title: Quercetin enhances epithelial barrier function and increases claudin-4 expression in Caco-2 cells.
abstract: Quercetin is the most abundant flavonoid and is assumed to have positive effects on the gastrointestinal mucosa after dietary intake. The aim of the study was to analyze the influence of quercetin on intestinal barrier function using the human colonic epithelial cell line Caco-2. Transepithelial resistance (R(t)), tracer fluxes of [(3)H]-mannitol, 22Na+, and 36Cl- as well as electrogenic ion transport were determined in Ussing chambers. Expression of tight junction (TJ) proteins and mRNA was analyzed in Western blots and quantitative RT-PCR, respectively. Regulation of transcription was analyzed by reporter gene assay. Cellular distribution of TJ proteins was examined by confocal laser scanning microscopy (LSM). Apoptotic rate was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. Quercetin induced a dose-dependent increase of R(t) persisting for >2 d. Daily addition of quercetin was able to perpetuate the effect, which was seen whether quercetin was added apically or to the basolateral compartment. Parallel to the R(t) increase, quercetin induced a strong increase of the TJ protein claudin-4 but not of other claudins. Confocal LSM showed a localization of claudin-4 in TJ. Apoptotic rate was not affected by quercetin. Consistent with these changes, fluxes of Na+ and Cl-, but not of mannitol, were reduced. Reporter gene assays revealed a stimulatory effect of quercetin on claudin-4 transcription. The flavonoid quercetin enhances barrier function via transcriptional expression regulation of the TJ protein claudin-4, which represents an important protective effect of this food component against barrier disturbance in intestinal inflammation.
authors.affiliation: Department of Gastroenterology and 5Institute of Clinical Physiology, Charité Campus Benjamin Franklin, 12200 Berlin, Germany.
authors.forename: Maren
authors.initials: M
authors.lastname: Amasheh
authors.forename: Susanne
authors.initials: S
authors.lastname: Schlichter
authors.forename: Salah
authors.initials: S
authors.lastname: Amasheh
authors.forename: Joachim
authors.initials: J
authors.lastname: Mankertz
authors.forename: Martin
authors.initials: M
authors.lastname: Zeitz
authors.forename: Michael
authors.initials: M
authors.lastname: Fromm
authors.forename: Jörg D
authors.initials: JD
authors.lastname: Schulzke
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D018938:Caco-2 Cells; D002450:Cell Communication; D062506:Claudin-4; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011794:Quercetin / Q000494:pharmacology*; D050794:STAT1 Transcription Factor
chemical_list: D000975:Antioxidants; C568157:CLDN4 protein, human; D062506:Claudin-4; D008565:Membrane Proteins; D050794:STAT1 Transcription Factor; D011794:Quercetin