The role of Toxoplasma gondii amino acid hydroxylase 2 in chronic infection

弓形虫氨基酸羟化酶2在慢性感染中的作用

• 批准号: 9120661
• 负责人: Nicole D. Marino
• 金额: $ 3.55万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9120661
• 关键词: Affect; Amino Acids; Antibodies; Automobile Driving; Back; Behavior; Behavioral; Biology; Bobcat; Brain; Cells; Chorioretinitis; Chronic; Cyst; Differentiation and Growth; Disease; Dopa; Dopamine; Encephalitis; Enzymes; Evolution; Family Felidae; Felis catus; Fright; Gastrointestinal tract structure; Gilles de la Tourette syndrome; Goals; Growth; Harvest; Health; High Pressure Liquid Chromatography; Human; Immune response; Immune system; Immunocompromised Host; In Vitro; Individual; Infection; Knowledge; Link; Measures; Mental disorders; Metabolism; Microscopy; Mission; Mixed Function Oxygenases; Mus; Neurons; Neurotransmitters; Nutrient; Odors; Oral; Oryctolagus cuniculus; PC12 Cells; Parasite Control; Parasites; Parasitic infection; Parkinson Disease; Pepsin A; Phenylalanine; Plaque Assay; Population; Process; Reaction; Reporting; Rodent; Role; Schizophrenia; Staging; Staining method; Stains; Stomach; Testing; Time; Tissues; Toxoplasma; Toxoplasma gondii; Tyrosine; Tyrosine Metabolism Pathway; Urine; Vacuole; Work; amino acid metabolism; crosslink; cytokine; dityrosine; dopaminergic neuron; feeding; insight; mutant; neurochemistry; nutrition; preference; public health relevance; seroconversion; seropositive; therapeutic development; transmission process

 DESCRIPTION (provided by applicant): Toxoplasma infection has been linked to a variety of mental disorders and behavioral alterations, including schizophrenia and Parkinson's disease. Interestingly, chronic Toxoplasma infection has been shown to increase dopamine levels and alter behavior in rodents, causing them to lose their innate fear of cat odors. Because the feline is the definitive host for Toxoplasma, it has been proposed that evolution has selected for a parasite that alters rodent behavior to increase its transmission back to the cat. Importantly, Toxoplasma increases dopamine content and secretion in neurons in vitro, suggesting that the parasite can increase dopamine metabolism independently of the immune system. It has been proposed that Toxoplasma alters dopamine and behavior using amino acid hydroxylase 2 (TgAAH2), which it expresses during chronic infection. AAH2 catalyzes the conversion of phenylalanine to tyrosine and tyrosine to DOPA, with preference for the latter reaction. Because the conversion of tyrosine to DOPA is the rate-limiting step in dopamine synthesis, Toxoplasma may increase dopamine by catalyzing the formation of DOPA, the direct precursor to dopamine. The overarching goal of this work is to determine the role of AAH2 in chronic infection, dopamine metabolism, and behavioral alteration in rodents. Previous reports show that the tissue cyst wall Toxoplasma forms during chronic infection consists of dityrosine crosslinks and DOPA, suggesting a structural role for this enzyme. The hypothesis driving this work is that AAH2 regulates amino acid metabolism during differentiation to the encysted form, contributes to formation of the cyst wall, and/or alters dopamine metabolism and behavior in the rodent host. To determine if AAH2 is important for amino acid metabolism and nutrition, growth and differentiation of the AAH2 mutant and control strains in nutrient-rich and tyrosine-deficient media will be measured by plaque assay and microscopy. To determine if AAH2 is important for synthesizing DOPA and dityrosines in the tissue cyst wall, the brains of mice chronically infected with the AAH2 mutant and control strains will be fixed, harvested, processed into sections, and stained with antibodies for dityrosine and DOPA. The infectivity of the AAH2 mutant and control cysts during passage through the gastric tract will be measured by orally infecting naïve mice and measuring seroconversion and dissemination to the brain. Structural integrity of the cyst wall will be determined by treating cysts with pepsin digestive solution and measuring parasite viability by plaque assay. To determine if AAH2 affects neurotransmitter levels during chronic infection, HPLC-ED will be performed on neurons infected with the AAH2 mutant and controls. To determine if AAH2 affects behavior in rodents, the behavior of mice around bobcat or rabbit urine during chronic infection with these strains will be measured. The completion of this work will identify the function of AAH2 during chronic Toxoplasma infection, for which there is no cure or treatment. Furthermore, it will test whether AAH2 contributes to dopamine dysregulation and behavioral alteration.

 描述（由申请人提供）：弓形虫感染与多种精神障碍和行为改变有关，包括精神分裂症和帕金森病，因为猫科动物是弓形虫的最终宿主。进化选择了一种改变啮齿动物行为的寄生虫重要的是，弓形虫在体外增加了神经元的多巴胺含量和分泌，这表明弓形虫可以独立于免疫系统增加多巴胺代谢，并且可以利用氨基酸羟化酶来改变多巴胺和行为。 2 (TgAAH2)，在慢性感染期间表达，AAH2 催化苯丙氨酸转化为酪氨酸以及酪氨酸转化为酪氨酸。 DOPA，由于酪氨酸转化为 DOPA 是多巴胺合成的限速步骤，因此弓形虫可能通过催化 DOPA（多巴胺的直接前体）的形成来增加多巴胺。这项工作的总体目标是。确定 AAH2 在啮齿动物慢性感染、多巴胺代谢和行为改变中的作用 先前的报告表明，弓形虫在慢性感染过程中形成的组织囊壁由以下部分组成。二酪氨酸交联和多巴，表明该酶的结构作用，推动这项工作的假设是，AAH2 在分化为包膜形式期间调节氨基酸代谢，有助于囊壁的形成，和/或改变多巴胺代谢和行为。为了确定 AAH2 对氨基酸代谢和营养是否重要，将通过噬菌斑测定来测量 AAH2 突变体和对照菌株在营养丰富和酪氨酸缺乏的培养基中的生长和分化。为了确定 AAH2 对于组织囊壁中合成多巴和二酪氨酸是否重要，将长期感染 AAH2 突变体和对照菌株的小鼠大脑进行固定、收获、加工成切片，并用二酪氨酸和二酪氨酸抗体染色。 DOPA。通过口服感染幼鼠并测量血清转化和在通过胃道期间的感染性。通过用胃蛋白酶消化液处理囊肿并通过斑块测定测量寄生虫活力来确定囊肿壁的结构完整性。为了确定 AAH2 在慢性感染期间是否影响神经递质水平，将对感染的神经元进行 HPLC-ED。为了确定 AAH2 是否影响啮齿动物的行为，将测量这些菌株慢性感染期间山猫或兔子尿液周围的小鼠的行为。慢性弓形虫感染期间的 AAH2 尚无治愈或治疗方法。此外，它将测试 AAH2 是否会导致多巴胺失调和行为改变。