Tumor necrosis factor-alpha down-regulates human Cu/Zn superoxide dismutase 1 promoter via JNK/AP-1 signaling pathway.
Overexpression of Cu/Zn superoxide dismutase 1 (SOD1) in monocytes blocks reactive oxygen species-induced inhibition of cell growth and apoptosis and renders cells resistant to the toxic effect of tumor necrosis factor (TNF)-alpha, suggesting that TNF-alpha represses the SOD1 gene in these cells. We herein show that TNF-alpha decreases SOD1 mRNA, protein, and promoter activity in U937 cells. Electrophoretic mobility-shift assays (EMSA) show that TNF-alpha decreased binding of three different complexes. Ectopic Sp1 overexpression markedly increased SOD1-basal promoter activity and partially antagonized the TNF-alpha inhibitory effect. In contrast, ectopic c-Jun overexpression mimics TNF-alpha inhibitory effects and antagonizes Sp1 stimulatory effects. In agreement with these findings, EMSA shows a TNF-alpha-induced increase in AP-1 and a decrease in Sp1 DNA binding. Disruption of the C/EBP site decreases, whereas mutation in the Sp1/Egr-1 site completely abolishes DNA-binding and promoter activity. A JNK inhibitor antagonized the negative effects of TNF-alpha on SOD1 promoter activity, suggesting that JNK signaling through c-Jun protein activation is critical for the TNF-alpha-dependent SOD1 repression. A greater understanding of the mechanisms of TNF-alpha-induced SOD1 repression could facilitate the design and development of novel therapeutic drugs for inflammatory conditions.
Afonso
Valéry
V
INSERM U606, Lariboisiere Hospital, Paris, France.
Santos
Guilherme
G
Collin
Pascal
P
Khatib
Abdel-Majid
AM
Mitrovic
Dragoslav R
DR
Lomri
Noureddine
N
Leitman
Dale C
DC
Lomri
Abderrahim
A
D001483:Base Sequence; D015536:Down-Regulation; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D020298:U937 Cells
D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D013482:Superoxide Dismutase; D048670:MAP Kinase Kinase 4