title: Interfering with interferon-γ signalling in intestinal epithelial cells: selective inhibition of apoptosis-maintained secretion of anti-inflammatory interleukin-18 binding protein.
abstract: The intestinal epithelial barrier represents an important component in the pathogenesis of inflammatory bowel diseases. Interferon (IFN)-γ, a T helper type 1 (Th1) cytokine, regulated by the interleukin (IL)-18/IL-18 binding protein (bp) system, modulates the integrity of this barrier. The aim of this work was to study functionally the consequences of IFN-γ on intestinal epithelial cells (IEC) and to interfere selectively with identified adverse IFN-γ effects. IEC lines were stimulated with IFN-γ. IL-18 and IL-18bp were assessed by enzyme-linked immunosorbent assay. Staining of phosphatidylserine, DNA laddering, lactate dehydrogenase (LDH) release, cleavage of poly-adenosine diphosphate-ribose-polymerase (PARP) and activation of caspase-3 were analysed to determine cell death. Inhibitors of tyrosine kinase, caspase-3 or p38 mitogen-activated kinase ((MAP) activity were used. Cytokines were measured in supernatants of colonic biopsies of healthy controls and inflammatory bowel disease (IBD) patients. In IEC lines, IFN-γ up-regulated IL-18bp selectively. Ex vivo, IFN-γ was present in supernatants from cultured biopsies and up-regulated with inflammation. Contrary to previous reports, IFN-γ alone induced apoptosis in IEC lines, as demonstrated by phosphatidylserin staining, DNA cleavage and LDH release. Further, activation of caspase-3, PARP cleavage and expression of pro-apoptotic Bad were induced. Partial inhibition of caspase-3 and of p38 but not JAK tyrosine kinase, preserved up-regulation of IL-18bp expression. Selective inhibition of IFN-γ mediated apoptosis, while preserving its beneficial consequences on the ratio of IL-18/IL-18bp, could contribute to the integrity of the mucosal barrier in intestinal inflammation.
authors.affiliation: Department of Medicine II and Department of Pediatrics, University Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Schuhmann
authors.forename: P
authors.initials: P
authors.lastname: Godoy
authors.forename: C
authors.initials: C
authors.lastname: Weiss
authors.forename: A
authors.initials: A
authors.lastname: Gerloff
authors.forename: M V
authors.initials: MV
authors.lastname: Singer
authors.forename: S
authors.initials: S
authors.lastname: Dooley
authors.forename: U
authors.initials: U
authors.lastname: Böcker
mesh_terms: D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000276:immunology*; D053148:Caspase 3 / Q000032:analysis / Q000276:immunology; D061945:Caspase Inhibitors; D002478:Cells, Cultured; D016207:Cytokines / Q000032:analysis / Q000276:immunology; D004247:DNA / Q000032:analysis / Q000276:immunology / Q000378:metabolism; D053938:DNA Fragmentation; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000276:immunology* / Q000473:pathology / Q000601:surgery; D036341:Intercellular Signaling Peptides and Proteins / Q000276:immunology*; D007371:Interferon-gamma / Q000276:immunology*; D007413:Intestinal Mucosa / Q000276:immunology*; D007770:L-Lactate Dehydrogenase / Q000276:immunology / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010718:Phosphatidylserines / Q000032:analysis; D011065:Poly(ADP-ribose) Polymerases / Q000032:analysis / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D015854:Up-Regulation; D055815:Young Adult; D051025:bcl-Associated Death Protein / Q000032:analysis / Q000276:immunology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000276:immunology
chemical_list: D061945:Caspase Inhibitors; D016207:Cytokines; D036341:Intercellular Signaling Peptides and Proteins; D010718:Phosphatidylserines; D051025:bcl-Associated Death Protein; C118370:interleukin-18 binding protein; D007371:Interferon-gamma; D004247:DNA; D007770:L-Lactate Dehydrogenase; D011065:Poly(ADP-ribose) Polymerases; D011505:Protein-Tyrosine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D053148:Caspase 3