Cyclooxygenase-2 Expression In A549 Cells Research Articles

Inhibitive effect of proanthocyanidins on cyclooxygenase-2 expression in A549 cells induced by cytokine interleukin-1 beta

Cyclooxygenase-2 (COX-2), an important enzyme, plays a pathological role in diseases, which can be inhibited by proanthocyanidins (PCs) effectively. In this paper, we investigated the inhibitive mechanism of COX-2 performed by PCs. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to identify the mRNA expression level of COX-2 in A549 cell, which was induced by interleukin-1 beta (IL-1β). The pGL3 luciferase reporter vector containing the COX-2 gene promoter fragment (pGL3/COX-2p) was transfected into A549 cell induced by IL-1β, the interference on the COX-2 promoter activity from PCs was analyzed using a dualluciferase reporter assay, and the expressions of the nuclear factor κB composed of subunit p65 (NF-κB/p65) and the inhibitor-κB (I-κB) were measured by the Western blotting and immunocytochemistry. The results exhibited that PCs not only inhibited the transcript of COX-2 mRNA and the COX-2 promoter activity, but also suppressed the nuclear translocation of NF-κB/p65 protein and the degradation of I-κB protein.

Extract from <i>Nandina domestica</i> Inhibits Lipopolysaccharide-Induced Cyclooxygenase-2 Expression in Human Pulmonary Epithelial A549 Cells

Extract from fruits of Nandina domestica THUNBERG (NDE) has been used to improve cough and breathing difficulty in Japan for many years. To explore whether NDE may alleviate respiratory inflammation, we investigated its effect on expression of cyclooxygenase-2 (COX-2) and production of prostaglandin E₂ (PGE₂) in human pulmonary epithelial A549 cells in culture. Treatment with lipopolysaccharide (LPS; 6 µg/mL) resulted in an increase of COX-2 expression and PGE₂ production in A549 cells. Both the LPS-induced COX-2 expression and PGE₂ production were significantly inhibited by NDE (1-10 µg/mL) in a concentration-dependent manner. NDE did not affect COX-1 expression nor COX activity. These results suggest that NDE downregulates LPS-induced COX-2 expression and inhibits PGE₂ production in pulmonary epithelial cells. Furthermore, higenamine and nantenine, two major constituents responsible for tracheal relaxing effect of NDE, did not mimic the inhibitory effect of NDE on LPS-induced COX-2 expression in A549 cells. To identify active constituent(s) of NDE responsible for the anti-inflammatory effect, NDE was introduced in a polyaromatic absorbent resin column and stepwise eluted to yield water fraction, 20% methanol fraction, 40% methanol fraction, 99.8% methanol fraction, and 99.5% acetone fraction. However, none of these five fractions alone inhibited LPS-induced COX-2 expression. On the other hand, exclusion of water fraction from NDE abolished the inhibitory effect of NDE on LPS-induced COX-2 expression. These results suggest that constituent(s) present in water fraction is required but not sufficient for the anti-inflammatory activity of NDE, which may result from interactions among multiple constituents.

Triptolide inhibits COX-2 expression by regulating mRNA stability in TNF-α-treated A549 cells

Cyclooxygenase-2 (COX-2) over-expression is frequently associated with human non-small-cell lung cancer (NSCLC) and involved in tumor proliferation, invasion, angiogenesis and resistance to apoptosis. In the present study, the effects of triptolide on COX-2 expression in A549 cells were investigated and triptolide was found to inhibit TNF-α-induced COX-2 expression. In our further studies, it was found that triptolide decreased the half-life of COX-2 mRNA dramatically and that it inhibited 3′-untranslated region (3′-UTR) fluorescence reporter gene activity. Meanwhile, triptolide inhibited the HuR shuttling from nucleus to cytoplasm. After triptolide treatment, decreased COX-2 mRNA in pull-down experiments with anti-HuR antibodies was observed, indicating that the decreased cytoplasmic HuR is responsible for the decreased COX-2 mRNA. Taken together, our results provided evidence for the first time that triptolide inhibited COX-2 expression by COX-2 mRNA stability modulation and post-transcriptional regulation. These results provide a novel mechanism of action for triptolide which may be important in the treatment of lung cancer.

Redox Factor-1 Inhibits Cyclooxygenase-2 Expression via Inhibiting of p38 MAPK in the A549 Cells

In this study, we evaluated the role of apurinic/apyrimidinic endonuclease1/redox factor-1 (Ref-1) on the tumor necrosis factor-alpha (TNF-alpha) induced cyclooxygenase-2 (COX-2) expression using A549 lung adenocarcinoma cells. TNF-alpha induced the expression of COX-2 in A549 cells, but did not induce BEAS-2B expression. The expression of COX-2 in A549 cells was TNF-alpha dose-dependent (5~100 ng/ml). TNF-alpha-stimulated A549 cells evidenced increased Ref-1 expression in a dose-dependent manner. The adenoviral transfection of cells with AdRef-1 inhibited TNF-alpha-induced COX-2 expression relative to that seen in the control cells (Adbetagal). Pretreatment with 10 microM of SB203580 suppressed TNF-alpha-induced COX-2 expression, thereby suggesting that p38 MAPK might be involved in COX-2 expression in A549 cells. The phosphorylation of p38 MAPK was increased significantly after 5 minutes of treatment with TNF-alpha, reaching a maximum level at 10 min which persisted for up to 60 min. However, p38MAPK phosphorylation was markedly suppressed in the Ref-1-overexpressed A549 cells. Taken together, our results appear to indicate that Ref-1 negatively regulates COX-2 expression in response to cytokine stimulation via the inhibition of p38 MAPK phosphorylation. In the lung cancer cell lines, Ref-1 may be involved as an important negative regulator of inflammatory gene expression.

Fluoride-induced cyclooxygenase-2 expression and prostaglandin E2 production in A549 human pulmonary epithelial cells

To clarify the mechanisms of fluoride-induced airway diseases, we examined the expression of cyclooxygenase-2 (COX-2), an important mediator of airway inflammation, in A549 human pulmonary epithelial cells treated with sodium fluoride (NaF). Following exposure to 5mM NaF, COX-2 protein and COX-2 transcript increased markedly. However, no change was observed in COX-1 expression. NaF-induced accumulation of COX-2 transcript was abolished by actinomycin D, but not cycloheximide. The level of prostaglandin E(2), a major product of COX enzymes, increased in response to NaF exposure, and its production was abolished by the selective COX-2 inhibitor NS-398. Phosphorylated forms of mitogen-activated protein kinases (MAPKs)-including extracellular signal-regulated protein kinase (ERK), c-Jun NH(2)-terminal kinase, and p38-increased after NaF exposure, while treatment with the MAPK/ERK kinase inhibitor U0126 and the p38 inhibitor SB203580 markedly suppressed COX-2 expression. Furthermore, NaF-induced COX-2 expression was markedly suppressed by the Src family kinase (SFK) inhibitor PP2, but only partially suppressed by the epidermal growth factor receptor (EGFR) inhibitor PD153035. These results suggest that NaF induces COX-2 expression by transcriptional up-regulation via p38 and ERK pathways, at least in part, and that SFKs may be upstream tyrosine kinases responsible for NaF-induced COX-2 expression in A549 cells.

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-κB (NF-κB) 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-α (PKC-α) 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 IKKα/β activation and κB-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 IKKα/β and NF-κB activation, and ultimately causes COX-2 expression in A549 cells. Moreover, PKC-α and PI3K signal might be involved in YC-1-induced Raf-1 activation.

Effects of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor on lung cancer: Roles of cyclooxygenase-2

We examined the effects of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) on the lung cancer cell lines PC-9, LA-1 and A549. In addition, we examined if the effects of the cytokines on the cell lines are mediated by activation of cyclooxygenase (COX)-2. The three cell lines did not constitutively produce either G-CSF or GM-CSF. G-CSF did not influence cell growth in the three cell lines, while GM-CSF increased cell growth in the A549 and LA-1 lines. G-CSF and GM-CSF dose-dependently decreased cell death in the three cell lines. RT-PCR demonstrated GM-CSF receptor expression in the three lung cancer cell lines, whereas the G-CSF receptor exists only in the PC-9 line. We suggest that G-CSF might rescue the tumor cells from cytotoxicity due to serum deprivation through cellular pathways independent of the G-CSF receptor. G-CSF and GM-CSF increased cyclooxygenase-2 (COX-2) expression in PC-9 and LA-1 cells whereas they decreased COX-2 expression in A549 cells. The COX-2 inhibitor NS-398 increased cell death in PC-9 and LA-1 cells, whereas it decreased cell death in A549 cells. PC-9 and LA-1 clones transfected with sense G-CSF- or GM-CSF showed an increase in COX-2 expression, while COX-2 expression was decreased in transfected A549 clones. COX-2 expression was increased in anti-sense G-CSF- and GM-CSF-transfected A549 clones. Thus, although COX-2 activation seems to induce different biological behavior depending on the cell type, we propose that G-CSF and GM-CSF might accelerate tumor progression by directly regulating COX-2 expression, independently of an autocrine mechanism.

Lipoteichoic acid-induced cyclooxygenase-2 expression requires activations of p44/42 and p38 mitogen-activated protein kinase signal pathways

This study investigated the role of p44/42 and p38 mitogen-activated protein kinase (MAPK) in cyclooxygenase-2 expression caused by lipoteichoic acid in human pulmonary epithelial cell line (A549). Lipoteichoic acid-induced increases in cyclooxygenase activity and cyclooxygenase-2 expression were attenuated by tyrosine kinase inhibitors (genistein and tyrphostin AG126), a MAPK/extracellular signal-regulated protein kinase (MEK) inhibitor [2′-amino-3′-methoxyflavone] (PD 98059) and a p38 MAPK inhibitor [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1 H-imidazole] (SB 203580). Lipoteichoic acid-induced p44/42 MAPK activation was inhibited by protein kinase C (PKC) inhibitors [12-(2-cyanoethyl)6,7,12,13-tetrahydro-13-methyl-5-oxo-5 H-indolo(2,3-a)pyrrolo(3,4-c)-carbazole] (Go 6976) and {3-[1-[3-(amidinothio)propyl-1 H-indol-3-yl]-3-(1-methyl-1 H-indol-3-yl)maleimide]} (Ro 31-8220), genistein and PD 98059. Lipoteichoic acid-induced increase in p38 MAPK activity was inhibited by Go 6976, Ro 31-8220, genistein and SB 203580. Lipoteichoic acid-mediated formation of nuclear factor-κB (NF-κB)-specific DNA–protein complex was inhibited by genistein, tyrphostin AG126, PD 98059 and SB 203580. These results suggest that the activations of both p44/42 and p38 MAPK by lipoteichoic acid result in stimulation of NF-κB-specific DNA–protein binding and subsequent cyclooxygenase-2 expression in A549 cells. Both events required activation of upstream tyrosine kinase and PKC.