1. Iron Prevents Hypoxia-Associated Inflammation Through the Regulation of Nuclear Factor-κB in the Intestinal Epithelium
- Author
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Simona Simmen, Jesus Cosin-Roger, Cheryl de Valliere, Katharina Spanaus, Katharina Baebler, Chiaki Maeyashiki, Nikolaos Maliachovas, Jonas Zeitz, Gerhard Rogler, Pedro A. Ruiz, Hassan Melhem, Stephan R. Vavricka, Bruce Weder, Max Maane, Martin Hausmann, Michael Scharl, University of Zurich, and Ruiz, Pedro A
- Subjects
0301 basic medicine ,DMT-1, divalent metal transporter 1 ,RNA Stability ,Interleukin-1beta ,IRE, iron-responsive elements ,IEC, intestinal epithelial cell ,0302 clinical medicine ,PCR, polymerase chain reaction ,540 Chemistry ,IL1β, interleukin 1β ,Intestinal Mucosa ,Hypoxia ,Promoter Regions, Genetic ,10038 Institute of Clinical Chemistry ,Original Research ,DFO, deferoxamine ,Aged, 80 and over ,TNF, tumor necrosis factor ,biology ,IBD, inflammatory bowel disease ,Chemistry ,TTP, tristetraprolin ,Gastroenterology ,NF-kappa B ,Middle Aged ,Intestinal epithelium ,mRNA, messenger RNA ,Cell biology ,Oxygen tension ,Deferoxamine ,ChIP, chromatin immunoprecipitation ,HIF, hypoxia-inducible transcription factor ,10219 Clinic for Gastroenterology and Hepatology ,FPN, ferroportin ,030211 gastroenterology & hepatology ,Tumor necrosis factor alpha ,medicine.symptom ,HT29 Cells ,medicine.drug ,Adult ,Iron ,NF-κB, nuclear factor-κB ,610 Medicine & health ,Inflammation ,mTOR, mammalian target of rapamycin ,PHD, prolyl hydroxylase ,Models, Biological ,H2DCF-DA, 2′,7′-dichlorofluorescein diacetate ,IRP, iron regulatory protein ,03 medical and health sciences ,Young Adult ,ROS, reactive oxygen species ,Tf, transferrin ,medicine ,Autophagy ,Humans ,2715 Gastroenterology ,lcsh:RC799-869 ,Aged ,Hepatology ,Tumor Necrosis Factor-alpha ,Inflammatory Bowel Disease ,Transcription Factor RelA ,Caco-2 ,Hypoxia (medical) ,LC3, light chain 3 ,Ferritin ,FAC, ferric ammonion iron citrate ,030104 developmental biology ,ARE, adenylate and uridylate-rich elements ,biology.protein ,2721 Hepatology ,lcsh:Diseases of the digestive system. Gastroenterology ,Caco-2 Cells - Abstract
Background & Aims: Hypoxia-associated pathways influence the development of inflammatory bowel disease. Adaptive responses to hypoxia are mediated through hypoxia-inducible factors, which are regulated by iron-dependent hydroxylases. Signals reflecting oxygen tension and iron levels in enterocytes regulate iron metabolism. Conversely, iron availability modulates responses to hypoxia. In the present study we sought to elucidate how iron influences the responses to hypoxia in the intestinal epithelium. Methods: Human subjects were exposed to hypoxia, and colonic biopsy specimens and serum samples were collected. HT-29, Caco-2, and T84 cells were subjected to normoxia or hypoxia in the presence of iron or the iron chelator deferoxamine. Changes in inflammatory gene expression and signaling were assessed by quantitative polymerase chain reaction and Western blot. Chromatin immunoprecipitation was performed using antibodies against nuclear factor (NF)-κB and primers for the promoter of tumor necrosis factor (TNF) and interleukin (IL)1β. Results: Human subjects presented reduced levels of ferritin in the intestinal epithelium after hypoxia. Hypoxia reduced iron deprivation–associated TNF and IL1β expression in HT-29 cells through the induction of autophagy. Contrarily, hypoxia triggered TNF and IL1β expression, and NF-κB activation in Caco-2 and T84 cells. Iron blocked autophagy in Caco-2 cells, while reducing hypoxia-associated TNF and IL1β expression through the inhibition of NF-κB binding to the promoter of TNF and IL1β. Conclusions: Hypoxia promotes iron mobilization from the intestinal epithelium. Hypoxia-associated autophagy reduces inflammatory processes in HT-29 cells. In Caco-2 cells, iron uptake is essential to counteract hypoxia-induced inflammation. Iron mobilization into enterocytes may be a vital protective mechanism in the hypoxic inflamed mucosa. Keywords: Inflammatory Bowel Disease, Autophagy, Deferoxamine, Caco-2
- Published
- 2018