Clostridium difficile toxin A triggers human colonocyte IL-8 release via mitochondrial oxygen radical generation

Gastroenterology. 2002 Apr;122(4):1048-57. doi: 10.1053/gast.2002.32386.


Background & aims: Clostridium difficile toxin A causes mitochondrial dysfunction resulting in generation of oxygen radicals and adenosine triphosphate (ATP) depletion. We investigated whether mitochondrial dysfunction is involved in nuclear factor kappaB (NF-kappaB) activation and interleukin (IL)-8 release from toxin A-exposed enterocytes.

Methods: NF-kappaB activation and IL-8 release in response to toxin A were correlated with reactive oxygen intermediate (ROI) generation and ATP production in HT-29 monolayers or HT-29 cells exposed to ethidium bromide (EB) to inhibit mitochondrial function.

Results: HT-29 cells exposed to EB showed damaged mitochondria and diminished resting levels of ATP. ROI production in EB-treated cells exposed to toxin A for 30 minutes was significantly reduced. Exposure of wild-type HT-29 cells to toxin A resulted in increased oxygen radical generation and IL-8 production (P < 0.01 vs. control) that was inhibited by antioxidant pretreatment. Degradation of IkappaB was observed within 30 minutes of toxin exposure, before ras homologue (Rho) glucosylation, and was followed by nuclear translocation of NF-kappaB. Toxin A did not increase IL-8 levels in EB-treated cells, whereas IL-8 release in response to IL-1beta was not affected.

Conclusions: Our data support an early role for mitochondria-derived ROIs in stimulation of IL-8 release from colonocytes by toxin A. ROI generation is independent of Rho inactivation and involves nuclear translocation of NF-kappaB before release of IL-8.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Bacterial Toxins / pharmacology*
  • DNA-Binding Proteins / metabolism
  • Enterotoxins / pharmacology*
  • Glycosylation
  • HT29 Cells
  • Humans
  • I-kappa B Proteins*
  • Interleukin-8 / metabolism*
  • Mitochondria / metabolism*
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / metabolism
  • Reactive Oxygen Species / metabolism
  • rho GTP-Binding Proteins / metabolism


  • Bacterial Toxins
  • DNA-Binding Proteins
  • Enterotoxins
  • I-kappa B Proteins
  • Interleukin-8
  • NF-kappa B
  • NFKBIA protein, human
  • Reactive Oxygen Species
  • tcdA protein, Clostridium difficile
  • NF-KappaB Inhibitor alpha
  • Adenosine Triphosphate
  • rho GTP-Binding Proteins