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-kappaB.
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-alpha) in polarized epithelial cells. However, the increase in IL-8 secretion was independent of Campylobacter-stimulated TNF-alpha 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-kappaB 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-kappaB through TLR signaling and CDT in human intestinal epithelial cells.
Zheng
Jie
J
Department of Nutrition and Food Science, University of Maryland, College Park, Maryland 20742, USA.
Meng
Jianghong
J
Zhao
Shaohua
S
Singh
Ruby
R
Song
Wenxia
W
D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D016123:Campylobacter jejuni / Q000276:immunology*; D002460:Cell Line; D019286:Endopeptidase K / Q000378:metabolism; D004847:Epithelial Cells / Q000276:immunology* / Q000382:microbiology*; D017353:Gene Deletion; D006358:Hot Temperature; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology; D016328:NF-kappa B / Q000378:metabolism*; D011489:Protein Denaturation; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D001427:Bacterial Toxins; C508606:CXCL8 protein, human; D016209:Interleukin-8; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; C067044:cytolethal distending toxin; D019286:Endopeptidase K