Salmonella typhimurium induces epithelial IL-8 expression via Ca2+-mediated activation of the NF-κB pathway
Andrew T. Gewirtz, … , James L. Madara, Andrew S. Neish
Andrew T. Gewirtz, … , James L. Madara, Andrew S. Neish
Published January 1, 2000
Citation Information: J Clin Invest. 2000;105(1):79-92. https://doi.org/10.1172/JCI8066.
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Article

Salmonella typhimurium induces epithelial IL-8 expression via Ca2+-mediated activation of the NF-κB pathway

Abstract

Interactions between the enteric pathogen Salmonella typhimurium and the luminal surface of the intestine provoke an acute inflammatory response, mediated in part by epithelial cell secretion of the chemokine IL-8 and other proinflammatory molecules. This study investigated the mechanism by which this pathogen induces IL-8 secretion in physiologically polarized model intestinal epithelia. IL-8 secretion induced by both the prototypical proinflammatory cytokine TNF-α and S. typhimurium was NF-κB dependent. However, NF-κB activation and IL-8 secretion induced by S. typhimurium, but not by TNF-α, was preceded by and required an increase in intracellular [Ca2+]. Additionally, agonists that increased intracellular [Ca2+] by receptor-dependent (carbachol) or independent (thapsigargin, ionomycin) means also induced IL-8 secretion. Furthermore, the ability of S. typhimurium mutants to induce IκB-α degradation, NF-κB translocation, and IL-8 transcription and secretion correlated precisely with their ability to induce an intracellular [Ca2+] increase in model intestinal epithelia, but not with their ability to invade these cells. Finally, S. typhimurium, but not TNF-α, induced a Ca2+-dependent phosphorylation of IκB-α. These results indicate that S. typhimurium–induced activation of NF-κB–dependent epithelial inflammatory responses proceeds by a Ca2+-mediated activation of an IκB-α kinase. These observations raise the possibility that pharmacologic intervention of the acute inflammatory response can be selectively matched to the specific class of initiating event.

Authors

Andrew T. Gewirtz, Anjali S. Rao, Peter O. Simon Jr., Didier Merlin, Denice Carnes, James L. Madara, Andrew S. Neish

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S. typhimurium and TNF-α induce IL-8 expression by an NF-κB–mediated mec...
S. typhimurium and TNF-α induce IL-8 expression by an NF-κB–mediated mechanism. (a) EMSAs with an IL-8 NF-κB motif probe. Nuclear extracts were derived from model intestinal epithelia maintained under control conditions or coincubated with wild-type S. typhimurium as described in Methods for the indicated times. Addition of unlabeled competitor probe or antisera when indicated. Inset: nuclear extracts were Western blotted with anti-p65 as described in Methods. (b) Transient transfection assay with IL-8 reporter constructs. Transfected HT-29 cl19A cells were treated as indicated. Data are reported as fold induction of CAT activity over basal. (c) IL-8 ELISA from model epithelia. Cells were incubated with basolateral TNF-α (10 ng/mL) or apical wild-type S. typhimurium, either with or without 1 hour pretreatment with 50 μM MG-132. Basolateral IL-8 secretion was measured 5 hours later.