Human Alveolar Macrophages and Granulocyte-macrophage Colony-stimulating Factor-induced Monocyte-derived Macrophages are Resistant to H2O 2 via Their High Basal and Inducible Levels of Catalase Activity

Abstract

Human alveolar macrophages (A-MΦ) and macrophages (MΦ) generated from human monocytes under the influence of granulocyte-macrophage colony-stimulating factors (GM-MΦ) express high levels of catalase activity and are highly resistant to H2O2. In contrast, MΦ generated from monocytes by macrophage colony-stimulating factors (M-MΦ) express low catalase activity and are about 50-fold more sensitive to H 2O2 than GM-MΦ or A-MΦ. Both A-MΦ and GM-MΦ but not M-MΦ can induce catalase expression in both protein and mRNA levels when stimulated with H2O2 or zymosan. M-MΦ but not GM-MΦ produce a large amount of H2O2 in response to zymosan or heat-killed Staphylococcus aureus. These findings indicate that GM-MΦ and A-MΦ but not M-MΦ 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 MΦ is regulated by colony-stimulating factors during differentiation.