The β2-subtype of adrenoceptors mediates inhibition of pro-fibrotic events in human lung fibroblasts

Abstract

Fibrosis is part of airway remodelling observed in bronchial asthma and COPD. Pro-fibrotic activity of lung fibroblasts may be suppressed by β-adrenoceptor activation. We aimed, first, to characterise the expression pattern of β-adrenoceptor subtypes in human lung fibroblasts and, second, to probe β-adrenoceptor signalling with an emphasis on anti-fibrotic actions. Using reverse transcription PCR, messenger RNA (mRNA) encoding β 2 -adrenoceptors was detected in MRC-5, HEL-299 and primary human lung fibroblasts, whereas transcripts for β 1 -and β 3 -adrenoceptors were not found. Real-time measurement of dynamic mass redistribution in MRC-5 cells revealed β-agonistinduced G s -signalling. Proliferation of MRC-5 cells (determined by [ 3 H]-thymidine incorporation) was significantly inhibited by β-agonists including the β 2 -selective agonist formoterol (−logIC 50 , 10.2) and olodaterol (−logIC 50 , 10.6). Formoterol's effect was insensitive to β 1 -antagonism (GCP 20712, 3 μM), but sensitive to β 2 -antagonism (ICI 118,551; apparent, pA 2 , 9.6). Collagen synthesis in MRC-5 cells (determined by [ 3 H]-proline incorporation) was inhibited by β-agonists including formoterol (−logIC 50 , 10.0) and olodaterol (−logIC 50 , 10.3) in a β 2 -blockersensitive manner. α-Smooth muscle actin, a marker of myofibroblast differentiation, was down-regulated at the mRNA and the protein level by about 50% following 24 and 48 h exposure to 1 nM formoterol, a maximally active concentration. In conclusion, human lung fibroblasts exclusively express β 2 -adrenoceptors and these mediate inhibition of various markers of pro-fibrotic cellular activity. Under clinical conditions, anti-fibrotic actions may accompany the therapeutic effect of long-term β 2 -agonist treatment of bronchial asthma and COPD.

Prostaglandin D2 Inhibits Collagen Secretion From Lung Fibroblasts by Activating the DP Receptor

“…In this study, treatment with PGD 2 and BW245C immediately increased intracellular cAMP level. Previous reports showed that other agents known to increase intracellular cAMP in lung fibroblasts, including β-agonists and PGE 2 , inhibit collagen synthesis (21,22). Together with our results, DP agonism may inhibit lung fibroblast activation through intracellular cAMP accumulation.…”

Olodaterol shows anti‐fibrotic efficacy in in vitro and in vivo models of pulmonary fibrosis

“…In this study, we demonstrated that olodaterol inhibits the growth factor-induced motility and proliferation of human primary lung fibroblasts with significantly different potency in HLF compared to IPF-LF. Accordingly, other β 2 -adrenoceptor agonists like isoprenaline or formoterol were shown to inhibit proliferation and migration upon FGF-and PDGF-stimulation in different cell lines (Chen et al, 2008;Lamyel et al, 2011). There are several studies suggesting a link between cAMP-dependent PKA activation and cellular migration (Howe, 2004;Chen et al, 2008).…”

“…Upon agonist binding to the receptor, intracellular cAMP is synthesized. Besides their well-proven bronchodilatory properties, β 2 -adrenoceptor agonists, as well as other agents that increase cAMP levels, were shown to attenuate various pro-fibrotic mechanisms, such as proliferation or collagen and α-SMA expression, in cultured fibroblasts (Liu et al, 2004;Schiller et al, 2010;Lamyel et al, 2011). Inhibition of PDEs was also shown to inhibit TGF-β-induced fibrotic events in fibroblasts (Dunkern et al, 2007), and the PDE4 inhibitor roflumilast was shown to attenuate bleomycin-induced lung fibrosis in mice (Cortijo et al, 2009).…”

Exchange Protein Directly Activated by cAMP (epac): A Multidomain cAMP Mediator in the Regulation of Diverse Biological Functions

“…In human lung fibroblasts, cAMP-elevating compounds, such as PGE 2 , EP 2 receptor agonists, b-adrenoceptor agonists, the direct AC activator forskolin, and PDE inhibitors, suppress the transdifferentiation into myofibroblasts as indicated by a reduced expression of a-smooth muscle actin (Kolodsick et al, 2003;Liu et al, 2004;Baouz et al, 2005;Dunkern et al, 2007;Thomas et al, 2007;Lamyel et al, 2011). The PKA agonist 6-BnzcAMP and the Epac agonist 8-CPT-29-O-Me-cAMP also reduce the expression of a-smooth muscle actin (Lamyel et al, 2011), suggesting that fibroblast transformation is regulated by PKA and Epac (Fig. 8C).…”