Fig. 3
L. johnsonii protects against colitis and activates the AhR signaling pathway. A Experimental schema for B–P. Mice were treated with 1 × 108 CFU of L. johnsonii, heat-killed L. johnsonii, or L. johnsonii ATCC 33200 in 100 μL of sterile anaerobic PBS by daily gavage for 14 days, and 3% (w/v) DSS was added to the drinking water from day 7 to day 14. B The abundance of L. johnsonii in the feces of mice. C, D Body weight (C) and disease activity index (D) were monitored daily after DSS treatment. E Representative photographs (left) and length quantification (right) of colon tissues. F Colonic levels of MPO, IL-6, and TNF-α. G Representative H&E-stained sections (upper) and AB/PAS-stained sections (lower) of the distal colon. Scale bars, 50 μm. H Histology scores were determined from H&E-stained sections. I The number of goblet cells per crypt was determined from AB/PAS-stained sections. J–M Transcriptomic changes in the colon were regulated by L. johnsonii. n = 3 mice per group. J Principal component analysis (PCA) of transcriptional profiling. K Volcano plot of differentially expressed genes induced by L. johnsonii. L Heatmap of reported AhR target mediators and IL-22-related barriers regulating genes. M Correlation network of colitis-related parameters and AhR-related genes as in Fig. 3L. Purple nodes indicate colitis-related parameters; orange nodes indicate genes. Only nodes with FDR-adjusted P < 0.1 were shown. The edges are colored based on the positive or negative Spearman correlation coefficients, with orange indicating a positive correlation and purple a negative correlation, and the stronger the correlation, the thicker the edge. N–P Colon tissues were harvested from PBS- or L. johnsonii-treated mice. Q–T Colon tissues were harvested from PBS- or BG-treated mice. Related to Fig. 1. N, Q Relative gene expression of AhR-related genes in colon tissue assessed by RT-qPCR. R Relative gene expression of pattern recognition receptors involved in recognizing fungal-derived BG in colon tissue assessed by RT-qPCR. O, S Colonic levels of IL-22. P, T Representative Muc2-stained colon sections (left) and quantified Muc2-positive area (right). Scale bars, 50 μm. Data are presented as the mean ± SEM. n = 6 mice per group if not specifically mentioned. Statistical analysis was performed using one-way ANOVA followed by Dunnett’s post hoc tests for B, H and I, two-way ANOVA followed by Tukey’s post hoc test for C and D, one-way ANOVA followed by Tukey’s post hoc test for E and F, and t-test or t-test with Welch’s correction for N–T. LJ, L. johnsonii; HK-LJ, heat-killed L. johnsonii; LJ-ATCC, L. johnsonii ATCC 33200; H&E, hematoxylin and eosin; AB/PAS, Alcian Blue/periodic acid-Schiff; MPO, myeloperoxidase; HI, histological index