Exosomes from M2-polarized macrophages relieve oxygen/glucose deprivation/normalization-induced neuronal injury by activating the Nrf2/HO-1 signaling

Stroke is a life-threatening neurological disorder with limited therapeutic efficacy. Previous studies have demonstrated that macrophages play an important role in brain injury after a stroke. However, its underlying mechanism remains unclear and the role of exosomes derived from M2-polarized macrophages (M2-Exo) in ischemic stroke has not yet been reported. In this study, we established an in vitro oxygen/glucose deprivation and re-oxygen/glucose (OGD/R) model to investigate the potential role of M2-Exo in protecting HT22 neurons against ischemia-reperfusion injury. Interleukin-4 was used to induce the M2 phenotype in macrophages, following which the exosomes were isolated from the supernatant of M2-polarized macrophages and identified by western blotting, transmission electron microscopy, and nanoparticle tracking analysis. After co-incubation with M2-Exo, OGD/R-induced neuronal injury in HT22 cells was improved, accompanied by increased cell viability and decreased lactate dehydrogenase release. In addition, the increase in percentage of terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling-positive cells in OGD/R-treated HT22 cells was attenuated after incubation with M2-Exo. M2-Exo treatment also suppressed reactive oxygen species and malondialdehyde production and improved the reduction of superoxide dismutase activity. Moreover, M2-Exo treatment was found to activate the nuclear factor erythroid related factor 2 (Nrf2)/heme-oxygenase-1 (HO-1) signaling pathway in OGD/R-treated HT22 neurons. Importantly, inhibition of Nrf2 by ML385 partially reversed the protective effects of M2-Exo against OGD/R-induced oxidative damage. Taken together, these data demonstrated that M2-Exo exerted protective effects against OGD/R-induced oxidative damage in HT22 neurons, which was mediated by the activation of Nrf2/HO-1 signaling. Hence, our findings provide a promising therapeutic approach for ischemic stroke.