Modulation of peripheral cytotoxic cells and ictogenesis in a model of seizures

Neuroglia in epilepsy

Epilepsy is a group of neurologic diseases characterized by spontaneous, repetitive disruption to neuronal activity. Neurons have been at the core of epilepsy research efforts, and pharmacotherapies historically have been generated by targeting neuronal mechanisms. As a result, most currently available antiseizure drugs (ASDs) work to either decrease excitatory glutamatergic neurotransmission or to increase inhibitory GABAergic neurotransmission. However, ASDs may have undesirable side effects on cognition and also fail to control seizures in approximately 30% of epilepsy patients. In recent years, glia have surfaced as essential modulators of neuronal function in health and disease. The redirection of focus onto neuroglia provides new perspectives and opportunities to generate novel therapeutic targets that may treat refractory epilepsy and diminish the unwanted side effect profile of current treatments. In this chapter, we discuss the contribution of astroglia, oligodendroglia, and microglia to the genesis, development, and progression of epilepsy, and we highlight key enzymes, receptors, transporters, and channels that may be pursued as nonneuronal targets for novel ASDs.

[Yigong San improves learning and memory functions of APP/PS1 transgenic mice by regulating brain fluid metabolism]

OBJECTIVE

To explore the mechanism by which Yigong San (YGS) improves learning and memory abilities of APP/PS1 transgenic mice in light of cerebral fluid metabolism regulation.

METHODS

Three-month-old male APP/PS1 transgenic mice and wild-type C57BL/6 mice were both randomized into control group, model group, donepezil (1.67 mg/kg) group, and YGS (7.5 g/kg) group and received the corresponding treatments via gavage once daily for one month. After the treatments, the mice were assessed for learning and memory functions using Morris water maze test and examined for hippocampal and cortical pathologies and amyloid plaques using HE, immunohistochemical and thioflavin S staining; ELISA and Evans blue method were used for detecting Aβ1-40 and Aβ1-42 levels in the brain tissue and serum and assessing blood-brain barrier (BBB) integrity. Immunofluorescence colocalization was used to investigate AQP4 polarization on astrocytes. Western blotting was performed to detect the expressions of VE-cadherin, ZO-1, occludin, β-amyloid precursor protein (APP), BACE1, insulin-degrading enzyme (IDE), LRP1, RAGE, and AQP4 proteins.

RESULTS

Compared with the control mice, APP/PS1 mice showed significant impairment of learning and memory abilities, increased degeneration or necrosis of hippocampal and cortical neurons, pathological scores, Aβ-positive plaques, elevated Aβ1-40 and Aβ1-42 levels in the brain tissue and serum, increased BBB permeability, upregulated RAGE expression, lowered expressions of VE-cadherin, LRP1, ZO-1, occludin, and AQP4 proteins, and reduced AQP4- expressing GFAP-positive cells. YGS treatment significantly improved the performance of the transgenic mice in Morris water maze test, reduced hippocampal and cortical pathologies and Aβ-positive plaques, and ameliorated the abnormal changes in Aβ1-40 and Aβ1-42 levels, BBB permeability, protein expressions of RAGE, VE-cadherin, LRP1, ZO-1, occludin and AQP4, and the number of AQP4-expressing GFAP-positive cells.

CONCLUSION

YGS improves learning and memory changes in APP/PS1 mice by ameliorating neuronal damage and Aβ pathology in the brain and regulating brain fluid metabolism.

[Yigong San improves cognitive decline in a rat model of Alzheimer's disease by regulating intestinal microorganisms]

OBJECTIVE

To investigate the effect of Yigong San (YGS) on learning and memory abilities of rats with lipopolysaccharide (LPS)‑induced cognitive decline and explore its possible mechanism in light of intestinal microbiota.

METHODS

Forty SD rats were randomly divided into control group, model group, donepezil (1.3 mg/kg) group, and high-dose (5.25 g/kg) and low-dose (2.63 g/kg) YGS treatment groups. After 24 days of treatment with the corresponding drugs or water by gavage, the rats in the latter 4 groups received an intraperitoneal injection of LPS (0.5 mg/kg) to establish models of Alzheimer's disease (AD). Water maze test and HE staining were used to evaluate the changes in learning and memory abilities and pathomorphology of the hippocampus. The changes in gut microbial species of the rats were analyzed with 16S rRNA sequencing, and the levels of IL-6, TNF-α, and IL-1β in the brain tissue and serum were detected using ELISA.

RESULTS

Compared with the AD model group, the YGS-treated rats showed significantly shortened escape latency on day 5 after modeling, reduced neuronal degeneration and necrosis in the hippocampus, lowered pathological score of cell damage, and decreased levels IL-6, TNF-α and IL-1β in the brain tissue and serum. The YGS-treated rats showed also obvious reduction of Alpha diversity indicators (ACE and Chao1) of intestinal microbiota with significantly increased abundance of Prevotellaceae species at the family level and decreased abundance of Desulfovibrionaceae, which were involved in such metabolic signaling pathways as cell community prokaryotes, membrane transport, and energy metabolism.

CONCLUSION

YGS improves learning and memory abilities and hippocampal pathomorphology in AD rat models possibly by regulating the abundance of intestinal microbial species such as Prevotellaceae to affect the metabolic pathways for signal transduction, cofactors, and vitamin metabolism.

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

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

CNS autoimmune response in the MAM/pilocarpine rat model of epileptogenic cortical malformation

The development of seizures in epilepsy syndromes associated with malformations of cortical development (MCDs) has traditionally been attributed to intrinsic cortical alterations resulting from abnormal network excitability. However, recent analyses at single-cell resolution of human brain samples from MCD patients have indicated the possible involvement of adaptive immunity in the pathogenesis of these disorders. By exploiting the MethylAzoxyMethanol (MAM)/pilocarpine (MP) rat model of drug-resistant epilepsy associated with MCD, we show here that the occurrence of status epilepticus and subsequent spontaneous recurrent seizures in the malformed, but not in the normal brain, are associated with the outbreak of a destructive autoimmune response with encephalitis-like features, involving components of both cell-mediated and humoral immune responses. The MP brain is characterized by blood-brain barrier dysfunction, marked and persisting CD8+ T cell invasion of the brain parenchyma, meningeal B cell accumulation, and complement-dependent cytotoxicity mediated by antineuronal antibodies. Furthermore, the therapeutic treatment of MP rats with the immunomodulatory drug fingolimod promotes both antiepileptogenic and neuroprotective effects. Collectively, these data show that the MP rat could serve as a translational model of epileptogenic cortical malformations associated with a central nervous system autoimmune response. This work indicates that a preexisting brain maldevelopment predisposes to a secondary autoimmune response, which acts as a precipitating factor for epilepsy and suggests immune intervention as a therapeutic option to be further explored in epileptic syndromes associated with MCDs.

Biallelic CRELD1 variants cause a multisystem syndrome, including neurodevelopmental phenotypes, cardiac dysrhythmias, and frequent infections

PURPOSE

We sought to delineate a multisystem disorder caused by recessive cysteine-rich with epidermal growth factor-like domains 1 (CRELD1) gene variants.

METHODS

The impact of CRELD1 variants was characterized through an international collaboration utilizing next-generation DNA sequencing, gene knockdown, and protein overexpression in Xenopus tropicalis, and in vitro analysis of patient immune cells.

RESULTS

Biallelic variants in CRELD1 were found in 18 participants from 14 families. Affected individuals displayed an array of phenotypes involving developmental delay, early-onset epilepsy, and hypotonia, with about half demonstrating cardiac arrhythmias and some experiencing recurrent infections. Most harbored a frameshift in trans with a missense allele, with 1 recurrent variant, p.(Cys192Tyr), identified in 10 families. X tropicalis tadpoles with creld1 knockdown displayed developmental defects along with increased susceptibility to induced seizures compared with controls. Additionally, human CRELD1 harboring missense variants from affected individuals had reduced protein function, indicated by a diminished ability to induce craniofacial defects when overexpressed in X tropicalis. Finally, baseline analyses of peripheral blood mononuclear cells showed similar proportions of immune cell subtypes in patients compared with healthy donors.

CONCLUSION

This patient cohort, combined with experimental data, provide evidence of a multisystem clinical syndrome mediated by recessive variants in CRELD1.

Cytokines in New-Onset Refractory Status Epilepticus Predict Outcomes

OBJECTIVE

The objective of this study was to investigate inflammation using cerebrospinal fluid (CSF) and serum cytokines/chemokines in patients with new-onset refractory status epilepticus (NORSE) to better understand the pathophysiology of NORSE and its consequences.

METHODS

Patients with NORSE (n = 61, including n = 51 cryptogenic), including its subtype with prior fever known as febrile infection-related epilepsy syndrome (FIRES), were compared with patients with other refractory status epilepticus (RSE; n = 37), and control patients without SE (n = 52). We measured 12 cytokines/chemokines in serum or CSF samples using multiplexed fluorescent bead-based immunoassay detection. Cytokine levels were compared between patients with and without SE, and between the 51 patients with cryptogenic NORSE (cNORSE) and the 47 patients with a known-etiology RSE (NORSE n = 10, other RSE n = 37), and correlated with outcomes.

RESULTS

A significant increase of IL-6, TNF-α, CXCL8/IL-8, CCL2, MIP-1α, and IL-12p70 pro-inflammatory cytokines/chemokines was observed in patients with SE compared with patients without SE, in serum and CSF. Serum innate immunity pro-inflammatory cytokines/chemokines (CXCL8, CCL2, and MIP-1α) were significantly higher in patients with cNORSE compared to non-cryptogenic RSE. Patients with NORSE with elevated innate immunity serum and CSF cytokine/chemokine levels had worse outcomes at discharge and at several months after the SE ended.

INTERPRETATION

We identified significant differences in innate immunity serum and CSF cytokine/chemokine profiles between patients with cNORSE and non-cryptogenic RSE. The elevation of innate immunity pro-inflammatory cytokines in patients with NORSE correlated with worse short- and long-term outcomes. These findings highlight the involvement of innate immunity-related inflammation, including peripherally, and possibly of neutrophil-related immunity in cNORSE pathogenesis and suggest the importance of utilizing specific anti-inflammatory interventions. ANN NEUROL 2023.

From neurons to the neuro-glio-vascular unit: Seizures and brain homeostasis in networks

While seizures are undoubtedly neuronal events, an ensemble of auxiliary brain cells profoundly shapes synaptic transmission in health and disease conditions. Endothelial-astrocyte-pericyte assemblies at the blood-brain barrier (BBB) and neuroglia within the neuro-glio-vascular unit (NGVU) finely tune brain parenchymal homeostasis, safeguarding the ionic and molecular compositions of the interstitial fluid. BBB permeability with neuroinflammation and the resulting loss of brain homeostatic control are unifying mechanisms sustaining aberrant neuronal discharges, with temporal specificities linked to acute (head trauma, stroke, infections) and pre-existent (genetic) or chronic ( dysplasia, tumors, neurodegenerative disorders) pathological conditions. Within this research template, one hypothesis is that the topography of BBB damage and neuroinflammation could associate with symptoms, e.g., limbic structures for seizures or pre-frontal for psychiatric episodes. Another uncharted matter is whether seizure activity, without tissue lesions or sclerosis, is sufficient to promote stable cellular-level maladaptations in networks. Contingent to localization and duration, BBB damage and inflammation forecast pathological trajectories, and the concept of an epileptic NGVU could enable time-sensitive biomarkers to predict disease progression. The coherence between electrographic, imaging and molecular NGVU biomarkers could be established from the epileptogenic to the propagating zones. This paradigm shift could lead to new diagnostic and therapeutic modalities germane to specific epilepsies or when seizure activity represents a comorbidity.

The correlation of temporal changes of neutrophil-lymphocyte ratio with seizure severity and the following seizure tendency in patients with epilepsy

Background

Changes in the neutrophil-lymphocyte ratio (NLR) has been reported to be associated with epilepsy. Here we aim to investigate the correlation of temporal changes of NLR level with seizure severity and the follow-up seizure attacks in patients with epilepsy (PWE).

Methods

We performed a retrospective analysis of the laboratory data including leukocyte count and NLR within 24 h of acute seizure and during the follow-up period of 5–14 days after acute seizure (NLR1, NLR2, respectively) in 115 PWE, and 98 healthy individuals were included as controls in this study. The correlation of laboratory data with seizure types, etiology of epilepsy, anti-seizure drugs (ASDs), seizure severity, and the follow-up seizure attacks in PWE was studied.

Results

Leukocyte count (P < 0.001) and NLR level (P < 0.001) were found significantly different between PWE and controls. On the other hand, a multivariable logistic regression analysis showed that NLR1 level (OR = 2.992, P = 0.001) and admission leukocyte (OR = 2.307, P = 0.002) were both independently associated with acute epileptic seizures. Especially, higher NLR1 level was significantly associated with status epileptics (P = 0.013) and recurrent seizures after admission (P < 0.001). Furthermore, the multivariable logistic regression analysis indicated that higher NLR1 was a predictor for the tendency of the following recurrent seizure attacks (OR = 1.144, P = 0.002). NLR2 was inversely correlated with ASDs taken (P = 0.011). Levels of NLR1 (r = 0.441, P < 0.001) and NLR2 (r = 0.241, P = 0.009) were both positively correlated with seizure severity.

Conclusions

Seizures were correlated with the alterations of systemic inflammation reflected by leukocyte and NLR. NLR1 and admission leukocyte were both independently associated with acute epileptic seizures. Higher NLR1 was associated with status epilepticus and independently predicted the tendency of the following epileptic seizures. NLR2 was significantly associated with ASDs taken. Besides, NLR may be used as a biomarker for seizure severity.

What is the Role of Lithium in Epilepsy?

Lithium is a well-known FDA-approved treatment for bipolar and mood disorders. Lithium has been an enigmatic drug with multifaceted actions involving various neurotransmitters and intricate cell signalling cascades. Recent studies highlight the neuroprotective and neurotrophic actions of lithium in amyotrophic lateral sclerosis, Alzheimer's disease, intracerebral hemorrhage, and epilepsy. Of note, lithium holds a significant interest in epilepsy, where the past reports expose its non-specific proconvulsant action, followed lately by numerous studies for anti-convulsant action. However, the exact mechanism of action of lithium for any of its effects is still largely unknown. The present review integrates findings from several reports and provides detailed possible mechanisms of how a single molecule exhibits marked pro-epileptogenic as well as anti-convulsant action. This review also provides clarity regarding the safety of lithium therapy in epileptic patients.

Hypoxemia increases blood-brain barrier permeability during extreme apnea in humans

Voluntary asphyxia imposed by static apnea challenges blood-brain barrier (BBB) integrity in humans through transient extremes of hypertension, hypoxemia and hypercapnia. In the present study, ten ultra-elite breath-hold divers performed two maximal dry apneas preceded by normoxic normoventilation (NX: severe hypoxemia and hypercapnia) and hyperoxic hyperventilation (HX: absence of hypoxemia with exacerbating hypercapnia) with measurements obtained before and immediately after apnea. Transcerebral exchange of NVU proteins (ELISA, Single Molecule Array) were calculated as the product of global cerebral blood flow (gCBF, duplex ultrasound) and radial arterial to internal jugular venous concentration gradients. Apnea duration increased from 5 m 6 s in NX to 15 m 59 s in HX (P = <0.001) resulting in marked elevations in gCBF and venous S100B, glial fibrillary acidic protein, ubiquitin carboxy-terminal hydrolase-L1 and total tau (all P < 0.05 vs. baseline). This culminated in net cerebral output reflecting mildly increased BBB permeability and increased neuronal-gliovascular reactivity that was more pronounced in NX due to more severe systemic and intracranial hypertension (P < 0.05 vs. HX). These findings identify the hemodynamic stress to which the apneic brain is exposed, highlighting the critical contribution of hypoxemia and not just hypercapnia to BBB disruption.

Neurovascular unit dysfunction as a mechanism of seizures and epilepsy during aging

The term neurovascular unit (NVU) describes the structural and functional liaison between specialized brain endothelium, glial and mural cells, and neurons. Within the NVU, the blood‐brain barrier (BBB) is the microvascular structure regulating neuronal physiology and immune cross‐talk, and its properties adapt to brain aging. Here, we analyze a research framework where NVU dysfunction, caused by acute insults or disease progression in the aging brain, represents a converging mechanism underlying late‐onset seizures or epilepsy and neurological or neurodegenerative sequelae. Furthermore, seizure activity may accelerate brain aging by sustaining regional NVU dysfunction, and a cerebrovascular pathology may link seizures to comorbidities. Next, we focus on NVU diagnostic approaches that could be tailored to seizure conditions in the elderly. We also examine the impending disease‐modifying strategies based on the restoration of the NVU and, more in general, the homeostatic control of anti‐ and pro‐inflammatory players. We conclude with an outlook on current pre‐clinical knowledge gaps and clinical challenges pertinent to seizure onset and conditions in an aging population.

Blood-Brain Barrier Dysfunction in CNS Disorders and Putative Therapeutic Targets: An Overview

The blood-brain barrier (BBB) is a fundamental component of the central nervous system (CNS). Its functional and structural integrity is vital to maintain the homeostasis of the brain microenvironment by controlling the passage of substances and regulating the trafficking of immune cells between the blood and the brain. The BBB is primarily composed of highly specialized microvascular endothelial cells. These cells’ special features and physiological properties are acquired and maintained through the concerted effort of hemodynamic and cellular cues from the surrounding environment. This complex multicellular system, comprising endothelial cells, astrocytes, pericytes, and neurons, is known as the neurovascular unit (NVU). The BBB strictly controls the transport of nutrients and metabolites into brain parenchyma through a tightly regulated transport system while limiting the access of potentially harmful substances via efflux transcytosis and metabolic mechanisms. Not surprisingly, a disruption of the BBB has been associated with the onset and/or progression of major neurological disorders. Although the association between disease and BBB disruption is clear, its nature is not always evident, specifically with regard to whether an impaired BBB function results from the pathological condition or whether the BBB damage is the primary pathogenic factor prodromal to the onset of the disease. In either case, repairing the barrier could be a viable option for treating and/or reducing the effects of CNS disorders. In this review, we describe the fundamental structure and function of the BBB in both healthy and altered/diseased conditions. Additionally, we provide an overview of the potential therapeutic targets that could be leveraged to restore the integrity of the BBB concomitant to the treatment of these brain disorders.

The pilocarpine model of mesial temporal lobe epilepsy: Over one decade later, with more rodent species and new investigative approaches

Fundamental work on the mechanisms leading to focal epileptic discharges in mesial temporal lobe epilepsy (MTLE) often rests on the use of rodent models in which an initial status epilepticus (SE) is induced by kainic acid or pilocarpine. In 2008 we reviewed how, following systemic injection of pilocarpine, the main subsequent events are the initial SE, the latent period, and the chronic epileptic state. Up to a decade ago, rats were most often employed and they were frequently analysed only behaviorally. However, the use of transgenic mice has revealed novel information regarding this animal model. Here, we review recent findings showing the existence of specific neuronal events during both latent and chronic states, and how optogenetic activation of specific cell populations modulate spontaneous seizures. We also address neuronal damage induced by pilocarpine treatment, the role of neuroinflammation, and the influence of circadian and estrous cycles. Updating these findings leads us to propose that the rodent pilocarpine model continues to represent a valuable tool for identifying the basic pathophysiology of MTLE.

Exercise-linked consequences on epilepsy

OBJECTIVE

Epilepsy is a brain disorder that leads to seizures and neurobiological, cognitive, psychological, and social consequences. Physical inactivity can contribute to worse epilepsy pathophysiology. Here, we review how physical exercise affects epilepsy physiopathology.

METHODS

An extensive literature search was performed and the mechanisms of physical exercise on epilepsy were discussed. The search was conducted in Scopus and PubMed. Articles with relevant information were included. Only studies written in English were considered.

RESULTS

The regular practice of physical exercise can be beneficial for individuals with neurodegenerative diseases, such as epilepsy by decreasing the production of pro-inflammatory and stress biomarkers, increasing socialization, and reducing the incidence of epileptic seizures. Physical exercise is also capable of reducing the symptoms of depression and anxiety in epilepsy. Physical exercise can also improve cognitive function in epilepsy. The regular practice of physical exercise enhances the levels of brain-derived neuro factor (BDNF) in the hippocampi, induces neurogenesis, inhibits oxidative stress and reactive gliosis, avoids cognitive impairment, and stimulates the production of dopamine in the epileptic brain.

CONCLUSION

Physical exercise is an excellent non-pharmacological tool that can be used in the treatment of epilepsy.

Hemocompatible L-Type amino acid transporter 1 (LAT1)-Utilizing prodrugs of perforin inhibitors can accumulate into the pancreas and alleviate inflammation-induced apoptosis

Cytolytic pore-forming protein, perforin, has been associated with autoimmune destruction of pancreatic β-cells in type 1 diabetes mellitus (T1DM) once released from CD8⁺ T cells. Curiously, perforinopathy has also been implicated in numerous brain diseases. Therefore, inhibitors of perforin have been in demand with targeted delivery in mind. l-Type amino acid transporter 1 (LAT1) is known to be expressed in both the above-mentioned target tissues, in the pancreas as well as in the brain. Thus, in the present study, the distribution of two LAT1-utilizing prodrugs of investigational perforin inhibitors into the pancreas was explored after intraperitoneal (i.p., 30 μmol/kg) bolus injection to mice. The effects of prodrug 1 were also studied in lipopolysaccharide (LPS)-induced in vitro (50 μg/mL) and in vivo (250 μg/kg x 3 days) apoptosis and pancreatitis models by determining the cellular apoptotic levels with human umbilical vein endothelial cells (HUVEC) and pancreatic caspase-3/-7 activity in mice. Furthermore, the biocompatibility of prodrug 1 was explored in human plasma and towards red blood cells. According to the results, both prodrugs were accumulated more effectively into the pancreas than their parent drugs (in addition to the brain that has been previously reported). Prodrug 1 (30 μmol/kg) also decreased the pancreatic caspase-3/-7 activity (52%) and with 2.5 μM concentration, the number of early and late apoptotic cells (32-53%). Since prodrug 1 was also found to be hemocompatible and not affecting human plasma hemostasis or inducing hemolysis of erythrocytes at the concentration <50 μM, it can be considered biocompatible in systemic circulation and ready to be studied in the future as a dual-acting drug candidate (in the pancreas and brain) in diseases like T1DM with neurodegenerative comorbidities.

Varying modalities of perinatal exposure to a pesticide cocktail elicit neurological adaptations in mice and zebrafish

Epidemiological indications connect maternal and developmental presence or exposure to pesticides with an increased risk for a spectrum of neurological trajectories. To provide pre-clinical data in support of this hypothesis, we used two distinct experimental models. First, female and male mice were fed immediately prior to mating, and the resulting pregnant dams were continously fed during gestation and lactation periods using chow pellets containing a cocktail of six pesticides at tolerable daily intake levels. Male and female offspring were then tracked for behavioral and in vivo electrophysiological adaptations. Second, a zebrafish model allowed us to screen toxicity and motor-behavior outcomes specifically associated with the developmental exposure to a low-to-high concentration range of the cocktail and of each individual pesticide. Here, we report anxiety-like behavior in aging male mice maternally exposed to the cocktail, as compared to age and gender matched sham animals. In parallel, in vivo electrocorticography revealed a decrease in gamma (40-80 Hz) and an increase of theta (6-9 Hz) waves, delineating a long-term, age-dependent, neuronal slowing. Neurological changes were not accompanied by brain structural malformations. Next, by using zebrafish larvae, we showed an increase of all motor-behavioral parameters resulting from the developmental exposure to 10 μg/L of pesticide cocktail, an outcome that was not associated with midbrain structural or neurovascular modifications as assessed by in vivo 2-photon microscopy. When screening each pesticide, chlorpyrifos elicited modifications of swimming parameters at 0.1 μg/L, while other components provoked changes from 0.5 μg/L. Ziram was the single most toxic component inducing developmental malformations and mortality at 10 μg/L. Although we have employed non-equivalent modalities and timing of exposure in two dissimilar experimental models, these outcomes indicate that presence of a pesticide cocktail during perinatal periods represents an element promoting behavioral and neurophysiological modifications. The study limitations and the possible pertinence of our findings to ecotoxicology and public health are critically discussed.

Peripheral Blood and Salivary Biomarkers of Blood-Brain Barrier Permeability and Neuronal Damage: Clinical and Applied Concepts

Within the neurovascular unit (NVU), the blood–brain barrier (BBB) operates as a key cerebrovascular interface, dynamically insulating the brain parenchyma from peripheral blood and compartments. Increased BBB permeability is clinically relevant for at least two reasons: it actively participates to the etiology of central nervous system (CNS) diseases, and it enables the diagnosis of neurological disorders based on the detection of CNS molecules in peripheral body fluids. In pathological conditions, a suite of glial, neuronal, and pericyte biomarkers can exit the brain reaching the peripheral blood and, after a process of filtration, may also appear in saliva or urine according to varying temporal trajectories. Here, we specifically examine the evidence in favor of or against the use of protein biomarkers of NVU damage and BBB permeability in traumatic head injury, including sport (sub)concussive impacts, seizure disorders, and neurodegenerative processes such as Alzheimer's disease. We further extend this analysis by focusing on the correlates of human extreme physiology applied to the NVU and its biomarkers. To this end, we report NVU changes after prolonged exercise, freediving, and gravitational stress, focusing on the presence of peripheral biomarkers in these conditions. The development of a biomarker toolkit will enable minimally invasive routines for the assessment of brain health in a broad spectrum of clinical, emergency, and sport settings.

Targeting of Perforin Inhibitor into the Brain Parenchyma Via a Prodrug Approach Can Decrease Oxidative Stress and Neuroinflammation and Improve Cell Survival

The cytolytic protein perforin has a crucial role in infections and tumor surveillance. Recently, it has also been associated with many brain diseases, such as neurodegenerative diseases and stroke. Therefore, inhibitors of perforin have attracted interest as novel drug candidates. We have previously reported that converting a perforin inhibitor into an L-type amino acid transporter 1 (LAT1)-utilizing prodrug can improve the compound's brain drug delivery not only across the blood-brain barrier (BBB) but also into the brain parenchymal cells: neurons, astrocytes, and microglia. The present study evaluated whether the increased uptake into mouse primary cortical astrocytes and subsequently improvements in the cellular bioavailability of this brain-targeted perforin inhibitor prodrug could enhance its pharmacological effects, such as inhibition of production of caspase-3/-7, lipid peroxidation products and prostaglandin E2 (PGE2) in the lipopolysaccharide (LPS)-induced neuroinflammation mouse model. It was demonstrated that increased brain and cellular drug delivery could improve the ability of perforin inhibitors to elicit their pharmacological effects in the brain at nano- to picomolar levels. Furthermore, the prodrug displayed multifunctional properties since it also inhibited the activity of several key enzymes related to Alzheimer's disease (AD), such as the β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1), acetylcholinesterase (AChE), and most probably also cyclooxygenases (COX) at micromolar concentrations. Therefore, this prodrug is a potential drug candidate for preventing Aβ-accumulation and ACh-depletion in addition to combatting neuroinflammation, oxidative stress, and neural apoptosis within the brain. Graphical abstract.

Neurological Complications of Sturge-Weber Syndrome: Current Status and Unmet Needs

OBJECTIVE

We aimed to identify the current status and major unmet needs in the management of neurological complications in Sturge-Weber syndrome.

METHODS

An expert panel consisting of neurologists convened during the Sturge-Weber Foundation Clinical Care Network conference in September 2018. Literature regarding current treatment strategies for neurological complications was reviewed.

RESULTS

Although strong evidence-based standards are lacking, the implementation of consensus-based standards of care and outcome measures to be shared across all Sturge-Weber Foundation Clinical Care Network Centers are needed. Each patient with Sturge-Weber syndrome should have an individualized seizure action plan. There is a need to determine the appropriate abortive and preventive treatment of migraine headaches in Sturge-Weber syndrome. Likewise, a better understanding and better diagnostic modalities and treatments are needed for stroke-like episodes. As behavioral problems are common, the appropriate screening tools for mental illnesses and the timing for screening should be established. Brain magnetic resonance imaging (MRI) preferably done after age one year is the primary imaging modality of choice to establish the diagnosis, although advances in MRI techniques can improve presymptomatic diagnosis to identify patients eligible for preventive drug trials.

CONCLUSION

We identified the unmet needs in the management of neurological complications in Sturge-Weber syndrome. We define a minimum standard brain MRI protocol to be used by Sturge-Weber syndrome centers. Future multicenter clinical trials on specific treatments of Sturge-Weber syndrome-associated neurological complications are needed. An improved national clinical database is critically needed to understand its natural course, and for retrospective and prospective measures of treatment efficacy.

Immune Profile in Blood Following Non-convulsive Epileptic Seizures in Rats

Non-convulsive status epilepticus (NCSE) is a prolonged epileptic seizure with subtle symptoms that may delay clinical diagnosis. Emerging experimental evidence shows brain pathology and epilepsy development following NCSE. New diagnostic/prognostic tools are therefore needed for earlier and better stratification of treatment. Here we examined whether NCSE initiates a peripheral immune response in blood serum from rats that experienced electrically-induced NCSE. ELISA analysis showed an acute transient increase in serum protein levels including interleukin-6 6 h post-NCSE, similar to the immune reaction in the brain. At 4 weeks post-NCSE, when 75% of rats subjected to NCSE had also developed spontaneous seizures, several immune proteins were altered. In particular, markers associated with microglia, macrophages and antigen presenting cells, such as CD68, MHCII, and galectin-3, were increased and the T-cell marker CD4 was decreased in serum compared to both non-stimulated controls and NCSE rats without spontaneous seizures, without correlation to interictal epileptiform activity. Analyses of serum following intracerebral injection of lipopolysaccharide (LPS) showed an acute increase in interleukin-6, but at 4 weeks unaltered levels of MHCII and galectin-3, an increase in CD8 and CD11b and a decrease in CD68. None of the increased serum protein levels after NCSE or LPS could be confirmed in spleen tissue. Our data identifies the possibility to detect peripheral changes in serum protein levels following NCSE, which may be related to the development of subsequent spontaneous seizures.

Activation of the innate immune system is evident throughout epileptogenesis and is associated with blood-brain barrier dysfunction and seizure progression

OBJECTIVE

Because brain inflammation may contribute to the pathophysiology of temporal lobe epilepsy (TLE), we investigated the expression of various inflammatory markers of the innate and adaptive immune system in the epileptogenic human and rat hippocampus in relation to seizure activity and blood-brain barrier (BBB) dysfunction.

METHODS

Immunohistochemistry was performed using various immune cell markers (for microglia, monocytes, macrophages, T lymphocytes, and dendritic cells) on hippocampal sections of drug-resistant TLE patients and patients who died after status epilepticus. The expression of these markers was also studied in the electrical post-status epilepticus rat model for TLE, during the acute, latent, and chronic epileptic phase. BBB dysfunction was assessed using albumin immunohistochemistry and the BBB tracer fluorescein.

RESULTS

Monocyte infiltration, microglia, and perivascular macrophage activation were persistently increased in both epileptogenic human and rat hippocampus, whereas T lymphocytes and dendritic cells were not or were scarcely detected. In addition to this, increased expression of C-C motif ligand 2 (CCL2) and osteopontin was observed. In humans, the expression of CD68 and CCL2 was related to the duration of epilepsy and type of pathology. In rats, the expression of CD68, CCL2, and the perivascular macrophage marker CD163 was related to the duration of the initial insult and to the number of spontaneous seizures. Interestingly, the number of CD163-positive perivascular macrophages was also positively correlated to BBB dysfunction in chronic epileptic rats.

SIGNIFICANCE

These data suggest a proepileptogenic role for monocytes/macrophages and other cells of the innate immune response, possibly via increased BBB leakage, and indicate that T cells and dendritic cells, which are closely associated with the adaptive immune response, are only sparsely infiltrated during epileptogenesis in the electrical post-status epilepticus rat model. Future studies should reveal the relative importance of these immune cells and whether specific manipulation can modify or prevent epileptogenesis.

Do ketone bodies mediate the anti-seizure effects of the ketogenic diet?

Although the mechanisms underlying the anti-seizure effects of the high-fat ketogenic diet (KD) remain unclear, a long-standing question has been whether ketone bodies (i.e., β-hydroxybutyrate, acetoacetate and acetone), either alone or in combination, contribute mechanistically. The traditional belief has been that while ketone bodies reflect enhanced fatty acid oxidation and a general shift toward intermediary metabolism, they are not likely to be the key mediators of the KD's clinical effects, as blood levels of β-hydroxybutyrate do not correlate consistently with improved seizure control. Against this unresolved backdrop, new data support ketone bodies as having anti-seizure actions. Specifically, β-hydroxybutyrate has been shown to interact with multiple novel molecular targets such as histone deacetylases, hydroxycarboxylic acid receptors on immune cells, and the NLRP3 inflammasome. Clearly, as a diet-based therapy is expected to render a broad array of biochemical, molecular, and cellular changes, no single mechanism can explain how the KD works. Specific metabolic substrates or enzymes are only a few of many important factors influenced by the KD that can collectively influence brain hyperexcitability and hypersynchrony. This review summarizes recent novel experimental findings supporting the anti-seizure and neuroprotective properties of ketone bodies.

Participation of perforin in mediating dopaminergic neuron loss in MPTP-induced Parkinson's disease in mice

Both resident innate and peripheral immune aberrations have been demonstrated to influence Parkinson's disease (PD) progression. However, it is still enigmatic how and which immune components are lethal to the dopaminergic neuron in PD. We now show that levels of perforin, a pore-forming protein expressed in cytotoxic immune cells, was significantly increased in the serum of wild-type mice 4 weeks after injection of MPTP, a toxin used to induce PD-like symptoms. We demonstrate that perforin-deficiency attenuated the acute striatal dopamine reduction by 33%, ablated microglia activation 3 days post MPTP-injection; and retarded dopaminergic neuron death 4 weeks post MPTP-injection. Our study suggests that perforin plays a role in dopaminergic neuron loss in PD.

The effects of C5aR1 on leukocyte infiltration following pilocarpine-induced status epilepticus

This study aimed to determine the role C5aR1 plays in mediating immune responses acutely after pilocarpine-induced status epilepticus (SE), specifically those of brain-infiltrating leukocytes. Three days following pilocarpine SE, we determined by flow cytometry the brain immune cell phenotypes and measured key proinflammatory and antiinflammatory cytokine expression by infiltrating leukocytes and microglia in C5aR1-deficient and wild-type mice. Absence of C5aR1 reduced by 47% the numbers of Ly6G⁺ neutrophils in the brains of No-SE mice and decreased neutrophil entry after SE to levels found in wild-type brains that did not undergo SE (No-SE). Moreover, C5aR1-deficient mice showed increased interleukin (IL)-4 expression in infiltrating leukocytes, but not in microglia. Increases in IL-4 expression in infiltrating leukocytes coupled with decreased neutrophil invasion in C5aR1-deficient mice after SE is likely to contribute to the reduced neuronal loss previously found in these mice compared to their wild-type littermates. Although other SE models need to be investigated to substantiate our findings, this study provides further evidence that C5aR1 is an inflammatory mediator and may play a role in epileptogenesis.

Modulatory effects of perforin gene dosage on pathogen-associated blood-brain barrier (BBB) disruption

Background

CD8 T cell-mediated blood-brain barrier (BBB) disruption is dependent on the effector molecule perforin. Human perforin has extensive single nucleotide variants (SNVs), the significance of which is not fully understood. These SNVs can result in reduced, but not ablated, perforin activity or expression. However, complete loss of perforin expression or activity results in the lethal disease familial hemophagocytic lymphohistiocytosis type 2 (FHL 2). In this study, we address the hypothesis that a single perforin allele can alter the severity of BBB disruption in vivo using a well-established model of CNS vascular permeability in C57Bl/6 mice. The results of this study provide insight into the significance of perforin SNVs in the human population.

Methods

We isolated the effect a single perforin allele has on CNS vascular permeability through the use of perforin-heterozygous (perforin+/−) C57BL/6 mice in the peptide-induced fatal syndrome (PIFS) model of immune-mediated BBB disruption. Seven days following Theiler’s murine encephalomyelitis virus (TMEV) CNS infection, neuroinflammation and TMEV viral control were assessed through flow cytometric analysis and quantitative real-time PCR of the viral genome, respectively. Following immune-mediated BBB disruption, gadolinium-enhanced T1-weighted MRI, with 3D volumetric analysis, and confocal microscopy were used to define CNS vascular permeability. Finally, the open field behavior test was used to assess locomotor activity of mice following immune-mediated BBB disruption.

Results

Perforin-null mice had negligible CNS vascular permeability. Perforin-WT mice have extensive CNS vascular permeability. Interestingly, perforin-heterozygous mice had an intermediate level of CNS vascular permeability as measured by both gadolinium-enhanced T1-weighted MRI and fibrinogen leakage in the brain parenchyma. Differences in BBB disruption were not a result of increased CNS immune infiltrate. Additionally, TMEV was controlled in a perforin dose-dependent manner. Furthermore, a single perforin allele is sufficient to induce locomotor deficit during immune-mediated BBB disruption.

Conclusions

Perforin modulates BBB disruption in a dose-dependent manner. This study demonstrates a potentially advantageous role for decreased perforin expression in reducing BBB disruption. This study also provides insight into the effect SNVs in a single perforin allele could have on functional deficit in neurological disease.

Inflammation and endothelium response in epileptic patients: A case-control study

BACKGROUND

Blood brain barrier (BBB) permeability plays an important role in the brain impairments. The barrier is composed of endothelium cells, due to the presence of tight junctions that connect endothelium cells. The failure of BBB function has triggering chronic or acute seizures through brain inflammation and BBB permeability. Seizure induces vasodilation, BBB leakage and up-regulation of vascular cell adhesion molecules which able to bind integrins blood leukocytes.

MATERIALS AND METHODS

In this case-control study we included 40 epileptic patients who were sampled during a seizure as a case group and 20 healthy subjects as a healthy control group. Plasma levels of the inflammation and endothelium markers including intercellular adhesion molecule (ICAM), vascular adhesion molecule (VCAM), interleukin 1 beta (IL-1β) and C-reactive protein (CRP) were measured by enzyme-linked immunosorbent assays (ELISAs).

RESULTS

The ICAM and VCAM concentration in the epileptic patients (135.8 ± 5.35) (52.04 ± 4.24) were significantly higher than healthy control group (110.32 ± 5.04) (23.38 ± 3.01) (P < 0.005). IL-1 beta concentration was not significantly different between groups (P = 0.594). However, CRP level was significantly up-regulated in epileptic patients (P < 0.005).

CONCLUSION

Epileptic patients have BBB leakage and dysfunction as the up-regulation of the endothelium cytokines showed. The BBB leakage may be the result of the inflammatory impairment.

Infraslow status epilepticus: A new form of subclinical status epilepticus recorded in a child with Sturge-Weber syndrome

BACKGROUND

Analysis of infraslow EEG activity (ISA) has shown potential in the evaluation of patients with epilepsy and in the differentiation between focal and generalized epilepsies. Infraslow EEG activity analysis may also provide insights into the pathophysiology of refractory clinical and subclinical status epilepticus. The purpose of this report is to describe a girl with Sturge-Weber syndrome (SWS) who presented with a 96-h refractory encephalopathy and nonischemic hemiparesis and who was identified to have infraslow status epilepticus (ISSE), which successfully resolved after midazolam administration.

METHODS

The continuous EEG recording of a 5-year-old girl with known structural epilepsy due to Sturge-Weber syndrome is presented. The patient presented to the ED with acute confusion, eye deviation, and right hemiparesis similar to two previous admissions. Despite administration of lorazepam, fosphenytoin, phenobarbital, and valproic loads, the patient showed no improvement in the clinical condition after 48 h. The continuous video-EEG monitoring (VEM) showed continuous severe diffuse nonrhythmic asymmetric slowing but no apparent ictal activity on continuous conventional EEG recording settings. As brain CT, CTA, CTV, and complete MRI scans including DWI obtained within 72 h of presentation failed to demonstrate any ischemic changes, analysis of the EEG infraslow (ISA) activity was undertaken using LFF: 0.01 Hz and HFF: of 0.1 Hz, respectively.

RESULTS

Continuous subclinical unilateral rhythmic ictal ISA was identified. This was only evident on the left hemisphere which correlated with the structural changes due to SWS. A trial of continuous 120 to 240 μg/kg/h of IV midazolam resulted in immediate resolution of the contralateral hemiparesis and encephalopathy.

CONCLUSION

Continuous prolonged rhythmic ictal infraslow activity (ISA) can cause super-refractory subclinical focal status epilepticus. This has not been previously reported, and we propose that this be called infraslow status epilepticus (ISSE). Infraslow EEG activity analysis should be performed in all patients with unexplained subclinical status epilepticus. This article is part of a Special Issue entitled "Status Epilepticus".

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.

What Elements of the Inflammatory System Are Necessary for Epileptogenesis In Vitro?

The inflammatory and central nervous systems share many signaling molecules, compromising the utility of traditional pharmacological and knockout approaches in defining the role of inflammation in CNS disorders such as epilepsy. In an in vitro model of post-traumatic epileptogenesis, the development of epilepsy proceeded in the absence of the systemic inflammatory system, and was unaffected by removal of cellular mediators of inflammation, including macrophages and T-lymphocytes.

Epileptogenesis in vivo can be altered by manipulation of molecules such as cytokines and complement that subserve intercellular signaling in both the inflammatory and central nervous systems. Because of the dual roles of these signaling molecules, it has been difficult to precisely define the role of systemic inflammation in epileptogenesis. Organotypic hippocampal brain slices can be maintained in culture independently of the systemic inflammatory system, and the rapid course of epileptogenesis in these cultures supports the idea that inflammation is not necessary for epilepsy. However, this preparation still retains key cellular inflammatory mediators. Here, we found that rodent hippocampal organotypic slice cultures depleted of T lymphocytes and microglia developed epileptic activity at essentially the same rate and to similar degrees of severity as matched control slice cultures. These data support the idea that although the inflammatory system, neurons, and glia share key intercellular signaling molecules, neither systemic nor CNS-specific cellular elements of the immune and inflammatory systems are necessary components of epileptogenesis.

Therapeutic window for cyclooxygenase-2 related anti-inflammatory therapy after status epilepticus

As a prominent inflammatory effector of cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2) mediates brain inflammation and injury in many chronic central nervous system (CNS) conditions including seizures and epilepsy, largely through its receptor subtype EP2. However, EP2 receptor activation might also be neuroprotective in models of excitotoxicity and ischemia. These seemingly incongruent observations expose the delicacy of immune and inflammatory signaling in the brain; thus the therapeutic window for quelling neuroinflammation might vary with injury type and target molecule. Here, we identify a therapeutic window for EP2 antagonism to reduce delayed mortality and functional morbidity after status epilepticus (SE) in mice. Importantly, treatment must be delayed relative to SE onset to be effective, a finding that could be explained by the time-course of COX-2 induction after SE and compound pharmacokinetics. A large number of inflammatory mediators were upregulated in hippocampus after SE with COX-2 and IL-1β temporally leading many others. Thus, EP2 antagonism represents a novel anti-inflammatory strategy to treat SE with a tightly-regulated therapeutic window.

Epileptic seizures as a manifestation of cow's milk allergy: a studied relationship and description of our pediatric experience

Adverse reactions after ingestion of cow's milk proteins can occur at any age, from birth and even amongst exclusively breast-fed infants, although not all of these are hypersensitivity reactions. The most common presentations related to cow's milk protein allergy are skin reactions, failure to thrive, anaphylaxis as well as gastrointestinal and respiratory disorders. In addition, several cases of cow's milk protein allergy in the literature have documented neurological involvement, manifesting with convulsive seizures in children. This may be due to CNS spread of a peripheral inflammatory response. Furthermore, there is evidence that pro-inflammatory cytokines are responsible for disrupting the blood-brain barrier, causing focal CNS inflammation thereby triggering seizures, although further studies are needed to clarify the pathogenic relationship between atopy and its neurological manifestations. This review aims to analyze current published data on the link between cow's milk protein allergy and epileptic events, highlighting scientific evidence for any potential pathogenic mechanism and describing our clinical experience in pediatrics.

The blood-brain barrier-gatekeeper to neuronal homeostasis: clinical implications in the setting of stroke

The blood-brain barrier is part of the neurovascular unit and serves as a functional and anatomical barrier between the blood and the extracellular space. It controls the flow of solutes in and out of the brain thereby providing an optimal environment for neuronal functioning. Paracellular transport between endothelial cells is restricted by tight junctions and transendothelial transport is reduced and more selective compared to capillaries of other organs. Further, the blood-brain barrier is involved in controlling blood flow and it is the site for signaling damage of the nervous system to the peripheral immune system. As an important player in brain homeostasis, blood-brain barrier dysfunction has been implicated in the pathophysiology of many brain diseases including stroke, traumatic brain injury, brain tumors, epilepsy and neurodegenerative disorders. In this article - highlighting recent advances in basic science - we review the features of the blood-brain barrier and their significance for neuronal homeostasis to discuss clinical implications for neurological complications following cerebral ischemia.

Perforin competent CD8 T cells are sufficient to cause immune-mediated blood-brain barrier disruption

Numerous neurological disorders are characterized by central nervous system (CNS) vascular permeability. However, the underlying contribution of inflammatory-derived factors leading to pathology associated with blood-brain barrier (BBB) disruption remains poorly understood. In order to address this, we developed an inducible model of BBB disruption using a variation of the Theiler's murine encephalomyelitis virus (TMEV) model of multiple sclerosis. This peptide induced fatal syndrome (PIFS) model is initiated by virus-specific CD8 T cells and results in severe CNS vascular permeability and death in the C57BL/6 mouse strain. While perforin is required for BBB disruption, the cellular source of perforin has remained unidentified. In addition to CD8 T cells, various innate immune cells also express perforin and therefore could also contribute to BBB disruption. To investigate this, we isolated the CD8 T cell as the sole perforin-expressing cell type in the PIFS model through adoptive transfer techniques. We determined that C57BL/6 perforin^−/− mice reconstituted with perforin competent CD8 T cells and induced to undergo PIFS exhibited: 1) heightened CNS vascular permeability, 2) increased astrocyte activation as measured by GFAP expression, and 3) loss of linear organization of BBB tight junction proteins claudin-5 and occludin in areas of CNS vascular permeability when compared to mock-treated controls. These results are consistent with the characteristics associated with PIFS in perforin competent mice. Therefore, CD8 T cells are sufficient as a sole perforin-expressing cell type to cause BBB disruption in the PIFS model.

Some cross-talks between immune cells and epilepsy should not be forgotten

Recent studies have reported that immune cells were not always found in brain specimens from epileptic patients, then should we stop investigating the relationship between these cells and epilepsy? The answer is no! In addition to immunocyte infiltration in brain parenchyma, a flurry of papers have demonstrated that there were significant alterations in peripheral blood cells (PBCs) immediately after seizure onset, especially changes in some specific transporters of neurotransmitters expressed on the membrane of immunocyte. These transporters may regulate neuronal excitability in mature neurons. Besides, many researchers did find activated leukocytes adhered to the endothelium of blood brain barrier or infiltrated into the brain parenchyma in several types of epilepsy both in human and animal studies; moreover, it is worth noting that different immune cells play different roles in epilepsy development, which was indicated by in vitro and in vivo evidence. This review is going to summarize available evidence supporting changes in PBCs after seizures, and will also focus on some specific effects of immune cells on epilepsy development.

Is peripheral immunity regulated by blood-brain barrier permeability changes?

S100B is a reporter of blood-brain barrier (BBB) integrity which appears in blood when the BBB is breached. Circulating S100B derives from either extracranial sources or release into circulation by normal fluctuations in BBB integrity or pathologic BBB disruption (BBBD). Elevated S100B matches the clinical presence of indices of BBBD (gadolinium enhancement or albumin coefficient). After repeated sub-concussive episodes, serum S100B triggers an antigen-driven production of anti-S100B autoantibodies. We tested the hypothesis that the presence of S100B in extracranial tissue is due to peripheral cellular uptake of serum S100B by antigen presenting cells, which may induce the production of auto antibodies against S100B. To test this hypothesis, we used animal models of seizures, enrolled patients undergoing repeated BBBD, and collected serum samples from epileptic patients. We employed a broad array of techniques, including immunohistochemistry, RNA analysis, tracer injection and serum analysis. mRNA for S100B was segregated to barrier organs (testis, kidney and brain) but S100B protein was detected in immunocompetent cells in spleen, thymus and lymph nodes, in resident immune cells (Langerhans, satellite cells in heart muscle, etc.) and BBB endothelium. Uptake of labeled S100B by rat spleen CD4+ or CD8+ and CD86+ dendritic cells was exacerbated by pilocarpine-induced status epilepticus which is accompanied by BBBD. Clinical seizures were preceded by a surge of serum S100B. In patients undergoing repeated therapeutic BBBD, an autoimmune response against S100B was measured. In addition to its role in the central nervous system and its diagnostic value as a BBBD reporter, S100B may integrate blood-brain barrier disruption to the control of systemic immunity by a mechanism involving the activation of immune cells. We propose a scenario where extravasated S100B may trigger a pathologic autoimmune reaction linking systemic and CNS immune responses.

Antagomirs targeting microRNA-134 increase hippocampal pyramidal neuron spine volume in vivo and protect against pilocarpine-induced status epilepticus

Emerging data support roles for microRNA (miRNA) in the pathogenesis of various neurologic disorders including epilepsy. MicroRNA-134 (miR-134) is enriched in dendrites of hippocampal neurons, where it negatively regulates spine volume. Recent work identified upregulation of miR-134 in experimental and human epilepsy. Targeting miR-134 in vivo using antagomirs had potent anticonvulsant effects against kainic acid-induced seizures and was associated with a reduction in dendritic spine number. In the present study, we measured dendritic spine volume in mice injected with miR-134-targeting antagomirs and tested effects of the antagomirs on status epilepticus triggered by the cholinergic agonist pilocarpine. Morphometric analysis of over 6,400 dendritic spines in Lucifer yellow-injected CA3 pyramidal neurons revealed increased spine volume in mice given antagomirs compared to controls that received a scrambled sequence. Treatment of mice with miR-134 antagomirs did not alter performance in a behavioral test (novel object location). Status epilepticus induced by pilocarpine was associated with upregulation of miR-134 within the hippocampus of mice. Pretreatment of mice with miR-134 antagomirs reduced the proportion of animals that developed status epilepticus following pilocarpine and increased animal survival. In antagomir-treated mice that did develop status epilepticus, seizure onset was delayed and total seizure power was reduced. These studies provide in vivo evidence that miR-134 regulates spine volume in the hippocampus and validation of the seizure-suppressive effects of miR-134 antagomirs in a model with a different triggering mechanism, indicating broad conservation of anticonvulsant effects.

Nonconvulsive seizures in subarachnoid hemorrhage link inflammation and outcome

OBJECTIVE

Nonconvulsive seizures (NCSz) are frequent following acute brain injury and have been implicated as a cause of secondary brain injury, but mechanisms that cause NCSz are controversial. Proinflammatory states are common after many brain injuries, and inflammation-mediated changes in blood-brain barrier permeability have been experimentally linked to seizures.

METHODS

In this prospective observational study of aneurysmal subarachnoid hemorrhage (SAH) patients, we explored the link between the inflammatory response following SAH and in-hospital NCSz studying clinical (systemic inflammatory response syndrome [SIRS]) and laboratory (tumor necrosis factor receptor 1 [TNF-R1], high-sensitivity C-reactive protein [hsCRP]) markers of inflammation. Logistic regression, Cox proportional hazards regression, and mediation analyses were performed to investigate temporal and causal relationships.

RESULTS

Among 479 SAH patients, 53 (11%) had in-hospital NCSz. Patients with in-hospital NCSz had a more pronounced SIRS response (odds ratio [OR]=1.9 per point increase in SIRS, 95% confidence interval [CI]=1.3-2.9), inflammatory surges were more likely immediately preceding NCSz onset, and the negative impact of SIRS on functional outcome at 3 months was mediated in part through in-hospital NCSz. In a subset with inflammatory serum biomarkers, we confirmed these findings linking higher serum TNF-R1 and hsCRP to in-hospital NCSz (OR=1.2 per 20-point hsCRP increase, 95% CI=1.1-1.4; OR=2.5 per 100-point TNF-R1 increase, 95% CI=2.1-2.9). The association of inflammatory biomarkers with poor outcome was mediated in part through NCSz.

INTERPRETATION

In-hospital NCSz were independently associated with a proinflammatory state following SAH as reflected in clinical symptoms and serum biomarkers of inflammation. Our findings suggest that inflammation following SAH is associated with poor outcome and that this effect is at least in part mediated through in-hospital NCSz.

The search for circulating epilepsy biomarkers

Few would experience greater benefit from the development of biomarkers than those who suffer from epilepsy. Both the timing of individual seizures and the overall course of the disease are highly unpredictable, and the associated morbidity is considerable. Thus, there is an urgent need to develop biomarkers that can predict the progression of epilepsy and treatment response. Doing so may also shed light on the mechanisms of epileptogenesis and pharmacoresistance, which remain elusive despite decades of study. However, recent advances suggest the possible identification of circulating epilepsy biomarkers – accessible in blood, cerebrospinal fluid or urine. In this review, we focus on advances in several areas: neuroimmunology and inflammation; neurological viral infection; exemplary pediatric syndromes; and the genetics of pharmacoresistance, as relevant to epilepsy. These are fertile areas of study with great potential to yield accessible epilepsy biomarkers.

What non-neuronal mechanisms should be studied to understand epileptic seizures?

While seizures ultimately result from aberrant firing of neuronal networks, several laboratories have embraced a non-neurocentric view of epilepsy to show that other cells in the brain also bear an etiologic impact in epilepsy. Astrocytes and brain endothelial cells are examples of controllers of neuronal homeostasis; failure of proper function of either cell type has been shown to have profound consequences on neurophysiology. Recently, an even more holistic view of the cellular and molecular mechanisms of epilepsy has emerged to include white blood cells, immunological synapses, the extracellular matrix and the neurovascular unit. This review will briefly summarize these findings and propose mechanisms and targets for future research efforts on non-neuronal features of neurological disorders including epilepsy.

Pathophysiogenesis of mesial temporal lobe epilepsy: is prevention of damage antiepileptogenic?

Temporal lobe epilepsy (TLE) is frequently associated with hippocampal sclerosis, possibly caused by a primary brain injury that occurred a long time before the appearance of neurological symptoms. This type of epilepsy is characterized by refractoriness to drug treatment, so to require surgical resection of mesial temporal regions involved in seizure onset. Even this last therapeutic approach may fail in giving relief to patients. Although prevention of hippocampal damage and epileptogenesis after a primary event could be a key innovative approach to TLE, the lack of clear data on the pathophysiological mechanisms leading to TLE does not allow any rational therapy. Here we address the current knowledge on mechanisms supposed to be involved in epileptogenesis, as well as on the possible innovative treatments that may lead to a preventive approach. Besides loss of principal neurons and of specific interneurons, network rearrangement caused by axonal sprouting and neurogenesis are well known phenomena that are integrated by changes in receptor and channel functioning and modifications in other cellular components. In particular, a growing body of evidence from the study of animal models suggests that disruption of vascular and astrocytic components of the blood-brain barrier takes place in injured brain regions such as the hippocampus and piriform cortex. These events may be counteracted by drugs able to prevent damage to the vascular component, as in the case of the growth hormone secretagogue ghrelin and its analogues. A thoroughly investigation on these new pharmacological tools may lead to design effective preventive therapies.

Intracellular and circulating neuronal antinuclear antibodies in human epilepsy

There are overwhelming data supporting the inflammatory origin of some epilepsies (e.g., Rasmussen's encephalitis and limbic encephalitis). Inflammatory epilepsies with an autoimmune component are characterized by autoantibodies against membrane-bound, intracellular or secreted proteins (e.g., voltage gated potassium channels). Comparably, little is known regarding autoantibodies targeting nuclear antigen. We tested the hypothesis that in addition to known epilepsy-related autoantigens, the human brain tissue and serum from patients with epilepsy contain autoantibodies recognizing nuclear targets. We also determined the specific nuclear proteins acting as autoantigen in patients with epilepsy. Brain tissue samples were obtained from patients undergoing brain resections to treat refractory seizures, from the brain with arteriovenous malformations or from post-mortem multiple sclerosis brain. Patients with epilepsy had no known history of autoimmune disease and were not diagnosed with autoimmune epilepsy. Tissue was processed for immunohistochemical staining. We also obtained subcellular fractions to extract intracellular IgGs. After separating nuclear antibody-antigen complexes, the purified autoantigen was analyzed by mass spectrometry. Western blots using autoantigen or total histones were probed to detect the presence of antinuclear antibodies in the serum of patients with epilepsy. Additionally, HEp-2 assays and antinuclear antibody ELISA were used to detect the staining pattern and specific presence of antinuclear antibodies in the serum of patients with epilepsy. Brain regions from patients with epilepsy characterized by blood-brain barrier disruption (visualized by extravasated albumin) contained extravasated IgGs. Intracellular antibodies were found in epilepsy (n=13/13) but not in multiple sclerosis brain (n=4/4). In the brain from patients with epilepsy, neurons displayed higher levels of nuclear IgGs compared to glia. IgG colocalized with extravasated albumin. All subcellular fractions from brain resections of patients with epilepsy contained extravasated IgGs (n=10/10), but epileptogenic cortex, where seizures originated from, displayed the highest levels of chromatin-bound IgGs. In the nuclear IgG pool, anti-histone autoantibodies were identified by two independent immunodetection methods. HEp-2 assay and ELISA confirmed the presence of anti-histone (n=5/8) and anti-chromatin antibodies in the serum from patients with epilepsy. We developed a multi-step approach to unmask autoantigens in the brain and sera of patients with epilepsy. This approach revealed antigen-bound antinuclear antibodies in neurons and free antinuclear IgGs in the serum of patients with epilepsy. Conditions with blood-brain barrier disruption but not seizures, were characterized by extravasated but not chromatin-bound IgGs. Our results show that the pool of intracellular IgG in the brain of patients with epilepsy consists of nucleus-specific autoantibodies targeting chromatin and histones. Seizures may be the trigger of neuronal uptake of antinuclear antibodies.