Novel mechanism of glucocorticoid-mediated gene repression. Nuclear factor-kappa B is target for glucocorticoid-mediated interleukin 8 gene repression.
A glucocorticoid, dexamethasone, inhibited the production of a leukocyte chemotactic cytokine, interleukin 8 (IL-8), as well as mRNA expression by a glioblastoma cell line, T98G, stimulated with interleukin 1 (IL-1). Dexamethasone also inhibited IL-8 promoter-driven chloramphenicol acetyltransferase (CAT) activities induced by IL-1, suggesting that dexamethasone inhibited IL-8 production mainly at the transcriptional level. Moreover, CAT assay revealed that the nuclear factor-kappa B (NF-kappa B) binding site was the crucial cis-element required for conferring IL-1 responsiveness in conjunction with the CCAAT enhancer binding protein/nuclear factor-IL-6 (NF-IL6) and/or the AP-1 binding site(s). Mutation of either the AP-1 or NF-IL6 binding site did not abolish IL-8 gene repression by dexamethasone, suggesting that these sites were not targets for dexamethasone. Trimerized kappa B sequence in the IL-8 gene was enough for conferring the induction by IL-1 and inhibition by dexamethasone of CAT activity. Finally, dexamethasone diminished the IL-1-induced formation of NF-kappa B complexes, which were identified immunochemically to consist of p50 and p65, without reducing the amount of translocated factors. Collectively, dexamethasone interfered with the binding of the most essential transcription factor, NF-kappa B, to its cognate cis-element, thereby suppressing the transcription of IL-8 gene.
Mukaida
N
N
Department of Pharmacology, Kanazawa University, Japan.
Morita
M
M
Ishikawa
Y
Y
Rice
N
N
Okamoto
S
S
Kasahara
T
T
Matsushima
K
K
D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics; D016209:Interleukin-8 / Q000235:genetics*; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D007375:Interleukin-1; D016209:Interleukin-8; D016328:NF-kappa B; D003907:Dexamethasone