Novel neurotrophic therapy in a mouse model of ALS

描述(由申请人提供)： 肌萎缩侧索硬化症(ALS)是一种神秘的神经退行性疾病，其特征是运动神经元选择性丧失，导致快速进行性运动无力和呼吸衰竭导致的早期死亡。ALS神经变性的病因尚不清楚，但可能是由多种机制共同引起的，包括蛋白质错误折叠、线粒体功能障碍、氧化损伤、轴突运输缺陷、兴奋性、生长因子信号转导不足和炎症。最近的一份报告显示，SOD1突变体介导的内皮损伤发生在运动神经元变性之前，随后是神经血管炎症反应，这表明内皮损伤是疾病发生的关键因素。7，8-二羟基黄酮(7，8-DHF)是黄酮类化合物家族的一员。黄酮类化合物存在于水果和蔬菜中，已被证明具有多种生物学作用，包括神经保护、抗氧化和抗细胞凋亡特性。研究表明，类黄酮改善了空间记忆，这种作用与增加小鼠海马齿状回的血管生成和神经元棘密度有关。此外，结合锻炼，空间记忆的改善也得到了加强。黄酮类化合物通过与包括PI3K/Akt在内的信号通路相互作用，影响学习和记忆的长时程增强，进而影响记忆和认知能力。最近，7，8-DHF被证明与TrkB受体具有高亲和力，并刺激其二聚化和自磷酸化，导致下游信号级联激活。在小鼠体内全身性给予这种化合物可显著激活大脑中的TrkB，抑制神经细胞死亡，以TrkB依赖的方式减少中风中的脑梗塞体积，并在帕金森氏病和中风的动物模型中具有神经保护作用。这些数据表明，7，8-二羟基黄酮作为一种有效的、选择性的TrkB激动剂，通过激活类似的信号机制，几乎模拟了BDNF的生化和生理作用。7，8-二羟基黄酮的作用表明，它可能是一种治疗神经系统疾病的有效药物。我们将监测7，8-DHF给药对体重、运动能力和寿命的影响，并利用组织病理学、神经化学技术和死后及活体磁共振成像(MRI)检测对运动神经元和腹角大小、数量、树突分支和脊柱密度的影响。此外，还将在ALS小鼠中使用磁共振波谱检测神经元健康的神经化学标记物(N-乙酰天冬氨酸)和神经胶质标记物(肌醇、牛磺酸)。我们将使用ALS小鼠脊髓的在体MRI进一步评估血脊髓屏障的变化。我们将使用神经化学技术来测量BDNF，并使用神经病理学/体视学技术来量化脊髓中的生物标记物。我们提出的新研究将产生数据，以提高我们对疾病机制的理解，并测试7，8-DHF在ALS中的有益效果。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is an enigmatic neurodegenerative disorder characterized by the selective loss of motor neurons that results in rapid progressive motor weakness and early death due to respiratory failure. The etiology of neurodegeneration in ALS is not known but likely arises from a combination of mechanisms, including protein misfolding, mitochondria dysfunction, oxidative damage, defective axonal transport, excitoxicity, deficient growth factor signaling, and inflammation. A very recent report shows that SOD1 mutant-mediated endothelial damage develops before motor neuron degeneration followed later by a neurovascular inflammatory response suggesting that endothelial damage is a key contributor to disease initiation. 7,8-dihydroxyflavone (7,8-DHF) is a member of the flavonoid family. Flavonoids, present in fruits and vegetables, have been shown to exert diverse biological actions including neuroprotective, anti-oxidant and anti-apoptotic properties. It has been shown that flavonoids improved spatial memory and this effect was associated with increased angiogenesis and neuronal spine density in the dentate gyrus of the hippocampus in mice. Furthermore, improvement in spatial memory was enhanced in combination with exercise. Flavonoids exert effects on long-term potentiation underlying learning and memory, on and consequently memory and cognitive performance, through their interactions with the signaling pathways including PI3K/Akt. Most recently, 7,8-DHF was shown to bind with high affinity to the TrkB receptor and provoke its dimerization and autophosphorylation, leading to downstream-signaling cascade activation. Systemic administration of this compound in mice substantially activates TrkB in the brain, inhibits neuronal cell death, decreases infarct volumes in stroke in a TrkB-dependent manner, and is neuroprotective in an animal model of Parkinson's disease and stroke. This data indicate that 7,8-dihydroxyflavone shows it's effects as a potent and selective TrkB agonists that virtually mimic BDNF's biochemical and physiological actions by activating similar signaling mechanism. The effects of 7,8-dihydroxyflavone suggest that it could be a powerful therapeutic drug for the treatment of neurological diseases. We will monitor the effects of 7,8-DHF administration on body weight, motor performance and longevity and examine the effects on motor neuron and ventral horn changes in size, number, dendritic branching, spine density using histopathological, neurochemical techniques and magnetic resonance imaging (MRI) post mortem and in vivo. In addition neurochemical markers for neuronal health (N- acetylaspartate) and glial markers (myo-inosotol, taurine) will be detected using magnetic resonance spectroscopy in ALS mice. We will further evaluate blood spinal cord barrier changes using in vivo MRI of the spinal cord in the ALS mice. We will use neurochemical techniques to measure BDNF, and neuropathological/stereological techniques to quantify biomarkers in the spinal cord. The novel studies we propose will produce data to improve our understanding of disease mechanisms and test the beneficial effects of 7,8-DHF in ALS.