Expression of indoleamine 2, 3-dioxygenase modulates macrophage polarization in THP-1 cells

Abstract

OBJECTIVE: To investigate whether indoleamine 2, 3-dioxygenase (IDO) has an effect on macrophage polarization of differentiated THP-1 (dTHP-1) cells. METHODS: The macrophage model was established through incubating the human monocyte line (THP-1 cells) with phorbol-12-myristate 13-acetate (PMA) (10 ng/mL) for 48 hours. To generate M1/M2-polarized macrophages, dTHP-1 cells were cultured with IFN-γ (100 U/mL) and M-CSF (100 ng/mL), respectively. The expressions of molecular markers of macrophages (including HLA-DR, CCR7, IL-12p35, IL-10, CXCR4) and IDO were examined by real-time quantitative PCR (qRT-PCR), flow cytometry, and Western blotting. To investigate the role of IDO in the dTHP-1 cell polarization, the plasmid pEGFP-N1-IDO and siRNA-IDO were respectively transfected into cells. The mRNA levels of molecular markers of macrophages were examined by qRT-PCR. RESULTS: IFN-γ could induce the differentiation of THP-1 cells into M1 phenotype and up-regulate the IDO expression. Interestingly, our results also indicated that the ectopic IDO could trigger the transformation of dTHP-1 cells to M2 phenotype. In contrast, the knockdown of IDO expression in dTHP-1 cells resulted in increased M1 markers and lower M2 markers. CONCLUSION: The expression intensity of IDO could modulate macrophage polarization in THP-1 cells.