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A5740 - The Selective Prostacyclin Receptor Agonist ACT-333679 Attenuates and Reverses TGFb1-Induced Profibrotic Phenotype in Primary Human Lung Fibroblasts
Author Block: K. Zmajkovicova, K. Menyhart, Y. Bauer, B. Renault, R. Studer, M. Bollinger, M. Schnoebelen, O. Nayler, J. Gatfield; Actelion Pharmaceuticals Ltd., Allschwil, Switzerland.
Rationale: Idiopathic pulmonary fibrosis (IPF) is a life-threatening progressive disease characterized by aberrant fibroblast activation, proliferation and extracellular matrix (ECM) synthesis, finally leading to lung tissue dysfunction. Novel treatments should not only slow down, but halt or even revert tissue remodeling. Cyclic adenosine monophosphate (cAMP) signaling is known to confer anti-fibrotic effects by inhibiting key fibroblast functions such as proliferation, migration, growth factor/cytokine secretion and ECM synthesis, but the molecular mechanisms of this inhibition are not well understood. ACT-333679 is a selective agonist of the prostacyclin receptor (IP receptor), a G protein coupled receptor known to increase cellular cAMP levels. Since the IP receptor is expressed in lung fibroblasts, it represents a viable target to analyze the anti-fibrotic effects of cAMP elevation in this cell type and to decipher the molecular mechanisms linking cAMP elevation and inhibition of fibrosis. Methods and Results: As an in vitro disease model system, we used primary human lung fibroblasts derived from non-IPF and IPF donors that we stimulated with pro-fibrotic factors in the presence or absence of ACT-333679 and in which we then measured a multitude of fibrosis-related parameters. Treatment of fibroblasts with ACT-333679 activated the IP receptor and induced downstream cAMP signaling. ACT-333679 prevented fibroblast-to-myofibroblast transformation, proliferation, ECM synthesis and profibrotic cytokine secretion with potencies in the low nM range. It also exerted relaxant effects in cell contraction assays. Furthermore, ACT-333679 was able to revert an already established fibrotic phenotype. Via gene-expression profiling of IPF fibroblasts treated with TGFb1 together with ACT-333679 we identified a unique gene signature and established a novel molecular link between IP receptor/cAMP signaling and inhibition of profibrotic pathways. Conclusion: In this study we characterize ACT-333679 as a potent and efficacious anti-fibrotic agent in primary human lung fibroblasts and identify a novel signaling mechanism involved in its anti-fibrotic properties.