Two-pore domain potassium channels and aldosterone secretion

描述（由申请方提供）：低肾素高血压（LREH）和特发性原发性醛固酮增多症（IHA）常见，易发生心血管和肾脏疾病。在低肾素高血压（LRH）的疾病谱中，醛固酮增多症的范围从轻度到显著，但它总是不适合血浆肾素水平。LRH的主要原因仍然不明确。在这里，我们认为过量的醛固酮产生可能不是导致LREH或IHA低肾素高血压的唯一致病因素。我们的一般假设是，LRH的低肾素高血压状态是对血管紧张素II（Ang II）敏感性增加的结果，该敏感性在多个部位表现为：肾上腺（醛固酮增多症）、血管系统（高血压）和/或肾小球体（反馈抑制肾素分泌，低肾素）。我们以前证明，全球破坏的基因编码的任务双孔结构域钾通道产生LREH和IHA的主要特征（低肾素高血压与高醛固酮：肾素比，对血管紧张素II和自主醛固酮生产的可变程度的超敏性）。因此，我们进一步假设，破坏TASK通道活性，以及TASK蛋白本身的去除，是产生高反应性所必需的。 Ang II.为了提供人类疾病的相关性，我们提出的工作，我们使用基因组学来测试新的关联人类的任务通道基因变异与测量高血压，醛固酮，肾素活性和ARR在梅萨（动脉粥样硬化的多种族研究）。我们建议使用分子/细胞生物学和电生理记录技术的组合，沿着基因组方法，以测试我们的假设在两个特定的目标。在目的1中，我们生成并验证了新的小鼠模型，其中在产生醛固酮的肾小球细胞（ZG）中特异性地删除了ASK通道，并且其中用绿色荧光蛋白标记了ASK KO ZG细胞。我们使用这些独特的LRH小鼠模型来确定哪些LRH表型特征是由醛固酮增多症本身产生的。我们利用这些发现为人类的遗传分析提供信息。在目的2中，我们确定了对Ang II超敏反应的细胞基础，测试了以下因素的贡献：i）ASK通道活性; ii）AT 1受体活性状态; iii）细胞电兴奋性;和iv）改变的Ca通道活性我们提出的2+研究将提供关于ZG细胞的细胞生物学的新信息，LRH中过度反应的细胞机制，以及任务通道中的遗传差异对人类高血压的贡献。如果我们的假设是正确的，他们也将提供一个合理的基础，开发或评估新的药物治疗LRH，这仍然是一个高流行率的耐药目前可用的疗法。

DESCRIPTION (provided by applicant): Low-renin hypertension (LREH) and idiopathic primary hyperaldosteronism (IHA) occur commonly, and predispose to the development of cardiovascular and renal disease. Within the disease spectrum of low renin hypertension (LRH), hyperaldosteronism ranges from mild to marked, but it always remains inappropriate for the level of plasma renin. The primary causes for LRH remain ill-defined. Here, we propose that excess aldosterone production may not be the sole causative factor contributing to low-renin hypertension in LREH or IHA. Our general hypothesis is that the low renin-hypertensive state in LRH is a consequence of an increased sensitivity to Angiotensin II (Ang II) manifest at multiple sites: the adrenal gland (hyperaldosteronism) the vasculature (hypertension) and/or the juxtaglomerular apparatus (feed-back inhibition of renin secretion, low- renin). We previously demonstrated that global disruption of genes encoding TASK two-pore domain potassium channels produces cardinal features of LREH and IHA (low renin hypertension with high aldosterone:renin ratios, hypersensitivity to Ang II and variable degrees of autonomous aldosterone production). Therefore, we further hypothesize that disrupting TASK channel activity, as well as the removal of TASK protein itself, is required to produce hyper-reactivity to Ang II. To provide human disease relevance to our proposed work, we use genomics to test for novel associations of human TASK channel gene variants with measures of hypertension, aldosterone, renin activity and ARR in MESA (Multi-Ethnic Study of Atherosclerosis) We propose to use a combination of molecular/cell biological and electrophysiological recording techniques, along with genomic approaches, to test our hypotheses in two Specific Aims. In Aim 1, we generate and validate new mouse models in which TASK channels are deleted specifically in aldosterone producing zona glomerulosa cells (ZG) and in which TASK KO ZG cells are marked by green fluorescent protein. We use these unique mouse models of LRH to determine which phenotypic features of LRH are produced by hyperaldosteronism, per se. We use these findings to inform a genetic analysis in humans. In Aim 2, we determine the cellular basis for hypersensitivity to Ang II testing contributions of: i) TASK channel activity; ii) AT1 receptor activity-state; iii) cellular electrical excitability; and iv) altered Ca channel activity Our 2+ proposed studies will provide new information about the cell biology of ZG cells, the cellular mechanisms that underlie exaggerated responses in LRH, and the contribution of genetic differences in TASK channels to human hypertension. If our hypotheses are correct, they also will provide a rational basis for development or evaluation of new medical treatments for LRH, for which there remains a high prevalence of resistance to currently available therapies.