OXIDATITIVE STRESS IN PATIENTS WITH ATAXIA-TELANGIECTASIA

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。共济失调-毛细血管扩张症（A-T）是一种遗传性疾病，可导致神经变性、免疫缺陷、基因组不稳定、对电离辐射敏感性增加以及易患淋巴网状细胞恶性肿瘤。A-T是由ATM（A-T突变）基因突变引起的，该基因编码丝氨酸和苏氨酸激酶蛋白（ATM），该蛋白在DNA双链断裂后的细胞周期停滞和DNA修复中起信号作用。淋巴细胞和神经元凋亡的机制在很大程度上是未知的。据推测，A-T细胞可能无法抵消活性氧（ROS）对DNA的损伤作用。此外，A-T患者可能会增加ROS的产生，部分原因是慢性/复发性感染。事实上，在表达ATM功能缺失突变的人类和小鼠中已经检测到对脂质和DNA的氧化损伤水平增加。具有A-T突变的淋巴母细胞样细胞系具有响应于基因毒性应激的通路的组成性激活，其中p53、p21、磷酸丝氨酸-15 p53和磷酸酪氨酸-15 cdc 2的基础水平升高。当细胞在抗氧化剂α-硫辛酸存在下培养时，这些应激蛋白中的每一种的水平都会降低。 有几种潜在的方法可以抵消氧化应激的影响。一种方法是使用抗氧化剂。一种这样的化合物，α-硫辛酸，可以直接清除活性氧（ROS），刺激本身是ROS清除剂的谷胱甘肽的合成，并再生其他抗氧化剂，如维生素C和E。事实上，当A-T细胞与α-硫辛酸一起培养时，应激蛋白的细胞水平降低。另一种方法是阻止氧化应激的后果。聚ADP核糖聚合酶（PARP）引起的蛋白质ADP核糖基化在氧化损伤后DNA修复中起重要作用。然而，PARP激活可导致细胞NAD+和ATP的快速消耗，并导致细胞生长和/或凋亡的异常。PARP抑制剂可能能够最大限度地减少这些次要影响。 我们建议在青少年和成人（> 12岁）A-T患者中进行一项抗氧化剂（α-硫辛酸）和PARP抑制剂（烟酰胺）的双盲、安慰剂对照初步研究。主要结果指标将是脂质和DNA氧化损伤水平的变化。次要结局指标将是淋巴细胞计数和神经功能的变化以及安全性。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ataxia-Telangiectasia (A-T) is an inherited disorder that causes neurodegeneration, immunodeficiency, genomic instability, increased sensitivity to ionizing radiation, and a predisposition to lymphoreticular malignancy . A-T is caused by mutations in the ATM (A-T mutated) gene, encoding a serine and threonine kinase protein (ATM) that has roles in signaling cell-cycle arrest and DNA repair after double-stranded breaks in DNA . The mechanisms underlying the apoptotic death of lymphocytes and neurons are largely unknown. It has been hypothesized that A-T cells may have an inability to counteract the damaging effects of reactive oxygen species (ROS) on DNA. In addition, A-T patients may have increased production of ROS due, in part, to chronic/recurrent infections. Indeed, increased levels of oxidative damage to lipids and DNA have been detected in humans and mice expressing loss of function mutations of ATM. Lymphoblastoid cell lines with A-T mutations have constitutive activation of pathways that respond to genotoxic stress with elevated basal levels of p53, p21, phosphoserine-15 p53, and phosphotyrosine-15 cdc2. The levels of each of these stress proteins decreases when cells are cultured in the presence of the anti-oxidant, alpha-lipoic acid. There are several potential ways to counteract the effects of oxidative stress. One approach is to use anti-oxidants. One such compound, alpha-lipoic acid, can directly scavage reactive oxygen species (ROS), stimulate the synthesis of glutathrione which is itself an ROS scavenger, and regenerate other anti-oxidants such as vitamins C and E. In fact, when A-T cells are cultured with alpha-lipoic acid, the cellular levels of stress proteins decrease. Another approach is to block the consequences of oxidative stress. Protein ADP-ribosylation by poly ADP ribose polymerase (PARP) is thought to play an important role in DNA repair after oxidative damage. However, PARP activationn can cause rapid depletion of cellular NAD+ and ATP with subsquent abnormalities in cell growth and/or apoptosis. PARP inhibitors may be able to minimize these secondary effects. We propose a double-blind, placebo-controlled pilot study of an anti-oxidant (alpha-lipoic acid) and a PARP inhibitor (nicotinamide) in adolescents and adults (> 12 years old) with A-T. The primary outcome measures will be changes in levels of oxidative damage to lipids and DNA. Secondary outcome measures will be changes in lymphocyte count and neurologic function, and safety.