title: Inflammasome activation contributes to interleukin-23 production in response to Clostridium difficile.
abstract: Clostridium difficile is the most common hospital-acquired pathogen, causing antibiotic-associated diarrhea in over 250,000 patients annually in the United States. Disease is primarily mediated by toxins A and B, which induce potent proinflammatory signaling in host cells and can activate an ASC-containing inflammasome. Recent findings suggest that the intensity of the host response to infection correlates with disease severity. Our lab has identified the proinflammatory cytokine interleukin-23 (IL-23) as a pathogenic mediator during C. difficile infection (CDI). The mechanisms by which C. difficile induces IL-23, however, are not well understood, and the role of toxins A and B in this process is unclear. Here, we show that toxins A and B alone are not sufficient for IL-23 production but synergistically increase the amount of IL-23 produced in response to MyD88-dependent danger signals, including pathogen-associated molecular patterns (PAMPs) and host-derived damage associated molecular patterns (DAMPs). Danger signals also enhanced the secretion of IL-1β in response to toxins A and B, and subsequent IL-1 receptor signaling accounted for the majority of the increase in IL-23 that occurred in the presence of the toxins. Inhibition of inflammasome activation in the presence of extracellular K(+) likewise decreased IL-23 production. Finally, we found that IL-1β was increased in the serum of patients with CDI, suggesting that this systemic response could influence downstream production of pathogenic IL-23. Identification of the synergy of danger signals with toxins A and B via inflammasome signaling represents a novel finding in the mechanistic understanding of C. difficile-induced inflammation.
  
  
  OBJECTIVE
  Clostridium difficile is among the leading causes of death due to health care-associated infection, and factors determining disease severity are not well understood. C. difficile secretes toxins A and B, which cause inflammation and tissue damage, and recent findings suggest that some of this tissue damage may be due to an inappropriate host immune response. We have found that toxins A and B, in combination with both bacterium- and host-derived danger signals, can induce expression of the proinflammatory cytokines IL-1β and IL-23. Our results demonstrate that IL-1β signaling enhances IL-23 production and could lead to increased pathogenic inflammation during CDI.
authors: Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, USA.
authors: Carrie A
authors: CA
authors: Cowardin
authors: Nottingham Digestive Diseases Centre, University of Nottingham, Nottingham, United Kingdom.
authors: Sarah A
authors: SA
authors: Kuehne
authors: Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, USA.
authors: Erica L
authors: EL
authors: Buonomo
authors: Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA.
authors: Chelsea S
authors: CS
authors: Marie
authors: Nottingham Digestive Diseases Centre, University of Nottingham, Nottingham, United Kingdom.
authors: Nigel P
authors: NP
authors: Minton
authors: wap3g@virginia.edu.
authors: William A
authors: WA
authors: Petri
mesh_terms: D001426:Bacterial Proteins / Q000276:immunology; D001427:Bacterial Toxins / Q000276:immunology; D016360:Clostridioides difficile / Q000235:genetics / Q000276:immunology* / Q000502:physiology; D003015:Clostridium Infections / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D003713:Dendritic Cells / Q000276:immunology / Q000382:microbiology; D004768:Enterotoxins / Q000276:immunology; D006801:Humans; D058847:Inflammasomes / Q000235:genetics / Q000276:immunology*; D053583:Interleukin-1beta / Q000235:genetics / Q000276:immunology; D053759:Interleukin-23 / Q000235:genetics / Q000276:immunology*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004768:Enterotoxins; D058847:Inflammasomes; D053583:Interleukin-1beta; D053759:Interleukin-23; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile
references: Nature. 2014 Sep 11;513(7517):237-41
references: 24919149
references: J Infect Dis. 2014 Jan 1;209(1):83-6
references: 23935202
references: Dig Dis Sci. 1992 Jun;37(6):818-26
references: 1587185
references: J Clin Invest. 1994 Mar;93(3):1257-65
references: 7907603
references: Nature. 1995 Jun 8;375(6531):500-3
references: 7777059
references: J Clin Invest. 1997 Oct 1;100(7):1734-41
references: 9312171
references: Clin Diagn Lab Immunol. 1997 Nov;4(6):719-22
references: 9384296
references: Curr Protoc Immunol. 2001 May;Chapter 7:Unit 7.32
references: 18432844
references: J Mol Med (Berl). 2009 Feb;87(2):169-80
references: 18985311
references: J Biol Chem. 2009 Sep 4;284(36):24006-16
references: 19592489
references: Genome Biol. 2009;10(9):R102
references: 19781061
references: Appl Environ Microbiol. 2010 Feb;76(4):1103-9
references: 20023081
references: Gastroenterology. 2010 Aug;139(2):542-52, 552.e1-3
references: 20398664
references: Nature. 2010 Oct 7;467(7316):711-3
references: 20844489
references: J Infect Dis. 2010 Dec 1;202(11):1708-12
references: 20977342
references: BMC Gastroenterol. 2010;10:133
references: 21067563
references: Nat Rev Gastroenterol Hepatol. 2011 Jan;8(1):17-26
references: 21119612
references: Infect Control Hosp Epidemiol. 2011 Apr;32(4):387-90
references: 21460491
references: J Immunol. 2011 Apr 15;186(8):4872-80
references: 21411735
references: PLoS Pathog. 2011 Jun;7(6):e1002076
references: 21738466
references: Emerg Infect Dis. 2011 Jun;17(6):976-82
references: 21749757
references: J Infect Dis. 2012 Feb 1;205(3):384-91
references: 22147798
references: Methods Mol Biol. 2012;844:199-222
references: 22262445
references: Infect Immun. 2012 Aug;80(8):2704-11
references: 22615253
references: Infect Immun. 2012 Sep;80(9):2989-96
references: 22689818
references: J Immunol. 2012 Sep 15;189(6):3085-91
references: 22888139
references: J Immunol. 2012 Oct 15;189(8):4144-53
references: 22972933
references: PLoS One. 2012;7(11):e50288
references: 23209696
references: PLoS Pathog. 2012;8(12):e1003072
references: 23236283
references: Life Sci. 2013 Feb 27;92(3):211-7
references: 23261530
references: Annu Rev Immunol. 2013;31:73-106
references: 23215645
references: Clin Infect Dis. 2013 Jun;56(12):1713-21
references: 23487367
references: Immunity. 2013 Jun 27;38(6):1142-53
references: 23809161
references: PLoS One. 2013;8(7):e69846
references: 23922820
references: J Infect Dis. 2013 Sep;208(6):917-20
references: 23776194
references: Nat Rev Immunol. 2013 Nov;13(11):790-801
references: 24096337
references: J Immunol. 1999 Nov 15;163(10):5183-91
references: 10553038
references: Nat Rev Immunol. 2004 Jul;4(7):499-511
references: 15229469
references: N Engl J Med. 1978 Mar 9;298(10):531-4
references: 625309