Department of Molecular Biology, University of Bergen, PB 7803, N-5020 Bergen, Norway.
Aquat Toxicol. 2010 Oct 1;100(1):51-65. doi: 10.1016/j.aquatox.2010.07.008. Epub 2010 Jul 13.
The molecular mechanisms underlying the neurotoxicity of methylmercury (MeHg), a ubiquitous environmental contaminant, are not yet fully understood. Furthermore, there is a lack of biomarkers of MeHg neurotoxicity for use in environmental monitoring. We have undertaken a proteomic analysis of brains from Atlantic cod (Gadus morhua) exposed to 0, 0.5 and 2 mg/kg MeHg administered by intraperitoneal injection. The doses were given in two injections, half of the dose on the first day and the second half after 1 week, and the total exposure period lasted 2 weeks. Using 2-DE coupled with MALDI-TOF MS and MS/MS, we observed the level of 71 protein spots to be 20% or more significantly altered following MeHg exposure, and successfully identified 40 of these protein spots. Many of these proteins are associated with main known molecular targets and mechanisms of MeHg-induced neurotoxicity in mammals, such as mitochondrial dysfunction, oxidative stress, altered calcium homeostasis and tubulin/disruption of microtubules. More interestingly, several of the affected proteins, with well-established or recently demonstrated critical functions in nervous system-specific processes, have not previously been associated with MeHg exposure in any species. These proteins include the strongest up-regulated protein, pyridoxal kinase (essential for synthesis of several neurotransmitters), G protein (coupled to neurotransmitter receptors), nicotinamide phosphoribosyl-transferase (protection against axonal degeneration), dihydropyrimidinase-like 5 (or collapsin response mediator protein 5, CRMP-5) (axon guidance and regeneration), septin (dendrite development), phosphatidylethanolamine binding protein (precursor for hippocampal cholinergic neurostimulating peptide) and protein phosphatase 1 (control of brain recovery by synaptic plasticity). The results of the present study aid our understanding of molecular mechanisms underlying MeHg neurotoxicity and defense responses, and provide a large panel of protein biomarker candidates for aquatic environmental monitoring.
甲基汞（MeHg）是一种普遍存在的环境污染物，其神经毒性的分子机制尚不完全清楚。此外，用于环境监测的甲基汞神经毒性生物标志物也很缺乏。我们对经腹腔注射 0、0.5 和 2 mg/kg MeHg 暴露的大西洋鳕鱼（Gadus morhua）大脑进行了蛋白质组学分析。这些剂量分两次注射，第一天注射一半，一周后再注射另一半，总暴露期为 2 周。通过 2-DE 结合 MALDI-TOF MS 和 MS/MS，我们观察到 71 个蛋白点中有 20%或更多的蛋白点的水平因 MeHg 暴露而显著改变，并成功鉴定了其中的 40 个蛋白点。这些蛋白中的许多与哺乳动物中已知的 MeHg 诱导的神经毒性的主要分子靶点和机制有关，如线粒体功能障碍、氧化应激、钙稳态改变和微管蛋白/微管破坏。更有趣的是，其中一些受影响的蛋白，具有神经系统特定过程中已建立或最近证明的关键功能，以前与任何物种的 MeHg 暴露都没有关联。这些蛋白包括上调最明显的蛋白，即吡哆醛激酶（几种神经递质合成所必需）、G 蛋白（与神经递质受体偶联）、烟酰胺磷酸核糖基转移酶（防止轴突退化）、二氢嘧啶酶样 5（或塌陷反应介质蛋白 5，CRMP-5）（轴突导向和再生）、凝缩蛋白（树突发育）、磷酸乙醇胺结合蛋白（海马胆碱能神经刺激肽的前体）和蛋白磷酸酶 1（通过突触可塑性控制大脑恢复）。本研究的结果有助于我们理解 MeHg 神经毒性和防御反应的分子机制，并为水生环境监测提供了大量的蛋白质生物标志物候选物。
