Different types of Status Epilepticus may lead to similar hippocampal epileptogenesis processes.

About 1-2% of people worldwide suffer from epilepsy, which is characterized by unpredictable and intermittent seizure occurrence. Despite the fact that the exact origin of temporal lobe epilepsy is frequently unknown, it is frequently linked to an early triggering insult like brain damage, tumors, or Status Epilepticus (SE). We used an experimental approach consisting of electrical stimulation of the amygdaloid complex to induce two behaviorally and structurally distinct SE states: Type I (fully convulsive), with more severe seizure behaviors and more extensive brain damage, and Type II (partial convulsive), with less severe seizure behaviors and brain damage. Our goal was to better understand how the various types of SE impact the hippocampus leading to the development of epilepsy. Despite clear variations between the two behaviors in terms of neurodegeneration, study of neurogenesis revealed a comparable rise in the number of Ki-67 + cells and an increase in Doublecortin (DCX) in both kinds of SE.

Inhibition of sodium glucose cotransporters following status epilepticus induced by intrahippocampal pilocarpine affects neurodegeneration process in hippocampus.

Temporal lobe epilepsy (TLE) is characterized by spontaneous recurrent seizures, starting from secondary functional disorders due to several insults, including self-sustaining continuous seizures identified as status epilepticus (SE). Although hypoglycemia has been associated with SE, the effect of inhibition of the Na(+)/glucose cotransporters (SGLTs) on hippocampus during SE is still unknown. Here we evaluated the functional role of SGLT in the pattern of limbic seizures and neurodegeneration process after pilocarpine (PILO)-induced SE. Vehicle (VEH, 1µL) or phlorizin, a specific SGLT inhibitor (PZN, 1µL, 50µg/µL), was administered in the hippocampus of rats 30min before PILO (VEH+PILO or PZN+PILO, respectively). The limbic seizures were classified using the Racine's scale, and the amount of wet dog shakes (WDS) was quantified before and during SE. Neurodegeneration process was evaluated by Fluoro-Jade C (FJ-C), and FJ-C-positive neurons (FJ-C+) were counted 24h and 15days after SE. The PZN-treated rats showed higher (p<0.05) number of WDS when compared with VEH+PILO. There was no difference in seizure severity between PZN+PILO and VEH+PILO groups. However, the pattern of limbic seizures significantly changed in PZN+PILO. Indeed, the class 5 seizures repeated themselves more times (p<0.05) than the other classes in the PZN group at 50min after SE induction. The PZN+PILO animals had a higher (p<0.05) number of FJ-C+ cells in the dentate gyrus (DG), hilus, and CA3 and CA1 of hippocampus, when compared with VEH+PILO. The PZN+PILO animals had a decreased number (p<0.05) of FJ-C+ cells in CA1 compared with VEH+PILO 15days after SE induction. Taken together, our data suggest that SGLT inhibition with PZN increased the severity of limbic seizures during SE and increased neurodegeneration in hippocampus 24h after SE, suggesting that SGLT1 and SGLT2 could participate in the modulation of earlier stages of epileptogenic processes.

Effects of Iron Overload on the Activity of Na,K-ATPase and Lipid Profile of the Human Erythrocyte Membrane.

Iron is an essential chemical element for human life. However, in some pathological conditions, such as hereditary hemochromatosis type 1 (HH1), iron overload induces the production of reactive oxygen species that may lead to lipid peroxidation and a change in the plasma-membrane lipid profile. In this study, we investigated whether iron overload interferes with the Na,K-ATPase activity of the plasma membrane by studying erythrocytes that were obtained from the whole blood of patients suffering from iron overload. Additionally, we treated erythrocytes of normal subjects with 0.8 mM H2O2 and 1 µM FeCl3 for 24 h. We then analyzed the lipid profile, lipid peroxidation and Na,K-ATPase activity of plasma membranes derived from these cells. Iron overload was more frequent in men (87.5%) than in women and was associated with an increase (446%) in lipid peroxidation, as indicated by the amount of the thiobarbituric acid reactive substances (TBARS) and an increase (327%) in the Na,K-ATPase activity in the plasma membrane of erythrocytes. Erythrocytes treated with 1 µM FeCl3 for 24 h showed an increase (132%) in the Na,K-ATPase activity but no change in the TBARS levels. Iron treatment also decreased the cholesterol and phospholipid content of the erythrocyte membranes and similar decreases were observed in iron overload patients. In contrast, erythrocytes treated with 0.8 mM H2O2 for 24 h showed no change in the measured parameters. These results indicate that erythrocytes from patients with iron overload exhibit higher Na,K-ATPase activity compared with normal subjects and that this effect is specifically associated with altered iron levels.

Gene expression changes in an animal model of in utero irradiation-induced Cortical Dysplasia.

PURPOSE: Cortical Dysplasia (CD) is the histopathological substrate in almost half of all drug-resistant focal epilepsies. Little is known about the gene expression profile of CD. As such information may help target therapeutics more effectively, our aim was to perform a gene expression analysis of an animal model of cortical dysplasia induced by in utero irradiation. METHODS: Nine offspring from irradiated animals, and nine age-matched controls were sacrificed at post-natal day 60. Cortical and hippocampal regions were separated, and total ribonucleic acid (RNA) was extracted using a commercially available kit (Qiagen). RNA was then subjected to a gene expression analysis using an oligonucleotide microarray platform (Illumina). After statistical analysis, genes were considered differentially expressed when a p value less than 0.001 was observed. Real-time, quantitative polymerase chain reaction (RT-qPCR) was used to confirm microarray results for three genes via the Livak method. RESULTS: Twenty three genes from cortical tissue met criteria for altered gene expression. Six genes from cortex seemed relevant to the pathogenesis of CD. Two genes that promoted cell survival (connective tissue growth factor and peroxiredoxin) were upregulated. One gene that promoted excitotoxic neurodegeneration (latrophilin-2) was downregulated. Two genes involved in glutamate (protein kinase C-alpha) and AMPA receptor recycling (NEEP-21) were downregulated. One gene, (Shank-1) involved in the control of dendritic maturation, was downregulated. CONCLUSION: Gene expression analysis in this animal model revealed some of the potential mechanisms by which CD may lead to the phenotype of intractable epilepsy. The downregulation of genes that are involved in glutamate and AMPA receptor recycling may lead to increased excitability. Disinhibition of aberrant dendritic branching, resulting from a downregulation of Shank-1, may also result in an increase in sprouting, excitation and/or hypersynchrony. Finally, genes promoting cell survival, either directly (connective tissue growth factor, peroxiredoxin) or indirectly (latrophilin-2) may allow CD tissue to survive the excitotoxic injury that it produces, thus allowing it to perpetuate the epileptic condition over time.

Single injection of a low dose of pentylenetetrazole leads to epileptogenesis in an animal model of cortical dysplasia.

PURPOSE: Cortical dysplasia (CD) is one of the most frequent causes of pharmacoresistent focal epilepsy. Despite significant advances in various diagnostic and therapeutic methods, the basic mechanisms of higher susceptibility for seizures in patients with CD are unknown. Animal models of CD present with a lower threshold for seizure induction. The purpose of this study is to further characterize the animal model of in utero radiation-induced CD and to illustrate the effect of a late postnatal second hit (low dose of pentylenetetrazole, PTZ) on the development of spontaneous seizures. METHODS: Pregnant Sprague-Dawley rats were irradiated on E17 (145 cGy; control group was left untreated). Litters were implanted with bifrontal epidural and hippocampal depth electrodes. After baseline electroencephalography (EEG) recording, animals received 30 mg/kg PTZ and were chronically monitored. Histopathology of the brains was verified. RESULTS: No seizures were detected in animals that did not receive PTZ. PTZ-injected irradiated (XRT) rats showed severe prolonged, repetitive seizures during the acute period. During the chronic period, XRT rats had recurrent seizures and epileptiform spikes. PTZ-injected control animals exhibited milder and fewer acute seizures and did not show seizures during the chronic period. Histology was consistent with cortical and hippocampal dysplasia. CONCLUSIONS: This study shows that a single treatment with a low dose of PTZ renders XRT rats (but not age-matched controls) epileptic, exhibiting spontaneous epileptiform spikes and seizures on EEG. These results might mirror the natural history of patients with CD thought to be caused by prenatal/congenital or perinatal insults.

APOE epsilon4 is associated with postictal confusion in patients with medically refractory temporal lobe epilepsy.

This study examined the relationship between the APOE epsilon4 allele and postictal confusion in patients with medically intractable temporal lobe epilepsy (TLE). Patients with at least one epsilon4 allele (n=22) were three times more likely to exhibit postictal confusion (68%) than the 63 patients without epsilon4 (43%). These preliminary results demonstrate that APOE epsilon4 is associated with an increased risk of postictal confusion in patients with medically intractable TLE, suggesting possible dysfunction in neuronal recovery mechanisms.

Pathophysiological mechanisms of focal cortical dysplasia: a critical review of human tissue studies and animal models.

Cortical dysplasia (CD, also known as malformations of cortical development) are the pathological substrates in a large percentage of patients with pharmacoresistant epilepsy who may be amenable to surgical treatment. Therefore, research on the mechanisms of dysplastic lesion formation and epileptogenicity is of paramount importance for the prevention, detection, and treatment of CD-induced epilepsy. The purpose of this review is to discuss and critically evaluate the current state and results of human tissue experimentation (focusing on reported results of studies done on neocortical dysplastic tissue resected from patients with pharmacoresistant epilepsy), and to discuss some of the concerns related to research that uses surgically resected epileptic human tissue. The use of better animal models of CD as a tool toward the better understanding of the mechanisms of pathogenesis, epileptogenesis, and epileptogenicity of dysplastic lesions will be reviewed from the perspective of their usefulness in a model of translational research that should ultimately result in better diagnostic and therapeutic techniques of CD.