BACKGROUND: Treatment with the aminoglycoside antibiotic gentamicin can be associated with severe side effects including renal Ca2+ wasting. The underlying mechanism is unknown but proposed to involve activation of the Ca2+ -sensing receptor (CaSR) in the thick ascending limb (TAL), which would increase expression of claudin-14 (CLDN14) and limit Ca2+ reabsorption. However, no direct evidence for this hypothesis has been presented. METHODS: The effect of gentamicin on renal Ca2+ handling was studied in vivo using mouse models with impaired Ca2+ reabsorption in the proximal tubule and TAL. The effects of gentamicin in CaSR activation were studied in vitro using a Cldn14 promoter luciferase-reporter assay, while the effect of gentamicin on the distal nephron Ca2+ channel transient potential receptor vanilloid 5 (TPRV5) activity was determined by patch-clamp in HEK293 cells. RESULTS: Gentamicin increased urinary Ca2+ excretion in wildtype mice following acute and chronic administration. This calciuretic effect was unaltered in mice with genetic CaSR overactivation and remained present in furosemide-treated animals. Moreover, gentamicin-induced calciuresis was not significantly different in Cldn14-/- mice or mice with impaired proximal tubular Ca2+ reabsorption (Cldn2-/- mice), compared to wildtype animals. In vitro, gentamicin failed to activate the CaSR. In contrast, patch-clamp analysis revealed that gentamicin inhibited rabbit and human TRPV5 channel currents in a dose-dependent manner. In accordance with a direct effect of gentamicin on TRPV5, chronic gentamicin administration downregulated gene expression of distal nephron Ca2+ transporters in mice. CONCLUSION: We show here that gentamicin does not cause hypercalciuria via activation of the CaSR-CLDN14 pathway or by interfering with proximal tubular CLDN2-dependent Ca2+ reabsorption. Instead, gentamicin blocks distal Ca2+ reabsorption by direct inhibition of the Ca2+ channel TRPV5. These findings offer new insights into Ca2+ wasting in patients treated with gentamicin.
|Original language||English (US)|
|Journal||FASEB journal : official publication of the Federation of American Societies for Experimental Biology|
|State||Published - May 1 2022|
ASJC Scopus subject areas
- Molecular Biology