Aryl Hydrocarbon Receptor Deficiency Impairs Intestinal Barrier Development, While 2′-Fucosyllactose Reduces Paracellular Permeability in Caco-2 Cells

Chronic kidney disease (CKD) is increasingly linked to intestinal barrier dysfunction, which contributes to systemic inflammation and disease progression. We investigated whether 2′-fucosyllactose (2′-FL), a human milk oligosaccharide, could modulate intestinal epithelial barrier function under uremic toxin exposure and examined the role of the aryl hydrocarbon receptor (AhR). Using wild-type (WT) and AhR knockout (AhR KO) Caco-2 cell lines, we assessed barrier function and cellular responses through transepithelial electrical resistance (TEER), paracellular permeability (Papp), tight junction (TJ) gene expression, AhR target gene activation, and metabolic assays. AhR deficiency impaired epithelial maturation, confirming its role in barrier development. Short-term exposure to uremic toxins (UTs) did not significantly affect TEER or paracellular permeability under the conditions tested. However, 2′-FL reduced paracellular permeability in both WT and AhR KO cells in the presence of FCS. These effects occurred without changes in TJ gene expression, indicating mechanisms beyond transcriptional regulation. AhR target genes were not induced by UTs, suggesting limited receptor activation, and metabolic activity was unaffected. Overall, 2′-FL reduced paracellular permeability under selected experimental conditions, while the impaired barrier development observed in AhR-deficient cells supports a role for AhR in intestinal epithelial barrier development.