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Transforming growth factor-? impairs glucocorticoid activity in the A549 lung adenocarcinoma cell line.

ABSTRACT:

Background and purpose

The lung adenocarcinoma cell line, A549, undergoes epithelial-mesenchymal cell transition (EMT) in response to TGF-?. Glucocorticoids do not prevent the EMT response, but TGF-? induced resistance to the cytokine-regulatory action of glucocorticoids. We sought to characterize the impairment of glucocorticoid response in A549 cells.

Experimental approach

A549 cells were exposed to TGF-? for up to 96?h before glucocorticoid treatment and challenge with IL-1? to assess glucocorticoid regulation of IL-6 and CXCL8 production. Nuclear localization of the glucocorticoid receptor ? (GR?) was ascertained by immunofluorescence and Western blotting. Transactivation of the glucocorticoid response element (GRE) was measured with a transfected GRE-secreted human placental alkaline phosphatase reporter.

Key results

TGF-? (40-400?pM) reduced the maximum inhibitory effect of dexamethasone on IL-1?-induced IL-6 and CXCL8 production. The impaired glucocorticoid response was detected with 4?h of TGF-? (40?pM) exposure (and 4?h IL-1? to induce CXCL8 expression) and therefore was not secondary to EMT, a process that requires longer incubation periods and higher concentrations of TGF-?. TGF-? also impaired dexamethasone regulation of granulocyte-macrophage colony-stimulating factor in thrombin-stimulated BEAS-2B epithelial cells. Impaired regulation of CXCL8 was associated with markedly reduced GRE transactivation and reduced induction of mRNA for I?B?, the glucocorticoid-inducible leucine zipper and the epithelial sodium channel (SCNN1A). The expression, cellular levels and nuclear localization of GR? were reduced by TGF-?.

Conclusions and implications

We have identified mechanisms underlying the impairment of responses to glucocorticoids by TGF-? in the A549 and BEAS-2B cell lines.

SUBMITTER: Salem S

PROVIDER: S-EPMC3402769 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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Publications

Transforming growth factor-β impairs glucocorticoid activity in the A549 lung adenocarcinoma cell line.

Salem S S Harris T T Mok J S L JS Li M Y S MY Keenan C R CR Schuliga M J MJ Stewart A G AG

British journal of pharmacology 20120801 7

<h4>Background and purpose</h4>The lung adenocarcinoma cell line, A549, undergoes epithelial-mesenchymal cell transition (EMT) in response to TGF-β. Glucocorticoids do not prevent the EMT response, but TGF-β induced resistance to the cytokine-regulatory action of glucocorticoids. We sought to characterize the impairment of glucocorticoid response in A549 cells.<h4>Experimental approach</h4>A549 cells were exposed to TGF-β for up to 96 h before glucocorticoid treatment and challenge with IL-1α to ...[more]

PMID: 22300324

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