Neuroinflammation microenvironment sharpens seizure circuit

Acute rapamycin treatment reveals novel mechanisms of behavioral, physiological, and functional dysfunction in a maternal inflammation mouse model of autism and sensory over-responsivity

Maternal inflammatory response (MIR) during early gestation in mice induces a cascade of physiological and behavioral changes that have been associated with autism spectrum disorder (ASD). In a prior study and the current one, we find that mild MIR results in chronic systemic and neuro-inflammation, mTOR pathway activation, mild brain overgrowth followed by regionally specific volumetric changes, sensory processing dysregulation, and social and repetitive behavior abnormalities. Prior studies of rapamycin treatment in autism models have focused on chronic treatments that might be expected to alter or prevent physical brain changes. Here, we have focused on the acute effects of rapamycin to uncover novel mechanisms of dysfunction and related to mTOR pathway signaling. We find that within 2 hours, rapamycin treatment could rapidly rescue neuronal hyper-excitability, seizure susceptibility, functional network connectivity and brain community structure, and repetitive behaviors and sensory over-responsivity in adult offspring with persistent brain overgrowth. These CNS-mediated effects are also associated with alteration of the expression of several ASD-,ion channel-, and epilepsy-associated genes, in the same time frame. Our findings suggest that mTOR dysregulation in MIR offspring is a key contributor to various levels of brain dysfunction, including neuronal excitability, altered gene expression in multiple cell types, sensory functional network connectivity, and modulation of information flow. However, we demonstrate that the adult MIR brain is also amenable to rapid normalization of these functional changes which results in the rescue of both core and comorbid ASD behaviors in adult animals without requiring long-term physical alterations to the brain. Thus, restoring excitatory/inhibitory imbalance and sensory functional network modularity may be important targets for therapeutically addressing both primary sensory and social behavior phenotypes, and compensatory repetitive behavior phenotypes.

Pharmacological elevation of glutathione inhibits status epilepticus-induced neuroinflammation and oxidative injury

Glutathione (GSH) is a major endogenous antioxidant, and its depletion has been observed in several brain diseases including epilepsy. Previous studies in our laboratory have shown that dimercaprol (DMP) can elevate GSH via post-translational activation of glutamate cysteine ligase (GCL), the rate limiting GSH biosynthetic enzyme and inhibit neuroinflammation in vitro. Here we determined 1) the role of cysteamine as a new mechanism by which DMP increases GSH biosynthesis and 2) its ability to inhibit neuroinflammation and neuronal injury in the rat kainate model of epilepsy. DMP depleted cysteamine in a time- and concentration-dependent manner in a cell free system. To guide the in vivo administration of DMP, its pharmacokinetic profile was determined in the plasma, liver, and brain. The results confirmed DMP's ability to cross the blood-brain-barrier. Treatment of rats with DMP (30 mg/kg) depleted cysteamine in the liver and hippocampus that was associated with increased GCL activity in these tissues. GSH levels were significantly increased (20 %) in the hippocampus 1 h after 30 mg/kg DMP administration. Following DMP (30 mg/kg) administration once daily, a marked attenuation of GSH depletion was seen in the SE model. SE-induced inflammatory markers including cytokine release, microglial activation, and neuronal death were significantly attenuated in the hippocampus with DMP treatment. Taken together, these results highlight the importance of restoring redox status with rescue of GSH depletion by DMP in post epileptogenic insults.

Neuroimmune response and oxidative stress in the prefrontal cortex mediate seizure susceptibility in experimental colitis in male mice

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disorder. Oxidative stress and inflammatory responses have a vital role in the pathophysiology of IBD as well as seizure. IBD is associated with extraintestinal manifestations. This study aimed to explore the relationship between colitis and susceptibility to seizures, with a focus on the roles of neuroinflammation and oxidative stress in acetic acid-induced colitis in mice. Forty male Naval Medical Research Institute mice were divided into four groups: control, colitis, pentylenetetrazole (PTZ), and colitis + PTZ. Colitis was induced by intrarectal administration of acetic acid, and seizures were induced by intravenous injection of PTZ 7 days postcolitis induction. Following the measurement of latency to seizure, the mice were killed, and their colons and prefrontal cortex (PFC) were dissected. Gene expression of inflammatory markers including interleukin-1β, tumor necrosis factor-alpha, NOD-like receptor protein 3, and toll-like receptor 4, as well as total antioxidant capacity (TAC), malondialdehyde (MDA), and nitrite levels were measured in the colon and PFC. Histopathological evaluations were performed on the colon samples. Data were analyzed by t-test or one-way variance analysis. Colitis decreased latency to seizure, increased gene expression of inflammatory markers, and altered levels of MDA, nitrite, and TAC in both the colon and PFC. Simultaneous induction of colitis and seizure exacerbated the neuroimmune response and oxidative stress in the PFC and colon. Results concluded that neuroinflammation and oxidative stress in the PFC at least partially mediate the comorbid decrease in seizure latency in mice with colitis.

Characterization of soticlestat, a novel cholesterol 24-hydroxylase inhibitor, in acute and chronic neurodegeneration models

We investigated whether soticlestat (TAK-935), a newly discovered cholesterol 24-hydroxylase (CH24H) inhibitor now in phase 3 clinical trials for Dravet and Lennox-Gastaut syndromes, has effects on neurodegeneration in both chronic and acute animal models associated with glutamate hyperexcitation. Soticlestat was administered at doses that approximately halve 24S-hydroxycholesterol in both experiments. In the kainic acid (KA)-induced acute hippocampal degeneration model, soticlestat ameliorated inflammatory cytokine expression, hippocampal degeneration, and memory impairment. We ruled out the possibility that soticlestat directly interferes with KA binding to the KA receptor, or that 24S-hydroxycholesterol modulates KA receptor signaling, by conducting receptor binding and cell death assays. In the PS19 chronic degeneration model of tauopathy, treatment effects were observed in neurodegeneration markers. Notably, there was a significant correlation between the levels of brain 24S-hydroxycholesterol and a proinflammatory cytokine, tumor necrosis factor-α, which is implicated in cognitive decline and lowering of seizure threshold. This is the first study demonstrating that CH24H inhibition can alleviate neurodegeneration concomitant with neuroinflammation. Herein, we discuss the interplay among 24S-hydroxycholesterol production, neuroinflammation, and excitotoxicity. Effects on neurodegeneration and neuroinflammation demonstrated in two preclinical models suggest that soticlestat is effective in ameliorating seizures and addressing cognitive dysfunction in seizure disorders.

A Systematic Review of the Predictive and Diagnostic Uses of Neuroinflammation Biomarkers for Epileptogenesis

A central role for neuroinflammation in epileptogenesis has recently been suggested by several investigations. This systematic review explores the role of inflammatory mediators in epileptogenesis, its association with seizure severity, and its correlation with drug-resistant epilepsy (DRE). The study analysed articles published in JCR journals from 2019 to 2024. The search strategy comprised the MESH, free terms of "Neuroinflammation", and selective searches for the following single biomarkers that had previously been selected from the relevant literature: "High mobility group box 1/HMGB1", "Toll-Like-Receptor 4/TLR-4", "Interleukin-1/IL-1", "Interleukin-6/IL-6", "Transforming growth factor beta/TGF-β", and "Tumour necrosis factor-alpha/TNF-α". These queries were all combined with the MESH terms "Epileptogenesis" and "Epilepsy". We found 243 articles related to epileptogenesis and neuroinflammation, with 356 articles from selective searches by biomarker type. After eliminating duplicates, 324 articles were evaluated, with 272 excluded and 55 evaluated by the authors. A total of 21 articles were included in the qualitative evaluation, including 18 case-control studies, 2 case series, and 1 prospective study. As conclusion, this systematic review provides acceptable support for five biomarkers, including TNF-α and some of its soluble receptors (sTNFr2), HMGB1, TLR-4, CCL2 and IL-33. Certain receptors, cytokines, and chemokines are examples of neuroinflammation-related biomarkers that may be crucial for the early diagnosis of refractory epilepsy or may be connected to the control of epileptic seizures. Their value will be better defined by future studies.

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.

Participation of the spleen in the neuroinflammation after pilocarpine-induced status epilepticus: implications for epileptogenesis and epilepsy

Epilepsy, a chronic neurological disorder characterized by recurrent seizures, affects millions of individuals worldwide. Despite extensive research, the underlying mechanisms leading to epileptogenesis, the process by which a normal brain develops epilepsy, remain elusive. We, here, explored the immune system and spleen responses triggered by pilocarpine-induced status epilepticus (SE) focusing on their role in the epileptogenesis that follows SE. Initial examination of spleen histopathology revealed transient disorganization of white pulp, in animals subjected to SE. This disorganization, attributed to immune activation, peaked at 1-day post-SE (1DPSE) but returned to control levels at 3DPSE. Alterations in peripheral blood lymphocyte populations, demonstrated a decrease following SE, accompanied by a reduction in CD3+ T-lymphocytes. Further investigations uncovered an increased abundance of T-lymphocytes in the piriform cortex and choroid plexus at 3DPSE, suggesting a specific mobilization toward the Central Nervous System. Notably, splenectomy mitigated brain reactive astrogliosis, neuroinflammation, and macrophage infiltration post-SE, particularly in the hippocampus and piriform cortex. Additionally, splenectomized animals exhibited reduced lymphatic follicle size in the deep cervical lymph nodes. Most significantly, splenectomy correlated with improved neuronal survival, substantiated by decreased neuronal loss and reduced degenerating neurons in the piriform cortex and hippocampal CA2-3 post-SE. Overall, these findings underscore the pivotal role of the spleen in orchestrating immune responses and neuroinflammation following pilocarpine-induced SE, implicating the peripheral immune system as a potential therapeutic target for mitigating neuronal degeneration in epilepsy.

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.

RIPK3 promotes neuronal survival by suppressing excitatory neurotransmission during CNS viral infection

While recent work has identified roles for immune mediators in the regulation of neural activity, the capacity for cell intrinsic innate immune signaling within neurons to influence neurotransmission remains poorly understood. However, the existing evidence linking immune signaling with neuronal function suggests that modulation of neurotransmission may serve previously undefined roles in host protection during infection of the central nervous system. Here, we identify a specialized function for RIPK3, a kinase traditionally associated with necroptotic cell death, in preserving neuronal survival during neurotropic flavivirus infection through the suppression of excitatory neurotransmission. We show that RIPK3 coordinates transcriptomic changes in neurons that suppress neuronal glutamate signaling, thereby desensitizing neurons to excitotoxic cell death. These effects occur independently of the traditional functions of RIPK3 in promoting necroptosis and inflammatory transcription. Instead, RIPK3 promotes phosphorylation of the key neuronal regulatory kinase CaMKII, which in turn activates the transcription factor CREB to drive a neuroprotective transcriptional program and suppress deleterious glutamatergic signaling. These findings identify an unexpected function for a canonical cell death protein in promoting neuronal survival during viral infection through the modulation of neuronal activity, highlighting new mechanisms of neuroimmune crosstalk.

Neuroinflammation and Epilepsy: From Pathophysiology to Therapies Based on Repurposing Drugs

Neuroinflammation and epilepsy are different pathologies, but, in some cases, they are so closely related that the activation of one of the pathologies leads to the development of the other. In this work, we discuss the three main cell types involved in neuroinflammation, namely (i) reactive astrocytes, (ii) activated microglia, and infiltration of (iii) peripheral immune cells in the central nervous system. Then, we discuss how neuroinflammation and epilepsy are interconnected and describe the use of different repurposing drugs with anti-inflammatory properties that have been shown to have a beneficial effect in different epilepsy models. This review reinforces the idea that compounds designed to alleviate seizures need to target not only the neuroinflammation caused by reactive astrocytes and microglia but also the interaction of these cells with infiltrated peripheral immune cells.

Unraveling the Neural Circuits: Techniques, Opportunities and Challenges in Epilepsy Research

Epilepsy, a prevalent neurological disorder characterized by high morbidity, frequent recurrence, and potential drug resistance, profoundly affects millions of people globally. Understanding the microscopic mechanisms underlying seizures is crucial for effective epilepsy treatment, and a thorough understanding of the intricate neural circuits underlying epilepsy is vital for the development of targeted therapies and the enhancement of clinical outcomes. This review begins with an exploration of the historical evolution of techniques used in studying neural circuits related to epilepsy. It then provides an extensive overview of diverse techniques employed in this domain, discussing their fundamental principles, strengths, limitations, as well as their application. Additionally, the synthesis of multiple techniques to unveil the complexity of neural circuits is summarized. Finally, this review also presents targeted drug therapies associated with epileptic neural circuits. By providing a critical assessment of methodologies used in the study of epileptic neural circuits, this review seeks to enhance the understanding of these techniques, stimulate innovative approaches for unraveling epilepsy's complexities, and ultimately facilitate improved treatment and clinical translation for epilepsy.

A meta-analysis of the changes in the Gut microbiota in patients with intractable epilepsy compared to healthy controls

OBJECTIVE

To explore gut microbiota changes in intractable epilepsy patients compared to healthy control individuals through meta-analysis.

METHODS

PubMed, Web of Science, CNKI, Wanfang, medRxiv, bioRxiv, ilae.org, clinical trial databases, and papers from the International Epilepsy Congress (IEC) were searched, and the literature on the correlation between intractable epilepsy and the gut microbiota reported from database establishment to June 2023 was included. Literature meeting the inclusion criteria was screened, and meta-analysis of the included literature was performed using RevMan5.4 software.

RESULTS

Ten case-control studies were included in the meta-analysis. There were 183 patients with intractable epilepsy and 283 healthy control subjects. The analysis results indicated that Bacteroidetes (MD = -0.64, 95 %-CI = -1.21 to -0.06) and Ruminococcaceae (MD = -1.44, 95 % CI = -1.96 to -0.92) were less abundant in the patients with intractable epilepsy than in the normal population. Proteobacteria (MD = 0.53, 95 % CI = 0.02 to 1.05) and Verrucomicrobia (MD = 0.26, 95 % CI = 0.06 to 0.45) were more abundant in the patients with intractable epilepsy than in the normal population.

CONCLUSION

This meta-analysis indicated that the abundances of Bacteroidetes and Ruminococcaceae were reduced while those of Proteobacteria and Verrucomicrobia were significantly increased in patients with intractable epilepsy. The above changes in these four taxa of the gut microbiota may have been induced by intractable epilepsy, which may increase the risk of seizures. Their roles in the pathogenesis of intractable epilepsy need to be further explored, and related factors that influence microbiota changes should be considered in future studies.

Do vaccines cause epilepsy? Review of cases in the National Vaccine Injury Compensation Program

OBJECTIVE

The National Childhood Vaccine Injury Act of 1986 created the National Vaccine Injury Compensation Program (VICP), a no-fault alternative to the traditional tort system. Since 1988, the total compensation paid exceeds $5 billion. Although epilepsy is one of the leading reasons for filing a claim, there has been no review of the process and validity of the legal outcomes given current medical information. The objectives were to review the evolution of the VICP program in regard to vaccine-related epilepsy and assess the rationale behind decisions made by the court.

METHODS

Publicly available cases involving epilepsy claims in the VICP were searched through Westlaw and the US Court of Federal Claims websites. All published reports were reviewed for petitioner's theories supporting vaccine-induced epilepsy, respondent's counterarguments, the final decision regarding compensation, and the rationale underlying these decisions. The primary goal was to determine which factors went into decisions regarding whether vaccines caused epilepsy.

RESULTS

Since the first epilepsy case in 1989, there have been many changes in the program, including the removal of residual seizure disorder as a vaccine-related injury, publication of the Althen prongs, release of the acellular form of pertussis, and recognition that in genetic conditions the underlying genetic abnormality rather than the immunization causes epilepsy. We identified 532 unique cases with epilepsy: 105 with infantile spasms and 427 with epilepsy without infantile spasms. The petitioners' experts often espoused outdated, erroneous causation theories that lacked an acceptable medical or scientific foundation and were frequently criticized by the court.

SIGNIFICANCE

Despite the lack of epidemiological or mechanistic evidence indicating that childhood vaccines covered by the VICP result in or aggravate epilepsy, these cases continue to be adjudicated. After 35 years of intense litigation, it is time to reconsider whether epilepsy should continue to be a compensable vaccine-induced injury.

The Contribution of Microglia and Brain-Infiltrating Macrophages to the Pathogenesis of Neuroinflammatory and Neurodegenerative Diseases during TMEV Infection of the Central Nervous System

The infection of the central nervous system (CNS) with neurotropic viruses induces neuroinflammation and is associated with the development of neuroinflammatory and neurodegenerative diseases, including multiple sclerosis and epilepsy. The activation of the innate and adaptive immune response, including microglial, macrophages, and T and B cells, while required for efficient viral control within the CNS, is also associated with neuropathology. Under healthy conditions, resident microglia play a pivotal role in maintaining CNS homeostasis. However, during pathological events, such as CNS viral infection, microglia become reactive, and immune cells from the periphery infiltrate into the brain, disrupting CNS homeostasis and contributing to disease development. Theiler's murine encephalomyelitis virus (TMEV), a neurotropic picornavirus, is used in two distinct mouse models: TMEV-induced demyelination disease (TMEV-IDD) and TMEV-induced seizures, representing mouse models of multiple sclerosis and epilepsy, respectively. These murine models have contributed substantially to our understanding of the pathophysiology of MS and seizures/epilepsy following viral infection, serving as critical tools for identifying pharmacological targetable pathways to modulate disease development. This review aims to discuss the host-pathogen interaction during a neurotropic picornavirus infection and to shed light on our current understanding of the multifaceted roles played by microglia and macrophages in the context of these two complexes viral-induced disease.

Palmatine attenuates LPS-induced neuroinflammation through the PI3K/Akt/NF-κB pathway

To investigate the key molecular mechanisms of palmatine for the treatment of neuroinflammation through modulation of a pathway using molecular docking, molecular dynamics (MD) simulation combined with network pharmacology, and animal experiments. Five alkaloid components were obtained from the traditional Chinese medicine Huangteng through literature mining. Molecular docking and MD simulation with acetylcholinesterase were used to screen palmatine. At the animal level, mice were injected with LPS intracerebrally to cause a neuroinflammatory model, and the Morris water maze experiment was performed to examine the learning memory of mice. Anxiety levels were tested using the autonomous activity behavior experiment with the open field and elevated behavior experiments. HE staining and Niss staining were performed on brain tissue sections to observe morphological lesions and apoptosis; serum was examined for inflammatory factors TNF-α, IL-6, and IL-1β; Western blot was performed to detect the protein expression. The expression of PI3K/AKT/NFkB signaling pathway-related proteins was examined by Western blot. The results of network pharmacology showed that the screening of palmatine activation containing the PI3K/Akt/NFkB signaling pathway exerts antineuroinflammatory effects. Results from behavioral experiments showed that Pal enhanced learning memory in model mice, improved anxiety behavior, and significantly improved brain damage caused by neuroinflammation. The results of HE staining and Niss staining of brain tissue sections showed that palmatine could alleviate morphological lesions and nucleus damage in brain tissue. Palmatine improved the levels of serum inflammatory factors TNF-α, IL-6, and IL-1β. SOD, MDA, CAT, ACH, and ACHE in the hippocampus were improved. Western blot results showed that palmatine administration ameliorated LPS-induced neuroinflammation through the PI3K/Akt/NFkB pathway.

Mechanisms and Emerging Therapies for Treatment of Seizures in Pediatric Autoimmune Encephalitis and Autoinflammatory/Autoimmune-Associated Epilepsy

There has been increasing understanding of the role of inflammation in seizures and epilepsy, as well as targeted immunomodulatory treatments. In children, immune-mediated seizures often present acutely in the setting of autoimmune encephalitis and are very responsive to immunotherapy with low rates of subsequent epilepsy. Conversely, seizures in autoimmune-associated epilepsies, such as Rasmussen syndrome, can remain refractory to multimodal therapy, including immunomodulation. In this review, the authors discuss the presentations of immune-mediated seizures in children, underlying mechanisms, and emerging therapies.