title: Opposite effects of interferon regulatory factor 1 and osteopontin on the apoptosis of epithelial cells induced by TNF-α in inflammatory bowel disease.
abstract: BACKGROUND
  Inflammatory bowel disease (IBD) is characterized by a damaged intestinal epithelium barrier. Interferon regulatory factor 1 (IRF1) and osteopontin (OPN) regulate cell survival and growth in a variety of circumstances but their effects on the intestinal epithelium have not been elucidated. In this study, we sought to determine the effects of OPN on intestinal epithelial cells under conditions of tumor necrosis factor (TNF)-α-induced inflammation and whether IRF1 regulates OPN expression, the activation of downstream pathways, and inflammatory responses.
  
  
  METHODS
  The expression levels of OPN and IRF1 were assessed by immunohistochemical analyses of human IBD and experimental mouse colitis. The effects of IRF1 and OPN on inflammatory responses were investigated in vitro in NCM460 and Caco-2 cells stimulated by TNF-α. Changes in p-AKT, p-P38, and p-ERK levels were quantified by western blotting assays. The regulation of OPN expression by IRF1 was determined by luciferase activity and chromatin immunoprecipitation assays.
  
  
  RESULTS
  IRF1 was upregulated in human IBD and in the colon epithelium of mice with dextran sulfate sodium-induced colitis. Additionally, IRF1 was correlated with high-sensitivity C-reactive protein, erythrocyte sedimentation rate, Crohn's disease activity index, Crohn's disease endoscopic index of severity, and simple endoscopic score for Crohn's disease in Crohn's disease and with high-sensitivity C-reactive protein, erythrocyte sedimentation rate, Mayo score, Baron score, modified Baron score, Rachmilewitz score, ulcerative colitis endoscopic index of severity, ulcerative colitis colonoscopic index of severity, and disease duration in ulcerative colitis. The expression of OPN was significantly decreased in patients with IBD compared with controls and in dextran sulfate sodium-induced experimental colitis and was also inversely correlated with clinical and endoscopic activities in both Crohn's disease and ulcerative colitis. TNF-α treatment upregulated IRF1 and diminished OPN in both NCM460 and Caco-2 cells. The overexpression of OPN and rhOPN ameliorated the apoptosis induced by TNF-α, whereas the overexpression of IRF1 aggravated apoptosis, indicating opposite effects of OPN and IRF1 in inflamed epithelial cells. The luciferase and chromatin immunoprecipitation assays showed that IRF1 transcriptionally modulated the expression of OPN. TNF-α inhibited the OPN-induced upregulation of p-ERK, p-P38, and p-AKT.
  
  
  CONCLUSIONS
  Our data suggest that during intestinal inflammation, the TNF-α-mediated activation of IRF1 is related to the subsequent suppression of OPN expression, further reducing p-AKT, p-P38, and p-ERK activities and resulting in aggravation of the injury to intestinal epithelial cells.
authors.affiliation: *Department of Gastroenterology, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China; †Department of Medical Imaging and Interventional Radiology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Guangzhou, China; and ‡Department of Immunology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Ruihan
authors.initials: R
authors.lastname: Tang
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
authors.forename: Shenghong
authors.initials: S
authors.lastname: Zhang
authors.forename: Changyou
authors.initials: C
authors.lastname: Wu
authors.forename: Minhu
authors.initials: M
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D018938:Caco-2 Cells; D016022:Case-Control Studies; D049109:Cell Proliferation; D002478:Cells, Cultured; D002648:Child; D047369:Chromatin Immunoprecipitation; D003092:Colitis / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D003093:Colitis, Ulcerative / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D003424:Crohn Disease / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D016264:Dextran Sulfate / Q000633:toxicity; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005500:Follow-Up Studies; D006801:Humans; D007124:Immunoenzyme Techniques; D050856:Interferon Regulatory Factor-1 / Q000235:genetics / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism*; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D055815:Young Adult
chemical_list: C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D053495:Osteopontin; D016264:Dextran Sulfate