Abstract: SA-PO1032
Cyclosporin A Aggravates Hypomagnesemia and Hypercalciuria in Claudin 16-Deficient Mice
Session Information
- Fluid and Electrolytes: Basic - II
October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid and Electrolytes
- 901 Fluid and Electrolytes: Basic
Authors
- Mutig, Kerim, Charite-Universitaetsmedizin Berlin, Berlin, Germany
- Drewell, Hoora, Charité-Universitätsmedizin Berlin, Berlin, Germany
- Fähling, Michael, Charité - Universitätsmedizin Berlin, Berlin, Germany
- Breiderhoff, Tilman, Charité-Universitätsmedizin Berlin, Berlin, Germany
- Müller, Dominik, Charité-Universitätsmedizin Berlin, Berlin, Germany
- Bachmann, Sebastian, Charité - Universitätsmedizin Berlin, Berlin, Germany
Background
Calcineurin inhibitors are instrumental for immunosuppression in patients after organ transplantation but renal side effects such as hypomagnesemia and hypercalciuria often limit their therapeutic benefits. The tight junctions protein claudin 16 (Cldn16) is essential for paracellular reabsorption of calcium and magnesium along the cortical thick ascending limb (cTAL). In this study we treated wild-type (WT) and Cldn16-deficient (Cldn16-/-) mice with a calcineurin inhibitor cyclosporin A (CsA) to identify the role of Cldn16 in calcineurin inhibitor-induced abnormalities of renal divalent cation handling.
Methods
Kidney performance was evaluated in metabolic cages. Key paracellular and transcellular distal calcium and magnesium transport proteins were assessed by quantitative PCR, immunoblotting and immunofluorescence.
Results
Labeling of Cldn16 produced strong signal in cTAL tight junctions of WT but not of Cldn16-/- kidneys. Physiological analysis showed baseline hypomagnesaemia and hypercalciuria in Cln16-/- mice compared to controls. CsA administration (25 mg/kg i.p. for 7 days) induced hypomagnesaemia and hypercalciuria in WT and aggravated calcium and magnesium wasting in Cldn16-/- mice. Analysis of Cldn10, Cldn14, Cldn16, and Cldn19 isoforms did not reveal any CsA-dependent changes of their expression or protein abundance. In contrast, expression and abundance levels of relevant transcellular divalent cation transporters including the transient receptor potential channel TRPM6, calbindin, parvalbumin, and divalent metal cation transporter CNNM2 were significantly reduced upon CsA in both genotypes with stronger decreases in Cldn16-/- mice.
Conclusion
In summary, our data suggest that calcineurin inhibitors cause renal calcium and magnesium loss via suppression of transcellular reabsorption pathways, rather than via inhibition of the Cldn16-mediated paracellular transport.