Pinoresinol enhances intestinal tight junction integrity via activation of the CaMKKβ-AMPKα1 pathway in Caco-2 cells.

BACKGROUND: The intestinal epithelial barrier plays an essential role in protecting the body while allowing selective nutrient absorption. Natural bioactive compounds that strengthen this barrier contribute to gut health. However, the effects of pinoresinol, a dietary lignan known for its various bioactivities, on intestinal barrier function and underlying molecular mechanisms remain to be elucidated. METHODS: Caco-2 monolayers were treated with pinoresinol, and barrier function was evaluated using fluorescein permeability and transepithelial electrical resistance (TEER) assays. The expression and localization of tight junction (TJ)-related proteins were analyzed by RT-PCR, western blotting, and immunofluorescence. The involvement of the CaMKKβ-AMPKα1 signaling pathway was also investigated. RESULTS: Pinoresinol improved barrier integrity by decreasing apparent permeability coefficient (Papp) and increasing TEER. It enhanced the expression and junctional localization of TJ-related proteins, including cingulin, occludin, and claudin-1. These effects were associated with activation of the CaMKKβ-AMPKα1 pathway, suggesting a mechanism through which pinoresinol reinforces the epithelial barrier function. CONCLUSIONS: This study identifies pinoresinol as a dietary bioactive compound that strengthens the intestinal barrier via activation of the CaMKKβ-AMPKα1 signaling axis. These findings provide mechanistic insight into its potential use as a functional ingredient for maintaining gut integrity and promoting overall intestinal health.