Despite the recent launch of Tolvaptan, the search for safer polycystic kidney disease (PKD) drugs continues. Ciclopirox (CPX) or its olamine salt (CPX-O) are contained in number of commercially available antifungal agents. CPX is also reported to possess anticancer activity. Several mechanisms of action have been proposed including chelation of iron and inhibition of iron dependent enzymes. Here, we show that CPX-O inhibited in vitro cystogenesis of primary human PKD cyst-lining epithelial cells cultured in a 3D collagen matrix. To assess in vivo role of CPX-O, we treated PKD mice with CPX-O. CPX-O reduced the kidney-to-body weight ratios of PKD mice. This was also associated with decreased cell proliferation, decreased cystic area and improved renal function. Ferritin levels were significantly elevated in cystic kidneys of PKD mice, and CPX-O treatment reduced renal ferritin levels. The reduction in ferritin was associated with increased ferritinophagy marker, NCOA4 which reversed upon CPX-O treatment in PKD mice. Interestingly, these effects on ferritin appeared independent of iron. These data suggest that CPX-O can induce ferritin degradation via ferritinophagy which is associated with decreased cyst growth progression in PKD mice. Most importantly these data indicate that CPX-O has the potential to treat autosomal dominant PKD.

No abstract

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Polycystic kidney disease (PKD) is a genetic disorder that affects cilia homeostasis and causes progressive growth of tubular-derived cysts within the kidney. Efforts to find safer drugs for PKD have increased in the past few years after the successful launch of tolvaptan, the first approved drug to combat autosomal dominant PKD progression. Here we investigate the effects of Quinomycin A on progression of PKD. Quinomycin A is a bis-intercalator peptide that has previously shown to be effective against cancer progression. Quinomycin A treatment decreased cyst progression of human ADPKD primary renal epithelial cells grown in a 3D collagen gel to form cysts. In an orthologous mouse model of PKD, Quinomycin A administration reduced kidney to body weight ratios, and reduced cystogenesis. This was accompanied by decreased cell proliferation and fibrosis. Quinomycin treatments efficiently reduced the expression of Notch pathway proteins, RBPjk and HeyL in kidneys of PKD mice. Interestingly, Quinomycin treatments also normalized cilia lengths of collecting duct cyst-lining renal epithelia of PKD mice. This is the first preclinical study to our knowledge that demonstrates Quinomycin A has protective effects against PKD progression, in part by reducing Notch signaling and renal epithelial cilia lengths. Our findings suggest Quinomycin A has potential therapeutic value for PKD patients.

Despite the recent launch of Tolvaptan, the search for safer polycystic kidney disease (PKD) drugs continues. Ciclopirox, as the free acid (CPX) and its olamine salt (CPX-O) , are contained in number of commercially available topical antifungal agents. CPX is reported in the literature to possess anticancer activity in number of solid tumor cancers and hematological malignancy by several proposed mechanisms of action including chelation of iron and inhibition of iron dependent enzymes. Here, we show that CPX-O inhibited in vitro cystogenesis of primary human cyst epithelial cells cultured in 3D collagen matrix. To determine if CPX-O inhibits PKD progression, we treated PKD mice with a low dose of 10 mg/kg CPX-O by daily intraperitoneal injections from day 21 to day 49 post- partum. CPX-O reduced the kidney to body weight ratio of the PKD mice. This was associated with decreased cell proliferation decrease cystic area and improved renal function. We found that ferritin levels were significantly elevated in cystic kidneys of PKD mice, and that CPX-O treatment reduced renal ferritin levels and increased ferritinophagy marker, NCOA4. Our data suggest that CPX-O dose dependently induces ferritin degradation via ferritinophagy which is associated with decreased cyst growth and disease progression in PKD mice. Most importantly these data indicate that CPX-O, a drug used to treat skin infections and currently in clinical trials for cancer, has the potential to treat ADPKD.