Kainate-induced apoptotic cell death in hippocampal neurons

SRF-deficient astrocytes provide neuroprotection in mouse models of excitotoxicity and neurodegeneration

Reactive astrogliosis is a common pathological hallmark of CNS injury, infection, and neurodegeneration, where reactive astrocytes can be protective or detrimental to normal brain functions. Currently, the mechanisms regulating neuroprotective astrocytes and the extent of neuroprotection are poorly understood. Here, we report that conditional deletion of serum response factor (SRF) in adult astrocytes causes reactive-like hypertrophic astrocytes throughout the mouse brain. These SrfGFAP-ERCKO astrocytes do not affect neuron survival, synapse numbers, synaptic plasticity or learning and memory. However, the brains of Srf knockout mice exhibited neuroprotection against kainic-acid induced excitotoxic cell death. Relevant to human neurodegenerative diseases, SrfGFAP-ERCKO astrocytes abrogate nigral dopaminergic neuron death and reduce β-amyloid plaques in mouse models of Parkinson's and Alzheimer's disease, respectively. Taken together, these findings establish SRF as a key molecular switch for the generation of reactive astrocytes with neuroprotective functions that attenuate neuronal injury in the setting of neurodegenerative diseases.

Paeonol exerts neuroprotective and anticonvulsant effects in intrahippocampal kainate model of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is presented the most common form of focal epilepsy with involvement of oxidative stress and neuroinflammation as important factors in its development. About one third of epileptic patients are intractable to currently available medications. Paeonol isolated from some herbs with traditional and medicinal uses has shown anti-oxidative and anti-inflammatory effects in different models of neurological disorders. In this research, we tried to evaluate the possible protective effect of paeonol in intrahippocampal kainate murine model of TLE. To induce TLE, kainate was microinjected into CA3 area of the hippocampus and paeonol was administered at two doses of 30 or 50mg/kg. The results of this study showed that paeonol at the higher dose significantly reduces incidence of status epilepticus, hippocampal aberrant mossy fiber sprouting and also preserves neuronal density. Beneficial protective effect of paeonol was in parallel with partial reversal of some hippocampal oxidative stress markers (reactive oxygen species and malondialdehyde), caspase 1, glial fibrillary acidic protein, heme oxygenase 1, DNA fragmentation, and inflammation-associated factors (nuclear factor-kappa B, toll-like receptor 4, and tumor necrosis factor α). Our obtained data indicated anticonvulsant and neuroprotective effects of paeonol which is somewhat attributed to its anti-oxidative and anti-inflammation properties besides its attenuation of apoptosis, pyroptosis, and astrocyte activity.

Design, Synthesis, and Biological Evaluation of Novel Tomentosin Derivatives in NMDA-Induced Excitotoxicity

N-methyl-D-aspartate (NMDA) receptor stimulation may lead to excitotoxicity, which triggers neuronal death in brain disorders. In addition to current clinical therapeutic approaches, treatment strategies by phytochemicals or their derivatives are under investigation for neurodegenerative diseases. In the present study, novel amino and 1,2,3-triazole derivatives of tomentosin were prepared and tested for their protective and anti-apoptotic effects in NMDA-induced excitotoxicity. Amino-tomentosin derivatives were generated through a diastereoselective conjugate addition of several secondary amines to the α-methylene-γ-butyrolactone function, while the 1,2,3-triazolo-tomentosin was prepared by a regioselective Michael-type addition carried out in the presence of trimethylsilyl azide (TMSN3) and the α-methylene-γ-lactone function. The intermediate key thus obtained underwent 1,3-dipolar Huisgen cycloaddition using a wide range of terminal alkynes. The possible effects of the derivatives on cell viability and free-radical production following NMDA treatment were measured by Water-Soluble Tetrazolium Salts (WST-1) and Dichlorofluorescein Diacetate (DCF-DA) assays, respectively. The alterations in apoptosis-related proteins were examined by Western blot technique. Our study provides evidence that synthesized triazolo- and amino-tomentosin derivatives show neuroprotective effects by increasing cellular viability, decreasing ROS production, and increasing the Bcl-2/Bax ratio in NMDA-induced excitotoxicity. The findings highlight particularly 2e, 2g, and 6d as potential regulators and neuroprotective agents in NMDA overactivation.

Treatment effects of the combination of ceftriaxone and valproic acid on neuronal and behavioural functions in a rat model of epilepsy

NEW FINDINGS

What is the central question of this study? Imbalance of activities between GABAergic and glutamatergic systems is involved in epilepsy. It is not known whether simultaneously increasing GABAergic and decreasing glutamatergic activity using valproic acid and ceftriaxone, respectively, leads to better seizure control. What is the central question of this study? Ceftriaxone suppressed seizure and cognitive deficits and restored neuronal density and the number of newborn cells in the hippocampus in a rat model of epilepsy. Combined treatment with ceftriaxone and valproic acid showed additive effects in seizure suppression.

ABSTRACT

The pathophysiology of epilepsy is typically considered as an imbalance between inhibitory GABA and excitatory glutamate neurotransmission. Valproic acid (Val), a GABA agonist, is one of the first-line antiepileptic drugs in the treatment of epilepsy, but it exhibits adverse effects. Ceftriaxone (CEF) elevates expression of glutamate transporter-1, enhances the reuptake of synaptic glutamate, increases the number of newborn cells and exhibits neuroprotective effects in animal studies. In this study, we evaluated effects of the combination of CEF and Val on behavioural and neuronal measures in a rat epilepsy model. Male Wistar rats were injected i.p. with pentylenetetrazol (35 mg/kg, every other day for 13 days) to induce the epilepsy model. Ceftriaxone (10 or 50 mg/kg), Val (50 or 100 mg/kg) or the combination of CEF and Val were injected daily after the fourth pentylenetetrazol injection for seven consecutive days. Epileptic rats exhibited seizure and impairments in motor and cognitive functions. Treatment with CEF and Val reduced the seizure and enhanced motor and cognitive functions in a dose-dependent manner. The combination of CEF (10 mg/kg) and Val (50 mg/kg) improved behaviours considerably. Histologically, compared with control animals, epileptic rats exhibited lower neuronal density and a reduction in hippocampal newborn cells but higher apoptosis in the basolateral amygdala, all of which were restored by the treatment with CEF, Val or the combination of CEF and Val. The study findings demonstrated that the combination of low doses of CEF and Val has beneficial effects on seizure suppression, neuroprotection and improvement in motor and cognitive functions in epilepsy.

The Perils of Navigating Activity-Dependent Alternative Splicing of Neurexins

Neurexins are presynaptic cell-adhesion molecules essential for synaptic function that are expressed in thousands of alternatively spliced isoforms. Recent studies suggested that alternative splicing at splice site 4 (SS4) of Nrxn1 is tightly regulated by an activity-dependent mechanism. Given that Nrxn1 alternative splicing at SS4 controls NMDA-receptor-mediated synaptic responses, activity-dependent SS4 alternative splicing would suggest a new synaptic plasticity mechanism. However, conflicting results confound the assessment of neurexin alternative splicing, prompting us to re-evaluate this issue. We find that in cortical cultures, membrane depolarization by elevated extracellular K+-concentrations produced an apparent shift in Nrxn1-SS4 alternative splicing by inducing neuronal but not astroglial cell death, resulting in persistent astroglial Nrxn1-SS4+ expression and decreased neuronal Nrxn1-SS4- expression. in vivo, systemic kainate-induced activation of neurons in the hippocampus produced no changes in Nrxn1-SS4 alternative splicing. Moreover, focal kainate injections into the mouse cerebellum induced small changes in Nrxn1-SS4 alternative splicing that, however, were associated with large decreases in Nrxn1 expression and widespread DNA damage. Our results suggest that although Nrxn1-SS4 alternative splicing may represent a mechanism of activity-dependent synaptic plasticity, common procedures for testing this hypothesis are prone to artifacts, and more sophisticated approaches will be necessary to test this important question.

Seizure activity and brain damage in a model of focal non-convulsive status epilepticus

AIMS

Focal non-convulsive status epilepticus (FncSE) is a common emergency condition that may present as the first epileptic manifestation. In recent years, it has become increasingly clear that de novo FncSE should be promptly treated to improve post-status outcome. Whether seizure activity occurring during the course of the FncSE contributes to ensuing brain damage has not been demonstrated unequivocally and is here addressed.

METHODS

We used continuous video-EEG monitoring to characterise an acute experimental FncSE model induced by unilateral intrahippocampal injection of kainic acid (KA) in guinea pigs. Immunohistochemistry and mRNA expression analysis were utilised to detect and quantify brain injury, 3-days and 1-month after FncSE.

RESULTS

Seizure activity occurring during the course of FncSE involved both hippocampi equally. Neuronal loss, blood-brain barrier permeability changes, gliosis and up-regulation of inflammation, activity-induced and astrocyte-specific genes were observed in the KA-injected hippocampus. Diazepam treatment reduced FncSE duration and KA-induced neuropathological damage. In the contralateral hippocampus, transient and possibly reversible gliosis with increase of aquaporin-4 and Kir4.1 genes were observed 3 days post-KA. No tissue injury and gene expression changes were found 1-month after FncSE.

CONCLUSIONS

In our model, focal seizures occurring during FncSE worsen ipsilateral KA-induced tissue damage. FncSE only transiently activated glia in regions remote from KA-injection, suggesting that seizure activity during FncSE without local pathogenic co-factors does not promote long-lasting detrimental changes in the brain. These findings demonstrate that in our experimental model, brain damage remains circumscribed to the area where the primary cause (KA) of the FncSE acts. Our study emphasises the need to use antiepileptic drugs to contain local damage induced by focal seizures that occur during FncSE.

Ripple-related firing of identified deep CA1 pyramidal cells in chronic temporal lobe epilepsy in mice

OBJECTIVE

Temporal lobe epilepsy (TLE) is often associated with memory deficits. Reactivation of memory traces in the hippocampus occurs during sharp-wave ripples (SWRs; 140-250 Hz). To better understand the mechanisms underlying high-frequency oscillations and cognitive comorbidities in epilepsy, we evaluated how rigorously identified deep CA1 pyramidal cells (dPCs) discharge during SWRs in control and TLE mice.

METHODS

We used the unilateral intraamygdala kainate model of TLE in video-electroencephalography (EEG) verified chronically epileptic adult mice. Local field potential and single-cell recordings were performed using juxtacellular recordings from awake control and TLE mice resting on a spherical treadmill, followed by post hoc identification of the recorded cells.

RESULTS

Hippocampal SWRs in TLE mice occurred with increased intraripple frequency compared to control mice. The frequency of SWR events was decreased, whereas the overall frequency of SWRs, interictal epileptiform discharges, and high-frequency ripples (250-500 Hz) together was not altered. CA1 dPCs in TLE mice showed significantly increased firing during ripples as well as between the ripple events. The strength of ripple modulation of dPC discharges increased in TLE without alteration of the preferred phase of firing during the ripple waves.

SIGNIFICANCE

These juxtacellular electrophysiology data obtained from identified CA1 dPCs from chronically epileptic mice are in general agreement with recent findings indicating distortion of normal firing patterns during offline SWRs as a mechanism underlying deficits in memory consolidation in epilepsy. Because the primary seizure focus in our experiments was in the amygdala and we recorded from the CA1 region, these results are also in agreement with the presence of altered high-frequency oscillations in areas of secondary seizure spread.

Inhibition of microRNA-34a Suppresses Epileptiform Discharges Through Regulating Notch Signaling and Apoptosis in Cultured Hippocampal Neurons

Epilepsy is characterized by recurrent unprovoked seizures and some seizures can cause neuronal apoptosis, which is possible to make contributions to the epilepsy phenotype, impairments in cognitive function or even epileptogenesis. Moreover, many studies have indicated that microRNA-34a (miRNA-34a) is involved in apoptosis through regulating Notch signaling. However, whether miRNA-34a participates in neuronal apoptosis after seizures remain unclear. Therefore, we aimed to explore the expression of miRNA-34a and its effects on the epileptiform discharge in spontaneous recurrent epileptiform discharges (SREDs) rat hippocampal neuronal pattern. Mg²⁺-free medium was used to induce SREDs, quantitative reverse-transcription polymerase chain reaction was used to detect the expression of miRNA-34a, western blot was used to determine the expression of Notch pathway and apoptosis-related proteins, and whole cell current clamp recordings was used to observe the alteration of epileptiform discharge. We found obvious apoptosis, increased expression of miRNA-34a and decreased expression of Notch signaling in Mg²⁺-free-treated neurons. Treatment with miRNA-34a inhibitor decreased the frequency of action potentials, activated Notch signaling and prevented neuronal apoptosis in Mg²⁺-free-treated neurons. However, treatment with miRNA-34a mimics increased the frequency of action potentials, down-regulated Notch signaling and promoted neuronal apoptosis in Mg²⁺-free-treated neurons. Furthermore, γ-secretase inhibitor N-[N-(3,5-di-uorophenacetyl)-1-alanyl]-S-phenylglycine t-butylester (DAPT), an inhibitor of Notch signaling, could weaken anti-apoptosis effect of miRNA-34a inhibitor. These results suggest that inhibition of miRNA-34a could suppress epileptiform discharges through regulating Notch signaling and apoptosis in the rat hippocampal neuronal model of SREDs.

Electroconvulsive Shock Enhances Responsive Motility and Purinergic Currents in Microglia in the Mouse Hippocampus

Microglia are in a privileged position to both affect and be affected by neuroinflammation, neuronal activity and injury, which are all hallmarks of seizures and the epilepsies. Hippocampal microglia become activated after prolonged, damaging seizures known as status epilepticus (SE). However, since SE causes both hyperactivity and injury of neurons, the mechanisms triggering this activation remain unclear, as does the relevance of the microglial activation to the ensuing epileptogenic processes. In this study, we use electroconvulsive shock (ECS) to study the effect of neuronal hyperactivity without neuronal degeneration on mouse hippocampal microglia. Unlike SE, ECS did not alter hippocampal CA1 microglial density, morphology, or baseline motility. In contrast, both ECS and SE produced a similar increase in ATP-directed microglial process motility in acute slices, and similarly upregulated expression of the chemokine C-C motif chemokine ligand 2 (CCL2). Whole-cell patch-clamp recordings of hippocampal CA1sr microglia showed that ECS enhanced purinergic currents mediated by P2X7 receptors in the absence of changes in passive properties or voltage-gated currents, or changes in receptor expression. This differs from previously described alterations in intrinsic characteristics which coincided with enhanced purinergic currents following SE. These ECS-induced effects point to a "seizure signature" in hippocampal microglia characterized by altered purinergic signaling. These data demonstrate that ictal activity per se can drive alterations in microglial physiology without neuronal injury. These physiological changes, which up until now have been associated with prolonged and damaging seizures, are of added interest as they may be relevant to electroconvulsive therapy (ECT), which remains a gold-standard treatment for depression.

Emerging Roles of Sonic Hedgehog in Adult Neurological Diseases: Neurogenesis and Beyond

Sonic hedgehog (Shh), a member of the hedgehog (Hh) family, was originally recognized as a morphogen possessing critical characters for neural development during embryogenesis. Recently, however, Shh has emerged as an important modulator in adult neural tissues through different mechanisms such as neurogenesis, anti-oxidation, anti-inflammation, and autophagy. Therefore, Shh may potentially have clinical application in neurodegenerative diseases and brain injuries. In this article, we present some examples, including ours, to show different aspects of Shh signaling and how Shh agonists or mimetics are used to alter the neuronal fates in various disease models, both in vitro and in vivo. Other potential mechanisms that are discussed include alteration of mitochondrial function and anti-aging effect; both are critical for age-related neurodegenerative diseases. A thorough understanding of the protective mechanisms elicited by Shh may provide a rationale to design innovative therapeutic regimens for various neurodegenerative diseases.

To evaluate the anti-kindling effect of allopregnanolone alone and its interaction with sodium valporate in pentylenetetrazole induced kindling model

Background and purpose Studies in the animal models of epilepsy have suggested the anti-seizure effects of neuroactive steroids and its derivatives in kainic acid and pilocarpine induced limbic seizures and status epilepticus in mice, but no such studies have been reported in the published literature on the role of allopregnanolone in chemical kindling model and its interaction with sodium valproate. The purpose of this study was to evaluate the interaction between sodium valproate and allopregnanolone in pentylenetetrazole induced kindling model in rats.

Methods In a PTZ kindled Wistar rat model, sodium valproate and allopregnanolone were administered 30 min before the PTZ injection. The PTZ injection was given on alternate day till the animal became fully kindled or till 10 weeks. The parameters measured were latency to develop kindling and incidence of kindling, histopathological study of hippocampus, hippocampal anti-oxidant parameters and hippocampal DNA fragmentation studies.

Results In this study, the combination of low dose of allopregnanolone with low dose of sodium valproate showed a similar beneficial effect to that of a higher dose of sodium valproate in significantly reducing the number of kindled animals (0/8) as compare to PTZ control group (5/8) as well as the seizure scores and the histopathological scores. The combination significantly reduces oxidative stress by significantly decreasing the MDA levels, and increasing the SOD levels and GSH levels in the hippocampus of rats as compared to PTZ control group. So all these data suggest the antiepileptic effect of the combination and confers the synergistic interaction between the allopregnanolone and sodium valproate.

Conclusions It can be concluded that by choosing this combination the dose of sodium valproate can be reduced and thereby reduces the incidence of adverse effects caused by sodium valproate and hence proves to be a useful combination clinically. This study has lead the basis to further investigate the various combinations of neurosteroids and valproate in the process of epileptogenesis with better side effect profile.

Upregulation of GH, but not IGF1, in the hippocampus of the lactating dam after kainic acid injury

Lactation embodies a natural model of morphological, neurochemical, and functional brain plasticity. In this reproductive stage, the hippocampus of the female is less sensitive to excitotoxins in contrast to nulliparity. Growth hormone (GH) and insulin-like growth factor 1 (IGF1) are known to be neuroprotective in several experimental models of brain lesion. Here, activation of the GH-IGF1 pituitary-brain axis following kainic acid (7.5 mg/kg i.p. KA) lesion was studied in lactating and nulliparous rats. Serum concentrations of GH and IGF1 were uncoupled in lactation. Compared to virgin rats, the basal concentration of GH increased up to 40% but IGF1 decreased 58% in dams, and only GH increased further after KA treatment. In the hippocampus, basal expression of GH mRNA was higher (2.8-fold) in lactating rats than in virgin rats. GH mRNA expression in lactating rats increased further after KA administration in the hippocampus and in the hypothalamus, in parallel to GH protein concentration in the hippocampus of KA-treated lactating rats (43% vs lactating control), as detected by Western blot and immunofluorescence. Except for the significantly lower mRNA concentration in the liver of lactating rats, IGF1 expression was not altered by the reproductive condition or by KA treatment in the hippocampus and hypothalamus. Present results indicate upregulation of GH expression in the hippocampus after an excitotoxic lesion, suggesting paracrine/autocrine actions of GH as a factor underlying neuroprotection in the brain of the lactating dam. Since no induction of IGF1 was detected, present data suggest a direct action of GH.

Methylene Blue Exerts Anticonvulsant and Neuroprotective Effects on Self-Sustaining Status Epilepticus (SSSE) Induced by Prolonged Basolateral Amygdala Stimulation in Wistar Rats

BACKGROUND This study was designed to investigate the potential anticonvulsant and neuroprotective effects of methylene blue (MB) on self-sustaining status epilepticus (SSSE) induced by prolonged basolateral amygdala stimulation (BLA) in Wistar rats. MATERIAL AND METHODS The rats were randomly divided into 4 groups: (1) the Control group (rats without any treatment); (2) the Sham group (rats received electrode implantation but without electrical stimulation); (3) the SSSE group (rats received electrode implantation and additional electrical stimulation); and (4) the SSSE+MB group (rats received 1 mg/kg MB intraperitoneal injection 5 min after SSSE). SSSE models were established by prolonged BLA stimulation. The severities of SSSE were assessed by the number of separate seizures and the accumulated time of seizures. The variations of malondialdehyde/glutathione (MDA/GSH) were assessed 24 h after the establishment of SSSE. Nissl staining was performed to detect the surviving neurons in hippocampal CA1 and CA3 regions, and Western blotting assays were used to detect Caspase-3 (CASP3), B cell lymphoma 2 (BCL2), and BCL2-associated X protein (BAX). RESULTS Compared with the SSSE group, treatment with MB (1) markedly reduced the number and accumulated time of seizure activities; (2) significantly attenuated the increase of MDA and the decrease of GSH hippocampal levels; (3) markedly improved the cell morphology and alleviated the neuronal loss in hippocampal CA1 and CA3 regions; (4) significantly attenuated the increase of CASP3 and BAX and the decrease of BCL2 hippocampal levels. CONCLUSIONS MB has a protective effect in the SSSE model and may be useful as an adjuvant for preventing or treating epilepsy in humans.

Neural stem cells and epilepsy: functional roles and disease-in-a-dish models

Epilepsy is a disorder of the central nervous system characterized by spontaneous recurrent seizures. Although current therapies exist to control the number and severity of clinical seizures, there are no pharmacological cures or disease-modifying treatments available. Use of transgenic mouse models has allowed an understanding of neural stem cells in their relation to epileptogenesis in mesial temporal lobe epilepsy. Further, with the significant discovery of factors necessary to reprogram adult somatic cell types into pluripotent stem cells, it has become possible to study monogenic epilepsy-in-a-dish using patient-derived neurons. This discovery along with some of the newest technological advances in recapitulating brain development in a dish has brought us closer than ever to a platform in which to study and understand the mechanisms of this disease. These technologies will be critical in understanding the mechanism of epileptogenesis and ultimately lead to improved therapies and precision medicine for patients with epilepsy.

Anti-epileptic Effects of Valepotriate Isolated from Valeriana jatamansi Jones and Its Possible Mechanisms

Objective:

This work aimed to investigate the anti-epileptic effects of valepotriate isolated from Valeriana jatamansi Jones and studied its possible mechanisms.

Methods:

The anti-epileptic effects of valepotriate were studied using maximal electroshock-induced seizure (MES), pentylenetetrazole (PTZ)-induced epilepsy, and pentobarbital sodium-induced sleeping model in mice. The possible anti-epileptic mechanisms of valepotriate were investigated by analyzing the expressions of GABA_A, GABA_B, glutamic acid decarboxylase (GAD65), Bcl-2, and caspase-3 in the brain using Western blot assay.

Results:

The results indicated that valepotriate showed significant anti-epileptic activity against MES- and PTZ-induced epilepsy at doses of 5, 10, and 20 mg/kg, and ED₅₀ values for MES- and PTZ-induced epilepsy were 7.84 and 7.19 mg/kg, respectively. Furthermore, valepotriate (10 and 20 mg/kg) can significantly prolong sleeping time and shorten the latency time on the pentobarbital sodium-induced sleeping time test. Furthermore, valepotriate (5, 10, and 20 mg/kg) could significantly up-regulate the expression of GABA_A, GAD65, and Bcl-2 and down-regulate the expression of caspase-3, but had no significant effect on the expression of GABA_B.

Conclusion:

The results indicated that valepotriate had anti-epileptic activity and the mechanisms might be associated with regulation of GABA and inhibition of neuronal apoptosis.

SUMMARY

Anti-epileptic effect of valepotriate was investigated for the 1^st time

Valepotriate showed notable anti-epileptic activity

Valepotriate can significantly increase the expression of GABA_A, glutamic acid decarboxylase 65, and Bcl-2 and reduce the expression of caspase-3.

Enhanced AMPA receptor-mediated neurotransmission on CA1 pyramidal neurons during status epilepticus

Status epilepticus (SE) is a common neurological emergency that results from the failure of the mechanisms responsible for seizure termination or the initiation of mechanisms that lead to abnormally prolonged seizures. Although the failure of inhibitory mechanisms during SE is well understood, the seizure-initiating mechanisms are poorly understood. We tested whether hippocampal α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated transmission was enhanced during SE and assessed the underlying molecular mechanism. In animals in self-sustaining limbic SE the amplitudes of the miniature, spontaneous, and AMPA-evoked excitatory currents recorded from the CA1 pyramidal neurons were larger than those recorded in the controls. The evoked EPSCs rectified inwardly. In these animals, the surface expression of GluA1 subunit-containing AMPARs was increased in the CA1 pyramidal neurons. The phosphorylation of the GluA1 subunit on S831 and S845 residues was reduced in animals in SE. In contrast, the GluA1 subunit surface expression and AMPAR-mediated neurotransmission of dentate granule cells (DGCs) was not altered. Treating animals in SE with the NMDAR antagonist MK-801 or with diazaepam blocked the increased surface expression of the GluA1 subunits. NMDAR blockade also prevented the dephosphorylation of the S845 residue but not that of S831. Targeting NMDARs and AMPARs may provide novel strategies to treat benzodiazepine-refractory SE.

Status Epilepticus and Beyond: A Clinical Review of Status Epilepticus and an Update on Current Management Strategies in Super-refractory Status Epilepticus

Status epilepticus and refractory status epilepticus represent some of the most complex conditions encountered in the neurological intensive care unit. Challenges in management are common as treatment options become limited and prolonged hospital courses are accompanied by complications and worsening patient outcomes. Antiepileptic drug treatments have become increasingly complex. Rational polytherapy should consider the pharmacodynamics and kinetics of medications. When seizures cannot be controlled with medical therapy, alternative treatments, including early surgical evaluation can be considered; however, evidence is limited. This review provides a brief overview of status epilepticus, and a recent update on the management of refractory status epilepticus based on evidence from the literature, evidence-based guidelines, and experiences at our institution.

Management of status epilepticus

Status epilepticus is a neurologic and medical emergency manifested by prolonged seizure activity or multiple seizures without return to baseline. It is associated with substantial medical cost, morbidity, and mortality. There is a spectrum of severity dependent on the type of seizure, underlying pathology, comorbidities, and appropriate and timely medical management. This chapter discusses the evolving definitions of status epilepticus and multiple patient and clinical factors which influence outcome. The pathophysiology of status epilepticus is reviewed to provide a better understanding of the mechanisms which contribute to status epilepticus, as well as the potential long-term effects. The clinical presentations of different types of status epilepticus in adults are discussed, with emphasis on the hospital course and management of the most dangerous type, generalized convulsive status epilepticus. Strategies for the evaluation and management of status epilepticus are provided based on available evidence from clinical trials and recommendations from the Neurocritical Care Society and the European Federation of Neurological Societies.

Mesial Temporal Lobe Epilepsy: Pathogenesis, Induced Rodent Models and Lesions

Mesial temporal lobe epilepsy (MTLE), the most common epilepsy in adults, is generally intractable and is suspected to be the result of recurrent excitation or inhibition circuitry. Recurrent excitation and the development of seizures have been associated with aberrant mossy fiber sprouting in the hippocampus. Of the animal models developed to investigate the pathogenesis of MTLE, post-status epilepticus models have received the greatest acceptance because they are characterized by a latency period, the development of spontaneous motor seizures, and a spectrum of lesions like those of MTLE. Among post-status epilepticus models, induction of systemic kainic acid or pilocarpine-induced epilepsy is less labor-intensive than electrical-stimulation models and these models mirror the clinicopathologic features of MTLE more closely than do kindling, tetanus toxin, hyperthermia, post-traumatic, and perinatal hypoxia/ischemia models. Unfortunately, spontaneous motor seizures do not develop in kindling or adult hyperthermia models and are not a consistent finding in tetanus toxin-induced or perinatal hypoxia/ischemia models. This review presents the mechanistic hypotheses for seizure induction, means of model induction, and associated pathology, especially as compared to MTLE patients. Animal models are valuable tools not only to study the pathogenesis of MTLE, but also to evaluate potential antiepileptogenic drugs.

Relationship between seizure frequency and number of neuronal and non-neuronal cells in the hippocampus throughout the life of rats with epilepsy

The relationship between seizure frequency and cell death has been a subject of controversy. To tackle this issue, we determined the frequency of seizures and the total number of hippocampal cells throughout the life of rats with epilepsy using the pilocarpine model. Seizure frequency varied in animals with epilepsy according to which period of life they were in, with a progressive increase in the number of seizures until 180 days (sixth months) of epileptic life followed by a decrease (330 days-eleventh month) and subsequently stabilization of seizures. Cell counts by means of isotropic fractionation showed a reduction in the number of hippocampal neuronal cells following 30, 90, 180 and 360 days of spontaneous recurrent seizures (SRS) in rats compared to their controls (about 25%-30% of neuronal cell reduction). In addition, animals with 360 days of SRS showed a reduction in the number of neuronal cells when compared with animals with 90 and 180 days of seizures. The total number of hippocampal non-neuronal cells was reduced in rats with epilepsy after 30 days of SRS, but no significant alteration was observed on the 90th, 180th and 360th days. The total number of neuronal cells was negatively correlated with seizure frequency, indicating an association between occurrence of epileptic seizures throughout life and neuronal loss. In sum, our results add novel data to the literature concerning the time-course of SRS and hippocampal cell number throughout epileptic life.

Mitochondrial respiration deficits driven by reactive oxygen species in experimental temporal lobe epilepsy

Metabolic alterations have been implicated in the etiology of temporal lobe epilepsy (TLE), but whether or not they have a functional impact on cellular energy producing pathways (glycolysis and/or oxidative phosphorylation) is unknown. The goal of this study was to determine if alterations in cellular bioenergetics occur using real-time analysis of mitochondrial oxygen consumption and glycolytic rates in an animal model of TLE. We hypothesized that increased steady-state levels of reactive oxygen species (ROS) initiated by epileptogenic injury result in impaired mitochondrial respiration. We established methodology for assessment of bioenergetic parameters in isolated synaptosomes from the hippocampus of Sprague-Dawley rats at various times in the kainate (KA) model of TLE. Deficits in indices of mitochondrial respiration were observed at time points corresponding with the acute and chronic phases of epileptogenesis. We asked if mitochondrial bioenergetic dysfunction occurred as a result of increased mitochondrial ROS and if it could be attenuated in the KA model by pharmacologically scavenging ROS. Increased steady-state ROS in mice with forebrain-specific conditional deletion of manganese superoxide dismutase (Sod2(fl/fl)NEX(Cre/Cre)) in mice resulted in profound deficits in mitochondrial oxygen consumption. Pharmacological scavenging of ROS with a catalytic antioxidant restored mitochondrial respiration deficits in the KA model of TLE. Together, these results demonstrate that mitochondrial respiration deficits occur in experimental TLE and ROS mechanistically contribute to these deficits. Furthermore, this study provides novel methodology for assessing cellular metabolism during the entire time course of disease development.

Profiling status epilepticus-induced changes in hippocampal RNA expression using high-throughput RNA sequencing

Status epilepticus (SE) is a life-threatening condition that can give rise to a number of neurological disorders, including learning deficits, depression, and epilepsy. Many of the effects of SE appear to be mediated by alterations in gene expression. To gain deeper insight into how SE affects the transcriptome, we employed the pilocarpine SE model in mice and Illumina-based high-throughput sequencing to characterize alterations in gene expression from the induction of SE, to the development of spontaneous seizure activity. While some genes were upregulated over the entire course of the pathological progression, each of the three sequenced time points (12-hour, 10-days and 6-weeks post-SE) had a largely unique transcriptional profile. Hence, genes that regulate synaptic physiology and transcription were most prominently altered at 12-hours post-SE; at 10-days post-SE, marked changes in metabolic and homeostatic gene expression were detected; at 6-weeks, substantial changes in the expression of cell excitability and morphogenesis genes were detected. At the level of cell signaling, KEGG analysis revealed dynamic changes within the MAPK pathways, as well as in CREB-associated gene expression. Notably, the inducible expression of several noncoding transcripts was also detected. These findings offer potential new insights into the cellular events that shape SE-evoked pathology.

Histamine H3 receptor antagonism by ABT-239 attenuates kainic acid induced excitotoxicity in mice

The multifaceted pathogenesis of temporal lobe epilepsy (TLE) offers a number of adjunctive therapeutic prospects. One such therapeutic strategy could be targeting H3 receptor (H3R) by selective H3R antagonists which are perceived to have antiepileptic and neuroprotective potential. Kainic acid (KA) induced seizure, a reliable model of TLE, triggers epileptogenic events resulting from initial neuronal death and ensuing recurring seizures. The present study aimed to determine whether pre-treatment with ABT-239, a novel H3R antagonist, and its combinations with sodium valproate (SVP) and TDZD-8 (glycogen synthase kinase-3β (GSK3β) inhibitor) can prevent the excitotoxic events in mice exposed to KA (10 mg/kg i.p.). ABT-239 (1 and 3 mg/kg i.p.) significantly attenuated KA-mediated behavioural and excitotoxic anomalies and restored altered expression of Bax, cleaved caspase-3, phospho-Akt (Ser473) and cAMP response element binding protein (CREB). Surprisingly, restoration of Bcl2 and phospho-GSK3β (Ser9) by ABT-239 did not reach the level of statistical significance. Co-administration of ABT-239 (1 and 3 mg/kg) with a sub-effective dose of SVP (150 mg/kg i.p.) yielded improved efficacy than when given alone. Similarly, low and high dose combinations of ABT-239 (1 and 3 mg/kg) with TDZD-8 (5 and 10 mg/kg i.p.) produced greater neuroprotection than any other treatment group. Our findings suggests a neuroprotective potential of ABT-239 and its combinations with SVP and TDZD-8 against KA-induced neurotoxicity, possibly mediated through in part each by modulating Akt/GSK3β and CREB pathways. The use of H3R antagonists as adjuvant in the treatment of human TLE might find potential utility, and can be pursued further.

Diagnostic yield of electroencephalography in the medical and surgical intensive care unit

BACKGROUND

To determine the incidence of electrographic seizures during continuous electroencephalography (cEEG) in the medical and surgical ICU.

METHODS

We retrospectively reviewed the records of all adults who underwent cEEG in our medical and surgical ICU over a 4.5 year period. Patients with acute brain injury were excluded. Our primary outcome was cEEG documentation of an electrographic seizure, defined as a rhythmic discharge or spike and wave pattern demonstrating definite evolution and lasting at least 10 s. To assess inter-rater variability in cEEG interpretation, two electrophysiologists independently reviewed all available cEEGs of subjects with electrographic seizures documented on their clinical cEEG report and those of an equal number of randomly selected subjects from the remaining cohort.

RESULTS

Kappa analysis showed a value of 0.88, indicating excellent inter-rater agreement. Electrographic seizures were identified in 12 of 105 patients (11 %, 95 % CI 5-18 %). This rate did not change after excluding patients with a history of seizure, remote brain injury, or seizure-like events before cEEG. In an ordinal logistic regression model controlling for age, sex, and SOFA score, electrographic seizures were associated with lower odds of good outcomes on the Glasgow Outcome Scale at discharge (OR 0.3, 95 % CI 0.1-0.8).

CONCLUSION

In a tertiary care medical and surgical ICU, electrographic seizures were seen on 11 % of cEEGs ordered for the evaluation of encephalopathy, and were associated with worse functional outcomes at discharge. Our findings confirm the results of a prior study suggesting a substantial burden of electrographic seizures in critically ill encephalopathic patients.

The SHH/Gli pathway is reactivated in reactive glia and drives proliferation in response to neurodegeneration-induced lesions

In response to neurodegeneration, the adult mammalian brain activates a cellular cascade that results in reactive astrogliosis and microgliosis. The mechanism through which astrocytes become reactive and the physiological consequences of their activation in response to neurodegeneration is complex. While the activation and proliferation of astrocytes has been shown to occur during massive neuronal cell death, the functional relationship between these two events has not been clearly elucidated. Here we show that in response to kainic acid- (KA) induced neurodegeneration, the mitogen sonic hedgehog (SHH) is upregulated in reactive astrocytes. SHH activity peaks at 7 days and is accompanied by increased Gli activity and elevated proliferation in several cell types. To determine the functional role of SHH-Gli signaling following KA lesions, we used a pharmacological approach to show that SHH secreted by astrocytes drives the activation and proliferation of astrocytes and microglia. The consequences of SHH-Gli signaling in KA-induced lesions appear to be independent of the severity of neurodegeneration.

Fosb gene products contribute to excitotoxic microglial activation by regulating the expression of complement C5a receptors in microglia

The Fosb gene encodes subunits of the activator protein-1 transcription factor complex. Two mature mRNAs, Fosb and ΔFosb, encoding full-length FOSB and ΔFOSB proteins respectively, are formed by alternative splicing of Fosb mRNA. Fosb products are expressed in several brain regions. Moreover, Fosb-null mice exhibit depressive-like behaviors and adult-onset spontaneous epilepsy, demonstrating important roles in neurological and psychiatric disorders. Study of Fosb products has focused almost exclusively on neurons; their function in glial cells remains to be explored. In this study, we found that microglia express equivalent levels of Fosb and ΔFosb mRNAs to hippocampal neurons and, using microarray analysis, we identified six microglial genes whose expression is dependent on Fosb products. Of these genes, we focused on C5ar1 and C5ar2, which encode receptors for complement C5a. In isolated Fosb-null microglia, chemotactic responsiveness toward the truncated form of C5a was significantly lower than that in wild-type cells. Fosb-null mice were significantly resistant to kainate-induced seizures compared with wild-type mice. C5ar1 mRNA levels and C5aR1 immunoreactivity were increased in wild-type hippocampus 24 hours after kainate administration; however, such induction was significantly reduced in Fosb-null hippocampus. Furthermore, microglial activation after kainate administration was significantly diminished in Fosb-null hippocampus, as shown by significant reductions in CD68 immunoreactivity, morphological change and reduced levels of Il6 and Tnf mRNAs, although no change in the number of Iba-1-positive cells was observed. These findings demonstrate that, under excitotoxicity, Fosb products contribute to a neuroinflammatory response in the hippocampus through regulation of microglial C5ar1 and C5ar2 expression.

Selective androgen receptor modulator RAD140 is neuroprotective in cultured neurons and kainate-lesioned male rats

The decline in testosterone levels in men during normal aging increases risks of dysfunction and disease in androgen-responsive tissues, including brain. The use of testosterone therapy has the potential to increase the risks for developing prostate cancer and or accelerating its progression. To overcome this limitation, novel compounds termed "selective androgen receptor modulators" (SARMs) have been developed that lack significant androgen action in prostate but exert agonist effects in select androgen-responsive tissues. The efficacy of SARMs in brain is largely unknown. In this study, we investigate the SARM RAD140 in cultured rat neurons and male rat brain for its ability to provide neuroprotection, an important neural action of endogenous androgens that is relevant to neural health and resilience to neurodegenerative diseases. In cultured hippocampal neurons, RAD140 was as effective as testosterone in reducing cell death induced by apoptotic insults. Mechanistically, RAD140 neuroprotection was dependent upon MAPK signaling, as evidenced by elevation of ERK phosphorylation and inhibition of protection by the MAPK kinase inhibitor U0126. Importantly, RAD140 was also neuroprotective in vivo using the rat kainate lesion model. In experiments with gonadectomized, adult male rats, RAD140 was shown to exhibit peripheral tissue-specific androgen action that largely spared prostate, neural efficacy as demonstrated by activation of androgenic gene regulation effects, and neuroprotection of hippocampal neurons against cell death caused by systemic administration of the excitotoxin kainate. These novel findings demonstrate initial preclinical efficacy of a SARM in neuroprotective actions relevant to Alzheimer's disease and related neurodegenerative diseases.

When and how do seizures kill neurons, and is cell death relevant to epileptogenesis?

The effect of seizures on neuronal death and the role of seizure-induced neuronal death in acquired epileptogenesis have been debated for decades. Isolated brief seizures probably do not kill neurons; however, severe and repetitive seizures (i.e., status epilepticus) certainly do. Because status epilepticus both kills neurons and also leads to chronic epilepsy, neuronal death has been proposed to be an integral part of acquired epileptogenesis. Several studies, particularly in the immature brain, have suggested that neuronal death is not necessary for acquired epileptogenesis; however, the lack of neuronal death is difficult if not impossible to prove, and more recent studies have challenged this concept. Novel mechanisms of cell death, beyond the traditional concepts of necrosis and apoptosis, include autophagy, phagoptosis, necroptosis, and pyroptosis. The traditional proposal for why neuronal death may be necessary for epileptogenesis is based on the recapitulation of development hypothesis, where a loss of synaptic input from the dying neurons is considered a critical signal to induce axonal sprouting and synaptic-circuit reorganization. We propose a second hypothesis - the neuronal death pathway hypothesis, which states that the biochemical pathways causing programmed neurodegeneration, rather than neuronal death per se, are responsible for or contribute to epileptogenesis. The reprogramming of neuronal death pathways - if true - is proposed to derive from necroptosis or pyroptosis. The proposed new hypothesis may inform on why neuronal death seems closely linked to epileptogenesis, but may not always be.

The effect of STAT3 inhibition on status epilepticus and subsequent spontaneous seizures in the pilocarpine model of acquired epilepsy

Pilocarpine-induced status epilepticus (SE), which results in temporal lobe epilepsy (TLE) in rodents, activates the JAK/STAT pathway. In the current study, we evaluate whether brief exposure to a selective inhibitor of the JAK/STAT pathway (WP1066) early after the onset of SE affects the severity of SE or reduces later spontaneous seizure frequency via inhibition of STAT3-regulated gene transcription. Rats that received systemic WP1066 or vehicle at the onset of SE were continuously video-EEG monitored during SE and for one month to assess seizure frequency over time. Protein and/or mRNA levels for pSTAT3, and STAT3-regulated genes including: ICER, Gabra1, c-myc, mcl-1, cyclin D1, and bcl-xl were evaluated in WP1066 and vehicle-treated rats during stages of epileptogenesis to determine the acute effects of WP1066 administration on SE and chronic epilepsy. WP1066 (two 50mg/kg doses) administered within the first hour after onset of SE results in transient inhibition of pSTAT3 and long-term reduction in spontaneous seizure frequency. WP1066 alters the severity of chronic epilepsy without affecting SE or cell death. Early WP1066 administration reduces known downstream targets of STAT3 transcription 24h after SE including cyclin D1 and mcl-1 levels, known for their roles in cell-cycle progression and cell survival, respectively. These findings uncover a potential effect of the JAK/STAT pathway after brain injury that is physiologically important and may provide a new therapeutic target that can be harnessed for the prevention of epilepsy development and/or progression.

Neuronal degeneration is observed in multiple regions outside the hippocampus after lithium pilocarpine-induced status epilepticus in the immature rat

Although hippocampal sclerosis is frequently identified as a possible epileptic focus in patients with temporal lobe epilepsy, neuronal loss has also been observed in additional structures, including areas outside the temporal lobe. The claim from several researchers using animal models of acquired epilepsy that the immature brain can develop epilepsy without evidence of hippocampal neuronal death raises the possibility that neuronal death in some of these other regions may also be important for epileptogenesis. The present study used the lithium pilocarpine model of acquired epilepsy in immature animals to assess which structures outside the hippocampus are injured acutely after status epilepticus. Sprague-Dawley rat pups were implanted with surface EEG electrodes, and status epilepticus was induced at 20 days of age with lithium pilocarpine. After 72 h, brain tissue from 12 animals was examined with Fluoro-Jade B, a histochemical marker for degenerating neurons. All animals that had confirmed status epilepticus demonstrated Fluoro-Jade B staining in areas outside the hippocampus. The most prominent staining was seen in the thalamus (mediodorsal, paratenial, reuniens, and ventral lateral geniculate nuclei), amygdala (ventral lateral, posteromedial, and basomedial nuclei), ventral premammillary nuclei of hypothalamus, and paralimbic cortices (perirhinal, entorhinal, and piriform) as well as parasubiculum and dorsal endopiriform nuclei. These results demonstrate that lithium pilocarpine-induced status epilepticus in the immature rat brain consistently results in neuronal injury in several distinct areas outside of the hippocampus. Many of these regions are similar to areas damaged in patients with temporal lobe epilepsy, thus suggesting a possible role in epileptogenesis.

X-ray irradiation promotes apoptosis of hippocampal neurons through up-regulation of Cdk5 and p25

BACKGROUND

Cranial radiation therapy has been used for the treatment of primary and metastatic brain tumors. A prominent feature of brain injury induced by the radiation therapy is hippocampal dysfunction, characterized by a decline in memory. Cdk5 plays an important role in memory formation. Abnormal Cdk5 activity is associated with neuronal apoptosis induced by neurotoxic stimuli. However, the roles of Cdk5 in hippocampal apoptosis in response to X-ray irradiation have not been explored.

METHODS

The expression of Cdk5 activators, p35 and p25, in hippocampal neurons was tested in both in vivo animal and in vitro couture after X-ray irradiation.

RESULTS

After X-ray irradiation at 20 Gy and 30 Gy in rats, the number of hippocampal neuronal pyknosis was increased, but the number of hippocampal neuron was decreased, in the hippocampal CA1 region of rats. In these animals undergone with X-ray irradiation, the expression of p35 was significantly down-regulated, but it was up-regulated in p25. These opposite expressions were also shown in the primary cultured hippocampal neurons with 30 Gy irradiation. The apoptosis induced by X-ray irradiation were significantly prevented by the pretreatment of Cdk5 inhibitor, roscovitine, in both in vivo and in vitro settings.

CONCLUSIONS

X-ray irradiation resulted in a hippocampal neuronal apoptosis through up-regulation of p25, the Cdk5 activator. Hyperactivity of Cdk5 was involved in the pathogenesis of X-ray irradiation-induced hippocampal neuronal apoptosis. Blockade of Cdk5 signal pathway effectively protected neurons from the irradiation-induced brain injury.

Kainic acid-induced seizure activity alters the mRNA expression and G-protein activation of the opioid/nociceptin receptors in the rat brain cortex

The opioid/nociceptin receptors are involved in many neurological disorders such as Alzheimer's disease, Parkinson's disease and epilepsy. Kainic acid (KA) is an analog of the excitatory amino acid transmitter glutamate and the systemic administration of KA induces status epilepticus (SE) in rodents. In this study, we examined the alterations in the G-protein activity and the gene expression levels of mu, kappa, delta opioid and nociceptin receptors (MOPr, KOPr, DOPr and NOPr) as well as PNOC, the precursor polypeptide of nociceptin-OFQ (N/OFQ) in KA-induced seizures in the rat brain cortex. KA was used to create seizures with the dose of 10 mg/kg body weight i.p. Following the KA administration, the rats were observed for 3 h to assess seizure activity. Seizures occurred approximately 45 min after the KA injection. Only rats exhibiting full limbic seizures, forelimb clonus with rearing, were used in this study. All animals were decapitated 4 h after the administration of KA. Our [(35)S]GTPγS binding results showed that there was a significant difference in both the affinity and efficacy particularly one of NOPr stimulation following KA treatment. Slight, but significant increase was observed for MOPr. Moreover PNOC, NOPr and MOPr mRNA levels were increased by KA treatment but there were no significant changes in the levels of DOPr and KOPr mRNAs. These results show that the activities of opioid/nociceptin receptors can be modified by KA-treatment, and MOPr, PNOC and NOPr are the most responsive to KA-induced seizures in the rat brain cortex.

Uncaria rhynchophylla (Miq) Jack Plays a Role in Neuronal Protection in Kainic Acid-Treated Rats

Uncaria rhynchophylla (Miq) Jack (UR) is one of many Chinese herbs. Our previous studies have shown that UR has both anticonvulsive and free radical-scavenging activities in kainic acid (KA)-treated rats. The aim of the present study was to use the effect of UR on activated microglia, nitric oxide synthase, and apoptotic cells to investigate its function in neuroproction in KA-treated rats. UR of 1.0 or 0.5 g/kg was orally administered for 3 days (first day, second day, and 30 min prior to KA administration on the third day), or 10 mg/kg (intraperitoneal injection, i.p.) N-nitro-L-arginine methyl ester (L-NAME) 30 min prior to KA (2 μg/2 μl) was injected into the right hippocampus region of Sprague-Dawly rats. ED1 (mouse anti rat CD68), neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS) immunoreactive cells and apoptotic cells were observed in the hippocampus region. The results indicated that 1.0 g/kg, 0.5 g/kg of UR and 10 mg/kg of L-NAME reduced the counts of ED1, nNOS, iNOS immunoreactive cells and apoptotic cells in KA-treated rats. This study demonstrates that UR can reduce microglia activation, nNOS, iNOS and apoptosis, suggesting that UR plays a neuro-protective role against neuronal damage in KA-treated rats.

Lithium pilocarpine-induced status epilepticus in postnatal day 20 rats results in greater neuronal injury in ventral versus dorsal hippocampus

Many quantitative animal studies examining the possible relationship between hippocampal neuronal loss and the development of epilepsy have examined only the dorsal hippocampus. The ventral hippocampus, however, represents the more homologous structure to the anterior hippocampus in humans, which is the area associated with the maximal damage in patients with temporal lobe epilepsy. This study tested the hypothesis that the ventral hippocampus has greater neuronal injury than the dorsal hippocampus in an animal model of chemoconvulsant-status epilepticus at postnatal day 20. Status epilepticus was induced in postnatal day 20 Sprague-Dawley rat pups with the chemoconvulsant lithium-pilocarpine and brain tissue was examined with Fluoro-Jade B. Horizontal sections (n=7) favoring a visualization of the ventral hippocampus showed marked Fluoro-Jade B staining in CA1, CA3, and hilar region. Coronal sections favoring a visualization of the dorsal hippocampus did not consistently show as robust a staining pattern in these regions. In coronal sections where both the dorsal and ventral hippocampus could be viewed, greater staining was always seen in ventral versus dorsal hippocampus. Quantitative analysis of cell counts demonstrated a significant difference between ventral and dorsal hippocampus in CA1 and CA3, but not hilus. These results demonstrate that in ventral hippocampus, lithium pilocarpine-induced status epilepticus consistently results in hippocampal neuronal injury in postnatal day 20 rats. This study shows the importance of including the ventral hippocampus in any analysis of seizure-induced hippocampal neuronal injury, and raises concerns about the accuracy of studies quantifying hippocampal neuronal loss when only the dorsal hippocampus is examined.

Visualization of spatiotemporal energy dynamics of hippocampal neurons by mass spectrometry during a kainate-induced seizure

We report the use of matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry combined with capillary electrophoresis (CE) mass spectrometry to visualize energy metabolism in the mouse hippocampus by imaging energy-related metabolites. We show the distribution patterns of ATP, ADP, and AMP in the hippocampus as well as changes in their amounts and distribution patterns in a murine model of limbic, kainate-induced seizure. As an acute response to kainate administration, we found massive and moderate reductions in ATP and ADP levels, respectively, but no significant changes in AMP levels--especially in cells of the CA3 layer. The results suggest the existence of CA3 neuron-selective energy metabolism at the anhydride bonds of ATP and ADP in the hippocampal neurons during seizure. In addition, metabolome analysis of energy synthesis pathways indicates accelerated glycolysis and possibly TCA cycle activity during seizure, presumably due to the depletion of ATP. Consistent with this result, the observed energy depletion significantly recovered up to 180 min after kainate administration. However, the recovery rate was remarkably low in part of the data-pixel population in the CA3 cell layer region, which likely reflects acute and CA3-selective neural death. Taken together, the present approach successfully revealed the spatiotemporal energy metabolism of the mouse hippocampus at a cellular resolution--both quantitatively and qualitatively. We aim to further elucidate various metabolic processes in the neural system.

Effects of kainic acid lesions of the cerebellar interpositus and dentate nuclei on amygdaloid kindling in rats

Some neurophysiological studies suggest that the cerebellum could participate in epileptic activity. Therefore, to study the participation of the main efferent projections from the cerebellum to the forebrain, we injected small doses of kainic acid (KA) into the deep cerebellar nuclei to selectively injure neighboring cells while avoiding fiber lesions. Uninjured fibers were confirmed using histological findings and by assessing the number of cells in the main cerebellar afferents, compared with controls. Under such conditions, we found that dentate and interpositus nuclei lesions interfere with seizure expression, both at early kindling acquisition and at the kindled stage. We hypothesize that the cerebellar effect on epilepsy drives skeletal motor responses, mainly in generalized seizures when the thalamus and neocortex are affected.

Overexpression of μ-calpain in the anterior temporal neocortex of patients with intractable epilepsy correlates with clinicopathological characteristics

PURPOSE

This study aims to investigate μ-calpain expression profiles in the anterior temporal neocortex in patients with intractable epilepsy, and to determine whether its pattern of expression is related to pathological changes seen in these patients.

METHODS

The study subjects consisted of 30 patients with intractable epilepsy and a control group of 10 patients with brain trauma who underwent resection of the anterior temporal lobe. μ-Calpain expression in surgically resected anterior temporal cortices of patients with intractable epilepsy were analyzed using the RT-PCR, Western blot, immunohistochemistry and immunofluorescence staining. GFAP expression was detected by immunohistochemical staining. The related pro-inflammatory cytokines were quantified by elisa. Clinicopathological characteristics were evaluated by HE staining.

RESULTS

Analysis by Western blot and RT-PCR revealed that inactive μ-calpain expression and the calpain-cleaved spectrin fragment in surgically resected anterior temporal cortices of patients with intractable epilepsy were significantly increased compared to the tissues from corresponding regions of the control group. Immunohistological staining demonstrated that μ-calpain was overexpressed in the cell cytoplasm of neurons and glial cells in patients with intractable epilepsy and GFAP was overexpressed in the cell cytoplasm of glial cells in patients with intractable epilepsy. The level of pro-inflammatory cytokines, such as IL-1β, IL-6 and TGF-β1 were significantly increased in patients with intractable epilepsy. HE staining indicated μ-calpain overexpression is an independent prognostic factor for pathological changes such as neuronal loss, neuronal degeneration, gliosis and astrocytosis.

CONCLUSION

These data suggest that overexpression of μ-calpain is relationship with intractable epilepsy as well as the clinicopathological characteristics in these patients.

Involvement of IRE1α signaling in the hippocampus in patients with mesial temporal lobe epilepsy

Cumulative evidence suggests that programmed cell death (apoptosis) may contribute to the progressive hippocampal sclerosis seen in patients with refractory mesial temporal lobe epilepsy (MTLE). The endoplasmic reticulum (ER) stress-mediated cell apoptotic pathway has recently emerged as a vital intrinsic pathway, but the molecular mechanisms underlying this process in the epileptic brain remain unclear. We investigated inositol-requiring protein 1α (IRE1α)-mediated ER stress pro-and anti-apoptotic signaling pathways in resected hippocampi from 32 patients with intractable MTLE. Immunoreactivity for the ER stress markers glucose-regulated proteins 78 and 94 was significantly higher in MTLE hippocampi than in controls. The levels of IRE1α, tumor necrosis factor receptor associated factor 2 (TRAF2), apoptosis signal-regulating kinase 1 (ASK1) and c-Jun N-terminal kinase (JNK), which together constitute the IRE1α/TRAF2/ASK1/JNK pro-apoptotic signaling pathway, were significantly upregulated in patients with MTLE. Immunoreactivity for caspase-4, a homologue of caspase-12 that is possibly activated by IRE1α via TRAF2 following ER stress, and caspase-3 which was a downstream effector of caspase-4, were both detected in MTLE tissue samples. In contrast, immunoreactivity for caspase-4 and caspase-3 were low or absent in control samples. Simultaneously, the X-box binding protein 1 (XBP1), a basic leucine zipper (bZIP) family transcription factor downstream of IRE1α which can promote cell survival by upregulation of multiple ER-targeted genes, was also overexpressed and activated in MTLE hippocampi. Our data suggest that chronic epilepsy is associated with ER stress, as well as induction of both IRE1α-mediated pro- and anti-apoptotic signaling pathways.

Kainic acid-induced microglial activation is attenuated in aged interleukin-18 deficient mice

Background

Previously, we found that interleukin (IL)-18 deficiency aggravates kainic acid (KA)-induced hippocampal neurodegeneration in young C57BL/6 mice due to an over-compensation by IL-12. Additionally, IL-18 participates in fundamental inflammatory processes that increase during aging. In the present study, we were interested in the role of IL-18 in KA-induced neurodegeneration in aged female C57BL/6 mice.

Methods

Fifteen aged female IL-18 knockout (KO) and 15 age-matched wild-type (WT) mice (18 to 19 months old) were treated with KA at a dose of 25 mg/kg body weight intranasally. Seizure activities and behavioral changes were rated using a 6-point scoring system and open-field test, respectively. Seven days after KA treatment, degenerating neurons were detected by Nissl's method and Fluoro-Jade B staining; and microglial activation was analyzed by immunohistochemistry and flow cytometry.

Results

Aged female IL-18 KO and WT mice showed similar responses to treatment with KA as demonstrated by comparable seizure activities, behavioral changes and neuronal cell death. However, aged female IL-18 KO mice failed to exhibit the strong microglial activation shown in WT mice. Interestingly, even though the number of activated microglia was less in KA-treated IL-18 KO mice than in KA-treated WT mice, the proportion of microglia that expressed the cytokines tumor necrosis factor (TNF)-α, IL-6 and IL-10 was higher in KA-treated IL-18 KO mice.

Conclusion

Deficiency of IL-18 attenuates microglial activation after KA-induced excitotoxicity in aged brain, while the net effects of IL-18 deficiency are balanced by the enhancement of other cytokines, such as TNF-α, IL-6 and IL-10.

Selective vulnerability of hippocampal cornu ammonis 1 pyramidal cells to excitotoxic insult is associated with the expression of polyamine-sensitive N-methyl-D-asparate-type glutamate receptors

Excess glutamate release and stimulation of post-synaptic glutamatergic receptors have been implicated in the pathophysiology of many neurological diseases. The hippocampus, and the pyramidal cell layer of the cornu ammonus 1 (CA1) region in particular, has been noted for its selective sensitivity to excitotoxic insults. The current studies examined the role of N-methyl-D-aspartate (NMDA) receptor subunit composition and sensitivity to stimulatory effects of the polyamine spermidine, an allosteric modulator of NMDA NR2 subunit activity, in hippocampal CA1 region sensitivity to excitotoxic insult. Organotypic hippocampal slice cultures of 8 day-old neonatal rat were obtained and maintained in vitro for 5 days. At this time, immunohistochemical analysis of mature neuron density (NeuN); microtubule associated protein-2(a,b) density (MAP-2); and NMDA receptor NR1 and NR2B subunit density in the primary cell layers of the dentate gyrus (DG), CA3, and CA1 regions, was conducted. Further, autoradiographic analysis of NMDA receptor distribution and density (i.e. [(125)I]MK-801 binding) and spermidine (100 microM)-potentiated [(125)I]MK-801 binding in the primary cell layers of these regions was examined. A final series of studies examined effects of prolonged exposure to NMDA (0.1-10 microM) on neurodegeneration in the primary cell layers of the DG, CA3, and CA1 regions, in the absence and presence of spermidine (100 microM) or ifenprodil (100 microM), an allosteric inhibitor of NR2B polypeptide subunit activity. The pyramidal cell layer of the CA1 region demonstrated significantly greater density of mature neurons, MAP-2, NR1 and NR2B subunits, and [(125)I]MK-801 binding than the CA3 region or DG. Twenty-four hour NMDA (10 microM) exposure produced marked neurodegeneration (approximately 350% of control cultures) in the CA1 pyramidal cell region that was significantly reduced by co-exposure to ifenprodil or DL-2-Amino-5-phosphonopentanoic acid (APV). The addition of spermidine significantly potentiated [(125)I]MK-801 binding and neurodegeneration induced by exposure to a non-toxic concentration of NMDA, exclusively in the CA1 region. This neurodegeneration was markedly reduced with co-exposure to ifenprodil. These data suggest that selective sensitivity of the CA1 region to excitotoxic stimuli may be attributable to the density of mature neurons expressing polyamine-sensitive NR2B polypeptide subunits.

Allopregnanolone, the active metabolite of progesterone protects against neuronal damage in picrotoxin-induced seizure model in mice

Progesterone exerts anti-seizure effect against several chemoconvulsants. However, there is no published report on the interaction between progesterone and picrotoxin (PTX). The present study evaluated the effects of progesterone and its active metabolite, allopregnanolone against PTX-induced seizures, brain lipid peroxidation and DNA fragmentation in male mice. Finasteride, a 5alpha-reductase inhibitor and indomethacin, an inhibitor of 3infinity-hydroxysteroid dehydrogenase were assessed against progesterone's effects on PTX-induced seizures, brain lipid peroxidation and DNA fragmentation. PTX produced clonic-tonic seizures in mice with CD50 and CD97 of 2.4 and 4.0mg/kg, i.p. respectively. Progesterone significantly countered PTX-induced seizures, with ED50 of 78.30mg/kg and ED97 of 200mg/kg. Progesterone antagonized PTX-induced DNA fragmentation. Finasteride (200mg/kg) and indomethacin (1mg/kg) reversed the anti-seizure and anti-DNA fragmentation effects of progesterone. Allopregnanolone, also protected against PTX-induced seizures and DNA fragmentation. There was no significant change in the brain lipid peroxidation parameters in any of the treatment groups. It may be concluded that progesterone protects against PTX-induced seizures and DNA fragmentation through its active metabolites allopregnanolone and 5alpha-pregnan-3,20-dione. However, it appears from the present study that, the neuroprotection with progesterone is primarily on account of allopregnalone. The therapeutic potential of allopregnanolone deserves to be evaluated clinically.

Ultrastructure of hippocampal field CA1 in rats after status epilepticus induced by systemic administration of kainic acid

The ultrastructure of hippocampal field CA1 in rats was studied 14 days after status epilepticus induced by administration of kainic acid. Structural changes were seen in 40% of cells, predominantly interneurons, which showed both reversible changes (mitochondria with an electron-dense matrix or small numbers of short cristae, moderate dilation of rough endoplasmic reticulum (RER) cisterns, and small numbers of ribosomes) and more significant abnormalities: swollen mitochondria with very small numbers of cristae, which were partially degraded, some with damaged mitochondrial membranes, along with pathologically damaged RER components and focal or peripheral chromatolysis. Chromatolyzed areas sometimes contained membrane-like includes and vacuoles. In addition, the neuropil contained occasional large osmiophilic formations surrounded by astrocyte processes with accumulations of glycogen or gliofibrils. Synaptoarchitectonics were also altered. Asymmetrical synapses were often seen on small dendrites and spines, with highly osmiophilic postsynaptic zones, their synaptic terminals containing numerous synaptic vesicles and large vesicles with electron-dense cores. Some presynaptic endings showed clear signs of classical dark-type degeneration. As the nucleus remained intact in all types of altered neurons, it appears that most cells underwent pathological changes of the necrotic type.

Immunohistochemical analysis of human brain suggests pathological synergism of Alzheimer's disease and diabetes mellitus

It has been extensively reported that diabetes mellitus (DM) patients have a higher risk of developing Alzheimer's disease (AD), but a mechanistic connection between both pathologies has not been provided so far. Carbohydrate-derived advanced glycation endproducts (AGEs) have been implicated in the chronic complications of DM and have been reported to play an important role in the pathogenesis of AD. The earliest histopathological manifestation of AD is the apparition of extracellular aggregates of the amyloid beta peptide (Abeta). To investigate possible correlations between AGEs and Abeta aggregates with both pathologies, we have performed an immuhistochemical study in human post-mortem samples of AD, AD with diabetes (ADD), diabetic and nondemented controls. ADD brains showed increased number of Abeta dense plaques and receptor for AGEs (RAGE)-positive and Tau-positive cells, higher AGEs levels and major microglial activation, compared to AD brain. Our results indicate that ADD patients present a significant increase of cell damage through a RAGE-dependent mechanism, suggesting that AGEs may promote the generation of an oxidative stress vicious cycle, which can explain the severe progression of patients with both pathologies.

Contribution of a mitochondrial pathway to excitotoxic neuronal necrosis

It is traditionally thought that excitotoxic necrosis is a passive mechanism that does not require the activation of a cell death program. In this study, we examined the contribution of the cytochrome c-dependent mitochondrial death pathway to excitotoxic neuronal necrosis, induced by exposing cultured cortical neurons to 1 mM glutamate for 6 hr and blocked by the NMDA antagonist, dizocilpine. Glutamate treatment induced early cytochrome c release, followed by activation of caspase-9 and caspase-3. Preincubation with the caspase-9 inhibitor z-LEHD-fmk, the caspase-3 inhibitor z-DEVD-fmk, or the specific pan-caspase inhibitor Q-VD-oph decreased the percentage of propidium iodide-positive neurons (52.5% +/- 3.1%, 39.4% +/- 3.5%, 44.6% +/- 3%, respectively, vs. 65% +/- 3% in glutamate + vehicle). EM studies showed mitochondrial release of cytochrome c in neurons in the early stages of necrosis and cleaved caspase-3 immunoreactivity in morphologically necrotic neurons. These results suggest that an active mechanism contributes to the demise of a subpopulation of excitotoxic necrotic neurons.