Abstract: PUB211
Vaptans, New-Generation Diuretics, Exert Their Aquaretic Effect Through Inhibition of Aquaporin 2 Trafficking in Renal Collecting Duct Cells
Session Information
Category: Genetic Diseases of the Kidneys
- 1001 Genetic Diseases of the Kidneys: Cystic
Authors
- Di Mise, Annarita, University of Bari, Bari, Italy
- Venneri, Maria, University of Bari, Bari, Italy
- Ranieri, Marianna, University of Bari, Bari, Italy
- Centrone, Mariangela, University of Bari, Bari, Italy
- Pellegrini, Lorenzo, Palladio Biosciences, Newtown, Pennsylvania, United States
- Tamma, Grazia, University of Bari, Bari, Italy
- Valenti, Giovanna, University of Bari, Bari, Italy
Background
Selective vasopressin V2 receptor (V2R) antagonists (vaptans) are a new generation of diuretics. Compared with classical diuretics, vaptans promote the excretion of retained body water in disorders where plasma vasopressin concentrations are inappropriately high for any given plasma osmolality. Under these conditions an aquaretic drug would be preferable over a conventional diuretic. The clinical efficacy of vaptans is in principle due to impaired vasopressin-regulated water reabsorption via the water channel aquaporin-2 (AQP2).
Methods
Here, the effect of lixivaptan - a novel selective V2R antagonist - on the vasopressin-cAMP/PKA signaling cascade was investigated in mouse renal collecting duct cells expressing AQP2 (MCD4) and the human V2R. Compared to tolvaptan - a selective V2R antagonist indicated for the treatment of clinically significant hypervolemic and euvolemic hyponatremia -, lixivaptan has been predicted to be less likely to cause liver injury.
Results
In MCD4 cells, immunofluorescence localization of AQP2 and analysis by confocal microscopy showed that clinically-relevant concentrations of lixivaptan (100nM for 1h) prevented dDAVP-induced AQP2 phosphorylation at ser-256 and AQP2 translocation to the plasma membrane. Consistent with this finding, real-time fluorescence kinetic measurements demonstrated that lixivaptan prevented dDAVP-induced increase in osmotic water permeability.
Conclusion
These data represent the first detailed demonstration of the central role of AQP2 blockade in the aquaretic effect of lixivaptan and suggest that lixivaptan has the potential to become a safe and effective therapy for the treatment of disorders characterized by high plasma vasopressin concentrations and water retention.
Funding
- Commercial Support – Palladio Biosciences, Inc.