Nephrotoxicity of platinum complexes is related to basolateral organic cation transport

Abstract

Background: Cisplatin and its analogs oxaliplatin and carboplatin are widely used antitumor drugs. Nephrotoxicity is a common and relevant adverse effect that occurs especially in cisplatin therapy. Cellular and molecular mechanisms of cisplatin-induced nephrotoxicity are not completely understood. The nephrotoxicity of platinum complexes was evaluated by a new in vitro system that utilizes the high Trans Epithelial Electrical Resistance (TEER) of the C7 clone of the MDCK (Madin-Darby canine kidney) cells. By means of this assay system we addressed the question whether the side of application of renal epithelia influences platinum complex toxicity.

Methods: C7 cells were grown in membrane filter cups, and the apical or basolateral membranes were exposed to 100-micromol/L cis-, oxali-, or carboplatin. TEER and caspase-3 activity were determined. Cimetidine was used as an inhibitor of organic cation transporters (OCTs). C7 cell lysates were analyzed for OCT-1 and -2 by Western blot analysis.

Results: TEER dropped by 89.5 +/- 9.3% (mean +/- SEM; N= 6) within 24 hours after addition of cisplatin to the basolateral side of C7 cells, while caspase activity increased up to 840.6 +/- 17.4% (mean +/- SEM; N= 6) compared to control cells. Exposure of the apical membrane to cisplatin reduced TEER by only 13.4 +/- 8.7% (mean +/- SEM; N= 6), and increased caspase-3 activity up to 213.9 +/- 7.6% (mean +/- SEM; N= 6). Oxaliplatin and carboplatin reduced TEER to a lesser extent than cisplatin. Oxaliplatin lowered TEER stronger than carboplatin. In general, basolateral application led to higher caspase activities and lower TEERs. The OCT-inhibitor cimetidine inhibited the TEER decrease induced by platinum complexes. Immunoblotting confirmed the presence of OCT-2 in C7 cells.

Conclusion: Toxic effects of platinum complexes on renal epithelia depend on the platinum complex used and the site of application. We conclude that cell polarity and basolateral transport mechanisms are essential in nephrotoxicity of platinum drugs.