InflammationHypoxia-Inducible Factor Signaling Compensates for Aryl Hydrocarbon Receptor in Maintaining Gut Barrier Integrity.

Background: Inflammatory bowel disease remains an enigma in terms of its etiology, with breakdown of the intestinal barrier attributed to the elusive leaky gut syndrome. In this study, we investigated the role of interplay between hypoxia-inducible factor (HIF) and aryl hydrocarbon receptor (AhR) in maintaining intestinal barrier homeostasis.

Methods: An enteroid system and AhR-deficient mouse models were used, with HIF stabilized by a prolyl hydroxylase inhibitor. Barrier function of enteroids was assessed by measuring size, budding number, Ki-67+ cell proliferation, and tight junction-related gene expression. In mice, gut barrier function was evaluated by histology, bacterial translocation, and barrier-related transcripts.

Results: AhR-deficient enteroids derived from the small intestinal crypts of AhR-deficient mice showed increased cellular proliferation and budding and decreased expression of tight junction molecules that regulate barrier permeability. Moreover, AhR-deficient mice showed enhanced bacterial translocation from normal flora in the mesenteric lymph nodes and spleen and elevated serum endotoxin concentrations, indicating enhanced barrier permeability in vivo. Stabilizing HIFs through a prolyl hydroxylase inhibitor restored the expression of barrier molecules in AhR-deficient enteroids and decreased the translocation of enteric bacteria, suggesting the restoration of gut barrier function.

Conclusions: Our findings suggested that high intestinal permeability due to AhR deficiency can be ameliorated by the stabilization of HIFs, indicating a compensatory role in barrier maintenance. This discovery holds promise for advancing therapeutic strategies for patients with gut permeability issues such as inflammatory bowel disease.