NAD+ metabolism and signaling in ALS models

该提案的长期目标是利用机械洞察力开发新的治疗策略。 源自对肌萎缩侧索硬化症(ALS)中星形胶质细胞-运动神经元相互作用的了解。在……里面 特别是，这项建议的主要目标是更好地描述负责 通过提高肌萎缩侧索硬化症模型中烟酰胺腺嘌呤二核苷酸(NAD+)的可用性来提供保护。肌萎缩侧索硬化症 或卢·格里克病约占美国成人死亡人数的1/500到1/1000， 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。 运动神经元死亡导致肌肉无力和瘫痪，导致一到五年后死亡 症状出现的可能性。大多数肌萎缩侧索硬化症病例是散发性的(Sals)，并暴露在尚未确定的环境中。 毒物可能是导致SALS的原因。大约5%-10%的病例是遗传性的(家族性ALS，FALS)，但 FAL和SAL在表观上是难以区分的，我们很大一部分的理解来自于 高表达肌萎缩侧索硬化症连锁突变型人超氧化物歧化酶1啮齿动物模型的研究 有几条证据强调了非神经细胞在神经退变过程中的作用 星形胶质细胞似乎在疾病的发展中起着决定性的作用。因此，主要的 从突变的hSOD1高表达小鼠分离的星形胶质细胞在共培养中诱导运动神经元死亡，并且它 已证实星形胶质细胞从脊髓尸检衍生的神经前体细胞分化而来 来自FALS和SALS患者的细胞在共培养中也对运动神经元有毒性。我们已经证明，NAD+合成酶NAMPT的过度表达或增加两个sirtuins(SIRT3和/或 SIRT6)在ALS的共培养模型中具有保护性。Sirtuins是一类能够催化依赖NAD+的脱酰化和单(ADPriBosyl)反应的酶，在转录、DNA修复、 新陈代谢和抗氧化性。我们之前公布的数据和正在进行的实验 证明在ALS的共培养模型中，调节NAD+代谢和信号是有保护作用的，而 参与NAD+合成和NAD+依赖信号转导的酶在ALS中的表达发生改变 病人。此外，通过饮食补充代谢前体来提高NAD+水平 (烟酰胺核苷)在ALS小鼠模型中发挥神经保护作用。因此，我们寻求更好地定义 NAD+依赖的信号在运动神经元退变中的作用。在调查期间取得的成果 上一个资助期合理支持制定细胞类型的具体方法，以更好地实现目标 肌萎缩侧索硬化症中的NAD+代谢和信号转导。因为我们已经证明了在我们的 星形胶质细胞-运动神经元共培养系统在移植到ALS动物模型中时具有有益的效果， 该提议很可能为调节NAD+的价值提供一种机械性的洞察和活体证明 代谢和信号转导作为ALS的治疗方法。

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 better delineate the mechanisms responsible for the protection conferred by enhancing nicotinamide adenine dinucleotide (NAD+) availability 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). Several lines of evidence underscored the contribution of non-neuronal cells in the neurodegenerative process and astrocytes appear to have a decisive role in the progression of the disease. Accordingly, 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. We have shown that over-expression of the NAD+-synthesizing enzyme, NAMPT, or increasing the activity of two sirtuins (SIRT3 and/or SIRT6) is protective in a co-culture model of ALS. Sirtuins are a family of enzymes capable of catalyzing NAD+-dependent deacylation and mono(ADPribosyl)ation reactions, and play a key role in transcription, DNA repair, metabolism, and oxidative stress resistance. Our previously published data and ongoing experiments demonstrate that modulating NAD+ metabolism and signaling is protective in a co-culture model of ALS, while the expression of enzymes involved in NAD+ synthesis and NAD+-dependent signaling is altered in ALS patients. Moreover, enhancing NAD+ levels by dietary supplementation with a metabolic precursor (nicotinamide riboside) exerts neuroprotective effects in an ALS mouse model. Thus, we seek to better define the role of NAD+-dependent signaling during motor neuron degeneration. The results obtained during the previous funding period rationally support the development of cell-type specific approaches to better target NAD+ metabolism and signaling in ALS. 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 a mechanistic insight and in vivo proof of the value of modulating NAD+ metabolism and signaling as a therapeutic approach in ALS.