STIMULATION OF THE BACTERICIDAL ACTIVITY OF POLYMORPHONUCLEAR LEUKOCYTES BY MANGANESE

An antioxidant effect of manganese (Mn) complexes due to the scavengin g of the superoxide anion (O2.-) or to the decomposition of hydrogen p eroxide (H2O2) has been described. We report here that Mn also can exe rt a prooxidant effect under certain experimental conditions. Thus Mn2 + in phosphate buffer increased the bactericidal effect of phorbol myr istate acetate-stimulated polymorphonuclear leukocytes (PMNs) on extra cellular Escherichia coli. This effect was inhibited by azide, catalas e, and a decrease in chloride concentration and was not observed when normal PMNs were replaced by those of patients with chronic granulomat ous disease or myeloperoxidase (MPO) deficiency. Mn2+ could be replace d by Mn3+ or by superoxide dismutase (SOD). These findings suggest tha t Mn (or SOD), by increasing the conversion of O- to H2O2, can increas e the activity of the MPO-H2O2-chloride antimicrobial system released by stimulated PMNs.