甘草素调控绝经早期阿尔茨海默病海马神经发生的机制研究

Estrogen therapy (ET), when timely initiated at the onset of menopause, can potentially counteract the cognitive changes and reduce the risk of AD. However, the therapeutic application of ET, in particular for disease prevention or risk reduction, has been hampered by safety concerns. So the major issue associated with ET is not the lack of efficacy, but the potential risk for increased breast cancer cell proliferation, etc. The potential adverse effect of ET highlights the fact that new treatment strategies for hormone replacement therapies are needed. Recent investigations have focused on identification of compounds that are neuro-selective estrogen receptor agonists, which mimic the beneficial actions of estrogen in the brain but have negligible effects on non-neural estrogen-responsive tissues, such as phytoestrogens. Phytoestrogens are a diverse group of plant-derived non-steroidal structural analogs of mammalian estrogens that can interact with estrogen receptors (ER) and mediate estrogenic responses. Translational research in animals provides initial evidence for the neuroprotective effects of phytoestrogens, which could alleviate risk of AD progression. However, the mechanisms underlying its protection are still unknown..Liquiritigenin, a licorice flavonoid that is derived from glycyrrhizae radix, has been proved a highly selective estrogen ERβ agonist. Our previous study showed that treatment with liquiritigenin significantly ameliorated the spatial learning and memory deficits and reduced the Aβ associated proteins in 7-day ovariectomized AD model mice. In addition, liquiritigenin selectively increased the ERβ protein level, promoted the number of DCX- and NeuN-positive cells and increased the postsynaptic density protein 95 (PSD95) protein level. Our in-vitro study also showed that liquiritigenin increased the growth and differentiation of brain-derived progenitor cells which obtained from human embryo. Our findings indicate that liquiritigenin may induce hippocampal neurogenesis, which in turn improve the cognitive impairment and delay the progression of AD. .To test this hypothesis, the present study is designed to examine the effect of Liquirtigenin on hippocampal neurogenesis of early menopause of AD model mice and its possible underlying mechanism, by using Liquirtigenin treatment to primary cultured progenitor cells and APP/PS/Nestin-GFP triple transgenic AD model mice, assisted with various techniques, such as behavioral test, physiological test, morphological test, cellular and molecular biological methods. The outcome of this study may not only provide noval approaches to prevent and treat multi-factorial neurodegenerative AD, but also help to promote the treatment program to other hormone-related diseases.

雌激素是防治绝经早期阿尔茨海默病(AD)的有效药物，但因其多靶标(ERα和ERβ)产生的副作用未能真正进入临床应用。植物雌激素是一类从植物中提取、具有雌激素效能又能避免雌激素副作用的天然化合物，有望成为理想的雌激素替代物。申请人前期研究发现，中药甘草的植物提取物甘草素可显著改善绝经早期AD小鼠的学习记忆障碍，选择性上调脑内ERβ表达、增加海马内新生及成熟神经元数量；离体实验发现甘草素可促进胚胎神经干细胞的增殖分化。那么，甘草素是否通过诱导海马神经发生从而改善AD认知功能障碍？为此，本项目拟以APP/PS1/Nestin-GFP三转基因AD小鼠及原代培养神经干细胞为研究对象，结合行为学、电生理、形态学、细胞及分子生物学技术，深入探讨甘草素对绝经早期AD小鼠海马神经发生的影响，并阐明其有效作用机制，该项目不仅为AD的防治提供新思路和新途径，同时为其他激素相关疾病的防治提供借鉴。

雌激素是防治绝经早期阿尔茨海默病(AD)的有效药物，但因其多靶标产生的副作用限制了其在临床的应用。植物雌激素是一类从植物中提取、具有雌激素效能又能避免雌激素副作用的天然化合物，有望成为理想的雌激素替代物。甘草素（LG）是从中药材甘草中提取的活性单体，是雌激素受体β(ERβ)高度选择性的激动剂，本项目主要研究了植物雌激素LG对绝经早期AD小鼠认知功能的影响及可能的内在机制。研究首先用APP/PS1双转基因及同窝野生型小鼠构建了绝经早期和绝经中晚期（双侧卵巢切除，OVX）的小鼠模型,确认了OVX不同时间段（1W、1M、3M）小鼠脑内葡萄糖代谢、神经元内线粒体结构、神经元突触、脑内线粒体ERβ及海马神经干细胞增殖分化与小鼠认知变化的关系；然后在细胞和动物水平，应用基因技术过表达和敲低ERβ并结合LG处理，明确了LG通过上调ERβ显著改善绝经早期小鼠的学习记忆能力、显著促进海马神经干细胞的增殖和分化以及促进神经元的成熟，该过程与ERβ/IGF-1R/GSK-3β通路相关；实验发现LG亦可通过抑制神经炎症发挥作用。根据当前国际前沿的研究进展，适时的将研究拓展到雌激素缺乏引起的其他退行性疾病如骨质疏松症（OP）上，初步探讨LG是否对绝经后认知障碍以及OP发挥“异病同治”的效果，实验结果发现LG可显著促进OP模型小鼠的成骨形成，提示LG对AD和OP的双重作用可能也与ERβ介导的信号通路相关。该项目的研究结果不仅可为AD的有效防治提供新思路和新方法，同时对其他激素相关疾病的研究进展也有促进作用，具有潜在的临床应用前景。本项目以通讯作者发表SCI论文4篇，非通讯作者论文2篇，CSCD核心期刊4篇（均标注课题资助）。