Fujian Key Laboratory of Translational Research in Cancer and Neurodegenerative Diseases, Institute for Translational Medicine, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, 350122, Fujian, China.
Department of Pathology, Longyan First Hospital Affiliated to Fujian Medical University, Longyan, 364000, Fujian, China.
Transl Neurodegener. 2022 May 9;11(1):27. doi: 10.1186/s40035-022-00302-4.
Intracellular accumulation of the microtubule-associated protein tau and its hyperphosphorylated forms is a key neuropathological feature of Alzheimer's disease (AD). Melatonin has been shown to prevent tau hyperphosphorylation in cellular and animal models. However, the molecular mechanisms by which melatonin attenuates tau hyperphosphorylation and tau-related pathologies are not fully understood.
Immunofluorescence, immunoblotting analysis and thioflavin-S staining were employed to examine the effects of early and late treatment of melatonin on tau-related pathology in hTau mice, in which nonmutated human tau is overexpressed on a mouse tau knockout background. High-throughput microRNA (miRNA) sequencing, quantitative RT-PCR, luciferase reporter assay and immunoblotting analysis were performed to determine the molecular mechanism.
We found that both early and late treatment of melatonin efficiently decreased the phosphorylation of soluble and insoluble tau at sites related to AD. Moreover, melatonin significantly reduced the number of neurofibrillary tangles (NFTs) and attenuated neuronal loss in the cortex and hippocampus. Furthermore, using miRNA microarray analysis, we found that miR-504-3p expression was upregulated by melatonin in the hTau mice. The administration of miR-504-3p mimics dramatically decreased tau phosphorylation by targeting p39, an activator of the well-known tau kinase cyclin-dependent kinase 5 (CDK5). Compared with miR-504-3p mimics alone, co-treatment with miR-504-3p mimics and p39 failed to reduce tau hyperphosphorylation.
Our results suggest for the first time that melatonin alleviates tau-related pathologies through upregulation of miR-504-3p expression by targeting the p39/CDK5 axis and provide novel insights into AD treatment strategies.
细胞内微管相关蛋白 tau 及其过度磷酸化形式的积累是阿尔茨海默病（AD）的关键神经病理学特征。褪黑素已被证明可防止细胞和动物模型中的 tau 过度磷酸化。然而，褪黑素减轻 tau 过度磷酸化和 tau 相关病理的分子机制尚不完全清楚。
采用免疫荧光、免疫印迹分析和硫黄素 S 染色检测褪黑素早期和晚期处理对 hTau 小鼠 tau 相关病理的影响，其中非突变人 tau 在小鼠 tau 敲除背景下过表达。进行高通量 microRNA（miRNA）测序、定量 RT-PCR、荧光素酶报告基因分析和免疫印迹分析以确定分子机制。
我们发现，褪黑素的早期和晚期治疗均能有效降低 AD 相关位点可溶性和不溶性 tau 的磷酸化。此外，褪黑素还显著减少了皮质和海马中的神经纤维缠结（NFTs）数量并减轻了神经元丢失。此外，通过 miRNA 微阵列分析，我们发现褪黑素可上调 hTau 小鼠中的 miR-504-3p 表达。miR-504-3p 模拟物的给药可通过靶向 p39（已知 tau 激酶周期蛋白依赖性激酶 5（CDK5）的激活剂）来显著降低 tau 磷酸化。与单独使用 miR-504-3p 模拟物相比，miR-504-3p 模拟物与 p39 的共同处理未能降低 tau 过度磷酸化。
我们的研究结果首次表明，褪黑素通过靶向 p39/CDK5 轴上调 miR-504-3p 表达来减轻 tau 相关病理，为 AD 治疗策略提供了新的见解。
