Biology of GDNF in Diabetic Neuropathy

描述（由申请人提供）：糖尿病性神经病变（DN）是许多糖尿病患者发生的严重神经并发症。小的无髓感觉纤维通常受到影响，导致皮肤感觉异常和疼痛。人们认为，相关的机制有助于DN和神经营养支持不足最近被添加到可能的缺陷列表中。影响小纤维DN的伤害性神经元对神经生长因子（NGF）或胶质细胞系来源的神经营养因子（GDNF）有反应。尽管有研究指出，神经生长因子对DN中感觉神经元的支持存在缺陷，但对神经生长因子的作用知之甚少。该项目的长期目标是在糖尿病动物模型中，检查gdnf相关配体和受体的生物学，并将缺陷与糖尿病引起的生理和行为缺陷联系起来。我们的目的是揭示DN发展的潜在机制，从而提供有助于开发新的DN治疗方法的信息。我们之前的研究表明，GDNF反应神经元的中枢过程对糖尿病敏感，GDNF给药可以逆转GDNF反应性脊髓末梢的缺陷。该提案将验证糖尿病患者对初级感觉神经元的GDNF支持受损的假设，以及GDNF反应神经元的解剖/生理缺陷可能导致对皮肤刺激的反应受损。第一个具体目的是表征stz诱导的糖尿病小鼠GDNF/GDNF受体合成和转运的缺陷，并测试GDNF治疗是否可以改善配体/受体异常。第二个目标将描述脊髓和皮肤中GDNF反应纤维的缺陷，然后测试GDNF刺激感觉轴突生长和神经再生的能力。最终目的是通过在体外皮肤神经制备中对单个已鉴定的神经元进行电生理记录来表征gdnf反应神经元的缺陷。生理缺陷将与糖尿病小鼠对有害的机械、化学和热刺激的异常反应有关。还将测试GDNF对皮肤刺激的神经元生理和行为反应的调节能力。总而言之，本项目拟采用分子、解剖、生理和行为等方法来了解GDNF在DN中的生物学作用，并测试GDNF是否对糖尿病动物的皮肤神经元有治疗作用。本研究的结果将1)提供GDNF支持受损有助于DN发展的证据，2)确立GDNF作为改善DN皮肤功能治疗的候选药物。

DESCRIPTION (provided by applicant): Diabetic neuropathy (DN) is a serious neural complication that develops in many diabetic patients. Small unmyelinated sensory fibers are commonly affected, leading to abnormal cutaneous sensation and pain. It is believed that interrelated mechanisms contribute to DN and insufficient neurotrophic support has recently been added to the list of possible deficits. Nociceptive neurons affected in small-fiber DN respond either to nerve growth factor (NGF) or glial cell line-derived neurotrophic factor (GDNF). Whereas studies have noted deficits in NGF support to sensory neurons in DN, little is known about the role of GDNF. The long-term goal of this project is in an animal model of diabetes, examine the biology of GDNF-related ligands and receptors and correlate deficits with physiological and behavioral deficits that are caused by diabetes. Our purpose is to uncover mechanisms underlying the development of DN, thus providing information that will aid in developing novel treatments for DN. Our previous studies demonstrate that the central processes of GDNF-responsive neurons are sensitive to diabetes and GDNF administration can reverse deficits in GDNF-responsive spinal terminals. This proposal will test the hypotheses that GDNF support to primary sensory neurons is impaired in diabetes and anatomical/physiological deficits in GDNF-responsive neurons can lead to impaired responses to cutaneous stimuli. The first specific aim will characterize deficits in GDNF/GDNF-receptor synthesis and transport in STZ-induced diabetic mice, and test whether GDNF treatment can improve ligand/receptor abnormalities. The second aim will characterize deficits in GDNF-responsive fibers in the spinal cord and skin, and then test the ability of GDNF to stimulate sensory axon growth and reinnervation. The final aim will characterize deficits in GDNF-responsive neurons by performing electrophysiological recordings of single, identified neurons in an in vitro skin-nerve preparation. Physiological deficits will be correlated with abnormalities in the response of diabetic mice to noxious mechanical, chemical and thermal stimuli. The capacity of GDNF to modify neuronal physiology and behavioral responses to cutaneous stimuli will also be tested. In sum, this grant proposes to use molecular, anatomical, physiological and behavioral approaches to understand the biology of GDNF in DN and to test whether GDNF has therapeutic actions on cutaneous neurons affected in diabetic animals. Results from this study will 1) provide evidence that impaired GDNF support contributes to the development of DN and 2) establish GDNF as a candidate to be used in treatments to improve cutaneous function in DN.