P2X7 receptor activation mediates retinal ganglion cell death in a human retina model of ischemic neurodegeneration

PURPOSE. There is evidence implicating ischemia and excitotoxicity in the pathogenesis of glaucoma. ATP-mediated excitotoxicity via activation of the P2X7 receptor (P2XR) has been proposed to play a role in retinal ganglion cell (RGC) degeneration in this disease. The aim of this research was to determine whether stimulation of the P2XR mediated ischemia-induced RGC death in the human retina. METHODS. Human organotypic retinal cultures were exposed to the P2XR agonist 20,30-O-(4-benzoylbenzoyl)-ATP (BzATP) and simulated ischemia (oxygen/glucose deprivation) in the presence or absence of the P2XR antagonist, Brilliant Blue G (BBG). Neuronal death in the RGC layer was quantified by neuronal nuclei (NeuN)-positive cell counts and quantitative real-time PCR for THY-1 mRNA. The P2XR was localized by immunohistochemistry and P2XR mRNA profiling using a cryosectioning technique. RESULTS. P2XR stimulation by BzATP (100 lM) induced loss of RGC markers in human organotypic retinal cultures (HORCs), which was inhibited by BBG (1 µM). Simulated ischemia led to loss of RGCs that was also inhibited by BBG, indicating that ischemia-induced RGC degeneration was mediated by the P2XR. The P2XR was immunolocalized to the outer and inner plexiform layers of the human retina, and P2XR mRNA expression was confirmed in the inner retina and ganglion cell layer. CONCLUSIONS. These studies demonstrated that stimulation of the P2XR can mediate RGC death and that this mechanism plays a role in ischemia-induced neurodegeneration in the human retina.