Ferroptosis Promotes Cyst Growth in Autosomal Dominant Polycystic Kidney Disease Mouse Models

Significance Statement This study demonstrates for the first time a role of ferroptosis in ADPKD. We show the Pkd1 mutation makes renal epithelial cells prone to ferroptosis through the dysregulation of iron and lipid metabolism. It also suggests the main form of regulated cell death in ADPKD kidneys is ferroptotic but not apoptotic, which helps clarify the controversy over the role of apoptosis in ADPKD. In addition, we found that induction of ferroptosis by erastin promotes cyst growth in Pkd1RC/RC mice, whereas inhibition of ferroptosis by Fer-1 delays cyst growth in rapidly and slowly progressive ADPKD mouse models. These observations suggest management of ferroptosis may be a novel strategy for the treatment of this disease. Background Autosomal dominant polycystic kidney disease (ADPKD), the most common inherited kidney disease, is regulated by different forms of cell death, including apoptosis and autophagy. However, the role in ADPKD of ferroptosis, a recently discovered form of cell death mediated by iron and lipid metabolism, remains elusive. Methods To determine a pathophysiologic role of ferroptosis in ADPKD, we investigated whether the absence of Pkd1 (encoding polycystin-1) affected the expression of key factors involved in the process of ferroptosis, using Western blot and qRT-PCR analysis in Pkd1 mutant renal cells and tissues. We also examined whether treatment with erastin, a ferroptosis inducer, and ferrostain-1, a ferroptosis inhibitor, affected cyst growth in Pkd1 mutant mouse models. Results We found that kidney cells and tissues lacking Pkd1 exhibit extensive metabolic abnormalities, including reduced expression of the system Xc − amino acid antiporter (critical for import of cystine), of iron exporter (ferroportin), and of GPX4 (a key and negative regulator of ferroptosis). The abnormalities also include increased expression of iron importers (TfR1, DMT1) and HO-1, which in turn result in high iron levels, low GSH and GPX4 activity, increased lipid peroxidation, and propensity to ferroptosis. We further found that erastin increased, and ferrostatin-1 inhibited ferroptotic cell death and proliferation of Pkd1 -deficient cells in kidneys from Pkd1 mutant mice. A lipid peroxidation product increased in Pkd1 -deficient cells, 4HNE, promoted the proliferation of survived Pkd1 mutant cells via activation of Akt, S6, Stat3, and Rb during the ferroptotic process, contributing to cyst growth. Conclusion These findings indicate that ferroptosis contributes to ADPKD progression and management of ferroptosis may be a novel strategy for ADPKD treatment.