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KMID : 0383820000480050682
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Tuberculosis and Respiratory Diseases
2000 Volume.48 No. 5 p.682 ~ p.698
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Inhibitory Mechanism on NF-κB Transactivation by Dexamethasone in Pulmonary Epithelial Cells
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1이계영/1Kye Young Lee
1김윤섭/1고미혜/1박재석/1지영구/1김건열/2관상준/1Yoon Seop Kim/1Mi Hye Ko/1Jae Seok Park/1Young Koo Jee/1keun Youl Kim/2Sahng June Kwak
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Abstract
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-Abstract-
Glucocorticoid receptor (GR) functions as a suppressor of inflammation by inhibiting
the expression of many cytokine gene activated by NF-κB. The goal of this study is
to investigate the mechanism by which GR repress NF-κB activation in lung epithelial
cells. We used A549 and BEAS-2B lung epithelial cell lines. Using IgGκ-NF-κB
luciferase reporter gene construct, we found that dexamethasone significantly suppressed
TNF-α-induced NF-κB activation and the overexpression of GR showed
dose-dependent reduction of TNF-α-induced NF-κB activity in both cell lines.
However, DNA binding of NF-κB induced by TNF-α in electromobility shift assay
was not inhibited by dexamethasone. Super shift assay with anti-p65 antibody
demonstrated the existence of p65 in NF-κB complex induced by TNF-α Western blot
showed that IκBα degradation induced by TNF-α was not affected by dexamethasone
and IκBκ was not induced by dexamethasone, neither. To evaluate p65 specific
transactivation, we adopted co-transfection study of Ga14-p65TA1 or TA2 fusion protein
expression system together with 5xGa14-luciferase vector. Co-transfection of GR with
Ga14-p65TA1 or TA2 repressed luciferase activity profoundly to the level of 10-20% of
p65TA1- or TA2-induced transcriptional activity. And this transrepressional effect was
abolished by co-transfection of CBP or SRC-1 expression vectors. These results suggest
that Gr-mediated transrepression of NF-κB in lung epithelial cells is through competing
for binding to limiting amount of transcriptional coactivators, CBP or SRC-1.
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KEYWORD
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