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

Summary

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.