CA2-DEPENDENT P47(PHOX) 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 mu M] enhances stimul ation of the respiratory burst, whereas higher concentrations inhibit stimulation. Both the enhancement and inhibition are markedly attenuat ed by buffering t-BOOH-induced changes in intracellular Ca2+ concentra tion ([Ca2+](i)), Phosphorylation of the NADPH oxidase component p47(p hox) and its translocation from cytoplasm to plasma membrane are essen tial in respiratory burst activation. Phorbol 12-myristate 13-acetate (PMA)-stimulated p47(phox) phosphorylation was negligibly affected by 25 or 100 mu M t-BOOH. Nonetheless, 25 mu M t-BOOH increased PMA-stimu lated p47(phox) translocation, whereas 100 mu M t-BOOH decreased PMA-s timulated translocation. In unstimulated cells, however, neither phosp horylation nor translocation of p47(phox) was affected by t-BOOH. Buff ering of the t-BOOH-mediated changes of [Ca2+](i) abolished the effect s of t-BOOH on PMA-stimulated translocation in parallel to effects upo n the respiratory burst. The results suggest that the dual effects of hydroperoxides are mediated, in part, by Ca2+-dependent processes affe cting the assembly of the respiratory burst oxidase at steps that are separate from p47(phox) phosphorylation.