EPA and DHA inhibit endocytosis of claudin-4 and protect against deoxynivalenol-induced intestinal barrier dysfunction through PPARγ dependent and independent pathways in jejunal IPEC-J2 cells

Abstract

Peroxisome proliferator activated receptor gamma (PPARγ) activation has been shown to protect against intestinal injury induced by different stimuli. PPARγ is known to regulate tight junction proteins (TJP) in epithelial cells. Both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are natural PPARγ agonists, but the implication of PPARγ in their physiological effects on the gut is poorly understood. Therefore, this study was conducted to investigate the mechanism of EPA and DHA effects on intestinal epithelial cell barrier function in IPEC-J2 cells exposed to deoxynivalenol (DON), a known food mycotoxin that is toxic to both humans and animals. Exposure of cells to EPA and DHA significantly increased mRNA expression of a PPARγ target gene, AP2, and concomitantly increased the protein expression of claudin-4. Treatment with EPA and DHA also reversed the endocytosis and degradation of claudin-4 caused by DON exposure. EPA and DHA also restored the membrane presence of claudin-4 and ZO-1 that was disrupted by DON. However, the protective effects of EPA and DHA against DON exposure was abolished by a specific PPARγ antagonist (T0070907), confirming the importance of PPARγ in regulating TJP expression by the fatty acids. Effect of PPARγ activation by EPA and DHA also included the restoration of transepithelial electrical resistance (TEER) and reduction of fluorescein isothiocyanate-labeled dextran (FITC-dextran) permeability that have been perturbed by DON. However, the effectiveness of EPA and DHA in opposing DON-induced decrease in TEER and the increase in FITC-dextran permeability was not affected by PPARγ inhibition, potentially suggesting the involvement of other PPARγ-independent mechanisms in the observed benefits from EPA and DHA. Collectively, this study shows that the protective effects of EPA and DHA against DON-induced intestinal barrier disruption are through both PPARγ-dependent and-independent pathways. Therefore, EPA and DHA containing ingredients could be used to prevent the DON-induced gut barrier dysfunction in humans and animals.