Dexamethasone inhibits IL-1 beta gene expression in LPS-stimulated RAW 264.7 cells by blocking NF-kappa B/Rel and AP-1 activation.
In the present study, the mechanism by which dexamethasone (DEX) inhibited IL-1beta gene expression in bacterial lipopolysaccharide (LPS)-activated RAW 264.7 cells was investigated. The decrease in LPS-induced IL-1beta mRNA expression was demonstrated by quantitative reverse transcription polymerase chain reaction (RT-PCR). Since the promoter in IL-1beta gene contains binding motifs for NF-kappaB/Rel, AP-1, NF-IL6, and CREB/ATF, which appear to be important in LPS-mediated IL-1beta 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-kappaB/Rel and AP-1 in chloramphenicol acetyltransferase activity, while neither NF-IL6 nor CREB/ATF activation was affected by DEX. Treatment of RAW 264.7 cells with DEX inhibited DNA binding of NF-kappaB/Rel and AP-1 proteins to their cognate DNA sites as measured by electrophoretic mobility shift assay (EMSA). 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. DEX treatment of RAW 264.7 cells did not inhibit the nuclear translocation of c-jun and c-fos. We found that the inhibition of IL-1beta production by DEX is not related to p38, which is important in the IL-1beta induction. These results suggest that DEX may inhibit IL-1beta gene expression by a mechanism involving the blocking of LPS-induced NF-kappaB/Rel and AP-1 activation.
Korea Research Institute of Bioscience and Biotechnology (KRIBB), PO Box 115, Yusong, 305-600, Taejon, South Korea. yjjeon@bioneer.kaist.ac.kr
Y J
YJ
Jeon
S H
SH
Han
Y W
YW
Lee
M
M
Lee
K H
KH
Yang
H M
HM
Kim
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004742:Enhancer Elements, Genetic / Q000187:drug effects / Q000276:immunology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D007375:Interleukin-1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors*; D008262:Macrophage Activation / Q000187:drug effects* / Q000235:genetics; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000276:immunology; D020569:Proto-Oncogene Proteins c-rel / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism
D007375:Interleukin-1; D008070:Lipopolysaccharides; D016328:NF-kappa B; D020569:Proto-Oncogene Proteins c-rel; D018808:Transcription Factor AP-1; D003907:Dexamethasone