Two-pore domain potassium channels and aldosterone secretion

描述(申请人提供)：低肾素性高血压(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。在低肾素性高血压(LRH)的疾病谱中，醛固酮增多症从轻微到明显不等，但始终不适合血浆肾素水平。LRH的主要原因仍不清楚。在这里，我们认为，过量的醛固酮产生可能不是导致LREH或IHA患者低肾素高血压的唯一原因。我们的一般假设是，LRH患者的低肾素-高血压状态是对血管紧张素II(Ang II)敏感性增加的结果，血管II表现在多个部位：肾上腺(醛固酮增多症)、血管系统(高血压)和/或肾小球旁装置(肾素分泌的反馈抑制，低肾素)。我们以前已经证明，编码任务双孔区域钾通道的基因的全球破坏产生了LREH和IHA(低肾素性高血压伴高醛固酮/肾素比率、对Ang II超敏和不同程度的自主醛固酮产生)的基本特征。因此，我们进一步假设，干扰任务通道活动以及任务蛋白本身的移除是产生高反应性所必需的。 为了提供人类疾病与我们建议的工作的相关性，我们使用基因组学在MESA(动脉粥样硬化的多种族研究)中测试人类任务通道基因变异与高血压、醛固酮、肾素活性和ARR的新关联。我们建议结合分子/细胞生物学和电生理记录技术，以及基因组方法，在两个特定目标下测试我们的假设。在目标1中，我们建立并验证了新的小鼠模型，在该模型中，产生醛固酮的肾小球带细胞(ZG)中的任务通道被特异性地删除，其中任务KO的ZG细胞被绿色荧光蛋白标记。我们使用这些独特的LRH小鼠模型来确定LRH的哪些表型特征本身是由醛固酮增多症产生的。我们利用这些发现为人类的基因分析提供信息。在目标2中，我们确定了对Ang II高敏感性的细胞基础，测试的贡献包括：i)任务通道活性；ii)AT1受体活性-状态；iii)细胞电兴奋性；以及iv)钙通道活性改变。我们提出的研究将提供有关ZG细胞生物学的新信息，LRH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，它们也将为开发或评估LRH的新药物治疗提供合理的基础，目前LRH对现有治疗方法的耐药性仍然很高。

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.