GI Endotoxin as an Environmental Trigger in an alpha-Synuclein Transgenic Mouse

胃肠道内毒素作为 α-突触核蛋白转基因小鼠的环境触发因素

• 批准号: 7985599
• 负责人: ROBERT L NUSSBAUM
• 金额: $ 39.16万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-06 至 2013-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7985599
• 关键词: Affect; Age; Age-Months; Alpha-Synuclein transgenic mouse; Animal Model; Animals; Artificial Chromosomes; Autonomic Dysfunction; Autonomic nervous system; Autopsy; Bacteria; Bacterial Toxins; Brain; Brain Stem; Breathing; Catecholamines; Central Nervous System Diseases; Characteristics; Chemical Agents; Complex; Corpus striatum structure; Defect; Dementia; Development; Disease; Drug Implants; Endotoxins; Engineering; Enteral; Enteric Nervous System; Environmental Exposure; Environmental Risk Factor; Epidemiology; Equilibrium; Escherichia coli; Etiology; Exposure to; Family; Family Study; Functional disorder; Gastrointestinal tract structure; Genetic; Genetic Predisposition to Disease; Genotype; Goals; Heavy Metals; Human; Individual; Inflammation; Inflammatory; Inherited; Intervention; Intestines; Label; Lipopolysaccharides; Measures; Mental Depression; Messenger RNA; Microarray Analysis; Microbe; Midbrain structure; Modeling; Motor; Movement Disorders; Mus; Mutation; Nerve Degeneration; Nervous system structure; Neurodegenerative Disorders; Neurologic; Olfactory Nerve; Oral; Oral Administration; Parkinson Disease; Parkinsonian Disorders; Pathogenesis; Pathology; Patients; Penetration; Pesticides; Plasma; Predisposition; Prevention; Process; Proteins; Recombinant DNA; Reporting; Research; Risk; Role; Rotenone; SNCA gene; Series; Severities; Staging; Substantia nigra structure; Symptoms; Testing; Time; Toxic Environmental Substances; Transgenic Animals; Transgenic Mice; Transgenic Model; Transgenic Organisms; Twin Multiple Birth; Twin Studies; United States; Variant; Virus Diseases; absorption; alpha synuclein; base; cell motility; cohort; cytokine; density; disability; dopaminergic neuron; environmental agent; gastrointestinal; gastrointestinal function; genetic association; human disease; implantable device; inflammatory marker; mutant; nervous system disorder; neuron loss; neurotoxic; neurotoxicity; overexpression; public health relevance; synuclein

DESCRIPTION (provided by applicant): Parkinson Disease (PD) is a common neurodegenerative disease affecting ~1 million people in the United States. While loss of substantia nigra dopaminergic neurons is primarily responsible for the characteristic parkinsonian movement disorder, non-motor disabilities including dementia, depression, gastrointestinal dysfunction, and autonomic instability arise from neurodegeneration elsewhere in the central, enteric and autonomic nervous systems. The cause of most PD is unknown despite decades of research. Family studies, twin studies, and genetic association studies in Parkinson disease (PD) support the view that PD is a complex systemic nervous system disorder caused by one or more environmental agents acting on genetically vulnerable individuals. The genetic predisposition can be strong, as in the rare, familial forms of PD caused by missense or copy number mutations in the 1-synuclein gene (SNCA), or subtle, as in the more common sporadic disease, where genetic association studies indicate that polymorphic variants at the SNCA locus contribute to genetic predisposition. Epidemiological and experimental observations have suggested many different environmental agents may contribute to the development of PD. These include viral infection, heavy metals, bacterial toxins, microbe-induced inflammation, and chemical agents including pesticides. The balance between genetic predisposition and environmental insult is likely to be different depending on the strength of the predisposition. The intensity of environmental exposure required to cause disease is likely inversely related to the degree of genetic vulnerability: the greater the genetic susceptibility, the less the environmental exposure required and the more apparently heritable the disease will appear to be. Exposure to the environmental agents implicated in PD is probably via the gastrointestinal (GI) tract (although inhalation exposing the olfactory nerves is also possible), suggesting that the enteric nervous system (ENS), which would be on the front lines of exposure to these environmental agents, might be affected early in the disease. Indeed, GI dysfunction is well documented to occur years to decades before the motor signs in PD patients. Braak and his colleagues reported that the youngest individuals in their large autopsy series showed pathological changes of PD only in the enteric nervous system (ENS), while PD pathology in the CNS appeared at older ages, affecting predominantly the brain stem, as well as in the ENS. Ultimately, CNS pathology in the midbrain (including substantia nigra) and cortex was seen in still older individuals. We propose to test the hypothesis that exposure of genetically predisposed mice to pathogenic environmental exposures through the GI tract will model PD and that early ENS dysfunction not only temporally precedes CNS dysfunction but actually contributes causally to it by increasing the exposure to these agents. We have developed a series of transgenic mice engineered to mimic genetically vulnerable individuals with familial PD due to SNCA mutations. These mice overexpress either wildtype or mutant (A53T and A30P) human 1-synuclein from a P1 artificial chromosome containing the human SNCA locus. Mice expressing either of the two mutant, but not wildtype, 1-synucleins have ENS dysfunction as early as 3 months of age, with prolonged Gl transit time and decreased colonic motility, but minimal CNS dysfunction and CNS neuronal loss. We will expose these transgenic animals to gram-negative endotoxin and rotenone, two agents frequently considered as environmental toxins most strongly implicated in PD. We will ask whether the enteric nervous system defect in our 1Syn transgenic models will (1) cause changes in distribution and composition of gut flora and exposure to intestinal bacteria, (2) enhance the absorption of endotoxin leading to systemic inflammatory effects and neurological defects, and (3) increase absorption and neurotoxicity of rotenone, a pesticide previously shown in cellular and animal models to cause neurodegeneration. PUBLIC HEALTH RELEVANCE: Evidence is accumulating that environmental exposures in individuals genetically predisposed to Parkinson disease are critical in the development of the disease. The applicant wants to know if mice, engineered to mimic the genetic make-up of humans with a form of hereditary Parkinson disease, are at significantly increased risk for developing a mouse equivalent of Parkinson disease when exposed through their gastrointestinal tract to two different environmental agents thought to have a role in causing human PD: endotoxin made by normal bacteria in the gut and the commonly used pesticide rotenone. The ultimate goal is to study in detail the role of gastrointestinal exposure to environmental agents in the development of neurodegeneration in a model of the natural human disease. By understanding the disease process, we can identify points at which interventions could slow or stop its progression.

描述（由申请人提供）：帕金森病（PD）是一种常见的神经退行性疾病，在美国影响约100万人。虽然黑质多巴胺能神经元的损失主要是造成特征性帕金森运动障碍的原因，但非运动性残疾包括痴呆、抑郁、胃肠功能障碍和自主神经不稳定性是由中枢、肠和自主神经系统中其他部位的神经变性引起的。大多数PD的原因是未知的，尽管几十年的研究。 帕金森病（PD）的家族研究、双胞胎研究和遗传关联研究支持这样的观点，即PD是一种复杂的全身性神经系统疾病，由一种或多种环境因子作用于遗传易感个体引起。遗传易感性可能很强，如在罕见的家族性PD中由1-突触核蛋白基因（SNCA）中的错义或拷贝数突变引起的，或微妙的，如在更常见的散发性疾病中，遗传关联研究表明SNCA基因座的多态性变异有助于遗传易感性。流行病学和实验观察表明，许多不同的环境因素可能有助于PD的发展。这些包括病毒感染，重金属，细菌毒素，微生物引起的炎症和化学制剂，包括杀虫剂。遗传易感性和环境损害之间的平衡可能会有所不同，这取决于易感性的强度。引起疾病所需的环境暴露强度可能与遗传脆弱性的程度成反比：遗传易感性越大，所需的环境暴露就越少，疾病似乎越容易遗传。 暴露于与PD有关的环境因子可能是通过胃肠道（GI）（尽管吸入暴露嗅觉神经也是可能的），这表明肠神经系统（ENS）可能在疾病早期受到影响，肠神经系统可能处于暴露于这些环境因子的第一线。事实上，GI功能障碍在PD患者出现运动体征前数年至数十年就已被充分记录。Braak和他的同事报告说，在他们的大型尸检系列中，最年轻的个体仅在肠神经系统（ENS）中显示出PD的病理变化，而CNS中的PD病理出现在年龄较大的个体中，主要影响脑干，以及ENS。最终，中脑（包括黑质）和皮质中的CNS病理在更年长的个体中观察到。我们建议测试的假设，即暴露的遗传易感小鼠致病性环境暴露通过胃肠道模型PD和早期ENS功能障碍不仅暂时先于CNS功能障碍，但实际上有助于因果关系，它通过增加暴露于这些代理。 我们已经开发了一系列转基因小鼠，这些小鼠被工程化以模仿由于SNCA突变而具有家族性PD的遗传易感个体。这些小鼠从含有人SNCA基因座的P1人工染色体过表达野生型或突变型（A53 T和A30 P）人1-突触核蛋白。表达两种突变型1-突触核蛋白中的任一种而非野生型1-突触核蛋白的小鼠早在3个月大时就具有ENS功能障碍，具有延长的GI通过时间和降低的结肠运动性，但具有最小的CNS功能障碍和CNS神经元损失。我们将这些转基因动物暴露于革兰氏阴性菌内毒素和鱼藤酮，这两种物质经常被认为是与PD最密切相关的环境毒素。我们将询问我们的1 Syn转基因模型中的肠神经系统缺陷是否会（1）引起肠道植物群的分布和组成的变化以及暴露于肠道细菌，（2）增强内毒素的吸收，导致全身炎症效应和神经缺陷，以及（3）增加鱼藤酮的吸收和神经毒性，鱼藤酮是一种先前在细胞和动物模型中显示会引起神经变性的杀虫剂。 公共卫生关系：越来越多的证据表明，在遗传上易患帕金森病的个体中，环境暴露对疾病的发展至关重要。申请人想知道，当小鼠通过胃肠道暴露于两种不同的被认为在引起人类PD中起作用的环境因子时，经工程改造以模拟具有遗传性帕金森病形式的人类遗传组成的小鼠是否具有显著增加的发展帕金森病小鼠等效物的风险：肠道中正常细菌产生的内毒素和常用的农药鱼藤酮。最终目标是详细研究胃肠道暴露于环境因子在自然人类疾病模型中神经变性发展中的作用。通过了解疾病过程，我们可以确定干预措施可以减缓或阻止其进展的点。