Gut microbiota-derived tryptophan metabolite indole-3-carboxaldehyde enhances intestinal barrier function via aryl hydrocarbon receptor/AMP-activated protein kinase signaling activation

Abstract

Objective: Intestinal inflammatory diseases significantly affect animal health, primarily by disrupting intestinal barrier function. Indole-3-carboxaldehyde (IAld), a key metabolite of tryptophan derived from gut microbiota, exhibits protective properties against intestinal inflammatory diseases. The regulatory mechanism by which IAld modulates intestinal barrier function requires further investigation.Methods: An intestinal epithelial cell injury model was established by tumor necrosis factor-alpha (TNF-α) stimulation, alongside a mouse colitis model induced by dextran sulfate sodium (DSS) administration. Intestinal barrier function was assessed by immunoblotting, immunofluorescence, in vitro permeability assays, and histopathological analysis. Mitochondrial integrity and function were evaluated using JC-1 staining and transmission electron microscopy. Additionally, key components of the aryl hydrocarbon receptor (AhR)/AMP-activated protein kinase (AMPK) signaling pathway were analyzed using immunoblotting, immunofluorescence, and immunoprecipitation techniques.Results: Our findings demonstrate that IAld treatment significantly enhanced tight junction protein expression in intestinal epithelial cells and effectively attenuated TNF-α-induced intestinal barrier injury. IAld activated cellular AMPK signaling, promoting autophagy, maintaining mitochondrial homeostasis, and ultimately improving intestinal barrier function. Importantly, the activation of AMPK signaling by IAld was found to be dependent on the AhR, as evidenced by the AhR-specific inhibitor CH-223191, which abolished both IAld-induced AMPK activation and enhancement of intestinal barrier integrity. Furthermore, in vivo< experiments confirmed that IAld ameliorated intestinal barrier dysfunction and mitochondrial damage in DSS-induced colitis mice, whereas pharmacological inhibition of AMPK largely abrogated these protective effects.Conclusion: Our findings demonstrate that IAld effectively preserves intestinal barrier integrity, highlighting its potential application in the treatment of intestinal inflammatory diseases in both animals and humans.