Vol. 293, Issue 1, 206-213, April 2000

Signal Transduction Cascade in Staurosporine-Induced Prostaglandin E₂ Production by Rat Peritoneal Macrophages¹

Kouya Yamaki, Takayuki Yonezawa and Kazuo Ohuchi

Department of Pathophysiological Biochemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba Aramaki, Aoba-ku, Sendai, Miyagi, Japan

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 PGE₂ production 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 cPLA₂ phosphorylation 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.