Beta Endorphin Neurons and the Control of Homeostasis

描述(申请人提供)：拟议研究的长期目标是阐明下丘脑神经元中17-雌二醇(E_2)信号控制动态平衡的机制(S)。已有研究表明，经典的雌激素受体ER和ER，以及可能不同的剪接变异体，通过快速和长期的基因组机制发挥作用，负责中枢神经系统(CNS)中E2的所有作用。然而，我们的研究表明，一种新的膜E2受体(Mer)参与了下丘脑阿片黑素原(POMC)神经元兴奋性增加和新基因转录的快速信号级联反应。我们已经开发了一种Mer选择性配体STX，并且E2和STX对雌激素受体和GPR30基因敲除小鼠都是完全有效的。此外，作为原理的证明，体内使用STX治疗，类似于E2，可以减轻雌激素水平较低的雌性豚鼠的体重增加。虽然瘦素和胰岛素输入到POMC和神经肽Y(NPY)神经元对能量平衡是重要的，但E2调节厌食性POMC和增食性NPY神经元瘦素和胰岛素信号的细胞机制(S)尚不清楚。我们还需要进一步研究MER与POMC神经元中其他激素信号通路的相互作用，以及它在调节其他下丘脑(NPY)神经元的兴奋性中所起的作用。因此，我们目前的工作主要集中在下丘脑弓状核POMC和NPY神经元，在这些神经元中，E2通过多个信号级联起作用。我们的多学科方法结合了一系列独特的细胞和分子工具以及我们的综合专业知识(即电生理学、化学、分子生物学、组织化学和整个动物生理学)。我们的工作假设是，E2的厌食效应部分是由于POMC和NPY神经元中除了ER(和ER)外还激活了Mer，最终上调了POMC，下调了NPY的兴奋性和基因表达。此外，我们假设在这些厌食症和厌食症神经元中，雌激素信号通路与瘦素和胰岛素信号通路协同作用。因此，我们的具体目标是：(1)阐明E2和STX对POMC神经元瘦素信号的影响；(2)研究E2和STX对NPY神经元胰岛素和瘦素信号的影响；(3)阐明POMC对NPY神经元的输入；(4)研究排卵周期早、晚期豚鼠POMC和NPY神经元的瘦素和胰岛素信号。了解E2的这些新的作用将为深入了解E2退出在更年期状态中的基础作用提供重要的洞察力，并允许进一步开发专门针对这些参与体内平衡控制的关键大脑回路的新的雌激素化合物。

DESCRIPTION (provided by applicant): The long-range goal of the proposed research is to elucidate the mechanism (s) by which 17 -estradiol (E2) signals in hypothalamic neurons to control homeostasis. It has been suggested that the classical estrogen receptors ER and ER, and possibly different splice variants, acting through rapid and long term genomic mechanisms are responsible for all of the actions of E2 in the central nervous system (CNS). However, our studies indicate that a novel membrane E2 receptor (mER) is involved in a rapid signaling cascade that leads to increased excitability and new gene transcription in hypothalamic proopiomelanocortin (POMC) neurons. We have developed a mER selective ligand STX, and both E2 and STX are fully efficacious in estrogen receptor , and GPR30 knockout mice. Moreover as proof of principle, in vivo treatment with STX, similar to E2, attenuates the weight gain in hypo-estrogenic female guinea pigs. Although it is known that leptin and insulin inputs to POMC and neuropeptide Y (NPY) neurons are important for energy homeostasis, the cellular mechanism (s) by which E2 modulates leptin and insulin signaling in anorexigenic POMC and orexigenic NPY neurons is relatively unexplored. Further studies are needed to characterize the cross-talk of the mER with other hormone signaling pathways in POMC neurons and its role in modulating the excitability of other hypothalamic (NPY) neurons involved in the control of energy homeostasis. Therefore, our current work focuses on hypothalamic arcuate POMC and NPY neurons in which E2 acts through multiple signaling cascades. Our multidisciplinary approach incorporates a unique range of cellular and molecular tools and our combined expertise (i.e., electrophysiology, chemistry, molecular biology, histochemistry and whole animal physiology). Our working hypothesis is that the anorexic effects of E2 are due, in part, to the activation of a mER in addition to ER (and ER) in POMC and NPY neurons that ultimately up regulates POMC and down-regulates NPY excitability and gene expression. In addition, we hypothesize that estrogen signaling pathways act in concert with leptin and insulin signaling pathways in these anorexigenic and orexigenic neurons. Therefore, our specific aims are the following: (1) to elucidate the effects of E2 and STX on leptin signaling in POMC neurons; (2) to characterize the effects of E2 and STX on insulin and leptin signaling in NPY neurons; (3) to elucidate the POMC input to NPY neurons; and (4) to characterize leptin and insulin signaling in guinea pig POMC and NPY neurons during the early and late follicular phases of the ovulatory cycle. Understanding these novel actions of E2 will provide critical insight into the fundamental role of E2 withdrawal in menopausal states and allow the further development of new estrogenic compounds specifically targeting these critical brain circuits involved in the control of homeostasis.