Temporal lobe epilepsy induces differential expression of hippocampal miRNAs including let-7e and miR-23a/b.

To understand the role of miRNAs in the molecular mechanisms of temporal lobe epilepsy (TLE), we investigated the changes in microRNA (miRNA) expression profiles of chronic TLE rat models. MiRNAs microarray analysis results showed that 125 miRNAs were detected in the hippocampus of lithium-pilocarpine-induced TLE rats and normal rats. Compared with normal rats (control group), 23 of the 125 miRNAs were expressed differentially in TLE rats including 5 down-regulated miRNAs (let-7 e included) and 18 up-regulated miRNAs (miR-23 a/b included). Furthermore, let-7 e and miR-23 a/b analysis in rat hippocampus were performed by real-time quantitative polymerase chain reaction at 0 h, 1h, 6h, 12h, 24h, 2 days, 7 days,10 days, 30 days,50 days after induction of status epilepticus (SE). let-7 e was detected down-regulated expression at 0 h, 1h, 6h, 2 days, 7 days, 50 days after SE and up-regulated expression at 12h, 24h, 10 days, 30 days after SE, which was significantly up-regulated expression at 24h after SE (10.49 folds, P<0.01). miR-23 a/b was detected down-regulated at 0 h, 1h, 6h, 12h, 2 days, 7 days, 10 days, 30 days after SE and significantly up-regulated at 24h (4.49 folds P<0.01), 50 d (2.4 folds, P<0.01) after SE. TLE alters the expression levels of a subset of miRNAs in the hippocampus and these deregulated miRNAs may be involved in the pathogenesis of epilepsy directly or indirectly. Also the temporal change of the let-7 e and miR-23 a/b expression in the epileptogenesis indicated their underlying functions on TLE.