Kidney Week

Abstract: FR-PO619

The Cystogenic Effects of Ouabain in Autosomal Dominant Polycystic Kidney Disease (ADPKD) Require Cell Caveolae

Session Information

• Cystic Kidney Diseases: Mechanisms and Models
  October 25, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1201 Genetic Diseases of the Kidneys: Cystic

Authors

• Trant, Jordan, University of Kansas Medical Center Department of Cell Biology and Physiology, Kansas City, Kansas, United States

Jordan Trant

• Mcdermott, Jeff P., University of Kansas Medical Center Department of Cell Biology and Physiology, Kansas City, Kansas, United States

Jeff P. Mcdermott

• De Blanco, Gladis Sanchez, University of Kansas Medical Center Department of Cell Biology and Physiology, Kansas City, Kansas, United States

Gladis Sanchez De Blanco

• Blanco, Gustavo, University of Kansas Medical Center Department of Cell Biology and Physiology, Kansas City, Kansas, United States

Gustavo Blanco, MD, PhD

Background

We have previously shown that the hormone ouabain is a circulating factor which can accelerate the progression of autosomal dominant polycystic kidney disease (ADPKD). At physiologic concentrations, ouabain increases cyst area and fibrosis in kidneys from ADPKD but not wildtype mice. These effects are mediated through ouabain binding to its specific receptor, Na,K-ATPase (NKA). In ADPKD, a fraction of the NKA has an abnormally high affinity for ouabain, leading to an over-activation of the NKA signal transduction cascade. Previous studies in cell lines suggest that ouabain’s effects are mediated by the NKA located in the cell caveolae. Here, we determined the role of caveolae in NKA-mediated and ouabain-induced effects in ADPKD using a new mouse model in which caveolar formation is disrupted on the background of ADPKD (Pkd1^RC/RCCav1^-/-).

Methods

Mice homozygous for the knockout of caveolin-1 (Cav1), a main structural component of caveolae, were crossed with Pkd1^RC/RC mice to obtain the Pkd1^RC/RCCav1^-/- model where caveolae no longer form in the kidney. Ouabain (0.3 mg/kg) or saline was injected intraperitoneally to Pkd1^RC/RC or Pkd1^RC/RCCav1^-/- mice daily for 5 months. Kidneys from these mice were analyzed for cyst area, kidney weight to body weight ratio (%KW/BW) and fibrosis. Cell proliferation (using Ki67 as a marker) and the activation of downstream members of ouabain-NKA signaling (ERK and Akt) were measured.

Results

The ablation of Cav1 and disruption of caveolae in the kidney was confirmed in Pkd1^RC/RCCav1^-/- mice by immunoblot and electron microscopy. Loss of caveolae abolished the high ouabain affinity component of NKA seen in Pkd1^RC/RC mice, with all NKA having the same ouabain affinity as wildtype mice. After 5 months of ouabain administration, Pkd1^RC/RCCav1^-/- kidneys did not show the ouabain-induced increase in cyst number or fibrosis seen in Pkd1^RC/RC mice. In addition, the ouabain-induced phosphorylation of ERK and AKT and the increase in cell proliferation in Pkd1^RC/RC kidneys was blunted in the Pkd1^RC/RCCav1^-/- mice.

Conclusion

Our results show that disruption of caveolae through deletion of caveolin-1 abolishes the abnormal high ouabain affinity fraction of NKA and the cystic effects of ouabain in ADPKD mice, providing in vivo evidence for the need of cell caveolae in the signaling function of NKA.

Funding

• NIDDK Support