title: Extracellular-superoxide dismutase expression during monocytic differentiation of U937 cells.
abstract: Leukemic cell lines, such as U937, THP-1, and HL60 cells, can differentiate into macrophages following exposure to various agents including 12-O-tetradecanoylphorbol-13-acetate (TPA) in vitro. It is well known that TPA enhances reactive oxygen species (ROS) generation through the activation of NADPH oxidase (NOX), and ROS act as mediators in TPA signaling. Extracellular-superoxide dismutase (EC-SOD) is a major anti-oxidative enzyme that protects the cells from damaging effects of superoxide. Recently, the reduction of Cu/Zn-SOD and the induction of Mn-SOD by TPA in leukemic cells have been reported; however, the regulation of EC-SOD by TPA remains poorly understood. Here, we explored the regulation of EC-SOD during the monocytic differentiation of U937 cells by TPA. We observed the reduction of EC-SOD and Cu/Zn-SOD, whereas the induction of Mn-SOD during the differentiation of U937 cells. The reduction of EC-SOD and Cu/Zn-SOD was attenuated by pretreatments with GF109203X (an inhibitor of protein kinase C, PKC), diphenyleneiodonium (an inhibitor of NOX), and U0126 (an inhibitor of mitogen-activated protein kinase kinase, MEK/extracellular-signal regulated kinase, ERK). Interestingly, pretreatment with BAY11-7082 (an inhibitor of nuclear factor-κB, NF-κB) suppressed the reduction of Cu/Zn-SOD, but not of EC-SOD. Furthermore, we also determined the involvement of newly synthesized protein and the instability of mRNA in the reduction of EC-SOD. Overall, our results suggest that the expression of EC-SOD is decreased by TPA through intracellular signaling consisting of PKC, NOX-derived ROS and MEK/ERK, but not of NF-κB signaling.
authors.affiliation: Department of Biomedical Pharmaceutics, Gifu Pharmaceutical University, Gifu 501-1196, Japan. tekamiya@gifu-pu.ac.jp
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Kamiya
authors.forename: Junya
authors.initials: J
authors.lastname: Makino
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Hara
authors.forename: Naoki
authors.initials: N
authors.lastname: Inagaki
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Adachi
mesh_terms: D002454:Cell Differentiation; D018922:HL-60 Cells; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D020298:U937 Cells
chemical_list: D016328:NF-kappa B; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase; D013755:Tetradecanoylphorbol Acetate