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。具体目标是研究糖尿病诱导的高血糖和炎症介质如何通过减少神经营养因子介导的信号通路加速视网膜神经元的死亡。这项提议的基本原理是，了解损害视网膜神经元存活的机制将导致预防糖尿病和其他视网膜变性视力丧失的改进方法。糖尿病通过多种损伤损害视网膜，包括高血糖症，炎症和改变的促生存信号，但导致神经元死亡的机制仍然不确定。通过Akt（蛋白激酶B）的生长因子信号传导对于神经元的存活至关重要，并且作为糖尿病、全身性感染、免疫介导的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已经证实糖尿病诱导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的视网膜促存活信号传导通常被胰岛素、胰岛素样生长因子和光激活，糖尿病降低了这种基础促存活活性，伴随着视网膜神经元死亡的发生。我们已经证明高血糖会破坏培养中视网膜神经元的存活，现在发现细胞因子会阻断生长因子的神经营养作用。根皮苷治疗降低糖尿病大鼠的高血糖症减少视网膜神经元的死亡并恢复促生存信号。此外，生长因子的眼部递送还增强促存活信号传导并减少视网膜细胞死亡。我们还产生了一种新的小鼠模型与条件性视网膜胰岛素受体敲低，提供了一个强大的工具来检查视网膜促生存信号的作用。总之，这些数据表明胰岛素受体/Akt信号传导是视网膜神经元的关键存活途径。因此，我们提出了一个普遍的假设，即高血糖和炎症损害神经营养因子介导的糖尿病视网膜神经元的存活。在视网膜神经元培养物、糖尿病大鼠和胰岛素受体/Akt通路敲低的小鼠中使用生物化学、分子和遗传方法的三个具体目标将检验该假设。一个强大的跨学科研究团队将阐明高血糖和细胞因子损害培养系统和糖尿病大鼠中神经营养因子介导的视网膜神经元存活的机制。我们还将使用新型转基因小鼠确定胰岛素受体/Akt信号传导对糖尿病视网膜神经元存活和视力的影响。 公共卫生相关性：该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。我们将检验这一假设，即过量的葡萄糖和炎症分子抑制了保持神经细胞存活的激素的正常作用。预计结果是有更好的方法来维持糖尿病患者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.