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。具体目的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，将有助于改进预防糖尿病和其他视网膜变性患者视力丧失的方法。糖尿病通过多种损害损害视网膜，包括高血糖、炎症和促生存信号的改变，但导致神经元死亡的机制仍不确定。通过Akt（蛋白激酶B）传递的生长因子信号对神经元的存活至关重要，并且是糖尿病、全身性感染、免疫介导的炎症和退行性脑疾病的共同特征。大量的临床和动物研究已经证实，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照激活，糖尿病降低了这种基础的促生存活性，同时伴有视网膜神经元死亡。我们已经证明，高血糖会破坏视网膜神经元在培养中的存活，现在发现细胞因子阻断了生长因子的神经营养作用。在糖尿病大鼠中，phenlorizin治疗降低高血糖可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也增加促生存信号并减少视网膜细胞死亡。我们还建立了一种具有条件视网膜胰岛素受体敲低的新型小鼠模型，为研究视网膜促生存信号的作用提供了有力的工具。总之，这些数据表明胰岛素受体/Akt信号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了糖尿病视网膜神经元中神经营养因子介导的存活。使用生化、分子和遗传学方法在视网膜神经元培养、糖尿病大鼠和胰岛素受体/Akt通路下调的小鼠中进行三个特定的目标，以验证这一假设。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视网膜神经元中神经营养因子介导的存活的机制。我们还将利用新型转基因小鼠确定胰岛素受体/Akt信号对糖尿病视网膜神经元存活和视力的影响。

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.