Pharmacological Blockade of A_2A Receptors Prevents Dermal Fibrosis in a Model of Elevated Tissue Adenosine

Adenosine is a potent modulator of inflammation and tissue repair. We have recently reported that activation of adenosine A_2A receptors promotes collagen synthesis by human dermal fibroblasts and that blockade or deletion of this receptor in mice protects against bleomycin-induced dermal fibrosis, a murine model of scleroderma. Adenosine deaminase (ADA) is the principal catabolic enzyme for adenosine in vivo, and its deficiency leads to the spontaneous development of pulmonary fibrosis in mice. The aim of this study was to characterize further the contributions of endogenous adenosine and adenosine A_2A receptors to skin fibrosis. Taking advantage of genetically modified ADA-deficient mice, we herein report a direct fibrogenic effect of adenosine on the skin, in which increased collagen deposition is accompanied by increased levels of key mediators of fibrosis, including transforming growth factor β1, connective tissue growth factor, and interleukin-13. Pharmacological treatment of ADA-deficient mice with the A_2A receptor antagonist ZM-241385 prevented the development of dermal fibrosis in this model of elevated tissue adenosine, by reducing dermal collagen content and expression of profibrotic cytokines and growth factors. These data confirm a fibrogenic role for adenosine in the skin and reveal A_2A receptor antagonists as novel therapeutic agents for the modulation of dermal fibrotic disorders.