IGF-I PROTECTS NEURONS FROM GLUCOSE INDUCED CELL DEATH

IGF-I 保护神经元免受葡萄糖引起的细胞死亡

• 批准号: 2036489
• 负责人: James W Russell
• 金额: $ 8.21万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-12-01 至 2001-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2036489
• 关键词: actins; apoptosis; axon; blood glucose; confocal scanning microscopy; dendrites; developmental neurobiology; diabetic neuropathy; electron microscopy; enzyme activity; growth factor receptors; hyperglycemia; in situ hybridization; insulinlike growth factor; laboratory rat; light microscopy; neurons; neuroprotectants; neurotoxicology; phosphatidylinositol 3 kinase; phosphorylation; receptor expression; southern blotting; tissue /cell culture; western blottings

Diabetic neuropathy (DN) is the most common cause of peripheral neuropathy in the United States, yet the pathogenesis remains unknown. Although diabetes can affect all peripheral neurons, sensory neurons are most commonly affected, possibly because dorsal root ganglion (DRG) neurons reside outside the blood-nerve barrier. Hyperglycemia has been implicated in both animal and human studies in the pathogenesis of DN and recent clinical trials have shown a reduction in the progression of DN with careful control of blood glucose an intensive insulin therapy. However even excellent glycemic control fails to prevent or reverse DN. Insulin-alike growth factor I (IGF-I) can improve glycemic control in diabetes and is able to promote neuronal growth, development, and regeneration of neurons. In ongoing preliminary studies, we find that hyperglycemia leads to impaired rat DRG sensory neuronal growth and programmed cell death (PCD). In both paradigms, IGF-I is neuroprotective. Our initial investigations of IGF-I neuroprotection reveal that 1) IGF-I acts trough the type I IGF receptor (IGF-IR activation results in downstream phosphorylation of focal adhesion proteins involved in organization of the actin cytoskeleton and neurite formative, and 3) IGF-IR activation of phosphatidylinositol-3 kinase (PI-3K) is essential for rescue of neuronal cells from PCD. We have developed a novel hypothesis to explain hyperglycemic coupled neurotoxicity. We speculate that high glucose alters IGF-IR activation in DRG neurons. This result in changes in the phosphorylation of focal adhesion proteins which results in disruption of the actin cytoskeleton and impairs DGR neurite growth. We believe subsequent cytoskeletal changes alone, or in conjunction with direct glucose toxicity, induce PCD in DRG neurons. Activation of IGF-IR 1) prevents PCD by enhancing focal adhesion protein phosphorylation and stabilizing the cytoskeleton, and/or 2) blocks PCD by activating PI 3K pathways, which may effect PCD regulatory proteins like bcl-2 and/or death proteases. In this proposal we will test each component of the model. We have 2 aims: 1. Examine the effect of high glucose on DRG neurons. In DRG neurons, in response to high glucose, examine: a) DRG neuronal morphology and neurite growth b) IGF-IR transcription, cell surface abundance, and autophosphorylation c) Phosphorylation of focal adhesion proteins and the DRG cytoskeleton and d) PCD in DRG 2. Characterize IGF-IR protection of DRG neurons following glucose exposure. In DRG neuron, in response to high glucose, examine the effect of IGR-I on: a) DRG neuronal morphology and neurite growth b) IGF-IR transcription, cell surface abundance, and autophosphorylation c) Phosphorylation of focal adhesion proteins and the DRG cytoskeleton 3. Investigate the components underlying IGF-IR rescue of DRG from glucose-induced PCD. a) Determine the association between the observed changes in focal adhesion proteins, the cytoskeleton, an PCD pathways in response to high glucose b) Examine the effect of high glucose and IGF-I on IGF-IR activation of PI-3K c) Ascertain if IGF-IR activation prevents PCD by promoting expression of regulatory proteins that suppress cell death, like bcl-2 d) Determine if high glucose promotes PCD by activation of death proteases, and the role of IGF-IR activation in modulating this PCD pathway. IGF-I is currently undergoing evaluation in clinical trails of diabetic neuropathy. The current proposal will help elucidate the mechanisms underlying the role of IGF-I in preventing changes in neuronal morphology and PCD in diabetic neuropathy.

糖尿病神经病（DN）是周围最常见的原因 在美国的神经病，但发病机理仍然未知。 尽管糖尿病会影响所有周围神经元，但感觉神经元是 最常见的影响，可能是因为背根神经节（DRG） 神经元居住在血液障碍物外。 高血糖已经存在 与动物和人类研究有关DN的发病机理 最近的临床试验表明， DN仔细控制血糖一种强化胰岛素疗法。 但是，即使是出色的血糖控制也无法预防或反向DN。 胰岛素类似生长因子I（IGF-I）可以改善血糖控制 糖尿病，能够促进神经元的生长，发育和 神经元的再生。 在正在进行的初步研究中，我们发现 高血糖导致大鼠DRG感觉神经元的生长和 程序性细胞死亡（PCD）。在这两个范式中，IGF-I是 神经保护性。 我们对IGF-I神经保护的初步研究 揭示1）IGF-I起作用I型IGF受体（IGF-IR） 激活导致局灶性粘附的下游磷酸化 参与肌动蛋白细胞骨架和神经突组织的蛋白质 形成性和3）磷脂酰肌醇-3激酶的IGF-IR激活 （PI-3K）对于从PCD中拯救神经元细胞至关重要。 我们有 开发了一种新的假设来解释高血糖耦合 神经毒性。 我们推测高葡萄糖会改变IGF-IR激活 在DRG神经元中。 这种结果导致局灶性磷酸化变化 粘附蛋白会导致肌动蛋白细胞骨架的破坏 并损害DGR神经突的生长。 我们相信随后的细胞骨架 单独变化，或与直接葡萄糖毒性一起诱导 DRG神经元中的PCD。 IGF-IR的激活1）通过增强来防止PCD 局灶性蛋白磷酸化并稳定细胞骨架， 和/或2）通过激活PI 3K途径阻止PCD，这可能会影响PCD 调节性蛋白质（例如Bcl-2和/或死亡蛋白酶）。 在此提案中 我们将测试模型的每个组件。我们有2个目标：1。 高葡萄糖对DRG神经元的影响。 在DRG神经元中，作为回应 要高葡萄糖，检查：a）DRG神经元形态和神经突生长 b）IGF-IR转录，细胞表面丰度和自磷酸化 c）焦点粘附蛋白和DRG细胞骨架的磷酸化 DRG 2中的PCD。 葡萄糖暴露后。 在DRG神经元中，响应高葡萄糖， 检查IGR-I对：a）DRG神经元形态和神经突的作用 生长b）IGF-IR转录，细胞表面丰度和 自磷酸化c）局灶性粘附蛋白和 DRG细胞骨架3。研究IGF-IR基础的组件 从葡萄糖诱导的PCD中营救DRG。 a）确定关联 在观察到的局灶性粘附蛋白的变化之间 细胞骨架，响应高葡萄糖的PCD途径b）检查 高葡萄糖和IGF-I对PI-3K C的IGF-IR激活的影响 确定IGF-IR激活是否通过促进表达来阻止PCD 抑制细胞死亡的调节蛋白，例如Bcl-2 d）确定是否确定是否是否 高葡萄糖通过激活死亡蛋白酶促进PCD，并且该作用 在调节此PCD途径时，IGF-IR激活的激活。 IGF-I目前是 在糖尿病神经病的临床踪迹中进行评估。 这 当前的建议将有助于阐明角色的基础机制 IGF-I预防神经元形态和PCD的变化 糖尿病神经病。