Chaperones in Diabetic Peripheral Neuropathy

描述(申请人提供)：糖尿病周围神经病变(DPN)的病因涉及一系列相互关联的代谢和血管损伤，最终导致感觉神经元退化。在寻求药物治疗DPN的过程中，小分子抑制剂针对的是被认为是“糖尿病特异性”的蛋白质和途径，以及在许多疾病状态下其活性会发生变化的其他蛋白质和途径。这些努力没有产生任何重要的治疗方法，部分原因是复杂的问题，即这些靶/途径对DPN进展的生化贡献不是在个体之间的时间和/或生化一致性的情况下发生的。因此，我们一直在寻求一种新的分子范例的合理鉴定，它提供了一个“可用药”的靶点，并为在疾病发展的不同阶段对DPN进行有效的医疗管理提供了翻译潜力。在阿尔茨海默病和DPN等复杂的慢性神经退行性疾病中，人们越来越认识到，有效的疾病管理可能不一定需要针对被认为有助于疾病进展的途径或蛋白质。或者，它可能被证明是有益的，从药物上增强内源性神经保护通路的活性，以帮助神经元恢复和应激耐受。为此，我们合成了一种新的小分子，通过抑制分子伴侣热休克蛋白90(Hsp90)来激活内源性细胞保护反应。HSP90是细胞保护性热休克反应的主要调节者，它上调HSP70和抗氧化基因的表达。我们的先导化合物是一种名为KU-32的无毒、生物可用分子，我们提供的证据表明，在1型和2型糖尿病模型中，它可以逆转DPN的多个临床指标，促进受损感觉纤维的恢复和进入表皮的重新神经支配，增加线粒体生物能量学，并降低氧化应激。从机制上讲，用KU-32抑制Hsp90可在糖尿病背根神经节诱导其他伴侣蛋白，如胞浆Hsp70和线粒体Hsp70(MtHsp70)。重要的是，KU-32的疗效需要Hsp70，因为该药物在逆转糖尿病Hsp70 KO小鼠的DPN方面无效。根据从动物和原代细胞模型收集的一组全面的初步数据，我们的广泛假设是，调节Hsp70及其类似物可以通过拮抗葡萄糖诱导的线粒体功能障碍来将感觉神经元从高血糖应激中拯救出来。为了解决这一假设，目的之一将确定KU-32逆转DPN的临床指数是否需要依赖于Hsp70的感觉神经元线粒体生物能量学的增加。目的2将确定HSP70是否通过降低成年感觉神经元的氧化应激来增强线粒体生物能量学。目的3将确定Hsp70和mtHsp70是否通过增加糖尿病神经元中的蛋白质输入来增强线粒体功能。我们的工作成果将为Hsp70类似物如何改善感觉神经元生物能量学提供基本的分子洞察，并验证调制分子伴侣是一种可行的医学管理DPN的方法。

DESCRIPTION (provided by applicant): The etiology of diabetic peripheral neuropathy (DPN) involves an inter-related series of metabolic and vascular insults that ultimately contribute to sensory neuron degeneration. In the quest to pharmacologically manage DPN, small molecule inhibitors have targeted proteins and pathways regarded as "diabetes specific" as well as others whose activity are altered in numerous disease states. These efforts have not yielded any significant therapies, due in part to the complicating issue that the biochemical contribution of these targets/pathways to the progression of DPN does not occur with temporal and/or biochemical uniformity between individuals. Thus, we have pursued the rational identification of a new molecular paradigm that offers a "druggable" target and provides translational potential for effective medical management of DPN at various stages of disease progression. In complex, chronic neurodegenerative diseases such as Alzheimer's disease and DPN, it is increasingly appreciated that effective disease management may not necessarily require targeting a pathway or protein considered to contribute to disease progression. Alternatively, it may prove beneficial to pharmacologically enhance the activity of endogenous neuroprotective pathways to aid neuronal recovery and stress tolerance. To this end, we have synthesized a novel small molecule that activates an endogenous cytoprotective response by inhibiting the molecular chaperone, heat shock protein 90 (Hsp90). Hsp90 is the master regulator of the cytoprotective heat shock response, which upregulates expression of Hsp70 and antioxidant genes. Our lead compound is a non-toxic, bioavailable molecule called KU-32 and we provide evidence that it reverses multiple clinical indices of DPN, promotes the recovery and reinnervation of damaged sensory fibers into the epidermis, increases mitochondrial bioenergetics and decreases oxidative stress in models of Type 1 and Type 2 diabetes. Mechanistically, inhibiting Hsp90 with KU-32 induces other chaperones such as cytosolic Hsp70 and mitochondrial Hsp70 (mtHsp70) in diabetic dorsal root ganglia. Importantly, the efficacy of KU-32 requires Hsp70 since the drug is ineffective in reversing DPN in diabetic Hsp70 KO mice. In response to a comprehensive set of preliminary data gathered from animal and primary cell models, our broad hypothesis is that modulating Hsp70 and its paralogs can rescue sensory neurons from hyperglycemic stress by antagonizing aspects of glucose-induced mitochondrial dysfunction. To address this hypothesis, aim one will identify if reversing the clinical indices of DPN by KU-32 requires an Hsp70-dependent increase in mitochondrial bioenergetics of sensory neurons. Aim 2 will determine if Hsp70 enhances mitochondrial bioenergetics by decreasing oxidative stress in adult sensory neurons. Aim 3 will identify if Hsp70 and mtHsp70 augment mitochondrial function by increasing protein import in diabetic neurons. The outcomes of our work will provide fundamental molecular insight into how Hsp70 paralogs improve sensory neuron bio- energetics and validate that modulating molecular chaperones is a viable approach to medically manage DPN.