NF-kappa B 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-kappaB) could regulate chemokine expression in intestinal epithelial cells. Toxin A increased the levels of NF-kappaB complexes containing p65/p50 heterodimers and p65/p65 homodimers. Concurrently, toxin A decreased the levels of IkappaBalpha. Toxin A stimulation also increased the signals of phosphorylated IkappaB kinase (IKK)alpha/beta and NF-kappaB-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-kappaB such as IL-8 and monocyte-chemotactic protein (MCP)-1 and similarly, inhibition of NF-kappaB also downregulated the expression of IL-8, growth-related oncogene-alpha, and MCP-1. These results suggest that NF-kappaB signalling events may be involved in the inflammatory responses to toxin A produced by toxigenic C. difficile.