YC‐1 increases cyclo‐oxygenase‐2 expression through protein kinase G‐ and p44/42 mitogen‐activated protein kinase‐dependent pathways in A549 cells

YC‐1, an activator of soluble guanylate cyclase (sGC), has been shown to increase the intracellular cGMP concentration. This study was designed to investigate the signaling pathway involved in the YC‐1‐induced COX‐2 expression in A549 cells. YC‐1 caused a concentration‐ and time‐dependent increase in COX activity and COX‐2 expression in A549 cells. Pretreatment of the cells with the sGC inhibitor (ODQ), the protein kinase G (PKG) inhibitor (KT‐5823), and the PKC inhibitors (Go 6976 and GF10923X), attenuated the YC‐1‐induced increase in COX activity and COX‐2 expression. Exposure of A549 cells to YC‐1 caused an increase in PKC activity; this effect was inhibited by ODQ, KT‐5823 or Go 6976. Western blot analyses showed that PKC‐α, ‐ι, ‐λ, ‐ζ and ‐μ isoforms were detected in A549 cells. Treatment of A549 cells with YC‐1 or PMA caused a translocation of PKC‐α, but not other isoforms, from the cytosol to the membrane fraction. Long‐term (24 h) treatment of A549 cells with PMA down‐regulated the PKC‐α. The MEK inhibitor, PD 98059 (10–50 μ M ), concentration‐dependently attenuated the YC‐1‐induced increases in COX activity and COX‐2 expression. Treatment of A549 cells with YC‐1 caused an activation of p44/42 MAPK; this effect was inhibited by KT‐5823, Go 6976, long‐term (24 h) PMA treatment or PD98059, but not the p38 MAPK inhibitor, SB 203580. These results indicate that in human pulmonary epithelial cells, YC‐1 might activate PKG through an upstream sGC/cGMP pathway to elicit PKC‐α activation, which in turn, initiates p44/42 MAPK activation, and finally induces COX‐2 expression.British Journal of Pharmacology (2002) 136 , 558–567; doi: 10.1038/sj.bjp.0704777