Department of Pharmacology and Toxicology, University of Kansas, 5064 Malott Hall, 1251 Wescoe Hall Dr., Lawrence, KS 66045, USA.
Department of Medicinal Chemistry, University of Kansas, Lawrence, KS, USA.
Exp Neurol. 2019 Mar;313:88-97. doi: 10.1016/j.expneurol.2018.12.006. Epub 2018 Dec 15.
Neuronal mitochondrial dysfunction and oxidative stress are key pathophysiologic mechanisms of diabetic peripheral neuropathy (DPN). KU-596 is a small molecule modulator of heat shock protein 90 (Hsp90) that can reverse clinically relevant measures of DPN in diabetic animal models. Mechanistically, drug efficacy requires Hsp70 and correlates with improving mitochondrial maximal respiratory capacity (MRC) and decreasing oxidative stress in diabetic sensory neurons. The goal of this study was to determine if ex vivo treatment of diabetic neurons with KU-596 improves MRC by decreasing glucose-induced oxidative stress in an Hsp70-dependent manner. Sensory neurons were isolated from non-diabetic or diabetic mice wild type (WT) or Hsp70 knockout (Hsp70 KO) mice and treated with KU-596 in the presence of low or high glucose concentrations. In diabetic WT and Hsp70 KO neurons, hyperglycemia significantly increased superoxide levels, but KU-596 only decreased superoxide in WT neurons. Similarly, KU-596 significantly improved MRC in diabetic WT neurons maintained in high glucose but did not improve MRC in diabetic Hsp70 KO neurons under the same conditions. Since manganese superoxide dismutase (MnSOD) is the main mechanism to detoxify mitochondrial superoxide radicals, the cause and effect relationship between improved respiration and decreased oxidative stress was examined after knocking down MnSOD. Downregulating MnSOD in diabetic WT neurons increased hyperglycemia-induced superoxide levels, which was still significantly decreased by KU-596. However, KU-596 did not improve MRC following MnSOD knockdown. These data suggest that the ability of KU-596 to improve MRC is not necessarily dependent on decreasing mitochondrial superoxide in a MnSOD-dependent manner.
神经元线粒体功能障碍和氧化应激是糖尿病周围神经病变（DPN）的关键病理生理机制。KU-596 是一种小分子热休克蛋白 90（Hsp90）调节剂，可逆转糖尿病动物模型中与临床相关的 DPN 测量值。从机制上讲，药物疗效需要 Hsp70，并且与改善糖尿病感觉神经元的线粒体最大呼吸能力（MRC）和减少氧化应激相关。本研究的目的是确定在体外用 KU-596 处理糖尿病神经元是否可以通过以 Hsp70 依赖的方式降低葡萄糖诱导的氧化应激来改善 MRC。从非糖尿病或糖尿病野生型（WT）或 Hsp70 敲除（Hsp70 KO）小鼠中分离感觉神经元，并在存在低或高葡萄糖浓度的情况下用 KU-596 处理。在糖尿病 WT 和 Hsp70 KO 神经元中，高血糖显着增加了超氧化物水平，但 KU-596 仅在 WT 神经元中降低了超氧化物。同样，KU-596 显着改善了在高葡萄糖中维持的糖尿病 WT 神经元的 MRC，但在相同条件下不能改善糖尿病 Hsp70 KO 神经元的 MRC。由于锰超氧化物歧化酶（MnSOD）是解毒线粒体超氧自由基的主要机制，因此在敲低 MnSOD 后检查了呼吸改善与氧化应激降低之间的因果关系。在糖尿病 WT 神经元中下调 MnSOD 增加了高血糖诱导的超氧化物水平，但仍被 KU-596 显着降低。然而，在 MnSOD 敲低后，KU-596 并未改善 MRC。这些数据表明，KU-596 改善 MRC 的能力不一定依赖于以 MnSOD 依赖的方式降低线粒体超氧化物。
