Cationic uremic toxins affect human renal proximal tubule cell functioning through interaction with the organic cation t
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ION CHANNELS, RECEPTORS AND TRANSPORTERS
Cationic uremic toxins affect human renal proximal tubule cell functioning through interaction with the organic cation transporter Carolien M. S. Schophuizen & Martijn J. Wilmer & Jitske Jansen & Lena Gustavsson & Constanze Hilgendorf & Joost G. J. Hoenderop & Lambert P. van den Heuvel & Rosalinde Masereeuw
Received: 3 January 2013 / Revised: 31 May 2013 / Accepted: 2 June 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Several organic cations, such as guanidino compounds and polyamines, have been found to accumulate in plasma of patients with kidney failure due to inadequate renal clearance. Here, we studied the interaction of cationic uremic toxins with renal organic cation transport in a conditionally immortalized human proximal tubule epithelial cell line (ciPTEC). Transporter activity was measured and validated in cell suspensions by studying uptake of the fluorescent substrate 4-(4-(dimethylamino)styryl)-N-methylpyridinium-iodide (ASP+). Subsequently, the inhibitory potencies of the cationic uremic toxins, cadaverine, putrescine, spermine and spermidine (polyamines), acrolein (polyamine breakdown product), guanidine, and methylguanidine (guanidino compounds) were determined. Concentration-dependent inhibition of ASP+ uptake by
TPA, cimetidine, quinidine, and metformin confirmed functional endogenous organic cation transporter 2 (OCT2) expression in ciPTEC. All uremic toxins tested inhibited ASP+ uptake, of which acrolein required the lowest concentration to provoke a half-maximal inhibition (IC50 =44±2 μM). A Dixon plot was constructed for acrolein using three independent inhibition curves with 10, 20, or 30 μM ASP+, which demonstrated competitive or mixed type of interaction (Ki =93 ± 16 μM). Exposing the cells to a mixture of cationic uremic toxins resulted in a more potent and biphasic inhibitory response curve, indicating complex interactions between the toxins and ASP+ uptake. In conclusion, ciPTEC proves a suitable model to study cationic xenobiotic interactions. Inhibition of cellular uptake transport was demonstrated for several
The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Carolien M.S. Schophuizen, Martijn J. Wilmer, Lambert P. van den Heuvel, and Rosalinde Masereeuw contributed equally to this work. Electronic supplementary material The online version of this article (doi:10.1007/s00424-013-1307-z) contains supplementary material, which is available to authorized users. C. M. S. Schophuizen : L. P. van den Heuvel Department of Pediatric Nephrology, Radboud University Nijmegen Medical Centre, 6525 GA Nijmegen, The Netherlands
L. Gustavsson Department of Laboratory Medicine (Malmö), Lund University, Skåne University Hospital, 205 02 Malmö, Sweden
M. J. Wilmer : J. Jansen : R. Masereeuw (*) Department of Pharmacology and Toxicology (149), Nijmegen Centre for Molecular Life Sciences/Institute for Genetic and Metabolic Disease, Radboud University Nijmegen Medi
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