Effect of dexamethasone on interleukin-1beta-(IL-1beta)-induced nuclear factor-kappaB (NF-kappaB) and kappaB-dependent transcription in epithelial cells.
The production of inflammatory mediators by epithelial cells in inflammatory lung diseases may represent an important target for the anti-inflammatory effects of glucocorticoids. Nuclear factor-kappaB (NF-kappaB) is a major activator of inflammatory genes and has been proposed as a target for inhibition by glucocorticoids. We have used human pulmonary type-II A549 and airway epithelial BEAS-2B cells to investigate the effect of glucocorticoids on NF-kappaB regulation and kappaB-dependent transcription. In A549 cells following interleukin-1beta (IL-1beta) treatment, there was no effect of dexamethasone on the disappearance of I kappaB alpha protein, its subsequent reappearance 90-min later or the rapid induction of I kappaB alpha mRNA and transcription rate. Expression of p65 and p50/p105 proteins were also unaffected by dexamethasone. In addition, the rapid IL-1beta-induction of NF-kappaB DNA binding and p65 nuclear localisation was unaffected by short (1-6 hours) dexamethasone pre-treatments. Similarly, BEAS-2B cells showed no effect of dexamethasone on IL-1beta-induced NF-kappaB (p50/p65). Stable transfection of a kappaB-dependent reporter in A549 cells resulted in an 8-9-fold activation by IL-1beta or phorbol ester, that was repressed 30-40% by dexamethasone. However, in these cells, IL-1beta induction of inducible nitric oxide synthase, granulocyte-macrophage colony stimulating factor and cyclooxygenase-2 mRNA showed 70-90% repression by dexamethsone. We, therefore, conclude that in these epithelial cells, the repressive effects of glucocorticoids are not mediated by up-regulation of I kappaB alpha, decreased p50/p65 gene expression or inhibition of NF-kappaB DNA binding. Furthermore, since the maximal repression of IL-1beta or phorbol-ester-induced kappaB-dependent transcription by dexamethasone was less than 40%, simple inhibition of kappaB-dependent transcription cannot by itself account for the full repressive effects of glucocorticoids observed in these cells.
Newton
R
R
Department of Thoracic Medicine, National Heart and Lung Institute, Imperial College School of Medicine, London, UK. robert.newton@ic.ac.uk
Hart
L A
LA
Stevens
D A
DA
Bergmann
M
M
Donnelly
L E
LE
Adcock
I M
IM
Barnes
P J
PJ
D002460:Cell Line; D051546:Cyclooxygenase 2; D004268:DNA-Binding Proteins / Q000032:analysis; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000503:physiopathology; D007375:Interleukin-1 / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D008168:Lung / Q000502:physiology*; D008565:Membrane Proteins; D016328:NF-kappa B / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009687:Nuclear Proteins / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects* / Q000235:genetics; D014162:Transfection / Q000235:genetics
D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D007375:Interleukin-1; D007527:Isoenzymes; D008565:Membrane Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D012333:RNA, Messenger; D003907:Dexamethasone; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D013755:Tetradecanoylphorbol Acetate