In Vivo Chromaffin Granule depletion and Blood Pressure

嗜铬粒蛋白A（Chromogranin A，CHGA）是一种分子量为48 kDa的酸性分泌蛋白，与神经递质共贮 （儿茶酚胺，ATP和神经肽Y [NPY]）在称为嗜铬颗粒的囊泡中，并在响应烟碱胆碱能刺激时共同释放。CHGA是产生生物活性肽的前蛋白，包括我们发现并命名为catestatin的儿茶酚胺释放抑制肽（牛CHGA 344.364和人CHGA 352.372）。由于转基因小鼠在旨在了解心血管功能基本机制的研究中变得越来越重要，我们已经产生了全身性和条件性Chga敲除（Chga-/-）小鼠。全身性Chga-/-小鼠显示以下表型：（i）嗜铬颗粒的消耗伴随较高的收缩压和舒张压（BP），（ii）“非浸渍”BP（无昼夜变化），（iii）左心室尺寸增加，（iv）肾上腺儿茶酚胺、NPY和ATP水平降低，（v）血浆儿茶酚胺和NPY水平增加，和（vi）对跑步机应激的夸大的BP反应。我们已经产生了含有人CHGA基因（CHGA+/+）的细菌人工染色体（BAG）转基因小鼠到Chga-/-小鼠（CHGA+/+;Chga-/-）的种系中，以“拯救”Chga敲除表型。本提案提出了三个具体目标：探索Chga-/-小鼠高血压（SBP和DBP）和“非浸渍”血压表型发生的机制，包括共递质的作用。Aim II.“拯救”英国石油公司和“不浸” 通过引入含有人BAG的BAG在Chga-/-小鼠中观察到的BP表型 将CHGA基因（CHGA+/+）导入Chga-/-小鼠（CHGA+/+\Chga-/-）的种系中。Aim III.建立 在小鼠中天然存在的人catestatin变体（表达BAC-catestatin变体转基因）在抵消交感肾上腺应激BP反应中的作用。这些研究，利用独特的基因敲除，转基因，和人的变体catestatin，可能会建立CHGA片段catestatin和儿茶酚胺共递质在复杂的表型，如高血压的发展中的作用，和天然存在的catestatin变体的影响，在抵消血压反应交感肾上腺紧张。

Chromogranin A (CHGA), a 48 kDa acidic secretory protein, is co-stored with neurotransmitters (catecholamines, ATP, and neuropetide Y [NPY]) in vesicles called chromaffin granules and co-released in response to nicotinic-cholinergic stimulation. CHGA is a proprotein giving rise to biologically active peptides including a catecholamine release inhibitory peptide (bovine CHGA344.364 and human CHGA352.372) that we discovered and named catestatin. Since genetically modified mice are becoming increasingly important in studies designed to understand basic mechanisms of cardiovascular function, we have generated systemic and conditional Chga knockout (Chga-/-) mice. The systemic Chga-/- mice displayed the following phenotypes: (i) Depletion of chromaffin granules accompanied by higher systolic and diastolic blood pressure (BP), (ii) "Non-dipping" BP (no diurnal variation), (iii) Increment of left ventricular dimension, (iv) Decrements of adrenal catecholamine, NPY and ATP levels, (v) Increments of plasma catecholamine and NPY levels, and (vi) Exaggerated BP response to treadmill stress. We have already generated bacterial artificial chromosome (BAG) transgenic mice containing the human CHGA gene (CHGA+/+) into the germline of Chga-/- mice (CHGA+/+;Chga-/-) to "rescue" Chga knockout phenotypes. The present proposal develops 3 specific aims: Aim I. Explore the mechanism of development of high BP (SBP and DBP) and "non-dipping" BP phenotypes in Chga-/- mice, including the role of cotransmitters. Aim II. "Rescue" the BP and "nondipping" BP phenotypes observed in Chga-/- mice by introduction of a BAG containing the human CHGA gene (CHGA+/+) into the germline of Chga-/- mice (CHGA+/+\Chga-/-). Aim III. Establish the role of a naturally occurring human catestatin variant in mice (expressing a BAC-catestatin variant transgene) in counteracting sympathoadrenal stress BP responses. These studies, utilizing unique knockout, transgenic, and human variants of catestatin, are likely to establish the role of CHGA fragment catestatin and catecholamine co-transmitters in the development of complex phenotypes such as hypertension, and the influence of naturally occurring catestatin variants in counteracting BP responses to sympathoadrenal stressors.