Chaperones in Diabetic Peripheral Neuropathy

描述（由申请人提供）：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变性。在寻求药物治疗DPN的过程中，小分子抑制剂靶向了被认为是“糖尿病特异性”的蛋白质和途径，以及其他在许多疾病状态下活性改变的蛋白质和途径。这些努力尚未产生任何重要的治疗方法，部分原因是这些靶点/途径对DPN进展的生化贡献在个体之间的时间和/或生化一致性中并不存在。因此，我们一直在追求一种新的分子模式的合理识别，这种模式提供了一个“可药物化”的靶点，并为DPN在疾病进展的各个阶段的有效医学管理提供了转化潜力。在复杂的慢性神经退行性疾病中，如阿尔茨海默病和DPN，人们越来越认识到有效的疾病管理可能不一定需要靶向被认为有助于疾病进展的途径或蛋白质。另外，从药理学上增强内源性神经保护通路的活性有助于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控因子，可上调Hsp70和抗氧化基因的表达。我们的先导化合物是一种无毒的生物可利用分子，称为KU-32，我们提供的证据表明，它可以逆转DPN的多个临床指标，促进受损感觉纤维在表皮的恢复和神经再生，增加线粒体生物能量，降低1型和2型糖尿病模型的氧化应激。在机制上，用KU-32抑制Hsp90可诱导糖尿病背根神经节中其他伴侣蛋白如胞质Hsp70和线粒体Hsp70 （mtHsp70）。重要的是，KU-32的疗效需要Hsp70，因为该药物对逆转糖尿病Hsp70 KO小鼠的DPN无效。根据从动物和原代细胞模型中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拯救感觉神经元免受高血糖应激。为了解决这一假设，目的一将确定是否通过KU-32逆转DPN的临床指标需要hsp70依赖的感觉神经元线粒体生物能量学的增加。目的2将确定Hsp70是否通过降低成人感觉神经元的氧化应激来增强线粒体生物能量。目的3将确定Hsp70和mtHsp70是否通过增加糖尿病神经元的蛋白质输入来增强线粒体功能。我们的工作结果将为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见解，并验证调节分子伴侣是医学上治疗DPN的可行方法。

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.