Blood-brain barrier dysfunction, TGFβ signaling, and astrocyte dysfunction in epilepsy

KEAP1 inhibition is neuroprotective and suppresses the development of epilepsy

Hippocampal sclerosis is a common acquired disease that is a major cause of drug-resistant epilepsy. A mechanism that has been proposed to lead from brain insult to hippocampal sclerosis is the excessive generation of reactive oxygen species, and consequent mitochondrial failure. Here we use a novel strategy to increase endogenous antioxidant defences using RTA 408, which we show activates nuclear factor erythroid 2-related factor 2 (Nrf2, encoded by NFE2L2) through inhibition of kelch like ECH associated protein 1 (KEAP1) through its primary sensor C151. Activation of Nrf2 with RTA 408 inhibited reactive oxygen species production, mitochondrial depolarization and cell death in an in vitro model of seizure-like activity. RTA 408 given after status epilepticus in vivo increased ATP, prevented neuronal death, and dramatically reduced (by 94%) the frequency of late spontaneous seizures for at least 4 months following status epilepticus. Thus, acute KEAP1 inhibition following status epilepticus exerts a neuroprotective and disease-modifying effect, supporting the hypothesis that reactive oxygen species generation is a key event in the development of epilepsy.

Proteomic analysis of human epileptic neocortex predicts vascular and glial changes in epileptic regions

Epilepsy is a common neurological disorder, which is not well understood at the molecular level. Exactly why some brain regions produce epileptic discharges and others do not is not known. Patients who fail to respond to antiseizure medication (refractory epilepsy) can benefit from surgical removal of brain regions to reduce seizure frequency. The tissue removed in these surgeries offers an invaluable resource to uncover the molecular and cellular basis of human epilepsy. Here, we report a proteomic study to determine whether there are common proteomic patterns in human brain regions that produce epileptic discharges. We analyzed human brain samples, as part of the Systems Biology of Epilepsy Project (SBEP). These brain pieces are in vivo electrophysiologically characterized human brain samples withdrawn from the neocortex of six patients with refractory epilepsy. This study is unique in that for each of these six patients the comparison of protein expression was made within the same patient: a more epileptic region was compared to a less epileptic brain region. The amount of epileptic activity was defined for each patient as the frequency of their interictal spikes (electric activity between seizures that is a parameter strongly linked to epilepsy). Proteins were resolved from three subcellular fractions, using a 2D differential gel electrophoresis (2D-DIGE), revealing 31 identified protein spots that changed significantly. Interestingly, glial fibrillary acidic protein (GFAP) was found to be consistently down regulated in high spiking brain tissue and showed a strong negative correlation with spike frequency. We also developed a two-step analysis method to select for protein species that changed frequently among the patients and identified these proteins. A total of 397 protein spots of interest (SOI) were clustered by protein expression patterns across all samples. These clusters were used as markers and this analysis predicted proteomic changes due to both histological differences and molecular pathways, revealed by examination of gene ontology clusters. Our experimental design and proteomic data analysis predicts novel glial changes, increased angiogenesis, and changes in cytoskeleton and neuronal projections between high and low interictal spiking regions. Quantitative histological staining of these same tissues for both the vascular and glial changes confirmed these findings, which provide new insights into the structural and functional basis of neocortical epilepsy.

Matrix Metalloproteinase-Mediated Blood-Brain Barrier Dysfunction in Epilepsy

The blood-brain barrier is dysfunctional in epilepsy, thereby contributing to seizure genesis and resistance to antiseizure drugs. Previously, several groups reported that seizures increase brain glutamate levels, which leads to barrier dysfunction. One critical component of barrier dysfunction is brain capillary leakage. Based on our preliminary data, we hypothesized that glutamate released during seizures mediates an increase in matrix-metalloproteinase (MMP) expression and activity levels, thereby contributing to barrier leakage. To test this hypothesis, we exposed isolated brain capillaries from male Sprague Dawley rats to glutamate ex vivo and used an in vivo/ex vivo approach of isolated brain capillaries from female Wistar rats that experienced status epilepticus as an acute seizure model. We found that exposing isolated rat brain capillaries to glutamate increased MMP-2 and MMP-9 protein and activity levels, and decreased tight junction protein levels, which resulted in barrier leakage. We confirmed these findings in vivo in rats after status epilepticus and in brain capillaries from male mice lacking cytosolic phospholipase A₂ Together, our data support the hypothesis that glutamate released during seizures signals an increase in MMP-2 and MMP-9 protein expression and activity levels, resulting in blood-brain barrier leakage.SIGNIFICANCE STATEMENT The mechanism leading to seizure-mediated blood-brain barrier dysfunction in epilepsy is poorly understood. In the present study, we focused on defining this mechanism in the brain capillary endothelium. We demonstrate that seizures trigger a pathway that involves glutamate signaling through cytosolic phospholipase A₂, which increases MMP levels and decreases tight junction protein expression levels, resulting in barrier leakage. These findings may provide potential therapeutic avenues within the blood-brain barrier to limit barrier dysfunction in epilepsy and decrease seizure burden.

Influence of white matter injury on gray matter reactive gliosis upon stab wound in the adult murine cerebral cortex

Traumatic brain injury frequently affects the cerebral cortex, yet little is known about the differential effects that occur if only the gray matter (GM) is damaged or if the injury also involves the white matter (WM). To tackle this important question and directly compare similarities and differences in reactive gliosis, we performed stab wound injury affecting GM and WM (GM+) and one restricted to the GM (GM-) in the adult murine cerebral cortex. First, we examined glial reactivity in the regions affected (WM and GM) and determined the influence of WM injury on reactive gliosis in the GM comparing the same area in the two injury paradigms. In the GM+ injury microglia proliferation is increased in the WM compared with GM, while proliferating astrocytes are more abundant in the GM than in the WM. Interestingly, WM lesion exerted a strong influence on the proliferation of the GM glial cells that was most pronounced at early stages, 3 days post lesion. While astrocyte proliferation was increased, NG2 glia proliferation was decreased in the GM+ compared with GM- lesion condition. Importantly, these differences were not observed when a lesion of the same size affected only the GM. Unbiased proteomic analyses further corroborate our findings in support of a profound difference in GM reactivity when WM is also injured and revealed MIF as a key regulator of NG2 glia proliferation.

Post-treatment with the GLP-1 analogue liraglutide alleviate chronic inflammation and mitochondrial stress induced by Status epilepticus

Glucagon-like peptide-1(GLP-1) is a growth factor that has neuroprotective and anti-inflammatory properties. The protease resistant GLP-1 analogue liraglutide has been shown to be neuroprotective in previous studies in animal models of Alzheimer's disease or Parkinson's disease. Status epilepticus (SE) is a complex disorder, involving many underlying pathological processes, including excitotoxic and chronic inflammatory events. The present pilot study aims to investigate whether liraglutide alleviates the chronic inflammation response and mitochondrial stress induced by SE in the lithium-pilocarpine animal model. We found that treatment with 25nmol/kg. i.p. once-daily after the induction of SE for 7 days reduced chronic inflammation as shown by reduced numbers of activated microglia and astrocytes, and reduced levels of TNF-α and IL-1ß in the hippocampus. The mitochondrial stress marker BAX was reduced and the survival factor Bcl-2 was enhanced by liraglutide. Blood glucose levels were not affected by liraglutide. We show for the first time that liraglutide can reduce the chronic inflammation and mitochondrial stress induced by SE, and the results suggest that GLP-1 receptor agonists such as liraglutide have restorative and protective effects in the brain after SE and could serve as a potential treatment.

Concussion, microvascular injury, and early tauopathy in young athletes after impact head injury and an impact concussion mouse model

The mechanisms underpinning concussion, traumatic brain injury, and chronic traumatic encephalopathy, and the relationships between these disorders, are poorly understood. We examined post-mortem brains from teenage athletes in the acute-subacute period after mild closed-head impact injury and found astrocytosis, myelinated axonopathy, microvascular injury, perivascular neuroinflammation, and phosphorylated tau protein pathology. To investigate causal mechanisms, we developed a mouse model of lateral closed-head impact injury that uses momentum transfer to induce traumatic head acceleration. Unanaesthetized mice subjected to unilateral impact exhibited abrupt onset, transient course, and rapid resolution of a concussion-like syndrome characterized by altered arousal, contralateral hemiparesis, truncal ataxia, locomotor and balance impairments, and neurobehavioural deficits. Experimental impact injury was associated with axonopathy, blood-brain barrier disruption, astrocytosis, microgliosis (with activation of triggering receptor expressed on myeloid cells, TREM2), monocyte infiltration, and phosphorylated tauopathy in cerebral cortex ipsilateral and subjacent to impact. Phosphorylated tauopathy was detected in ipsilateral axons by 24 h, bilateral axons and soma by 2 weeks, and distant cortex bilaterally at 5.5 months post-injury. Impact pathologies co-localized with serum albumin extravasation in the brain that was diagnostically detectable in living mice by dynamic contrast-enhanced MRI. These pathologies were also accompanied by early, persistent, and bilateral impairment in axonal conduction velocity in the hippocampus and defective long-term potentiation of synaptic neurotransmission in the medial prefrontal cortex, brain regions distant from acute brain injury. Surprisingly, acute neurobehavioural deficits at the time of injury did not correlate with blood-brain barrier disruption, microgliosis, neuroinflammation, phosphorylated tauopathy, or electrophysiological dysfunction. Furthermore, concussion-like deficits were observed after impact injury, but not after blast exposure under experimental conditions matched for head kinematics. Computational modelling showed that impact injury generated focal point loading on the head and seven-fold greater peak shear stress in the brain compared to blast exposure. Moreover, intracerebral shear stress peaked before onset of gross head motion. By comparison, blast induced distributed force loading on the head and diffuse, lower magnitude shear stress in the brain. We conclude that force loading mechanics at the time of injury shape acute neurobehavioural responses, structural brain damage, and neuropathological sequelae triggered by neurotrauma. These results indicate that closed-head impact injuries, independent of concussive signs, can induce traumatic brain injury as well as early pathologies and functional sequelae associated with chronic traumatic encephalopathy. These results also shed light on the origins of concussion and relationship to traumatic brain injury and its aftermath.awx350media15713427811001.

Increased gyrification and aberrant adult neurogenesis of the dentate gyrus in adult rats

A remarkable example of maladaptive plasticity is the development of epilepsy after a brain insult or injury to a normal animal or human. A structure that is considered central to the development of this type of epilepsy is the dentate gyrus (DG), because it is normally a relatively inhibited structure and its quiescence is thought to reduce hippocampal seizure activity. This characteristic of the DG is also considered to be important for normal hippocampal-dependent cognitive functions. It has been suggested that the brain insults which cause epilepsy do so because they cause the DG to be more easily activated. One type of brain insult that is commonly used is induction of severe seizures (status epilepticus; SE) by systemic injection of a convulsant drug. Here we describe an alteration in the DG after this type of experimental SE that may contribute to chronic seizures that has not been described before: large folds or gyri that develop in the DG by 1 month after SE. Large gyri appeared to increase network excitability because epileptiform discharges recorded in hippocampal slices after SE were longer in duration when recorded inside gyri relative to locations outside gyri. Large gyri may also increase excitability because immature adult-born neurons accumulated at the base of gyri with time after SE, and previous studies have suggested that abnormalities in adult-born DG neurons promote seizures after SE. In summary, large gyri after SE are a common finding in adult rats, show increased excitability, and are associated with the development of an abnormal spatial distribution of adult-born neurons. Together these alterations may contribute to chronic seizures and associated cognitive comorbidities after SE.

Do minocycline and other suppressors of microglia reactivity have a future in prevention or treatment of epilepsy?

Introduction.An increasing body of evidence points to an important role of neuroinflammatory processes in the pathomechanism of epilepsy. This hypothesis is mainly supported by data showing an increase of pro-inflammatory cytokine levels and glia activation in animal models of epilepsy and in brain tissue of epileptic patients. On the other hand, less emphasis has been put on pharmacological verification of this hypothesis.

Aim.The aim of this review is to summarize current knowledge on potential usefulness of microglia regulators and anti-inflammatory agents in designing antiepileptic/antiepileptogenic drugs, with the primary mechanism of action based on the inhibition of neuroinflammation.

Methods.We reviewed PubMed and MEDLINE databases to select publications in the topic: epilepsy, neuroinflammation, microglia and microglia regulators with antiepileptic properties. We searched the databases up to April 2017 with no date restrictions.

Review and Discussion.In the present paper, we will discuss new concepts of epileptogenesis which focus not only on changes in neurons but also take into consideration the role of activation of glial cells: microglia and astrocytes. Neuroinflammation, mainly through increased production of pro-inflammatory factors such as cytokines or chemokines, may play an important role in the development of epilepsy. Drugs regulating glial cells activation and consequently inflammatory status in the central nervous system have beneficial effects in different animal models of epilepsy as well as in clinical study in patients. The most promising compound seems to be minocycline which in some studies has been shown to possess antiepileptogenetic action. On the other hand, some antiepileptic drugs exhibit marked anti-inflammatory potency.

Conclusions.There are much data to suggest that there is significant opportunity for designing new antiepileptic drugs whose primary mechanism of action entails the inhibition of neuroinflammatory processes.

Brain expression of inflammatory mediators in Mesial Temporal Lobe Epilepsy patients

Neuroinflammation may be central in epileptogenesis. In this study we analysed inflammatory reaction markers in brain tissue of Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis (MTLE-HS) patients. TLR4, IL-1β and IL-10 gene expression as well as the presence of activated HLA-DR+ microglia was evaluated in 23 patients and 10 cadaveric controls. Inflammation characterized by the presence of HLA-DR⁺ microglia and TLR4, IL-1β overexpression was evident in hippocampus and anterior temporal cortex of MTLE-HS patients. Anti-inflammatory IL-10 was also overexpressed in MTLE-HS patients. Our results show that hippocampal neuroinflammation extends beyond lesional limits, as far as the anterior temporal cortex.

Alzheimer's brains show inter-related changes in RNA and lipid metabolism

Alzheimer's disease (AD) involves changes in both lipid and RNA metabolism, but it remained unknown if these differences associate with AD's cognition and/or post-mortem neuropathology indices. Here, we report RNA-sequencing evidence of inter-related associations between lipid processing, cognition level, and AD neuropathology. In two unrelated cohorts, we identified pathway-enriched facilitation of lipid processing and alternative splicing genes, including the neuronal-enriched NOVA1 and hnRNPA1. Specifically, this association emerged in temporal lobe tissue samples from donors where postmortem evidence demonstrated AD neuropathology, but who presented normal cognition proximate to death. The observed changes further associated with modified ATP synthesis and mitochondrial transcripts, indicating metabolic relevance; accordingly, mass-spectrometry-derived lipidomic profiles distinguished between individuals with and without cognitive impairment prior to death. In spite of the limited group sizes, tissues from persons with both cognitive impairment and AD pathology showed elevation in several drug-targeted genes of other brain, vascular and autoimmune disorders, accompanied by pathology-related increases in distinct lipid processing transcripts, and in the RNA metabolism genes hnRNPH2, TARDBP, CLP1 and EWSR1. To further detect 3'-polyadenylation variants, we employed multiple cDNA primer pairs. This identified variants that showed limited differences in scope and length between the tested cohorts, yet enabled superior clustering of demented and non-demented AD brains versus controls compared to total mRNA expression values. Our findings indicate inter-related cognition-associated differences in AD's lipid processing, alternative splicing and 3'-polyadenylation, calling for pursuing the underlying psychological and therapeutics implications.

Neuroinflammatory targets and treatments for epilepsy validated in experimental models

A large body of evidence that has accumulated over the past decade strongly supports the role of inflammation in the pathophysiology of human epilepsy. Specific inflammatory molecules and pathways have been identified that influence various pathologic outcomes in different experimental models of epilepsy. Most importantly, the same inflammatory pathways have also been found in surgically resected brain tissue from patients with treatment-resistant epilepsy. New antiseizure therapies may be derived from these novel potential targets. An essential and crucial question is whether targeting these molecules and pathways may result in anti-ictogenesis, antiepileptogenesis, and/or disease-modification effects. Therefore, preclinical testing in models mimicking relevant aspects of epileptogenesis is needed to guide integrated experimental and clinical trial designs. We discuss the most recent preclinical proof-of-concept studies validating a number of therapeutic approaches against inflammatory mechanisms in animal models that could represent novel avenues for drug development in epilepsy. Finally, we suggest future directions to accelerate preclinical to clinical translation of these recent discoveries.

Transforming growth factor-beta 1 signaling regulates neuroinflammation and apoptosis in mild traumatic brain injury

Mild traumatic brain injury (mTBI) is a low-level injury, which often remains undiagnosed, and in most cases it leads to death and disability as it advances as secondary injury. Therefore, it is important to study the underlying signaling mechanisms of mTBI-associated neurological ailments. While transforming growth factor-beta1 (TGF-β1) has a significant role in inflammation and apoptosis in myriads of other pathophysiological conditions, the precise function of increased TGF-β1 after mTBI is unknown. In this study, our objective is to study the physiological relevance and associated mechanisms of TGF-β1-mediated inflammation and apoptosis in mTBI. Using an in vitro stretch-injury model in rat neuronal cultures and the in vivo fluid percussion injury (FPI) model in rats, we explored the significance of TGF-β1 activation in mTBI. Our study demonstrated that the activation of TGF-β1 in mTBI correlated with the induction of free radical generating enzyme NADPH oxidase 1 (NOX1). Further, using TGF-β type I receptor (TGF-βRI) inhibitor SB431542 and transfection of TGF-β1 siRNA and TGF-β antagonist Smad7, we established the neuroinflammatory and apoptotic role of TGF-β1 in mTBI. Inhibition of TGF-βRI or TGF-β1 diminished TGF-β1-induced inflammation and apoptosis. Further, the enhanced TGF-β1 activation increased the phosphorylation of R-Smads including Smad2 and Smad3 proteins. By immunofluorescence, western blotting, ELISA and TUNEL experiments, we demonstrated the up-regulation of pro-inflammatory cytokines IL-1β and TNF-α and apoptotic cell death in neurons. In conclusion, this study could establish the significance of TGF-β1 in transforming the pathophysiology of mTBI into secondary injury.

TGF-β signaling directly regulates transcription and functional expression of the electrogenic sodium bicarbonate cotransporter 1, NBCe1 (SLC4A4), via Smad4 in mouse astrocytes

The electrogenic sodium bicarbonate cotransporter NBCe1 (SLC4A4) expressed in astrocytes regulates intracellular and extracellular pH. Here, we introduce transforming growth factor beta (TGF-β) as a novel regulator of NBCe1 transcription and functional expression. Using hippocampal slices and primary hippocampal and cortical astrocyte cultures, we investigated regulation of NBCe1 and elucidated the underlying signaling pathways by RT-PCR, immunoblotting, immunofluorescence, intracellular H(+ ) recording using the H(+ ) -sensitive dye 2',7'-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein, mink lung epithelial cell (MLEC) assay, and chromatin immunoprecipitation. Activation of TGF-β signaling significantly upregulated transcript, protein, and surface expression of NBCe1. These effects were TGF-β receptor-mediated and suppressed following inhibition of JNK and Smad signaling. Moreover, 4-aminopyridine (4AP)-dependent NBCe1 regulation requires TGF-β. TGF-β increased the rate and amplitude of intracellular H+ changes upon challenging NBCe1 in wild-type astrocytes but not in cortical astrocytes from Slc4a4-deficient mice. A Smad4 binding sequence was identified in the NBCe1 promoter and Smad4 binding increased after activation of TGF-β signaling. The data show for the first time that NBCe1 is a direct target of TGF-β/Smad4 signaling. Through activation of the canonical pathway TGF-β acts directly on NBCe1 by binding of Smad4 to the NBCe1 promoter and regulating its transcription, followed by increased protein expression and transport activity.

Imaging blood-brain barrier dysfunction as a biomarker for epileptogenesis

A biomarker that will enable the identification of patients at high-risk for developing post-injury epilepsy is critically required. Microvascular pathology and related blood-brain barrier dysfunction and neuroinflammation were shown to be associated with epileptogenesis after injury. Here we used prospective, longitudinal magnetic resonance imaging to quantitatively follow blood-brain barrier pathology in rats following status epilepticus, late electrocorticography to identify epileptic animals and post-mortem immunohistochemistry to confirm blood-brain barrier dysfunction and neuroinflammation. Finally, to test the pharmacodynamic relevance of the proposed biomarker, two anti-epileptogenic interventions were used; isoflurane anaesthesia and losartan. Our results show that early blood-brain barrier pathology in the piriform network is a sensitive and specific predictor (area under the curve of 0.96, P < 0.0001) for epilepsy, while diffused pathology is associated with a lower risk. Early treatments with either isoflurane anaesthesia or losartan prevented early microvascular damage and late epilepsy. We suggest quantitative assessment of blood-brain barrier pathology as a clinically relevant predictive, diagnostic and pharmaco!dynamics biomarker for acquired epilepsy.

Epileptogenesis in organotypic hippocampal cultures has limited dependence on culture medium composition

Rodent organotypic hippocampal cultures spontaneously develop epileptiform activity after approximately 2 weeks in vitro and are increasingly used as a model of chronic post-traumatic epilepsy. However, organotypic cultures are maintained in an artificial environment (culture medium), which contains electrolytes, glucose, amino acids and other components that are not present at the same concentrations in cerebrospinal fluid (CSF). Therefore, it is possible that epileptogenesis in organotypic cultures is driven by these components. We examined the influence of medium composition on epileptogenesis. Epileptogenesis was evaluated by measurements of lactate and lactate dehydrogenase (LDH) levels (biomarkers of ictal activity and cell death, respectively) in spent culture media, immunohistochemistry and automated 3-D cell counts, and extracellular recordings from CA3 regions. Changes in culture medium components moderately influenced lactate and LDH levels as well as electrographic seizure burden and cell death. However, epileptogenesis occurred in any culture medium that was capable of supporting neural survival. We conclude that medium composition is unlikely to be the cause of epileptogenesis in the organotypic hippocampal culture model of chronic post-traumatic epilepsy.

Post-stroke epilepsy

Post-stroke epilepsy (PSE) is a common complication after stroke, yet treatment options remain limited. While many physicians prescribe antiepileptic drugs (AED) for secondary prevention of PSE, it is unclear which treatments are most effective in the prevention of recurrence of symptoms, or whether such therapy is needed for primary prevention. This review discusses the current understanding of epidemiology, diagnoses, mechanisms, risk factors, and treatments of PSE.

Smad anchor for receptor activation contributes to seizures in temporal lobe epilepsy

PURPOSE

Smad anchor for receptor activation (SARA) is an important regulator of transforming growth factor β (TGF-β) signaling by recruiting Smad2/3 to TGF-β receptors. Although TGF-β signaling is critically involved in epileptogenesis, whether SARA activation is sufficient to facilitate TGF-β pathway to regulate epilepsy remains unknown.

METHODS

The expression of SARA and downstream Phospho-Smad3 (p-Smad3) was examined in rats with pilocarpine induced epilepsy. Additionally, knockdown of SARA was performed via recombinant lentiviral vector in the pilocarpine-induced rats.

RESULTS

Here we show that expressions of SARA and p-Smad3 are increased in the hippocampus as rats subjected to pilocarpine-induced status epilepticus (SE). Both SARA and p-Smad3 are also upregulated in the temporal cortex of epileptic rats. Furthermore, SARA mRNA levels reach peak as early as 6 hr following SE onset and remain elevated in the chronic phase. Transfection of recombinant lentiviral shRNA targeting SARA knocks down SARA expression, attenuates TGF-β/p-Smad3 signaling in the hippocampus, and postpones the SE onset.

CONCLUSION

Our results demonstrate that SARA/Smad3 pathway contributes to mechanism of seizure and SARA in TGF-β signaling may be a potential therapeutic target for epilepsy.

Inflammation in epileptogenesis after traumatic brain injury

Background

Epilepsy is a common and debilitating consequence of traumatic brain injury (TBI). Seizures contribute to progressive neurodegeneration and poor functional and psychosocial outcomes for TBI survivors, and epilepsy after TBI is often resistant to existing anti-epileptic drugs. The development of post-traumatic epilepsy (PTE) occurs in a complex neurobiological environment characterized by ongoing TBI-induced secondary injury processes. Neuroinflammation is an important secondary injury process, though how it contributes to epileptogenesis, and the development of chronic, spontaneous seizure activity, remains poorly understood. A mechanistic understanding of how inflammation contributes to the development of epilepsy (epileptogenesis) after TBI is important to facilitate the identification of novel therapeutic strategies to reduce or prevent seizures.

Body

We reviewed previous clinical and pre-clinical data to evaluate the hypothesis that inflammation contributes to seizures and epilepsy after TBI. Increasing evidence indicates that neuroinflammation is a common consequence of epileptic seizure activity, and also contributes to epileptogenesis as well as seizure initiation (ictogenesis) and perpetuation. Three key signaling factors implicated in both seizure activity and TBI-induced secondary pathogenesis are highlighted in this review: high-mobility group box protein-1 interacting with toll-like receptors, interleukin-1β interacting with its receptors, and transforming growth factor-β signaling from extravascular albumin. Lastly, we consider age-dependent differences in seizure susceptibility and neuroinflammation as mechanisms which may contribute to a heightened vulnerability to epileptogenesis in young brain-injured patients.

Conclusion

Several inflammatory mediators exhibit epileptogenic and ictogenic properties, acting on glia and neurons both directly and indirectly influence neuronal excitability. Further research is required to establish causality between inflammatory signaling cascades and the development of epilepsy post-TBI, and to evaluate the therapeutic potential of pharmaceuticals targeting inflammatory pathways to prevent or mitigate the development of PTE.

Protocol for intraoperative assessment of the human cerebrovascular glycocalyx

INTRODUCTION

Adequate functioning of the blood-brain barrier (BBB) is important for brain homoeostasis and normal neuronal function. Disruption of the BBB has been described in several neurological diseases. Recent reports suggest that an increased permeability of the BBB also contributes to increased seizure susceptibility in patients with epilepsy. The endothelial glycocalyx is coating the luminal side of the endothelium and can be considered as the first barrier of the BBB. We hypothesise that an altered glycocalyx thickness plays a role in the aetiology of temporal lobe epilepsy (TLE), the most common type of epilepsy. Here, we propose a protocol that allows intraoperative assessment of the cerebrovascular glycocalyx thickness in patients with TLE and assess whether its thickness is decreased in patients with TLE when compared with controls.

METHODS AND ANALYSIS

This protocol is designed as a prospective observational case-control study in patients who undergo resective brain surgery as treatment for TLE. Control subjects are patients without a history of epileptic seizures, who undergo a craniotomy or burr hole surgery for other indications. Intraoperative glycocalyx thickness measurements of sublingual, cortical and hippocampal microcirculation are performed by video microscopy using sidestream dark-field imaging. Demographic details, seizure characteristics, epilepsy risk factors, intraoperative haemodynamic parameters and histopathological evaluation are additionally recorded.

ETHICS AND DISSEMINATION

This protocol has been ethically approved by the local medical ethical committee (ID: NL51594.068.14) and complies with the Declaration of Helsinki and principles of Good Clinical Practice. Informed consent is obtained before study enrolment and only coded data will be stored in a secured database, enabling an audit trail. Results will be submitted to international peer-reviewed journals and presented at international conferences.

TRIAL REGISTRATION NUMBER

NTR5568.

Blockade of the IL-1R1/TLR4 pathway mediates disease-modification therapeutic effects in a model of acquired epilepsy

We recently discovered that forebrain activation of the IL-1 receptor/Toll-like receptor (IL-1R1/TLR4) innate immunity signal plays a pivotal role in neuronal hyperexcitability underlying seizures in rodents. Since this pathway is activated in neurons and glia in human epileptogenic foci, it represents a potential target for developing drugs interfering with the mechanisms of epileptogenesis that lead to spontaneous seizures. The lack of such drugs represents a major unmet clinical need. We tested therefore novel therapies inhibiting the IL-1R1/TLR4 signaling in an established murine model of acquired epilepsy. We used an epigenetic approach by injecting a synthetic mimic of micro(mi)RNA-146a that impairs IL1R1/TLR4 signal transduction, or we blocked receptor activation with antiinflammatory drugs. Both interventions when transiently applied to mice after epilepsy onset, prevented disease progression and dramatically reduced chronic seizure recurrence, while the anticonvulsant drug carbamazepine was ineffective. We conclude that IL-1R1/TLR4 is a novel potential therapeutic target for attaining disease-modifications in patients with diagnosed epilepsy.

Blood-brain barrier and intestinal epithelial barrier alterations in autism spectrum disorders

Background

Autism spectrum disorders (ASD) are complex conditions whose pathogenesis may be attributed to gene–environment interactions. There are no definitive mechanisms explaining how environmental triggers can lead to ASD although the involvement of inflammation and immunity has been suggested. Inappropriate antigen trafficking through an impaired intestinal barrier, followed by passage of these antigens or immune-activated complexes through a permissive blood–brain barrier (BBB), can be part of the chain of events leading to these disorders. Our goal was to investigate whether an altered BBB and gut permeability is part of the pathophysiology of ASD.

Methods

Postmortem cerebral cortex and cerebellum tissues from ASD, schizophrenia (SCZ), and healthy subjects (HC) and duodenal biopsies from ASD and HC were analyzed for gene and protein expression profiles. Tight junctions and other key molecules associated with the neurovascular unit integrity and function and neuroinflammation were investigated.

Results

Claudin (CLDN)-5 and -12 were increased in the ASD cortex and cerebellum. CLDN-3, tricellulin, and MMP-9 were higher in the ASD cortex. IL-8, tPA, and IBA-1 were downregulated in SCZ cortex; IL-1b was increased in the SCZ cerebellum. Differences between SCZ and ASD were observed for most of the genes analyzed in both brain areas. CLDN-5 protein was increased in ASD cortex and cerebellum, while CLDN-12 appeared reduced in both ASD and SCZ cortexes. In the intestine, 75% of the ASD samples analyzed had reduced expression of barrier-forming TJ components (CLDN-1, OCLN, TRIC), whereas 66% had increased pore-forming CLDNs (CLDN-2, -10, -15) compared to controls.

Conclusions

In the ASD brain, there is an altered expression of genes associated with BBB integrity coupled with increased neuroinflammation and possibly impaired gut barrier integrity. While these findings seem to be specific for ASD, the possibility of more distinct SCZ subgroups should be explored with additional studies.

NKCC1 up-regulation contributes to early post-traumatic seizures and increased post-traumatic seizure susceptibility

Traumatic brain injury (TBI) is not only a leading cause for morbidity and mortality in young adults (Bruns and Hauser, Epilepsia 44(Suppl 10):210, 2003), but also a leading cause of seizures. Understanding the seizure-inducing mechanisms of TBI is of the utmost importance, because these seizures are often resistant to traditional first- and second-line anti-seizure treatments. The early post-traumatic seizures, in turn, are a contributing factor to ongoing neuropathology, and it is critically important to control these seizures. Many of the available anti-seizure drugs target gamma-aminobutyric acid (GABA_A) receptors. The inhibitory activity of GABA_A receptor activation depends on low intracellular Cl⁻, which is achieved by the opposing regulation of Na⁺–K⁺–Cl⁻ cotransporter 1 (NKCC1) and K⁺–Cl⁻–cotransporter 2 (KCC2). Up-regulation of NKCC1 in neurons has been shown to be involved in neonatal seizures and in ammonia toxicity-induced seizures. Here, we report that TBI-induced up-regulation of NKCC1 and increased intracellular Cl⁻ concentration. Genetic deletion of NKCC1 or pharmacological inhibition of NKCC1 with bumetanide suppresses TBI-induced seizures. TGFβ expression was also increased after TBI and competitive antagonism of TGFβ reduced NKKC1 expression, ameliorated reactive astrocytosis, and inhibited seizures. Thus, TGFβ might be an important pathway involved in NKCC1 up-regulation after TBI. Our findings identify neuronal up-regulation of NKCC1 and its mediation by TGFβ, as a potential and important mechanism in the early post-traumatic seizures, and demonstrate the therapeutic potential of blocking this pathway.

Fit for purpose application of currently existing animal models in the discovery of novel epilepsy therapies

Animal seizure and epilepsy models continue to play an important role in the early discovery of new therapies for the symptomatic treatment of epilepsy. Since 1937, with the discovery of phenytoin, almost all anti-seizure drugs (ASDs) have been identified by their effects in animal models, and millions of patients world-wide have benefited from the successful translation of animal data into the clinic. However, several unmet clinical needs remain, including resistance to ASDs in about 30% of patients with epilepsy, adverse effects of ASDs that can reduce quality of life, and the lack of treatments that can prevent development of epilepsy in patients at risk following brain injury. The aim of this review is to critically discuss the translational value of currently used animal models of seizures and epilepsy, particularly what animal models can tell us about epilepsy therapies in patients and which limitations exist. Principles of translational medicine will be used for this discussion. An essential requirement for translational medicine to improve success in drug development is the availability of animal models with high predictive validity for a therapeutic drug response. For this requirement, the model, by definition, does not need to be a perfect replication of the clinical condition, but it is important that the validation provided for a given model is fit for purpose. The present review should guide researchers in both academia and industry what can and cannot be expected from animal models in preclinical development of epilepsy therapies, which models are best suited for which purpose, and for which aspects suitable models are as yet not available. Overall further development is needed to improve and validate animal models for the diverse areas in epilepsy research where suitable fit for purpose models are urgently needed in the search for more effective treatments.

Astroglial Scarring and Seizures

Epilepsy is among the most prevalent chronic neurological diseases and affects an estimated 2.2 million people in the United States alone. About one third of patients are resistant to currently available antiepileptic drugs, which are exclusively targeting neuronal function. Yet, reactive astrocytes have emerged as potential contributors to neuronal hyperexcitability and seizures. Astrocytes react to any kind of CNS insult with a range of cellular adjustments to form a scar and protect uninjured brain regions. This process changes astrocyte physiology and can affect neuronal network function in various ways. Traumatic brain injury and stroke, both conditions that trigger astroglial scar formation, are leading causes of acquired epilepsies and surgical removal of this glial scar in patients with drug-resistant epilepsy can alleviate the seizures. This review will summarize the currently available evidence suggesting that epilepsy is not a disease of neurons alone, but that astrocytes, glial cells in the brain, can be major contributors to the disease, especially when they adopt a reactive state in response to central nervous system insult.

Safe long-term repeated disruption of the blood-brain barrier using an implantable ultrasound device: a multiparametric study in a primate model

OBJECTIVE The main limitation to the efficacy of chemotherapy for brain tumors is the restricted access to the brain because of the limited permeability of the blood-brain barrier (BBB). Previous animal studies have shown that the application of pulsed ultrasound (US), in combination with the intravenous injection of microbubbles, can temporarily disrupt the BBB to deliver drugs that normally cannot reach brain tissue. Although many previous studies have been performed with external focused US transducers, the device described in the current work emits US energy using an unfocused transducer implanted in the skull thickness. This method avoids distortion of the US energy by the skull bone and allows for simple, repetitive, and broad disruption of the BBB without the need for MRI monitoring. The purpose of the present study was to determine if the BBB can be safely and repeatedly disrupted using such an implantable unfocused US device in a primate model. METHODS An 11.5-mm-diameter, 1-MHz, planar US device was implanted via a bur hole into the skull of 3 primates (2 Papio anubis [olive] baboons and 1 Macaca fascicularis [macaque]) for 4 months. Pulsed US sonications were applied together with the simultaneous intravenous injection of sulfur hexafluoride microbubbles (SonoVue) every 2 weeks to temporarily disrupt the BBB. In each primate, a total of 7 sonications were performed with a 23.2-msec burst length (25,000 cycles) and a 1-Hz pulse repetition frequency at acoustic pressure levels of 0.6-0.8 MPa. Potential toxicity induced by repeated BBB opening was analyzed using MRI, PET, electroencephalography (EEG), somatosensory evoked potential (SSEP) monitoring, behavioral scales, and histopathological analysis. RESULTS The T1-weighted contrast-enhanced MR images acquired after each sonication exhibited a zone of hypersignal underneath the transducer that persisted for more than 4 hours, indicating a broad region of BBB opening in the acoustic field of the implant. Positron emission tomography images with fluorine-18-labeled fluorodeoxyglucose (FDG) did not indicate any changes in the cerebral metabolism of glucose. Neither epileptic signs nor pathological central nerve conduction was observed on EEG and SSEP recordings, respectively. Behavior in all animals remained normal. Histological analysis showed no hemorrhagic processes, no petechia, and extravasation of only a few erythrocytes. CONCLUSIONS The studies performed confirm that an implantable, 1-MHz US device can be used to repeatedly open the BBB broadly in a large-animal model without inducing any acute, subacute, or chronic lesions.

1400W, a highly selective inducible nitric oxide synthase inhibitor is a potential disease modifier in the rat kainate model of temporal lobe epilepsy

Status epilepticus (SE) initiates epileptogenesis to transform normal brain to epileptic state which is characterized by spontaneous recurrent seizures (SRS). Prior to SRS, progressive changes occur in the brain soon after SE, for example, loss of blood-brain barrier (BBB) integrity, neuronal hyper-excitability (epileptiform spiking), neuroinflammation [reactive gliosis, high levels of reactive oxygen/nitrogen species (ROS/RNS)], neurodegeneration and synaptic re-organization. Our hypothesis was that modification of early epileptogenic events will alter the course of disease development and its progression. We tested the hypothesis in the rat kainate model of chronic epilepsy using a novel disease modifying drug, 1400W, a highly selective inhibitor of inducible nitric oxide synthase (iNOS/NOS-II). In an in vitro mouse brain slice model, using a multi-electrode array system, co-application of 1400W with kainate significantly suppressed kainate-induced epileptiform spiking. In the rats, in vivo, 4h after the induction of SE with kainate, 1400W (20mg/kg, i.p.) was administered twice daily for three days to target early events of epileptogenesis. The rats were subjected to continuous (24/7) video-EEG monitoring, remotely, for six months from epidurally implanted cortical electrodes. The 1400W treatment significantly reduced the epileptiform spike rate during the first 12-74h post-SE, which resulted in >90% reduction in SRS in long-term during the six month period when compared to the vehicle-treated control group (257±113 versus 19±10 episodes). Immunohistochemistry (IHC) of brain sections at seven days and six months revealed a significant reduction in; reactive astrogliosis and microgliosis (M1 type), extravascular serum albumin (a marker for BBB leakage) and neurodegeneration in the hippocampus, amygdala and entorhinal cortex in the 1400W-treated rats when compared to the vehicle control. In the seven day group, hippocampal Western blots revealed downregulation of inwardly-rectifying potassium (Kir 4.1) channels and glutamate transporter-1 (GLT-1) levels in the vehicle group, and 1400W treatment partially reversed Kir 4.1 levels, however, GLT-1 levels were unaffected. In the six month group, a significant reduction in mossy fiber staining intensity in the inner molecular layer of the dentate gyrus was observed in the 1400W-treated group. Overall these findings demonstrate that 1400W, by reducing the epileptiform spike rate during the first three days of post-insult, potentially modifies epileptogenesis and the severity of chronic epilepsy in the rat kainate model of TLE.

Independent impact of infections on the course and outcome of status epilepticus: a 10-year cohort study

Infections are frequent in patients with status epilepticus (SE). It remains unclear if infections merely reflect severity of the underlying illness or if they independently predict unfavourable course and outcome. We sought to determine if infections diagnosed within 48 h from SE onset are independent predictors of poor course and outcome and if their effect is modified by clinical characteristics. From 2005 to 2014, pertinent clinical data, microbiology, death, return to functional baseline, and unfavourable outcome in survivors were assessed in SE patients treated in the intensive care units (ICU) of an academic medical care center. Among 352 consecutive patients, 81 (23 %) were diagnosed with infections at SE onset. In-hospital mortality was higher in patients with infections (26 %) compared to 10 % in patients without infections (p < 0.001). Infections at SE onset increased the odds ratios (OR) for prolonged ICU (OR = 4.1, 95 %CI 1.87-6.74) and hospital stay (OR = 5.4, 95 %CI 1.24-9.63), refractory SE (OR = 3.1, 95 %CI 1.79-5.34), prolonged mechanical ventilation (OR = 3.8, 95 %CI 2.15-6.79), no return to functional baseline (OR = 2.1, 95 %CI 1.10-4.02), unfavourable outcome in survivors (OR = 2.0, 95 %CI 1.02-3.81), and death (OR = 2.5, 95 %CI 1.28-4.99). All associations were independent of confounders and without significant effect modification by age, level of consciousness, types and severity of SE, and etiologies. In addition, the number of infections increased the probability of unfavourable course and outcome. Infections at SE onset are frequent and associated with prolonged medical care, treatment refractory SE, higher morbidity and mortality independently of potential confounders calling for the evaluation of treatment strategies.

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.

Systemic attenuation of the TGF-β pathway by a single drug simultaneously rejuvenates hippocampal neurogenesis and myogenesis in the same old mammal

Stem cell function declines with age largely due to the biochemical imbalances in their tissue niches, and this work demonstrates that aging imposes an elevation in transforming growth factor β (TGF-β) signaling in the neurogenic niche of the hippocampus, analogous to the previously demonstrated changes in the myogenic niche of skeletal muscle with age. Exploring the hypothesis that youthful calibration of key signaling pathways may enhance regeneration of multiple old tissues, we found that systemically attenuating TGF-β signaling with a single drug simultaneously enhanced neurogenesis and muscle regeneration in the same old mice, findings further substantiated via genetic perturbations. At the levels of cellular mechanism, our results establish that the age-specific increase in TGF-β1 in the stem cell niches of aged hippocampus involves microglia and that such an increase is pro-inflammatory both in brain and muscle, as assayed by the elevated expression of β2 microglobulin (B2M), a component of MHC class I molecules. These findings suggest that at high levels typical of aged tissues, TGF-β1 promotes inflammation instead of its canonical role in attenuating immune responses. In agreement with this conclusion, inhibition of TGF-β1 signaling normalized B2M to young levels in both studied tissues.

Synaptic plasticity in area CA1 of rat hippocampal slices following intraventricular application of albumin

Epileptogenesis following insults to the brain may be triggered by a dysfunctional blood-brain barrier (BBB) associated with albumin extravasation and activation of astrocytes. Using ex vivo recordings from the BBB-disrupted hippocampus after neocortical photothrombotic stroke, we previously demonstrated abnormal activity-dependent accumulation of extracellular potassium with facilitated generation of seizure like events and spreading depolarizations. Similar changes could be observed after intracerebroventricular (icv) application of albumin. We hypothesized that alterations in extracellular potassium and glutamate homeostasis might lead to alterations in synaptic interactions. We therefore assessed the effects of icv albumin on homo- and heterosynaptic plasticity in hippocampal CA1, 24h after a single injection or 7days after continuous infusion of icv albumin. We demonstrate alterations in both homo- and heterosynaptic plasticity compared to control conditions in ex vivo slice studies. Albumin-treated tissue reveals (1) reduced long-term depression following low-frequency stimulation; (2) increased long-term potentiation of population spikes in response to 20Hz stimulation; (3) potentiated responses to Schaffer collateral stimulation following high-frequency stimulation of the direct cortical input and low-frequency stimulation of alveus and finally, (4) TGFβ receptor II (TGFβR-II) involvement in albumin-induced homosynaptic plasticity changes. We conclude that albumin-induced network hyperexcitability is associated with abnormal homo- and heterosynaptic plasticity that could partly be reversed by interference with TGFβR-II-mediated signaling and therefore it might be an important factor in the process of epileptogenesis.

Proteomic profiling of epileptogenesis in a rat model: Focus on inflammation

Detailed knowledge about the patterns of molecular alterations during epileptogenesis is a presupposition for identifying targets for preventive or disease-modifying approaches, as well as biomarkers of the disease. Large-scale differential proteome analysis can provide unique and novel perspectives based on comprehensive data sets informing about the complex regulation patterns in the disease proteome. Thus, we have completed an elaborate differential proteome analysis based on label-free LC-MS/MS in a rat model of epileptogenesis. Hippocampus and parahippocampal cortex tissues were sampled and analyzed separately at three key time points chosen for monitoring disease development following electrically-induced status epilepticus, namely, the early post-insult phase, the latency phase, and the chronic phase with spontaneous recurrent seizures. We focused the bioinformatics analysis on proteins linked to immune and inflammatory responses, because of the emerging evidence of the specific pathogenic role of inflammatory signalings during epileptogenesis. In the early post-insult and the latency phases, pathway enrichment analysis revealed an extensive over-representation of Toll-like receptor signaling, pro-inflammatory cytokines, heat shock protein regulation, and transforming growth factor beta signaling and leukocyte transendothelial migration. The inflammatory response in the chronic phase proved to be more moderate with differential expression in the parahippocampal cortex exceeding that in the hippocampus. The data sets provide novel information about numerous differentially expressed proteins, which serve as interaction partners or modulators in key disease-associated inflammatory signaling events. Noteworthy, a set of proteins which act as modulators of the ictogenic Toll-like receptor signaling proved to be differentially expressed. In addition, we report novel data demonstrating the regulation of different Toll-like receptor ligands during epileptogenesis. Taken together, the findings deepen our understanding of modulation of inflammatory signaling during epileptogenesis providing an excellent and comprehensive basis for the identification of target and biomarker candidates.

Montelukast reduces seizures in pentylenetetrazol-kindled mice

Cysteinyl leukotrienes (CysLTs) have been implicated in seizures and kindling; however, the effect of CysLT receptor antagonists on seizure frequency in kindled animals and changes in CysLT receptor expression after pentylenetetrazol (PTZ)-induced kindling have not been investigated. In this study, we evaluated whether the CysLT1 inverse agonist montelukast, and a classical anticonvulsant, phenobarbital, were able to reduce seizures in PTZ-kindled mice and alter CysLT receptor expression. Montelukast (10 mg/kg, sc) and phenobarbital (20 mg/kg, sc) increased the latency to generalized seizures in kindled mice. Montelukast increased CysLT1 immunoreactivity only in non-kindled, PTZ-challenged mice. Interestingly, PTZ challenge decreased CysLT2 immunoreactivity only in kindled mice. CysLT1 antagonists appear to emerge as a promising adjunctive treatment for refractory seizures. Nevertheless, additional studies are necessary to evaluate the clinical implications of this research.

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.

Mutation of ataxia-telangiectasia mutated is associated with dysfunctional glutathione homeostasis in cerebellar astroglia

Astroglial dysfunction plays an important role in neurodegenerative diseases otherwise attributed to neuronal loss of function. Here we focus on the role of astroglia in ataxia-telangiectasia (A-T), a disease caused by mutations in the ataxia-telangiectasia mutated (ATM) gene. A hallmark of A-T pathology is progressive loss of cerebellar neurons, but the mechanisms that impact neuronal survival are unclear. We now provide a possible mechanism by which A-T astroglia affect the survival of cerebellar neurons. As astroglial functions are difficult to study in an in vivo setting, particularly in the cerebellum where these cells are intertwined with the far more numerous neurons, we conducted in vitro coculture experiments that allow for the generation and pharmacological manipulation of purified cell populations. Our analyses revealed that cerebellar astroglia isolated from Atm mutant mice show decreased expression of the cystine/glutamate exchanger subunit xCT, glutathione (GSH) reductase, and glutathione-S-transferase. We also found decreased levels of intercellular and secreted GSH in A-T astroglia. Metabolic labeling of l-cystine, the major precursor for GSH, revealed that a key component of the defect in A-T astroglia is an impaired ability to import this rate-limiting precursor for the production of GSH. This impairment resulted in suboptimal extracellular GSH supply, which in turn impaired survival of cerebellar neurons. We show that by circumventing the xCT-dependent import of L-cystine through addition of N-acetyl-L-cysteine (NAC) as an alternative cysteine source, we were able to restore GSH levels in A-T mutant astroglia providing a possible future avenue for targeted therapeutic intervention.

Procalcitonin and mortality in status epilepticus: an observational cohort study

INTRODUCTION

Acute-phase proteins, such as procalcitonin (PCT), C-reactive protein (CRP) and albumin, may relate with course and outcome in status epilepticus (SE), as seizures bring about inflammation, changes of cytokine levels and blood-brain barrier breakdown. We aimed to determine the predictive value of serum levels of PCT at SE onset for the emergence of infections and unfavorable outcome in adult patients with SE. Furthermore, we sought to compare the predictive value of PCT, CRP and albumin for death.

METHODS

This observational cohort study was performed in the intensive care units of the University Hospital Basel (Switzerland), a university-affiliated tertiary care center. Adult patients with SE admitted from 2005 to 2012 were included. Serum levels of PCT, CRP and albumin were assessed at SE onset. Unfavorable outcome (i.e., death and a Glasgow Outcome Score of 1 to 3) during hospital stay and mortality after 30 days were considered the primary and infections as the secondary outcome measures.

RESULTS

In 91 SE patients, mortality was 23.1 % during hospital stay and at 30-days follow-up. Infections emerged in 30.8 % of patients. In the multivariable analysis, PCT predicted unfavorable outcome independently from possible confounders such as acute etiology, infections during SE, the Charlson Comorbidity Index, and the Status Epilepticus Severity Score (hazard ratio 1.44 per every increasing ug/L, 95 % confidence interval 1.11-1.87). Additional multivariable analysis including serum levels of PCT, CRP and albumin revealed PCT as the only biomarker independently associated with an increased hazard for unfavorable outcome. PCT levels at SE onset were not related to infections during SE.

CONCLUSIONS

Serum PCT levels measured at SE onset are independently associated with unfavorable outcome but do not predict the emergence of infections during SE. Procalcitonin may increase the predictive value of clinical scoring systems allowing for rapid risk stratification early in the course of SE.

Adenosinergic signaling in epilepsy

Despite the introduction of at least 20 new antiepileptic drugs (AEDs) into clinical practice over the past decades, about one third of all epilepsies remain refractory to conventional forms of treatment. In addition, currently used AEDs have been developed to suppress neuronal hyperexcitability, but not necessarily to address pathogenic mechanisms involved in epilepsy development or progression (epileptogenesis). For those reasons endogenous seizure control mechanisms of the brain may provide alternative therapeutic opportunities. Adenosine is a well characterized endogenous anticonvulsant and seizure terminator of the brain. Several lines of evidence suggest that endogenous adenosine-mediated seizure control mechanisms fail in chronic epilepsy, whereas therapeutic adenosine augmentation effectively prevents epileptic seizures, even those that are refractory to conventional AEDs. New findings demonstrate that dysregulation of adenosinergic mechanisms are intricately involved in the development of epilepsy and its comorbidities, whereas adenosine-associated epigenetic mechanisms may play a role in epileptogenesis. The first goal of this review is to discuss how maladaptive changes of adenosinergic mechanisms contribute to the expression of seizures (ictogenesis) and the development of epilepsy (epileptogenesis) by focusing on pharmacological (adenosine receptor dependent) and biochemical (adenosine receptor independent) mechanisms as well as on enzymatic and transport based mechanisms that control the availability (homeostasis) of adenosine. The second goal of this review is to highlight innovative adenosine-based opportunities for therapeutic intervention aimed at reconstructing normal adenosine function and signaling for improved seizure control in chronic epilepsy. New findings suggest that transient adenosine augmentation can have lasting epigenetic effects with disease modifying and antiepileptogenic outcome. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.

Glial regulation of the blood-brain barrier in health and disease

The brain is the organ with the highest metabolic demand in the body. Therefore, it needs specialized vasculature to provide it with the necessary oxygen and nutrients, while protecting it against pathogens and toxins. The blood-brain barrier (BBB) is very tightly regulated by specialized endothelial cells, two basement membranes, and astrocytic endfeet. The proximity of astrocytes to the vessel makes them perfect candidates to influence the function of the BBB. Moreover, other glial cells are also known to contribute to either BBB quiescence or breakdown. In this review, we summarize the knowledge on glial regulation of the BBB during development, in homeostatic conditions in the adult, and during neuroinflammatory responses.

Differential TGF-β Signaling in Glial Subsets Underlies IL-6-Mediated Epileptogenesis in Mice

TGF-β1 is a master cytokine in immune regulation, orchestrating both pro- and anti-inflammatory reactions. Recent studies show that whereas TGF-β1 induces a quiescent microglia phenotype, it plays a pathogenic role in the neurovascular unit and triggers neuronal hyperexcitability and epileptogenesis. In this study, we show that, in primary glial cultures, TGF-β signaling induces rapid upregulation of the cytokine IL-6 in astrocytes, but not in microglia, via enhanced expression, phosphorylation, and nuclear translocation of SMAD2/3. Electrophysiological recordings show that administration of IL-6 increases cortical excitability, culminating in epileptiform discharges in vitro and spontaneous seizures in C57BL/6 mice. Intracellular recordings from layer V pyramidal cells in neocortical slices obtained from IL-6 -: treated mice show that during epileptogenesis, the cells respond to repetitive orthodromic activation with prolonged after-depolarization with no apparent changes in intrinsic membrane properties. Notably, TGF-β1 -: induced IL-6 upregulation occurs in brains of FVB/N but not in brains of C57BL/6 mice. Overall, our data suggest that TGF-β signaling in the brain can cause astrocyte activation whereby IL-6 upregulation results in dysregulation of astrocyte -: neuronal interactions and neuronal hyperexcitability. Whereas IL-6 is epileptogenic in C57BL/6 mice, its upregulation by TGF-β1 is more profound in FVB/N mice characterized as a relatively more susceptible strain to seizure-induced cell death.

Type 1 diabetes exacerbates blood-brain barrier alterations during experimental epileptic seizures in an animal model

The aim of this study was to perform the effects of diabetes on the permeability of the blood-brain barrier (BBB) during pentylenetetrazole (PTZ)-induced epileptic attacks. For this propose, the animals were divided into four groups. These groups contained were intact, PTZ-treated, diabetic and PTZ-treated diabetic individuals, respectively. To evaluate the functioning of the BBB, Evans blue was used as a BBB permeability indicator, and the expressions of zonula occludens-1 and glial fibrillary acidic protein involving the functioning of the BBB were determined immunohistochemically. Also, the changes in the release of serum tumour necrosis factor-alpha and interleukin-10 and interleukin-12 were studied by using enzyme-linked immunosorbent assay method. BBB permeability in the seizures under diabetic conditions showed a considerable increase (p < 0·01) in all of the brain we studied. The immunoreactive staining intensity of zonula occludens-1 and glial fibrillary acidic protein was found reduced in the brain regions of diabetic rats (p < 0·01). However, the serum level of tumour necrosis factor-alpha increased in diabetes and diabetes + PTZ groups, and the serum level of interleukin-12 increased significantly in all experimental groups (p < 0·05). In conclusion, diabetes dramatically increases BBB damage during epileptic seizures, and it may be derived from an elevation of paracellular passage.

Reactive astrogliosis causes the development of spontaneous seizures

Epilepsy is one of the most common chronic neurologic diseases, yet approximately one-third of affected patients do not respond to anticonvulsive drugs that target neurons or neuronal circuits. Reactive astrocytes are commonly found in putative epileptic foci and have been hypothesized to be disease contributors because they lose essential homeostatic capabilities. However, since brain pathology induces astrocytes to become reactive, it is difficult to distinguish whether astrogliosis is a cause or a consequence of epileptogenesis. We now present a mouse model of genetically induced, widespread chronic astrogliosis after conditional deletion of β1-integrin (Itgβ1). In these mice, astrogliosis occurs in the absence of other pathologies and without BBB breach or significant inflammation. Electroencephalography with simultaneous video recording revealed that these mice develop spontaneous seizures during the first six postnatal weeks of life and brain slices show neuronal hyperexcitability. This was not observed in mice with neuronal-targeted β1-integrin deletion, supporting the hypothesis that astrogliosis is sufficient to induce epileptic seizures. Whole-cell patch-clamp recordings from astrocytes further suggest that the heightened excitability was associated with impaired astrocytic glutamate uptake. Moreover, the relative expression of the cation-chloride cotransporters (CCC) NKCC1 (Slc12a2) and KCC2 (Slc12a5), which are responsible for establishing the neuronal Cl(-) gradient that governs GABAergic inhibition were altered and the NKCC1 inhibitor bumetanide eliminated seizures in a subgroup of mice. These data suggest that a shift in the relative expression of neuronal NKCC1 and KCC2, similar to that observed in immature neurons during development, may contribute to astrogliosis-associated seizures.

Montelukast potentiates the anticonvulsant effect of phenobarbital in mice: an isobolographic analysis

Although leukotrienes have been implicated in seizures, no study has systematically investigated whether the blockade of CysLT1 receptors synergistically increases the anticonvulsant action of classic antiepileptics. In this study, behavioral and electroencephalographic methods, as well as isobolographic analysis, are used to show that the CysLT1 inverse agonist montelukast synergistically increases the anticonvulsant action of phenobarbital against pentylenetetrazole-induced seizures. Moreover, it is shown that LTD4 reverses the effect of montelukast. The experimentally derived ED50mix value for a fixed-ratio combination (1:1 proportion) of montelukast plus phenobarbital was 0.06±0.02 μmol, whereas the additively calculated ED50add value was 0.49±0.03 μmol. The calculated interaction index was 0.12, indicating a synergistic interaction. The association of montelukast significantly decreased the antiseizure ED50 for phenobarbital (0.74 and 0.04 μmol in the absence and presence of montelukast, respectively) and, consequently, phenobarbital-induced sedation at equieffective doses. The demonstration of a strong synergism between montelukast and phenobarbital is particularly relevant because both drugs are already used in the clinics, foreseeing an immediate translational application for epileptic patients who have drug-resistant seizures.