NAD+ metabolism and signaling in ALS models

该提案的长期目标是利用机械见解开发新的治疗策略 从了解肌萎缩侧索硬化症（ALS）中星形胶质细胞-运动神经元的相互作用中得出。在 特别是，这项建议的主要目标是更好地界定负责 通过增强ALS模型中烟酰胺腺嘌呤二核苷酸（NAD+）的可用性而提供的保护。ALS 在美国，Lou Gehrig病约占1/500至1/1，000的成人死亡， 由脊髓、脑干和运动皮层中的运动神经元的进行性退化引起。 运动神经元死亡导致肌肉无力和瘫痪，导致死亡，从时间一到五年 症状发作的时间大多数ALS病例是散发的（SALS），暴露于尚未确定的环境中， 有毒物质可能是导致SALS的原因。大约5-10%的病例是遗传的（家族性ALS，FALS）， FALS和SALS在表型上无法区分，我们的理解很大一部分来自于 过表达ALS连锁突变体人超氧化物歧化酶1（hSOD 1）的啮齿动物模型的研究。 一些证据强调了非神经元细胞在神经变性过程中的作用 星形胶质细胞似乎在疾病的进展中起决定性作用。因此，主要 从突变hSOD 1过表达小鼠中分离的星形胶质细胞在共培养中诱导运动神经元死亡， 已经证明星形胶质细胞从脊髓尸检衍生的神经元祖细胞分化 来自FALS和SALS患者的细胞在共培养中对运动神经元也是有毒的。我们已经表明，NAD+合成酶NAMPT的过表达或两种sirtuins（SIRT 3和/或SIRT 4）活性的增加， SIRT 6）在ALS的共培养模型中具有保护性。Sirtuins是一个能够催化NAD+依赖性脱酰和单（ADPribosyl）化反应的酶家族，并且在转录、DNA修复、 代谢和抗氧化应激。我们之前公布的数据和正在进行的实验 证明调节NAD+代谢和信号传导在ALS的共培养模型中是保护性的， 参与NAD+合成和NAD+依赖性信号传导的酶的表达在ALS中改变 患者此外，通过膳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+依赖性信号在运动神经元变性中的作用。期间获得的结果 前期资金合理支持发展细胞类型的具体方法，以更好地瞄准 ALS中的NAD+代谢和信号传导。由于我们已经证明，在我们的研究中确定的治疗靶点 星形胶质细胞-运动神经元共培养系统在转化为ALS动物模型时具有有益效果， 该建议可能提供调节NAD+的价值的机制见解和体内证据。 代谢和信号传导作为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.