NAD metabolsim and mitochondrial dysfunction in ALS models

 描述(申请人提供)：该提案的长期目标是利用从了解肌萎缩侧索硬化症(ALS)中星形胶质细胞-运动神经元相互作用中得出的机械性见解来开发新的治疗策略。特别是，这项建议的主要目的是确定增加烟酰胺腺嘌呤二核苷酸(NAD)的可用性是否可以改善ALS模型中运动神经元的退化。在美国，ALS或Lou Gehrig病约占成人死亡人数的1/500到1/1000，是由脊髓、脑干和运动皮质中运动神经元的进行性退化引起的。运动神经元死亡会导致肌肉无力和瘫痪，导致在症状出现后一到五年内死亡。大多数ALS病例是散发性的(SALS)，暴露于尚不确定的环境毒物可能是SALS的原因。大约5%-10%的病例是遗传性的(家族性ALS，FALS)，但FALS和SALS在表型上是无法区分的，我们的很大一部分了解来自对过度表达ALS连锁突变的人类超氧化物歧化酶1(HSOD1)的啮齿动物模型的研究。从hSOD1高表达突变小鼠分离的原代星形胶质细胞在共培养中诱导运动神经元死亡，已证实从FALS和SALS患者的脊髓尸检来源的神经前体细胞分化而来的星形胶质细胞在共培养中对运动神经元也有毒性。Sirtuins是一类能够催化NAD依赖的脱酰化和单(ADPriBosyl)反应的酶。值得注意的是，依赖NAD的sirtuin介导的脱乙酰化已被证明调节所有主要的线粒体过程。由于线粒体功能障碍与ALS和ALS-星形胶质细胞的毒性有关，我们试图更好地确定NAD依赖的信号在运动神经元退化中的作用，并确定NAD水平的调节是否可能成为ALS的潜在治疗策略。我们正在进行的实验表明，ALS-星形胶质细胞中NAD含量的增加可以逆转其对共培养运动神经元的毒性，而在突变的hSOD1小鼠中，NAD合成和NAD依赖的信号可能会受到影响。因此，该提案的具体目的是：目的1-确定NAD含量在表达ALS连锁突变体hSOD1的星形胶质细胞对共培养运动神经元的毒性中的作用。目的2-评价NAD合成和降解改变的转基因模型对ALS小鼠模型疾病发生和发展的影响。目的3-评估一种关键的NAD前体治疗对ALS小鼠模型疾病发生和发展的影响。该提案的结果将有助于目前对神经退行性变中NAD代谢和线粒体功能障碍的理解。更重要的是，由于我们已经证明，在我们的星形细胞-运动神经元共培养系统中确定的治疗靶点在转化为ALS动物模型时具有有益的效果，该提议可能提供体内证据，证明调节NAD代谢作为ALS治疗靶点的价值。

 DESCRIPTION (provided by applicant): The long-term goal of the proposal is to develop new therapeutic strategies using mechanistic insights drawn from understanding astrocyte-motor neuron interaction in amyotrophic lateral sclerosis (ALS). In particular, the primary objective of this proposal is to establish whether increased nicotinamide adenine dinucleotide (NAD) availability ameliorates motor neuron degeneration in ALS models. ALS or Lou Gehrig's disease accounts for about 1 in 500 to 1 in 1,000 adult deaths in the United States and is caused by the progressive degeneration of motor neurons in the spinal cord, brain stem, and motor cortex. Motor neuron death leads to muscle weakness and paralysis causing death in one to five years from the time of symptoms onset. Most ALS cases are sporadic (SALS) and exposure to yet unidentified environmental toxicants might be responsible for SALS. About 5-10% of the cases are inherited (familial ALS, FALS) but FALS and SALS are phenotypically indistinguishable, and a significant share of our understanding come from the study of rodent models over-expressing ALS-linked mutant human superoxide dismutase 1 (hSOD1). Primary astrocytes isolated from mutant hSOD1 over-expressing mice induce motor neuron death in co-culture, and it has been demonstrated that astrocytes differentiated from spinal cord autopsy-derived neuronal progenitor cells from FALS and SALS patients are also toxic for motor neurons in co-culture. Sirtuins are a family of enzymes capable of catalyzing NAD-dependent deacylation and mono(ADPribosyl)ation reactions. Remarkably, NAD- dependent sirtuin-mediated deacetylation has been shown to modulate all major mitochondrial processes. Since mitochondrial dysfunction has been linked to ALS and the toxicity of ALS-astrocytes, we seek to better define the role of NAD-dependent signaling in motor neuron degeneration and determine if the modulation of NAD levels may be a potential therapeutic strategy for ALS. Our ongoing experiments demonstrate that increasing NAD content in ALS-astrocytes reverts its toxicity towards co-cultured motor neurons, while NAD synthesis and NAD-dependent signaling may be compromised in mutant hSOD1 mice. Thus, the specific aims of the proposal are: Aim 1-To determine the role of NAD content in the toxicity of astrocytes expressing ALS- linked mutant hSOD1s toward co-cultured motor neurons. Aim 2-To evaluate the effect of transgenic models with altered NAD synthesis and degradation on the onset and progression of the disease in ALS mouse models. Aim 3-To evaluate the effect of treatment with a key NAD precursor on the onset and progression of the disease in ALS mouse models. The outcome of the proposal will contribute to the current understanding of NAD metabolism and mitochondrial dysfunction in neurodegeneration. More important, since we have shown that therapeutic targets identified in our astrocyte-motor neuron co-culture system have a beneficial effect when translated into animal models of ALS, the proposal is likely to provide in vivo proof of the value of modulating NAD metabolism as a therapeutic target in ALS.