In Vivo Chromaffin Granule depletion and Blood Pressure

嗜铬粒蛋白A(ChGA)是一种48 kDa的酸性分泌蛋白，与神经递质共存储 (儿茶酚胺、三磷酸腺苷和神经肽Y[NPY])在称为嗜铬颗粒的囊泡中，并在尼古丁-胆碱能刺激下共同释放。CHGA是一种具有生物活性的多肽，包括我们发现的儿茶酚胺释放抑制肽(牛CHGA344.364和人CHGA352.372)，并命名为儿茶酚素。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，我们产生了系统性和条件性Chga基因敲除(Chga-/-)小鼠。全身性Chga-/-小鼠表现出以下表型：(I)嗜铬颗粒减少伴随较高的收缩和舒张压(BP)，(Ii)“不下降”的BP(无日变化)，(Iii)左心室增大，(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，以及(Vi)血压对跑台应激反应增强。我们已经将含有人类CHGA基因(CHGA/)的细菌人工染色体(BAG)转基因小鼠培育成CHGA-/-小鼠(CHGA/；CHGA-/-)，以“挽救”CHGA基因敲除的表型。本提案提出了3个具体目标：目的1.探索CHGA-/-小鼠高血压(SBP和DBP)和“非浸泡”BP表型的形成机制，包括共递质的作用。AIM II.“抢救”血压与“不浸泡” 在CHGA-/-小鼠体内观察BP表型的研究 将CHGA基因(CHGA/)导入CHGA-/-小鼠种系(CHGA/\CHGA-/-)。目标三.建立 小鼠体内自然产生的人儿茶素变异体(表达BAC-儿茶素变异体转基因)在对抗交感肾上腺应激血压反应中的作用。这些研究利用独特的儿茶素基因敲除、转基因和人类变种，可能确定CHGA片段儿茶酚胺和儿茶酚胺共递质在高血压等复杂表型的发展中的作用，以及自然发生的儿茶素变种在对抗交感肾上腺应激源的血压反应中的影响。

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.