Pharmacological characterization of purine receptors in bovine fibroblast-like synoviocytes

Growing evidence also suggests that extracellular nucleotides, acting through purinergic receptors, play a central role in the regulation of bone and cartilage metabolism. Fibroblast-like synoviocytes are closely involved in the pathogenesis of joint destruction by an increased proliferation and by the secretion of a wide range of pro-inflammatory mediators including cytokines, growth factors and lipid mediators. The aim of the present study was to investigate from a biochemical, physico chemical and functional point of view A1, A2A, A2B and A3 adenosine receptors and P2X1 and P2X3 purinergic receptors in bovine fibroblast-like synoviocytes. Saturation binding experiments on purine receptors in bovine fibroblast-like synoviocytes were performed and demonstrated the presence of all the adenosine receptors and P2X1 and P2X3 purinergic subtypes. The affinity of typical adenosine and purinergic ligands were studied through competition binding experiments. Thermodynamic analysis of the binding of purine receptors was studied to investigate the forces driving drug-receptor coupling and to verify if adenosine and purinergic ligands were thermodynamically discriminated. The potency of typical purine agonists and antagonists was evaluated in different functional assays such as intracellular cyclic AMP accumulation, PGE2 release and NO production. In particular, A2A but not A3 agonists were involved in the negative modulation of PGE2 synthesis confirming the anti-inflammatory role of the A2A receptors. Well-known purinergic agonists were able to increase NO and PGE2 production suggesting that the stimulation of purinergic receptors increase the inflammation processes