Fig 1. Red 40 induces colitis in IL-23 overexpressing mice.

(A) Chemical structure of Red 40. (B) Experimental scheme. R23FR mice were treated with TAM and 0.025% Red 40 in drinking water (0.25g/L), or with TAM alone or with Red 40 in drinking water alone. (C) Fecal lipocalin-2 levels at day 56. (D,E) Representative H&E-stained sections (D) and histologic scores (E) of the cecum and colon of experimental mice described in Fig. 1B. (F) Experimental scheme. R23FR mice were treated with TAM + Red 40 for 2 cycles. For the final cycle, animals were treated with 0.25 g/L Red 40 in drinking water (positive control, 250mg/L), Kool aid (containing 200mg/L Red 40), Pedialyte AdvancedCare cherry punch flavor (containing 16 mg/L Red 40) or Pedialyte hydrating solution without Red 40 for 7 days. (G,H) Histologic scores (G) and representative H&E-stained sections (H) of the cecum of experimental mice described in Fig. 1F. (I) Experimental scheme. Unfractionated CD4⁺ T cells obtained from mLN of R23FR mice in remission (TAM + Red 40 treated group, d48) were injected into Rag1^−/− mice (10⁶ cells/mouse) fed with or without Red 40 in drinking water. (J,K) Representative H&E-stained sections (J) and histologic scores (K) of the cecum of experimental mice at day 21 described Fig. 1I.

Scale bars in (D) (H) and (J), 50 μm. In (C) (E) (G) and (K), each dot indicates an individual mouse. Error bars indicate SEM. ns p> 0.05, ** p<0.01, *** p<0.001, by nonparametric Mann-Whitney test.