Gut microbiota-derived arginine metabolism mitigates intestinal ischemia-reperfusion injury

Intestinal ischemia-reperfusion (I/R) injury is a severe pathological condition characterized by disruption of the mucosal barrier, immune dysregulation, and gut microbiota imbalance. However, whether the gut microbiota regulates immune homeostasis and mucosal repair through arginine metabolism remains unclear. We employed antibiotic-treated and fecal microbiota transplantation (FMT) mouse models, MNK-3 cells, metabolomics, arginine supplementation, and CASTOR1 knockout mice to evaluate intestinal barrier integrity, inflammatory responses, and signaling pathways following I/R injury. I/R injury induced significant microbial dysbiosis and decreased fecal arginine levels. FMT demonstrated that microbial alterations reshaped arginine metabolism in recipient mice. Arginine supplementation restored tight junction protein expression, downregulated pro-inflammatory cytokines, enhanced interleukin (IL)-22 secretion, and suppressed IL-17 upregulation. Mechanistically, arginine activated mTORC1 signaling via CASTOR1, thereby promoting IL-22 production, whereas CASTOR1 deficiency or mTORC1 inhibition markedly impaired its protective effects. The gut microbiota functions as an upstream regulator of arginine metabolism during I/R injury. Arginine confers immunoprotection by activating the CASTOR1–mTORC1–ILC3 axis, enhancing cytokine secretion and promoting mucosal repair. These findings reveal a novel microbiota–metabolism–immunity interplay and suggest nutrient-sensing pathways as promising therapeutic targets in intestinal injury.