O-26 - Signal transduction cascade in staurosporine-induced prostaglandin E2 production by rat peritoneal macrophages

Abstract

The possible participation of phosphatidylinositol (PI) 3-kinase, p44/42 mitogen-activated protein (MAP) kinases and protein kinase C (PKC) in staurosporine-induced prostaglandin E2(PGE2) production was investigated pharmacologically in rat peritoneal macrophages. When the cells were incubated in the presence of staurosporine (63 nM), phosphorylation of p44/42 MAP kinases and cytosolic phospholipase A2 (cPLA2) was induced at 15 min and increased until 60 min, whereas PGE2production and expression of cyclooxygenase-2 (COX-2) protein began to increase at 2 h and increased thereafter. Both PD98059 and U0126, MAP kinase/extracellular signal-regulated kinase (ERK) kinase inhibitors, and LY294002, a PI 3-kinase inhibitor, inhibited staurosporine-induced phosphorylation of p44/42 MAP kinases and cPLA2 and PGE2 production. Moreover, U0126 inhibited staurosporine-induced arachidonic acid release at 1 h. Although PD98059 and U0126 at 30 μM partially inhibited staurosporine-induced COX-2 protein expression, they completely inhibited staurosporine-induced PGE2 production. LY294002 at 100 μM did not inhibit staurosporine-induced expression of COX-2 protein. In contrast, Ro-31-8220, a PKC inhibitor, completely inhibited staurosporine-induced PGE2 production and COX-2 protein expression at 8 h but did not inhibit staurosporine-induced phosphorylation of p44/42 MAP kinases and cPLA2. These findings suggest that staurosporine induces PGE2 production by two mechanisms. One is cPLA2phosphorylation through a signal transduction pathway from PI 3-kinase to p44/42 MAP kinases, by which arachidonic acid, a substrate for COX-1 and COX-2, is increased. The other is COX-2 protein expression, which is induced mainly by activation of PKC and partially by activation of p44/42 MAP kinases; thus, arachidonic acid is metabolized to PGE2.