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.
Footnotes
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Send reprint requests to: Kazuo Ohuchi, Ph.D., Prof., Department of Pathophysiological Biochemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan. E-mail:ohuchi-k{at}mail.pharm.tohoku.ac.jp
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↵1 The study was supported in part by a Grant-in-Aid for Scientific Research (B) (11470481) from the Ministry of Education, Science, Sports and Culture of Japan.
- Abbreviations:
- PGE2
- prostaglandin E2
- COX
- cyclooxygenase
- PLA2
- phospholipase A2
- cPLA2
- cytosolic phospholipase A2
- DMSO
- dimethyl sulfoxide
- MAP
- mitogen-activated protein
- ERK
- extracellular signal-regulated kinase
- MEK
- mitogen-activated protein kinase/ERK kinase
- PI
- phosphatidylinositol
- PKC
- protein kinase C
- TPA
- 12-O-tetradecanoylphorbol 13-acetate
- IL-8
- interleukin-8
- Received June 14, 1999.
- Accepted December 30, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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