P044. Identification of a novel role for interleukin-27 as mediator of intestinal epithelial barrier protection acting via differential STAT signalling and induction of antibacterial and anti-inflammatory proteins
J. Diegelmann1, T. Olszak2, B. Göke3, R.S. Blumberg4, S. Brand1
1University Hospital Munich-Grosshadern, Department of Medicine II, Munich, Germany; 2University Hospital Munich-Grosshadern, Germany; 3University Hospital Munich Grosshadern, LMU Munich, Munich, Germany; 4Brigham & Women's Hospital, Harvard Medical School, Boston, United States
Background: Interleukin-27 (IL‑27) belongs to the IL‑12 cytokine family and inhibits proinflammatory Th17 cell differentiation. Recent genome-wide association studies identified single nucleotide polymorphism (SNPs) in the IL27 gene region to be associated with susceptibility to Crohn's disease (CD). However, the role of IL‑27 in the IBD pathogenesis is contradictory and its influence on intestinal epithelial cells (IEC) is unknown. The aim of this study was therefore to analyze the functions of IL‑27 in IEC and its effects on the intestinal barrier.
Methods: Expression studies in IEC lines and in biopsies from CD patients were performed by quantitative PCR, Western blot and immunohistochemistry. Target genes of IL‑27 were analyzed by microarray in IEC and by quantitative PCR in murine DSS colitis. IEC restitution was measured using wounding assays. Signal transduction was analyzed by Western blot and siRNA transfection experiments. Bacterial growth in conditioned medium was assessed photometrically and in colony forming assays.
Results: IEC express both IL‑27 receptor subunits IL‑27RA and gp130. The IL‑27 receptor expression is up-regulated in intestinal inflammation in vitro and in vivo. IL‑27 activates ERK and p38 MAP kinases as well as Akt, STAT1, STAT3 and STAT6 in IEC. IL‑27 significantly enhances cell proliferation and IEC restitution. These functions of IL‑27 are dependent on the activation of STAT3 and STAT6 signalling pathways. As analyzed by microarray, IL‑27 modulates the expression of 428 target genes in IEC (316 up-regulated, 112 down-regulated; p < 0.05). IL‑27 as well as its main target genes are up-regulated in colonic tissue and IEC isolated from mice with DSS-induced colitis. The IL‑27-induced expression of the anti-bacterial gene DMBT1 is mediated by p38 and STAT3 signalling while the activation of the anti-inflammatory and anti-bacterial gene IDO1 is dependent on STAT1 signal transduction. Induction of IDO1 enzymatic activity by IL‑27 leads to growth inhibition of intestinal bacteria due to local tryptophan depletion.
Conclusions: IL‑27 acts as a protective factor for the intestinal epithelial barrier through STAT-mediated activation of anti-inflammatory and antibacterial target genes and functions.