Campylobacter-Induced Interleukin-8 Secretion in Polarized Human Intestinal Epithelial Cells Requires Campylobacter-Secreted Cytolethal Distending Toxin- and Toll-Like Receptor-Mediated Activation of NF-κB

• Published in: Infection and Immunity Vol. 76; no. 10; pp. 4498 - 4508
• Main Authors: Zheng, Jie, Meng, Jianghong, Zhao, Shaohua, Singh, Ruby, Song, Wenxia
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.10.2008; American Society for Microbiology (ASM)
• Subjects: Bacteriology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Host Response and Inflammation; Microbiology; Miscellaneous; Human; Microbiology; Digestive system; Secretion; Campylobacteraceae; Cytokine; Gut; Toll like receptor; Immunity; Toxin; Bacteria; Epithelial cell; Transcription factor NFκB; Interleukin 8; Campylobacter
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.01317-07

Campylobacter jejuni and Campylobacter coli colonize and infect the intestinal epithelium and cause acute inflammatory diarrhea. The intestinal epithelium serves as a physical barrier to, and a sensor of, bacterial infection by secreting proinflammatory cytokines. This study examined the mechanisms for Campylobacter-induced secretion of the proinflammatory chemokine interleukin-8 (IL-8) by using polarized T84 human colonic epithelial cells as a model. C. jejuni increased the secretion of both IL-8 and tumor necrosis factor alpha (TNF-α) in polarized epithelial cells. However, the increase in IL-8 secretion was independent of Campylobacter-stimulated TNF-α secretion. Polarized T84 cells secreted IL-8 predominantly to the basolateral medium independently of the inoculation direction. While there was a significant correlation between the levels of IL-8 secretion and Campylobacter invasion, all 11 strains tested increased IL-8 secretion by polarized T84 cells despite their differences in adherence, invasion, and transcytosis efficiencies. Cell-free supernatants of Campylobacter-T84-cell culture increased IL-8 secretion to levels similar to those induced by live bacterial inoculation. The ability of the supernatant to induce IL-8 secretion was reduced by flagellum and cytolethal distending toxin (CDT) gene mutants, treatment of the supernatant with protease K or heat, or treatment of T84 cells with the Toll-like receptor (TLR) inhibitor MyD88 inhibitory peptide or chloroquine. NF-κB inhibitors or cdtB mutation plus MyD88 inhibitor, but not flaA cdtB double mutations, abolished the ability of the supernatant to induce IL-8 secretion. Taken together, our results demonstrate that Campylobacter-induced IL-8 secretion requires functional flagella and CDT and depends on the activation of NF-κB through TLR signaling and CDT in human intestinal epithelial cells.