An ultralow dose of DPI inhibits the classical activation of macrophages. (A) Analysis of the M1-associated mRNA expression in the colonic lamina propria of DSS-induced colitis mice. The colon samples were analyzed on day 15 after DSS treatment (n = 5 per group). (B) The M1-associated marker, iNOS, was analyzed by immunofluorescence and (C) the number of iNOS+ cells/ visual field in the colonic tissues was enumerated. (D) IL-6 and (E) TNF-α levels in the supernatants of BMDMs treated with LPS and DPI for 6 h. M1-associated mRNA levels (F) and protein levels (G) in RAW264.7 cells and BMDMs. Cells were treated with LPS (500 ng/mL) and DPI (10-13 or 10-14 M) for 6 h and then analyzed by qRT-PCR and immunoblotting with the indicated antibodies. The experiment was repeated three times. The results are presented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.