Involvement of phospholipase A2 and lipoxygenase in lipopolysaccharide-induced inducible nitric oxide synthase expression in glial cells.
The present study underlines the importance of phospholipase A2 (PLA2)- and lipoxygenase (LO)-mediated signaling processes in the regulation of inducible nitric oxide synthase (iNOS) gene expression. In glial cells, lipopolysaccharide (LPS) induced the activities of PLA2 (calcium-independent PLA2; iPLA2 and cytosolic PLA2; cPLA2) as well as gene expression of iNOS. The inhibition of cPLA2 by methyl arachidonyl fluorophosphates (MAFP) or antisense oligomer against cPLA2 and inhibition of iPLA2 by bromoenol lactone reduced the LPS-induced iNOS gene expression and NFkappaB activation. In addition, the inhibition of LO by nordihydroguaiaretic acid (NDGA; general LO inhibitor) or MK886 (5-LO inhibitor), but not baicalein (12-LO inhibitor), completely abrogated the LPS-induced iNOS expression. Because NDGA could abrogate the LPS-induced activation of NFkappaB, while MK886 had no effect on it, LO-mediated inhibition of iNOS gene induction by LPS may involve an NFkappaB-dependent or -independent (by 5-LO) pathway. In contrast to LO, however, the cyclooxygenase (COX) may not be involved in the regulation of LPS-mediated induction of iNOS gene because COX inhibition by indomethacin (general COX inhibitor), SC560 (COX-1 inhibitor), and NS398 (COX-2 inhibitor) affected neither the LPS-induced iNOS expression nor activation of NFkappaB. These results indicate a role for cPLA2 and iPLA2 in LPS-mediated iNOS gene induction in glial cells and the involvement of LO in these reactions.
Won
Je-Seong
JS
Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Im
Yeong-Bin
YB
Khan
Mushfiquddin
M
Singh
Avtar K
AK
Singh
Inderjit
I
D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism; D015152:Blotting, Northern; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D017930:Genes, Reporter / Q000235:genetics; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008084:Lipoxygenase / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009457:Neuroglia / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D054467:Phospholipases A2; D012313:RNA / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D015533:Transcriptional Activation; D014162:Transfection
D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008070:Lipopolysaccharides; D016328:NF-kappa B; D016718:Arachidonic Acid; D012313:RNA; D008084:Lipoxygenase; D001094:Arachidonate 5-Lipoxygenase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D010741:Phospholipases A; D054467:Phospholipases A2