses in epilepsy. Furthermore, optogenetic stimulation of medial septal GABAergic neurons consistently modulated oscillations across multiple hippocampal locations in control and epileptic conditions. Finally, wireless optogenetic stimulation of medial septal GABAergic neurons, upon electrographic detection of spontaneous hippocampal seizures, resulted in reduced seizure durations. We propose medial septal GABAergic neurons as a novel target for optogenetic control of seizures in temporal lobe epilepsy.

Long-term music adjuvant therapy enhances the efficacy of sub-dose antiepileptic drugs in temporal lobe epilepsy

Aims

Noninvasive music adjuvant therapy shows great potential in improving seizure control when combined with routine antiepileptic drugs. However, the diversity of previous music protocols has resulted in disparate outcomes. The optimized protocol and features for music adjuvant therapy are still not fully understood which limits its feasibility.

Methods

By applying different regimens of music therapy in various temporal lobe epilepsy models, we evaluated the effect of music in combination with sub‐dose drugs on epileptic seizures to determine the optimized protocol.

Results

A subgroup of kindled mice that were responsive to music adjuvant therapy was screened. In those mice, sub‐dose drugs which were noneffective on kindled seizures, alleviated seizure severity after 12 h/day Mozart K.448 for 14 days. Shorter durations of music therapy (2 and 6 h/day) were ineffective. Furthermore, only full‐length Mozart K.448, not its episodes or other music varieties, was capable of enhancing the efficacy of sub‐dose drugs. This music therapeutic effect was not due to increasing cerebral drug concentration, but instead was related with the modulation of seizure electroencephalogram (EEG) spectral powers in the hippocampus.

Conclusion

These results indicate that long‐term full‐length Mozart K.448 could enhance the anti‐seizure efficacy of sub‐dose drugs and may be a promising noninvasive adjuvant therapy for temporal lobe epilepsy.

Deletion of the Na-K-2Cl cotransporter NKCC1 results in a more severe epileptic phenotype in the intrahippocampal kainate mouse model of temporal lobe epilepsy

Increased neuronal expression of the Na-K-2Cl cotransporter NKCC1 has been implicated in the generation of seizures and epilepsy. However, conclusions from studies on the NKCC1-specific inhibitor, bumetanide, are equivocal, which is a consequence of the multiple potential cellular targets and poor brain penetration of this drug. Here, we used Nkcc1 knockout (KO) and wildtype (WT) littermate control mice to study the ictogenic and epileptogenic effects of intrahippocampal injection of kainate. Kainate (0.23 μg in 50 nl) induced limbic status epilepticus (SE) in both KO and WT mice with similar incidence, latency to SE onset, and SE duration, but the number of intermittent generalized convulsive seizures during SE was significantly higher in Nkcc1 KO mice, indicating increased SE severity. Following SE, spontaneous recurrent seizures (SRS) were recorded by continuous (24/7) video/EEG monitoring at 0-1, 4-5, and 12-13 weeks after kainate, using depth electrodes in the ipsilateral hippocampus. Latency to onset of electrographic SRS and the incidence of electrographic SRS were similar in WT and KO mice. However, the frequency of electrographic seizures was lower whereas the frequency of electroclinical seizures was higher in Nkcc1 KO mice, indicating a facilitated progression from electrographic to electroclinical seizures during chronic epilepsy, and a more severe epileptic phenotype, in the absence of NKCC1. The present findings suggest that NKCC1 is dispensable for the induction, progression and manifestation of epilepsy, and they do not support the widely held notion that inhibition of NKCC1 in the brain is a useful strategy for preventing or modifying epilepsy.

Hippocampal low-frequency stimulation prevents seizure generation in a mouse model of mesial temporal lobe epilepsy

Mesial temporal lobe epilepsy (MTLE) is the most common form of focal, pharmacoresistant epilepsy in adults and is often associated with hippocampal sclerosis. Here, we established the efficacy of optogenetic and electrical low-frequency stimulation (LFS) in interfering with seizure generation in a mouse model of MTLE. Specifically, we applied LFS in the sclerotic hippocampus to study the effects on spontaneous subclinical and evoked generalized seizures. We found that stimulation at 1 Hz for 1 hr resulted in an almost complete suppression of spontaneous seizures in both hippocampi. This seizure-suppressive action during daily stimulation remained stable over several weeks. Furthermore, LFS for 30 min before a pro-convulsive stimulus successfully prevented seizure generalization. Finally, acute slice experiments revealed a reduced efficacy of perforant path transmission onto granule cells upon LFS. Taken together, our results suggest that hippocampal LFS constitutes a promising approach for seizure control in MTLE.

Systematic evaluation of rationally chosen multitargeted drug combinations: a combination of low doses of levetiracetam, atorvastatin and ceftriaxone exerts antiepileptogenic effects in a mouse model of acquired epilepsy

Epileptogenesis, the gradual process that leads to epilepsy after brain injury or genetic mutations, is a complex network phenomenon, involving a variety of morphological, biochemical and functional brain alterations. Although risk factors for developing epilepsy are known, there is currently no treatment available to prevent epilepsy. We recently proposed a multitargeted, network-based approach to prevent epileptogenesis by rationally combining clinically available drugs and provided first proof-of-concept that this strategy is effective. Here we evaluated eight novel rationally chosen combinations of 14 drugs with mechanisms that target different epileptogenic processes. The combinations consisted of 2-4 different drugs per combination and were administered systemically over 5 days during the latent epileptogenic period in the intrahippocampal kainate mouse model of acquired temporal lobe epilepsy, starting 6 h after kainate. Doses and dosing intervals were based on previous pharmacokinetic and tolerability studies in mice. The incidence and frequency of spontaneous electrographic and electroclinical seizures were recorded by continuous (24/7) video linked EEG monitoring done for seven days at 4 and 12 weeks post-kainate, i.e., long after termination of drug treatment. Compared to vehicle controls, the most effective drug combination consisted of low doses of levetiracetam, atorvastatin and ceftriaxone, which markedly reduced the incidence of electrographic seizures (by 60%; p<0.05) and electroclinical seizures (by 100%; p<0.05) recorded at 12 weeks after kainate. This effect was lost when higher doses of the three drugs were administered, indicating a synergistic drug-drug interaction at the low doses. The potential mechanisms underlying this interaction are discussed. We have discovered a promising novel multitargeted combination treatment for modifying the development of acquired epilepsy.

Modeling of post-traumatic epilepsy and experimental research aimed at its prevention

Research on the prevention of post-traumatic epilepsy (PTE) has seen remarkable advances regarding its physiopathology in recent years. From the search for biomarkers that might be used to indicate individual susceptibility to the development of new animal models and the investigation of new drugs, a great deal of knowledge has been amassed. Various groups have concentrated efforts in generating new animal models of traumatic brain injury (TBI) in an attempt to provide the means to further produce knowledge on the subject. Here we forward the hypothesis that restricting the search of biomarkers and of new drugs to prevent PTE by using only a limited set of TBI models might hamper the understanding of this relevant and yet not preventable medical condition.

In vivo γ-aminobutyric acid increase as a biomarker of the epileptogenic zone: An unbiased metabolomics approach

OBJECTIVE

Following surgery, focal seizures relapse in 20% to 50% of cases due to the difficulty of delimiting the epileptogenic zone (EZ) by current imaging or electrophysiological techniques. Here, we evaluate an unbiased metabolomics approach based on ex vivo and in vivo nuclear magnetic resonance spectroscopy (MRS) methods to discriminate the EZ in a mouse model of mesiotemporal lobe epilepsy (MTLE).

METHODS

Four weeks after unilateral injection of kainic acid (KA) into the dorsal hippocampus of mice (KA-MTLE model), we analyzed hippocampal and cortical samples with high-resolution magic angle spinning (HRMAS) magnetic resonance spectroscopy (MRS). Using advanced multivariate statistics, we identified the metabolites that best discriminate the injected dorsal hippocampus (EZ) and developed an in vivo MEGAPRESS MRS method to focus on the detection of these metabolites in the same mouse model.

RESULTS

Multivariate analysis of HRMAS data provided evidence that γ-aminobutyric acid (GABA) is largely increased in the EZ of KA-MTLE mice and is the metabolite that best discriminates the EZ when compared to sham and, more importantly, when compared to adjacent brain regions. These results were confirmed by capillary electrophoresis analysis and were not reversed by a chronic exposition to an antiepileptic drug (carbamazepine). Then, using in vivo noninvasive GABA-edited MRS, we confirmed that a high GABA increase is specific to the injected hippocampus of KA-MTLE mice.

SIGNIFICANCE

Our strategy using ex vivo MRS-based untargeted metabolomics to select the most discriminant metabolite(s), followed by in vivo MRS-based targeted metabolomics, is an unbiased approach to accurately define the EZ in a mouse model of focal epilepsy. Results suggest that GABA is a specific biomarker of the EZ in MTLE.

Drug Resistance in Epilepsy: Clinical Impact, Potential Mechanisms, and New Innovative Treatment Options

Epilepsy is a chronic neurologic disorder that affects over 70 million people worldwide. Despite the availability of over 20 antiseizure drugs (ASDs) for symptomatic treatment of epileptic seizures, about one-third of patients with epilepsy have seizures refractory to pharmacotherapy. Patients with such drug-resistant epilepsy (DRE) have increased risks of premature death, injuries, psychosocial dysfunction, and a reduced quality of life, so development of more effective therapies is an urgent clinical need. However, the various types of epilepsy and seizures and the complex temporal patterns of refractoriness complicate the issue. Furthermore, the underlying mechanisms of DRE are not fully understood, though recent work has begun to shape our understanding more clearly. Experimental models of DRE offer opportunities to discover, characterize, and challenge putative mechanisms of drug resistance. Furthermore, such preclinical models are important in developing therapies that may overcome drug resistance. Here, we will review the current understanding of the molecular, genetic, and structural mechanisms of ASD resistance and discuss how to overcome this problem. Encouragingly, better elucidation of the pathophysiological mechanisms underpinning epilepsies and drug resistance by concerted preclinical and clinical efforts have recently enabled a revised approach to the development of more promising therapies, including numerous potential etiology-specific drugs (“precision medicine”) for severe pediatric (monogenetic) epilepsies and novel multitargeted ASDs for acquired partial epilepsies, suggesting that the long hoped-for breakthrough in therapy for as-yet ASD-resistant patients is a feasible goal.

Digoxin enhances the effect of antiepileptic drugs with different mechanism of action in the pentylenetetrazole-induced seizures in mice

The worldwide prevalence of epilepsy with high percentage of multidrug-resistant patients make it urgent to find new approaches to treating, including the use of combinations of classic anticonvulsants with drugs that have an exclusively original mechanism of action, in particular digoxin. The aim of this work was to investigate the influence of low-dose digoxin on the anticonvulsant effect of sodium valproate, topiramate, levetiracetam, phenobarbital and clonazepam. A basic model of pentylenetetrazole-induced seizures in mice was used. Antiepileptic drugs were administered intragastrically in conditionally effective (ED₅₀) and sub-effective (½ ED₅₀) doses at 30 min, digoxin - subcutaneously at a dose of 0.8 mg/kg (¹/₁₀ LD₅₀) at 10-15 min before seizures induction. Pentylenetetrazole at a dose of 80 mg/kg was administered subcutaneously. Experimental data demonstrates that cardiac glycoside digoxin enhances the anticonvulsant activity of sodium valproate, topiramate, levetiracetam, phenobarbital and clonazepam in the model of pentylenetetrazole-induced seizures, providing a clear protective effect of their sub-effective doses. Digoxin may be a valuable component of adjuvant pharmacotherapy for epilepsy, as it reduces the doses of the classic AEDs without compromising the effectiveness of treatment.

The current approach of the Epilepsy Therapy Screening Program contract site for identifying improved therapies for the treatment of pharmacoresistant seizures in epilepsy

The Epilepsy Therapy Screening Program (ETSP), formerly known as the Anticonvulsant Screening Program (ASP), has played an important role in the preclinical evaluation of many of the antiseizure drugs (ASDs) that have been approved by the FDA and thus made available for the treatment of seizures. Recent changes to the animal models used at the contract site of the ETSP at the University of Utah have been implemented in an attempt to better model the unmet clinical needs of people with pharmacoresistant epilepsy and thus identify improved therapies. In this review, we describe the changes that have occurred over the last several years in the screening approach used at the contract site and, in particular, detail the pharmacology associated with several of the animal models and assays that are either new to the program or have been recently characterized in more depth. There is optimism that the refined approach used by the ETSP contract site, wherein etiologically relevant models that include those with spontaneous seizures are used, will identify novel, potentially disease modifying therapies for people with pharmacoresistant epilepsy and those at risk for developing epilepsy. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

A face-to-face comparison of the intra-amygdala and intrahippocampal kainate mouse models of mesial temporal lobe epilepsy and their utility for testing novel therapies

OBJECTIVE

Intracranial (intrahippocampal or intra-amygdala) administration of kainate in rodents leads to spatially restricted brain injury and development of focal epilepsy with characteristics that resemble mesial temporal lobe epilepsy. Such rodent models are used both in the search for more effective antiseizure drugs (ASDs) and in the development of antiepileptogenic strategies. However, it is not clear which of the models is best suited for testing different types of epilepsy therapies.

METHODS

In the present study, we performed a face-to-face comparison of the intra-amygdala kainate (IAK) and intrahippocampal kainate (IHK) mouse models using the same mouse inbred strain (C57BL/6). For comparison, some experiments were performed in mouse outbred strains.

RESULTS

Intra-amygdala kainate injection led to more severe status epilepticus and higher mortality than intrahippocampal injection. In male C57BL/6 mice, the latent period to spontaneous recurrent seizures (SRSs) was short or absent in both models, whereas a significantly longer latent period was determined in NMRI and CD-1 outbred mice. When SRSs were recorded from the ipsilateral hippocampus, relatively frequent electroclinical seizures were determined in the IAK model, whereas only infrequent electroclinical seizures but extremely frequent focal electrographic seizures were determined in the IHK model. As a consequence of the differences in SRS frequency, prolonged video-electroencephalographic monitoring and drug administration were needed for testing efficacy of the benchmark ASD carbamazepine in the IAK model, whereas acute drug testing was possible in the IHK model. In both models, carbamazepine was only effective at high doses, indicating ASD resistance to this benchmark drug.

SIGNIFICANCE

We found a variety of significant differences between the IAK and IHK models, which are important when deciding which of these models is best suited for studies on novel epilepsy therapies. The IAK model appears particularly interesting for studies on disease-modifying treatments, whereas the IHK model is well suited for studying the antiseizure activity of novel ASDs against difficult-to-treated focal seizures.

Long-term chemogenetic suppression of spontaneous seizures in a mouse model for temporal lobe epilepsy

OBJECTIVE

More than one-third of patients with temporal lobe epilepsy (TLE) continue to have seizures despite treatment with antiepileptic drugs, and many experience severe drug-related side effects, illustrating the need for novel therapies. Selective expression of inhibitory Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) allows cell-type-specific reduction of neuronal excitability. In this study, we evaluated the effect of chemogenetic suppression of excitatory pyramidal and granule cell neurons of the sclerotic hippocampus in the intrahippocampal mouse model (IHKA) for temporal lobe epilepsy.

METHODS

Intrahippocampal IHKA mice were injected with an adeno-associated viral vector carrying the genes for an inhibitory DREADD hM4Di in the sclerotic hippocampus or control vector. Next, animals were treated systemically with different single doses of clozapine-N-oxide (CNO) (1, 3, and 10 mg/kg) and clozapine (0.03 and 0.1 mg/kg) and the effect on spontaneous hippocampal seizures, hippocampal electroencephalography (EEG) power, fast ripples (FRs) and behavior in the open field test was evaluated. Finally, animals received prolonged treatment with clozapine for 3 days and the effect on seizures was monitored.

RESULTS

Treatment with both CNO and clozapine resulted in a robust suppression of hippocampal seizures for at least 15 hours only in DREADD-expressing animals. Moreover, total EEG power and the number of FRs were significantly reduced. CNO and/or clozapine had no effects on interictal hippocampal EEG, seizures, or locomotion/anxiety in the open field test in non-DREADD epileptic IHKA mice. Repeated clozapine treatment every 8 hours for 3 days resulted in almost complete seizure suppression in DREADD animals.

SIGNIFICANCE

This study shows the potency of chemogenetics to robustly and sustainably suppress spontaneous epileptic seizures and pave the way for an epilepsy therapy in which a systemically administered exogenous drug selectively modulates specific cell types in a seizure network, leading to a potent seizure suppression devoid of the typical drug-related side effects.

The mGlu7 receptor provides protective effects against epileptogenesis and epileptic seizures

Finding new targets to control or reduce seizure activity is essential to improve the management of epileptic patients. We hypothesized that activation of the pre-synaptic and inhibitory metabotropic glutamate receptor type 7 (mGlu7) reduces spontaneous seizures. We tested LSP2-9166, a recently developed mGlu7/4 agonist with unprecedented potency on mGlu7 receptors, in two paradigms of epileptogenesis. In a model of chemically induced epileptogenesis (pentylenetetrazole systemic injection), LSP2-9166 induces an anti-epileptogenic effect rarely observed in preclinical studies. In particular, we found a bidirectional modulation of seizure progression by mGlu4 and mGlu7 receptors, the latter preventing kindling. In the intra-hippocampal injection of kainic acid mouse model that mimics the human mesial temporal lobe epilepsy, we found that LSP2-9166 reduces seizure frequency and hippocampal sclerosis. LSP2-9166 also acts as an anti-seizure drug on established seizures in both models tested. Specific modulation of the mGlu7 receptor could represent a novel approach to reduce pathological network remodeling.

Herbal medicine for epilepsy seizures in Asia, Africa and Latin America: A systematic review

RELEVANCE

More than 70 million people suffer epilepsy worldwide. Low availability of anti-epileptic drugs, side-effects and drug-resistant epilepsy affect the quality of life of persons with epilepsy in countries with a poorly developed health system. Herbal medicine is frequently used for this neurological condition.

OBJECTIVES

The main objective was to provide a detailed analysis of Herbal Medicine used for neurological conditions related with epilepsy in Asia, Africa and Latin America. More broadly, this study aims to highlight species with assessed efficacy (cross-cultural use, pharmacological effects on models of epileptic seizures) and safety (toxicological data in laboratory) information, in order to point out species of interest for further studies. A critical assessment of models used in pharmacological evaluations was done.

MATERIALS AND METHODS

The systematic search for Herbal Medicine treatments for epilepsy was performed considering all the articles published until February 2017 through three scientific databases. It was made with MeSH terms and free text defining the epilepsy seizures and plant species. We included studies carried out in Asia, Africa and Latin America. All articles reporting the use of Herbal Medicine to treat epilepsy seizures and/or their pharmacological evaluation were retained for further analysis.

RESULTS

The search yielded 1886 articles, from 30 countries. Hundred and six articles published between 1982 and 2017 were included, corresponding to a total of 497 use reports for 351 plant species belonging to 106 families. Three hundred and seventy seven use reports corresponding to 264 species in ethnopharmacological surveys and 120 evaluation reports corresponding to 107 species were noted. Twenty-nine reports, for 29 species, combined both ethnopharmacological and pharmacological evaluation. Fifty eight studies originated from Africa, 35 studies from Asia and 18 from Latin America. Highest use report was noted for rhizomes of Acorus calamus L. (12 use report in 1 country) and leaves of Bacopa monnieri (L.) Wettst. (8 use report in 2 countries). Therefore these species display the highest use convergence. Regarding pharmacological evaluation most studied species were: Leonotis leonurus (L.) R.Br. (4 evaluation reports in 1 country), Uncaria rhynchophylla (Miq.) Miq. ex Havil. (3 evaluation reports in 2 countries) and Calotropis gigantea (L.) Dryand. (3 evaluation reports in 1 country). In vivo models of chronic epilepsy were more relevant than in vitro models or chemical models inducing acute seizures for pharmacological assessment.

CONCLUSION

Species with the highest use report were not those with pharmacological evaluation. It will be pertinent to assess the pharmacological effects and safety of medicinal plants used mostly by traditional healers on predictive models of seizures.

High-frequency oscillations and focal seizures in epileptic rodents

High-pass filtering (> 80 Hz) of EEG signals has enabled neuroscientists to analyze high-frequency oscillations (HFOs; i.e., ripples: 80-200 Hz and fast ripples: 250-500 Hz) in epileptic patients presenting with focal seizures and in animal models mimicking this condition. Evidence obtained from these studies indicate that HFOs mirror pathological network activity that may initiate and sustain ictogenesis and epileptogenesis. HFOs are observed in temporal lobe regions of epileptic animals during interictal periods but they also occur before seizure onset and during the ictal period, suggesting that they can pinpoint to the mechanisms of seizure generation. Accordingly, ripples and fast ripples predominate during two specific seizure onset patterns termed low-voltage fast and hypersynchronous, respectively. In this review we will: (i) summarize these experimental studies; (ii) consider the evolution of HFOs over time during epileptogenesis; (iii) address data obtained with optogenetic stimulating procedures both in vitro and in vivo, and (iv) take into account the impact of anti-epileptic drugs on HFOs. We expect these findings to contribute to understanding the neuronal mechanisms leading to ictogenesis and epileptogenesis thus leading to the development of mechanistically targeted anti-epileptic strategies.

A companion to the preclinical common data elements for pharmacologic studies in animal models of seizures and epilepsy. A Report of the TASK3 Pharmacology Working Group of the ILAE/AES Joint Translational Task Force

Preclinical pharmacology studies in animal models of seizures and epilepsy have provided a platform to identify more than 20 antiseizure drugs in recent decades. To minimize variability in lab‐to‐lab studies and to harmonize approaches to data collection and reporting methodology in pharmacologic evaluations of the next generation of therapies, we present common data elements (CDEs), case report forms (CRFs), and this companion manuscript to help with the implementation of methods for studies in established preclinical seizure and epilepsy models in adult rodents. The development of and advocacy for CDEs in preclinical research has been encouraged previously by both clinical and preclinical groups. It is anticipated that adoption and implementation of these CDEs in preclinical studies may help standardize approaches to minimize variability and increase the reproducibility of preclinical studies. Moreover, they may provide a methodologic framework for pharmacology studies in atypical animal models or models in development, which may ultimately promote novel therapy development. In the present document, we refer selectively to animal models that have a long history of preclinical use, and in some cases, are clinically validated.

A systems-level framework for drug discovery identifies Csf1R as an anti-epileptic drug target

The identification of drug targets is highly challenging, particularly for diseases of the brain. To address this problem, we developed and experimentally validated a general computational framework for drug target discovery that combines gene regulatory information with causal reasoning ("Causal Reasoning Analytical Framework for Target discovery"-CRAFT). Using a systems genetics approach and starting from gene expression data from the target tissue, CRAFT provides a predictive framework for identifying cell membrane receptors with a direction-specified influence over disease-related gene expression profiles. As proof of concept, we applied CRAFT to epilepsy and predicted the tyrosine kinase receptor Csf1R as a potential therapeutic target. The predicted effect of Csf1R blockade in attenuating epilepsy seizures was validated in three pre-clinical models of epilepsy. These results highlight CRAFT as a systems-level framework for target discovery and suggest Csf1R blockade as a novel therapeutic strategy in epilepsy. CRAFT is applicable to disease settings other than epilepsy.

Glial responses during epileptogenesis in Mus musculus point to potential therapeutic targets

The Mesio-Temporal Lobe Epilepsy syndrome is the most common form of intractable epilepsy. It is characterized by recurrence of focal seizures and is often associated with hippocampal sclerosis and drug resistance. We aimed to characterize the molecular changes occurring during the initial stages of epileptogenesis in search of new therapeutic targets for Mesio-Temporal Lobe Epilepsy. We used a mouse model obtained by intra-hippocampal microinjection of kainate and performed hippocampal whole genome expression analysis at 6h, 12h and 24h post-injection, followed by multilevel bioinformatics analysis. We report significant changes in immune and inflammatory responses, neuronal network reorganization processes and glial functions, predominantly initiated during status epilepticus at 12h and persistent after the end of status epilepticus at 24h post-kainate. Upstream regulator analysis highlighted Cyba, Cybb and Vim as central regulators of multiple overexpressed genes implicated in glial responses at 24h. In silico microRNA analysis indicated that miR-9, miR-19b, miR-129, and miR-223 may regulate the expression of glial-associated genes at 24h. Our data support the hypothesis that glial-mediated inflammatory response holds a key role during epileptogenesis, and that microglial cells may participate in the initial process of epileptogenesis through increased ROS production via the NOX complex.