Objective To explore the role of SAT1-mediated macrophage polarization in the pathogenesis of rheumatoid arthritis (RA).

Methods The RAW264.7 cells were selected and divided into the following groups: the control group which consisted of normally cultured cells; the M1 polarization induction group: the cells were treated with 100 ng/mL LPS and 20 ng/mL IFN-γ for 24 h; the M2 polarization induction group: the cells were treated with 20 ng/mL IL-4 for 24 h; the LPS + IFN-γ + SAT1 inhibitor group: the cells were treated with the addition of SAT1 inhibitor while adding LPS and IFN-γ for 24 h; the IL-4 + SAT1 inhibitor group: the cells were treated with the addition of SAT1 inhibitor while adding IL-4 for 24 hs. The cell viability was assessed by the CCK-8 method; the cytokine secretion was determined by ELISA; the related gene expression was detected by Real-time PCR; and the related protein expression was analyzed by Western blot; the macrophage polarization markers were identified by immunofluorescence staining; the macrophage surface markers were analyzed by flow cytometry.

Results Compared with the control group, the cell survival rate in the M1 polarization induction group was decreased significantly (P ＜ 0.01), while no significant change in the M2 polarization induction group (P ＞ 0.05); the cell survival rates in the LPS + IFN-γ + SAT1 inhibitor and IL-4 + SAT1 inhibitor groups were higher than those in the corresponding polarization induction groups (P ＜ 0.05). Compared with the control group, the OD values of IL-1β, IL-6 and TNF-α in the M1 polarization induction group were increased significantly (P ＜ 0.01), no significant change of IL-10 (P ＞ 0.05); the OD values of IL-1β, IL-6, and TNF-α in the M2 polarization induction group were decreased significantly (P ＜ 0.05), and the OD value of IL-10 was increased significantly (P ＜ 0.05). Compared with the control group, the mRNA expression levels of iNOS and SAT1 in the M1 polarization induction group were increased significantly (P ＜ 0.01), and the Arg-1 mRNA expression level was decreased (P ＜ 0.05); the Arg-1 mRNA expression level in the M2 polarization induction group was increased significantly (P ＜ 0.01), and the mRNA expression levels of iNOS and SAT1 were decreased significantly (P ＜ 0.05). Compared with the control group, the protein expression levels of iNOS, p-STAT6, and SAT1 in the M1 polarization induction group were increased significantly (P ＜ 0.01), and the Arg-1 protein expression level was decreased significantly (P ＜ 0.01); the Arg-1 protein expression level in the M2 polarization induction group was increased significantly (P ＜ 0.01), and the expression levels of iNOS, p-STAT6, and SAT1 proteins were decreased significantly (P ＜ 0.05).

Conclusions The SAT1 inhibitor can inhibit the expression of M1 polarization-related genes and proteins, and promote the expression of M2 polarization-related genes and proteins. Therefore, SAT1 may become a potential target for the treatment of RA.