Identification of targets of IL-13 and STAT6 signaling in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a life-threatening, highly prevalent monogenic disease caused by mutations in polycystin-1 (PC1) in 85% of patients. We have previously identified a COOH-terminal cleavage fragment of PC1, PC1-p30, which interacts with the transcription factor STAT6 to promote transcription. STAT6 is aberrantly active in PKD mouse models and human ADPKD, and genetic removal or pharmacological inhibition of STAT6 attenuates disease progression. High levels of IL-13, a STAT6-activating cytokine, are found in the cyst fluid of PKD mouse models and increased IL-13 receptors in ADPKD patient tissue, suggesting that a positive feedback loop exists between IL-13 and STAT6 is activated in cystic epithelial cells and contributes to disease progression. In this study, we aimed to identify genes aberrantly regulated by STAT6 to better understand how increased IL-13/STAT6 signaling may contribute to PKD progression. We demonstrate that the expression of periostin, galectin-3, and IL-24 is upregulated in various forms of PKD and that their aberrant regulation is mediated by IL-13 and STAT6 activity. Periostin and galectin-3 have previously been implicated in PKD progression. We support these findings by showing that periostin expression is increased after IL-13 treatment in kidney epithelial cells, that galectin-3 expression is increased after injecting IL-13 in vivo and that IL-24 expression is upregulated by both IL-13 treatment and PC1-p30 overexpression in mouse and human kidney cells. Overall, these findings provide insight into the possible mechanisms by which increased IL-13/STAT6 signaling contributes to PKD progression and suggest potential therapeutic targets.