Disease-modifying effects of a novel T-type calcium channel antagonist, Z944, in a model of temporal lobe epilepsy

Voltage-gated calcium channels in genetic epilepsies

Voltage-gated calcium channels (VGCC) are abundant in the central nervous system and serve a broad spectrum of functions, either directly in cellular excitability or indirectly to regulate Ca2+ homeostasis. Ca2+ ions act as one of the main connections in excitation-transcription coupling, muscle contraction and excitation-exocytosis coupling, including synaptic transmission. In recent years, many genes encoding VGCCs main α or additional auxiliary subunits have been associated with epilepsy. This review sums up the current state of knowledge on disease mechanisms and provides guidance on disease-specific therapies where applicable.

A spike is a spike: On the universality of spike features in four epilepsy models

OBJECTIVE

Frequency properties of the EEG characteristics of different seizure types including absence seizures have been described for various rodent models of epilepsy. However, little attention has been paid to the frequency properties of individual spike-wave complexes (SWCs), the constituting elements characterizing the different generalized seizure types. Knowledge of their properties is not only important for understanding the mechanisms underlying seizure generation but also for the identification of epileptiform activity in various seizure types. Here, we compared the frequency properties of SWCs in different epilepsy models.

METHODS

A software package was designed and used for the extraction and frequency analysis of SWCs from long-term EEG of four spontaneously seizing, chronic epilepsy models: a post-status epilepticus model of temporal lobe epilepsy, a lateral fluid percussion injury model of post-traumatic epilepsy, and two genetic models of absence epilepsy-GAERS and rats of the WAG/Rij strain. The SWCs within the generalized seizures were separated into fast (three-phasic spike) and slow (mostly containing the wave) components. Eight animals from each model were used (32 recordings, 104 510 SWCs in total). A limitation of our study is that the recordings were hardware-filtered (high-pass), which could affect the frequency composition of the EEG.

RESULTS

We found that the three-phasic spike component was similar in all animal models both in time and frequency domains, their amplitude spectra showed a single expressed peak at 18-20 Hz. The slow component showed a much larger variability across the rat models.

SIGNIFICANCE

Despite differences in the morphology of the epileptiform activity in different models, the frequency composition of the spike component of single SWCs is identical and does not depend on the particular epilepsy model. This fact may be used for the development of universal algorithms for seizure detection applicable to different rat models of epilepsy.

PLAIN LANGUAGE SUMMARY

There is a large variety between people with epilepsy regarding the clinical manifestations and the electroencephalographic (EEG) phenomena accompanying the epileptic seizures. Here, we show that one of the EEG signs of epilepsy, an epileptic spike, is universal, since it has the same shape and frequency characteristics in different animal models of generalized epilepsies, despite differences in recording sites and location.

Pharmacokinetics and brain uptake of sodium selenate and selenium in naïve rats and a lateral fluid percussion injury rat model

Post-traumatic epilepsy (PTE) is a life-long complication of traumatic brain injury (TBI). The development of PTE is associated with neurological morbidity and increases the risk of mortality. An aim of EpiBioS4Rx (Epilepsy Bioinformatics Study for Antiepileptogenic Therapy) was to test potential therapies to prevent the development of PTE in the lateral fluid percussion injury (LFPI) rat model of TBI, in which rats were subjected to injury at the left parietal cortex. Sodium selenate has been reported to be antiepileptogenic post-TBI in rodent models by activating protein phosphatase 2A and reducing phosphorylated tau (p-tau) protein. We aimed to characterize the pharmacokinetics (PK) and brain uptake of sodium selenate using naïve control and LFPI rats. Rats received either a single bolus dose or a single bolus dose followed by a 7-day subcutaneous minipump infusion of sodium selenate. Sodium selenate and selenium concentrations in plasma and brain were analyzed and used for PK estimation and brain exposure assessment. Selenium concentrations rapidly increased after sodium selenate administration, demonstrating biotransformation from sodium selenate to selenium. Sodium selenate and selenium PK parameters were estimated using non-compartmental analysis. Sodium selenate clearance (CL/F) and volume of distribution (Vd/F) varied by dose and route of administration, suggesting differences in bioavailability and nonlinear pharmacokinetics at the doses tested. Brain-to-plasma partition coefficients (AUCbrain/AUCplasma) for sodium selenate and selenium were found to be 0.7-1.3 and 0.1-0.3 following single-dose injection, respectively, indicating active transport of sodium selenate across the blood-brain barrier (BBB).

WONOEP appraisal: Targeted therapy development for early onset epilepsies

The early onset epilepsies encompass a heterogeneous group of disorders, some of which result in drug-resistant seizures, developmental delay, psychiatric comorbidities, and sudden death. Advancement in the widespread use of targeted gene panels as well as genome and exome sequencing has facilitated the identification of different causative genes in a subset of these patients. The ability to recognize the genetic basis of early onset epilepsies continues to improve, with de novo coding variants accounting for most of the genetic etiologies identified. Although current disease-specific and disease-modifying therapies remain limited, novel precision medicine approaches, such as small molecules, cell therapy, and other forms of genetic therapies for early onset epilepsies, have created excitement among researchers, clinicians, and caregivers. Here, we summarize the main findings of presentations and discussions on novel therapeutic strategies for targeted treatment of early onset epilepsies that occurred during the Workshop on Neurobiology of Epilepsy (WONOEP XVI, Talloires, France, July 2022). The presentations discussed the use of chloride transporter inhibitors for neonatal seizures, targeting orexinergic signaling for childhood absence epilepsy, targeting energy metabolism in Dravet syndrome, and the role of cannabinoid receptor type 2, reversible acetylcholinesterase inhibitors, cell therapies, and RNA-based therapies in early life epilepsies.

Low-frequency rTMS Plays a Neuroprotective role in Pilocarpine-induced Status Epilepticus Rat Models Through the AMPAR GluA1-STIM-Ca2+ Pathway

Low-frequency repetitive transcranial magnetic stimulation (rTMS) refers to the stimulation of the brain using repetitive magnetic field pulses at a low frequency (≤ 1 Hz) to reduce seizures. Currently, the mechanism is not well understood. Male Sprague-Dawley rats underwent pilocarpine-induced status epilepticus (SE) and were then stimulated with low-frequency rTMS. An epilepsy cell model was then established by incubating rat hippocampal neurons with Mg2+-free extracellular fluids. The effects of the low-frequency rTMS on epileptogenesis and hippocampal neuron injury were evaluated using a video electroencephalogram (vEEG) and Nissl staining, and the expression of AMPAR GluA1 and STIM in the hippocampus and hippocampal neurons was assessed using western blot and immunofluorescence. Additionally, the intracellular Ca2+ concentration and reactive oxygen species (ROS) were measured using flow cytometry. Low-frequency rTMS attenuated spontaneous recurrent seizures in rats with epilepsy, with the SE group exhibiting a higher incidence (100%) and frequency (3.00 ± 0.18 times/day) than the SE + 0.3 (50% incidence, 0.06 ± 0.03 times/day), SE + 0.5 (0.20 ± 0.02 times/day) and SE + 1 Hz (1.02 ± 0.05 times/day) groups. Additionally, rTMS reduced the damage and apoptosis of hippocampal pyramidal neurons, increasing their numbers in the CA1 and CA3 regions. Furthermore, AMPAR GluA1 and STIM expression were upregulated in the hippocampus when using rTMS, reversing the downregulation caused by seizures. Immunofluorescence verified the increased fluorescence intensity of AMPAR GluA1 and STIM. Moreover, rTMS inhibited Ca2+ overload and ROS in epileptic neuron models. Low-frequency rTMS may exert neuroprotective effects through the AMPAR GluA1-STIM-Ca2+ pathway.

Withaferin A protects against epilepsy by promoting LCN2-mediated astrocyte polarization to stopping neuronal ferroptosis

BACKGROUND

Epilepsy is among the most frequent severe brain diseases, with few treatment options available. Neuronal ferroptosis is an important pathogenic mechanism in epilepsy. As a result, addressing ferroptosis appears to be a promising treatment approach for epilepsy. Withaferin A (WFA) is a C28 steroidal lactone that has a broad range of neuroprotective properties. Nonetheless, the antiepileptic action of WFA and the intrinsic mechanism by which it inhibits ferroptosis following epilepsy remain unknown.

PURPOSE

This study aimed at investigating to the antiepileptic potential of WFA in epilepsy, as well as to propose a potential therapeutic approach for epilepsy therapy.

METHODS

We conducted extensive research to examine the impacts of WFA on epilepsy and ferroptosis, using the kainic acid (KA)-treated primary astrocyte as an in vitro model and KA-induced temporal lobe epilepsy mice as an in vivo model. To analyze the neuroprotective effects of WFA on epileptic mice, electroencephalogram (EEG) recording, Nissl staining, and neurological function assessments such as the Morris water maze (MWM) test, Y-maze test, Elevated-plus maze (O-maze) test, and Open field test were used. Furthermore, the mechanism behind the neuroprotective effect of WFA in epilepsy was investigated using the transcriptomics analysis and verified on epileptic patient and epileptic mouse samples using Western blotting (WB) and immunofluorescence (IF) staining. In addition, WB, IF staining and specific antagonists/agonists were used to investigate astrocyte polarization and the regulatory signaling pathways involved. More critically, ferroptosis was assessed utilizing lipocalin-2 (LCN2) overexpression cell lines, siRNA knockdown, JC-1 staining, WB, IF staining, flow cytometry, electron microscopy (TEM), and ferroptosis-related GSH and MDA indicators.

RESULTS

In this study, we observed that WFA treatment reduced the number of recurrent seizures and time in seizure, and the loss of neurons in the hippocampal area in in epileptic mice, and even improved cognitive and anxiety impairment after epilepsy in a dose depend. Furthermore, WFA treatment was proven to enhance to the transformation of post-epileptic astrocytes from neurotoxic-type A1 to A2 astrocytes in both in vivo and in vitro experiments by inhibiting the phosphoinositide 3-kinase /AKT signaling pathway. At last, transcriptomics analysis in combination with functional experimental validation, it was discovered that WFA promoted astrocyte polarity transformation and then LCN2 in astrocytes, which inhibited neuronal ferroptosis to exert neuroprotective effects after epilepsy. In addition, we discovered significant astrocytic LCN2 expression in human TLE patient hippocampal samples.

CONCLUSIONS

Taken together, for the first, our findings suggest that WFA has neuroprotective benefits in epilepsy by modulating astrocyte polarization, and that LCN2 may be a novel potential target for the prevention and treatment of ferroptosis after epilepsy.

Fluoxetine accelerates epileptogenesis and magnifies disease severity in a rat model of acquired epilepsy

OBJECTIVE

Many people with epilepsy experience comorbid anxiety and depression, and antidepressants remain a primary treatment for this. Emerging evidence suggests that these agents may modulate epileptogenesis to influence disease severity. Here, we assessed how treatment with the selective serotonin reuptake inhibitor (SSRI) antidepressant fluoxetine impacts epileptogenic, behavioral, and pathological sequelae following status epilepticus.

METHODS

Male Wistar rats received kainic acid to induce status epilepticus (SE) or vehicle (sham). Animals then received either fluoxetine (10 mg/kg/day) or vehicle for 8 weeks via subcutaneous osmotic pump. Video-electroencephalography was recorded continuously until behavioral testing at day 56, including assessments of anxiety- and depression-like behavior and spatial cognition. Postmortem immunocytochemistry studies examined mossy fiber sprouting.

RESULTS

Fluoxetine treatment significantly accelerated epileptogenesis following SE, reducing the average period to the first spontaneous seizure (from 32 days [vehicle] to 6 days [fluoxetine], p < .01). Also, fluoxetine exposure magnified the severity of the resultant epilepsy, increasing seizure frequency compared to vehicle (p < .01). Exposure to fluoxetine was associated with improved anxiety- and depression-like behaviors but significantly worsened cognition. Mossy fiber sprouting was more pronounced in fluoxetine-treated rats compared to vehicle (p < .0001).

SIGNIFICANCE

Our studies demonstrate that, using a model exhibiting spontaneous seizures, epileptogenesis is accelerated and magnified by fluoxetine, an effect that may be related to more severe pathological neuroplasticity. The differential influence of fluoxetine on behavior indicates that different circuitry and mechanisms are responsible for these comorbidities. These findings suggest that caution should be exercised when prescribing SSRI antidepressants to people at risk of developing epilepsy.

Epilepsy phenotype and its reproducibility after lateral fluid percussion-induced traumatic brain injury in rats: Multicenter EpiBioS4Rx study project 1

OBJECTIVE

This study was undertaken to assess reproducibility of the epilepsy outcome and phenotype in a lateral fluid percussion model of posttraumatic epilepsy (PTE) across three study sites.

METHODS

A total of 525 adult male Sprague Dawley rats were randomized to lateral fluid percussion-induced brain injury (FPI) or sham operation. Of these, 264 were assigned to magnetic resonance imaging (MRI cohort, 43 sham, 221 traumatic brain injury [TBI]) and 261 to electrophysiological follow-up (EEG cohort, 41 sham, 220 TBI). A major effort was made to harmonize the rats, materials, equipment, procedures, and monitoring systems. On the 7th post-TBI month, rats were video-EEG monitored for epilepsy diagnosis.

RESULTS

A total of 245 rats were video-EEG phenotyped for epilepsy on the 7th postinjury month (121 in MRI cohort, 124 in EEG cohort). In the whole cohort (n = 245), the prevalence of PTE in rats with TBI was 22%, being 27% in the MRI and 18% in the EEG cohort (p > .05). Prevalence of PTE did not differ between the three study sites (p > .05). The average seizure frequency was .317 ± .725 seizures/day at University of Eastern Finland (UEF; Finland), .085 ± .067 at Monash University (Monash; Australia), and .299 ± .266 at University of California, Los Angeles (UCLA; USA; p < .01 as compared to Monash). The average seizure duration did not differ between UEF (104 ± 48 s), Monash (90 ± 33 s), and UCLA (105 ± 473 s; p > .05). Of the 219 seizures, 53% occurred as part of a seizure cluster (≥3 seizures/24 h; p >.05 between the study sites). Of the 209 seizures, 56% occurred during lights-on period and 44% during lights-off period (p > .05 between the study sites).

SIGNIFICANCE

The PTE phenotype induced by lateral FPI is reproducible in a multicenter design. Our study supports the feasibility of performing preclinical multicenter trials in PTE to increase statistical power and experimental rigor to produce clinically translatable data to combat epileptogenesis after TBI.

Diurnal circadian clock gene expression is altered in models of genetic and acquired epilepsy

OBJECTIVES

Growing evidence demonstrates a relationship between epilepsy and the circadian system. However, relatively little is known about circadian function in disease states, such as epilepsy. This study aimed to characterize brain and peripheral core circadian clock gene expression in rat models of genetic and acquired epilepsy.

METHODS

For the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) study, we used 40 GAERS and 40 non-epileptic control (NEC) rats. For the kainic acid status epilepticus (KASE) study, we used 40 KASE and 40 sham rats. Rats were housed in a 7 am:7 pm light-dark cycle. Hypothalamus, hippocampus, liver, and small intestine samples were collected every 3 h throughout the light period. We then assessed core diurnal clock gene expression of per1, cry1, clock, and bmal1.

RESULTS

In the GAERS rats, all tissues exhibited significant changes in clock gene expression (P < 0.05) when compared to NEC. In the KASE rats, there were fewer effects of the epileptic condition in the hypothalamus, hippocampus, or small intestine (P > 0.05) compared with shams.

SIGNIFICANCE

These results indicate marked diurnal disruption to core circadian clock gene expression in rats with both generalized and focal chronic epilepsy. This could contribute to epileptic symptomology and implicate the circadian system as a viable target for future treatments.

E2730, an uncompetitive γ-aminobutyric acid transporter-1 inhibitor, suppresses epileptic seizures in a rat model of chronic mesial temporal lobe epilepsy

OBJECTIVE

More than one third of mesial temporal lobe epilepsy (MTLE) patients are resistant to current antiseizure medications (ASMs), and half experience mild-to-moderate adverse effects of ASMs. There is therefore a strong need to develop and test novel ASMs. The objective of this work is to evaluate the pharmacokinetics and neurological toxicity of E2730, a novel uncompetitive inhibitor of γ-aminobutyric acid transporter-1, and to test its seizure suppression effects in a rat model of chronic MTLE.

METHODS

We first examined plasma levels and adverse neurological effects of E2730 in healthy Wistar rats. Adult male rats were implanted with osmotic pumps delivering either 10, 20, or 100 mg/kg/day of E2730 subcutaneously for 1 week. Blood sampling and behavioral assessments were performed at several timepoints. We next examined whether E2730 suppressed seizures in rats with chronic MTLE. These rats were exposed to kainic acid-induced status epilepticus, and 9 weeks later, when chronic epilepsy was established, were assigned to receive one of the three doses of E2730 or vehicle for 1 week in a randomized crossover design. Continuous video-electroencephalographic monitoring was acquired during the treatment period to evaluate epileptic seizures.

RESULTS

Plasma levels following continuous infusion of E2730 showed a clear dose-related increase in concentration. The drug was well tolerated at all doses, and any sedation or neuromotor impairment was mild and transient, resolving within 48 h of treatment initiation. Remarkably, E2730 treatment in chronically epileptic rats led to seizure suppression in a dose-dependent manner, with 65% of rats becoming seizure-free at the highest dose tested. Mean seizure class did not differ between the treatment groups.

SIGNIFICANCE

This study shows that continuous subcutaneous infusion of E2730 over 7 days results in a marked, dose-dependent suppression of spontaneous recurrent seizures, with minimal adverse neurological effects, in a rat model of chronic MTLE. E2730 shows strong promise as an effective new ASM to be translated into clinical trials.

Effects of the T-type calcium channel CaV3.2 R1584P mutation on absence seizure susceptibility in GAERS and NEC congenic rats models

RATIONALE

Low-voltage-activated or T-type Ca²⁺ channels play a key role in the generation of seizures in absence epilepsy. We have described a homozygous, gain of function substitution mutation (R1584P) in the Ca_V3.2 T-type Ca²⁺ channel gene (Cacna1h) in the Genetic Absence Epilepsy Rats from Strasbourg (GAERS). The non-epileptic control (NEC) rats, derived from the same original Wistar strains as GAERS but selectively in-breed not to express seizures, are null for the R1584P mutation. To study the effects of this mutation in rats who otherwise have a GAERS or NEC genetic background, we bred congenic GAERS-Cacna1hNEC (GAERS null for R1584P mutation) and congenic NEC-Cacna1hGAERS (NEC homozygous for R1584P mutation) and evaluated the seizure and behavioral phenotype of these strains in comparison to the original GAERS and NEC strains.

METHODS

To evaluate seizure expression in the congenic strains, EEG electrodes were implanted in NEC, GAERS, GAERS^-Cacna1hNEC without the R1584P mutation, and NEC^{-Cacna1hGAERS} with the R1584P mutation rats. In the first study, continuous EEG recordings were acquired from week 4 (when seizures begin to develop in GAERS) to week 14 of age (when GAERS display hundreds of seizures per day). In the second study, the seizure and behavioral phenotype of GAERS and NEC^{-Cacna1hGAERS} strains were evaluated during young age (6 weeks of age) and adulthood (16 weeks of age) of GAERS, NEC, GAERS^-Cacna1hNEC and NEC^{-Cacna1hGAERS}. The Open field test (OFT) and sucrose preference test (SPT) were performed to evaluate anxiety-like and depressive-like behavior, respectively. This was followed by EEG recordings at 18 weeks of age to quantify the seizures, and spike-wave discharge (SWD) cycle frequency. At the end of the study, the whole thalamus was collected for T-type calcium channel mRNA expression analysis.

RESULTS

GAERS had a significantly shorter latency to first seizures and an increased number of seizures per day compared to GAERS^-Cacna1hNEC. On the other hand, the presence of the R1584P mutation in the NEC^{-Cacna1hGAERS} was not enough to generate spontaneous seizures in their seizure-resistant background. 6 and 16-week-old GAERS and GAERS^-Cacna1hNEC rats showed anxiety-like behavior in the OFT, in contrast to NEC and NEC^{-Cacna1hGAERS}. Results from the SPT showed that the GAERS developed depressive-like in the SPT compared to GAERS^-Cacna1hNEC, NEC, and NEC^{-Cacna1hGAERS}. Analysis of the EEG at 18 weeks of age showed that the GAERS had an increased number of seizures per day, increased total seizure duration and a higher cycle frequency of SWD relative to GAERS^-Cacna1hNEC. However, the average seizure duration was not significantly different between strains. Quantitative real-time PCR showed that the T-type Ca²⁺ channel isoform Ca_V3.2 channel expression was significantly increased in GAERS compared to NEC, GAERS^-Cacna1hNEC and NEC^{-Cacna1hGAERS}. The presence of the R1584P mutation increased the total ratio of Ca_V3.2 + 25/-25 splice variants in GAERS and NEC^{-Cacna1hGAERS} compared to NEC and GAERS^-Cacna1hNEC.

DISCUSSION

The data from this study demonstrate that the R1584P mutation in isolation on a seizure-resistant NEC genetic background was insufficient to generate absence seizures, and that a GAERS genetic background can cause seizures even without the mutation. However, the study provides evidence that the R1584P mutation acts as a modulator of seizures development and expression, and depressive-like behavior in the SPT, but not the anxiety phenotype of the GAERS model of absence epilepsy.

Spike and wave discharges detection in genetic absence epilepsy rat from Strasbourg and patients with genetic generalized epilepsy

OBJECTIVE

Generalised spike and wave discharges (SWDs) are pathognomonic EEG signatures for diagnosing absence seizures in patients with Genetic Generalized Epilepsy (GGE). The Genetic Absence Epilepsy Rats from Strasbourg (GAERS) is one of the best-validated animal models of GGE with absence seizures.

METHODS

We developed an SWDs detector for both GAERS rodents and GGE patients with absence seizures using a neural network method. We included 192 24-hour EEG sessions recorded from 18 GAERS rats, and 24-hour scalp-EEG data collected from 11 GGE patients.

RESULTS

The SWDs detection performance on GAERS showed a sensitivity of 98.01% and a false positive (FP) rate of 0.96/hour. The performance on GGE patients showed 100% sensitivity in five patients, while the remaining patients obtained over 98.9% sensitivity. Moderate FP rates were seen in our patients with 2.21/hour average FP. The detector trained within our patient cohort was validated in an independent dataset, TUH EEG Seizure Corpus (TUSZ), that showed 100% sensitivity in 11 of 12 patients and 0.56/hour averaged FP.

CONCLUSIONS

We developed a robust SWDs detector that showed high sensitivity and specificity for both GAERS rats and GGE patients.

SIGNIFICANCE

This detector can assist researchers and neurologists with the time-efficient and accurate quantification of SWDs.

Disease-modifying effects of sodium selenate in a model of drug-resistant, temporal lobe epilepsy

There are no pharmacological disease-modifying treatments with an enduring effect to mitigate the seizures and comorbidities of established chronic temporal lobe epilepsy (TLE). This study aimed to evaluate for disease modifying effects of sodium selenate treatment in the chronically epileptic rat post-status epilepticus (SE) model of drug-resistant TLE. Wistar rats underwent kainic acid-induced SE or sham. Ten-weeks post-SE, animals received sodium selenate, levetiracetam, or vehicle subcutaneousinfusion continuously for 4 weeks. To evaluate the effects of the treatments, one week of continuous video-EEG was acquired before, during, and 4, 8 weeks post-treatment, followed by behavioral tests. Targeted and untargeted proteomics and metabolomics were performed on post-mortem brain tissue to identify potential pathways associated with modified disease outcomes. Telomere length was investigated as a novel surrogate marker of epilepsy disease severity in our current study. The results showed that sodium selenate treatment was associated with mitigation of measures of disease severity at 8 weeks post-treatment cessation; reducing the number of spontaneous seizures (p< 0.05), cognitive dysfunction (p< 0.05), and sensorimotor deficits (p< 0.01). Moreover, selenate treatment was associated with increased protein phosphatase 2A (PP2A) expression, reduced hyperphosphorylated tau, and reversed telomere length shortening (p< 0.05). Network medicine integration of multi-omics/pre-clinical outcomes identified protein-metabolite modules positively correlated with TLE. Our results provide evidence that treatment with sodium selenate results in a sustained disease-modifying effect in chronically epileptic rats in the post-KA SE model of TLE, including improved comorbid learning and memory deficits.

Attenuation of Epileptogenesis and Cognitive Deficits by a Selective and Potent Kv7 Channel Opener in Rodent Models of Seizures

Targeting neuronal Kv7 channels by pharmacological activation has been proven to be an attractive therapeutic strategy for epilepsy. Here, we show that activation of Kv7 channels by an opener SCR2682 dose-dependently reduces seizure activity and severity in rodent models of epilepsy induced by a GABAa receptor antagonist pentylenetetrazole (PTZ), maximal electroshock, and a glutamate receptor agonist kainic acid (KA). Electroencephalographic recordings of rat cerebral cortex confirm that SCR2682 also decreases epileptiform discharges in KA-induced seizures. Nissl and neuronal nuclei staining further demonstrates that SCR2682 also protects neurons from injury induced by KA. In Morris water maze navigation and Y-maze tests, SCR2682 improves PTZ- and KA-induced cognitive impairment. Taken together, our findings demonstrate that pharmacological activation of Kv7 by novel opener SCR2682 may hold promise for therapy of epilepsy with cognitive impairment. SIGNIFICANCE STATEMENT: A neuronal Kv7 channel opener SCR2682 attenuates epileptogenesis and seizure-induced cognitive impairment in rodent models of seizures, thus possessing a developmental potential for effective therapy of epilepsy with cognitive impairment.

MEPIRAPIM-derived synthetic cannabinoids inhibit T-type calcium channels with divergent effects on seizures in rodent models of epilepsy

Background: T-type Ca²⁺ channels (Ca_v3) represent emerging therapeutic targets for a range of neurological disorders, including epilepsy and pain. To aid the development and optimisation of new therapeutics, there is a need to identify novel chemical entities which act at these ion channels. A number of synthetic cannabinoid receptor agonists (SCRAs) have been found to exhibit activity at T-type channels, suggesting that cannabinoids may provide convenient chemical scaffolds on which to design novel Ca_v3 inhibitors. However, activity at cannabinoid type 1 (CB₁) receptors can be problematic because of central and peripheral toxicities associated with potent SCRAs. The putative SCRA MEPIRAPIM and its analogues were recently identified as Ca_v3 inhibitors with only minimal activity at CB₁ receptors, opening the possibility that this scaffold may be exploited to develop novel, selective Ca_v3 inhibitors. Here we present the pharmacological characterisation of SB2193 and SB2193F, two novel Ca_v3 inhibitors derived from MEPIRAPIM. Methods: The potency of SB2193 and SB2193F was evaluated in vitro using a fluorometric Ca²⁺ flux assay and confirmed using whole-cell patch-clamp electrophysiology. In silico docking to the cryo-EM structure of Ca_v3.1 was also performed to elucidate structural insights into T-type channel inhibition. Next, in vivo pharmacokinetic parameters in mouse brain and plasma were determined using liquid chromatography-mass spectroscopy. Finally, anticonvulsant activity was assayed in established genetic and electrically-induced rodent seizure models. Results: Both MEPIRAPIM derivatives produced potent inhibition of Ca_v3 channels and were brain penetrant, with SB2193 exhibiting a brain/plasma ratio of 2.7. SB2193 was further examined in mouse seizure models where it acutely protected against 6 Hz-induced seizures. However, SB2193 did not reduce spontaneous seizures in the Scn1a ^+/- mouse model of Dravet syndrome, nor absence seizures in the Genetic Absence Epilepsy Rat from Strasbourg (GAERS). Surprisingly, SB2193 appeared to increase the incidence and duration of spike-and-wave discharges in GAERS animals over a 4 h recording period. Conclusion: These results show that MEPIRAPIM analogues provide novel chemical scaffolds to advance Ca_v3 inhibitors against certain seizure types.

Negative effects of brain regulatory T cells depletion on epilepsy

The infiltration of immune cells is observed in the epileptogenic zone; however, the relationship between epilepsy and regulatory T cells (Tregs) remains only partially understood. We aimed to investigate brain-infiltrating Tregs to reveal their underlying role in epilepsy. We analyzed the infiltration of Tregs in the epileptogenic zones from patients with epilepsy and a pilocarpine-induced temporal lobe epilepsy (TLE) model. Next, we evaluated the effects of brain Treg depletion on neuroinflammation, neuronal loss, oxidative stress, seizure activity and behavioral changes in the pilocarpine model. We also explored the impact of Treg expansion in the brain on seizure activity. There were a large number of Tregs in the epileptogenic zones of human and experimental epilepsy. The number of brain Tregs was negatively correlated with the frequency of seizures in patients with epilepsy. Our further findings demonstrated that brain Treg depletion promoted astrocytosis, microgliosis, inflammatory cytokine production, oxidative stress, and neuronal loss in the hippocampus after status epilepticus (SE). Moreover, brain Treg depletion increased seizure activity and contributed to behavioral impairments in experimental chronic TLE. Interestingly, intracerebroventricular injection of CCL20 amplified Tregs in brain tissue, thereby inhibiting seizure activity. Taken together, our study highlights the therapeutic potential of regulating Tregs in epileptic brain tissue.

An Integrated Multi-Omic Network Analysis Identifies Seizure-Associated Dysregulated Pathways in the GAERS Model of Absence Epilepsy

Absence epilepsy syndromes are part of the genetic generalized epilepsies, the pathogenesis of which remains poorly understood, although a polygenic architecture is presumed. Current focus on single molecule or gene identification to elucidate epileptogenic drivers is unable to fully capture the complex dysfunctional interactions occurring at a genetic/proteomic/metabolomic level. Here, we employ a multi-omic, network-based approach to characterize the molecular signature associated with absence epilepsy-like phenotype seen in a well validated rat model of genetic generalized epilepsy with absence seizures. Electroencephalographic and behavioral data was collected from Genetic Absence Epilepsy Rats from Strasbourg (GAERS, n = 6) and non-epileptic controls (NEC, n = 6), followed by proteomic and metabolomic profiling of the cortical and thalamic tissue of rats from both groups. The general framework of weighted correlation network analysis (WGCNA) was used to identify groups of highly correlated proteins and metabolites, which were then functionally annotated through joint pathway enrichment analysis. In both brain regions a large protein-metabolite module was found to be highly associated with the GAERS strain, absence seizures and associated anxiety and depressive-like phenotype. Quantitative pathway analysis indicated enrichment in oxidative pathways and a downregulation of the lysine degradation pathway in both brain regions. GSTM1 and ALDH2 were identified as central regulatory hubs of the seizure-associated module in the somatosensory cortex and thalamus, respectively. These enzymes are involved in lysine degradation and play important roles in maintaining oxidative balance. We conclude that the dysregulated pathways identified in the seizure-associated module may be involved in the aetiology and maintenance of absence seizure activity. This dysregulated activity could potentially be modulated by targeting one or both central regulatory hubs.

Pediatric traumatic brain injury and a subsequent transient immune challenge independently influenced chronic outcomes in male mice

Traumatic brain injury (TBI) is a major contributor to death and disability worldwide. Children are at particularly high risk of both sustaining a TBI and experiencing serious long-term consequences, such as cognitive deficits, mental health problems and post-traumatic epilepsy. Severe TBI patients are highly susceptible to nosocomial infections, which are mostly acquired within the first week of hospitalization post-TBI. Yet the potential chronic impact of such acute infections following pediatric TBI remains unclear. In this study, we hypothesized that a peripheral immune challenge, such as lipopolysaccharide (LPS)-mimicking a hospital-acquired infection-would worsen inflammatory, neurobehavioral, and seizure outcomes after experimental pediatric TBI. To test this, three-week old male C57Bl/6J mice received a moderate controlled cortical impact or sham surgery, followed by 1 mg/kg i.p. LPS (or 0.9% saline vehicle) at 4 days TBI. Mice were randomized to four groups; sham-saline, sham-LPS, TBI-saline or TBI-LPS (n = 15/group). Reduced general activity and increased anxiety-like behavior were observed within 24 h in LPS-treated mice, indicating a transient sickness response. LPS-treated mice also exhibited a reduction in body weights, which persisted chronically. From 2 months post-injury, mice underwent a battery of tests for sensorimotor, cognitive, and psychosocial behaviors. TBI resulted in hyperactivity and spatial memory deficits, independent of LPS; whereas LPS resulted in subtle deficits in spatial memory retention. At 5 months post-injury, video-electroencephalographic recordings were obtained to evaluate both spontaneous seizure activity as well as the evoked seizure response to pentylenetetrazol (PTZ). TBI increased susceptibility to PTZ-evoked seizures; whereas LPS appeared to increase the incidence of spontaneous seizures. Post-mortem analyses found that TBI, but not LPS, resulted in robust glial reactivity and loss of cortical volume. A TBI × LPS interaction in hippocampal volume suggested that TBI-LPS mice had a subtle increase in ipsilateral hippocampus tissue loss; however, this was not reflected in neuronal cell counts. Both TBI and LPS independently had modest effects on chronic hippocampal gene expression. Together, contrary to our hypothesis, we observed minimal synergy between TBI and LPS. Instead, pediatric TBI and a subsequent transient immune challenge independently influenced chronic outcomes. These findings have implications for future preclinical modeling as well as acute post-injury patient management.

Altered cardiac structure and function is related to seizure frequency in a rat model of chronic acquired temporal lobe epilepsy

OBJECTIVE

This study aimed to prospectively examine cardiac structure and function in the kainic acid-induced post-status epilepticus (post-KA SE) model of chronic acquired temporal lobe epilepsy (TLE), specifically to examine for changes between the pre-epileptic, early epileptogenesis and the chronic epilepsy stages. We also aimed to examine whether any changes related to the seizure frequency in individual animals.

METHODS

Four hours of SE was induced in 9 male Wistar rats at 10 weeks of age, with 8 saline treated matched control rats. Echocardiography was performed prior to the induction of SE, two- and 10-weeks post-SE. Two weeks of continuous video-EEG and simultaneous ECG recordings were acquired for two weeks from 11 weeks post-KA SE. The video-EEG recordings were analyzed blindly to quantify the number and severity of spontaneous seizures, and the ECG recordings analyzed for measures of heart rate variability (HRV). PicroSirius red histology was performed to assess cardiac fibrosis, and intracellular Ca²⁺ levels and cell contractility were measured by microfluorimetry.

RESULTS

All 9 post-KA SE rats were demonstrated to have spontaneous recurrent seizures on the two-week video-EEG recording acquired from 11 weeks SE (seizure frequency ranging from 0.3 to 10.6 seizures/day with the seizure durations from 11 to 62 s), and none of the 8 control rats. Left ventricular wall thickness was thinner, left ventricular internal dimension was shorter, and ejection fraction was significantly decreased in chronically epileptic rats, and was negatively correlated to seizure frequency in individual rats. Diastolic dysfunction was evident in chronically epileptic rats by a decrease in mitral valve deceleration time and an increase in E/E` ratio. Measures of HRV were reduced in the chronically epileptic rats, indicating abnormalities of cardiac autonomic function. Cardiac fibrosis was significantly increased in epileptic rats, positively correlated to seizure frequency, and negatively correlated to ejection fraction. The cardiac fibrosis was not a consequence of direct effect of KA toxicity, as it was not seen in the 6/10 rats from separate cohort that received similar doses of KA but did not go into SE. Cardiomyocyte length, width, volume, and rate of cell lengthening and shortening were significantly reduced in epileptic rats.

SIGNIFICANCE

The results from this study demonstrate that chronic epilepsy in the post-KA SE rat model of TLE is associated with a progressive deterioration in cardiac structure and function, with a restrictive cardiomyopathy associated with myocardial fibrosis. Positive correlations between seizure frequency and the severity of the cardiac changes were identified. These results provide new insights into the pathophysiology of cardiac disease in chronic epilepsy, and may have relevance for the heterogeneous mechanisms that place these people at risk of sudden unexplained death.

Selected Molecular Targets for Antiepileptogenesis

The term epileptogenesis defines the usually durable process of converting normal brain into an epileptic one. The resistance of a significant proportion of patients with epilepsy to the available pharmacotherapy prompted the concept of a causative treatment option consisting in stopping or modifying the progress of epileptogenesis. Most antiepileptic drugs possess only a weak or no antiepileptogenic potential at all, but a few of them appear promising in this regard; these include, for example, eslicarbazepine (a sodium and T-type channel blocker), lamotrigine (a sodium channel blocker and glutamate antagonist) or levetiracetam (a ligand of synaptic vehicle protein SV2A). Among the approved non-antiepileptic drugs, antiepileptogenic potential seems to reside in losartan (a blocker of angiotensin II type 1 receptors), biperiden (an antiparkinsonian drug), nonsteroidal anti-inflammatory drugs, antioxidative drugs and minocycline (a second-generation tetracycline with anti-inflammatory and antioxidant properties). Among other possible antiepileptogenic compounds, antisense nucleotides have been considered, among these an antagomir targeting microRNA-134. The drugs and agents mentioned above have been evaluated in post-status epilepticus models of epileptogenesis, so their preventive efficacy must be verified. Limited clinical data indicate that biperiden in patients with brain injuries is well-tolerated and seems to reduce the incidence of post-traumatic epilepsy. Exceptionally, in this regard, our own original data presented here point to c-Fos as an early seizure duration, but not seizure intensity-related, marker of early epileptogenesis. Further research of reliable markers of early epileptogenesis is definitely needed to improve the process of designing adequate antiepileptogenic therapies.

The T-type calcium channel antagonist, Z944, reduces spinal excitability and pain hypersensitivity

Background and Purpose

T‐type voltage‐gated calcium channels are an emerging therapeutic target for neurological disorders including epilepsy and pain. Inhibition of T‐type channels reduces the excitability of peripheral nociceptive sensory neurons and reverses pain hypersensitivity in male rodent pain models. However, administration of peripherally restricted T‐type antagonists failed to show efficacy in multiple clinical and preclinical pain trials, suggesting that inhibition of peripheral T‐type channels alone may be insufficient for pain relief.

Experimental Approach

We utilized the selective and CNS‐penetrant T‐type channel antagonist, Z944, in electrophysiological, calcium imaging and behavioural paradigms to determine its effect on lamina I neuron excitability and inflammatory pain behaviours.

Key Results

Voltage‐clamp recordings from lamina I spinal neurons of adult rats revealed that approximately 80% of neurons possess a low threshold T‐type current, which was blocked by Z944. Due to this highly prevalent T‐type current, Z944 potently blocked action‐potential evoked somatic and dendritic calcium transients in lamina I neurons. Moreover, application of Z944 to spinal cord slices attenuated action potential firing rates in over half of laminae I/II neurons. Finally, we found that intraperitoneal injection of Z944 (1–10 mg·kg⁻¹) dose‐dependently reversed mechanical allodynia in the complete Freund's adjuvant model of persistent inflammatory pain, with a similar magnitude and time course of analgesic effects between male and female rats.

Conclusion and Implications

T‐type calcium channels critically shape the excitability of lamina I pain processing neurons and inhibition of these channels by the clinical stage antagonist Z944 potently reverses pain hypersensitivity across sexes.

Modulation of human T-type calcium channels by synthetic cannabinoid receptor agonists in vitro

BACKGROUND AND PURPOSE

Consumption of Synthetic Cannabinoid Receptor agonists (SCRAs) is associated with severe adverse reactions including seizures, arrhythmias and death, but the molecular mechanisms surrounding SCRA toxicity are not yet established. These disease-like symptoms are also synonymous with altered T-type calcium channel activity which controls rhythmicity in the heart and brain. This study examined whether SCRAs alter T-type activity and whether this represents a possible mechanism of toxicity.

EXPERIMENTAL APPROACH

Fluorescence-based and electrophysiology assays were used to screen 16 structurally related synthetic cannabinoids for their ability to inhibit human T-type calcium channels expressed in HEK293 cells. The most potent compounds were then further examined using patch clamp electrophysiology.

KEY RESULTS

MDMB-CHMICA and AMB-CHMINACA potently blocked Cav3.2 with IC50 values of 1.5 and 0.74 μM respectively. Current inhibition increased from 47 to 80% and 45-87% respectively when the channel was in slow-inactivated state. Both SCRAs had little effect on steady state inactivation, however MDMB-CHMICA significantly shifted the half activation potential by -7mV. Neither drug produced frequency dependent block, in contrast to the phytocannabinoid Δ9-THC.

CONCLUSIONS AND IMPLICATIONS

SCRAs are potent agonists of CB1 receptors and can be extremely toxic, but observed toxicity also resembles symptoms associated with altered Cav3.2 activity. Many SCRAs tested were potent modulators of Cav3.2, raising the possibility that SC toxicity may be due in part to Cav3.2 modulation. This potent T-type channel modulation suggests the possibility of SCRAs as a new drug class with potential to treat diseases associated with altered T-type channel activity. This article is part of the special issue on 'Cannabinoids'.