Silencing microRNA-134 produces neuroprotective and prolonged seizure-suppressive effects

The Fourth Conference on Epileptogenesis aimed at discussing new and controversial issues in the area of epileptogenesis research in the format of a workshop. Epileptogenesis is a particularly integrative field of research, in which experimental data and clinical evidence are brought together, to provide insight into pathological plasticity phenomena and, more broadly, into the mechanisms of brain adaptation to environmental stimuli.

miRNA Expression Profile after Status Epilepticus and Hippocampal Neuroprotection by Targeting miR-132

Effects of conventional antiepileptic drugs in a model of spontaneous recurrent seizures in rats

Pilocarpine vs. lithium–pilocarpine for induction of status epilepticus in mice: Development of spontaneous seizures, behavioral alterations and neuronal damage

Progression of neuronal damage after status epilepticus and during spontaneous seizures in a rat model of temporal lobe epilepsy

Long-term consequences of a prolonged febrile seizure in a dual pathology model

Epilepsy is a neurological disorder characterized by the recurrence of spontaneous, unprovoked epileptic seizures. Mesial temporal lobe epilepsy (more briefly, MTLE) is a very common form of epilepsy which is featured by the occurrence of focal limbic seizures, and associated to a specific neuropathological alteration, the so-called Ammon’s horn sclerosis, whose main features are a selective loss of the CA1 and CA3/4 section of the Ammon’s horn (CA, from Latin Cornu Ammonis, abbreviated as CA), a selective cell loss of inhibitory interneurons in the hilus of the dentate gyrus (DG), and the abnormal sprouting of granule cells mossy fibers (the so called mossy fiber sprouting, MFS). The onset of spontaneous seizures (SRS) is the hallmark of a good model of epilepsy. For temporal lobe epilepsy (TLE), the most used models consist in administering systemically chemoconvulsants inducing limbic status epilepticus (i.e. seizures lasting for more than 30’, SE) and evaluating the occurrence of SRS. However, in these models, the widespread involvement of different structures which complicates the interpretation of experimental findings: limbic seizures and status epilepticus (SE) can be triggered by focal infusion of chemoconvulsants within anterior piriform cortex (abbreviated as APC) This brain region is densely innervated by noradrenergic fibers arising from the locus coeruleus (LC), and we recently showed that a lesion of LC (induced by a selective neurotoxin, DSP-4, i.p.), induces SE. LC plays a critical role in modulating several models of seizures, and it plays a critical role in plastic mechanisms and neuroprotection in the brain. Thus, we compared the group DSP-4+bicuculline and cyclothiazide+bicuculline, to evaluate whether the focal SE evoked from the APC is capable of inducing SRS and AHS, and whether LC plays a significant role in this phenomena. We found that: the loss of LC induced: (i)a higher incidence of SRS; (ii) cell loss in the hippocampal DG hilus and CA3 (iii)the loss of parvalbumin-positive neurons. In conclusion, our study confirms that focal induction of SE from the APC represents a good model of TLE, and that NE released from the fibers originating from the LC plays a significant role both in the hippocampal damage occurring after SE, and in the incidence of SRS.

Modeling epileptogenesis and temporal lobe epilepsy in a non-human primate

Objective To establish a reliable post-status epilepticus model of temporal lobe epilepsy in rats that mimics human temporal lobe epilepsy, and observe the occurrence of spontaneous recurrent seizures (SRS). Methods Status epilepticus which was monitored for 3 h was induced by a 20-min stimulation of the amygdala ( 100 ms train of 1 ms, 60 Hz bipolar pulses, 400 μA, every 0. 5 s). Stimulated rats ( n =21 ) were monitored with a video recording system for the 3-months follow-up period to record the appearance of SRS. Results SRS (total number 181 ) were detected in 14 of the 21 animals (67％) after a latency period of 8 to 73 days (mean 43 days), including 10 times of stage 3 seizure (5.53％), 77 times of stage 4 seizure (42. 54％ ), and 94 times of stage 5 seizure (51.93％). Of all the 14 rats, the seizure number beyond 30 was observed in 3 animals, from 20 to 30 in one animal, from 10 to 20 in 2 animals, between 5 and 10 in 2 animals, and less than 5 in 6 animals. Seventy-three percent of SRS appeared during daytime (07: 00-19: 00) and 74 percent of secondarily generalized seizures occurred during daytime. Conclusion This study has been successfully designed to develop a post-status epilepticus animal model induced by electrical stimulation of the amygdale. Key words: Temporal lobe epilepsy; Status epilepticus; Model,animal

Temporal lobe epilepsy (TLE) is a common and commonly devastating form of human epilepsy for which only symptomatic therapy is available. One cause of TLE is an episode of de novo prolonged seizures [status epilepticus (SE)]. Understanding the molecular signaling mechanisms by which SE transforms a brain from normal to epileptic may reveal novel targets for preventive and disease-modifying therapies. SE-induced activation of the BDNF receptor tyrosine kinase, TrkB, is one signaling pathway by which SE induces TLE. Although activation of TrkB signaling promotes development of epilepsy in this context, it also reduces SE-induced neuronal death. This led us to hypothesize that distinct signaling pathways downstream of TrkB mediate the desirable (neuroprotective) and undesirable (epileptogenesis) consequences. We subsequently demonstrated that TrkB-mediated activation of phospholipase Cγ1 is required for epileptogenesis. Here we tested the hypothesis that the TrkB-Shc-Akt signaling pathway mediates the neuroprotective consequences of TrkB activation following SE. We studied measures of molecular signaling and cell death in a model of SE in mice of both sexes, including wild-type and TrkBShc/Shc mutant mice in which a point mutation (Y515F) of TrkB prevents the binding of Shc to activated TrkB kinase. Genetic disruption of TrkB-Shc signaling had no effect on severity of SE yet partially inhibited activation of the prosurvival adaptor protein Akt. Importantly, genetic disruption of TrkB-Shc signaling exacerbated hippocampal neuronal death induced by SE. We conclude that therapies targeting TrkB signaling for preventing epilepsy should spare TrkB-Shc-Akt signaling and thereby preserve the neuroprotective benefits.SIGNIFICANCE STATEMENT Temporal lobe epilepsy (TLE) is a common and devastating form of human epilepsy that lacks preventive therapies. Understanding the molecular signaling mechanisms underlying the development of TLE may identify novel therapeutic targets. BDNF signaling thru TrkB receptor tyrosine kinase is one molecular mechanism promoting TLE. We previously discovered that TrkB-mediated activation of phospholipase Cγ1 promotes epileptogenesis. Here we reveal that TrkB-mediated activation of Akt protects against hippocampal neuronal death in vivo following status epilepticus. These findings strengthen the evidence that desirable and undesirable consequences of status epilepticus-induced TrkB activation are mediated by distinct signaling pathways downstream of this receptor. These results provide a strong rationale for a novel therapeutic strategy selectively targeting individual signaling pathways downstream of TrkB for preventing epilepsy.

Calpain activation and neuronal death during early epileptogenesis

ATP is released into the extracellular space during pathologic processes including increased neuronal firing. Once released, ATP acts on P2 receptors including ionotropic P2X and metabotropic P2Y receptors, resulting in changes to glial function and neuronal network excitability. Evidence suggests an involvement of P2Y receptors in the pathogenesis of epilepsy, but there has been no systematic effort to characterize the expression and function of the P2Y receptor family during seizures and in experimental and human epilepsy. Status epilepticus was induced using either intra-amygdala kainic acid or pilocarpine to characterize the acute- and long-term changes in hippocampal P2Y expression. P2Y expression was also investigated in brain tissue from patients with temporal lobe epilepsy. Finally, we analyzed the effects of two specific P2Y agonists, ADP and UTP, on seizure severity and seizure-induced cell death. Both intra-amygdala kainic acid and pilocarpine-induced status epilepticus increased the transcription of the uracil-sensitive P2Y receptors P2ry2 , P2ry4 , and P2ry6 and decreased the transcription of the adenine-sensitive P2Y receptors P2ry1 , P2ry12 , P2ry13 . Protein levels of P2Y1 , P2Y2 , P2Y4 , and P2Y6 were increased after status epilepticus, whereas P2Y12 expression was decreased. In the chronic phase, P2ry1 , P2ry2 , and P2ry6 transcription and P2Y1 , P2Y2 , and P2Y12 protein levels were increased with no changes for the other P2Y receptors. In hippocampal samples from patients with temporal lobe epilepsy, P2Y1 and P2Y2 protein expression was increased, whereas P2Y13 levels were lower. Demonstrating a functional contribution of P2Y receptors to seizures, central injection of ADP exacerbated seizure severity, whereas treatment with UTP decreased seizure severity during status epilepticus in mice. The present study is the first to establish the specific hippocampal expression profile and function of the P2Y receptor family after experimental status epilepticus and in human temporal lobe epilepsy and offers potential new targets for seizure control and disease modification.

Background and Objective: Temporal lobe epilepsy (TLE) is a chronic neurological disorder with spontaneous recurrent seizures and abnormal intracranial waves. Since the role of oxidative stress in the occurrence of epilepsy is inevitable, it seems that the use of antioxidants can prevent some of the complications resulting from this disease. This study was designed to assess the protective effect of carvacrol on seizure behavior and intracranial electroencephalographic (iEEG) recordings.Materials and Methods: In this study, male Wistar rats were randomly allocated into four groups: Sham-operated, carvacrol (10 mg/kg) pretreated-sham-operated, kainic acid (0.8 μg/μl), and carvacrol (10 mg/kg) pretreated-kainic acid. In this study, we evaluated the status epilepticus and spontaneous seizures according to Racine΄s scores and recorded iEEG for investigating the antiepileptic effect of carvacrol in kainite-injected rats. Results: The seizures behavior (status epilepticus and spontaneous seizures) appeared in kainite-injected rats and iEEG amplitude increased as compared to sham group (pConclusion: Collectively, the results of this study indicate that carvacrol is able to prevent some of the epilepsy disease complications in an experimental model of temporal lobe epilepsy.

MicroRNA-23a contributes to hippocampal neuronal injuries and spatial memory impairment in an experimental model of temporal lobe epilepsy

Neuronal Glypican4 promotes mossy fiber sprouting through the mTOR pathway after pilocarpine-induced status epilepticus in mice