# Development of Distal Nephron Diuretics Targeting Kir4.1/5.1 Heteromeric Potassium Channels

> **NIH NIH R01** · VANDERBILT UNIVERSITY MEDICAL CENTER · 2020 · $413,826

## Abstract

SUMMARY
Swelling caused by edematous fluid retention is a common, life-threatening symptom of heart failure (HF) and
chronic kidney disease (CKD). Loop diuretics are often prescribed as a first-line therapy to quickly reduce the
extracellular fluid volume burden in HF and CKD patients. This class of diuretic works by inhibiting NaCl
reabsorption in the thick ascending limb (TAL) of Henle's loop, and increases the delivery of NaCl and fluid to
the distal nephron comprised of the distal convoluted tubule (DCT) and collecting duct (CD). In response to the
increased NaCl and fluid load, the DCT and CD increase their NaCl reabsorbing capacity by upregulating the
expression of specific ion transporters and channels. This compensatory mechanism diminishes the
effectiveness of loop diuretics and gives rise to loop diuretic resistance. A growing consensus among
nephrologists is that distally acting diuretics that inhibit sodium (Na+) reabsorption in the DCT (i.e. thiazide
diuretics) or CD (potassium-sparing diuretics) downstream of the TAL should be administered in an effort to
overcome loop diuretic resistance. However, both diuretic classes have critical limitations that highlight the need
to discover more effective, safer, and novel-mechanism distal diuretics for circumventing loop diuretic resistance.
In this application, we propose to discover the first potent and selective inhibitors of heteromeric Kir4.1/5.1
potassium channels, which have emerged recently as key regulators of NaCl reabsorption and kinase signaling
in the distal nephron. In Aim 1, we will employ a fully validated, fluorescence-based thallium-flux assay to screen
approximately 110,000 structurally diverse compounds from the Vanderbilt Institute of Chemical Biology library
for novel inhibitors of Kir4.1/5.1 channels heterologously expressed in HEK-293 cells. A series of secondary
thallium-flux assays, as well as high-throughput automated patch clamp electrophysiology, will then be used to
evaluate the potency and selectivity of confirmed inhibitors for Kir4.1/5.1 over an extensive panel of related
inward rectifier potassium (Kir) channels. In Aim 2, we will select the most promising Kir4.1/5.1 inhibitors based
on their potency, selectivity, chemical structure, and in vitro metabolic stability properties to develop analog
libraries using state-of-the-art medicinal chemistry techniques with the goal of optimizing the pharmacological
properties of inhibitors for in vivo administration. In Aim 3, we will use single channel analysis to test the activity
lead inhibitors against native rat and human Kir4.1/5.1 channels in freshly isolated kidney tubules. In addition,
we will test the hypothesis that inhibition of Kir4.1/5.1 induces renal excretion of Na+, K+, and water in rats.
Completion of these aims will provide critically needed tool compounds for evaluating the therapeutic potential
of Kir4.1/5.1 channels as a diuretic target in the setting of loop diuretic resistance in HF and CKD pati...

## Key facts

- **NIH application ID:** 10015266
- **Project number:** 5R01DK120821-02
- **Recipient organization:** VANDERBILT UNIVERSITY MEDICAL CENTER
- **Principal Investigator:** Jerod S. Denton
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $413,826
- **Award type:** 5
- **Project period:** 2019-09-15 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10015266

## Citation

> US National Institutes of Health, RePORTER application 10015266, Development of Distal Nephron Diuretics Targeting Kir4.1/5.1 Heteromeric Potassium Channels (5R01DK120821-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10015266. Licensed CC0.

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