Microarray profile of seizure damage-refractory hippocampal CA3 in a mouse model of epileptic preconditioning

Abstract

A neuroprotected state can be acquired by preconditioning brain with a stimulus that is subthreshold for damage (tolerance). Acquisition of tolerance involves coordinate, bi-directional changes to gene expression levels and the re-programmed phenotype is determined by the preconditioning stimulus. While best studied in ischemic brain there is evidence brief seizures can confer tolerance against prolonged seizures (status epilepticus). Presently, we developed a model of epileptic preconditioning in mice and used microarrays to gain insight into the transcriptional phenotype within the target hippocampus at the time tolerance had been acquired. Epileptic tolerance was induced by an episode of non-damaging seizures in adult C57Bl/6 mice using a systemic injection of kainic acid. Neuron and DNA damage-positive cell counts 24 h after status epilepticus induced by intraamygdala microinjection of kainic acid revealed preconditioning given 24 h prior reduced CA3 neuronal death by ~45% compared with non-tolerant seizure mice. Microarray analysis of over 39,000 transcripts (Affymetrix 430 2.0 chip) from microdissected CA3 subfields was undertaken at the point at which tolerance was acquired. Results revealed a unique profile of small numbers of equivalently up-and down-regulated genes with biological functions that included transport and localization, ubiquitin metabolism, apoptosis and cell cycle control. Select microarray findings were validated post hoc by real-time polymerase chain reaction and Western blotting. The present study defines a paradigm for inducing epileptic preconditioning in mice and first insight into the global transcriptome of the seizure-damage refractory brain. Keywordsepilepsy; transcriptome; kainic acid; tolerance; neuroprotection; apoptosis Stressful and potentially noxious insults that are subthreshold for damage are capable of rendering brain refractory to damage incurred by a subsequent, prolonged and otherwise harmful stressor (Dirnagl et al., 2003). This process, termed preconditioning, is a highly conserved endogenous mechanism by which brain can protect itself (tolerance) (Chen and Simon, 1997 Tolerance in brain was originally identified as a gene synthesis-dependent process that took 1-3 days to be acquired in vivo (Kitagawa et al., 1991;Simon et al., 1993;Chen et al., 1996). The process is highly conserved, being readily elicited in numerous rat and mouse models of ischemic brain injury (Dirnagl et al., 2003;Gidday, 2006;Stenzel-Poore et al., 2007). It may also have clinical relevance as evinced by more favorable outcomes in patients experiencing transient ischemic attacks prior to a large stroke (Weih et al., 1999). Preconditioning can also be induced by other brain insults including seizure (Sasahira et al., 1995;Najm et al., 1998;El Bahh et al., 2001;Borges et al., 2007) and certain chemicals/drugs (Rosenzweig et al., 2004), and cross-tolerance whereby ischemic and other paradigms are combined has also been reported in rodents (Plamondon et al., 1999;Towfighi et al., 1999).Mi...

Differential DNA Methylation Patterns Define Status Epilepticus and Epileptic Tolerance

“…Animal experiments were performed as described previously (Hatazaki et al, 2007;Jimenez-Mateos et al, 2008) in accordance with the European Communities Council Directive (86/609/EEC) and were reviewed and approved by the Research Ethics Committee of the Royal College of Surgeons in Ireland, under license from the Department of Health, Dublin, Ireland. Adult male mice (C57BL/6, 20 -25 g) were obtained from Harlan.…”

“…The CA3 subfield of the ipsilateral and contralateral hippocampus was microdissected on dry ice and flash frozen in liquid nitrogen for temporary storage at Ϫ80°C, as described previously (Hatazaki et al, 2007).…”

“…In epilepsy models, brief seizures triggered by chemoconvulsants or electrical stimulation are the preconditioning stimuli, reducing neuronal death caused by a subsequent episode of status epilepticus (SE). For example, non-convulsive seizures elicited by low-dose systemic kainic acid (KA) prevent hippocampal injury by intraamygdala KA-induced SE in C57BL/6 and SJL mice (Hatazaki et al, 2007;Tanaka et al, 2010). In recent years, our understanding of the molecular processes underlying tolerance has been assisted by microarray profiling, which has revealed large-scale, genomic reprogramming of the response to injury (Stenzel-Poore et al, 2007;Johnson and Simon, 2009).…”

Bi-lateral changes to hippocampal cholesterol levels during epileptogenesis and in chronic epilepsy following focal-onset status epilepticus in mice

“…Previous studies reported an increase in cholesterol and certain oxysterols in the hippocampus of rats following kainic acid (KA)--induced seizures (Ong et al, 2003). We recently reported that brief seizures in mice increase the expression of StAR--related lipid transfer domain containing 4 (Stard4), which can bind cholesterol and is involved in intracellular cholesterol transport ( Hatazaki et al, 2007). A number of studies have also explored the effects of statins on seizure--induced neuronal death ( He et al, 2006, Lee et al, 2008and Xie et al, 2011.…”

Electroencephalographic and behavioral convulsant effects of hydrobromide and hydrochloride salts of bupropion in conscious rodents

“…Briefl y, mice received intraamygdala injection of 0.3 μKA (Sigma-Aldrich, St. Louis, MO, USA) and sections cut as described above at 24 hours as previously described. 20,21 Sections of the brains of mice with bupropion HCl-and bupropion HBr-induced seizures were also stained with Fluoro-Jade B by using the method described by Schmued and Hopkins. 17,18 The sections were then analyzed as described for the TUNEL-stained sections above.…”