Gonadal Steroid Receptors and the Hypothalamo-Pituitary-Adrenal Axis

描述（由申请人提供）：本项目的长期目标是确定成人下丘脑-垂体-肾上腺（HPA）轴功能性别差异的神经生物学机制。在人类和动物中，HPA反应性的性别差异是明确的;女性在应激后表现出比男性更强的HPA轴激活。我们的假设是，成人激素应激反应的性别差异主要是睾酮（T）和雌激素（E）对HPA功能的相反作用的结果。HPA轴的激活是动物对威胁内稳态的环境扰动的基本反应。这些反应由位于下丘脑室旁核（PVN）的神经元调节，这些神经元合成并分泌促肾上腺皮质激素释放激素（CRH）。其他PVN神经肽，如加压素（AVP）和催产素（OT），在PVN水平调节CRH神经元的活性，以及增强垂体前叶CRH促分泌活性。生殖类固醇E和T也可以调节应激反应。循环E增强应激激活的ACTH和CORT分泌。相反，T降低HPA轴的增益。已发表的和初步的数据表明，雄激素可以直接作用于PVN神经元在雄性大鼠通过一种新的途径，涉及雌激素受体β（ER β），而E的作用主要通过ER α。因此，我们假设在男性中，T通过结合ER β的雄激素代谢物抑制HPA功能。这种新作用的神经生物学机制的线索可以从研究中收集，这些研究显示ER β在PVN的含OT细胞中广泛共定位。因此，在本申请中，我们提出了睾酮通过代谢为结合ER β并调节PVN的含OT神经元的化合物来抑制HPA反应性的可能性。此外，我们假设这种作用与雌激素是通过ER α起作用的配体的女性不同。提出了五个具体目标。目的1将确定类固醇代谢酶在PVN神经元中的位置和调节，从而允许32-二醇的合成。目的2将使用小鼠模型来测试局部合成的32-二醇作用于PVN中的ER β神经元以抑制HPA反应性的假设。目的3将确定是否ER β神经元调节HPA轴的功能，通过局部释放OT或额外的PVN催产素能连接边缘核。目的4将检验32二醇和ER β以配体依赖性方式与催产素启动子功能性相互作用的假设。目的5将检验这样的假设，即与ER β结合的配体的性质决定了募集到OT启动子上的靶位点的共调节因子的组装。

DESCRIPTION (provided by applicant): The long-term goals of this project are to determine the neurobiological mechanisms that underlie the sex differences in the function of the adult hypothalamo-pituitary-adrenal (HPA) axis. In humans and animals, sex differences in HPA reactivity are well established; females exhibit a more robust activation of the HPA axis following stress than do males. Our hypothesis is that sex differences in adult hormonal stress responses are primarily the result of the opposing actions of testosterone (T) and estrogen (E) on HPA function. Activation of the HPA axis is a basic response of animals to environmental perturbations that threaten homeostasis. These responses are regulated by neurons residing in the paraventricular nucleus of the hypothalamus (PVN) that synthesize and secrete corticotropin-releasing hormone (CRH). Other PVN neuropeptides, such as vasopressin (AVP) and oxytocin (OT), modulate activity of CRH neurons at the level of the PVN as well as enhancing CRH secretogogue activity at the anterior pituitary gland. The reproductive steroids, E and T can also modulate stress responses. Circulating E enhances stress activated ACTH and CORT secretion. In contrast, T decreases the gain of the HPA axis. Published and preliminary data show that androgens can act directly on PVN neurons in the male rat through a novel pathway that involves estrogen receptor beta (ERbeta), whereas E acts predominantly through ERalpha. Thus, we hypothesize that in males, T suppresses HPA function by androgen metabolites that bind ERbeta. Clues to the neurobiological mechanisms underlying such a novel action can be gleaned from studies showing extensive colocalization of ERbeta in OT-containing cells of the PVN. Hence, in this application we address the possibility that testosterone inhibits HPA reactivity by metabolizing to a compound that binds ERbeta and regulates OT containing neurons of the PVN. Furthermore, we hypothesize that this action is distinct from that found in females where estradiol is the ligand acting through ERalpha. Five specific aims are proposed. Aim 1 will identify the location and regulation of steroid metabolizing enzymes in neurons of the PVN that allow synthesis of 32-Diol. Aim 2 will use mouse models to test the hypothesis that locally synthesized 32-Diol acts upon ERbeta neurons in the PVN to inhibit HPA reactivity. Aim 3 will determine if ERbeta containing neurons regulate HPA axis function through local release of OT or extra-PVN oxytocinergic connections with limbic nuclei. Aim 4 will test the hypothesis that 32 Diol and ERbeta functionally interact with the oxytocin promoter in a ligand dependent fashion. Aim 5 will test the hypothesis that the nature of the ligand bound to ERbeta determines the assembly of co-regulatory factors recruited to target sites on the OT promoter.