Inhibition of NF-kappa B/Rel nuclear translocation by dexamethasone: mechanism for the inhibition of iNOS gene expression.
The decrease in NO production was found to correlate well with a decrease in inducible nitric oxide synthase (iNOS) mRNA expression as demonstrated by Northern blot analysis and quantitative RT-PCR. Since the promoter in iNOS gene contains binding motifs for NF-kappa B/Rel, NF-IL6, and Oct which appear to be important for LPS-mediated iNOS induction, the effects of DEX on the activation of these transcription factors were examined. Treatment of DEX to RAW 264.7 cells induced a dose-related inhibition of NF-kappa B/Rel in chloramphenicol acetyltransferase activity, while NF-IL6 or Oct activation was not affected by DEX. Treatment of RAW 264.7 cells with DEX inhibited DNA binding of NF-kappa B/Rel proteins to their cognate DNA site as measured by electrophoretic mobility shift assay. In addition, DEX treatment caused a significant reduction in nuclear c-rel, p65, and p50 protein contents, and these decreases were paralleled by the accumulation of cytoplasmic c-rel, p65, and p50. These results suggest that DEX may inhibit iNOS gene expression by a mechanism involving the blockade of LPS-induced nuclear translocation of NF-kappa B/Rel.
Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejon, Korea.
Y J
YJ
Jeon
S H
SH
Han
Y W
YW
Lee
S S
SS
Yea
K H
KH
Yang
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D015151:Immunoblotting; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D014162:Transfection
D008070:Lipopolysaccharides; D016328:NF-kappa B; D003907:Dexamethasone; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse