Activation of NF-kappa B in intestinal epithelial cells by enteropathogenic Escherichia coli

The initial response to infection is recruitment of acute inflammatory cells to the involved site. Interleukin (IL)-8 is the prototypical effector molecule for this process. Transcription of the IL-8 gene is primarily governed by the nuclear transcription factor (NF)-kappa B. Intestinal epithelial cells produce IL-8 in response to infection by enteric pathogens yet remain quiescent in a milieu where they are literally bathed in normal bacterial flora. We therefore sought to investigate NF-kappa B activation in response to enteropathogenic Escherichia coli (EPEC), nonpathogenic E, coli, and bacterial lipopolysaccharide in an intestinal epithelial cell (T84) model and to determine whether EPEC-induced activation of NF-kappa B factor is causally linked to IL-8 production. We report herein that NF-kappa B is activated by EPEC, yet such a response is not extended to nonpathogenic organisms or purified E. coli lipopolysaccharide. Transcription factor decoys significantly diminished IL-8 production in response to EPEC, demonstrating a causal relationship. Furthermore, deletion of specific EPEC virulence genes abrogates the NF-kappa B-activating property of this pathogen, suggesting that specific bacterial factors are crucial for inducing this response. These studies show for the first;time that infection of intestinal epithelial cells with EPEC activates NF-kappa B, which in turn initiates IL-8 transcription, and highlight the differential response of these cells to bacterial pathogens vs. nonpathogens.