miRNA Expression Profile after Status Epilepticus and Hippocampal Neuroprotection by Targeting miR-132

Abstract

When an otherwise harmful insult to the brain is preceded by a brief, noninjurious stimulus, the brain becomes tolerant, and the resulting damage is reduced. Epileptic tolerance develops when brief seizures precede an episode of prolonged seizures (status epilepticus). MicroRNAs (miRNAs) are small, noncoding RNAs that function as post-transcriptional regulators of gene expression. We investigated how prior seizure preconditioning affects the miRNA response to status epilepticus evoked by intra-amygdalar kainic acid in mice. The miRNA was extracted from the ipsilateral CA3 subfield 24 hours after focal-onset status epilepticus in animals that had previously received either seizure preconditioning (tolerance) or no preconditioning (injury), and mature miRNA levels were measured using TaqMan low-density arrays. Expression of 21 miRNAs was increased, relative to control, after status epilepticus alone, and expression of 12 miRNAs was decreased. Increased miR-132 levels were matched with increased binding to Argonaute-2, a constituent of the RNA-induced silencing complex. In tolerant animals, expression responses of >40% of the injury-group-detected miRNAs differed, being either unchanged relative to control or down-regulated, and this included miR-132. In vivo microinjection of locked nucleic acid-modified oligonucleotides (antagomirs) against miR-132 depleted hippocampal miR-132 levels and reduced seizure-induced neuronal death. Thus, our data strongly suggest that miRNAs are important regulators of seizure-induced neuronal death.

Neuroprotection of microRNA in neurological disorders (Review)

“…However, the differential expression of miR-132 and miR-21 suggests different functions by modulating various targets in MTLE pathogenesis. In focal-onset status epilepticus, the expression of 21 miRNAs was increased, and the expression of 12 miRNAs was reduced (68). Of these, miR-132 was differentially upregulated.…”

miR-711 upregulation induces neuronal cell death after traumatic brain injury

“…Ago2 immunoprecipitation was performed as previously described. 49 Briefly, RCNs were suspended in 500 μl of lysis buffer (150 mM KCl, 25 mM Tris-HCl (pH 7.4), 5 mM EDTA, 0.5% NP-40, 5 mM DTT, and protease inhibitor and phosphatase inhibitor (2, 3) cocktails (Sigma-Aldrich, St. Louis, MO, USA) at 4°C for 20 min and the cell lysates were separated by centrifugation at 12,000 × g for 20 min at 4°C. A volume of 50 μl of protein A/G UltraLink Resin (Thermo Scientific, Waltham, MA, USA) and 20 μl of Argonaute 2 (Ago2) antibody (Cell Signaling, Danvers, MA, USA) were added to 400 μl of cell lysate (in a final 1 ml mixture filled with lysis buffer) and the mixture was rotated for 4 h at 4°C.…”

MicroRNAs and synaptic plasticity—a mutual relationship

“…Pilocarpine-induced epilepsy results in increase of hippocampal pri-miR-132 [60] and miR-132 level [60,85]. miR-132 is also upregulated in kainic-acid-induced epilepsy (via injections into amygdala) only if the destructive stimulus is applied, but not if the animals are preconditioned to the seizures [81]. Moreover, in vivo inhibition of miR-132 prior to the epileptic insult protects against the cellular damage in CA3, but has no effect on seizure occurrence [81].…”

“…Human temporal lobe epilepsy and experimentally induced epilepsy result in changes of the level of specific miRNAs in brain tissue in a region-and even neural compartment-dependent manner [78][79][80][81]. If one considers different induction protocols, experimental designs and animal species used, then a core set of four epilepsyrelated miRNAs has emerged (miR-132, miR-134, miR-124, miR-34a) [82][83][84][85].…”