MiR-223-3p promote microglia “M2” polarization by targeting FOXO3a in subarachnoid hemorrhage

Objective

Exosome-derived micorRNAs (miRs) play important role in regulation the inflammatory response in subarachnoid hemorrhage (SAH). However, the ability of miR-223-3p, which is enriched in astrocyte-derived exosomes, to regulate FOXO3a in microglia is still unclear.

Methods

MiR-223-3p in CSF from SAH patients was measured by qRT–PCR. Rats and BV2 cells were used to establish SAH model. Neurological function was evaluated by the mNSS, rotarod test, and Morris water maze. QRT–PCR and enzyme-linked immunosorbent assay (ELISA) were used to analyze oxidative stress and inflammatory factors interleukin-1β (IL-1β), IL-6 and tumor necrosis factor α (TNF-α). The levels of FOXO3a, TLR4, NLRP3, NF-κB, iNOS, Cox2, Nrf2 and HO-1 were detected by WB. The exosomes were labeled with KPH67, and uptaken by microglia, detecting by IF.

Results

Among the miRs involved in SAH, miR-223-3p exhibited one of the greatest change. MiR-223-3p in the brain tissue of SAH rats was upregulated. Moreover, the upregulation of miR-223-3p significantly improved neurological deficits and reduced brain edema. Meanwhile, miR-223-3p reduced the inflammatory factors like IL-1β, IL-6, TNF-α, and decreased oxidative stress, inhibited the activation of NF-κB, TLR4/NLRP3 in microglia by targeting Foxo3a. The “M1” polarization marker, including iNOS, Cox2, TLR4, NLRP3 and NF-κB, in microglia decreased markedly after the overexpression of miR-223-3p. Moreover, miR-223-3p targets FOXO3a and inhibits it expression no matter in vitro or in vivo. In vitro, both miR-223-3p mimics and astrocyte-derived exosomes obviously increased the expression of miR-223-3p in microglia.

Conclusion

In SAH, astrocyte-derived exosomes rich in miR-223-3p may regulate the activation and phenotype of microglia by targeting FOXO3a, resulting in the inhibition of inflammatory injury.