Ca21-dependent p47phox translocation in hydroperoxide modulation of the alveolar macrophage respiratory burst

Zhou, Huanfang, Roger F. Duncan, Timothy W. Robison, Lin Gao, and Henry Jay Forman. Ca21-dependent p47phox translocation in hydroperoxide modulation of the alveolar macrophage respiratory burst. Am. J. Physiol. 273 (Lung Cell. Mol. Physiol. 17): L1042–L1047, 1997.—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 μM] 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 Ca21 concentration ([Ca]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 μM t-BOOH. Nonetheless, 25 μM t-BOOH increased PMA-stimulated p47phox translocation, whereas 100 μM 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 [Ca]i abolished the effects of t-BOOH on PMAstimulated translocation in parallel to effects upon the respiratory burst. The results suggest that the dual effects of hydroperoxides are mediated, in part, by Ca21-dependent processes affecting the assembly of the respiratory burst oxidase at steps that are separate from p47phox phosphorylation.