Bifidobacterium modulates gut microbiota and aryl hydrocarbon receptor signaling in necrotizing enterocolitis rat model.

BACKGROUND

Neonatal necrotizing enterocolitis (NEC) is linked to gut microbiota dysbiosis and inflammation. Bifidobacterium-mediated tryptophan metabolites, including indole-3-lactic acid (ILA), may exert anti-inflammatory effects via the aryl hydrocarbon receptor (AhR) pathway. This study investigated the protective effects and mechanisms of Bifidobacterium BB-12 in NEC.

METHODS

Neonatal rats were assigned to a control, NEC, and Bifidobacterium-treated NEC groups. Clinical symptoms, survival, serum cytokines, intestinal pathology, microbiota structure (16S rRNA sequencing), and AhR/CYP1A1 expression (quantitative reverse transcription polymerase chain reaction, western blotting) were evaluated. Colon metabolomics and in vitro lipopolysaccharide (LPS)-induced intestinal epithelial cell assays with AhR knockdown were performed to assess the role of ILA.

RESULTS

Bifidobacterium markedly alleviated symptoms, reduced intestinal damage, increased survival, and suppressed inflammatory factors. It restored gut microbiota diversity by increasing beneficial taxa (Bacteroidetes, Actinobacteria, Bifidobacterium), and decreasing pathogenic bacteria (Proteobacteria, Shigella-Escherichia). AhR/CYP1A1 expression was upregulated and negatively correlated with tissue damage. Metabolomics revealed elevated levels of ILA, indole-3-aldehyde, and 3-hydroxyanthranilic acid. In vitro, ILA inhibited LPS-induced inflammation and upregulated AhR/CYP1A1, while AhR knockdown largely abolished these effects.

CONCLUSION

Bifidobacterium BB-12 protects against NEC by reshaping the gut microbiota, activating the AhR-CYP1A1 pathway, and regulating tryptophan metabolites, with ILA partially mediating its anti-inflammatory effects.

IMPACT: Neonatal necrotizing enterocolitis is a severe inflammatory bowel disease in premature infants with limited treatment options, highlighting the need for new preventive and therapeutic strategies. Bifidobacterium is an effective probiotic, but its molecular mechanisms in NEC through host metabolic-immune interactions remain unclear. This study strongly suggest that in a neonatal rat NEC model, Bifidobacterium alleviates intestinal inflammation and tissue damage by reshaping the gut microbiota, elevating tryptophan metabolites like ILA, and activating the AhR-CYP1A1 signaling pathway. The findings provide a framework for understanding probiotic-mediated gut protection and potential targets for interventions using microbial metabolites or AhR agonists.