Quercetin enhances epithelial barrier function and increases claudin-4 expression in Caco-2 cells

Area of Science:

• Gastroenterology
• Cell Biology
• Nutritional Science

Background:

• Flavonoids, particularly quercetin, are abundant in the diet.
• Quercetin is hypothesized to positively impact gastrointestinal mucosa.
• Intestinal barrier function is crucial for gut health.

Purpose of the Study:

• To investigate the effects of quercetin on intestinal barrier function.
• To analyze the molecular mechanisms underlying quercetin's influence on the intestinal barrier.
• To assess quercetin's impact on tight junction proteins and epithelial integrity.

Main Methods:

• Utilized the Caco-2 human colonic epithelial cell line.
• Measured transepithelial resistance (R(t)) and ion/tracer fluxes in Ussing chambers.
• Analyzed tight junction (TJ) protein and mRNA expression via Western blot and RT-PCR.
• Investigated TJ protein localization using confocal laser scanning microscopy (LSM).
• Assessed transcriptional regulation using reporter gene assays and apoptosis rates.

Main Results:

• Quercetin dose-dependently increased R(t), indicating enhanced barrier function.
• The effect persisted for over 2 days and was maintained with daily quercetin addition.
• Quercetin significantly upregulated claudin-4 expression and localized it to tight junctions.
• Reduced fluxes of Na+ and Cl- were observed, correlating with increased barrier function.
• Quercetin stimulated claudin-4 transcription without affecting apoptosis rates.

Conclusions:

• Quercetin enhances intestinal barrier function through transcriptional regulation of claudin-4.
• This mechanism highlights quercetin's protective role against intestinal barrier disturbances.
• Dietary quercetin may represent a valuable component for managing intestinal inflammation.