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Saeedi B.J.,Mucosal Inflammation Program | Kao D.J.,Mucosal Inflammation Program | Kitzenberg D.A.,Mucosal Inflammation Program | Dobrinskikh E.,Gastrointestinal Eosinophilic Diseases Program | And 12 more authors.
Molecular Biology of the Cell

Intestinal epithelial cells (IECs) are exposed to profound fluctuations in oxygen tension and have evolved adaptive transcriptional responses to a low-oxygen environment. These adaptations are mediated primarily through the hypoxia-inducible factor (HIF) complex. Given the central role of the IEC in barrier function, we sought to determine whether HIF influenced epithelial tight junction (TJ) structure and function. Initial studies revealed that short hairpin RNA-mediated depletion of the HIF1β in T84 cells resulted in profound defects in barrier and nonuniform, undulating TJ morphology. Global HIF1α chromatin immunoprecipitation (ChIP) analysis identified claudin-1 (CLDN1) as a prominent HIF target gene. Analysis of HIF1β-deficient IEC revealed significantly reduced levels of CLDN1. Overexpression of CLDN1 in HIF1β-deficient cells resulted in resolution of morphological abnormalities and restoration of barrier function. ChIP and site-directed mutagenesis revealed prominent hypoxia response elements in the CLDN1 promoter region. Subsequent in vivo analysis revealed the importance of HIF-mediated CLDN1 expression during experimental colitis. These results identify a critical link between HIF and specific tight junction function, providing important insight into mechanisms of HIF-regulated epithelial homeostasis. © 2015 Saeedi, Kao, et al. Source

McNamee E.N.,Mucosal Inflammation Program | Masterson J.C.,Mucosal Inflammation Program | Jedlicka P.,University of Colorado at Denver | Collins C.B.,Mucosal Inflammation Program | And 2 more authors.

Background: The earliest endoscopically-evident lesion in Crohn's disease is the aphthous ulcer, which develops over ectopic lymphoid tissues (ie, inducible lymphoid follicles (ILF), tertiary lymphoid tissue (TLT)) in the chronically inflamed intestine. ILF/TLT are induced within effector sites by homeostatic lymphoid chemokines, but their role in the development of intestinal ILF/TLT and in the pathogenesis of Crohn's disease is poorly understood. Design: Using a mouse model of Crohn's-like ileitis (TNFΔARE) which develops florid induction of ILF/TLT within its terminal ileum, the contribution of the CCR7/ CCL19/CCL21 chemokine axis during the development of TLT and its role in disease pathogenesis were assessed. Results: Both CCL19 and CCL21 were increased within the inflamed ileum of TNFΔARE mice, which resulted in CCR7 internalisation and impaired T cell chemotaxis. ILF/ TLT were a major source of CCL19 and CCL21 and increased local synthesis, augmented recruitment/ retention of effector, naïve and central memory T cell subsets within the inflamed ileum. Immunoblockade of CCR7 resulted in further effector T cell retention and exacerbation of ileitis. Conclusions: Induction of ILF/TLT in the chronically inflamed intestine alters the homeostatic CCL19-CCL21 lymphoid-chemokine gradient and increases recruitment/ retention of effector CCR7+ T cell subsets within the terminal ileum, contributing to the perpetuation of chronic inflammation. Thus, blockade of CCR7 or its ligands might result in deleterious consequences for subjects with chronic inflammatory diseases. Source

Collins C.B.,Mucosal Inflammation Program | Aherne C.M.,Mucosal Inflammation Program | Ehrentraut S.F.,Mucosal Inflammation Program | Gerich M.E.,Mucosal Inflammation Program | And 6 more authors.
Inflammatory Bowel Diseases

Background: Fecal alpha-1-antitrypsin (AAT) clearance has been a marker of clinical disease severity in inflammatory bowel diseases (IBDs) for many years. Although AAT deficiency is more often associated with lung and liver pathologies, AAT-deficient patients with concomitant IBD have been shown to develop more aggressive disease and rapid progression to surgery. Although recent studies have highlighted the pleiotropic anti-inflammatory functions of AAT, including reducing proinflammatory cytokine production and suppressing immune cell activation, its potential therapeutic role in IBD has not been described. Methods: The therapeutic potential of human AAT administration was assessed in murine models of IBD including new-onset and established chemically induced colitis and spontaneous chronic murine ileitis. Histological assessment of inflammation, cytokine secretion profiling, and flow cytometric evaluation of inflammatory infiltrate were performed in each model. The effect of AAT on intestinal barrier function was also examined both in vitro and in vivo. Results: AAT attenuated inflammation in small and large intestinal IBD models through reduced secretion of proinflammatory cytokines, inflammatory cell infiltration, and reduced tissue injury. AAT also increased intestinal restitution after chemically induced colitis. AAT significantly decreased intestinal permeability in vitro and in vivo as part of a protective mechanism for both acute and chronic models of IBD. Conclusions: Our findings describe a beneficial role for AAT in IBD models through suppression of cytokine production and enhanced intestinal barrier function. This raises the possibility that AAT supplementation, which has a long history of proven safety, may have a therapeutic effect in human IBD. Copyright © 2013 Crohn's & Colitis Foundation of America, Inc. Source

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