Hippocampal alterations of apolipoprotein E and D mRNA levels in vivo and in vitro following kainate excitotoxicity.

Abstract

Alteration in the expression of apolipoprotein E (ApoE) and apolipoprotein D (ApoD) genes was evaluated in rat, 7 days following status epilepticus (SE) induced by intra-amygdala injection of kainate (KA), and in organotypic hippocampal cultures, 2 days after a single 1 h exposure to KA. Global polyadenylated RNA (poly A+) steady state, assessing global regulation of mRNA transcription was first measured in cortices and hippocampi from each animal and in the organotypic cultures. No alteration due to KA treatment was observed and individual concentrations of ApoE and ApoD mRNA species were therefore measured and comparative analysis performed. In the cortices of KA-treated animals, ApoE and ApoD mRNA levels did not show statistically significant changes. In contrast, in hippocampi, 7 days after SE, ApoE and ApoD mRNA levels were significantly increased, respectively, by 123 and 138%. This in vivo effect was confirmed in vitro on organotypic cultures, where KA treatment increased ApoE and ApoD mRNA expressions, respectively, by 72 and 61%. These observations indicate that lipidic metabolism is modified in the lesioned structure and suggest an increased traffic of lipids and a need for more ApoE and D in the hippocampus during the period of recovery and restructuration that follows severe seizures.