Epithelial cells secrete interleukin-8 in response to adhesion and invasion of diffusely adhering Escherichia coli lacking Afa/Dr genes.
Escherichia coli that sparsely adhere to human epithelial cells are known as diffusely adherent E. coli (DAEC), and the role of the Afa/Dr family of adhesins is now understood. Strains that do not possess Afa/Dr, however, comprise another group of DAEC, of which the pathogenicity remains unknown. The ability to induce interleukin-8 (IL-8) secretion from intestinal epithelial cells might be a feature of enterovirulent bacteria. We previously found that some Afa/Dr DAEC strains induce IL-8 by stimulating epithelial cells with flagella. The present study examines whether non-Afa/Dr DAEC can induce IL-8 in epithelial cells (HEp-2, INT407, and T84). Among 21 strains, 11 (52%; 11/21) induced as much IL-8 as high inducer strains of Afa/Dr DAEC. Adhesion did not significantly differ between high and low inducers; therefore diffuse adhesion alone is probably insufficient to induce IL-8. It was shown that IL-8 induction and the number of intracellular bacteria directly correlated. Wortmannin, an inhibitor of the phosphatidylinositol-3-phosphate kinase, reduced both intracellular bacteria and IL-8 secretion. Motile strains were significantly more prevalent among high (10/11) than low (4/10) inducers. However, 4 low invasive strains hardly induced IL-8 despite their motility. In conclusion, some non-Afa/Dr DAEC invoke the induction of high levels of inflammatory cytokines. Unlike Afa/Dr DAEC, however, non-Afa/Dr strains may require invasion to cause strong induction. These non-Afa/Dr high inducers can be enteropathogenic for the cytokine-inducing properties.
Meraz
Ismail Mustafa
IM
Department of Food and Human Health Sciences, Graduate School of Human Life Science, Osaka City University, Osaka 558-8585, Japan.
Arikawa
Kentaro
K
Ogasawara
Jun
J
Hase
Atsushi
A
Nishikawa
Yoshikazu
Y
D018830:Adhesins, Escherichia coli / Q000235:genetics*; D001422:Bacterial Adhesion; D002460:Cell Line; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000276:immunology* / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics / Q000472:pathogenicity*; D017353:Gene Deletion; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D007422:Intestines / Q000166:cytology / Q000276:immunology / Q000382:microbiology
D018830:Adhesins, Escherichia coli; C465564:Dr adhesin, E coli; D016209:Interleukin-8