Regulation of Retinal Cell Death in Diabetes

描述(由申请人提供)：本提案的总体目标是了解糖尿病如何损害视网膜神经元的存活。其具体目的是研究糖尿病引起的高血糖和炎症介质如何通过减少神经营养素介导的信号通路来加速视网膜神经元的死亡。这项建议的基本原理是，了解损害视网膜神经元存活的机制将导致改进预防糖尿病和其他视网膜退化导致的视力丧失的方法。糖尿病通过多种方式损害视网膜，包括高血糖、炎症和支持生存的信号改变，但导致神经元死亡的机制尚不清楚。通过Akt(蛋白激酶B)的生长因子信号对神经元的生存至关重要，并且作为糖尿病、全身感染、免疫介导性炎症和退行性脑疾病的共同特征而受损。许多临床和动物研究现已证实糖尿病引起的视网膜神经元死亡是早期糖尿病视网膜病变的一个组成部分。研究人员已经证明，通过胰岛素受体和Akt的视网膜促生存信号通常被胰岛素、胰岛素样生长因子和光激活，而糖尿病会降低这种基础的促生存活性，伴随着视网膜神经元死亡的开始。我们已经证明了高血糖干扰了培养的视网膜神经元的存活，现在发现细胞因子阻断了生长因子的神经营养作用。根茎苷治疗降低高血糖可减少糖尿病大鼠视网膜神经元的死亡，并恢复有利于生存的信号。此外，眼部输送生长因子也增强了促生存信号，减少了视网膜细胞死亡。我们还建立了一种新的视网膜胰岛素受体条件性敲除的小鼠模型，为研究视网膜促生存信号的作用提供了一个强大的工具。综上所述，这些数据表明，胰岛素受体/Akt信号是视网膜神经元的关键生存途径。因此，我们提出了糖尿病患者高血糖和炎症损害神经营养素介导的视网膜神经元存活的普遍假设。在视网膜神经元培养、糖尿病大鼠和胰岛素受体/Akt通路被敲除的小鼠中，使用生化、分子和遗传学方法的三个特定目标将检验这一假设。一个强大的跨学科研究小组将阐明高血糖和细胞因子在培养系统和糖尿病大鼠中损害神经营养素介导的视网膜神经元存活的机制。我们还将使用新的转基因小鼠来确定胰岛素受体/Akt信号对糖尿病视网膜神经元存活和视力的影响。 与公共健康相关：这项提案旨在确定为什么视网膜中对视力最关键的神经细胞会在糖尿病中死亡。我们将测试一种假设，即过量的葡萄糖和炎症分子会抑制维持神经细胞存活的激素的正常作用。预计的结果是有更好的手段来维持糖尿病患者的视网膜神经细胞的健康，以保护视力并减少对激光治疗的需求。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to understand how diabetes impairs the survival of retinal neurons. The specific objective is to investigate how diabetes-induced hyperglycemia and inflammatory mediators accelerate the death of retinal neurons by reducing neurotrophin-mediated signaling pathways. The rationale for this proposal is that understanding the mechanisms that compromise the survival of retinal neurons will lead to improved means to prevent vision loss in diabetes and other retinal degenerations. Diabetes damages the retina by multiple insults, including hyperglycemia, inflammation and altered pro-survival signaling, but the mechanisms that cause neurons to die remain uncertain. Growth factor signaling through Akt (protein kinase B) is central to the survival of neurons, and is impaired as a shared feature of diabetes, systemic infections, immune-mediated inflammation, and degenerative brain diseases. Numerous clinical and animal studies have now established diabetes-induced death of retinal neurons as a component of early diabetic retinopathy. The investigators have demonstrated that retinal pro-survival signaling via the insulin receptor and Akt is normally activated by insulin, insulin-like growth factors and light, and diabetes reduces this basal pro-survival activity concomitant with the onset of retinal neurons death. We have shown that hyperglycemia disrupts the survival of retinal neurons in culture and now find that cytokines block the neurotrophic actions of growth factors. Reduction of hyperglycemia with phlorizin treatment reduces the death of retinal neurons and restores pro-survival signaling in diabetic rats. Moreover, ocular delivery of growth factors also augments pro-survival signaling and reduces retinal cell death. We have also generated a novel mouse model with conditional retinal insulin receptor knockdown that provides a powerful tool to examine the role of retinal pro-survival signaling. Together, these data demonstrate that insulin receptor/Akt signaling is a key survival pathway for retinal neurons. Thus, we propose the general hypothesis that hyperglycemia and inflammation impair neurotrophin-mediated survival of retinal neurons in diabetes. Three specific aims using biochemical, molecular and genetic approaches in retinal neuron cultures, diabetic rats, and mice with knockdown of the insulin receptor/Akt pathway will test the hypothesis. A strong interdisciplinary research team will elucidate the mechanisms by which hyperglycemia and cytokines impair neurotrophin-mediated survival of retinal neurons in a culture system and in diabetic rats. We will also determine the impact of insulin receptor/Akt signaling on retinal neuron survival and vision in diabetes using novel genetically modified mice. PUBLIC HEALTH RELEVANCE: This proposal is intended to determine why the nerve cells in the retina that are most critical for vision die in diabetes. We will test the hypothesis that excess glucose and inflammatory molecules suppress the normal effects of hormones that keep nerve cells alive. The projected outcome is to have better means to maintain the health of retinal nerve cells in persons with diabetes to preserve vision and reduce the need for laser treatments.