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D. Yang, S. G. Elner, A. J. Clark, H. R. Petty, V. M. Elner; Extracellular ATP Induces Ca2+ Signaling and Apoptosis in Human Retinal Pigment Epithelium. Invest. Ophthalmol. Vis. Sci. 2010;51(13):480.
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Studies have indicated that a variety of cell systems express P2 purinoceptors and undergo functional changes in response to extracellular adenosine triphosphate (ATP). The purpose of this study was to determine whether extracellular ATP induces Ca2+ signaling and apoptosis in primary cultures of human retinal pigment epithelial (RPE) cells.
Intracellular calcium levels were determined using calcium probe, indo-1-AM. P2X7 mRNA and protein expression were detected by reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence microscopy, respectively. RPE apoptosis was evaluated by caspase-3 detection, Hoechst staining and cell death detection ELISA.
Both ATP and the P2X7 agonist benzoylbenzoyl ATP (BzATP) increased intracellular Ca2+ in RPE cells. The Ca2+ induced by ATP was delayed and significantly inhibited by oxidized ATP (oATP), a P2X7 antagonist. Suramin only slightly inhibited the Ca2+ increase. ATP treatment increased the number of caspase-3 positive and apoptotic RPE cells, and DNA fragmentation. All these increases were significantly reduced by oATP. RT-PCR and immunofluorescence microscopy revealed the presence of P2X7 receptor mRNA and protein in RPE cells.
Extracellular ATP induces RPE Ca2+ signaling and apoptosis. Activation of P2 purinoceptors including P2X7 might contribute to ATP-induced Ca2+ signaling and apoptosis in the RPE.
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