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.
Article first Published online 18 March 2013
†Department of Medical Microbiology and Immunology;
‡Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada;
§Department of Medicine, University of Calgary, Calgary, Alberta, Canada;
‖Department of Computing Sciencel; and
¶Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada.
Reprints: Julia J. Liu, MSc, MD, Division of Gastroenterology, 1–10 Zeidler Ledcor Centre, University of Alberta, Edmonton, Alberta, Canada T6G 2X8 (e-mail: firstname.lastname@example.org).
Supported by the Canadian Institute of Health Research (J.J.L.), Canadian Association of Gastroenterology (J.J.L.), the Canadian Foundation for Innovations (R.N.F.), and Natural Sciences and Engineering Research Council of Canada (R.T.I.).
The authors have no conflicts of interest to disclose.
Received June 17, 2012
Accepted August 06, 2012