Glucocorticoids Modulate TGF-β Production

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TGF-β is thought to play a central role in pulmonary fibrosis inducing fibroblast differentiation and extracellular matrix synthesis. In human lung fibroblasts, it is still unclear how various TGB-β isoforms affect TGF-β production and whether glucocorticoids, commonly used agents to treat fibrotic lung disease, modulate these processes. To this end, human fetal lung fibroblasts (HFL-1) were cultured with various concentrations of glucocorticoids (budesonide, dexamethasone or hydrocortisone) with and without TFG-β1, -β2, and -β3. TGF-β mRNA was assessed by real time RT-PCR. Smad 2, 3, and 4 and AP-1 complex (c-fos and c-Jun) cellular localization were evaluated by immunostaining. TGF-β2 and -β3 stimulated TGF-β1 production significantly (p < 0.01 relative to control). TGF-β1 stimulated TGF-β2 production (p < 0.01 relative to control). TGF-β3 was undetectable. Glucocorticoids significantly inhibited TGF-β1 and -β2 production and reduced expression of the upregulated TGF-β1 and -β2 mRNA induced by exogenous TGF-β1, -β2 or -β3 (p < 0.01 for each) but had no effect on Smads. Although c-jun-related nuclear staining was not intensified in TGF-β-stimulated cells, it was reduced by glucocorticoids. Thus, TGF-β isoforms may stimulate production of various TGF-β isoforms in the lung. Glucocorticoids then may block TGF-β production by modulating mRNA levels and c-Jun.

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