Involvement of Ras/Raf-1/p44/42 MAPK in YC-1-induced cyclooxygenase-2 expression in human pulmonary epithelial cells.

Our previous study demonstrated that 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) might activate the soluble guanylate cyclase (sGC)/cGMP/protein kinase G (PKG) pathway to induce cyclooxygenase-2 (COX-2) expression in human pulmonary epithelial cells (A549). In this study, we further investigated the role of Raf-1 in YC-1-induced nuclear factor-kappaB (NF-kappaB) activation and COX-2 expression in A549 cells. YC-1-induced COX-2 expression was attenuated by a Raf-1 inhibitor (GW 5074) in a concentration-dependent manner. Treatment of A549 cells with YC-1 or 8-bromo-cGMP, a cell-permeable cGMP analogue, induced Raf-1 Ser338 phosphorylation in a time-dependent manner. YC-1-mediated Raf-1 activation was inhibited by an sGC inhibitor (ODQ), a PKG inhibitor (KT-5823), a Ras inhibitor (manumycin A), a dominant negative Ras mutant (RasN17), a protein kinase C-alpha (PKC-alpha) inhibitor (Ro 32-0432), and a phosphoinositide-3-OH-kinase (PI3K) inhibitor (LY 294002). Pretreatment of A549 cells with either manumycin A or GW 5074 attenuated YC-1-induced p44/42 MAPK activation. The YC-1-mediated increase in IKKalpha/beta activation and kappaB-luciferase activity were attenuated by GW 5074, a MAPK/ERK kinase (MEK) inhibitor (PD 98059), and an ERK2 inhibitor (AG 126). Furthermore, YC-1-induced COX-2 promoter activity was also inhibited by GW 5074, PD 98059, and AG 126. These results indicate that YC-1 might activate the sGC/cGMP/PKG pathway to elicit Ras/Raf-1/p44/42 MAPK activation, which in turn induces IKKalpha/beta and NF-kappaB activation, and ultimately causes COX-2 expression in A549 cells. Moreover, PKC-alpha and PI3K signal might be involved in YC-1-induced Raf-1 activation.

Lipoteichoic acid-induced nitric oxide synthase expression in RAW 264.7 macrophages is mediated by cyclooxygenase-2, prostaglandin E2, protein kinase A, p38 MAPK, and nuclear factor-kappaB pathways.

We recently reported that lipoteichoic acid (LTA), a cell wall component of the gram-positive bacterium Staphylococcus aureus, stimulated inducible nitric oxide synthase (iNOS) expression, nitric oxide (NO) release, and cyclooxygenase-2 (COX-2) expression in RAW 264.7 macrophages. This study was carried out to further investigate the roles of COX-2 and prostaglandin E2 (PGE2) in LTA-induced iNOS expression and NO release in RAW 264.7 macrophages. Treatment of RAW 264.7 macrophages with LTA caused a time-dependent increase in PGE2 release. LTA-induced iNOS expression and NO release were inhibited by a non-selective COX inhibitor (indomethacin), a selective COX-2 inhibitor (NS-398), an adenylyl cyclase (AC) inhibitor (dideoxyadenosine, DDA), and a protein kinase A (PKA) inhibitor (KT-5720). Furthermore, both PGE2 and the direct PKA activator, dibutyryl-cAMP, also induced iNOS expression in a concentration-dependent manner. Stimulation of RAW 264.7 macrophages with LTA, PGE2, and dibutyryl-cAMP all caused p38 MAPK activation in a time-dependent manner. LTA-mediated p38 MAPK activation was inhibited by indomethacin, NS-398, and SB 203580, but not by PD 98059. The PGE2-mediated p38 MAPK activation was inhibited by DDA, KT-5720, and SB 203580, but not by PD 98059. LTA caused time-dependent activation of the nuclear factor-kappaB (NF-kappaB)-specific DNA-protein complex formation. The LTA-induced increase in kappaB-luciferase activity was inhibited by indomethacin, NS-398, KT-5720, and a dominant negative mutant of p38 alphaMAPK (p38 alphaMAPK DN). These results suggest that LTA-induced iNOS expression and NO release involve COX-2-generated PGE2 production, and AC, PKA, p38 MAPK, and NF-kappaB activation in RAW 264.7 macrophages.

Lipoteichoic acid induces nuclear factor-kappaB activation and nitric oxide synthase expression via phosphatidylinositol 3-kinase, Akt, and p38 MAPK in RAW 264.7 macrophages.

We previously demonstrated that lipoteichoic acid (LTA) might activate phosphatidylcholine-phospholipase C (PC-PLC) and phosphatidylinositol-phospholipase C (PI-PLC) to induce protein kinase C activation, which in turn initiates nuclear factor-kappaB (NF-kappaB) activation and finally induces inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) release in RAW 264.7 macrophages. In this study, we further investigated the roles of tyrosine kinase, phosphatidylinositiol 3-kinase (PI3K)/Akt, and p38 mitogen-activated protein kinase (MAPK) in LTA-induced iNOS expression and NO release in RAW 264.7 macrophages. Tyrosine kinase inhibitors (genistein and tyrphostin AG126), PI3K inhibitors (wortmannin and LY 294002), and a p38 MAPK inhibitor (SB 203580) attenuated LTA-induced iNOS expression and NO release in concentration-dependent manners. Treatment of RAW 264.7 macrophages with LTA caused time-dependent activations of Akt and p38 MAPK. The LTA-induced Akt activation was inhibited by wortmannin, LY 294002, genistein, and tyrphostin AG126. The LTA-induced p38 MAPK activation was inhibited by genistein, tyrphostin AG126, wortmannin, LY 294002, and SB 203580. The LTA-induced formation of an NF-kappaB-specific DNA-protein complex in the nucleus was inhibited by wortmannin, LY 294002, genistein, tyrphostin AG126, and SB 203580. Treatment of macrophages with LTA caused an increase in kappaB-luciferase activity, and this effect was inhibited by tyrphostin AG126, wortmannin, LY 294002, the Akt dominant negative mutant (AktDN), and SB 203580. Based on those findings, we suggest that LTA might activate the PI3K/Akt pathway through tyrosine kinase to induce p38 MAPK activation, which in turn initiates NF-kappaB activation, and ultimately induces iNOS expression and NO release in RAW 264.7 macrophages.

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

In this study, we investigated the signaling pathway involved in cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE2) 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 tyrosine kinase inhibitor (genistein) or a p38 MAPK inhibitor (SB 203580). PMA also caused the activation of Ras, Raf-1, and ERK1/2. 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 PGE2 release in A549 cells.

Bradykinin B2 receptor mediates NF-kappaB activation and cyclooxygenase-2 expression via the Ras/Raf-1/ERK pathway in human airway epithelial cells.

In this study, we investigated the signaling pathways involved in bradykinin (BK)-induced NF-kappaB activation and cyclooxygenase-2 (COX-2) expression in human airway epithelial cells (A549). BK caused concentration- and time-dependent increase in COX-2 expression, which was attenuated by a selective B2 BK receptor antagonist (HOE140), a Ras inhibitor (manumycin A), a Raf-1 inhibitor (GW 5074), a MEK inhibitor (PD 098059), an NF-kappaB inhibitor (pyrrolidine dithiocarbate), and an IkappaB protease inhibitor (L-1-tosylamido-2-phenylethyl chloromethyl ketone). The B1 BK receptor antagonist (Lys-(Leu8)des-Arg9-BK) had no effect on COX-2 induction by BK. BK-induced increase in COX-2-luciferase activity was inhibited by cells transfected with the kappaB site deletion of COX-2 construct. BK-induced Ras activation was inhibited by manumycin A. Raf-1 phosphorylation at Ser338 by BK was inhibited by manumycin A and GW 5074. BK-induced ERK activation was inhibited by HOE140, manumycin A, GW 5074, and PD 098059. Stimulation of cells with BK activated IkappaB kinase alphabeta (IKKalphabeta), IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 and p50 translocation from the cytosol to the nucleus, the formation of an NF-kappaB-specific DNA-protein complex, and kappaB-luciferase activity. BK-mediated increase in IKKalphabeta activity and formation of the NF-kappaB-specific DNA-protein complex were inhibited by HOE140, a Ras dominant-negative mutant (RasN17), manumycin A, GW 5074, and PD 098059. Our results demonstrated for the first time that BK, acting through B2 BK receptor, induces activation of the Ras/Raf-1/ERK pathway, which in turn initiates IKKalphabeta and NF-kappaB activation, and ultimately induces COX-2 expression in human airway epithelial cell line (A549).

YC-1-induced cyclooxygenase-2 expression is mediated by cGMP-dependent activations of Ras, phosphoinositide-3-OH-kinase, Akt, and nuclear factor-kappaB in human pulmonary epithelial cells.

We demonstrated previously that 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1), an activator of soluble guanylate cyclase (sGC), induces cyclooxygenase-2 (COX-2) expression via cGMP- and p44/42 mitogen-activated protein kinase-dependent pathways in human pulmonary epithelial A549 cells. In this study, we explore the role of Ras, phosphoinositide-3-OH-kinase (PI3K), Akt, and transcription factor nuclear factor-kappaB (NF-kappaB) in YC-1-induced COX-2 expression in A549 cells. A Ras inhibitor (manumycin A), a PI3K inhibitor (wortmannin), an Akt inhibitor (1l-6-Hydroxymethyl-chiro-inositol2-[(R)-2-O-methyl-3-O-octadecylcarbonate]), and an NF-kappaB inhibitor [pyrrolidine dithiocarbamate (PDTC)] all reduced YC-1-induced COX-2 expression. The YC-1-induced increase in COX activity was also blocked by manumycin A, wortmannin, PDTC, and the dominant-negative mutants for Ras (RasN17), Akt (Akt DN), and IkappaBalpha (IkappaBalphaM). The YC-1-induced increase in Ras activity was inhibited by an sGC inhibitor [1H-(1,2,4)oxadiazolo[4,3-a]quinozalin-1-one (ODQ)], a protein kinase G (PKG) inhibitor [1-oxo-9.12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-I][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT-5823)], and manumycin A. YC-1-induced Akt activation was also inhibited by ODQ, KT-5823, manumycin A, and wortmannin. YC-1 caused the formation of an NF-kappaB-specific DNA-protein complex and an increase in kappaB-luciferase activity. YC-1-induced kappaB-luciferase activity was inhibited by ODQ, KT-5823, manumycin A, wortmannin, an Akt inhibitor, PDTC, RasN17, Akt DN, and IkappaBalphaM. Likewise, YC-1-induced IKKalpha/beta activation was inhibited by ODQ, KT-5823, manumycin A, wortmannin, and an Akt inhibitor. Furthermore, YC-1-induced COX-2 promoter activity was inhibited by manumycin A, RasN17, Akt DN, PDTC, and IkappaBalphaM. Taken together, these results indicate that YC-1 might activate the sGC/cGMP/PKG pathway to induce Ras and PI3K/Akt activation, which in turn initiates IKKalpha/beta and NF-kappaB activation and finally induces COX-2 expression in A549 cells.

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-alpha, -iota, -lambda, -zeta and -mu isoforms were detected in A549 cells. Treatment of A549 cells with YC-1 or PMA caused a translocation of PKC-alpha, 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-alpha. The MEK inhibitor, PD 98059 (10 - 50 microM), 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-alpha activation, which in turn, initiates p44/42 MAPK activation, and finally induces COX-2 expression.