Indole-3-carbinol prevents colitis and associated microbial dysbiosis in an IL-22–dependent manner
Philip B. Busbee, Lorenzo Menzel, Haider Rasheed Alrafas, Nicholas Dopkins, William Becker, Kathryn Miranda, Chaunbing Tang, Saurabh Chatterjee, Udai P. Singh, Mitzi Nagarkatti, Prakash S. Nagarkatti
Philip B. Busbee, Lorenzo Menzel, Haider Rasheed Alrafas, Nicholas Dopkins, William Becker, Kathryn Miranda, Chaunbing Tang, Saurabh Chatterjee, Udai P. Singh, Mitzi Nagarkatti, Prakash S. Nagarkatti
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Research Article Immunology Inflammation

Indole-3-carbinol prevents colitis and associated microbial dysbiosis in an IL-22–dependent manner

Abstract

Colitis, an inflammatory bowel disease, is caused by a variety of factors, but luminal microbiota are thought to play crucial roles in disease development and progression. Indole is produced by gut microbiota and is believed to protect the colon from inflammatory damage. In the current study, we investigated whether indole-3-carbinol (I3C), a naturally occurring plant product found in numerous cruciferous vegetables, can prevent colitis-associated microbial dysbiosis and attempted to identify the mechanisms. Treatment with I3C led to repressed colonic inflammation and prevention of microbial dysbiosis caused by colitis, increasing a subset of gram-positive bacteria known to produce butyrate. I3C was shown to increase production of butyrate, and when mice with colitis were treated with butyrate, there was reduced colonic inflammation accompanied by suppression of Th17 and induction of Tregs, protection of the mucus layer, and upregulation in Pparg expression. Additionally, IL-22 was increased only after I3C but not butyrate administration, and neutralization of IL-22 prevented the beneficial effects of I3C against colitis, as well as blocked I3C-mediated dysbiosis and butyrate induction. This study suggests that I3C attenuates colitis primarily through induction of IL-22, which leads to modulation of gut microbiota that promote antiinflammatory butyrate.

Authors

Philip B. Busbee, Lorenzo Menzel, Haider Rasheed Alrafas, Nicholas Dopkins, William Becker, Kathryn Miranda, Chaunbing Tang, Saurabh Chatterjee, Udai P. Singh, Mitzi Nagarkatti, Prakash S. Nagarkatti

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Figure 6

Neutralization of IL-22 prevents I3C-mediated protection against colitis and ability to increase butyric acid.

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Neutralization of IL-22 prevents I3C-mediated protection against colitis...
(A) Washed colonic explanted tissue (1 cm from cecum) were cultured for 24 hours (n = 5 per group). Supernatants were collected for analysis of IL-22 secretion by ELISA. (B) Total number of IL-22–expressing Th cells (n = 5 per group). (C) Total number of ILC3s expressing IL-22 (n = 5 per group). (D) TNBS colitis was induced in mice as described in Methods, and the efficacy of treatment with I3C in the presence or absence of neutralizing IL-22 antibody (aIL-22) was tested with the following experimental groups: TNBS + Isotype (n = 5), TNBS + IL-22 (n = 5), TNBS + I3C + Isotype (n = 5), and TNBS + I3C + aIL-22 (n = 5). Vehicle + Isotype (n = 5) and Vehicle + aIL-22 (n = 5) were included to assess weight and colon length compared with disease controls. (E–G) Weight loss (E) and colon length (F and G) were assessed. (H) Representative colonoscopy images taken during day 3 of the TNBS model are depicted, along with colonoscopy scores (I, n = 5). (J and K) Fold change of bacteria from colonic flushes using real-time PCR were determined for B. acidifaciens (J) and Roseburia (K). (L) SCFA n-butyric concentration was determined using GC-FID. Data are representative of 2 independent experiments. Data within dot plots and box-and-whisker plots equal the mean ± SEM, and significance was determined using 1-way ANOVA and Tukey’s multiple comparison test; *P < 0.05; **P < 0.01; ***P < 0.005; ****P < 0.001.