Bacteroides uniformis ameliorates pro-inflammatory diet-exacerbated colitis by targeting endoplasmic reticulum stress-mediated ferroptosis

INTRODUCTION: A pro-inflammatory diet is positively associated with the risk and progression of inflammatory bowel diseases (IBD). Recently, ferroptosis has been observed in patients with different dietary patterns-associated intestinal inflammation, while the mechanisms underlying the effects of a pro-inflammatory diet and whether it mediates ferroptosis are unknown. OBJECTIVES: This study aims to elucidate the mechanisms underlying pro-inflammatory diet-mediated colitis and explore potential intervention strategies. METHODS: Mice were fed a dietary inflammatory index-based pro-inflammatory diet for 12 weeks. Subsequently, colitis was chemically induced using 2.5 % dextran sulfate sodium. The body weight, pathological score, immune response and mucosal barrier function were evaluated to assess intestinal inflammation. Intestine tissue transcriptomics, fecal microbiome analysis and serum metabolomics were applied to identify diet-microbe-host interactions. Additionally, the dietary inflammatory index (DII) scores and intestinal specimens of 32 patients with Crohn's disease were evaluated. The biological functions of Bacteroides uniformis were observed in vitro and in vivo. RESULTS: Pro-inflammatory diet induces low-grade intestinal inflammation in mice and exacerbates colitis by activating glutathione peroxidase 4-associated ferroptosis in the endoplasmic reticulum stress-mediated pathway. These effects are reversed by ferrostatin-1 treatment. Additionally, the pro-inflammatory diet triggers colitis by modulating the gut microbiota and metabolites. Notably, supplementation with B. uniformis improves the pro-inflammatory diet-aggravated colitis by inhibiting endoplasmic reticulum stress-mediated ferroptosis. Moreover, B. uniformis is non-enterotoxigenic and non-enteroinvasive in co-cultures with intestinal epithelial cells. CONCLUSIONS: Pro-inflammatory diet drives colitis by targeting endoplasmic reticulum stress-mediated ferroptosis, possibly in a gut microbiota-dependent manner. Pro-inflammatory diet restriction and microbial-based therapies may be effective strategies for preventing and treating IBD.