Purines and the Health of Retinal Ganglion Cells

描述（由申请人提供）：青光眼是世界上致盲的主要原因之一，其特征是视网膜神经节细胞的丧失。虽然该疾病与眼压升高密切相关，但目前尚不清楚眼压升高如何导致细胞死亡。这一建议是基于一种新的假设，即IOP升高会触发ATP的释放，从而过度刺激视网膜神经节细胞上的细胞毒性P2X7受体。压力依赖性ATP释放的证据将在青光眼大鼠模型中得到证实，而P2X7受体刺激的毒性作用将在体内被确定。通过这两种方法激活的凋亡前基因将被表征和比较，以确定体内压力反应的嘌呤能成分。ATP释放和P2X7受体刺激的机制将在细胞水平上进行探讨。pannexin半通道在伴随神经节细胞伸展和肿胀的ATP释放中的作用将被确定，并且这种释放的ATP自刺激神经节细胞P2X7受体的能力将通过记录细胞内钙水平和全细胞离子电流来评估。将体内过量ATP的证据与相关机制的识别相结合，确保该建议既具有创新性又具有相关性，为青光眼中压力增加如何损害神经节细胞提供了新的见解。

DESCRIPTION (provided by applicant): Glaucoma is a major cause of blindness in the world and is characterized by a loss of retinal ganglion cells. Although the disease is closely associated with elevated intraocular pressure (IOP), it is unclear how this pressure leads to cell death. This proposal is based upon the novel hypothesis that elevated IOP triggers the release of ATP which over-stimulates cytotoxic P2X7 receptors on retinal ganglion cells. Evidence for pressure-dependent ATP release will be confirmed using rat models of glaucoma, while the toxic effects of P2X7 receptor stimulation will be determined in vivo. The pre-apoptotic genes activated by both approaches will be characterized and compared to identify the purinergic component of the response to pressure in vivo. The mechanisms underlying the release of ATP and of P2X7 receptor stimulation will be probed on a cellular level. The role of pannexin hemichannels in the ATP release that accompanies ganglion cell stretch and swelling will be determined, and the ability of this released ATP to autostimulate P2X7 receptors on ganglion cells will be evaluated by recording intracellular calcium levels and whole cell ion currents. Combining in vivo evidence for excess ATP with the identification of the responsible mechanisms ensures this proposal will be both innovative and relevant, providing new insight into how increased pressure damages ganglion cells in glaucoma. PUBLIC HEALTH RELEVANCE: This project is based on the hypothesis that retinal ganglion cells are damaged in glaucoma by pressure-dependent release of excess ATP into the retina which stimulates P2X7 receptors on retinal ganglion cells. This proposal will confirm this relationship and explore how this pathological release occurs with the aim of preventing the initial stages of damage in glaucoma.