Gonadal Steroid Receptors and the Hypothalamo-Pituitary-Adrenal Axis

描述(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确定的；女性在应激后表现出比男性更强烈的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动态平衡的环境扰动的基本反应。这些反应由下丘脑室旁核(PVN)中的神经元调节，这些神经元合成和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水平上调节CRH神经元的活动，并增强垂体前叶的CRH分泌活动。生殖类固醇E和T也可以调节应激反应。循环E促进应激激活的ACTH和皮质醇的分泌。相反，T会降低HPA轴的增益。已发表的和初步的数据表明，雄激素可以通过一种涉及雌激素受体β(ERbeta)的新途径直接作用于雄性大鼠的PVN神经元，而E主要通过ERα作用。因此，我们假设在男性中，T通过结合ERβ的雄激素代谢产物抑制HPA的功能。这种新的作用背后的神经生物学机制的线索可以从研究中收集到，研究表明ERbeta在PVN中含有OT的细胞中广泛共存。因此，在这一应用中，我们讨论了睾酮通过代谢成结合ERbeta并调节PVN中含有OT的神经元的化合物来抑制HPA反应的可能性。此外，我们假设这一作用不同于在女性中发现的，在女性中，雌二醇是通过ERα起作用的配体。提出了五个具体目标。目的1将确定类固醇代谢酶在下丘脑室旁核神经元中的位置和调节，以允许合成32-二醇。目的2将使用小鼠模型来验证局部合成的32-Diol作用于PVN中的ERbeta神经元以抑制HPA反应的假设。目的3将确定含ERbeta的神经元是否通过局部释放OT或PVN外的催产素能与边缘核的联系来调节HPA轴的功能。目的4将验证32Diol和ERbeta以配体依赖的方式与催产素启动子功能相互作用的假设。Aim 5将检验这一假设，即与ERbeta结合的配体的性质决定了招募到OT启动子上的靶点的协同调节因子的组装。

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.