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

Human alveolar macrophages (A-MPhi) and macrophages (MPhi) generated from human monocytes under the influence of granulocyte-macrophage colony-stimulating factors (GM-MPhi) express high levels of catalase activity and are highly resistant to H(2)O(2). In contrast, MPhi generated from monocytes by macrophage colony-stimulating factors (M-MPhi) express low catalase activity and are about 50-fold more sensitive to H(2)O(2) than GM-MPhi or A-MPhi. Both A-MPhi and GM-MPhi but not M-MPhi can induce catalase expression in both protein and mRNA levels when stimulated with H(2)O(2) or zymosan. M-MPhi but not GM-MPhi produce a large amount of H(2)O(2) in response to zymosan or heat-killed Staphylococcus aureus. These findings indicate that GM-MPhi and A-MPhi but not M-MPhi are strong scavengers of H(2)O(2) via the high basal level of catalase activity and a marked ability of catalase induction and that catalase activity of MPhi is regulated by colony-stimulating factors during differentiation.