Fut2 deficiency aggravates chronic colitis through 2-oxindole-AHR mediated cGAS-STING pathway.

Objective: This study aims to disclose how loss of fucosyltransferase 2 (Fut2) impacts intestinal inflammation through cGAS-STING pathway that is closely associated with gut microbiota, and which microbial metabolite improves colitis in Fut2 deficiency.
Methods: Chronic colitis was induced in intestinal epithelial Fut2 knock out mice (Fut2 ^△IEC ), whose intestinal inflammation and activity of cGAS-STING pathway were evaluated. 16S rRNA sequencing and metabolomics were performed using intestinal samples. 2-oxindole was used to treat RAW264.7 cells and Fut2 ^△IEC mice with colitis (Fut2 ^△IEC -DSS) to investigate the effect of 2-oxindole on cGAS-STING response and intestinal inflammation.
Results: Fut2 loss exacerbated chronic colitis in mice, manifested by declined body weight, reduced colon length, increased disease activity index (DAI) and more colon injury in Fut2 ^△IEC -DSS mice compared with WT-DSS (wild type mice with colitis). Lack of Fut2 promoted activation of cGAS-STING pathway. Fut2 deficiency had a primary impact on colonic microbiota, as shown by alteration of microbial diversity and structure, as well as decreased Lactobacillus. Metabolic structure and tryptophan metabolism in colonic luminal microbiota were also influenced by Fut2 loss. Fut2 deficiency also led to decreased levels of aryl hydrocarbon receptor (AHR) and its ligand 2-oxindole derived from tryptophan metabolism. 2-oxindole compromised cGAS-STING response through activating AHR in macrophages, and protected against intestinal inflammation and overactive cGAS-STING pathway in Fut2 ^△IEC -DSS mice.
Conclusion: Fut2 deficiency promotes cGAS-STING pathway through suppressing 2-oxindole-AHR axis, ultimately facilitating the susceptibility to chronic colitis.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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