High glucose modulates P2X(7) receptor-mediated function in human primary fibroblasts

Aims/hypothesis. Purinergic receptors are a family of newly characterized p lasma membrane molecules involved in several and as yet only partially know n cellular functions such as vascular reactivity, apoptosis and cytokine se cretion. Little is known about the effect extracellular microenvironment ha s on their function. Fibroblasts share several features with smooth muscle cells and are an important constituent of the atherosclerotic plaque. Our a im was to evaluate the effect of high glucose concentration on ATP-mediated responses in human fibroblasts. Methods. Fibroblasts were obtained by skin biopsies and grown at two differ ent glucose concentrations. We evaluated receptor expression by RT-PCR and immunoblotting and receptor localization by immunofluorescence. Plasma memb rane potential and calcium changes were measured by fluorescent indicators. Apoptosis was determined by ethidium bromide staining and caspase-3 activa tion. Results. We show that cells grown in a medium with high glucose concentrati on underwent great ATP; mediated morphological changes, enhanced apoptosis, caspase 3 activation and interleukin-6 release. We identified P2X(7) as th e main purinergic receptor involved in these responses. Furthermore, high g lucose concentration triggered the assembly of P2X(7) into ring-like struct ures located at the periphery of the cells. Conclusion/interpretation. Given that ATP is frequently released into the e xtracellular milieu upon cell and tissue damage, secretory exocytosis or ac tivation of plasma membrane transporters, we hypothesize that ATP receptors participate in the pathogenesis of vascular complications of diabetes.