Molecular mechanisms involved in interleukin-8 production by normal human oesophageal epithelial cells

Abstract

Background: Increase in interleukin-8 in the oesophageal mucosa has been associated with the pathogenesis of reflux oesophagitis. Aim: To assess the effect of bile acids on the interleukin-8 expression in normal human oesophageal epithelial cells and to determine its molecular mechanisms. Methods: Human oesophageal epithelial cells were stimulated with unconjugated bile acids, conjugated bile acids and inflammatory cytokines. Protein and mRNA of interleukin-8 were measured by enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction, respectively. In addition, we examined protein kinases and transcription factors involved in interleukin-8 synthetic pathways using protein kinase inhibitors and luciferase expression vectors, respectively. Results: Unconjugated bile acids induced interleukin-8 production from human oesophageal epithelial cells stronger than conjugated bile acids. However, conjugated bile acids in acidic media resulted in remarkable increase of interleukin-8 production compared with those in neutral-pH media. Mutation of the binding site of NF-kB, AP-1 and NF-IL6 abrogated the induction of luciferase activities by 100%, 70% and 30%, respectively. Inhibitor of protein kinase A, protein kinase C or p38 mitogen-activated protein kinase attenuated the production of interleukin-8 by cholic acid. Conclusions: These results indicate that bile acids induce interleukin-8 expression from oesophageal epithelial cells mainly via the activation of NF-kB as well as AP-1. © 2006 The Authors.