Exosomes derived from M2-type microglia ameliorate oxygen-glucose deprivation/reoxygenation-induced HT22 cell injury by regulating miR-124-3p/NCOA4-mediated ferroptosis

Background: Although it has been reported that miRNA carried by M2 microglial exosomes pro-tects neurons from ischemia-reperfusion brain injury, the mechanism of action remains poorly understood. This study aimed to explore the miRNA signaling pathway by which M2-type microglia-derived exosomes (M2-exosomes) ameliorate oxygen-glucose deprivation/reoxygena-tion (OGD/R)-induced cytotoxicity in HT22 cells.Methods: BV2 microglia were induced by M2 polarization. Then, M2-exosomes were identified via transmission electron microscopy and special biomarker detection and co-cultured with HT22 cells. Cell proliferation was evaluated using the Cell Counting Kit-8 (CCK-8) assay. Intracellular concentrations of reactive oxygen species (ROS), Fe2+, glutathione (GSH), and malondialdehyde (MDA) were determined using dichlorofluorescein fluorescence and biochemical determination. miR-124-3p levels were determined using qRT-PCR, and protein expressions were examined via western blotting.Results: OGD/R suppressed the proliferation and induced the accumulation of Fe2+, ROS, and MDA and reduction of GSH in mouse HT22 cells, suggesting ferroptosis of HT22 cells. OGD/R-induced changes in the above mentioned indexes was ameliorated by M2-exosomes but restored by the exosome inhibitor GW4869. M2-exosomes with (mimic-exo) or without miR-124-3p (inhibitor-exo) promoted and suppressed proliferation and ferroptosis-associated indexes of HT22 cells, respectively. Moreover, mimic-exo and inhibitor-exo inhibited and enhanced NCOA4 expression in HT22 cells, respectively. NCOA4 overexpression reversed the protective effects of miR-124-3p mimic-exo in OGD/R-conditioned cells. NCOA4 was targeted and regulated by miR-124-3p.Conclusions: M2-exosome protects HT22 cells against OGD/R-induced ferroptosis injury by transferring miR-124-3p and NCOA4 into HT22 cells, with the latter being a target gene for miR-124-3p.