Inserm UMR837, Alzheimer and Tauopathies Lille, France ; Jean Pierre Aubert Research Centre, Faculté de Médecine-Pôle Recherche, Institut de Médecine Prédictive et de Recherche Thérapeutique, Université Droıt et Santé de Lille, CHU-Lille Lille, France.
Laboratoire de Toxicologie Génétique, Institut Pasteur de Lille Lille, France.
Front Cell Neurosci. 2014 Mar 18;8:84. doi: 10.3389/fncel.2014.00084. eCollection 2014.
Nucleic acid protection is a substantial challenge for neurons, which are continuously exposed to oxidative stress in the brain. Neurons require powerful mechanisms to protect DNA and RNA integrity and ensure their functionality and longevity. Beside its well known role in microtubule dynamics, we recently discovered that Tau is also a key nuclear player in the protection of neuronal genomic DNA integrity under reactive oxygen species (ROS)-inducing heat stress (HS) conditions in primary neuronal cultures. In this report, we analyzed the capacity of Tau to protect neuronal DNA integrity in vivo in adult mice under physiological and HS conditions. We designed an in vivo mouse model of hyperthermia/HS to induce a transient increase in ROS production in the brain. Comet and Terminal deoxyribonucleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assays demonstrated that Tau protected genomic DNA in adult cortical and hippocampal neurons in vivo under physiological conditions in wild-type (WT) and Tau-deficient (KO-Tau) mice. HS increased DNA breaks in KO-Tau neurons. Notably, KO-Tau hippocampal neurons in the CA1 subfield restored DNA integrity after HS more weakly than the dentate gyrus (DG) neurons. The formation of phosphorylated histone H2AX foci, a double-strand break marker, was observed in KO-Tau neurons only after HS, indicating that Tau deletion did not trigger similar DNA damage under physiological or HS conditions. Moreover, genomic DNA and cytoplasmic and nuclear RNA integrity were altered under HS in hippocampal neurons exhibiting Tau deficiency, which suggests that Tau also modulates RNA metabolism. Our results suggest that Tau alterations lead to a loss of its nucleic acid safeguarding functions and participate in the accumulation of DNA and RNA oxidative damage observed in the Alzheimer's disease (AD) brain.
核酸保护是神经元面临的一个重大挑战，因为神经元在大脑中不断受到氧化应激的影响。神经元需要强大的机制来保护 DNA 和 RNA 的完整性，确保其功能和寿命。除了其在微管动力学中的众所周知的作用外，我们最近发现，Tau 也是神经元基因组 DNA 完整性在原代神经元培养物中活性氧（ROS）诱导的热应激（HS）条件下的关键核保护因子。在本报告中，我们分析了 Tau 在生理和 HS 条件下保护成年小鼠体内神经元 DNA 完整性的能力。我们设计了一种体内小鼠高热/HS 模型，以诱导大脑中 ROS 产生的短暂增加。彗星和末端脱氧核糖核苷酸转移酶介导的脱氧尿苷三磷酸缺口末端标记（TUNEL）分析表明，Tau 在野生型（WT）和 Tau 缺失（KO-Tau）小鼠的生理条件下保护体内皮质和海马神经元的基因组 DNA。HS 增加了 KO-Tau 神经元中的 DNA 断裂。值得注意的是，与齿状回（DG）神经元相比，KO-Tau 海马 CA1 亚区神经元在 HS 后恢复 DNA 完整性的能力较弱。只有在 HS 后，才会在 KO-Tau 神经元中观察到磷酸化组蛋白 H2AX 焦点的形成，这是双链断裂的标志物，这表明 Tau 缺失在生理或 HS 条件下不会引发类似的 DNA 损伤。此外，在表现出 Tau 缺失的海马神经元中，HS 会改变基因组 DNA 以及细胞质和核 RNA 的完整性，这表明 Tau 还调节 RNA 代谢。我们的结果表明，Tau 的改变导致其核酸保护功能丧失，并参与了阿尔茨海默病（AD）大脑中观察到的 DNA 和 RNA 氧化损伤的积累。
