052 Differential expression of intestinal ion transporters and water channel aquaporins in young piglets challenged with enterotoxigenic Escherichia coli K88

Abstract

Enterotoxigenic Escherichia coli (ETEC) K88 can induce severe watery diarrhea and subsequent growth retardation for neonatal and postweaning piglets, which causes great economic loss in swine production. Our previous study has shown that the incidence of diarrhea in young piglets was significantly increased following ETEC K88 challenge. The study was to determine whether the expression of genes involved in water and ion transports would be affected by ETEC K88 both in vitro and in vivo. 1) Thirty-six male piglets (4 d old) were randomly allotted to either the Control or the K88 group. Each group had 6 replicates with 3 piglets in each replicate. All piglets were fed the same diets for 18 d. On d 15, piglets in the K88 group were challenged with ETEC K88 (serotype O149:K91:K88ac) of 1 × 108 cfu/pig, whereas those in the Control group received the same volume of sterilized PBS. After challenging with ETEC K88 for 72 h (d 18), 1 piglet from each replicate was selected for slaughter to collect samples from the jejunum, ileum, and colon. The mRNA expression and protein abundance of cystic fibrosis transmembrane conductance regulator (CFTR) in the ileum and colon were significantly increased compared with that in the control group (P < 0.05). Furthermore, the mRNA expression of Na–K–Cl cotransporter 1 (NKCC1) in the ileum and colon was significantly increased, whereas in the jejunum, both its mRNA and protein expression were significantly increased by ETEC K88 treatment (P < 0.05). 2) Additionally, an established porcine intestinal epithelial cell line (IPEC-J2) was used to investigate the effect and possible mechanism of ETEC K88 on expression of water channel aquaporins (AQP) and ion transporters. Cells (1.17 × 106/well) were grown in 6-well plates and treated with ETEC K88 (5.6 × 107 cfu/well) for 3 h. AQP3 and AQP11 mRNA were abundantly expressed in IPEC-J2 cells. The mRNA expression of AQP3, AQP11, and Na+/H+ exchanger 3 (NHE3) in IPEC-J2 cells was significantly reduced after ETEC K88 treatment (P < 0.05). Further analyses by immunofluorescence and western blotting also demonstrated that ETEC K88 significantly decreased the protein expression of AQP3, AQP9, and AQP11 in IPEC-J2 cells (P < 0.05). Moreover, the phosphorylation level of protein kinase A (PKA) of the cyclic adenosine monophosphate (cAMP) pathway was significantly decreased by ETEC K88 challenge (P < 0.05). The results indicate that the cAMP-PKA signaling pathway might regulate the differential expression of intestinal ion transporters and AQP, therefore contributing to fluid imbalance and the development of ETEC diarrhea in young piglets.