Neurotrophin Interactions and Retinal Ganglion Cell Survival after Axotomy

轴索切除术后神经营养蛋白相互作用和视网膜神经节细胞存活

• 批准号: 6766594
• 负责人: ROSA E BLANCO
• 金额: $ 15.5万
• 依托单位: UNIVERSITY OF PUERTO RICO MED SCIENCES
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6766594
• 关键词: Rana; active sites; axon; biological signal transduction; brain derived neurotrophic factor; cAMP response element binding protein; cell growth regulation; confocal scanning microscopy; cytoprotection; denervation; enzyme activity; fibroblast growth factor; gene expression; growth factor receptors; immunocytochemistry; mitogen activated protein kinase; nerve injury; neural plasticity; neurotrophic factors; optic nerve; polymerase chain reaction; protein kinase C; retinal ganglion; western blottings

In most higher animals, injury to axons within the central nervous system (CNS) leads to the death of axotomized neurons, probably due to loss of target-derived growth factors. The long-term goal of this research is to understand the mechanisms by which growth factors promote the survival of axotomized ganglion cells in the retina. Due to its great accessibility, and ability to regenerate, the frog visual system is an excellent model with which to address this question. After lesioning the frog optic nerve, regeneration occurs and retinal ganglion cells (RGCs) reconnect to their targets. Nevertheless, approximately 50% of the retinal ganglion cells die. We have shown that application of fibroblast growth factor-2 (FGF-2) prevents this cell death in the retina, but only when it is applied to the optic nerve stump. There is accumulating evidence from in vitro studies that the signaling pathways activated by neurotrophins differ based on the location of stimulation, but little is known about how this site-specificity affects the responses to neurotrophins in vivo. In this proposal, we will determine the different intracellular signaling pathways that are activated by the neurotrophic factor FGF-2 when it is applied to the cut nerve, compared to intraocular application, that may explain its location-specific effects on neuronal survival. In the first aim we will test the hypothesis that FGF-2 applied to the cut axons, but not to the cell bodies, activates the transcription factor CREB via the MAPK pathway, in particular via Erk1/2. In the second aim we will determine the mechanisms by which FGF-2 upregulates the synthesis of brain-derived neurotrophic factor (BDNF), another neurotrophin essential for retinal ganglion cell survival, and of the BDNF receptor, TrkB. Finally, in the third aim we will investigate the location-specific effects and signaling pathways of BDNF itself, and determine how the site of application of the factor affects retinal ganglion cell survival. The proposed research will make a significant contribution towards understanding how neurotrophins modulate neuronal survival in a location-specific manner, in an in vivo adult system, which should lead to improved therapeutic methods to promote recovery after injury and disease.

在大多数高等动物中，中枢神经系统（CNS）内轴突的损伤会导致轴突神经元死亡，这可能是由于靶标衍生的生长因子的丧失。这项研究的长期目标是了解生长因子促进视网膜轴突神经节细胞存活的机制。由于其良好的可访问性和再生能力，青蛙视觉系统是解决这个问题的绝佳模型。青蛙视神经受损后，会发生再生，视网膜神经节细胞（RGC）重新连接到它们的目标。然而，大约 50% 的视网膜神经节细胞死亡。我们已经证明，成纤维细胞生长因子-2 (FGF-2) 的应用可以防止视网膜中的细胞死亡，但仅限于将其应用于视神经残端时。体外研究中越来越多的证据表明，神经营养因子激活的信号通路因刺激位置而异，但人们对这种位点特异性如何影响体内神经营养因子的反应知之甚少。在本提案中，我们将确定与眼内应用相比，当神经营养因子 FGF-2 应用于切割神经时，由神经营养因子 FGF-2 激活的不同细胞内信号通路，这可能解释其对神经元存活的位置特异性影响。在第一个目标中，我们将测试以下假设：FGF-2 应用于切割的轴突，但不应用于细胞体，通过 MAPK 途径，特别是通过 Erk1/2 激活转录因子 CREB。在第二个目标中，我们将确定 FGF-2 的机制 上调脑源性神经营养因子 (BDNF)（另一种对视网膜神经节细胞存活至关重要的神经营养因子）和 BDNF 受体 TrkB 的合成。最后，在第三个目标中，我们将研究 BDNF 本身的位置特异性效应和信号通路，并确定该因子的应用位置如何影响视网膜神经节细胞的存活。拟议的研究将为理解神经营养素如何在成人体内系统中以特定位置的方式调节神经元存活做出重大贡献，这将导致改进治疗方法以促进损伤后的恢复和 疾病。