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.

Extracellular-Superoxide Dismutase Expression in COS7 Cells Exposed to Cadmium Chloride

“…In fact, we and others have previously reported that intracellular ROS is involved in the reduction of EC-SOD 20,27) or the induction of heme oxygenase-1 31) in several kinds of cells. According to previous reports, we investigated the involvement of intracellular ROS in the reduction of EC-SOD by using an anti-oxidant, NAC.…”

“…20,[25][26][27] Since Cd is known to activate MAPK through intracellular ROS generation, we investigated the involvement of MAPK in the reduction of EC-SOD in COS7 cells. As shown in Fig.…”

MCP-1-Induced Protein Promotes Endothelial-Like and Angiogenic Properties in Human Bone Marrow Monocytic Cells

“…We tested whether MCPIP plays a role in MCP-1-mediated differentiation of BMNCs into ECs. Differentiation of BMNCs was assessed by analysis of the expression of CD11b, a cell-surface marker of differentiated monocytic cells (Alessio M, et al, 1996;Kamiya et al, 2011), and Tie-2, a surface marker of differentiated ECs (Sharifi et al, 2006;Kim et al, 2009). MCP-1 treatment of BMNCs resulted in upregulation of Tie-2 and downregulation of CD11b (Fig.…”

Down-regulation of superoxide dismutase 1 by PMA is involved in cell fate determination and mediated via protein kinase D2 in myeloid leukemia cells

“…It was reported that in human primary megakaryocyte (MK), the mRNA expression level of sod1 in CD41 + cells is higher than that in CD41 -cells [16]. Moreover, the down-regulation of SOD1 mRNA induced by PMA during cell differentiation has been reported in acute leukemia cell lines, such as U937, HL60, and HEL cells [17,18]. Furthermore, in murine thymic lymphoma, the inhibition of SOD1 leads to cell death via the nitric oxide-peroxynitrite-dependent pathway [4].…”