Microglial mTOR is Neuronal Protective and Antiepileptogenic in the Pilocarpine Model of Temporal Lobe Epilepsy

Anti‑epileptic mechanism of isopimaric acid from Platycladi cacumen based on network pharmacology, molecular docking and biological validation

Platycladi cacumen (PC) is derived from the dry twigs and leaves of Platycladi orientalis (L.) Franco and exerts anti-epileptic effects. However, its mechanism of action remains unknown. The present study explored the potential anti-epileptic components and mechanisms of PC. The primary active components and targets of PC were analyzed using network pharmacology and a lipopolysaccharide (LPS)-induced murine microglial cell line (BV2) was used to confirm anti-epileptic effects by detecting reactive oxygen species (ROS), apoptosis, inflammatory markers, cell migration and signaling pathways. A total of 13 core active components showed druggable properties, of which deoxypicrop odophyllotoxin, hinokinin and isopimaric acid (IPA) were predicted to cross the blood-brain barrier. In total, 255 potential targets of these three compounds were predicted using SwissTargetPrediction and Similarity Ensemble Approach websites and 150 were associated with epilepsy. In vitro experiments confirmed that IPA significantly inhibited LPS-induced microglial oxidative stress and inflammation by decreasing the migration area, cellular ROS content, lactate dehydrogenase release and early phase of apoptosis. IPA also increased the mRNA expression of anti-oxidative enzymes (superoxide dismutase-1 and -2) and suppressed inflammatory cytokines (interleukin-1β and tumor necrosis factor-α). Furthermore, IPA phosphorylated AKT and mTOR proteins. Taken together, the present findings suggested that IPA is a potential anti-epileptic compound derived from PC.

Rethinking the role of microglia in obesity

Microglia are the macrophages of the central nervous system (CNS), implying their role in maintaining brain homeostasis. To achieve this, these cells are sensitive to a plethora of endogenous and exogenous signals, such as neuronal activity, cellular debris, hormones, and pathological patterns, among many others. More recent research suggests that microglia are highly responsive to nutrients and dietary variations. In this context, numerous studies have demonstrated their significant role in the development of obesity under calorie surfeit. Because many reviews already exist on this topic, we have chosen to present the state of our reflections on various concepts put forth in the literature, bringing a new perspective whenever possible. Our literature review focuses on studies conducted in the arcuate nucleus of the hypothalamus, a key structure in the control of food intake. Specifically, we present the recent data available on the modifications of microglial energy metabolism following the consumption of an obesogenic diet and their consequences on hypothalamic neuron activity. We also highlight the studies unraveling the mechanisms underlying obesity-related sexual dimorphism. The review concludes with a list of questions that remain to be addressed in the field to achieve a comprehensive understanding of the role of microglia in the regulation of body energy metabolism. This article is part of the Special Issue on "Microglia".

mTORC2: A neglected player in aging regulation

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that plays a pivotal role in various biological processes, through integrating external and internal signals, facilitating gene transcription and protein translation, as well as by regulating mitochondria and autophagy functions. mTOR kinase operates within two distinct protein complexes known as mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), which engage separate downstream signaling pathways impacting diverse cellular processes. Although mTORC1 has been extensively studied as a pro-proliferative factor and a pro-aging hub if activated aberrantly, mTORC2 received less attention, particularly regarding its implication in aging regulation. However, recent studies brought increasing evidence or clues for us, which implies the associations of mTORC2 with aging, as the genetic elimination of unique subunits of mTORC2, such as RICTOR, has been shown to alleviate aging progression in comparison to mTORC1 inhibition. In this review, we first summarized the basic characteristics of mTORC2, including its protein architecture and signaling network. We then focused on reviewing the molecular signaling regulation of mTORC2 in cellular senescence and organismal aging, and proposed the multifaceted regulatory characteristics under senescent and nonsenescent contexts. Next, we outlined the research progress of mTOR inhibitors in the field of antiaging and discussed future prospects and challenges. It is our pleasure if this review article could provide meaningful information for our readers and call forth more investigations working on this topic.

ABCG2 shields against epilepsy, relieves oxidative stress and apoptosis via inhibiting the ISGylation of STAT1 and mTOR

The transporter protein ABC subfamily G member 2 (ABCG2) is implicated in epilepsy; however, its specific role remains unclear. In this study, we assessed changes in ABCG2 expression and its role in epilepsy both in vitro and in vivo. We observed an instantaneous increase in ABCG2 expression in epileptic animals and cells. Further, ABCG2 overexpression significantly suppressed the oxidative stress and apoptosis induced by glutamate, kainic acid (KA), and lipopolysaccharide (LPS) in neuronal and microglia cells. Furthermore, inhibiting ABCG2 activity offset this protective effect. ABCG2-deficient mice (ABCG2-/-) showed shorter survival times and decreased survival rates when administered with pentylenetetrazole (PTZ). We also noticed the accumulation of signal transducer and activator of transcription 1 (STAT1) and decreased phosphorylation of mammalian target of rapamycin kinase (mTOR) along with increased ISGylation in ABCG2-/- mice. ABCG2 overexpression directly interacted with STAT1 and mTOR, leading to a decrease in their ISGylation. Our findings indicate the rapid increase in ABCG2 expression acts as a shield in epileptogenesis, indicating ABCG2 may serve as a potential therapeutic target for epilepsy treatment.

Molecular Genetics of Acquired Temporal Lobe Epilepsy

An epilepsy diagnosis reduces a patient's quality of life tremendously, and it is a fate shared by over 50 million people worldwide. Temporal lobe epilepsy (TLE) is largely considered a nongenetic or acquired form of epilepsy that develops in consequence of neuronal trauma by injury, malformations, inflammation, or a prolonged (febrile) seizure. Although extensive research has been conducted to understand the process of epileptogenesis, a therapeutic approach to stop its manifestation or to reliably cure the disease has yet to be developed. In this review, we briefly summarize the current literature predominately based on data from excitotoxic rodent models on the cellular events proposed to drive epileptogenesis and thoroughly discuss the major molecular pathways involved, with a focus on neurogenesis-related processes and transcription factors. Furthermore, recent investigations emphasized the role of the genetic background for the acquisition of epilepsy, including variants of neurodevelopmental genes. Mutations in associated transcription factors may have the potential to innately increase the vulnerability of the hippocampus to develop epilepsy following an injury-an emerging perspective on the epileptogenic process in acquired forms of epilepsy.

Vitamin D Relieves Epilepsy Symptoms and Neuroinflammation in Juvenile Mice by Activating the mTOR Signaling Pathway via RAF1: Insights from Network Pharmacology and Molecular Docking Studies

Epilepsy is a common neurological disorder, and the exploration of potential therapeutic drugs for its treatment is still ongoing. Vitamin D has emerged as a promising treatment due to its potential neuroprotective effects and anti-epileptic properties. This study aimed to investigate the effects of vitamin D on epilepsy and neuroinflammation in juvenile mice using network pharmacology and molecular docking, with a focus on the mammalian target of rapamycin (mTOR) signaling pathway. Experimental mouse models of epilepsy were established through intraperitoneal injection of pilocarpine, and in vitro injury models of hippocampal neurons were induced by glutamate (Glu) stimulation. The anti-epileptic effects of vitamin D were evaluated both in vivo and in vitro. Network pharmacology and molecular docking analysis were used to identify potential targets and regulatory pathways of vitamin D in epilepsy. The involvement of the mTOR signaling pathway in the regulation of mouse epilepsy by vitamin D was validated using rapamycin (RAPA). The levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6) were assessed by enzyme-linked immunosorbent assay (ELISA). Gene and protein expressions were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot, respectively. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) staining was used to analyze the apoptosis of hippocampal neurons. In in vivo experiments, vitamin D reduced the Racine scores of epileptic mice, prolonged the latency of epilepsy, and inhibited the production of TNF-α, IL-1β, and IL-6 in the hippocampus. Furthermore, network pharmacology analysis identified RAF1 as a potential target of vitamin D in epilepsy, which was further confirmed by molecular docking analysis. Additionally, the mTOR signaling pathway was found to be involved in the regulation of mouse epilepsy by vitamin D. In in vitro experiments, Glu stimulation upregulated the expressions of RAF1 and LC3II/LC3I, inhibited mTOR phosphorylation, and induced neuronal apoptosis. Mechanistically, vitamin D activated the mTOR signaling pathway and alleviated mouse epilepsy via RAF1, while the use of the pathway inhibitor RAPA reversed this effect. Vitamin D alleviated epilepsy symptoms and neuroinflammation in juvenile mice by activating the mTOR signaling pathway via RAF1. These findings provided new insights into the molecular mechanisms underlying the anti-epileptic effects of vitamin D and further supported its use as an adjunctive therapy for existing anti-epileptic drugs.

Mechanism of NLRP3 Inflammasome in Epilepsy and Related Therapeutic Agents

Epilepsy is one of the most widespread and complex diseases in the central nervous system (CNS), affecting approximately 65 million people globally, an important factor resulting in neurological disability-adjusted life year (DALY) and progressive cognitive dysfunction. Medication is the most essential treatment. The currently used drugs have shown drug resistance in some patients and only control symptoms; the development of novel and more efficacious pharmacotherapy is imminent. Increasing evidence suggests neuroinflammation is involved in the occurrence and development of epilepsy, and high expression of NLRP3 inflammasome has been observed in the temporal lobe epilepsy (TLE) brain tissue of patients and animal models. The inflammasome is a crucial cause of neuroinflammation by activating IL-1β and IL-18. Many preclinical studies have confirmed that regulating NLRP3 inflammasome pathway can prevent the development of epilepsy, reduce the severity of epilepsy, and play a neuroprotective role. Therefore, regulating NLRP3 inflammasome could be a potential target for epilepsy treatment. In summary, this review describes the priming and activation of inflammasome and its biological function in the progression of epilepsy. In addition, we reviewes the current pharmacological researches for epilepsy based on the regulation of NLRP3 inflammasome, aiming to provide a basis and reference for developing novel antiepileptic drugs.

mTOR and neuroinflammation in epilepsy: implications for disease progression and treatment

Epilepsy remains a major health concern as anti-seizure medications frequently fail, and there is currently no treatment to stop or prevent epileptogenesis, the process underlying the onset and progression of epilepsy. The identification of the pathological processes underlying epileptogenesis is instrumental to the development of drugs that may prevent the generation of seizures or control pharmaco-resistant seizures, which affect about 30% of patients. mTOR signalling and neuroinflammation have been recognized as critical pathways that are activated in brain cells in epilepsy. They represent a potential node of biological convergence in structural epilepsies with either a genetic or an acquired aetiology. Interventional studies in animal models and clinical studies give strong support to the involvement of each pathway in epilepsy. In this Review, we focus on available knowledge about the pathophysiological features of mTOR signalling and the neuroinflammatory brain response, and their interactions, in epilepsy. We discuss mitigation strategies for each pathway that display therapeutic effects in experimental and clinical epilepsy. A deeper understanding of these interconnected molecular cascades could enhance our strategies for managing epilepsy. This could pave the way for new treatments to fill the gaps in the development of preventative or disease-modifying drugs, thus overcoming the limitations of current symptomatic medications.

PI3K-AKT/mTOR Signaling in Psychiatric Disorders: A Valuable Target to Stimulate or Suppress?

Economic development and increased stress have considerably increased the prevalence of psychiatric disorders in recent years, which rank as some of the most prevalent diseases globally. Several factors, including chronic social stress, genetic inheritance, and autogenous diseases, lead to the development and progression of psychiatric disorders. Clinical treatments for psychiatric disorders include psychotherapy, chemotherapy, and electric shock therapy. Although various achievements have been made researching psychiatric disorders, the pathogenesis of these diseases has not been fully understood yet, and serious adverse effects and resistance to antipsychotics are major obstacles to treating patients with psychiatric disorders. Recent studies have shown that the mammalian target of rapamycin (mTOR) is a central signaling hub that functions in nerve growth, synapse formation, and plasticity. The PI3K-AKT/mTOR pathway is a critical target for mediating the rapid antidepressant effects of these pharmacological agents in clinical and preclinical research. Abnormal PI3K-AKT/mTOR signaling is closely associated with the pathogenesis of several neurodevelopmental disorders. In this review, we focused on the role of mTOR signaling and the related aberrant neurogenesis in psychiatric disorders. Elucidating the neurobiology of the PI3K-AKT/mTOR signaling pathway in psychiatric disorders and its actions in response to antidepressants will help us better understand brain development and quickly identify new therapeutic targets for the treatment of these mental illnesses.

Leukocyte differential gene expression prognostic value for high versus low seizure frequency in temporal lobe epilepsy

BACKGROUND

This study was performed to test the hypothesis that systemic leukocyte gene expression has prognostic value differentiating low from high seizure frequency refractory temporal lobe epilepsy (TLE).

METHODS

A consecutive series of patients with refractory temporal lobe epilepsy was studied. Based on a median baseline seizure frequency of 2.0 seizures per month, low versus high seizure frequency was defined as ≤ 2 seizures/month and > 2 seizures/month, respectively. Systemic leukocyte gene expression was analyzed for prognostic value for TLE seizure frequency. All differentially expressed genes were analyzed, with Ingenuity® Pathway Analysis (IPA®) and Reactome, to identify leukocyte gene expression and biological pathways with prognostic value for seizure frequency.

RESULTS

There were ten males and six females with a mean age of 39.4 years (range: 16 to 62 years, standard error of mean: 3.6 years). There were five patients in the high and eleven patients in the low seizure frequency cohorts, respectively. Based on a threshold of twofold change (p < 0.001, FC > 2.0, FDR < 0.05) and expression within at least two pathways from both Reactome and Ingenuity® Pathway Analysis (IPA®), 13 differentially expressed leukocyte genes were identified which were all over-expressed in the low when compared to the high seizure frequency groups, including NCF2, HMOX1, RHOB, FCGR2A, PRKCD, RAC2, TLR1, CHP1, TNFRSF1A, IFNGR1, LYN, MYD88, and CASP1. Similar analysis identified four differentially expressed genes which were all over-expressed in the high when compared to the low seizure frequency groups, including AK1, F2R, GNB5, and TYMS.

CONCLUSIONS

Low and high seizure frequency TLE are predicted by the respective upregulation and downregulation of specific leukocyte genes involved in canonical pathways of neuroinflammation, oxidative stress and lipid peroxidation, GABA (γ-aminobutyric acid) inhibition, and AMPA and NMDA receptor signaling. Furthermore, high seizure frequency-TLE is distinguished prognostically from low seizure frequency-TLE by differentially increased specific leukocyte gene expression involved in GABA inhibition and NMDA receptor signaling. High and low seizure frequency patients appear to represent two mechanistically different forms of temporal lobe epilepsy based on leukocyte gene expression.

Investigation of the mechanism of tanshinone IIA to improve cognitive function via synaptic plasticity in epileptic rats

CONTEXT

Tanshinone IIA is an extract of Salvia miltiorrhiza Bunge (Labiatae) used to treat cardiovascular disorders. It shows potential anticonvulsant and cognition-protective properties.

OBJECTIVE

We investigated the mechanism of tanshinone IIA on antiepileptic and cognition-protective effects in the model of epileptic rats.

MATERIALS AND METHODS

Lithium chloride (LiCl)-pilocarpine-induced epileptic Wistar rats were randomly assigned to the following groups (n = 12): control (blank), model, sodium valproate (VPA, 189 mg/kg/d, positive control), tanshinone IIA low dose (TS IIA-L, 10 mg/kg/d), medium dose (TS IIA-M, 20 mg/kg/d) and high dose (TS IIA-H, 30 mg/kg/d). Then, epileptic behavioural observations, Morris water maze test, Timm staining, transmission electron microscopy, immunofluorescence staining, western blotting and RT-qPCR were measured.

RESULTS

Compared with the model group, tanshinone IIA reduced the frequency and severity of seizures, improved cognitive impairment, and inhibited hippocampal mossy fibre sprouting score (TS IIA-M 1.50 ± 0.22, TS IIA-H 1.17 ± 0.31 vs. model 2.83 ± 0.31), as well as improved the ultrastructural disorder. Tanshinone IIA increased levels of synapse-associated proteins synaptophysin (SYN) and postsynaptic dense substance 95 (PSD-95) (SYN: TS IIA 28.82 ± 2.51, 33.18 ± 2.89, 37.29 ± 1.69 vs. model 20.23 ± 3.96; PSD-95: TS IIA 23.10 ± 0.91, 26.82 ± 1.41, 27.00 ± 0.80 vs. model 18.28 ± 1.01).

DISCUSSION AND CONCLUSIONS

Tanshinone IIA shows antiepileptic and cognitive function-improving effects, primarily via regulating synaptic plasticity. This research generates a theoretical foundation for future research on potential clinical applications for tanshinone IIA.

New insights on the potential anti-epileptic effect of metformin: Mechanistic pathway

Epilepsy is a chronic neurological disease characterized by recurrent seizures. Epilepsy is observed as a well-controlled disease by anti-epileptic agents (AEAs) in about 69%. However, 30%-40% of epileptic patients fail to respond to conventional AEAs leading to an increase in the risk of brain structural injury and mortality. Therefore, adding some FDA-approved drugs that have an anti-seizure activity to the anti-epileptic regimen is logical. The anti-diabetic agent metformin has anti-seizure activity. Nevertheless, the underlying mechanism of the anti-seizure activity of metformin was not entirely clarified. Henceforward, the objective of this review was to exemplify the mechanistic role of metformin in epilepsy. Metformin has anti-seizure activity by triggering adenosine monophosphate-activated protein kinase (AMPK) signalling and inhibiting the mechanistic target of rapamycin (mTOR) pathways which are dysregulated in epilepsy. In addition, metformin improves the expression of brain-derived neurotrophic factor (BDNF) which has a neuroprotective effect. Hence, metformin via induction of BDNF can reduce seizure progression and severity. Consequently, increasing neuronal progranulin by metformin may explain the anti-seizure mechanism of metformin. Also, metformin reduces α-synuclein and increases protein phosphatase 2A (PPA2) with modulation of neuroinflammation. In conclusion, metformin might be an adjuvant with AEAs in the management of refractory epilepsy. Preclinical and clinical studies are warranted in this regard.

Recent Progress in the Development of New Antiepileptic Drugs with Novel Targets

Background

Epilepsy is a chronic neurological disorder that affects approximately 50-70 million people worldwide. Epilepsy has a significant economic and social burden on patients as well as on the country. The recurrent, spontaneous seizure activity caused by abnormal neuronal firing in the brain is a hallmark of epilepsy. The current antiepileptic drugs provide symptomatic relief by restoring the balance of excitatory and inhibitory neurotransmitters. Besides, about 30% of epileptic patients do not achieve seizure control. The prevalence of adverse drug reactions, including aggression, agitation, irritability, and associated comorbidities, is also prevalent. Therefore, researchers should focus on developing more effective, safe, and disease-modifying agents based on new molecular targets and signaling cascades.

Summary

This review overviews several clinical trials that help identify promising new targets like lactate dehydrogenase inhibitors, c-jun n-terminal kinases, high mobility group box-1 antibodies, astrocyte reactivity inhibitors, cholesterol 24-hydroxylase inhibitors, glycogen synthase kinase-3 beta inhibitors, and glycolytic inhibitors to develop a new antiepileptic drug.

Key messages

Approximately 30% of epileptic patients do not achieve seizure control. The current anti-seizure drugs are not disease modifying, cure or prevent epilepsy. Lactate dehydrogenase inhibitor, cholesterol 24-hydroxylase inhibitor, glycogen synthase kinase-3 beta inhibitors, and mTOR inhibitors have a promising antiepileptogenic effect.

Microglia in epilepsy

Epilepsy is one of most common chronic neurological disorders, and the antiseizure medications developed by targeting neurocentric mechanisms have not effectively reduced the proportion of patients with drug-resistant epilepsy. Further exploration of the cellular or molecular mechanism of epilepsy is expected to provide new options for treatment. Recently, more and more researches focus on brain network components other than neurons, among which microglia have attracted much attention for their diverse biological functions. As the resident immune cells of the central nervous system, microglia have highly plastic transcription, morphology and functional characteristics, which can change dynamically in a context-dependent manner during the progression of epilepsy. In the pathogenesis of epilepsy, highly reactive microglia interact with other components in the epileptogenic network by performing crucial functions such as secretion of soluble factors and phagocytosis, thus continuously reshaping the landscape of the epileptic brain microenvironment. Indeed, microglia appear to be both pro-epileptic and anti-epileptic under the different spatiotemporal contexts of disease, rendering interventions targeting microglia biologically complex and challenging. This comprehensive review critically summarizes the pathophysiological role of microglia in epileptic brain homeostasis alterations and explores potential therapeutic or modulatory targets for epilepsy targeting microglia.

Targeting ANXA7/LAMP5-mTOR axis attenuates spinal cord injury by inhibiting neuronal apoptosis via enhancing autophagy in mice

Spinal cord injury (SCI) could lead to severe disabilities in motor and sensory functions, and cause a heavy burden on patient physiology and psychology due to lack of specific repair measures so far. ANXA7 is an annexin with Ca2+ -dependent GTPase activity, which were mainly expressed in neuron in spinal cord and downregulated significantly after SCI in mice. In our study, GTPase activity activation of ANXA7 plays the protective role in neuron after OGD/R through inhibiting neuron apoptosis, which mediated by enhancing autophagy via mTOR/TFEB pathway. We also discovered that ANXA7 has significant interaction with neural-specific lysosomal-associated membrane protein LAMP5, which together with ANXA7 regulates autophagy and apoptosis. Asp411 mutation of ANXA7 obviously impaired the interaction of ANXA7 and LAMP5 compared with the wild type. Furthermore, it was found that activation of ANXA7 could help to stabilize the protein expression of LAMP5. Overexpression of LAMP5 could attenuate the destruction of lysosomal acidic environment, inhibition of autophagy and activation of apoptosis caused by ANXA7 downregulation after OGD/R. We verified that injecting ANXA7 overexpression lentivirus and activation of ANXA7 both have significant repair effects on SCI mice by using CatWalk assay and immunohistochemistry staining. In summary, our findings clarify the new role of ANXA7 and LAMP5 in SCI, provided a new specific target of neuronal repair and discovered new molecular mechanisms of ANXA7 to regulate autophagy and apoptosis. Targeting ANXA7 may be a prospective therapeutic strategy for SCI in future.

Microglia play beneficial roles in multiple experimental seizure models

Seizure disorders are common, affecting both the young and the old. Currently available antiseizure drugs are ineffective in a third of patients and have been developed with a focus on known neurocentric mechanisms, raising the need for investigations into alternative and complementary mechanisms that contribute to seizure generation or its containment. Neuroinflammation, broadly defined as the activation of immune cells and molecules in the central nervous system (CNS), has been proposed to facilitate seizure generation, although the specific cells involved in these processes remain inadequately understood. The role of microglia, the primary inflammation-competent cells of the brain, is debated since previous studies were conducted using approaches that were less specific to microglia or had inherent confounds. Using a selective approach to target microglia without such side effects, we show a broadly beneficial role for microglia in limiting chemoconvulsive, electrical, and hyperthermic seizures and argue for a further understanding of microglial contributions to contain seizures.

Melatonin regulates microglial polarization to M2 cell via RhoA/ROCK signaling pathway in epilepsy

BACKGROUND

Melatonin (MEL), an endogenous hormone, has been widely investigated in neurological diseases. Microglia (MG), a resident immunocyte localizing in central nervous system is reported to play important functions in the animal model of temporal lobe epilepsy (TLE). Some evidence showed that MEL influenced activation of MG, but the detailed model of action that MEL plays in remains uncertain.

METHODS

In this study, we established a model of TLE in mice by stereotactic injection of kainic acid (KA). We treated the mice with MEL. Lipopolysaccharide, ROCK2-knockdown (ROCK-KD) and -overexpression (ROCK-OE) of lentivirus-treated cells were used in cell experiments to simulate an in vitro inflammatory model.

RESULTS

The results of electrophysiological tests showed that MEL reduced frequency and severity of seizure. The results of behavioral tests indicated MEL improved cognition, learning, and memory ability. Histological evidences demonstrated a significant reduction of neuronal death in the hippocampus. In vivo study showed that MEL changed the polarization status of MG from a proinflammatory M1 phenotype to an anti-inflammatory M2 phenotype by inversely regulating the RhoA/ROCK signaling pathway. In cytological study, we found that MEL had a significant protective effect in LPS-treated BV-2 cells and ROCK-KD cells, while the protective effect of MEL was significantly attenuated in ROCK-OE cells.

CONCLUSION

MEL played an antiepileptic role in the KA-induced TLE modeling mice both in behavioral and histological levels, and changed MG polarization status by regulating the RhoA/ROCK signaling pathway.

Advances in the mTOR signaling pathway and its inhibitor rapamycin in epilepsy

INTRODUCTION

Epilepsy is one of the most common and serious brain syndromes and has adverse consequences on a patient's neurobiological, cognitive, psychological, and social wellbeing, thereby threatening their quality of life. Some patients with epilepsy experience poor treatment effects due to the unclear pathophysiological mechanisms of the syndrome. Dysregulation of the mammalian target of the rapamycin (mTOR) pathway is thought to play an important role in the onset and progression of some epilepsies.

METHODS

This review summarizes the role of the mTOR signaling pathway in the pathogenesis of epilepsy and the prospects for the use of mTOR inhibitors.

RESULTS

The mTOR pathway functions as a vital mediator in epilepsy development through diverse mechanisms, indicating that the it has great potential as an effective target for epilepsy therapy. The excessive activation of mTOR signaling pathway leads to structural changes in neurons, inhibits autophagy, exacerbates neuron damage, affects mossy fiber sprouting, enhances neuronal excitability, increases neuroinflammation, and is closely associated with tau upregulation in epilepsy. A growing number of studies have demonstrated that mTOR inhibitors exhibit significant antiepileptic effects in both clinical applications and animal models. Specifically, rapamycin, a specific inhibitor of TOR, reduces the intensity and frequency of seizures. Clinical studies in patients with tuberous sclerosis complex have shown that rapamycin has the function of reducing seizures and improving this disease. Everolimus, a chemically modified derivative of rapamycin, has been approved as an added treatment to other antiepileptic medicines. Further explorations are needed to evaluate the therapeutic efficacy and application value of mTOR inhibitors in epilepsy.

CONCLUSIONS

Targeting the mTOR signaling pathway provides a promising prospect for the treatment of epilepsy.

Microglia play beneficial roles in multiple experimental seizure models

Seizure disorders are common, affecting both the young and the old. Currently available antiseizure drugs are ineffective in a third of patients and have been developed with a focus on known neurocentric mechanisms, raising the need for investigations into alternative and complementary mechanisms that contribute to seizure generation or its containment. Neuroinflammation, broadly defined as the activation of immune cells and molecules in the central nervous system (CNS), has been proposed to facilitate seizure generation, although the specific cells involved in these processes remain inadequately understood. The role of microglia, the primary inflammation-competent cells of the brain, is debated since previous studies were conducted using approaches that were less specific to microglia or had inherent confounds. Using a selective approach to target microglia without such side effects, we show a broadly beneficial role for microglia in limiting chemoconvulsive, electrical, and hyperthermic seizures and argue for a further understanding of microglial contributions to contain seizures.

Emerging Molecular Targets for Anti-Epileptogenic and Epilepsy Modifying Drugs

The pharmacological treatment of epilepsy is purely symptomatic. Despite many decades of intensive research, causal treatment of this common neurologic disorder is still unavailable. Nevertheless, it is expected that advances in modern neuroscience and molecular biology tools, as well as improved animal models may accelerate designing antiepileptogenic and epilepsy-modifying drugs. Epileptogenesis triggers a vast array of genomic, epigenomic and transcriptomic changes, which ultimately lead to morphological and functional transformation of specific neuronal circuits resulting in the occurrence of spontaneous convulsive or nonconvulsive seizures. Recent decades unraveled molecular processes and biochemical signaling pathways involved in the proepileptic transformation of brain circuits including oxidative stress, apoptosis, neuroinflammatory and neurotrophic factors. The "omics" data derived from both human and animal epileptic tissues, as well as electrophysiological, imaging and neurochemical analysis identified a plethora of possible molecular targets for drugs, which could interfere with various stages of epileptogenetic cascade, including inflammatory processes and neuroplastic changes. In this narrative review, we briefly present contemporary views on the neurobiological background of epileptogenesis and discuss the advantages and disadvantages of some more promising molecular targets for antiepileptogenic pharmacotherapy.

Castor1 overexpression regulates microglia M1/M2 polarization via inhibiting mTOR pathway

Microglia are resident immune cells in the brain and are closely associated with central nervous system inflammation and neurodegenerative diseases. It is known that mammalian target of rapamycin (mTOR) pathway plays an important role in the polarization of microglia. Castor1 has been identified as the cytosolic arginine sensor for the mTOR complex 1 (mTORC1) pathway, but the role of Castor1 in microglial polarization is still unknown. The purpose of this study was to explore the regulatory effect of Castor1 on microglial polarization and the underlying mechanism. The results demonstrated that Castor1 expression was significantly decreased in lipopolysaccharides (LPS) and interferon (IFN)-γ treated microglia. Castor1 overexpression inhibited the microglia M1 polarization by reducing the expression of M1 related markers. However, the expression of M2-related genes was promoted when Castor1 was overexpressed in IL-4 treated microglia. Mechanistically, Castor1 overexpression inhibited the activation of mTOR signaling pathway. In addition, after treatment with the mTOR activator MHY1485, the inhibitory effect of Castor1 overexpression on M1 polarization was attenuated, indicating that the regulation effects of Castor1 on M1 polarization was dependent on its inhibition of mTOR pathway. We propose that Castor1-mTOR signaling pathway could be considered as a potential target for treatment and intervention of central nervous system-related diseases by regulating microglia polarization.

Microglial activation and over pruning involved in developmental epilepsy

To understand the potential role of microglia in synaptic pruning following status epilepticus (SE), we examined the time course of expression of Iba-1, and immune and neuroinflammatory regulators, including CD86, CD206, and CX3CR1, and TLR4/NF-κB after SE induced by pilocarpine in rats. Behavioral tests, TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining, immunohistochemical staining, Western blotting, PCR, and fluorescence double staining assessments were performed. The expression of Iba-1 protein was lowest in the control group, and peaked after 2 days (p < 0.001). CD86 and CD206 mRNA levels increased gradually in the microglia of the epilepsy group after 12 hours, 1 day, 2 days, and 3 days; peak expression was on the second day. The expression of the chemokine receptor CX3CR1 in microglia increased to varying degrees after SE, and expression of the presynaptic protein synapsin decreased. The expression of TLR4/NF-κB in microglia positively correlated with Iba-1 protein expression. These findings indicate that the TLR4/NF-κB signaling pathway may be involved in the activation and polarization of microglia in epilepsy and in excess synaptic pruning, which could lead to an increase in brain injury.

Glycyrrhizin regulates the HMGB1/P38MAPK signalling pathway in status epilepticus

In recent decades, studies have reported that inflammation serves key roles in epilepsy and that high mobility group box protein‑1 (HMGB1) may be involved in status epilepticus. However, it has not been reported whether HMGB1 participates in the pathogenesis of status epilepticus through the regulation of the p38 mitogen‑activated protein kinase (p38MAPK) signalling pathway. In the present study, Sprague‑Dawley rats were randomly divided into four groups as follows: Control, status epilepticus (SE), dimethyl sulfoxide treatment (DMSO + SE), and glycyrrhizin treatment (GL + SE) groups. Behavioural changes were then evaluated using the Racine score. In the hippocampus, the protein expression levels of HMGB1 were assessed using western blotting, the neuronal damage was evaluated using haematoxylin and eosin staining and transmission electron microscopy, and the activation of microglia was assessed using immunochemistry and immunofluorescence. The results demonstrated that, in the hippocampal region, HMGB1 existed in neurons and astrocytes and the protein expression levels of HMGB1, p38MAPK and phosphorylated‑p38MAPK were significantly inhibited after treatment with GL. Furthermore, GL could alleviate neuronal injury in the CA1 region of the hippocampus and prevented HMGB1 translocation from the nucleus into the cytoplasm in these areas. These findings expand the understanding of how HMGB1 may participate in SE and lay a foundation for evaluation of HMGB1 as a drug target.

Scoping review of disease-modifying effect of drugs in experimental epilepsy

Objective

Epilepsy affects ~50 million people worldwide causing significant medical, financial, and sociologic concerns for affected patients and their families. To date, treatment of epilepsy is primarily symptomatic management because few effective preventative or disease-modifying interventions exist. However, recent research has identified neurobiological mechanisms of epileptogenesis, providing new pharmacologic targets to investigate. The current scientific evidence remains scattered across multiple studies using different model and experimental designs. The review compiles different models of anti-epileptogenic investigation and highlights specific compounds with potential epileptogenesis-modifying experimental drugs. It provides a platform for standardization of future epilepsy research to allow a more robust compound analysis of compounds with potential for epilepsy prevention.

Methods

PubMed, Ovid MEDLINE, and Web of Science were searched from 2007 to 2021. Studies with murine models of epileptogenesis and explicitly detailed experimental procedures were included in the scoping review. In total, 51 articles were selected from 14,983 and then grouped by five core variables: (1) seizure frequency, (2) seizure severity, (3) spontaneous recurrent seizures (SRS), (4) seizure duration, and (5) mossy fiber sprouting (MFS). The variables were differentiated based on experimental models including methods of seizure induction, treatment schedule and timeline of data collection. Data was categorized by the five core variables and analyzed by converting original treatment values to units of percent of its respective control.

Results

Discrepancies in current epileptogenesis models significantly complicate inter-study comparison of potential anti-epileptogenic interventions. With our analysis, many compounds showed a potential to reduce epileptogenic characteristics defined by the five core variables. WIN55,212-2, aspirin, rapamycin, 1400W, and LEV + BQ788 were identified compounds with the potential of effective anti-epileptic properties.

Significance

Our review highlights the need for consistent methodology in epilepsy research and provides a novel approach for future research. Inconsistent experimental designs hinder study comparison, slowing the progression of treatments for epilepsy. If the research community can optimize and standardize parameters such as methods of seizure induction, administration schedule, sampling time, and aniMal models, more robust meta-analysis and collaborative research would follow. Additionally, some compounds such as rapamycin, WIN 55,212-2, aspirin, 1400W, and LEV + BQ788 showed anti-epileptogenic modulation across multiple variables. We believe they warrant further study both individually and synergistically.

Advances and Challenges of Cannabidiol as an Anti-Seizure Strategy: Preclinical Evidence

The use of Cannabis for medicinal purposes has been documented since ancient times, where one of its principal cannabinoids extracted from Cannabis sativa, cannabidiol (CBD), has emerged over the last few years as a promising molecule with anti-seizure potential. Here, we present an overview of recent literature pointing out CBD's pharmacological profile (solubility, metabolism, drug-drug interactions, etc.,), CBD's interactions with multiple molecular targets as well as advances in preclinical research concerning its anti-seizure effect on both acute seizure models and chronic models of epilepsy. We also highlight the recent attention that has been given to other natural cannabinoids and to synthetic derivatives of CBD as possible compounds with therapeutic anti-seizure potential. All the scientific research reviewed here encourages to continue to investigate the probable therapeutic efficacy of CBD and its related compounds not only in epilepsy but also and specially in drug-resistant epilepsy, since there is a dire need for new and effective drugs to treat this disease.

Leverage biomaterials to modulate immunity for type 1 diabetes

The pathogeny of type 1 diabetes (T1D) is mainly provoked by the β-cell loss due to the autoimmune attack. Critically, autoreactive T cells firsthand attack β-cell in islet, that results in the deficiency of insulin in bloodstream and ultimately leads to hyperglycemia. Hence, modulating immunity to conserve residual β-cell is a desirable way to treat new-onset T1D. However, systemic immunosuppression makes patients at risk of organ damage, infection, even cancers. Biomaterials can be leveraged to achieve targeted immunomodulation, which can reduce the toxic side effects of immunosuppressants. In this review, we discuss the recent advances in harness of biomaterials to immunomodulate immunity for T1D. We investigate nanotechnology in targeting delivery of immunosuppressant, biological macromolecule for β-cell specific autoreactive T cell regulation. We also explore the biomaterials for developing vaccines and facilitate immunosuppressive cells to restore immune tolerance in pancreas.

Integrative Analyses Identify KCNJ15 as a Candidate Gene in Patients with Epilepsy

INTRODUCTION

Although there is accumulating evidence that genetic factors play a vital role in the pathogenesis of epilepsy, few epilepsy-associated genes have been identified. Additionally, the role of KCNJ15 in epilepsy has not been evaluated so far.

METHODS

Here, we performed differentially expressed gene analysis, expression quantitative trait loci analysis, gene co-expression analysis, and protein-protein interaction analysis to evaluate the role of KCNJ15 in epilepsy.

RESULTS

Analysis of gene expression and expression quantitative trait loci data revealed that KCNJ15 was significantly downregulated in patients with epilepsy (adjusted P = 0.0146 and log₂ Fold change = - 1.0025), and an epilepsy-associated polymorphism (rs2833098) was linked to altered KCNJ15 expression level in human temporal lobe brain tissue (P = 0.0036). Gene co-expression analysis revealed that KCNJ15 was co-expressed with genes that have been reported to be associated with epilepsy in human brain tissue. Furthermore, protein-protein interaction analysis revealed strong supportive evidence for the role of KCNJ15 in epilepsy.

CONCLUSION

Our results show that KCNJ15 may be a candidate target for epilepsy. Functional analysis of KCNJ15 may provide novel insights for epilepsy treatment.

The Coordination of mTOR Signaling and Non-Coding RNA in Regulating Epileptic Neuroinflammation

Epilepsy accounts for a significant proportion of the burden of neurological disorders. Neuroinflammation acting as the inflammatory response to epileptic seizures is characterized by aberrant regulation of inflammatory cells and molecules, and has been regarded as a key process in epilepsy where mTOR signaling serves as a pivotal modulator. Meanwhile, accumulating evidence has revealed that non-coding RNAs (ncRNAs) interfering with mTOR signaling are involved in neuroinflammation and therefore articipate in the development and progression of epilepsy. In this review, we highlight recent advances in the regulation of mTOR on neuroinflammatory cells and mediators, and feature the progresses of the interaction between ncRNAs and mTOR in epileptic neuroinflammation.

Impact of Raptor and Rictor Deletion on Hippocampal Pathology Following Status Epilepticus

Neuronal hyperactivation of the mTOR signaling pathway may play a role in driving the pathological sequelae that follow status epilepticus. Animal studies using pharmacological tools provide support for this hypothesis, however, systemic inhibition of mTOR-a growth pathway active in every mammalian cell-limits conclusions on cell type specificity. To circumvent the limitations of pharmacological approaches, we developed a viral/genetic strategy to delete Raptor or Rictor, inhibiting mTORC1 or mTORC2, respectively, from excitatory hippocampal neurons after status epilepticus in mice. Raptor or Rictor was deleted from roughly 25% of hippocampal granule cells, with variable involvement of other hippocampal neurons, after pilocarpine status epilepticus. Status epilepticus induced the expected loss of hilar neurons, sprouting of granule cell mossy fiber axons and reduced c-Fos activation. Gene deletion did not prevent these changes, although Raptor loss reduced the density of c-Fos-positive granule cells overall relative to Rictor groups. Findings demonstrate that mTOR signaling can be effectively modulated with this approach and further reveal that blocking mTOR signaling in a minority (25%) of granule cells is not sufficient to alter key measures of status epilepticus-induced pathology. The approach is suitable for producing higher deletion rates, and altering the timing of deletion, which may lead to different outcomes.

TAU ablation in excitatory neurons and postnatal TAU knockdown reduce epilepsy, SUDEP, and autism behaviors in a Dravet syndrome model

Intracellular accumulation of TAU aggregates is a hallmark of several neurodegenerative diseases. However, global genetic reduction of TAU is beneficial also in models of other brain disorders that lack such TAU pathology, suggesting a pathogenic role of nonaggregated TAU. Here, conditional ablation of TAU in excitatory, but not inhibitory, neurons reduced epilepsy, sudden unexpected death in epilepsy, overactivation of the phosphoinositide 3-kinase-AKT-mammalian target of rapamycin pathway, brain overgrowth (megalencephaly), and autism-like behaviors in a mouse model of Dravet syndrome, a severe epileptic encephalopathy of early childhood. Furthermore, treatment with a TAU-lowering antisense oligonucleotide, initiated on postnatal day 10, had similar therapeutic effects in this mouse model. Our findings suggest that excitatory neurons are the critical cell type in which TAU has to be reduced to counteract brain dysfunctions associated with Dravet syndrome and that overall cerebral TAU reduction could have similar benefits, even when initiated postnatally.

Adjudin prevents neuronal damage and neuroinflammation via inhibiting mTOR activation against pilocarpine-induced status epilepticus

Inflammatory responses in the brain play an etiological role in the development of epilepsy, suggesting that finding novel molecules for controlling neuroinflammation may have clinical value in developing the disease-modifying strategies for epileptogenesis. Adjudin, a multi-functional small molecule compound, has pleiotropic effects, including anti-inflammatory properties. In the present study, we aimed to investigate the effects of adjudin on pilocarpine-induced status epilepticus (SE) and its role in the regulation of reactive gliosis and neuroinflammation. SE was induced in male C57BL/6 mice that were then treated with adjudin (50mg/kg) for 3 days after SE onset. Immunofluorescence staining, terminal deoxynucleotidyl transferase dUTP nick end labeling staining, and western blot analysis were used to evaluate the effects of adjudin treatment in the hippocampus after SE. Our results showed that adjudin treatment significantly mitigated apoptotic cell death in the hippocampus after SE onset. Moreover, adjudin treatment suppressed SE-induced glial activation and activation of mammalian target of rapamycin signaling in the hippocampus. Concomitantly, adjudin treatment significantly reduced SE-induced inflammatory processes, as confirmed by changes in the expression of inflammatory mediators such as tumor necrosis factor-α, interleukin-1β, and arginase-1. In conclusion, these findings suggest that adjudin may serve as a potential neuroprotective agent for preventing pathological mechanisms implicated in epileptogenesis.

Sleep Disruption Worsens Seizures: Neuroinflammation as a Potential Mechanistic Link

Sleep disturbances, such as insomnia, obstructive sleep apnea, and daytime sleepiness, are common in people diagnosed with epilepsy. These disturbances can be attributed to nocturnal seizures, psychosocial factors, and/or the use of anti-epileptic drugs with sleep-modifying side effects. Epilepsy patients with poor sleep quality have intensified seizure frequency and disease progression compared to their well-rested counterparts. A better understanding of the complex relationship between sleep and epilepsy is needed, since approximately 20% of seizures and more than 90% of sudden unexpected deaths in epilepsy occur during sleep. Emerging studies suggest that neuroinflammation, (e.g., the CNS immune response characterized by the change in expression of inflammatory mediators and glial activation) may be a potential link between sleep deprivation and seizures. Here, we review the mechanisms by which sleep deprivation induces neuroinflammation and propose that neuroinflammation synergizes with seizure activity to worsen neurodegeneration in the epileptic brain. Additionally, we highlight the relevance of sleep interventions, often overlooked by physicians, to manage seizures, prevent epilepsy-related mortality, and improve quality of life.

Microglial ASD-related genes are involved in oligodendrocyte differentiation

Autism spectrum disorders (ASD) are associated with mutations of chromodomain-helicase DNA-binding protein 8 (Chd8) and tuberous sclerosis complex 2 (Tsc2). Although these ASD-related genes are detected in glial cells such as microglia, the effect of Chd8 or Tsc2 deficiency on microglial functions and microglia-mediated brain development remains unclear. In this study, we investigated the role of microglial Chd8 and Tsc2 in cytokine expression, phagocytosis activity, and neuro/gliogenesis from neural stem cells (NSCs) in vitro. Chd8 or Tsc2 knockdown in microglia reduced insulin-like growth factor-1(Igf1) expression under lipopolysaccharide (LPS) stimulation. In addition, phagocytosis activity was inhibited by Tsc2 deficiency, microglia-mediated oligodendrocyte development was inhibited, in particular, the differentiation of oligodendrocyte precursor cells to oligodendrocytes was prevented by Chd8 or Tsc2 deficiency. These results suggest that ASD-related gene expression in microglia is involved in oligodendrocyte differentiation, which may contribute to the white matter pathology relating to ASD.

MicroRNA 223 Targeting ATG16L1 Affects Microglial Autophagy in the Kainic Acid Model of Temporal Lobe Epilepsy

This study aimed to explore whether microRNA (miR) 223 affects microglial autophagy by targeting autophagy-related 16-like 1 (ATG16L1) in the kainic acid (KA) model of temporal lobe epilepsy (TLE). The miRNA and mRNA expression levels were quantified using quantitative real-time polymerase chain reaction (qRT-PCR), and the protein expression was investigated using western blotting. A dual-luciferase reporter assay was used to test the direct interaction between miR 223 and ATG16L1. In situ hybridization was performed to measure the hippocampal expression of miR 223. We used immunofluorescence staining to assess the expression of ATG16L1 and microtubule-associated protein light chain 3 (LC3) in the murine hippocampal microglia. Inhibitor of miR 223 was utilized to investigate the role of miR 223 in TLE, and the epileptic activity was assessed using electroencephalography (EEG). The autophagosomes were observed by transmission electron microscopy. In patients with TLE, the murine KA model of TLE, and the KA-stimulated BV2 cells, miR 223, and sequestosome 1 (SQSTM1/P62) expressions were remarkably increased, whereas ATG16L1 and LC3 levels were significantly decreased. Using a dual-luciferase reporter assay, ATG16L1 was determined as a direct target of miR 223. Treatment with antagomir 223 alleviated epilepsy, prevented abnormalities in EEG recordings and increased the ATG16L1 and LC3 levels in KA-treated mice. Inhibition of miR 223 induced increased autophagy in BV2 cells upon Rapamycin stimulation. These findings show that miR 223 affects microglial autophagy via ATG16L1 in the KA model of TLE. The miR 223/ATG16L1 pathway may offer a new treatment option for TLE.

Targeting Neuroinflammation via Purinergic P2 Receptors for Disease Modification in Drug-Refractory Epilepsy

Treatment of epilepsy remains a clinical challenge, with >30% of patients not responding to current antiseizure drugs (ASDs). Moreover, currently available ASDs are merely symptomatic without altering significantly the progression of the disease. Inflammation is increasingly recognized as playing an important role during the generation of hyperexcitable networks in the brain. Accordingly, the suppression of chronic inflammation has been suggested as a promising therapeutic strategy to prevent epileptogenesis and to treat drug-refractory epilepsy. As a consequence, a strong focus of ongoing research is identification of the mechanisms that contribute to sustained inflammation in the brain during epilepsy and whether these can be targeted. ATP is released in response to several pathological stimuli, including increased neuronal activity within the central nervous system, where it functions as a neuro- and gliotransmitter. Once released, ATP activates purinergic P2 receptors, which are divided into metabotropic P2Y and ionotropic P2X receptors, driving inflammatory processes. Evidence from experimental models and patients demonstrates widespread expression changes of both P2Y and P2X receptors during epilepsy, and critically, drugs targeting both receptor subtypes, in particular the P2Y₁ and P2X₇ subtypes, have been shown to possess both anticonvulsive and antiepileptic potential. This review provides a detailed summary of the current evidence suggesting ATP-gated receptors as novel drug targets for epilepsy and discusses how P2 receptor–driven inflammation may contribute to the generation of seizures and the development of epilepsy.

Deficiency of Microglial Autophagy Increases the Density of Oligodendrocytes and Susceptibility to Severe Forms of Seizures

Excessive activation of mTOR in microglia impairs CNS homeostasis and causes severe epilepsy. Autophagy constitutes an important part of mTOR signaling. The contribution of microglial autophagy to CNS homeostasis and epilepsy remains to be determined. Here, we report that ATG7KO mice deficient for autophagy in microglia display a marked increase of myelination markers, a higher density of mature oligodendrocytes (ODCs), and altered lengths of the nodes of Ranvier. Moreover, we found that deficiency of microglial autophagy (ATG7KO) leads to increased seizure susceptibility in three seizure models (pilocarpine, kainic acid, and amygdala kindling). We demonstrated that ATG7KO mice develop severe generalized seizures and display nearly 100% mortality to convulsions induced by pilocarpine and kainic acid. In the amygdala kindling model, we observed significant facilitation of contralateral propagation of seizures, a process underlying the development of generalized seizures. Taken together, our results reveal impaired microglial autophagy as a novel mechanism underlying altered homeostasis of ODCs and increased susceptibility to severe and fatal generalized seizures.