The use of plasma aldosterone and urinary sodium to potassium ratio as translatable quantitative biomarkers of mineralocorticoid receptor antagonism

<p>Abstract</p> <p>Background</p> <p>Accumulating evidence supports the role of the mineralocorticoid receptor (MR) in the pathogenesis of diabetic nephropathy. These findings have generated renewed interest in novel MR antagonists with improved selectivity against other nuclear hormone receptors and a potentially reduced risk of hyperkalemia. Characterization of novel MR antagonists warrants establishing translatable biomarkers of activity at the MR receptor. We assessed the translatability of urinary sodium to potassium ratio (Na⁺/K⁺) and plasma aldosterone as biomarkers of MR antagonism using eplerenone (Inspra^®), a commercially available MR antagonist. Further we utilized these biomarkers to demonstrate antagonism of MR by PF-03882845, a novel compound.</p> <p>Methods</p> <p>The effect of eplerenone and PF-03882845 on urinary Na⁺/K⁺and plasma aldosterone were characterized in Sprague-Dawley rats and spontaneously hypertensive rats (SHR). Additionally, the effect of eplerenone on these biomarkers was determined in healthy volunteers. Drug exposure-response data were modeled to evaluate the translatability of these biomarkers from rats to humans.</p> <p>Results</p> <p>In Sprague-Dawley rats, eplerenone elicited a rapid effect on urinary Na⁺/K⁺yielding an EC₅₀that was within 5-fold of the functional <it>in vitro </it>IC₅₀. More importantly, the effect of eplerenone on urinary Na⁺/K⁺in healthy volunteers yielded an EC₅₀that was within 2-fold of the EC₅₀generated in Sprague-Dawley rats. Similarly, the potency of PF-03882845 in elevating urinary Na⁺/K⁺in Sprague-Dawley rats was within 3-fold of its <it>in vitro </it>functional potency. The effect of MR antagonism on urinary Na⁺/K⁺was not sustained chronically; thus we studied the effect of the compounds on plasma aldosterone following chronic dosing in SHR. Modeling of drug exposure-response data for both eplerenone and PF-03882845 yielded EC₅₀values that were within 2-fold of that estimated from modeling of drug exposure with changes in urinary sodium and potassium excretion. Importantly, similar unbound concentrations of eplerenone in humans and SHR rats yielded the same magnitude of elevations in aldosterone, indicating a good translatability from rat to human.</p> <p>Conclusions</p> <p>Urinary Na⁺/K⁺and plasma aldosterone appear to be translatable biomarkers of MR antagonism following administration of single or multiple doses of compound, respectively.</p> <p>Trial Registration</p> <p>For clinical study reference EE3-96-02-004, this study was completed in 1996 and falls out scope for disclosure requirements.</p> <p>Clinical study reference A6141115: <url>http://clinicaltrials.gov</url>, <url>http://NIHclinicaltrails.gov</url>; NCTID: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00990223">NCT00990223</a></p

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG

Urinary Single-Cell Profiling Captures the Cellular Diversity of the Kidney.

BACKGROUND: Microscopic analysis of urine sediment is probably the most commonly used diagnostic procedure in nephrology. The urinary cells, however, have not yet undergone careful unbiased characterization. METHODS: Single-cell transcriptomic analysis was performed on 17 urine samples obtained from five subjects at two different occasions, using both spot and 24-hour urine collection. A pooled urine sample from multiple healthy individuals served as a reference control. In total 23,082 cells were analyzed. Urinary cells were compared with human kidney and human bladder datasets to understand similarities and differences among the observed cell types. RESULTS: Almost all kidney cell types can be identified in urine, such as podocyte, proximal tubule, loop of Henle, and collecting duct, in addition to macrophages, lymphocytes, and bladder cells. The urinary cell-type composition was subject specific and reasonably stable using different collection methods and over time. Urinary cells clustered with kidney and bladder cells, such as urinary podocytes with kidney podocytes, and principal cells of the kidney and urine, indicating their similarities in gene expression. CONCLUSIONS: A reference dataset for cells in human urine was generated. Single-cell transcriptomics enables detection and quantification of almost all types of cells in the kidney and urinary tract