Sirtuin 1 inhibition delays cyst formation in autosomal-dominant polycystic kidney disease
Xia Zhou, Lucy X. Fan, William E. Sweeney Jr., John M. Denu, Ellis D. Avner, Xiaogang Li
Xia Zhou, Lucy X. Fan, William E. Sweeney Jr., John M. Denu, Ellis D. Avner, Xiaogang Li
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Research Article

Sirtuin 1 inhibition delays cyst formation in autosomal-dominant polycystic kidney disease

Abstract

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

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Figure 7

Silence or inhibition of SIRT1 decreased renal epithelial cell proliferation, but increased apoptosis.

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Silence or inhibition of SIRT1 decreased renal epithelial cell prolifera...
(A) Overexpressing WT SIRT1, but not deacetylase catalytically inactive mutant SIRT1 H355A, increased BrdU incorporation in mouse IMCD3 cells compared with cells transfected with vector alone. (B–E) Silencing SIRT1 with siRNA (B and C) or inhibiting SIRT1 with the indicated concentrations of nicotinamide (D and E) decreased BrdU incorporation in (B and D) Pkd1-null MEK and (C and E) PN24 cells. BrdU incorporation index in the control cells was assigned as 100%. An average of 300 cells was counted for each experiment. n = 3. (F and G) Flow cytometry analysis indicated that apoptosis was induced in (F) Pkd1-null MEK cells treated with 10 mM nicotinamide for 24 hours and (G) PN24 cells treated with 40 mM nicotinamide for 48 hours. Nicotinamide-treated cells were labeled with annexin V and PI and analyzed by flow cytometry. Early and late apoptotic cells were represented by annexin V+PI– and annexin V+PI+ cells, respectively. n = 3. (H) Caspase-3 activation was examined from whole cell lysates of WT MEK, Pkd1-null MEK, PH2, and PN24 cells treated or not with 10 mM nicotinamide for 24 hours. Nicotinamide treatment increased caspase-3 activation and caused the appearance of cleaved PARP (a substrate of caspase-3) in Pkd1-null MEK and PN24 cells. *P < 0.05; **P < 0.01.