title: Helicobacter pylori induces promoter methylation of E-cadherin via interleukin-1β activation of nitric oxide production in gastric cancer cells.
abstract: BACKGROUND
  Helicobacter pylori infection causes gastric mucosal inflammatory responses, resulting in up-regulation of interleukin-1β (IL-1β) and overproduction of mutagenic nitric oxide (NO). The authors previously demonstrated that IL-1β plays an important role in H. pylori-induced E-cadherin (E-cad) methylation. Here, they extend the study to investigate the downstream effect of IL-1β on H. pylori-induced gastric inflammation and aberrant DNA methylation.
  
  
  METHODS
  Human gastric cancer cell lines (MKN7, MKN74, and TMK-1) with and without pretreatment of IL-1 receptor antagonist (IL-1ra) were treated with IL-1β or infected with H. pylori. Promoter methylation status of E-cad was examined by methylation-specific polymerase chain reaction (PCR). Expression of E-cad, inducible nitric oxide synthase (iNOS), and nuclear factor κB (NFκB) was assessed by quantitative reverse transcriptase PCR, Western blotting, or immunofluorescence. NO production and total DNA methyltransferase (DNMT) activity were assayed fluorometrically.
  
  
  RESULTS
  Both IL-1β treatment and H. pylori infection-induced E-cad methylation led to a decrease in E-cad expression at both mRNA and protein levels. Total DNMT enzymatic activity was significantly elevated in treated cells, accounting for the observed E-cad methylation induction. Increased expression of NFκB was accompanied by up-regulation of iNOS and production of NO in treated cells. Reversal of all these phenomena in cells pretreated with IL-1ra suggested H. pylori-induced E-cad methylation via IL-1β stimulation of the NFκB transcriptional system, leading to activation of DNMT activity by NO production.
  
  
  CONCLUSIONS
  These findings reveal a previously unknown effect of IL-1β and NO on H. pylori-induced aberrant DNA methylation. This possible pathway indicates the role of NO in epigenetic modification that links inflammation to carcinogenesis.
authors.affiliation: Department of Medicine, University of Hong Kong, Queen Mary Hospital, Hong Kong.
authors.forename: Fung-Yu
authors.initials: FY
authors.lastname: Huang
authors.forename: Annie On-On
authors.initials: AO
authors.lastname: Chan
authors.forename: Asif
authors.initials: A
authors.lastname: Rashid
authors.forename: Danny Ka-Ho
authors.initials: DK
authors.lastname: Wong
authors.forename: Chi-Hin
authors.initials: CH
authors.lastname: Cho
authors.forename: Man-Fung
authors.initials: MF
authors.lastname: Yuen
mesh_terms: D015820:Cadherins / Q000235:genetics*; D045744:Cell Line, Tumor; D019175:DNA Methylation; D016480:Helicobacter pylori / Q000378:metabolism*; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein / Q000378:metabolism; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D011401:Promoter Regions, Genetic; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D015820:Cadherins; D053590:Interleukin 1 Receptor Antagonist Protein; D053583:Interleukin-1beta; D016328:NF-kappa B; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II