Project description:Mesial Temporal Lobe Epilepsy (MTLE) is a chronic disease characterized by recurrent unprovoked partial seizures. Current treatments lack long-term efficacy and typically act only to ameliorate the symptomology, rather than to modify the course of the disease. Chronic kainic acid (KA)-induced models of MTLE mimic prominent histopathological and electroencephalographic features of human MTLE, including hippocampal sclerosis, CA1 neuronal loss, astrogliosis, microgliosis, and electrographic hippocampal discharges. Here we examined the transcriptional profiles of the hippocampus of KA - vs sham-injected mice from epileptogenesis to the stabilization of spontaneous recurring seizures. KA (1 nmol) or saline (sham) was injected unilaterally into the dorsal hippocampus of 12 week old C57BL/6J mice, and the ipsilateral (IL) and contralateral (CL) hippocampi were isolated for whole-genome expression profiling (Illumina microarray) or immunohistochemistry 7, 28 and 60 d later. Differential gene expression analysis of the IL hippocampus indicated that 1349, 484, and 439 genes were significantly (fdr<0.05) altered in KA compared to sham at 7, 28 and 60 d, respectively. 108 genes were altered at all time-points assessed, while others were altered in a time-dependent manner, indicative of distinct hippocampal gene expression profiles across the course of disease. Ingenuity Pathway Analysis revealed that specific immune cell and inflammatory signaling pathways were upregulated at 7 and 28 d, in support of a role of neuroinflammation in the disease etiology. The top canonical pathways profile at 60 d was quite distinct from that at 7 and 28 d, although certain inflammatory pathways were still prevalent, indicative of pathways involved in the maintenance of the disease. Consistent with a role of neuroinflammation in MTLE, immunohistochemical analyses demonstrated time-dependent changes in both the intensity of immunoreactivity and number of Iba1- and GFAP-positive cells. To reveal gene networks not apparent with differential expression data alone, weighted gene co-expression analysis (WGCNA) was performed. A gene network that highly associated with 7 d IL-KA (but not 28 and 60 d) was identified, which may point to changes involved in the process of epileptogenesis. Another gene network revealed a group of genes highly associated with changes occurring at 28 and 60 d, but not 7 d, which may point to molecules involved in the generation of spontaneous recurring seizures. Collectively, results indicate that specific pathways, including many associated with neuroinflammation, are activated in a time-dependent manner in MTLE.

Project description:Early childhood convulsions have been correlated with hippocampal neuron loss in patients with intractable temporal lobe epilepsy. Using a "two-hit" rat seizure model, we have shown that animals subjected to kainate (KA)- or hypoxia-induced seizures during early postnatal period showed no cell death, yet sustained more extensive neuronal death after second seizures in adulthood. An early life seizure, without causing overt cellular injury, predisposes the brain to the damaging effect of seizures in later life. Cellular and molecular changes that accompany early seizures and that lead to subsequent epileptogenesis and increased susceptibility to seizure-induced neuronal injury, however, remain poorly understood. We propose to investigate age-specific, time-dependent changes in gene expression that may underlie this priming effect of early-life seizures. We will determine the sequence of gene expression pattern in the hippocampus at various times following KA induced seizures at postnatal day (P) 15. Previous studies have shown that AMPA receptor subtype of glutamate receptors play a crucial role in the age-specific vulnerability and in the long-term epileptogenic effects of perinatal hypoxia seizures. We found that AMPA receptor antagonists block the increased susceptibility caused by early life seizures to later seizures and seizure-induced brain damage. We hypothesize that an alteration of AMPA receptor composition is one of many changes caused by early-life seizures that leads to an increase in Ca2+ permeability, which then results in cascade of downstream events and modifies array of gene expression that promote epileptogenesis and susceptibility to neuronal death in later life. We will examine three time points: 1hr, 72 hr, and 15 days following systemic KA-induced seizures at P15 as we have previously observed structural changes within the hippocampus at these time points. Within an hour of KA seizures, a marked swelling of dendrites, disassembly of dendritic microtubules and glycogen depletion are observed by electron microscopy. Within 5 days, basal dendrites of CA3 hippocampal pyramidal neurons show abnormal spine morphology and decreased branching pattern. 15 days after the seizures, aberrant growth of mossy fibers in the CA3 stratum oriens is observed in animals exposed to KA. Ten hippocampi will be pooled from five animals treated with KA (3mg/kg i.p.) and from five littermate controls injected with PBS. Animals will be decapitated and hippocampi will be rapidly dissected from the brain, flash frozen in liquid nitrogen, and stored at -80C until extraction of total RNA, which will be sent to the center. We will provide 4 tissue samples-2 controls and 2 KA, each a pool of five animals - for each time points. Mixing tissues from multiple rats will normalize single nucleotide polymorphisms and tissue heterogeneity.

Project description:In this study we used microarray analysis to reveal the gene expression profile of the hippocampal CA1 subregion, which was laser-capture microdissected one week after kainic acid (KA)-induced status epilepticus (SE) in postnatal day 21 (P21) rats. These rats are developmentally roughly comparable to juvenile children, and KA-induced SE leads to selective damage of hippocampal CA1 pyramidal neurons in this age group while saving neurons of the other sub-regions. We searched for alterations in the gene expression pattern during the early epileptogenetic phase, i.e. one week after SE, and compared the results with those of age-matched control rats. To detect specifically changes in the CA1 pyramidal neurons, we used the laser-capture microdissection technique that allows the precise isolation of the region of interest. The RNA of this region was isolated, amplified, and labeled, and then hybridized to Illumina RatRef-12 Expression BeadChip Arrays. The gene expression data generated from the microarray was first normalized by the guantile normalization method, and then filtered by using the empirical Bayes method, and the contrasts were created by using the Limma R/Bioconductor. Finally, the data was clustered by using the non-hierarchical K-means clustering for genes, and the pathway analysis was performed by âGene set testâ, which analyzes the statistical significance of a set of genes simultaneously ranked by p-value and generates the KEGG categories (Chipster manual). The Illumina microarray analysis with the Chipster software v1.1.0 (http://chipster.csc.fi; CSC, Espoo, Finland) generated a total of 1592 differently expressed genes in the CA1 subregion of KA-treated rats compared to control rats. Using the K-means method the genes were classified in 10 different clusters. The subsequent KEGG-test for the probe set over-representation analysis revealed the 15 significantly (p<0.05) changed KEGG-pathways in response to KA-treatment, e.g. oxidative phosphorylation (26 genes changed), and long-term potentiation (LTP; 18 genes changed). Some of the differentially expressed genes were also identified to be involved in Ca2+ homeostasis, gliosis, inflammation, and GABAergic transmission.

Project description:Early childhood convulsions have been correlated with hippocampal neuron loss in patients with intractable temporal lobe epilepsy. Using a "two-hit" rat seizure model, we have shown that animals subjected to kainate (KA)- or hypoxia-induced seizures during early postnatal period showed no cell death, yet sustained more extensive neuronal death after second seizures in adulthood. An early life seizure, without causing overt cellular injury, predisposes the brain to the damaging effect of seizures in later life. Cellular and molecular changes that accompany early seizures and that lead to subsequent epileptogenesis and increased susceptibility to seizure-induced neuronal injury, however, remain poorly understood. We propose to investigate age-specific, time-dependent changes in gene expression that may underlie this priming effect of early-life seizures. We will determine the sequence of gene expression pattern in the hippocampus at various times following KA induced seizures at postnatal day (P) 15. Previous studies have shown that AMPA receptor subtype of glutamate receptors play a crucial role in the age-specific vulnerability and in the long-term epileptogenic effects of perinatal hypoxia seizures. We found that AMPA receptor antagonists block the increased susceptibility caused by early life seizures to later seizures and seizure-induced brain damage. We hypothesize that an alteration of AMPA receptor composition is one of many changes caused by early-life seizures that leads to an increase in Ca2+ permeability, which then results in cascade of downstream events and modifies array of gene expression that promote epileptogenesis and susceptibility to neuronal death in later life. We will examine three time points: 1hr, 72 hr, and 15 days following systemic KA-induced seizures at P15 as we have previously observed structural changes within the hippocampus at these time points. Within an hour of KA seizures, a marked swelling of dendrites, disassembly of dendritic microtubules and glycogen depletion are observed by electron microscopy. Within 5 days, basal dendrites of CA3 hippocampal pyramidal neurons show abnormal spine morphology and decreased branching pattern. 15 days after the seizures, aberrant growth of mossy fibers in the CA3 stratum oriens is observed in animals exposed to KA. Ten hippocampi will be pooled from five animals treated with KA (3mg/kg i.p.) and from five littermate controls injected with PBS. Animals will be decapitated and hippocampi will be rapidly dissected from the brain, flash frozen in liquid nitrogen, and stored at -80C until extraction of total RNA, which will be sent to the center. We will provide 4 tissue samples-2 controls and 2 KA, each a pool of five animals - for each time points. Mixing tissues from multiple rats will normalize single nucleotide polymorphisms and tissue heterogeneity. Keywords: time-course

Project description:Neuropsychiatric consequences of poorly controlled seizures that begin in childhood can be devastating. School failure or behavioral difficulty in a child with epilepsy is common and can become the focus of concern for families. Current antiepileptic drugs compound problems with their CNS side effects; effective therapy is currently limited as little is known about the cellular and molecular changes caused by seizures in the developing brain. This study will investigate transcriptional regulation induced by early-life seizures and explore alternative nonpharmacological therapeutic strategies in reversing damages of early-life seizures. We will study the therapeutic efficacy of environmental enrichment in reducing seizure-induced neuronal injury and in modifying gene expression alterations. We will explore molecular mechanisms underlying the beneficial effects of enriched environment and examine how different genes act in concert to influence the outcome of seizure-induced damage. To test the effect of environmental enrichment in modifying KA seizure-induced alterations in gene expression. We hypothesize that environmental enrichment enhances plastic, homeostatic response of immature brain to excessive, dysregulating seizure activity and protect against maladaptive response of developing animals to seizures. After inducing seizures by systemic injection of KA (8 mg/kg) or PBS injections (control) at P20, we will randomly assign P21 male Long Evans rats to 4 groups: enrichment housing (control-enriched; SE-enriched) or to standard vivarium cages (control; SE). Sixteen animals (8 control-enriched; 8 SE-enriched) will be housed as a group in a plastic rectangular cage measuring 115cm x 80 cm containing a running wheel, tunnels, rubber balls, a maze, a mirror, and a clock with a cyclist pendulum. Control and KA will be housed individually in a standard cage. Four litters will be used for each run of experiment and the experiment will be repeated once to obtain 16 animals per group. At P30, 240 h after KA or PBS, animals will be deeply anesthetized with isoflurane, decapitated for total RNA preparation (half brain for each, n = 12 per group). Total RNA will be isolated from each hippocampus individually, and equal amounts of RNA from 4 hippocampi will be pooled for each Genechip. Three independent hybridizations will be performed per condition (total of 12 Genechip Rat Expression Set 230).

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NAP provides neuroprotection against kainic acid-induced cell death

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