Transforming growth factor-beta 1 increases glucocorticoid binding and signaling in macrophages through a Smad- and activated protein-1-mediated process.
BACKGROUND
Renal inflammation is regulated by a network of local and systemic mediators. Of them, transforming growth factor-beta1 (TGF-beta 1) and glucocorticoids play an important role in deactivating monocytes/macrophages. We examined the hypothesis that TGF-beta 1 effects may be partially achieved through modulation of the sensitivity of these cells to glucocorticoids.


METHODS
Human promonocytic U 937 cells differentiated to a mature macrophage-like phenotype were exposed to recombinant TGF-beta 1 before specific binding of [3H] dexamethasone was measured. The expression of glucocorticoid receptor (GR) was examined by RNase protection assay and Western blot analysis. The role of Smad 2/3 and activator protein 1 (AP-1) in the response to TGF-beta 1 was determined by introducing transdominant negative mutants and decoy oligodeoxynucleotides, respectively.


RESULTS
U 937 cell exposure to TGF-beta 1 caused a dose- and time-dependent increase in [3H] dexamethasone binding to these cells, with a < or =twofold increase in the number of binding sites per cell, without modification of the affinity. The changes in glucocorticoid binding were associated with identical changes in GR protein and mRNA levels, that were explained by an increase in GR gene transcription rather than by posttranscriptional mechanisms. Functional inactivation of Smad 2/3 and AP-1 limited the response to TGF-beta 1, indicating a role for these transcription factors. Finally, increases in glucocorticoid binding to GR were responsible for increases in the ability of GR to transactivate minimal promoters containing glucocorticoid-responsive elements (GRE) [MMTV-Luc and (GRE)2 TK-Luc].


CONCLUSIONS
TGF-beta 1 increases glucocorticoid binding and signaling in inflammatory cells through a Smad 2/3- and AP-1-mediated process. This may represent a new target for intervention to increase glucocorticoid responsiveness.
Peltier
Julie
J
Unité INSERM 489/Service d'Explorations Fonctionnelles Multidisciplinaires, AP-HP Hôpital Tenon, Paris, France.
Perez
Joëlle
J
Bellocq
Agnès
A
Escoubet
Brigitte
B
Fouqueray
Bruno
B
Baud
Laurent
L
D002273:Carcinogens / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D005938:Glucocorticoids / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D011965:Receptors, Glucocorticoid / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology; D051899:Smad2 Protein; D051900:Smad3 Protein; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000276:immunology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D020298:U937 Cells; D015854:Up-Regulation / Q000187:drug effects
D002273:Carcinogens; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D016209:Interleukin-8; D011965:Receptors, Glucocorticoid; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; C508960:TGFB1 protein, human; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D013755:Tetradecanoylphorbol Acetate