MicroRNA 125b-5p Protects Against Cerebral Ischemia Injury Inhibiting Microglia Activation

Objective:We observed that the expression of miR125b-5p was reduced in the plasma and cortices of mice flowing MCAO.Hence,we investigated the effects of miR125b-5p on cerebral ischemia and the potential mechanisms.Methods:Male ICR mice were subjected to middle cerebral artery occlusion(MCAO).Infarction was determined with 2,3,5-triphenyltetrazolium chloride(TTC).Two behavioral tests,modified Neurological Severity Scores(mNSS)and Corner test,were utilized to assess the neurological deficits following MCAO.BV2 microglia cells were activated with LPS,conditioned medium collected from neurons subject to oxygen-glucose deprivation(OGD).The expression of miR125b-5p in the brain tissue and microglia was analyzed with quantitative PCR(qPCR).The expression of pro-inflammatory mediators in the ischemic brain and activated microglia was analyzed with qPCR,western blot and ELISA.Microglia-mediated neuronal cell death of mouse hippocampal HT-22 cells was determined by flow cytometry.Results:miR125b-5p levels were significantly decreased in mouse plasma,leukocyte and ipsilateral cortex at 24 hours following MCAO.Cerebral miR125b-5p mimic decreased infarction and attenuated the expression of potential target TNF-a and other pro-inflammatory mediators in the ischemic brain following MCAO.In the in vitro study,miR125b-5p mimic significantly reduced expression of TNF-a and other 3 pro-inflammatory mediators in activated microglia.Compared to Conditioned media from OGD-stimulated BV2 microglia,conditioned media from OGD-stimulated BV2 microglia with miR125b-5p mimic transfection remarkably reduced HT-22 neuronal cell death.Conclusions:MiR125b-5p protects against ischemic stroke by suppressing microglia activation possibly via potentially downregulation of TNF-a.