REGULATION OF ARGININE-NITRIC OXIDE CYCLE IN BRAIN

精氨酸对一氧化氮(NO)的调节合成在 正常的神经发育、信号和大脑对创伤的反应 和感染。然而，过量的NO产生(可能会导致 创伤或炎症应激)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 一氧化氮合酶(INOS)对合成的协调调节 细菌脂多糖或S100B对星形胶质细胞的诱导。 精氨酸琥珀酸合成酶(AS)的增强，它催化 精氨酸合成酶中的限速步骤，促进循环 瓜氨酸支持精氨酸条件下持续一氧化氮的产生 耗尽。我们假设精氨酸-一氧化氮循环在 神经组织，以确保精氨酸的可用性不会限制NO 综合。多条证据表明大脑新陈代谢的改变 在应对这些问题时，调解人可能会在发展中发挥作用 精神发育迟滞。流行病学研究表明两者之间存在联系 宫内或围产期感染与智力发育的关系 精神发育迟缓的一些非遗传原因。对病人来说 伴随着先天代谢的努力，并发高氨血症 感染被认为是导致神经损伤的原因。S100B (已被证明可诱导神经毒性水平的NO)映射到Down 21号染色体的综合征区域。它的表达从头到尾都在提升 唐氏综合征患者的发展状况。在建议的研究中，我们会 用脂多糖(LPS，模拟感染)干扰脑细胞或 使用S100B，我们将确定影响 脑细胞在稳态和非稳态条件下合成精氨酸的能力 压力条件。我们将评估可能的隔间 大脑皮层和小脑的精氨酸和一氧化氮代谢 大脑的两个区域，它们的氮能含量不同 神经元。此外，我们还将确定内毒素刺激的影响 炎症应激对精氨酸氮代谢通量的影响 而不是谷氨酰胺合成。脂多糖与多糖结合的分子机制(S) S100B协同上调精氨酸琥珀酸合成酶和诱导型 将用生化方法测定星形胶质细胞中的一氧化氮合酶 和分子遗传技术。我们将研究作为酶的动力学， 合成和基因表达。这些研究将提供对 脑氮代谢的改变 感染或创伤，并将为设计治疗方法奠定基础 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.