Human alveolar macrophages and granulocyte-macrophage colony-stimulating factor-induced manocyte-derived macrophages are resistant to H2O2 via their high basal and inducible levels of catalase activity

Human alveolar macrophages (A-M Phi) and macrophages (M Phi) generated from human monocytes under the influence of granulocyte-macrophage colony-stimu lating factors (GM-M Phi) express high Levels of catalase activity and are highly resistant to H2O2. In contrast, M Phi generated from monocytes by ma crophage colony-stimulating factors (M-M Phi) express low catalase activity and are about 50-fold more sensitive to H2O2 than GM-M Phi or A-M Phi. Bot h A-M Phi, and GM-M Phi, but not M-M Phi can induce catalase expression in both protein and mRNA levels when stimulated with H,OZ or zymosan. M-M Phi but not GM-M Phi, produce a Large amount of H2O2 in response to zymosan or heat-killed Staphylococcus aureus. These findings indicate that GM-M Phi, a nd A-M Phi but not M-X Phi are strong scavengers of H2O2 via the high basal level of catalase activity and a marked ability of catalase induction and that catalase activity of M Phi is regulated by colony-stimulating factors during differentiation.