Perucho Juan, Gómez Ana, Muñoz María Paz, de Yébenes Justo García, Mena María Ángeles, Casarejos María José
Department of Neurobiology, Ramon y Cajal Hospital, Madrid, Spain; CIBERNED, Instituto de Salud Carlos III, Madrid, Spain.
Department of Neurology, Ramon y Cajal Hospital, Madrid, Spain; CIBERNED, Instituto de Salud Carlos III, Madrid, Spain.
Mol Cell Neurosci. 2016 Jul;74:128-45. doi: 10.1016/j.mcn.2016.05.002. Epub 2016 May 26.
The pathological hallmark of Huntington disease (HD) is the intracellular aggregation of mutant huntingtin (mHTT) in striatal neurons and glia associated with the selective loss of striatal medium-sized spiny neurons. Up to the present, the role of glia in HD is poorly understood and has been classically considered secondary to neuronal disorder. Trehalose is a disaccharide known to possess many pharmacological properties, acting as an antioxidant, a chemical chaperone, and an inducer of autophagy. In this study, we analyzed at an early postnatal development stage the abnormalities observed in striatal glial cell cultures of postnatal R6/1 mice (HD glia), under baseline and stressing conditions and the protective effects of trehalose. Our data demonstrate that glial HD alterations already occur at early stages of postnatal development. After 20 postnatal days in vitro, striatal HD glia cultures showed more reactive astrocytes with increased expression of glial fibrillary acidic protein (GFAP) but with less replication capacity, less A2B5(+) glial progenitors and more microglia than wild-type (WT) cultures. HD glia had lower levels of intracellular glutathione (GSH) and was more susceptible to H2O2 and epoxomicin insults. The amount of expressed GDNF and secreted mature-BDNF by HD astrocytes were much lower than by WT astrocytes. In addition, HD glial cultures showed a deregulation of the major proteolytic systems, the ubiquitin-proteasomal system (UPS), and the autophagic pathway. This produces a defective protein quality control, indicated by the elevated levels of ubiquitination and p62 protein. Interestingly, we show that trehalose, through its capacity to induce autophagy, inhibited p62/SQSTM1 accumulation and facilitated the degradation of cytoplasmic aggregates from mHTT and α-synuclein proteins. Trehalose also reduced microglia activation and reversed the disrupted cytoskeleton of astrocytes accompanied with an increase in the replication capacity. In addition, trehalose up-regulated mature-BDNF neurotrophic factor expression and secretion, probably mediating cytoskeletal organization and helping in vesicular BDNF transport. Together, these findings indicate that glia suffers functional early changes in the disease process, changes that may contribute to HD neurodegeneration. Trehalose could be a very promising compound for treatment of HD and other diseases with abnormal protein aggregates. Furthermore our study identifies glial cells as a novel target for trehalose to induce neurotrophic and neuroprotective actions in HD.
亨廷顿舞蹈症（HD）的病理特征是突变型亨廷顿蛋白（mHTT）在纹状体神经元和神经胶质细胞内聚集，这与纹状体中等大小棘状神经元的选择性丧失相关。到目前为止，神经胶质细胞在HD中的作用仍知之甚少，传统上认为其作用继发于神经元紊乱。海藻糖是一种二糖，已知具有多种药理特性，可作为抗氧化剂、化学伴侣和自噬诱导剂。在本研究中，我们在出生后早期发育阶段分析了出生后R6/1小鼠（HD神经胶质细胞）纹状体神经胶质细胞培养物在基线和应激条件下观察到的异常情况以及海藻糖的保护作用。我们的数据表明，神经胶质细胞HD改变在出生后发育的早期阶段就已发生。在体外培养20天后，纹状体HD神经胶质细胞培养物显示出更多反应性星形胶质细胞，胶质纤维酸性蛋白（GFAP）表达增加，但复制能力较低，A2B5(+)神经胶质祖细胞较少，且与野生型（WT）培养物相比小胶质细胞更多。HD神经胶质细胞的细胞内谷胱甘肽（GSH）水平较低，对过氧化氢和环氧霉素损伤更敏感。HD星形胶质细胞表达的胶质细胞源性神经营养因子（GDNF）和分泌的成熟脑源性神经营养因子（BDNF）的量远低于WT星形胶质细胞。此外，HD神经胶质细胞培养物显示主要蛋白水解系统、泛素-蛋白酶体系统（UPS）和自噬途径失调。这导致蛋白质量控制存在缺陷，表现为泛素化水平和p62蛋白水平升高。有趣的是，我们发现海藻糖通过其诱导自噬的能力，抑制了p62/SQSTM1的积累，并促进了mHTT和α-突触核蛋白细胞质聚集体的降解。海藻糖还减少了小胶质细胞的活化，并逆转了星形胶质细胞破坏的细胞骨架，同时增加了复制能力。此外，海藻糖上调了成熟BDNF神经营养因子表达和分泌，可能介导细胞骨架组织并有助于BDNF的囊泡运输。总之，这些发现表明神经胶质细胞在疾病过程中会发生早期功能变化，这些变化可能导致HD神经退行性变。海藻糖可能是治疗HD和其他有异常蛋白聚集体疾病的非常有前景的化合物。此外，我们的研究将神经胶质细胞确定为海藻糖在HD中诱导神经营养和神经保护作用的新靶点。
