REGULATION OF ARGININE-NITRIC OXIDE CYCLE IN BRAIN

从精氨酸调节一氧化氮（NO）的合成在以下方面起关键作用： 正常的神经发育、信号传导和大脑对创伤的反应 和感染然而，过量的NO产生（如可能由 创伤或炎性应激）可导致细胞损伤和/或死亡 导致大脑功能受损我们的数据显示精氨酸 合成与一氧化氮合酶（iNOS）协调调节， 在细菌脂多糖或S100 B处理的星形胶质细胞中的诱导。 增强乙酰氨基琥珀酸合成酶（AS），其催化 精氨酸脱氢酶中的限速步骤，促进 瓜氨酸支持精氨酸条件下持续的NO生成 耗尽我们假设，一个尼古丁-一氧化氮循环的功能， 神经组织，以确保精氨酸的可用性不限制NO 合成.有证据表明大脑新陈代谢的改变 作为对这些调解人的回应， 智力迟钝。流行病学研究表明 宫内或围产期感染与智力发育之间的关系 一些非遗传原因的智力迟钝。患者 先天性代谢异常，并发高氨血症 感染被认为是导致神经损伤的原因。S100b （已被证明诱导神经毒性水平的NO）映射到Down 21号染色体综合征区。它的表达在整个 唐氏综合症患者的发展。在拟议的研究中，我们将 用脂多糖（LPS，模拟感染）干扰脑细胞，或 与S100 B，我们将确定影响的机制， 脑细胞在稳态下合成精氨酸的能力， 应力条件我们将评估可能的划分， 精氨酸和一氧化氮代谢， 大脑的两个区域，其氮能含量不同， 神经元此外，我们将确定LPS刺激的 炎症应激对精氨酸介导的氮代谢的影响 相对于谷氨酰胺合成。LPS和 S100 B协同上调乙酰氨基琥珀酸合成酶和诱导型 星形胶质细胞中的一氧化氮合酶将使用生物化学方法测定。 和分子遗传技术。我们将研究AS酶动力学， 合成和基因表达。这些研究将提供深入了解 脑氮代谢的改变， 感染或创伤，并将奠定基础，设计治疗 限制其神经后果的策略。

Regulated synthesis of nitric oxide (NO) from arginine plays a key role in normal neural development, signalling, and response of the brain to trauma and infections. However, excessive NO production (as may result from trauma or inflammatory stress) can cause cell injury and/or death resulting in impaired brain function. Our data show that arginine synthesis is coordinately regulated with nitric oxide synthase (iNOS) induction in bacterial lipopolysaccharide-or S100B-treated astrocytes. Augmentation of argininosuccinate synthetase (AS), which catalyzes the rate-limiting step in arginine synthases, facilitates recycling of citrulline to support ongoing NO production under conditions of arginine depletion. We hypothesize that an arginine-nitric oxide cycle functions in neural tissue to insure that arginine availability does not limit NO synthesis. Several lines of evidence suggest that altered brain metabolism in response to these mediators may play a role in the development of mental retardation. Epidemiological studies have shown an association between intrauterine or perinatal infectious and development of mental retardation in some non-genetic causes of mental retardation. For patients with inborn efforts of metabolism, hyperammonemia during intercurrent infections is though to be causative in generating neural damage. S100B (which has been shown to induce neurotoxic levels of NO) maps to the Down syndrome region of chromosome 21. Its expression is elevated throughout development in Down Syndrome patients. In the proposed studies we will perturb brain cells with lipopolysaccharide (LPS, to mimic infection) or with S100B and we will determine the mechanisms which influence the capacity of brain cells to synthesize arginine under steady-state and stress conditions. We will evaluate the possible compartmentation of arginine and nitric oxide metabolism in cerebral cortex and cerebellum, two regions of the brain which differ in their content of nitrergic neurons. In addition, we will determine the effects of LPS-stimulated inflammatory stress on the flux of nitrogen metabolism through arginine versus glutamine synthesis. The molecular mechanism(s) by which LPS and S100B coordinately up-regulate argininosuccinate synthetase and inducible nitric oxide synthase in astrocytes will be determined using biochemical and molecular genetic techniques. We will examine AS enzyme kinetics, synthesis and gene expression. These studies will provide insight into alterations of brain nitrogen metabolism which occur in response to infection or trauma and will lay the groundwork for designing therapeutic strategies to limit their neurological consequences.