5,7-Dimethoxyflavone enhances barrier function by increasing occludin and reducing claudin-2 in human intestinal Caco-2 cells

Abstract Defects in intestinal tight junction (TJ) barrier cause intestinal inflammation. We investigated the effects of 5,7-dimethoxyflavone (DMF), abundantly found in black ginger, on the TJ barrier in human intestinal Caco-2 cells. DMF reinforced TJ barrier integrity, indicated by increased transepithelial electrical resistance and reduced dextran permeability in Caco-2 cells. Immunoblot analysis revealed that the increases in the barrier-forming TJ molecules occludin and claudin-1 and the decrease in pore-forming claudin-2 in the cytoskeletal fraction of the cells were responsible for the TJ regulation. Increased occludin expression was sensitive to cycloheximide (an inhibitor of protein translation) and rapamycin (mechanistic target of rapamycin [mTOR] inhibitor). DMF reduced Cldn2 mRNA levels without suppressing its transcriptional activity; the reduction was associated with the upregulation of miR-16-5p. Thus, DMF-mediated reinforcement of intestinal TJ barrier was partly involved in the induction of occludin protein translation via mTOR and silencing Cldn2 mRNA via miR-16-5p.