Interrogating distinct angiotensin type-1 and type-2 receptor containing brain circuits to understand and alleviate hypertension

项目摘要 高血压是一个普遍的健康问题，也是心血管疾病的主要风险因素。将近一个- 三分之一的高血压患者患有抗药性高血压；这是一种与激活 脑血管紧张素受体、交感神经系统活动增强和循环水平升高 加压素。拟议中的实验旨在识别大脑中的神经元，这些神经元的兴奋或抑制 与顽固性高血压的病理生理学有关。我们用CRE小鼠进行的初步研究 血管紧张素1a或2型受体基因控制的重组酶或绿色荧光蛋白 (AT1R或AT2R)提供了耐人寻味的见解。我们发现，血管细胞器中的神经元 终板(OVLT)和正中视前核(MnPO)表达AT1R或AT2R并发出致密信号 兴奋性投射分别投射到下丘脑室旁核和下丘脑室旁核周围区。 令人着迷的是，这种AT1R神经元的光遗传兴奋引起强劲的(&gt；40毫米汞)和持续的增加 在血压中，提示交感神经兴奋和加压素分泌增加。在 绝大多数AT2R(S)不表达在也合成AT1R的神经元上，而是， 是一个独立的神经元群体，其兴奋可能与高血压的发生相反。与一致 这种解释，我们最近发现，AT2R的药理激活促进了GABA能 介导对加压素神经元的抑制，降低全身加压素和血压。我们有 发展了全面的假设，即在MnPO/OVLT中表达AT1R或AT2R的神经元投射到 PVN和PVN周围区域协调交感神经流出和加压素的分泌 这些神经元的活动预示着对高血压的抵抗或易感性。为了解决这一假设， 建议的研究结合了Cre-loxP技术、体外/体内光遗传学和经典系统生理学 用一种高血压的小鼠模型。目标1将使用光遗传学来探索脑内神经元之间的联系 表达AT1R或AT2R的MnPO/OVLT和表达加压素的PVN神经元。充分性 和/或这些连接的必要性将被确定为交感神经系统活动的增加 和促进神经源性高血压的加压素分泌。然后，AIM 2将使用CRE-loxP系统来 删除MnPO/OVLT中的AT1R和/或AT2R，并确定这些信令中的AT1R/AT2R 大脑核团与高血压的病因有关。总的来说，这些实验将决定是否 这个神经回路中的兴奋性和/或AT1R/AT2R信号可以改变，以防止高血压。 这些研究有可能在详细和机械的水平上揭示神经回路 在高血压期间受到损害，从长远来看，可能会提供最佳靶点的治疗策略 兴奋AT1R和AT2R神经元以缓解高血压。

Project Summary Hypertension is a widespread health problem and a major risk factor for cardiovascular disease. Nearly one- third of hypertensive patients suffer from drug-resistant hypertension; a condition associated with activation of brain angiotensin receptors, enhanced sympathetic nervous system activity and elevated levels of circulating vasopressin. The proposed experiments aim to identify neurons within the brain whose excitation or inhibition is coupled to the pathophysiology underlying resistant hypertension. Our preliminary studies using mice with Cre recombinase or green fluorescent protein directed by the genes for the angiotensin type 1a or type 2 receptors (AT1R or AT2R) have provided intriguing insight. We have discovered that neurons in the organum vasculosum of the lamina terminalis (OVLT) and median preoptic nucleus (MnPO) express AT1R or AT2R and send dense excitatory projections to the paraventricular nucleus of the hypothalamus (PVN) and peri-PVN area, respectively. Fascinatingly, optogenetic excitation of such AT1R neurons elicits robust (>40 mmHg) and sustained increases in blood pressure, suggestive of sympathoexcitation and augmented vasopressin secretion. Within the MnPO/OVLT the vast majority of AT2R(s) are NOT expressed on neurons that also synthesize AT1R, but rather, are a separate population of neurons whose excitation may oppose the onset of hypertension. Consistent with this interpretation, we recently discovered that pharmacological activation of AT2R facilitates GABAergic mediated inhibition of vasopressin neurons and reduces systemic vasopressin and blood pressure. We have developed the overall hypothesis that neurons within the MnPO/OVLT that express AT1R or AT2R project to the PVN and peri-PVN area to coordinate sympathetic outflow and vasopressin secretion, and that the relative activities of these neurons predict resistance or susceptibility to hypertension. To address this hypothesis, the proposed studies combine Cre-LoxP technology, in vitro/in vivo optogenetics and classical systems physiology with a mouse model of hypertension. Aim 1 will use optogenetics to probe the connection between neurons in the MnPO/OVLT that express AT1R or AT2R and neurons in the PVN that express vasopressin. Sufficiency and/or necessity of these connections will be determined for the increased sympathetic nervous system activity and vasopressin secretion that promote neurogenic hypertension. Then, Aim 2 will use the Cre-loxP system to delete AT1R and/or AT2R within the MnPO/OVLT and determine whether AT1R/AT2R signaling within these brain nuclei contribute to the etiology of hypertension. Collectively, these experiments will determine whether excitability and/or AT1R/AT2R signaling within this neural circuit can be altered to prevent high blood pressure. These studies have the potential to uncover, at a detailed and mechanistic level, the neural circuits that are compromised during hypertension and, in the long-term, may inform a therapeutic strategy that optimally targets excitation of AT1R- and AT2R-containing neurons to relieve hypertension.