Signal transduction cascade in staurosporine-induced prostaglandin E-2 production by rat peritoneal macrophages

The possible participation of phosphatidylinositol (PI) 3-kinase, p44/42 mi togen-activated protein (MAP) kinases and protein kinase C (PKC) in stauros porine-induced prostaglandin E-2 (PGE(2)) production was investigated pharm acologically in rat peritoneal macrophages. When the cells were incubated i n the presence of staurosporine (63 nM), phosphorylation of p44/42 MAP kina ses and cytosolic phospholipase A(2) (cPLA(2)) was induced at 15 min and in creased until 60 min, whereas PGE(2) production and expression of cyclooxyg enase-2 (COX-2) protein began to increase at 2 h and increased thereafter. Both PD98059 and U0126, MAP kinase/extracellular signal-regulated kinase (E RK) kinase inhibitors, and LY294002, a PI 3-kinase inhibitor, inhibited sta urosporine-induced phosphorylation of p44/42 MAP kinases and cPLA(2) and PG E(2) production. Moreover, U0126 inhibited staurosporine-induced arachidoni c acid release at 1 h. Although PD98059 and U0126 at 30 mu M partially inhi bited staurosporine-induced COX-2 protein expression, they completely inhib ited staurosporine-induced PGE(2) production. LY294002 at 100 mu M did not inhibit staurosporine-induced expression of COX-2 protein. in contrast, Ro- 31-8220, a PKC inhibitor, completely inhibited staurosporine-induced PGE(2) production and COX-2 protein expression at 8 h but did not inhibit stauros porine-induced phosphorylation of p44/42 MAP kinases and cPLA(2). These fin dings suggest that staurosporine induces PGE, production by two mechanisms. One is cPLA(2) phosphorylation through a signal transduction pathway from PI 3-kinase to p44/42 MAP kinases, by which arachidonic acid, a substrate f or COX-1 and COX-2, is increased. The other is COX-2 protein expression, wh ich is induced mainly by activation of PKC and partially by activation of p 44/42 MAP kinases; thus, arachidonic acid is metabolized to PGE(2).