title: Functional coupling between secretory and cytosolic phospholipase A2 modulates tumor necrosis factor-alpha- and interleukin-1beta-induced NF-kappa B activation.
abstract: Tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta are potent activators of the transcription factor NF-kappaB, induced during inflammatory conditions. We have previously shown that both secretory and cytosolic phospholipase A(2) (PLA(2)) are involved in TNF-alpha- and IL-1beta-induced NF-kappaB activation. In this study, we have addressed the mechanism of PLA(2) involvement with respect to downstream arachidonic acid (AA) metabolites and the functional coupling between PLA(2)s mediating NF-kappaB activation. We show that in addition to inhibitors of secretory and cytosolic PLA(2)s, 5-lipoxygenase inhibitors attenuate TNF-alpha- and IL-1beta-stimulated NF-kappaB activation. Exogenous addition of leukotriene B(4) (LTB(4)) restored NF-kappaB activation reduced by 5-lipoxygenase inhibitors or an LTB(4) receptor antagonist, thus identifying LTB(4) as a mediator in signaling to NF-kappaB. TNF-alpha- and IL-1beta-induced AA release from cellular membranes was accompanied by phosphorylation of cytosolic PLA(2). Inhibitors of secretory PLA(2) and of 5-lipoxygenase/LTB(4) functionality markedly reduced AA release and nearly completely abolished cytosolic PLA(2) phosphorylation. This demonstrates that secretory PLA(2), through 5-lipoxygenase metabolites, is an essential upstream regulator of cytosolic PLA(2) and AA release. Our results therefore suggest the existence of a functional link between secretory and cytosolic PLA(2) in cytokine-activated keratinocytes, providing a molecular explanation for the participation of both secretory and cytosolic PLA(2) in arachidonic acid signaling and NF-kappaB activation in response to proinflammatory cytokines.
authors.affiliation: UNIGEN Center for Molecular Biology, Faculty of Chemistry and Biology, Norwegian University of Science and Technology, N-7489 Trondheim, Norway. Marit.W.Anthonsen@chembio.ntnu.no
authors.forename: M W
authors.initials: MW
authors.lastname: Anthonsen
authors.forename: A
authors.initials: A
authors.lastname: Solhaug
authors.forename: B
authors.initials: B
authors.lastname: Johansen
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001426:Bacterial Proteins; D015153:Blotting, Western; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology* / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism*; D015603:Keratinocytes / Q000378:metabolism; D007975:Leukotriene B4 / Q000378:metabolism; D016859:Lipoxygenase Inhibitors; D008156:Luciferases / Q000378:metabolism; D008954:Models, Biological; D016328:NF-kappa B / Q000737:chemistry / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D054467:Phospholipases A2; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013301:Streptolysins / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D016207:Cytokines; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D016859:Lipoxygenase Inhibitors; D016328:NF-kappa B; D010710:Phosphates; D020033:Protein Isoforms; D013301:Streptolysins; D014409:Tumor Necrosis Factor-alpha; C025964:streptolysin O; D007975:Leukotriene B4; D016718:Arachidonic Acid; D008156:Luciferases; D010741:Phospholipases A; D054467:Phospholipases A2