Food(cassava) cyanogen exposure and motor neuron degeneration

描述（由申请人提供）：运动神经元疾病是一个总括术语，经常用于指定疾病，特别是以一种仍然神秘的方式显著打击运动系统的神经退行性疾病。人类运动神经元疾病（如关岛肌萎缩性侧索硬化症、konzo和/或lathyrism）高发病灶的存在表明，环境因素（如暴露于某些神经毒素）导致运动系统退化。这种神经毒素的鉴定是高度相关的，因为它们可以用作实验工具来探测这种类型的神经病理学的分子机制。在我们以前的研究中，我们已经广泛地描述了konzo的病变，konzo是一种发生在撒哈拉以南非洲的高度流行但被忽视的运动神经元疾病。我们已经表明，konzo是一种纯粹的，永久性的和不可逆的疾病，突出的目标是金字塔运动的人群中，饮食几乎仅限于不良解毒生氰（linamarin）-含有木薯。此外，受影响的受试者摄入的含硫氨基酸（SAA）较低，需要对内源性产生的氰化物（CN）进行解毒。在这些条件下，CN的氧化代谢是有利的，并且氰酸盐（OCN）（一种蛋白质氨甲酰化剂）的产生增加。OCN通过尚不清楚但可能与蛋白质错误折叠相关的机制诱导灵长类动物的脊髓神经病。已知SAA缺乏本身会改变半胱氨酸依赖性酶（例如rodhanese）的活性，但其与konzo的关系尚不清楚。SAA缺乏也可能改变蛋白质二硫键异构酶（PDI）的表达/活性，PDI是一种通过催化硫醇/二硫键交换反应调节蛋白质正确折叠的酶，因此损害酶的“修复”能力。我们已经使用神经蛋白质组学研究神经毒性蛋白反应物诱导轴突病变的机制。在这个R21项目中，我们将使用类似的方法来阐明OCN/linamarin神经毒性的生物标志物，并测试linamarin（木薯）运动神经元疾病是由OCN和/或SAA缺乏持续蛋白质错误折叠介导的假设。因此，我们将确定OCN的（神经）蛋白靶点，定量OCN加合物，表征神经病理学，并评估幼年Wistar大鼠脑/脊髓组织中蛋白质错误折叠的选定指标的变化，这些大鼠保持SAA缺乏饮食，并用亚麻苦苷、NaOCN（阳性对照）或等量的5%葡萄糖水溶液（阴性对照）治疗长达8周。这一系列研究与FIC/NIH的目标非常吻合，因为它解决了发展中国家的公共卫生问题，同时为刚果民主共和国的培训和研究能力建设提供了一个以神经科学为重点的框架，刚果民主共和国是目前受konzo影响最严重的国家。公共卫生相关性：木薯（木薯）含有有毒化合物，例如linamarin，可导致腿部瘫痪（疾病称为konzo）和其他神经系统疾病。我们寻求Fogarty国际中心/国立卫生研究院的资金，以澄清它（木薯）诱导神经毒性的机制，并培训来自刚果民主共和国（受到konzo严重影响）的科学家进行毒理学研究。该项目与全球卫生相关，因为作物（木薯）是居住在热带地区的4亿多人的主食，而且越来越多地出口到世界各地，用于生产零食和动物饲料。

DESCRIPTION (provided by applicant): Motor neuron disease is an umbrella term frequently used to designate diseases, especially neurodegenerative conditions that prominently strike the motor system in a fashion that has remained enigmatic. The existence of high incidence foci of motor neuron diseases among human populations (e.g. the Guam amyotrophic lateral sclerosis, konzo, and/or lathyrism) suggests that environmental factors e.g. exposure to certain neurotoxins cause the motor system to degenerate. The identification of such neurotoxins is highly relevant as they can be used as experimental tools to probe molecular mechanisms underlying this type of neuropathology. In our previous research, we have extensively characterized the lesion in konzo, a highly prevalent but neglected motor neuron disease occurring in sub-Saharan Africa. We have shown that konzo is a pure, permanent and irreversible disease that prominently targets the pyramidal motor tracts among populations in which the diet is almost restricted to poorly detoxified cyanogenic (linamarin)-containing cassava. In addition, affected subjects have a low intake in sulfur amino acids (SAA) needed to detoxify endogenously produced cyanide (CN). Under these conditions, oxidative metabolism of CN is favored and there is increased production of cyanate (OCN), a protein-carbamoylating agent. OCN induces myeloneuropathy in primates through mechanisms that are not understood but possibly associated with protein misfolding. SAA deficiency by itself is known to alter the activities of cystein-dependent enzymes (e.g. rodhanese) but its relationship to konzo is unkown. It is possible that SAA deficiency also alters the expression/activity of protein disulfide isomerase (PDI), an enzyme that modulates proper folding of proteins by catalyzing thiol/disulfide exchange reactions and hence, impairs the "repair" capabilities of the enzyme. We have used neuroproteomics to study mechanisms by which neurotoxic protein-reactants induce axonopathy. In this R21 project, we will use a similar approach to elucidate biomarkers of OCN/linamarin neurotoxicity and test the hypothesis that linamarin (cassava) motor neuron disease is mediated by OCN and/or SAA deficiency-sustained protein misfolding. Accordingly, we will identify (neuro)protein targets of OCN, quantify OCN adducts, characterize the neuropathology, and assess changes in selected indicators of protein misfolding in brain/spinal cord tissues of young Wistar rats kept on SAA-deficient diets and treated with linamarin, NaOCN (positive control) or equivalent amount of 5% glucose in aqueous solution (negative control) for up to 8 weeks. This line of research fits well with FIC/NIH objectives in that it addresses an issue of public health concern in the developing world while providing a neuroscience-focused framework for training and research capacity building in the Democratic Republic of Congo, a country that is currently the most affected by konzo. PUBLIC HEALTH RELEVANCE: Cassava (manioc) contains toxic compounds e.g. linamarin that are incriminated in the paralysis of legs (disease is called konzo) and other diseases of the nervous system across the lifespan. We seek funds from the Fogarty International Center/National Institutes of Health to clarify mechanisms by which it (cassava) induces neurotoxicity and to train scientists from the Democratic Republic of Congo (seriously affected by konzo) to conduct toxicological research. This project has a global heath relevance because the crop (cassava) is a staple for more than 400 million people dwelling under the tropics and it is increasingly exported worldwide for snack production and animal feed.