Phorbol 12-myristate 13-acetate upregulates cyclooxygenase-2 expression in human pulmonary epithelial cells via Ras, Raf-1, ERK, and NF-κB, but not p38 MAPK, pathways

In this study, we investigated the signaling pathway involved in cyclooxygenase-2 (COX-2) expression and prostaglandin E-2 (PGE(2)) release by phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator. in human pulmonary, epithelial cells (A549) PMA-induced COX-2 expression was attenuated by PKC inhibitors (Go 6976 and Ro 31-8220), a Ras inhibitor (manumycin A). a Raf-1 inhibitor (GW 5074), a MEK inhibitor (PD 098059), and an NF-kappaB inhibitor (PDTC), but not by a ryrosme kinase inhibitor (genistein,) or a p38 MAPK inhibitor (SB 203580). PMA also caused the activation of Ras, Raf-1, and ERR 1/2. PMA-induced activation of Ras and Raf-1 was inhibited by Ro 31-8220 and manumycin A. PMA-mediated activation of ERK1/2 was inhibited by Ro 31-8220. manumycin A. GW 5074. and PD 098059. Stimulation of cells with PMA caused IkappaBalpha phosphorylation, IkappaBalpha degradation. and the formation of a NF-kappaB-specific DNA-protein complex. The PMA-mediated increase in kappaB-luciferase activity was inhibited by Ro 31-8220. manumycin A. GW5074, PD 098059, and PDTC. Taken together, these results indicate that PMA might activate PKC to elicit activation of the Ras Raf-1/ERK1/2 pathway, which in turn initiates NF-kappaB activation. and finally induces COX-2 expression and PGE(2) release in A549 cells. (C) 2004 Elsevier Inc. All rights reserved.