Fig. 1.
Dietary Trp ameliorates a mouse model of colitis in a microbiome-dependent manner. (A) C57BL/6 mice were pretreated with antibiotics (ABX: ampicillin [9 mg/kg], metronidazole [9 mg/kg], neomycin [9 mg/kg], and vancomycin [4.5 mg/kg], intragastrically) for 7 d and then fed a Trp-rich diet (42 g Trp/kg diet) or standard chow (2 g Trp/kg diet) for 7 d, followed by administration of DSS (3%, wt/vol) or vehicle for 7 d (ad libitum) with continued antibiotic treatment and Trp feeding. (B) The mice were weighed daily. (C) Mice were orally gavaged with FITC-dextran (900 mg/kg) on day 14, and serum levels of FITC-dextran were measured 4 h later. (D) On day 14, the mice were killed, and colon lengths were measured, (E) disease activity index was measured, and (F and G) the distal colon was stained with hematoxylin and eosin (H&E) and blindly scored (0 = none, 1 = very mild, 2 = mild, 3 = moderate, 4 = severe) for epithelial damage, mononuclear and polymorphonuclear infiltrate, and submucosal edema. (Scale bar: 50 μm.) (H–M) Colon sections were stained for TJ and AJ proteins and imaged by confocal microscopy (see also SI Appendix, Fig. S1, for occludin and β-catenin). (Scale bars: 20 μm.) (J–M) Relative (rel.) brightness of images with error as SD from the mean was calculated (n = 15). (H and J) ZO1. (I and L) E-cadherin. (K) Occludin. (M) β-catenin. Data are representative of at least three independent experiments; n = 5 mice per group. One-way ANOVA followed by post hoc Tukey’s test: **P < 0.01, ***P < 0.001, n.s.: not significant.