MOLECULAR MECHANISMS OF HEXACARBON-INDUCED AXON ATROPHY

六碳诱发轴突萎缩的分子机制

• 批准号: 6524758
• 负责人: Richard Michael Lopachin
• 金额: $ 26.1万
• 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/6524758
• 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-己酮（HD），工业溶剂甲基N-丁基酮和N-己烷的神经毒性γ-二酮代谢产物会导致远端轴突病。 巨大的神经丝轴肿胀已被认为是形态学的标志，因此，这是机械研究的重点。 然而，已发表的证据表明，轴突萎缩也可能是响应γ-二酮中毒，可能是一个重大的致病事件。 在当前资助期间，在PI实验室进行的定量形态学研究表明，HD毒性大鼠的外周神经的纤维萎缩是一种特异性的，普遍的效应，在时间上与神经传导异常相关，并在行为缺陷之前。这些发现暗示萎缩是γ-二酮诱导的神经毒性的重要病理生理成分。 平行分子测定表明，神经丝（NF）遗传表达和神经含量的降低是HD暴露大鼠轴突口径降低的直接原因。 相比之下，我们的研究表明，巨大的轴突肿胀是与低剂量HD暴露有关的epiphenomenon。 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合成的选择性降低是未知的。 在过去的十年中，研究表明，成熟的轴突口径是由目标衍生的神经营养因子对NF表达的影响保持的。因此，我们假设γ-二酮诱导的轴突萎缩是通过神经元营养因子信号传导的破坏产生的。该假设将根据以下特定目的进行检验：（1）神经营养蛋白（BDNF，NGF）的形成，激活和逆行转运将以γ-二酮酮陶醉的大鼠的外周神经轴进行测量。 （2）将确定γ-二酮对神经营养蛋白-TRK受体结合和神经元内在化的影响。 （3）评估γ-二酮中毒对RAS信号转导途径的神经营养蛋白受体复合物刺激的影响以及MAP激酶的激活以及随后的核转运。 拟议的研究代表了对毒性轴突病机制的一个新的研究领域，并且对与纤维萎缩相关的获得或遗传的人神经病具有广泛的影响。 此外，我们的研究可能建议基于神经营养蛋白干预或替代的新型药物疗法。