RT Journal Article
SR Electronic
T1 Fibrotic Lung Fibroblasts Show Blunted Inhibition by cAMP Due to Deficient cAMP Response Element-Binding Protein Phosphorylation
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 678
OP 687
DO 10.1124/jpet.105.090324
VO 315
IS 2
A1 Xiaoqiu Liu
A1 Shu Qiang Sun
A1 Rennolds S. Ostrom
YR 2005
UL http://jpet.aspetjournals.org/content/315/2/678.abstract
AB Pulmonary fibroblasts regulate extracellular matrix production and degradation; thus, they are critical for maintenance of lung structure, function, and repair. In pulmonary fibrosis, fibroblasts produce excess collagen and form fibrotic foci that eventually impair lung function, but the mechanisms responsible for these alterations are not known. Receptors coupled to the stimulation of cAMP production can inhibit activation of fibroblasts and thereby are antifibrotic. To test whether this signaling pathway is altered in pulmonary fibrosis, we compared the ability of normal adult human pulmonary fibroblasts to generate and respond to cAMP with that of cells isolated from lungs with idiopathic pulmonary fibrosis. Serum- and transforming growth factor (TGF)-β-stimulated cell proliferation was inhibited ∼50% by forskolin and ∼100% by prostaglandin (PG) E2 in the normal cells but substantially less in the diseased cells. Collagen synthesis was also inhibited >50% by the same drugs in the normal cells but significantly less so in the diseased cells, despite responding with similar increases in cAMP production. Although expression of protein kinase A (PKA) and cAMP-stimulated PKA activity were similar in both the normal and diseased cell types, forskolin- and PGE2-stimulated cAMP response element-binding protein (CREB) phosphorylation was decreased in the diseased cell lines compared with the normal cells. cAMP-mediated activation and TGF-β-mediated inhibition of CREB DNA binding was also diminished in the diseased cells. Thus, pulmonary fibroblasts derived from patients with pulmonary fibrosis are refractory to the inhibition by cAMP due to altered activity of components distal to the activity of PKA, in particular the phosphorylation of CREB. The American Society for Pharmacology and Experimental Therapeutics