Abstract

not-yet-known not-yet-known not-yet-known unknown Background and purpose: Idiopathic pulmonary fibrosis (IPF), evokes scarring of the lung due to extracellular matrix deposition by fibroblasts. Evidence suggests that inhaled treprostinil slows the decline in pulmonary function in IPF. The molecular mechanisms by which cAMP mobilizing agents, alter human lung fibroblast (HLF) expression of matrix proteins remain unclear. We posit that the antifibrotic properties of treprostinil are driven by differential cAMP mobilizing responses mediated by the IP receptor. Experimental approach: As a model of lung fibrosis, TGF-β-stimulated primary HLF were used to measure collagen 1A1, PAI1, and growth factor levels in the presence and absence of cAMP mobilizing agents. The necessity of receptor activation in inhibiting TGF-β-induced fibrosis was determined using soluble receptor inhibitors and selective inhibition of receptor expression with siRNA. Key results: Treprostinil decreased TGF-β-induced extracellular matrix and growth factors production by HLF, the magnitude of the inhibition was greater than other cAMP mobilizing GPCR agonists despite comparable increases in cAMP levels. Treprostinil inhibition of TGF-β-induced collagen 1A1, PAI-1, and IGFBP3 was mediated through the activation of the IP receptor. The EP2 receptor was partially involved in the inhibition of TGF-β-induced collagen 1A1 by treprostinil or prostaglandin E2. β2 agonists had little effect on TGF-β-induced collagen 1A1, PAI-1, and IGFBP3 expression. The inhibitory effects on TGF-β-induced matrix expression by treprostinil required Gαs activation. Treprostinil inhibition of TGF-β-induced IGFBP3 expression also correlated with the inhibition of TGF-β-induced phosphorylation of AKT. Conclusion and implications: Understanding the differential effects of cAMP mobilizing pathways on HLF fibrotic signatures can provide insight into developing novel targets to manage IPF.