adenosine-5--(n-ethylcarboxamide) and Pulmonary-Fibrosis

Development of pulmonary hypertension is a common and deadly complication of interstitial lung disease. Little is known regarding the cellular and molecular mechanisms that lead to pulmonary hypertension in patients with interstitial lung disease, and effective treatment options are lacking. The purpose of this study was to examine the adenosine 2B receptor (A(2B)R) as a regulator of vascular remodeling and pulmonary hypertension secondary to pulmonary fibrosis. To accomplish this, cellular and molecular changes in vascular remodeling were monitored in mice exposed to bleomycin in conjunction with genetic removal of the A(2B)R or treatment with the A(2B)R antagonist GS-6201. Results demonstrated that GS-6201 treatment or genetic removal of the A(2B)R attenuated vascular remodeling and hypertension in our model. Furthermore, direct A(2B)R activation on vascular cells promoted interleukin-6 and endothelin-1 release. These studies identify a novel mechanism of disease progression to pulmonary hypertension and support the development of A(2B)R antagonists for the treatment of pulmonary hypertension secondary to interstitial lung disease.

Topics: Adenosine-5'-(N-ethylcarboxamide); Animals; Bleomycin; Cells, Cultured; Endothelin-1; Endothelium, Vascular; Humans; Hypertension, Pulmonary; Interleukin-6; Lung Diseases, Interstitial; Male; Mice; Mice, Inbred C57BL; Pulmonary Fibrosis; Purinergic P1 Receptor Agonists; Purines; Pyrazoles; Receptor, Adenosine A2B

Pulmonary fibroblasts regulate extracellular matrix production and degradation and are critical in maintenance of lung structure, function, and repair, but they also play a central role in lung fibrosis. cAMP-elevating agents inhibit cytokine- and growth factor-stimulated myofibroblast differentiation and collagen synthesis in pulmonary fibroblasts. In the present study, we overexpressed adenylyl cyclase 6 (AC6) in pulmonary fibroblasts and measured cAMP production and collagen synthesis. AC6 overexpression enhanced cAMP production and the inhibition of collagen synthesis mediated by isoproterenol and beraprost, but not the responses to butaprost or PGE(2). To examine if increased AC6 expression would impact the development of fibrosis in an animal model, we generated transgenic mice that overexpress AC6 under a fibroblast-specific promoter, FTS1. Lung fibrosis was induced in FTS1-AC6(+/-) mice and littermate controls by intratracheal instillation of saline or bleomycin. Wild-type mice treated with bleomycin showed extensive peribronchial and interstitial fibrosis and collagen deposition. By contrast, FTS1-AC6(+/-) mice displayed decreased fibrotic development, lymphocyte infiltration (as determined by pathological scoring), and lung collagen content. Thus, AC6 overexpression inhibits fibrogenesis in the lung by reducing pulmonary fibroblast-mediated collagen synthesis and myofibroblast differentiation. Because AC6 overexpression does not lead to enhanced basal or PGE(2)-stimulated levels of cAMP, we conclude that endogenous catecholamines or prostacyclin is produced during bleomycin-induced lung fibrosis and that these signals have antifibrotic potential.

Topics: Adenosine-5'-(N-ethylcarboxamide); Adenylyl Cyclases; Alprostadil; Animals; Bleomycin; Calcium-Binding Proteins; Catecholamines; Colforsin; Collagen; Cyclic AMP; Epoprostenol; Fibroblasts; Isoproterenol; Lung; Membrane Microdomains; Mice; Mice, Transgenic; Pulmonary Fibrosis; Rats; S100 Calcium-Binding Protein A4; S100 Proteins; Signal Transduction