Fig. 2: The colon tissue-resident microbiota triggers succinate-mediated pro-inflammatory responses in mice with oxazolone-induced colitis.

A Schematic of mouse gut microbiome depletion using an antibiotic cocktail [amphotericin-B (0.1 mg/ml; Sigma), ampicillin (1 g/l; Sigma), vancomycin (5 mg/ml; Sigma), metronidazole (10 mg/ml; Sigma), and neomycin (10 mg/ml; Sigma)]. B Body weight reduction is less pronounced in AIMD mice than in wild-type mice following colitis induction with oxazolone. C Inflammatory lesion formation is significantly suppressed in AIMD mice compared to wild-type mice after colitis induction. D Representative hematoxylin and eosin-stained sections of mouse colon tissue, accompanied by blinded histologic scores (scale bar: 100 μm). E Fecal succinate levels measured in various groups of animals. F Flow cytometry plots of CD4⁺IL-9⁺ helper T cells from the colonic lamina propria, along with percentages. G The expression levels of Th9-associated genes, including IL-9, Foxo1, IL-9R, and BATF, were quantified using qPCR from the MLNs of treated mice. H The expression level of SUCNR1, a surrogate indicator of succinate availability, was measured using qPCR in the MLNs of treated mice. I Schematic of fecal succinate elevation using FMT from diseased and streptomycin donors (a concentration of 20 mg in 200 μl of PBS by gavage per mouse for 72 h, followed by colitis induction using oxazolone). J Succinate levels measured in stools from diseased and streptomycin-donor mice. K Body weight reduction in FMT donors. L Inflammatory lesion formation in FMT donors. M Body weight reduction in FMT recipients. N Inflammatory lesion formation in stool recipients from oxazolone donors and oxazolone-streptomycin-donors. O Representative hematoxylin and eosin-stained sections of mouse colon tissue from recipients of oxazolone and oxazolone-streptomycin stools, accompanied by blinded histologic scores. P Succinate levels were measured in the stools of recipients of oxazolone and oxazolone-streptomycin stools. Q The expression levels of Th9-associated genes, including IL-9, Foxo1, IL-9R, BATF, AHR, and IRF-4, were quantified using qPCR from the MLNs of recipients of oxazolone and oxazolone-streptomycin stools. R The expression level of SUCNR1, a surrogate indicator of succinate availability, was measured using qPCR in the MLNs of recipients of oxazolone and oxazolone-streptomycin stools. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001 (Student’s t-test, one-way ANOVA, or two-way ANOVA).