Mechanisms of diuretic resistance in heart failure

心力衰竭(HF)的症状和住院主要是由充血引起的，形成循环 利尿剂是心衰治疗的基石.这是有问题的，因为环状利尿剂抵抗(DR)很常见，而且 持续拥堵和随之而来的糟糕结果的驱动因素。我们最近证实：1) 人类心力衰竭中DR的主要驱动因素是肾小管水平，而不是利尿剂输送不良。2)近端 肾小管钠重吸收不是一个重要因素，而是作用部位的反应降低。 Henle环和代偿性远端肾小管钠重吸收驱动Dr.4)环上的阻力 亨勒似乎可以用利尿剂剂量解决，传统上认为利尿剂剂量高于上限剂量。尽管 确定糖尿病视网膜病变的一般位置、罪魁祸首转运体以及特定药物的研究进展 目标仍未定义。有共识认为存在三个化学计量相关的远端 钠(Na)的运输途径。这三种途径的中心成分是氯化钠。 辅转运蛋白(NCC)、上皮钠通道(ENaC)和氯代碳酸氢盐交换蛋白(Pendrin)。 重要的是，这些靶点可以用FDA批准的药物在人类身上操纵；NCC可以选择性地 由苯并氟甲肼(一种对碳酸酐酶有最小抑制作用的噻氮化物)抑制，由阿米洛利抑制ENaC， 氯化铵负荷量下调吊环蛋白的表达。我们还了解到，钠在循环中的重吸收 Henle是动态的，对NKCC2具有实质性的调节和可塑性。重要的是，NKCC2剪接变体具有 已被鉴定为具有显著不同的离子亲和力、转运能力和利尿剂敏感性。 这项建议的主要目标是将上述知识转化为治疗学。 为了实现这一点，我们将进行3个机械聚焦的临床试验 使用不同转运途径的药物操纵试验，内源性锂清除 了解区域肾单位钠处理和尿胞外小泡的差异。 管状溶质转运体水平和剪接变异体。具体地说，Aim 1将调查这一机制 在人类心力衰竭中，利尿剂剂量反应曲线的环路显著右移。在这里，我们将 连续滴定高选择性NKCC2拮抗剂布美他尼至10毫克(400毫克呋塞米当量) 稳定的糖尿病视网膜病变和利尿剂反应性心衰患者。在目标2中，我们试图了解急性对抗的影响。 环上对阿米洛利敏感、对噻嗪敏感或对阿米洛利和噻嗪联合敏感的转运通路 稳定期DR心衰患者的利尿剂反应。我们将通过管理以下各项组合来实现这一点 安慰剂、阿米洛利和/或苯达氟甲肼联合布美他尼用于稳定的DR HF患者。在……里面 目的3我们将确定NH4CL负荷是否可以减少非阿米洛利/非阿米洛利 硫氮化物敏感的远端钠重吸收。通过完成这些目标，我们将获得实质性的 了解心衰DR的具体机制，从而制定有针对性的治疗策略。

Symptoms and hospitalizations for heart failure (HF) are primarily driven by congestion, making loop diuretics a cornerstone therapy in HF. This is problematic since loop diuretic resistance (DR) is common and a driver of persistent congestion and the poor outcomes that follow. We have recently confirmed that: 1) The dominant driver of DR in human HF is at the renal tubular level, rather than poor diuretic delivery. 2) Proximal tubular sodium reabsorption is not a substantial contributor, rather 3) reduced response at the site of action in the loop of Henle and compensatory distal tubular sodium reabsorption drive DR. 4) Resistance at the loop of Henle appears to be addressable with diuretic doses traditionally considered above the ceiling dose. Despite progress in defining the general locations for DR, the culprit transporters and thus specific druggable targets remain undefined. There is consensus on the existence of three stoichiometrically relevant distal sodium (Na) transport pathways. The central components to these three pathways are the sodium chloride cotransporter (NCC), the epithelial sodium channel (ENaC), and the chloride bicarbonate exchanger, pendrin. Importantly, these targets can be manipulated in humans with FDA approved drugs; NCC can be selectively inhibited by bendroflumethiazide (a thiazide with minimal carbonic anhydrase inhibition), ENaC by amiloride, and pendrin downregulated by NH4Cl loading. We have also learned that sodium reabsorption in the loop of Henle is dynamic with substantial regulation and plasticity of NKCC2. Importantly, NKCC2 splice variants have been identified that have dramatically different ion affinities, transport capacity, and diuretic sensitivities. The primary goal of this proposal is to translate the above knowledge into therapeutically actionable approaches to human DR. To accomplish this, we will conduct 3 mechanistically focused clinical trials using pharmacologic manipulation of different transport pathways, endogenous lithium clearance to understand regional nephron sodium handling, and urinary extracellular vesicles to investigate differences in tubular solute transporter levels and splice variants. Specifically, Aim 1 will investigate the mechanism underlying the substantial shift in the loop diuretic dose response curve to the right in human HF. Here we will serially titrate the highly selective NKCC2 antagonist bumetanide to 10mg (400mg furosemide equivalents) in stable DR and diuretic responsive HF patients. In Aim 2 we seek to understand the effect of acute antagonism of amiloride sensitive, thiazide sensitive, or combined amiloride & thiazide sensitive transport pathways on loop diuretic response in stable DR HF patients. We will accomplish this by administration of the combinations of placebo, amiloride, and/or bendroflumethiazide, in conjunction with bumetanide, to stable DR HF patients. In Aim 3 we will determine if NH4CL loading, known to downregulate pendrin, can reduce non-amiloride/non- thiazide sensitive distal sodium reabsorption. Through the completion of these aims we will gain substantial understanding of the specific mechanisms underlying DR in HF allowing targeted therapeutic strategies.