title: Epithelial cell extrusion leads to breaches in the intestinal epithelium.
abstract: BACKGROUND
  Two distinct forms of intestinal epithelial cell (IEC) extrusion are described: 1 with preserved epithelial integrity and 1 that introduced breaches in the epithelial lining. In this study, we sought to determine the mechanism underlying the IEC extrusion that alters the permeability of the gut epithelium.
  
  
  METHODS
  IEC extrusions in polarized T84 monolayer were induced with nigericin. Epithelial permeability was assessed with transepithelial electrical resistance and movements of latex microspheres and green fluorescent protein-transfected Escherichia coli across the monolayer. In vivo IEC extrusion was modulated in wild-type and a colitic (interleukin-10 knock-out) mouse model with caspase-1 activation and inhibition. Luminal aspirates and mucosal biopsies from control patients and patients with inflammatory bowel disease were analyzed for caspase-1 and caspase-3&7 activation.
  
  
  RESULTS
  Caspase-1-induced IEC extrusion in T84 monolayers resulted in dose-dependent and time-dependent barrier dysfunction, reversible with caspase-1 inhibition. Moreover, the movements of microspheres and microbes across the treated epithelial monolayers were observed. Increased caspase-1-mediated IEC extrusion in interleukin-10 knock-out mice corresponded to enhanced permeation of dextran, microspheres, and translocation of E. coli compared with wild type. Caspase-1 inhibition in interleukin-10 knock-out mice resulted in a time-dependent reduction in cell extrusion and normalization of permeability to microspheres. Increased IEC extrusion in wild-type mice was induced with caspase-1 activation. In human luminal aspirates, the ratio of positively stained caspase-1 to caspase-3&7 cells were 1:1 and 2:1 in control patients and patients with inflammatory bowel disease, respectively; these observations were confirmed by cytochemical analysis of mucosal biopsies.
  
  
  CONCLUSIONS
  IEC extrusion mediated by caspase-1 activation contributes to altered intestinal permeability in vitro and in vivo.
authors.affiliation: Gastroenterology Division, University of Alberta, Edmonton, Alberta, Canada. julia.liu@ualberta.ca
authors.forename: Julia J
authors.initials: JJ
authors.lastname: Liu
authors.forename: Elisabeth M
authors.initials: EM
authors.lastname: Davis
authors.forename: Eytan
authors.initials: E
authors.lastname: Wine
authors.forename: Yuefei
authors.initials: Y
authors.lastname: Lou
authors.forename: Jan K
authors.initials: JK
authors.lastname: Rudzinski
authors.forename: Misagh
authors.initials: M
authors.lastname: Alipour
authors.forename: Pierre
authors.initials: P
authors.lastname: Boulanger
authors.forename: Aducio L
authors.initials: AL
authors.lastname: Thiesen
authors.forename: Consolato
authors.initials: C
authors.lastname: Sergi
authors.forename: Richard N
authors.initials: RN
authors.lastname: Fedorak
authors.forename: Daniel
authors.initials: D
authors.lastname: Muruve
authors.forename: Karen L
authors.initials: KL
authors.lastname: Madsen
authors.forename: Randall T
authors.initials: RT
authors.lastname: Irvin
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D016022:Case-Control Studies; D020170:Caspase 1 / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002454:Cell Differentiation; D002463:Cell Membrane Permeability; D049109:Cell Proliferation; D022081:Cell Surface Extensions / Q000378:metabolism / Q000473:pathology*; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000378:metabolism / Q000473:pathology*; D016753:Interleukin-10 / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout
chemical_list: D016207:Cytokines; D016753:Interleukin-10; D053148:Caspase 3; D020170:Caspase 1