Abstract
It has been reported that interleukin-8 (IL-8) and cyclooxygenase-2 (COX-2) expression is regulated by peroxisome proliferator-activated receptor (PPAR)-gamma synthetic ligands. We have shown previously that cytosolic phospholipase A2 (cPLA2) is able to activate gene expression through PPAR-gamma response elements (Pawliczak, R., Han, C., Huang, X. L., Demetris, A. J., Shelhamer, J. H., and Wu, T. (2002) J. Biol. Chem. 277, 33153-33163). In this study we investigated the influence of cPLA2 and secreted phospholipase A2 (sPLA2) Group IIA, Group V, and Group X on IL-8 and COX-2 expression in human lung epithelial cells (A549 cells). We also studied the results of cPLA2 activation by epidermal growth factor (EGF) and calcium ionophore (A23187) on IL-8 and COX-2 reporter gene activity, mRNA level, and protein synthesis. cPLA2 overexpression and activation increased both IL-8 and COX-2 reporter gene activity. Overexpression and activation of Group IIA, Group V, or Group X sPLA2s did not increase IL-8 and COX-2 reporter gene activity. Methyl arachidonyl fluorophosphate, a cPLA2 inhibitor, inhibited the effect of A23187 and of EGF on both IL-8 and COX-2 reporter gene activity, steady state levels of IL-8 and COX-2 mRNA, and IL-8 and COX-2 protein expression. Small inhibitory RNAs directed against PPAR-gamma1 and -gamma2 blunted the effect of A23187 and of EGF on IL-8 and COX-2 protein expression. Moreover small inhibitory RNAs directed against cPLA2 decreased the effect of A23187 and EGF on IL-8 and COX-2 protein expression. These results demonstrate that cPLA2 has an influence on IL-8 and COX 2 gene and protein expression at least in part through PPAR-gamma.
Highlights
From the ‡Critical Care Medicine Department, National Institutes of Health, Bethesda, Maryland 20892, the §Department of Allergy and Clinical Immunology, Medical University of Lodz, Lodz 92213, Poland, and the ¶Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
In this study we investigated the influence of cytosolic phospholipase A2 (cPLA2) and secreted phospholipase A2 Group IIA, Group V, and Group X on IL-8 and COX-2 expression in human lung epithelial cells (A549 cells)
We studied the results of cPLA2 activation by epidermal growth factor (EGF) and calcium ionophore (A23187) on IL-8 and COX-2 reporter gene activity, mRNA level, and protein synthesis. cPLA2 overexpression and activation increased both IL-8 and COX-2 reporter gene activity
Summary
From the ‡Critical Care Medicine Department, National Institutes of Health, Bethesda, Maryland 20892, the §Department of Allergy and Clinical Immunology, Medical University of Lodz, Lodz 92213, Poland, and the ¶Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213. In this study we investigated the influence of cPLA2 and secreted phospholipase A2 (sPLA2) Group IIA, Group V, and Group X on IL-8 and COX-2 expression in human lung epithelial cells (A549 cells). Small inhibitory RNAs directed against PPAR-␥1 and -␥2 blunted the effect of A23187 and of EGF on IL-8 and COX-2 protein expression. Small inhibitory RNAs directed against cPLA2 decreased the effect of A23187 and EGF on IL-8 and COX-2 protein expression. CPLA2 appears to play a role in intracellular arachidonate release, whereas low molecular weight PLA2s (such as Groups IA, IB, IIA, IIC, and V) may be involved in extracellular arachidonic acid release due to the fact that they are secreted into extracellular milieu upon cell stimulation. The IL-8 promoter contains a PPAR-␥ response element localized to Ϫ1060 relative to the transcription start site, suggesting that PPAR-␥ may play a role in regulation of IL-8 small inhibitory RNA; thioetheramide-PC, 1-palmitylthio-2-palmitoylamido-1,2-dideoxy-sn-glycero-3-phosphorylcholine; BEL, bromoenol lactone; CMV, cytomegalovirus
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