Tetrahydrobiopterin in Hypoxia-Ischemia Induced Fetal Brain Dysfunction

四氢生物蝶呤在缺氧缺血引起的胎儿脑功能障碍中的作用

• 批准号: 7383759
• 负责人: JEANNETTE M. VASQUEZ VIVAR
• 金额: $ 16.59万
• 依托单位: MEDICAL COLLEGE OF WISCONSIN
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7383759
• 关键词: Acute; Affect; Antioxidants; Arginine; Arts; Biochemical; Biopterin; Brain; Brain Hypoxia-Ischemia; Brain Injuries; Brain Part; Calcium; Cells; Cerebral Palsy; Child; Chronic; Citrulline; Clinical; Cognitive; Defect; Detection; Development; Developmental Biology; Disease; Dopa-Responsive Dystonia; Dystonia; Enzymes; Equilibrium; Etiology; Event; Free Radicals; Functional disorder; Generations; Genetic Models; Glutamates; Goals; High Pressure Liquid Chromatography; Homeostasis; Human; Hydrogen Peroxide; Hypoxia; Impaired cognition; Injury; Levodopa; Light; Link; Measurement; Measures; Mediating; Medical; Metabolism; Methods; Modeling; Motor Seizures; Mus; Muscle Hypertonia; N-Methyl-D-Aspartate Receptors; Neonatal; Neopterin; Nervous System Physiology; Neurologic; Nitric Oxide; Nitric Oxide Synthase Type I; Oral; Oryctolagus cuniculus; Oxidants; Oxidation-Reduction; Oxidative Stress; Oxygen; Pathway interactions; Perinatal Brain Injury; Perinatal Hypoxia; Play; Predisposition; Prevention; Preventive; Production; Protocols documentation; Reactive Nitrogen Species; Receptor Activation; Reporting; Research Personnel; Risk Factors; Role; Staining method; Stains; Superoxides; Supplementation; Techniques; Testing; Therapeutic; Therapeutic Intervention; Variant; Western Blotting; age related; ascorbate; base; cold temperature; dihydroethidium; dimer; disability; dopaminergic neuron; excitotoxicity; fetal; indexing; inhibitor/antagonist; monomer; motor deficit; motor impairment; neonate; omega-N-Methylarginine; outcome forecast; prevent; response; tetrahydrobiopterin

DESCRIPTION (provided by applicant): The broad objective of this proposal is to determine the link between hypoxia-ischemia (H-I) and loss of tetrahydrobiopterin (BH4) and neurological function in the preterm fetal brain. The mechanism by which H-I causes damage to the developing brain remains unknown, although evidence indicates that oxidative stress plays a role. Loss of dopaminergic neurons may occur as a consequence. Congenital BH4 deficiency causes motor deficits that, in some cases, can be treated with BH4. We recently presented a model of global H-I injury in preterm fetal rabbit brain that causes hypertonia and motor deficits in the neonates and shows that BH4 levels in the preterm fetal rabbit brain are much lower compared to those reported in the hph-1 mice, a model for genetic BH4 deficiency and L-dopa-responsive-dystonia. Thus, low BH4 levels may be a critical developmental factor associated with H-I induced fetal brain dysfunction. We also showed that limited BH4 levels supports nNOS uncoupling to increase superoxide formation. Thus, preterm fetal rabbit brain gives investigators an opportunity that was not available before to ascertain the connection between H-I and BH4- dependent mechanisms (NO, superoxide, L-dopa) in the etiology of motor impairments. Hypothesis: High oxidative stress induced by hypoxia-ischemia disrupts BH4-homeostasis in the preterm fetal brain leading to motor deficits. Aims: 1) Examine whether the developmental susceptibility of the premature brain can be explained by BH4 modulation of superoxide and NO production from nNOS; 2) Examine the acute and chronic mechanisms causing loss of BH4 and nNOS uncoupling after H-I; and the effects of BH4 supplementation alone or in combination with ascorbate, a BH4 stabilizing antioxidant. Methods: Brain BH4, 7,8-BH2 and neopterin levels and activity of BH4-dependent enzymes will be measured by HPLC. Superoxide quantification following conversion of dihydroethidium to 2-hydroxyethidium will be performed by HPLC. nNOS activity will be followed by 14 C-citrulline and NO-derived chemiluminescence. Significance: Perinatal H-I is an important risk factor for disability in children often resulting in cognitive and motor impairment (cerebral palsy). Currently, there is no effective treatment to prevent the consequences of H-I mediated injury to the developing brain. The information obtained from this proposal will provide the basis to define the use of BH4 in preventing fetal brain dysfunction. Hypoxia-ischemia (H-I) or low oxygen supply is considered a major risk factor for brain damage in the immature fetal brain. Currently, there are no interventional measures to prevent or decrease brain damage after any clinical situation where deficient oxygen supply is suspected. The complications and prognosis of H-I are age related, indicating the importance of developmental factors in the disease. Tetrahydrobiopterin is a key metabolite in the brain regulating several functions and oxidant production. It is possibly involved in brain dysfunction, following H-I. We expect to provide important new information on the developmental biology of tetrahydrobiopterin and its involvement in the mechanisms of oxidative damage in fetal brain. This information will likely define the use of tetrahydrobiopterin in the prevention and/or amelioration of H-I induced fetal brain dysfunction, which remains a major medical challenge.

描述（由申请人提供）：本提案的主要目的是确定早产胎儿大脑中缺氧缺血（H-I）与四氢生物蝶呤（BH4）丢失和神经功能之间的联系。H-I对发育中的大脑造成损害的机制尚不清楚，尽管有证据表明氧化应激起了一定作用。多巴胺能神经元可能因此丧失。先天性BH4缺乏导致运动缺陷，在某些情况下，可以用BH4治疗。我们最近提出了一种导致新生儿高张力和运动障碍的早产兔胎儿脑内整体H-I损伤模型，并表明早产兔胎儿脑内BH4水平远低于hph-1小鼠（遗传BH4缺乏和左旋多巴反应性肌张力障碍模型）。因此，低BH4水平可能是与H-I诱导的胎儿脑功能障碍相关的关键发育因素。我们还发现，有限的BH4水平支持nNOS解耦以增加超氧化物的形成。因此，早产儿兔脑为研究人员提供了一个以前无法获得的机会，以确定运动障碍病因中H-I和BH4依赖机制（NO，超氧化物，左旋多巴）之间的联系。假设：缺氧缺血引起的高氧化应激破坏了早产胎儿大脑中bh4的稳态，导致运动障碍。目的：1)探讨BH4对nNOS超氧化物和一氧化氮生成的调节是否可以解释早产儿脑的发育易感性；2)探讨H-I后BH4和nNOS失偶的急性和慢性机制；以及单独补充BH4或与抗坏血酸（一种BH4稳定抗氧化剂）联合使用的效果。方法：采用高效液相色谱法测定脑内BH4、7、8-BH2、新蝶呤水平及BH4依赖性酶活性。二氢乙锭转化为2-羟乙锭后的超氧化物定量将采用高效液相色谱法进行。nNOS活性之后是14c -瓜氨酸和no衍生的化学发光。意义：围产期H-I是儿童残疾的重要危险因素，常导致认知和运动障碍（脑瘫）。目前，还没有有效的治疗方法来预防H-I介导的脑损伤对发育中的大脑的影响。从该建议中获得的信息将为确定BH4在预防胎儿脑功能障碍中的使用提供基础。缺氧缺血（H-I）或低氧供应被认为是未成熟胎儿脑损伤的主要危险因素。目前，在临床疑似缺氧的情况下，还没有预防或减少脑损伤的介入措施。H-I的并发症和预后与年龄相关，提示发育因素在疾病中的重要性。四氢生物蝶呤是大脑中调节多种功能和氧化剂产生的关键代谢物。它可能与H-I之后的脑功能障碍有关。我们期望在四氢生物蝶呤的发育生物学及其参与胎儿脑氧化损伤机制方面提供重要的新信息。这一信息可能会定义四氢生物蝶呤在预防和/或改善H-I诱导的胎儿脑功能障碍中的使用，这仍然是一个主要的医学挑战。