Arachidonic acid increases activation of NADPH oxidase in monocytic U937 cells by accelerated translocation of p47-phox and co-stimulation of protein kinase C.
Arachidonic acid (AA) has been implicated as an important amphiphilic co-factor in the activation of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in neutrophils and reconstituted cell-free systems. To assess the role of AA in the activation of O2- generation in monocytic cells, we studied pre-monocytic U937 cells differentiated with 1,25-(OH)2-vitamin D3 plus interferon-gamma (IFN-gamma). AA dose-dependently enhanced phorbol myristate acetate (PMA)-stimulated O2- generation, with a maximum increase of 4,5-fold, through: (1) a more than 50% reduction of the lag-phase, defined as the time between addition of PMA and detection of O2-; and (2) a more than 60% increase in the constant rate of O2- generation. Reduction of the lag phase was associated with increased protein kinase C (PKC)-independent translocation of the cytosolic subunit of NADPH oxidase p47-phox to the cell membrane, whereas increased generation of O2- correlated with enhanced activation of PKC. The data indicate that AA increases activation of NADPH oxidase by accelerating its assembly and by co-stimulating PKC in monocytic U937 cells.
Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Klinikum Innenstadt, Universität München, Germany.
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A
Sellmayer
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H
Obermeier
U
U
Danesch
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M
Aepfelbacher
P C
PC
Weber
D016718:Arachidonic Acid / Q000494:pharmacology*; D006801:Humans; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D019255:NADPH Oxidases / Q000378:metabolism*; D010087:Oxides; D010741:Phospholipases A / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D010087:Oxides; D010750:Phosphoproteins; D016718:Arachidonic Acid; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D011493:Protein Kinase C; D010741:Phospholipases A; D013755:Tetradecanoylphorbol Acetate