Mitogen-activated protein kinase/I kappa B kinase/NF-kappa B-dependent and AP-1-independent CX₃CL₁ expression in intestinal epithelial cells stimulated with Clostridium difficile toxin A

Abstract

Clostridium difficile toxin A causes acute colitis associated with inflammatory cell infiltration and increased production of proinflammatory mediators. Although CX₃CL₁ (fractalkine) plays a role in chemoattracting monocytes/macrophages, NK cells, and T cells, little information is available on the regulated expression of CX₃CL₁ in response to toxin A stimulation. In this study, we investigated the role of C. difficile toxin A on CX₃CL₁ induction in intestinal epithelial cells. Stimulation of murine intestinal epithelial cells with toxin A resulted in the upregulation of CX₃CL₁. Expression of CX₃CL₁ was dependent on nuclear factor-kappaB (NF-kappa B) and I kappa B kinase (IKK) activation, while the suppression of activator protein-1 (AP₋₁) did not affect toxin A-induced CX₃CL₁ expression. Suppression of p38 mitogen-activated protein kinase (MAPK) significantly inhibited IKK-NF-kappa B signaling leading to CX₃CL₁ induction in C. difficile toxin A-stimulated cells. CX₃CL₁ was mainly secreted from the basolateral surfaces in toxin A-treated cells. Furthermore, inhibition of p38 activity attenuated the toxin A-induced upregulation of CX₃CL₁ in the mouse ileum in vivo. These results suggest that a pathway, including p38 MAPK, IKK, and NF-kappa B activation, is required for CX₃CL₁ induction in intestinal epithelial cells exposed to C. difficile toxin A and may regulate the development of intestinal inflammation induced by infection with toxigenic C. difficile. <UnorderedList Mark="Bullet"> <ItemContent> <Para> C. difficile toxin A causes colitis with inflammatory cell infiltration. CX₃CL₁ plays a role in chemoattracting immune cells. MAPK-NF-kappa B signaling is required for CX₃CL₁ induction in toxin A-exposed cells. CX₃CL₁ is mainly secreted from the basolateral surfaces. CX₃CL₁1 may contribute to the regulation of toxigenic C. difficile infection.