Abstract: 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-α) using ELISA. The protein expressions of the inflammatory factors (iNOS, TNF-α, 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-α and IL-6 secretions, increased intracellular levels of TNF-α, IL-6 and iNOS (P<0.05), and reduced intracellular FKN, Wnt-4 and β-catenin levels (P<0.01). In FKN-overexpressing RAW264.7 cells, LPS treatment significantly reduced the secretion of TNF-α and IL-6 and intracellular levels of TNF-α, IL-6 and iNOS (P<0.01), increased intracellular FKN, Wnt-4 and β-catenin protein contents (P<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. Conclusion FKN overexpression suppresses LPS-induced M1 type polarization of RAW264.7 cells by activating Wnt/β-catenin signaling
pathway.

Key words: macrophages; polarization; fractalkine; Wnt/β-catenin signaling pathway