Calcium-sensing receptor antagonism or lithium treatment ameliorates aminoglycoside-induced cell death in renal epithelial cells

The aminoglycoside antibiotic gentamicin is able to alter metabolic activity and morphology of MDCK-C11 cells: a cell model of intercalated cells

It is well known that the aminoglycoside antibiotic gentamicin is capable of causing damage to kidney cells. Given the known involvement of Ca²⁺ in the nephrotoxic action of gentamicin, the purpose of this study was to establish a relationship between the concentration of intracellular Ca²⁺ ([Ca²⁺]_i) and cellular cytotoxicity using MDCK-C11 cells, a clone that has several properties that resemble those of intercalated cells of the distal nephron. Changes in [Ca²⁺]_i was determined using fluorescence microscopy. Cell viability was evaluated by the neutral red method, and cell cytotoxicity by the MTT method. The [Ca²⁺]_i gradually increased when cells were exposed to 0.1 mM gentamicin for 10, 20, and 30 min. The presence of extracellular Ca²⁺ was found to be necessary to stimulate the increase in [Ca²⁺]_i induced by gentamicin, since this stimulus disappeared by using 1.8 mM EGTA (a Ca²⁺ chelator). Morphological changes were observed with scanning electron microscopy in epithelial cells exposed to the antibiotic. Furthermore, with the MTT method, a decrease in metabolic activity induced by gentamicin was observed, which indicates a cytotoxic effect. In conclusion, gentamicin was able to alter [Ca²⁺]_i, change the morphology of MDCK-C11 cells, and promote cytotoxicity.

New concepts in calcium-sensing receptor pharmacology and signalling

The calcium-sensing receptor (CaR) is the key controller of extracellular calcium (Ca(2+)(o)) homeostasis via its regulation of parathyroid hormone (PTH) secretion and renal Ca(2+) reabsorption. The CaR-selective calcimimetic drug Cinacalcet stimulates the CaR to suppress PTH secretion in chronic kidney disease and represents the world's first clinically available receptor positive allosteric modulator (PAM). Negative CaR allosteric modulators (NAMs), known as calcilytics, can increase PTH secretion and are being investigated as possible bone anabolic treatments against age-related osteoporosis. Here we address the current state of development and clinical use of a series of positive and negative CaR modulators. In addition, clinical CaR mutations and transgenic mice carrying tissue-specific CaR deletions have provided a novel understanding of the relative functional importance of CaR in both calciotropic tissues and those elsewhere in the body. The development of CaR-selective modulators and signalling reagents have provided us with a more detailed appreciation of how the CaR signals in vivo. Thus, both of these areas of CaR research will be reviewed.

Mechanisms of multimodal sensing by extracellular Ca(2+)-sensing receptors: a domain-based survey of requirements for binding and signalling

In this article we consider the molecular basis of sensing and signalling by the extracellular calcium-sensing receptor. We consider the nature of its ligands and sensing modalities, the identities of its major protein domains and their roles in sensing, signalling and trafficking as well as the significance of receptor homo- and hetero-dimerization. Finally, we consider the current, incomplete, state of knowledge regarding the requirements for ligand-specific signalling.