MOLECULAR MECHANISMS OF HEXACARBON-INDUCED AXON ATROPHY

六碳诱发轴突萎缩的分子机制

• 批准号: 6197400
• 负责人: Richard Michael Lopachin
• 金额: $ 25.8万
• 依托单位: MONTEFIORE MEDICAL CENTER (BRONX, NY)
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-01-01 至 2004-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6197400
• 关键词: atrophy; axon; environmental toxicology; enzyme activity; laboratory rat; neural degeneration; neurofilament; neuropharmacology; neurotoxins; pharmacokinetics; phosphorylation

2,5-Hexanedione (HD), the neurotoxic gamma-diketone metabolite of industrial solvents methyl n-butyl ketone and n-hexane, causes distal axonopathy. Giant neurofilamentous axonal swellings have been considered the morphologic hallmark and, accordingly, have been the focus of mechanistic research. However, published evidence suggests that axon atrophy, which also occurs in response to gamma-diketone intoxication, might be a significant pathogenic event. Quantitative morphometric studies conducted in the PI's laboratory during the current funding period showed that fiber atrophy in peripheral nerve of HD-intoxicated rats was a specific, prevalent effect that was temporally correlated to nerve conduction abnormalities and preceded behavioral defects. These findings implied atrophy was an essential pathophysiologic component of gamma-diketone-induced neurotoxicity. Parallel molecular determinations suggested that a reduction in neurofilament (NF) genetic expression and nerve content were the immediate cause of decreased axon caliber in HD exposed rats. In contrast, our research indicated giant axonal swellings were an epiphenomenon related to low dose HD exposure. The long-term objectives of this research project are to evaluate the neurotoxicological relevance of axonal atrophy and determine the corresponding molecular mechanism. How HD induces a selective reduction in NF synthesis is unknown. Research over the past decade has shown that mature axon caliber is maintained by target-derived neurotrophic factor influence on NF expression. Therefore, we hypothesize gamma-diketone-induced axon atrophy is produced by disruption of neuronal trophic factor signaling. This hypothesis will be tested according to the following specific aims: (1) The formation, activation and retrograde transport of neurotrophin (BDNF, NGF) signal complexes will be measured in peripheral nerve axis of gamma-diketone intoxicated rats. (2) gamma-Diketone influences on neurotrophin-trk receptor binding and neuronal internalization will be determined. (3) Assess the effects of gamma-diketone intoxication on neurotrophin-receptor complex stimulation of the Ras signal transduction pathway and activation of MAP kinase and subsequent nuclear translocation. The proposed research represents a new area of investigation into mechanisms of toxic axonopathies and has broad-based implications for acquired or inherited human neuropathies associated with fiber atrophy. In addition, our studies might suggest novel pharmacotherapies based on neurotrophin intervention or replacement.

2,5-己二酮 (HD) 是工业溶剂甲基正丁基酮和正己烷的神经毒性 γ-二酮代谢物，会导致远端轴突病变。 巨大的神经丝状轴突肿胀被认为是形态学标志，因此也成为机制研究的焦点。 然而，已发表的证据表明，轴突萎缩（也因γ-二酮中毒而发生）可能是一个重要的致病事件。 在当前资助期间在 PI 实验室进行的定量形态测量研究表明，HD 中毒大鼠周围神经纤维萎缩是一种特定的、普遍的效应，与神经传导异常和先前的行为缺陷暂时相关。这些发现表明萎缩是γ-二酮诱导的神经毒性的重要病理生理学组成部分。 平行分子测定表明，神经丝 (NF) 基因表达和神经含量的减少是 HD 暴露大鼠轴突口径减小的直接原因。 相比之下，我们的研究表明巨大的轴突肿胀是与低剂量 HD 暴露相关的附带现象。 该研究项目的长期目标是评估轴突萎缩的神经毒理学相关性并确定相应的分子机制。 HD 如何诱导 NF 合成的选择性减少尚不清楚。 过去十年的研究表明，成熟的轴突口径是通过靶源性神经营养因子对 NF 表达的影响来维持的。因此，我们假设γ-二酮诱导的轴突萎缩是由神经元营养因子信号传导破坏引起的。该假设将根据以下具体目标进行检验：（1）将在γ-二酮中毒大鼠的周围神经轴中测量神经营养蛋白（BDNF，NGF）信号复合物的形成、激活和逆行转运。 (2)将确定γ-二酮对神经营养蛋白-trk受体结合和神经元内化的影响。 (3) 评估γ-二酮中毒对神经营养蛋白-受体复合物刺激Ras信号转导途径以及MAP激酶激活和随后的核转位的影响。 拟议的研究代表了毒性轴突病机制研究的新领域，并对与纤维萎缩相关的获得性或遗传性人类神经病具有广泛的影响。 此外，我们的研究可能提出基于神经营养蛋白干预或替代的新药物疗法。