Estrogen and High-Affinity Choline Transport

女性罹患阿尔茨海默病(AD)的风险是男性的2-3倍。有证据表明，雌激素替代疗法可以降低这种风险。然而，这种保护作用的生物学机制还没有得到证实。AD时，基底前脑内含乙酰胆碱的神经元变性。因此，我们推测雌激素的作用机制之一是刺激基底前脑胆碱能神经元。更具体地说，雌激素刺激高亲和力胆碱转运体的活性，这是合成乙酰胆碱的关键步骤。 为了验证这一假设，将从胚胎大鼠的基底前脑制备原代神经元培养。这些培养物将丰富胆碱能神经元，并优化其生存条件。将对培养物进行高亲和力胆碱转运蛋白活性测试。细胞将被雌激素处理，这种处理对高亲和力胆碱转运体活性的影响将被测量。高亲和力胆碱转运与胆碱能神经元的数量和胆碱能功能的其他指标，包括乙酰胆碱含量、胆碱乙酰转移酶活性和高亲和力胆碱转运体mRNA水平相关。如果雌激素增加转运蛋白的活性，这一假说将得到证实。这也是意料之中的 雌激素将提高这些神经元在培养中的存活率。这些实验将扩展到植物雌激素，即植物衍生的雌激素类化合物，对胆碱能存活和功能的影响。确定雌激素在AD中起保护作用的机制(S)很重要，原因有几个。首先，它为绝经后妇女的雌激素替代治疗提供了生物学基础。其次，它提供了对AD潜在的病理生理过程的洞察，从而确定了AD治疗的新靶点。最后，对雌激素作用机制的了解使人们能够设计出既能模拟其治疗效果，又能消除其不良副作用的药物。

Women have a 2-3-fold greater risk of developing Alzheimer's disease (AD) than men. There is evidence that estrogen replacement therapy reduces this risk. However, no biological mechanism is proven for this protective effect. In AD, acetylcholine-containing neurons in the basal forebrain degenerate. Thus, it is hypothesized that one mechanism for estrogen's effect is to stimulate basal forebrain cholinergic neurons. More specifically, estrogen stimulates the activity of the high affinity choline transporter, which carries out the critical step in the synthesis of acetylcholine. To test this hypothesis, primary neuronal cultures will be prepared from basal forebrain of embryonic rats. These cultures will be enriched for cholinergic neurons and conditions optimized for their surivival. Cultures will be tested for high affinity choline transporter activity. Cells will be treated with estrogen and the effect of this treatment on the activity of the high affinity choline transporter will be measured. High affinity choline transport will be correlated with the number of cholinergic neurons and other markers of cholinergic function including acetylcholine content, choline acetyltransferase activity and high affinity choline transporter mRNA level. The hypothesis will be proven if estrogen increases the activity of the transporter. It is also expected that estrogen will enhance the survival of these neurons in culture. These experiments will be extended to address the effects that phytoestrogens, plant-derived estrogen-like compounds, have on cholinergic survival and function. Identifying the mechanism(s) by which estrogen is protective in AD is important for several reasons. First, it provides a biological rationale for estrogen replacement therapy in postmenopausal women. Second, it provides insights into the pathophysiological processes underlying AD and therefore identifies new targets for the treatment of AD. Lastly, knowledge of estrogen's mechanism of action allows design of drugs that mimic its therapeutic effects, but lack its undesirable side effects.