A comparison of the metabolic response to phagocytosis in human granulocytes and monocytes.

Abstract

A B S T R A C T Recent studies indicate that oxygen radicals such as superoxide or singlet oxygen may be important in the functional activity of human granulocytes. We have examined the possible importance of these radicals in the functional capacity of human blood monocytes. Monocytes, like granulocytes, generate chemiluminescence during phagocytosis. Chemiluminescence is impaired 50-90% by superoxide dismutase, an enzyme which enhances the dismutation of superoxide to hydrogen peroxide. These results indicate that superoxide is related to the chemiluminescence generated by monocytes. Superoxide dismutase in a concentration which impaired chemiluminescence also impaired the staphylococcal killing by monocytes. Hexose monophosphate shunt activity and hydrogen peroxide production by granulocytes and monocytes were also evaluated. The oxidation of [1-14C]glucose was used as a measure of hexose monophosphate shunt activity and the oxidation of ["4C]formate as an estimation of hydrogen peroxide production. The oxidation of both substrates by monocytes was increased during phagocytosis but, in contrast to results in granulocytes, was not further increased by the addition of superoxide dismutase.These data indicate that superoxide may be important in bactericidal activity of human monocytes. Our results also suggest that the metabolism of oxygen radicals in monocytes and granulocytes may be different.

Free Radicals and Detoxification Enzymes of Inflammatory Peritoneal Neutrophils and Macrophages.

“…This suggestion is in accordance with the present finding that neutrophils, whose number declined sharply on elicitation, emitted more intense chemiluminescence when compared with macrophages. In fact, this supports the earlier reports by Johnston et al [29] and Sagone et al [30] that granulocytes are capable of producing a more intense peak of chemiluminescence than monocytes/macrophages. However, in human blood, such differences in peak chemiluminescence have been attributed to differences in their ability to produce hydroxyl radicals [31].…”

Superoxide production and reducing activity in human platelets.

“…Granulocytes and monocytes were essentially absent from the final platelet suspensions. The only contaminating cells seen on stained smears were lymphocytes, which do not generate superoxide radicals (38,39). An additional experiment was carried out in which leukocyte contamination was reduced further.…”

Oxidative Metabolism of Cord Blood Neutrophils: Relationship to Content and Degranulation of Cytoplasmic Granules

“…By themselves, 0 2 and H202 are weakly bactericidal. Studies using neutrophils or chemical systems suggests that the product of the interaction between these two metabolites, OH, is a critically important oxygen metabolite in microbial killing (16,30,31). Generation of 'OH efficiently in chemical and biological systems depends on the presence of iron (28,29).…”