Human primary fibroblasts in vitro express a purinergic P2X(7) receptor counted to ion fluxes, microvesicle formation and IL-6 release

We have investigated reponses to extracellular ATP in human fibroblasts obt ained by skin biopsies. Our data show that these cells express a P2X(7) pur inergic receptor, as judged by (1) RT-PCR with specific primers, (2) reacti vity with a specific anti-P2X(7) antiserum, (3) activation by the selective P2X agonist benzoylbenzoylATP and (4) stimulation of transmembrane ion flu xes, Stimulation with benzoylbenzoylATP, and to a lesser extent with ATP, a lso caused striking morphological changes and increased formation of cytopl asmic microvesicles. These changes were fully reversible upon nucleotide re moval. Two known blockers of P2X receptors, oxidised ATP and pyridoxalphosp hate-6-azophenyl-2',4'-disulfonic acid, inhibited the morphological changes fully and the ion fluxes partially. The residual rise in intracellular Ca2 + levels and membrane depolarization observed in the presence of the inhibi tors were dependent upon activation of a P2Y-type receptor exhibiting a pec uliar pharmacological profile, in that CTP was the preferred agonist, ATP s timulation triggered release of the pro-inflammatory cytokine IL-6 in fibro blasts pre-treated with PMA and bacterial endotoxin. These observations rev eal a novel pathway for fibroblast activation and for their recruitment in the inflammatory response.