Vanilloid Receptors in Diabetic Peripheral Neuropathy

糖尿病周围神经病变中的香草酸受体

• 批准号: 6930403
• 负责人: LOUIS S PREMKUMAR
• 金额: $ 25.74万
• 依托单位: SOUTHERN ILLINOIS UNIVERSITY SCH OF MED
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6930403
• 关键词: Xenopus; Xenopus oocyte; calcium flux; confocal scanning microscopy; diabetic neuropathy; enzyme activity; gene expression; genetically modified animals; growth factor receptors; immunocytochemistry; insulin; insulin receptor; insulinlike growth factor; intracellular transport; laboratory mouse; laboratory rat; membrane activity; membrane channels; mitogen activated protein kinase; newborn animals; nociceptors; phosphorylation; protein kinase C; protein structure function; protein transport; receptor binding; receptor expression

DESCRIPTION (provided by applicant): Peripheral neuropathy is one of the most common complications of diabetes, yet the mechanisms responsible for abnormal sensory perception are poorly understood. In individuals with type 1 diabetes (T1D), insulin and insulin-like growth factor-1 (IGF1) levels are reduced. Elevated blood glucose is implicated in diabetic peripheral neuropathy (DPN), however, lack of an absolute correlation between neuropathy and hyperglycemia suggests that other mechanisms likely contribute to the pathogenesis of DPN. Insulin and IGF1 have established neuroendocrine functions that include maintenance of synaptic integrity and neurotrophic effects on sensory neurons. Our studies demonstrate that vanilloid receptor-1 (VR1), an ion channel that functions to transmit thermal and inflammatory pain, is potentiated by insulin and IGF1. We hypothesize that insulin and IGF1 are required for proper VR1 function, thereby maintaining the integrity, of sensory nerve terminals. By extension, a lack of insulin and/or IGF1 is expected to reduce nociception resulting in neuropathy as observed in T1D. In this study we will explore the molecular mechanisms that allow insulin and IGF 1 to potentiate membrane current and intracellular calcium levels through VR1. Insulin and IGF 1 bind the insulin (IR) and IGF (IGFR) receptors, respectively. However, each hormone can also bind the opposing receptor albeit with lower affinity and both receptors use similar second messengers. Our studies show that protein kinase C (PKC)- mediated phosphorylation of VR1 induces an increase in membrane current and calcium flux. We hypothesize that insulin and IGF 1 as a short-term effect cause PKC-mediated phosphorylation of VR1 and promotes translocation of VR1 from cytosol to plasma membrane. As a long-term effect by activating second messenger molecules, particularly p38 MAPK, insulin/IGF1 alter VR1 expression levels,. Thus, we will identify signal transduction molecules that link IR_GFR signaling with VR1 phosphorylation. To confirm these hypotheses in vivo, we will compare VR1 function in normal and T1D mice. This will include testing the ability of exogenous insulin and IGF1 to restore the otherwise abnormal thermal nociception observed in TID mice to near normal values. To confirm the involvement of VR1 we will measure changes in VR-dependent CGRP release and nerve function in these animals. We hypothesize that VR1 function is down regulated in diabetic animals due to insulin/IGF1 deficiency. Information gained here will provide a mechanistic link between T1D and peripheral neuropathy that includes VR1 as a central player in peripheral pain perception and insulin/IGF1 as modifiers that help to maintain normal nerve function, but when absent contribute to neuropathy.

描述（由申请人提供）：周围神经病变是糖尿病最常见的并发症之一，但人们对异常感觉的机制知之甚少。在1型糖尿病（T1 D）患者中，胰岛素和胰岛素样生长因子-1（IGF 1）水平降低。血糖升高与糖尿病周围神经病变（DPN）有关，然而，神经病变和高血糖之间缺乏绝对相关性表明其他机制可能有助于DPN的发病机制。胰岛素和IGF 1已经建立了神经内分泌功能，包括维持突触的完整性和对感觉神经元的神经营养作用。我们的研究表明，香草素受体-1（VR 1），一种传递热和炎性疼痛的离子通道，被胰岛素和IGF 1增强。我们推测，胰岛素和IGF 1需要适当的VR 1功能，从而保持完整性，感觉神经末梢。推而广之，预期缺乏胰岛素和/或IGF 1会减少伤害感受，导致T1 D中观察到的神经病变。在这项研究中，我们将探讨的分子机制，使胰岛素和IGF 1，以加强膜电流和细胞内钙水平通过VR 1。胰岛素和IGF 1分别与胰岛素（IR）和IGF（IGFR）受体结合。然而，每种激素也可以结合相反的受体，尽管亲和力较低，两种受体使用相似的第二信使。我们的研究表明，蛋白激酶C（PKC）介导的VR 1磷酸化诱导膜电流和钙通量的增加。我们推测胰岛素和IGF 1作为短期效应引起PKC介导的VR 1磷酸化，并促进VR 1从胞质溶胶易位到质膜。作为通过激活第二信使分子，特别是p38 MAPK的长期效应，胰岛素/IGF 1改变VR 1表达水平。因此，我们将确定连接IR_GFR信号传导与VR 1磷酸化的信号转导分子。为了在体内证实这些假设，我们将比较正常和T1 D小鼠中的VR 1功能。这将包括测试外源性胰岛素和IGF 1将TID小鼠中观察到的异常热伤害感受恢复至接近正常值的能力。为了证实VR 1的参与，我们将测量这些动物中VR依赖性CGRP释放和神经功能的变化。我们推测，VR 1功能下调糖尿病动物由于胰岛素/IGF 1缺乏。本文获得的信息将提供T1 D和周围神经病变之间的机制联系，包括VR 1作为周围疼痛感知的核心参与者，胰岛素/IGF 1作为有助于维持正常神经功能的调节剂，但当缺乏时会导致神经病变。