中国神经再生研究(英文版) ›› 2017, Vol. 12 ›› Issue (3): 372-375.doi: 10.4103/1673-5374.202928

• 综述:神经损伤修复保护与再生 • 上一篇    下一篇

神经黑色素:现代医学中最被忽视的分子之一,它不是观众

  

  • 收稿日期:2017-03-10 出版日期:2017-03-15 发布日期:2017-03-15

Neuromelanin, one of the most overlooked molecules in modern medicine, is not a spectator

Robert L. Haining, Cindy Achat-Mendes   

  1. Georgia Gwinnett College, 1000 University Center Ln, School of Science and Technology, Lawrenceville, GA, USA
  • Received:2017-03-10 Online:2017-03-15 Published:2017-03-15
  • Contact: Robert L. Haining, Ph.D., rhaining@ggc.edu.

摘要:

通常认为多巴胺通过抗坏血酸和其它抗氧化剂的共定位被保护因而免受分泌小泡中的自氧化。最终研究发现神经黑素(NM)被隔离在神经元内的双膜颗粒中,并且包含在体内结合其结构的脂质和肽当中。这种结构被仔细包装并保留下来,这一发现是该分子具有重要功能的有利证据,然而我们对NM对细胞的影响仍然知之甚少。因为缺乏大量帕金森病例的中心遗传基础,目前只了解这种色素沉着不是多巴胺能神经元中的酶促驱动过程,但可能高度相关。
本文提出,许多研究者已经假设NM色素的积累是老化不可避免的副产物。仅仅是细胞并不能处理的该分子的垃圾形式,他们对解释NM是否存在于这个过程中不感兴趣,并且认为这是没有必要的。在这种观点中,有毒化学物质与NM的结合可能仅仅是垃圾本身存在的副产物,最终导致由于氧化应激导致含黑色素神经元的不稳定和死亡。其他研究者已经建议,色素的积累起到保护作用,响应由积极运作的儿茶酚胺能神经元施加的氧化应激。在这种观点中,研究焦点经常是由线粒体反应性氧物种施加的应激,其中NM通过捕获和解毒自由基起到保护作用,类似于皮肤黑色素在防止紫外线引起的损伤中的作用。或者,有研究已经提出NM具有双重功能,在早期阶段通过铁螯合保护细胞免受氧化应激,但是通过在最终细胞死亡时释放新抗原而导致帕金森病的自身免疫加重。超快激光光谱研究表明,组织中色素颗粒的完整性可能归因于黑色素的光保护和光损伤行为之间平衡的重要作用。

ORCID:0000-0002-3944-056X(Robert L. Haining)

Abstract:

The loss of pigmented neurons from the human brain has long been the hallmark of Parkinson’s disease (PD). Neuromelanin (NM) in the pre-synaptic terminal of dopamine neurons is emerging as a primary player in the etiology of neurodegenerative disorders including PD. This mini-review discusses the interactions between neuromelanin and different molecules in the synaptic terminal and describes how these interactions might affect neurodegenerative disorders including PD. Neuromelanin can reversibly bind and interact with amine containing neurotoxins, e.g., MPTP, to augment their actions in the terminal, eventually leading to the instability and degeneration of melanin-containing neurons due to oxidative stress and mitochondrial dysfunction. In particular, neuromelanin appears to confer susceptibility to chemical toxicity by providing a large sink of iron-bound, heme-like structures in a pi-conjugated system, a system seemingly purposed to allow for stabilizing interactions including pi-stacking as well as ligand binding to iron. Given the progressive accumulation of NM with age corresponding with an apparent decrease in dopamine synthetic pathways, the immediate question of whether NM is also capable of binding dopamine, the primary functional monoamine utilized in this cell, should be raised. Despite the rather glaring implications of this finding, this idea appears not to have been adequately addressed. As such, we postulate on potential mechanisms by which dopamine might dissociate from neuromelanin and the implications of such a reversible relationship. Intriguingly, if neuromelanin is able to sequester and release dopamine in membrane bound vesicles, this intracellular pre-synaptic mechanism could be the basis for a form of chemical memory in dopamine neurons.

Key words: dopamine, dopamine storage, Parkinson’s disease, neurodegeneration, neuromelanin, neurotoxicity