title: Dynamic increase in extracellular ATP accelerates photoreceptor cell apoptosis via ligation of P2RX7 in subretinal hemorrhage.
abstract: Photoreceptor degeneration is the most critical cause of visual impairment in age-related macular degeneration (AMD). In neovascular form of AMD, severe photoreceptor loss develops with subretinal hemorrhage due to choroidal neovascularization (CNV), growth of abnormal blood vessels from choroidal circulation. However, the detailed mechanisms of this process remain elusive. Here we demonstrate that neovascular AMD with subretinal hemorrhage accompanies a significant increase in extracellular ATP, and that extracellular ATP initiates neurodegenerative processes through specific ligation of Purinergic receptor P2X, ligand-gated ion channel, 7 (P2RX7; P2X7 receptor). Increased extracellular ATP levels were found in the vitreous samples of AMD patients with subretinal hemorrhage compared to control vitreous samples. Extravascular blood induced a massive release of ATP and photoreceptor cell apoptosis in co-culture with primary retinal cells. Photoreceptor cell apoptosis accompanied mitochondrial apoptotic pathways, namely activation of caspase-9 and translocation of apoptosis-inducing factor (AIF) from mitochondria to nuclei, as well as TUNEL-detectable DNA fragmentation. These hallmarks of photoreceptor cell apoptosis were prevented by brilliant blue G (BBG), a selective P2RX7 antagonist, which is an approved adjuvant in ocular surgery. Finally, in a mouse model of subretinal hemorrhage, photoreceptor cells degenerated through BBG-inhibitable apoptosis, suggesting that ligation of P2RX7 by extracellular ATP may accelerate photoreceptor cell apoptosis in AMD with subretinal hemorrhage. Our results indicate a novel mechanism that could involve neuronal cell death not only in AMD but also in hemorrhagic disorders in the CNS and encourage the potential application of BBG as a neuroprotective therapy.
authors: Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors: Shoji
authors: S
authors: Notomi
authors: Toshio
authors: T
authors: Hisatomi
authors: Yusuke
authors: Y
authors: Murakami
authors: Hiroto
authors: H
authors: Terasaki
authors: Shozo
authors: S
authors: Sonoda
authors: Ryo
authors: R
authors: Asato
authors: Atsunobu
authors: A
authors: Takeda
authors: Yasuhiro
authors: Y
authors: Ikeda
authors: Hiroshi
authors: H
authors: Enaida
authors: Taiji
authors: T
authors: Sakamoto
authors: Tatsuro
authors: T
authors: Ishibashi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051033:Apoptosis Inducing Factor / Q000235:genetics / Q000378:metabolism; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism; D002829:Choroid / Q000098:blood supply / Q000378:metabolism / Q000473:pathology; D020256:Choroidal Neovascularization; D018920:Coculture Techniques; D053938:DNA Fragmentation / Q000187:drug effects; D006801:Humans; D008268:Macular Degeneration / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010786:Photoreceptor Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D061251:Primary Cell Culture; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology; D058486:Receptors, Purinergic P2X7 / Q000235:genetics / Q000378:metabolism*; D012166:Retinal Hemorrhage / Q000378:metabolism* / Q000473:pathology; D055213:Retinal Pigment Epithelium; D012394:Rosaniline Dyes / Q000494:pharmacology; D014822:Vitreous Body / Q000098:blood supply / Q000378:metabolism / Q000473:pathology
chemical_list: D051033:Apoptosis Inducing Factor; C494830:AIFM1 protein, mouse; D058920:Purinergic P2X Receptor Antagonists; D058486:Receptors, Purinergic P2X7; D012394:Rosaniline Dyes; D000255:Adenosine Triphosphate; D053453:Caspase 9; C004692:coomassie Brilliant Blue