No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The PPARc agonist rosiglitazone prevents cognitive impairment by inhibiting astrocyte activation and oxidative stress following pilocarpine-induced status epilepticus
Abstract
Epilepsy is commonly associated with cognitive impairment. Astrocyte activation and oxidative stress occur following seizures, and play a role in the pathological injury of epilepsy with cognitive impairment. The peroxisome proliferator-activated receptor gamma (PPARγ) has been shown to exhibit neuroprotective and antioxidative effects in CNS diseases. Thus, we hypothesized that rosiglitazone, a PPARγ agonist, would prevent cognitive impairment by inhibiting astrocyte activation and regulating glutathione (GSH) homeostasis after status epilepticus (SE). Using a lithium pilocarpine-induced SE model, we found that rosiglitazone significantly prevented cognitive impairment induced by SE, and potently inhibited astrocyte activation with maintenance of GSH homeostasis in the hippocampus after SE. These protective effects were significantly reversed by co-treatment with the PPARγ antagonist T0070907. These data suggest that rosiglitazone can improve cognitive impairment, and inhibit astrocyte activation and oxidative damage following SE. Rosiglitazone may be a promising agent for treatment of epilepsy involving SE-induced cognitive impairment.
... PPARs are involved in the metabolism of fat and carbohydrate, energy homeostasis, inflammation, cell proliferation and differentiation, as well as various diseases including cancer, cardiovascular diseases, and neurological disorders (Mirza and AlthagafiShamshad, 2019). Previous findings also suggested that PPARs exert protective effects in seizures through regulating oxidative stress, inflammatory responses, BDNF/ TrkB, or energy metabolism (Sun et al., 2008;Hong et al., 2012Hong et al., , 2013. Specifically, both PPAR α and PPAR γ show the potential of controlling seizures responses including suppressing abnormal electrical activity and reducing clonic-and tonic-like behavior in rodent models and clinical studies (Auvin, 2012;Abdallah, 2010;Puligheddu et al., 2017). ...
... Interestingly, we found that the expression of PPAR α and PPAR γ is slightly increased following PTZ treatment, which is possibly due to stress responses could be induced by PPARs. It has been reported that PPARs activate anti-oxidative stress and anti-inflammatory responses, and revert disturbances levels in neurotransmitter levels after an insult to the brain (Sun et al., 2008;Hong et al., 2012Hong et al., , 2013Abdallah, 2010). As a group of nuclear hormone receptors, the activation of PPARs is initiated via binding of a ligand (Nuclear Receptors Nomenclature, 1999;McKenna and O'Malley, 2002). ...
... (C) α-asaronol possibly activate PPAR γ through direct binding, leading to further expression of PPAR γ, which could relieve PTZ-induced seizures in zebrafish. (Sun et al., 2008;Hong et al., 2012Hong et al., , 2013. In addition, previous studied have shown that PPAR γ, which is expressed in cells of the central nervous system, is involved in the regulation of energy balance (Ryan et al., 2011). ...
In mammals, peroxisome proliferators activated receptors (PPARs), the nuclear hormone receptors, have been reported to be involved in seizure control. Selective agonists and antagonists of PPARs raise seizure thresholds and suppress seizures, respectively. In this study, we evaluated the anticonvulsant effects of α-asaronol, a metabolic product of α-asarone, on pentylenetetrazole (PTZ)-induced seizures in zebrafish and investigated the underlying mechanisms. As a result, α-asaronol ameliorated seizures with increase of seizure latency, as well as decrease of seizure-like behavior, c-fos expression, and abnormal neuronal discharge in a concentration dependent manner. By comparing gene expression profiles of zebrafish undergoing seizures and α-asaronol pretreated zebrafish, we found that α-asaronol attenuate seizures through increase of PPAR γ expression, while PPAR γ antagonist GW9662 inhibit the anti-seizures actions of α-asaronol. Moreover, molecular docking simulation implied the physical interaction between α-asaronol and PPAR γ. The overall results indicated that the anticonvulsant effects of α-asaronol are regulated through PPAR γ-mediated pathway, which shed light on development of α-asaronol as a potential antiepileptic drug. In addition, it is for first time to report that PPAR γ is associated with seizures in zebrafish, supporting previous evidence that zebrafish is a suitable alternative for studying seizures.
... Нейропротекторное действие агонистов PPARγ было показано в модели острых судорог, индуцированных пентилентетразолом [147] и в хронической литий-пилокарпиновой модели височной эпилепсии [153][154][155]. В частности, было выявлено, что использование агониста PPARγ росиглитазона в литий-пилокарпиновой модели эпилепсии предотвращает когнитивный дефицит, активацию астроцитов и развитие спонтанных рецидивирующих судорог [153,154], снижает воспалительную реакцию микроглии [155,156], уменьшает оксидативный стресс [155], ингибирует воспалительные реакции в гиппокампе [155] и подавляет NMDA-опосредованные эпилептиформные разряды [157]. ...
... Нейропротекторное действие агонистов PPARγ было показано в модели острых судорог, индуцированных пентилентетразолом [147] и в хронической литий-пилокарпиновой модели височной эпилепсии [153][154][155]. В частности, было выявлено, что использование агониста PPARγ росиглитазона в литий-пилокарпиновой модели эпилепсии предотвращает когнитивный дефицит, активацию астроцитов и развитие спонтанных рецидивирующих судорог [153,154], снижает воспалительную реакцию микроглии [155,156], уменьшает оксидативный стресс [155], ингибирует воспалительные реакции в гиппокампе [155] и подавляет NMDA-опосредованные эпилептиформные разряды [157]. Также показано, что фенофибрат и безафибрат, агонисты PPARα, проявляют противосудорожные свойства в пентилентеразоловой и литий-пилокарпиновой моделях [158,159]. ...
A large proportion of patients with epilepsy suffer from pharmacoresistant forms of the disease, and this makesthe search for new treatments urgent. The possible role of gut-brain interactions in the pathogenesis of epilepsyis widely discussed. Recent experimental and clinical studies show a correlation between the balance of gut mi-crobiota and the severity of epileptogenesis. Various methods to modify the microbiota composition demonstrateits significant impact on the clinical course of epilepsy. Nevertheless, the question remains open as to the basicreceptor element of the gut-brain axis, a sort of an interface between the gut microorganisms and the body’s reg-ulatory systems.This review aims to analyze the pathways and levels of gut microbiota involvement in the pathogenesis and sano-genesis of epilepsy. Among these pathways, the neural, metabolic, immune, and endocrine pathways are distin-guished. Analysis of the data obtained to date shows a significant role for peroxisome proliferator-activated re-ceptors (PPARs) in these processes. The expression of these receptors in the main structures of the gut-brain axis,the presence of their ligands among the metabolites of microbiota, as well as anticonvulsant and/or neuroprotec-tive activities described for some PPAR agonists, allow a hypothesis to be proposed on the role of PPARs as theabove-mentioned signaling interface in the gut-brain axis. Separate attention is paid to the therapeutic potentialof PPAR agonists in epilepsy treatment.
... Especially, among the brain regions, the hippocampus is known as one of the most vulnerable brain region in epilepsy. Pyramidal cell loss and glial activation in the hippocampus are distinctive neuropathological changes in various animal models of epilepsy (Matsuoka et al., 1999;Sun et al., 2008;Yu et al., 2008;Hong et al., 2012;Hong et al., 2013). In addition, it has been widely accepted that neuroinflammatory reaction occurs in epilepsy. ...
... Astrocytes have been known to be associated with the increased neuronal excitability in epilepsy (Ricci et al., 2009). In addition, It was suggested that activation of astrocytes and reactive astrogliosis, which are induced by seizure, contributes to epileptogenesis, spread of seizure activity and cognitive impairment, and that rosiglitazone could attenuated the astrocyte activation after status epilepticus (Hong et al., 2012). Microglia are known as the principal immune cells and resident macrophages of the brain. ...
Pioglitazone (PGZ), a synthetic peroxisome proliferator-activated receptor γ agonist, is known to regulate inflammatory process and to have neuroprotective effects against neurological disorders. In the present study, we examined the effects of 30 mg/kg PGZ on excitotoxic neuronal damage and glial activation in the mouse hippocampus following intracerebroventricular injection of kainic acid (KA). PGZ treatment significantly reduced seizure-like behavior. PGZ had the neuroprotective effect against KA-induced neuronal damage and attenuated the activations of astrocytes and microglia in the hippocampal CA3 region. In addition, MPO and NFκB immunoreactivities in the glial cells were also decreased in the PGZ-treated group. These results indicate that PGZ had anticonvulsant and neuroprotective effects against KA-induced excitotocix injury, and that neuroprotective effect of PGZ might be due to the attenuation of KA-induced activation in astrocytes and microglia as well as KA-induced increases in MPO and NFκB.
... The ability of astrocytes to promote inflammation and their responsiveness to PPAR agonists positions these cells to play a critical role in the progression and treatment of neurological disease. PPAR agonists attenuate pathological astrocyte activation and improve disease progression (Diab et al., 2002(Diab et al., , 2004Storer et al., 2005aStorer et al., , 2005bMandrekar-Colucci and Landreth, 2010;Hong et al., 2012). Given that astrocytes play an important role in most CNS disorders, targeting them with PPAR agonists may prove effective in multiple settings. ...
... Modulating inflammation is one of the best-studied roles of PPAR activation in astrocytes and has been examined in multiple experimental models (Diab et al., 2002;Giri et al., 2004;Storer et al., 2005aStorer et al., , 2005bLee et al., 2008;Tjalkens et al., 2008;Pineau et al., 2010;Cowley et al., 2012;Hong et al., 2012). In the spinal cord, the PPARγ agonist pioglitazone reduces astrocyte activation in a receptor-dependent manner (Jia et al., 2013). ...
Traumatic injury or disease of the spinal cord and brain elicits multiple cellular and biochemical reactions that together cause or are associated with neuropathology. Specifically, injury or disease elicits acute infiltration and activation of immune cells, death of neurons and glia, mitochondrial dysfunction, and the secretion of substrates that inhibit axon regeneration. In some diseases, inflammation is chronic or non-resolving. Ligands that target peroxisome proliferator-activated receptors (PPARs), a group of ligand activated transcription factors, are promising therapeutics for neurologic disease and CNS injury because their activation affects many, if not all, of these interrelated pathologic mechanisms. PPAR activation can simultaneously weaken or reprogram the immune response, stimulate metabolic and mitochondrial function, promote axon growth and induce progenitor cells to differentiate into myelinating oligodendrocytes. PPAR activation has beneficial effects in many pre-clinical models of neurodegenerative diseases and CNS injury; however, the mechanisms through which PPARs exert these effects have yet to be fully elucidated. In this review we discuss current literature supporting the role of PPAR activation as a therapeutic target for treating traumatic injury and degenerative diseases of the CNS.
... PPARγ protects against seizures by limiting oxidative stress, inflammatory responses, BDNF/TrkB, and energy metabolism [315][316][317]. UCPs are members of a mitochondrial anion transporter superfamily that uncouples ATP synthesis from oxidative phosphorylation by causing proton leakage across the inner membrane of the mitochondria, resulting in energy loss and heat production [318]. ...
The cytokine-activated Janus kinase (JAK)–signal transducer and activator of transcription (STAT) cascade is a pleiotropic pathway that involves receptor subunit multimerization. The mammalian target of rapamycin (mTOR) is a ubiquitously expressed serine-threonine kinase that perceives and integrates a variety of intracellular and environmental stimuli to regulate essential activities such as cell development and metabolism. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a prototypical metabolic nuclear receptor involved in neural differentiation and axon polarity. The JAK-STAT, mTOR, and PPARγ signaling pathways serve as a highly conserved signaling hub that coordinates neuronal activity and brain development. Additionally, overactivation of JAK/STAT, mTOR, and inhibition of PPARγ signaling have been linked to various neurocomplications, including neuroinflammation, apoptosis, and oxidative stress. Emerging research suggests that even minor disruptions in these cellular and molecular processes can have significant consequences manifested as neurological and neuropsychiatric diseases. Of interest, target modulators have been proven to alleviate neuronal complications associated with acute and chronic neurological deficits. This research-based review explores the therapeutic role of JAK-STAT, mTOR, and PPARγ signaling modulators in preventing neuronal dysfunctions in preclinical and clinical investigations.
... Stimulated astrocytes elevate calcium influx and therefore release glutamate to enhance synaptic excitatory transmission after SE (Ding et al., 2007). Hong et al. reported that rosiglitazone significantly reduced the cognitive impairment caused by SE and potently blocked the activation of astrocyte while balancing GSH homeostasis in the hippocampus, following a lithium pilocarpine-induced SE (Hong et al., 2012). Importantly, one week after SE, rosiglitazone efficiently diminished neuronal loss in the hippocampus and lowered the formation of reactive oxygen species (ROS) and lipid peroxidation considerably. ...
The peroxisome proliferator-activated receptor gamma (PPARγ), which belongs to the family of nuclear receptors, has been mainly studied as an important factor in metabolic disorders. However, in recent years the potential role of PPARγ in different neurological diseases has been increasingly investigated. Especially, in the search of therapeutic targets for patients with epilepsy the question of the involvement of PPARγ in seizure control has been raised. Epilepsy is a chronic neurological disorder causing a major impact on the psychological, social, and economic conditions of patients and their families, besides the problems of the disease itself. Considering that the world prevalence of epilepsy ranges between 0.5%-1.0%, this condition is the fourth for importance among the other neurological disorders, following migraine, stroke, and dementia. Among others, temporal lobe epilepsy (TLE) is the most common form of epilepsy in adult patients. About 65% of individuals who receive antiseizure medications (ASMs) experience seizure independence. For those in whom seizures still recur, investigating PPARγ could lead to the development of novel ASMs. This review focuses on the most important findings from recent investigations about the potential intracellular PPARγ-dependent processes behind different compounds that exhibited anti-seizure effects. Additionally, recent clinical investigations are discussed along with the promising results found for PPARγ agonists, and the ketogenic diet (KD) in various rodent models of epilepsy.
... bacterial endotoxin administration [45]. The PPARγ agonist rosiglitazone prevents neuronal death in the temporal cortex and hippocampus [46], and also reduces astrocyte activation and attenuates cognitive deficits [47] developing after pilocarpine induced status epilepticus. Neuro protective properties of PPARγ agonists are real ized through the regulation of different signaling pathways [48]: through the activation of Wnt pathway associated with cell differentiation and regeneration [49]; activation of Nrf2 pathway responsible for cell protection against oxidative stress [50], inhibition of NF κB mediated cas cades [51], also associated with oxidative stress and inflammation. ...
... RXR-activated PPARγ regulates oxidative stress response and prevents autophagy in association with increased expression of NRF2 in vivo in status epilepticus (SE) [111]. It was shown that PPARγ/RXR complex upon binding to its agonist rosiglitazone provided significant protection against hippocampal neuronal loss in epileptic rat model, attributed to enhanced expression of antioxidant GSH [111,112] (Fig. 2 (7)). The overexpression of the PPARγ also led to increased expression of anti-apoptotic protein Bcl-2, leading to mitochondrial stabilisation in Content courtesy of Springer Nature, terms of use apply. ...
Retinoid X receptors (RXRs) present a subgroup of the nuclear receptor superfamily with particularly high evolutionary conservation of ligand binding domain. The receptor exists in α, β, and γ isotypes that form homo-/heterodimeric complexes with other permissive and non-permissive receptors. While research has identified the biochemical roles of several nuclear receptor family members, the roles of RXRs in various neurological disorders remain relatively under-investigated. RXR acts as ligand-regulated transcription factor, modulating the expression of genes that plays a critical role in mediating several developmental, metabolic, and biochemical processes. Cumulative evidence indicates that abnormal RXR signalling affects neuronal stress and neuroinflammatory networks in several neuropathological conditions. Protective effects of targeting RXRs through pharmacological ligands have been established in various cell and animal models of neuronal injury including Alzheimer disease, Parkinson disease, glaucoma, multiple sclerosis, and stroke. This review summarises the existing knowledge about the roles of RXR, its interacting partners, and ligands in CNS disorders. Future research will determine the importance of structural and functional heterogeneity amongst various RXR isotypes as well as elucidate functional links between RXR homo- or heterodimers and specific physiological conditions to increase drug targeting efficiency in pathological conditions.
... Rosi (Selleckchem, Houston, USA) was dissolved in saline supplemented with dimethylsulfoxide (DMSO) (10% final concentration) and injected intraperitoneally (i.p.) (Churi et al., 2008;Hong et al., 2012). To induce hypothyroidism, propylthiouracil (PTU) was added to the drinking water (0.05% PTU). ...
The effects of the well‑known peroxisome proliferator‑activated receptor gamma (PPAR-γ) agonist rosiglitazone (Rosi) on brain‑derived neurotrophic factor (BDNF), nitric oxide (NO), and learning and memory were investigated in hypothyroid rats. Hypothyroidism was induced in immature Wistar rats by administration of propylthiouracil in drinking water. Rats were divided into four groups: control, hypothyroid, and hypothyroid treated with Rosi at doses of 2 mg/kg or 4 mg/kg. Memory was then assessed by the Morris water maze (MWM) and passive avoidance (PA) tests. Following anesthetization, brain samples were collected for biochemical measurements. Hypothyroidism increased the escape latency and traveled path in the learning trials of the MWM and decreased the time spent and the distance traveled in the target quadrant on the probe day. Hypothyroidism also impaired the avoidance behavior of rats in the PA test. Rosi improved the performance of rats in both MWM and PA tasks. Hypothyroidism also decreased hippocampal BDNF levels, increased NO metabolites, and induced oxidative damage in the brain. Treatment of hypothyroid rats with both doses of Rosi increased BDNF levels and decreased NO metabolites and malondialdehyde concentrations. In addition, thiol content and superoxide dismutase and catalase activities were increased in the brain regions of hypothyroid rats receiving Rosi. The administration of 4 mg/kg Rosi also significantly increased serum thyroxin levels. The results of the present study showed that BDNF and NO play a role in the protective effects of Rosi against learning and memory impairment in hypothyroid rats.
... 28 Sun et al 35 found that PPAR γ agonist prevents neuronal loss and attenuates development of spontaneous recurrent seizures (SRS) through BDNF/TrkB signaling following pilocarpine-induced status epilepticus, and another report supports the idea that PPARγ agonist might be a potential neuroprotective agent for epilepsy by inhibiting oxidative stress and preventing astrocyte activation. 36,37 However, the role of the PPAR γ agonist rosiglitazone in protection against epilepsy from the point of microglia remains unknown. This study aimed to test whether the PPARγ agonist rosiglitazone can protect against pilocarpine-induced status epilepticus resulting from the overactivation of microglia by reversing M1/M2 phenotypic changes. ...
Aims:
Activated microglia have been found in the forebrains and hippocampi of temporal lobe epilepsy (TLE) patients and status epileptic (SE) animal models. The peroxisome proliferator-activated receptor γ (PPAR γ) agonist rosiglitazone has been shown to prevent microglial activation. However, its role in pilocarpine-induced status epilepticus remains unknown. We aimed to examine the effect of the PPAR γ agonist rosiglitazone in protecting against pilocarpine-induced status epileptic resulting from over-activation and to explore phenotypic changes in microglia as the underlying mechanism.
Methods:
Male C57BL/6 mice were assigned to three groups: the control group, pilocarpine-induced (SE) group, and rosiglitazone-treated (SE+Rosi) group. Status epileptic mice were administered 300 mg/kg pilocarpine via intraperitoneal injection. SE+Rosi mice were administered rosiglitazone (0.1 mg/kg, i.p.) after SE. Flow cytometry, immunofluorescence staining, and quantitative real-time PCR were used to examine the activation of and phenotypic changes in microglia in the brain and to evaluate neuroinflammation.
Results:
We found that the expression of proinflammatory CD86 and iNOS was increased and that the expression of antiinflammatory CD206 and Arg-1 was decreased in the brains of pilocarpine-induced SE mice compared to control mice. The mRNA levels of proinflammatory and antiinflammatory cytokines were not significantly changed in the brain. Rosiglitazone treatment significantly inhibited the proinflammatory polarization of microglia and rescued neuron loss in the temporal lobe and hippocampi of the brain after SE.
Conclusion:
Rosiglitazone reverses microglial polarization in the brains of SE mice and also affords neuroprotection against pilocarpine-induced status epilepticus without inducing significant changes in brain inflammation.
... Other studies also have confirmed that PPARc agonists supplementation was capable of reducing cognitive deficits in an animal model of diabetes [70]. The beneficial effects on the cognitive function have repeatedly been attributed to the antioxidant effects of PPARc agonists [71]. Considering this fact, many investigators have used pioglitazone to prevent or subdue the occurrence of oxidative stress in tissues [67][68][69]. ...
Aim: The effect of PPAR-γ agonist pioglitazone on the brain tissues oxidative damage and learning and memory impairment in the juvenile hypothyroid rats was evaluated.
Main methods: Rats were classified as: (1) Control; (2) Propylthiouracil (PTU); (3) PTU-Pio 10 and (4) PTU-Pio 20. PTU was given in drinking water (0.05%) during six weeks. Pioglitazone (10 or 20 mg/kg) was daily injected intraperitoneally. Passive avoidance (PA) and Morris water maze (MMW) were conducted. Then the animals were sacrificed and the brain tissues were removed for biochemical measurements.
Key funding: The results indicated that in the MWM escape latency as well as traveled path increased in the PTU group as compared to the control group. Also, the time spent in the target quadrant in the probe test of MWM and step-through latency in the PA test were decreased in the PTU group as compared to the control group. Pioglitazone reversed all the negative behavioral effects of hypothyroidism. Administration of PTU attenuated thiol and superoxide dismutase (SOD), and catalase (CAT) activities in the brain tissues, whereas increased malondialdehyde (MDA) and nitric oxide (NO) metabolites. PPARγ agonist improved thiol, SOD and CAT, while diminished MDA concentration.
Significance: Our finding in the present study indicated that PPARγ agonist pioglitazone prevented the brain tissues from oxidative damage and learning and memory impairments in juvenile hypothyroid rats.
... The ability of astrocytes to promote inflammation and their responsiveness to PPAR agonists position these cells to play a critical role in the progression of neurological diseases and make them a suitable cell model for nervous abnormalities and a promising target for their treatment and prevention. It has been already demonstrated that PPAR agonists attenuate pathological astrocyte activation and modulate disease progression (Hong et al., 2012). Thus, four different newly synthesized PPAR-γ agonists were here tested on the astrocytes cell line CTX-TNA2, in comparison with the reference compound, rosiglitazone. ...
Aims:
The worldwide increase in aging population is prevalently associated with the increase of neurodegenerative diseases. Peroxisome Proliferator-Activated Receptors (PPARs) are ligand-modulated transcriptional factors which belong to the nuclear hormone receptor superfamily which regulates peroxisome proliferation. The PPAR-γ is the most extensively studied among the three isoforms and the neuroprotective effects of PPAR-γ agonists have been recently demonstrated in a variety of preclinical models of neurological disorders. The aim of the study is to biologically evaluate the neuroprotective effects of new PPAR-γ selective agonists in an in vitro model.
Main methods:
CTX-TNA2 rat astrocytes were treated with G3335, a PPAR-γ antagonist, to simulate the conditions of a neurological disorder. Newly synthetized PPAR-γ selective agonists were added to the cell culture. Cytotoxicity was assessed by MTT assay, catalase activity was investigated by a colorimetric assay, Reactive Oxygen Species (ROS) production and apoptosis occurrence were measured by flow cytometry. Western blotting were performed to measure the levels of protein involved in the apoptotic pathway.
Key findings:
Four PPAR-γ agonists were selected. Among them, the GL516, a fibrate derivative, showed low cytotoxicity and proved effective in restoring the catalase activity, reducing ROS production and decreasing the apoptosis occurrence triggered by the G3335 administration. The effects of this molecule appear to be comparable to the reference compound rosiglitazone, a potent and selective PPAR-γ agonist, mainly at prolonged exposure times (96 h).
Significance:
Based on recent evidence, hypofunctionality of the PPAR-γ in glial cells could be present in neurodegenerative diseases and could participate in pathological mechanisms through peroxisomal damage. The fibrate derivative PPAR-γ agonist GL516 emerged as the most promising molecule of the series and could have a role in preventing the pathophysiology of neurodegenerative disorders.
... Majority of studies concluded with a rosiglitazone-mediated reduction in injury-induced GFAP. Namely, in conditions like epilepsy, aging, Alzheimer's Disease (AD), cerebrovascular toxicity and cerebral ischemia, rosiglitazone interfered with the already increased astroglial activation and regulated inflam- matory processes within the brain ( Toledo and Inestrosa 2010;Cowley et al. 2012;Hong et al. 2012;Astakhova et al. 2015). A study indeed showed rosiglitazone-mediated GFAP increase, but in terms of restored astrocyte activity in subarachnoid hemorrhage ( Lin et al. 2014). ...
The anti‐diabetic drug and peroxisome proliferator‐activated receptor‐gamma (PPARγ) agonist, rosiglitazone, alters astrocyte activation; however, its mechanism remains less‐known. We hypothesized participation of epidermal growth factor receptor (EGFR), known to control astrocyte reactivity. We first detected that rosiglitazone promoted glial fibrillary acidic protein (GFAP) expression in primary astrocytes as well as the mouse cerebral cortex, associated with increased EGFR activation. Screening for EGFR ligands revealed a rosiglitazone‐mediated increase of heparin‐binding epidermal growth factor (HB‐EGF) in astrocytes, resulting in HB‐EGF release into culture medium and mouse cerebrospinal fluid too. Treatment with HB‐EGF‐siRNA and EGFR inhibitors showed that the rosiglitazone‐induced HB‐EGF and p‐EFGR were interdependent, which participated in GFAP increase. Interestingly, we observed that rosiglitazone could induce cellular and secreted‐HB‐EGF in neurons also, contributing towards the activated EGFR‐induced GFAP in astrocytes. Probing whether these effects of rosiglitazone were PPARγ‐linked, revealed potential PPARγ‐responsive elements within HB‐EGF gene. Moreover, gel‐shift, site‐directed mutagenesis, chromatin‐immunoprecipitation and luciferase‐reporter assays demonstrated a PPARγ‐dependent HB‐EGF‐transactivation. Subsequently, we examined effects of rosiglitazone in a high‐fat diet (HFD)‐fed diabetes mouse model, and supporting observations in the normal cortical cells, identified a rosiglitazone‐induced GFAP, astrocyte and neuronal HB‐EGF and secreted‐HB‐EGF in the cerebral cortex of diabetic mice. Moreover, assessing relevance of increased HB‐EGF and GFAP revealed an anti‐apoptotic role of rosiglitazone in the cerebral cortex, supported by a GFAP‐siRNA as well as HB‐EGF‐siRNA‐mediated increase in cleaved‐caspase‐3 and 9 levels in the rosiglitazone‐treated astrocyte‐neuron co‐culture. Overall, our study indicates that rosiglitazone may protect the brain, via a PPARγ‐dependent HB‐EGF/EGFR signalling and increased GFAP.
This article is protected by copyright. All rights reserved.
... Epileptogenesis might also be fostered by a relative deficiency of molecules that limit neuronal activation. These molecules include neuroactive peptides 89 , neurosteroids from astrocytes that promote GABA A receptor inhibition 90 , astrocytic sphingosine 1phosphate receptors (which have anti-inflammatory activity) 91 , erythropoietin and peroxisome proliferator-activated receptor-γ activation 92 . Deficits in these molecules are speculated to lead to hyperexcitability. ...
Epilepsy affects all age groups and is one of the most common and most disabling neurological disorders. The accurate diagnosis of seizures is essential as some patients will be misdiagnosed with epilepsy, whereas others will receive an incorrect diagnosis. Indeed, errors in diagnosis are common, and many patients fail to receive the correct treatment, which often has severe consequences. Although many patients have seizure control using a single medication, others require multiple medications, resective surgery, neuromodulation devices or dietary therapies. In addition, one-third of patients will continue to have uncontrolled seizures. Epilepsy can substantially impair quality of life owing to seizures, comorbid mood and psychiatric disorders, cognitive deficits and adverse effects of medications. In addition, seizures can be fatal owing to direct effects on autonomic and arousal functions or owing to indirect effects such as drowning and other accidents. Deciphering the pathophysiology of epilepsy has advanced the understanding of the cellular and molecular events initiated by pathogenetic insults that transform normal circuits into epileptic circuits (epileptogenesis) and the mechanisms that generate seizures (ictogenesis). The discovery of >500 genes associated with epilepsy has led to new animal models, more precise diagnoses and, in some cases, targeted therapies.
... In addition to the positive cognitive effects of losartan in models of AD, losartan shows promising results in cognitive impairment associated with other neurological diseases, such as epilepsy. The cognitive impairment associated with epilepsy is exacerbated by high frequency seizures [100,101]. Losartan improved status epilepticus-induced cognitive impairment in lithium pilocarpine-induced status epilepticus in rats [102]. The mechanism includes suppression of microglial-mediated inflammation and attenuation of hippocampal neuronal loss [74]. ...
For many years, modulators of the renin angiotensin system (RAS) have been trusted by clinicians for the control of essential hypertension. It was recently demonstrated that these modulators have other pleiotropic properties independent of their hypotensive effects, such as enhancement of cognition. Within the brain, different components of the RAS have been extensively studied in the context of neuroprotection and cognition. Interestingly, a crosstalk between the RAS and other systems such as cholinergic, dopaminergic and adrenergic systems have been demonstrated. In this review, the preclinical and clinical evidence for the impact of RAS modulators on cognitive impairment of multiple etiologies will be discussed. In addition, the expression and function of different receptor subtypes within the RAS such as: Angiotensin II type I receptor (AT1R), Angiotensin II type II receptor (AT2R), Angiotensin IV receptor (AT4R), Mas receptor (MasR), and Mas-related-G protein-coupled receptor (MrgD), on different cell types within the brain will be presented. We aim to direct the attention of the scientific community to the plethora of evidence on the importance of the RAS on cognition and to the different disease conditions in which these agents can be beneficial.
... On the other hand, the hippocampal oxidative stress observed in this model [75,76], characterized here by the decrease in GSH, was completely reversed by dexamethasone administration. Rosiglitazone, an agonist of the peroxisome proliferatoractivated receptor gamma that has anti-inflammatory activity, also prevented the GSH imbalance in the hippocampus after pilocarpine-induced SE [77]. ...
Background:
Temporal lobe epilepsy (TLE) is the most common form of partial epilepsy and is accompanied, in one third of cases, by resistance to antiepileptic drugs (AED). Most AED target neuronal activity modulated by ionic channels, and the steroid sensitivity of these channels has supported the use of corticosteroids as adjunctives to AED. Assuming the importance of astrocytes in neuronal activity, we investigated inflammatory and astroglial markers in the hippocampus, a key structure affected in TLE and in the Li-pilocarpine model of epilepsy.
Methods:
Initially, hippocampal slices were obtained from sham rats and rats subjected to the Li-pilocarpine model of epilepsy, at 1, 14, and 56 days after status epilepticus (SE), which correspond to the acute, silent, and chronic phases. Dexamethasone was added to the incubation medium to evaluate the secretion of S100B, an astrocyte-derived protein widely used as a marker of brain injury. In the second set of experiments, we evaluated the in vivo effect of dexamethasone, administrated at 2 days after SE, on hippocampal inflammatory (COX-1/2, PGE2, and cytokines) and astroglial parameters: GFAP, S100B, glutamine synthetase (GS) and water (AQP-4), and K+(Kir 4.1) channels.
Results:
Basal S100B secretion and S100B secretion in high-K+medium did not differ at 1, 14, and 56 days for the hippocampal slices from epileptic rats, in contrast to sham animal slices, where high-K+medium decreased S100B secretion. Dexamethasone addition to the incubation medium per se induced a decrease in S100B secretion in sham and epileptic rats (1 and 56 days after SE induction). Following in vivo dexamethasone administration, inflammatory improvements were observed, astrogliosis was prevented (based on GFAP and S100B content), and astroglial dysfunction was partially abrogated (based on Kir 4.1 protein and GSH content). The GS decrease was not prevented by dexamethasone, and AQP-4 was not altered in this epileptic model.
Conclusions:
Changes in astroglial parameters emphasize the importance of these cells for understanding alterations and mechanisms of epileptic disorders in this model. In vivo dexamethasone administration prevented most of the parameters analyzed, reinforcing the importance of anti-inflammatory steroid therapy in the Li-pilocarpine model and possibly in other epileptic conditions in which neuroinflammation is present.
... Meanwhile, the GFAP expression was significantly increased in the pilocarpine-treated group compared with the control group. These findings suggest that SE induced reactive astrogliosis, which was consistent with the previous studies (Damaye et al., 2011;Hong et al., 2012;Li et al., 2012;Sherafat et al., 2013). However, further studies are required to explore the exact role of astrocyte activation in cognitive impairment associated with SE. ...
Status epilepticus (SE) is a severe clinical manifestation of epilepsy accompanying with cognitive impairment and brain damage. Astrocyte activation occurs following seizures and plays an important role in epilepsy-induced pathological injury, including cognitive impairment. FK506, an immunosuppressant used in clinical settings to prevent allograft rejection, has been shown to exhibit neuroprotective effects in central nervous system diseases. The present study was designed to investigate the effect of FK506 on cognitive impairment in a lithium-pilocarpine-induced SE rat model. It's found that FK506 treatment significantly increased the latency period to seizures and decreased the maximal intensity of seizures. FK506 treatment also markedly increased the surviving cells and reduced the neuron apoptosis after seizures. Meanwhile, FK506 treatment reduced the escape latency and prolonged the swimming distance in the Morris water maze test. In addition, FK506 treatment down-regulated the expression level of GFAP, a specific marker of astrocytes. In conclusion, FK506 could prevent and recover cognitive impairment by inhibiting reactive astrogliosis in pilocarpine-induced status epilepticus rats, suggesting that FK506 may be a promising agent for the treatment of epilepsy.
... function and elimination of synapses, processes that are vital for the neural circuit formation and the processing of information in the brain (45,46). As a result, astrocyte dysfunction is reported to be involved in several brain disorders that are associated with cognitive impairment, therefore, astrocytes are considered to have a number of roles in addition to their role in supporting cells (47,48) Notably, previous studies have demonstrated that isoflurane markedly disrupted the response of astrocytes to neuronal activity by suppression of calcium transients in astrocytes (49), and astrocytes protected against isoflurane-induced neurotoxicity by buffering pro-BDNF (50). Additionally, isoflurane alters the ability of cultured astrocytes to support neuronal growth (51). ...
Neonatal isoflurane exposure in rodents disrupts hippocampal cognitive functions, including learning and memory, and astrocytes may have an important role in this process. However, the molecular mechanisms underlying this disruption are not fully understood. The present study investigated the role of TWIK‑related K+ channel (TREK‑1) in isoflurane‑induced cognitive impairment. Lentiviruses were used to overexpress or knockdown TREK‑1 in astrocytes exposed to increasing concentrations of isoflurane or O2 for 2 h. Subsequently, the mRNA and protein expression of brain‑derived neurotrophic factor (BDNF), caspase‑3, Bcl‑2‑associated X (Bax) and TREK‑1 was measured by reverse transcription‑ quantitative polymerase chain reaction and western blot analysis, respectively. In addition, cell viability was assessed by a 2‑(4‑Iodophenyl)‑3‑(4‑nitrophenyl)‑5‑(2,4‑disulfophenyl)‑ 2H‑tetrazolium monosodium salt assay. The results demonstrated that, prior to manipulating TREK‑1, isoflurane significantly decreased the cell viability and BDNF expression, and increased Bax, caspase‑3 and TREK‑1 expression was observed. However, TREK‑1 overexpression in astrocytes significantly downregulated BDNF expression, and upregulated Bax and caspase‑3 expression. Furthermore, lentiviral‑mediated short hairpin RNA knockdown of TREK‑1 effectively inhibited the isoflurane‑induced changes in BDNF, Bax and caspase‑3 expression. Taken together, the results of the present study indicate that isoflurane‑induced cell damage in astrocytes may be associated with TREK‑1‑mediated inhibition of BDNF and provide a reference for the safe use of isoflurane anesthesia in infants and children.
... Peak density (pA/pF) Activation V 1/2 (mV) k act (mV) Inactivation V 1/2 (mV) k inact (mV) FGF14-GFP −13.43 ± 2.63 (n = 8) −21.5 ± 1 (n = 8) 5 ± 0.25 (n = 8) −57.2 ± 2.3 (n = 8) 4.9 ± 0.57 (n = 8) FGF14 S226A -GFP −6.02 ± 1.02** (n = 11) −26.35 ± 2.8 (n = 11) 5.5 ± 0.77 (n = 11) −60.4 ± 2.3 (n = 11) 5.8 ± 0.61 (n = 11) globally restores neuronal activity by normalizing the expression of critical target molecules, ultimately affecting intracellular signaling (Harrington et al., 2007;Denner et al., 2012;Jahrling et al., 2014;Escribano et al., 2009;Mandrekar-Colucci et al., 2012). In addition, we and others have demonstrated additional beneficial effects of RSG, indicating links between insulin signaling, cognition and AD Bosco et al., 2011;Hong et al., 2012;Mattos et al., 2012;Li et al., 2011). However, we currently lack mechanistic insights into how this network operates and affects key molecular targets. ...
Background:
Cognitive impairment in humans with Alzheimer's disease (AD) and in animal models of Aβ-pathology can be ameliorated by treatments with the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARγ) agonists, such as rosiglitazone (RSG). Previously, we demonstrated that in the Tg2576 animal model of AD, RSG treatment rescued cognitive deficits and reduced aberrant activity of granule neurons in the dentate gyrus (DG), an area critical for memory formation.
Methods:
We used a combination of mass spectrometry, confocal imaging, electrophysiology and split-luciferase assay and in vitro phosphorylation and Ingenuity Pathway Analysis.
Results:
Using an unbiased, quantitative nano-LC-MS/MS screening, we searched for potential molecular targets of the RSG-dependent rescue of DG granule neurons. We found that S226 phosphorylation of fibroblast growth factor 14 (FGF14), an accessory protein of the voltage-gated Na(+) (Nav) channels required for neuronal firing, was reduced in Tg2576 mice upon treatment with RSG. Using confocal microscopy, we confirmed that the Tg2576 condition decreased PanNav channels at the AIS of the DG, and that RSG treatment of Tg2576 mice reversed the reduction in PanNav channels. Analysis from previously published data sets identified correlative changes in action potential kinetics in RSG-treated T2576 compared to untreated and wildtype controls. In vitro phosphorylation and mass spectrometry confirmed that the multifunctional kinase GSK-3β, a downstream target of insulin signaling highly implicated in AD, phosphorylated FGF14 at S226. Assembly of the FGF14:Nav1.6 channel complex and functional regulation of Nav1.6-mediated currents by FGF14 was impaired by a phosphosilent S226A mutation. Bioinformatics pathway analysis of mass spectrometry and biochemistry data revealed a highly interconnected network encompassing PPARγ, FGF14, SCN8A (Nav 1.6), and the kinases GSK-3 β, casein kinase 2β, and ERK1/2.
Conclusions:
These results identify FGF14 as a potential PPARγ-sensitive target controlling Aβ-induced dysfunctions of neuronal activity in the DG underlying memory loss in early AD.
... In the HIR+RIPC group (n=6), animals were subjected to 3 cycles of limb ischemia and reperfusion and then received 60 min of liver ischemia. And in the HIR+RIPC+T0070907 group (n=6), animals were received T0070907 (T0070907, a new PPAR-γ selective inhibitor, 1.5 mg/kg [18] , total 2 mL, intraperitoneally, Selleck Chemicals, Houston, TX, USA) one hour before RIPC and then subjected to RIPC and then received 60 min of liver ischemia before the reperfusion. Other animals not treated with T0070907, received the same volume of vehicle (20% v/v dimethylsulfoxide solution, intraperitoneally). ...
Objective:
To investigate the effect of limb remote ischemic preconditioning (RIPC) on hepatic ischemia/reperfusion (IR) injury and the underlying mechanisms.
Methods:
Rats were subjected to partial hepatic IR (60 min ischemia followed by 24 hours reperfusion) with or without RIPC, which was achieved by 3 cycles of 10 min-occlusion and 10 min-
reperfusion at the bilateral femoral arteries interval 30 min before ischemia. Some rats were treated with a new PPAR-γ inhibitor, T0070907, before RIPC.
Results:
At the end of reperfusion, liver injury was significantly increased (increases in Suzike's injury score, AST and ALT release), concomitant with elevated oxidative stress (increases in MDA formation, MPO activity, as well as the decrease in SOD activity) and inflammation (increases in TNF-α and IL-6 levels, decrease in IL-10 content). RIPC improved liver function and reduced histologic damage, accompanied by the increased PPAR-γ activation and autophagosome formation as well as the reduced autophagosome clearance. The beneficial effects of RIPC were markedly attenuated by T0070907, an inhibitor of PPAR-γ.
Conclusion:
RIPC exerts the protective effects on liver by activation of autophagy via PPAR-γ.
... PPARγ agonists and the KD regulate similar anti-inflammatory, anti-oxidant and pro-mitochondrial pathways. These include, but are not limited to, upregulation of IκB, inhibition of NFκB, reduction of cytokines such as IL-1β, IL-6 and TNF-α, upregulation of genes encoding mitochondrial enzymes involved in oxidative phosphorylation (e.g., multiple subunits of complexes I, II, IV and V), induction of mitochondrial biogenesis and upregulation of UCP2, catalase and glutathione (Masino and Rho, 2012;Mandrekar-Colucci et al., 2013;Fong et al., 2010;Bernardo et al., 2006;Heneka and Landreth, 2007;Chuang et al., 2012;Hong et al., 2008Hong et al., , 2012Hong et al., , 2013Abdallah, 2010;Adabi Mohazab et al., 2012;Bough et al., 2006;Miglio et al., 2009;Sullivan et al., 2004;Yang and Cheng, 2010;. All of these have been suggested as possible disease modifying targets for epilepsy. ...
The ketogenic diet (KD) is an effective therapy primarily used in pediatric patients whom are refractory to current anti-seizure medications. The mechanism of the KD is not completely understood, but is thought to involve anti-inflammatory and anti-oxidant processes. The nutritionally-regulated transcription factor peroxisome proliferator activated receptor gamma, PPARγ, regulates genes involved in anti-inflammatory and anti-oxidant pathways. Moreover, endogenous ligands of PPARγ include fatty acids suggesting a potential role in the effects of the KD. Here, we tested the hypothesis that PPARγ contributes to the anti-seizure efficacy of the KD. We found that the KD increased nuclear protein content of the PPARγ2 splice variant by 2-4 fold (P<0.05) in brain homogenates from wild-type (WT) and epileptic Kv1.1 knockout (KO) mice, while not affecting PPARγ1. The KD reduced the frequency of seizures in Kv1.1KO mice by ~70% (P<0.01). GW9662, a PPARγ antagonist, prevented KD-mediated changes in PPARγ2 expression and prevented the anti-seizure efficacy of the KD in Kv1.1KO mice. Further supporting the association of PPARγ2 in mediating KD actions, the KD significantly prolonged the latency to flurothyl-induced seizure in WT mice by ~20-35% (P<0.01), but was ineffective in PPARγ2KO mice and neuron-specific PPARγKO mice. Finally, administering the PPARγ agonist pioglitazone increased PPARγ2 expression by 2-fold (P<0.01) and reduced seizures in Kv1.1KO mice by ~80% (P<0.01).Our findings implicate brain PPARγ2 among the mechanisms by which the KD reduces seizures and strongly support the development of PPARγ2 as a therapeutic target for severe, refractory epilepsy.
... PPARγ activation protects the brain in other models of astrocyte activation. For instance, rosiglitazone (a TZD drug) treatment in rat model of epilepsy (status epilepticus induced with lithium pilocarpine) reduces reactive astrocytes and increases GSH in comparison to epileptic rat treated with vehicle [208]. In the same way, PPARγ agonist increases EAAT2 expression in astrocytes, having a big impact in the reduction of glutamate excitotoxicity that is a pro-convulsant cause in epilepsy or cancer (glioblastoma multiforme) [209]. ...
Astrocyte-mediated inflammation is associated with degenerative pathologies such as Alzheimer's and Parkinson's diseases and multiple sclerosis. The acute inflammation and morphological and metabolic changes that astrocytes develop after the insult are known as reactive astroglia or astrogliosis that is an important response to protect and repair the lesion. Astrocytes optimize their metabolism to produce lactate, glutamate, and ketone bodies in order to provide energy to the neurons that are deprived of nutrients upon insult. Firstly, we review the basis of inflammation and morphological changes of the different cell population implicated in reactive gliosis. Next, we discuss the more active metabolic pathways in healthy astrocytes and explain the metabolic response of astrocytes to the insult in different pathologies and which metabolic alterations generate complications in these diseases. We emphasize the role of peroxisome proliferator-activated receptors isotypes in the inflammatory and metabolic adaptation of astrogliosis developed in ischemia or neurodegenerative diseases. Based on results reported in astrocytes and other cells, we resume and hypothesize the effect of peroxisome proliferator-activated receptor (PPAR) activation with ligands on different metabolic pathways in order to supply energy to the neurons. The activation of selective PPAR isotype activity may serve as an input to better understand the role played by these receptors on the metabolic and inflammatory compensation of astrogliosis and might represent an opportunity to develop new therapeutic strategies against traumatic brain injuries and neurodegenerative diseases.
... On the other hand, the effect of rosiglitazone on glia cells is not univocally depending by pathological condition and by CNS area. In rats, 0.1 mg kg 21 rosiglitazone (i.p.) was able to decrease the cognitive impairment after status epilepticus and to inhibit astrocyte activation in the striatum [71]. On the contrary, in a rat Parkinson's model, the neuroprotective effect induced by Scale bar 50 mm. ...
The development of neuropathic syndromes is an important, dose limiting side effect of anticancer agents like platinum derivates, taxanes and vinca alkaloids. The causes of neurotoxicity are still unclear but the impairment of the oxidative equilibrium is strictly related to pain. Two intracellular organelles, mitochondria and peroxisomes cooperate to the maintaining of the redox cellular state. Whereas a relationship between chemotherapy-dependent mitochondrial alteration and neuropathy has been established, the role of peroxisome is poor explored. In order to study the mechanisms of oxaliplatin-induced neurotoxicity, peroxisomal involvement was evaluated in vitro and in vivo. In primary rat astrocyte cell culture, oxaliplatin (10 µM for 48 h or 1 µM for 5 days) increased the number of peroxisomes, nevertheless expression and functionality of catalase, the most important antioxidant defense enzyme in mammalian peroxisomes, were significantly reduced. Five day incubation with the selective Peroxisome Proliferator Activated Receptor-γ (PPAR-γ) antagonist G3335 (30 µM) induced a similar peroxisomal impairment suggesting a relationship between PPARγ signaling and oxaliplatin neurotoxicity. The PPARγ agonist rosiglitazone (10 µM) reduced the harmful effects induced both by G3335 and oxaliplatin. In vivo, in a rat model of oxaliplatin induced neuropathy, a repeated treatment with rosiglitazone (3 and 10 mg kg-1 per os) significantly reduced neuropathic pain evoked by noxious (Paw pressure test) and non-noxious (Cold plate test) stimuli. The behavioral effect paralleled with the prevention of catalase impairment induced by oxaliplatin in dorsal root ganglia. In the spinal cord, catalase protection was showed by the lower rosiglitazone dosage without effect on the astrocyte density increase induced by oxaliplatin. Rosiglitazone did not alter the oxaliplatin-induced mortality of the human colon cancer cell line HT-29. These results highlight the role of peroxisomes in oxaliplatin-dependent nervous damage and suggest PPARγ stimulation as a candidate to counteract oxaliplatin neurotoxicity.
... Fenofibrate displayed anticonvulsant effects in the lithium-pilocarpine SE model and against pentylentetrazol-induced seizures [124]. Another PPARγ agonist, rosiglitazone, consistently displayed significant neuroprotective effects and attenuated inflammatory responses after induction of SE [125][126][127]. Importantly, intracerebroventricular rosiglitazone administered prior to the administration of lithium-pilocarpine also decreased the number of spontaneous recurrent seizures in the chronic phase beginning 2 weeks after SE, although it did not affect the severity of SE in the acute phase; some of its protective effects were indirectly mediated by TrkB signaling [128]. ...
A major goal of contemporary epilepsy research is the identification of therapies to prevent the development of recurrent seizures in individuals at risk, including those with brain injuries, infections, or neoplasms; status epilepticus; cortical dysplasias; or genetic epilepsy susceptibility. In this review we consider the evidence largely from preclinical models for the antiepileptogenic activity of a diverse range of potential therapies, including some marketed antiseizure drugs, as well as agents that act by immune and inflammatory mechanisms; reduction of oxidative stress; activation of the mammalian target of rapamycin or peroxisome proliferator-activated receptors γ pathways; effects on factors related to thrombolysis, hematopoesis, and angiogenesis; inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reducatase; brain-derived neurotrophic factor signaling; and blockade of α2 adrenergic and cannabinoid receptors. Antiepileptogenesis refers to a therapy of which the beneficial action is to reduce seizure frequency or severity outlasting the treatment period. To date, clinical trials have failed to demonstrate that antiseizure drugs have such disease-modifying activity. However, studies in animal models with levetiracetam and ethosuximide are encouraging, and clinical trials with these agents are warranted. Other promising strategies are inhibition of interleukin 1β signaling by drugs such as VX-765; modulation of sphingosine 1-phosphate signaling by drugs such as fingolimod; activation of the mammalian target of rapamycin by drugs such as rapamycin; the hormone erythropoietin; and, paradoxically, drugs such as the α2 adrenergic receptor antagonist atipamezole and the CB1 cannabinoid antagonist SR141716A (rimonabant) with proexcitatory activity. These approaches could lead to a new paradigm in epilepsy drug therapy where treatment for a limited period prevents the occurrence of spontaneous seizures, thus avoiding lifelong commitment to symptomatic treatment.
Glial cells have been implicated in temporal lobe epilepsy in humans and in its models. Astrocytes are lost in several brain regions after acute seizures induced by pilocarpine and may suffer hyperplasia at subsequent time points. This study investigated the effect of N-methyl-(2S,4R)-trans-4-hydroxy-L-proline (NMP) on astrocytes exposed to cytotoxic concentrations of pilocarpine. Astrocytes were incubated with pilocarpine (half maximal inhibitory concentration (IC50)=31.86 mM) for 24 h. Afterwards, they were treated with NMP at concentrations ranging from 3.12 to 100 μg/mL for 24 h. Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cytoplasmic reactive oxygen species (ROS) and mitochondrial transmembrane potential (ΔΨm) were analyzed by flow cytometry using 2',7'-dichlorofluorescein diacetate (DCFH-DA) and rhodamine-123 (Rho123), respectively. Expression of glial fibrillary acidic protein (GFAP) and voltage-dependent anion channel-1 (VDAC-1) were measured by western blot. Pilocarpine significantly decreased cell viability and mitochondrial potential and increased ROS concentration significantly by 6.7 times compared to the control. NMP concentrations ≥25 µg/mL protected astrocytes against pilocarpine-induced injury in a concentration-dependent manner. Concomitantly, NMP reduced cytoplasmic ROS accumulation to 27.3, 24.8, and 12.3% in the groups treated with 25, 50, and 100 µg/mL NMP, respectively. NMP also protected mitochondria from pilocarpine-induced depolarization. These effects were associated with improvement of pilocarpine-induced GFAP and VDAC-1 overexpression, which are important biomarkers of astrocyte dysfunction. In conclusion, the improvement of ROS accumulation, VDAC-1 overexpression, and mitochondrial depolarization are possible mechanisms of the NMP protective action on reactive astrocytes.
Ketogenic diets have been used to treat epilepsy for nearly a century. Alongside enduring clinical success with a ketogenic diet, metabolism’s critical role in health and in diseases in the central nervous system and throughout the body is increasingly appreciated. Furthermore, metabolism-based strategies have been proven equal or even superior to pharmacological treatments in specific cases and for specific diseases. Rather than causing unwanted off-target pharmacological side effects, addressing metabolic dysfunction can improve overall health simultaneously. Enduring interest in the ketogenic diet’s proven efficacy in stopping seizures and emerging efficacy in other disorders has fueled renewed efforts to determine key mechanisms and diverse applications of metabolic therapies. In parallel, multiple strategies are being developed to mobilize similar metabolic benefits without reliance on such a strict diet. Research interest in metabolic therapies has spread into laboratories and clinics of every discipline, and could yield entirely new classes of drugs and treatment regimens. This work is the first comprehensive scientific resource on the ketogenic diet, covering the latest research into the mechanisms, established and emerging applications, metabolic alternatives, and implications for health and disease. Experts in clinical and basic research share their research into mechanisms spanning from ion channels to epigenetics, their insights based on decades of experience with the ketogenic diet in epilepsy, and their evidence for emerging applications ranging from autism to Alzheimer’s disease to brain cancer.
The most severe form of epilepsy, status epilepticus (SE), causes brain damage and results in the development of recurring seizures. Currently, the management of SE remains a clinical challenge because patients do not respond adequately to conventional treatments. Evidence suggests that neural cell death worsens the occurrence and progression of SE. The main forms of cell death are apoptosis, necroptosis, pyroptosis, and ferroptosis. Herein, these mechanisms of neuronal death in relation to SE and the alleviation of SE by potential modulators that target neuronal death have been reviewed. An understanding of these pathways and their possible roles in SE may assist in the development of SE therapies and in the discovery of new agents.
The ketogenic diet (KD) is an effective therapy for many patients with refractory epilepsy. It engages a wide array of antioxidant and anti-inflammatory processes and improves mitochondrial functions that are thought to underlie its neuroprotective, antiseizure, and disease-modifying effects. Potential roles of ketone bodies in these mechanisms are discussed elsewhere in this volume. Here, we focus on the role of KD fatty acids as potential ligands for the nutritionally regulated nuclear transcription factor peroxisome proliferator-activated receptor γ (PPARγ). PPARγ regulates many of the pathways identified in the mechanism of the KD and, in recent years, has become a potential therapeutic target for neurodegenerative diseases. This chapter reviews current knowledge concerning PPARγ in the brain, the evidence that PPARγ has neuroprotective and antiseizure properties, and the evidence suggesting that PPARγ may be involved in the antiseizure mechanisms of the KD.
It is known that hippocampal epileptogenesis is accompanied by hyperexcitability, glutamate-related neuronal dysfunctions and consequently cognitive deficits. However, the neuroprotective role of astrocytic glutamate uptake through the Glutamate Transporter-1 (GLT-1) remains to be unknown in these processes. Therefore, to assess the effect of glutamate uptake, pharmacological upregulation of GLT-1 using ceftriaxone administration (200 mg/kg/day, i.p, 5 days) was utilized in Li-PIL animal models of temporal lobe epilepsy (TLE). Glutamate concentration and glutamine synthetase activity were analyzed using biochemical assays. In addition, GLT-1 gene expression was assessed by RT-qPCR. Finally, cognitive function was studied using Morris water maze (MWM) test and novel object recognition task (NORT). Our results demonstrated that the acute phase of epileptogenesis (first 72 hours after Status Epilepticus) was accompanied by an increase in the hippocampal glutamate and downregulation of GLT-1 mRNA expression compared to controls. Ceftriaxone administration in epileptic animals led to a reduction of glutamate along with elevation of the level of glutamine synthetase activity and GLT-1 expression in the acute phase. In the chronic phase of epileptogenesis (4 weeks after Status Epilepticus), glutamate levels and GLT-1 expression were decreased compared to controls. Ceftriaxone treatment increased the levels of GLT-1 expression. Furthermore, impaired learning and memory ability in the chronic phase of epileptogenesis was rescued by Ceftriaxone administration. This study shows that astrocytic glutamate uptake can profoundly impact the processes of hippocampal epileptogenesis through the reduction of glutamate-induced excitotoxicity and consequently rescuing of cognitive deficits caused by epilepsy.
Status epilepticus (SE) leads to irreversible neuronal damage and consists of a complex pathogenesis that involves oxidative stress and subsequent autophagy. Rosiglitazone has recently been considered as a potential neuroprotective factor in epilepsy because of its antioxidative function. The aim of this study was to assess the effects of rosiglitazone in SE rat models and investigate whether its mechanisms of action involve autophagy via the antioxidant factor, nuclear factor erythroid 2-related factor 2 (Nrf2). The male Sprague-Dawley rats (200–220 g) were used to establish lithium-pilocarpine-induced SE model. We found that rosiglitazone markedly improved neuronal survival at 24-h post-SE as indicated via Hematoxylin-Eosin and Nissl staining. Furthermore, along with a reduction in reactive oxygen species, rosiglitazone pretreatment enhanced the antioxidative activity of superoxide dismutase and the expression level of Nrf2, as detected via chemical assay kits and Western blotting, respectively. In addition, the microtubule-associated protein light chain 3II (LC3II)/LC3I ratio was increased and peaked at 24 h after SE, whereas p62 mRNA levels were sharply elevated at 72 h after SE, both SE-induced increases of which were reversed via rosiglitazone pretreatment. To further test our hypothesis of the key role of Nrf2 in this process, small-interfering RNA for Nrf2 (siNrf2) was then transfected into SE rats to knockdown Nrf2 expression. We found that siNrf2 partially blocked the above effects of rosiglitazone on autophagy-related proteins in SE rats. Taken together, our findings suggest that rosiglitazone attenuates oxidative-stress-induced autophagy via increasing Nrf2 in SE rats and may be used as a promising therapeutic strategy for SE treatment.
Epilepsy is a common neurological disease characterized by recurrent seizures. About 70 million people were affected by epilepsy or epileptic seizures. Epilepsy is a complicated complex or symptomatic syndromes induced by structural, functional, and genetic causes. Meanwhile, several comorbidities are accompanied by epileptic seizures. Cognitive dysfunction is a long-standing complication associated with epileptic seizures, which severely impairs quality of life. Although the definitive pathogenic mechanisms underlying epilepsy-related cognitive dysfunction remain unclear, accumulating evidence indicates that multiple risk factors are probably involved in the development and progression of cognitive dysfunction in patients with epilepsy. These factors include the underlying etiology, recurrent seizures or status epilepticus, structural damage that induced secondary epilepsy, genetic variants, and molecular alterations. In this review, we summarize several theories that may explain the genetic and molecular basis of epilepsy-related cognitive dysfunction.
Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder in children. It is diagnosed by two main behavioral phenotypes i.e. social-communication impairments and repetitive behavior. ASD is complex disorder with unsolved etiology due to multiple genes involvement, epigenetic mechanism and environmental factors. The clinical and preclinical studies have been indicating the association of propionic acid with autism spectrum disorder. Numerous studies suggest the potential therapeutic effects of peroxisome proliferator-activated receptor-gamma (PPAR-γ) in different brain disorders. This research evaluates the utility of selective agonist of PPAR-γ, pioglitazone in postnatal propionic acid induced ASD related symptomatology in male Wistar rats. PPA (250 mg/kg, p.o.) was administered to male offspring for three consecutive days from postnatal 21st day to 23rd day. PPA induced social impairment, repetitive behavior, hyperlocomotion, anxiety and low exploratory activity in rats. Also, postnatal propionic acid-treated rats showed higher levels of oxidative stress (increased in thiobarbituric acid reactive species and decreased in reduced glutathione) as well as inflammation (increased in interleukin-6, tumor necrosis factor-alpha and decreased in interleukin-10) in the cerebellum, brainstem and prefrontal cortex. The rats were treated daily with pioglitazone (10 mg/kg and 20 mg/kg, p.o.) from postnatal 24th day to end of the study. Treatment with pioglitazone, significantly attenuated the postnatal propionic acid-induced social impairment, repetitive behavior, hyperactivity, anxiety and low exploratory activity. Furthermore, pioglitazone also reduced the postnatal propionic acid-induced oxidative stress and neuroinflammation in aforementioned brain regions. Hence, pioglitazone improved the propionic acid-induced neurobehavioral and biochemical impairments in rats.
Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder in children. It is diagnosis by two main behavioral phenotypes i.e. social-communication impairments and repetitive behavior. ASD is complex disorder with unsolved etiology due to multiple genes involvement, epigenetic mechanism and environmental factors. Valproic acid (VPA), a teratogen is known to induce characteristic features related to ASD in rodents. Numerous studies suggest the potential therapeutic effects of peroxisome proliferator-activated receptor-gamma (PPAR-γ) in different brain disorders. This research evaluates the utility of selective agonist of PPAR-γ, pioglitazone in prenatal VPA induced experimental ASD symptomatology in Wistar rats. The prenatal administration of VPA has induced social impairment, repetitive behavior, hyperlocomotion, anxiety and low exploratory activity in rats. Also, prenatal VPA-treated rats have shown higher levels of oxidative stress (increased in thiobarbituric acid reactive species, and decreased in reduced glutathione level) and inflammation (increased in interleukin-6, tumor necrosis factor-alpha and decreased in interleukin-10) in the cerebellum, brainstem and prefrontal cortex. Treatment with pioglitazone significantly attenuated the prenatal VPA-induced social impairment, repetitive behavior, hyperactivity, anxiety and low exploratory activity. Furthermore, pioglitazone also reduced the prenatal VPA-induced oxidative stress and neuroinflammation in aforementioned brain regions. Hence, it may be concluded that pioglitazone may provide neurobehavioral and biochemical benefits in prenatal VPA-induced autistic phenotypes in rats.
The pathogenesis of Alzheimer’s disease involves multiple pathways that, at the macrolevel, include decreased proliferation plus increased loss affecting neurons, astrocytes, and capillaries and, at the subcellular level, involve several elements: amyloid/amyloid precursor protein, presenilins, the unfolded protein response, the ubiquitin/proteasome system, the Wnt/catenin system, the Notch signaling system, mitochondria, mitophagy, calcium, and tau. Data presented show the intimate, anatomical interactions between neurons, astrocytes, and capillaries; the interactions between the several subcellular factors affecting those cells; and the treatments that are currently available and that might correct dysfunctions in the subcellular factors. Available treatments include lithium, valproate, pioglitazone, erythropoietin, and prazosin. Since the subcellular pathogenesis involves multiple interacting elements, combination treatment would be more effective than administration of a single drug directed at only 1 element. The overall purpose of this presentation is to describe the pathogenesis in detail and to explain the proposed treatments.
The neuroprotective and anti-inflammatory effects of the peroxisome proliferator-activated receptor γ (PPARγ) agonist rosiglitazone are of particular interest for disease-modifying and antiepileptogenic approaches. We studied the expression of PPARγ and the impact of rosiglitazone on the consequences of status epilepticus (SE) in a rat post-SE model. Immunohistochemical analysis revealed a selective overexpression of PPARγ in the piriform cortex of rats with spontaneous seizures. Rosiglitazone administration initiated following SE failed to exert relevant effects on the development of spontaneous seizures and neuronal cell loss. Whereas spatial learning in the Morris water maze was delayed in SE animals with vehicle administration, the learning curve of rosiglitazone-treated SE rats showed no significant difference to that of controls. The study provides first evidence arguing against a robust antiepileptogenic effect. However, the findings in the spatial learning paradigm indicate disease-modifying effects.
Copyright © 2015. Published by Elsevier Ireland Ltd.
Calcineurin plays an important role in development of neuronal excitability, modulation of receptor's function, and induction of apoptosis in neurons. It has been established in kindling models that status epilepticus induces brain focal edema and astrocyte activation. However, the role of calcineurin in brain focal edema and astrocyte activation in status epilepticus has not been fully understood. In this study, we employed a model of lithium-pilocarpine-induced status epilepticus and detected calcineurin expression in hippocampus by immunoblotting, brain focal edema by non-invasive Magnetic resonance imaging (MRI-7T) and astrocyte expression by immunohistochemistry. We found that the brain focal edema was seen at 24h after status epilepticus, and astrocyte expression was obviously seen at 7d after status epilepticus. Meanwhile, calcineurin expression was seen at 24 h and retained to 7d after status epilepticus. A FK506,a calcineurin inhibitor, remarkably suppressed the status epilepticus-induced brain focal edema and astrocyte expression. Our data suggested that calcineurin overexpression plays a very important role in brain focal edema and astrocyte expression. Therefore, calcineurin may be a novel candidate for brain focal edema occurring and intracellular trigger of astrogliosis in status epilepticus.
Neuroinflammation plays a role in the pathology of epilepsy and in cognitive impairment. Angiotensin II (AII) and the angiotensin receptor type 1 (AT1) have been shown to regulate seizure susceptibility in different models of epilepsy. Inhibition of AT1 attenuates neuroinflammatory responses in different neurological diseases. In the present study, we showed that the protein expression of AII and AT1 was increased in activated microglia following lithium pilocarpine-induced status epilepticus (SE) in rats. Furthermore, the AT1 receptor antagonist, losartan, significantly inhibited SE-induced cognitive impairment and microglia-mediated inflammation. Losartan also prevented SE induced neuronal loss in the hippocampus and exerted neuroprotection. These data suggest that losartan improves SE-induced cognitive impairment by suppressing microglia mediated inflammatory responses and attenuating hippocampal neuronal loss. Overall, our findings provide a possible therapeutic strategy for the treatment of cognitive impairment in epilepsy.
Copyright © 2015. Published by Elsevier Inc.
Hippocampal neuronal loss plays an important role in epileptogenesis, and it is considered a trigger of repeated spontaneous recurrent seizures (SRS). The BDNF/TrkB signaling pathway regulates neuronal plasticity in the CNS, and promotes epileptogenesis. Previous studies have shown that Peroxisome proliferator-activated receptor gamma (PPARγ) agonists exert neuroprotective effects by inhibiting oxidative stress and inflammation in epilepsy. In the present study, the PPARγ agonist rosiglitazone inhibited increases in BDNF and TrkB after status epilepticus (SE), and also prevented hippocampal neuronal loss. More importantly, our study showed that rosiglitazone suppressed SRS. However, the effects of rosiglitazone were significantly reversed by cotreatment with K252a, an antagonist of TrkB. Additionally, rosiglitazone did not affect the development and severity of SE. Thus, our data provide evidence that rosiglitazone exerts neuroprotective and antiepileptic effects involve BDNF/TrkB signaling. Our study also offers new perspectives for the treatment of epilepsy.
Accumulating evidence has shown that neuroinflammation plays a key role in epileptogenesis. However, the efficacy of anti-inflammatory agents for preventing epilepsy remains controversial. Fingolimod (FTY720), a sphingosine-1-phosphate (S1P) analog, has potent anti-inflammatory effects in multiple sclerosis (MS) patients and animal models. Here, we tested whether FTY720 could exert antiepileptogenic effects in an adult rat model of lithium-pilocarpine induced epilepsy. 24h after onset of status epilepticus (SE), the epileptic rats received saline or 1mg/kg FTY720 i.p. once daily for 14 consecutive days. Thereafter, spontaneous convulsions (SCs), mossy fiber sprouting (MFS), neuronal loss, activation of microglia and astrocytes, expressions of interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNFα) were evaluated in the SE rats. We found that FTY720 treatment reduced neuronal loss and decreased activation of microglia and astrocytes in hippocampus at four days post-SE. Simultaneously, abnormal expressions of IL-1β and TNFα in hippocampus were restrained by FTY720 treatment. In addition, neuroprotective effects of FTY720 were demonstrated by increasing neuronal nuclei (NeuN)-positive cells and decreasing Fluoro-Jade B (FJB)-positive cells in the hippocampus. During 21-34days post-SE, the incidence, duration, frequency and severity of SCs significantly decreased in FTY720 treated rats compared with saline treated rats. Aberrant MFS was also attenuated by FTY720 administration. These results suggest that FTY720 exerts anti-inflammatory and antiepileptogenic effects in lithium-pilocarpine model of epilepsy and it may provide a new therapeutic approach for prevention of epileptogenesis.
Oxygen free radicals and lipid peroxidation may play significant roles in the progress of injury induced by chronic cerebral hypoperfusion of the central nervous system. Rosiglitazone, a well known activator of PPARγ, has neuroprotective properties in various animal models of acute central nervous system damage. In the present study, we evaluate the possible impact of rosiglitazone on chronic cerebral hypoperfused-rats in regard to the levels of oxidative stress, reduced glutathione, and hippocampal neuronal damage. Chronic cerebral hypoperfusion was generated by permanent ligation of both common carotid arteries of Wistar rats for one month. Animals in treatment group were given rosiglitazone orally at doses of 1.5, 3, or 6mg/kg per day of the 1month duration. The treatment significantly lowered the levels of both malondialdehyde and neuronal damage, while elevated the reduced glutathione level markedly. These findings suggest that the beneficial effect of rosiglitazone on hypoperfusion-induced hippocampal neuronal damage might be the result of inhibition of oxidative insult.
Disturbances in cognitive function, particularly memory, are a common complaint of patients with epilepsy. Factors contributing to cognitive dysfunction are the type of epilepsy, type and frequency of seizures, anti-epileptic drugs and the location of underlying brain lesions. Whilst a great deal of attention has been paid to permanent cognitive impairment, the nature and underlying mechanisms of ictal and peri-ictal cognitive changes are poorly understood. In-depth investigation of seizure related cognitive dysfunction is of great clinical relevance, as these changes are potentially reversible and treatable, thus reducing the cumulative effect of frequent seizures Greater knowledge of peri-ictal and ictal cognitive dysfunction would improve seizure prediction, localization of seizure focus and assessment of treatment effectiveness, greatly reducing distress and disability. This paper will review current understanding of peri-ictal and ictal cognitive dysfunction and discuss future directions for research.
Disturbances in cognitive function, particularly memory, are a common complaint of patients with epilepsy. Factors contributing to cognitive dysfunction are the type of epilepsy, type and frequency of seizures, anti-epileptic drugs and the location of underlying brain lesions. Whilst a great deal of attention has been paid to permanent cognitive impairment, the nature and underlying mechanisms of ictal and peri-ictal cognitive changes are poorly understood. In-depth investigation of seizure related cognitive dysfunction is of great clinical relevance, as these changes are potentially reversible and treatable, thus reducing the cumulative effect of frequent seizures. Greater knowledge of peri-ictal and ictal cognitive dysfunction would improve seizure prediction, localization of seizure focus and assessment of treatment effectiveness, greatly reducing distress and disability. This paper will review current understanding of peri-ictal and ictal cognitive dysfunction and discuss future directions for research.
J. Neurochem. (2010) 115 , 1172–1182.
Abstract
Mitochondrial dysfunction and oxidative stress are known to occur following acute seizure activity but their contribution during epileptogenesis is largely unknown. The goal of this study was to determine the extent of mitochondrial oxidative stress, changes to redox status, and mitochondrial DNA (mtDNA) damage during epileptogenesis in the lithium‐pilocarpine model of temporal lobe epilepsy. Mitochondrial oxidative stress, changes in tissue and mitochondrial redox status, and mtDNA damage were assessed in the hippocampus and neocortex of Sprague–Dawley rats at time points (24 h to 3 months) following lithium‐pilocarpine administration. A time‐dependent increase in mitochondrial hydrogen peroxide (H 2 O 2 ) production coincident with increased mtDNA lesion frequency in the hippocampus was observed during epileptogenesis. Acute increases (24–48 h) in H 2 O 2 production and mtDNA lesion frequency were dependent on the severity of convulsive seizure activity during initial status epilepticus. Tissue levels of GSH, GSH/GSSG, coenzyme A (CoASH), and CoASH/CoASSG were persistently impaired at all measured time points throughout epileptogenesis, that is, acutely (24–48 h), during the ‘latent period’ (48 h to 7 days), and chronic epilepsy (21 days to 3 months). Together with our previous work, these results demonstrate the model independence of mitochondrial oxidative stress, genomic instability, and persistent impairment of mitochondrial specific redox status during epileptogenesis. Lasting impairment of mitochondrial and tissue redox status during the latent period, in addition to the acute and chronic phases of epileptogenesis, suggests that redox‐dependent processes may contribute to the progression of epileptogenesis in experimental temporal lobe epilepsy.
Seizures in focal epilepsies are sustained by a highly synchronous neuronal discharge that arises at restricted brain sites and subsequently spreads to large portions of the brain. Despite intense experimental research in this field, the earlier cellular events that initiate and sustain a focal seizure are still not well defined. Their identification is central to understand the pathophysiology of focal epilepsies and to develop new pharmacological therapies for drug-resistant forms of epilepsy. The prominent involvement of astrocytes in ictogenesis was recently proposed. We test here whether a cooperation between astrocytes and neurons is a prerequisite to support ictal (seizure-like) and interictal epileptiform events. Simultaneous patch-clamp recording and Ca2+ imaging techniques were performed in a new in vitro model of focal seizures induced by local applications of N-methyl-D-aspartic acid (NMDA) in rat entorhinal cortex slices. We found that a Ca2+ elevation in astrocytes correlates with both the initial development and the maintenance of a focal, seizure-like discharge. A delayed astrocyte activation during ictal discharges was also observed in other models (including the whole in vitro isolated guinea pig brain) in which the site of generation of seizure activity cannot be precisely monitored. In contrast, interictal discharges were not associated with Ca2+ changes in astrocytes. Selective inhibition or stimulation of astrocyte Ca2+ signalling blocked or enhanced, respectively, ictal discharges, but did not affect interictal discharge generation. Our data reveal that neurons engage astrocytes in a recurrent excitatory loop (possibly involving gliotransmission) that promotes seizure ignition and sustains the ictal discharge. This neuron-astrocyte interaction may represent a novel target to develop effective therapeutic strategies to control seizures.
Glutathione (GSH) is a major antioxidant as well as redox and cell signaling regulator. GSH guards cells against oxidative injury by reducing H(2)O(2) and scavenging reactive oxygen and nitrogen radicals. In addition, GSH-induced redox shift with or without ROS subjects some cellular proteins to varied forms of oxidation, altering the function of signal transduction and transcription factor molecules. Increasing evidence supports the important role of ROS and GSH in modulating multiple signaling pathways. TNF-alpha and Fas signaling, NF-kappaB, JNK and mitochondrial apoptotic pathways are the focus of this review. The redox regulation either can switch on/off or regulate the threshold for some crucial events in these pathways. Notably, mitochondrial GSH depletion induces increased mitochondrial ROS exposure which impairs bioenergetics and promotes mitochondrial permeability transition pore opening which is critical for cell death. Depending on the extent of mitochondrial damage, NF-kappaB inhibition and JNK activation, hepatocytes may either undergo different modes of cell death (apoptosis or necrosis) or be sensitized to cell-death stimuli (i.e. TNF-alpha). These processes have been implicated in the pathogenesis of many liver diseases.
In the last two decades, many experiments have demonstrated that the hippocampus plays a role in the learning and processing of spatial and contextual information. Despite these demonstrations, some recent publications have indicated that the hippocampus is not the only structure involved in spatial learning and that even after hippocampal lesions, rats can perform spatial tasks. However, it is not well established whether animals with hippocampal dysfunction still have some spatial learning capacities or develop non-spatial solutions; these may require lengthier acquisition training. We now report the effects of conventional, dorsal hippocampal ablation on rats' performance on the water maze. We tested rats using a short (4 days) versus a long (16 days) acquisition period. We demonstrated that animals with dorsal hippocampal lesions have some residual capacity for learning the localization of a hidden escape platform in a pool during both a reference memory task and a working memory task. The animals with dorsal hippocampal lesions learned to escape at a fixed location, but only with extended training. It is suggested that these animals used non-spatial strategies to compensate for a spatial memory impairment. The results are discussed with respect to the experimental procedure and the strategy applied by the lesioned rats.
Status epilepticus (SE), an unremitting seizure, is known to cause a variety of traumatic responses including delayed neuronal death and later cognitive decline. Although excitotoxicity has been implicated in this delayed process, the cellular mechanisms are unclear. Because our previous brain slice studies have shown that chemically induced epileptiform activity can lead to elevated astrocytic Ca2+ signaling and because these signals are able to induce the release of the excitotoxic transmitter glutamate from these glia, we asked whether astrocytes are activated during status epilepticus and whether they contribute to delayed neuronal death in vivo. Using two-photon microscopy in vivo, we show that status epilepticus enhances astrocytic Ca2+ signals for 3 d and that the period of elevated glial Ca2+ signaling is correlated with the period of delayed neuronal death. To ask whether astrocytes contribute to delayed neuronal death, we first administered antagonists which inhibit gliotransmission: MPEP [2-methyl-6-(phenylethynyl)pyridine], a metabotropic glutamate receptor 5 antagonist that blocks astrocytic Ca2+ signals in vivo, and ifenprodil, an NMDA receptor antagonist that reduces the actions of glial-derived glutamate. Administration of these antagonists after SE provided significant neuronal protection raising the potential for a glial contribution to neuronal death. To test this glial hypothesis directly, we loaded Ca2+ chelators selectively into astrocytes after status epilepticus. We demonstrate that the selective attenuation of glial Ca2+ signals leads to neuronal protection. These observations support neurotoxic roles for astrocytic gliotransmission in pathological conditions and identify this process as a novel therapeutic target.
Alzheimer's disease is a complex neurodegenerative disorder, with aging, genetic and environmental factors contributing to its development and progression. The complexity of Alzheimer's disease presents substantial challenges for the development of new therapeutic agents. Alzheimer's disease is typified by pathological depositions of beta-amyloid peptides and neurofibrillary tangles within the diseased brain. It has also been demonstrated to be associated with a significant microglia-mediated inflammatory component, dysregulated lipid homeostasis and regional deficits in glucose metabolism within the brain. The peroxisome proliferator-activated receptor-gamma (PPARgamma) is a prototypical ligand-activated nuclear receptor that coordinates lipid, glucose and energy metabolism, and is found in elevated levels in the brains of individuals with Alzheimer's disease. A recently appreciated physiological function of this type of receptor is its ability to modulate inflammatory responses. In animal models of Alzheimer's disease, PPARgamma agonist treatment results in the reduction of amyloid plaque burden, reduced inflammation and reversal of disease-related behavioural impairment. In a recent phase II clinical trial, the use of the PPARgamma agonist rosiglitazone was associated with improved cognition and memory in patients with mild to moderate Alzheimer's disease. Thus, PPARgamma may act to modulate multiple pathophysiological mechanisms that contribute to Alzheimer's disease, and represents an attractive therapeutic target for the treatment of the disease.
Inflammatory responses in the brain are involved in the etiopathogenesis and sequelae of seizures. Ligation of microglial CD40 plays a role in the development of inflammatory responses in the central nervous system (CNS). Our study showed that there was an increased CD40 expression on activated microglia in the brain injury after lithium pilocarpine-induced status epilepticus (SE) in rats. Since peroxisome proliferator-activated receptor gamma (PPARgamma) acts as a regulator of CNS inflammation and a powerful pharmacological target for counteracting CNS diseases, we investigated the role of the PPARgamma agonist, rosiglitazone, in the modulation of CD40 expression and in the pathological processes of inflammation after SE. We found that rosiglitazone inhibited the expression of CD40, tumor necrosis factor (TNF-alpha), and microglial activation in different regions of hippocampus. The results were indicated by immunohistochemistry, Western blot, and ELISA, respectively. Rosiglitazone also prevented neuronal loss in the CA1 area after SE observed by Nissl-staining. These protective effects were significantly reversed by the co-treatment with T0070907, a selective antagonist of the PPARgamma, which clearly demonstrated a PPARgamma-dependent mechanism. Our data provide evidence that rosiglitazone considerably attenuates inflammatory responses after SE by suppressing CD40 expression and microglial activation. Our data also support the idea that rosiglitazone might be a potential neuroprotective agent in epilepsy.
Kindling-induced activation of dopaminergic neurones in the nucleus accumbens in pentylenetetrazol (PTZ)-kindled rats was studied using microdialysis. Dopamine (DA) release after PTZ challenge was measured: (1) two weeks and (2) ten weeks after kindling completion and (3) two weeks after a kindling procedure with diazepam (DZP) treatment. In (1) a significant increase in DA concentration was found after PTZ challenge and this increase was still evident 10 weeks after kindling completion (2). Coadministration of DZP in the course of kindling development inhibited the increase in sensitivity of the accumbens dopaminergic system (3).
The present study has been designed to investigate the potential of peroxisome proliferator-activated receptor-gamma ([PPAR]-γ) agonists, pioglitazone, and rosiglitazone in hyperhomocysteinemia-induced vascular dementia of rats. l-methionine was administered for 8 weeks to induce hyperhomocysteinemia and associated vascular dementia. Pioglitazone and rosiglitazone were administered to l-methionine-treated rats for 4 weeks (starting from 5th to 8th weeks of methionine treatment). Donepezil served as a positive control in this study. On 52nd day onward, the animals were exposed to Morris water maze (MWM) for testing learning and memory abilities. Vascular endothelial function, serum nitrite/nitrate levels, brain thiobarbituric acid reactive species (TBARS), brain reduced glutathione (GSH) levels, and brain acetylcholinesterase (AChE) activity were also measured. l-methionine-treated animals have shown impairment of learning, memory, endothelial function, decrease in serum nitrite/nitrate levels, and brain GSH levels along with increase in brain TBARS levels and AChE activity. Pioglitazone, rosiglitazone, and donepezil significantly improved hyperhomocysteinemia-induced impairment of learning, memory, endothelial dysfunction, and changes in various biochemical parameters. It is concluded that pioglitazone and rosiglitazone may be considered as potential pharmacological agents for the management of hyperhomocysteinemia-induced vascular dementia.
Studies of epilepsy and memory are tied by their common dependence on the hippocampal formation and the adjacent brain structures in the temporal lobe. With the discovery of adult neurogenesis and the consequent revisions of our understanding of how the hippocampus works, the role of neurogenesis in epilepsy needs to be addressed. In this article, we outline two theories describing how neurogenesis contributes to the hippocampus-dependent learning. We speculate that any drastic changes in neurogenesis will negatively impact the hippocampal memory processing.
Adult generated neurons in the dentate gyrus become functionally integrated into the existing hippocampal circuit by forming synapses with mature neurons. It is now well established that seizure activity increases neural proliferation, but only recently has the fate of seizure-induced newborn neurons been examined. An emerging consensus proposes that newborn neurons are highly sensitive to their environment, such that synaptic integration is profoundly altered following insults such as seizures. Whether these changes contribute to or counteract epileptogenesis is a subject of great interest because neurogenesis provides a potential target for therapeutic intervention. In this review, we summarize the current understanding of the functional integration of adult generated granule cells in the normal rodent hippocampus, and describe how this process can be altered during epileptogenesis.
Daily electrical stimulations of the amygdala and hippocampus at intensities sufficient to evoke after-discharges (ADs) resulted in the development of motor seizures, which could not initially be evoked by these stimulations. The triggering of ADs was critical for this development, as well as for the development of permanent changes in the characteristics of the AD. The wave form of the AD "spikes" became more complex. The frequency of these spikes and the duration of AD increased. The amplitude of the AD spikes increased in the structure stimulated as well as in secondary structures to which the AD was "projected". This increase in amplitude of "projected" spikes often correlated with the appearance of motor seizures. Other electrographic developments are discussed including the appearance of spontaneous "inter-ictal" spiking in the amygdala. It was found that the development of motor seizures by stimulation of the amygdala resulted in an increased ability of the contralateral amygdala, and the septal area, but not of the hippocampus, to drive motor seizures when stimulated ("transfer"). Motor seizure development in the hippocampus transferred to the contralateral hippocampus. These developments were shown, by means of control subjects, with lesions in the primary focus to involve changes outside the primary focus. The implications of these developments with respect to seizure development are discussed.
Brain function depends on complex metabolic interactions among only a few different cell types, with astrocytes providing critical support for neurons. Astrocyte functions include buffering the extracellular space, providing substrates to neurons, interchanging glutamate and glutamine for synaptic transmission with neurons, and facilitating access to blood vessels. Whereas neurons possess highly oxidative metabolism and easily succumb to ischemia, astrocytes rely more on glycolytic metabolism and hence are less susceptible tolack of oxygen. Astrocytoma cells seem to retain basic metabolic mechanisms of astrocytes; for example, they show a high glycolytic rate, lactate extrusion, ability to flourish under hypoxia, and opportunistic use of mechanisms to enhance cell division and maintain growth. Differences in metabolism between neurons and astrocytes may also extend to astrocytoma cells, providing therapeutic opportunities against astrocytomas, including sensitivity to acetate, a high rate of glycolysis and lactate extrusion, glutamate uptake transporters, differential sensitivities of monocarboxylate transporters, presence of glycogen, high interlinking with gap junctions, use of nicotinamide adenine dinucleotide phosphate for lipid synthesis, using different isoforms of synthetic enzymes (e.g. isocitrate dehydrogenase, pyruvate carboxylase, pyruvate kinase, lactate dehydrogenase), and different glucose uptake mechanisms. These unique metabolic susceptibilities may augment conventional therapeutic attacks based on cell division differences and surface receptors alone.
Cognitive impairment is frequently observed in epileptic patients. It has been seen that not only epilepsy but antiepileptic drugs also impair cognitive functions. The present study was undertaken to assess the effect of three anticonvulsants viz. lamotrigine (5mg/kg, p.o.), oxcarbazepine (15mg/kg, p.o.) and topiramate (10mg/kg, p.o.) on cognitive function and oxidative stress during pentylenetetrazole (PTZ)-kindling in mice. Kindling was induced by the administration of PTZ (25mg/kg, i.p.) on every alternate day till 5 weeks. Cognition was assessed after the development of kindling. Elevated plus maze (EPM) and passive avoidance response (PAR) tests were carried out after 24h and 48h of the last PTZ administration. After completion of behavioural tests malondialdehyde (MDA), glutathione levels, superoxide dismutase and catalase activity were measured as an indicator of oxidative stress. The results of the present study indicate that topiramate (10mg/kg) administration to kindled animals increased transfer latency and decreased step-down latency in EPM and PAR tests, respectively. However, lamotrigine and oxcarbazepine did not alter the two parameters. Topiramate administration to kindled as well as non-kindled animals has shown increase in MDA and decrease in glutathione levels. Lamotrigine and oxcarbazepine did not show significant alteration in oxidative stress parameters. To conclude, long term administration of topiramate impairs cognitive functions during experimental epilepsy while lamotrigine and oxcarbazepine are safer.
Following traumatic brain injury (TBI) there is significant neuropathology which includes mitochondrial dysfunction, loss of cortical gray matter, microglial activation, and cognitive impairment. Previous evidence has shown that activation of the peroxisome proliferator-activated receptors (PPARs) provide neuroprotection following traumatic brain and spinal injuries. In the current study we hypothesized that treatment with the PPAR ligand Pioglitazone would promote neuroprotection following a rat controlled cortical impact model of TBI. Animals received a unilateral 1.5mm controlled cortical impact followed by administration of Pioglitazone at 10mg/kg beginning 15min after the injury and subsequently every 24h for 5days. Beginning 1day after the injury there was significant impairment in mitochondrial bioenergetic function which was attenuated by treatments with Pioglitazone at 15min and 24h (p<0.05). In an additional set of animals, cognitive function was assessed using the Morris Water Maze (MWM) and it was observed that over the course of 4days of testing the injury produced a significant increase in both latency (p<0.05) and distance (p<0.05) to the platform. Animals treated with Pioglitazone performed similarly to sham animals and did not exhibit any impairment in MWM performance. Sixteen days after the injury tissue sections through the lesion site were quantified to determine the size of the cortical lesion. Vehicle-treated animals had an average lesion size of 5.09±0.73mm(3) and treatment with Pioglitazone significantly reduced the lesion size by 55% to 2.27±0.27mm(3) (p<0.01). Co-administration of the antagonist T0070907 with Pioglitazone blocked the protective effect seen with administration of Pioglitazone by itself. Following the injury there was a significant increase in the number of activated microglia in the area of the cortex adjacent to the site of the lesion (p<0.05). Treatment with Pioglitazone prevented the increase in the number of activated microglia and no difference was observed between sham and Pioglitazone-treated animals. From these studies we conclude that following TBI Pioglitazone is capable ameliorating multiple aspects of neuropathology. These studies provide further support for the use of PPAR ligands, specifically Pioglitazone, for neuroprotection.
Astrocytes form a significant constituent of seizure foci in the human brain. For a long time it was believed that astrocytes play a significant role in the causation of seizures. With the increase in our understanding of the unique biology of these cells, their precise role in seizure foci is receiving renewed attention. This article reviews the information now available on the role of astrocytes in the hippocampal seizure focus in patients with temporal lobe epilepsy with hippocampal sclerosis. Our intent is to try to integrate the available data. Astrocytes at seizure foci seem to not be a homogeneous population of cells, and in addition to typical glial fibrillary acidic protein, positive reactive astrocytes also include a population of neuron glia-2-like cells The astrocytes in sclerotic hippocampi differ from those in nonsclerotic hippocampi in their membrane physiology, having elevated Na+ channels and reduced inwardly rectifying potassium ion channels, and some having the capacity to generate action potentials. They also have reduced glutamine synthetase and increased glutamate dehydrogenase activity. The molecular interface between the astrocyte and microvasculature is also changed. The astrocytes are also associated with increased expression of many molecules normally concerned with immune and inflammatory functions. A speculative mechanism postulates that neuron glia-2-like cells may be involved in creating a high glutamate environment, whereas the function of more typical reactive astrocytes contribute to maintain high extracellular K+ levels; both factors contributing to the hyperexcitability of subicular neurons to generate epileptiform activity. The functions of the astrocyte vascular interface may be more critical to the processes involved in epileptogenesis.
Transient global cerebral ischemia results in acute neurodegeneration in selective brain areas. Global cerebral ischemic-reperfusion (IR) injury induced selective hippocampal damage results into various neurobehavioral deficits including spatial memory and learning deficiencies. In this study, we have investigated the protective effects of a nonthiazolidinedione PPARγ agonist, N-(2-benzoylphenyl)-O-[2-(methyl-2-pyridinylamino)ethyl]-l-tyrosine (GW1929), against global cerebral IR injury induced neurobehavioral deficits and brain damage in gerbils. Bilateral carotid artery occlusion induced global cerebral ischemia in gerbils resulted in neurological deficits, hyperlocomotion, reduced response latency in passive avoidance test and hippocampal damage. Hippocampal neurodegeneration after cerebral IR injury was also associated with significant increase in iNOS and MMP-9 immunoreactivity along with TNFα and IL-6 levels. Massive apoptotic DNA fragmentation as evident from increased TUNEL (terminal deoxynucleotidyl transferase mediated dUTP nick end labelling)-positive cells was also observed in the CA1 hippocampal region of IR challenged gerbils. GW1929 treatment significantly ameliorated cerebral IR induced neurological symptoms, hyperlocomotion, cognitive deficits and hippocampal neuronal damage in CA1 hippocampus region in gerbils. Significant reduction in IR injury induced iNOS and MMP-9 immunoreactivity, TNFα and IL-6 levels and apoptotic DNA fragmentation was also observed with GW1929 treatment. Pioglitazone, thiazolidinedione PPARγ agonist also exhibited similar effects on inflammatory parameters after global cerebral IR injury. In summary, this study demonstrates neuroprotective effects of GW1929 in global cerebral IR injury induced neurobehavioral deficits and brain pathology which may be attributed to reduced inflammation and apoptotic DNA fragmentation, suggesting therapeutic potential of PPARγ agonists in cerebral IR injury.
Reactive oxygen species (ROS) appear to be involved in several neurodegenerative disorders. We tested the hypothesis that oxidative stress could have a role in the hippocampal neurodegeneration observed in temporal lobe epilepsy induced by pilocarpine. We first determined the spatio-temporal pattern of ROS generation, by means of detection with dihydroethidium oxidation, in the CA1 and CA3 areas and the dentate gyrus of the dorsal hippocampus during status epilepticus induced by pilocarpine. Fluoro-Jade B assays were also performed to detect degenerating neurons. ROS generation was increased in CA1, CA3 and the dentate gyrus after pilocarpine-induced seizures, which was accompanied by marked cell death. Treatment of rats with a NADPH oxidase inhibitor (apocynin) for 7 days prior to induction of status epilepticus was effective in decreasing both ROS production (by an average of 20%) and neurodegeneration (by an average of 61%). These results suggest an involvement of ROS generated by NADPH oxidase in neuronal death in the pilocarpine model of epilepsy.
Converging lines of evidence associate gluco-regulatory abnormalities and peroxisome-proliferator-activated receptor (PPAR) gamma function with increased risk for Alzheimer's disease (AD). In this study, we used the Tg2576 AD mouse model to test the hypothesis that cognitive improvement following 1 month of PPAR gamma agonism with rosiglitazone (RTZ) correlates with peripheral gluco-regulatory status. We assessed cognition and peripheral gluco-regulatory status of Tg2576 mice following 1 month treatment with RTZ initiated prior to, coincident with, or after, the onset of peripheral gluco-regulatory abnormalities (4, 8, and 12 months of age, respectively). Whereas 5 months old (MO) and 13 MO Tg2576 did not gain cognitive improvement after 1 month treatment with RTZ, 9 MO Tg2576 mice exhibited reversal of associative learning and memory deficits. Peripheral gluco-regulatory abnormalities were improved in 9 and 13 MO Tg2576 with RTZ treatment; RTZ treatment had no effect on the normal glucose status of 5 MO Tg2576 mice. These findings suggest that RTZ-mediated cognitive improvement does not correlate with peripheral gluco-regulatory abnormalities per se, but reflects the age-dependent mechanistic differences that underlie cognitive decline in this mouse model.
The ageing of an inevitable life function is an unavoidable regressive physical process. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor family. PPARgamma plays an important role in regulating several metabolic pathways. Recently, PPARgamma has been implicated in inflammatory responses and age-related diseases. The aim of this study was to determine the anti-inflammatory reaction of PPARgamma in an induced ageing progress. The late passage of human diploid fibroblasts (HDF), an in vitro ageing model, reveals the biological index materials of ageing. Aged cells showed decreased PPARgamma expression and elevated levels of intracellular adhesion molecule-1 (ICAM-1), an inflammatory molecule. To induce the aged cell phenotype, the middle stage of HDF cells (PD31) were induced stress induced premature senescence (SIPS) with 200 microM H(2)O(2) for 2 h. SIPS-HDF cells showed high levels of ICAM-1, extracellular signal regulated kinase (ERK1/2) activity and matrix metallomatrix protease (MMP-2, -9) activity, and low levels of PPARgamma expression. A reconstitution of SIPS HDF cells with Ad/PPARgamma resulted in the downregulation of ICAM-1, ERK1/2, MMP-2 and -9, and normalized growth of SIPS-HDF cells. Moreover, PPARgamma in aged HDF cells reduced pro-inflammatory molecules and eliminated the formation of reactive oxygen species (ROS) through the ERK1/2 pathway. These results strongly suggest that PPARgamma plays a key role in age-related inflammation and may have clinical applications as a molecular target in the treatment of age-related inflammation.
Astrocytes have important functions in the metabolism of the brain. These cells provide neurons with metabolic substrates for energy production as well as with precursors for neurotransmitter and glutathione synthesis. Both the metabolism of astrocytes and the subsequent supply of metabolites from astrocytes to neurons are strongly affected by alterations in the cellular redox state. The cytosolic redox state of astrocytes depends predominantly on the ratios of the oxidised and reduced partners of the redox pairs NADH/NAD(+), NADPH/NADP(+) and GSH/GSSG. The NADH/NAD(+) pair is predominately in the oxidised state to accept electrons that are produced during glycolysis. In contrast, the redox pairs NADPH/NADP(+) and GSH/GSSG are biased towards the reduced state under unstressed conditions to provide electrons for reductive biosyntheses and antioxidative processes, respectively. In this review article we describe the metabolic processes that maintain the redox pairs in their desired redox states in the cytosol of astrocytes and discuss the consequences of alterations of the normal redox state for the regulation of cellular processes and for metabolite trafficking from astrocytes to neurons.
Astrocytes have long been considered as just providing trophic support for neurons in the central nervous system, but recently several studies have highlighted their importance in many functions such as neurotransmission, metabolite and electrolyte homeostasis, cell signaling, inflammation, and synapse modulation. Astrocytes are, in fact, part of a bidirectional crosstalk with neurons. Moreover, increasing evidence is stressing the emerging role of astrocyte dysfunction in the pathophysiology of neurological disorders, including neurodegenerative disease, stroke, epilepsy, migraine, and neuroinflammatory diseases.
The present study was undertaken to investigate possible mechanism of pioglitazone-induced beneficial effect in memory deficits associated with experimental dementia. Dementia was induced in Swiss albino mice by administration of streptozotocin (STZ; 3 mg/kg administered intracerebroventricularly on 1st & 3rd day). Morris Water-Maze test was employed to assess learning and memory of the animals. Brain acetylcholinesterase (AChE) activity was measured by Ell Mann's method. Brain thiobarbituric acid reactive species (TBARS) levels and reduced glutathione (GSH) levels were measured by Ohokawa's and Beutler's method respectively to assess total oxidative stress. Blood glucose level was also measured. Streptozotocin (STZ) produced a significant decrease in water-maze performance of mice hence reflecting loss of learning and memory. Pioglitazone (20 mg/kg p.o. daily for 14 days) successfully attenuated STZ-induced memory deficits, without any significant per se effect on blood glucose levels. Higher levels of brain AChE activity, TBARS and lower levels of GSH were observed in STZ treated animals, which were significantly attenuated by pioglitazone. Further, the noted beneficial effect of pioglitazone on STZ-induced dementia was significantly abolished by pre-treatment of nitric oxide (NO) synthase inhibitor L-NAME (3 mg/kg i.p.) manifested in the terms of decrease in water-maze performance and increase in brain AChE activity as well as oxidative stress. It is concluded that anti-dementic effect of pioglitazone may involve central cholinergic, oxidative and NO pathways.
The relationship between free radical and scavenger enzymes has been found in the epileptic phenomena and reactive oxygen species have been implicated in seizure-induced neurodegeneration. Using the epilepsy model obtained by systemic administration of pilocarpine in rats, we investigated the lipid peroxidation, nitrite content, superoxide dismutase (SOD) and catalase activities in the hippocampus of rats during chronic period. The enzyme activities as well as the lipid peroxidation and nitrite concentrations were measured using spectrophotometric methods and the results compared to values obtained from saline-treated animals. The superoxide dismutase and catalase activities increased during the chronic phase. In addition, lipid peroxidation and nitrite levels increased in same period in the hippocampus of animals observed during spontaneous recurrent seizures. Previous studies showed that animals presenting seizures and submitted to 24h of status epilepticus showed normal levels of superoxide dismutase and increased in catalase activities as well as an increase in hippocampal lipid peroxidation and nitrite concentrations. These results show a direct evidence of lipid peroxidation and nitrite during seizure activity that could be responsible for neuronal damage in the hippocampus of rats, during the establishment of pilocarpine model of epilepsy.
Electroconvulsive therapy (ECT) is a very efficient treatment for severe depression. However, cognitive side effects have raised concern to whether ECT can cause cellular damage in vulnerable brain regions. A few recent animal studies have reported limited hippocampal cell loss, while a number of other studies have failed to find any signs of cellular damage and some even report that electroconvulsive seizures (ECS; the animal counterpart of ECT) has neuroprotective effects. We previously have described gliogenesis in response to ECS. Loss of glial cells is seen in depression and de novo formation of glial cells may thus have an important therapeutic role. Glial cell proliferation and activation is however also seen in response to neuronal damage. The aim of the present study was to further characterize glial cell activation in response to ECS. Two groups of rats were treated with 10 ECS using different sets of stimulus parameters. ECS-induced changes in the morphology and expression of markers typical for reactive microglia, astrocytes and NG2+ glial cells were analyzed immunohistochemically in prefrontal cortex, hippocampus, amygdala, hypothalamus, piriform cortex and entorhinal cortex. We observed changes in glial cell morphology and an enhanced expression of activation markers 2 h following ECS treatment, regardless of the stimulus parameters used. Four weeks later, few activated glial cells persisted. In conclusion, ECS treatment induced transient glial cell activation in several brain areas. Whether similar processes play a role in the therapeutic effect of clinically administered ECT or contribute to its side effects will require further investigations.
Several studies have shown the existence of sex differences in the sensitivity to various convulsants in animals and to the development of some epilepsy types in humans. The purpose of this study was to investigate whether there are sex differences in seizure susceptibility and sensitivity of different brain regions to oxidative stress in rats with status epilepticus (SE) induced by lithium-pilocarpine administration, that provides a common experimental model of temporal lobe epilepsy (TLE) in humans.
The aim of this study was to evaluate the long-term efficacy of temporal lobe epilepsy (TLE) surgery and potential risk factors for seizure recurrence after surgery.
This retrospective study included 434 consecutive adult patients who underwent TLE surgery at Bethel Epilepsy Centre between 1991 and 2002.
Hippocampal sclerosis was found in 62% of patients, gliosis in 17.3%, tumors in 20%, and focal cortical dysplasia (FCD) in 6.9%. Based on a Kaplan-Meier analysis, the probability of Engel Class I outcome for the patients overall was 76.2% (95% CI 71-81%) at 6 months, 72.3% (95% CI 68-76%) at 2 years, 71.1% (95% CI 67-75%) at 5 years, 70.8% (95% CI 65-75%) at 10 years, and 69.4% (95% CI 64-74%) at 16 years postoperatively. The likelihood of remaining seizure free after 2 years of freedom from seizures was 90% (95% CI 82-98%) for 16 years. Seizure relapse occurred in all subgroups. Patients with FCD had the highest risk of recurrence (hazard ratio 2.15, 95% CI 0.849-5.545). Predictors of remission were the presence of hippocampal atrophy on preoperative MR imaging and a family history of epilepsy. Predictors of relapse were the presence of bilateral interictal sharp waves and versive seizures. Six-month follow-up electroencephalography predicted relapse in patients with FCD. Short epilepsy duration was predictive of seizure remission in patients with tumors and gliosis; 28.1% of patients were able to discontinue antiepileptic medications without an increased risk of seizure recurrence (hazard ratio 1.05, 95% CI 0.933-1.20).
These findings highlight the role of etiology in prediction of long-term outcome after TLE surgery.
Subjective cognitive side effects (CSEs) are common in patients taking antiepileptic drugs (AEDs). The objective of this study was to predict which patients are at risk for CSEs, and compare the CSE profiles of all commonly used AEDs. In this nonrandomized retrospective study, medical records of 1694 adult outpatients with epilepsy seen at our center over a 5-year period who had taken one or more AEDs were examined. Non-AED predictors of CSEs were investigated, and rates of AED-related CSEs were compared in 1189 patients (546 on monotherapy) newly started on an AED at our center. The average rate of AED-related intolerable CSEs (leading to dosage change or discontinuation) was 12.8%. On multivariate analysis, no significant non-AED predictors of CSEs were found. Significantly more intolerable CSEs were attributed to topiramate (21.5% of 130 patients) than to most other AEDs, including carbamazepine (9.9%), gabapentin (7.3%), levetiracetam (10.4%), lamotrigine (8.9%), oxcarbazepine (11.6%), and valproate (8.3%). CSE rates with zonisamide (14.9%) were significantly higher than those for gabapentin and lamotrigine. After exclusion of CSEs during the first 8 weeks of therapy, rates of CSEs were lower, but relative differences remained unchanged. In monotherapy, significantly more intolerable CSEs occurred with topiramate (11.1% of 18 patients) than with carbamazepine or valproate, and both phenytoin and zonisamide were associated with more CSEs than valproate. From this study, it can be concluded that intolerable patient-reported CSEs are most common with topiramate, followed by zonisamide, phenytoin, and oxcarbazepine. They are least likely to be reported with gabapentin, valproate, lamotrigine, carbamazepine, and levetiracetam.
The compound N-(1-pyrenyl)maleimide (NPM) reacts with free sulfhydryl groups to form fluorescent derivatives. A new method for measurement of glutathione and other biological thiols utilizing reverse-phase high-performance liquid chromatography to separate and quantify these derivatives is described. Separation and quantification of glutathione, cysteine, homocysteine, cysteinylglycine, and gamma-glutamylcysteine derivatives are achieved. The method allows for the measurement of glutathione disulfide by masking free glutathione with 2-vinylpyridine, reducing glutathione disulfide with glutathione reductase, and measuring the resulting glutathione. Coefficient of variations for the various thiols measured by the NPM method range from 1.5 to 8.8%. The lower detection limit is around 50 fmol of glutathione. NPM derivatives are shown to be stable for 2 months at 4 degrees C. Between 94.2 and 97.2% of glutathione and/or glutathione disulfide added to a sample is recovered using the NPM method. The NPM method is compared to the monobromobimane high-performance liquid chromatography method and the Tietze assay by measuring glutathione in homogenates from five different cell lines. The newly developed method offers some advantages over the currently accepted techniques, including specificity, speed, sensitivity, and ease of use.
We have recently found that intracerebroventricular (i.c.v.) administration of glutathione (GSH) inhibits pentylenetetrazol-induced convulsions in mice, suggesting that GSH has an anticonvulsive action. In the present study, we investigated whether endogenous GSH play a role in regulating seizure susceptibility, using L-buthionine-[S,R]-sulfoximine (BSO), a specific inhibitor of GSH biosynthesis. BSO treatment (3.2 micromol i.c.v. x 2, 48 and 24 h prior to experiments) decreased brain GSH level to 31.5% of control, and potentiated pentylenetetrazol-induced convulsions. Potentiation of convulsions by BSO treatment was recovered by supplying GSH (10 nmol, i.c.v.). These results suggest that endogenous GSH functions as an anticonvulsant.
Both excitotoxicity and apoptosis contribute to neuronal loss in various neurodegenerative diseases such as Alzheimer's disease as well as stroke, and a drug inhibiting both types of cell death may lead to practical treatment for these diseases. Post-treatment with troglitazone, a potent and specific activator of peroxisome proliferator-activated receptor (PPAR)-gamma attenuated the cell death of cerebellar granule neurons, triggered by glutamate exposure. The inhibitory effect of troglitazone against glutamate excitotoxicity, in vitro, was observed even when added 2.5 h after the end of glutamate exposure, a time when glutamate antagonists are no longer neuroprotective. However, troglitazone did not block the glutamate-induced elevation of calcium influx, suggesting that troglitazone interfered with downstream consequences of excitotoxic glutamate receptor overactivation. In addition, troglitazone also suppressed low-potassium-induced apoptosis in cerebellar granule neurons in a phosphatidylinositol 3-kinase independent manner. In conclusion, although the mechanisms of troglitazone's neuroprotective effects are unknown, the post-treatment-neuroprotective effect and the dual-inhibitory-activity against both excitotoxicity and apoptosis may provide a novel therapy for various neurodegenerative diseases.
Patients with epilepsy are more prone to cognitive and behavioral deficits. Epilepsy per se may induce or exacerbate an underlying cognitive impairment, a variety of factors contribute to such deficits, i.e., underlying neuropathology, seizure type, age of onset, psychosocial problems, and treatment side effects. Epilepsy treatment may offset the cognitive and behavioral impairments by stopping or decreasing the seizures, but it may also induce untoward effects on cognition and behavior. The neurocognitive burden of epilepsy may even start through in utero exposure to medications. Epilepsy surgery can also induce certain cognitive deficits, although in most cases this can be minimized. Clinicians should consider cognitive side effect profiles of antiepileptic medications, particularly in extreme age groups. While no effective treatments are available for cognitive and behavioral impairments in epilepsy, comprehensive pretreatment evaluation and meticulous selection of antiepileptic drugs or surgical approach may minimize such untoward effects.
Recurring seizures in infants and children are often associated with cognitive deficits, but the reason for the learning difficulties is unclear. Recent studies in several animal models suggest that seizures themselves may contribute in important ways to these deficits. Other studies in animals have shown that recurring seizures result in dendritic spine loss. This change, coupled with a down-regulation in NMDA receptor subunit expression, suggests that repetitive seizures may interrupt the normal development of glutamatergic synaptic transmission. We hypothesize that homeostatic, neuroprotective processes are induced by recurring early-life seizures. These processes, by diminishing glutamatergic synaptic transmission, are aimed at preventing the continuation of seizures. However, by preventing the normal development of glutamatergic synapses, and particularly NMDA receptor-mediated synaptic transmission, such homeostatic processes also reduce synaptic plasticity and diminish the ability of neuronal circuits to learn and store memories.
Recent evidences suggest key roles of abnormal neurogenesis and astrogliosis in the pathogenesis of epilepsy. Alterations in the microenvironment of the stem cell, such as microglial activation and cyclooxygenase-2 induction may cause ectopic neurogenesis or astrogliosis. Here, we examined if inflammatory blockade with celecoxib, a selective cyclooxygenase-2 inhibitor, could modulate the altered microenvironment in the epileptic rat brain. Celecoxib attenuated the likelihood of developing spontaneous recurrent seizures after pilocarpine-induced prolonged seizure. During the latent period, celecoxib prevented neuronal death and microglia activation in the hilus and CA1 and inhibited the generation of ectopic granule cells in the hilus and new glia in CA1. The direct inhibition of precursor cells by celecoxib was further demonstrated in human neural stem cells culture. These findings raise the evidence of COX-2 induction to act importantly on epileptogenesis and suggest a potential therapeutic role for COX-2 inhibitors in chronic epilepsy.
Diabetes mellitus is characterized by cytokine-induced insulitis and a deficit in beta-cell mass. Ligands for peroxisome proliferator-activated receptor-gamma (PPAR-gamma) have been shown to have anti-inflammatory effects in various experimental models. We questioned whether activation of endogenous PPAR-gamma by either PPAR-gamma ligands or adenoviral-directed overexpression of PPAR-gamma (Ad-PPAR-gamma) could inhibit cytokine-induced beta-cell death in RINm5F (RIN) cells, a rat insulinoma cell line. Treatment of RIN cells with interleukin-1 beta (IL-1 beta) and interferon-gamma (IFN-gamma) induced beta-cell damage through NF kappaB-dependent signaling pathways. Activation of PPAR-gamma by PPAR-gamma ligands or Ad-PPAR-gamma inhibited IL-1 beta and IFN-gamma-stimulated nuclear translocation of the p65 subunit and DNA binding activity. NF kappaB target gene expression and their product formation, namely inducible nitric oxide synthase and cyclooxygenase-2 were decreased by PPAR-gamma activation, as established by real-time PCR, Western blots and measurements of NO and PGE(2). The mechanism by which PPAR-gamma activation inhibited NF kappaB-dependent cell death signals appeared to involve the inhibition of I kappa B alpha degradation, evidenced by inhibition of cytokine-induced NF kappaB-dependent signaling events by Ad-I kappaB alpha (S32A, S36A), non-degradable I kappaB alpha mutant. I kappaB beta mutant, Ad-I kappaB beta (S19A, S23A) was not effective in preventing cytokine toxicity. Furthermore, a protective effect of PPAR-gamma ligands was proved by assaying for normal insulin secreting capacity in response to glucose in isolated rat pancreatic islets. The beta-cell protective function of PPAR-gamma ligands might serve to counteract cytokine-induced beta-cell destruction.
Status epilepticus (SE) can cause severe neuronal loss and oxidative damage. As peroxisome proliferator-activated receptor gamma (PPARgamma) agonists possess antioxidative activity, we hypothesize that rosiglitazone, a PPARgamma agonist, might protect the central nervous system (CNS) from oxidative damage in epileptic rats. Using a lithium-pilocarpine-induced SE model, we found that rosiglitazone significantly reduced hippocampal neuronal loss 1 week after SE, potently suppressed the production of reactive oxygen species (ROS) and lipid peroxidation. We also found that treatment with rosiglitazone enhanced antioxidative activity of superoxide dismutase (SOD) and glutathione hormone (GSH), together with decreased expression of heme oxygenase-1 (HO-1) in the hippocampus. The above effects of rosiglitazone can be blocked by co-treatment with PPARgamma antagonist T0070907. The current data suggest that rosiglitazone exerts a neuroprotective effect on oxidative stress-mediated neuronal damage followed by SE. Our data also support the idea that PPARgamma agonist might be a potential neuroprotective agent for epilepsy.
Statins are inhibitors of HMG-CoA reductase that have been recently recognized as anti-inflammatory and neuroprotective drugs. Herein, we investigated anti-excitotoxic and anti-seizure effects of statins by using kainic acid (KA)-rat seizure model, an animal model for temporal lobe epilepsy and excitotoxic neurodegeneration. We observed that pre-treatment with Lipitor (atorvastatin) efficiently reduced KA-induced seizure activities, hippocampal neuron death, monocyte infiltration and proinflammatory gene expression. In addition, we also observed that lovastatin treatment attenuated KA- or glutamate-induced excitotoxicity of cultured hippocampal neurons. These observations suggest a potential for use of statin treatment in modulation of seizures and other neurological diseases associated with excitotoxicity.
Activation of perxisome proliferator-activated receptor-gamma protects pancreatic beta-cells from cytokine-induced cytotoxicity via NF kappaB path-way
- Kim Ek Kown
- Kb
- Koo
- Bs
- Han
- Mj
- My Song
- Song
- Ek
- Han
- Mk
- Jw Park
- Dg
- Park
- Bh
Kim EK, Kown KB, Koo BS, Han MJ, Song MY, Song EK, Han MK, Park JW, Ryu DG, Park BH (2007) Activation of perxisome proliferator-activated receptor-gamma protects pancreatic beta-cells from cytokine-induced cytotoxicity via NF kappaB path-way. Int J Biochem Cell Biol 39:1260–1275
China e-mail: sunhongxjt@yahoo.cn Y. Xin Department of Neurology, People's Liberation Army 401
- Road
- Xi
- Shaanxi
- Province
Road, Xi'an 710004, Shaanxi Province, China e-mail: sunhongxjt@yahoo.cn Y. Xin Department of Neurology, People's Liberation Army 401