The murine gastric mucosa possesses very high secretory type
phospholipase A2 activity. Northern and Western blots indicated that the pancreatic-type,
sPLA2-IB represents the predominant form of
sPLA2 enzymes present in the gastric mucosa. Both
sPLA2-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
sPLA2-IB gene is not expressed in the murine small intestine and colon.
Infection by the
gastritis-inducing bacteria, Helicobacterfelis (H. felis) dramatically and time dependently decreased the PLA2 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
sPLA2-IB present in the active form. This bacterial-induced reduction in PLA2 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
PLA2-II enzyme. The H. felis-induced reduction in
sPLA2-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
sPLA2-IB and sPLA2-II
enzymes may contribute to the gastric response to
Helicobacter infection.