Kainate-induced Status Epilepticus Research Articles

An aqueous extract of Syzygium cumini protects against kainate-induced status epilepticus and amnesia: evidence for antioxidant and anti-inflammatory intervention.

Temporal lobe epilepsy is the most common drug-resistant epilepsy. To cure epilepsy, drugs must target the mechanisms at the origin of seizures. Thus, the present investigation aimed to evaluate the antiepileptic- and anti-amnesic-like effects of an aqueous extract of Syzygium cumini against kainate-induced status epilepticus in mice, and possible mechanisms of action. Mice were divided into 7 groups and treated as follows: normal group or kainate group received po distilled water (10 mL/kg), four test groups received Syzygium cumini (28.8, 72, 144, and 288mg/kg, po), and the positive control group treated intraperitoneally (ip) with sodium valproate (300mg/kg). An extra group of normal mice was treated with piracetam (200mg/kg, po). Treatments were administered 60min before the induction of status epilepticus with kainate (15mg/kg, ip), and continued daily throughout behavioral testing. Twenty-four hours after the induction, T-maze and Morris water maze tasks were successively performed. The animals were then sacrificed and some markers of oxidative stress and neuroinflammation were estimated in the hippocampus. The extract significantly prevented status epilepticus and mortality. In the T-maze, the aqueous extract markedly increased the time spent and the number of entries in the discriminated arm. In the Morris water maze, the extract significantly increased the time spent in the target quadrant during the retention phase. Furthermore, the aqueous extract induced a significant reduction of oxidative stress and neuroinflammation. These results suggest that the aqueous extract of Syzygium cumini has antiepileptic- and anti-amnesic-like effects, likely mediated in part by antioxidant and anti-inflammatory activities.

Alix is required for activity-dependent bulk endocytosis at brain synapses.

In chemical synapses undergoing high frequency stimulation, vesicle components can be retrieved from the plasma membrane via a clathrin-independent process called activity-dependent bulk endocytosis (ADBE). Alix (ALG-2-interacting protein X/PDCD6IP) is an adaptor protein binding to ESCRT and endophilin-A proteins which is required for clathrin-independent endocytosis in fibroblasts. Alix is expressed in neurons and concentrates at synapses during epileptic seizures. Here, we used cultured neurons to show that Alix is recruited to presynapses where it interacts with and concentrates endophilin-A during conditions triggering ADBE. Using Alix knockout (ko) neurons, we showed that this recruitment, which requires interaction with the calcium-binding protein ALG-2, is necessary for ADBE. We also found that presynaptic compartments of Alix ko hippocampi display subtle morphological defects compatible with flawed synaptic activity and plasticity detected electrophysiologically. Furthermore, mice lacking Alix in the forebrain undergo less seizures during kainate-induced status epilepticus and reduced propagation of the epileptiform activity. These results thus show that impairment of ADBE due to the lack of neuronal Alix leads to abnormal synaptic recovery during physiological or pathological repeated stimulations.

Theta and gamma hippocampal–neocortical oscillations during the episodic-like memory test: Impairment in epileptogenic rats

Cortical oscillations in different frequency bands have been shown to be intimately involved in exploration of environment and cognition. Here, the local field potentials in the hippocampus, the medial prefrontal cortex (mPFC), and the medial entorhinal cortex (mEC) were recorded simultaneously in rats during the execution of the episodic-like memory task. The power of theta (~4–10 Hz), slow gamma (~25–50 Hz), and fast gamma oscillations (~55–100 Hz) was analyzed in all structures examined. Particular attention was paid to the theta coherence between three mentioned structures. The modulation of the power of gamma rhythms by the phase of theta cycle during the execution of the episodic-like memory test by rats was also closely studied. Healthy rats and rats one month after kainate-induced status epilepticus (SE) were examined. Paroxysmal activity in the hippocampus (high amplitude interictal spikes), excessive excitability of animals, and the death of hippocampal and dentate granular cells in rats with kainate-evoked SE were observed, which indicated the development of seizure focus in the hippocampus (epileptogenesis). One month after SE, the rats exhibited a specific impairment of episodic memory for the what-where-when triad: unlike healthy rats, epileptogenic SE animals did not identify the objects during the test. This impairment was associated with the changes in the characteristics of theta and gamma rhythms and specific violation of theta coherence and theta/gamma coupling in these structures in comparison with the healthy animals. We believe that these disturbances in the cortical areas play a role in episodic memory dysfunction in kainate-treated animals. These findings can shed light on the mechanisms of cognitive deficit during epileptogenesis.

Acetyl-L-Carnitine Exerts Neuroprotective and Anticonvulsant Effect in Kainate Murine Model of Temporal Lobe Epilepsy

The most well-known type of focal epilepsy that is resistant to existing treatments is temporal lobe epilepsy (TLE), with seizure foci in various structures including temporal lobe, hippocampus, amygdala, entorhinal cortex, and subcortex. The most significant processes involved in the pathophysiology of temporal lobe epilepsy (TLE) are oxidative stress, inflammation, and pyroptosis. There are evidences indicating that acetyl-l-carnitine (ALC) has anti-oxidative, anti-inflammatory, and anti-pyroptotic effects. In the present study, rat model of TLE was induced by intrahippocampal kainate and animals received ALC (100mg/kg, p.o.). ALC properly attenuated intensity of seizures and also incidence of kainate-induced status epilepticus (SE). As well, obtained findings showed that ALC can partially reverse hippocampal levels of MDA, ROS, SOD, TNFa, NF-kB, TLR4, GFAP, and caspase 1. Besides, treatment of kainate group with ALC exerted a protective effect against CA1 neuronal loss and abnormal mossy fiber sprouting (MFS). Conclusively, these results suggest that ALC is capable to attenuate kainate-induced SE which is somewhat mediated through its lowering of oxidative stress, neuroinflammation, and pyroptosis that are related to its neuroprotective effect.

Toward Evidence-Based Severity Assessment in Mouse Models with Repeated Seizures: (II.) Impact of Surgery and Intrahippocampal Kainate

Introduction: Chronic epilepsy models require neurosurgical procedures including depth electrode implants. The intrahippocampal kainate model is a frequently used chronic paradigm, which is based on chemoconvulsant administration and status epilepticus induction during the surgical procedure. This experimental approach raises the question of the extent to which this approach affects postsurgical recovery. In addition to the short- and long-term impact of the surgical intervention, a potential impact of highly frequent electrographic seizure events needs to be considered in the context of severity assessment. Methods: Various behavioral, biochemical, and telemetric parameters were analyzed in four experimental groups of mice: 1st naive, 2nd with transmitter implants, 3rd with transmitter and electrode implants, and 4th with transmitter implants, electrode implants, and kainate-induced status epilepticus. Results: During the early postsurgical phase, transmitter implants caused a transient impact on Mouse Grimace scores and intragroup increase of fecal corticosterone metabolites. Additional craniotomy was associated with an influence on total heart rate variability and fecal corticosterone metabolites. Heart rate and Irwin score increases as well as a prolonged increase in Mouse Grimace scores pointed to an added burden related to the induction of a nonconvulsive status epilepticus. Data from the chronic phase argued against a relevant influence of frequent electrographic seizures on behavioral patterns, fecal corticosterone metabolites, heart rate, and its variability. However, Irwin scores indicated long-term changes in some animals with increased reactivity, body tone, and Straub tail. Interestingly, selected behavioral and telemetric data from the early post-status epilepticus phase correlated with the frequency of electrographic seizure events in the chronic phase. Conclusion: In conclusion, our findings argue against the pronounced impact of highly frequent electrographic seizures on the well-being of mice. However, an increased level of nervousness in a subgroup of animals should be considered for handling procedures and refinement measures. In the early postsurgical phase, several parameters indicate an influence of the interventions with evidence that the nonconvulsive status epilepticus can negatively affect the recovery. Thus, the development and validation of refinement efforts should focus on this experimental phase. Finally, the datasets suggest that simple readout parameters may predict the long-term consequences of the epileptogenic insult. Respective biomarker candidates require further validation in the follow-up studies in models with subgroups of animals with or without epilepsy development.

The Anticonvulsant Effect of a Novel Indole-Related Compound in the Kainate-Induced Status Epilepticus in Mice: The Role of the Antioxidant and Anti-inflammatory Mechanism.

We synthesized a series of novel indole compounds containing aroylhydrazone moieties and evaluated them in mice to check their anticonvulsant activity. In the present study the most potent C3-modified derivative 3e, containing 2-furyl fragment was evaluated in kainate (KA)-induced status epilepticus (SE) and the consequences on oxidative stress and inflammation in the hippocampus in mice were explored. Melatonin was used as positive control while the melatonin receptor antagonist Luzindol was studied alone or in combination with melatonin or 3e, respectively. After intraperitoneal (i.p.) pre-treatment with melatonin 3e, Luzindol + melatonin and Luzindol + 3e for 7 days (melatonin and 3e-30mgkg-1 or 60mgkg-1, Luzindol 10mgkg-1) the animals were i.p. injected with KA (30mgkg-1, i.p.). The 3e decreased the SE-induced seizure intensity while melatonin suppressed seizures at the higher dose of 60mgkg-1. Luzindol blocked the anticonvulsant effect of both Mel and 3e. The dose-dependent antioxidant effect of 3e measured by reduced glutathione (GSH) and total GSH in the hippocampus, was comparable to the effect of melatonin. Luzindol fully blocked the effect of melatonin but affected partially the antioxidant activity of 3e. The KA-induced increased amplifier of neuroinflammation high-mobility group box protein 1 (HMGB1) was neither alleviated by melatonin, nor by 3e. The activation by this DNA-binding protein receptor for advanced glycation end products (RAGE) was not affected by SE, melatonin and 3e pre-treatment. Our results suggest that the novel indole derivate 3e, containing 2-furyl fragment, might be clinically useful as an adjunct therapy against SE and concomitant oxidative stress.

Dynamic alteration of dendrites and dendritic spines in the hippocampus and microglia in mouse brain tissues after kainate-induced status epilepticus

Purpose To study the alteration of microglial subtypes, the representative markers of microglia, and the morphology of dendrites and dendritic spines after acute status epilepticus (SE) and during recurrent seizures. Methods A mouse kainate-induced SE model was used. Dendrites and dendritic spines of granule neurons in the dentate gyrus (DG) subregion and pyramidal neurons in the cornu ammonis (CA)1 and cornu ammonis (CA)3 subregions of the hippocampus were visualized by Golgi staining. Synaptic proteins were evaluated by Western blot analysis, and microglia and their markers were evaluated by flow cytometry. Results Extensive partial spine loss was observed in the dendrites of granule and pyramidal cells in the acute and early chronic stages of SE. In terms of spine loss, the thin and mushroom types predominated. Accompanying the spine loss in these two stages, the proportion of M1 microglia increased significantly with high CX3CR1 expression and low CD200R expression. However, at the transiting stage, the proportion of M2 microglia was increased dramatically, and high expression levels of CXCR3 on all microglia and CD68 on M1 microglia were observed. Morris water maze tests revealed significant learning and memory impairment in the chronic phase of epilepsy. Conclusion Dendritic spines in the hippocampus and microglia in the central nevus system are dynamically altered in epilepsy during the establishment and maintenance of spontaneous seizures. Microglia may contribute to the spine loss and related learning and memory impairment.

Cardiac dysregulation following intrahippocampal kainate-induced status epilepticus

Status epilepticus (SE) is a prevalent disorder associated with significant morbidity, including the development of epilepsy and mortality. Cardiac arrhythmias (i.e. inappropriate sinus tachycardia and bradycardia, asystole, and atrioventricular blocks) are observed in patients following SE. We characterized ictal (during a seizure) and interictal (between seizure) cardiac arrhythmogenesis following SE using continuous electrocardiography and video electroencephalography (vEEG) recordings throughout a 14-day monitoring period in an intrahippocampal chemoconvulsant mouse model that develops epilepsy. We quantified heart rhythm abnormalities and examined whether the frequency of cardiac events correlated with epileptiform activity, circadian (light/dark) cycle, the presence of seizures, and survival during this period of early epileptogenesis (the development of epilepsy) following SE. Shortly following SE, mice developed an increased interictal heart rate and heart rhythm abnormalities (i.e. sinus pause and sinus arrhythmias) when compared to control mice. Heart rhythm abnormalities were more frequent during the light cycle and were not correlated with increased epileptiform activity or seizure frequency. Finally, SE animals had early mortality, and a death event captured during vEEG recording demonstrated severe bradycardia prior to death. These cardiac changes occurred within 14 days after SE and may represent an early risk factor for sudden death following SE.

The effects of ammonia stimulation on kainate-induced status epilepticus and anterior piriform cortex electrophysiology

ObjectiveStrong olfactory stimulation (OS) with such substances as toluene or ammonia has been reported to suppress seizures. We aimed to investigate the role of ammonia stimulation on acute kainic acid (KA)-induced seizures. We also investigated any possible effects of ammonia stimulation on the electrophysiology of the anterior piriform cortex (APC). MethodsAdult male Sprague–Dawley rats were implanted with bilateral hippocampal electrodes and an electrode in the left APC. Animals were exposed to either distilled water (control) or ammonia stimulation for 20 s every 5 min during KA induction of status epilepticus (SE). The electroencephalogram (EEG) was analyzed for seizure frequency, duration, severity, and total KA doses given prior to reaching SE. Seizure-free EEG epochs that coincided with OS were chosen and analyzed via wavelet analysis for any spectral changes. ResultsWe found no significant differences in seizure frequency, duration, severity, or administered KA doses before SE between the groups. In the experimental group, a wavelet analysis of variance (WANOVA) revealed a significant stimulation-induced increase of power in the delta and alpha bands prior to the first KA injection and higher power in the delta and theta bands after KA injection. ConclusionsWhereas the spectral analysis of the APC revealed specific OS-induced changes, our findings suggest that OS with ammonia does not result in altering the threshold of attaining KA-induced SE. This does not rule out a potential role for OS in reducing recurrent seizures in the KA or other epilepsy models.

Intranasally Administered Human MSC-Derived Extracellular Vesicles Pervasively Incorporate into Neurons and Microglia in both Intact and Status Epilepticus Injured Forebrain.

Extracellular vesicles (EVs) derived from human bone marrow mesenchymal stem cells (hMSCs) have great promise as biologics to treat neurological and neurodegenerative conditions due to their robust antiinflammatory and neuroprotective properties. Besides, intranasal (IN) administration of EVs has caught much attention because the procedure is noninvasive, amenable for repetitive dispensation, and leads to a quick penetration of EVs into multiple regions of the forebrain. Nonetheless, it is unknown whether brain injury-induced signals are essential for the entry of IN-administered EVs into different brain regions. Therefore, in this study, we investigated the distribution of IN-administered hMSC-derived EVs into neurons and microglia in the intact and status epilepticus (SE) injured rat forebrain. Ten billion EVs labeled with PKH26 were dispensed unilaterally into the left nostril of naïve rats, and rats that experienced two hours of kainate-induced SE. Six hours later, PKH26 + EVs were quantified from multiple forebrain regions using serial brain sections processed for different neural cell markers and confocal microscopy. Remarkably, EVs were seen bilaterally in virtually all regions of intact and SE-injured forebrain. The percentage of neurons incorporating EVs were comparable for most forebrain regions. However, in animals that underwent SE, a higher percentage of neurons incorporated EVs in the hippocampal CA1 subfield and the entorhinal cortex, the regions that typically display neurodegeneration after SE. In contrast, the incorporation of EVs by microglia was highly comparable in every region of the forebrain measured. Thus, unilateral IN administration of EVs is efficient for delivering EVs bilaterally into neurons and microglia in multiple regions in the intact or injured forebrain. Furthermore, incorporation of EVs by neurons is higher in areas of brain injury, implying that injury-related signals likely play a role in targeting of EVs into neurons, which may be beneficial for EV therapy in various neurodegenerative conditions including traumatic brain injury, stroke, multiple sclerosis, and Alzheimer’s disease.

Effect of Exercise Interventions on Kainate Induced Status Epilepticus and Associated Co-morbidities; A Systematic Review and Meta-Analysis

To conduct a systematic review and meta-analysis of studies testing the effect of exercise in Kainic-acid (KA) induced status-epilepticus (SE) and to quantify the efficacy of exercise strategies in the prognosis of SE and co-morbidities. Two authors searched online databases (Pubmed and Web of Science) independently for studies testing the efficacy of exercise programs in KA-induced SE models. Reviewers autonomously extracted data on models used, exercise interventions and prognosis in all reported outcomes (behavioral, histological, biochemical and cognitive outcomes). All studies were summarized and relevant outcomes' data were pooled by means of a meta-analysis. Among 14 selected studies; Quantitative analysis of studies with pre-SE exercise interventions showed significant reduction in mortality rate among 76 animals of four studies (RR = 0.57, [95% CI 0.34, 0.95], p = 0.03, I2 = 57%) and seizure rating score among three studies (n = 56) with MD = - 1.04, [95% CI - 2.07, - 0.00], p = 0.05, I2 = 71%. Three studies (n = 62) presented with improved anti-oxidant enzymes' profile (SMD = 0.75, [95% CI 0.55, 2.31], p = 0.0008, I2 = 44%) as a result of exercise intervention. Same intervention failed to show any significant measure for BDNF level and neuroprotection assessed through neuronal number in different brain areas with MD = - 1.22, [95% CI - 136.66, 134.22], p = 0.99, I2 = 0% and SMD = - 0.05, [95% CI - 0.62, 0.52], p = 0.86, I2 = 61% respectively. Qualitative review concluded in the reduction of median seizure score, depression and anxiety-like behaviors with improved cognitive performances in pre-SE exercised animals while improved memory and learning capabilities with increased neurogenesis were observed in post-SE exercised models. Exercise before SE reduces behavioral seizures and oxidative stress with improvements in cognitive abilities. Post-SE exercise enhances learning and memory with neurogenesis in KA models. More extensive research on morphological and biochemical profiles is needed to explore underlying mechanisms.

Suppressing pro-inflammatory prostaglandin signaling attenuates excitotoxicity-associated neuronal inflammation and injury

Glutamate receptor-mediated excitotoxicity is a common pathogenic process in many neurological conditions including epilepsy. Prolonged seizures induce elevations in extracellular glutamate that contribute to excitotoxic damage, which in turn can trigger chronic neuroinflammatory reactions, leading to secondary damage to the brain. Blocking key inflammatory pathways could prevent such secondary brain injury following the initial excitotoxic insults. Prostaglandin E2 (PGE2) has emerged as an important mediator of neuroinflammation-associated injury, in large part via activating its EP2 receptor subtype. Herein, we investigated the effects of EP2 receptor inhibition on excitotoxicity-associated neuronal inflammation and injury in vivo. Utilizing a bioavailable and brain-permeant compound, TG6-10-1, we found that pharmacological inhibition of EP2 receptor after a one-hour episode of kainate-induced status epilepticus (SE) in mice reduced seizure-promoted functional deficits, cytokine induction, reactive gliosis, blood-brain barrier impairment, and hippocampal damage. Our preclinical findings endorse the feasibility of blocking PGE2/EP2 signaling as an adjunctive strategy to treat prolonged seizures. The promising benefits from EP2 receptor inhibition should also be relevant to other neurological conditions in which excitotoxicity-associated secondary damage to the brain represents a pathogenic event.

AMPA receptors and seizures mediate hippocampal radial glia-like stem cell proliferation.

Neurogenesis is sustained throughout life in the mammalian brain, supporting hippocampus-dependent learning and memory. Its permanent alteration by status epilepticus (SE) is associated with learning and cognitive impairments. The mechanisms underlying the initiation of altered neurogenesis after SE are not understood. Glial fibrillary acidic protein-positive radial glia (RG)-like cells proliferate early after SE, but their proliferation dynamics and signaling are largely unclear. We have previously reported a polarized distribution of AMPA receptors (AMPARs) on RG-like cells in vivo and postulated that these may signal their proliferation. Here, we examined the acute effects of kainate on hippocampal precursor cells in vitro and in kainate-induced SE on proliferating and quiescent clones of 5-bromo-2-deoxyuridine prelabeled hippocampal precursors in vivo. In vitro, we found that 5 μM kainate shortened the cell cycle time of RG-like cells via AMPAR activation and accelerated cell cycle re-entry of their progeny. It also shifted their fate choice expanding the population of RG-like cells and reducing the population of downstream amplifying neural progenitors. Kainate enhanced the survival of all precursor cell subtypes. Pharmacologically, kainate's proliferative and survival effects were abolished by AMPAR blockade. Functional AMPAR expression was confirmed on RG-like cells in vitro. In agreement with these observations, kainate/seizures enhanced the proliferation and expansion predominantly of constitutively cycling RG-like cell clones in vivo. Our results identify AMPARs as key potential players in initiating the proliferation of dentate RG-like cells and unravel a possible receptor target for modifying the radial glia-like cell response to SE.

Recurrent epileptiform discharges in the medial entorhinal cortex of kainate-treated rats are differentially sensitive to antiseizure drugs.

Approximately 30% of patients with epilepsy are refractory to existing antiseizure drugs (ASDs). Given that the properties of the central nervous systems of these patients are likely to be altered due to their epilepsy, tissues from rodents that have undergone epileptogenesis might provide a therapeutically relevant disease substrate for identifying compounds capable of attenuating pharmacoresistant seizures. To facilitate the development of such a model, this study describes the effects of classical glutamate receptor antagonists and 20 ASDs on recurrent epileptiform discharges (REDs) in brain slices derived from the kainate-induced status epilepticus model of temporal lobe epilepsy (KA-rats). Horizontal brain slices containing the medial entorhinal cortex (mEC) were prepared from KA-rats, and REDs were recorded from the superficial layers. 6-cyano-7-nitroquinoxaline-2,3-dione, (2R)-amino-5-phosphonovaleric acid, tetrodotoxin, or ASDs were bath applied for 20minutes. Concentration-dependent effects and half maximal effective concentration values were determined for RED duration, frequency, and amplitude. ASDs targeting sodium and potassium channels (carbamazepine, eslicarbazepine, ezogabine, lamotrigine, lacosamide, phenytoin, and rufinamide) attenuated REDs at concentrations near their average therapeutic plasma concentrations. γ-aminobutyric acid (GABA)ergic synaptic transmission-modulating ASDs (clobazam, midazolam, phenobarbital, stiripentol, tiagabine, and vigabatrin) attenuated REDs only at higher concentrations and, in some cases, prolonged RED durations. ASDs with other/mixed mechanisms of action (bumetanide, ethosuximide, felbamate, gabapentin, levetiracetam, topiramate, and valproate) and glutamate receptor antagonists weakly or incompletely inhibited RED frequency, increased RED duration, or had no significant effects. Taken together, these data suggest that epileptiform activity recorded from the superficial layers of the mEC in slices obtained from KA-rats is differentially sensitive to existing ASDs. The different sensitivities of REDs to these ASDs may reflect persistent molecular, cellular, and/or network-level changes resulting from disease. These data are expected to serve as a foundation upon which future therapeutics may be differentiated and assessed for potentially translatable efficacy in patients with refractory epilepsy.

RASgrf1, a Potential Methylatic Mediator of Anti-epileptogenesis?

Epileptogenesis, induced by status epilepticus (SE), is a chronic process, and intervention in this progress may prevent chronic epilepsy. It has been proposed that DNA methylation might be related with epileptogenesis. RASgrf1 has a differentially methylated region at the promoter which can silence gene expression. We have previously observed the down-regulation of RASgrf1 in epilepsy patients and proved that hypermethylation of RASgrf1 reaches maximal level at the latent period in mice after kainate-induced SE (KA mice), with corresponding alteration of RASgrf1 expression. In the present study, N-phthalyl-L-tryptophan (RG108), a DNA methyltransferase inhibitor, was applied in KA mice at latent phase and the behavior, electroencephalogram and pathological changes were observed in chronic phase. Methylation and expression of RASgrf1 were determined by polymerase chain reaction (PCR), western blotting, and bisulfite sequencing PCR. The results showed that the incidence of spontaneous recurrent seizures (SRS) was significantly lower in the RG108 group than the normal saline (NS) group. Subgroup analysis showed significant hypermethylation and lower expression of RASgrf1 in the RG108-SRS subgroup and the NS-SRS subgroup but not in the RG108-NSRS (no SRS) subgroup and the NS-NSRS subgroup compared with the control group. No significant difference was found between the RG108-SRS and NS-SRS subgroups. Meanwhile, hippocampal neuronal loss was observed in RG108-SRS and NS-SRS subgroups. We thus demonstrated that RG108 could modify the progression of epileptogenesis after KA induced SE and prevent chronic epilepsy. Meanwhile, hypermethylation of RASgrf1 after KA induced SE could be reversed with corresponding changes of RASgrf1 expression. Additionally, we speculated that RASgrf1 might be a potential epigenetic mediator in epileptogenesis and chronic epilepsy.

Anti-epileptogenic and Anti-convulsive Effects of Fingolimod in Experimental Temporal Lobe Epilepsy.

Temporal lobe epilepsy (TLE) represents a devastating neurological condition, in which approximately 4/5 of patients remain refractory for anti-convulsive drugs. Epilepsy surgery biopsies often reveal the damage pattern of "hippocampal sclerosis" (HS) characterized not only by neuronal loss but also pronounced astrogliosis and inflammatory changes. Since TLE shares distinct pathogenetic aspects with multiple sclerosis (MS), we have here scrutinized therapeutic effects in experimental TLE of the immunmodulator fingolimod, which is established in MS therapy. Fingolimod targets sphingosine-phosphate receptors (S1PRs). mRNAs of fingolimod target S1PRs were augmented in two experimental post status epilepticus (SE) TLE mouse models (suprahippocampal kainate/pilocarpine). SE frequently induces chronic recurrent seizures after an extended latency referred to as epileptogenesis. Transient fingolimod treatment of mice during epileptogenesis after suprahippocampal kainate-induced SE revealed substantial reduction of chronic seizure activity despite lacking acute attenuation of SE itself. Intriguingly, fingolimod exerted robust anti-convulsive activity in kainate-induced SE mice treated in the chronic TLE stage and had neuroprotective and anti-gliotic effects and reduced cytotoxic T cell infiltrates. Finally, the expression profile of fingolimod target-S1PRs in human hippocampal biopsy tissue of pharmacoresistant TLE patients undergoing epilepsy surgery for seizure relief suggests repurposing of fingolimod as novel therapeutic perspective in focal epilepsies.

Prolonged seizure activity causes caspase dependent cleavage and dysfunction of G-protein activated inwardly rectifying potassium channels

Recurrent high-frequency epileptic seizures cause progressive hippocampal sclerosis, which is associated with caspase-3 activation and NMDA receptor-dependent excitotoxicity. However, the identity of caspase-3 substrates that contribute to seizure-induced hippocampal atrophy remains largely unknown. Here, we show that prolonged high-frequency epileptiform discharges in cultured hippocampal neurons leads to caspase-dependent cleavage of GIRK1 and GIRK2, the major subunits of neuronal G protein-activated inwardly rectifying potassium (GIRK) channels that mediate membrane hyperpolarization and synaptic inhibition in the brain. We have identified caspase-3 cleavage sites in GIRK1 (387ECLD390) and GIRK2 (349YEVD352). The YEVD motif is highly conserved in GIRK2-4, and located within their C-terminal binding sites for Gβγ proteins that mediate membrane-delimited GIRK activation. Indeed, the cleaved GIRK2 displays reduced binding to Gβγ and cannot coassemble with GIRK1. Loss of an ER export motif upon cleavage of GIRK2 abolishes surface and current expression of GIRK2 homotetramic channels. Lastly, kainate-induced status epilepticus causes GIRK1 and GIRK2 cleavage in the hippocampus in vivo. Our findings are the first to show direct cleavage of GIRK1 and GIRK2 subunits by caspase-3, and suggest the possible role of caspase-3 mediated down-regulation of GIRK channel function and expression in hippocampal neuronal injury during prolonged epileptic seizures.

Development of In Vivo Imaging Tools for Investigating Astrocyte Activation in Epileptogenesis.

Insights into the dynamic changes in molecular processes occurring in the brain during epileptogenesis can substantially improve our understanding of their pathogenetic relevance. In this context, neuroinflammation is a potential mechanism of epileptogenesis which has recently been investigated in animal models by MRI or PET molecular imaging. Here, we developed an alternative and complementary molecular imaging strategy by designing a serotype 8 recombinant adeno-associated virus (AAV8) harboring promoter fragments of the GFAP or IL-1β promoter and a luciferase reporter gene. Mice were injected intrahippocampally with rAAV8 and treated with intracortical kainic acid to induce status epilepticus (SE) and hence epileptogenesis. In vivo bioluminescence imaging combined with immunohistochemistry revealed a significant activation of the GFAP promoter 24h and 3days after kainate-induced SE. For IL-1β, we identified the promoter region required for studying cell-specific induction of the promoter in longitudinal studies. We conclude that the GFAP promoter fragment represents a useful tool for monitoring the in vivo activation of astrocytes with an inflammatory phenotype during epileptogenesis, or under other pathophysiological conditions.

Effect of Training at Lactate Threshold Intensity on Maximal Time to Exhaustion, Depression and Anxiety Behaviour of Spontaneously Hypertensive Rats after Kainate-Induced Status Epilepticus.

The objective of the present study was to investigate the effect of treadmill training at lactate threshold intensity on maximum time to exhaustion (MTE) and heart rate (HR) as well as behavioral changes after kainate (KA)-induced status epilepticus (SE) of spontaneously hypertensive rats (SHRs). Male SHRs were divided in four groups: two sedentary (vehicle- and KA-treated) and two exercised (vehicle- and KA-treated), respectively. The exercised rats were trained on a treadmill at a speed of 20 m.min-1 and 0° elevation for 40 min.d-1, for 4 wk. Maximal time to exhaustion and HR was measured at the beginning and at the end of the training period. Status epilepticus was evoked in half of the sedentary and trained rats by a repetitive intraperitoneal injection of KA in low subconvulsive doses. The other half of the groups received saline. Sucrose preference test (SPT) for depression-like behavior and hole board test (HBT) for impulsivity were performed a month after KA/veh injection. The maximum time of exhaustion was elongated in the SHRs at the end of the training period in comparison with the beginning. However, no effect on HR was detected in trained rats. Kainate treatment after one month of training alleviated the SE-induced anhedonia in SPT and stereotyped behavior in HBT, respectively. Taken together, these results demonstrate that exercise exerts a beneficial influence on physical working capacity, depression and impulsive behavior in a co-morbid model of essential hypertension and SE.

Ablation of neuropsin\u2013neuregulin 1 signaling imbalances ErbB4 inhibitory networks and disrupts hippocampal gamma oscillation

Parvalbumin-expressing interneurons are pivotal for the processing of information in healthy brain, whereas the coordination of these functions is seriously disrupted in diseased brain. How these interneurons in the hippocampus participate in pathological functions remains unclear. We previously reported that neuregulin 1 (NRG1)–ErbB4 signaling, which is actuated by neuropsin, is important for coordinating brain plasticity. Neuropsin cleaves mature NRG1 (bound to extracellular glycosaminoglycans) in response to long-term potentiation or depression, liberating a soluble ligand that activates its receptor, ErbB4. Here, we show in mice that kainate-induced status epilepticus transiently elevates the proteolytic activity of neuropsin and stimulates cFos expression with a time course suggesting that activation of ErbB4- and parvalbumin-expressing interneurons follows the excitation and subsequent silencing of pyramidal neurons. In neuropsin-deficient mice, kainate administration impaired signaling and disrupted the neuronal excitation–inhibition balance (E/I balance) in hippocampal networks, by decreasing the activity of parvalbumin-positive interneurons while increasing that of pyramidal neurons, resulting in the progression of status epilepticus. Slow, but not fast, gamma oscillations in neuropsin-deficient mice showed reduced power. Intracerebroventricular infusion of the soluble NRG1 ligand moiety restored the E/I balance, status epilepticus and gamma oscillations to normal levels. These results suggest that the neuropsin–NRG1 signaling system has a role in pathological processes underlying temporal lobe epilepsy by regulating the activity of parvalbumin-expressing interneurons, and that neuropsin regulates E/I balance and gamma oscillations through NRG1–ErbB4 signaling toward parvalbumin-expressing interneurons. This neuronal system may be a useful target of pharmacological therapies against cognitive disorders.