Fig. 5: The MEK/ERK Pathway is involved in Il11 upregulation in DSS-induced colitis.

a, b Wild-type mice were treated with DSS, without or with NAC (a) or Abx (b). Colon cells were prepared and stained with CellRox-green, and ROS accumulation was analyzed by flow cytometry. Left panels show representative histograms of ROS levels in colon cells. Right panels show percentages of CellRox-green⁺ cells from an individual mouse. Results are mean ± SEM. n = 4 (untreated or NAC-treated) or 3 (untreated or Abx-treated) mice. c Wild-type mice were treated as in a. Colonic expression of 16S rRNA, Hmox1, and Il11 mRNA was determined using qPCR. Results are mean  ± SEM. n = 11 (untreated) or 9 (NAC-treated) mice; pooled data from three independent experiments. d Abx blocks Il11 mRNA upregulation in the colon in DSS-treated mice. Wild-type mice were untreated or treated with DSS in the absence or presence of Abx. On day 5 after DSS treatment, qPCR was performed to determine the expression of bacterial 16S rRNA and Il11 mRNA in the colon. Results are mean ± SEM. n = 8 (untreated), 3 (Abx-treated), 10 (DSS-treated), or 8 (DSS + Abx-treated) mice; pooled data from three independent experiments. e–g Trametinib inhibits ERK phosphorylation and Il11 mRNA expression in the colon in DSS-treated mice. Wild-type mice were treated with DSS in the absence or presence of trametinib injection (at –6 and –30 h), and then colon sections were prepared and stained with anti-pERK antibody (e). Scale bars, 100 μm. pERK⁺ and DAPI⁺ areas were calculated, and the ratios of pERK⁺/DAPI⁺ areas (%) were plotted (f). Results are mean ± SEM. n = 7 (untreated) or 5 (Trametinib-treated) mice; pooled data from two independent experiments. Il11 mRNA expression was determined using qPCR (g). Results are mean ± SEM. n = 6 (untreated) or 7 (Trametinib-treated) mice; Pooled data from two independent experiments. h, i NAC inhibits ERK phosphorylation in the colon in DSS-treated mice. Wild-type mice were treated with DSS in the absence or presence of NAC in the drinking water for 5 days. Colon sections were stained with anti-pERK antibody (h). Scale bar, 100 μm. The ratios of pERK⁺/DAPI⁺ areas (%) are plotted as in (f) (i). Results are mean ± SEM. n = 7 (untreated) or 8 (NAC-treated) mice; pooled data from two independent experiments. Statistical significance was determined using the unpaired two-tailed Student’s t-test (c, f, i), two-tailed Mann–Whitney U test (g), two-way ANOVA with Tukey’s multiple comparison test (d), or one-way ANOVA with Tukey’s multiple comparison test (a, b). Source data are provided as a Source Data file.