Abrahám István M, Han Seong-Kyu, Todman Martin G, Korach Kenneth S, Herbison Allan E
Laboratory of Neuroendocrinology, The Babraham Institute, Cambridge CB2 4AT, United Kingdom.
J Neurosci. 2003 Jul 2;23(13):5771-7. doi: 10.1523/JNEUROSCI.23-13-05771.2003.
The gonadal steroid estrogen exerts an important modulatory influence on the activity of multiple neuronal networks. In addition to classical genomic mechanisms of action, estrogen also exerts poorly understood rapid, nongenomic effects on neurons. To examine whether estrogen may exert rapid actions on intracellular signaling within gonadotropin-releasing hormone (GnRH) neurons in vivo,we examined the phosphorylation status of cAMP response element-binding protein (CREB) in these cells after the administration of 17-beta-estradiol to ovariectomized (OVX) mice. The percentage of GnRH neurons expressing phosphorylated CREB was increased more than sixfold (p < 0.05) in a time- and dose-dependent manner by estrogen, with the increase first observed 15 min after estrogen administration. A series of in vitro studies demonstrated that estrogen acted directly on native GnRH neurons to phosphorylate CREB, but that estrogen conjugated to bovine serum albumin was without effect. The role of classical estrogen receptors (ERs) was evaluated using ER knock-out mice in vivo. The effect of estrogen on CREB phosphorylation in GnRH neurons was normal in ERalpha knock-out mice but completely absent in ERbeta knock-out mice. Finally, studies in intact female mice revealed levels of CREB phosphorylation within GnRH neurons that were equivalent to those of estrogen-treated OVX mice. These observations demonstrate that ERbeta mediates the rapid, direct effects of estrogen on the GnRH neuronal phenotype, and that these actions persist under physiological conditions. They also provide the first evidence for a role of ERbeta in nongenomic estrogen signaling within the brain in vivo.
性腺类固醇雌激素对多个神经网络的活动具有重要的调节作用。除了经典的基因组作用机制外，雌激素还对神经元产生了尚未完全了解的快速非基因组效应。为了研究雌激素是否可能在体内对促性腺激素释放激素（GnRH）神经元的细胞内信号传导产生快速作用，我们在给去卵巢（OVX）小鼠注射17-β-雌二醇后，检测了这些细胞中cAMP反应元件结合蛋白（CREB）的磷酸化状态。雌激素以时间和剂量依赖性方式使表达磷酸化CREB的GnRH神经元百分比增加了六倍多（p < 0.05），在注射雌激素后15分钟首次观察到增加。一系列体外研究表明，雌激素直接作用于天然GnRH神经元使CREB磷酸化，但与牛血清白蛋白结合的雌激素则无此作用。在体内使用雌激素受体（ER）基因敲除小鼠评估了经典雌激素受体的作用。雌激素对GnRH神经元中CREB磷酸化的影响在ERα基因敲除小鼠中正常，但在ERβ基因敲除小鼠中完全不存在。最后，对完整雌性小鼠的研究揭示了GnRH神经元内CREB磷酸化水平与雌激素处理的OVX小鼠相当。这些观察结果表明，ERβ介导了雌激素对GnRH神经元表型的快速直接作用，并且这些作用在生理条件下持续存在。它们还为ERβ在体内大脑非基因组雌激素信号传导中的作用提供了首个证据。
