title: Hyperosmotic stress enhances interleukin-1beta expression in Helicobacter pylori-infected murine gastric epithelial cells in vitro.
abstract: OBJECTIVE
  Gastric cancer is associated not only with Helicobacter pylori (H. pylori) infection, but also with the intake of a high salt diet. Interleukin-1beta (IL-1beta) is highly expressed in H. pylori-infected gastric mucosa. The aim of the present study was to determine if hyperosmotic stress induces IL-1beta expression in gastric epithelial cells in vitro.
  
  
  METHODS
  Murine gastric epithelial cells, GSM06, were cultured with or without H. pylori (Sydney strain-1) at different osmolarities in the range of 300-450 mOsM. Expressions of IL-1beta mRNA and mature IL-1beta protein were evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and an IL-1beta enzyme-linked immunosorbent assay (ELISA), respectively. IL-1beta converting enzyme (ICE) activity was measured by an ICE colorimetric assay. Apoptosis was evaluated by a single stranded-DNA assay.
  
  
  RESULTS
  Addition of H. pylori at 300 mosM caused significant increases in IL-1beta mRNA, IL-1beta protein, ICE activity and apoptosis. Hyperosmotic stress alone also caused upregulation of IL-1beta mRNA and IL-1beta protein, enhanced ICE activity and accelerated apoptosis. Hyperosmotic stress accentuated the increases in IL-1beta mRNA, IL-1beta protein, ICE activity and apoptosis induced by H. pylori alone. Enhancement of IL-1beta protein release induced by hyperosmotic stress was significantly attenuated by an ICE inhibitor, Z-YVAD-FMK.
  
  
  CONCLUSIONS
  Hyperosmotic stress enhances the release of bioactive mature IL-1beta protein in H. pylori-infected gastric epithelial cells, in part by upregulating IL-1beta mRNA expression, and in part by enhancing ICE activity. These results may explain the mechanisms by which chronic intake of a high salt diet increases the risk of gastric cancer among H. pylori-infected human subjects.
authors: Department of Gastroenterology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.
authors: Songhua
authors: S
authors: Zhang
authors: Akinori
authors: A
authors: Yanaka
authors: Masafumi
authors: M
authors: Tauchi
authors: Hideo
authors: H
authors: Suzuki
authors: Takeshi
authors: T
authors: Shibahara
authors: Hirofumi
authors: H
authors: Matsui
authors: Akira
authors: A
authors: Nakahara
authors: Naomi
authors: N
authors: Tanaka