Theaflavins enhance intestinal barrier of Caco-2 Cell monolayers through the expression of AMP-activated protein kinase-mediated Occludin, Claudin-1, and ZO-1
<div><p>We investigated the effect of theaflavins (TFs) on membrane barrier of Caco-2 cells. For fluorescein-transport experiments, the apparent permeability (<i>P</i><sub>app</sub>) of fluorescein in Caco-2 cells pretreated with 20 μM TFs were significantly decreased compared with that in untreated cells. Although the respective monomeric catechins did not show any <i>P</i><sub>app</sub> reduction, purpurogallin pretreatment resulted in a significant <i>P</i><sub>app</sub> reduction similar to that of TF-3′-<i>O</i>-gallate (TF3′G) pretreatment. This indicates that the benzotropolone moiety may play a crucial role in the <i>P</i><sub>app</sub> reduction or tight junction (TJ)-closing effect induced by TFs. In TF-3′-<i>O</i>-gallate-pretreated Caco-2 cells, fluorescein transport was completely restored by compound C (AMPK inhibitor). In addition, TF3′G significantly increased both the mRNA and protein expression of TJ-related proteins (occludin, claudin-1, and ZO-1) as well as the phosphorylation of AMPK. It was, thus, concluded that TFs could enhance intestinal barrier function by increasing the expression of TJ-related proteins through the activation of AMPK in Caco-2 cells.</p></div
