SULFITE STIMULATES NADPH OXIDASE OF HUMAN NEUTROPHILS TO PRODUCE ACTIVE OXYGEN RADICALS VIA PROTEIN-KINASE-C AND CA2+ CALMODULIN PATHWAYS/

The effect of sulfite on the oxidative metabolism of human neutrophils was studied in vitro. Superoxide anion production of PMN was determin ed using superoxide dismutase-inhibitable lucigenin-dependent CL. The addition of sulfite in concentrations of 0.01 mM-1 mM results in an up to 6-fold increase in CL of nonstimulated neutrophils at 37-degrees-C and pH 7. Neutrophils stimulated with zymosan or PMA have an addition al 2-fold stimulation when sulfite is added. Higher sulfite concentrat ions (2 mM-10 mM) decrease the CL of both nonstimulated and stimulated cells. The activity of NADPH oxidase, responsible for O2.- production , is significantly increased in neutrophils incubated with 1 mM sulfit e. Neutrophils from patients with chronic granulomatous disease, which are cytochrome b558 negative or have p47phox deficiency, exhibit no s ignificant NADPH oxidase activity and show no increase in CL by sulfit e. Inhibitors of protein kinase C, H7, and calphostin C, as well as in hibitors of Ca2+- and calmodulin-dependent processes, W7, and R 24 571 , completely inhibited the increased CL of sulfite-treated neutrophils . These findings indicate that sulfite in low concentrations stimulate s neutrophils to produce superoxide anions by activation of NADPH oxid ase through a signal transduction pathway involving protein kinase C a nd Ca2+/calmodulin.