Dysregulation of CD177(+) neutrophils on intraepithelial lymphocytes exacerbates gut inflammation via decreasing microbiota-derived DMF

Neutrophils synergize with intestinal resident intraepithelial lymphocytes (IELs) to serve as the first-line defense and maintain intestinal homeostasis. However, the underlying mechanisms whereby neutrophils regulate IELs to inhibit intestinal inflammation are still not completely understood. Here, we found that depletion of neutrophils (especially CD177(+) subset) caused expansion of colitogenic TCRγδ(+)CD8αα(+) IELs, increased intestinal inflammation, and dysbiosis after dextran sulfate sodium exposure or Citrobacter rodentium infection in mice. scRNA-seq analysis revealed a pyroptosis-related gene signature and hyperresponsiveness to microbiota in TCRγδ(+)CD8αα(+) IELs from colitic Cd177(−/−) mice. Microbiota-derived fumarate and its derivative dimethyl fumarate (DMF), as well as fumarate-producing microbiotas, decreased in the feces of colitic Cd177(−/−) mice. Elimination of dysbiosis by antibiotics treatment or co-housing procedure and DMF supplementation restrained TCRγδ(+)CD8αα(+) IEL activation. Consistently, DMF significantly alleviated intestinal mucosal inflammation in mice through restricting gasdermin D (GSDMD)-induced pyroptosis of TCRγδ(+)CD8αα(+) IELs. Therefore, our data reveal that neutrophils inhibit intestinal inflammation by promoting microbiota-derived DMF to regulate TCRγδ(+)CD8αα(+) IEL activation in a GSDMD-mediated pyroptosis-dependent manner, and that DMF may serve as a therapeutic target for the management of intestinal inflammation.