A mitogen-activated protein kinase independent pathway involved in the phosphorylation and activation of cytosolic phospholipase A2 in human neutrophils stimulated with tumor necrosis factor-alpha.

Although tumor necrosis factor (TNF)-alpha stimulation of human neutrophils does not result in a significant release of arachidonic acid, it primes the cell for arachidonic acid release when cells are further stimulated by agents that induce an intracellular calcium increase. We demonstrate that TNF-alpha stimulation of neutrophils induces the phosphorylation of cytosolic phospholipase A2 (cPLA2) and also increases its activity. These results indicate that although TNF-alpha, by itself, does not cause the release of arachidonic acid in intact cells, it increases the phosphorylation and activation of the enzyme cPLA2. Since we recently found that TNF-alpha stimulation of neutrophils does not increase the tyrosine phosphorylation or activation of the p42erk2 and p44erk1 mitogen-activated protein kinases (MAPKs), the present studies demonstrate the involvement of a MAPK independent pathway in the phosphorylation and activation of cPLA2.