Adenosine A2A receptors in diffuse dermal fibrosis pathogenic role in human dermal fibroblasts and in a murine model of scleroderma

Objective. Adenosine regulates inflammation and tissue repair, and adenosine A(2A) receptors promote wound healing by stimulating collagen matrix production. We therefore examined whether adenosine A(2A) receptors contribute to the pathogenesis of dermal fibrosis. Methods. Collagen production by primary human dermal fibroblasts was analyzed by real-time polymerase chain reaction, C-14-proline incorporation, and Sircol assay. Intracellular signaling for dermal collagen production was investigated using inhibitors of MEK-1 and by demonstration of ERK phosphorylation. In vivo effects were studied in a bleomycin-induced dermal fibrosis model using adenosine A(2A) receptor-deficient wild-type littermate mice, C57BL/6 mice, and mice treated with adenosine A(2A) receptor antagonist. Morphometric features and levels of hydroxyproline were determined as measures of dermal fibrosis. Results. Adenosine A(2A) receptor occupancy promoted collagen production by primary human dermal fibroblasts, which was blocked by adenosine A(2A), but not A(1) or A(2B), receptor antagonism. Adenosine A(2A) receptor ligation stimulated ERK phosphorylation, and A(2A) receptor-mediated collagen production by dermal fibroblasts was blocked by MEK-1 inhibitors. Adenosine A(2A) receptor-deficient and A(2A) receptor antagonist-treated mice were protected from developing bleomycin-induced dermal fibrosis. Conclusion. These results demonstrate that adenosine A(2A) receptors play an active role in the pathogenesis of dermal fibrosis and suggest a novel therapeutic target in the treatment and prevention of dermal fibrosis in diseases such as scleroderma.