BIOPTERIN & CATECHOLAMINES IN AGING & NEURO-DEGENERATION

四氢生物蝶呤（BH 4）是酪氨酸羟化酶的辅因子， 酪氨酸羟化酶和色氨酸羟化酶，它们是初始的， 儿茶酚胺和5-羟色胺合成中的限速酶。 BH 4是一种 自从BH 4给药以来，是儿茶酚胺合成的重要调节剂 增加大脑多巴胺合成，而抑制BH 4合成 导致儿茶酚胺缺乏 在BH 4生物合成中，GTP环化水解酶 是最初的酶，而sepiapterin还原酶催化最终的酶。 反应 在啮齿类动物中，GTP环化水解酶可能是主要的速率控制酶 BH 4合成酶;在人类中，其他酶如sepiapterin 还原酶可能有助于调节BH 4的产生，但进一步的研究 是必需的. 在大鼠肾上腺髓质，儿茶酚胺耗竭升高 酪氨酸羟化酶和GTP环化水解酶活性，并提高BH 4 水平，表明这些酶的“协调调节”可能发生。 协调调节是指酪氨酸 羟化酶、GTP环化水解酶和sepiapterin还原酶基因表达 当BH 4和儿茶酚胺代谢发生改变时。 肾上腺皮质升高 由于儿茶酚胺消耗而产生的BH 4被认为对维持 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阶段合成。 在大脑中， 初步数据表明，非多巴胺细胞的红藻氨酸损伤 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， 几种BH 4生物合成酶中任何一种的缺陷都会导致BH 4 肝脑两虚。 这导致生物胺缺乏症 大脑和神经系统损伤 由于许多其他系统需要 这些患者生物胺合成功能正常，非典型PKU 可能是由BH 4代谢的组织特异性调节突变引起的。 BH 4生物合成的突变可以解释BH 4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BH 4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， 环水解酶和sepiapterin还原酶基因在动物模型中的表达 衰老和神经退化，以及药物治疗后， 肾上腺髓质肿瘤细胞系中的BH 4和儿茶酚胺合成， 嗜铬细胞瘤（PC 12）细胞。 作为动物的替代品，PC 12细胞可以 暴露于多种影响肾上腺BH 4的药物， 在良好控制的组织培养条件下的儿茶酚胺代谢。 因此，在BH 4和儿茶酚胺基因水平上协调调节 将在大鼠肾上腺髓质，PC 12细胞中研究表达， 第一次在大脑中 这些酶的表达将通过 测量组织MRNAS（北方印迹或核糖核酸酶保护测定）， 酶的量（蛋白质印迹）、酶活性和终产物 生物合成（BH 4和儿茶酚胺），用以下物质处理：1） 这些酶中的每一种的抑制剂; 2）BH 4和儿茶酚胺的活化剂 合成; 3）和海人酸在纹状体中的作用。 红藻氨酸也将是 用于研究衰老对存活的黑质纹状体细胞基因表达的影响， 多巴胺神经元神经毒性损伤。 这些结果将提供 人类BH 4和儿茶酚胺相关基因研究方向 表达，并存在神经精神疾病相关的 BH 4生物合成的调节突变。 人类研究可以 一旦人类BH 4相关基因探针被克隆， 在PI的实验室进行。

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.