Real-time monitoring of trans-epithelial electrical resistance in cultured intestinal epithelial cells: the barrier protection of water-soluble dietary fiber

AIM Measuring trans-epithelial electrical resistance (TEER) in vitro is a method to evaluate barrier function. The first aim of this study is to verify a real-time TEER monitoring system in Caco-2 monolayer. The second aim is to investigate the therapeutic effect of partially hydrolyzed guar gum (PHGG), a dietary fiber, on interferon (IFN)-γ-induced intestinal barrier dysfunction using this monitoring system. METHODS We measured TEER using real-time monitoring system and evaluated epithelial paracellular permeability using fluorescein isothiocyanate-conjugated dextran (4 kDa; FD4) in Caco-2 monolayers treated by IFN-γ for 48 h. The expression and distribution of tight junction (TJ)-associated proteins, ZO-1 and occludin, were analyzed by Western blotting and immunocytochemistry respectively. In some experiments, PHGG was added prior to IFN-γ treatment in order to investigate its protective effect on barrier function. RESULTS Using this system, we could evaluate the dynamic TEER change induced by IFN-γ precisely. In this study, IFN-γ treatment significantly decreased TEER and increased FD4 flux across Caco-2 monolayers, indicating the great influence of IFN-γ on intestinal epithelial paracellular permeability. In contrast, the pretreatment of PHGG significantly reduced the IFN-γ-induced increment of FD4 flux without affecting TEER. IFN-γ or PHGG treatment did not affect the expression of TJ-associated proteins, while immunocytochemistry showed that the IFN-γ-induced re-distribution of occludin was clearly restored by PHGG. CONCLUSIONS Real-time TEER monitoring enabled us to evaluate the dynamic change of barrier function. PHGG might have a protective effect against IFN-γ-induced barrier dysfunction by attenuating the paracellular hyper-permeability; thus, its promotion as a functional food is anticipated.