Article

Epithelial NEMO links innate immunity to chronic intestinal inflammation.

Institute for Genetics, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany.
Nature (Impact Factor: 42.35). 04/2007; 446(7135):557-61. DOI: 10.1038/nature05698
Source: PubMed

ABSTRACT Deregulation of intestinal immune responses seems to have a principal function in the pathogenesis of inflammatory bowel disease. The gut epithelium is critically involved in the maintenance of intestinal immune homeostasis-acting as a physical barrier separating luminal bacteria and immune cells, and also expressing antimicrobial peptides. However, the molecular mechanisms that control this function of gut epithelial cells are poorly understood. Here we show that the transcription factor NF-kappaB, a master regulator of pro-inflammatory responses, functions in gut epithelial cells to control epithelial integrity and the interaction between the mucosal immune system and gut microflora. Intestinal epithelial-cell-specific inhibition of NF-kappaB through conditional ablation of NEMO (also called IkappaB kinase-gamma (IKKgamma)) or both IKK1 (IKKalpha) and IKK2 (IKKbeta)-IKK subunits essential for NF-kappaB activation-spontaneously caused severe chronic intestinal inflammation in mice. NF-kappaB deficiency led to apoptosis of colonic epithelial cells, impaired expression of antimicrobial peptides and translocation of bacteria into the mucosa. Concurrently, this epithelial defect triggered a chronic inflammatory response in the colon, initially dominated by innate immune cells but later also involving T lymphocytes. Deficiency of the gene encoding the adaptor protein MyD88 prevented the development of intestinal inflammation, demonstrating that Toll-like receptor activation by intestinal bacteria is essential for disease pathogenesis in this mouse model. Furthermore, NEMO deficiency sensitized epithelial cells to tumour-necrosis factor (TNF)-induced apoptosis, whereas TNF receptor-1 inactivation inhibited intestinal inflammation, demonstrating that TNF receptor-1 signalling is crucial for disease induction. These findings demonstrate that a primary NF-kappaB signalling defect in intestinal epithelial cells disrupts immune homeostasis in the gastrointestinal tract, causing an inflammatory-bowel-disease-like phenotype. Our results identify NF-kappaB signalling in the gut epithelium as a critical regulator of epithelial integrity and intestinal immune homeostasis, and have important implications for understanding the mechanisms controlling the pathogenesis of human inflammatory bowel disease.

1 Bookmark
 · 
252 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mucosal surfaces represent the largest areas of interactions of the host with its environment. Subsequently, the mucosal immune system has evolved complex strategies to maintain the integrity of the host by inducing protective immune responses against pathogenic and tolerance against dietary and commensal microbial antigens within the broad range of molecules the intestinal epithelium is exposed to. Among many other specialized cell subsets, myeloid cell populations - due to their strategic location in the subepithelial lamina propria - are the first ones to scavenge and process these intestinal antigens and to send consecutive signals to other immune and non-immune cell subsets. Thus, myeloid cell populations represent attractive targets for clinical intervention in chronic inflammatory bowel diseases (IBDs) such as ulcerative colitis (UC) and Crohn's disease (CD) as they initiate and modulate inflammatory or regulatory immune response and shape the intestinal T cell pool. Here, we discuss the interactions of the intestinal microbiota with dendritic cell and macrophage populations and review in this context the literature on four promising candidate molecules that are critical for the induction and maintenance of intestinal homeostasis on the one hand, but also for the initiation and propagation of chronic intestinal inflammation on the other. Copyright © 2014. Published by Elsevier GmbH.
    Immunobiology 11/2014; 220(2). DOI:10.1016/j.imbio.2014.11.014 · 2.81 Impact Factor
  • Frontiers in Bioscience 01/2008; Volume(13):4838. DOI:10.2741/3043 · 4.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Although vitamin D receptor (VDR) is highly expressed in the intestine, the role of VDR signaling in the gut is not fully understood. Our recent studies unveil a regulatory circuit that centers gut epithelial VDR as a key molecule in the control of mucosal inflammation and colitis development. On the one hand, intestinal epithelial VDR signaling protects the integrity of the mucosal barrier by inhibiting inflammation-induced epithelial cell apoptosis. This barrier-protecting, anti-colitic activity is independent of the non-epithelial immune VDR actions. A healthy and intact mucosal barrier prevents bacterial invasion and thus reduces mucosal inflammation. On the other hand, inflammation in turn down-regulates epithelial VDR expression by inducing VDR-targeting microRNA-346, thus compromising mucosal barrier functions. Consistently, colonic epithelial VDR levels are markedly reduced in patients with inflammatory bowel diseases or in experimental colitis models, whereas vitamin D analog therapy that ameliorates colitis up-regulates epithelial VDR. Thus, gut epithelial VDR signaling appears to play an essential role in controlling mucosal inflammation and thus could be a useful therapeutic target in the management of inflammatory bowel diseases. This article is part of a special issue entitled '17th Vitamin D Workshop' . Copyright © 2015. Published by Elsevier Ltd.
    The Journal of Steroid Biochemistry and Molecular Biology 01/2015; 148. DOI:10.1016/j.jsbmb.2015.01.011 · 4.05 Impact Factor

Full-text (2 Sources)

Download
51 Downloads
Available from
May 16, 2014