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

SGCP: a spectral self-learning method for clustering genes in co-expression networks

BACKGROUND

A widely used approach for extracting information from gene expression data employs the construction of a gene co-expression network and the subsequent computational detection of gene clusters, called modules. WGCNA and related methods are the de facto standard for module detection. The purpose of this work is to investigate the applicability of more sophisticated algorithms toward the design of an alternative method with enhanced potential for extracting biologically meaningful modules.

RESULTS

We present self-learning gene clustering pipeline (SGCP), a spectral method for detecting modules in gene co-expression networks. SGCP incorporates multiple features that differentiate it from previous work, including a novel step that leverages gene ontology (GO) information in a self-leaning step. Compared with widely used existing frameworks on 12 real gene expression datasets, we show that SGCP yields modules with higher GO enrichment. Moreover, SGCP assigns highest statistical importance to GO terms that are mostly different from those reported by the baselines.

CONCLUSION

Existing frameworks for discovering clusters of genes in gene co-expression networks are based on relatively simple algorithmic components. SGCP relies on newer algorithmic techniques that enable the computation of highly enriched modules with distinctive characteristics, thus contributing a novel alternative tool for gene co-expression analysis.

Exploring the effect of 6-BIO and sulindac in modulation of Wnt/β-catenin signaling pathway in chronic phase of temporal lobe epilepsy

The prospective involvement of the Wnt/β-catenin signaling pathway in epilepsy, with the proposed therapeutic uses of its modulators, has been suggested; however, comprehensive knowledge in this regard is currently limited. Despite postulations about the pathway's significance and treatment potential, a systematic investigation is required to better understand its implications in chronic epilepsy. We investigated the role of key proteins like β-catenin, GSK-3β, and their modulators sulindac and 6-BIO, in Wnt/β-catenin pathway during chronic phase of temporal lobe epilepsy. We also evaluated the role of modulators in seizure score, seizure frequency and neurobehavioral parameters in temporal lobe epilepsy. We developed status epilepticus model using lithium-pilocarpine. The assessment of neurobehavioral parameters was done followed by histopathological examination and immunohistochemistry staining of hippocampus as well as RT-qPCR and western blotting to analyse gene and protein expression. In SE rats, seizure score and frequency were significantly high compared to control rats, with notable changes in neurobehavioral parameters and neuronal damage observed in hippocampus. Our study also revealed a substantial upregulation of the Wnt/β-catenin pathway in chronic epilepsy, as evidenced by gene and protein expression studies. Sulindac emerged as a potent modulator, reducing seizure score, frequency, neuronal damage, apoptosis, and downregulating the Wnt/β-catenin pathway when compared to 6-BIO. Our findings emphasize the potential of GSK-3β and β-catenin as promising drug targets for chronic temporal lobe epilepsy, offering valuable treatment options for chronic epilepsy. The promising outcomes with sulindac encourages further exploration in clinical trials to assess its therapeutic potential.

The multifaceted role of Wnt canonical signalling in neurogenesis, neuroinflammation, and hyperexcitability in mesial temporal lobe epilepsy

Epilepsy is a neurological disorder characterised by unprovoked, repetitive seizures caused by abnormal neuronal firing. The Wnt/β-Catenin signalling pathway is involved in seizure-induced neurogenesis, aberrant neurogenesis, neuroinflammation, and hyperexcitability associated with epileptic disorder. Wnt/β-Catenin signalling is crucial for early brain development processes including neuronal patterning, synapse formation, and N-methyl-d-aspartate receptor (NMDAR) regulation. Disruption of molecular networks such as Wnt/β-catenin signalling in epilepsy could offer encouraging anti-epileptogenic targets. So, with a better understanding of the canonical Wnt/-Catenin pathway, we highlight in this review the important elements of Wnt/-Catenin signalling specifically in Mesial Temporal Lobe Epilepsy (MTLE) for potential therapeutic targets.

Canonical Wnt activator Chir99021 prevents epileptogenesis in the intrahippocampal kainate mouse model of temporal lobe epilepsy

The Wnt signaling pathway mediates the development of dentate granule cell neurons in the hippocampus. These neurons are central to the development of temporal lobe epilepsy and undergo structural and physiological remodeling during epileptogenesis, which results in the formation of epileptic circuits. The pathways responsible for granule cell remodeling during epileptogenesis have yet to be well defined, and represent therapeutic targets for the prevention of epilepsy. The current study explores Wnt signaling during epileptogenesis and for the first time describes the effect of Wnt activation using Wnt activator Chir99021 as a novel anti-epileptogenic therapeutic approach. Focal mesial temporal lobe epilepsy was induced by intrahippocampal kainate (IHK) injection in wild-type and POMC-eGFP transgenic mice. Wnt activator Chir99021 was administered daily, beginning 3 h after seizure induction, and continued up to 21-days. Immature granule cell morphology was quantified in the ipsilateral epileptogenic zone and the contralateral peri-ictal zone 14 days after IHK, targeting the end of the latent period. Bilateral hippocampal electrocorticographic recordings were performed for 28-days, 7-days beyond treatment cessation. Hippocampal behavioral tests were performed after completion of Chir99021 treatment. Consistent with previous studies, IHK resulted in the development of epilepsy after a 14 day latent period in this well-described mouse model. Activation of the canonical Wnt pathway with Chir99021 significantly reduced bilateral hippocampal seizure number and duration. Critically, this effect was retained after treatment cessation, suggesting a durable antiepileptogenic change in epileptic circuitry. Morphological analyses demonstrated that Wnt activation prevented pathological remodeling of the primary dendrite in both the epileptogenic zone and peri-ictal zone, changes in which may serve as a biomarker of epileptogenesis and anti-epileptogenic treatment response in pre-clinical studies. These findings were associated with improved object location memory with Chir99021 treatment after IHK. This study provides novel evidence that canonical Wnt activation prevents epileptogenesis in the IHK mouse model of mesial temporal lobe epilepsy, preventing pathological remodeling of dentate granule cells. Wnt signaling may therefore play a key role in mesial temporal lobe epileptogenesis, and Wnt modulation may represent a novel therapeutic strategy in the prevention of epilepsy.

Therapeutic Potential of Natural Compounds from Herbs and Nutraceuticals in Alleviating Neurological Disorders: Targeting the Wnt Signaling Pathway

As an important signaling pathway in multicellular eukaryotes, the Wnt signaling pathway participates in a variety of physiological processes. Recent studies have confirmed that the Wnt signaling pathway plays an important role in neurological disorders such as stroke, Alzheimer's disease, and Parkinson's disease. The regulation of Wnt signaling by natural compounds in herbal medicines and nutraceuticals has emerged as a potential strategy for the development of new drugs for neurological disorders. Purpose: The aim of this review is to evaluate the latest research results on the efficacy of natural compounds derived from herbs and nutraceuticals in the prevention and treatment of neurological disorders by regulating the Wnt pathway in vivo and in vitro. A manual and electronic search was performed for English articles available from PubMed, Web of Science, and ScienceDirect from the January 2010 to February 2023. Keywords used for the search engines were "natural products,″ "plant derived products,″ "Wnt+ clinical trials,″ and "Wnt+,″ and/or paired with "natural products″/″plant derived products", and "neurological disorders." A total of 22 articles were enrolled in this review, and a variety of natural compounds from herbal medicine and nutritional foods have been shown to exert therapeutic effects on neurological disorders through the Wnt pathway, including curcumin, resveratrol, and querctrin, etc. These natural products possess antioxidant, anti-inflammatory, and angiogenic properties, confer neurovascular unit and blood-brain barrier integrity protection, and affect neural stem cell differentiation, synaptic formation, and neurogenesis, to play a therapeutic role in neurological disorders. In various in vivo and in vitro studies and clinical trials, these natural compounds have been shown to be safe and tolerable with few adverse effects. Natural compounds may serve a therapeutic role in neurological disorders by regulating the Wnt pathway. This summary of the research progress of natural compounds targeting the Wnt pathway may provide new insights for the treatment of neurological disorders and potential targets for the development of new drugs.

Differential Regulation of Wnt/β-catenin Signaling in Acute and Chronic Epilepsy in Repeated Low Dose Lithium-Pilocarpine Rat Model of Status Epilepticus

Epilepsy is a chronic neurological complication characterized by unprovoked seizure episodes due to the imbalance between excitatory and inhibitory neurons. The epileptogenesis process has been reported to be involved in chronic epilepsy however, the mechanism underlying epileptogenesis remains unclear. Recent studies have shown the possible involvement of Wnt/β-catenin signaling in the neurogenesis and neuronal reorganization in epileptogenesis. In this study, we used repeated low dose lithium-pilocarpine model of status epilepsy (SE) to study the involvement of Wnt/β-catenin signaling at acute and chronic stages post SE induction. The acute study ranged from day 0 to day 28 post SE induction and the chronic study ranged from day 0 to day 56 post SE induction. Several neurobehavioral parameters and seizure score and seizure frequency was analysed until the end of the study. The proteins involved in the regulation of Wnt/β-catenin signaling and downstream cascading were analysed using western blot and quantitative real-time PCR analysis. The Wnt/β-catenin pathway was found inactive in acute SE, while the same was found activated at the chronic stage. Our findings suggest that the activated Wnt/β-catenin signaling in chronic epilepsy might be the possible mechanism underlying epileptogenesis as indicated by increased neuronal count, increased synaptic density, astrogliosis and apoptosis in chronic epilepsy. These findings can help target the Wnt/β-catenin pathway differentially depending upon the type of epilepsy. The acute stage characterized by SE can be improved by targeting GSK-3β levels and the chronic stage characterized by temporal lobe epilepsy can be improved by targeting β-catenin and disheveled proteins.

Integrated network-based multiple computational analyses for identification of co-expressed candidate genes associated with neurological manifestations of COVID-19

'Tripartite network' (TN) and 'combined gene network' (CGN) were constructed and their hub-bottleneck and driver nodes (44 genes) were evaluated as 'target genes' (TG) to identify 21 'candidate genes' (CG) and their relationship with neurological manifestations of COVID-19. TN was developed using neurological symptoms of COVID-19 found in literature. Under query genes (TG of TN), co-expressed genes were identified using pair-wise mutual information to genes available in RNA-Seq autopsy data of frontal cortex of COVID-19 victims. CGN was constructed with genes selected from TN and co-expressed in COVID-19. TG and their connecting genes of respective networks underwent functional analyses through findings of their enrichment terms and pair-wise 'semantic similarity scores' (SSS). A new integrated 'weighted harmonic mean score' was formulated assimilating values of SSS and STRING-based 'combined score' of the selected TG-pairs, which provided CG-pairs with properties of CGs as co-expressed and 'indispensable nodes' in CGN. Finally, six pairs sharing seven 'prevalent CGs' (ADAM10, ADAM17, AKT1, CTNNB1, ESR1, PIK3CA, FGFR1) showed linkages with the phenotypes (a) directly under neurodegeneration, neurodevelopmental diseases, tumour/cancer and cellular signalling, and (b) indirectly through other CGs under behavioural/cognitive and motor dysfunctions. The pathophysiology of 'prevalent CGs' has been discussed to interpret neurological phenotypes of COVID-19.

Transcriptome Profiling of the Hippocampal Seizure Network Implicates a Role for Wnt Signaling during Epileptogenesis in a Mouse Model of Temporal Lobe Epilepsy

Mesial temporal lobe epilepsy (mTLE) is a life-threatening condition characterized by recurrent hippocampal seizures. mTLE can develop after exposure to risk factors such as febrile seizure, trauma, and infection. Within the latent period between exposure and onset of epilepsy, pathological remodeling events occur that contribute to epileptogenesis. The molecular mechanisms responsible are currently unclear. We used the mouse intrahippocampal kainite model of mTLE to investigate transcriptional dysregulation in the ipsilateral and contralateral dentate gyrus (DG), representing the epileptogenic zone (EZ) and peri-ictal zone (PIZ). DG were analyzed after 3, 7, and 14 days by RNA sequencing. In both the EZ and PIZ, transcriptional dysregulation was dynamic over the epileptogenic period with early expression of genes representing cell signaling, migration, and proliferation. Canonical Wnt signaling was upregulated in the EZ and PIZ at 3 days. Expression of inflammatory genes differed between the EZ and PIZ, with early expression after 3 days in the PIZ and delayed expression after 7-14 days in the EZ. This suggests that critical gene changes occur early in the hippocampal seizure network and that Wnt signaling may play a role within the latent epileptogenic period. These findings may help to identify novel therapeutic targets that could prevent epileptogenesis.

An insight into crosstalk among multiple signaling pathways contributing to epileptogenesis

Despite the years of research, epilepsy remains uncontrolled in one-third of afflicted individuals and poses a health and economic burden on society. Currently available anti-epileptic drugs mainly target the excitatory-inhibitory imbalance despite targeting the underlying pathophysiology of the disease. Recent research focuses on understanding the pathophysiologic mechanisms that lead to seizure generation and on possible new treatment avenues for preventing epilepsy after a brain injury. Various signaling pathways, including the mechanistic target of rapamycin (mTOR) pathway, mitogen-activated protein kinase (MAP-ERK) pathway, JAK-STAT pathway, wnt/β-catenin signaling, cAMP pathway, and jun kinase pathway, have been suggested to play an essential role in this regard. Recent work suggests that the mTOR pathway intervenes epileptogenesis and proposes that mTOR inhibitors may have antiepileptogenic properties for epilepsy. In the same way, several animal studies have indicated the involvement of the Wnt signaling pathway in neurogenesis and neuronal death induced by seizures in different phases (acute and chronic) of seizure development. Various studies have also documented the activation of JAK-STAT signaling in epilepsy and cAMP involvement in epileptogenesis through CREB (cAMP response element-binding protein). Although studies are there, the mechanism for how components of these pathways mediate epileptogenesis requires further investigation. This review summarises the current role of various signaling pathways involved in epileptogenesis and the crosstalk among them. Furthermore, we will also discuss the mechanical base for the interaction between these pathways and how these interactions could be a new emerging promising target for future epilepsy therapies.

Molecular tools for the characterization of seizure susceptibility in genetic rodent models of epilepsy

Epilepsy is a chronic neurological disorder characterized by abnormal neuronal activity that arises from imbalances between excitatory and inhibitory synapses, which are highly correlated to functional and structural changes in specific brain regions. The difference between the normal and the epileptic brain may harbor genetic alterations, gene expression changes, and/or protein alterations in the epileptogenic nucleus. It is becoming increasingly clear that such differences contribute to the development of distinct epilepsy phenotypes. The current major challenges in epilepsy research include understanding the disease progression and clarifying epilepsy classifications by searching for novel molecular biomarkers. Thus, the application of molecular techniques to carry out comprehensive studies at deoxyribonucleic acid, messenger ribonucleic acid, and protein levels is of utmost importance to elucidate molecular dysregulations in the epileptic brain. The present review focused on the great diversity of technical approaches available and new research methodology, which are already being used to study molecular alterations underlying epilepsy. We have grouped the different techniques according to each step in the flow of information from DNA to RNA to proteins, and illustrated with specific examples in animal models of epilepsy, some of which are our own. Separately and collectively, the genomic and proteomic techniques, each with its own strengths and limitations, provide valuable information on molecular mechanisms underlying seizure susceptibility and regulation of neuronal excitability. Determining the molecular differences between genetic rodent models of epilepsy and their wild-type counterparts might be a key in determining mechanisms of seizure susceptibility and epileptogenesis as well as the discovery and development of novel antiepileptic agents. This article is part of the Special Issue "NEWroscience 2018".

Antiepileptogenic Effect of Retinoic Acid

Retinoic acid, a metabolite of vitamin A, acts through either genomic or nongenomic actions. The genomic action of retinoids exerts effects on gene transcription through interaction with retinoid receptors such as retinoic acid receptors (RARα, β, and γ) and retinoid X receptors (RXRα, β, and γ) that are primarily concentrated in the amygdala, pre-frontal cortex, and hippocampal areas in the brain. In response to retinoid binding, RAR/RXR heterodimers undergo major conformational changes and orchestrate the transcription of specific gene networks. Previous experimental studies have reported that retinoic acid exerts an antiepileptogenic effect through diverse mechanisms, including the modulation of gap junctions, neurotransmitters, long-term potentiation, calcium channels and some genes. To our knowledge, there are no previous or current clinical trials evaluating the use of retinoic acid for seizure control.

Insights into Potential Targets for Therapeutic Intervention in Epilepsy

Epilepsy is a chronic brain disease that affects approximately 65 million people worldwide. However, despite the continuous development of antiepileptic drugs, over 30% patients with epilepsy progress to drug-resistant epilepsy. For this reason, it is a high priority objective in preclinical research to find novel therapeutic targets and to develop effective drugs that prevent or reverse the molecular mechanisms underlying epilepsy progression. Among these potential therapeutic targets, we highlight currently available information involving signaling pathways (Wnt/β-catenin, Mammalian Target of Rapamycin (mTOR) signaling and zinc signaling), enzymes (carbonic anhydrase), proteins (erythropoietin, copine 6 and complement system), channels (Transient Receptor Potential Vanilloid Type 1 (TRPV1) channel) and receptors (galanin and melatonin receptors). All of them have demonstrated a certain degree of efficacy not only in controlling seizures but also in displaying neuroprotective activity and in modifying the progression of epilepsy. Although some research with these specific targets has been done in relation with epilepsy, they have not been fully explored as potential therapeutic targets that could help address the unsolved issue of drug-resistant epilepsy and develop new antiseizure therapies for the treatment of epilepsy.

Pan-TGFβ inhibition by SAR439459 relieves immunosuppression and improves antitumor efficacy of PD-1 blockade

TGFβ is a pleiotropic cytokine that may have both tumor inhibiting and tumor promoting properties, depending on tissue and cellular context. Emerging data support a role for TGFβ in suppression of antitumor immunity. Here we show that SAR439459, a pan-TGFβ neutralizing antibody, inhibits all active isoforms of human and murine TGFβ, blocks TGFβ-mediated pSMAD signaling, and TGFβ-mediated suppression of T cells and NK cells. In vitro, SAR439459 synergized with anti-PD1 to enhance T cell responsiveness. In syngeneic tumor models, SAR439459 treatment impaired tumor growth, while the combination of SAR439459 with anti–PD-1 resulted in complete tumor regression and a prolonged antitumor immunity. Mechanistically, we found that TGFβ inhibition with PD-1 blockade augmented intratumoral CD8⁺ T cell proliferation, reduced exhaustion, evoked proinflammatory cytokines, and promoted tumor-specific CD8⁺ T cell responses. Together, these data support the hypothesis that TGFβ neutralization using SAR439459 synergizes with PD-1 blockade to promote antitumor immunity and formed the basis for the ongoing clinical investigation of SAR439459 in patients with cancer (NCT03192345).

Multi-scale top-down approach for modelling epileptic protein-protein interaction network analysis to identify driver nodes and pathways

Protein - Protein Interaction Network (PPIN) analysis unveils molecular level mechanisms involved in disease condition. To explore the complex regulatory mechanisms behind epilepsy and to address the clinical and biological issues of epilepsy, in silico techniques are feasible in a cost- effective manner. In this work, a hierarchical procedure to identify influential genes and regulatory pathways in epilepsy prognosis is proposed. To obtain key genes and pathways causing epilepsy, integration of two benchmarked datasets which are exclusively devoted for complex disorders is done as an initial step. Using STRING database, PPIN is constructed for modelling protein-protein interactions. Further, key interactions are obtained from the established PPIN using network centrality measures followed by network propagation algorithm -Random Walk with Restart (RWR). The outcome of the method reveals some influential genes behind epilepsy prognosis, along with their associated pathways like PI3 kinase, VEGF signaling, Ras, Wnt signaling etc. In comparison with similar works, our results have shown improvement in identifying unique molecular functions, biological processes, gene co-occurrences etc. Also, CORUM provides an annotation for approximately 60% of similarity in human protein complexes with the obtained result. We believe that the formulated strategy can put-up the vast consideration of indigenous drugs towards meticulous identification of genes encoded by protein against several combinatorial disorders.

Transcriptome analysis of rat dorsal hippocampal CA1 after an early life seizure induced by kainic acid

Seizures that occur during early development are associated with adverse neurodevelopmental outcomes. Causation and mechanisms are currently under investigation. Induction of an early life seizure by kainic acid (KA) in immature rats on post-natal day (P) 7 results in behavioral changes in the adult rat that reflect social and intellectual deficits without overt cellular damage. Our previous work also demonstrated increased expression of CA1 hippocampal long-term potentiation (LTP) and reduced desensitization of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type ionotropic glutamate receptors (AMPA-R) one week following a kainic acid induced seizure (KA-ELS). Here we used RNA sequencing (RNAseq) of mRNA from dorsal hippocampal CA1 to probe changes in mRNA levels one week following KA-ELS as a means to investigate the mechanisms for these functional changes. Ingenuity pathway analysis (IPA) confirmed our previous results by predicting an up-regulation of the synaptic LTP pathway. Differential gene expression results revealed significant differences in 7 gene isoforms. Additional assessments included AMPA-R splice variants and adenosine deaminase acting on RNA 2 (ADAR2) editing sites as a means to determine the mechanism for reduced AMPA-R desensitization. Splice variant analysis demonstrated that KA-ELS result in a small, but significant decrease in the "flop" isoform of Gria3, and editing site analysis revealed significant changes in the editing of a kainate receptor subunit, Grik2, and a serotonin receptor, Htr2c. While these specific changes may not account for altered AMPA-R desensitization, the differences indicate that KA-ELS alters gene expression in the hippocampal CA1 one week after the insult.

Utility of the RIG-I Agonist Triphosphate RNA for Melanoma Therapy

The pattern recognition receptor RIG-I plays an important role in the recognition of nonself RNA and antiviral immunity. RIG-I's natural ligand, triphosphate RNA (ppp-RNA), is proposed to be a valuable addition to the growing arsenal of cancer immunotherapy treatment options. In this study, we present comprehensive data validating the concept and utility of treatment with synthetic RIG-I agonist ppp-RNA for the therapy of human cancer, with melanoma as potential entry indication amenable to intratumoral treatment. Using mRNA expression data of human tumors, we demonstrate that RIG-I expression is closely correlated to cellular and cytokine immune activation in a wide variety of tumor types. Furthermore, we confirm susceptibility of cancer cells to ppp-RNA treatment in different cellular models of human melanoma, revealing unexpected heterogeneity between cell lines in their susceptibility to RNA agonist features, including sequence, secondary structures, and presence of triphosphate. Cellular responses to RNA treatment (induction of type I IFN, FasR, MHC-I, and cytotoxicity) were demonstrated to be RIG-I dependent using KO cells. Following ppp-RNA treatment of a mouse melanoma model, we observed significant local and systemic antitumor effects and survival benefits. These were associated with type I IFN response, tumor cell apoptosis, and innate and adaptive immune cell activation. For the first time, we demonstrate systemic presence of tumor antigen-specific CTLs following treatment with RIG-I agonists. Despite potential challenges in the generation and formulation of potent RIG-I agonists, ppp-RNA or analogues thereof have the potential to play an important role for cancer treatment in the next wave of immunotherapy.

Neuronal network remodeling and Wnt pathway dysregulation in the intra-hippocampal kainate mouse model of temporal lobe epilepsy

Mouse models of mesial temporal lobe epilepsy recapitulate aspects of human epilepsy, which is characterized by neuronal network remodeling in the hippocampal dentate gyrus. Observational studies suggest that this remodeling is associated with altered Wnt pathway signaling, although this has not been experimentally examined. We used the well-characterized mouse intrahippocampal kainate model of temporal lobe epilepsy to examine associations between hippocampal neurogenesis and altered Wnt signaling after seizure induction. Tissue was analyzed using immunohistochemistry and confocal microscopy, and gene expression analysis was performed by RT-qPCR on RNA extracted from anatomically micro-dissected dentate gyri. Seizures increased neurogenesis and dendritic arborization of newborn hippocampal dentate granule cells in peri-ictal regions, and decreased neurogenesis in the ictal zone, 2-weeks after kainate injection. Interestingly, administration of the novel canonical Wnt pathway inhibitor XAV939 daily for 2-weeks after kainate injection further increased dendritic arborization in peri-ictal regions after seizure, without an effect on baseline neurogenesis in control animals. Transcriptome analysis of dentate gyri demonstrated significant canonical Wnt gene dysregulation in kainate-injected mice across all regions for Wnt3, 5a and 9a. Intriguingly, certain Wnt genes demonstrated differential patterns of dysregulation between the ictal and peri-ictal zones, most notably Wnt5B, 7B and DKK-1. Together, these results demonstrate regional variation in Wnt pathway dysregulation early after seizure induction, and surprisingly, suggest that some Wnt-mediated effects might actually temper aberrant neurogenesis after seizures. The Wnt pathway may therefore provide suitable targets for novel therapies that prevent network remodeling and the development of epileptic foci in high-risk patients.

Activation of BDNF-TrkB signaling pathway-regulated brain inflammation in pentylenetetrazole-induced seizures in zebrafish

Seizures are sustained neuronal hyperexcitability in brain that result in loss of consciousness and injury. Understanding how the brain responds to seizures is critical to help developing new therapeutic strategies for epilepsy, a neurological disorder characterized by recurrent and unprovoked seizures. However, the mechanisms underlying seizure-dependent alterations of biological properties are poorly understood. In this study, we analyzed gene expression profiles of the zebrafish heads that were undergoing seizures and identified 1776 differentially expressed genes. Gene-regulatory network analysis revealed that BDNF-TrkB signaling pathway positively regulated brain inflammation in zebrafish during seizures. Using K252a, a TrkB inhibitor to block BDNF-TrkB signaling pathway, attenuated pentylenetetrazole (PTZ)-induced seizures, which also confirmed BDNF-TrkB mediated inflammatory responses including regulation of il1β and nfκb, and neutrophil and macrophage infiltration of brain. Our results have provided novel insights into seizure-induced brain inflammation in zebrafish and anti-inflammatory related therapy for epilepsy.

Effects of metformin on apoptosis and α-synuclein in a rat model of pentylenetetrazole-induced epilepsy

The present study was designed to examine the possible neuroprotective and antiepileptic effects of metformin (Metf) in a rat model of pentylenetetrazole (PTZ)-induced epilepsy and its possible underlying mechanisms. Forty male albino rats were assigned to 4 groups of equal size: (1) normal control (NC) group, (2) Metf group: daily treatment with Metf (200 mg/kg, i.p.) for 2 weeks, (3) PTZ group: treatment with PTZ (50 mg/kg, i.p.) every other day for 2 weeks, and (4) Metf + PTZ group: daily treatment with PTZ and metformin (200 mg/kg, i.p.) for 2 weeks. Administration of PTZ caused a significant increase in seizure score and duration, induced a state of oxidative stress (high malondialdehyde, low reduced glutathione and catalase activity), and led to the upregulation of β-catenin, caspase-3, and its cleavage products, Hsp70 and α-synuclein, in hippocampal regions as well as a significant reduction in seizure latency. While Metf treatment significantly ameliorated PTZ-induced seizures, attenuated oxidative stress, and upregulated α-synuclein and β-catenin expression, it also inhibited caspase-3 activation and the release of the cleavage product and caused more upregulation in Hsp70 expression in hippocampal regions (p < 0.05). In conclusion, the antiepileptic and neuroprotective effects of Metf in PTZ-induced epilepsy might be due to the inhibition of apoptosis, attenuation of oxidative stress and α-synuclein expression, and upregulation of Hsp70.

Wnt/β-catenin signaling as a potential target for novel epilepsy therapies

Epilepsy is one of the most common neurological disorders, and yet many afflicted individuals are resistant to all available therapeutic treatments. Existing pharmaceutical treatments function primarily to reduce hyperexcitability and prevent seizures, but fail to influence the underlying pathophysiology of the disorder. Recently, research efforts have focused on identifying alternative mechanistic targets for anti-epileptogenic therapies that can prevent the development of chronic epilepsy. The Wnt/β-catenin pathway, one possible target, has been demonstrated to be disrupted in both acute and chronic phases of epilepsy. Wnt/β-catenin signaling can regulate many seizure-induced changes in the brain, including neurogenesis and neuronal death, as well as can influence seizure susceptibility and potentially the development of chronic epilepsy. Several genome-wide studies and in vivo knockout animal models have provided evidence for an association between disrupted Wnt/β-catenin signaling and epilepsy. Furthermore, approved pharmaceutical drugs and other small molecule compounds that target components of the β-catenin destruction complex or antagonize endogenous inhibitors of the pathway have shown to be protective following seizures. However, additional studies are needed to determine the optimal time period in which modulation of the pathway may be most beneficial. Overall, disrupted molecular networks such as Wnt/β-catenin signaling, could be a promising anti-epileptogenic target for future epilepsy therapies.

l-Carnitine Modulates Epileptic Seizures in Pentylenetetrazole-Kindled Rats via Suppression of Apoptosis and Autophagy and Upregulation of Hsp70

l-Carnitine is a unique nutritional supplement for athletes that has been recently studied as a potential treatment for certain neuropsychiatric disorders. However, its efficacy in seizure control has not been investigated. Sprague Dawley rats were randomly assigned to receive either saline (Sal) (negative control) or pentylenetetrazole (PTZ) 40 mg/kg i.p. × 3 times/week × 3 weeks. The PTZ group was further subdivided into two groups, the first received oral l-carnitine (l-Car) (100 mg/kg/day × 4 weeks) (PTZ + l-Car), while the second group received saline (PTZ + Sal). Daily identification and quantification of seizure scores, time to the first seizure and the duration of seizures were performed in each animal. Molecular oxidative markers were examined in the animal brains. l-Car treatment was associated with marked reduction in seizure score (p = 0.0002) that was indicated as early as Day 2 of treatment and continued throughout treatment duration. Furthermore, l-Car significantly prolonged the time to the first seizure (p < 0.0001) and shortened seizure duration (p = 0.028). In addition, l-Car administration for four weeks attenuated PTZ-induced increase in the level of oxidative stress marker malondialdehyde (MDA) (p < 0.0001) and reduced the activity of catalase enzyme (p = 0.0006) and increased antioxidant GSH activity (p < 0.0001). Moreover, l-Car significantly reduced PTZ-induced elevation in protein expression of caspase-3 (p < 0.0001) and β-catenin (p < 0.0001). Overall, our results suggest a potential therapeutic role of l-Car in seizure control and call for testing these preclinical results in a proof of concept pilot clinical study.

Altered microRNA profiles in plasma exosomes from mesial temporal lobe epilepsy with hippocampal sclerosis

Mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE-HS) is the most common type of focal epilepsy. The present study aimed to explore the expression and functions of exosomal microRNAs in mTLE-HS. A total of 50 microRNAs were found to be differentially expressed in mTLE-HS compared with healthy controls. Among them, 2 were increased and 48 were decreased. The 6 significant differentially expressed candidate microRNAs (miR-3613-5p, miR-4668-5p, miR-8071, miR-197-5p, miR-4322, and miR-6781-5p ) in exosome were validated. The bioinformatics analysis showed that the potential target genes of these microRNAs were involved in biological processes, molecular functions, and cellular components. Similarly, these microRNAs also affected axon guidance, pathways in cancer, regulation of the actin cytoskeleton, focal adhesion, the calcium signaling pathway, the MAPK signaling pathway, and the PI3K-Akt signaling pathway. Among 6 candidate microRNAs, miR-8071 had the best diagnostic value for mTLE-HS with 83.33% sensitivity and 96.67% specificity, and was associated with seizure severity. This study indicated that exosomal microRNAs, may be regulators for the seizure development in mTLE-HS, and can be used as potential therapeutic targets and biomarker for diagnosis in mTLE-HS.

Mechanistic target of rapamycin complex 1 and 2 in human temporal lobe epilepsy

OBJECTIVE

Temporal lobe epilepsy (TLE) is a chronic epilepsy syndrome defined by seizures and progressive neurological disabilities, including cognitive impairments, anxiety, and depression. Here, human TLE specimens were investigated focusing on the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) and complex 2 (mTORC2) activities in the brain, given that both pathways may represent unique targets for treatment.

METHODS

Surgically resected hippocampal and temporal lobe samples from therapy-resistant TLE patients were analyzed by western blotting to quantify the expression of established mTORC1 and mTORC2 activity markers and upstream or downstream signaling pathways involving the two complexes. Histological and immunohistochemical techniques were used to assess hippocampal and neocortical structural abnormalities and cell-specific expression of individual biomarkers. Samples from patients with focal cortical dysplasia (FCD) type II served as positive controls.

RESULTS

We found significantly increased expression of phospho-mTOR (Ser2448), phospho-S6 (Ser235/236), phospho-S6 (Ser240/244), and phospho-Akt (Ser473) in TLE samples compared to controls, consistent with activation of both mTORC1 and mTORC2. Our work identified the phosphoinositide 3-kinase and Ras/extracellular signal-regulated kinase signaling pathways as potential mTORC1 and mTORC2 upstream activators. In addition, we found that overactive mTORC2 signaling was accompanied by induction of two protein kinase B-dependent prosurvival pathways, as evidenced by increased inhibitory phosphorylation of forkhead box class O3a (Ser253) and glycogen synthase kinase 3 beta (Ser9).

INTERPRETATION

Our data demonstrate that mTOR signaling is significantly dysregulated in human TLE, offering new targets for pharmacological interventions. Specifically, clinically available drugs that suppress mTORC1 without compromising mTOR2 signaling, such as rapamycin and its analogs, may represent a new group of antiepileptogenic agents in TLE patients. Ann Neurol 2018;83:311-327.

Kainic Acid Induces mTORC1-Dependent Expression of Elmo1 in Hippocampal Neurons

Epileptogenesis is a process triggered by initial environmental or genetic factors that result in epilepsy and may continue during disease progression. Important parts of this process include changes in transcriptome and the pathological rewiring of neuronal circuits that involves changes in neuronal morphology. Mammalian/mechanistic target of rapamycin (mTOR) is upregulated by proconvulsive drugs, e.g., kainic acid, and is needed for progression of epileptogenesis, but molecular aspects of its contribution are not fully understood. Since mTOR can modulate transcription, we tested if rapamycin, an mTOR complex 1 inhibitor, affects kainic acid-evoked transcriptome changes. Using microarray technology, we showed that rapamycin inhibits the kainic acid-induced expression of multiple functionally heterogeneous genes. We further focused on engulfment and cell motility 1 (Elmo1), which is a modulator of actin dynamics and therefore could contribute to pathological rewiring of neuronal circuits during epileptogenesis. We showed that prolonged overexpression of Elmo1 in cultured hippocampal neurons increased axonal growth, decreased dendritic spine density, and affected their shape. In conclusion, data presented herein show that increased mTORC1 activity in response to kainic acid has no global effect on gene expression. Instead, our findings suggest that mTORC1 inhibition may affect development of epilepsy, by modulating expression of specific subset of genes, including Elmo1, and point to a potential role for Elmo1 in morphological changes that accompany epileptogenesis.

The radial organization of neuronal primary cilia is acutely disrupted by seizure and ischemic brain injury

BACKGROUND

Neuronal primary cilia are sensory organelles that are critically involved in the proper growth, development, and function of the central nervous system (CNS). Recent work also suggests that they signal in the context of CNS injury, and that abnormal ciliary signaling may be implicated in neurological diseases.

METHODS

We quantified the distribution of neuronal primary cilia alignment throughout the normal adult mouse brain by immunohistochemical staining for the primary cilia marker adenylyl cyclase III (ACIII) and measuring the angles of primary cilia with respect to global and local coordinate planes. We then introduced two different models of acute brain insult-temporal lobe seizure and cerebral ischemia, and re-examined neuronal primary cilia distribution, as well as ciliary lengths and the proportion of neurons harboring cilia.

RESULTS

Under basal conditions, cortical cilia align themselves radially with respect to the cortical surface, while cilia in the dentate gyrus align themselves radially with respect to the granule cell layer. Cilia of neurons in the striatum and thalamus, by contrast, exhibit a wide distribution of ciliary arrangements. In both cases of acute brain insult, primary cilia alignment was significantly disrupted in a region-specific manner, with areas affected by the insult preferentially disrupted. Further, the two models promoted differential effects on ciliary lengths, while only the ischemia model decreased the proportion of ciliated cells.

CONCLUSIONS

These findings provide evidence for the regional anatomical organization of neuronal primary cilia in the adult brain and suggest that various brain insults may disrupt this organization.

mTOR inhibitors rescue premature lethality and attenuate dysregulation of GABAergic/glutamatergic transcription in murine succinate semialdehyde dehydrogenase deficiency (SSADHD), a disorder of GABA metabolism

Recent studies have identified a role for supraphysiological gamma-aminobutyric acid (GABA) in the regulation of mechanistic target of rapamycin (mTOR), a protein kinase with pleiotropic roles in cellular development and homeostasis, including integration of growth factors and nutrient sensing and synaptic input in neurons (Lakhani et al. 2014; Vogel et al. 2015). Aldehyde dehydrogenase 5a1-deficient (aldh5a1 ^-/- ) mice, the murine orthologue of human succinic semialdehyde dehydrogenase deficiency (SSADHD), manifest increased GABA that disrupts mitophagy and increases mitochondria number with enhanced oxidant stress. Treatment with the mTOR inhibitor, rapamycin, significantly attenuates these GABA-related anomalies. We extend those studies through characterization of additional rapamycin analog (rapalog) agents including temsirolimus, dual mTOR inhibitors [Torin 1 and 2 (Tor 1/ Tor 2), Ku-0063794, and XL-765], as well as mTOR-independent autophagy inducers [trehalose, tat-Beclin 1, tacrolimus (FK-506), and NF-449) in aldh5a1 ^-/- mice. Rapamycin, Tor 1, and Tor 2 rescued these mice from premature lethality associated with status epilepticus. XL-765 extended lifespan significantly and induced weight gain in aldh5a1 ^-/- mice; untreated aldh5a1 ^-/- mice failed to increase body mass. Expression profiling of animals rescued with Tor 1/Tor 2 and XL-765 revealed multiple instances of pharmacological compensation and/or correction of GABAergic and glutamatergic receptors, GABA/glutamate transporters, and GABA/glutamate-associated proteins, with Tor 2 and XL-765 showing optimal outcomes. Our studies lay the groundwork for further evaluation of mTOR inhibitors in aldh5a1 ^-/- mice, with therapeutic ramifications for heritable disorders of GABA and glutamate neurotransmission.

Wnt/β-catenin signaling mediates the seizure-facilitating effect of postischemic reactive astrocytes after pentylenetetrazole-kindling

Ischemia not only leads to tissue damage, but also induces seizures, which in turn worsens the outcome of ischemia. Recent studies have revealed the impaired homeostatic functions of reactive astrocytes, which were thought to facilitate the development of seizures. However, how this phenotype of reactive astrocytes is regulated remains unclear. Here, using pentylenetetrazole (PTZ)-kindling model, we investigated the roles of reactive astrocytes and their intracellular Wnt/β-catenin signaling in the ischemia-increased seizure susceptibility. Our data showed that somatosensory cortical ischemia significantly increased the susceptibility to PTZ-induced seizure. Genetic ablation of Nestin-positive reactive astrocytes significantly decreased the incidence and severity of seizures. By using a Wnt signaling reporter mice line Topgal mice, we found that Wnt/β-catenin signaling was upregulated in reactive astrocytes after ischemia. Depletion of β-catenin in reactive astrocytes significantly decreased the susceptibility of seizures and the expression of c-Fos induced by PTZ in the ischemic cortex. Overexpression of β-catenin in reactive astrocytes, in contrast, significantly increased seizure susceptibility and the expression of c-Fos. Furthermore, the expression of aquaporin-4 (AQP-4) and inwardly rectifying K(+) channel 4.1 (Kir4.1), two molecules reportedly associated with seizure development, was oppositely affected in reactive astrocytes with β-catenin depletion or overexpression. Taken together, these data indicated that astrocytic Wnt/β-catenin signaling accounts, at least partially, for the ischemia-increased seizure susceptibility. Inhibiting Wnt/β-catenin signaling may be utilized in the future for preventing postischemic seizures.

Epileptogenesis

Epileptogenesis is a chronic process that can be triggered by genetic or acquired factors, and that can continue long after epilepsy diagnosis. In 2015, epileptogenesis is not a treatment indication, and there are no therapies available in clinic to treat individuals at risk of epileptogenesis. However, thanks to active research, a large number of animal models have become available for search of molecular mechanisms of epileptogenesis. The first glimpses of treatment targets and biomarkers that could be developed to become useful in clinic are in sight. However, the heterogeneity of the epilepsy condition, and the dynamics of molecular changes over the course of epileptogenesis remain as challenges to overcome.

Focal Cortical Dysplasia

Focal cortical dysplasias are common malformations of cerebral cortical development and are highly associated with medically intractable epilepsy. They have been classified into neuropathological subtypes (type Ia, Ib, IIa, IIb, and III) based on the severity of cytoarchitectural disruption--tangential or radial dispersion, or loss of laminar structure--and the presence of unique cells types such as cytomegalic neurons or balloon cells. Most focal cortical dysplasias can be identified on neuroimaging and many require resective epilepsy surgery to cure refractory seizures. The pathogenesis of focal cortical dysplasias remains to be defined, although there is recent evidence to suggest that focal cortical dysplasias arise from de novo somatic mutations occurring during brain development. Some focal cortical dysplasia subtypes show a link to the mammalian target of rapamycin signaling cascade; this has now extended to other cortical malformations, including hemimegalencephaly.

The Role of Wnt/β-Catenin Signaling Pathway in Disrupted Hippocampal Neurogenesis of Temporal Lobe Epilepsy: A Potential Therapeutic Target?

Temporal lobe epilepsy is one of the most common clinical neurological disorders. One of the major pathological findings in temporal lobe epilepsy is hippocampal sclerosis, characterized by massive neuronal loss and severe gliosis. The epileptogenesis process of temporal lobe epilepsy usually starts with initial precipitating insults, followed by neurodegeneration, abnormal hippocampus circuitry reorganization, and the formation of hypersynchronicity. Experimental and clinical evidence strongly suggests that dysfunctional neurogenesis is involved in the epileptogenesis. Recent data demonstrate that neurogenesis is induced by acute seizures or precipitating insults, whereas the capacity of neuronal recruitment and proliferation substantially decreases in the chronic phase of epilepsy. Participation of the Wnt/β-catenin signaling pathway in neurogenesis reveals its importance in epileptogenesis; its dysfunction contributes to the structural and functional abnormality of temporal lobe epilepsy, while rescuing this pathway exerts neuroprotective effects. Here, we summarize data supporting the involvement of Wnt/β-catenin signaling in the epileptogenesis of temporal lobe epilepsy. We also propose that the Wnt/β-catenin signaling pathway may serve as a promising therapeutic target for temporal lobe epilepsy treatment.

mTOR signaling in epilepsy: insights from malformations of cortical development

Over the past decade enhanced activation of the mammalian target of rapamycin (mTOR)-signaling cascade has been identified in focal malformations of cortical development (MCD) subtypes, which have been collectively referred to as "mTORopathies." Mutations in mTOR regulatory genes (e.g., TSC1, TSC2, AKT3, DEPDC5) have been associated with several focal MCD highly associated with epilepsy such as tuberous sclerosis complex (TSC), hemimegalencephaly (HME; brain malformation associated with dramatic enlargement of one brain hemisphere), and cortical dysplasia. mTOR plays important roles in the regulation of cell division, growth, and survival, and, thus, aberrant activation of the cascade during cortical development can cause dramatic alterations in cell size, cortical lamination, and axon and dendrite outgrowth often observed in focal MCD. Although it is widely believed that structural alterations induced by hyperactivated mTOR signaling are critical for epileptogenesis, newer evidence suggests that mTOR activation on its own may enhance neuronal excitability. Clinical trials with mTOR inhibitors have shown efficacy in the treatment of seizures associated with focal MCD.

Early life seizures: evidence for chronic deficits linked to autism and intellectual disability across species and models

Recent work in Exp Neurol by Lugo et al. (2014b) demonstrated chronic alterations in sociability, learning and memory following multiple early life seizures (ELS) in a mouse model. This work adds to the growing body of evidence supporting the detrimental nature of ELS on the developing brain to contribute to aspects of an autistic phenotype with intellectual disability. Review of the face validity of behavioral testing and the construct validity of the models used informs the predictive ability and thus the utility of these models to translate underlying molecular and cellular mechanisms into future human studies.