Inhibition of microRNA-34a Suppresses Epileptiform Discharges Through Regulating Notch Signaling and Apoptosis in Cultured Hippocampal Neurons

Abstract

Epilepsy is characterized by recurrent unprovoked seizures and some seizures can cause neuronal apoptosis, which is possible to make contributions to the epilepsy phenotype, impairments in cognitive function or even epileptogenesis. Moreover, many studies have indicated that microRNA-34a (miRNA-34a) is involved in apoptosis through regulating Notch signaling. However, whether miRNA-34a participates in neuronal apoptosis after seizures remain unclear. Therefore, we aimed to explore the expression of miRNA-34a and its effects on the epileptiform discharge in spontaneous recurrent epileptiform discharges (SREDs) rat hippocampal neuronal pattern. Mg2+-free medium was used to induce SREDs, quantitative reverse-transcription polymerase chain reaction was used to detect the expression of miRNA-34a, western blot was used to determine the expression of Notch pathway and apoptosis-related proteins, and whole cell current clamp recordings was used to observe the alteration of epileptiform discharge. We found obvious apoptosis, increased expression of miRNA-34a and decreased expression of Notch signaling in Mg2+-free-treated neurons. Treatment with miRNA-34a inhibitor decreased the frequency of action potentials, activated Notch signaling and prevented neuronal apoptosis in Mg2+-free-treated neurons. However, treatment with miRNA-34a mimics increased the frequency of action potentials, down-regulated Notch signaling and promoted neuronal apoptosis in Mg2+-free-treated neurons. Furthermore, γ-secretase inhibitor N-[N-(3,5-di-uorophenacetyl)-1-alanyl]-S-phenylglycine t-butylester (DAPT), an inhibitor of Notch signaling, could weaken anti-apoptosis effect of miRNA-34a inhibitor. These results suggest that inhibition of miRNA-34a could suppress epileptiform discharges through regulating Notch signaling and apoptosis in the rat hippocampal neuronal model of SREDs.