8β-hydroxy-9(11),13-abietadien-12-one and margolone ameliorate intestinal epithelial barrier dysfunction via aryl hydrocarbon receptor activation in a Caco-2 monolayer model

Background: Disrupting the intestinal epithelial barrier function causes several diseases, including inflammatory bowel disease (IBD). Indole metabolite 6-formylindolo[3,2-b]carbazole (FICZ) has been reported to ameliorate this disruption by activating the aryl hydrocarbon receptor (AhR). We previously isolated and identified seven diterpenoids as novel AhR agonists from common sages. However, it is unclear whether isolated diterpenoids exhibit protective effects similar to FICZ. Methods: Using a Caco2-cell monolayer model, we investigated whether these diterpenoids exert protective effects on the intestinal epithelial barrier function via AhR activation by measuring transepithelial electrical resistance (TEER), performing western blotting, and conducting fluorescence microscopy. Results: We found that 8β-hydroxy-9(11),13-abietadien-12-one (1) and margolone (6) prevented a tumor necrosis factor-α (TNF-α)/interferon-γ (IFN-γ)-induced decrease in TEER via AhR activation. To elucidate the underlying mechanism, we examined the localization of tight junction (TJ) proteins associated with barrier function. The results showed that 1 and 6 maintained the localization of TJ proteins under TNF-α/IFN-γ treatment. Furthermore, these compounds suppressed myosin light-chain kinase (MLCK) expression by inhibiting the NF-κB signaling pathway. Conclusion: Compounds 1 and 6 may serve as potential therapeutic agents against IBD through AhR activation.