title: Higher activity of the inducible nitric oxide synthase contributes to very early onset inflammatory bowel disease.
abstract: OBJECTIVE
  The NOS2 gene encodes for the inducible nitric oxide synthase (iNOS), responsible for nitric oxide (NO) production, which contributes to antimicrobial and antipathogenic activities. Higher levels of both iNOS and NO-induced damage have been observed in inflammatory bowel disease (IBD) patients. NOS2 may have a role in a specific subset of IBD patients with severe and/or extensive colitis. Therefore, the aim of this study is to examine the role of NOS2 in such a subset, very early onset IBD (VEO-IBD).
  
  
  METHODS
  Seventeen tag single nucleotide polymorphisms (SNPs) in the NOS2 gene were successfully genotyped in VEO-IBD patients. Genetic associations were replicated in an independent VEO-IBD cohort. Functional analysis for iNOS activity was performed on the most significantly associated functional variant.
  
  
  RESULTS
  The NOS2 rs2297518 SNP was found to be associated in VEO-IBD in two independent cohorts. Upon combined analysis, a coding variant (S608L) showed the strongest association with VEO-IBD (Pcombined=1.13 × 10(-6), OR (odds ratio)=3.398 (95% CI (confidence interval) 2.02-5.717)) as well as associations with VEO-Crohn's disease and VEO-ulcerative colitis (UC). This variant also showed an association with UC diagnosed between 11 and 17 years of age but not with adult-onset IBD (>17 years). B-cell lymphoblastoid cell lines genotyped for the risk variant as well as Henle-407 cells transfected with a plasmid construct with the risk variant showed higher NO production. Colonic biopsies of VEO-IBD patients showed higher immunohistochemical staining of nitrotyrosine, indicating more nitrosative stress and tissue damage.
  
  
  CONCLUSIONS
  These studies suggest the importance of iNOS in genetic susceptibility to younger IBD presentation due to higher NO production.
authors.affiliation: 1] SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada [2] Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Sandeep S
authors.initials: SS
authors.lastname: Dhillon
authors.affiliation: SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Lucas A
authors.initials: LA
authors.lastname: Mastropaolo
authors.affiliation: SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Ryan
authors.initials: R
authors.lastname: Murchie
authors.affiliation: SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Christopher
authors.initials: C
authors.lastname: Griffiths
authors.affiliation: 1] SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada [2] Division of Cell Biology, Biocenter Innsbruck, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Thöni
authors.affiliation: 1] SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada [2] Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada [3] Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Abdul
authors.initials: A
authors.lastname: Elkadri
authors.affiliation: Princess Margaret Hospital and Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: Division of Pediatric Gastroenterology, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada.
authors.forename: Amanda
authors.initials: A
authors.lastname: Mack
authors.affiliation: 1] SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada [2] Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Walters
authors.affiliation: SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Conghui
authors.initials: C
authors.lastname: Guo
authors.affiliation: Division of Pediatric Gastroenterology, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Mack
authors.affiliation: Division of Pediatric Gastroenterology, Stollery Children's Hospital, Edmonton, Alberta, Canada.
authors.forename: Hien
authors.initials: H
authors.lastname: Huynh
authors.affiliation: Division of Pediatric Gastroenterology, Stollery Children's Hospital, Edmonton, Alberta, Canada.
authors.forename: Shairaz
authors.initials: S
authors.lastname: Baksh
authors.affiliation: 1] Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada [2] Mount Sinai Hospital Inflammatory Bowel Disease Group, University of Toronto Group, Dr Zane Cohen Digestive Diseases Clinical Research Centre, 600 University Ave, Toronto, Ontario, Canada.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Silverberg
authors.affiliation: 1] SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada [2] Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada [3] Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: John H
authors.initials: JH
authors.lastname: Brumell
authors.affiliation: 1] Division of Pediatric Gastroenterology, Hepatology, and Nutrition, Department of Medicine, Children's Hospital Boston, Massachusetts, USA [2] Division of Gastroenterology and Hepatology, Brigham & Women's Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Snapper
authors.affiliation: 1] SickKids Inflammatory Bowel Disease Center and Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada [2] Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada [3] Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Aleixo M
authors.initials: AM
authors.lastname: Muise