Helicobacter infection and phospholipase A_2 enzymes: Effect of Helicobacter felis-infection on the expression and activity of sPLA_2 enzymes in mouse stomach

摘要

The murine gastric mucosa possesses very high secretory type phospholipase A_2 activity. Northern and Western blots indicated that the pancreatic-type, sPLA_2-IB represents the predominant form of sPLA_2 enzymes present in the gastric mucosa. Both sPLA_2-IB mRNA and protein in the gastric mucosa exceeded levels found in the pancreas, and in contrast to the pancreatic enzyme it was present primarily in the active state. The sPLA_2-IB gene is not expressed in the murine small intestine and colon. Infection by the gastritis-inducing bacteria, Helicobacter felis (H. felis) dramatically and time dependently decreased the PLA_2 activity in the glandular stomach of the mouse strain, C57BL/6, sensitive to the organism, which appeared to be related to a decrease in the percentage of sPLA_2-IB present in the active form. This bacterial-induced reduction in PLA_2 activity was not observed in BALB/c mice that fail to develop gastritis in response to H. felis infection. C57BL/6 mice do not, while BALB/c mice express, the PLA_2-II enzyme. The H. felis-induced reduction in sPLA_2-IB activity may weaken the gastric barrier by reducing the local concentration of arachidonic and linoleic acid, liberated from membrane phospholipids, the major precursors of 'cytoprotective' prostaglandins. Data presented here suggest that both sPLA_2-IB and sPLA_2-II enzymes may contribute to the gastric response to Helicobacter infection.