Estrogen, Astrocyte Reactivity, and Sex Differences in Alzheimer's Disease

摘要 在600多万患有阿尔茨海默病(AD)的美国人中，近三分之二是女性；然而， 阿尔茨海默病易感性的性别差异背后的分子机制很大程度上是未知的。前期研究 据报道，患有阿尔茨海默病的女性大脑中雌激素水平较低。此应用程序的长期目标是 目的是确定雌激素缺乏在观察到的AD易感性性别差异中的作用。芳香酶， 它将雄激素转化为雌激素，主要在小鼠的大脑和性腺中表达。我们演示了 小鼠大脑局部(Barko)或全身(Tarko)芳香酶的敲除会导致性行为-- 老年雌性小鼠的特异性记忆缺陷。这种表型在服用雌激素的Tarko小鼠中更为严重。 全身缺乏症与只有大脑雌激素缺乏症的Barko小鼠。雌激素发挥其作用 通过与雌激素受体(ER)结合发挥生物学作用。选择性ER-α激动剂的治疗 丙基吡唑三醇挽救雌性Tarko小鼠的记忆丧失。年迈的雌性塔尔科老鼠，但不是年老的雄性塔尔科老鼠， 与野生型乳鼠相比，海马区的神经元较少。RNA-seq、qPCR和 免疫荧光分析显示，年轻或老年雄性Barko小鼠的海马区 星形胶质细胞反应性及相关基因表达和形态变化仅见于老年雌性Barko小鼠。这些 数据表明，雌激素缺乏导致星形胶质细胞反应的新机制。我们假设 绝经后大脑中雌激素/ERα信号的缺失会导致性别特异性星形胶质细胞的反应， 导致与AD相关的神经病理和记忆丧失，导致女性AD易感性增加。至 确定大脑中雌激素缺乏与AD易感性的性别差异有关的机制 提出以下目标：1.确定芳香酶缺失和雌激素缺乏的逆转 降低星形胶质细胞的反应性，防止神经退化和记忆力丧失。我们将使用转基因技术 以及恢复Barko和Tarko脑芳香酶表达或雌激素作用的药理学方法 不同年龄的小鼠。雌激素/内质网α介导的基因组机制抑制卵巢癌细胞增殖 性别特异性的海马星形胶质细胞反应性、神经退行性变和记忆丧失将通过 使用单核(SN)rna-seq、ERα-chIP-seq和Snatac-seq的全基因组综合分析 新鲜分离的海马区星形胶质细胞。2.确定海马区ERα是否存在条件性敲除 APPNL-G-F小鼠的星形胶质细胞加速星形胶质细胞的反应、记忆丧失和AD相关的神经病理。在……里面 同时，我们将评估雌激素水平，芳香酶和ERα的表达，以及性别特异性表达 现有人类数据集和死后海马组织中的反应性星形胶质细胞相关基因及其意义 女性及年龄匹配患者病历与AD病理严重程度及记忆障碍的相关性 阿尔茨海默病患者。我们预计，拟议研究的结果将确定新的药物靶点，并导致 防治阿尔茨海默病的新治疗策略。

SUMMARY Nearly two-thirds of the more than 6 million Americans living with Alzheimer’s disease (AD) are women; however, the molecular mechanisms underlying this sex difference in AD vulnerability are largely unknown. Prior research has reported lower levels of estrogen in the brain of women with AD. The long-term objective of this application is to define the role of estrogen deficiency in the observed sex-specific difference in AD vulnerability. Aromatase, which converts androgens to estrogens, is mainly expressed in the brain and gonads of mice. We demonstrated that knockout of aromatase locally in the mouse brain (bArKO) or totally in whole body (tArKO) causes sex- specific memory deficits in old female mice. This phenotype is more severe in tArKO mice with estrogen deficiency throughout the body vs. bArKO mice with estrogen deficiency only in the brain. Estrogen exerts its biological action via binding to estrogen receptors (ERs). Treatment with the selective ERα agonist propylpyrazoletriol rescued memory loss in female tArKO mice. Old female tArKO, but not old male tArKO mice, exhibited fewer neurons in the hippocampus compared to wild-type littermates. RNA-seq, qPCR, and immunofluorescence analyses of the hippocampus from young or old bArKO mice of both sexes revealed astrocyte reactivity and related gene expression and morphologic changes only in old female bArKO mice. These data suggested a novel mechanism in which estrogen deficiency leads to astrocyte reactivity. We hypothesize that deficiency of estrogen/ERα signaling in the brain after menopause causes sex-specific astrocyte reactivity, resulting in AD-related neuropathology and memory loss, leading to increased AD vulnerability in females. To ascertain the mechanisms connecting estrogen deficiency in the brain to sex differences in AD vulnerability, we propose the following aims: 1. Determine whether reversal of aromatase deletion and estrogen deficiency reduces astrocyte reactivity and protects against neurodegeneration and memory loss. We will use transgenic and pharmacological approaches to restore brain aromatase expression or estrogen action in bArKO and tArKO mice at different ages. The estrogen/ERα-mediated genomic mechanisms responsible for the suppression of sex-specific hippocampal astrocyte reactivity, neurodegeneration, and memory loss will be determined using integrative genome-wide analyses employing single-nucleus (sn) RNA-seq, ERα-ChIP-seq, and snATAC-seq on freshly isolated hippocampal astrocytes. 2. Determine whether conditional knockout of ERα in hippocampal astrocytes of APPNL-G-F mice accelerates astrocyte reactivity, memory loss, and AD-related neuropathology. In parallel, we will assess estrogen levels, expression of aromatase and ERα, and sex-specific expression of reactive astrocyte-related genes in existing human datasets and postmortem hippocampal tissues and their correlation with the severity of AD pathology and memory deficits in medical records of women and age-matched men with AD. We expect that the findings from the proposed studies will identify new drug targets and lead to novel therapeutical strategies for the prevention and treatment of AD.