Interleukin-8 induction due to diffusely adherent Escherichia coli possessing Afa/Dr genes depends on flagella and epithelial Toll-like receptor 5
Article first published online: 14 JUN 2010
© 2010 The Societies and Blackwell Publishing Asia Pty Ltd
Microbiology and Immunology
Volume 54, Issue 9, pages 491–501, September 2010
How to Cite
Arikawa, K. and Nishikawa, Y. (2010), Interleukin-8 induction due to diffusely adherent Escherichia coli possessing Afa/Dr genes depends on flagella and epithelial Toll-like receptor 5. Microbiology and Immunology, 54: 491–501. doi: 10.1111/j.1348-0421.2010.00244.x
- Issue published online: 27 AUG 2010
- Article first published online: 14 JUN 2010
- Received 25 September 2009; revised 24 May 2010; accepted 30 May 2010.
- diffusely adherent Escherichia coli (DAEC);
- interleukin 8 (IL-8)
DAEC is considered potentially diarrheagenic. For diffuse adhesion, the role of the Afa, which was originally identified as a uropathogenic factor, is now understood. However, the role of DAEC in diarrheal disease remains controversial because DAEC is often isolated not only from patients but also from healthy individuals. Previously, we suggested that Afa/Dr DAEC, which can induce high levels of IL-8 secretion in cultures of human carcinoma epithelial cells (HEp-2, Caco-2), is enterovirulent. In the present study, we examined whether IL-8 secretion induced by certain Afa/Dr DAEC strains was primarily due to flagella via TLR5. All IL-8 high-inducing strains were highly motile in swarming tests. Partially purified flagella induced IL-8 in a dose-dependent manner. However, IL-8 induction was inhibited by small-interfering RNA against TLR5 or by treating flagella with disialoganglioside-GD1a, a TLR5 blocker. TLR5 is reportedly located on the basolateral side of intestinal epithelia; flagella should not have reached TLR5 from the apical side beyond tight junctions. Reduction in the number of intracellular organisms by wortmannin, a PI3K inhibitor, did not reduce IL-8 secretion. Afa/Dr DAEC seemed to loosen the tight junctions because it quickly reduced transepithelial electrical resistance after infection. Decreased resistance led to increased IL-8 production. In conclusion, diffuse adhesion itself is insufficient to induce high levels of IL-8, and simultaneous stimulation by flagella via TLR5 is likely required for additional induction. Clinically, high motility may be a candidate criterion for predicting the ability of Afa/Dr DAEC strains to induce higher levels of IL-8 secretion.