慢性高眼压视网膜Müller细胞激活对神经节细胞损伤的作用及机制探讨

青光眼是重要的致盲性眼病，主要病理变化是神经节细胞（RGC）的凋亡。近期研究发现，激活RGC的P2X7受体可诱导RGC凋亡，提示嘌呤受体在RGC损伤中有重要作用。在青光眼病理过程中，激活的Müller细胞释放多种活性物质（可能包括ATP），参与RGC损伤。我们初步实验结果发现，慢性高眼压早期Müller细胞的激活和mGluR I受体活化有关，而mGluR I受体是Gq偶联受体，与细胞ATP释放密切相关。因此，我们提出的假设是，慢性眼压增高，细胞间隙过量的谷氨酸作用于mGluR I，导致Müller细胞激活，并且ATP释放增加，ATP作用于RGC上P2X7受体，导致细胞膜通透性增加、钙离子内流等，最终导致RGC凋亡。为此，本课题拟采用体内及体外实验，利用膜片钳电生理、免疫组织化学、Western blot等多种技术，探讨慢性高眼压大鼠Müller细胞激活后对RGC凋亡的作用及其机制。

Glaucoma is a leading cause of blindness, and apoptosis of retinal ganlion cells (RGCs) occures in all forms of glaucoma. Up to date, the mechanisms underlying RGC death in glaucoma have not been completely cleared. Recent studies showed that activation of P2X7 receptors may induce RGC apoptosis, indicating that purinergic receptors play an important role in RGC injuries. Reactivation (gliosis) of Müller cell in glaucoma may produce and release various cytotoxic factors, such as NO, TNF-?, ROS and PGE2, etc., even including ATP, which have been shown to induce RGC apoptosis and death. Our preliminary data showed that Müller cell gliosis was due to over-activation of mGluR I in a rat chronic intraocular hypertension (COH) model. mGluR I is coupled with Gq subunit of G proteins. It has been reported that activation of Gq protein induced ATP release from glial cells. Therefore, we hypothesized that over-activation of mGluR I by extracellular eccessive glutamate in the COH triggers Müller cell gliosis. At the same time, activation of mGluR I also induces vesicular ATP release from reactivated Müller cells. ATP may bind and activate P2X7 receptor in RGCs, thus increasing membrane permeability and Ca2+ influx, thereby, leading to RGCs apoptosis. Our proposal aims to study the effects of Müller cell gliosis on RGC apoptosis in the COH, and to explore the underlying mechanisms by using whole-cell patch-clamp, immunohistochemistry, Western blot and calcium imaging techniques.