Inhibition of asparagine synthetase effectively retards polycystic kidney disease progression.

Polycystic kidney disease (PKD) is a genetic disorder characterized by bilateral cyst formation. We showed that PKD cells and kidneys display metabolic alterations, including the Warburg effect and glutaminolysis, sustained in vitro by the enzyme asparagine synthetase (ASNS). Here, we used antisense oligonucleotides (ASO) against Asns in orthologous and slowly progressive PKD murine models and show that treatment leads to a drastic reduction of total kidney volume (measured by MRI) and a prominent rescue of renal function in the mouse. Mechanistically, the upregulation of an ATF4-ASNS axis in PKD is driven by the amino acid response (AAR) branch of the integrated stress response (ISR). Metabolic profiling of PKD or control kidneys treated with Asns-ASO or Scr-ASO revealed major changes in the mutants, several of which are rescued by Asns silencing in vivo. Indeed, ASNS drives glutamine-dependent de novo pyrimidine synthesis and proliferation in cystic epithelia. Notably, while several metabolic pathways were completely corrected by Asns-ASO, glycolysis was only partially restored. Accordingly, combining the glycolytic inhibitor 2DG with Asns-ASO further improved efficacy. Our studies identify a new therapeutic target and novel metabolic vulnerabilities in PKD.

Raising serum uric acid with a uricase inhibitor worsens PKD in rat and mouse models.

Humans are predisposed to gout because they lack uricase that converts uric acid to allantoin. Rodents have uricase, resulting in low basal serum uric acid. A uricase inhibitor raises serum uric acid in rodents. There were two aims of the study in polycystic kidney disease (PKD): 1) to determine whether increasing serum uric acid with the uricase inhibitor, oxonic acid, resulted in faster cyst growth and 2) to determine whether treatment with the xanthine oxidase inhibitor, oxypurinol, reduced the cyst growth caused by oxonic acid. Orthologous models of human PKD were used: PCK rats, a polycystic kidney and hepatic disease 1 (Pkhd1) gene model of autosomal recessive PKD (ARPKD) and Pkd1RC/RC mice, a hypomorphic Pkd1 gene model. In PCK rats and Pkd1RC/RC mice, oxonic acid resulted in a significant increase in serum uric acid, kidney weight, and cyst index. Mechanisms of increased cyst growth that were investigated were proinflammatory cytokines, the inflammasome, and crystal deposition in the kidney. Oxonic acid resulted in an increase in proinflammatory cytokines in the serum and kidney in Pkd1RC/RC mice. Oxonic acid did not cause activation of the inflammasome or uric acid crystal deposition in the kidney. In Pkd1RC/RC male and female mice analyzed together, oxypurinol decreased the oxonic acid-induced increase in cyst index. In summary, increasing serum uric acid by inhibiting uricase with oxonic acid results in an increase in kidney weight and cyst index in PCK rats and Pkd1RC/RC mice. The effect is independent of inflammasome activation or crystal deposition in the kidney.NEW & NOTEWORTHY This is the first reported study of uric acid measurements and xanthine oxidase inhibition in polycystic kidney disease (PKD) rodents. Raising serum uric acid with a uricase inhibitor resulted in increased kidney weight and cyst index in Pkd1RC/RC mice and PCK rats, elevated levels of proinflammatory cytokines in the serum and kidney in Pkd1RC/RC mice, and no uric acid crystal deposition or activation of the caspase-1 inflammasome in the kidney.

Investigation of Basolateral Targeting Micelles for Drug Delivery Applications in Polycystic Kidney Disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a complex disorder characterized by uncontrolled renal cyst growth, leading to kidney function decline. The multifaceted nature of ADPKD suggests that single-pathway interventions using individual small molecule drugs may not be optimally effective. As such, a strategy encompassing combination therapy that addresses multiple ADPKD-associated signaling pathways could offer synergistic therapeutic results. However, severe off-targeting side effects of small molecule drugs pose a major hurdle to their clinical transition. To address this, we identified four drug candidates from ADPKD clinical trials, bardoxolone methyl (Bar), octreotide (Oct), salsalate (Sal), and pravastatin (Pra), and incorporated them into peptide amphiphile micelles containing the RGD peptide (GRGDSP), which binds to the basolateral surface of renal tubules via integrin receptors on the extracellular matrix. We hypothesized that encapsulating drug combinations into RGD micelles would enable targeting to the basolateral side of renal tubules, which is the site of disease, via renal secretion, leading to superior therapeutic benefits compared to free drugs. To test this, we first evaluated the synergistic effect of drug combinations using the 20% inhibitory concentration for each drug (IC20) on renal proximal tubule cells derived from Pkd1flox/-:TSLargeT mice. Next, we synthesized and characterized the RGD micelles encapsulated with drug combinations and measured their in vitro therapeutic effects via a 3D PKD growth model. Upon both IV and IP injections in vivo, RGD micelles showed a significantly higher accumulation in the kidneys compared to NT micelles, and the renal access of RGD micelles was significantly reduced after the inhibition of renal secretion. Specifically, both Bar+Oct and Bar+Sal in the RGD micelle treatment showed enhanced therapeutic efficacy in ADPKD mice (Pkd1fl/fl;Pax8-rtTA;Tet-O-Cre) with a significantly lower KW/BW ratio and cyst index as compared to PBS and free drug-treated controls, while other combinations did not show a significant difference. Hence, we demonstrate that renal targeting through basolateral targeting micelles enhances the therapeutic potential of combination therapy in genetic kidney disease.

Kidney organoid models reveal cilium-autophagy metabolic axis as a therapeutic target for PKD both in vitro and in vivo.

Human pluripotent stem cell-derived kidney organoids offer unprecedented opportunities for studying polycystic kidney disease (PKD), which still has no effective cure. Here, we developed both in vitro and in vivo organoid models of PKD that manifested tubular injury and aberrant upregulation of renin-angiotensin aldosterone system. Single-cell analysis revealed that a myriad of metabolic changes occurred during cystogenesis, including defective autophagy. Experimental activation of autophagy via ATG5 overexpression or primary cilia ablation significantly inhibited cystogenesis in PKD kidney organoids. Employing the organoid xenograft model of PKD, which spontaneously developed tubular cysts, we demonstrate that minoxidil, a potent autophagy activator and an FDA-approved drug, effectively attenuated cyst formation in vivo. This in vivo organoid model of PKD will enhance our capability to discover novel disease mechanisms and validate candidate drugs for clinical translation.

A combination of ß-hydroxybutyrate and citrate ameliorates disease progression in a rat model of polycystic kidney disease.

Our research has shown that interventions producing a state of ketosis are highly effective in rat, mouse, and cat models of polycystic kidney disease (PKD), preventing and partially reversing cyst growth and disease progression. The ketone ß-hydroxybutyrate (BHB) appears to underlie this effect. In addition, we have demonstrated that naturally formed microcrystals within kidney tubules trigger a renoprotective response that facilitates tubular obstruction clearance in healthy animals but, alternatively, leads to cyst formation in PKD. The administration of citrate prevents microcrystal formation and slows PKD progression. Juvenile Cy/+ rats, a nonorthologous PKD model, were supplemented from 3 to 8 wk of age with water containing titrated BHB, citrate, or in combination to find minimal effective and optimal dosages, respectively. Adult rats were given a reduced BHB/citrate combination or equimolar control K/NaCl salts from 8 to 12 wk of age. In addition, adult rats were placed in metabolic cages following BHB, citrate, and BHB/citrate administration to determine the impact on mineral, creatinine, and citrate excretion. BHB or citrate alone effectively ameliorates disease progression in juvenile rats, decreasing markers of cystic disease and, in combination, producing a synergistic effect. BHB/citrate leads to partial disease regression in adult rats with established cystic disease, inhibiting cyst formation and kidney injury. BHB/citrate confers benefits via multiple mechanisms, increases creatinine and citrate excretion, and normalizes mineral excretion. BHB and citrate are widely available and generally recognized as safe compounds and, in combination, exhibit high promise for supporting kidney health in polycystic kidney disease.NEW & NOTEWORTHY Combining ß-hydroxybutyrate (BHB) and citrate effectively slows and prevents cyst formation and expansion in young Cy/+ rats using less BHB and citrate than when used alone, demonstrating synergy. In adult rats, the combination causes a partial reversal of existing disease, reducing cyst number and cystic area, preserving glomerular health, and decreasing markers of kidney injury. Our results suggest a safe and feasible strategy for supporting kidney health in polycystic kidney disease (PKD) using a combination of BHB and citrate.

Thiamet G as a Potential Treatment for Polycystic Kidney Disease.

BACKGROUND/AIM: Autosomal dominant polycystic kidney disease (ADPKD) is a prevalent genetic disorder primarily caused by mutations in Pkd1 (PC1), which account for the majority of ADPKD cases. These mutations contribute to the formation of cysts in the kidneys and other organs, ultimately leading to renal failure. Unfortunately, there are currently no available preventive treatments for this disease. MATERIALS AND METHODS: In this study, we utilized Pkd1-knockdown mice and cells to investigate the potential involvement of O-GlcNAcylation in the progression of PKD. Additionally, we examined the effects of thiamet G, an inhibitor of O-GlcNAcase (OGA), on PKD mice. RESULTS: Our findings indicate that both O-GlcNAcylation and OGT (O-GlcNAc transferase) were downregulated in the renal tissues of Pkd1-silenced mice. Furthermore, O-GlcNAcylation was shown to regulate the stability and function of the C-terminal cytoplasmic tail (CTT) of PC1. Treatment of PKD mice with thiamet G resulted in a reduction of renal cytogenesis in these animals. CONCLUSION: These results highlight the unique role of O-GlcNAcylation in the development of cyst formation in PKD and propose it as a potential therapeutic target for the treatment of PKD.

Folate conjugated nanomedicines for selective inhibition of mTOR signaling in polycystic kidneys at clinically relevant doses.

Although rapamycin is a very effective drug for rodents with polycystic kidney disease (PKD), it is not encouraging in the clinical trials due to the suboptimal dosages compelled by the off-target side effects. We here report the generation, characterization, specificity, functionality, pharmacokinetic, pharmacodynamic and toxicology profiles of novel polycystic kidney-specific-targeting nanoparticles (NPs). We formulated folate-conjugated PLGA-PEG NPs, which can be loaded with multiple drugs, including rapamycin (an mTOR inhibitor) and antioxidant 4-hydroxy-TEMPO (a nephroprotective agent). The NPs increased the efficacy, potency and tolerability of rapamycin resulting in an increased survival rate and improved kidney function by decreasing side effects and reducing biodistribution to other organs in PKD mice. The daily administration of rapamycin-alone (1 mg/kg/day) could now be achieved with a weekly injection of NPs containing rapamycin (379 µg/kg/week). This polycystic kidney-targeting nanotechnology, for the first time, integrated advances in the use of 1) nanoparticles as a delivery cargo, 2) folate for targeting, 3) near-infrared Cy5-fluorophore for in vitro and in vivo live imaging, 4) rapamycin as a pharmacological therapy, and 5) TEMPO as a combinational therapy. The slow sustained-release of rapamycin by polycystic kidney-targeting NPs demonstrates a new era of nanomedicine in treatment for chronic kidney diseases at clinically relevant doses.

Metformin does not slow cyst growth in the PCK rat model of polycystic kidney disease.

Metformin (MET) has the potential to activate p-AMPK and block mTORC1-induced proliferation of tubular cells in PKD kidneys. The aim of this study was to determine the effects of MET on cyst growth, kidney function, AMPK and mTOR signaling, and lactate levels in male PCK rats, a Pkhd1 gene mutation model of human autosomal recessive polycystic kidney disease (ARPKD). MET 300 mg/kg/day IP from days 28 to 84 of age resulted in a mean serum metformin level that was 10 times the upper limit of therapeutic, no effect on cyst indices, nephrotoxicity, and increased serum lactate. MET 150 mg/kg resulted in a therapeutic serum metformin level but had no effect on kidney weight, cyst indices, kidney function, or mTOR and autophagy proteins. In summary, a standard dose of MET was ineffective in reducing PKD, did not activate p-AMPK or suppress mTOR and the higher dose resulted in increased lactate levels and nephrotoxicity. In conclusion, the study dampens enthusiasm for human studies of MET in PKD. Doubling the metformin dose resulted in a 10-fold increase in mean blood levels and toxicity suggesting that the dosage range between therapeutic and toxic is narrow.

Culture of Three-Dimensional Madin-Darby Canine Kidney (MDCK) Cysts for In Vitro Drug Testing in Polycystic Kidney Disease.

The formation and growth of kidney cysts (fluid-filled structures lined by epithelial cells) is the primary pathological abnormality in polycystic kidney disease (PKD). Multiple molecular pathways are disrupted in kidney epithelial precursor cells, which lead to altered planar cell polarity, increased proliferation, and fluid secretion, which together with extracellular matrix remodelling culminates in the formation and growth of cysts. Three-dimensional (3D) in vitro cyst models serve as suitable preclinical models to screen candidate drugs for PKD. Madin-Darby Canine Kidney (MDCK) epithelial cells form polarized monolayers with a fluid-filled lumen when suspended in a collagen gel, and their growth is accelerated with the addition of forskolin, a cyclic adenosine monophosphate (cAMP) agonist. Candidate drugs for PKD can be screened for their ability to modulate growth of forskolin-treated MDCK cysts by measuring and quantifying cyst images acquired at progressive timepoints. In this chapter, we describe the detailed methods for the culture and growth of MDCK cysts in a collagen matrix and a protocol for their use in testing candidate drugs to prevent cyst formation and growth.

[Inositol 1,4,5-triphosphate receptor 3 promotes renal cyst development in autosomal dominant polycystic kidney disease].

The purpose of the present study was to determine the role of inositol 1,4,5-trisphosphate receptor 3 (IP3R3) in renal cyst development in autosomal dominant polycystic kidney disease (ADPKD). 2-aminoethoxy-diphenyl borate (2-APB) and shRNA were used to suppress the expression of IP3R3. The effect of IP3R3 on cyst growth was investigated in Madin-Darby canine kidney (MDCK) cyst model, embryonic kidney cyst model and kidney specific Pkd1 knockout (PKD) mouse model. The underlying mechanism of IP3R3 in promoting renal cyst development was investigated by Western blot and immunofluorescence staining. The results showed that the expression level of IP3R3 was significantly increased in the kidneys of PKD mice. Inhibiting IP3R3 by 2-APB or shRNA significantly retarded cyst expansion in MDCK cyst model and embryonic kidney cyst model. Western blot and immunofluorescence staining results showed that hyperactivated cAMP-PKA signaling pathway in the growth process of ADPKD cyst promoted the expression of IP3R3, which was accompanied by a subcellular redistribution process in which IP3R3 was translocated from endoplasmic reticulum to intercellular junction. The abnormal expression and subcellular localization of IP3R3 further promoted cyst epithelial cell proliferation by activating MAPK and mTOR signaling pathways and accelerating cell cycle. These results suggest that the expression and subcellular distribution of IP3R3 are involved in promoting renal cyst development, which implies IP3R3 as a potential therapeutic target of ADPKD.

Prioritized polycystic kidney disease drug targets and repurposing candidates from pre-cystic and cystic mouse Pkd2 model gene expression reversion.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is one of the most prevalent monogenic human diseases. It is mostly caused by pathogenic variants in PKD1 or PKD2 genes that encode interacting transmembrane proteins polycystin-1 (PC1) and polycystin-2 (PC2). Among many pathogenic processes described in ADPKD, those associated with cAMP signaling, inflammation, and metabolic reprogramming appear to regulate the disease manifestations. Tolvaptan, a vasopressin receptor-2 antagonist that regulates cAMP pathway, is the only FDA-approved ADPKD therapeutic. Tolvaptan reduces renal cyst growth and kidney function loss, but it is not tolerated by many patients and is associated with idiosyncratic liver toxicity. Therefore, additional therapeutic options for ADPKD treatment are needed. METHODS: As drug repurposing of FDA-approved drug candidates can significantly decrease the time and cost associated with traditional drug discovery, we used the computational approach signature reversion to detect inversely related drug response gene expression signatures from the Library of Integrated Network-Based Cellular Signatures (LINCS) database and identified compounds predicted to reverse disease-associated transcriptomic signatures in three publicly available Pkd2 kidney transcriptomic data sets of mouse ADPKD models. We focused on a pre-cystic model for signature reversion, as it was less impacted by confounding secondary disease mechanisms in ADPKD, and then compared the resulting candidates' target differential expression in the two cystic mouse models. We further prioritized these drug candidates based on their known mechanism of action, FDA status, targets, and by functional enrichment analysis. RESULTS: With this in-silico approach, we prioritized 29 unique drug targets differentially expressed in Pkd2 ADPKD cystic models and 16 prioritized drug repurposing candidates that target them, including bromocriptine and mirtazapine, which can be further tested in-vitro and in-vivo. CONCLUSION: Collectively, these results indicate drug targets and repurposing candidates that may effectively treat pre-cystic as well as cystic ADPKD.

The lonidamine derivative H2-gamendazole reduces cyst formation in polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a debilitating renal neoplastic disorder with limited treatment options. It is characterized by the formation of large fluid-filled cysts that develop from kidney tubules through abnormal cell proliferation and cyst-filling fluid secretion driven by cAMP-dependent Cl- secretion. We tested the effectiveness of the indazole carboxylic acid H2-gamendazole (H2-GMZ), a derivative of lonidamine, to inhibit these processes using in vitro and in vivo models of ADPKD. H2-GMZ was effective in rapidly blocking forskolin-induced, Cl--mediated short-circuit currents in human ADPKD cells, and it significantly inhibited both cAMP- and epidermal growth factor-induced proliferation of ADPKD cells. Western blot analysis of H2-GMZ-treated ADPKD cells showed decreased phosphorylated ERK and decreased hyperphosphorylated retinoblastoma levels. H2-GMZ treatment also decreased ErbB2, Akt, and cyclin-dependent kinase 4, consistent with inhibition of heat shock protein 90, and it decreased levels of the cystic fibrosis transmembrane conductance regulator Cl- channel protein. H2-GMZ-treated ADPKD cultures contained a higher proportion of smaller cells with fewer and smaller lamellipodia and decreased cytoplasmic actin staining, and they were unable to accomplish wound closure even at low H2-GMZ concentrations, consistent with an alteration in the actin cytoskeleton and decreased cell motility. Experiments using mouse metanephric organ cultures showed that H2-GMZ inhibited cAMP-stimulated cyst growth and enlargement. In vivo, H2-GMZ was effective in slowing postnatal cyst formation and kidney enlargement in the Pkd1flox/flox: Pkhd1-Cre mouse model. Thus, H2-GMZ treatment decreases Cl- secretion, cell proliferation, cell motility, and cyst growth. These properties, along with its reported low toxicity, suggest that H2-GMZ might be an attractive candidate for treatment of ADPKD.NEW & NOTEWORTHY Autosomal dominant polycystic kidney disease (ADPKD) is a renal neoplastic disorder characterized by the formation of large fluid-filled cysts that develop from kidney tubules through abnormal cell proliferation and cyst-filling fluid secretion driven by cAMP-dependent Cl- secretion. This study shows that the lonidamine derivative H2-GMZ inhibits Cl- secretion, cell proliferation, and cyst growth, suggesting that it might have therapeutic value for the treatment of ADPKD.

Efficacy of Prolonged Antibiotic Therapy for Renal Cyst Infections in Polycystic Kidney Disease.

OBJECTIVE: To determine the impact of antibiotic therapy (ATBT) on outcomes of renal cyst infection (CyI) in patients with polycystic kidney disease. PATIENTS AND METHODS: We undertook a single-center retrospective study of CyI in autosomal dominant polycystic kidney disease (January 1, 2000, through December 31, 2018). Cyst infections were classified as definite (microbiologically proven), probable (radiologic signs), or possible (clinical or biologic signs only). We studied the determinants of ATBT failure (persistence of infection beyond 72 hours of microbiologically adequate initial ATBT, with requirement for ATBT change, cyst drainage, or nephrectomy) and recurrences (>14 days after the end of ATBT). RESULTS: Among 90 patients, 139 CyIs (11 definite, 74 probable, 54 possible) were compiled. Cultures were positive in 106 of 139 (76%) episodes, with Escherichia coli found in 89 of 106 (84%). Treatment failures and recurrences within 1 year of follow-up were more frequent in definite/probable CyI (20/85 [34%] and 16/85 [19%]) than in possible CyI (2/54 [4%] and 4/54 [7%]; P<.01 and P=.08, respectively). Male sex (odds ratio [OR], 7.79; 95% CI, 1.72 to 46.68; P<.01), peak C-reactive protein level above 250 mg/L (OR, 7.29; 95% CI, 1.78 to 35.74; P<.01; to convert C-reactive protein values to nmol/L, multiply by 9.524), and cyst wall thickening (OR, 7.70; 95% CI, 1.77 to 43.47; P=.01) but not the modalities of initial ATBT were independently associated with higher risk of failure. In a Cox proportional hazards model, kidney transplant recipients exhibited higher risk of recurrence (hazard ratio, 3.76; 95% CI, 1.06 to 13.37; P=.04), whereas a total duration of ATBT of 28 days or longer was protective (hazard ratio, 0.02; 95% CI, 0.00 to 0.16; P<.001), with an inverse correlation between duration and recurrence (81% for treatment <21 days, 47% for 21 to 27 days, 2% for ≥28 days; P<.0001). CONCLUSION: Initial first-line ATBT had no significant effect on renal CyI treatment failure. Treatment duration of 28 days and longer reduced recurrences.

Potential Application of Gambogic Acid for Retarding Renal Cyst Progression in Polycystic Kidney Disease.

Abnormal cell proliferation and accumulation of fluid-filled cysts along the nephrons in polycystic kidney disease (PKD) could lead to a decline in renal function and eventual end-stage renal disease (ESRD). Gambogic acid (GA), a xanthone compound extracted from the brownish resin of the Garcinia hanburyi tree, exhibits various pharmacological properties, including anti-inflammation, antioxidant, anti-proliferation, and anti-cancer activity. However, its effect on inhibiting cell proliferation in PKD is still unknown. This study aimed to determine the pharmacological effects and detailed mechanisms of GA in slowing an in vitro cyst growth model of PKD. The results showed that GA (0.25-2.5 µM) significantly retarded MDCK cyst growth and cyst formation in a dose-dependent manner, without cytotoxicity. Using the BrdU cell proliferation assay, it was found that GA (0.5-2.5 µM) suppressed MDCK and Pkd1 mutant cell proliferation. In addition, GA (0.5-2.5 µM) strongly inhibited phosphorylation of ERK1/2 and S6K expression and upregulated the activation of phosphorylation of AMPK, both in MDCK cells and Pkd1 mutant cells. Taken together, these findings suggested that GA could retard MDCK cyst enlargement, at least in part by inhibiting the cell proliferation pathway. GA could be a natural plant-based drug candidate for ADPKD intervention.

Pharmacological Effects of Panduratin A on Renal Cyst Development in In Vitro and In Vivo Models of Polycystic Kidney Disease.

Renal cyst expansion in polycystic kidney disease (PKD) involves abnormalities in both cyst-lining-cell proliferation and fluid accumulation. Suppression of these processes may retard the progression of PKD. Evidence suggests that the activation of 5' AMP-activated protein kinase (AMPK) inhibits cystic fibrosis transmembrane conductance regulator (CFTR)-mediated chloride secretion, leading to reduced progression of PKD. Here we investigated the pharmacological effects of panduratin A, a bioactive compound known as an AMPK activator, on CFTR-mediated chloride secretion and renal cyst development using in vitro and animal models of PKD. We demonstrated that AMPK was activated in immortalized normal renal cells and autosomal dominant polycystic kidney disease (ADPKD) cells following treatment with panduratin A. Treatment with panduratin A reduced the number of renal cyst colonies corresponding with a decrease in cell proliferation and phosphorylated p70/S6K, a downstream target of mTOR signaling. Additionally, panduratin A slowed cyst expansion via inhibition of the protein expression and transport function of CFTR. In heterozygous Han:Sprague-Dawley (Cy/+) rats, an animal model of PKD, intraperitoneal administration of panduratin A (25 mg/kg BW) for 5 weeks significantly decreased the kidney weight per body weight ratios and the cystic index. Panduratin A also reduced collagen deposition in renal tissue. Intraperitoneal administration of panduratin A caused abdominal bleeding and reduced body weight. However, 25 mg/kg BW of panduratin A via oral administration in the PCK rats, another non-orthologous PKD model, showed a significant decrease in the cystic index without severe adverse effects, indicating that the route of administration is critical in preventing adverse effects while still slowing disease progression. These findings reveal that panduratin A might hold therapeutic properties for the treatment of PKD.

Pinostrobin inhibits renal CFTR-mediated Cl- secretion and retards cyst growth in cell-derived cyst and polycystic kidney disease rats.

Cystic fibrosis transmembrane conductance regulator (CFTR) plays crucial role in renal cyst expansion via increase in fluid accumulation. Inhibition of CFTR has been proposed to retard cyst development and enlargement in polycystic kidney disease (PKD). Pinostrobin, a bioactive natural flavonoid, possesses several pharmacological effects. The present study investigated pharmacological effects of pinostrobin on CFTR-mediated Cl- secretion and renal cyst expansion in in vitro and in vivo models. Pinostrobin (10 and 50 µM) reduced number of MDCK cell-derived cyst colonies and inhibited cyst expansion via inhibition of cell proliferation and CFTR-mediated Cl- secretion. The inhibitory effect of pinostrobin was not due to the decrease in cell viability and activity of Na+-K+-ATPase. We also investigated the natural analogue pinocembrin as well as the synthetic analogue pinostrobin oxime. Both pinocembrin and pinostrobin oxime did not reduce CFTR-mediated Cl- secretion. In PKD rats, oral administration of pinostrobin (40 mg/kg/day) exhibited a decreasing in cystic area compared to vehicle-treated rats. Pinostrobin treatment inhibited renal expression of CFTR protein in PKD rats. Our findings highlighted the potential therapeutic application of pinostrobin in PKD.

Illuminating a Dark Kinase: Structure-Guided Design, Synthesis, and Evaluation of a Potent Nek1 Inhibitor and Its Effects on the Embryonic Zebrafish Pronephros.

NIMA-related kinase 1 (Nek1) has lately garnered attention for its widespread function in ciliogenesis, apoptosis, and the DNA-damage response. Despite its involvement in various diseases and its potential as a cancer drug target, no directed medicinal chemistry efforts toward inhibitors against this dark kinase are published. Here, we report the structure-guided design of a potent small-molecule Nek1 inhibitor, starting from a scaffold identified by kinase cross-screening analysis. Seven lead compounds were identified in silico and evaluated for their inhibitory activity. The top compound, 10f, was further profiled for efficacy, toxicity, and bioavailability in a zebrafish polycystic kidney disease model. Administration of 10f caused the expansion of fluorescence-labeled proximal convoluted tubules, supporting our hypothesis that Nek1-inhibition causes cystic kidneys in zebrafish embryos. Compound 10f displayed insignificant inhibition in 48 of 50 kinases in a selectivity test panel. The findings provide a powerful tool to further elucidate the function and pharmacology of this neglected kinase.