Triazolothienopyrimidine inhibitors of urea transporter UT-B reduce urine concentration

摘要

Urea transport (UT) proteins facilitate the concentration of urine by the kidney, suggesting that inhibition of these proteins could have therapeutic use as a diuretic strategy. We screened 100,000 compounds for UT-B inhibition using an optical assay based on the hypotonic lysis of acetamide-loaded mouse erythrocytes. We identified a class of triazolothienopyrimidine UT-B inhibitors; the most potent compound, UTB inh-14, fully and reversibly inhibited urea transport with IC 50 values of 10 nM and 25 nM for human and mouse UT-B, respectively. UTB inh-14 competed with urea binding at an intracellular site on the UT-B protein. UTB inh-14 exhibited low toxicity and high selectivity for UT-B over UT-A isoforms. After intraperitoneal administration of UTB inh-14 in mice to achieve predicted therapeutic concentrations in the kidney, urine osmolality after administration of 1-deamino-8-D-arginine-vasopressin was approximately 700 mosm/kg H 2O lower in UTB inh-14-treated mice than vehicle-treated mice. UTB inh-14 also increased urine output and reduced urine osmolality in mice given free access to water. UTB inh-14 did not reduce urine osmolality in UT-B knockout mice. In summary, these data provide proof of concept for the potential utility of UT inhibitors to reduce urinary concentration in high-vasopressin, fluid-retaining conditions. The diuretic mechanism of UT inhibitors may complement the action of conventional diuretics, which target sodium transport.