Elucidation of nitric oxide resistance mechanisms in motor neurons

描述（由申请人提供）：一氧化氮（NO）是一种自由基，被中枢神经系统用于正常的生理功能。然而，当它在不适当的位置或过量释放时，NO导致硝基酪氨酸的形成，硝基酪氨酸是NO介导的损伤和大量细胞死亡的标志。细胞死亡和硝基酪氨酸形成见于脊髓损伤和神经退行性疾病，如阿尔茨海默氏症、多发性硬化症（MS）和肌萎缩侧索硬化症（ALS）。有趣的是，用亚毒性剂量的NO预处理的运动神经元细胞对正常毒性剂量的NO产生了显著的抗性，我们将这种现象称为诱导适应性抗性（IAR）。此外，当暴露于有毒剂量的NO时，适应的细胞很少或没有硝基酪氨酸的形成。IAR依赖于血红素代谢酶血红素加氧酶1 （HO-1）。该资助的总体目标是阐明和解剖IAR现象，并由此开始了解中枢神经系统的天然抗性机制，该机制可用于保护神经元免受中枢神经系统损伤和神经退行性疾病中no介导的损伤。目标是：1。确定no诱导的细胞死亡是否由于细胞蛋白的相关硝化作用。如果是这样，那么a)阻断3NY的形成也应该阻断NO的杀伤，b)在没有NO处理的情况下，细胞蛋白质的硝化作用应该足以杀死细胞。2. 目的探讨HO1诱导NO适应性抵抗的机制。HO1可能通过以下途径诱导对NO的适应性抵抗：a)降低细胞内血红素浓度，b)生成血红素代谢物如胆红素和一氧化碳，c)这些作用的联合，d)或其他一些与HO1相关的未知活性。3. 确定持续暴露于低水平一氧化氮是否会对有毒的一氧化氮产生持续的抗性。研究IAR窗口是否可以扩大具有明显的治疗意义。

DESCRIPTION (provided by applicant): Nitric oxide (NO) is a free radical that is utilized by the CNS for normal physiological functions. However, when it is released in inappropriate locations or in excess, NO results in the formation of nitrotyrosine, a marker for NO-mediated damage, and massive cell death. Cell death and nitrotyrosine formation are seen in spinal cord injury and in neurodegenerative diseases such as Alzheimer's, multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Interestingly, motor neuron cells pretreated with sub-toxic doses of NO gain significant resistance to normally toxic doses of NO, a phenomenon we termed induced adaptive resistance (IAR). Furthermore, when exposed to toxic doses of NO, adapted cells have little to no nitrotyrosine formation. IAR is dependent on the heme metabolizing enzyme, heme oxygenase 1 (HO-1). The overall aim of this grant is elucidate and dissect the IAR phenomenon and by so doing, begin to understand native resistance mechanisms in the CNS that can be utilized to protect neurons against NO-mediated damage seen in CNS injury and neurodegenerative disease. The aims are: 1. To determine whether NO-induced cell death is due to the associated nitration of cellular proteins. If so then a) blocking 3NY formation should also block killing by NO and b) the nitration of cellular proteins, in the absence of NO treatment, should be sufficient to kill cells. 2. To determine how HO1 induces adaptive resistance to NO. Potentially, HO1 may induce adaptive resistance to NO by a.) lowering intracellular concentration of heme, b.) by the generation of heme metabolites such as bilirubin and carbon monoxide, c) by the combination of these actions, d) or by some other unknown activity associated with HO1. 3. To determine whether continuous exposure to low levels of NO will give continuous resistance to toxic NO challenge. An investigation of whether the window of IAR can be expanded has obvious therapeutic implications. PUBLIC HEALTH RELEVANCE: Cell damage and death from the free radical, nitric oxide (NO), is seen in neurodegenerative diseases such as multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS), as well as in acute injuries, such as stroke, brain trauma and spinal cord injury. Low dose NO induces production of a gene product, heme oxygenase 1 (HO1), which protects neurons against NO-mediated cell damage from high doses of NO and the aims of this grant are to find out how. The dissection and manipulation of the HO1- mediated pathway by which low dose NO lends protection against out of context or high dose NO will help us identify therapeutic targets for the treatment or prevention of NO mediated damage and thus mitigate the effects of MS, ALS and CNS injury.