Amyloid beta protein (25-35) activation of phospholipase A2 in LA-N-2 cells

Amyloid ß protein (25-35) stimulated the release of free arachidonic acid from [3H]arachidonic acid prelabeled LA-N-2 cells in a dose and time dependent manner. This activation was prevented by the phospholipase A2 inhibitors, bromophenacylbromide and aristolochic acid. The IC50 for the latter was 7 to 11 µM. Mepacrine was less inhibitory. The release of [3H]arachidonic acid was dependent upon intracellular calcium. The deletion of calcium from the incubation medium with the inclusion of 10 mM each of EGTA and EDTA did not diminish the appearance of [3H]arachidonic acid, but this release was prevented by BAPTA/AM. Ryanodine but not TMB-8 inhibited the release of[3H]arachidonic acid. The IC50 for ryanodine was about 2 µM. A pertussis toxin sensitive GTP binding protein is implicated in this amyloid ß protein stimulated [3H]arachidonate release. This process does not appear to require protein kinases or phosphoprotein phosphatases since the various inhibitors of these enzymes were ineffective in preventing the [3H]arachidonic acid release. Several antioxidants were ineffective in preventing the [3H]arachidonic acid release. It is suggested that if a similar situation occurs in the Alzheimer's disease patients it might explain the observed elevated amounts of glycerophosphorylcholine and glycerophosphorylethanolamine found in the brains tissue of these patients.