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.

四氢生物蝶呤 (BH4) 是酪氨酸羟化酶的辅助因子， 酪氨酸羟化酶和色氨酸羟化酶，它们是初始和 儿茶酚胺和血清素合成中的限速酶。 BH4 是 自 BH4 给药以来，儿茶酚胺合成的重要调节剂 增加大脑多巴胺合成，而抑制 BH4 合成 导致儿茶酚胺缺乏。 在 BH4 生物合成中，GTP 环化水解酶 是初始酶，而墨蝶呤还原酶催化最终酶 反应。 在啮齿动物中，GTP 环水解酶可能是主要的速率控制酶 BH4合成酶；在人类中，其他酶如墨蝶呤 还原酶可能有助于调节 BH4 的产生，但需进一步研究 是必须的。 在大鼠肾上腺髓质中，儿茶酚胺消耗升高 酪氨酸羟化酶和 GTP 环化水解酶活性并提高 BH4 水平，表明这些酶可能发生“协调调节”。 协调调节是指酪氨酸的协调反应 羟化酶、GTP 环化水解酶和墨蝶呤还原酶基因表达 当 BH4 和儿茶酚胺代谢发生改变时。 肾上腺升高 由于儿茶酚胺耗尽而产生的 BH4 被认为对于维持 当催化活性较低时，体内酪氨酸羟基化增加 酪氨酸羟化酶分子在早期合成。 在大脑中， 初步数据表明红藻氨酸损伤非多巴胺细胞 纹状体中的纹状体酪氨酸羟化酶和 CTP 环化水解酶升高 活动。 在患有非典型苯丙酮尿症 (PKU) 的新生儿中，遗传因素 几种 BH4 生物合成酶中任何一种的缺陷都会导致 BH4 肝、脑不足。 这导致生物胺缺乏 大脑和神经系统损伤。 由于许多其他系统需要 这些患者的生物胺合成功能正常，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 生物合成的突变可以解释 BH4 和儿茶酚胺的改变 在正常衰老、阿尔茨海默病和帕金森病中观察到的缺陷， 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）的协调调节而获得 动物模型中环水解酶和墨蝶呤还原酶基因表达 衰老和神经退行性变以及药物治疗后的影响 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 接触更广泛的影响肾上腺 BH4 的药物，并且 儿茶酚胺代谢在良好控制的组织培养条件下。 因此，BH4和儿茶酚胺基因水平的协调调控 将在大鼠肾上腺髓质、PC12 细胞中研究表达，并用于 第一次在大脑中。 这些酶的表达将通过以下方式监测 测量组织 MRNAS（Northern 印迹或核糖核酸酶保护测定）， 酶量（蛋白质印迹）、酶活性和最终产物 经过以下处理后的生物合成（BH4 和儿茶酚胺）：1) 这些酶的抑制剂； 2)BH4和儿茶酚胺激活剂 合成，3) 和纹状体中的红藻氨酸。 红藻氨酸也将 用于检查衰老对幸存黑质纹状体基因表达的影响 神经毒性损伤后的多巴胺神经元。 这些结果将提供 检测人类 BH4 和儿茶酚胺相关基因的研究方向 表达以及相关神经精神疾病的存在 BH4生物合成的调节突变。 人类研究可以 一旦克隆了人类 BH4 相关基因探针，就完成了 PI 实验室正在进行中。