title: Gastric acid induces mitochondrial superoxide production and lipid peroxidation in gastric epithelial cells.
abstract: BACKGROUND
  Gastric hydrochloric acid (HCl) has been regarded as an inciting factor in gastric mucosal injuries and has been reported to induce lipid peroxidation in vitro. However, because HCl is not an oxidant per se, the exact mechanism by which the acid induces lipid peroxidation is unknown. We hypothesized that gastric acid may disrupt mitochondrial transmembrane potential and induce the production of superoxide in mitochondria, which subsequently may induce lipid peroxidation and apoptosis in gastric mucosal cells.
  
  
  METHODS
  Firstly we treated gastric epithelial RGM1 cells with solutions containing various concentrations of HCl (i.e., of varying pH), and examined cellular injury, lipid peroxidation, and apoptosis with specific fluorescent dyes. Secondly, we performed electron paramagnetic resonance (EPR) spectroscopy of isolated, acid-exposed mitochondria from the cells, using a spin-trapping reagent for superoxide, 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO). Finally, we established novel RGM1 cells that overexpressed manganese superoxide dismutase (MnSOD), which removes superoxide from mitochondria, and examined the effect of acid treatment on cellular membrane lipid peroxidation.
  
  
  RESULTS
  The results indicated that the exposure to acid indeed induced cellular injury, cellular lipid peroxidation, apoptosis, and the demonstration of the exact superoxide spectra on EPR spectroscopy in gastric epithelial cells, and that overexpression of MnSOD decreased superoxide production and prevented cellular lipid peroxidation.
  
  
  CONCLUSIONS
  These results suggested that gastric acid, like nonsteroidal anti-inflammatory drugs (NSAIDs), induces mitochondrial superoxide production, which induces gastric cellular injury by triggering cellular lipid peroxidation and apoptosis.
authors.affiliation: The Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan. hmatsui@md.tsukuba.ac.jp
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Matsui
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Nagano
authors.forename: Osamu
authors.initials: O
authors.lastname: Shimokawa
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kaneko
authors.forename: Kanho
authors.initials: K
authors.lastname: Rai
authors.forename: Jumpei
authors.initials: J
authors.lastname: Udo
authors.forename: Aki
authors.initials: A
authors.lastname: Hirayama
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Hiroko P
authors.initials: HP
authors.lastname: Indo
authors.forename: Hideyuki J
authors.initials: HJ
authors.lastname: Majima
authors.forename: Ichinosuke
authors.initials: I
authors.lastname: Hyodo
mesh_terms: D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D004578:Electron Spin Resonance Spectroscopy; D004847:Epithelial Cells / Q000378:metabolism*; D005744:Gastric Acid / Q000502:physiology*; D005753:Gastric Mucosa / Q000378:metabolism / Q000473:pathology*; D006851:Hydrochloric Acid / Q000008:administration & dosage / Q000633:toxicity; D006863:Hydrogen-Ion Concentration; D015227:Lipid Peroxidation / Q000502:physiology; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism*; D051381:Rats; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
chemical_list: D013481:Superoxides; D013482:Superoxide Dismutase; D006851:Hydrochloric Acid