Causal links between brain cytokines and experimental febrile convulsions in the rat

Interleukins in Epilepsy: Friend or Foe

Epilepsy is a chronic neurological disorder with recurrent unprovoked seizures, affecting ~ 65 million worldwide. Evidence in patients with epilepsy and animal models suggests a contribution of neuroinflammation to epileptogenesis and the development of epilepsy. Interleukins (ILs), as one of the major contributors to neuroinflammation, are intensively studied for their association and modulatory effects on ictogenesis and epileptogenesis. ILs are commonly divided into pro- and anti-inflammatory cytokines and therefore are expected to be pathogenic or neuroprotective in epilepsy. However, both protective and destructive effects have been reported for many ILs. This may be due to the complex nature of ILs, and also possibly due to the different disease courses that those ILs are involved in. In this review, we summarize the contributions of different ILs in those processes and provide a current overview of recent research advances, as well as preclinical and clinical studies targeting ILs in the treatment of epilepsy.

Neuroactive Steroids, Toll-like Receptors, and Neuroimmune Regulation: Insights into Their Impact on Neuropsychiatric Disorders

Pregnane neuroactive steroids, notably allopregnanolone and pregnenolone, exhibit efficacy in mitigating inflammatory signals triggered by toll-like receptor (TLR) activation, thus attenuating the production of inflammatory factors. Clinical studies highlight their therapeutic potential, particularly in conditions like postpartum depression (PPD), where the FDA-approved compound brexanolone, an intravenous formulation of allopregnanolone, effectively suppresses TLR-mediated inflammatory pathways, predicting symptom improvement. Additionally, pregnane neurosteroids exhibit trophic and anti-inflammatory properties, stimulating the production of vital trophic proteins and anti-inflammatory factors. Androstane neuroactive steroids, including estrogens and androgens, along with dehydroepiandrosterone (DHEA), display diverse effects on TLR expression and activation. Notably, androstenediol (ADIOL), an androstane neurosteroid, emerges as a potent anti-inflammatory agent, promising for therapeutic interventions. The dysregulation of immune responses via TLR signaling alongside reduced levels of endogenous neurosteroids significantly contributes to symptom severity across various neuropsychiatric disorders. Neuroactive steroids, such as allopregnanolone, demonstrate efficacy in alleviating symptoms of various neuropsychiatric disorders and modulating neuroimmune responses, offering potential intervention avenues. This review emphasizes the significant therapeutic potential of neuroactive steroids in modulating TLR signaling pathways, particularly in addressing inflammatory processes associated with neuropsychiatric disorders. It advances our understanding of the complex interplay between neuroactive steroids and immune responses, paving the way for personalized treatment strategies tailored to individual needs and providing insights for future research aimed at unraveling the intricacies of neuropsychiatric disorders.

Additive interaction between birth asphyxia and febrile seizures on autism spectrum disorder: a population-based study

BACKGROUND

Autism Spectrum Disorder (ASD) is a pervasive neurodevelopmental disorder that can significantly impact an individual's ability to socially integrate and adapt. It's crucial to identify key factors associated with ASD. Recent studies link both birth asphyxia (BA) and febrile seizures (FS) separately to higher ASD prevalence. However, investigations into the interplay of BA and FS and its relationship with ASD are yet to be conducted. The present study mainly focuses on exploring the interactive effect between BA and FS in the context of ASD.

METHODS

Utilizing a multi-stage stratified cluster sampling, we initially recruited 84,934 Shanghai children aged 3-12 years old from June 2014 to June 2015, ultimately including 74,251 post-exclusion criteria. A logistic regression model was conducted to estimate the interaction effect after controlling for pertinent covariates. The attributable proportion (AP), the relative excess risk due to interaction (RERI), the synergy index (SI), and multiplicative-scale interaction were computed to determine the interaction effect.

RESULTS

Among a total of 74,251 children, 192 (0.26%) were diagnosed with ASD. The adjusted odds ratio for ASD in children with BA alone was 3.82 (95% confidence interval [CI] 2.42-6.02), for FS alone 3.06 (95%CI 1.48-6.31), and for comorbid BA and FS 21.18 (95%CI 9.10-49.30), versus children without BA or FS. The additive interaction between BA and FS showed statistical significance (P < 0.001), whereas the multiplicative interaction was statistically insignificant (P > 0.05).

LIMITATIONS

This study can only demonstrate the relationship between the interaction of BA and FS with ASD but cannot prove causation. Animal brain experimentation is necessary to unravel its neural mechanisms. A larger sample size, ongoing monitoring, and detailed FS classification are needed for confirming BA-FS interaction in ASD.

CONCLUSION

In this extensive cross-sectional study, both BA and FS were significantly linked to ASD. The coexistence of these factors was associated with an additive increase in ASD prevalence, surpassing the cumulative risk of each individual factor.

Febrile Seizure Causes Deficit in Social Novelty, Gliosis, and Proinflammatory Cytokine Response in the Hippocampal CA2 Region in Rats

Febrile seizure (FS), which occurs as a response to fever, is the most common seizure that occurs in infants and young children. FS is usually accompanied by diverse neuropsychiatric symptoms, including impaired social behaviors; however, research on neuropsychiatric disorders and hippocampal inflammatory changes following febrile seizure occurrences is very limited. Here, we provide evidence linking FS occurrence with ASD pathogenesis in rats. We developed an FS juvenile rats model and found ASD-like abnormal behaviors including deficits in social novelty, repetitive behaviors, and hyperlocomotion. In addition, FS model juvenile rats showed enhanced levels of gliosis and inflammation in the hippocampal CA2 region and cerebellum. Furthermore, abnormal levels of social and repetitive behaviors persisted in adults FS model rats. These findings suggest that the inflammatory response triggered by febrile seizures in young children could potentially serve as a mediator of social cognitive impairments.

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.

Diagnostic and therapeutic value of P2Y12R in epilepsy

There lacks biomarkers in current epilepsy diagnosis, and epilepsy is thus exposed to inadequate treatment, making it necessarily important to conduct search on new biomarkers and drug targets. The P2Y12 receptor is primarily expressed on microglia in the central nervous system, and acts as intrinsic immune cells in the central nervous system mediating neuroinflammation. In previous studies, P2Y12R in epilepsy has been found capable of controlling neuroinflammation and regulating neurogenesis as well as immature neuronal projections, and its expression is altered. P2Y12R is involved in microglia inhibition of neuronal activity and timely termination of seizures in acute seizures. In status epilepticus, the failure of P2Y12R in the process of "brake buffering" may not terminate the neuronal hyperexcitability timely. In chronic epilepsy, neuroinflammation causes seizures, which can in turn induce neuroinflammation, while on the other hand, neuroinflammation leads to neurogenesis, thereby causing abnormal neuronal discharges that give rise to seizures. In this case, targeting P2Y12R may be a novel strategy for the treatment of epilepsy. The detection of P2Y12R and its expression changes can contribute to the diagnosis of epilepsy. Meanwhile, the P2Y12R single-nucleotide polymorphism is associated with epilepsy susceptibility and endowed with the potential to individualize epilepsy diagnosis. To this end, functions of P2Y12R in the central nervous system were hereby reviewed, the effects of P2Y12R in epilepsy were explored, and the potential of P2Y12R in the diagnosis and treatment of epilepsy was further demonstrated.

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.

Association between high-mobility group box 1 levels and febrile seizures in children: a systematic review and meta-analysis

The relationship between High-mobility group box 1 (HMGB1) and febrile seizures (FS) in children remains unclear. This study aimed to apply meta-analysis to reveal the correlation between HMGB1 levels and FS in children. Databases including PubMed, EMBASE, Web of science, Cochrane library, CNKI, SinoMed and WanFangData were searched for relevant studies. Pooled standard mean deviation and 95% confidence interval were calculated as effect size since the random-effects model was used when I² > 50%. Meanwhile, between-study heterogeneity was determined by performing subgroup and sensitivity analyses. A total of 9 studies were finally included. Meta-analysis showed that the children with FS had significantly higher HMGB1 levels compared with healthy children and children with fever but no seizures (P<0.05). Additionally, subgroup analysis showed that the HMGB1 level in children with complex FS was higher than those with simple FS (P<0.05), and children with duration >15 min were higher than those with duration ≤15min (P<0.05). There were no statistical differences between children with or without a family history of FS (P>0.05). Finally, children with FS who converted to epilepsy exhibited higher HMGB1 levels than those who did not convert to epilepsy (P<0.05). The level of HMGB1 may be implicated in the prolongation, recurrence and development of FS in children. Thus, it was necessary to evaluate the precise concentrations of HMGB1 in FS patients and to further determine the various activities of HMGB1 during FS by well-designed, large-scale, and case-controlled trials.

Modulating Expression of Endogenous Interleukin 1 Beta in the Acute Phase of the Pilocarpine Model of Epilepsy May Change Animal Survival

The pilocarpine-induced (PILO) model has helped elucidate the electrophysiological and molecular aspects related to mesial temporal lobe epilepsy. It has been suggested that the extensive cell death and edema observed in the brains of these animals could be induced by increased inflammatory responses, such as the rapid release of the inflammatory cytokine interleukin 1 beta (Il1b). In this study, we investigate the role of endogenous Il1b in the acute phase of the PILO model. Our aim is twofold. First, we want to determine whether it is feasible to silence Il1b in the central nervous system using a non-invasive procedure. Second, we aim to investigate the effect of silencing endogenous Il1b and its antagonist, Il1rn.We used RNA interference applied non-invasively to knockdown Il1b and its endogenous antagonist Il1rn. We found that knocking down Il1b prior to pilocarpine injection increased the mortality rate of treated animals. Furthermore, we observed that, when exposing the animals to more Il1b by silencing its endogenous antagonist Il1rn, there was a better response to status epilepticus with decreased animal mortality in the acute phase of the PILO model. Thus, we show the feasibility of using a novel, less invasive approach to study genes involved in the inflammatory response in the central nervous system. Furthermore, our results provide suggestive evidence that modulating endogenous Il1b improves animal survival in the acute phase of the PILO model and may have effects that extend into the chronic phase.

Effects of Diclofenac Sodium on Seizure Activity in Rats with Pentylenetetrazole-Induced Convulsions

Epilepsy is a disease which affects between 1 and 2% of the population, and a large proportion of these people do not react to currently available anticonvulsant medications, indicating the need for further research into novel pharmacological therapies. Numerous studies have demonstrated that oxidative stress and inflammation occur during epilepsy and may contribute to its development and progression, indicating higher levels of oxidative and inflammatory parameters in experimental models and clinical patients. This research aimed to assess the impact of diclofenac sodium, a nonsteroidal anti-inflammatory medicine, on seizure and levels of oxidative stress and inflammatory biomarkers in a rat model of epilepsy triggered by pentylenetetrazole (PTZ). 60 rats were randomly allocated to one of two groups: electroencephalography (EEG) recordings or behavioral evaluation. Rats received diclofenac sodium at three various doses (25, 50, and 75 mg/kg) intraperitoneally (IP) or a placebo, followed by intraperitoneal (IP) pentylenetetrazole, a powerful seizure-inducing medication. To investigate if diclofenac sodium had antiseizure properties, seizure activity in rats was evaluated using EEG recordings, the Racine convulsion scale (RCS) behaviour score, the duration of the first myoclonic jerk (FMJ), and the levels of MDA, TNF-α, and SOD. The average percentage of EEG spike waves decreased from 76.8% (placebo) to 64.1% (25 mg/kg diclofenac), 55.9% (50 mg/kg diclofenac), and 37.8% (75 mg/kg diclofenac). FMJ had increased from a mean of 58.8 s (placebo), to 93.6 s (25 mg/kg diclofenac), 185.8 s (50 mg/kg diclofenac) and 231.7 s (75 mg/kg diclofenac). RCS scores decreased from a mean score of 5.6 (placebo), to 3.75 (25 mg/kg diclofenac), 2.8 (50 mg/kg diclofenac) and 1.75 (75 mg/kg diclofenac). MDA levels reduced from 14.2 ng/gr (placebo) to 9.6 ng/gr (25 mg/kg diclofenac), 8.4 ng/gr (50 mg/kg diclofenac) and 5.1 ng/gr (75 mg/kg diclofenac). Likely, TNF-α levels decreased from 67.9 ng/gr (placebo) to 48.1 ng/gr (25 mg/kg diclofenac), 33.5 ng/gr (50 mg/kg diclofenac) and 21.3 ng/gr (75 mg/kg diclofenac). SOD levels, however, enhanced from 0.048 U/mg (placebo) to 0.055 U/mg (25 mg/kg diclofenac), 0.14 U/mg (50 mg/kg diclofenac), and 0.18 U/mg (75 mg/kg diclofenac). Diclofenac sodium (25, 50, and 75 mg/kg i.p.) effectively lowered the spike percentages and RCS scores linked with PTZ-induced epilepsy in rats, as well as significantly decreased MDA, TNF-α, IL-1β, PGE2 and increased SOD levels. Probably as a result of its anti-oxidative and anti-inflammatory effects, diclofenac sodium dramatically lowered seizure activity at both doses compared to placebo control. Each of these results were significant, with p-values of < 0.01, < 0.05. Therefore, the therapeutic application diclofenac sodium as a potential anticonvulsant should be investigated further.

Lipopolysaccharide (LPS) increases susceptibility to epilepsy via interleukin-1 type 1 receptor signaling

Epilepsy is the most common disease of the nervous system, characterized by aberrant normal brain activity. Neuroinflammation is a prominent feature in the brain in epileptic humans and animal models of epilepsy. However, it remains elusive as to how peripheral inflammation affects epilepsy. Herein we demonstrated significantly greater seizure susceptibility and severity of epilepsy under kainic acid (KA) via intraperitoneal (i.p.) injection of lipopolysaccharide (LPS) in mouse model of epilepsy. Nissl staining was employed for assessment of the neuronal damage, immunofluorescence for staining of the microglial cells and astrocytes in the mouse brain slices, and ELISA for detection of the changes of inflammatory factors. We observed a smaller population of viable neurons in CA1 and CA3 regions, a greater population of IBA-1-positive and GFAP-positive cells, with a significant upregulation of IL-1β and IL-6 in hippocampus of epileptic mice when treated with LPS, indicating that LPS aggravates hippocampal neuron injury in epilepsy, and induces neuroinflammation in the hippocampus. In addition, we provide an evident increase in BrdU⁺/DCX⁺ and Nestin⁺ cell populations in dentate gyrus (DG) in LPS-treated group, versus saline group on epileptic mouse model, which demonstrated LPS treatment enhanced hippocampal neurogenesis. In order to investigate whether interleukin-1 type 1 (IL-1R1) signaling is involved in this process, we adopted IL-1R1 globally restored mice (IL-1R1^GR/GR) as an IL-1R1 reporter to visualize labeling of IL-1R1 mRNA and protein by means of RFP staining. Strikingly, the RFP immunofluorescence revealed increased IL-1R1 expression in LPS-treated group, versus saline group. Further, blockage of central IL-1R1 alleviated seizure susceptibility and severity of epilepsy. In summary, our findings suggested that LPS could enhance central inflammatory response and aggravate the susceptibility to epileptic seizure, which we postulated to be mediated by IL-1R1.

Correlation of Clinicopathological Factors with Brain Tumor-Related Epilepsy in Glioma

Objectives. Glioma patients with brain tumor-related epilepsy (BTRE) have a complex profile due to the simultaneous presence of two pathologies, glioma and epilepsy; however, they have not traditionally received as much attention as those with more malignant brain tumors. The underlying pathophysiology of brain tumor-related epilepsy remains poorly understood. The purpose of this study was to investigate the possible correlation between molecular neuropathology and glioma with BTRE and a wide range of BTRE-associated molecular markers of glioma patients. Methods. A retrospective cohort study of 186 glioma patients was evaluated at our hospital, of which 64 had BTRE. The chi-square test, Spearman rank correlation, and multivariate logistic analyses were used to identify clinicopathological factors associated with BTRE in glioma patients. Results. Of the 186 patients examined in this study, 64 (34.4%) had BTRE. Based on the analysis of the characteristics of these patients, the results showed that patient age (over 40 years; $P=0.007$ ), low WHO grade (grade I, II; $P=0.001$ ), IDH-1 positive mutation ( $P=0.027$ ), low ATR-X expression level ( $\text{OR}=0.44$ ; 95% CI: 0.21, 0.92), and low Ki-67 PI ( $\text{OR}=0.25$ ; 95% CI: 0.10, 0.68) were associated with the occurrence of BTRE. In our cohort, BTRE patients did not differ by sex, tumor location, or expression of olig-2 and CD34. The results of the matching study showed that low Ki-67 PI and negative ATR-X expression levels were independent factors for a higher incidence of preoperative seizures in glioma patients. Conclusion. The current study updates existing information on genetic markers in gliomas with BTRE and explores the correlation of a wide range of clinicopathological factors and glioma patients with BTRE and suggests three putative biomarkers for BTRE: positive IDH1 mutation, low Ki-67 PI, and negative ATR-X expression. These factors may provide insights for developing a more thorough understanding of the pathogenesis of epilepsy and effective treatment strategies aimed at seizure control.

Hippocampal Cytokine Release in Experimental Epileptogenesis—A Longitudinal In Vivo Microdialysis Study

Background: Inflammation, particularly cytokine release, contributes to epileptogenesis by influencing the cerebral tissue remodeling and neuronal excitability that occurs after a precipitating epileptogenic insult. While several cytokines have been explored in this process, release kinetics are less well investigated. Determining the time course of cytokine release in the epileptogenic zone is necessary for precisely timed preventive or therapeutic anti-inflammatory interventions. Methods: Hippocampal extracellular levels of six cytokines and chemokines (IL-1β, IL-6, IL-10, CCL2, CCL3, and CCL5) were quantified at various time points during epileptogenesis in a rat model of mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE-HS) using microdialysis (MD). Results: The analysis of microdialysates demonstrated consistent elevation at all time points during epileptogenesis for IL-1β and IL-10. IL-10 release was maximal on day 1, IL-1β release peaked at day 8. No correlation between local hippocampal IL-1β concentrations and IL-1β blood levels was found. Conclusion: The release kinetics of IL-1β are consistent with its established pro-epileptogenic properties, while the kinetics of IL-10 suggest a counter-regulatory effect. This proof-of-concept study demonstrates the feasibility of intraindividual longitudinal monitoring of hippocampal molecular inflammatory processes via repetitive MD over several weeks and sheds light on the kinetics of hippocampal cytokine release during epileptogenesis.

Sex Differences in Depression Caused by Early Life Stress and Related Mechanisms

Depression is a common psychiatric disease caused by various factors, manifesting with continuous low spirits, with its precise mechanism being unclear. Early life stress (ELS) is receiving more attention as a possible cause of depression. Many studies focused on the mechanisms underlying how ELS leads to changes in sex hormones, neurotransmitters, hypothalamic pituitary adrenocortical (HPA) axis function, and epigenetics. The adverse effects of ELS on adulthood are mainly dependent on the time window when stress occurs, sex and the developmental stage when evaluating the impacts. Therefore, with regard to the exact sex differences of adult depression, we found that ELS could lead to sex-differentiated depression through multiple mechanisms, including 5-HT, sex hormone, HPA axis, and epigenetics.

Microglia and Status Epilepticus in the Immature Brain

Microglia are the resident immune cells of the Central Nervous System (CNS), which are activated due to brain damage, as part of the neuroinflammatory response. Microglia undergo morphological and biochemical modifications during activation, adopting a pro-inflammatory or an anti-inflammatory state. In the developing brain, status epilepticus (SE) promotes microglia activation that is associated with neuronal injury in some areas of the brain, such as the hippocampus, thalamus and amygdala. However, the timing of this activation, the anatomical pattern, and the morphological and biochemical characteristics of microglia in the immature brain are age-dependent and have not been fully characterized. Therefore, this review focuses on the response of microglia to SE and its relationship to neurodegeneration.

Molecular Mechanisms in the Genesis of Seizures and Epilepsy Associated With Viral Infection

Seizures are a common presenting symptom during viral infections of the central nervous system (CNS) and can occur during the initial phase of infection ("early" or acute symptomatic seizures), after recovery ("late" or spontaneous seizures, indicating the development of acquired epilepsy), or both. The development of acute and delayed seizures may have shared as well as unique pathogenic mechanisms and prognostic implications. Based on an extensive review of the literature, we present an overview of viruses that are associated with early and late seizures in humans. We then describe potential pathophysiologic mechanisms underlying ictogenesis and epileptogenesis, including routes of neuroinvasion, viral control and clearance, systemic inflammation, alterations of the blood-brain barrier, neuroinflammation, and inflammation-induced molecular reorganization of synapses and neural circuits. We provide clinical and animal model findings to highlight commonalities and differences in these processes across various neurotropic or neuropathogenic viruses, including herpesviruses, SARS-CoV-2, flaviviruses, and picornaviruses. In addition, we extensively review the literature regarding Theiler's murine encephalomyelitis virus (TMEV). This picornavirus, although not pathogenic for humans, is possibly the best-characterized model for understanding the molecular mechanisms that drive seizures, epilepsy, and hippocampal damage during viral infection. An enhanced understanding of these mechanisms derived from the TMEV model may lead to novel therapeutic interventions that interfere with ictogenesis and epileptogenesis, even within non-infectious contexts.

Recruitment of α4β7 monocytes and neutrophils to the brain in experimental colitis is associated with elevated cytokines and anxiety-like behavior

Background

Behavioral comorbidities, such as anxiety and depression, are a prominent feature of IBD. The signals from the inflamed gut that cause changes in the brain leading to these behavioral comorbidities remain to be fully elucidated. We tested the hypothesis that enhanced leukocyte–cerebral endothelial cell interactions occur in the brain in experimental colitis, mediated by α4β7 integrin, to initiate neuroimmune activation and anxiety-like behavior.

Methods

Female mice treated with dextran sodium sulfate were studied at the peak of acute colitis. Circulating leukocyte populations were determined using flow cytometry. Leukocyte–cerebral endothelial cell interactions were examined using intravital microscopy in mice treated with anti-integrin antibodies. Brain cytokine and chemokines were assessed using a multiplex assay in animals treated with anti-α4β7 integrin. Anxiety-like behavior was assessed using an elevated plus maze in animals after treatment with an intracerebroventricular injection of interleukin 1 receptor antagonist.

Results

The proportion of classical monocytes expressing α4β7 integrin was increased in peripheral blood of mice with colitis. An increase in the number of rolling and adherent leukocytes on cerebral endothelial cells was observed, the majority of which were neutrophils. Treatment with anti-α4β7 integrin significantly reduced the number of rolling leukocytes. After anti-Ly6C treatment to deplete monocytes, the number of rolling and adhering neutrophils was significantly reduced in mice with colitis. Interleukin-1β and CCL2 levels were elevated in the brain and treatment with anti-α4β7 significantly reduced them. Enhanced anxiety-like behavior in mice with colitis was reversed by treatment with interleukin 1 receptor antagonist.

Conclusions

In experimental colitis, α4β7 integrin-expressing monocytes direct the recruitment of neutrophils to the cerebral vasculature, leading to elevated cytokine levels. Increased interleukin-1β mediates anxiety-like behavior.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02431-z.

Targeting Inflammatory Mediators in Epilepsy: A Systematic Review of Its Molecular Basis and Clinical Applications

Introduction

Recent studies prompted the identification of neuroinflammation as a potential target for the treatment of epilepsy, particularly drug-resistant epilepsy, and refractory status epilepticus. This work provides a systematic review of the clinical experience with anti-cytokine agents and agents targeting lymphocytes and aims to evaluate their efficacy and safety for the treatment of refractory epilepsy. Moreover, the review analyzes the main therapeutic perspectives in this field.

Methods

A systematic review of the literature was conducted on MEDLINE database. Search terminology was constructed using the name of the specific drug (anakinra, canakinumab, tocilizumab, adalimumab, rituximab, and natalizumab) and the terms “status epilepticus,” “epilepsy,” and “seizure.” The review included clinical trials, prospective studies, case series, and reports published in English between January 2016 and August 2021. The number of patients and their age, study design, specific drugs used, dosage, route, and timing of administration, and patients outcomes were extracted. The data were synthesized through quantitative and qualitative analysis.

Results

Our search identified 12 articles on anakinra and canakinumab, for a total of 37 patients with epilepsy (86% febrile infection-related epilepsy syndrome), with reduced seizure frequency or seizure arrest in more than 50% of the patients. The search identified nine articles on the use of tocilizumab (16 patients, 75% refractory status epilepticus), with a high response rate. Only one reference on the use of adalimumab in 11 patients with Rasmussen encephalitis showed complete response in 45% of the cases. Eight articles on rituximab employment sowed a reduced seizure burden in 16/26 patients. Finally, one trial concerning natalizumab evidenced a response in 10/32 participants.

Conclusion

The experience with anti-cytokine agents and drugs targeting lymphocytes in epilepsy derives mostly from case reports or series. The use of anti-IL-1, anti-IL-6, and anti-CD20 agents in patients with drug-resistant epilepsy and refractory status epilepticus has shown promising results and a good safety profile. The experience with TNF inhibitors is limited to Rasmussen encephalitis. The use of anti-α4-integrin agents did not show significant effects in refractory focal seizures. Concerning research perspectives, there is increasing interest in the potential use of anti-chemokine and anti-HMGB-1 agents.

Occurrence of early epilepsy in children with traumatic brain injury: a retrospective study

BACKGROUND

Early post-traumatic seizures (EPTS) refer to epileptic seizures occurring within one week after brain injury. This study aimed to define the risk factors of EPTS and the protective factors that could prevent its occurrence.

METHODS

This is a single-center retrospective study in the PICU, Beijing Children's Hospital. Patients diagnosed with traumatic brain injury (TBI), admitted with and without EPTS between January 2016 and December 2020 were included in the study.

RESULTS

We included 108 patients diagnosed with TBI. The overall EPTS incidence was 33.98% (35/108). The correlation between EPTS and depressed fractures is positive (P = 0.023). Positive correlations between EPTS and intracranial hemorrhage and subarachnoid hemorrhage had been established (P = 0.011and P = 0.004, respectively). The detection rates of EPTS in the electroencephalogram (EEG) monitoring was 80.00%. There was a significant difference in the EEG monitoring rate between the two groups (P = 0.041). Forty-one (37.86%, 41/108) post-neurosurgical patients were treated with prophylactic antiepileptic drugs (AEDs), and eight (19.51%, 8/41) still had seizures. No statistical significance was noted between the two groups in terms of prophylactic AEDs use (P = 0.519). Logistic regression analysis revealed that open craniocerebral injury and fever on admission were risk factors for EPTS, whereas, surgical intervention and use of hypertonic saline were associated with not developing EPTS.

CONCLUSIONS

Breakthrough EPTS occurred after severe TBI in 33.98% of pediatric cases in our cohort. This is a higher seizure incidence than that reported previously. Patients with fever on admission and open craniocerebral injuries are more likely to develop EPTS.

Protective effect of Toll-like receptor 4 antagonist on inflammation, EEG, and memory changes following febrile seizure in Wistar rats

Neuroinflammation and fever are the main triggers in febrile seizures (FS). Focusing on inflammatory pathways and anti-inflammatory drugs could compensate for the limitations of existing medications. The aim of this study is to evaluate the neuroprotective effect of specific antagonizing Toll-like receptor 4 (TLR4), as a prominent inflammatory axis, on the consequences of FS and adulthood using animal models. Complex FS was induced on 9-11 day old male rat pups using a heated chamber. TAK-242, as a specific TLR4 inhibitor, was injected intraperitoneally before seizure induction. Seizure threshold, duration, and spike number were measured by electrocorticography. The levels of inflammatory cytokines, TLR4 protein expression, and oxidative stress markers were detected by enzyme-linked immunosorbent assay, western blotting, malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD) assessments in the cortex and hippocampus. Also, spatial and non-spatial memory were evaluated using the novel object recognition test (NORT) and double Y-maze test during adulthood. The results revealed that provoked inflammatory responses in neonate rats, after FS, were associated with the increase of the tumor necrosis factor alpha, interleukin-1β, and enhanced TLR4 protein expression. Meanwhile, based on performed behavioral tests, the inflammatory process was also involved in adulthood memory deficit. Pretreatment with TAK-242 reduced the inflammatory cytokines and TLR4 protein expression in the cortex and hippocampus of neonate rats and improvement in memory deficit in NORT and double Y-maze tasks. Also, pretreatment with TAK-242 elevated seizure threshold, SOD, and CAT activities, and decreased seizure duration and MDA level with no significant change in spike number. TAK-242 possibly controlled FS via inhibiting inflammation.

The role of inflammatory mediators in epilepsy: Focus on developmental and epileptic encephalopathies and therapeutic implications

In recent years, there has been an increasing interest in the potential involvement of neuroinflammation in the pathogenesis of epilepsy. Specifically, the role of innate immunity (that includes cytokines and chemokines) has been extensively investigated either in animal models of epilepsy and in clinical settings. Developmental and epileptic encephalopathies (DEE) are a heterogeneous group of epileptic disorders, in which uncontrolled epileptic activity results in cognitive, motor and behavioral impairment. By definition, epilepsy in DEE is poorly controlled by common antiepileptic drugs but may respond to alternative treatments, including steroids and immunomodulatory drugs. In this review, we will focus on how cytokines and chemokines play a role in the pathogenesis of DEE and why expanding our knowledge about the role of neuroinflammation in DEE may be crucial to develop new and effective targeted therapeutic strategies to prevent seizure recurrence and developmental regression.

A Review of Febrile Seizures: Recent Advances in Understanding of Febrile Seizure Pathophysiology and Commonly Implicated Viral Triggers

Febrile seizures are one of the commonest presentations in young children, with a 2-5% incidence in Western countries. Though they are generally benign, with rare long-term sequelae, there is much to be learned about their pathophysiology and risk factors. Febrile seizures are propagated by a variety of genetic and environmental factors, including viruses and vaccines. These factors must be taken into consideration by a clinician aiming to assess, diagnose and treat a child presenting with fevers and seizures, as well as to explain the sequelae of the febrile seizures to the concerned parents of the child. Our article provides an overview of this common childhood condition, outlining both the underlying mechanisms and the appropriate clinical approach to a child presenting with febrile seizures.

The Pathogenesis of Fever-Induced Febrile Seizures and Its Current State

Febrile seizures, commonly in children between the ages of 3 months to 5 years, are a neurological abnormality characterized by neuronal hyper-excitability, that occur as a result of an increased core body temperature during a fever, which was caused by an underlying systemic infection. Such infections cause the immune system to elicit an inflammatory response resulting in the release of cytokines from macrophages. The cytokines such as interleukin (IL)- 1β, IL-6, and tumour necrosis factor-α (TNF-α) combat the infection in the localized area ultimately spilling over into circulation resulting in elevated cytokine levels. The cytokines, along with pathogen-associated molecular patterns (PAMPs) expressed on pathogens for example, lipopolysaccharide (LPS), interact with the blood brain barrier (BBB) causing a ‘leaky’ BBB which facilitates cytokines and LPS entry into the central nervous system. The cytokines activate the microglia which release their own cytokines, specifically IL1β. IL-β interacts with the brain endothelium resulting in the activation of cyclooxygenase 2 which catalyzes the production of prostaglandin 2 (PGE2). PGE2 enters the hypothalamic region and induces a fever. Abnormally increased IL-1β levels also progressively increases excitatory (glutamatergic) neurotransmission, and decreases inhibitory (GABAergic) neurotransmission, thus mediating the pathogenesis of convulsions. Current treatments for febrile seizures present with side effects that are detrimental to health, which fosters the need for an alternative, more affordable treatment with fewer adverse side effects, and 1 that is easily accessible, especially in low income areas that are also affected by other underlying socio-economic factors, in which febrile seizures are of growing concern.

Inflammatory and immune mechanisms underlying epileptogenesis and epilepsy: From pathogenesis to treatment target

Epilepsy is a brain disease associated with epileptic seizures as well as with neurobehavioral outcomes of this condition. In the last century, inflammation emerged as a crucial factor in epilepsy etiology. Various brain insults through activation of neuronal and non-neuronal brain cells initiate a series of inflammatory events. Growing observations strongly suggest that abnormal activation of critical inflammatory processes contributes to epileptogenesis, a gradual process by which a normal brain transforms into the epileptic brain. Increased knowledge of inflammatory pathways in epileptogenesis has unveiled mechanistic targets for novel antiepileptic therapies. Molecules specifically targeting the pivotal inflammatory pathways may serve as promising candidates to halt the development of epilepsy. The present paper reviews the pieces of evidence conceptually supporting the potential role of inflammatory mechanisms and the relevant blood-brain barrier (BBB) disruption in epileptogenesis. Also, it discusses the mechanisms underlying inflammation-induced neuronal-glial network impairment and highlights innovative neuroregulatory actions of typical inflammatory molecules. Finally, it presents a brief analysis of observations supporting the therapeutic role of inflammation-targeting tiny molecules in epileptic seizures.

Presynaptic L-Type Ca2+ Channels Increase Glutamate Release Probability and Excitatory Strength in the Hippocampus during Chronic Neuroinflammation

Neuroinflammation is involved in the pathogenesis of several neurologic disorders, including epilepsy. Both changes in the input/output functions of synaptic circuits and cell Ca²⁺ dysregulation participate in neuroinflammation, but their impact on neuron function in epilepsy is still poorly understood. Lipopolysaccharide (LPS), a toxic byproduct of bacterial lysis, has been extensively used to stimulate inflammatory responses both in vivo and in vitro LPS stimulates Toll-like receptor 4, an important mediator of the brain innate immune response that contributes to neuroinflammation processes. Although we report that Toll-like receptor 4 is expressed in both excitatory and inhibitory mouse hippocampal neurons (both sexes), its chronic stimulation by LPS induces a selective increase in the excitatory synaptic strength, characterized by enhanced synchronous and asynchronous glutamate release mechanisms. This effect is accompanied by a change in short-term plasticity with decreased facilitation, decreased post-tetanic potentiation, and increased depression. Quantal analysis demonstrated that the effects of LPS on excitatory transmission are attributable to an increase in the probability of release associated with an overall increased expression of L-type voltage-gated Ca²⁺ channels that, at presynaptic terminals, abnormally contributes to evoked glutamate release. Overall, these changes contribute to the excitatory/inhibitory imbalance that scales up neuronal network activity under inflammatory conditions. These results provide new molecular clues for treating hyperexcitability of hippocampal circuits associated with neuroinflammation in epilepsy and other neurologic disorders.SIGNIFICANCE STATEMENT Neuroinflammation is thought to have a pathogenetic role in epilepsy, a disorder characterized by an imbalance between excitation/inhibition. Fine adjustment of network excitability and regulation of synaptic strength are both implicated in the homeostatic maintenance of physiological levels of neuronal activity. Here, we focused on the effects of chronic neuroinflammation induced by lipopolysaccharides on hippocampal glutamatergic and GABAergic synaptic transmission. Our results show that, on chronic stimulation with lipopolysaccharides, glutamatergic, but not GABAergic, neurons exhibit an enhanced synaptic strength and changes in short-term plasticity because of an increased glutamate release that results from an anomalous contribution of L-type Ca²⁺ channels to neurotransmitter release.

Increased levels of NLRP3 in children with febrile seizures

OBJECTIVE

Febrile seizures (FS) are the most common convulsions in childhood. Interleukin-1beta (IL-1β) is proposed to play an important role in the development of FS, from in vitro data and data from peripheral blood samples. IL-1β secretion is needed for activation of the NLR family, pyrin-domain containing 3(NLRP3) inflammasome. However, whether NLRP3 play a role in the development of FS remains unknown. This study aimed to investigate the role of NLRP3 in FS.

METHODS

Thirty-two FS cases and twenty-two matched controls were included in this study. Control samples were collected from children with febrile illness without seizures. We detected their levels of IL-1β and NLRP3 by Enzyme linked immunosorbent assay and Western blot, respectively.

RESULTS

Serum IL-1β levels weresignificantlyhigher in FS patients (Median = 301.64 pg/ml) than in fever only controls (Median = 159.48 pg/ml) (P < 0.05). Additionally, NLRP3 protein levels of peripheral blood mononuclear cells (PBMC) were significantly higher in typical FS than in fever only controls (P < 0.05). Moreover, serum levels of IL-1β were significantly correlated with levels of NLRP3 protein (r = 0.787, P < 0.001).

CONCLUSIONS

In this study, our results firstly indicated that NLRP3 protein was significantly up-regulated in the typical FS children compared in fever only controls. Increased NLRP3 can mediate IL-1β secretion that is responsible for the occurrence of FS.

Effect of a novel prolonged febrile seizure model on GABA associated ion channels

Prolonged febrile seizures are usually modelled in animals using hyperthermia as an inducer. In this study, a modified simple febrile seizure model using a combination of lipopolysaccharide (LPS) and kainic acid (KA) was used to develop a prolonged febrile seizure animal model, which we used to assess effects on the expression of the sodium- potassium-chloride cotransporter 1 (NKCC1) and potassium-chloride cotransporter 2 (KCC2) and their possible role in seizure exacerbation. At post-natal day (PND) 14, rat pups were divided into a saline (S), simple febrile seizure (FSA-), prolonged febrile seizure (FSB-), saline A (SA+) and saline B (SB+) groups. SA+ and SB+ groups received different concentrations of KA (1.75 mg/kg, 1.83 μg/kg respectively) but no LPS. Changes in temperature, seizure activity and duration were recorded. Gene and protein expression of NKCC1, KCC2 and KCC2 phosphorylated serine (KCC2 ser) 940 were measured 1 h post seizure termination and on PND 15 using RT- PCR and western blot. There was an initial increase in temperature that was immediately followed by a temperature decrease and an increase in seizure severity and duration in the FSB- group. There was a decrease in KCC2 ser 940 protein expression. NKCC1 protein expression was increased in both FS groups suggesting decreased GABA receptor functionality. Therefore, the novel FSB- model resulted in more severe and sustained seizure activity by altering cotransporter gene and protein expression. This suggests that this model can be used to mimic prolonged febrile seizures and hence can be used to investigate the physiological changes accompanying this condition.

Immune Challenges and Seizures: How Do Early Life Insults Influence Epileptogenesis?

The development of epilepsy, a process known as epileptogenesis, often occurs later in life following a prenatal or early postnatal insult such as cerebral ischemia, stroke, brain trauma, or infection. These insults share common pathophysiological pathways involving innate immune activation including neuroinflammation, which is proposed to play a critical role in epileptogenesis. This review provides a comprehensive overview of the latest preclinical evidence demonstrating that early life immune challenges influence neuronal hyperexcitability and predispose an individual to later life epilepsy. Here, we consider the range of brain insults that may promote the onset of chronic recurrent spontaneous seizures at adulthood, spanning intrauterine insults (e.g. maternal immune activation), perinatal injuries (e.g. hypoxic–ischemic injury, perinatal stroke), and insults sustained during early postnatal life—such as fever-induced febrile seizures, traumatic brain injuries, infections, and environmental stressors. Importantly, all of these insults represent, to some extent, an immune challenge, triggering innate immune activation and implicating both central and systemic inflammation as drivers of epileptogenesis. Increasing evidence suggests that pro-inflammatory cytokines such as interleukin-1 and subsequent signaling pathways are important mediators of seizure onset and recurrence, as well as neuronal network plasticity changes in this context. Our current understanding of how early life immune challenges prime microglia and astrocytes will be explored, as well as how developmental age is a critical determinant of seizure susceptibility. Finally, we will consider the paradoxical phenomenon of preconditioning, whereby these same insults may conversely provide neuroprotection. Together, an improved appreciation of the neuroinflammatory mechanisms underlying the long-term epilepsy risk following early life insults may provide insight into opportunities to develop novel immunological anti-epileptogenic therapeutic strategies.

Dexamethasone Attenuates Hyperexcitability Provoked by Experimental Febrile Status Epilepticus

The role of neuroinflammation in the mechanisms of epilepsy development is important because inflammatory mediators provide tractable targets for intervention. Inflammation is intrinsically involved in the generation of childhood febrile seizures (FSs), and prolonged FS [febrile status epilepticus (FSE)] precedes a large proportion of adult cases of temporal lobe epilepsy (TLE). As TLE is often refractory to therapy and is associated with serious cognitive and emotional problems, we investigated whether its development can be prevented using anti-inflammatory strategies. Using an immature rat model of FSE [experimental FSE (eFSE)], we administered dexamethasone (DEX), a broad anti-inflammatory agent, over 3 d following eFSE. We assessed eFSE-provoked hippocampal network hyperexcitability by quantifying the presence, frequency, and duration of hippocampal spike series, as these precede and herald the development of TLE-like epilepsy. We tested whether eFSE provoked hippocampal microgliosis, astrocytosis, and proinflammatory cytokine production in male and female rats and investigated blood–brain barrier (BBB) breaches as a potential contributor. We then evaluated whether DEX attenuated these eFSE sequelae. Spike series were not observed in control rats given vehicle or DEX, but occurred in 41.6% of eFSE-vehicle rats, associated with BBB leakage and elevated hippocampal cytokines. eFSE did not induce astrocytosis or microgliosis but provoked BBB disruption in 60% of animals. DEX significantly reduced spike series prevalence (to 7.6%) and frequency, and abrogated eFSE-induced cytokine production and BBB leakage (to 20%). These findings suggest that a short, postinsult intervention with a clinically available anti-inflammatory agent potently attenuates epilepsy-predicting hippocampal hyperexcitability, potentially by minimizing BBB disruption and related neuroinflammation.

Ethanol and Cytokines in the Central Nervous System

The innate immune system plays a critical role in the ethanol-induced neuroimmune response in the brain. Ethanol initiates the innate immune response via activation of the innate immune receptors Toll-like receptors (TLRs, e.g., TLR4, TLR3, TLR7) and NOD-like receptors (inflammasome NLRs) leading to a release of a plethora of chemokines and cytokines and development of the innate immune response. Cytokines and chemokines can have pro- or anti-inflammatory properties through which they regulate the immune response. In this chapter, we will focus on key cytokines (e.g., IL-1, IL-6, TNF-α) and chemokines (e.g., MCP-1/CCL2) that mediate the ethanol-induced neuroimmune responses. In this regard, we will use IL-1β, as an example cytokine, to discuss the neuromodulatory properties of cytokines on cellular properties and synaptic transmission. We will discuss their involvement through a set of evidence: (1) changes in gene and protein expression following ethanol exposure, (2) association of gene polymorphisms (humans) and alterations in gene expression (animal models) with increased alcohol intake, and (3) modulation of alcohol-related behaviors by transgenic or pharmacological manipulations of chemokine and cytokine systems. Over the last years, our understanding of the molecular mechanisms mediating cytokine- and chemokine-dependent regulation of immune responses has advanced tremendously, and we review evidence pointing to cytokines and chemokines serving as neuromodulators and regulators of neurotransmission.

Molecular Mechanism Involved in the Pathogenesis of Early-Onset Epileptic Encephalopathy

Recent studies have shown that neurologic inflammation may both precipitate and sustain seizures, suggesting that inflammation may be involved not only in epileptogenesis but also in determining the drug-resistant profile. Extensive literature data during these last years have identified a number of inflammatory markers involved in these processes of “neuroimmunoinflammation” in epilepsy, with key roles for pro-inflammatory cytokines such as: IL-6, IL-17 and IL-17 Receptor (IL-17R) axis, Tumor-Necrosis-Factor Alpha (TNF-α) and Transforming-Growth-Factor Beta (TGF-β), all responsible for the induction of processes of blood-brain barrier (BBB) disruption and inflammation of the Central Nervous System (CNS) itself. Nevertheless, many of these inflammatory biomarkers have also been implicated in the pathophysiologic process of other neurological diseases. Future studies will be needed to identify the disease-specific biomarkers in order to distinguish epilepsies from other neurological diseases, as well as recognize different epileptic semiology. In this context, biological markers of BBB disruption, as well as those reflecting its integrity, can be useful tools to determine the pathological process of a variety of neurological diseases. However; how these molecules may help in the diagnosis and prognostication of epileptic disorders remains yet to be determined. Herein, authors present an extensive literature review on the involvement of both, systemic and neuronal immune systems, in the early onset of epileptic encephalopathy.

Pharmacological targeting of brain inflammation in epilepsy: Therapeutic perspectives from experimental and clinical studies

Increasing evidence supports a pathogenic role of unabated neuroinflammation in various central nervous system (CNS) diseases, including epilepsy. Neuroinflammation is not a bystander phenomenon of the diseased brain tissue, but it may contribute to neuronal hyperexcitability underlying seizure generation, cell loss, and neurologic comorbidities. Several molecules, which constitute the inflammatory milieu in the epileptogenic area, activate signaling pathways in neurons and glia resulting in pathologic modifications of cell function, which ultimately lead to alterations in synaptic transmission and plasticity. Herein we report the up-to-date experimental and clinical evidence that supports the neuromodulatory role of inflammatory mediators, their related signaling pathways, and involvement in epilepsy. We discuss how these mechanisms can be harnessed to discover and validate targets for novel therapeutics, which may prevent or control pharmacoresistant epilepsies.

Effect of early-life inflammation and magnesium sulfate on hyperthermia-induced seizures in infant rats: Susceptibility to pentylenetetrazol-induced seizures later in life

This study investigated the effect of inflammation and MgSO₄ pretreatment on behaviors caused by hyperthermia (HT) and the effect of these interventions on PTZ-induced seizure a week later. In this experimental study, rat pups experienced inflammation on postnatal day 10 (P10). On P18-19, the pups received either saline or MgSO₄ then subjected to hyperthermia. On P25-26, PTZ-induced seizure was initiated in the rats. Neonatal inflammation increased the susceptibility to HT-induced seizure. Inflammation and HT increased the susceptibility to PTZ-induced seizure. Pretreatment with MgSO₄ before hyperthermia decreased the susceptibility to both HT- and PTZ-induced seizure. Furthermore, calcium and magnesium blood levels significantly decreased compared to control rats. It can be concluded that neonatal inflammation potentiates while pretreatment with MgSO₄ attenuates HT-induced seizures. Also, neonatal inflammation and HT potentiate PTZ-induced seizure initiated one week later.

Benzodiazepine-refractory status epilepticus, neuroinflammation, and interneuron neurodegeneration after acute organophosphate intoxication

Nerve agents and some pesticides such as diisopropylfluorophosphate (DFP) cause neurotoxic manifestations that include seizures and status epilepticus (SE), which are potentially lethal and carry long-term neurological morbidity. Current antidotes for organophosphate (OP) intoxication include atropine, 2-PAM and diazepam (a benzodiazepine for treating seizures and SE). There is some evidence for partial or complete loss of diazepam anticonvulsant efficacy when given 30 min or later after exposure to an OP; this condition is known as refractory SE. Effective therapies for OP-induced SE are lacking and it is unclear why current therapies do not work. In this study, we investigated the time-dependent efficacy of diazepam in the nerve agent surrogate DFP model of OP intoxication on seizure suppression and neuroprotection in rats, following an early and late therapy. Diazepam (5 mg/kg, IM) controlled seizures when given 10 min after DFP exposure ("early"), but it was completely ineffective at 60 or 120 min ("late") after DFP. DFP-induced neuronal injury, neuroinflammation, and neurodegeneration of principal cells and GABAergic interneurons were significantly reduced by early but not late therapy. These findings demonstrate that diazepam failed to control seizures, SE and neuronal injury when given 60 min or later after DFP exposure, confirming the benzodiazepine-refractory SE and brain damage after OP intoxication. In addition, this study indicates that degeneration of inhibitory interneurons and inflammatory glial activation are potential mechanisms underlying these morbid outcomes of OP intoxication. Therefore, novel anticonvulsant and neuroprotectant antidotes, superior to benzodiazepines, are desperately needed for controlling nerve agent-induced SE and brain injury.

Is Targeting the Inflammasome a Way Forward for Neuroscience Drug Discovery?

Neuroinflammation is becoming increasingly recognized as a critical factor in the pathology of both acute and chronic neurological conditions. Inflammasomes such as the one formed by NACHT, LRR, and PYD domains containing protein 3 (NLRP3) are key regulators of inflammation due to their ability to induce the processing and secretion of interleukin 1β (IL-1β). IL-1β has previously been identified as a potential therapeutic target in a variety of conditions due to its ability to promote neuronal damage under conditions of injury. Thus, inflammasome inhibition has the potential to curtail inflammatory signaling, which could prove beneficial in certain diseases. In this review, we discuss the evidence for inflammasome contributions to the pathology of neurodegenerative conditions such as Alzheimer's disease and Parkinson's disease, epilepsy, and acute degeneration following brain trauma or stroke. In addition, we review the current landscape of drug development targeting the NLRP3 inflammasome.

NADPH oxidases as potential pharmacological targets against increased seizure susceptibility after systemic inflammation

BACKGROUND

Systemic inflammation associated with sepsis can induce neuronal hyperexcitability, leading to enhanced seizure predisposition and occurrence. Brain microglia are rapidly activated in response to systemic inflammation and, in this activated state, release multiple cytokines and signaling factors that amplify the inflammatory response and increase neuronal excitability. NADPH oxidase (NOX) enzymes promote microglial activation through the generation of reactive oxygen species (ROS), such as superoxide anion. We hypothesized that NOX isoforms, particularly NOX2, are potential targets for prevention of sepsis-associated seizures.

METHODS

To reduce NADPH oxidase 2-derived ROS production, mice with deficits of NOX regulatory subunit/NOX2 organizer p47phox (p47phox-/-) or NOX2 major subunit gp91phox (gp91phox-/-) were used or the NOX2-selective inhibitor diphenyleneiodonium (DPI) was used to treat wild-type (WT) mice. Systemic inflammation was induced by intraperitoneal injection of lipopolysaccharide (LPS). Seizure susceptibility was compared among mouse groups in response to intraperitoneal injection of pentylenetetrazole (PTZ). Brain tissues were assayed for proinflammatory gene and protein expression, and immunofluorescence staining was used to estimate the proportion of activated microglia.

RESULTS

Increased susceptibility to PTZ-induced seizures following sepsis was significantly attenuated in gp91phox-/- and p47phox-/- mice compared with WT mice. Both gp91phox-/- and p47phox-/- mice exhibited reduced microglia activation and lower brain induction of multiple proconvulsive cytokines, including TNFα, IL-1β, IL-6, and CCL2, compared with WT mice. Administration of DPI following LPS injection significantly attenuated the increased susceptibility to PTZ-induced seizures and reduced both microglia activation and brain proconvulsive cytokine concentrations compared with vehicle-treated controls. DPI also inhibited the upregulation of gp91phox transcripts following LPS injection.

CONCLUSIONS

Our results indicate that NADPH oxidases contribute to the development of increased seizure susceptibility in mice after sepsis. Pharmacologic inhibition of NOX may be a promising therapeutic approach to reducing sepsis-associated neuroinflammation, neuronal hyperexcitability, and seizures.

The genetics and molecular biology of fever-associated seizures or epilepsy

Fever-associated seizures or epilepsy (FASE) is primarily characterised by the occurrence of a seizure or epilepsy usually accompanied by a fever. It is common in infants and children, and generally includes febrile seizures (FS), febrile seizures plus (FS+), Dravet syndrome (DS) and genetic epilepsy with febrile seizures plus (GEFSP). The aetiology of FASE is unclear. Genetic factors may play crucial roles in FASE. Mutations in certain genes may cause a wide spectrum of phenotypical overlap ranging from isolated FS, FS+ and GEFSP to DS. Synapse-associated proteins, postsynaptic GABAA receptor, and sodium channels play important roles in synaptic transmission. Mutations in these genes may involve in the pathogenesis of FASE. Elevated temperature promotes synaptic vesicle (SV) recycling and enlarges SV size, which may enhance synaptic transmission and contribute to FASE occurring. This review provides an overview of the loci, genes, underlying pathogenesis and the fever-inducing effect of FASE. It may provide a more comprehensive understanding of pathogenesis and contribute to the clinical diagnosis of FASE.

Immunity and inflammation in status epilepticus and its sequelae: possibilities for therapeutic application

Status epilepticus (SE) is a life-threatening neurological emergency often refractory to available treatment options. It is a very heterogeneous condition in terms of clinical presentation and causes, which besides genetic, vascular and other structural causes also include CNS or severe systemic infections, sudden withdrawal from benzodiazepines or anticonvulsants and rare autoimmune etiologies. Treatment of SE is essentially based on expert opinions and antiepileptic drug treatment per se seems to have no major impact on prognosis. There is, therefore, urgent need of novel therapies that rely upon a better understanding of the basic mechanisms underlying this clinical condition. Accumulating evidence in animal models highlights that inflammation ensuing in the brain during SE may play a determinant role in ongoing seizures and their long-term detrimental consequences, independent of an infection or auto-immune cause; this evidence encourages reconsideration of the treatment flow in SE patients.

Differential response of hippocampal and prefrontal oscillations to systemic LPS application

•

1 mg/kg LPS i.p. injection robustly suppresses theta frequency in hippocampus.

•

LPS administration augments delta frequency in hippocampus but not mPFC.

•

LPS injection triggers hippocampal spike-wave discharges.

The early electrophysiological phenomena linked to systemic inflammation are largely underexplored. We developed here local field analyses to detect prodromal oscillatory abnormalities. We identified early band-specific patterns in local field potential recorded from freely-moving rats injected intraperitoneally with lipopolysaccharide (LPS, 1 mg/kg). Theta frequency was significantly reduced and this effect was not related to the decreased locomotion of the animal. Furthermore, LPS-induced alterations show a region-specific response when compared between the hippocampal region and medial prefrontal cortex. Delta mean frequency increased in the hippocampal region but not in the prefrontal cortex. We explored also the hypothesis that systemic inflammation increases the propensity of abnormally synchronized brain activity. Our data indicate that the LPS-evoked alteration of delta and theta frequency parameters reflects the formation of abnormal synchronization in similar frequency ranges. The onset of abnormal brain activity was indicated by spike-wave discharges in the range of 1–10 Hz with three main frequency domains. Importantly, the occurrence of spike-wave discharges was observed in the hippocampus but not in the cortex. In summary, the hippocampal theta rhythm is an accurate indicator of the oscillatory changes evoked by LPS application. The findings offer clear patterns of altered brain function that will facilitate mechanistic investigations of brain dysfunction and delirium occurring during sepsis.

Plasma cytokines associated with febrile status epilepticus in children: A potential biomarker for acute hippocampal injury

OBJECTIVE

Our aim was to explore the association between plasma cytokines and febrile status epilepticus (FSE) in children, as well as their potential as biomarkers of acute hippocampal injury.

METHODS

Analysis was performed on residual samples of children with FSE (n = 33) as part of the Consequences of Prolonged Febrile Seizures in Childhood study (FEBSTAT) and compared to children with fever (n = 17). Magnetic resonance imaging (MRI) was obtained as part of FEBSTAT within 72 h of FSE. Cytokine levels and ratios of antiinflammatory versus proinflammatory cytokines in children with and without hippocampal T2 hyperintensity were assessed as biomarkers of acute hippocampal injury after FSE.

RESULTS

Levels of interleukin (IL)-8 and epidermal growth factor (EGF) were significantly elevated after FSE in comparison to controls. IL-1β levels trended higher and IL-1RA trended lower following FSE, but did not reach statistical significance. Children with FSE were found to have significantly lower ratios of IL-1RA/IL-1β and IL-1RA/IL-8. Specific levels of any one individual cytokine were not associated with FSE. However, lower ratios of IL-1RA/IL-1β, IL-1RA/1L-6, and IL-1RA/ IL-8 were all associated with FSE. IL-6 and IL-8 levels were significantly higher and ratios of IL-1RA/IL-6 and IL-1RA/IL-8 were significantly lower in children with T2 hippocampal hyperintensity on MRI after FSE in comparison to those without hippocampal signal abnormalities. Neither individual cytokine levels nor ratios of IL-1RA/IL-1β or IL-1RA/IL-8 were predictive of MRI changes. However, a lower ratio of IL-1RA/IL-6 was strongly predictive (odds ratio [OR] 21.5, 95% confidence interval [CI] 1.17-393) of hippocampal T2 hyperintensity after FSE.

SIGNIFICANCE

Our data support involvement of the IL-1 cytokine system, IL-6, and IL-8 in FSE in children. The identification of the IL-1RA/IL-6 ratio as a potential biomarker of acute hippocampal injury following FSE is the most significant finding. If replicated in another study, the IL-1RA/IL-6 ratio could represent a serologic biomarker that offers rapid identification of patients at risk for ultimately developing mesial temporal lobe epilepsy (MTLE).

Early-life febrile seizures worsen adult phenotypes in Scn1a mutants

Mutations in the voltage-gated sodium channel (VGSC) gene SCN1A, encoding the Na_v1.1 channel, are responsible for a number of epilepsy disorders including genetic epilepsy with febrile seizures plus (GEFS+) and Dravet syndrome (DS). Patients with SCN1A mutations often experience prolonged early-life febrile seizures (FSs), raising the possibility that these events may influence epileptogenesis and lead to more severe adult phenotypes. To test this hypothesis, we subjected 21-23-day-old mice expressing the human SCN1A GEFS+ mutation R1648H to prolonged hyperthermia, and then examined seizure and behavioral phenotypes during adulthood. We found that early-life FSs resulted in lower latencies to induced seizures, increased severity of spontaneous seizures, hyperactivity, and impairments in social behavior and recognition memory during adulthood. Biophysical analysis of brain slice preparations revealed an increase in epileptiform activity in CA3 pyramidal neurons along with increased action potential firing, providing a mechanistic basis for the observed worsening of adult phenotypes. These findings demonstrate the long-term negative impact of early-life FSs on disease outcomes. This has important implications for the clinical management of this patient population and highlights the need for therapeutic interventions that could ameliorate disease progression.

Pro-epileptogenic effects of viral-like inflammation in both mature and immature brains

BACKGROUND

Infectious encephalitides are most often associated with acute seizures during the infection period and are risk factors for the development of epilepsy at later times. Mechanisms of viral encephalitis-induced epileptogenesis are poorly understood. Here, we evaluated the contribution of viral encephalitis-associated inflammation to ictogenesis and epileptogenesis using a rapid kindling protocol in rats. In addition, we examined whether minocycline can improve outcomes of viral-like brain inflammation.

METHODS

To produce viral-like inflammation, polyinosinic-polycytidylic acid (PIC), a toll-like receptor 3 (TLR3) agonist, was applied to microglial/macrophage cell cultures and to the hippocampus of postnatal day 13 (P13) and postnatal day 74 (P74) rats. Cell cultures permit the examination of the inflammation induced by PIC, while the in vivo setting better suits the analysis of cytokine production and the effects of inflammation on epileptogenesis. Minocycline (50 mg/kg) was injected intraperitoneally for 3 consecutive days prior to the kindling procedure to evaluate its effects on inflammation and epileptogenesis.

RESULTS

PIC injection facilitated kindling epileptogenesis, which was evident as an increase in the number of full limbic seizures at both ages. Furthermore, in P14 rats, we observed a faster seizure onset and prolonged retention of the kindling state. PIC administration also led to an increase in interleukin 1β (IL-1β) levels in the hippocampus in P14 and P75 rats. Treatment with minocycline reversed neither the pro-epileptogenic effects of PIC nor the increase of IL-1β in the hippocampus in both P14 and P75 rats.

CONCLUSIONS

Hippocampal injection of PIC facilitates rapid kindling epileptogenesis at both P14 and P75, suggesting that viral-induced inflammation increases epileptogenesis irrespective of brain maturation. Minocycline, however, was unable to reverse the increase of epileptogenesis, which might be linked to its absence of effect on hippocampal IL-1β levels at both ages.

Magnesium Sulfate Provides Neuroprotection in Eclampsia-Like Seizure Model by Ameliorating Neuroinflammation and Brain Edema

Eclampsia is a hypertensive disorder of pregnancy that is defined by the new onset of grand mal seizures on the basis of preeclampsia and a leading cause of maternal and fetal mortality worldwide. Presently, magnesium sulfate (MgSO₄) is the most effective treatment, but the mechanism by which MgSO₄ prevents eclampsia has yet to be fully elucidated. We previously showed that systemic inflammation decreases the seizure threshold in a rat eclampsia-like model, and MgSO₄ treatment can decrease systemic inflammation. Here, we hypothesized that MgSO₄ plays a neuroprotective role in eclampsia by reducing neuroinflammation and brain edema. Pregnant Sprague-Dawley rats were given an intraperitoneal injection of pentylenetetrazol following a tail vein injection of lipopolysaccharide to establish the eclampsia-like seizure model. Seizure activity was assessed by behavioral testing. Neuronal loss in the hippocampal CA1 region (CA1) was detected by Nissl staining. Cerebrospinal fluid levels of S100-B and ferritin, indicators of neuroinflammation, were detected by enzyme-linked immunosorbent assay, and ionized calcium binder adapter molecule 1 (Iba-1, a marker for microglia) and glial fibrillary acid protein (GFAP, a marker for astrocytes) expression in the CA1 area was determined by immunofluorescence staining. Brain edema was measured. Our results revealed that MgSO₄ effectively attenuated seizure severity and CA1 neuronal loss. In addition, MgSO₄ significantly reduced cerebrospinal fluid levels of S100-B and ferritin, Iba-1 and GFAP activation in the CA1 area, and brain edema. Our results indicate that MgSO₄ plays a neuroprotective role against eclampsia-like seizure by reducing neuroinflammation and brain edema.

TRPV1 deletion exacerbates hyperthermic seizures in an age-dependent manner in mice

Febrile seizures (FS) are the most common seizure disorder to affect children. Although there is mounting evidence to support that FS occur when children have fever-induced hyperventilation leading to respiratory alkalosis, the underlying mechanisms of hyperthermia-induced hyperventilation and links to FS remain poorly understood. As transient receptor potential vanilloid-1 (TRPV1) receptors are heat-sensitive, play an important role in adult thermoregulation and modulate respiratory chemoreceptors, we hypothesize that TRPV1 activation is important for hyperthermia-induced hyperventilation leading to respiratory alkalosis and decreased FS thresholds, and consequently, TRPV1 KO mice will be relatively protected from hyperthermic seizures. To test our hypothesis we subjected postnatal (P) day 8-20 TRPV1 KO and C57BL/6 control mice to heated dry air. Seizure threshold temperature, latency and the rate of rise of body temperature during hyperthermia were assessed. At ages where differences in seizure thresholds were identified, head-out plethysmography was used to assess breathing and the rate of expired CO₂ in response to hyperthermia, to determine if the changes in seizure thresholds were related to respiratory alkalosis. Paradoxically, we observed a pro-convulsant effect of TRPV1 deletion (∼4min decrease in seizure latency), and increased ventilation in response to hyperthermia in TRPV1 KO compared to control mice at P20. This pro-convulsant effect of TRPV1 absence was not associated with an increased rate of expired CO₂, however, these mice had a more rapid rise in body temperature following exposure to hyperthermia than controls, and the expected linear relationship between body weight and seizure latency was absent. Based on these findings, we conclude that deletion of the TRPV1 receptor prevents reduction in hyperthermic seizure susceptibility in older mouse pups, via a mechanism that is independent of hyperthermia-induced respiratory alkalosis, but possibly involves impaired development of thermoregulatory mechanisms, although at present the mechanism remain unknown.

Generation of Febrile Seizures and Subsequent Epileptogenesis

Febrile seizures (FSs) occur commonly in children aged from 6 months to 5 years. Complex (repetitive or prolonged) FSs, but not simple FSs, can lead to permanent brain modification. Human infants and immature rodents that have experienced complex FSs have a high risk of subsequent temporal lobe epilepsy. However, the causes of FSs and the mechanisms underlying the subsequent epileptogenesis remain unknown. Here, we mainly focus on two major questions concerning FSs: how fever triggers seizures, and how epileptogenesis occurs after FSs. The risk factors responsible for the occurrence of FSs and the epileptogenesis after prolonged FSs are thoroughly summarized and discussed. An understanding of these factors can provide potential therapeutic targets for the prevention of FSs and also yield biomarkers for identifying patients at risk of epileptogenesis following FSs.

Effect of diclofenac sodium on seizures and inflammatory profile induced by kindling seizure model

Epilepsy is a disorder that affects 1-2% of the population and a significant percentage of these patients do not respond to anticonvulsant drugs available in the market suggesting the need to investigate new pharmacological treatments. Several studies have shown that inflammation occurs during epileptogenesis and may contribute to the development and progression of epilepsy, demonstrating increased levels of pro-inflammatory interleukins in animal models and human patients. The objective of this study was to evaluate the effect of non-steroidal anti-inflammatory diclofenac sodium on the severity of seizures and levels of pro-inflammatory interleukins in animals with kindling model induced by PTZ. The kindling model was induced by injections of subconvulsant doses of PTZ (20mg/kg) in alternated days for 15days of treatment. The animals were divided into four groups: control group given saline, group treated with diazepam (2mg/kg) and groups treated with diclofenac sodium (5 and 10mg/kg). After treatment the open field tests was conducted. The severity of seizures was evaluated by the Racine scale. We evaluated the levels of IL-1β, IL-6 and TNF-α in the blood, hippocampus and cortex of animals. The treatment with diclofenac sodium, in the PTZ induced kindling model, decreased severity of seizures and interleukin-6 and TNF-α levels in the hippocampus of animals treated with doses of 5 and 10mg/kg. New studies are needed to investigate a new therapeutic approach in the treatment of epilepsy with this anti-inflammatory non-steroidal drug.