[Fractalkine inhibits lipopolysaccharide-induced M1 polarization of macrophages by activating Wnt/β-catenin signaling pathway].

OBJECTIVE

To explore the mechanism by which fractalkine (CX3CL1; FKN) inhibits lipopolysaccharide (LPS)-induced immunological response in RAW264.7 cells.

METHODS

A RAW264.7 cell model overexpressing FKN was established by transfection with the lentiviral vector CX3CL1. The effects of LPS, ICG-001 (a Wnt/β-catenin signaling pathway inhibitor), either alone or in combination, on M1 polarization of na?ve and FKN-overexpressing RAW264.7 cells were evaluated by detecting of intereukin-6 (IL-6) and tumor necrosis factor-α (TNF-) using ELISA. The protein expressions of the inflammatory factors (iNOS, TNF-, and IL-6), FKN, Wnt-4, and β-catenin were detected by Western blotting. The subcellular localization of IL-6 in the cells was detected by immunofluorescence assay.

RESULTS

The RAW264.7 cell model of FKN overexpression was successfully established. In na?ve RAW264.7 cells, treatment with both ICG-001 and LPS, as compared with LPS alone, significant promoted TNF- and IL-6 secretions, increased intracellular levels of TNF-, IL-6 and iNOS ( < 0.05), and reduced intracellular FKN, Wnt-4 and β-catenin levels ( < 0.01). In FKN-overexpressing RAW264.7 cells, LPS treatment significantly reduced the secretion of TNF- and IL-6 and intracellular levels of TNF-, IL-6 and iNOS ( < 0.01), increased intracellular FKN, Wnt-4 and β-catenin protein contents ( < 0.01), and inhibited IL-6 localization in the cytoplasm; compared with LPS, the combined treatment with ICG-001 and LPS obviously enhanced IL-6 localization in the cytoplasm of the cells.

CONCLUSIONS

FKN overexpression suppresses LPS-induced M1 type polarization of RAW264.7 cells by activating Wnt/β-catenin signaling pathway.