ABSTRACT
Antioxidant enzymes levels were determined in monocytes during phorbol myristate acetate (PMA)-induced differentiation. PMA induced the differentiation of a human monocytic leukemia cell line THP-1 into macrophage-like cells as indicated by activity of acid phosphatase and morphological changes. The level of Mn-superoxide dismutase (SOD) was selectively increased in PMA-treated THP-1 cells after one day of culture, while the levels of Cu/Zn-SOD and catalase were progressively decreased by Western blot analysis. In contrast, levels of Cu/Zn-SOD and catalase protein and enzyme activitiy remained unchanged in THP-1 cells after transforming growth factor-p, treatment. Cu/Zn-SOD is oxidatively inactivated by exposure to H,O, which is produced by PMA-treated THP-1 cells, and then the inactivated enzyme undergoes proteolysis and fragmentation as analyzed by radiolabeled method. Thus monocytes have a coordinated system for synthesis and degradation of antioxidant enzymes during PMA-induced differentiation.