The effect of ascorbic acid on Helicobacter pylori induced cyclooxygenase 2 expression and prostaglandin E2 production by gastric epithelial cells in vitro.
BACKGROUND
Cyclooxygenase 2 (COX-2) is induced by the presence of Helicobacter pylori (H. pylori) on the gastric mucosa as part of the inflammatory response; this results in the synthesis of prostaglandins that amplify the local inflammatory response. The presence of H. pylori inhibits the secretion of ascorbate into the gastric lumen. Interestingly, ascorbate inhibits the growth of H. pylori and low dietary levels are associated with an increased risk of gastric adenocarcinoma. We therefore investigated the effect of ascorbate on H. pylori mediated COX-2 induction and prostaglandin production in vitro.


METHODS
H. pylori was cocultured with gastric epithelial cells in the presence of ascorbate at physiological concentrations. The expression of COX-2 was assessed by Western blotting and prostaglandin E(2) (PGE(2)) was assessed by ELISA.


RESULTS
Ascorbate inhibited gastric cell PGE(2) synthesis but not in COX-2 expression in response to H. pylori. In the absence of the organism, ascorbate also reduced PGE(2) expression in cells that constitutively express COX-2, again with no reduction of COX-2 protein expression.


CONCLUSIONS
Physiological concentrations of ascorbate inhibit PGE(2) but not COX-2 expression in response to H. pylori in gastric epithelial cells.
Smith
Geoff V
GV
Department of Adult and Paediatric Gastroenterology, St Bart's and the London School of Medicine and Dentistry, Turner Street, London E1 2AD, UK.
Farthing
Michael J G
MJ
D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology*; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis*; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology; D016480:Helicobacter pylori / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D013274:Stomach Neoplasms
D000975:Antioxidants; D008565:Membrane Proteins; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D001205:Ascorbic Acid