Adenosine A2A receptor promotes collagen type III synthesis via β-catenin activation in human dermal fibroblasts.

Background and purpose: Adenosine A2A receptor stimulation promotes the synthesis of collagen type I and type III (Col1 and Col3), mediators of fibrosis and scarring. The A2A receptor modulates collagen balance via cAMP/PKA/p38-MAPK/Akt pathways. Wnt signalling is important in fibrosis and the cAMP and Wnt pathways converge. Because the A2A receptor is Gs-linked and increases cAMP, we determined whether A2A receptors and Wnt signalling interact. Experimental approach: Total β-catenin, de-phosphorylated β-catenin (canonical activation, de-phospho β-catenin) and phosphorylated β-catenin at Ser552 (non-canonical activation, p-Ser552 β-catenin) levels were determined in primary human dermal fibroblasts, cytosol and nucleus, by western blot analysis and fluorescence microscopy, before and after stimulation by A2A receptor-selective agonist CGS21680, with/without A2A receptor-selective antagonist (SCH56261) pretreatment. β-Catenin was knocked down by transfection with scrambled-siRNA or specific-siRNA, and Col1 and Col3 levels determined by western blots. Key

Results: CGS21680 stimulation rapidly (15 min) increased cellular β-catenin levels. Both de-phospho β-catenin and p-Ser552 β-catenin levels were also increased. CGS21680 stimulated the translocation of total de-phospho and p-Ser552 β-catenin to the nucleus. A2A receptor-stimulation increased Col1 synthesis similarly in β-catenin knockeddown and scrambled cells. However, β-catenin knockdown abolished the increase in Col3 synthesis induced in A2A receptor-stimulated fibroblasts. Conclusions and implications: A2A receptor stimulation promotes Col3 synthesis via the activation of canonical and non-canonical β-catenin, consistent with a role for A2A receptors in dermal fibrosis and scarring.