Bifidobacterium longum engineered with artificial enzymes alleviates high-altitude colitis via inhibition of GPD2-dependent ferroptosis.

Intestinal inflammation and barrier disruption induced by high-altitude exposure are recognized contributors to colitis. Although artificial-enzyme-engineered Bifidobacterium longum (AE-BL) has demonstrated therapeutic potential against inflammatory bowel disease, the precise mechanisms remain elusive. The present study aimed to assess the efficacy of AE-BL against high-altitude colitis and to elucidate its underlying mechanisms. AE-BL was generated through the assembly of single-atom enzymes (SAzymes) with Bifidobacterium longum (BL). In vivo investigations involved housing mice in a hypobaric hypoxic chamber to replicate high-altitude conditions, followed by AE-BL administration. After seven days, colon specimens were collected for histopathological evaluation, inflammatory and ferroptosis-related parameter analyses, and the expression of glycerol-3-phosphate dehydrogenase 2 (GPD2), tight junction proteins, and ferroptosis markers. An in vitro colitis model was also established using Caco-2 cells subjected to lipopolysaccharide (LPS) and hypoxia, followed by AE-BL treatment. Administration of AE-BL markedly ameliorated high-altitude-induced colitis in mice, as reflected by attenuated weight loss, increased colon length, reduced disease activity index (DAI), and diminished histopathological injury. Pro-inflammatory cytokine production was suppressed, and intestinal barrier integrity was preserved. Mechanistic investigations indicated that the protective actions of AE-BL were potentially mediated through suppression of GPD2-driven ferroptosis. Under hypoxic conditions, AE-BL significantly reduced ferroptosis in colon tissue and colonic epithelial cells both in vivo and in vitro, thereby alleviating inflammation and restoring intestinal barrier function.