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.

Full-text

Available from: Deborah L Gumucio, Apr 26, 2015
1 Follower
 · 
257 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Inflammatory bowel diseases, ulcerative colitis and Crohn׳s disease are characterized by chronic relapsing inflammation of the gastrointestinal tract of unknown etiology that seems to be the consequence of a genetically driven dysregulated immune response against various local and environmental triggers through a defective epithelial barrier. During the last decades, a large number of animal experimental models of intestinal inflammation have been generated and provided valuable insights into the mechanisms that either maintain mucosal homeostasis or drive intestinal inflammation. Their study enabled the identification of various treatment targets and the development a large pipeline of new drugs, mostly biologics. Safety and therapeutic efficacy of these agents have been evaluated in a large number of clinical trials but only a minority has reached the clinic so far. Translational successes but mostly translational failures have prompted to re-evaluate results of efficacy and safety generated by pre-clinical testing and to re-examine the way to interpret experimental in vivo data. This review examines the contribution of the most popular experimental colitis models to our understanding of the pathogenesis of human inflammatory bowel diseases and their translational input in drug development and discusses ways to improve translational outcome. Copyright © 2015. Published by Elsevier B.V.
    European journal of pharmacology 03/2015; DOI:10.1016/j.ejphar.2015.03.017 · 2.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The NF-í µí¼…B is a transcription factor which plays a key role in regulating biological processes. In response to signals, NF-í µí¼…B activation occurs via phosphorylation of its inhibitor, which dissociates from the NF-í µí¼…B dimer allowing the translocation to the nucleus, inducing gene expression. NF-í µí¼…B activation has direct screening applications for drug discovery for several therapeutic indications. Thus, pathway-specific reporter cell systems appear as useful tools to screen and unravel the mode of action of probiotics and natural and synthetic compounds. Here, we describe the generation, characterization, and validation of human epithelial reporter cell lines for functional studies of NF-í µí¼…B activation by different pro-and anti-inflammatory agents. Caco-2 and HT-29 cells were transfected with a pNF-í µí¼…B-hrGFP plasmid which contains the GFP gene under the control of NF-í µí¼…B binding elements. Three proinflammatory cytokines (TNF-í µí»¼, IL-1í µí»½, and LPS) were able to activate the reporter systems in a dose-response manner, which corresponds to the activation of the NF-í µí¼…B signaling pathway. Finally, the reporter cell lines were validated using lactic acid bacteria and a natural compound. We have established robust Caco-2-NF-í µí¼…B-hrGFP and HT-29-NF-í µí¼…B-hrGFP reporter cell lines which represent a valuable tool for primary screening and identification of bacterial strains and compounds with a potential therapeutic interest.
    Mediators of Inflammation 04/2015; 2015. DOI:10.1155/2015/860534 · 2.42 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: AbstractNF-?B (p50/p65) is the best characterized transcription factor known to regulate cell responses to inflammation. However, NF-?B is also constitutively expressed. We used inhibitors of the classical NF-?B signaling pathway to determine whether this transcription factor has a role in regulating alveolar epithelial tight junctions. Primary rat type II alveolar epithelial cells were isolated and cultured on Transwell permeable supports coated with collagen for five days to generate a model type I cell monolayer. Treatment of alveolar epithelial monolayers overnight with one of two different I?B kinase inhibitors (Bay 11-7082 or BMS-345541) resulted in a dose-dependent decrease in TER at concentrations that did not affect cell viability. In response to BMS-345541 treatment there was an increase in total claudin-4 and claudin-5 along with a decrease in claudin-18, as determined by immunoblot. However, there was little effect on the total amount of cell-associated claudin-7, occludin, junctional adhesion molecule A (JAM-A), zonula occludens (ZO)-1 or ZO-2. Moreover, treatment with BMS-345541 resulted in altered tight junction morphology as assessed by immunofluorescence microscopy. Cells treated with BMS-345541 had an increase in claudin-18 containing projections emanating from tight junctions (?spikes?) that were less prominent in control cells. There also were several areas of cell-cell contact which lacked ZO-1 and ZO-2 localization as well as rearrangements to the actin cytoskeleton in response to BMS-345541. Consistent with an anti-inflammatory effect, BMS-345541 antagonized the deleterious effects of lipopolysaccharide (LPS) on alveolar epithelial barrier function. However, BMS-345541 also inhibited the ability of GM-CSF to increase alveolar epithelial TER. These data suggest a dual role for NF-?B in regulating alveolar barrier function and that constitutive NF-?B function is required for the integrity of alveolar epithelial tight junctions
    01/2015; 3(1-2). DOI:10.4161/21688370.2014.982424