Decreased Microglia Exosomal Notch1 Attenuates Ischemia-Reperfusion Brain Injury through STAT3/NF-κB Signaling Pathway

Abstract

Background: Ischemic is one of the major types of strokes and is regarded as the third important cause of mortality and the leading factor of permanent disability. Especially, the ischemia-reperfusion (I/R) injury always induces traumatic tissue damage and irreversible loss of neurons, making it crucial to explore novel therapeutic strategies for treating I/R injury. This study investigated the function of microglial exosomes in I/R injury and explored the association of underlying mechanisms with Notch1 and signal transducer and activator of transcription 3 (STAT3)/nuclear factor kappa B (NF-κB) signaling pathway. Methods: The immortalized murine microglial cell line BV2 was purchased and the oxygen-glucose deprivation (OGD)-treated neurons were established in this study. In addition, real-time reverse transcriptase-polymerase chain reaction (RT-qPCR), western blot, transmission electron microscope, particle size analysis, cell counting kit-8 (CCK-8), the terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) assay, and lactate dehydrogenase (LDH) assay were utilized for mechanistic studies. Results: BV2 cells were successfully polarized (M2) and exosomes were successfully isolated in this study. OGD treatment resulted in increased apoptosis and decreased viability of neuronal cells (p < 0.05), which could be reversed by exosomes of polarized BV2 cells (p < 0.05). Decreased Notch1 expression was associated with the attenuation of OGD-induced neuronal apoptosis (p < 0.05). Decreased Notch1 expression could activate STAT3/NF-κB pathway, and activated STAT3/NF-κB pathway was associated with less cell apoptosis and more cell viability (p < 0.05). Conclusion: The present study demonstrates that the down-regulated Notch1 in exosomes secreted by M2 microglia attenuates the ischemia-reperfusion brain injury by targeting the downstream STAT3/NF-κB pathway.