Ca(2+)-dependent p47phox translocation in hydroperoxide modulation of the alveolar macrophage respiratory burst.
Oxidative stress produces dual effects on the respiratory burst of rat alveolar macrophages. Preincubation with hydroperoxide concentrations [H2O2 or tert-butyl hydroperoxide (t-BOOH); < 50 microM] enhances stimulation of the respiratory burst, whereas higher concentrations inhibit stimulation. Both the enhancement and inhibition are markedly attenuated by buffering t-BOOH-induced changes in intracellular Ca2+ concentration ([Ca2+]i). Phosphorylation of the NADPH oxidase component p47phox and its translocation from cytoplasm to plasma membrane are essential in respiratory burst activation. Phorbol 12-myristate 13-acetate (PMA)-stimulated p47phox phosphorylation was negligibly affected by 25 or 100 microM t-BOOH. Nonetheless, 25 microM t-BOOH increased PMA-stimulated p47phox translocation, whereas 100 microM t-BOOH decreased PMA-stimulated translocation. In unstimulated cells, however, neither phosphorylation nor translocation of p47phox was affected by t-BOOH. Buffering of the t-BOOH-mediated changes of [Ca2+]i abolished the effects of t-BOOH on PMA-stimulated translocation in parallel to effects upon the respiratory burst. The results suggest that the dual effects of hydroperoxides are mediated, in part, by Ca(2+)-dependent processes affecting the assembly of the respiratory burst oxidase at steps that are separate from p47phox phosphorylation.
Zhou
H
H
Department of Molecular Pharmacology and Toxicology, University of Southern California, Los Angeles 90033, USA.
Duncan
R F
RF
Robison
T W
TW
Gao
L
L
Forman
H J
HJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000502:physiology*; D008297:Male; D019255:NADPH Oxidases / Q000378:metabolism; D010545:Peroxides / Q000494:pharmacology*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species; D016897:Respiratory Burst / Q000187:drug effects* / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D020122:tert-Butylhydroperoxide
D010545:Peroxides; D010750:Phosphoproteins; D017382:Reactive Oxygen Species; D020122:tert-Butylhydroperoxide; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium