(894) M2 Microglia-Derived Exosomes Protect Sepsis-Associated Encephalopathy via Exosomal miR-124-3p

Introduction: Although it has been reported that miRNAs carried by M2-type microglial exosomes have neuroprotective effects in stroke, traumatic brain injury and Alzheimer's disease, whether they have protective effects in sepsis associated encephalopathy remains unclear.This study aimed to explore the miRNA signaling pathway by which M2-type microglia-derived exosomes (M2-exosomes) ameliorate the L-Glu induced neuronal injury，and to provide new ideas for the treatment of sepsis associated encephalopathy.

Methods: The L-Glu neuron injury model was established, and metabolomic analysis was performed to search for differential metabolites. BV2 cells were induced to M1 and M2 polarization.BV2-exosomes were identified via transmission electron microscopy and special biomarker detection and co-cultured with HT22 cells.Cell Counting Kit-8 and LDH kit were used to detect cell viability, flow cytometry was used to detect apoptosis, and Western Blot experiments was used to detect protein expression level. The target genes of miR-124-3p were predicted by bioinformatics analysis, verified by dual-luciferase reporter assay. Sepsis mouse model was established by cecal ligation, exosomes were injected into tail vein, and the learning, memory and cognitive abilities of mice were evaluated by Morris water maze.

Results: Through metabolomics, 81 different metabolites were found, including GABA, 2, 4-diaminobutyric acid, etc. The enrichment analysis of differential metabolites showed that they were mainly enriched in glutathione metabolism, glycine and serine metabolism, and urea cycle. M2-BV2 exosomes could reduce L-Glu induced apoptosis, restore mitochondrial membrane potential, reduce intracellular ROS accumulation, and restore the anti-oxidative stress ability of cells. After transfection of miR-124-3p into HT22 cells, it was found that its protective effect on neurons was comparable to that of M2-EXOs. Our mechanistic study further demonstrated that ROCK was the direct downstream target of miR-124-3p. Animal experiments have shown that M2-EXOs can significantly improve the learning, memory and cognitive abilities of sepsis mice.

Conclusions: We demonstrated that M2 microglia-derived exosomes attenuated L-Glu induced neuron damage and promoted neuronal survival via exosomal miR-124-3p and its downstream target ROCK.