Glucocorticoid receptor down-Regulates c-jun amino terminal kinases induced by tumor necrosis factor α in fetal rat hepatocyte primary cultures
✍ Scribed by Juan-José Ventura; César Roncero; Isabel Fabregat; Manuel Benito
- Book ID
- 102244962
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 203 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0270-9139
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✦ Synopsis
The effect of dexamethasone on Jun N-terminal kinase (JNK) activity was assayed by using fetal hepatocytes in primary culture. The addition of tumor necrosis factor ␣ (TNF-␣) caused an increase in JNK in a dose-and timedependent manner. We show that activation of JNK by this extracellular signal is inhibited by dexamethasone in a dose-dependent fashion. This inhibitory effect was observed in cells treated for 10 minutes with dexamethasone in the presence of protein phosphatase inhibitors such as orthovanadate or okadaic acid, or in cells previously treated with actinomycin D. Glucocorticoid receptor (GR) can be precipitated with the fusion protein, GST-c-Jun (1-79), bound to agarose beads. However, the inhibitory effect of glucocorticoids on JNK activity was also observed using ATF-2 as substrate. In addition, dexamethasone inhibits JNK phosphorylation induced by TNF-␣. Finally, we show that GR can also be phosphorylated in tyrosine residues in response to TNF-␣ and epidermal growth factor (EGF) upon ligand-binding. Our results suggest that the antiinflammatory effect of glucocorticoids on the inflammatory pathways induced by TNF-␣ can be explained, at least in part, by modulating JNK activity through a direct proteinprotein interaction; the JNK phosphorylation and tyrosinephosphorylation state of GR may be regulatory steps also involved in that effect. (HEPATOLOGY 1999;29:849-857.