Effects of Peptidoglycan on inflammation, nutrient transporter gene expression and barrier function in porcine intestinal epithelial cells (IPEC-J2 cells)

Peptidoglycan (PGN) is a polymer in bacterial cell walls and may constrain the gut functionality and lowering intestinal efficiencies in livestock. Previous studies demonstrated that dietary muramidase, an enzyme to cleave the β-1, 4 glycosidic linkages between N-acetylmuramic acid and N-acetyl glucosamine in the carbohydrate backbone of peptidoglycan, contributes to improving feed conversation ratio and gastrointestinal function in broiler chickens and swine. However, in the small intestine, how PGN regulates inflammatory response and influences nutrient absorption and barrier function are poorly elucidated in livestock. In this study, IPEC-J2, a jejunal epithelial cell line was used as an intestine epithelial cell model, and the effects of PGN on inflammation, nutrient transporter gene expression and barrier function were investigated by measuring gene and protein expression of cytokine IL-8 and TNFα, gene expression of nutrient transporters, gene expression of tight junction proteins and transepithelial electrical resistance (TEER). The results showed that PGN stimulation induced a significant amount of IL-8 and TNFα expression on both mRNA and protein levels (P < 0.05 compared with control) in a dose-dependent manner. PGN challenge also significantly reduced the mRNA abundance of sodium-dependent glucose transporter 1 (SGLT1) and glutamate transporter (EAAC1) while did not alter mRNA abundance of neutral amino acid transporter (B⁰AT1), neutral amino acid exchanger (ASCT2) and peptide transporter 1 (PepT1). However, PGN treatment did not alter the mRNA abundance of Zonula occludes 1 (ZO-1) and claudin-3 and structural integrity of tight junction and cytoskeleton respectively. Furthermore, it also did not affect TEER value. These results suggest that infection of gram-positive bacteria such as Staphylococcus aureus may induce inflammation in the intestine epithelial cells and compromise some nutrient absorption. 

Keywords: Peptidoglycan; IPEC-J2; inflammation; transepithelial electrical resistance (TEER); nutrient transporters.

Published in the proceedings of the Animal Nutrition Conference of Canada 2020. For information on the event, past and future editions, check out https://animalnutritionconference.ca/.