['The retinal pigment epithelium (RPE) is considered a primary site of pathology in age-related macular degeneration (AMD), which is the most prevalent form of irreversible blindness worldwide in the elderly population. Extracellular adenosine triphosphate (ATP) acts as a key signaling molecule in numerous cellular processes, including cell death. The purpose of this study was to determine whether extracellular ATP induces apoptosis in cultured human RPE.', 'RPE apoptosis was evaluated by caspase-3 activation, Hoechst staining, and DNA fragmentation. Intracellular Ca(2+) levels were determined by both a cell-based fluorometric Ca(2+) assay and a ratiometric Ca(2+) imaging technique. P2X(7) mRNA and protein expression were detected by reverse transcription-polymerase chain reaction (RT-PCR) and confocal microscopy, respectively.', "The authors found that both the endogenous P2X(7) agonist ATP and the synthetic, selective P2X(7) agonist 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP) induced RPE apoptosis, which was significantly inhibited by P2X(7) antagonist oxidized ATP (oATP) but not by the P2 receptor antagonist suramin; both ATP and BzATP increase intracellular Ca(2+) via extracellular Ca(2+) influx; both ATP- and BzATP-induced Ca(2+) responses were significantly inhibited by oATP but not by suramin; ATP-induced apoptosis was significantly inhibited or blocked by BAPTA-AM or by low or no extracellular Ca(2+); and P2X(7) receptor mRNA and protein were expressed in RPE cells."] Does activation of P2X receptors induce apoptosis in human retinal pigment epithelium?