NF-κB activation pathway is essential for the chemokine expression in intestinal epithelial cells stimulated with Clostridium difficile toxin A

Intestinal epithelial cells are known to upregulate the expression of several chemokines in response to stimulation with bacterial toxin. However, the cellular mechanisms of Clostridium difficile toxin A-induced mucosal inflammation have not yet been fully elucidated. In this study, we investigated whether nuclear factor-kappa B (NF-kappa B) could regulate chemokine expression in intestinal epithelial cells. Toxin A increased the levels of NF-kappa B complexes containing p65/p50 heterodimers and p65/p65 homodimers. Concurrently, toxin A decreased the levels of I kappa B alpha. Toxin A stimulation also increased the signals of phosphorylated I kappa B kinase (IKK)alpha/beta and NF-kappa B-inducing kinase (NIK). In the toxin A-stimulated HT-29 cells, the suppression of IKK or NIK inhibited the upregulation of downstream target genes of NF-kappa B such as IL-8 and monocytechemotactic protein (MCP)-1 and similarly, inhibition of NF-kappa B also downregulated the expression of IL-8, growth-related oncogene-alpha, and MCP-1. These results suggest that NF-kappa B signalling events may be involved in the inflammatory responses to toxin A produced by toxigenic C. difficile.