Autosomal-dominant polycystic kidney disease (ADPKD) is caused by mutations in either PKD1 or PKD2 and is characterized by the development of multiple bilateral renal cysts that replace normal kidney tissue. Here, we used Pkd1 mutant mouse models to demonstrate that the nicotinamide adenine dinucleotide–dependent (NAD-dependent) protein deacetylase sirtuin 1 (SIRT1) is involved in the pathophysiology of ADPKD. SIRT1 was upregulated through c-MYC in embryonic and postnatal Pkd1-mutant mouse renal epithelial cells and tissues and could be induced by TNF-α, which is present in cyst fluid during cyst development. Double conditional knockouts of Pkd1 and Sirt1 demonstrated delayed renal cyst formation in postnatal mouse kidneys compared with mice with single conditional knockout of Pkd1. Furthermore, treatment with a pan-sirtuin inhibitor (nicotinamide) or a SIRT1-specific inhibitor (EX-527) delayed cyst growth in Pkd1 knockout mouse embryonic kidneys, Pkd1 conditional knockout postnatal kidneys, and Pkd1 hypomorphic kidneys. Increased SIRT1 expression in Pkd1 mutant renal epithelial cells regulated cystic epithelial cell proliferation through deacetylation and phosphorylation of Rb and regulated cystic epithelial cell death through deacetylation of p53. This newly identified role of SIRT1 signaling in cystic renal epithelial cells provides the opportunity to develop unique therapeutic strategies for ADPKD.
Authors
Xia Zhou, Lucy X. Fan, William E. Sweeney Jr., John M. Denu, Ellis D. Avner, Xiaogang Li
(A–D) Histologic examination of P7 kidneys from (A) Pkd1+/+:Sirt1flox/flox:Ksp-Cre, (B) Pkd1flox/flox:Sirt1+/+:Ksp-Cre, (C) Pkd1flox/flox:Sirt1flox/+:Ksp-Cre, and (D) Pkd1flox/flox:Sirt1flox/flox:Ksp-Cre neonates. (E) Percent cystic area relative to total kidney section area was significantly decreased in P7 kidneys from Pkd1flox/flox:Sirt1flox/flox:Ksp-Cre (Sirt1flox/flox) versus Pkd1flox/flox:Sirt1+/+:Ksp-Cre (Sirt1+/+) neonates. Data reflect all sections quantified for each condition (n = 10 per group). (F) KW/BW ratios were dramatically reduced in P7 Pkd1flox/flox:Sirt1flox/flox:Ksp-Cre versus Pkd1flox/flox:Sirt1+/+:Ksp-Cre neonates. (G) BUN levels of P7 Pkd1flox/flox:Sirt1+/+:Ksp-Cre, Pkd1flox/flox:Sirt1flox/+:Ksp-Cre, and Pkd1flox/flox:Sirt1flox/flox:Ksp-Cre neonates. (H) Cell proliferation (arrows) was decreased in P7 Pkd1flox/flox:Sirt1flox/flox:Ksp-Cre versus Pkd1flox/flox:Sirt1+/+:Ksp-Cre neonate kidneys, as detected with PCNA staining. The percentage of PCNA-positive nuclei in cystic lining epithelial cells was calculated from an average of 1,000 nuclei per mouse kidney section; only strongly stained nuclei were considered PCNA-positive. (I) Pkd1flox/flox:Sirt1flox/flox:Ksp-Cre mice lived to 21.9 ± 3.6 days, whereas Pkd1flox/flox:Sirt1+/+:Ksp-Cre mice died of polycystic kidney disease at 14.1 ± 0.9 days. Scale bars: 2 mm (A–D); 30 μm (H). *P < 0.05; **P < 0.01.