Quercetin ameliorates intestinal barrier dysfunction by suppressing the PKCα/MLCK signaling pathway in piglets

Intestinal barrier dysfunction can cause gastrointestinal diseases and retardation in both human infants and young animals. Quercetin, a natural flavonoid, exhibits diverse physiological activities such as anti-inflammatory and antioxidant effects and has demonstrated potential to enhance intestinal health. However, the exact underlying mechanisms linking quercetin with the intestinal barrier integrity remains unclear. Thus, this study aimed to evaluate whether and how quercetin can ameliorate intestinal barrier dysfunction in LPS-challenged weaned piglets and TNF-α challenged IPEC-J2 cells models. The results showed that quercetin supplementation significantly reduced serum, jejunal, and ileal mucosa TNF-α and IFN-γ concentrations in the LPS-challenged piglets ( P  < 0.05). Quercetin also decreased crypt depth in jejunum and ileum ( P  < 0.05), while significantly increasing the villus height:crypt depth ratio in the jejunum ( P  < 0.05). Meanwhile, quercetin improved intestinal barrier function, as evidenced by decreased serum endotoxin levels and diamine oxidase activity ( P  < 0.05) as well as up-regulated jejunal protein expression and immunofluorescence intensity of tight junction proteins (ZO-1, occludin, and claudin-1) ( P  < 0.05), ileal occludin and claudin-1 protein expression ( P  < 0.05). In vitro studies further revealed that quercetin pretreatment effectively ameliorated ( P  < 0.05) TNF-α-induced intestinal barrier dysfunction by suppressing the key proteins expression in PKCα-/MLCK signaling pathway in IPEC-J2 cells. These findings indicated that quercetin ameliorates intestinal barrier dysfunction by upregulating the expression of tight junction proteins, potentially through the suppression of the PKCα/MLCK signaling pathway.