Neuroestrogen restraint of GnRH in juvenile female primates

 描述(申请人提供)：青少年发育的特点是明显抑制生殖激素的释放，这是一种维持性腺静止直到生殖成熟开始的机制。在灵长类动物中，这种幼年的“刹车”被认为是由大脑中产生的信号介导的，并积极抑制下丘脑神经分泌生殖激素释放的主要神经效应物促性腺激素释放激素(GnRH)。这种中枢抑制的减弱被认为有助于加速脉动性GnRH释放，进而启动青春期成熟。这种束缚的过早解除可能是真性性早熟以及在正常变异范围内的厄尔青春期发病的基础。施加少年刹车的神经信号仍不清楚。成年后，“促性腺激素释放激素脉冲发生器”被性腺类固醇的负反馈作用抑制，雌性性腺类固醇主要是雌二醇。最近的研究表明，大脑本身产生的雌激素可能调节GnRH的释放，我们已经获得了初步证据，提示性腺外雌激素可能有助于抑制GnRH脉冲发生器。因此，拟议的研究旨在检验这一新的假设，即神经雌激素在雌性灵长类动物幼年发育期的青春期前对GnRH释放的抑制。在目标1中，将对青春期前雌性恒河猴进行卵巢切除，并用雌激素合成酶芳香化酶(CYP19A1)抑制剂来曲唑或赋形剂进行治疗。我们将监测垂体促性腺激素、促黄体生成素和卵泡刺激素的分泌，以确定全身抑制非性腺组织中的芳香酶是否会导致促性腺激素释放提前激活。在目标2中，表达对应于芳香酶的shRNA的病毒载体或表达加扰RNA序列的载体将被注射到下丘脑对GnRH释放进行负反馈调节的关键区域。将监测促性腺激素水平，以确定下丘脑对芳香酶表达的局部抑制是否同样会导致GnRH释放的提前激活。我们预测，目标1的结果将证明非性腺雌激素对GnRH脉冲发生器起到部分或全部幼体抑制作用，而目标2将证实神经雌激素是这一重要生理过程的特定介质。

 DESCRIPTION (provided by applicant): Juvenile development is characterized by pronounced suppression of reproductive hormone release, a mechanism that maintains gonadal quiescence until the onset of reproductive maturation. In primates, this juvenile "brake" is believed to be mediated by signals that arise within the brain and actively suppress hypothalamic neurosecretion of the major neural effector of reproductive hormone release, gonadotropin- releasing hormone (GnRH). Diminishment of this central restraint is believed to contribute to the acceleration of pulsatile GnRH release that, in turn, initiates pubertal maturation. Premature lifting of this restraint may underlie the pathogenesis of true precocious puberty, as well as earl pubertal onset within the range of normal variation. The neural signals that impose the juvenile brake remain unclear. In adulthood, the "GnRH pulse generator" is homeostatically suppressed by negative feedback actions of gonadal steroids, principally estradiol in females. Recent studies have demonstrated that estrogens produced in the brain itself may modulate GnRH release, and we have obtained preliminary evidence to suggest that extra-gonadal estrogens may contribute to the suppression of the GnRH pulse generator. The proposed studies are therefore designed to test the novel hypothesis that neuroestrogens mediate the prepubertal restraint of GnRH release during the juvenile period of development in female primates. In Aim 1, prepubertal female rhesus macaques will be ovariectomized and treated with a vehicle or letrazole, an inhibitor of the estrogen synthesizing enzyme, aromatase (CYP19A1). We will monitor secretion of pituitary gonadotropins, LH and FSH, to determine if systemic inhibition of aromatase in non-gonadal tissues results in a premature activation of GnRH release. In Aim 2, a viral vector expressing shRNA corresponding to aromatase, or a vector expressing a scrambled RNA sequence, will be injected into the hypothalamic areas critical for negative feedback regulation of GnRH release. Gonadotropin levels will be monitored to determine if localized hypothalamic inhibition of aromatase expression likewise results in premature activation of GnRH release. We predict that the results obtained in Aim 1 will demonstrate that non-gonadal estrogens exert some or all of the juvenile restraint on the GnRH pulse generator, and that Aim 2 will confirm neuroestrogens as specific mediators of this important physiological process.