Oxidative stress markers in the neocortex of drug-resistant epilepsy patients submitted to epilepsy surgery

Exploring ncRNAs in epilepsy: From oxidative stress regulation to therapy

Epilepsy is a prevalent neurological illness which is linked with high worldwide burdens. Oxidative stress (OS) is recognized to be among the contributors that trigger the advancement of epilepsy, affecting neuronal excitability and synaptic transmission. Various types of non-coding RNAs (ncRNAs) are known to serve vital functions in many disease mechanisms, including epilepsy. The current review sought to understand better the mechanisms through which these ncRNAs regulate epilepsy's OS-related pathways. We investigated the functions of microRNAs in controlling gene expression at the post-translatory stage and their involvement in OS and neuroinflammation. We also looked at the different regulatory roles of long ncRNAs, including molecular scaffolding, enhancer, and transcriptional activator, during OS. Circular RNAs and their capability to act as miRNA decoys and their consequential impact on epilepsy development were also explored. Our review aimed to improve the current understanding of novel therapies for epilepsy based on the role of ncRNAs in OS pathways. We also demonstrated the roles of ncRNAs in epilepsy treatment and diagnosis, explaining that these molecules play vital roles that could be used in therapy as biomarkers.

Heparin-Modified Superparamagnetic Iron Oxide Nanoparticles Suppress Lithium Chloride/Pilocarpine-Induced Temporal Lobe Epilepsy in Rats through Attenuation of Inflammation and Oxidative Stress

The development of antiepileptic drugs is still a long process. In this study, heparin-modified superparamagnetic iron oxide nanoparticles (UFH-SPIONs) were prepared, and their antiepileptic effect and underlying mechanism were investigated. UFH-SPIONs are stable, homogeneous nanosystems with antioxidant enzyme activity that are able to cross the blood-brain barrier (BBB) and enriched in hippocampal epileptogenic foci. The pretreatment with UFH-SPIONs effectively prolonged the onset of seizures and reduced seizure severity after lithium/pilocarpine (LP)-induced seizures in rats. The pretreatment with UFH-SPIONs significantly decreased the expression of inflammatory factors in hippocampal tissues, including IL-6, IL-1β, and TNF-α. LP-induced oxidative stress in hippocampal tissues was in turn reduced upon pretreatment with UFH-SPIONs, as evidenced by an increase in the levels of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) and a decrease in the level of lipid peroxidation (MDA). Moreover, the LP-induced upregulation of apoptotic cells was decreased upon pretreatment with UFH-SPIONs. Together, these observations suggest that the pretreatment with UFH-SPIONs ameliorates LP-induced seizures and downregulates the inflammatory response and oxidative stress, which exerts neuronal protection during epilepsy.

Activatable Dual-Optical Molecular Probe for Bioimaging Superoxide Anion in Epilepsy

Superoxide anion (O2•-) plays a pivotal role in the generation of other reactive oxygen species within the body and is closely linked to epilepsy. Despite this connection, achieving precise imaging of O2•- during epilepsy pathology remains a formidable challenge. Herein, we develop an activatable molecular probe, CL-SA, to track the fluctuation of the level of O2•- in epilepsy through simultaneous fluorescence imaging and chemiluminescence sensing. The developed probe CL-SA demonstrated its efficacy in imaging of O2•- in neuronal cells, showcasing its dual optical imaging capability for O2•- in vitro. Furthermore, CL-SA was successfully used to observe aberrantly expressed O2•- in a mouse model of epilepsy. Overall, CL-SA provides us with a valuable tool for chemical and biomedical studies of O2•-, promoting the investigation of O2•- fluctuations in epilepsy, as well as providing a reliable means to explore the diagnosis and therapy of epilepsy.

Increased production of inflammatory cytokines by circulating monocytes in mesial temporal lobe epilepsy: A possible role in drug resistance

We analyzed peripheral blood mononuclear cells (PBMCs) and serum inflammatory biomarkers in patients with mesial temporal lobe epilepsy (drug-resistant - DR, vs. drug-sensitive - DS). Patients with epilepsy showed higher levels of serum CCL2, CCL3, IL-8 and AOPP, and lower levels of FRAP and thiols compared to healthy controls (HC). Although none of the serum biomarkers distinguished DR from DS patients, when analysing intracellular cytokines after in vitro stimulation, DR patients presented higher percentages of IL-1β and IL-6 positive monocytes compared to DS patients and HC. Circulating innate immune cells might be implicated in DR epilepsy and constitute potential new targets for treatments.

Novel Near-Infrared Fluorescence Probe for Bioimaging and Evaluating Superoxide Anion Fluctuations in Ferroptosis-Mediated Epilepsy

Ferroptosis is an iron-regulated, caspase-mediated pathway of cell death that is associated with the excessive aggregation of lipid-reactive oxygen species and is extensively involved in the evolution of many diseases, including epilepsy. The superoxide anion (O2•-), as the primary precursor of ROS, is closely related to ferroptosis-mediated epilepsy. Therefore, it is crucial to establish a highly effective and convenient method for the real-time dynamic monitoring of O2•- during the ferroptosis process in epilepsy for the diagnosis and therapy of ferroptosis-mediated epilepsy. Nevertheless, no probes for detecting O2•- in ferroptosis-mediated epilepsy have been reported. Herein, we systematically conceptualized and developed a novel near-infrared (NIR) fluorescence probe, NIR-FP, for accurately tracking the fluctuation of O2•- in ferroptosis-mediated epilepsy. The probe showed exceptional sensitivity and outstanding selectivity toward O2•-. In addition, the probe has been utilized effectively to bioimage and evaluate endogenous O2•- variations in three types of ferroptosis-mediated epilepsy models (the kainic acid-induced chronic epilepsy model, the pentylenetetrazole-induced acute epilepsy model, and the pilocarpine-induced status epilepticus model). The above applications illustrated that NIR-FP could serve as a reliable and suitable tool for guiding the accurate diagnosis and therapy of ferroptosis-mediated epilepsy.

Regulatory Basis of Adipokines Leptin and Adiponectin in Epilepsy: from Signaling Pathways to Glucose Metabolism

Epilepsy is a common and severe neurological disorder in which impaired glucose metabolism leads to changes in neuronal excitability that slow or promote the development of epilepsy. Leptin and adiponectin are important mediators regulating glucose metabolism in the peripheral and central nervous systems. Many studies have reported a strong association between epilepsy and these two adipokines involved in multiple signaling cascades and glucose metabolism. Due to the complex regulatory mechanisms between them and various signal activation networks, their role in epilepsy involves many aspects, including the release of inflammatory mediators, oxidative damage, and neuronal apoptosis. This paper aims to summarize the signaling pathways involved in leptin and adiponectin and the regulation of glucose metabolism from the perspective of the pathogenesis of epilepsy. In particular, we discuss the dual effects of leptin in epilepsy and the relationship between antiepileptic drugs and changes in the levels of these two adipokines. Clinical practitioners may need to consider these factors in evaluating clinical drugs. Through this review, we can better understand the specific involvement of leptin and adiponectin in the pathogenesis of epilepsy, provide ideas for further exploration, and bring about practical significance for the treatment of epilepsy, especially for the development of personalized treatment according to individual metabolic characteristics.

Crosstalk between neuroinflammation and oxidative stress in epilepsy

The roles of both neuroinflammation and oxidative stress in the pathophysiology of epilepsy have begun to receive considerable attention in recent years. However, these concepts are predominantly studied as separate entities despite the evidence that neuroinflammatory and redox-based signaling cascades have significant crosstalk. Oxidative post-translational modifications have been demonstrated to directly influence the function of key neuroinflammatory mediators. Neuroinflammation can further be controlled on the transcriptional level as the transcriptional regulators NF-KB and nrf2 are activated by reactive oxygen species. Further, neuroinflammation can induce the increased expression and activity of NADPH oxidase, leading to a highly oxidative environment. These factors additionally influence mitochondria function and the metabolic status of neurons and glia, which are already metabolically stressed in epilepsy. Given the implication of this relationship to disease pathology, this review explores the numerous mechanisms by which neuroinflammation and oxidative stress influence one another in the context of epilepsy. We further examine the efficacy of treatments targeting oxidative stress and redox regulation in animal and human epilepsies in the literature that warrant further investigation. Treatment approaches aimed at rectifying oxidative stress and aberrant redox signaling may enable control of neuroinflammation and improve patient outcomes.

DNA damage and repair and epigenetic modification in the role of oxoguanine glycosylase 1 (OGG1) in brain development

Oxoguanine glycosylase 1 (OGG1) repairs the predominant reactive oxygen species (ROS)-initiated DNA lesion 8-oxoguanine (8-oxoG). Human OGG1 polymorphisms resulting in reduced DNA repair associate with an increased risk for disorders like cancer and diabetes, but the role of OGG1 in brain development is unclear. Herein, we show that Ogg1 knockout mice at 2-3 months of age exhibit enhanced gene- and sex-dependent DNA damage (strand breaks) and decreased epigenetic DNA methylation marks (5-methylcytosine, 5-hydroxymethylcytosine), both of which were associated with increased cerebellar calbindin levels, reduced hippocampal postsynaptic function, altered body weight with age and disorders of brain function reflected in behavioural tests for goal-directed repetitive behaviour, anxiety and fear, object recognition and spatial memory, motor coordination and startle response. These results suggest that OGG1 plays an important role in normal brain development, possibly via both its DNA repair activity and its role as an epigenetic modifier, with OGG1 deficiencies potentially contributing to neurodevelopmental disorders.

Circulating glutathione peroxidase and superoxide dismutase levels in patients with epilepsy: A meta-analysis

PURPOSE

Glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) are assessed as oxidative stress markers to determine the impact of oxidation on the levels of GSH-Px and SOD in patients with epilepsy (PWE) and healthy controls.

METHODS

A meta-analysis was completed on twenty-nine published studies. A total of 636 PWE and 665 healthy controls, 303 PWE and 191 controls, and 22 PWE and 22 controls were included to study GSH-Px levels in erythrocytes, serum and plasma, respectively. For SOD studies, there were 610 PWE and 680 controls, 464 PWE and 382 controls, and 62 PWE with 77 controls for erythrocytes, serum and plasma, respectively.

RESULTS

Meta-analysis showed that the erythrocyte SOD level was significantly lower in PWE than in healthy controls (SMD =-1.96; 95% CI [-2.93, -0.99]; P<0.0001). Moreover, the meta-analysis demonstrated that in serum and plasma, SOD levels in PWE were significantly lower than those in healthy controls (SMD =-1.47; 95% CI [-2.47, -0.48]; P<0.0001). Erythrocyte GSH-Px levels had a tendency to decrease in PWE compared with healthy controls (SMD =-0.31; 95% CI [-1.48, 0.85]; P=0.598), but the results showed no significant difference.

CONCLUSION

Our results showed reduced SOD levels in erythrocytes, serum and plasma in PWE, which may be an indicator of oxidative damage in epilepsy. This is the first meta-analysis of circulating GSH-Px and SOD levels in PWE and healthy controls.

Neuroprotective Effect of Protaetia brevitarsis seulensis' Water Extract on Trimethyltin-Induced Seizures and Hippocampal Neurodegeneration

This study aimed to investigate whether the Protaetia brevitarsis seulensis (PB)’ water extract (PBWE) ameliorates trimethyltin (TMT)-induced seizures and hippocampal neurodegeneration. To investigate the potential neuroprotective effect of the PBWE in vitro, a lactate dehydrogenase (LDH) assay was conducted in TMT-treated primary cultures of mouse hippocampal neurons. In TMT-treated adult C57BL/6 mice, behavioral and histopathological changes were evaluated by seizure scoring and Fluoro-Jade C staining, respectively. In our in vitro assay, we observed that pretreating mice hippocampal neuron cultures with the PBWE reduced TMT-induced cytotoxicity, as indicated by the decreased LDH release. Furthermore, pretreatment with the PBWE alleviated seizures and hippocampal neurodegeneration in TMT-treated mice. The antioxidant activity of the PBWE increased in a dose-dependent manner; moreover, pretreatment with the PBWE mitigated the TMT-induced Nrf2 stimulation. In addition, six major compounds, including adenine, hypoxanthine, uridine, adenosine, inosine, and benzoic acid, were isolated from the PBWE, and among them, inosine and benzoic acid have been confirmed to have an essential antioxidative activity. In conclusion, the PBWE ameliorated TMT-induced toxicity in hippocampal neurons in both in vitro and in vivo assays, through a potential antioxidative effect. Our findings suggest that the PBWE may have pharmacotherapeutic potential in neurodegenerative diseases such as seizures or epilepsy.

Approaches for Reactive Oxygen Species and Oxidative Stress Quantification in Epilepsy

Oxidative stress (OS) and excessive reactive oxygen species (ROS) production have been implicated in many neurological pathologies, including acute seizures and epilepsy. Seizure-induced damage has been demonstrated both in vitro and in several in vivo seizure and epilepsy models by direct determination of ROS, and by measuring indirect markers of OS. In this manuscript, we review the current reliable methods for quantifying ROS-related and OS-related markers in pre-clinical and clinical epilepsy studies. We first provide pieces of evidence for the involvement of different sources of ROS in epilepsy. We then discuss general methods and assays used for the ROS measurements, mainly superoxide anion, hydrogen peroxide, peroxynitrite, and hydroxyl radical in in vitro and in vivo studies. In addition, we discuss the role of these ROS and markers of oxidative injury in acute seizures and epilepsy pre-clinical studies. The indirect detection of secondary products of ROS such as measurements of DNA damage, lipid peroxidation, and protein oxidation will also be discussed. This review also discusses reliable methods for the assessment of ROS, OS markers, and their by-products in epilepsy clinical studies.

Anxiety Therapeutic Interventions of β-Caryophyllene: A Laboratory-Based Study

The bicyclic sesquiterpene β-caryophyllene (BCP) has diverse biological activities, including antioxidant, anti-inflammatory, antidiabetic, and analgesic effects. This study evaluates anxiolytic, toxicity, and antioxidant effects of BCP using in vitro and in vivo test models. The anxiolytic effects were tested in Swiss albino mice ( Mus musculus) by applying the elevated plus-maze, rota-rod, light and dark, and hiding sphere models, while the toxicity was evaluated by brine shrimp ( Artemia salina) lethality bioassay. Additionally, the antioxidant capacity was tested by using 2,2-diphenyl-1-picrylhydrazyl radical, 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid hydroxyl radical scavenging, and the Saccharomyces cerevisiae test model. The results suggest that BCP exerted a dose-dependent anxiolytic-like effect on the experimental animals. It did not show toxicity in A. salina at 24 hours. BCP showed a concentration-dependent free-radical-scavenging capacity, similar to the standard antioxidant Trolox. It also showed protective and repair capacities against hydrogen peroxide-induced damaging effects in isogenic and wild-type S. cerevisiae strains. Taken together, BCP exerted antioxidant and protective effects, which can be targeted to treat neurological diseases and disorders such as anxiety.

Modulating neuroinflammation and oxidative stress to prevent epilepsy and improve outcomes after traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability in young adults worldwide. TBI survival is associated with persistent neuropsychiatric and neurological impairments, including posttraumatic epilepsy (PTE). To date, no pharmaceutical treatment has been found to prevent PTE or ameliorate neurological/neuropsychiatric deficits after TBI. Brain trauma results in immediate mechanical damage to brain cells and blood vessels that may never be fully restored given the limited regenerative capacity of brain tissue. This primary insult unleashes cascades of events, prominently including neuroinflammation and massive oxidative stress that evolve over time, expanding the brain injury, but also clearing cellular debris and establishing homeostasis in the region of damage. Accumulating evidence suggests that oxidative stress and neuroinflammatory sequelae of TBI contribute to posttraumatic epileptogenesis. This review will focus on possible roles of reactive oxygen species (ROS), their interactions with neuroinflammation in posttraumatic epileptogenesis, and emerging therapeutic strategies after TBI. We propose that inhibitors of the professional ROS-generating enzymes, the NADPH oxygenases and myeloperoxidase alone, or combined with selective inhibition of cyclooxygenase mediated signaling may have promise for the treatment or prevention of PTE and other sequelae of TBI. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Shedding light on human cerebral lipofuscin: An explorative study on identification and quantification

Increased oxidative stress has been associated with several neurodegenerative diseases such as Alzheimer's disease, but also with neurological diseases sharing pathophysiological pathways like epilepsy. Lipofuscin is a nondegradable end-product of oxidative stress; its cerebral presence reflects the cumulative amount of oxidative stress the brain has endured. In this study, we have observed prominent autofluorescent particles in the pial arterial wall and in neocortical parenchyma of young, drug-resistant epilepsy patients (18-28 years old) who underwent resective brain surgery (n = 6), as well as in older control patients (n = 3). With fluorescence spectroscopic imaging, brightfield microscopy, histochemistry and fluorescence lifetime imaging, these autofluorescent particles were identified as the age pigment lipofuscin. An evaluation of these lipofuscin particles using Imaris© software allowed robust quantification, while the 3D properties allowed visualization of the complex configuration. We elaborate on the usefulness of lipofuscin as a marker of cumulative oxidative stress in the brain. Furthermore, we speculate on the observed differences in particle size and density that we found between young patients and older controls, which could imply a role for lipofuscin in the pathophysiology of epilepsy and possibly other neurological diseases.

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

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

Inflammation and reactive oxygen species as disease modifiers in epilepsy

Neuroinflammation and reactive oxygen and nitrogen species are rapidly induced in the brain after acute cerebral injuries that are associated with an enhanced risk for epilepsy in humans and related animal models. These phenomena reinforce each others and persist during epileptogenesis as well as during chronic spontaneous seizures. Anti-inflammatory and anti-oxidant drugs transiently administered either before, or shortly after the clinical onset of symptomatic epilepsy, similarly block the progression of spontaneous seizures, and may delay their onset. Moreover, neuroprotection and rescue of cognitive deficits are also observed in the treated animals. Therefore, although these treatments do not prevent epilepsy development, they offer clinically relevant disease-modification effects. These therapeutic effects are mediated by targeting molecular signaling pathways such as the IL-1β-IL-1 receptor type 1 and TLR4, P2X7 receptors, the transcriptional anti-oxidant factor Nrf2, while the therapeutic impact of COX-2 inhibition for reducing spontaneous seizures remains controversial. Some anti-inflammatory and anti-oxidant drugs that are endowed of disease modification effects in preclinical models are already in medical use and have a safety profile, therefore, they provide potential re-purposed treatments for improving the disease course and for reducing seizure burden. Markers of neuroinflammation and oxidative stress can be measured in blood or by neuroimaging, therefore they represent testable prognostic and predictive biomarkers for selecting the patient's population at high risk for developing epilepsy therefore eligible for novel treatments. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Functional Nutrients for Epilepsy

Epilepsy is a common neurological disorder of which seizures are a core symptom. Approximately one third of epileptic patients are resistant to antiepileptic drugs and therefore require alternative therapeutic options. Dietary and nutritional supplements can in some cases replace drugs, but with the exception of ketogenic diets, there are no officially recommended dietary considerations for patients with epilepsy. In this review we summarize a selection of nutritional suggestions that have proved beneficial in treating different types of epilepsy. We describe the types of seizures and epilepsy and follow this with an introduction to basic molecular mechanisms. We then examine several functional nutrients for which there is clinical evidence of therapeutic efficacy in reducing seizures or epilepsy-associated sudden death. We also discuss experimental results that demonstrate possible molecular mechanisms elicited by the administration of various nutrients. The availability of multiple dietary and nutritional candidates that show favorable outcomes in animals implies that assessing the clinical potential of these substances will improve translational medicine, ultimately benefitting epilepsy patients.

Oxidative stress and DNA damage in the mechanism of fetal alcohol spectrum disorders

This review covers molecular mechanisms involving oxidative stress and DNA damage that may contribute to morphological and functional developmental disorders in animal models resulting from exposure to alcohol (ethanol, EtOH) in utero or in embryo culture. Components covered include: (a) a brief overview of EtOH metabolism and embryopathic mechanisms other than oxidative stress; (b) mechanisms within the embryo and fetal brain by which EtOH increases the formation of reactive oxygen species (ROS); (c) critical embryonic/fetal antioxidative enzymes and substrates that detoxify ROS; (d) mechanisms by which ROS can alter development, including ROS-mediated signal transduction and oxidative DNA damage, the latter of which leads to pathogenic genetic (mutations) and epigenetic changes; (e) pathways of DNA repair that mitigate the pathogenic effects of DNA damage; (f) related indirect mechanisms by which EtOH enhances risk, for example by enhancing the degradation of some DNA repair proteins; and, (g) embryonic/fetal pathways like NRF2 that regulate the levels of many of the above components. Particular attention is paid to studies in which chemical and/or genetic manipulation of the above mechanisms has been shown to alter the ability of EtOH to adversely affect development. Alterations in the above components are also discussed in terms of: (a) individual embryonic and fetal determinants of risk and (b) potential risk biomarkers and mitigating strategies. FASD risk is likely increased in progeny which/who are biochemically predisposed via genetic and/or environmental mechanisms, including enhanced pathways for ROS formation and/or deficient pathways for ROS detoxification or DNA repair.

Immunohistochemical Study of Antioxidant Enzymes Regulated by Nrf2 in the Models of Epileptic Seizures (KA and PTZ)

Epilepsy is a neurological disorder characterized by recurrent spontaneous seizures due to an imbalance between cerebral excitability and inhibition, with a tendency towards uncontrolled excitability. Epilepsy has been associated with oxidative and nitrosative stress due to prolonged neuronal hyperexcitation and loss neurons during seizures. The experimental animal models report level of ATP diminished and increase in lipid peroxidation, catalase, and glutathione altered activity in the brain. We studied the immunohistochemical expression and localization of antioxidant enzymes GPx, SOD, and CAT in the rat brains treated with KA and PTZ. A significant decrease was observed in the number of immunoreactive cells to GPx, without significant changes for SOD and CAT in KA-treated rats, and decrease in the number of immunoreactive cells to SOD, without significant changes for GPx and only CAT in PTZ-treated rats. Evident immunoreactivity of GPx, SOD, and CAT was observed mainly in astrocytes and neurons of the hippocampal brain region in rats exposed at KA; similar results were observed in rats treated with PTZ at the first hours. These results provide evidence supporting the role of activation of the Nrf2 antioxidant system pathway against oxidative stress effects in the experimental models of epileptic seizures.

[Oxidative stress in epilepsy]

This article contains an analysis of clinical and experimental studies in which oxidative stress is considered as a possible mechanism in the pathogenesis of epilepsy. Oxidative stress occurs as a result of brain damage after epileptic seizures and may later cause epileptogenesis. Patients with epilepsy showed a high level of lipid peroxidation markers, while the activity of antioxidant defense system was low. The level of oxidative stress was shown to be significantly higher in epileptics with associated mental disorders and in patients with refractory epilepsy. Further study of oxidative stress in epilepsy may play the key role in the treatment of this disease.

The interaction between P2X7Rs and T-type calcium ion channels in penicillin-induced epileptiform activity

Limited information exists on the link between purinergic class P2X7 receptors (P2X7Rs) and calcium ion channels in epilepsy; no data has been reported regarding the interaction between P2X7Rs and T-type calcium ion channels in epilepsy. Thus, this study is an evaluation of the role that T-type calcium ion channels play in the effect of P2X7Rs on penicillin-induced epileptiform activity. In the first set of experiments, P2X7R agonist BzATP (at 25-, 50-, 100- and 200-μg doses), P2X7R antagonist A-438079 (at 5-, 10-, 20- and 40-μg doses) and T-type calcium ion channel antagonist, NNC-550396 were administered for electrophysiological analyses 30 min after penicillin injection (2.5 μl, 500 IU). In the second set of experiments, the effective doses of these substances were used for biochemical analyses. Malondialdehyde (MDA), advanced oxidation protein product (AOPP), glutathione (GSH), glutathione reductase (GR), glutathione peroxide (GPx), catalase (CAT) and superoxide dismutase (SOD) levels were measured in the cerebrum, cerebellum and brainstem of rats. BzATP (100 μg, icv) increased the mean frequency of epileptiform activity, whereas A-438079 (40 μg, icv) and NNC-550396 (30 μg, ic) reduced it. Both A-438079 and NNC-550396 reversed BzATP's proconvulsant action. BzATP increased lipid peroxidation and protein oxidation; it also altered other antioxidant enzymes measured in this study, which were all then reversed via A-438079 and NNC-550396, at least in the cerebrum. The electrophysiological and biochemical analysis of present study suggest that P2X7Rs and its interaction with T-type calcium ion channels play an important role in the experimental model of epilepsy.

Naringin in a combined therapy with phenytoin on pentylenetetrazole-induced kindling in rats

Phenytoin (Dilantin) is an orally active, use-dependent voltage-gated sodium channel inhibitor and is a potent, economical, and widely used anticonvulsant agent. The objective of the present study was to investigate the effect of the combined treatment of naringin (40 mg/kg and 80 mg/kg) and phenytoin on prevention of seizure attacks, development of kindling, oxidative stress, cognitive impairment, and neurochemicals in the frontal cortex, temporal cortex, and hippocampus, and morphological changes in the hippocampus. Treatment with the high dose of naringin (80 mg/kg) along with phenytoin has shown to offer protection against seizures, development of kindling, and cognition enhancement through Y-maze test and improved % conditioned avoidance response (% CAR) through pole climbing test in pentylenetetrazole (PTZ)-induced kindling model. It has also been shown to improve neurochemical balance by elevating levels of Gamma amino butyric acid (GABA) and dopamine, decreasing levels of glutamate, oxidative biomarker (malondialdehyde (MDA)), and increasing levels of antioxidants (glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and total thiol and offered neuroprotection in the hippocampus. So, coadministration of naringin with phenytoin offers a potential treatment option for drug-resistant epilepsy and associated comorbidities. Interpretable research on flavonoids will support the clinical evidence for the recommendation of flavonoids as supplements with antiepileptic drugs (AEDs) for curtailing pharmacoresistant epilepsy and AED-associated comorbidities.

Oxidative stress and inflammation in a spectrum of epileptogenic cortical malformations: molecular insights into their interdependence

Oxidative stress (OS) occurs in brains of patients with epilepsy and coincides with brain inflammation, and both phenomena contribute to seizure generation in animal models. We investigated whether expression of OS and brain inflammation markers co-occurred also in resected brain tissue of patients with epileptogenic cortical malformations: hemimegalencephaly (HME), focal cortical dysplasia (FCD) and cortical tubers in tuberous sclerosis complex (TSC). Moreover, we studied molecular mechanisms linking OS and inflammation in an in vitro model of neuronal function. Untangling interdependency and underlying molecular mechanisms might pose new therapeutic strategies for treating patients with drug-resistant epilepsy of different etiologies. Immunohistochemistry was performed for specific OS markers xCT and iNOS and brain inflammation markers TLR4, COX-2 and NF-κB in cortical tissue derived from patients with HME, FCD IIa, IIb and TSC. Additionally, we studied gene expression of these markers using the human neuronal cell line SH-SY5Y in which OS was induced using H₂ O₂ . OS markers were higher in dysmorphic neurons and balloon/giant cells in cortex of patients with FCD IIb or TSC. Expression of OS markers was positively correlated to expression of brain inflammation markers. In vitro, 100 µM, but not 50 µM, of H₂ O₂ increased expression of TLR4, IL-1β and COX-2. We found that NF-κB signaling was activated only upon stimulation with 100 µM H₂ O₂ leading to upregulation of TLR4 signaling and IL-1β. The NF-κB inhibitor TPCA-1 completely reversed this effect. Our results show that OS positively correlates with neuroinflammation and is particularly evident in brain tissue of patients with FCD IIb and TSC. In vitro, NF-κB is involved in the switch to an inflammatory state after OS. We propose that the extent of OS can predict the neuroinflammatory state of the brain. Additionally, antioxidant treatments may prevent the switch to inflammation in neurons thus targeting multiple epileptogenic processes at once.

Effects of propofol and isoflurane on excitatory amino acid carrier 1 mRNA and glutathione protein levels in rat hippocampus

OBJECTIVE

We compared the effects of two anesthetics, isoflurane and propofol, on the nuclear or cytosolic localization of nuclear factor erythroid 2-related factor 2 (Nrf2), mRNA expression levels of excitatory amino acid carrier 1 (EAAC1), and glutathione (GSH) protein levels in the rat hippocampus.

METHODS

Fifty-two adult male Sprague-Dawley rats were randomly divided into three groups: a control group, a group that received propofol for 240 minutes (P240), and a group that received isoflurane for 240 minutes (I240). We compared GSH protein and EAAC1 mRNA expression levels in the rat hippocampus and evaluated Nrf2 content in cytosolic and nuclear fractions in the three groups.

RESULTS

GSH protein and EAAC1 mRNA expression levels were significantly higher in the I240 and P240 groups compared with the control group. The I240 and P240 groups showed lower Nrf2 protein levels in the cytosolic fractions, but higher levels in the nuclear fractions compared with the control group.

CONCLUSION

Treatment with isoflurane or propofol may enhance GSH production by facilitating translocation of Nrf2 into the nucleus and increasing EAAC1mRNA expression in the rat hippocampus. Isoflurane and propofol show similar profiles in EAAC1 expression-associated GSH production.

Drug-Resistant Epilepsy and Surgery

BACKGROUND

Epilepsy is a chronic brain disease that is caused by various factors and characterized by recurrent, episodic and temporary central nervous system dysfunction which results due to excessive discharge of brain neurons. In the past decades, despite the continuous development of antiepileptic drugs, there are still many patients with epilepsy progressing to drugresistant epilepsy. Currently, surgical treatment is one of important way to cure drug-resistant epilepsy.

METHODS

Data were collected from Web of Science, Medline, Pubmed, through searching of these keywords: "surgery" and "drug-resistant epilepsy".

RESULTS

An increasing number of studies have shown that surgery plays an important role in the treatment of drug-resistant epilepsy. Moreover, the comprehensive treatment mainly based on surgery can achieve the remission and even cure of drug-resistant epilepsy.

CONCLUSION

In this review, we discuss the pathogenesis of drug-resistant epilepsy and the comprehensive treatment mainly based on surgery; this review may provide a reference for the clinical treatment of drug-resistant epilepsy.

Metabolic Dysfunction and Oxidative Stress in Epilepsy

The epilepsies are a heterogeneous group of disorders characterized by the propensity to experience spontaneous recurrent seizures. Epilepsies can be genetic or acquired, and the underlying mechanisms of seizure initiation, seizure propagation, and comorbid conditions are incompletely understood. Metabolic changes including the production of reactive species are known to result from prolonged seizures and may also contribute to epilepsy development. In this review, we focus on the evidence that metabolic and redox disruption is both cause and consequence of epileptic seizures. Additionally, we discuss the promise of targeting redox processes as a therapeutic option in epilepsy.

Potential application of the oxidative nucleic acid damage biomarkers in detection of diseases

Reactive oxygen species (ROS) are generated after exposure to harmful environmental factors and during normal cellular metabolic processes. The balance of the generating and scavenging of ROS plays a significant role in living cells. The accumulation of ROS will lead to oxidative damage to biomolecules including nucleic acid. Although many types of oxidative nucleic acid damage products have been identified, 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoG) has been commonly chosen as the biomarkers of oxidative damage to DNA and RNA, respectively. It has been demonstrated that oxidative damage to nucleic acid is an initiator in pathogenesis of numerous diseases. Thus, oxidative nucleic acid damage biomarkers have the potential to be utilized for detection of diseases. Herein, we reviewed the relationship of oxidative nucleic acid damage and development of various diseases including cancers (colorectal cancer, gastrointestinal cancer, breast cancer, lung cancer, epithelial ovarian carcinoma, esophageal squamous cell carcinoma), neurodegenerative disorders and chronic diseases (diabetes and its complications, cardiovascular diseases). The potential of oxidative nucleic acid damage biomarkers for detection of diseases and drug development were described. Moreover, the approaches for detection of these biomarkers were also summarized.

Effect of Oxidative Stress on ABC Transporters: Contribution to Epilepsy Pharmacoresistance

Epilepsy is a neurological disorder affecting around 1%–2% of population worldwide and its treatment includes use of antiepileptic drugs to control seizures. Failure to respond to antiepileptic drug therapy is a major clinical problem and over expression of ATP-binding cassette transporters is considered one of the major reasons for pharmacoresistance. In this review, we have summarized the regulation of ABC transporters in response to oxidative stress due to disease and antiepileptic drugs. Further, ketogenic diet and antioxidants were examined for their role in pharmacoresistance. The understanding of signalling pathways and mechanism involved may help in identifying potential therapeutic targets and improving drug response.

Selenium in the Therapy of Neurological Diseases. Where is it Going?

Selenium (₃₄Se), an antioxidant trace element, is an important regulator of brain function. These beneficial properties that Se possesses are attributed to its ability to be incorporated into selenoproteins as an amino acid. Several selenoproteins are expressed in the brain, in which some of them, e.g. glutathione peroxidases (GPxs), thioredoxin reductases (TrxRs) or selenoprotein P (SelP), are strongly involved in antioxidant defence and in maintaining intercellular reducing conditions. Since increased oxidative stress has been implicated in neurological disorders, including Parkinson’s disease, Alzheimer’s disease, stroke, epilepsy and others, a growing body of evidence suggests that Se depletion followed by decreased activity of Se-dependent enzymes may be important factors connected with those pathologies. Undoubtedly, the remarkable progress that has been made in understanding the biological function of Se in the brain has opened up new potential possibilities for the treatment of neurological diseases by using Se as a potential drug. However, further research in the search for optimal Se donors is necessary in order to achieve an effective and safe therapeutic income.

Reactive oxygen species mediate cognitive deficits in experimental temporal lobe epilepsy

Cognitive dysfunction is an important comorbidity of temporal lobe epilepsy (TLE). However, no targeted therapies are available and the mechanisms underlying cognitive impairment, specifically deficits in learning and memory associated with TLE remain unknown. Oxidative stress is known to occur in the pathogenesis of TLE but its functional role remains to be determined. Here, we demonstrate that oxidative stress and resultant processes contribute to cognitive decline associated with epileptogenesis. Using a synthetic catalytic antioxidant, we show that pharmacological removal of reactive oxygen species (ROS) prevents 1) oxidative stress, 2) deficits in mitochondrial oxygen consumption rates, 3) hippocampal neuronal loss and 4) cognitive dysfunction without altering the intensity of the initial status epilepticus (SE) or epilepsy development in a rat model of SE-induced TLE. Moreover, the effects of the catalytic antioxidant on cognition persisted beyond the treatment period suggestive of disease-modification. The data implicate oxidative stress as a novel mechanism by which cognitive dysfunction can arise during epileptogenesis and suggest a potential disease-modifying therapeutic approach to target it.

Fish oil provides protection against the oxidative stress in pilocarpine model of epilepsy

Temporal lobe epilepsy (TLE), the most common form of epilepsy is often resistant to pharmacological treatment. Neuronal loss observed in epileptic brain may be result of an overproduction of free radicals (oxidative stress). Oxidative stress is characterized by an imbalance between antioxidant defenses and oxidizing agents (free radicals), which can lead to tissue injury. The n-3 PUFAs are important for the development and maintenance of central nervous system functions. Research by our group has shown that chronic treatment with fish oil, immediately after status epilepticus (SE), exhibits both neuroprotective effects and effects on neuroplasticity. The main purpose of this research was to evaluate if fish oil exhibits a protective effect against oxidative stress. Animals were subjected to TLE model by pilocarpine administration. After 3 h of SE they were randomly divided into the following groups: control animals treated daily with vehicle or with 85 mg/kg of fish oil and animals with epilepsy treated daily with vehicle or with 85 mg/kg of fish oil. After 90 days, superoxide anion production, enzymatic activity of superoxide dismutase (SOD) and catalase (CAT) and protein expression of NAD(P)H oxidase subunits (p47(PHOX) and gp91(PHOX)) were analyzed. Our results showed evidences that reactive oxygen species are increased in animals with epilepsy and that fish oil supplementation could counteract it. Fish oil supplementation promoted protection against oxidative stress by multiple ways, which involved the reduction of activity and expression of NAD(P)H oxidase subunits and increased the activity and expression of antioxidants enzymes, contributing to well-known neuroprotective effect in epilepsy.

Anti-oxidative effects produced by environmental enrichment in the hippocampus and cerebral cortex of male and female rats

Both physical and intellectual activity may reduce the incidence of neurodegenerative disorders. There is evidence that environmental enrichment (EE) can induce profound behavioral, neurochemical and neuroanatomical changes, thus producing lasting improvements in memory and learning tasks. In this study we evaluated the anti-oxidative effects produced by EE in the hippocampus and the cerebral cortex of male and female rats. The animals had been reared in either EE or control conditions. The parameters studied were: thiobarbituric acid reactive substances (TBARS), protein oxidation, total radical antioxidant parameter, catalase, superoxide dismutase and superoxide anion activity. The results showed that our EE protocol reduced markers of oxidative stress in the hippocampus and in the cerebral cortex. Overall, the measures taken in the two cerebral regions revealed that EE rats showed higher values for antioxidant measures and lower values for oxidative stress parameters than control animals. More importantly, a consistent sex difference was found, indicating that in female rats the hippocampus and cerebral cortex are plastic brain regions receptive to external stimulation such as EE. Although EE males have higher levels for antioxidant capacity, catalase and SOD, it is likely that females do not need to activate all the antioxidant defenses since they have a greater capacity to assimilate external stimuli. This is suggested by the similarity of protein oxidation and TBARS levels in hippocampus in both sexes, and the even lower levels of protein oxidation and superoxide anion activity in the cerebral cortex in EE females.

Montelukast inhibits pentylenetetrazol-induced seizures in rats

Background

Montelukast is an antiinflammatory drug with an antioxidant property. In this study, we aimed to reveal whether montelukast has a preventive effect against seizures and post-seizure oxidative stress in pentylenetetrazol (PTZ)-induced seizures in rats.

Material/Methods

Of the 48 male Sprague-Dawley rats used in the study, 24 were assigned to EEG recordings (group A) and 24 were assigned to behavioral studies (group B). In group A, the electrodes were implanted on dura over the left frontal cortex for EEG recording. After 10 days, in group A, i.p. saline, 25, 50, or 100 mg/kg montelukast+35 mg/kg PTZ was administered to the rats. EEG was recorded and spike percentage was evaluated. In group B, i.p. saline, 25, 50, or 100 mg/kg montelukast+70 mg/kg PTZ was administered to the rats. Racine’s Convulsion Scale (RCS) and onset times of first myoclonic jerk (FMJ) was used to evaluate the seizures. Malondialdehyde (MDA) and superoxide dismutase (SOD) levels were determined in the brain tissue of animals.

Results

Animals treated with 50 or 100 mg/kg montelukast had significantly lower RCS and significantly increased FMJ onset time compared to the saline-treated animals. Moreover, groups given 25, 50, or 100 mg/kg montelukast had significantly lower MDA and higher SOD levels compared to the saline-treated group. The differences were more pronounced in the 100 mg/kg montelukast-pretreated group (p<0.001).

Conclusions

Montelukast showed anticonvulsant action and led to amelioration of oxidative stress markers in PTZ-induced seizures in rats.

Seizure-induced oxidative stress in temporal lobe epilepsy

An insult to the brain (such as the first seizure) causes excitotoxicity, neuroinflammation, and production of reactive oxygen/nitrogen species (ROS/RNS). ROS and RNS produced during status epilepticus (SE) overwhelm the mitochondrial natural antioxidant defense mechanism. This leads to mitochondrial dysfunction and damage to the mitochondrial DNA. This in turn affects synthesis of various enzyme complexes that are involved in electron transport chain. Resultant effects that occur during epileptogenesis include lipid peroxidation, reactive gliosis, hippocampal neurodegeneration, reorganization of neural networks, and hypersynchronicity. These factors predispose the brain to spontaneous recurrent seizures (SRS), which ultimately establish into temporal lobe epilepsy (TLE). This review discusses some of these issues. Though antiepileptic drugs (AEDs) are beneficial to control/suppress seizures, their long term usage has been shown to increase ROS/RNS in animal models and human patients. In established TLE, ROS/RNS are shown to be harmful as they can increase the susceptibility to SRS. Further, in this paper, we review briefly the data from animal models and human TLE patients on the adverse effects of antiepileptic medications and the plausible ameliorating effects of antioxidants as an adjunct therapy.