Celecoxib treatment restores pharmacosensitivity in a rat model of pharmacoresistant epilepsy

A Narrative Review of the Published Pre-Clinical Evaluations: Multiple Effects of Arachidonic Acid, its Metabolic Enzymes and Metabolites in Epilepsy

Arachidonic acid (AA), an important polyunsaturated fatty acid in the brain, is hydrolyzed by a direct action of phospholipase A2 (PLA2) or through the combined action of phospholipase C and diacylglycerol lipase, and released into the cytoplasm. Various derivatives of AA can be synthesized mainly through the cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (P450) enzyme pathways. AA and its metabolic enzymes and metabolites play important roles in a variety of neurophysiological activities. The abnormal metabolites and their catalytic enzymes in the AA cascade are related to the pathogenesis of various central nervous system (CNS) diseases, including epilepsy. Here, we systematically reviewed literatures in PubMed about the latest randomized controlled trials, animal studies and clinical studies concerning the known features of AA, its metabolic enzymes and metabolites, and their roles in epilepsy. The exclusion criteria include non-original studies and articles not in English.

Neuroinflammation in epileptogenesis: from pathophysiology to therapeutic strategies

Epilepsy is a group of enduring neurological disorder characterized by spontaneous and recurrent seizures with heterogeneous etiology, clinical expression, severity, and prognosis. Growing body of research investigates that epileptic seizures are originated from neuronal synchronized and excessive electrical activity. However, the underlying molecular mechanisms of epileptogenesis have not yet been fully elucidated and 30% of epileptic patients still are resistant to the currently available pharmacological treatments with recurrent seizures throughout life. Over the past two decades years accumulated evidences provide strong support to the hypothesis that neuroinflammation, including microglia and astrocytes activation, a cascade of inflammatory mediator releasing, and peripheral immune cells infiltration from blood into brain, is associated with epileptogenesis. Meanwhile, an increasing body of preclinical researches reveal that the anti-inflammatory therapeutics targeting crucial inflammatory components are effective and promising in the treatment of epilepsy. The aim of the present study is to highlight the current understanding of the potential neuroinflammatory mechanisms in epileptogenesis and the potential therapeutic targets against epileptic seizures.

Revisiting the concept of drug-resistant epilepsy: A TASK1 report of the ILAE/AES Joint Translational Task Force

Despite progress in the development of anti-seizure medications (ASMs), one third of people with epilepsy have drug-resistant epilepsy (DRE). The working definition of DRE, proposed by the International League Against Epilepsy (ILAE) in 2010, helped identify individuals who might benefit from presurgical evaluation early on. As the incidence of DRE remains high, the TASK1 workgroup on DRE of the ILAE/American Epilepsy Society (AES) Joint Translational Task Force discussed the heterogeneity and complexity of its presentation and mechanisms, the confounders in drawing mechanistic insights when testing treatment responses, and barriers in modeling DRE across the lifespan and translating across species. We propose that it is necessary to revisit the current definition of DRE, in order to transform the preclinical and clinical research of mechanisms and biomarkers, to identify novel, effective, precise, pharmacologic treatments, allowing for earlier recognition of drug resistance and individualized therapies.

ABCB1 and ABCG2 Regulation at the Blood-Brain Barrier: Potential New Targets to Improve Brain Drug Delivery

The drug efflux transporters ABCB1 and ABCG2 at the blood-brain barrier limit the delivery of drugs into the brain. Strategies to overcome ABCB1/ABCG2 have been largely unsuccessful, which poses a tremendous clinical problem to successfully treat central nervous system (CNS) diseases. Understanding basic transporter biology, including intracellular regulation mechanisms that control these transporters, is critical to solving this clinical problem.In this comprehensive review, we summarize current knowledge on signaling pathways that regulate ABCB1/ABCG2 at the blood-brain barrier. In Section I, we give a historical overview on blood-brain barrier research and introduce the role that ABCB1 and ABCG2 play in this context. In Section II, we summarize the most important strategies that have been tested to overcome the ABCB1/ABCG2 efflux system at the blood-brain barrier. In Section III, the main component of this review, we provide detailed information on the signaling pathways that have been identified to control ABCB1/ABCG2 at the blood-brain barrier and their potential clinical relevance. This is followed by Section IV, where we explain the clinical implications of ABCB1/ABCG2 regulation in the context of CNS disease. Lastly, in Section V, we conclude by highlighting examples of how transporter regulation could be targeted for therapeutic purposes in the clinic. SIGNIFICANCE STATEMENT: The ABCB1/ABCG2 drug efflux system at the blood-brain barrier poses a significant problem to successful drug delivery to the brain. The article reviews signaling pathways that regulate blood-brain barrier ABCB1/ABCG2 and could potentially be targeted for therapeutic purposes.

The role of neuroinflammation in canine epilepsy

The lack of therapeutics that prevent the development of epilepsy, improve disease prognosis or overcome drug resistance represents an unmet clinical need in veterinary as well as in human medicine. Over the past decade, experimental studies and studies in human epilepsy patients have demonstrated that neuroinflammatory processes are involved in epilepsy development and play a key role in neuronal hyperexcitability that underlies seizure generation. Targeting neuroinflammatory signaling pathways may provide a basis for clinically relevant disease-modification strategies in general, and moreover, could open up new therapeutic avenues for human and veterinary patients with drug-resistant epilepsy. A sound understanding of the neuroinflammatory mechanisms underlying seizure pathogenesis in canine patients is therefore essential for mechanism-based discovery of selective epilepsy therapies that may enable the development of new disease-modifying treatments. In particular, subgroups of canine patients in urgent needs, e.g. dogs with drug-resistant epilepsy, might benefit from more intensive research in this area. Moreover, canine epilepsy shares remarkable similarities in etiology, disease manifestation, and disease progression with human epilepsy. Thus, canine epilepsy is discussed as a translational model for the human disease and epileptic dogs could provide a complementary species for the evaluation of antiepileptic and antiseizure drugs. This review reports key preclinical and clinical findings from experimental research and human medicine supporting the role of neuroinflammation in the pathogenesis of epilepsy. Moreover, the article provides an overview of the current state of knowledge regarding neuroinflammatory processes in canine epilepsy emphasizing the urgent need for further research in this specific field. It also highlights possible functional impact, translational potential and future perspectives of targeting specific inflammatory pathways as disease-modifying and multi-target treatment options for canine epilepsy.

Neuroinflammatory mediators in acquired epilepsy: an update

Epilepsy is a group of chronic neurological disorders that have diverse etiologies but are commonly characterized by spontaneous seizures and behavioral comorbidities. Although the mechanisms underlying the epileptic seizures mostly remain poorly understood and the causes often can be idiopathic, a considerable portion of cases are known as acquired epilepsy. This form of epilepsy is typically associated with prior neurological insults, which lead to the initiation and progression of epileptogenesis, eventually resulting in unprovoked seizures. A convergence of evidence in the past two decades suggests that inflammation within the brain may be a major contributing factor to acquired epileptogenesis. As evidenced in mounting preclinical and human studies, neuroinflammatory processes, such as activation and proliferation of microglia and astrocytes, elevated production of pro-inflammatory cytokines and chemokines, blood-brain barrier breakdown, and upregulation of inflammatory signaling pathways, are commonly observed after seizure-precipitating events. An increased knowledge of these neuroinflammatory processes in the epileptic brain has led to a growing list of inflammatory mediators that can be leveraged as potential targets for new therapies of epilepsy and/or biomarkers that may provide valued information for the diagnosis and prognosis of the otherwise unpredictable seizures. In this review, we mainly focus on the most recent progress in understanding the roles of these inflammatory molecules in acquired epilepsy and highlight the emerging evidence supporting their candidacy as novel molecular targets for new pharmacotherapies of acquired epilepsy and the associated behavioral deficits.

Cyclooxygenase-2 Inhibition as an Add-On Strategy in Drug Resistant Epilepsy—A Canine Translational Study

Drug-resistant epilepsy is a common complaint in dogs and affects up to 30% of dogs with idiopathic epilepsy. Experimental data suggest that targeting cyclooxygenase-2 (COX-2) mediated signaling might limit excessive excitability and prevent ictogenesis. Moreover, the role of COX-2 signaling in the seizure-associated induction of P-glycoprotein has been described. Thus, targeting this pathway may improve seizure control based on disease-modifying effects as well as enhancement of brain access and efficacy of the co-administered antiseizure medication. The present open-label non-controlled pilot study investigated the efficacy and tolerability of a COX-2 inhibitor (firocoxib) add-on therapy in a translational natural occurring chronic epilepsy animal model (client-owned dogs with phenobarbital-resistant idiopathic epilepsy). The study cohort was characterized by frequent tonic–clonic seizures and cluster seizures despite adequate phenobarbital treatment. Enrolled dogs (n = 17) received a firocoxib add-on therapy for 6 months. Tonic–clonic seizure and cluster seizure frequencies were analyzed at baseline (6 months) months during the study (6 months). The responders were defined by a substantial reduction of tonic–clonic seizure and cluster seizure frequency (≥50%). In total, eleven dogs completed the study and were considered for the statistical analysis. Two dogs (18%, 2/11) were classified as responders based on their change in seizure frequency. Interestingly, those two dogs had the highest baseline seizure frequency. The overall tolerability was good. However, given the low percentage of responders, the present data do not support an overall considerable efficacy of COX-2 inhibitor add-on therapy to overcome naturally occurring phenobarbital-resistant epilepsy in dogs. Further translational evaluation should only be considered in the canine patients with a very high baseline seizure density.

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

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

Emerging therapeutic targets for epilepsy: Preclinical insights

INTRODUCTION

Around 30% of patients with epilepsy suffer from drug-resistant seizures. Drug-resistant seizures may have significant consequences such as sudden death in epilepsy, injuries, memory disturbances, and childhood learning and developmental problems. Conventional and newer available antiepileptic drugs (AEDs) work via numerous mechanisms - mainly through inhibition of voltage-operated Na⁺ and/or Ca²⁺ channels, excitation of K⁺ channels, enhancement of GABA-mediated inhibition and/or blockade of glutamate-produced excitation. However, the discovery and development of novel brain targets may improve the future pharmacological management of epilepsy and hence is of pivotal importance.

AREAS COVERED

This article examines novel drug targets such as brain multidrug efflux transporters and inflammatory pathways; it progresses to discuss possible strategies for the management of drug-resistant seizures. Reduction of the consequences of blood brain barrier dysfunction and enhancement of anti-oxidative defense are discussed.

EXPERT OPINION

Novel drug targets comprise brain multidrug efflux transporters, TGF-β, Nrf2-ARE or m-TOR signaling and inflammatory pathways. Gene therapy and antagomirs seem the most promising targets. Epileptic foci may be significantly suppressed by viral-vector-mediated gene transfer, leading to an increased in situ concentration of inhibitory factors (for instance, galanin). Also, antagomirs offer a promising possibility of seizure inhibition by silencing micro-RNAs involved in epileptogenesis and possibly in seizure generation.

Mollusc-Derived Brominated Indoles for the Selective Inhibition of Cyclooxygenase: A Computational Expedition

Inflammation plays an important role in different chronic diseases. Brominated indoles derived from the Australian marine mollusk Dicathais orbita (D. orbita) are of interest for their anti-inflammatory properties. This study evaluates the binding mechanism and potentiality of several brominated indoles (tyrindoxyl sulfate, tyrindoleninone, 6-bromoisatin, and 6,6′-dibromoindirubin) against inflammatory mediators cyclooxygenases-1/2 (COX-1/2) using molecular docking, followed by molecular dynamics simulation, along with physicochemical, drug-likeness, pharmacokinetic (pk), and toxicokinetic (tk) properties. Molecular docking identified that these indole compounds are anchored, with the main amino acid residues, positioned in the binding pocket of the COX-1/2, required for selective inhibition. Moreover, the molecular dynamics simulation based on root mean square deviation (RMSD), radius of gyration (Rg), solvent accessible surface area (SASA), and root mean square fluctuation (RMSF) analyses showed that these natural brominated molecules transit rapidly to a progressive constant configuration during binding with COX-1/2 and seem to accomplish a consistent dynamic behavior by maintaining conformational stability and compactness. The results were comparable to the Food and Drug Administration (FDA)-approved selective COX inhibitor, aspirin. Furthermore, the free energy of binding for the compounds assessed by molecular mechanics–Poisson–Boltzmann surface area (MM–PBSA) confirmed the binding capacity of indoles towards COX-1/2, with suitable binding energy values except for the polar precursor tyrindoxyl sulfate (with COX-1). The physicochemical and drug-likeness analysis showed zero violations of Lipinski’s rule, and the compounds are predicted to have excellent pharmacokinetic profiles. These indoles are projected to be non-mutagenic and free from hepatotoxicity, with no inhibition of human ether-a-go–go gene (hERG) I inhibitors, and the oral acute toxicity LD₅₀ in rats is predicted to be similar or lower than aspirin. Overall, this work has identified a plausible mechanism for selective COX inhibition by natural marine indoles as potential therapeutic candidates for the mitigation of inflammation.

Neuroinflammation in neurological disorders: pharmacotherapeutic targets from bench to bedside

Neuroinflammation is one of the host defensive mechanisms through which the nervous system protects itself from pathogenic and or infectious insults. Moreover, neuroinflammation occurs as one of the most common pathological outcomes in various neurological disorders, makes it the promising target. The present review focuses on elaborating the recent advancement in understanding molecular mechanisms of neuroinflammation and its role in the etiopathogenesis of various neurological disorders, especially Alzheimer's disease (AD), Parkinson's disease (PD), and Epilepsy. Furthermore, the current status of anti-inflammatory agents in neurological diseases has been summarized in light of different preclinical and clinical studies. Finally, possible limitations and future directions for the effective use of anti-inflammatory agents in neurological disorders have been discussed.

New anticonvulsant candidates prevent P-glycoprotein (P-gp) overexpression in a pharmacoresistant seizure model in mice

Despite the approval of a considerable number of last generation antiepileptic drugs (AEDs) (only in the last decade, six drugs have gained Food and Drug Administration approval), the global figures of seizure control have seemingly not improved, and available AED can still be regarded as symptomatic treatments. Fresh thinking in AEDs drug discovery, including the development of drugs with novel mechanisms of action, is required to achieve truly innovative antiepileptic medications. The transporter hypothesis proposes that inadequate penetration of AEDs across the blood-brain barrier, caused by increased expression of efflux transporters such as P-glycoprotein (P-gp), contributes to drug-resistant epilepsy. Neuroinflammation due to high levels of glutamate has been identified as one of the causes of P-gp upregulation, and several studies in animal models of epilepsy suggest that antiinflammatory drugs might prevent P-gp overexpression and, thus, avoid the development of refractory epilepsy. We have applied ligand-based in silico screening to select compounds that exert dual anticonvulsant and antiinflammatory effects. Five of the hits were tested in animal models of seizure, with protective effects. Later, two of them (sebacic acid (SA) and gamma-decanolactone) were submitted to the recently described MP23 model of drug-resistant seizures. All in all, SA displayed the best profile, showing activity in the maximal electroshock seizure (MES) and pentylenetetrazol (PTZ) seizure models, and reversing resistance to phenytoin (PHT) and decreasing the P-gp upregulation in the MP23 model. Furthermore, pretreatment with SA in the pilocarpine status epilepticus (SE) model resulted in decreased histamine release in comparison with nontreated animals. This is the first report of the use of the MP23 model to screen for novel anticonvulsant compounds that may avoid the development of P-gp-related drug resistance.

Chaihu plus Longgu Muli Decoction Alleviated Brain Injury in Pentylenetetrazole-Kindled Epileptic Mice by Regulating Cyclooxygenase-2/Prostaglandin E2/Multidrug Transporter Pathway

Objective. To evaluate the effect of CLMD administration on epileptic seizures and brain injury in pentylenetetrazole- (PZT-) kindled mice. Methods. The effect of pretreatment with CLMD (5, 10, and 20 ml/kg (mg/kg) by gavage) for seven days on PTZ-induced kindling, duration and grade of kindling-induced seizures, and pathological injury in the cortex and hippocampus was evaluated. Male BALB/c mice with adenosine A1 receptor knockout were subjected to intraperitoneal injection of PTZ (35 mg/kg) once every day until kindling was successfully induced. Quantitative reverse transcription polymerase chain reaction, immunofluorescence, and western blot were performed to assess the mRNA and protein levels of p-glycoprotein (PGP), multidrug resistance-associated protein 1 (MRP1), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), and adenylate kinase (ADK) in the cortex and hippocampus. Results. PTZ successfully induced kindling in mice after 21 days, wherein CLMD showed an obvious dose-dependent antiepileptic effect. High-dose CLMD significantly increased the latency of epileptic seizures, decreased the sustained time of epileptic seizures and the seizure grade, and ameliorated the histopathological changes in the cortex and hippocampus. Furthermore, PTZ kindling induced significantly higher levels of PGP, MRP1, COX-2, PGE2, and ADK, but this effect was inhibited by pretreatment with CLMD in a dose-dependent manner. Conclusion. Pretreatment with CLMD attenuates PTZ-kindled convulsions and brain injury in mice. The mechanism may be related to the cyclooxygenase-2/prostaglandin E2/multidrug transporter pathway.

Epilepsy Associated Depression: An Update on Current Scenario, Suggested Mechanisms, and Opportunities

Depression is one of the most frequent psychiatric comorbidities associated with epilepsy having a major impact on the patient's quality of life. Several screening tools are available to identify and follow up psychiatric disorders in epilepsy. Out of various psychiatric disorders, people with epilepsy (PWE) are at greater risk of developing depression. This bidirectional relationship further hinders pharmacotherapy of comorbid depression in PWE as some antiepileptic drugs (AEDs) worsen associated depression and coadministration of existing antidepressants (ADs) to alleviate comorbid depression has been reported to worsen seizures. Selective serotonin reuptake inhibitors (SSRIs) and selective serotonin and norepinephrine reuptake inhibitors (SNRIs) are first choice of ADs and are considered safe in PWE, but there are no high-quality evidences. Similar to observations in people with depression, PWE also showed pharmacoresistant to available SSRI/SNRIs, which further complicates the disease prognosis. Randomized double-blind placebo-controlled clinical trials are necessary to report efficacy and safety of available ADs in PWE. We should also move beyond ADs, and therefore, we reviewed common pathological mechanisms such as neuroinflammation, dysregulated hypothalamus pituitary adrenal (HPA) axis, altered neurogenesis, and altered tryptophan metabolism responsible for coexistent relationship of epilepsy and depression. Based on these common pertinent pathways involved in the genesis of epilepsy and depression, we suggested novel targets and therapeutic approaches for safe management of comorbid depression in epilepsy.

Treatment-Resistant Depression Revisited: A Glimmer of Hope

Major Depressive Disorder (MDD) is a highly prevalent psychiatric disorder worldwide. It causes individual suffering, loss of productivity, increased health care costs and high suicide risk. Current pharmacologic interventions fail to produce at least partial response to approximately one third of these patients, and remission is obtained in approximately 30% of patients. This is known as Treatment-Resistant Depression (TRD). The burden of TRD exponentially increases the longer it persists, with a higher risk of impaired functional and social functioning, vast losses in quality of life and significant risk of somatic morbidity and suicidality. Different approaches have been suggested and utilized, but the results have not been encouraging. In this review article, we present new approaches to identify and correct potential causes of TRD, thereby reducing its prevalence and with it the overall burden of this disease entity. We will address potential contributory factors to TRD, most of which can be investigated in many laboratories as routine tests. We discuss endocrinological aberrations, notably, hypothalamic-pituitary-adrenal (HPA) axis dysregulation and thyroid and gonadal dysfunction. We address the role of Vitamin D in contributing to depression. Pharmacogenomic testing is being increasingly used to determine Single Nucleotide Polymorphisms in Cytochrome P450, Serotonin Transporter, COMT, folic acid conversion (MTHFR). As the role of immune system dysregulation is being recognized as potentially a major contributory factor to TRD, the measurement of C-reactive protein (CRP) and select immune biomarkers, where testing is available, can guide combination treatments with anti-inflammatory agents (e.g., selective COX-2 inhibitors) reversing treatment resistance. We focus on established and emerging test procedures, potential biomarkers and non-biologic assessments and interventions to apply personalized medicine to effectively manage treatment resistance in general and TRD specifically.

Novel Intrinsic Mechanisms of Active Drug Extrusion at the Blood-Brain Barrier: Potential Targets for Enhancing Drug Delivery to the Brain?

The blood-brain barrier (BBB) limits the pharmacotherapy of several brain disorders. In addition to the structural and metabolic characteristics of the BBB, the ATP-driven, drug efflux transporter P-glycoprotein (Pgp) is a selective gatekeeper of the BBB; thus, it is a primary hindrance to drug delivery into the brain. Here, we review the complex regulation of Pgp expression and functional activity at the BBB with an emphasis on recent studies from our laboratory. In addition to traditional processes such as transcriptional regulation and posttranscriptional or posttranslational modification of Pgp expression and functionality, novel mechanisms such as intra- and intercellular Pgp trafficking and intracellular Pgp-mediated lysosomal sequestration in BBB endothelial cells with subsequent disposal by blood neutrophils are discussed. These intrinsic mechanisms of active drug extrusion at the BBB are potential therapeutic targets that could be used to modulate P-glycoprotein activity in the treatment of brain diseases and enhance drug delivery to the brain.

Drug Resistance in Epilepsy: Clinical Impact, Potential Mechanisms, and New Innovative Treatment Options

Epilepsy is a chronic neurologic disorder that affects over 70 million people worldwide. Despite the availability of over 20 antiseizure drugs (ASDs) for symptomatic treatment of epileptic seizures, about one-third of patients with epilepsy have seizures refractory to pharmacotherapy. Patients with such drug-resistant epilepsy (DRE) have increased risks of premature death, injuries, psychosocial dysfunction, and a reduced quality of life, so development of more effective therapies is an urgent clinical need. However, the various types of epilepsy and seizures and the complex temporal patterns of refractoriness complicate the issue. Furthermore, the underlying mechanisms of DRE are not fully understood, though recent work has begun to shape our understanding more clearly. Experimental models of DRE offer opportunities to discover, characterize, and challenge putative mechanisms of drug resistance. Furthermore, such preclinical models are important in developing therapies that may overcome drug resistance. Here, we will review the current understanding of the molecular, genetic, and structural mechanisms of ASD resistance and discuss how to overcome this problem. Encouragingly, better elucidation of the pathophysiological mechanisms underpinning epilepsies and drug resistance by concerted preclinical and clinical efforts have recently enabled a revised approach to the development of more promising therapies, including numerous potential etiology-specific drugs (“precision medicine”) for severe pediatric (monogenetic) epilepsies and novel multitargeted ASDs for acquired partial epilepsies, suggesting that the long hoped-for breakthrough in therapy for as-yet ASD-resistant patients is a feasible goal.

Regulation of liver regeneration by prostaglandin E2 and thromboxane A2 following partial hepatectomy in rats

The implication of prostaglandin E₂ (PGE₂) and thromboxane A₂ (TXA₂) in the striking process of liver regeneration has been previously reported. However, their exact roles and downstream signals have not been utterly revealed. Therefore, the present study was conducted to explore whether inhibition of cyclooxygenase-2 (COX-2)-derived PGE₂ by celecoxib and blocking of TXA₂ action by seratrodast could alter the progression of liver regeneration after 70% partial hepatectomy (PHx) in rats. Celecoxib (20 mg/kg/day) and seratrodast (2 mg/kg/day) were given orally 1 h before PHx and then daily till the end of experiment (1, 3, or 7 days after the operation). Interestingly, celecoxib-treated rats showed a further increase in interleukin-6, p65 nuclear factor κB, and phosphorylated signal transducer and activator of transcription 3 as compared with PHx control rats. Furthermore, the liver contents of growth factors as well as β-catenin and cyclin D1protein expressions were also enhanced by celecoxib. Accordingly, celecoxib significantly improved hepatic proliferation as indicated by the increase in Ki67 expression and liver index. Contrariwise, seratrodast hindered the normal regeneration process and completely abolished the proliferative effect of celecoxib. In conclusion, TXA₂ has a major role in liver regeneration that could greatly mediate the triggering effect of celecoxib on hepatocytes proliferation following PHx.

Altered plasma prostaglandin E2 levels in epilepsy and in response to antiepileptic drug monotherapy

Prostaglandin E₂ (PGE₂), a physiologically active lipid compound, is increased in several diseases characterized by chronic inflammation. To determine its significance in epilepsy-associated inflammation and response to antiepileptic drug (AED), we evaluated the plasma PGE₂ (median, pg/ml) levels in drug-free patients with epilepsy (N = 34) and patients receiving AED monotherapy (N = 55) in addition to that in healthy controls (N = 34). When compared to controls, plasma PGE₂ levels were significantly elevated in all drug-free patients independent of the type of epilepsy (137.2 versus 475.7 pg/ml, p < 0.0001). Among the patients receiving AED monotherapy, only valproate responders showed a significant decrease compared to both drug-free patients (232.1 versus 475.7 pg/ml, p < 0.01) as well as valproate non-responders (232.1 versus 611.9 pg/ml, p < 0.0001). Both responders and non-responders on phenytoin or carbamazepine monotherapy had elevated PGE₂ levels similar to drug-free patients. In addition, no difference was observed in plasma profiles of PGE₂ precursor, arachidonic acid among the groups. Our work presents the clinical evidence of the association between plasma PGE₂ levels and valproate efficacy in patients with epilepsy.

Cyclooxygenase-2 (COX-2) inhibitors: future therapeutic strategies for epilepsy management

Epilepsy, a common multifactorial neurological disease, affects about 69 million people worldwide constituting nearly 1% of the world population. Despite decades of extensive research on understanding its underlying mechanism and developing the pharmacological treatment, very little is known about the biological alterations leading to epileptogenesis. Due to this gap, the currently available antiepileptic drug therapy is symptomatic in nature and is ineffective in 30% of the cases. Mounting evidences revealed the pathophysiological role of neuroinflammation in epilepsy which has shifted the focus of epilepsy researchers towards the development of neuroinflammation-targeted therapeutics for epilepsy management. Markedly increased expression of key inflammatory mediators in the brain and blood-brain barrier may affect neuronal function and excitability and thus may increase seizure susceptibility in preclinical and clinical settings. Cyclooxygenase-2 (COX-2), an enzyme synthesizing the proinflammatory mediators, prostaglandins, has widely been reported to be induced during seizures and is considered to be a potential neurotherapeutic target for epilepsy management. However, the efficacy of such therapy involving COX-2 inhibition depends on various factors viz., therapeutic dose, time of administration, treatment duration, and selectivity of COX-2 inhibitors. This article reviews the preclinical and clinical evidences supporting the role of COX-2 in seizure-associated neuroinflammation in epilepsy and the potential clinical use of COX-2 inhibitors as a future strategy for epilepsy treatment.

Cytosolic phospholipase A2 is a key regulator of blood-brain barrier function in epilepsy

Blood-brain barrier dysfunction in epilepsy contributes to seizures and resistance to antiseizure drugs. Reports show that seizures increase brain glutamate levels, leading to barrier dysfunction. One component of barrier dysfunction is overexpression of the drug efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP). Based on our previous studies, we hypothesized that glutamate released during seizures activates cytosolic phospholipase A2 (cPLA2), resulting in P-gp and BCRP overexpression. We exposed isolated rat brain capillaries to glutamate ex vivo and used an in vivo-ex vivo approach of isolating brain capillaries from rats after status epilepticus (SE) and in chronic epileptic (CE) rats. Glutamate increased cPLA2, P-gp, and BCRP protein and activity levels in isolated brain capillaries. We confirmed the role of cPLA2 in the signaling pathway in brain capillaries from male and female mice lacking cPLA2. We also demonstrated, in vivo, that cPLA2 inhibition prevents overexpression of P-gp and BCRP at the blood-brain barrier in rats after status epilepticus and in CE rats. Our data support the hypothesis that glutamate signals cPLA2 activation, resulting in overexpression of blood-brain barrier P-gp and BCRP.-Hartz, A. M. S., Rempe, R. G., Soldner, E. L. B., Pekcec, A., Schlichtiger, J., Kryscio, R., Bauer, B. Cytosolic phospholipase A2 is a key regulator of blood-brain barrier function in epilepsy.

Inhibition of human microsomal PGE2 synthase-1 reduces seizure-induced increases of P-glycoprotein expression and activity at the blood-brain barrier

The cause of antiseizure drug (ASD) resistance in epilepsy is poorly understood. Here, we focus on the transporter P-glycoprotein (P-gp) that is partly responsible for limited ASD brain uptake, which is thought to contribute to ASD resistance. We previously demonstrated that cyclooxygenase-2 (COX-2) and the prostaglandin E receptor, prostanoid E receptor subtype 1, are involved in seizure-mediated P-gp up-regulation. Thus, we hypothesized that inhibiting microsomal prostaglandin E₂ (PGE2) synthase-1 (mPGES-1), the enzyme generating PGE2, prevents blood-brain barrier P-gp up-regulation after status epilepticus (SE). To test our hypothesis, we exposed isolated brain capillaries to glutamate ex vivo and used a combined in vivo-ex vivo approach by isolating brain capillaries from humanized mPGES-1 mice to study P-gp levels. We demonstrate that glutamate signaling through the NMDA receptor, cytosolic phospholipase A2, COX-2, and mPGES-1 increases P-gp protein expression and transport activity levels. We show that mPGES-1 is expressed in human, rat, and mouse brain capillaries. We show that BI1029539, an mPGES-1 inhibitor, prevented up-regulation of P-gp expression and transport activity in capillaries exposed to glutamate and in capillaries from humanized mPGES-1 mice after SE. Our data provide key signaling steps underlying seizure-induced P-gp up-regulation and suggest that mPGES-1 inhibitors could potentially prevent P-gp up-regulation in epilepsy.-Soldner, E. L. B., Hartz, A. M. S., Akanuma, S.-I., Pekcec, A., Doods, H., Kryscio, R. J., Hosoya, K.-I., Bauer, B. Inhibition of human microsomal PGE2 synthase-1 reduces seizure-induced increases of P-glycoprotein expression and activity at the blood-brain barrier.

ABC transporters in drug-resistant epilepsy: mechanisms of upregulation and therapeutic approaches

Drug-resistant epilepsy (DRE) affects approximately one third of epileptic patients. Among various theories that try to explain multidrug resistance, the transporter hypothesis is the most extensively studied. Accordingly, the overexpression of efflux transporters in the blood-brain barrier (BBB), mainly from the ATP binding cassette (ABC) superfamily, may be responsible for hampering the access of antiepileptic drugs into the brain. P-glycoprotein and other efflux transporters are known to be upregulated in endothelial cells, astrocytes and neurons of the neurovascular unit, a functional barrier critically involved in the brain penetration of drugs. Inflammation and oxidative stress involved in the pathophysiology of epilepsy together with uncontrolled recurrent seizures, drug-associated induction and genetic polymorphisms are among the possible causes of ABC transporters overexpression in DRE. The aforementioned pathological mechanisms will be herein discussed together with the multiple strategies to overcome the activity of efflux transporters in the BBB - from direct transporters inhibition to down-regulation of gene expression resorting to RNA interference (RNAi), or by targeting key modulators of inflammation and seizure-mediated signalling.

Magnolia officinalis reduces the long-term effects of the status epilepticus induced by kainic acid in immature rats

During critical periods of neurodevelopment, the immature brain is susceptible to neuronal hyperexcitability, alterations such as hyperthermia, hypoxia, brain trauma or a preexisting neuroinflammatory condition can trigger, promote and prolong epileptiform activity and facilitate the development of epilepsy. The goal of the present study was to evaluate the long-term neuroprotective effects Magnolia officinalis extract, on a model of recurrent status epilepticus (SE) in immature rats. Sprague-Dawley rats were treated with kainic acid (KA) (3 mg/kg, dissolved in saline solution) beginning at day 10 P N every 24 h for five days (10 P N-14PN). Two experimental groups (KA) received two treatments for 10 days (14-24 P N): one group was treated with 300 mg/kg Magnolia Officinalis (MO) (KA-MO), and another was treated with 20 mg/kg of celecoxib (Clbx) (KA-Clbx) as a control drug. A SHAM control group at day 90 P N was established. Seizure susceptibility was analyzed through an after-discharge threshold (ADT) evaluation, and electroencephalographic activity was recorded. The results obtained from the ADT evaluation and the analysis of the electroencephalographic activity under basal conditions showed that the MO and Clbx treatments protected against epileptiform activity, and decreases long-term excitability. All rats in the KA-MO and KA-Clbx groups presented a phase I seizure on the Racine scale, corresponding to the shaking of a wet dog. In contrast, the KA group showed phase V convulsive activity on the Racine scale. Similarly, MO and Clbx exerted neuroprotective effects on hippocampal neurons and reduced gliosis in the same areas. Based on these results, early intervention with MO and Clbx treatments to prevent the inflammatory activity derived from SE in early phases of neurodevelopment exerts neuroprotective effects on epileptogenesis in adult stages.

Excess glutamate secreted from astrocytes drives upregulation of P-glycoprotein in endothelial cells in amyotrophic lateral sclerosis

In amyotrophic lateral sclerosis (ALS), upregulation in expression and activity of the ABC transporter P-glycoprotein (P-gp) driven by disease advancement progressively reduces CNS penetration and efficacy of the ALS drug, riluzole. Post-mortem spinal cord tissues from ALS patients revealed elevated P-gp expression levels in endothelial cells of the blood-spinal cord barrier compared to levels measured in control, non-diseased individuals. We recently found that astrocytes expressing familial ALS-linked SOD1 mutations regulate expression levels of P-gp in endothelial cells, which also exhibit a concomitant, significant increase in reactive oxygen species production and NFκB nuclear translocation when exposed to mutant SOD1 astrocyte conditioned media. In this study, we found that glutamate, which is abnormally secreted by mutant SOD1 and sporadic ALS astrocytes, drives upregulation of P-gp expression and activity levels in endothelial cells via activation of N-Methyl-D-Aspartic acid (NMDA) receptors. Surprisingly, astrocyte-secreted glutamate regulation of endothelial P-gp levels is not a mechanism shared by all forms of ALS. C9orf72-ALS astrocytes had no effect on endothelial cell P-gp expression and did not display increased glutamate secretion. Utilizing an optimized in vitro human BBB model consisting of patient-derived induced pluripotent stem cells, we showed that co-culture of endothelial cells with patient-derived astrocytes increased P-gp expression levels and transport activity, which was significantly reduced when endothelial cells were incubated with the NMDAR antagonist, MK801. Overall, our findings unraveled a complex molecular interplay between astrocytes of different ALS genotypes and endothelial cells potentially occurring in disease that could differentially impact ALS prognosis and efficacy of pharmacotherapies.

Impact of a selective cyclooxygenase-2 inhibitor, celecoxib, on cortical excitability and electrophysiological properties of the brain in healthy volunteers: A randomized, double-blind, placebo-controlled study

The inflammatory response is considered a defence mechanism against physical or infectious insults and is prevalent within the central nervous system. Seizures also result in a robust inflammatory cascade, leading to enhanced activation of excitatory synaptic networks. Ample evidence based on animal models of epilepsy has demonstrated that celecoxib, a highly selective inhibitor of cyclooxygenase-2, has anticonvulsant effects. We aimed to evaluate the impact of celecoxib on the cortical excitability and electrophysiological properties of the brain in healthy humans. Electroencephalography (EEG) or transmagnetic stimulation (TMS) was used to measure neurophysiological activity. Forty healthy volunteers were randomized to 4 groups (n = 10 in each group): 1) celecoxib and EEG, 2) placebo and EEG, 3) celecoxib and TMS, and 4) placebo and TMS. For the EEG study, resting EEG was performed at baseline just before administering 400 mg of celecoxib or placebo and repeated 4 hours after administration. The subjects took 200 mg of celecoxib or placebo twice a day for 7 subsequent days, and a third EEG was conducted 4 hours after the final dose. Power spectra were compared at each time point. For the TMS study, the resting motor threshold (RMT), motor evoked potential (MEP) peak-to-peak amplitude, and cortical silent period (CSP) were measured at baseline and after taking 200 mg of celecoxib or placebo twice a day for 7 days. Celecoxib did not significantly change brain activity in the EEG study. However, the sum of power recorded from all electrodes tended to increase in the celecoxib group only at 4 hours after administration (p = 0.06). In detail, one dose of celecoxib (400 mg) transiently and significantly increased the alpha band power recorded in the frontal and parietal areas as well as in the whole brain (p = 0.049, 0.017, and 0.014, respectively) and the beta frequency in the central and parietal regions (p = 0.013 and 0.005, respectively), whereas the placebo did not. This effect was abolished after 7 days of treatment. In the TMS study, we found no statistically significant change in the RMT, MEP peak-to-peak amplitude or CSP. This evidence suggests that celecoxib transiently alters the electrophysiological properties of the brain but does not suppress neuronal excitability in healthy humans.

An update of cyclooxygenase (COX)-inhibitors in epilepsy disorders

INTRODUCTION

Neuroinflammation has a critical role in brain disorders. Cyclooxygenase (COX) is one of the principal drug targets for the reduction of neuroinflammation; however, studies have yielded mixed results for COX-inhibitors in the treatment of diverse acute and chronic models of epilepsy.

AREAS COVERED

The article covers the effects of COX-inhibitors in epilepsy disorders. A considerable emphasis has been placed on the antiepileptic and 'disease-modifying' properties of COX-1 and COX-2 inhibitors in various preclinical epilepsy models.

EXPERT OPINION

The effect of COX-inhibitors on epilepsy is inconclusive. Studies have indicated beneficial effects in preclinical models; however, proconvulsant or no effects have also been observed. These molecules may have a bidirectional role with early neuroprotective and delayed neurotoxic effects. Further systematic preclinical studies to establish the use of COX-inhibitors in epilepsy are necessary.

Understanding the controversial drug targets in epilepsy and pharmacoresistant epilepsy

Accumulating experimental data suggests a number of successful drug targets against epilepsy which eventually failed in the clinical setup. Mammalian target of rapamycin inhibitors, multi-drug resistance transporter inhibitors, cyclo-oxygenase-2 inhibitors, statins, etc. are the most promising and well studied among them. Drugs aiming at these targets produced beneficial response in most of the in vitro and in vivo seizure models. However, in certain situations, they have produced differential rather controversial results. Their effects varied with the seizure model, species, time and route of administration, different drugs from the same class, etc. This review emphasises on such drugs which presented with variability in their beneficial effects against seizures and epilepsy. This review critically summarises the preclinical evidence of these targets in the context of seizures and the probable reasons for their variability and clinical failures.

In vitro and in vivo experimental models employed in the discovery and development of antiepileptic drugs for pharmacoresistant epilepsy

Epilepsy is one of the most common chronic, recurrent and progressive neurological diseases. In spite of the large number of antiepileptic drugs currently available for the suppression of seizures, about one-third of patients develop drug-resistant epilepsy, even when they are administered the most appropriate treatment available. Thus, nonclinical models can be valuable tools for the elucidation of the mechanisms underlying the development of pharmacoresistance and also for the development of new therapeutic agents that may be promising therapeutic approaches for this unmet medical need. Up today, several epilepsy and seizure models have been developed, exhibiting similar physiopathological features of human drug-resistant epilepsy; moreover, pharmacological response to antiepileptic drugs clinically available tends to be similar in animal models and humans. Therefore, they should be more intensively used in the preclinical discovery and development of new candidates to antiepileptic drugs. Although useful, in vitro models cannot completely replicate the complexity of a living being and their potential for a systematic use in antiepileptic drug screening is limited. The whole-animal models are the most commonly employed and they can be classified as per se drug-resistant due to an inherent poor drug response or be based on the selection of subgroups of epileptic animals that respond or not to a specific antiepileptic drug. Although more expensive and time-consuming, the latter are chronic models of epilepsy that better exhibit the disease-associated alterations found in human epilepsy. Several antiepileptic drugs in development or already marketed have been already tested and shown to be effective in these models of drug-resistant epilepsy, constituting a new hope for the treatment of drug-resistant epilepsy. This review will provide epilepsy researchers with detailed information on the in vitro and in vivo nonclinical models of interest in drug-resistant epilepsy, which may enable a refined selection of most relevant models for understanding the mechanisms of the disease and developing novel antiepileptic drugs.

MiR-466b-1-3p regulates P-glycoprotein expression in rat cerebral microvascular endothelial cells

Epilepsy is one of the most common neurological disorders, and approximately one-third of epilepsy cases are resistant to treatment with anti-epileptic drug (AED). P-glycoprotein (P-gp) is a multi-drug transporter that is thought to play a pivotal role in multiple drug resistance (MDR) in epilepsy. The regulatory mechanism of P-gp remains largely unknown; however, recent studies have demonstrated that microRNAs (miRNAs) may regulate the chemo-resistance mediated by P-gp. This study investigated the effect of specific miRNAs that regulate P-gp expression in rat cerebral microvascular endothelial cells (RCMECs). Primary cultures of RCMECs were treated with phenobarbital (PB) at various concentrations to induce P-gp overexpression. MiRNA microarrays were used to investigate the expression profiles of miRNAs in the resistant RCMECs induced by PB and corresponding non-resistant cells. Our data demonstrated decreased miR-466b-1-3p expression in the resistant cells compared with the non-resistant cells. Moreover, the recombinant RNA of 466b-1-3p (mimic) and the artificial antisense RNA of miR-466b-1-3p (inhibitor) were constructed and transfected into resistant RCMECs. The expression and function of P-gp were measured by Western blotting, quantitative real-time polymerase chain reaction (qRT-PCR) and flow cytometry using rhodamine efflux. The mRNA and protein levels of P-gp increased as the concentration of PB increased, whereas miR-466b-1-3p levels decreased with increasing PB concentrations (P<0.05). The miR-466b-1-3p mimic down-regulated P-gp expression, whereas the miR-466b-1-3p inhibitor up-regulated P-gp expression (P<0.05). These findings demonstrate that miR-466b-1-3p may regulate PB-induced P-gp expression in RCMECs.

Staged anticonvulsant screening for chronic epilepsy

OBJECTIVE

Current anticonvulsant screening programs are based on seizures evoked in normal animals. One-third of epileptic patients do not respond to the anticonvulsants discovered with these models. We evaluated a tiered program based on chronic epilepsy and spontaneous seizures, with compounds advancing from high-throughput in vitro models to low-throughput in vivo models.

METHODS

Epileptogenesis in organotypic hippocampal slice cultures was quantified by lactate production and lactate dehydrogenase release into culture media as rapid assays for seizure-like activity and cell death, respectively. Compounds that reduced these biochemical measures were retested with in vitro electrophysiological confirmation (i.e., second stage). The third stage involved crossover testing in the kainate model of chronic epilepsy, with blinded analysis of spontaneous seizures after continuous electrographic recordings.

RESULTS

We screened 407 compound-concentration combinations. The cyclooxygenase inhibitor, celecoxib, had no effect on seizures evoked in normal brain tissue but demonstrated robust antiseizure activity in all tested models of chronic epilepsy.

INTERPRETATION

The use of organotypic hippocampal cultures, where epileptogenesis occurs on a compressed time scale, and where seizure-like activity and seizure-induced cell death can be easily quantified with biomarker assays, allowed us to circumvent the throughput limitations of in vivo chronic epilepsy models. Ability to rapidly screen compounds in a chronic model of epilepsy allowed us to find an anticonvulsant that would be missed by screening in acute models.

[Effects of cyclooxygenase-2 selective inhibitor celecoxib on the expression of major vault protein in rats with status epilepticus]

OBJECTIVE

To study the effect of cyclooxygenase -2 selective inhibitor celecoxib on the expression of major vault protein ( MVP) in the brain of rats with status epilepticus and its possible roles in the treatment of refractory epilepsy.

METHODS

Sixty adult male Sprague-Dawley rats were randomly assigned to blank control (n=16), epilepsy model (n=22) and celecoxib treatment groups (n=22). After the status epilepticus was induced in rats by injecting lithium and pilocarpine, each group had 16 rats enrolled as subjects. Immunohistochemical method and Western blot method were used to detect the expression of MVP in the frontal cortex and hippocampus.

RESULTS

The expression of MVP was significantly higher in the epilepsy model group than in the control group (P<0.01). The expression of MVP in the celecoxib treatment group was significantly decreased compared with the epilepsy model group, but it was still higher than in the control group (P<0.01).

CONCLUSIONS

Celecoxib could decrease the expression of MVP in brain tissue of rats with status epilepticus, suggesting that it is promising for the treatment of intractable epilepsy.

Exploring novel AEDs from drugs used for treatment of non-epileptic disorders

Epilepsy is a chronic neurological disease. Although many anti-epileptic drugs (AEDs) have been developed for clinical use, they have no effect on 20-30% of patients and do not generally prevent epileptogenesis. Because of the long development cycle for new AEDs and the high cost, increasing efforts are being made to find anti-epileptic effects among drugs that are already listed for the treatment of other diseases and repurpose them as potential anti-epileptic treatments. Here, we review the progress that has been made in this field as a result of animal and clinical trials of drugs such as rapamycin, everolimus, losartan, celecoxib, bumetanide and other non-epileptic drugs. These drugs can prevent the epileptogenesis, reduce the epileptic pathological changes, and even be used to treat intractable epilepsy. Their mechanisms of action are completely different from those of existing AEDs, prompting researchers to change their perspectives in the search for new AEDs.

P2X7 receptor antagonism reduces the severity of spontaneous seizures in a chronic model of temporal lobe epilepsy

BACKGROUND

The available pharmacotherapy for patients with epilepsy primarily address the symptoms and are ineffective in about 40% of patients. Brain inflammation gained support as potential target for developing new therapies, especially the P2X7 receptor (P2X7R), involved in processing of IL-1β, might be an interesting candidate. This study was designed to investigate the effect of a novel P2X7R antagonist on the severity and on the number of chronic spontaneous recurrent seizures (SRS), which was unexplored until now.

METHODS

After one-week of vehicle treatment (20% HP-β-cyclodextrin), JNJ-42253432 was administered subcutaneously for another week under continuous video-electroencephalography monitoring (n = 17) in Sprague Dawley rats 3 months after kainic acid-induced status epilepticus. The proportion of different seizure classes, as well as the number of SRS/day were calculated for the vehicle and treatment period. In addition, post-mortem microglial activation and astrogliosis were assessed.

RESULTS

A significant decrease of the proportion of type 4-5 SRS (p < 0.05), while an increase of type 1-3 was demonstrated (p < 0.05) from the vehicle to the treatment period. There was no effect of the P2X7R antagonist on the number of SRS/day or the glial markers.

CONCLUSIONS

The P2X7R antagonist gave rise to a less severe profile of the chronic seizure burden without suppressing the SRS frequency. More studies are needed to unravel the underlying mechanisms of the beneficial effect on seizure severity and whether the administration of the compound during early epileptogenesis could induce long-term disease-modifying effects.

Glutamate-Mediated Down-Regulation of the Multidrug-Resistance Protein BCRP/ABCG2 in Porcine and Human Brain Capillaries

Breast cancer resistance protein (BCRP) functions as a major molecular gatekeeper at the blood-brain barrier. Considering its impact on access to the brain by therapeutic drugs and harmful xenobiotics, it is of particular interest to elucidate the mechanisms of its regulation. Excessive glutamate concentrations have been reported during epileptic seizures or as a consequence of different brain insults including brain ischemia. Previously, we have demonstrated that glutamate can trigger an induction of the transporter P-glycoprotein. These findings raised the question whether other efflux transporters are affected in a comparable manner. Glutamate exposure proved to down-regulate BCRP transport function and expression in isolated porcine capillaries. The reduction was efficaciously prevented by coincubation with N-methyl-d-aspartate (NMDA) receptor antagonist MK-801. The involvement of the NMDA receptor in the down-regulation of BCRP was further confirmed by experiments showing an effect of NMDA exposure on brain capillary BCRP transport function and expression. Pharmacological targeting of cyclooxygenase-1 and -2 (COX-1 and -2) using the nonselective inhibitor indomethacin, COX-1 inhibitor SC-560, and COX-2 inhibitor celecoxib revealed a contribution of COX-2 activity to the NMDA receptor's downstream signaling events affecting BCRP. Translational studies were performed using human capillaries isolated from surgical specimens of epilepsy patients. The findings confirmed a glutamate-induced down-regulation of BCRP transport activity in human capillaries, which argued against major species differences. In conclusion, our data reveal a novel mechanism of BCRP down-regulation in porcine and human brain capillaries. Moreover, together with previous data sets for P-glycoprotein, the findings point to a contrasting impact of the signaling pathway on the regulation of BCRP and P-glycoprotein. The effect of glutamate and arachidonic acid signaling on BCRP function might have implications for brain drug delivery and for radiotracer brain access in epilepsy patients and patients with other brain insults.

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.

Co-administration of subtherapeutic diazepam enhances neuroprotective effect of COX-2 inhibitor, NS-398, after lithium pilocarpine-induced status epilepticus

RATIONALE

Seizures during status epilepticus (SE) cause neuronal death and induce cyclooxygenase-2 (COX-2). Pilocarpine-induced SE was used to determine if COX-2 inhibition with NS-398, when administered alone or with diazepam, decreases the duration and/or intensity of SE and/or reduces neuronal injury in the rat hippocampus.

METHODS

Electroencephalogram (EEG) electrodes were implanted in male Sprague-Dawley rats. SE was induced with lithium-pilocarpine, and continuous EEG and video monitoring were performed for 24 h. Rats were divided into four groups (n=8-14 rats/group) and received NS-398, diazepam, NS-398 and diazepam, or vehicle 30 min after the first motor seizure. Six hours later, NS-398 injection was repeated in the NS-398 and in the NS-398+diazepam groups. The duration of SE (continuous spiking) and the EEG power in the γ-band were analyzed. FluoroJade B staining in the dorsal hippocampus at 24h after SE was analyzed semi-quantitatively in the CA1, CA3 and hilus.

RESULTS

The duration and intensity of electrographic SE was not significantly different across the four groups. In rats treated with NS-398 alone, compared to vehicle-treated rats, neuronal damage was significantly lower compared to vehicle-treated rats in the CA3 (27%) and hilus (27%), but neuroprotection was not detected in the CA1. When NS-398 was administered with diazepam, decreased neuronal damage was further obtained in all areas investigated (CA1: 61%, CA3: 63%, hilus: 60%).

CONCLUSIONS

NS-398, when administered 30 min after the onset of SE with a repeat dose at 6h, decreased neuronal damage in the hippocampus. Administration of diazepam with NS-398 potentiates the neuroprotective effect of the COX-2 inhibitor. These neuroprotective effects occurred with no detectable effect on electrographic SE.

Indomethacin can downregulate the levels of inflammatory mediators in the hippocampus of rats submitted to pilocarpine-induced status epilepticus

OBJECTIVE

Refractory status epilepticus is one of the most life-threatening neurological emergencies and is characterized by high morbidity and mortality. Additionally, the use of anti-inflammatory drugs during this period is very controversial. Thus, this study has been designed to analyze the effect of a low dose of indomethacin (a COX inhibitor) on the expression of inflammatory molecules.

METHOD

The hippocampus of rats submitted to pilocarpine-induced long-lasting status epilepticus was analyzed to determine the expression of inflammatory molecules with RT-PCR and immunohistochemistry.

RESULTS

Compared with controls, reduced levels of the kinin B2 receptors IL1β and TNFα were found in the hippocampus of rats submitted to long-lasting status epilepticus and treated with indomethacin.

CONCLUSIONS

These data show that low doses of indomethacin could be employed to minimize inflammation during long-lasting status epilepticus.

(R)-[11C]PK11195 brain uptake as a biomarker of inflammation and antiepileptic drug resistance: evaluation in a rat epilepsy model

Neuroinflammation has been suggested as a key determinant of the intrinsic severity of epilepsy. Glial cell activation and associated inflammatory signaling can influence seizure thresholds as well as the pharmacodynamics and pharmacokinetics of antiepileptic drugs. Based on these data, we hypothesized that molecular imaging of microglia activation might serve as a tool to predict drug refractoriness of epilepsy. Brain uptake of (R)-[11C]PK11195, a ligand of the translocator protein 18 kDa and molecular marker of microglia activation, was studied in a chronic model of temporal lobe epilepsy in rats with selection of phenobarbital responders and non-responders. In rats with drug-sensitive epilepsy, (R)-[11C]PK11195 brain uptake values were comparable to those in non-epileptic controls. Analysis in non-responders revealed enhanced brain uptake of up to 39% in different brain regions. The difference might be related to the fact that non-responders exhibited higher baseline seizure frequencies than responders indicating a more pronounced intrinsic disease severity. In hippocampal sections, ED1 immunostaining argued against a general difference in microglia activation between both groups. Our data suggest that TSPO PET imaging might serve as a biomarker for drug resistance in temporal lobe epilepsy. However, it needs to be considered that our findings indicate that the TSPO PET data might merely reflect seizure frequency. Future experimental and clinical studies should further evaluate the validity of TSPO PET data to predict the response to phenobarbital and other antiepileptic drugs in longitudinal studies with scanning before drug exposure and with a focus on the early phase following an epileptogenic brain insult.

Targeting inflammation as a therapeutic strategy for drug-resistant epilepsies: an update of new immune-modulating approaches

An increasing body of literature data suggests that inflammation, and in particular neuroinflammation, is involved in the pathophysiology of particular forms of epilepsy and convulsive disorders. Animal models have been used to identify inflammatory triggers in epileptogenesis and inflammation has recently been shown to enhance seizures. For example, pharmacological blockade of the IL-1beta/IL-1 receptor type 1 axis during epileptogenesis has been demonstrated to provide neuroprotection in temporal lobe epilepsy. Furthermore, experimental models have suggested that neural damage and the onset of spontaneous recurrent seizures are modulated via complex interactions between innate and adaptive immunity. However, it has also been suggested that inflammation can occur as a result of epilepsy, since animal models have also shown that seizure activity can induce neuroinflammation, and that recurrent seizures maintain chronic inflammation, thereby perpetuating seizures. On the basis of these observations, it has been suggested that immune-mediated therapeutic strategies may be beneficial for treating some drug resistant epilepsies with an underlying demonstrable inflammatory process. Although the potential mechanisms of immunotherapeutic strategies in drug-resistant seizures have been extensively discussed, evidence on the efficacy of such therapy is limited. However, recent research efforts have been directed toward utilizing the potential therapeutic benefits of anti-inflammatory agents in neurological disease and these are now considered prime candidates in the ongoing search for novel anti-epileptic drugs. The objective of our review is to highlight the immunological features of the pathogenesis of seizures and to analyze possible immunotherapeutic approaches for drug resistant epilepsies that can alter the immune-mediated pathogenesis.

Transport rankings of non-steroidal antiinflammatory drugs across blood-brain barrier in vitro models

The aim of this work was to conduct a comprehensive study about the transport properties of NSAIDs across the blood-brain barrier (BBB) in vitro. Transport studies with celecoxib, diclofenac, ibuprofen, meloxicam, piroxicam and tenoxicam were accomplished across Transwell models based on cell line PBMEC/C1-2, ECV304 or primary rat brain endothelial cells. Single as well as group substance studies were carried out. In group studies substance group compositions, transport medium and serum content were varied, transport inhibitors verapamil and probenecid were added. Resulted permeability coefficients were compared and normalized to internal standards diazepam and carboxyfluorescein. Transport rankings of NSAIDs across each model were obtained. Single substance studies showed similar rankings as corresponding group studies across PBMEC/C1-2 or ECV304 cell layers. Serum content, glioma conditioned medium and inhibitors probenecid and verapamil influenced resulted permeability significantly. Basic differences of transport properties of the investigated NSAIDs were similar comparing all three in vitro BBB models. Different substance combinations in the group studies and addition of probenecid and verapamil suggested that transporter proteins are involved in the transport of every tested NSAID. Results especially underlined the importance of same experimental conditions (transport medium, serum content, species origin, cell line) for proper data comparison.