Mechanism of Schisandra Chinensis-mediated microglia phenotypic transformation by regulation of the TLR4 pathway based on miR-124 / 药学学报

ABSTRACT

To investigate the mechanism by which Schisandra Chinensis mediates the phenotypic transformation of microglia via microRNA-124 (miR-124)-based regulation of the Toll-like receptor 4 (TLR4) pathway, a model was established using lipopolysaccharide (LPS) stimulation of BV2 cells. Cells were treated with different doses of Schisandra Chinensis extract (SCE). MiR-124 inhibitors and negative control sequences (NC inhibitor) were transfected into LPS-induced BV2 cells and treated with SCE. The MTT assay was used for cell activity detection; an NO kit was used to measure NO release; ELISA kits were used to measure the levels of interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α). Microglia markers, including ionized calcium binding adapter molecule-1 (IBA-1) and arginase-1 (Arg-1), and the nuclear translocation of nuclear factor-kappa B (NF-κB) were evaluated by immunofluorescent staining. NF-κB p65, IBA-1, Arg-1, TLR4, myeloid differentiation primary factor 88 (MyD88), inhibitor of nuclear factor-kappa B kinases-α (IKK-α), IL-10, TNF-α were detected by immunoblot. SCE at concentrations ranging from 31.25 to 250 μg·mL-1 had no significant effect on cell activity. SCE treatment significantly inhibited NO release induced by LPS (P < 0.001, P < 0.01), increased the level of IL-10 (P < 0.05), and decreased the level of TNF-α (P < 0.001). In addition, SCE significantly reduced the expression of TNF-α, IBA-1, TLR4, and MyD88 (P < 0.01, P < 0.001) and elevated the expression of IL-10, Arg-1, NF-κB P65 and IKK-α (P < 0.001, P < 0.01, P < 0.05). SCE treatment could also promote the expression of miR-124 (P < 0.01). However, transfection with the miR-124 inhibitor increased TNF-α (P < 0.001), decreased the level of IL-10 (P < 0.05), increased the mRNA level and the protein expression of TNF-α and IBA-1 (P < 0.05, P < 0.01, P < 0.001), and decreased the mRNA level and protein expression of IL-10 and Arg-1 (P < 0.001, P < 0.01). In addition, the inhibition of TLR4 and MyD88 was attenuated. In conclusion, SCE appears to inhibit the activation of TLR4 signaling pathway by upregulating miR-124 so as to inhibit microglia M1 polarization and promote microglia M2 polarization.