MicroRNAs:the New Players In Mesial Temporal Lobe Epilepsy Pathogenesis In The Developing Brains

Part One:Interleukin-1β and microRNA-146a in an Immature Rat Model and Children with Mesial Temporal Lobe EpilepsyObjective:Increasing evidence indicates that neuroinflammation plays a critical role in the pathogenesis of mesial temporal lobe epilepsy (MTLE). The aim of this study was to investigate the dynamic expression of interleukin (IL)-1β as a proinflammatory cytokine and microRNA (miR)-146a as a posttranscriptional inflammation-associated microRNA (miRNA) in the hippocampi of an immature rat model and children with MTLE.Methods:To study the expression of IL-1β and miR-146a, we performed a reverse transcription polymerase chain reaction, Western blot, and real-time quantitative PCR on the hippocampi of immature rats at11days of age. Expression was monitored in the acute, latent, and chronic stages of disease (2h and3and8weeks after induction of lithium-pilocarpine status epilepticus, respectively), and in control hippocampal tissues corresponding to the same timeframes. Similar expression methods were applied to hippocampi obtained from children with MTLE and normal controls.Results:The expression of IL-1β and miR-146a in both children and immature rats with MTLE differs according to the stage of MTLE development. Both IL-1β and miR-146a are significantly up-regulated, but in opposite ways:IL-1β expression is highest in the acute stage, when expression of miR-146a is at its lowest level; miR146a expression is highest in the latent stage, when IL-1β expression is at its lowest level. Both IL-1β and miR-146a are up-regulated in the chronic stage, but not as much as in the other stages. Conclusion:Our study is the first to focus on the expression of miR-146a in the immature rat model of lithium pilocarpine MTLE and in children with MTLE. We have detected that the expression of proinflammatory cytokine IL-1β and posttranscriptional inflammation associated miR-146a is variable depending on the disease stage. Furthermore, both IL-1β and miR-146a are upregulated in immature rats and children with MTLE. Our findings elucidate the role of inflammation in the pathogenesis of MTLE in the immature rat model and children. Therefore, modulation of the IL-1β-miR-146a axis may be a novel therapeutic target in the treatment of MTLE. Part Two:Expression Patterns of miR-124, miR-134, miR-132, and miR-21in an Immature Rat Model and Children with Mesial Temporal Lobe EpilepsyObjective:Mesial temporal lobe epilepsy (MTLE) is a particularly devastating form of human epilepsy with significant incidence of medical intractability. MicroRNAs (miRs) are small, noncoding RNAs that regulate the posttranscriptional expression of protein-coding mRNAs, which may have key roles in the pathogenesis of MTLE development. The aim of this study was to investigate the dynamic changes in the expressions of brain-specific (miR-124and miR-134) and inflammation-related (miR-132and miR-21) in the three stages of MTLE development in the immature rat model and children with MTLE.Methods:To study the dynamic expression patterns of brain-specific miR-124and miR-134and inflammation-related miR-132and miR-21, we performed qPCR on the hippocampi of immature rats at25days of age. Expressions were monitored in the acute, latent, and chronic stages of disease (2h and3and8weeks after induction of lithium-pilocarpine status epilepticus, respectively), and in control hippocampal tissues corresponding to the same timeframes. A similar expression method was applied to hippocampi obtained from children with MTLE and normal controls.Results:The expression patterns of miR-124and miR-134nearly showed the same dynamics in the three stages of MTLE development. On the other hand, miR-132and miR-21showed significant upregulation in acute and chronic stages, while in the latent stage, miR-132was upregulated and miR-21was downregulated. The four miRs were upregulated in hippocampal tissues obtained from children with MTLE.Conclusion:The significant upregulation of miR-124and miR-134in the seizure-related stages and children suggested that both can be potential targets for anticonvulsant drugs in the epileptic developing brains, while the different expression patterns of miR-132and miR-21may suggest different functions in MTLE pathogenesis. Part Three:Dynamic Expression Patterns of Brain-enriched miR-9and miR-138in an Immature Rat Model and Children with Mesial Temporal Lobe EpilepsyObjective:Recently, microRNAs (miRs) have attached a great attention as novel players in the pathogenesis of mesial temporal lobe epilepsy (MTLE) in mature and developing brains. This study aimed to investigate the dynamic expression patterns of brain-enriched miR-9and miR-138in the hippocampi of an immature rat model in the three stages of MTLE and in children with MTLE.Methods:We performed qPCR on the hippocampi of immature rats at25days of age. Expressions were monitored in the three stages of MTLE development (2h,3and8weeks after induction of lithium-pilocarpine status epilepticus, respectively), and in control hippocampal tissues corresponding to the same timeframes. Similar expression method was applied to hippocampi obtained from children with MTLE and normal controls.Results:miR-9showed significant upregulation in the acute and chronic stages while in the latent stage it was nearly equal to the control. miR-138was downregulated in the three stages of MTLE development.Conclusion:This is the first study to examine the dynamic expression patterns of brain-enriched miR-9and miR-138in the immature rat model and children with MTLE. Modulation of these miRs expressions may be new targets for antiepileptic and anticonvulsant therapies in the developing brains.