Lipopolysaccharide potentiates hyperthermia-induced seizures

Effects of Muse Cell on a Mouse Model With Acute Encephalopathy

INTRODUCTION

Acute encephalopathy (AE) in childhood due to a viral infection causes convulsions and altered consciousness, leading to severe sequelae and death. Among the four types of AE, cytokine storm-induced AE is the most severe and causes serious damage to the brain. Moreover, a fundamental treatment for AE has not been established yet. Recently, it has been shown that the administration of multilineage-differentiating stress-enduring (Muse) cells, a population of mesenchymal stem cells, improves symptoms in various types of brain injuries when administered in the subacute phase (1-7 days after brain damage). We aimed to examine the effects of Muse cells in a cytokine storm-induced AE animal model using immunocompromised nonobese diabetic/severe combined immunodeficiency (NOD/SCID) neonatal mice.

METHODS

We established a modified protocol to induce AE-like symptoms in NOD/SCID. Then, Muse cells were injected at an acute phase (2-4 h after hyperthermia treatment).

RESULTS

Injection of Muse cells significantly improved body weight gain 1 day after treatment and the survival ratio for 3 weeks.

CONCLUSION

These effects could be a result of the direct and/or indirect upregulation of IL-10, an anti-inflammatory cytokine, in the Muse cell-treated brain. Although non-Muse cells, a residual cell population in the bone marrow after isolating Muse cells, also improved some symptoms, their effects were weaker than those of Muse cells. Our results indicate that the injection of Muse cells in the acute phase has an effect on AE, suggesting that they exert their therapeutic effects not only in the subacute phase but also in the acute phase.

Febrile Seizures, Ongoing Epileptiform Activity, and the Resulting Long-Term Consequences: Lessons From Animal Models

Febrile seizures affect 2% to 14% of children. Prospective studies indicate that following a relatively prolonged febrile seizure there are long-term consequences. Although controlled experiments in children have ethical limitations, nonhuman animal models give us the ability to discover new phenomena, determine their mechanisms, and test treatments that can potentially translate to the human clinical population. Rat models of febrile seizures show two temporally distinct phases: (1); behavioral seizures and (2); ongoing epileptiform activity associated with hyperoxia. The behavioral seizures mimic those displayed by children including tonic-clonic convulsions and loss of postural control. Recordings show classic spiking discharges from cortical regions during the behavioral seizures. Following behavioral seizure termination electrical recordings in rodent models reveal that there is ongoing epileptiform activity that lasts longer than the duration of the behavioral seizures themselves. This ongoing epileptiform activity is also associated with hyperoxia-levels of brain tissue oxygen well above the normoxic zone (typical oxygen levels)-and can last more than an hour. When this hyperoxia, but not the epileptiform activity, is prevented in febrile rat pups the long-term learning impairments are also prevented. This leaves important questions unanswered, "Do children also have ongoing and long-lasting epileptiform activity and associated hyperoxia following termination of their febrile behavioral seizures and does this second phase have long-term consequences"? Here we discuss appropriate animal models of febrile seizures that replicate much of the human condition with special attention to the long-term effects of occult epileptiform activity following termination of a behavioral febrile seizure.

Animal Models of Febrile Seizures: Limitations and Recent Advances in the Field

Febrile seizures (FSs) are defined as seizures occurring in children aged 6 months to 5 years with a background of elevated body temperature. It is one of the most common neurological disorders of childhood, emphasizing the importance of understanding the causes of FSs and their impact on the developing nervous system. However, there are significant limitations to the technologies currently available for studying the etiology and pathophysiology of seizures in humans. It is currently not possible to adequately capture the subtle molecular and structural rearrangements of the nervous system that can occur after seizures in humans. The use of animal models can be invaluable for these purposes. The most commonly used models in modern research are hyperthermic models in rats and mice aged 10-12 days. While these models can reproduce many of the characteristics of FSs, they have certain limitations. This review outlines the key considerations when working with models of FSs, provides an overview of current approaches to producing seizures in different model subjects, and presents a summary of key findings regarding morphological and functional changes in the brain and behavioral alterations that have been identified in studies using animal models of FSs.

NORSE/FIRES: how can we advance our understanding of this devastating condition?

Introduction

New onset refractory status epilepticus (NORSE) is a rare and devastating condition characterised by the sudden onset of refractory status epilepticus (RSE) without an identifiable acute or active structural, toxic, or metabolic cause in an individual without a pre-existing diagnosis of epilepsy. Febrile infection-related epilepsy syndrome (FIRES) is considered a subcategory of NORSE and presents following a febrile illness prior to seizure onset. NORSE/FIRES is associated with high morbidity and mortality in children and adults.

Methods and results

In this review we first briefly summarise the reported clinical, paraclinical, treatment and outcome data in the literature. We then report on existing knowledge of the underlying pathophysiology in relation to in vitro and in vivo pre-clinical seizure and epilepsy models of potential relevance to NORSE/FIRES.

Discussion

We highlight how pre-clinical models can enhance our understanding of FIRES/NORSE and propose future directions for research.

The Impact of Inflammation on Thermal Hyperpnea: Relevance for Heat Stress and Febrile Seizures

Extreme heat caused by climate change is increasing the transmission of infectious diseases, resulting in a sharp rise in heat-related illness and mortality. Understanding the mechanistic link between heat, inflammation, and disease is thus important for public health. Thermal hyperpnea, and consequent respiratory alkalosis, is crucial in febrile seizures and convulsions induced by heat stress in humans. Here, we address what causes thermal hyperpnea in neonates and how it is affected by inflammation. Transient receptor potential cation channel subfamily V member 1 (TRPV1), a heat-activated channel, is sensitized by inflammation and modulates breathing and thus may play a key role. To investigate whether inflammatory sensitization of TRPV1 modifies neonatal ventilatory responses to heat stress, leading to respiratory alkalosis and an increased susceptibility to hyperthermic seizures, we treated neonatal rats with bacterial LPS, and breathing, arterial pH, in vitro vagus nerve activity, and seizure susceptibility were assessed during heat stress in the presence or absence of a TRPV1 antagonist (AMG-9810) or shRNA-mediated TRPV1 suppression. LPS-induced inflammatory preconditioning lowered the threshold temperature and latency of hyperthermic seizures. This was accompanied by increased tidal volume, minute ventilation, expired CO2, and arterial pH (alkalosis). LPS exposure also elevated vagal spiking and intracellular calcium concentrations in response to hyperthermia. TRPV1 inhibition with AMG-9810 or shRNA reduced the LPS-induced susceptibility to hyperthermic seizures and altered the breathing pattern to fast shallow breaths (tachypnea), making each breath less efficient and restoring arterial pH. These results indicate that inflammation exacerbates thermal hyperpnea-induced respiratory alkalosis associated with increased susceptibility to hyperthermic seizures, primarily mediated by TRPV1 localized to vagus neurons.

Saiga antelope horn suppresses febrile seizures in rats by regulating neurotransmitters and the arachidonic acid pathway

BACKGROUND

Saiga antelope horn (SAH) is a traditional Chinese medicine for treating febrile seizure (FS) with precise efficacy, but its mechanism of action and functional substances are still unclear. Given the need for further research on SAH, our group conducted studies to elucidate its mechanisms and active substances.

METHODS

An FS rat pup model was constructed through intraperitoneal injection of LPS and hyperthermia induction. Behavioural indicators of seizures, hippocampal histopathological alterations, serum levels of inflammatory cytokines and hippocampal levels of neurotransmitters were observed and measured to investigate the effects of SAH on FS model rats. Hippocampal metabolomics and network pharmacology analyses were conducted to reveal the differential metabolites, key peptides and pathways involved in the suppression of FS by SAH.

RESULTS

SAH suppressed FS, decreased the inflammatory response and regulated the Glu-GABA balance. Metabolomic analysis revealed 13 biomarkers of FS, of which SAH improved the levels of 8 differential metabolites. Combined with network pharmacology, a "biomarker-core target-key peptide" network was constructed. The peptides of SAH, such as YGQL and LTGGF, could exert therapeutic effects via the arachidonic acid pathway. Molecular docking and ELISA results indicated that functional peptides of SAH could bind to PTGS2 target, inhibiting the generation of AA and its metabolites in hippocampal samples.

CONCLUSION

In summary, the functional peptides contained in SAH are the main material basis for the treatment of FS, potentially acting through neurotransmitter regulation and the arachidonic acid pathway.

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.

Jujuboside B inhibits febrile seizure by modulating AMPA receptor activity

ETHNOPHARMACOLOGICAL RELEVANCE

Febrile seizure is a common neurologic disorder with limited treatment occurring in infants and children under the age of five. Jujuboside B (JuB) is a main bioactive saponin component isolated from the Chinese anti-insomnia herbal medicine Ziziphi Spinosae Semen (ZSS), seed of Ziziphus jujuba Mill, which has been proved to exhibit neuroprotective effects recently.

AIM OF THE STUDY

In this study, we aimed at elucidating the effect of JuB on suppressing febrile seizure and the potential mechanisms.

METHODS

Electroencephalogram (EEG) recording was used to monitor the severity of febrile seizures. The JuB in the brain was identified by mass spectrometry. Neuronal excitability was investigated using patch clamp.

RESULTS

JuB (30 mg/kg) significantly prolonged seizure latency and reduced the severity in hyperthermia-induced seizures model mice. Hippocampal neuronal excitability was significantly decreased by JuB. And JuB significantly reduced the excitatory synaptic transmission mediated by α-amino-3-hydroxy-5-methyl-4-iso-xazolepropionic acid receptor (AMPAR), including evoked excitatory postsynaptic currents (eEPSCs), and miniature EPSCs (mEPSCs) in hippocampal neurons. Furthermore, JuB also significantly inhibited recombinant GluA1 and GluA2 mediated AMPA current in HEK293 cell and decreased the upregulation of [Ca²⁺]_i induced by AMPA in primary cultured cortex neurons.

CONCLUSIONS

JuB suppressed the excitability of hippocampal neurons by inhibiting the activity of AMPAR and reducing the intracellular free calcium, thereby relieving febrile seizures.

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.

Insight into Drug Resistance in Status Epilepticus: Evidence from Animal Models

Status epilepticus (SE), a condition with abnormally prolonged seizures, is a severe type of epilepsy. At present, SE is not well controlled by clinical treatments. Antiepileptic drugs (AEDs) are the main therapeutic approaches, but they are effective for SE only with a narrow intervening window, and they easily induce resistance. Thus, in this review, we provide an updated summary for an insight into drug-resistant SE, hoping to add to the understanding of the mechanism of refractory SE and the development of active compounds. Firstly, we briefly outline the limitations of current drug treatments for SE by summarizing the extensive experimental literature and clinical data through a search of the PubMed database, and then summarize the common animal models of refractory SE with their advantages and disadvantages. Notably, we also briefly review some of the hypotheses about drug resistance in SE that are well accepted in the field, and furthermore, put forward future perspectives for follow-up research on SE.

Augmented impulsive behavior in febrile seizure-induced mice

Febrile seizure (FS) is one of the most prevalent etiological events in childhood affecting 2-5% of children from 3 months to 5 years old. Debates on whether neurodevelopmental consequences rise in later life following a febrile seizure or not are still ongoing however there is limited evidence of its effect, especially in a laboratory setting. Moreover, the comparative study using both male and female animal models is sparse. To examine the effect of FS on the behavioral features of mice, both sexes of ICR mice were induced with hyperthermic seizures through exposure to an infrared heat lamp. The mice were divided into two groups, one receiving a single febrile seizure at postnatal day 11 (P11) and one receiving three FS at P11, P13, and P15. Starting at P30 the FS-induced mice were subjected to a series of behavioral tests. Mice with seizures showed no locomotor and motor coordination deficits, repetitive, and depressive-like behavior. However, the FS-induced mice showed impulsive-like behavior in both elevated plus maze and cliff avoidance tests, which is more prominent in male mice. A greater number of mice displayed impaired CAT in both males and females in the three-time FS-induced group compared to the single induction group. These results demonstrate that after induction of FS, male mice have a higher susceptibility to consequences of febrile seizure than female mice and recurrent febrile seizure has a higher chance of subsequent disorders associated with decreased anxiety and increased impulsivity. We confirmed the dysregulated expression of impulsivity-related genes such as 5-HT1A and tryptophan hydroxylase 2 from the prefrontal cortices of FS-induced mice implying that the 5-HT system would be one of the mechanisms underlying the increased impulsivity after FS. Taken together, these findings are useful in unveiling future discoveries about the effect of childhood febrile seizure and the mechanism behind it.

Variances of quantifying of Virchow-Robin spaces detecting the different functional status of glymphatic system in simple febrile seizures affected by seizures duration

The Virchow-Robin spaces (VRs) in the cerebral glymphatic system play a vital role in waste clearance from the brain. Simple febrile seizures (SFS) are a common type of seizures marked by an inappropriate fluid exchange. The mechanism of evident differences in glymphatic function among SFS with varying seizure duration is unknown. Therefore, the goal of this study was to see whether there were any variations in glymphatic function among SFS based on seizures duration. We retrospectively studied 30 children with SFS lasting more than 5 minutes (SFS > 5M), 40 children with SFS lasting 5 minutes or less (SFS ≤ 5M), and 35 healthy controls aged 6 to 60 months who underwent magnetic resonance imaging (MRI). A custom-designed automated method that used T2-weighted imaging (T2WI) to segment the visible VRs. The VRs metrics were measured and compared studied groups. The VRs metrics, seizure duration the time gap between seizure onset and MRI scan were studied as well. VRs counts were lower (P < .001) in the SFS ≤ 5M (445.80 ± 66.10) and the control (430.77 ± 182.55) groups in comparison to SFS > 5M (642.70 ± 100.62). Similar results were found for VRs volume (VRsvol_SFS > 5M, 8514.63 ± 835.33mm3, VRsvol_SFS ≤ 5M, 6390.43 ± 692.74 mm3, VRsvol_control, 6048.37 ± 111.50 mm3; P < .001). However, in the SFS ≤ 5M, VRs measurements were lower than in the SFS > 5M (P < .001). VRs measurements were positively connected with seizure duration and inversely correlated with the course following seizure onset and MRI scan time in both SFS groups. SFS are positively correlated to glymphatic dysfunction since they cause enlarged VRs; additionally, VRs can be used as a biomarker in SFS > 5M and contribute to the mechanism.

A companion to the preclinical common data elements for rodent models of pediatric acquired epilepsy: A report of the TASK3-WG1B, Pediatric and Genetic Models Working Group of the ILAE/AES Joint Translational Task Force

Epilepsy syndromes during the early years of life may be attributed to an acquired insult, such as hypoxic-ischemic injury, infection, status epilepticus, or brain trauma. These conditions are frequently modeled in experimental rodents to delineate mechanisms of epileptogenesis and investigate novel therapeutic strategies. However, heterogeneity and subsequent lack of reproducibility of such models across laboratories is an ongoing challenge to maintain scientific rigor and knowledge advancement. To address this, as part of the TASK3-WG1B Working Group of the International League Against Epilepsy/American Epilepsy Society Joint Translational Task Force, we have developed a series of case report forms (CRFs) to describe common data elements for pediatric acquired epilepsy models in rodents. The "Rodent Models of Pediatric Acquired Epilepsy" Core CRF was designed to capture cohort-general information; while two Specific CRFs encompass physical induction models and chemical induction models, respectively. This companion manuscript describes the key elements of these models and why they are important to be considered and reported consistently. Together, these CRFs provide investigators with the tools to systematically record critical information regarding their chosen model of acquired epilepsy during early life, for improved standardization and transparency across laboratories. These outcomes will support the ultimate goal of such research; that is, to understand the childhood onset-specific biology of epileptogenesis after acquired insults, and translate this knowledge into therapeutics to improve pediatric patient outcomes and minimize the lifetime burden of epilepsy.

Cattle Bile Arisaema Aqueous Extracts Protect Against Febrile Seizures in Rats Through Regulating Neurotransmitters and Suppressing Neuroinflammation

Cattle bile Arisaema (CBA) is a traditional medicine used for the treatment of febrile seizures (FS) for thousands of years in China. However, its application is greatly limited due to cost reasons, and pig bile Arisaema (PBA) is the main commercial product instead. Additionally, the underlying mechanism of CBA for the treatment of FS still remains unknown. In this study, we investigated the anti-convulsant effect and potential mechanism of the CBA aqueous extract for the first time through a hot-water bath-induced FS rat model. Our results showed that pre-treatment with CBA dramatically lowered the incidence rate and generation times and prolonged the latency of FS. In addition, CBA effectively ameliorated neuronal damage and regulated neurotransmitter disorder induced by FS in the rat hippocampus. The enzyme-linked immunosorbent assay, western blotting, immunohistochemical, and qRT-PCR results exhibited that CBA suppressed the expression of GFAP, TLR4, NF-κB, HMGB1, NLRP3, TNF-α, IL-1β, and IL-6 and consequently inhibited the neuroinflammation induced by FS. Interestingly, although the CBA and PBA aqueous extracts possessed the same trend on the changes caused by FS, the improvement of FS by CBA is markedly better than that by PBA. These findings indicate that CBA exerts a protective effect on febrile seizures through regulating neurotransmitter disorder and suppressing neuroinflammation.

Natural bear bile powder suppresses neuroinflammation in lipopolysaccharide-treated mice via regulating TGR5/AKT/NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

According to the Tang Dynasty classics Dietetic Material Medica and the Ming Dynasty classics Compendium of Materia Medica records, bear bile powder (BBP) has been used to treat a variety of diseases, such as febrile seizures, the pathogenesis of which is associated to neuroinflammation. However, the mechanism of BBP on alleviating neuroinflammation remains unclear.

AIMS OF THE STUDY

Microglia can be activated by peripheral lipopolysaccharide (LPS) and play an important role in the pathogenesis of neuroinflammation. The purpose of this study is to investigate the effects and mechanism of BBP in inhibiting LPS-induced microglia inflammation in vitro and in vivo.

MATERIALS AND METHODS

The anti-microglia inflammatory effects and mechanism of BBP were assessed in LPS-treated BV2 microglial cells and in LPS-treated mice. The mRNA expression levels of the inflammatory factor and the protein expressions of cyclooxygenase-2 (COX2), inducible nitric oxide synthase (iNOS), takeda G-protein coupled receptor 5 (TGR5), nuclear factor-κB (NF-κB), inhibitor of NF-κB (IκBɑ), protein kinase B (AKT) in BV2 cells, mouse hippocampus and cortex were detected. The NF-κB transcription activity and NF-κB nuclear translocation were observed.

RESULTS

Our findings showed that BBP reduces branched process retraction and NO in LPS-treated BV2 cells, inhibits the protein expression of ionized calcium binding adaptor molecule 1 in the hippocampus of LPS-treated mice. Moreover, we observed that BBP decreases tumor necrosis factor α, interleukin (IL)-6 and IL-1β mRNA levels, deceases iNOS and COX-2 protein levels, increases TGR5 protein levels, suppresses the phosphorylation of AKT, NF-κB and IκBɑ protein in microglia both in vitro and in vivo. Further, we found that triamterene, the inhibitor of TGR5, abolishes the effects of BBP in LPS- treated BV2 cells.

CONCLUSION

BBP inhibits LPS-induced microglia activation, and the mechanism of its action is partly through TGR5/AKT/NF-κB signaling pathway.

A rat model of a focal mosaic expression of PCDH19 replicates human brain developmental abnormalities and behaviors

Protocadherin 19 gene-related epilepsy or protocadherin 19 clustering epilepsy is an infantile-onset epilepsy syndrome characterized by psychiatric (including autism-related), sensory, and cognitive impairment of varying degrees. Protocadherin 19 clustering epilepsy is caused by X-linked protocadherin 19 protein loss of function. Due to random X-chromosome inactivation, protocadherin 19 clustering epilepsy-affected females present a mosaic population of healthy and protocadherin 19-mutant cells. Unfortunately, to date, no current mouse model can fully recapitulate both the brain histological and behavioural deficits present in people with protocadherin 19 clustering epilepsy. Thus, the search for a proper understanding of the disease and possible future treatment is hampered. By inducing a focal mosaicism of protocadherin 19 expression using in utero electroporation in rats, we found here that protocadherin 19 signalling in specific brain areas is implicated in neuronal migration, heat-induced epileptic seizures, core/comorbid behaviours related to autism and cognitive function.

Peripheral Infection after Traumatic Brain Injury Augments Excitability in the Perilesional Cortex and Dentate Gyrus

Peripheral infections occur in up to 28% of patients with traumatic brain injury (TBI), which is a major etiology for structural epilepsies. We hypothesized that infection occurring after TBI acts as a “second hit” and facilitates post-traumatic epileptogenesis. Adult male Sprague–Dawley rats were subjected to lateral fluid-percussion injury or sham-operation. At 8 weeks post-injury, rats were treated with lipopolysaccharide (LPS, 5 mg/kg) to mimic Gram-negative peripheral infection. T2-weighted magnetic resonance imaging was used to detect the cortical lesion type (small focal inflammatory [TBI_FI] vs. large cavity-forming [TBI_CF]). Spontaneous seizures were detected with video-electroencephalography, and seizure susceptibility was determined by the pentylenetetrazole (PTZ) test. Post-PTZ neuronal activation was assessed using c-Fos immunohistochemistry. LPS treatment increased the percentage of rats with PTZ-induced seizures among animals with TBI_FI lesions (p < 0.05). It also increased the cumulative duration of PTZ-induced seizures (p < 0.01), particularly in the TBI_FI group (p < 0.05). The number of c-Fos immunopositive cells was higher in the perilesional cortex of injured animals compared with sham-operated animals (p < 0.05), particularly in the TBI-LPS group (p < 0.05). LPS treatment increased the percentage of injured rats with bilateral c-Fos staining in the dentate gyrus (p < 0.05), particularly in the TBI_FI group (p < 0.05). Our findings demonstrate that peripheral infection after TBI increases PTZ-induced seizure susceptibility and neuronal activation in the perilesional cortex and bilaterally in the dentate gyrus, particularly in animals with prolonged perilesional T2 enhancement. Our data suggest that treatment of infections and reduction of post-injury neuro-inflammation are important components of the treatment regimen aiming at preventing epileptogenesis after TBI.

Maternal intake of docosahexaenoic acid decreased febrile seizure sensitivity by increasing estrogen synthesis in offspring

Febrile seizures, which are convulsion in children, are caused by an abrupt increase in body temperature. They are sometimes recurrent, and the more seizures are triggered, the higher the risk of epilepsy and psychiatric disorders increase after growing up. Prevention of febrile seizure is considered to be one of the effective countermeasures in protecting the future health of children; however, pharmacological prevention in the developmental stage is not realistic from the health aspects of the offspring. Docosahexaenoic acid (DHA) is an important nutrient especially during pregnancy and childhood and is reported to suppress several types of epilepsy. The purpose of this study was to examine the effect of DHA intake during pregnancy and infancy on febrile seizures in mice. We used a heat chamber for febrile seizure induction in offspring at the age of from 10 to 11 days old. Intake of DHA during pregnancy and infancy significantly increased the amount of DHA in the brain of offspring. Although DHA had no effect on seizure severity, DHA significantly prolonged the seizure latency and increased body temperature at which the first seizure occurred, indicating that maternal DHA intake decreases febrile seizure sensitivity. Brain estrogen levels significantly increased by DHA intake and administration of an inhibitor for cytochrome P450 aromatase, which is a rate-limiting enzyme for estrogen synthesis, clearly decreased seizure latency and body temperature at which the first seizure occurred. Taken together, DHA could reduce susceptibility to febrile seizures owing to increases in brain estrogen contents. DHA intake during pregnancy and infancy is of significance in protecting infant from seizures as well as conserving health after growth.

Dextromethorphan Dampens Neonatal Astrocyte Activation and Endoplasmic Reticulum Stress Induced by Prenatal Exposure to Buprenorphine

Prenatal exposure to buprenorphine renders offspring vulnerable to cerebral impairments. In this study, our data demonstrate, for the first time, that prenatal exposure to buprenorphine escalates astrocyte activation concurrent with indications of endoplasmic reticulum (ER) stress in the hippocampi of neonates, and this can be prevented by the coadministration of dextromethorphan with buprenorphine. Furthermore, dextromethorphan can inhibit the accumulation of GPR37 in the hippocampus of newborns caused by buprenorphine and is accompanied by the proapoptotic ER stress response that involves the procaspase-3/CHOP pathway. Primary astrocyte cultures derived from the neonates of the buprenorphine group also displayed aberrant ER calcium mobilization and elevated basal levels of cyclooxygenase-2 (COX-2) at 14 days in vitro while showing sensitivity to lipopolysaccharide-activated expression of COX-2. Similarly, these long-lasting defects in the hippocampus and astrocytes were abolished by dextromethorphan. Our findings suggest that prenatal exposure to buprenorphine might instigate long-lasting effects on hippocampal and astrocytic functions. The beneficial effects of prenatal coadministration of dextromethorphan might be, at least in part, attributed to its properties in attenuating astrocyte activation and hippocampal ER stress in neonates.

Structure-based discovery of CZL80, a caspase-1 inhibitor with therapeutic potential for febrile seizures and later enhanced epileptogenic susceptibility

BACKGROUND AND PURPOSE

Febrile seizures (FS), the most common seizures in childhood and often accompanied by later epileptogenesis, are not well controlled. Inflammatory processes have been implicated in the pathophysiology of epilepsy. However, whether caspase-1 is involved in FS generation and could be a target for the treatment of FS is still unclear.

EXPERIMENTAL APPROACH

By using pharmacological and gene intervention methods in C57BL/6J mice, we assessed the role of caspase-1 in FS generation. We used structural virtual screening against the active site of caspase-1, to screen compounds for druggable and safe low MW inhibitors of caspase-1 in vitro. One compound was chosen to test in vivo for therapeutic potential, using FS models in neonatal mice and epileptogenesis in adult mice.

KEY RESULTS

In mice, levels of cleaved caspase-1 increased prior to FS onset. Caspase-1^-/- mice were resistant to FS and showed lower neuronal excitability than wild-type littermates. Conversely, overexpression of caspase-1 using in utero electroporation increased neuronal excitability and enhanced susceptibility to FS. The structural virtual screening, using molecular docking approaches for the active site of caspase-1 of over 1 million compounds yielded CZL80, a brain-penetrable, low MW inhibitor of caspase-1. In neonatal mice, CZL80 markedly reduced neuronal excitability and incidence of FS generation, and, in adult mice, relieved later enhanced epileptogenic susceptibility. CZL80 was devoid of acute diazepam-like respiratory depression and chronic liver toxicity.

CONCLUSION AND IMPLICATIONS

Caspase-1 is essential for FS generation. CZL80 is a promising low MW inhibitor of FS and later enhanced epileptogenic susceptibility.

The Frail Male: Early Life Inflammation Promotes Chloride Loading in Adult Male Mice

Early Life Inflammation Increases CA1 Pyramidal Neuron Excitability in a Sex and Age-Dependent Manner Through a Chloride Homeostasis Disruption

Gomez CD, Read J, Acharjee S, Pittman QJ. J Neurosci. 2019;39(37):7244.

Early life, systemic inflammation causes long-lasting changes in behavior. To unmask possible mechanisms associated with this phenomenon, we asked whether the intrinsic membrane properties in hippocampal neurons were altered as a consequence of early life inflammation. C57BL/6 mice were bred in-house and both male and female pups from multiple litters were injected with lipopolysaccharide (LPS; 100 g/kg, intraperitoneally.) or vehicle at postnatal day (P)14, and kept until adolescence (P35-P45) or adulthood (P60-P70), when brain slices were prepared for whole-cell and perforated-patch recordings from CA1 hippocampal pyramidal neurons. In neurons of adult male mice pretreated with LPS, the number of action potentials elicited by depolarizing current pulses was significantly increased compared with control neurons, concomitant with increased input resistance, and a lower action potential threshold. Although these changes were not associated with changes in relevant sodium channel expression or differences in capacitance or dendritic architecture, they were linked to a mechanism involving intracellular chloride overload, revealed through a depolarized γ aminobutyric acid reversal potential and increased expression of the chloride transporter, NKCC1. In contrast, no significant changes were observed in neurons of adult female mice pretreated with LPS, nor in adolescent mice of either sex. These data uncover a potential mechanism involving neonatal inflammation induced plasticity in chloride homeostasis, which may contribute to early life inflammation-induced behavioral alterations.

Pregabalin inhibits in vivo and in vitro cytokine secretion and attenuates spleen inflammation in Lipopolysaccharide/Concanavalin A -induced murine models of inflammation

Immune system alteration has been implicated in the pathogenesis of chronic pain conditions, epilepsy and generalized anxiety disorder. Targeting cytokines has recently been proposed for the management of such conditions. Pregabalin (PGB) is an antiepileptic agent used for the management of these conditions. However, little is known about its immunomodulatory effects on cytokine secretion in vivo and in vitro. Hence, a mitogen (Lipopolysaccharide [LPS] or Concanavalin A [ConA])-induced murine model of inflammation was used to investigate the effect of PGB on in vivo and in vitro IL-1β, IL-6, TNF-α and IL-2 cytokine secretion using ELISA. In addition, PGB effect on spleen histology, as a lymphoid organ, was examined. Our results revealed that PGB significantly inhibited the secretion of ConA-induced IL-6 secretion, basal and ConA-induced TNF-α and IL-2 secretion in splenocytes in vitro. In vivo, PGB inhibited basal and LPS/ConA-induced IL-6 and TNF-α secretion in addition to LPS-induced IL-1β and ConA-induced IL-2 secretion. Moreover, PGB attenuated mitogen-induced inflammatory changes in the spleen. These findings provide an evidence of the anti-inflammatory properties of PGB on cytokine secretion and lymphoid organ inflammation. This might give insights into the role of PGB in the management of the inflammatory state in PGB-indicated conditions.

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.

dCas9-Based Scn1a Gene Activation Restores Inhibitory Interneuron Excitability and Attenuates Seizures in Dravet Syndrome Mice

Dravet syndrome (DS) is a severe epileptic encephalopathy caused mainly by heterozygous loss-of-function mutations of the SCN1A gene, indicating haploinsufficiency as the pathogenic mechanism. Here we tested whether catalytically dead Cas9 (dCas9)-mediated Scn1a gene activation can rescue Scn1a haploinsufficiency in a mouse DS model and restore physiological levels of its gene product, the Na_v1.1 voltage-gated sodium channel. We screened single guide RNAs (sgRNAs) for their ability to stimulate Scn1a transcription in association with the dCas9 activation system. We identified a specific sgRNA that increases Scn1a gene expression levels in cell lines and primary neurons with high specificity. Na_v1.1 protein levels were augmented, as was the ability of wild-type immature GABAergic interneurons to fire action potentials. A similar enhancement of Scn1a transcription was achieved in mature DS interneurons, rescuing their ability to fire. To test the therapeutic potential of this approach, we delivered the Scn1a-dCas9 activation system to DS pups using adeno-associated viruses. Parvalbumin interneurons recovered their firing ability, and febrile seizures were significantly attenuated. Our results pave the way for exploiting dCas9-based gene activation as an effective and targeted approach to DS and other disorders resulting from altered gene dosage.

In Up to My Ears and Temporal Lobes: Effects of Early Life Stress on Epilepsy Development

Epilepsy and stress are each significant concerns in today's society, bearing heavy impacts on mental and physical health and overall quality of life. Unfortunately, the intersection between these is potentially even more concerning, as stress is a frequent trigger of seizures and may contribute to neural hyperexcitability. A growing body of research suggests a connection between early life stress (occurring in the prenatal or postnatal stage) and later development of epilepsy. While the larger part of this literature suggests that early life stress increases vulnerability for epilepsy development, there are a number of interacting factors influencing this relationship. These factors include developmental stage at which both stressor and seizure assessment occur, type of stressor, sex effects, and type of seizure (convulsive or non-convulsive). Additionally, a number of potential mechanisms have been identified, including activation of the hypothalamic-pituitary-adrenal axis, neuroinflammation, altered inhibitory/excitatory balance, and temporal lobe structures. Developing a clearer understanding of this relationship between early life stress and epilepsy, the factors that influence it, and underlying mechanisms that may serve as targets for intervention is crucial to improving quality of life for persons with epilepsy.

Inflammation and reactive oxygen species in status epilepticus: Biomarkers and implications for therapy

Preclinical studies in immature and adult rodents and clinical observations show that neuroinflammation and oxidative stress are rapid onset phenomena occurring in the brain during status epilepticus and persisting thereafter. Notably, both neuroinflammation and oxidative stress contribute to the acute and long-term sequelae of status epilepticus thus representing potential druggable targets. Antiinflammatory drugs that interfere with the IL-1β pathway, such as anakinra, can control benzodiazepine-refractory status epilepticus in animals, and there is recent proof-of-concept evidence for therapeutic effects in children with Febrile infection related epilepsy syndrome (FIRES). Inhibitors of monoacylglycerol lipase and P2X7 receptor antagonists are also promising antiinflammatory drug candidates for rapidly aborting de novo status epilepticus and provide neuroprotection. Antiinflammatory and antioxidant drugs administered to rodents during status epilepticus and transiently thereafter, prevent long-term sequelae such as cognitive deficits and seizure progression in animals developing epilepsy. Some drugs are already in medical use and are well-tolerated, therefore, they may be considered for treating status epilepticus and its neurological consequences. Finally, markers of neuroinflammation and oxidative stress are measureable in peripheral blood and by neuroimaging, which offers an opportunity for developing prognostic and predictive mechanistic biomarkers in people exposed to status epilepticus. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures.

Activation of TRPV1 Contributes to Recurrent Febrile Seizures via Inhibiting the Microglial M2 Phenotype in the Immature Brain

Transient receptor potential vanilloid type 1 (TRPV1) is a nonselective cation channel implicated in the nervous system as a key component of several inflammatory diseases. A massive amount of evidence has demonstrated that TRPV1 is extensively expressed in the central nervous system (CNS) and there might be a close relationship between TRPV1 and neuroinflammation, which is a crucial pathogenic factor in seizure generation, although it’s signaling mechanism has been less well characterized. Herein, we identified that TRPV1 is functionally expressed in the primary cultured mouse microglia and the membrane expression of TRPV1 is upregulated in rFS mice brain and specifically in activated microglia. Stimulation of TRPV1 promoted microglia activation and indirectly enhanced seizure susceptibility by inhibiting the neuroprotective effects of microglial transforming growth factor-beta1 (TGF-β1) via interaction with Toll-like receptor 4 (TLR4) in mice. Conversely, genetic deletion of TRPV1 alleviated hyperthermia or LPS-induced abnormal microglial activation and restored a balanced inflammatory microenvironment in the brain. Taken together, these findings show that microglial TRPV1, as a potential pro-inflammatory mediator, and participate in neuroinflammatory response, which will provide a novel therapeutic strategy for controlling the neuroinflammation-induced seizure.

Brain diseases in changing climate

Climate change is one of the biggest and most urgent challenges for the 21st century. Rising average temperatures and ocean levels, altered precipitation patterns and increased occurrence of extreme weather events affect not only the global landscape and ecosystem, but also human health. Multiple environmental factors influence the onset and severity of human diseases and changing climate may have a great impact on these factors. Climate shifts disrupt the quantity and quality of water, increase environmental pollution, change the distribution of pathogens and severely impacts food production - all of which are important regarding public health. This paper focuses on brain health and provides an overview of climate change impacts on risk factors specific to brain diseases and disorders. We also discuss emerging hazards in brain health due to mitigation and adaptation strategies in response to climate changes.

Developing a mouse model of acute encephalopathy using low-dose lipopolysaccharide injection and hyperthermia treatment

IMPACT STATEMENT

Acute encephalopathy (AE), mainly reported in East Asia, is classified into four categories based on clinical and neuropathological findings. Among them, AE caused by cytokine storm is known as the severest clinical entity that causes cerebral edema with poor prognosis. Because suitable and convenient model animal of AE had not been developed, the treatment of patients with AE is not established. In the present study, we established a simple and convenient protocol to mimic AE due to cytokine storm. Our model animal should be useful to elucidate the pathogenesis of AE.

Chitinase-3-like protein 1 may be a potential biomarker in patients with drug-resistant epilepsy

The mechanisms of the pathogenesis of epilepsy remain unclear. Recent research shows that the inflammatory process occurring in the brain may be a common and critical mechanism of seizures. Chitinase-3-like protein 1 (CHI3L1 or YKL-40) is a newly discovered inflammatory factor. We aimed to evaluate the role of YKL-40 as a biomarker for epilepsy. 124 subjects were classified as control group (n = 23), new-diagnosis epilepsy group (NDE, n = 34), drug responsive epilepsy group (DPE, n = 37), and drug-resistant epilepsy group (DRE, n = 30) YKL-40 was measured by ELISA in serum and cerebrospinal fluid (CSF). The concentrations of serum and CSF YKL-40 and its diagnostic accuracy for epilepsy were analysed. Patients with DRE had higher concentrations of YKL-40 in serum and CSF, while patients with NDE and DPE had increased YKL-40 levels in CSF but not serum in comparison with control. Moreover, serum and CSF YKL-40 provide high diagnostic accuracy for DRE. YKL-40 may play a possible pathogenic role in epilepsy. YKL-40 may represent a potential biomarker of brain inflammation in patients with DRE.

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.

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).

Pharmacological Tools to Activate Microglia and their Possible use to Study Neural Network Patho-physiology

BACKGROUND

Microglia are the resident immunocompetent cells of the CNS and also constitute a unique cell type that contributes to neural network homeostasis and function. Understanding microglia cell-signaling not only will reveal their diverse functions but also will help to identify pharmacological and non-pharmacological tools to modulate the activity of these cells.

METHODS

We undertook a search of bibliographic databases for peer-reviewed research literature to identify microglial activators and their cell-specificity. We also looked for their effects on neural network function and dysfunction.

RESULTS

We identified several pharmacological targets to modulate microglial function, which are more or less specific (with the proper control experiments). We also identified pharmacological targets that would require the development of new potent and specific modulators. We identified a wealth of evidence about the participation of microglia in neural network function and their alterations in pathological conditions.

CONCLUSION

The identification of specific microglia-activating signals provides experimental tools to modulate the activity of this heterogeneous cell type in order to evaluate its impact on other components of the nervous system, and it also helps to identify therapeutic approaches to ease some pathological conditions related to microglial dysfunction.

Interactive effects of maternal cigarette smoke, heat stress, hypoxia, and lipopolysaccharide on neonatal cardiorespiratory and cytokine responses

Maternal cigarette smoke (CS) exposure exhibits a strong epidemiological association with Sudden Infant Death Syndrome, but other environmental stressors, including infection, hyperthermia, and hypoxia, have also been postulated as important risk factors. This study examines whether maternal CS exposure causes maladaptations within homeostatic control networks by influencing the response to lipopolysaccharide, heat stress, and/or hypoxia in neonatal rats. Pregnant dams were exposed to CS or parallel sham treatments daily for the length of gestation. Offspring were studied at postnatal days 6-8 at ambient temperatures (T_a) of 33°C or 38°C. Within each group, rats were allocated to control, saline, or LPS (200 µg/kg) treatments. Cardiorespiratory patterns were examined using head-out plethysmography and ECG surface electrodes during normoxia and hypoxia (10% O₂). Serum cytokine concentrations were quantified from samples taken at the end of each experiment. Our results suggest maternal CS exposure does not alter minute ventilation (V̇e) or heart rate (HR) response to infection or high temperature, but independently increases apnea frequency. CS also primes the inflammatory system to elicit a stronger cytokine response to bacterial insult. High T_a independently depresses V̇e but augments the hypoxia-induced increase in V̇e Moreover, higher T_a increases HR during normoxia and hypoxia, and in the presence of an immune challenge, increases HR during normoxia, and reduces the increase normally associated with hypoxia. Thus, while most environmental risk factors increase the burden on the cardiorespiratory system in early life, hyperthermia and infection blunt the normal HR response to hypoxia, and gestational CS independently destabilizes breathing by increasing apneas.

Confounding effect of EEG implantation surgery: Inadequacy of surgical control in a two hit model of temporal lobe epilepsy

In rodent models of epilepsy, EEG implantation surgery is an essential modality to evaluate electrographic seizures. The inflammatory consequences of EEG electrode-implantation and their resultant effects on seizure susceptibility are unclear. We evaluated electrode-implantation in a two-hit model of epileptogenesis in C57BL/6 mice that included brief, recurrent febrile seizures (FS) at P14 and kainic acid induced seizures (KA-SZ) at P28. During KA-SZ, latencies to first electrographic and behavioral seizures, seizure severity, and KA dose sensitivity were measured. Mice that received subdural screw electrode implants at P25 for EEG monitoring at P28 had significantly shorter latencies to seizures than sham mice, regardless of early life seizure experience. Electrode-implanted mice were sensitive to low dose KA as shown by high mortality rate at KA doses above 10mg/kg. We then directly compared electrode-implantation and KA-SZ in seizure naive CX3CR1(GFP/+) transgenic C57BL/6 mice, wherein microglia express green fluorescent protein (GFP), to determine if microglia activation related to surgery was associated with the increased seizure susceptibility in electrode-implanted mice from the two-hit model. Hippocampal microglia activation, as demonstrated by percent area GFP signal and GFP positive cell counts, prior to seizures was indistinguishable between electrode-implanted mice and controls, but was significantly greater in electrode-implanted mice following seizures. Electrode-implantation had a confounding priming effect on the inflammatory response to subsequent seizures.

Brain Inflammation in an Infant With Hemimegalencephaly, Escalating Seizures, and Epileptic Encephalopathy

Hemimegalencephaly, a congenital brain malformation typically characterized by enlargement of one hemisphere, is frequently associated with intractable epilepsy. The authors report a case of a 12-month-old girl with hemimegalencephaly who underwent semiurgent hemispherectomy because of rapidly escalating seizures, arrested development, and associated encephalopathy. The brain tissue was examined and evaluated for neuroinflammation. Immunohistochemical analysis of the brain tissue revealed the presence of abundant activated CD68-positive microglia and reactive astrogliosis. Detection of active inflammatory changes in the brain of a patient with hemimegalencephaly complicated by intractable epilepsy suggests a potential role of ongoing brain inflammation in seizure exacerbation and epileptic encephalopathy.

A postnatal peak in microglial development in the mouse hippocampus is correlated with heightened sensitivity to seizure triggers

BACKGROUND

Explosive synaptogenesis and synaptic pruning occur in the hippocampus during the first two weeks of postnatal life, coincident with a heightened susceptibility to seizures in rodents. To determine the temporal correlation between microglial development and age-dependent susceptibility and response to seizures, we quantified developmental changes in basal microglia levels and seizure-induced microglial activation in the hippocampus of Cx3Cr1(GFP /+) transgenic mice.

METHODS

Basal levels of microglia were quantified in the hippocampi of Cx3Cr1(GFP /+) mice at P0, P5, P10, P15, P20, P25, P30, P40, and P60. Seizure susceptibility and seizure-induced microglial activation were assessed in response to febrile seizures (lipopolysaccharide followed by hyperthermia) and kainic acid-induced status epilepticus.

RESULTS

The density of microglia within the hippocampus increased rapidly after birth, reaching a peak during the second week of life - the age at which the animals became most vulnerable to seizure triggers. In addition, this peak of microglial development and seizure vulnerability during the second postnatal week represented the time of maximal seizure-induced microglia activation.

CONCLUSIONS

Overreactive innate immunity mediated by activated microglia may exacerbate acute injury to neuronal synapses and contribute to the long-term epileptogenic effects of early-life seizures. Anti-inflammatory therapy targeting excessive production of inflammatory mediators by activated microglia, therefore, may be an effective age-specific therapeutic strategy to minimize neuronal dysfunction and prevent increases in susceptibility to subsequent seizures in developing animals.