Dexamethasone prevents interleukin-1beta-induced nuclear factor-kappaB activation by upregulating IkappaB-alpha synthesis, in lymphoblastic cells.
OBJECTIVE
Glucocorticoids (GCs) exert some of their anti-inflammatory actions by preventing the activation of the transcription factor nuclear factor (NF)-kappaB. The GC-dependent inhibition of NF-kappaB may occur at different levels, but the mechanisms involved are still incompletely understood. In this work, we investigated whether the synthetic GC, dexamethasone (Dex), modulates the activity of NF-kappaB in the lymphoblastic CCRF-CEM cell line. We also evaluated the ability of Dex to prevent the activation of NF-kappaB in response to the potent proinflammatory cytokine, interleukin (IL)-1beta.


RESULTS
Exposure of the cells to Dex (1 microM) induced the rapid degradation of IkappaB-alpha, leading to the transient translocation of the NF-kappaB family members p65 and p50 from the cytoplasm to the nucleus, as evaluated by western blot. Electrophoretic mobility shift assays revealed that, in the nucleus, these NF-kappaB proteins formed protein-DNA complexes, indicating a transient activation of NF-kappaB. Additionally, Dex also induced de novo synthesis of IkappaB-alpha, following its degradation. Finally, when the cells were exposed to Dex (1 microM) prior to stimulation with IL-1beta (20 ng/ml), Dex was efficient in preventing IL-1beta-induced NF-kappaB activation. The GC antagonist, RU 486 (10 microM), did not prevent any of the effects of Dex reported here.


CONCLUSIONS
Our results indicate that, in CCRF-CEM cells, Dex prevents NF-kappaB activation, induced by IL-1beta, by a mechanism that involves the upregulation of IkappaB-alpha synthesis, and that depends on the early and transient activation of NF-kappaB.
Centre for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, 3004-517 Coimbra, Portugal.
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Castro-Caldas
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Mendes
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Carvalho
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Lopes
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D020672:I-kappa B Proteins / Q000096:biosynthesis* / Q000187:drug effects; D007375:Interleukin-1 / Q000494:pharmacology*; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000188:drug therapy / Q000378:metabolism*; D015735:Mifepristone / Q000494:pharmacology; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D051841:Transcription Factor RelB; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects
D005938:Glucocorticoids; D020672:I-kappa B Proteins; D007375:Interleukin-1; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011518:Proto-Oncogene Proteins; C497593:RELB protein, human; D014157:Transcription Factors; D000072000:NF-KappaB Inhibitor alpha; D051841:Transcription Factor RelB; D015735:Mifepristone; D003907:Dexamethasone