The dual role of TNF-α and its receptors in seizures

Necrostatin-1 as a Potential Anticonvulsant: Insights from Zebrafish Larvae Model of PTZ-Induced Seizures

Epilepsy is a common neurological disorder affecting around 70 million people worldwide. Despite significant research and advancements in pharmaceutical therapies, the exact mechanisms underlying epileptogenesis remain unclear. As a result, current antiepileptic drug treatments are ineffective for approximately 30% of patients, providing only symptomatic relief. The epileptic process is influenced by the signaling of tumor necrosis factor alpha (TNFα), which affects neuronal excitability. The TNFα/TNFR1 signaling pathway and the role of RIPK1 in initiating inflammatory cell death pathways are well studied in human disorders. Dysregulation of RIPK1 is linked to inflammation and neurodegenerative diseases. Necrostatin-1 (Nec-1) selectively inhibits RIPK1 in various pathological conditions. The current study aimed to investigate the anticonvulsant properties of Nec-1 (a selective RIPK1 inhibitor) in PTZ-induced seizures in zebrafish larvae. Before the onset of seizures, zebrafish were treated with Nec-1 (15 µM) for 24 h at 6 days post-fertilization (dpf), followed by exposure to 15 mM of PTZ for 30 min. Behavioral assessments were conducted to observe changes in locomotor activity. Additionally, c-Fos expression was measured as an indicator of neuronal activation and analyzed mRNA levels of the astrocyte activation marker (GFAP) along with various inflammatory cytokines. Western blot analysis was conducted to evaluate GABAA receptor expression. Pretreatment with Nec-1 restored normal behavior and reversed the expression of c-Fos in zebrafish larvae induced by PTZ. Additionally, Nec-1 reduced the elevated mRNA expression of inflammatory cytokines and significantly suppressed TNF/TNFR1 signaling, thereby inhibiting the enhanced internalization of GABAA receptors. Our findings indicate that Nec-1 reduced the severity of PTZ-induced seizures in zebrafish by regulating behavior changes, suppressing inflammatory mediators, and enhancing the expression of GABAA receptors, suggesting potential anticonvulsant properties.

Cytotoxicity and Immunomodulatory Effects of Cannabidiol on Canine PBMCs: A Study in LPS-Stimulated and Epileptic Dogs

Cannabidiol, the primary non-psychoactive phytocannabinoid found in cannabis, has generated significant research interest due to its potential for biological effects, such as anti-inflammatory, analgesic, immunomodulatory, and anticonvulsant properties. Several studies have demonstrated the potential of CBD to alter inflammatory cytokines; however, data on CBD's effects on cell viability and pro-inflammatory cytokines in target animals, such as dogs, are limited. Therefore, in this study, we investigated the effects of CBD on the cell viability and modulation of pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α), in canine PBMCs stimulated with LPS. To evaluate the effect of CBD on neuroinflammation in epilepsy pathology, an independent study of five refractory epileptic dogs co-treated with CBD for 30 days was conducted. The current findings revealed that CBD concentrations of 16 µg/mL had a statistically significant effect on the viability of canine PBMCs with a calculated IC50 of 15.54 µg/mL. The effect of CBD on inflammatory cytokines in LPS-stimulated PBMCs tended to be dose-dependent, with CBD concentrations of 5-30 μg/mL resulting in decreased production of the tested pro-inflammatory cytokines. Considering the effect of CBD on cytokine production by PBMCs from epileptic dogs, CBD has the potential to modulate immune responses and provide benefits when used in combination with antiepileptic drugs. The findings provided evidence of CBD cytotoxicity and its effect on the alteration of pro-inflammatory cytokines in canine PBMCs.

Unraveling the Interplay of 5-hydroxytryptamine-3 and N-methyl-d-aspartate Receptors in Seizure Susceptibility

BACKGROUND

Epilepsy, a prevalent neurological disorder characterized by recurrent seizures, presents significant challenges in treatment and management. This study aimed to evaluate the effect of tropisetron, a selective 5-HT3 receptor antagonist on pentylenetetrazole (PTZ) - induced seizure in mice by exploring the potential role of the NMDA receptor and inflammatory responses.

METHODS

For this purpose, seizures were induced by intravenous PTZ infusion. Tropisetron at 1-, 2-, 3-, 5-, 10- mg/kg were administered intraperitoneally 30 minutes before PTZ. To evaluate probable role of NMDA signaling, selective NMDAR antagonists, ketamine and MK-801, were injected 15 minutes before tropisetron. Also, TNF-α level of hippocampus were measured following administration of mentioned drugs in mice.

RESULTS

Our results demonstrate that tropisetron displayed a dose-dependent impact on seizure threshold, with certain doses (5 and 10 mg/kg) exhibiting anticonvulsant properties. In addition, the noncompetitive NMDAR antagonists, ketamine (1 mg/kg) and MK-801 (0.5 mg/kg), at doses that had no effect on seizure threshold, augmented the anticonvulsant effect of tropisetron (3 mg/kg). Also, tropisetron led to a reduction in hippocampal TNF-α levels, indicating its anti-inflammatory potential independent of 5-HT receptor activity.

CONCLUSION

In conclusion, we demonstrated that the anticonvulsant effect of tropisetron is mediated by the inhibition of NMDA receptors and a decline in hippocampal TNF-α level. These findings highlight a potential connection between 5-HT3 and NMDA receptors in the pharmacological treatment of inflammatory diseases, such as seizure, warranting further investigation into their combined therapeutic effects.

TNFR1 signaling converging on FGF14 controls neuronal hyperactivity and sickness behavior in experimental cerebral malaria

BACKGROUND

Excess tumor necrosis factor (TNF) is implicated in the pathogenesis of hyperinflammatory experimental cerebral malaria (eCM), including gliosis, increased levels of fibrin(ogen) in the brain, behavioral changes, and mortality. However, the role of TNF in eCM within the brain parenchyma, particularly directly on neurons, remains underdefined. Here, we investigate electrophysiological consequences of eCM on neuronal excitability and cell signaling mechanisms that contribute to observed phenotypes.

METHODS

The split-luciferase complementation assay (LCA) was used to investigate cell signaling mechanisms downstream of tumor necrosis factor receptor 1 (TNFR1) that could contribute to changes in neuronal excitability in eCM. Whole-cell patch-clamp electrophysiology was performed in brain slices from eCM mice to elucidate consequences of infection on CA1 pyramidal neuron excitability and cell signaling mechanisms that contribute to observed phenotypes. Involvement of identified signaling molecules in mediating behavioral changes and sickness behavior observed in eCM were investigated in vivo using genetic silencing.

RESULTS

Exploring signaling mechanisms that underlie TNF-induced effects on neuronal excitability, we found that the complex assembly of fibroblast growth factor 14 (FGF14) and the voltage-gated Na+ (Nav) channel 1.6 (Nav1.6) is increased upon tumor necrosis factor receptor 1 (TNFR1) stimulation via Janus Kinase 2 (JAK2). On account of the dependency of hyperinflammatory experimental cerebral malaria (eCM) on TNF, we performed patch-clamp studies in slices from eCM mice and showed that Plasmodium chabaudi infection augments Nav1.6 channel conductance of CA1 pyramidal neurons through the TNFR1-JAK2-FGF14-Nav1.6 signaling network, which leads to hyperexcitability. Hyperexcitability of CA1 pyramidal neurons caused by infection was mitigated via an anti-TNF antibody and genetic silencing of FGF14 in CA1. Furthermore, knockdown of FGF14 in CA1 reduced sickness behavior caused by infection.

CONCLUSIONS

FGF14 may represent a therapeutic target for mitigating consequences of TNF-mediated neuroinflammation.

Neuroinflammation and status epilepticus: a narrative review unraveling a complex interplay

Status epilepticus (SE) is a medical emergency resulting from the failure of the mechanisms involved in seizure termination or from the initiation of pathways involved in abnormally prolonged seizures, potentially leading to long-term consequences, including neuronal death and impaired neuronal networks. It can eventually evolve to refractory status epilepticus (RSE), in which the administration of a benzodiazepine and another anti-seizure medications (ASMs) had been ineffective, and super-refractory status epilepticus (SRSE), which persists for more than 24 h after the administration of general anesthesia. Objective of the present review is to highlight the link between inflammation and SE. Several preclinical and clinical studies have shown that neuroinflammation can contribute to seizure onset and recurrence by increasing neuronal excitability. Notably, microglia and astrocytes can promote neuroinflammation and seizure susceptibility. In fact, inflammatory mediators released by glial cells might enhance neuronal excitation and cause drug resistance and seizure recurrence. Understanding the molecular mechanisms of neuroinflammation could be crucial for improving SE treatment, wich is currently mainly addressed with benzodiazepines and eventually phenytoin, valproic acid, or levetiracetam. IL-1β signal blockade with Anakinra has shown promising results in avoiding seizure recurrence and generalization in inflammatory refractory epilepsy. Inhibiting the IL-1β converting enzyme (ICE)/caspase-1 is also being investigated as a possible target for managing drug-resistant epilepsies. Targeting the ATP-P2X7R signal, which activates the NLRP3 inflammasome and triggers inflammatory molecule release, is another avenue of research. Interestingly, astaxanthin has shown promise in attenuating neuroinflammation in SE by inhibiting the ATP-P2X7R signal. Furthermore, IL-6 blockade using tocilizumab has been effective in RSE and in reducing seizures in patients with febrile infection-related epilepsy syndrome (FIRES). Other potential approaches include the ketogenic diet, which may modulate pro-inflammatory cytokine production, and the use of cannabidiol (CBD), which has demonstrated antiepileptic, neuroprotective, and anti-inflammatory properties, and targeting HMGB1-TLR4 axis. Clinical experience with anti-cytokine agents such as Anakinra and Tocilizumab in SE is currently limited, although promising. Nonetheless, Etanercept and Rituximab have shown efficacy only in specific etiologies of SE, such as autoimmune encephalitis. Overall, targeting inflammatory pathways and cytokines shows potential as an innovative therapeutic option for drug-resistant epilepsies and SE, providing the chance of directly addressing its underlying mechanisms, rather than solely focusing on symptom control.

Distribution of peripheral blood mononuclear cell subtypes in patients with West syndrome: Impact of synacthen treatment

BACKGROUND

West Syndrome (WS) is an epileptic encephalopathy that typically occurs in infants and is characterized by hypsarrhythmia, infantile spasms, and neurodevelopmental impairment. Demonstration of autoantibodies and cytokines in some WS patients and favorable response to immunotherapy have implicated inflammation as a putative trigger of epileptiform activity in WS. Our aim was to provide additional support for altered inflammatory responses in WS through peripheral blood immunophenotype analysis.

METHODS

Eight WS cases treated with synacthen and 11 age- and sex-matched healthy volunteers were included. Peripheral blood mononuclear cells (PBMC) were isolated and immunophenotyping was performed in pre-treatment baseline (8 patients) and 3 months post-treatment (6 patients) samples. The analysis included PBMC expressing NFκB transcription and NLRP3 inflammasome factors.

RESULTS

In pre-treatment baseline samples, switched memory B cells (CD19+IgD-CD27+) were significantly reduced, whereas plasma cells (CD19+CD38+CD138+) and cytotoxic T cells (CD3+CD8+) were significantly increased. Regulatory T and B cell ratios were not significantly altered. Synacthen treatment only marginally reduced helper T cell ratios and did not significantly change other T, B, NK and NKT cell and monocyte ratios.

CONCLUSIONS

Our findings lend further support for the involvement of inflammation-related mechanisms in WS. New-onset WS patients are inclined to display increased plasma cells in the peripheral blood. Synacthen treatment does not show a beneficial effect on most effector acquired and innate immunity subsets.

Cytokines as emerging regulators of central nervous system synapses

Cytokines are key messengers by which immune cells communicate, and they drive many physiological processes, including immune and inflammatory responses. Early discoveries demonstrated that cytokines, such as the interleukin family members and TNF-α, regulate synaptic scaling and plasticity. Still, we continue to learn more about how these traditional immune system cytokines affect neuronal structure and function. Different cytokines shape synaptic function on multiple levels ranging from fine-tuning neurotransmission, to regulating synapse number, to impacting global neuronal networks and complex behavior. These recent findings have cultivated an exciting and growing field centered on the importance of immune system cytokines for regulating synapse and neural network structure and function. Here, we highlight the latest findings related to cytokines in the central nervous system and their regulation of synapse structure and function. Moreover, we explore how these mechanisms are becoming increasingly important to consider in diseases-especially those with a large neuroinflammatory component.

Neuroinflammation microenvironment sharpens seizure circuit

A large set of inflammatory molecules and their receptors are induced in epileptogenic foci of patients with pharmacoresistant epilepsies of structural etiologies or with refractory status epilepticus. Studies in animal models mimicking these clinical conditions have shown that the activation of specific inflammatory signallings in forebrain neurons or glial cells may modify seizure thresholds, thus contributing to both ictogenesis and epileptogenesis. The search for mechanisms underlying these effects has highlighted that inflammatory mediators have CNS-specific neuromodulatory functions, in addition to their canonical activation of immune responses for pathogen recognition and clearance. This review reports the neuromodulatory effects of inflammatory mediators and how they contribute to alter the inhibitory/excitatory balance in neural networks that underlie seizures. In particular, we describe key findings related to the ictogenic role of prototypical inflammatory cytokines (IL-1β and TNF) and danger signals (HMGB1), their modulatory effects of neuronal excitability, and the mechanisms underlying these effects. It will be discussed how harnessing these neuromodulatory properties of immune mediators may lead to novel therapies to control drug-resistant seizures.

An involvement of COX and 5-LOX pathways in the penicillin- and pentylenetetrazole (PTZ)-induced epilepsy models

This study aimed to examine the relationship between epilepsy and COX/5-LOX inflammation pathways in the penicillin and pentylenetetrazole (PTZ)-induced epilepsy models. For this purpose, 42 albino male Wistar rats were used in this study. In the penicillin and PTZ-induced epilepsy models, epileptiform activity was induced by injection of penicillin (500 IU, i.c.) and PTZ (35 mg/kg, i.p., three times a week), respectively. Licofelone (20 mg/kg, i.p.), a dual inhibitor of COX/5-LOX, and esculetin (20 mg/kg, i.p.), a 5-LOX inhibitor, were given. In the penicillin-induced epilepsy model, ECoG activity was recorded for 180 min. In the PTZ-induced epilepsy model, both ECoG activity was recorded, and behavioral parameters were performed. In the penicillin groups, both licofelone and esculetin decreased the mean spike frequency and amplitude during the experiments. In the PTZ groups, licofelone (20 mg/kg, i.p.) was more effective than esculetin (20 mg/kg, i.p.). Licofelone showed its protective effects both in ECoG activity and in behavioral parameters. Esculetin was less effective when compared to licofelone. The electrophysiological and behavioral data from the present study indicated that inflammation pathways might have a crucial role in controlling epileptiform activity in rats. Licofelone might be a valuable candidate in advanced studies.

An in vitro model of drug-resistant seizures for selecting clinically effective antiseizure medications in Febrile Infection-Related Epilepsy Syndrome

Introduction

FIRES is a rare epileptic encephalopathy induced by acute unremitting seizures that occur suddenly in healthy children or young adults after a febrile illness in the preceding 2 weeks. This condition results in high mortality, neurological disability, and drug-resistant epilepsy. The development of new therapeutics is hampered by the lack of validated experimental models. Our goal was to address this unmet need by providing a simple tool for rapid throughput screening of new therapies that target pathological inflammatory mechanisms in FIRES. The model was not intended to mimic the etiopathogenesis of FIRES which is still unknown, but to reproduce salient features of its clinical presentation such as the age, the cytokine storm and the refractoriness of epileptic activity to antiseizure medications (ASMs).

Methods

We refined an in vitro model of mouse hippocampal/temporal cortex acute slices where drug-resistant epileptic activity is induced by zero Mg²⁺/100 μM 4-aminopirydine. Clinical evidence suggests that acute unremitting seizures in FIRES are promoted by neuroinflammation triggered in the brain by the preceding infection. We mimicked this inflammatory component by exposing slices for 30 min to 10 μg/ml lipopolysaccharide (LPS).

Results

LPS induced a sustained neuroinflammatory response, as shown by increased mRNA levels of IL-1β, CXCL1 (IL-8), TNF, and increased IL-1β/IL-1Ra ratio. Epileptiform activity was exacerbated by neuroinflammation, also displaying increased resistance to maximal therapeutic concentrations of midazolam (100 μM), phenytoin (50 μM), sodium valproate (800 μM), and phenobarbital (100 μM). Treatment of LPS-exposed slices with two immunomodulatory drugs, a mouse anti-IL-6 receptor antibody (100 μM) corresponding to tocilizumab in humans, or anakinra (1.3 μM) which blocks the IL-1 receptor type 1, delayed the onset of epileptiform events and strongly reduced the ASM-resistant epileptiform activity evoked by neuroinflammation. These drugs were shown to reduce ASM-refractory seizures in FIRES patients.

Discussion

The neuroinflammatory component and the pharmacological responsiveness of epileptiform events provide a proof-of-concept validation of this in vitro model for the rapid selection of new treatments for acute ASM-refractory seizures in FIRES.

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.

Influence of methadone on the anticonvulsant efficacy of valproate sodium gabapentin against maximal electroshock seizure in mice by regulation of brain MDA TNF-α

Methadone is the most frequently used opioid therapy worldwide, with controversial effects on oxidative stress homeostasis. This study investigated the effects of intraperitoneal (i.p.) co-administration of methadone (0.1, 0.3, 1, and 3 mg/kg) and valproate sodium (300 mg/kg) or gabapentin (50 mg/kg) in the mice maximal electroshock (MES)-induced seizure model. The adverse effect of drugs was assessed using the chimney test. The levels of tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA) contents were measured in mice brains after a single seizure. Administration of methadone alone resulted in a significant reduction in the duration of hind limb extension (HLE) than that in the control group. Methadone pretreatment at doses of 0.1 and 0.3 mg/kg i.p. decreased, and at doses of 1 and 3 mg/kg i.p. had an increasing effect on anticonvulsant efficacy of gabapentin. Pretreatment with all doses of methadone significantly decreased the valproate anticonvulsive efficacy. At doses of 1 and 3 mg/kg i.p. methadone per se increased brain MDA levels after MES-induced seizure. Administration of methadone (0.3 mg/kg i.p.) enhanced and at 3 mg/kg decreased gabapentin effect on brain MDA level, but their co-treatment did not lead to further increase in MDA. Methadone at 0.3–3 mg/kg enhanced the effect of sodium valproate on MDA levels in the brain, but at all doses significantly potentiated its effect on brain TNF-α levels. The drugs did not produce any side effects on motor coordination in experimental animals. In conclusion, methadone showed different effects on anticonvulsant actions of gabapentin and valproate through regulation of brain levels of MDA and TNF-α.

Immune Mechanism of Epileptogenesis and Related Therapeutic Strategies

Immunologic and neuroinflammatory pathways have been found to play a major role in the pathogenesis of many neurological disorders such as epilepsy, proposing the use of novel therapeutic strategies. In the era of personalized medicine and in the face of the exhaustion of anti-seizure therapeutic resources, it is worth looking at the current or future possibilities that neuroimmunomodulator or anti-inflammatory therapy can offer us in the management of patients with epilepsy. For this reason, we performed a narrative review on the recent advances on the basic epileptogenic mechanisms related to the activation of immunity or neuroinflammation with special attention to current and future opportunities for novel treatments in epilepsy. Neuroinflammation can be considered a universal phenomenon and occurs in structural, infectious, post-traumatic, autoimmune, or even genetically based epilepsies. The emerging research developed in recent years has allowed us to identify the main molecular pathways involved in these processes. These molecular pathways could constitute future therapeutic targets for epilepsy. Different drugs current or in development have demonstrated their capacity to inhibit or modulate molecular pathways involved in the immunologic or neuroinflammatory mechanisms described in epilepsy. Some of them should be tested in the future as possible antiepileptic drugs.

Factors not considered in the study of drug-resistant epilepsy: Drug-resistant epilepsy: assessment of neuroinflammation

More than one‐third of people with epilepsy develop drug‐resistant epilepsy (DRE). Different hypotheses have been proposed to explain the origin of DRE. Accumulating evidence suggests the contribution of neuroinflammation, modifications in the integrity of the blood‐brain barrier (BBB), and altered immune responses in the pathophysiology of DRE. The inflammatory response is mainly due to the increase of cytokines and related molecules; these molecules have neuromodulatory effects that contribute to hyperexcitability in neural networks that cause seizure generation. Some patients with DRE display the presence of autoantibodies in the serum and mainly cerebrospinal fluid. These patients are refractory to the different treatments with standard antiseizure medications (ASMs), and they could be responding well to immunomodulatory therapies. This observation emphasizes that the etiopathogenesis of DRE is involved with immunology responses and associated long‐term events and chronic inflammation processes. Furthermore, multiple studies have shown that functional polymorphisms as risk factors are involved in inflammation processes. Several relevant polymorphisms could be considered risk factors involved in inflammation‐related DRE such as receptor for advanced glycation end products (RAGE) and interleukin 1β (IL‐1β). All these evidences sustained the hypothesis that the chronic inflammation process is associated with the DRE. However, the effect of the chronic inflammation process should be investigated in further clinical studies to promote the development of novel therapeutics useful in treatment of DRE.

Neuroinflammation and Proinflammatory Cytokines in Epileptogenesis

Increasing evidence corroborates the fundamental role of neuroinflammation in the development of epilepsy. Proinflammatory cytokines (PICs) are crucial contributors to the inflammatory reactions in the brain. It is evidenced that epileptic seizures are associated with elevated levels of PICs, particularly interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α), which underscores the impact of neuroinflammation and PICs on hyperexcitability of the brain and epileptogenesis. Since the pathophysiology of epilepsy is unknown, determining the possible roles of PICs in epileptogenesis could facilitate unraveling the pathophysiology of epilepsy. About one-third of epileptic patients are drug-resistant, and existing treatments only resolve symptoms and do not inhibit epileptogenesis; thus, treatment of epilepsy is still challenging. Accordingly, understanding the function of PICs in epilepsy could provide us with promising targets for the treatment of epilepsy, especially drug-resistant type. In this review, we outline the role of neuroinflammation and its primary mediators, including IL-1β, IL-1α, IL-6, IL-17, IL-18, TNF-α, and interferon-γ (IFN-γ) in the pathophysiology of epilepsy. Furthermore, we discuss the potential therapeutic targeting of PICs and cytokine receptors in the treatment of epilepsy.

Inflammatory and neurotrophic factor plasma levels are related to epilepsy independently of etiology

OBJECTIVE

Inflammation plays an essential role in epilepsy. Studies indicate that cytokines and neurotrophic factors can act in neuroexcitability and epileptogenesis. We aimed to investigate the association between plasma inflammatory and neurotrophic markers, seizure frequency, and chronic epilepsy subtypes.

METHODS

We studied 446 patients with epilepsy and 166 healthy controls. We classified patients according to etiology and seizure frequency. We measured plasma levels of interleukin-1 (IL-1), IL-2, IL-4, IL-6, IL-10, IL-17, interferon-γ (IFNγ), tumor necrosis factor α (TNFα), soluble TNF receptor 1 (sTNFr1), sTNFr2, brain-derived neurotrophic factor (BDNF), neurotrophic factor 3 (NT3), NT4/5, ciliary neurotrophic factor (CNTF), nerve growth factor (NGF), and glial cell line-derived neurotrophic factor (GDNF) by enzyme-linked immunosorbent assay or cytometric bead array.

RESULTS

The plasma levels of BDNF, NT3, NGF, and sTNFr2 were higher, whereas IL-2, IL-4, IL-6, IL-10, IL-17, IFNγ, TNFα, CNTF, and sTNFr1 were lower in patients than controls. IL1, GDNF, and NT4/5 were similar between groups. These markers did not correlate with age, sex, and epilepsy duration. The molecule sTNFr2 was the best marker to discriminate patients from controls (area under the curve = .857), also differing between patients with frequent and infrequent seizures.

SIGNIFICANCE

This large cohort confirmed that patients with epilepsy have abnormal levels of plasma inflammatory and neurotrophic markers independent of the underlying etiology. Plasma level of sTNFr2 was related to seizure frequency and discriminated people with or without epilepsy with good accuracy, making it a potential biomarker for epilepsy and seizure burden.

Viral infections and their relationship to neurological disorders

The chronic dysfunction of neuronal cells, both central and peripheral, a characteristic of neurological disorders, may be caused by irreversible damage and cell death. In 2016, more than 276 million cases of neurological disorders were reported worldwide. Moreover, neurological disorders are the second leading cause of death. Generally, the etiology of neurological diseases is not fully understood. Recent studies have related the onset of neurological disorders to viral infections, which may cause neurological symptoms or lead to immune responses that trigger these pathological signs. Currently, this relationship is mostly based on epidemiological data on infections and seroprevalence of patients who present with neurological disorders. The number of studies aiming to elucidate the mechanism of action by which viral infections may directly or indirectly contribute to the development of neurological disorders has been increasing over the years but these studies are still scarce. Comprehending the pathogenesis of these diseases and exploring novel theories may favor the development of new strategies for diagnosis and therapy in the future. Therefore, the objective of the present study was to review the main pieces of evidence for the relationship between viral infection and neurological disorders such as Alzheimer's disease, Parkinson's disease, Guillain-Barré syndrome, multiple sclerosis, and epilepsy. Viruses belonging to the families Herpesviridae, Orthomyxoviridae, Flaviviridae, and Retroviridae have been reported to be involved in one or more of these conditions. Also, neurological symptoms and the future impact of infection with SARS-CoV-2, a member of the family Coronaviridae that is responsible for the COVID-19 pandemic that started in late 2019, are reported and discussed.

Possible interplay between the theories of pharmacoresistant epilepsy

Epilepsy is one of the oldest known neurological disorders and is characterized by recurrent seizure activity. It has a high incidence rate, affecting a broad demographic in both developed and developing countries. Comorbid conditions are frequent in patients with epilepsy and have detrimental effects on their quality of life. Current management options for epilepsy include the use of anti-epileptic drugs, surgery, or a ketogenic diet. However, more than 30% of patients diagnosed with epilepsy exhibit drug resistance to anti-epileptic drugs. Further, surgery and ketogenic diets do little to alleviate the symptoms of patients with pharmacoresistant epilepsy. Thus, there is an urgent need to understand the underlying mechanisms of pharmacoresistant epilepsy to design newer and more effective anti-epileptic drugs. Several theories of pharmacoresistant epilepsy have been suggested over the years, the most common being the gene variant hypothesis, network hypothesis, multidrug transporter hypothesis, and target hypothesis. In our review, we discuss the main theories of pharmacoresistant epilepsy and highlight a possible interconnection between their mechanisms that could lead to the development of novel therapies for pharmacoresistant epilepsy.

The role of inflammation in epileptogenesis

Epilepsy is a chronic neurological disorder that has an extensive impact on a patient’s life. Accumulating evidence has suggested that inflammation participates in the progression of spontaneous and recurrent seizures. Pro-convulsant incidences can stimulate immune cells, augment the release of pro-inflammatory cytokines, elicit neuronal excitation as well as blood-brain barrier (BBB) dysfunction, and finally trigger the generation or recurrence of seizures. Understanding the pathogenic roles of inflammatory mediators, including inflammatory cytokines, cells, and BBB, in epileptogenesis will be beneficial for the treatment of epilepsy. In this systematic review, we performed a literature search on the PubMed database using the following keywords: “epilepsy” or “seizures” or “epileptogenesis”, and “immunity” or “inflammation” or “neuroinflammation” or “damage-associated molecular patterns” or “cytokines” or “chemokines” or “adhesion molecules” or “microglia” or “astrocyte” or “blood-brain barrier”. We summarized the classic inflammatory mediators and their pathogenic effects in the pathogenesis of epilepsy, based on the most recent findings from both human and animal model studies.

Gut microbiota modulation by both Lactobacillus fermentum MSK 408 and ketogenic diet in a murine model of pentylenetetrazole-induced acute seizure

PURPOSE

Seizures are a threat to the host brain and body and can even cause death in epileptic children. Ketogenic diet (KD) is suggested for children suffering from epileptic seizures and has been investigated for its anti-seizure effect. However, the relationships between KD and gut microbiota (GM) is not yet been deeply understood. Herein, we investigated the anti-seizure effect by administering KD and a lactic acid bacteria (LAB) in murine model of chemically induced seizures. We hypothesized that a single Lactobacillus fermentum MSK 408 (MSK 408) strain with or without KD may exert a neuroprotection by modulating host gut microbiota.

METHOD

We performed animal study using pentylenetetrazole (PTZ) to induce seizure. Thirty 3-week-old male Institute of Cancer research (ICR) mice were divided in six groups, Normal diet (ND), ND + PTZ, ND + PTZ + LAB, KD, KD + PTZ, and KD + PTZ. Based on our previous study, 4:1 KD and selected MSK 408 strain was orally gavaged (4 × 10⁹ CFU/mL) with both diets for 4 weeks. PTZ (40 mg/kg) was injected intraperitoneally 30 min before euthanization.

RESULTS

Compared to ND, KD significantly reduced the seizure frequency. Administration of MSK 408 with both ND and KD for 4 weeks restored serum lipid profile and tight junction protein mRNA expression of the gut and brain. Additionally, PCoA revealed that MSK 408 independently affected fecal short chain fatty acid (SCFA) content via gut microbiota (GM) modulation. PICRUSt suggested that the modulation of microbiota by KD and MSK 408 led to increased GABA (gamma-aminobutyric acid) metabolism.

SIGNIFICANCE

Our findings suggest that MSK 408 strain can be consumed with KD as supplement without interfering the anti-seizure action of KD, and may improve the serum lipid profile, and brain barrier function via gut microbiota and SCFA modulation.

Endoplasmic reticulum stress increases inflammatory cytokines in an epilepsy mouse model Gabrg2+/Q390X knockin: A link between genetic and acquired epilepsy?

OBJECTIVE

Neuroinflammation is a major theme in epilepsy, which has been characterized in acquired epilepsy but is poorly understood in genetic epilepsy. γ-Aminobutyric acid type A receptor subunit gene mutations are significant causes of epilepsy, and we have studied the pathophysiology directly resulting from defective receptor channels. Here, we determined the proinflammatory factors in a genetic mouse model, the Gabrg2^+/Q390X knockin (KI). We have identified increased cytokines in multiple brain regions of the KI mouse throughout different developmental stages and propose that accumulation of the trafficking-deficient mutant protein may increase neuroinflammation, which would be a novel mechanism for genetic epilepsy.

METHODS

We used enzyme-linked immunosorbent assay, immunoprecipitation, nuclei purification, immunoblot, immunohistochemistry, and confocal microscopy to characterize increased neuroinflammation and its potential causes in a Gabrg2^+/Q390X KI mouse and a Gabrg2^+/- knockout (KO) mouse, each associated with a different epilepsy syndrome with different severities.

RESULTS

We found that proinflammatory cytokines such as tumor necrosis factor alpha, interleukin 1-beta (IL-1β), and IL-6 were increased in the KI mice but not in the KO mice. A major underlying basis for the discrepancy in cytokine expression between the two mouse models is likely chronic mutant protein accumulation and endoplasmic reticulum (ER) stress. The presence of mutant protein dampened cytokine induction upon further cellular stimulation or external stress such as elevated temperature. Pharmacological induction of ER stress upregulated cytokine expression in the wild-type and KO but not in the KI mice. The increased cytokine expression was independent of seizure occurrence, because it was upregulated in both mice and cultured neurons.

SIGNIFICANCE

Together, these data demonstrate a novel pathophysiology for genetic epilepsy, increased neuroinflammation, which is a common mechanism for acquired epilepsy. The findings thus provide the first link of neuroinflammation between genetic epilepsy associated with an ion channel gene mutation and acquired epilepsy.

Transcranial direct current stimulation (tDCS) affects neuroinflammation parameters and behavioral seizure activity in pentylenetetrazole-induced kindling in rats

Despite the introduction of new antiepileptic drugs, about 30 % of patients with epilepsy are refractory to drug therapy. Thus, the search for non-pharmacological interventions such as transcranial direct current stimulation (tDCS) may be an alternative, either alone or in combination with low doses of anticonvulsants. This study evaluated the effect of anodal (a-tDCS) and cathodal tDCS (c-tDCS) on seizure behavior and neuroinflammation parameters. Rats were submitted to the kindling model induced by pentylenetetrazole (PTZ) using diazepam (DZP) as anticonvulsant standard. tDCS groups were submitted to 10 sessions of a-tDCS or c-tDCS or SHAM-tDCS. Every 3 days they received saline (SAL), low dose of DZP (alone or in combination with tDCS) or effective dose of DZP 30 min before administration of PTZ, totaling 16 days of protocol. Neither a-tDCS nor c-tDCS reduced the occurrence of clonic forelimb seizures (convulsive motor seizures - stage 3 by the adapted Racine scale we based on). Associated with DZP, c-tDCS (c-tDCS/DZP0.15) increased the latency to first clonic forelimb seizure on the 10th and 16th days. Hippocampal IL-1β levels were reduced by c-tDCS and c-tDCS/DZP0.15. In contrast, these treatments induced an increase in cortical IL-1β levels. Hippocampal TNF-α levels were not altered by c-tDCS or a-tDCS, but c-tDCS and c-tDCS/DZP0.15 increased those levels in cerebral cortex. Cortical NGF levels were increased by c-tDCS and c-tDCS/DZP0.15. a-tDCS/DZP0.15 reduced hippocampal BDNF levels and c-tDCS/DZP0.15 increased these levels in cerebral cortex. In conclusion, c-tDCS alone or in combination with a low dose of DZP showed to affect neuroinflammation, improving central neurotrophin levels and decreasing hippocampal IL-1β levels after PTZ-induced kindling without statistically significant effect on seizure behavior.

Tumor Necrosis Factor-α, the Pathological Key to Post-Traumatic Epilepsy: A Comprehensive Systematic Review

Post-traumatic epilepsy (PTE) is one of the detrimental outcomes of traumatic brain injury (TBI), resulting in recurrent seizures that impact daily life. However, the pathological relationship between PTE and TBI remains unclear, and commonly prescribed antiepileptic drugs (AED) are ineffective against PTE. Fortunately, emerging research implicates neuroinflammation, particularly, tumor necrosis factor-α (TNF-α), as the key mediator for PTE development. Thus, this review aims to examine the available literature regarding the role of TNF-α in PTE pathology and, subsequently, evaluate TNF-α as a possible target for its treatment. A comprehensive literature search was conducted on four databases including PubMed, CINAHL, Embase, and Scopus. Articles with relevance in investigating TNF-α expression in PTE were considered in this review. Critical evaluation of four articles that met the inclusion criteria suggests a proportional relationship between TNF-α expression and seizure susceptibilit and that neutralization or suppression of TNF-α release results in reduced susceptibility to seizures. In conclusion, this review elucidates the importance of TNF-α expression in epileptogenesis postinjury and urges future research to focus more on clinical studies involving TNF-α, which may provide clearer insight into PTE prevention, therefore improving the lives of PTE patients.

Effects of Diclofenac Versus Meloxicam in Pentylenetetrazol-Kindled Mice

Epilepsy comes after stroke as the most common chronic neurological disorder worldwide. Inflammation enhances neuronal hyperexcitability that could provide a background setting for the development of epilepsy. The aim of this study was to assess the effect of valproate (VAL), diclofenac (DIC), meloxicam (MEL), VAL + MEL and VAL + DIC in pentylenetetrazol (PTZ) kindled mice. Seventy mice were randomly allocated into 7 equal groups; Control, PTZ, VAL, DIC, MEL, VAL + MEL and VAL + DIC groups. Kindling was induced by PTZ (40 mg/kg, i.p.) injection every other day for 17 days. The drugs were administered, 30 min before each PTZ injection till the end of the schedule. Seizure score, latency, duration and mortality rate were recorded in all groups. Tumor necrosis factor- α (TNF-α), interleukin-1β (IL-1β), malondialdehyde (MDA) and prostaglandin E2 (PGE2) levels as well as reduced glutathione (GSH) content were assessed in brain homogenate at the end of the schedule. VAL, DIC, MEL, VAL + MEL and VAL + DIC decreased seizure score and duration. Meanwhile, they increased the latency period. PTZ increased TNF-α, IL-1β, MDA, and PGE2 levels meanwhile, it decreased GSH content. Administration of VAL, DIC, MEL, VAL + MEL and VAL + DIC decreased TNF-α, IL-1β, MDA, and PGE2 levels meanwhile, they increased GSH content in the brain homogenates. Effects of VAL + DIC combination on the studied parameters were significant in relation to VAL. VAL, DIC, MEL, VAL + MEL and VAL + DIC produced anticonvulsant effect and mitigated inflammation and oxidative stress in PTZ-kindled mice. Interestingly, DIC rather than MEL enhanced the anticonvulsant effect VAL.

Neuroinflammation impact in epileptogenesis and new treatment strategy

Epilepsy is considered a major serious chronic neurological disorder, characterized by recurrent seizures. It is usually associated with a history of a lesion in the nervous system. Irregular activation of inflammatory molecules in the injured tissue is an important factor in the development of epilepsy. It is unclear how the imbalanced regulation of inflammatory mediators contributes to epilepsy. A recent research goal is to identify interconnected inflammation pathways which may be involved in the development of epilepsy. The clinical use of available antiepileptic drugs is often restricted by their limitations, incidence of several side effects, and drug interactions. So development of new drugs, which modulate epilepsy through novel mechanisms, is necessary. Alternative therapies and diet have recently reported positive treatment outcomes in epilepsy. Vitamin D (Vit D) has shown prophylactic and therapeutic potential in different neurological disorders. So, the aim of current study was to review the associations between different brain inflammatory mediators and epileptogenesis, to strengthen the idea that targeting inflammatory pathway may be an effective therapeutic strategy to prevent or treat epilepsy. In addition, neuroprotective effects and mechanisms of Vit D in clinical and preclinical studies of epilepsy were reviewed.

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.

Acute and chronic neurological consequences of early-life Zika virus infection in mice

Although congenital Zika virus (ZIKV) exposure has been associated with microcephaly and other neurodevelopmental disorders, long-term consequences of perinatal infection are largely unknown. We evaluated short- and long-term neuropathological and behavioral consequences of neonatal ZIKV infection in mice. ZIKV showed brain tropism, causing postnatal-onset microcephaly and several behavioral deficits in adulthood. During the acute phase of infection, mice developed frequent seizures, which were reduced by tumor necrosis factor-α (TNF-α) inhibition. During adulthood, ZIKV replication persisted in neonatally infected mice, and the animals showed increased susceptibility to chemically induced seizures, neurodegeneration, and brain calcifications. Altogether, the results show that neonatal ZIKV infection has long-term neuropathological and behavioral complications in mice and suggest that early inhibition of TNF-α-mediated neuroinflammation might be an effective therapeutic strategy to prevent the development of chronic neurological abnormalities.

n-3 Docosapentaenoic acid-derived protectin D1 promotes resolution of neuroinflammation and arrests epileptogenesis

Epilepsy therapy is based on drugs that treat the symptoms rather than the underlying mechanisms of the disease (epileptogenesis). There are no treatments for preventing seizures or improving disease prognosis, including neurological comorbidities. The search of pathogenic mechanisms of epileptogenesis highlighted that neuroinflammatory cytokines [i.e. interleukin-1β (IL-1β), tumour necrosis factor-α (Tnf-α)] are induced in human and experimental epilepsies, and contribute to seizure generation in animal models. A major role in controlling the inflammatory response is played by specialized pro-resolving lipid mediators acting on specific G-protein coupled receptors. Of note, the role that these pathways have in epileptogenic tissue remains largely unexplored. Using a murine model of epilepsy, we show that specialized pro-resolving mechanisms are activated by status epilepticus before the onset of spontaneous seizures, but with a marked delay as compared to the neuroinflammatory response. This was assessed by measuring the time course of mRNA levels of 5-lipoxygenase (Alox5) and 15-lipoxygenase (Alox15), the key biosynthetic enzymes of pro-resolving lipid mediators, versus Il1b and Tnfa transcripts and proteins. In the same hippocampal tissue, we found a similar delayed expression of two main pro-resolving receptors, the lipoxin A₄ receptor/formyl peptide receptor 2 and the chemerin receptor. These receptors were also induced in the human hippocampus after status epilepticus and in patients with temporal lobe epilepsy. This evidence supports the hypothesis that the neuroinflammatory response is sustained by a failure to engage pro-resolving mechanisms during epileptogenesis. Lipidomic LC-MS/MS analysis showed that lipid mediator levels apt to resolve the neuroinflammatory response were also significantly altered in the hippocampus during epileptogenesis with a shift in the biosynthesis of several pro-resolving mediator families including the n-3 docosapentaenoic acid (DPA)-derived protectin D1. Of note, intracerebroventricular injection of this mediator during epileptogenesis in mice dose-dependently reduced the hippocampal expression of both Il1b and Tnfa mRNAs. This effect was associated with marked improvement in mouse weight recovery and rescue of cognitive deficit in the novel object recognition test. Notably, the frequency of spontaneous seizures was drastically reduced by 2-fold on average and the average seizure duration was shortened by 40% after treatment discontinuation. As a result, the total time spent in seizures was reduced by 3-fold in mice treated with n-3 DPA-derived protectin D1. Taken together, the present findings demonstrate that epilepsy is characterized by an inadequate engagement of resolution pathways. Boosting endogenous resolution responses significantly improved disease outcomes, providing novel treatment avenues.

In search of antiepileptogenic treatments for post-traumatic epilepsy

Post-traumatic epilepsy (PTE) is diagnosed in 20% of individuals with acquired epilepsy, and can impact significantly the quality of life due to the seizures and other functional or cognitive and behavioral outcomes of the traumatic brain injury (TBI) and PTE. There is no available antiepileptogenic or disease modifying treatment for PTE. Animal models of TBI and PTE have been developed, offering useful insights on the value of inflammatory, neurodegenerative pathways, hemorrhages and iron accumulation, calcium channels and other target pathways that could be used for treatment development. Most of the existing preclinical studies test efficacy towards pathologies of functional recovery after TBI, while a few studies are emerging testing the effects towards induced or spontaneous seizures. Here we review the existing preclinical trials testing new candidate treatments for TBI sequelae and PTE, and discuss future directions for efforts aiming at developing antiepileptogenic and disease-modifying treatments.

TNFα-Driven Astrocyte Purinergic Signaling during Epileptogenesis

The etiology of temporal lobe epilepsy is unclear, but proinflammatory molecules and disturbed neuron-glia communications are emerging as potential causers. A recent study (Nikolic et al. Glia 2018; https://doi.org/10.1002/glia.23519) revealed that pathologically elevated tumor necrosis factor α contributes to epileptogenesis, by boosting hyperexcitation through an autocrine mechanism involving purinergic signaling, astrocyte glutamate release, and modulation of neuronal transmitter release.

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.

Intranasally administered pitavastatin ameliorates pentylenetetrazol-induced neuroinflammation, oxidative stress and cognitive dysfunction

AIM

The present study aimed to evaluate the neuroprotective potential of intranasally administered pitavastatin in the PTZ-induced kindling model.

MATERIALS AND METHODS

Subconvulsant dose of PTZ (35 mg/kg, i.p) was administered on an alternate day until the development of kindling. Behavioural test, biochemical tests and inflammatory cytokines were estimated. Comparative molecular docking study of sodium valproate (VPA) and pitavastatin was performed to predict the binding affinity with GABA_A and GABA transaminase. Intranasally administered pitavastatin (0.5 mg/kg and 1 mg/kg) and VPA (200 mg/kg) were used to investigate its protective effect.

KEY FINDINGS

Comparative in-silico study showed docking score of -4.56 and -2.86 against GABA_A receptor whereas -5.56 and -1.86, against GABA transaminase. Root mean square deviation (RMSD) of 0.39A and 0.55A was found for pitavastatin and VPA, respectively. The present study showed the dose-dependent protective effect of intranasally administered pitavastatin and oral VPA against PTZ-induced seizure, cognitive impairment, oxidative stress, and neuroinflammation.

SIGNIFICANCE

Our findings suggest that the intranasally administered pitavastatin is potential therapeutic approach to managing PTZ-induced kindling and associated comorbid conditions via its antioxidant, anti-inflammatory, and anticonvulsant potential. Further, pitavastatin can modulate GABA_A receptor and GABA transaminase enzyme to ameliorate seizure. Meanwhile, more extensive studies are required to establish the molecular mechanism underlying the neuroprotective effect of pitavastatin.

Potential Role of miRNAs as Theranostic Biomarkers of Epilepsy

Epilepsy includes a group of disorders of the brain characterized by an enduring predisposition to generate epileptic seizures. Although familial epilepsy has a genetic component and heritability, the etiology of the majority of non-familial epilepsies has no known associated genetic mutations. In epilepsy, recent epigenetic profiles have highlighted a possible role of microRNAs in its pathophysiology. In particular, molecular profiling identifies a significant number of microRNAs (miRNAs) altered in epileptic hippocampus of both animal models and human tissues. In this review, analyzing molecular profiles of different animal models of epilepsy, we identified a group of 20 miRNAs commonly altered in different epilepsy-animal models. As emerging evidences highlighted the poor overlap between signatures of animal model tissues and human samples, we focused our analysis on miRNAs, circulating in human biofluids, with a principal role in epilepsy hallmarks, and we identified a group of 8 diagnostic circulating miRNAs. We discussed the functional role of these 8 miRNAs in the epilepsy hallmarks. A few of them have also been proposed as therapeutic molecules for epilepsy treatment, revealing a great potential for miRNAs as theranostic molecules in epilepsy.

Role of inflammation in epilepsy and neurobehavioral comorbidities: Implication for therapy

Epilepsy is a devastating condition affecting around 70 million people worldwide. Moreover, the quality of life of people with epilepsy (PWE) is worsened by a series of comorbidities. The neurobehavioral comorbidities discussed herein share a reciprocal and complex relationship with epilepsy, which ultimately complicates the treatment process in PWE. Understanding the mechanistic pathway by which these comorbidities are associated with epilepsy might be instrumental in developing therapeutic interventions. Inflammatory cytokine signaling in the brain regulates important brain functions including neurotransmitter metabolism, neuroendocrine function, synaptic plasticity, dopaminergic transmission, the kynurenine pathway, and affects neurogenesis as well as the neural circuitry of moods. In this review, we hypothesize that the complex relationship between epilepsy and its related comorbidities (cognitive impairment, depression, anxiety, autism, and schizophrenia) can be unraveled through the inflammatory mechanism that plays a prominent role in all these individual conditions. An ample amount of evidence is available reporting the role of inflammation in epilepsy and all individual comorbid condition but their complex relationship with epilepsy has not yet been explored through the prospective of inflammatory pathway. Our review suggests that epilepsy and its neurobehavioral comorbidities are associated with elevated levels of several key inflammatory markers. This review also sheds light on the mechanistic association between epilepsy and its neurobehavioral comorbidities. Moreover, we analyzed several anti-inflammatory therapies available for epilepsy and its neurobehavioral comorbidities. We suggest, these anti-inflammatory therapies might be a possible intervention and could be a promising strategy for preventing epileptogenesis and its related neurobehavioral comorbidities.

Intrinsic Inflammation Is a Potential Anti-Epileptogenic Target in the Organotypic Hippocampal Slice Model

Understanding the mechanisms of epileptogenesis is essential to develop novel drugs that could prevent or modify the disease. Neuroinflammation has been proposed as a promising target for therapeutic interventions to inhibit the epileptogenic process that evolves from traumatic brain injury. However, it remains unclear whether cytokine-related pathways, particularly TNFα signaling, have a critical role in the development of epilepsy. In this study, we investigated the role of innate inflammation in an in vitro model of post-traumatic epileptogenesis. We combined organotypic hippocampal slice cultures, representing an in vitro model of post-traumatic epilepsy, with multi-electrode array recordings to directly monitor the development of epileptiform activity and to examine the concomitant changes in cytokine release, cell death, and glial cell activation. We report that synchronized ictal- and interictal-like activities spontaneously evolve in this culture. Dynamic changes in the release of the pro-inflammatory cytokines IL-1β, TNFα, and IL-6 were observed throughout the culture period (3 to 21 days in vitro) with persistent activation of microglia and astrocytes. We found that neutralizing TNFα with a polyclonal antibody significantly reduced ictal discharges, and this effect lasted for 1 week after antibody washout. Neither phenytoin nor an anti-IL-6 polyclonal antibody was efficacious in inhibiting the development of epileptiform activity. Our data show a sustained effect of the anti-TNFα antibody on the ictal progression in organotypic hippocampal slice cultures supporting the critical role of inflammatory mediators in epilepsy and establishing a proof-of-principle evidence for the utility of this preparation to test the therapeutic effects of anti-inflammatory treatments.

Intrinsic Inflammation Is a Potential Anti-Epileptogenic Target in the Organotypic Hippocampal Slice Model

Understanding the mechanisms of epileptogenesis is essential to develop novel drugs that could prevent or modify the disease. Neuroinflammation has been proposed as a promising target for therapeutic interventions to inhibit the epileptogenic process that evolves from traumatic brain injury. However, it remains unclear whether cytokine-related pathways, particularly TNFα signaling, have a critical role in the development of epilepsy. In this study, we investigated the role of innate inflammation in an in vitro model of post-traumatic epileptogenesis. We combined organotypic hippocampal slice cultures, representing an in vitro model of post-traumatic epilepsy, with multi-electrode array recordings to directly monitor the development of epileptiform activity and to examine the concomitant changes in cytokine release, cell death, and glial cell activation. We report that synchronized ictal- and interictal-like activities spontaneously evolve in this culture. Dynamic changes in the release of the pro-inflammatory cytokines IL-1β, TNFα, and IL-6 were observed throughout the culture period (3 to 21 days in vitro) with persistent activation of microglia and astrocytes. We found that neutralizing TNFα with a polyclonal antibody significantly reduced ictal discharges, and this effect lasted for 1 week after antibody washout. Neither phenytoin nor an anti-IL-6 polyclonal antibody was efficacious in inhibiting the development of epileptiform activity. Our data show a sustained effect of the anti-TNFα antibody on the ictal progression in organotypic hippocampal slice cultures supporting the critical role of inflammatory mediators in epilepsy and establishing a proof-of-principle evidence for the utility of this preparation to test the therapeutic effects of anti-inflammatory treatments.

α-Asarone Attenuates Cognitive Deficit in a Pilocarpine-Induced Status Epilepticus Rat Model via a Decrease in the Nuclear Factor-κB Activation and Reduction in Microglia Neuroinflammation

Background

Temporal lobe epilepsy (TLE) is one of the most drug-resistant types of epilepsy with about 80% of TLE patients falling into this category. Increasing evidence suggests that neuroinflammation, which has a critical role in the epileptogenesis of TLE, is associated with microglial activation. Therefore, agents that act toward the alleviation in microglial activation and the attenuation of neuroinflammation are promising candidates to treat TLE. α-Asarone is a major active ingredient of the Acori Graminei Rhizoma used in Traditional Chinese Medicine, which has been used to improve various disease conditions including stroke and convulsions. In addition, an increasing number of studies suggested that α-asarone can attenuate microglia-mediated neuroinflammation. Thus, we hypothesized that α-asarone is a promising neuroprotective agent for the treatment of the TLE.

Methods

The present study evaluated the therapeutic effects of α-asarone on microglia-mediated neuroinflammation and neuroprotection in vitro and in vivo, using an untreated control group, a status epilepticus (SE)-induced group, and an SE-induced α-asarone pretreated group. A pilocarpine-induced rat model of TLE was established to investigate the neuroprotective effects of α-asarone in vivo. For the in vitro study, lipopolysaccharide (LPS)-stimulated primary cultured microglial cells were used.

Results

The results indicated that the brain microglial activation in the rats of the SE rat model led to important learning and memory deficit. Preventive treatment with α-asarone restrained microglial activation and reduced learning and memory deficit. In the in vitro studies, α-asarone significantly suppressed proinflammatory cytokine production in primary cultured microglial cells and attenuated the LPS-stimulated neuroinflammatory responses. Our mechanistic study revealed that α-asarone inhibited inflammatory processes by regulation the transcription levels of kappa-B, by blocking the degradation pathway of kappa B-alpha [inhibitor kappa B-alpha (IκB-α)] and kappa B-beta (IκB-β) kinase in both the SE rats and in primary cultured microglial cells.

Conclusion

Taken together, these data demonstrate that α-asarone is a promising neuroprotective agent for the prevention and treatment of microglia-mediated neuroinflammatory conditions including TLE, for which further assessment studies are pertinent.

Fingolimod Exerts only Temporary Antiepileptogenic Effects but Longer-Lasting Positive Effects on Behavior in the WAG/Rij Rat Absence Epilepsy Model

One of the major challenges in the epilepsy field is identifying disease-modifying drugs in order to prevent or delay spontaneous recurrent seizure onset or to cure already established epilepsy. It has been recently reported that fingolimod, currently approved for the treatment of relapsing-remitting multiple sclerosis, has demonstrated antiepileptogenic effects in 2 different preclinical models of acquired epilepsy. However, to date, no data exist regarding the role of fingolimod against genetic epilepsy. Therefore, we have addressed this issue by studying the effects of fingolimod in Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats, a well-established genetic model of absence epilepsy, epileptogenesis, and neuropsychiatric comorbidity. Our results have demonstrated that an early long-term treatment with fingolimod (1 mg/kg/day), started before absence seizure onset, has both antiepileptogenic and antidepressant-like effects in WAG/Rij rats. However, these effects were transitory, as 5 months after treatment discontinuation, both absence seizure and depressive like-behavior returned to control levels. Furthermore, a temporary reduction of mTOR signaling pathway activity, indicated by reduced phosphorylated mammalian target of rapamycin and phosphorylated p70S6k levels, and by increased phosphorylated Akt in WAG/Rij rats of 6 months of age accompanied the transitory antiepileptogenic effects of fingolimod. Surprisingly, fingolimod has demonstrated longer-lasting positive effects on cognitive decline in this strain. This effect was accompanied by an increased acetylation of lysine 8 of histone H4 (at both 6 and 10 months of age). In conclusion, our results support the antiepileptogenic effects of fingolimod. However, the antiepileptogenic effects were transitory. Moreover, fingolimod might also have a positive impact on animal behavior and particularly in protecting the development of memory decline.

Inflammation in Epileptic Encephalopathies

West syndrome (WS) is an infantile epileptic encephalopathy that manifests with infantile spasms (IS), hypsarrhythmia (in ~60% of infants), and poor neurodevelopmental outcomes. The etiologies of WS can be structural-metabolic pathologies (~60%), genetic (12%-15%), or of unknown origin. The current treatment options include hormonal treatment (adrenocorticotropic hormone and high-dose steroids) and the GABA aminotransferase inhibitor vigabatrin, while ketogenic diet can be given as add-on treatment in refractory IS. There is a need to identify new therapeutic targets and more effective treatments for WS. Theories about the role of inflammatory pathways in the pathogenesis and treatment of WS have emerged, being supported by both clinical and preclinical data from animal models of WS. Ongoing advances in genetics have revealed numerous genes involved in the pathogenesis of WS, including genes directly or indirectly involved in inflammation. Inflammatory pathways also interact with other signaling pathways implicated in WS, such as the neuroendocrine pathway. Furthermore, seizures may also activate proinflammatory pathways raising the possibility that inflammation can be a consequence of seizures and epileptogenic processes. With this targeted review, we plan to discuss the evidence pro and against the following key questions. Does activation of inflammatory pathways in the brain cause epilepsy in WS and does it contribute to the associated comorbidities and progression? Can activation of certain inflammatory pathways be a compensatory or protective event? Are there interactions between inflammation and the neuroendocrine system that contribute to the pathogenesis of WS? Does activation of brain inflammatory signaling pathways contribute to the transition of WS to Lennox-Gastaut syndrome? Are there any lead candidates or unexplored targets for future therapy development for WS targeting inflammation?

Recent advances in epilepsy

This paper reviews advances in epilepsy in recent years with an emphasis on therapeutics and underlying mechanisms, including status epilepticus, drug and surgical treatments. Lessons from rarer epilepsies regarding the relationship between epilepsy type, mechanisms and choice of antiepileptic drugs (AED) are explored and data regarding AED use in pregnancy are reviewed. Concepts evolving towards a move from treating seizures to treating epilepsy are discussed, both in terms of the mechanisms of epileptogenesis, and in terms of epilepsy's broader comorbidity, especially depression.

The effects of topiramate on lipopolysaccharide (LPS)-induced proinflammatory cytokine release from primary rat microglial cell cultures

A growing body of evidence suggests that inflammatory processes and activation of glial cells could contribute to seizures and epileptogenesis. In various animal studies on epilepsy, proinflammatory cytokines have been demonstrated to exert a proconvulsive activity. On the other hand, it is suggested that antiepileptic drugs could modulate immune system activity. The aim of the present study was to investigate whether topiramate, a new generation antiepileptic drug with a complex mechanism of action, could affect the lipopolysaccharide (LPS)-induced release of TNF-α, IL-1β and IL-6 from primary rat microglial cell cultures. Proinflammatory cytokines were measured in supernatants of primary rat microglial cell culture with enzyme-linked immunosorbent assay kits. Additionally, the effect of the drug on LPS-evoked changes in mitochondrial metabolic activity was evaluated with the aid of the MTT test. Topiramate (1, 10, 100μg/ml; 24h incubation) produced a statistically significant decrease in LPS-stimulated IL-1β and IL-6 levels from primary rat microglial cells in a concentration-dependent manner. The drug used at a concentration of 100μg/ml also significantly suppressed TNF-α release. Incubation of microglial cells with topiramate for 24h prevented the LPS-induced increase in their mitochondrial activity. It is suggested that the anti-cytokine action of topiramate could provide an additional mechanism in its antiepileptic activity.

Anti-Inflammatory Small Molecules To Treat Seizures and Epilepsy: From Bench to Bedside

As a crucial component of brain innate immunity, neuroinflammation initially contributes to neuronal tissue repair and maintenance. However, chronic inflammatory processes within the brain and associated blood-brain barrier (BBB) impairment often cause neurotoxicity and hyperexcitability. Mounting evidence points to a mutual facilitation between inflammation and epilepsy, suggesting that blocking the undesired inflammatory signaling within the brain might provide novel strategies to treat seizures and epilepsy. Neuroinflammation is primarily characterized by the upregulation of proinflammatory mediators in epileptogenic foci, among which cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2), interleukin-1β (IL-1β), transforming growth factor-β (TGF-β), toll-like receptor 4 (TLR4), high-mobility group box 1 (HMGB1), and tumor necrosis factor-α (TNF-α) have been extensively studied. Small molecules that specifically target these key proinflammatory perpetrators have been evaluated for antiepileptic and antiepileptogenic effects in animal models. These important preclinical studies provide new insights into the regulation of inflammation in epileptic brains and guide drug discovery efforts aimed at developing novel anti-inflammatory therapies for seizures and epilepsy.

Apoptosis through Death Receptors in Temporal Lobe Epilepsy-Associated Hippocampal Sclerosis

Seizure models have demonstrated that neuroinflammation and neurodegeneration are preponderant characteristics of epilepsy. Considering the lack of clinical studies, our aim is to investigate the extrinsic pathway of apoptosis in pharmacoresistant temporal lobe epilepsy (TLE) associated with hippocampal sclerosis (HS) patients, TLE(HS). By a specific death receptor-mediated apoptosis array plate, 31 upregulated targets were revealed in the sclerotic hippocampus from TLE(HS) patients. Amongst them are the encoding genes for ligands (FASLG, TNF, and TNFSF10) and death receptors (FAS, TNFRSF1A, TNFRSF10A, and TNFRSF10B). In addition, we evaluated the hippocampal relative mRNA expression of the two TNF receptors, TNFRSF1A and TNFRSF1B, in patients, being both upregulated (n = 14; P < 0.01 and P < 0.04, resp.) when compared to the post mortem control group (n = 4). Our results have clearly suggested that three different death receptor apoptotic systems may be associated with the maintenance and progression of TLE-associated HS: (1) TNF-TNFRSF1A, (2) FASLG-FAS, and (3) TNFSF10-TNFRSF10A/B. Their effects on epilepsy are still scarcely comprehended. Our study points out to TNF and TNF receptor superfamily pathways as important targets for pharmacological studies regarding the benefits of an anti-inflammatory therapy in these patients.

Infections, inflammation and epilepsy

Epilepsy is the tendency to have unprovoked epileptic seizures. Anything causing structural or functional derangement of brain physiology may lead to seizures, and different conditions may express themselves solely by recurrent seizures and thus be labelled "epilepsy." Worldwide, epilepsy is the most common serious neurological condition. The range of risk factors for the development of epilepsy varies with age and geographic location. Congenital, developmental and genetic conditions are mostly associated with the development of epilepsy in childhood, adolescence and early adulthood. Head trauma, infections of the central nervous system (CNS) and tumours may occur at any age and may lead to the development of epilepsy. Infections of the CNS are a major risk factor for epilepsy. The reported risk of unprovoked seizures in population-based cohorts of survivors of CNS infections from developed countries is between 6.8 and 8.3 %, and is much higher in resource-poor countries. In this review, the various viral, bacterial, fungal and parasitic infectious diseases of the CNS which result in seizures and epilepsy are discussed. The pathogenesis of epilepsy due to brain infections, as well as the role of experimental models to study mechanisms of epileptogenesis induced by infectious agents, is reviewed. The sterile (non-infectious) inflammatory response that occurs following brain insults is also discussed, as well as its overlap with inflammation due to infections, and the potential role in epileptogenesis. Furthermore, autoimmune encephalitis as a cause of seizures is reviewed. Potential strategies to prevent epilepsy resulting from brain infections and non-infectious inflammation are also considered.

Immunity and Inflammation in Epilepsy

This review reports the available evidence on the activation of the innate and adaptive branches of the immune system and the related inflammatory processes in epileptic disorders and the putative pathogenic role of inflammatory processes developing in the brain, as indicated by evidence from experimental and clinical research. Indeed, there is increasing knowledge supporting a role of specific inflammatory mediators and immune cells in the generation and recurrence of epileptic seizures, as well as in the associated neuropathology and comorbidities. Major challenges in this field remain: a better understanding of the key inflammatory pathogenic pathways activated in chronic epilepsy and during epileptogenesis, and how to counteract them efficiently without altering the homeostatic tissue repair function of inflammation. The relevance of this information for developing novel therapies will be highlighted.

Modulation of neuronal excitability by immune mediators in epilepsy

A complex set of inflammatory molecules and their receptors has been described in epileptogenic foci in different forms of pharmacoresistant epilepsies. By activating receptor-mediated pathways in neurons, these molecules have profound neuromodulatory effects that are distinct from their canonical activation of immune functions. Importantly, the neuromodulatory actions of some inflammatory molecules contribute to hyperexcitability in neural networks that underlie seizures. This review summarizes recent findings related to the role of cytokines (IL-1beta and TNF-alpha) and danger signals (HMGB1) in decreasing seizure threshold, thereby contributing to seizure generation and the associated neuropathology. We will discuss preclinical studies suggesting that pharmacological inhibition of specific inflammatory signals may be useful to treat drug-resistant seizures in human epilepsy, and possibly arrest epileptogenesis in individuals at risk of developing the disease.

Community structure analysis of transcriptional networks reveals distinct molecular pathways for early- and late-onset temporal lobe epilepsy with childhood febrile seizures

Age at epilepsy onset has a broad impact on brain plasticity and epilepsy pathomechanisms. Prolonged febrile seizures in early childhood (FS) constitute an initial precipitating insult (IPI) commonly associated with mesial temporal lobe epilepsy (MTLE). FS-MTLE patients may have early disease onset, i.e. just after the IPI, in early childhood, or late-onset, ranging from mid-adolescence to early adult life. The mechanisms governing early (E) or late (L) disease onset are largely unknown. In order to unveil the molecular pathways underlying E and L subtypes of FS-MTLE we investigated global gene expression in hippocampal CA3 explants of FS-MTLE patients submitted to hippocampectomy. Gene coexpression networks (GCNs) were obtained for the E and L patient groups. A network-based approach for GCN analysis was employed allowing: i) the visualization and analysis of differentially expressed (DE) and complete (CO) - all valid GO annotated transcripts - GCNs for the E and L groups; ii) the study of interactions between all the system's constituents based on community detection and coarse-grained community structure methods. We found that the E-DE communities with strongest connection weights harbor highly connected genes mainly related to neural excitability and febrile seizures, whereas in L-DE communities these genes are not only involved in network excitability but also playing roles in other epilepsy-related processes. Inversely, in E-CO the strongly connected communities are related to compensatory pathways (seizure inhibition, neuronal survival and responses to stress conditions) while in L-CO these communities harbor several genes related to pro-epileptic effects, seizure-related mechanisms and vulnerability to epilepsy. These results fit the concept, based on fMRI and behavioral studies, that early onset epilepsies, although impacting more severely the hippocampus, are associated to compensatory mechanisms, while in late MTLE development the brain is less able to generate adaptive mechanisms, what has implications for epilepsy management and drug discovery.

Complex alterations in microglial M1/M2 markers during the development of epilepsy in two mouse models

OBJECTIVE

To characterize the changes in microglial proinflammatory M1 and antiinflammatory M2 marker expression during epileptogenesis in the chronic pilocarpine and intrahippocampal kainate models.

METHODS

M1-activated microglia express proinflammatory cytokines driving infiltration of cells, whereas M2-activated microglia are more reparative, promoting phagocytosis of debris and expression of proteins associated with cellular stability and repair. Microglial markers were characterized as acute (3 days after status epilepticus [SE]), early chronic (21 days post-SE), and late chronic epileptic (5-12 months post-SE) time points. Following pilocarpine-SE, microglial markers were assessed by flow cytometry. Quantitative real-time polymerase chain reaction (RT-PCR) was used to measure messenger RNA (mRNA) levels of selected M1 (interleukin [IL] 1β, tumor necrosis factor α [TNFα] cluster of differentiation [CD],CD16, and CD86), interleukin-6 [IL-6], interleukin-12 [IL-12], Fc receptors 16, and CD86) and M2 (arginase 1 [Arg1], chitinase-3-like protein [Ym1], found in inflammatory zone [FIZZ-1] [FIZZ-1], mannose receptor C type-1 [CD206], interleukin-4 [IL-4], and interleukin-10 (IL-10)) markers in both models. Video-electroencephalography (EEG) recordings were used to quantify late chronic seizure frequency.

RESULTS

Three days post-SE microglia in the pilocarpine model expressed M1 and M2 markers, but only M1 markers were upregulated after kainate-induced SE. After 3 weeks, M1/M2 marker expression was largely ablated in the hippocampal formation of both models. Small mRNA level increases of CD11b, glial fibrillary acidic protein (GFAP), and IL-1β were found in the pilocarpine model, consistent with IL-1β contributing to spontaneous seizures, whereas mRNA levels of TNFα and Ym1 were decreased. In the late chronic phase, some M1/M2 markers, IL-1β, TNFα, Arg1, Ym1, and CD206, resurged in the kainate, but not pilocarpine model, which may reflect and/or contribute to highly frequent seizures in kainate-SE mice.

SIGNIFICANCE

The common M1 upregulation acutely post-SE may signal a role early in epileptogenesis, with a more pure "inflamed" central nervous system state after kainate-SE, potentially contributing to the development of more frequent seizures. The difference may also be due to the contribution of peripheral inflammation after pilocarpine injection. In summary, the microglial inflammatory response during epileptogenesis is complex, varies between models, and appears to correlate with chronic seizure frequency.