Developing Antiepileptogenic Drugs for Acquired Epilepsy: Targeting the Mammalian Target of Rapamycin (mTOR) Pathway

Effect of Duvelisib, a Selective PI3K Inhibitor on Seizure Activity in Pentylenetetrazole-Induced Convulsions Animal Model

Epilepsy is one of the most common neurological diseases, which is caused by abnormal brain activity. A wide variety of studies have shown the importance of the phosphatidylinositol-3-kinase (PI3K) signaling pathway in epilepsy pathogenesis. Duvelisib (DUV) is a selective inhibitor of PI3K. The present study investigated the anticonvulsant potential of DUV in a rat model of pentylenetetrazole (PTZ)-induced convulsions. Male Wistar rats (200-250 g, 8 weeks old) were injected intraperitoneally (IP) with DUV at different doses of 5 and 10 mg/kg, or vehicle 30 minutes prior to PTZ (70 mg/kg, IP) treatment. Based on Racine's scale, behavioral seizures were assessed. The results showed that pretreatment with DUV prolonged the seizure stages according to the Racine scale, significantly decreased the duration of general tonic-clonic seizure and reduced the number of myoclonic jerks (P < .05). In conclusion, we found that PI3K antagonist DUV significantly reduced PTZ-induced seizures, indicating that DUV exerts an anticonvulsant effect by inhibiting PI3K signaling pathway.

Early Treatment with Vigabatrin Does Not Decrease Focal Seizures or Improve Cognition in Tuberous Sclerosis Complex: The PREVeNT Trial

OBJECTIVE

This study was undertaken to test the hypothesis that early vigabatrin treatment in tuberous sclerosis complex (TSC) infants improves neurocognitive outcome at 24 months of age.

METHODS

A phase IIb multicenter randomized double-blind placebo-controlled trial was conducted of vigabatrin at first epileptiform electroencephalogram (EEG) versus vigabatrin at seizure onset in infants with TSC. Primary outcome was Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) cognitive assessment score at 24 months. Secondary outcomes were prevalence of drug-resistant epilepsy, additional developmental outcomes, and safety of vigabatrin.

RESULTS

Of 84 infants enrolled, 12 were screen failures, 4 went straight to open label vigabatrin, and 12 were not randomized (normal EEG throughout). Fifty-six were randomized to early vigabatrin (n = 29) or placebo (n = 27). Nineteen of 27 in the placebo arm transitioned to open label vigabatrin, with a median delay of 44 days after randomization. Bayley-III cognitive composite scores at 24 months were similar for participants randomized to vigabatrin or placebo. Additionally, no significant differences were found between groups in overall epilepsy incidence and drug-resistant epilepsy at 24 months, time to first seizure after randomization, and secondary developmental outcomes. Incidence of infantile spasms was lower and time to spasms after randomization was later in the vigabatrin group. Adverse events were similar across groups.

INTERPRETATION

Preventative treatment with vigabatrin based on EEG epileptiform activity prior to seizure onset does not improve neurocognitive outcome at 24 months in TSC children, nor does it delay onset or lower the incidence of focal seizures and drug-resistant epilepsy at 24 months. Preventative vigabatrin was associated with later time to onset and lower incidence of infantile spasms. ANN NEUROL 2023.

Mammalian target of rapamycin inhibitors for the treatment of astrocytic hamartoma in tuberous sclerosis complex (TSC)

PURPOSE

Tuberous sclerosis complex (TSC) is an inherited neurocutaneous disorder. Fifty percent of patients with TSC will develop retinal astrocytic hamartoma (RAH). The mammalian target of rapamycin (mTOR) inhibitors interferes with the pathological mechanisms of TSC. Treatment of RAH with mTOR inhibitors has been described in only a few isolated case reports. The purpose of this study was to assess the effect of mTOR inhibitors on RAH in a small cohort of patients.

METHODS

The medical records of all consecutive patients with ocular manifestations of TSC that were treated with mTOR inhibitors at the Sheba Medical Center from January 2014 to December 2018 were retrospectively reviewed. Data collection included demographics, medical history, ocular presentation, ocular treatment, and treatment outcome. Tumor size was assessed by a masked observer, before and after treatment. Lesion measurements were made with Heidelberg SD-OCT (HRA + OCT SPECTRALIS), and fundus photos were taken with RetCam3® (Natus, USA) and analyzed by "ImageJ" software.

RESULTS

Eleven patients with tuberous sclerosis and astrocytic hamartoma were treated with mTOR inhibitors in the study period. Of them, 6 children (11 eyes, 20 tumors) had proper imaging of tumor size before and after treatment. The analysis included these 11 eyes. All six patients had non-ocular manifestations of TSC, including dermatologic (n = 5), neurologic (n = 5), and renal (n = 3) involvement. Ocular involvement included in five eyes (45%) tumors near the optic disc and in four eyes (37%) foveal tumors. The mean follow-up duration was 2.15 ± 1.4 years (range 10 months to 4.5 years). The average tumor base reduction in the treated group was 17.8% ± 15.9. The average maximal thickness at baseline was 414 ± 174 μm (range 152-686 μm). There was a 14% ± 7.1 reduction after treatment. None of the tumors showed evidence of growth at the final follow-up.

CONCLUSION

The findings of this study suggest that mTOR inhibitors can reduce tumor size and that they can be considered as an optional treatment in certain conditions. This preliminary report is the first to quantitatively assess pre- and posttreatment tumor size, in young patients.

Mitophagy in neurological disorders

Selective autophagy is an evolutionarily conserved mechanism that removes excess protein aggregates and damaged intracellular components. Most eukaryotic cells, including neurons, rely on proficient mitophagy responses to fine-tune the mitochondrial number and preserve energy metabolism. In some circumstances (such as the presence of pathogenic protein oligopolymers and protein mutations), dysfunctional mitophagy leads to nerve degeneration, with age-dependent intracellular accumulation of protein aggregates and dysfunctional organelles, leading to neurodegenerative disease. However, when pathogenic protein oligopolymers, protein mutations, stress, or injury are present, mitophagy prevents the accumulation of damaged mitochondria. Accordingly, mitophagy mediates neuroprotective effects in some forms of neurodegenerative disease (e.g., Alzheimer's disease, Parkinson’s disease, Huntington's disease, and Amyotrophic lateral sclerosis) and acute brain damage (e.g., stroke, hypoxic–ischemic brain injury, epilepsy, and traumatic brain injury). The complex interplay between mitophagy and neurological disorders suggests that targeting mitophagy might be applicable for the treatment of neurodegenerative diseases and acute brain injury. However, due to the complexity of the mitophagy mechanism, mitophagy can be both harmful and beneficial, and future efforts should focus on maximizing its benefits. Here, we discuss the impact of mitophagy on neurological disorders, emphasizing the contrast between the positive and negative effects of mitophagy.

Sirolimus Can Increase the Disappearance Rate of Cardiac Rhabdomyomas Associated with Tuberous Sclerosis: A Prospective Cohort and Self-Controlled Case Series Study

OBJECTIVES

To investigate the efficacy and safety of sirolimus in the treatment of cardiac rhabdomyomas associated with tuberous sclerosis complex and the specific benefits in different subgroups.

STUDY DESIGN

The study was a prospective cohort and self-controlled case series study. Based on the prevalence of cardiac rhabdomyoma at different ages, we estimated the natural tumor disappearance rate. The subgroup analysis was done by Cox regression. Self-controlled case series method was used to assess the magnitude and duration of the drug effect. Adverse events were described.

RESULTS

A total of 217 patients were included in the cohort study. Tumor disappearance rate was higher in younger age groups (hazard ratio = 0.99, P = .027) and female patients (hazard ratio = 2.08, P = .015). The age-adjusted incidence ratio showed that the disappearance of rhabdomyomas between 3 and 6 months was more related to sirolimus. Adverse events were observed 60 times in 42 of 217 children, mainly stomatitis.

CONCLUSIONS

Sirolimus can increase the disappearance rate of cardiac rhabdomyoma in the tuberous sclerosis complex population. Efficacy varies by sex and age: female and younger patients have higher tumor disappearance rate. Sirolimus is well-tolerated.

How to Find Candidate Drug-targets for Antiepileptogenic Therapy?

Although over 25 antiepileptic drugs (AEDs) have become currently available for clinical use, the incidence of epilepsy worldwide and the proportions of drug-resistant epilepsy among them are not significantly reduced during the past decades. Traditional screens for AEDs have been mainly focused on their anti-ictogenic roles, and their efficacies primarily depend on suppressing neuronal excitability or enhancing inhibitory neuronal activity, almost without the influence on the epileptogenesis or with inconsistent results from different studies. Epileptogenesis refers to the pathological process of a brain from its normal status to the alterations with the continuous prone of unprovoked spontaneous seizures after brain insults, such as stroke, traumatic brain injury, CNS infectious, and autoimmune disorders, and even some specific inherited conditions. Recently growing experimental and clinical studies have discovered the underlying mechanisms for epileptogenesis, which are multi-aspect and multistep. These findings provide us a number of interesting sites for antiepileptogenic drugs (AEGDs). AEGDs have been evidenced as significantly roles of postponing or completely blocking the development of epilepsy in experimental models. The present review will introduce potential novel candidate drug-targets for AEGDs based on the published studies.

Increased epileptogenicity in a mouse model of neurofibromatosis type 1

RATIONALE

Neurofibromatosis type 1 (NF1) is associated with higher rates of epilepsy compared to the general population. Some NF1 patients with epilepsy do not have intracranial lesions, suggesting the genetic mutation itself may contribute to higher rates of epilepsy in these patients. We have recently demonstrated increased seizure susceptibility in the Nf1^+/- mouse, but it is unknown whether this model displays altered epileptogenicity, as has been reported in patients with NF1. The aim of this study was to determine whether the Nf1^+/- mouse is more susceptible to electrical kindling-induced epileptogenesis.

METHODS

Young male or female adult Nf1^+/- or Nf1^+/+ (wild-type; WT) mice were implanted with electrodes for neocortical or hippocampal kindling paradigms. Neocortical kindling was performed for 40 stimulation sessions followed by baseline EEG monitoring to detect possible SRSs. Hippocampal kindling was performed with a modified extended kindling paradigm, completed to a maximum of 80 sessions to try to induce spontaneous repetitive seizures (SRSs). Western blot assays were performed in naïve and kindled mice to compare levels of Akt and MAPK (ERK1/2), proteins downstream of the NF1 mutation.

RESULTS

The average initial neocortical after-discharge threshold (ADT) was significantly lower in the Nf1^+/- group, which also required fewer stimulations to reach stage 5 seizure, had greater average seizure severity across all kindling sessions, had a greater number of convulsive seizures, and had a faster progression of after-discharge duration and Racine score during kindling. No WT mice exhibited SRS after neocortical kindling, versus 33% of Nf1^+/- mice. The average initial hippocampal ADT was not significantly different between the WT and Nf1^+/- groups, nor was there a difference in the number of stimulations required to reach the kindled state. The WT group had a significantly higher average seizure severity across all kindling sessions as compared with the Nf1^+/- mice. The WT group also had faster progression of the Racine seizure score over the kindling sessions, mainly due to a faster increase in seizures severity early during the kindling process. However, SRSs were seen in 50% of Nf1^+/- mice after modified extended kindling and in no WT mice. Western blots showed hippocampal kindling increased the ratio of phosphorylated/total Akt in both the WT and Nf1^+/- mice, while neocortical kindling led to increased ratios of phosphorylated/total Akt and MAPK in Nf1^+/- mice only.

CONCLUSIONS

We have demonstrated for the first time an increased rate of epileptogenesis in an animal model of NF1 with no known macroscopic/neoplastic brain lesions. This work provides evidence for the genetic mutation itself playing a role in seizures and epilepsy in patients with NF1, and supports the use of the Nf1^+/- mouse model in future mechanistic studies.

Neurodegenerative pathways as targets for acquired epilepsy therapy development

There is a growing body of clinical and experimental evidence that neurodegenerative diseases and epileptogenesis after an acquired brain insult may share common etiological mechanisms. Acquired epilepsy commonly develops as a comorbid condition in patients with neurodegenerative diseases such as Alzheimer's disease, although it is likely much under diagnosed in practice. Progressive neurodegeneration has also been described after traumatic brain injury, stroke, and other forms of brain insults. Moreover, recent evidence has shown that acquired epilepsy is often a progressive disorder that is associated with the development of drug resistance, cognitive decline, and worsening of other neuropsychiatric comorbidities. Therefore, new pharmacological therapies that target neurobiological pathways that underpin neurodegenerative diseases have potential to have both an anti-epileptogenic and disease-modifying effect on the seizures in patients with acquired epilepsy, and also mitigate the progressive neurocognitive and neuropsychiatric comorbidities. Here, we review the neurodegenerative pathways that are plausible targets for the development of novel therapies that could prevent the development or modify the progression of acquired epilepsy, and the supporting published experimental and clinical evidence.

Anterior thalamic nucleus stimulation protects hippocampal neurons by activating autophagy in epileptic monkeys

Deep brain stimulation of the anterior nucleus of the thalamus (ANT-DBS) is effective in treating temporal lobe epilepsy (TLE) and protects hippocampal neurons. Autophagy plays an essential role in epileptogenesis; however, the underlying effect of autophagy on ANT-DBS-mediated neuroprotection remains unclear. A monkey model of epilepsy was established by injecting kainic acid into the hippocampus and amygdala using a robot-assisted system. ANT-DBS was delivered in the chronic stage of the epileptic model and continued for 8 weeks. We found that ANT-DBS reduced the frequency of seizures and exerted neuroprotective effects via activating autophagy in hippocampal neurons. ANT-DBS increased light chain 3 (LC3) II level and co-localization of LC3 and lysosomal-associated membrane protein-1, accompanied by decreased expression of the autophagy substrate ubiquitin-binding protein p62, suggesting increased autophagosome formation. Most importantly, brain-derived neurotrophic factor (BDNF) –tropomyosin-related kinase type B (TrkB) pathway were involved in the regulation of autophagy. Both protein levels were reduced by ANT-DBS, and there was less phosphorylation of downstream regulators, extracellular signal-regulated kinase and Akt, followed by inactivation of mammalian target of rapamycin complex 1. Taken together, chronic ANT-DBS exerts neuroprotective effects on hippocampal neurons through inducing autophagy via suppressing the BDNF–TrkB pathway in a TLE monkey model.

Autophagy and Epilepsy

Epilepsy is a long-term neurological disease characterized by convulsions that can be recurrent. It is mainly caused by an imbalance between excitation and inhibition in the central nervous system. Currently, the pathogenesis is still unclear, although it may be related to changes in ion channels, neurotransmitters and glial cells. In recent years, increasing attention has been paid to the role of autophagy in the development of epilepsy. This chapter focuses on the role of the mTOR pathway in epileptogenesis and the relationship between autophagy, glycogen metabolism and Lafora disease and discusses the potential role of autophagy as a target for the treatment of epilepsy.

KA-11, a Novel Pyrrolidine-2,5-dione Derived Broad-Spectrum Anticonvulsant: Its Antiepileptogenic, Antinociceptive Properties and in Vitro Characterization

Recently, compound KA-11 was identified as a promising candidate for a new broad-spectrum anticonvulsant. This compound revealed wide protective activity across the most important animal models of seizures such as the maximal electroshock test (MES), the subcutaneous pentylenetetrazole test ( scPTZ), and the six-hertz test (6 Hz, 32 mA). Importantly, KA-11 was devoid of acute neurological activity, which was assessed by applying the chimney test (TD₅₀ value higher than 1500 mg/kg). The preliminary in vivo results confirmed favorable anticonvulsant and safety properties of KA-11. With the aim of further biological characterization of KA-11, in the current studies we evaluated its antiepileptogenic activity in the kindling model of epilepsy induced by repeated injection of PTZ in mice. Furthermore, we assessed the antinociceptive activity of KA-11 in several animal pain models. As a result, KA-11 (at all doses applied: 25, 50, and 100 mg/kg) significantly delayed the progression of kindling induced by repeated injection of PTZ in mice. Additionally, KA-11 revealed potent antinociceptive activity in the formalin-induced tonic pain and, importantly, in the oxaliplatin-induced neuropathic pain model in mice. Moreover, KA-11 did not induce motor deficits in the rotarod test. Patch-clamp experiments revealed that one of the mechanisms of action of KA-11 is inhibition of voltage-gated sodium currents. Compound KA-11 appeared to be safe in relation to hepatotoxic properties as no phospholipidosis induction was determined in HepG2 cells at 50 μM, and a small, statistically significant decrease of cell viability was observed only at the highest used dose of 100 μM. Moreover, KA-11 did not affect the function of CYP2D6. The aforementioned hybrid substance proved to penetrate the biological membranes in the in vitro permeability assays.

Structural Analysis of Hippocampal Kinase Signal Transduction

Kinases are a major clinical target for human diseases. Identifying the proteins that interact with kinases in vivo will provide information on unreported substrates and will potentially lead to more specific methods for therapeutic kinase regulation. Here, endogenous immunoprecipitations of evolutionally distinct kinases (i.e., Akt, ERK2, and CAMK2) from rodent hippocampi were analyzed by mass spectrometry to generate three highly confident kinase protein-protein interaction networks. Proteins of similar function were identified in the networks, suggesting a universal model for kinase signaling complexes. Protein interactions were observed between kinases with reported symbiotic relationships. The kinase networks were significantly enriched in genes associated with specific neurodevelopmental disorders providing novel structural connections between these disease-associated genes. To demonstrate a functional relationship between the kinases and the network, pharmacological manipulation of Akt in hippocampal slices was shown to regulate the activity of potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel(HCN1), which was identified in the Akt network. Overall, the kinase protein-protein interaction networks provide molecular insight of the spatial complexity of in vivo kinase signal transduction which is required to achieve the therapeutic potential of kinase manipulation in the brain.

Ginkgo biloba L. attenuates spontaneous recurrent seizures and associated neurological conditions in lithium-pilocarpine rat model of temporal lobe epilepsy through inhibition of mammalian target of rapamycin pathway hyperactivation

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. (Ginkgoaceae) has been widely used in traditional medicine for variety of neurological conditions particularly behavioral and memory impairments.

AIM OF THE STUDY

The present study was envisaged to explore the effect of a standardized fraction of Ginkgo biloba leaves (GBbf) in rat model of lithium-pilocarpine induced spontaneous recurrent seizures, and associated behavioral impairments and cognitive deficit.

MATERIALS AND METHODS

Rats showing appearance of spontaneous recurrent seizures following lithium pilocarpine (LiPc)-induced status epilepticus (SE) were treated with different doses of GBbf or vehicle for subsequent 4 weeks. The severity of seizures and aggression in rats were scored following treatment with GBbf. Further, open field, forced swim, novel object recognition and Morris water maze tests were conducted. Histopathological, protein levels and gene expression studies were performed in the isolated brains.

RESULTS

Treatment with GBbf reduced seizure severity score and aggression in epileptic animals. Improved spatial cognitive functions and recognition memory, along with reduction in anxiety-like behavior were also observed in the treated animals. Histopathological examination by Nissl staining showed reduction in neuronal damage in the hippocampal pyramidal layer. The dentate gyrus and Cornu Ammonis 3 regions of the hippocampus showed reduction in mossy fiber sprouting. GBbf treatment attenuated ribosomal S6 and pS6 proteins, and hippocampal mTOR, Rps6 and Rps6kb1 mRNA levels.

CONCLUSIONS

The results of present study concluded that GBbf treatment suppressed lithium-pilocarpine induced spontaneous recurrent seizures severity and incidence with improved cognitive functions, reduced anxiety-like behavior and aggression. The effect was found to be due to inhibition of mTOR pathway hyperactivation linked with recurrent seizures.

Improving Outcomes in Infantile Spasms: Role of Pharmacotherapy

Infantile spasms, and specifically within the context of West syndrome , is one of the most common epileptic encephalopathies to occur in early infancy. Early recognition and treatment can improve neurodevelopmental outcome in some cases, although the underlying aetiology is probably the most important prognostic factor in both spasm suppression and developmental outcome. Corticosteroids, either adrenocorticotrophic hormone (ACTH) or prednisolone, and vigabatrin are currently the preferred first-line treatment options. Vigabatrin is the treatment of choice when the underlying cause is tuberous sclerosis complex (TSC). Emerging evidence suggests that a combination of steroid and vigabatrin may be more effective in the suppression of spasms and resolution of hypsarrhythmia, the electro-encephalographic signal of spasms. Several other anti-epileptic drugs (AEDs) (levetiracetam, nitrazepam, sodium valproate, topiramate, zonisamide) are usually used as add-on or adjunctive treatment in refractory cases. Pyridoxine (or pyridoxal phosphate) and the ketogenic diet are established treatment options in refractory cases. There is some evidence that neuro-active steroids, including ganaxolone, may be effective; however, clinical trials undertaken intermittently for over a decade have yet to prove their efficacy, not only for the suppression of infantile spasms but also for the resolution of hypsarrhythmia, which may be as important as seizure control in developmental outcome in these children. Insights into developing novel treatment options have emerged from rodent models of infantile spasms, and research is continuing into the efficacy of rapamycin in improving outcomes in infantile spasms. This review provides a brief overview of the existing scientific literature around treatment options and outlines emerging newer treatment options in infantile spasms.

The mTOR signalling cascade: paving new roads to cure neurological disease

Defining the multiple roles of the mechanistic (formerly 'mammalian') target of rapamycin (mTOR) signalling pathway in neurological diseases has been an exciting and rapidly evolving story of bench-to-bedside translational research that has spanned gene mutation discovery, functional experimental validation of mutations, pharmacological pathway manipulation, and clinical trials. Alterations in the dual contributions of mTOR - regulation of cell growth and proliferation, as well as autophagy and cell death - have been found in developmental brain malformations, epilepsy, autism and intellectual disability, hypoxic-ischaemic and traumatic brain injuries, brain tumours, and neurodegenerative disorders. mTOR integrates a variety of cues, such as growth factor levels, oxygen levels, and nutrient and energy availability, to regulate protein synthesis and cell growth. In line with the positioning of mTOR as a pivotal cell signalling node, altered mTOR activation has been associated with a group of phenotypically diverse neurological disorders. To understand how altered mTOR signalling leads to such divergent phenotypes, we need insight into the differential effects of enhanced or diminished mTOR activation, the developmental context of these changes, and the cell type affected by altered signalling. A particularly exciting feature of the tale of mTOR discovery is that pharmacological mTOR inhibitors have shown clinical benefits in some neurological disorders, such as tuberous sclerosis complex, and are being considered for clinical trials in epilepsy, autism, dementia, traumatic brain injury, and stroke.

Mammalian target of rapamycin inhibitors for intractable epilepsy and subependymal giant cell astrocytomas in tuberous sclerosis complex

OBJECTIVES

To evaluate the efficacy and side effects of oral mammalian target of rapamycin (mTOR) inhibitors in children and adolescents with tuberous sclerosis complex (TSC) and intractable epilepsy or subependymal giant cell astrocytoma (SEGA).

STUDY DESIGN

Single-center series of 13 children and adolescents with TSC who received sirolimus or everolimus (mTOR inhibitors). The anticonvulsant response was evaluated in 7 patients with TSC and refractory seizures. Six patients with SEGAs were treated with either sirolimus or everolimus for nonsurgical management. SEGA volumes were assessed longitudinally using 1.5-T magnetic resonance imaging.

RESULTS

Of the intractable seizure group (7 patients), 1 patient had >90% reduction, 4 had 50%-90% reduction, and 2 had <50% reduction. Three reported subjective improvements in learning. By 12 months of treatment, there were statistically significant reductions in the SEGA volumes in 4 patients who received mTOR inhibitors (P < .04). The mean SEGA volume after 6 months of treatment was 2.18 cm(3), which represents 33% reduction in the mean baseline volume of 3.26 cm(3). The mTOR inhibitors were well tolerated. Adverse effects include dyslipidaemia (3 of 13), gingivitis (1 of 13), anorexia (1 of 13), and mild gastrointestinal side effects (1 of 13).

CONCLUSION

This case series suggests that mTOR inhibitors can improve seizures in those with TSC and refractory epilepsy. They are also an effective treatment for reducing the volume of SEGAs in patients with TSC not amenable to surgery with an acceptable side effect profile.

Seizure-induced reduction in PIP3 levels contributes to seizure-activity and is rescued by valproic acid

Phosphatidylinositol (3–5) trisphosphate (PIP₃) is a central regulator of diverse neuronal functions that are critical for seizure progression, however its role in seizures is unclear. We have recently hypothesised that valproic acid (VPA), one of the most commonly used drugs for the treatment of epilepsy, may target PIP₃ signalling as a therapeutic mode of action. Here, we show that seizure induction using kainic acid in a rat in vivo epilepsy model resulted in a decrease in hippocampal PIP₃ levels and reduced protein kinase B (PKB/AKT) phosphorylation, measured using ELISA mass assays and Western blot analysis, and both changes were restored following VPA treatment. These finding were reproduced in cultured rat hippocampal primary neurons and entorhinal cortex–hippocampal slices during exposure to the GABA(A) receptor antagonist pentylenetetrazol (PTZ), which is widely used to generate seizures and seizure-like (paroxysmal) activity. Moreover, VPA's effect on paroxysmal activity in the PTZ slice model is blocked by phosphatidylinositol 3-kinase (PI3K) inhibition or PIP₂ sequestration by neomycin, indicating that VPA's efficacy is dependent upon PIP₃ signalling. PIP₃ depletion following PTZ treatment may also provide a positive feedback loop, since enhancing PIP₃ depletion increases, and conversely, reducing PIP₃ dephosphorylation reduces paroxysmal activity and this effect is dependent upon AMPA receptor activation. Our results therefore indicate that PIP₃ depletion occurs with seizure activity, and that VPA functions to reverse these effects, providing a novel mechanism for VPA in epilepsy treatment.

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In vivo seizure induction (using kainic acid) reduces hippocampal PIP₃ levels.

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In vivo seizure induction (using kainic acid) reduces hippocampal phospho-PKB levels.

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Valproic acid protects against these reductions under seizure conditions only.

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Similar regulation is seen with PTZ-induced in vitro seizure activity.

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Seizure-induced PIP₃ reduction causes a feedback activation of seizure activity.

Gene expression profiling of a hypoxic seizure model of epilepsy suggests a role for mTOR and Wnt signaling in epileptogenesis

Microarray profiling was used to investigate gene expression in the hypoxic seizure model of acquired epilepsy in the rat, with the aim of characterizing functional pathways which are persistently activated or repressed during epileptogenesis. Hippocampal and cortical tissues were transcriptionally profiled over a one week period following an initial series of seizures induced by mild hypoxia at post-natal day 10 (P10), and the gene expression data was then analyzed with a focus on gene set enrichment analysis, an approach which emphasizes regulation of entire pathways rather than of individual genes. Animals were subjected to one of three conditions: a control with no hypoxia, hypoxic seizures, and hypoxic seizures followed by treatment with the AMPAR antagonist NBQX, a compound currently proposed to be a modulator of epileptogenesis. While temporal gene expression in the control samples was found to be consistent with known processes of neuronal maturation in the rat for the given time window, the hypoxic seizure response was found to be enriched for components of the PI3K/mTOR and Wnt signaling pathways, alongside gene sets representative of glutamatergic, synaptic and axonal processes, perhaps regulated as a downstream consequence of activation of these pathways. Wnt signaling components were also found enriched in the more specifically epileptogenic NBQX-responsive gene set. While activation of the mTOR pathway is consistent with its known role in epileptogenesis and strengthens the case for mTOR or PI3K pathway inhibitors as potential anti-epileptogenic drugs, investigation of the role of Wnt signaling and the effect of appropriate inhibitors might offer a parallel avenue of research toward anti-epileptogenic treatment of epilepsy.

Everolimus treatment of refractory epilepsy in tuberous sclerosis complex

OBJECTIVE

Epilepsy is a major manifestation of tuberous sclerosis complex (TSC). Everolimus is an mammalian target of rapamycin complex 1 inhibitor with demonstrated benefit in several aspects of TSC. We report the first prospective human clinical trial to directly assess whether everolimus will also benefit epilepsy in TSC patients.

METHODS

The effect of everolimus on seizure control was assessed using a prospective, multicenter, open-label, phase I/II clinical trial. Patients≥2 years of age with confirmed diagnosis of TSC and medically refractory epilepsy were treated for a total of 12 weeks. The primary endpoint was percentage of patients with a ≥50% reduction in seizure frequency over a 4-week period before and after treatment. Secondary endpoints assessed impact on electroencephalography (EEG), behavior, and quality of life.

RESULTS

Twenty-three patients were enrolled, and 20 patients were treated with everolimus. Seizure frequency was reduced by ≥50% in 12 of 20 subjects. Overall, seizures were reduced in 17 of the 20 by a median reduction of 73% (p<0.001). Seizure frequency was also reduced during 23-hour EEG monitoring (p=0.007). Significant reductions in seizure duration and improvement in parent-reported behavior and quality of life were also observed. There were 83 reported adverse events that were thought to be treatment-related, all of which were mild or moderate in severity.

INTERPRETATION

Seizure control improved in the majority of TSC patients with medically refractory epilepsy following treatment with everolimus. Everolimus demonstrated additional benefits on behavior and quality of life. Treatment was safe and well tolerated. Everolimus may be a therapeutic option for refractory epilepsy in this population.

Role of the mTOR signaling pathway in epilepsy

Epilepsy, a common neurological disorder and cause of significant morbidity and mortality, places an enormous burden on the individual and society. Presently, most drugs for epilepsy primarily suppress seizures as symptomatic therapies but do not possess actual antiepileptogenic or disease-modifying properties. The mTOR (mammalian target of rapamycin) signaling pathway is involved in major multiple cellular functions, including protein synthesis, cell growth and proliferation and synaptic plasticity, which may influence neuronal excitability and be responsible for epileptogenesis. Intriguing findings of the frequent hyperactivation of mTOR signaling in epilepsy make it a potential mechanism in the pathogenesis as well as an attractive target for the therapeutic intervention, and have driven the significant ongoing efforts to pharmacologically target this pathway. This review explores the relevance of the mTOR pathway to epileptogenesis and its potential as a therapeutic target in epilepsy treatment by presenting the current results on mTOR inhibitors, in particular, rapamycin, in animal models of diverse types of epilepsy. Limited clinical studies in human epilepsy, some paradoxical experimental data and outstanding questions have also been discussed.

Dysfunction of the mTOR pathway is a risk factor for Alzheimer's disease

Background

The development of disease-modifying therapies for Alzheimer’s disease is hampered by our lack of understanding of the early pathogenic mechanisms and the lack of early biomarkers and risk factors.

We have documented the expression pattern of mTOR regulated genes in the frontal cortex of Alzheimer’s disease patients. We have also examined the functional integrity of mTOR signaling in peripheral lymphocytes in Alzheimer’s disease patients relative to healthy controls.

Results

In the brain mTOR is seen to control molecular functions related to cell cycle regulation, cell death and several metabolic pathways. These downstream elements of the mTOR signaling cascade are deregulated in the brain of Alzheimer’s disease patients well before the development of pathology. This dysregulation of the mTOR downstream signaling cascade is not restricted to the brain but appears to be systemic and can be detected in peripheral lymphocytes as a reduced Rapamycin response.

Conclusions

The dysfunction of the signaling pathways downstream of mTOR may represent a risk factor for Alzheimer’s disease and is independent of the ApoE status of the patients.

We have also identified the molecular substrates of the beneficial effects of Rapamycin on the nervous system. We believe that these results can further inform the development of clinical predictive tests for the risk of Alzheimer’s disease in patients with mild cognitive impairment.

Epilepsy Surgery in Childhood

Historically, epilepsy surgery has been considered a treatment of last resort. Advances in neuroimaging, particularly high resolution magnetic resonance imaging (MRI) techniques and functional neuroimaging, advances in neuroanesthesia and neurosurgery have all contributed to the development of safe and effective epilepsy surgery in infants and children. Furthermore, epilepsy surgery may prevent the chronic deleterious effects that uncontrolled epileptic seizures have on brain development. The main challenges that clinicians face are early identification of infants and children who have epilepsy which is amenable to epilepsy surgery, the timing of epilepsy surgery and the investigation of patients where no lesion is demonstrable on MRI. It is imperative that children be followed after epilepsy surgery to assess the long-term outcomes not only in relation to seizure control, but also to assess quality of life, psychoeducational achievement, and psychiatric co-morbidity.

Spatio-temporal expression study of phosphorylated 70-kDa ribosomal S6 kinase (p70S6k) in mesial temporal lobe epilepsy

OBJECTIVE

To determine the spatio-temporal expression of p70S6k activation in hippocampus in mesial temporal lobe epilepsy.

METHODS

Temporal lobe epilepsy model was established by stereotaxically unilateral and intrahippocampal injection of kainite acid (KA) in adult male C57BL/6 mice. Latent and chronic epileptogenesis were represented by mice 5 days after KA injection (n = 5) and mice 5 weeks after KA injection (n = 8), respectively. Control mice (n = 5) were injected with saline. Immunohistochemical assays were performed on brain sections of the mice.

RESULTS

Hippocampus both ipsilateral and contralateral to the KA injection displayed significantly up-regulated pS6 immunoreactivity in dispersed granule cells in 5-day and 5-week model mice.

CONCLUSION

The activation of p70S6k is mainly located in the dentate gyrus in KA-induced mouse model of temporal lobe epilepsy, indicating that the activation may be related with the disperse degree and hypertrophy of granule cells.

Protein kinase inhibitor as a potential candidate for epilepsy treatment

PURPOSE

Effects of the "VID-82925" kinase inhibitor molecule were investigated both during the developing phase as well as during the stable phase of the focus with spontaneous recurrent seizures using the 4-AP-induced in vivo epilepsy model in anesthetized rats.

METHODS

In electrophysiologic experiments, VID-82925 (0.85 mg/kg) was injected intravenously either before the induction (pretreatment) or after the development of the stable focus (treatment). Reference drugs carbamazepine (4.8 mg/kg) and levetiracetam (50 mg/kg) were employed using the same experimental paradigm. The antiepileptic effect of VID-82925 was also compared to those of the broad-spectrum gap junction channel blocker carbenoxolone (10 mm).

KEY FINDINGS

Pretreatment with VID-82925 revealed an antiepileptogenic effect as it suppressed significantly the manifestation of the epileptiform activity not only during the developing phase, but also for a considerable long period during the stable phase of the focus. The current data do not allow us to differentiate an antiictal treatment effect from an antiepileptogenic effect of the compound during the stable phase of the focus. Treatment with VID-82925 was also effective against ictogenesis during the stable phase of the focus. Pretreatment with levetiracetam failed to exert any antiepileptogenic effect. The antiepileptic effects of VID-82925 and of the reference drugs on the epileptiform activity of the stable focus were comparable in intensity; however, the effect of VID-82925 was 2-3 times longer. The effects of VID-82925 and of carbenoxolone overlapped one another to some extent, suggesting that VID-82925 may exert its effects at least partially through blocking of gap junctional communication.

SIGNIFICANCE

Our results indicate that inhibition of protein kinases may also provide an effective strategy for the development of a drug that is not only antiepileptic but also depresses the course of epileptogenesis.

A novel Akt3 mutation associated with enhanced kinase activity and seizure susceptibility in mice

In a phenotype-driven mutagenesis screen, a novel, dominant mouse mutation, Nmf350, caused low seizure threshold, sporadic tonic-clonic seizures, brain enlargement and ectopic neurons in the dentate hilus and molecular layer of the hippocampus. Genetic mapping implicated Akt3, one of four candidates within the critical interval. Sequencing analysis revealed that mutants have a missense mutation in Akt3 (encoding one of three AKT/protein kinase B molecules), leading to a non-synonymous amino acid substitution in the highly conserved protein kinase domain. Previous knockout studies showed that Akt3 is pivotal in postnatal brain development, including a smaller brain, although seizures were not observed. In contrast to Akt3(Nmf350), we find that Akt3 null mice exhibit an elevated seizure threshold. An in vitro kinase assay revealed that Akt3(Nmf350) confers higher enzymatic activity, suggesting that Akt3(Nmf350) might enhance AKT signaling in the brain. In the dentate gyrus of Akt3(Nmf350) homozygotes, we also observed a modest increase in immunoreactivity of phosphorylated ribosomal protein S6, an AKT pathway downstream target. Together these findings suggest that Akt3(Nmf350) confers an increase of AKT3 activity in specific neuronal populations in the brain, and a unique dominant phenotype. Akt3(Nmf350) mice provide a new tool for studying physiological roles of AKT signaling in the brain, and potentially novel mechanisms for epilepsy.