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. 2009 May;139(5):965-74.
doi: 10.3945/jn.108.100867. Epub 2009 Mar 18.

Quercetin enhances intestinal barrier function through the assembly of zonula [corrected] occludens-2, occludin, and claudin-1 and the expression of claudin-4 in Caco-2 cells

Takuya Suzuki  1 , Hiroshi Hara
Affiliations
Free article

Quercetin enhances intestinal barrier function through the assembly of zonula [corrected] occludens-2, occludin, and claudin-1 and the expression of claudin-4 in Caco-2 cells

Takuya Suzuki et al. J Nutr. 2009 May.
Free article

Abstract

Dietary flavonoids provide various beneficial effects for our health. We investigated the promotive effects of quercetin and myricetin on the intestinal barrier function in human intestinal Caco-2 cell monolayers. Transepithelial electrical resistance (TER) across the monolayers increased rapidly during incubation with quercetin, peaking at 6 h. Lucifer yellow flux, a paracellular marker, was dose-dependently lower after quercetin and myricetin treatments, although quercetin exhibited a more potent effect. Immunoblot analysis of tight junction (TJ) proteins revealed that zonula occludens (ZO)-2, occludin, and claudin-1 were distributed to the actin cytoskeleton fraction by quercetin without increasing their respective whole-cell levels and this distribution was correlated with the increases in TER. The claudin-4 level was elevated by quercetin in both the cytoskeleton fraction and whole cells after 12 h. Confocal microscopy showed the assembly of claudin-1 and -4 at the TJ by quercetin. An inhibitor of protein kinase Cdelta (PKCdelta), rottlerin, enhanced the barrier function with changes in the distribution and expression of TJ proteins in a manner very similar to that of quercetin. Phosphorylation of PKCdelta indicating the enzymatic activity in the cells was decreased by quercetin after 1 h. In the kinase assay, quercetin exhibits direct inhibition of the PKCdelta isoform. This study demonstrates that quercetin enhances the intestinal barrier function through the assembly of ZO-2, occludin, and claudin-1 by inhibiting PKCdelta and the increase in claudin-4 expression has an additional role after 12 h.

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