Stimulation of the bactericidal activity of polymorphonuclear leukocytes by manganese.

An antioxidant effect of manganese (Mn) complexes due to the scavenging of the superoxide anion (O2-.) or to the decomposition of hydrogen peroxide (H2O2) has been described. We report here that Mn also can exert a prooxidant effect under certain experimental conditions. Thus Mn2+ in phosphate buffer increased the bactericidal effect of phorbol myristate acetate-stimulated polymorphonuclear leukocytes (PMNs) on extracellular Escherichia coli. This effect was inhibited by azide, catalase, and a decrease in chloride concentration and was not observed when normal PMNs were replaced by those of patients with chronic granulomatous disease or myeloperoxidase (MPO) deficiency. Mn2+ could be replaced by Mn3+ or by superoxide dismutase (SOD). These findings suggest that Mn (or SOD), by increasing the conversion of O2-. to H2O2, can increase the activity of the MPO-H2O2-chloride antimicrobial system released by stimulated PMNs.