Long-Chain Polyunsaturated Fatty Acids Attenuate Enterotoxigenic Escherichia coli K88-Induced Intestinal Barrier Damage via PPARγ Regulation in IPEC-J2 Cells

OBJECTIVES: Enterotoxigenic Escherichia coli (ETEC) impairs the intestinal barrier function and triggers inflammatory response in infants and young animals. Long-chain polyunsaturated fatty acids (LC-PUFA) have been reported to improve intestinal health and limit inflammation. The objective is to define the role of LC-PUFA on intestinal barrier integrity with ETEC induced inflammation in intestinal porcine epithelial cells (IPEC-J2). METHODS: Cultured IPEC-J2 cells were pretreated with 30 μM LC-PUFA and then incubated without ETEC challenge (NE) or with ETEC challenge (CE). Transepithelial electrical resistance (TEER) value, fluorescein isothiocyanate-dextran (FITC-dextran) flux, released cytosolic lactate dehydrogenase (LDH), and interleukin 8 (IL-8) measures were evaluated. Protein abundance of claudin-1, occludin, and nuclear peroxisome proliferator-activated receptor-gamma (PPARγ) were measured by Western blot analysis. RESULTS: Treatment of cells with docosahexaenoic acid (DHA) significantly increased TEER when compared to the bovine serum albumin (BSA; 14% NE and 25% CE, respectively) and compared to oleate control (25% NE and 27% CE, respectively) (P < 0.05). Further, DHA decreased FITC-dextran across the epithelial barrier by 56% (P < 0.05) and decreased IL-8 secretion by 26% compared to oleate, regardless of ETEC challenge (P > 0.05). In the presence of ETEC, eicosapentaenoic acid (EPA) protected against a decline in membrane claudin-1 compared to EPA non-challenged cells (P > 0.05). In addition, arachidonic acid (ARA) and DHA tended to increase membrane occludin (P < 0.1). Additionally, there was a 1.6-fold increase in nuclear PPARγ by treatments of both ARA and DHA compared to BSA, regardless of challenge (P < 0.05). Release of LDH, a measure of cell cytotoxicity, was decreased by the ARA (64%), EPA (27%), and DHA (34%) in ETEC treated cells compared to BSA ETEC treated cells (P < 0.05). CONCLUSIONS: These data suggest that LC-PUFA protect tight junction proteins by modulating PPARγ, thereby improving epithelial integrity in ETEC-challenged IPEC-J2 cells. FUNDING SOURCES: United States Department of Agriculture Hatch Project.