Urea transporter inhibitors identified as novel diuretics

Urea transporters （UT）, including isoforms of UT-A endothelia and erythrocytes, play an important role in the urine in kidney tubule epithelia and UT-B in vasa recta concentration mechanism by mediated an intrarenalurea recycling, suggesting that functional inhibition of these proteins could have therapeutic use as diuretic. By in- tegrated cell based high throughput screening and in silico methods, a class of small-molecule drug-like compounds with thienoquinolin core structure was found to have inhibition activity on both UT-A and UT-B. The structure and activity relationship analysis showed a compound PU-48, named chemically as methyl 3-amino-6-methoxythieno[ 2, 3-b] quinoline-2-carboxylate, had the best UT-A and UT-B inhibition activity. IC50s of PU-48 on UT-B facilitated as determined by erythrocyte lysis assay. In vivo urea transport were micromole level in human, rat, and mouse, activity of PU-48 on urinary concentrating function was evaluated in rats fed ad libitum in metabolic cages. Urine output significantly increased in a dose-dependent manner in rats subcutaneously administered PU-48. Urinary os- molality and urea concentration were significantly decreased. The peak changes of urine output, urinary osmolality and urinary urea concentration occurred between 2 and 4 h after PU/18 administration, with values returning to was subcutaneously injected every 6 h the 24 h urine output in baseline by 10 h. When PU-48 at 50 mg · kg^-1 PU-48 treated rats was significantly higher than that in vehicle control rats. Urinary osmolality and urea concentra- tion in PU-48 treated rats were significantly lower than in vehicle control rats. The excretion of Na ＋ , K ＋ , C1- was PU-48 treated rats had significantly higher urea excre- similar in PU-48 treated and vehicle control rats. However, tion than vehicle control rats. The data suggest that PU-48 caused a urea-selective diuresis without disturbing elec- TGs, and LDL-C in PU-48-treated rats were similar with those trolyte metabolism. Notably, blood urea, T-CHO, in vehicle control rats, which are normal levels. These data indicate that the diuretic effect of PU-14 does not cause electrolyte imbalance and abnormal metabolism. It is predicated that UT inhibitors have potential clinical applica- tions as sodium-sparing diuretics in edema from different etiologies, such as congestive heart failure and cirrhosis.