Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, United States of America.
PLoS One. 2012;7(1):e30406. doi: 10.1371/journal.pone.0030406. Epub 2012 Jan 20.
Impairments in mitochondria and transcription are important factors in the pathogenesis of Huntington disease (HD), a neurodegenerative disease caused by a polyglutamine expansion in the huntingtin protein. This study investigated the effect of different metabolic states and peroxisome proliferator-activated receptor γ (PPARγ) activation on sensitivity to cellular stressors such as H(2)O(2) or thapsigargin in HD. Striatal precursor cells expressing wild type (STHdh(Q7)) or mutant huntingtin (STHdh(Q111)) were prepared in different metabolic conditions (glucose vs. pyruvate). Due to the fact that STHdh(Q111) cells exhibit mitochondrial deficits, we expected that in the pyruvate condition, where ATP is generated primarily by the mitochondria, there would be greater differences in cell death between the two cell types compared to the glucose condition. Intriguingly, it was the glucose condition that gave rise to greater differences in cell death. In the glucose condition, thapsigargin treatment resulted in a more rapid loss of mitochondrial membrane potential (ΔΨm), a greater activation of caspases (3, 8, and 9), and a significant increase in superoxide/reactive oxygen species (ROS) in STHdh(Q111) compared to STHdh(Q7), while both cell types showed similar kinetics of ΔΨm-loss and similar levels of superoxide/ROS in the pyruvate condition. This suggests that bioenergetic deficiencies are not the primary contributor to the enhanced sensitivity of STHdh(Q111) cells to stressors compared to the STHdh(Q7) cells. PPARγ activation significantly attenuated thapsigargin-induced cell death, concomitant with an inhibition of caspase activation, a delay in ΔΨm loss, and a reduction of superoxide/ROS generation in STHdh(Q111) cells. Expression of mutant huntingtin in primary neurons induced superoxide/ROS, an effect that was significantly reduced by constitutively active PPARγ. These results provide significant insight into the bioenergetic disturbances in HD with PPARγ being a potential therapeutic target for HD.
线粒体和转录损伤是亨廷顿病（HD）发病机制中的重要因素，HD 是一种神经退行性疾病，由亨廷顿蛋白中的多聚谷氨酰胺扩展引起。本研究探讨了不同代谢状态和过氧化物酶体增殖物激活受体γ（PPARγ）激活对 HD 细胞应激敏感的影响，如 H₂O₂或他普西醇。在不同代谢条件（葡萄糖与丙酮酸）下制备表达野生型（STHdh（Q7））或突变亨廷顿蛋白（STHdh（Q111））的纹状体前体细胞。由于 STHdh（Q111）细胞表现出线粒体缺陷，我们预计在丙酮酸条件下，那里的 ATP 主要由线粒体产生，两种细胞类型之间的细胞死亡差异会比葡萄糖条件下更大。有趣的是，正是葡萄糖条件导致细胞死亡差异更大。在葡萄糖条件下，他普西醇处理导致 STHdh（Q111）中更迅速的线粒体膜电位（ΔΨm）丧失，半胱天冬酶（3、8 和 9）的更大激活，以及超氧化物/活性氧（ROS）的显著增加，而两种细胞类型在丙酮酸条件下均表现出相似的 ΔΨm 丧失动力学和相似的超氧化物/ROS 水平。这表明与 STHdh（Q7）细胞相比，生物能缺陷并不是 STHdh（Q111）细胞对应激原更敏感的主要原因。PPARγ 激活显著减弱了他普西醇诱导的细胞死亡，同时抑制了半胱天冬酶的激活，延迟了 ΔΨm 的丧失，并减少了 STHdh（Q111）细胞中超氧化物/ROS 的产生。在原代神经元中表达突变型亨廷顿蛋白诱导超氧化物/ROS，这种作用被组成型激活的 PPARγ 显著降低。这些结果为 HD 中的生物能障碍提供了重要的见解，PPARγ 可能成为 HD 的潜在治疗靶点。
