p38 MAP kinase activation by Clostridium difficile toxin A mediates monocyte necrosis, IL-8 production, and enteritis

Clostridium difficile toxin A causes acute neutrophil infiltration and inte stinal mucosal injury. In cultured cells, toxin A inactivates Rho proteins by monoglucosylation. In monocyes, toxin A induces IL-8 production and necr osis by unknown mechanisms. We investigated the role of mitogen-activated p rotein (MAP) kinases in these events. In THP-1 monocytic cells, toxin A act ivated the 3 main MAP kinase cascades within 1 to 2 minutes. Activation of p38 was sustained, whereas stimulation of extracellular signal-regulated ki nases and c-Jun NH2-terminal kinase was transient. Rho glucosylation became evident after 15 minutes. IL-8 gene expression was reduced by 70% by the M EK inhibitor PD98059 and abrogated by the p38 inhibitor SB203580 or by over expression of dominant-negative mutants of the p38-activating kinases MKK3 and MHK6. SB203580 also blocked monocyte necrosis and IL-1 beta release cau sed by toxin A but not by other toxins. Finally, in mouse ileum, SB203580 p revented toxin A-induced neutrophil recruitment by 92% and villous destruct ion by 90%. Thus, in monocytes exposed to toxin A, MAP kinase activation ap pears to precede Rho glucosylation and is required for IL-8 transcription a nd cell necrosis. p38 MAP kinase also mediates intestinal inflammation and mucosal damage induced by toxin A.