FIG 6.

Supplementation with Trp-derived AhR ligands rescues the protective effects of Trp on E. coli-induced endometritis. (A) Microbiota-mediated Trp metabolism pathways are shown. (B-D) Intestinal indole-3-aldehyde (IAld; B), indole (C), and indole-3-propionic acid (IPA; D) levels were determined from different treatment groups (n = 5). (E) A schematic representation of AhR ligand supplementation is shown. Mice were pretreated with ABX for 1 week and then treated with Trp (1% in diet) and ABX for the next 2 weeks. IAld, indole, or IPA were supplemented during Trp and ABX treatment. Control mice were treated with ABX and vehicle of indole derivatives (0.2% sodium carboxymethylcellulose and 0.25% polysorbate-80 in PBS). (F) Representative H&E-stained images of uterine sections are shown. The red arrow shows inflammatory changes and the black arrow shows endometrial damage (scale bar = 20 μm). (G-J) Histological scores (G), MPO activity (H), and TNF-α (I) and IL-1β (J) levels were assessed in different treatment groups (n = 5). Data are expressed as the mean ± SD, and one-way ANOVA was performed for statistical analysis (B-D and G-J). *, P < 0.05; **, P < 0.01; and ***, P < 0.001 indicate significant differences. ns, no significance; ABX, cocktail of antibiotics; IAld, indole-3-aldehyde; IPA, indole-3-propionic acid; Trp, tryptophan; IAld, indole-3-aldehyde; IPA, indole-3-propionic acid; acdA, acyl-CoA dehydrogenase; AraT, aromatic amino acid aminotransferase; fldBC, phenyllactate dehydratase; fldH, phenyllactate dehydrogenase; porB, C, pyruvate: ferredoxin oxidoreductase B and C; TMO, tryptophan 2-monooxygenase; TNA, tryptophanase; TrD, tryptophan decarboxylase.