Nobiletin Restores Colonic Epithelial Homeostasis in DSS-induced Colitis with Involvement of the Aryl hydrocarbon Receptor.

Aryl hydrocarbon receptor (AhR) agonist facilitates the repair of damaged intestinal barriers in experimental colitis. Nobiletin, a distinct polymethoxyflavone present in citrus peel, has been reported to mitigate Dextran sulfate sodium (DSS) induced colitis in mice. Nevertheless, its specific roles in improving the colonic barrier homeostasis through AhR remain to be fully defined. This study was designed to determine the effects of nobiletin on AhR and intestinal barrier integrity during colitis and to uncover the involved mechanism. Models of intestinal injury were established using DSS-treated mice and TNF-α-stimulated HT-29 cells, followed by intervention with nobiletin. A series of techniques, including immunofluorescence, immunohistochemistry, hematoxylin and eosin (H&E)/alcian blue-periodic acid-Schiff (AB-PAS) staining, fluorescein isothiocyanate-dextran (FITC-dextran) flux assay, quantitative real-time polymerase chain reaction (qPCR), and Western blotting, were employed to assess its effects on colitis progression and barrier function. Mechanistic insights were gained using the AhR antagonist CH223191, AhR-knockout mice, and AhR-specific siRNA. The findings indicated that nobiletin markedly alleviated DSS-induced colitis, enhanced the expression of tight junction proteins, and improved barrier function. Concurrently, it acts as an AhR agonist and increases its downstream gene, CYP1A1. Crucially, these beneficial effects were eliminated upon pharmacological inhibition or genetic ablation of AhR. In summary, nobiletin attenuates intestinal epithelial barrier impairment in colitis involving activation of the AhR pathway, highlighting its therapeutic potential for conditions characterized by barrier dysfunction.