title: Clostridium difficile toxin-induced inflammation and intestinal injury are mediated by the inflammasome.
abstract: OBJECTIVE
  Clostridium difficile-associated disease (CDAD) is the leading cause of nosocomial diarrhea in the United States. C difficile toxins TcdA and TcdB breach the intestinal barrier and trigger mucosal inflammation and intestinal damage. The inflammasome is an intracellular danger sensor of the innate immune system. In the present study, we hypothesize that TcdA and TcdB trigger inflammasome-dependent interleukin (IL)-1beta production, which contributes to the pathogenesis of CDAD.
  
  
  METHODS
  Macrophages exposed to TcdA and TcdB were assessed for IL-1beta production, an indication of inflammasome activation. Macrophages deficient in components of the inflammasome were also assessed. Truncated/mutated forms of TcdB were assessed for their ability to activate the inflammasome. The role of inflammasome signaling in vivo was assessed in ASC-deficient and IL-1 receptor antagonist-treated mice.
  
  
  RESULTS
  TcdA and TcdB triggered inflammasome activation and IL-1beta secretion in macrophages and human mucosal biopsy specimens. Deletion of Nlrp3 decreased, whereas deletion of ASC completely abolished, toxin-induced IL-1beta release. TcdB-induced IL-1beta release required recognition of the full-length toxin but not its enzymatic function. In vivo, deletion of ASC significantly reduced toxin-induced inflammation and damage, an effect that was mimicked by pretreatment with the IL-1 receptor antagonist anakinra.
  
  
  CONCLUSIONS
  TcdA and TcdB trigger IL-1beta release by activating an ASC-containing inflammasome, a response that contributes to toxin-induced inflammation and damage in vivo. Pretreating mice with the IL-1 receptor antagonist anakinra afforded the same level of protection that was observed in ASC-/- mice. These data suggest that targeting inflammasome or IL-1beta signaling may represent new therapeutic targets in the treatment of CDAD.
authors.affiliation: Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Ng
authors.forename: Simon A
authors.initials: SA
authors.lastname: Hirota
authors.forename: Olaf
authors.initials: O
authors.lastname: Gross
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Annegret
authors.initials: A
authors.lastname: Ulke-Lemee
authors.forename: Mireille S
authors.initials: MS
authors.lastname: Potentier
authors.forename: L Patrick
authors.initials: LP
authors.lastname: Schenck
authors.forename: Akosua
authors.initials: A
authors.lastname: Vilaysane
authors.forename: Mark E
authors.initials: ME
authors.lastname: Seamone
authors.forename: Hanping
authors.initials: H
authors.lastname: Feng
authors.forename: Glen D
authors.initials: GD
authors.lastname: Armstrong
authors.forename: Jurg
authors.initials: J
authors.lastname: Tschopp
authors.forename: Justin A
authors.initials: JA
authors.lastname: Macdonald
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Muruve
authors.forename: Paul L
authors.initials: PL
authors.lastname: Beck
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics; D001706:Biopsy; D053468:CARD Signaling Adaptor Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D020170:Caspase 1 / Q000378:metabolism; D002460:Cell Line; D016360:Clostridioides difficile / Q000235:genetics / Q000472:pathogenicity*; D003598:Cytoskeletal Proteins / Q000172:deficiency / Q000235:genetics; D004195:Disease Models, Animal; D004705:Endocytosis; D011992:Endosomes / Q000276:immunology / Q000382:microbiology; D004768:Enterotoxins / Q000235:genetics; D006801:Humans; D007079:Ileitis / Q000276:immunology* / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control; D007082:Ileum / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D007113:Immunity, Innate / Q000187:drug effects; D018836:Inflammation Mediators / Q000378:metabolism*; D053590:Interleukin 1 Receptor Antagonist Protein / Q000494:pharmacology; D053583:Interleukin-1beta / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D053468:CARD Signaling Adaptor Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D004768:Enterotoxins; D018836:Inflammation Mediators; D053590:Interleukin 1 Receptor Antagonist Protein; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; C498534:Pycard protein, mouse; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile; D020170:Caspase 1