gms | German Medical Science

124. Kongress der Deutschen Gesellschaft für Chirurgie

Deutsche Gesellschaft für Chirurgie

01. - 04.05.2007, München

IFN-Gamma induces Apoptosis in Inflammation by Inhibition of the Wnt signaling Pathway

Meeting Abstract

  • corresponding author M.G. Laukoetter - Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, USA
  • P. Nava - Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, USA
  • W. Lee - Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, USA
  • M. Bruewer - Klinik und Poliklinik fuer Allgemeine Chirurgie, Universitaetsklinikum Muenster, Deutschland
  • J.M. Klapproth - Division of Digestive Diseases, Emory University, Atlanta, USA
  • C. Parkos - Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, USA
  • B.A. Babbin - Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, USA
  • A. Nusrat - Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, USA

Deutsche Gesellschaft für Chirurgie. 124. Kongress der Deutschen Gesellschaft für Chirurgie. München, 01.-04.05.2007. Düsseldorf: German Medical Science GMS Publishing House; 2007. Doc07dgch7264

Die elektronische Version dieses Artikels ist vollständig und ist verfügbar unter: http://www.egms.de/de/meetings/dgch2007/07dgch217.shtml

Veröffentlicht: 1. Oktober 2007

© 2007 Laukoetter et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielf&aauml;ltigt, verbreitet und &oauml;ffentlich zug&aauml;nglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Introduction: The gastrointestinal epithelium is essential to maintain gut function and homoeostatic balance between proliferation and apoptosis. The Wnt-signaling pathway which is critical in regulating epithelial proliferation functions through the interaction of GSK3 beta and beta catenin. Exaggerated intestinal epithelial apoptosis leads to villus atrophy and epithelial destruction, which play a central role in inflammatory bowel disease (IBD). While it is well known that pro-inflammatory cytokines such as interferon gamma (IFNg) induce apoptosis in epithelial cells, the underlying mechanisms that mediate this are incompletely understood. Our study suggests involvement of a Wnt signaling inhibitor Dickkopf-Homolog-1 (DKK-1) in mediating IFNg induced epithelial apoptosis.

Materials and methods: Cell culture: The human intestinal epithelial cell lines (IECs), SKCO-15 and T84 were passaged and seeded on collagen-coated permeable supports or tissue culture-treated plates for western blot (WB) analysis, p53 transfection, cytokine treatment, GSK3 beta-, DKK-1 inhibitor studies and immunofluorescence labeling (IF). Confocal microscopy was performed using the Zeiss LSM 510 microscope (Thornwood, NY). Animal model: C57BL/6J mice were administered 5% DSS (40 kDa; ICN USA) dissolved in water that was filter-purified (Millipore Corp., USA) for 7 days (day 0–6 ad libitum). Control mice received the filtered water alone. For each animal, disease activity index, MPO measurements, histological (HE) and IF examinations were performed on four samples from the distal colon.Patients: Colonoscopic biopsies form 5 Patients with active Chron’s disease and 5 healthy control patients were analyzed by IF.

Results: IECs incubated basolaterally with human IFN-g (100 U/mL) for 72hrs showed a 3 fold upregulation of DKK-1 and downregulation of its receptor LRP6 without any change in the coreceptor, Kremen1 compared to controls as determined by WB. Furthermore, WBs revealed that IFN-g induced upregulation of p53 which is a well known DKK-1 inducer. To further analyze the relationship of IFNg induced upregulation of DKK and p53, we transfected SK-CO15 cells with a p53 plasmid. P53 overexpression induced a significant increase in DKK-1 expression compared to cells transfected with the vector alone control and this effect was reversed by expression of dominant negative p53. Apoptosis was confirmed by presence of caspase3 and cleavage of PARP as determined by WB and IF labeling. The effect of DKK-1 in the onset of apoptosis was prevented using a GSK-3 beta inhibitor and an inhibitory antibody to DKK-1. As an in vivo correlate, we observed significant upregulation of DKK-1 in inflamed DSS treated murine colonic mucosa and mucosa from Crohn’s disease patients.

Discussion: The above findings support a novel role for the Wnt signaling pathway inhibitor, DKK1 in IFNg induced epithelial apoptosis. We propose the following scenario. Upon stimulation by IFN-g, p53 induces DKK-1 secretion and its engagement to the cell surface receptors Kremen1 and LRP-6. The APC–axin–GSK-3 beta complex is activated resulting in phosphorylation and degradation of beta-catenin thereby inhibiting cell proliferation and stimulating cell death. This is the first direct evidence of participation of the Wnt signaling pathway in an inflammatory response.

Supported by a grant from the German Research Foundation (Deutsche Forschungsgemeinschaft) La 2359/1-1 to M.L.