活化星形胶质细胞和PGE2信号通路在青光眼视神经变性过程中的作用机制

Our long-term objective is to determine how astrocytes contribute to glaucomatous optic neuropathy. Elevated intraocular pressure (IOP) is a major risk factor in glaucoma, resulting in many patients in loss of retinal ganglion cell (RGC) and cupping of the optic disc. Astrocytes are the major cell type in optic nerve head (ONH), support the RGC axons and maintain their functions. Astrocyte-RGC axon communication is key factor maintaining of ONH homeostasis. Previous studies (Zhang et al) demonstrated that epidermal growth factor receptor (EGFR) activation causes early cyclooxygenase-2 (COX-2) induction and makes prostaglandin E2 (PGE2) which may active the astrocytes following optic nerve injury. We also found that nitric oxide (NO) made by activated astrocyte may be responsible for damaging neuron. We hypothesize that PGE2, made by COX2 in reactive astrocytes, is neurotoxic to the axons of the RGC in glaucoma. In this application we propose to identify the signal transduction pathways required for the induction of PGE2/EP receptors and determine the neuroprotective potential of inhibiting PGE2 synthesis in elevated intraocular pressure (IOP) models. Specific aims: 1) Determine the molecular mechanisms by which activation of EGFR tyrosine kinase acts as a signal transduction pathway regulating the induction of PGE2 EP2 in response to elevated IOP (in vivo model). 2) Determine the intracellular mediator pathways that act downstream to activated EGFR to induce COX-2/PGE2 and whether iNOS is downstream of PGE2 synthesis using astrocytes culture model. 3) Determine whether specific inhibition of COX2/PGE2 pathways is neuroprotective for RGC in glaucomatous model. This study will characterize the molecular interactions of reactive astrocytes and RGC axons degeneration and provide novel therapeutic strategies in glaucoma.

青光眼视神经变性的病理基础为视网膜神经节细胞（RGC）轴突损伤后发生细胞凋亡，而越来越多的研究表明介导神经变性的炎性介质也直接参与了视神经损伤。申请人前期工作表明视神经乳头（ONH）星形胶质细胞活化产生的COX-2/PGE-2等促炎因子介导RGC死亡和OHN结构功能失衡。但是，有关的分子调节机制不明。我们假设是抑制星形胶质细胞 PGE2受体表达将有助于改善视神经乳头的功能。我们拟用细胞和动物模型以及特异性抑制途径研究PGE2和其受体在ONH中的表达及其来源并揭示其在青光眼视神经乳头变性过程中的作用机制，明确MAPK信号通路的调节作用。我们的研究将从分子和细胞水平上揭示炎性因子影响视功能的内在调节机制，并为开展以PGE2为靶标的药物研究打下良好基础，也将为探索神经损伤性疾病的发病机制和过程提供新的思路。申请者的研究工作已发表在IOVS，JBC，EER和PNAS等杂志上。

青光眼视神经乳头星型胶质细胞活化，炎性因子的释放和其对视乳头部位结构功能的影响，是青光眼研究领域的重要内容之一。为了明确青光眼的“炎性假说”，在本项目中我们用大鼠视神经乳头的原代星型胶质细胞作为细胞模型，结合青光眼损伤的体内模型探讨了促炎因子）PGE2及其受体EP1-4是如何参与青光眼神经细胞变性机制。我们的研究结果发现PGE2-EPs受体活化参与胶质细胞活化后炎症因子对视神经细胞的损伤，同时也发现活化星型胶质细胞激活mTOR增殖信号通路，mTOR蛋白抑制剂雷帕霉素（rapamycin）（RAPA）对RGC变性具有保护作用。研究结果将为青光眼视神经变性疾病的治疗靶点提供一个很好的思路和方向。