BIOPTERIN & CATECHOLAMINES IN AGING & NEURO-DEGENERATION

生物蝶呤

• 批准号: 3415458
• 负责人: ROBERT A LEVINE
• 金额: $ 4.43万
• 依托单位: HENRY FORD HEALTH SYSTEM
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-08-01 至 1996-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3415458
• 关键词: PC12 cells; adenosine monophosphate; adrenal medulla; adrenal medulla neoplasm; aging; biological models; brain cell; catalyst; catecholamine inhibitor; catecholamines; chemical kinetics; corpus striatum; dopamine; enzyme activity; enzyme biosynthesis; enzyme induction /repression; enzyme inhibitors; enzyme mechanism; gene expression; genetic regulation; hydrolase; kainate; laboratory rat; messenger RNA; neural degeneration; neurotoxins; neurotransmitter biosynthesis; neurotrophic factors; northern blottings; oxidoreductase; pteridines; serotonin; tissue /cell culture; tyrosine 3 monooxygenase; western blottings

Tetrahydrobiopterin (BH4) is the cofactor for tyrosine hydroxylase and tyrosine hydroxylase and tryptophan hydroxylase, which are the initial and rate-limiting enzymes in catecholamine and serotonin synthesis. BH4 is an important regulator of catecholamine synthesis, since BH4 administration increases brain dopamine synthesis, whereas inhibition of BH4 synthesis leads to catecholamine deficits. In BH4 biosynthesis, GTP cyclohydrolase is the initial enzyme, whereas sepiapterin reductase catalyzes the final reaction. In rodent, GTP cyclohydrolase may be the main rate-controlling enzyme in BH4 synthesis; in humans, other enzymes such as sepiapterin reductase may contribute to regulating BH4 production, though further study is required. In rat adrenal medulla, catecholamine depletion elevates tyrosine hydroxylase and GTP cyclohydrolase activities and raises BH4 levels, indicating that "coordinate regulation" of these enzymes may occur. Coordinate regulation refers to a coordinated response in tyrosine hydroxylase, GTP cyclohydrolase, and sepiapterin reductase gene expression when BH4 and catecholamine metabolism is altered. The elevation of adrenal BH4 due to catecholamine depletion is thought o be crucial for maintaining increased tyrosine hydroxylation in vivo when less catalytically-active tyrosine hydroxylase molecules are synthesized at early stages. In brain, preliminary data indicates that kainic acid lesions of non-dopamine cells in striatum elevates striatal tyrosine hydroxylase and CTP cyclohydrolase activities. In newborns with atypical phenylketonuria (PKU), genetic defects in any one of the several BH4 biosynthetic enzymes lead to BH4 deficiency in liver and brain. This results in a biogenic amine deficiency in brain and neurological impairment. Since many other systems requiring biogenic amine synthesis function normally in these patients, atypical PKU may be caused by tissue-specific regulatory mutations of BH4 metabolism. Mutations of BH4 biosynthesis may explain altered BH4 and catecholamine deficits observed in normal aging, Alzheimer's and Parkinson's diseases, and familial dystonia. Further understanding of BH4 biosynthesis will be obtained by studying coordinate regulation of tyrosine hydroxylase, GTP cyclohydrolase, and sepiapterin reductase gene expression in animal models of aging and neuro-degeneration, and following drug treatments influencing BH4 and catecholamine synthesis in the adrenal medulla tumor cell line, pheochromocytoma (PC12) cells. As a substitute for animals, PC12 cells can be exposed to a wider variety of drugs affecting adrenal BH4 and catecholamine metabolism under well-controlled tissue culture conditions. Thus, coordinate regulation at the level of BH4 and catecholamine gene expression will be studied in rat adrenal medulla, PC12 cells, and for the first time in brain. Expression of these enzymes will be monitored by measuring tissue MRNAS (Northern blots or ribonuclease protection assays), amounts of enzymes (Western blots), enzyme activities, and end-products of biosynthesis (BH4 and catecholamines) following treatments with: 1) inhibitors of each of these enzymes; 2)activators of BH4 and catecholamine synthesis, and 3) and kainic acid in striatum. Kainic acid will also be used to examine aging effects on gene expression in surviving nigrostriatal dopamine neurons following neurotoxic damage. These results will provide direction for studies examining human BH4 and catecholamine-related gene expression, and the existence of neuropsychiatric diseases related to regulatory mutations of BH4 biosynthesis. Human studies can be accomplished once the human BH4-related gene probes are cloned, which is ongoing in the PI's laboratory.

四氢无菌蛋白酶（BH4）是酪氨酸羟化酶的辅助因子和 酪氨酸羟化酶和色氨酸羟化酶，这是初始和 儿茶酚胺和5-羟色胺合成中的限速酶。 BH4是一个 自BH4给药以来，儿茶酚胺合成的重要调节剂 增加脑多巴胺合成，而BH4合成的抑制作用 导致儿茶酚胺缺陷。 在BH4生物合成中，GTP环溶酶 是初始酶，而棕虫还原酶催化最终 反应。 在啮齿动物中，GTP环氢酶可能是主要速率控制 BH4合成中的酶；在人类中，其他酶，例如形蛋白酶 还原酶可能有助于调节BH4的产生，尽管进一步研究 是必须的。 在大鼠肾上腺髓质中，儿茶酚胺的耗竭升高 酪氨酸羟化酶和GTP环溶酶活性并提高BH4 水平，表明可能发生这些酶的“协调调节”。 协调法规是指酪氨酸中的协调反应 羟化酶，GTP环丙基酶和肌蛋白还原酶基因表达 当BH4和Catecholamine代谢发生变化时。 肾上腺升高 BH4由于儿茶酚胺耗竭而被认为对维持至关重要 当催化活性较少时，体内酪氨酸羟基化增加 酪氨酸羟化酶分子在早期阶段合成。 在大脑中， 初步数据表明非多巴胺细胞的海藻酸病变 在纹状体中，抬高纹状体酪氨酸羟化酶和CTP环氢酶 活动。 在具有非典型苯酮尿症（PKU）的新生儿中，遗传 几种BH4生物合成酶中的任何一种缺陷导致BH4 肝脏和大脑缺乏。 这导致生物胺缺乏 在大脑和神经系统障碍中。 由于许多其他系统需要 生物胺合成通常在这些患者中起作用，非典型PKU 可能是由BH4代谢的组织特异性调节突变引起的。 BH4生物合成的突变可能解释了变化的BH4和儿茶酚胺 在正常衰老，阿尔茨海默氏症和帕金森氏病中观察到的赤字， 和家族性肌张力障碍。 对BH4生物合成的进一步了解将是 通过研究酪氨酸羟化酶GTP的坐标调节获得 动物模型中的环羟酶和形肌蛋白还原酶基因表达 衰老和神经脱生，以及影响影响的药物治疗 肾上腺髓质肿瘤细胞系中的BH4和儿茶酚胺合成， 嗜铬细胞瘤（PC12）细胞。 作为动物的替代品，PC12细胞可以 暴露于影响肾上腺BH4和 在良好控制的组织培养条件下的儿茶酚胺代谢。 因此，在BH4和Catecholamine基因的水平上进行调节 表达将在大鼠肾上腺髓质，PC12细胞中进行研究，并在 第一次在大脑中。 这些酶的表达将由 测量组织mRNA（北印迹或核糖核酸酶保护测定）， 酶（蛋白印迹），酶活性和最终产物的数量 生物合成（BH4和Catecholamines）处理以下处理：1） 每种酶的抑制剂； 2）BH4和Catecholamine的激活剂 合成，3）和纹状体中的海藻酸。 海藻酸也将是 用于检查存活的骨纹状体中对基因表达的衰老作用 神经毒性损伤后多巴胺神经元。 这些结果将提供 研究人BH4和儿茶酚胺相关基因的研究方向 表达，以及与 BH4生物合成的调节突变。 人类研究可能是 一旦将与人类BH4相关的基因探针克隆到 在Pi的实验室中持续。