Chali Farah, Djelti Fathia, Eugene Emmanuel, Valderrama Mario, Marquer Catherine, Aubourg Patrick, Duykaerts Charles, Miles Richard, Cartier Nathalie, Navarro Vincent
Inserm U1127, CNRS UMR7225, Sorbonne Universités, UPMC Université Paris 6, UMR S1127, Institut du Cerveau et de la Moelle épinière, ICM, CHU Pitié-Salpêtrière, 47 bd de l'Hôpital, Paris, 75013, France.
CNRS URA2210, MIRCen CEA, Fontenay aux Roses, 92265, France.
Eur J Neurosci. 2015 May;41(10):1345-55. doi: 10.1111/ejn.12911. Epub 2015 May 12.
Elevations in neuronal cholesterol have been associated with several degenerative diseases. An enhanced excitability and synchronous firing in surviving neurons are among the sequels of neuronal death in these diseases and also in some epileptic syndromes. Here, we attempted to increase neuronal cholesterol levels, using a short hairpin RNA to suppress expression of the enzyme cytochrome P450 family 46, subfamily A, polypeptide 1 gene (CYP46A1). This protein hydroxylates cholesterol and so facilitates transmembrane extrusion. A short hairpin RNA CYP46A1construction coupled to the adeno-associated virus type 5 was injected focally and unilaterally into mouse hippocampus. It was selectively expressed first in neurons of the cornu ammonis (hippocampus) (CA)3a region. Cytoplasmic and membrane cholesterol increased, and the neuronal soma volume increased and then decreased before pyramidal cells died. As CA3a pyramidal cells died, interictal electroencephalographic (EEG) events occurred during exploration and non-rapid eye movement sleep. With time, neuronal death spread to involve pyramidal cells and interneurons of the CA1 region. CA1 neuronal death was correlated with a delayed local expression of phosphorylated tau. Astrocytes were activated throughout the hippocampus and microglial activation was specific to regions of neuronal death. CA1 neuronal death was correlated with distinct aberrant EEG activity. During exploratory behaviour and rapid eye movement sleep, EEG oscillations at 7-10 Hz (theta) could accelerate to 14-21 Hz (beta) waves. They were accompanied by low-amplitude, high-frequency oscillations of peak power at ~300 Hz and a range of 250-350 Hz. Although episodes of EEG acceleration were not correlated with changes in exploratory behaviour, they were followed in some animals by structured seizure-like discharges. These data strengthen links between increased cholesterol, neuronal sclerosis and epileptic behaviour.
神经元胆固醇水平升高与多种退行性疾病有关。在这些疾病以及某些癫痫综合征中，存活神经元的兴奋性增强和同步放电是神经元死亡的后果之一。在此，我们试图通过短发夹RNA抑制细胞色素P450家族46亚家族A多肽1基因（CYP46A1）的表达来提高神经元胆固醇水平。该蛋白使胆固醇羟基化，从而促进跨膜挤出。将与5型腺相关病毒偶联的短发夹RNA CYP46A1构建体局部单侧注射到小鼠海马体中。它首先在海马角（海马体）（CA）3a区域的神经元中选择性表达。细胞质和膜胆固醇增加，神经元胞体体积先增大后在锥体细胞死亡前减小。随着CA3a锥体细胞死亡，在探索和非快速眼动睡眠期间出现发作间期脑电图（EEG）事件。随着时间的推移，神经元死亡扩散至CA1区域的锥体细胞和中间神经元。CA1神经元死亡与磷酸化tau蛋白的延迟局部表达相关。整个海马体中的星形胶质细胞被激活，小胶质细胞的激活则特异性地发生在神经元死亡区域。CA1神经元死亡与明显异常的EEG活动相关。在探索行为和快速眼动睡眠期间，7 - 10赫兹（θ波）的EEG振荡可加速至14 - 21赫兹（β波）。它们伴随着约300赫兹的峰值功率以及250 - 350赫兹范围内的低振幅、高频振荡。尽管EEG加速发作与探索行为的变化无关，但在一些动物中随后出现了结构化的癫痫样放电。这些数据加强了胆固醇升高、神经元硬化和癫痫行为之间的联系。
