PGE(2) induces MUC2 and MUC5AC expression in human intrahepatic biliary epithelial cells via EP4/p38MAPK activation

MUC2 and MUC5AC overproduction is considered to be associated with hepatolithiasis and related to inflammation. However, mechanisms underlying MUC upregulation under inflammatory stimulation in human intrahepatic biliary epithelial cells (HIBECs) are not completely understood.

Expression of MUC2 and MUC5AC mRNA in HIBECs was detected by real-time PCR. Expression of COX-2, EP4, and phosphorylated ERK, JNK and p38MAPK protein was detected by Western blot. Concentrations of PGE2, IL-1β and TNF-α in cell culture supernatants were measured using the Quantikine Elisa kit.

COX-2 expression as well as PGE2 production in HIBECs was upregulated significantly by LPS, which was completely blocked by either TLR4 antagonist or NFκB inhibitor. Selective COX-2 inhibitor suppressed LPS-induced MUC2 and MUC5AC mRNA expression remarkably. Exogenous PGE2 increased MUC2 and MUC5AC mRNA expression in a dosage-dependent manner independent of IL-1β and TNF-α. PGE2 receptor EP4 agonist elevated MUC2 and MUC5AC expression, whereas EP4 antagonist had the opposite effect. Expression of phosphorylated p38MAPK was upregulated by exogenous PGE2, and p38MAPK inhibitor reduced MUC2 and MUC5AC expression in HIBECs. In addition, it was found that levels of PGE2, MUC2 and MUC5AC in bile samples from the hepatic ducts affected by intrahepatic stones were significantly higher than those from the unaffected hepatic ducts of patients with hepatolithiasis.

Our findings indicate that PGE2 induces MUC2 and MUC5AC expression in HIBECs via EP4-p38MAPK signaling.