In vitro 3D phenotypic drug screen identifies celastrol as an effective in vivo inhibitor of polycystic kidney disease.

Polycystic kidney disease (PKD) is a prevalent genetic disorder, characterized by the formation of kidney cysts that progressively lead to kidney failure. The currently available drug tolvaptan is not well tolerated by all patients and there remains a strong need for alternative treatments. The signaling rewiring in PKD that drives cyst formation is highly complex and not fully understood. As a consequence, the effects of drugs are sometimes difficult to predict. We previously established a high throughput microscopy phenotypic screening method for quantitative assessment of renal cyst growth. Here, we applied this 3D cyst growth phenotypic assay and screened 2320 small drug-like molecules, including approved drugs. We identified 81 active molecules that inhibit cyst growth. Multi-parametric phenotypic profiling of the effects on 3D cultured cysts discriminated molecules that showed preferred pharmacological effects above genuine toxicological properties. Celastrol, a triterpenoid from Tripterygium Wilfordii, was identified as a potent inhibitor of cyst growth in vitro. In an in vivo iKspCre-Pkd1lox,lox mouse model for PKD, celastrol inhibited the growth of renal cysts and maintained kidney function.

Dose-Titrated Vasopressin V2 Receptor Antagonist Improves Renoprotection in a Mouse Model for Autosomal Dominant Polycystic Kidney Disease.

BACKGROUND: In autosomal dominant polycystic kidney disease, renoprotective treatment with a vasopressin V2 receptor antagonist (V2RA) is given in a fixed dose (FD). Disease progression and drug habituation could diminish treatment efficacy. We investigated whether the renoprotective effect of the V2RA can be improved by dose titration of the V2RA aiming to maintain aquaresis at a high level. METHODS: The V2RA OPC-31260 was administered to Pkd1-deletion mice in an FD (0.1%) or in a titrated dose (TD, up to 0.8% when drinking volume dropped). Total kidney weight (TKW) and cyst ratio were investigated and compared to non-treated Pkd1-deletion mice. Treatment was started early or late (21 or 42 days postnatal). RESULTS: Water intake was significantly higher throughout the experiment in the TD compared to the FD group. FD treatment that was initiated early reduced TKW and cyst ratio but lost its renoprotective effect later during the experiment. In contrast, TD treatment was able to maintain the renoprotective effect. TD treatment, however, was also associated with a higher early termination rate in comparison with FD treatment. Late start of treatment (FD or TD) did not show a renoprotective effect. CONCLUSIONS: Titration of a V2RA aimed to maintain aquaresis at a high level showed a better renoprotective effect compared to FD administration. However, this treatment regimen was poorly tolerated and did not overcome treatment unresponsiveness when started later in the disease.

An autopsy study suggests that diabetic nephropathy is underdiagnosed.

The reported prevalence of diabetic nephropathy (DN) among patients with diabetes varies widely. Most studies use the presence of microalbuminuria for clinical onset of DN in the absence of a histopathologic evaluation. In this autopsy study, we collected and analyzed data from a cohort of patients with type 1 or 2 diabetes and determined the prevalence of histologically proven DN in patients with or without clinical manifestations of renal disease. We also examined the distribution among histopathologic classes with respect to clinical parameters. Renal tissue specimens from autopsies and clinical data were collected retrospectively from 168 patients with diabetes. The histopathologic classification for DN was scored as were interstitial and vascular parameters. In this cohort, 106 of 168 patients had histopathologic changes in the kidney characteristic of DN. Twenty of the 106 histologically proven DN cases did not present with DN-associated clinical manifestations within their lifetime. Glomerular and interstitial lesions were associated with renal function but not with proteinuria. We also found that underdiagnosed DN may encompass all histopathologic classes except the sclerotic class. Thus, the prevalence of histologically proven DN was higher than previously appreciated, and we found a relatively high proportion of DN that was clinically underdiagnosed yet histologically proven, suggesting that DN lesions may develop before the onset of clinical findings.

Intrinsic carnosine metabolism in the human kidney.

Histidine-containing dipeptides like carnosine and anserine have protective functions in both health and disease. Animal studies suggest that carnosine can be metabolized within the kidney. The goal of this study was to obtain evidence of carnosine metabolism in the human kidney and to provide insight with regards to diabetic nephropathy. Expression, distribution, and localization of carnosinase-1 (CNDP1), carnosine synthase (CARNS), and taurine transporters (TauT) were measured in human kidneys. CNDP1 and CARNS activities were measured in vitro. CNDP1 and CARNS were located primarily in distal and proximal tubules, respectively. Specifically, CNDP1 levels were high in tubular cells and podocytes (20.3 ± 3.4 and 15 ± 3.2 ng/mg, respectively) and considerably lower in endothelial cells (0.5 ± 0.1 ng/mg). CNDP1 expression was correlated with the degradation of carnosine and anserine (r = 0.88 and 0.81, respectively). Anserine and carnosine were also detectable by HPLC in the renal cortex. Finally, TauT mRNA and protein were found in all renal epithelial cells. In diabetic patients, CNDP1 seemed to be reallocated to proximal tubules. We report compelling evidence that the kidney has an intrinsic capacity to metabolize carnosine. Both CNDP1 and CARNS are expressed in glomeruli and tubular cells. Carnosine-synthesizing and carnosine-hydrolyzing enzymes are localized in distinct compartments in the nephron and increased CNDP1 levels suggest a higher CNDP1 activity in diabetic kidneys.