Kidney-specific deletion of multidrug resistance-related protein 2 does not aggravate acute cyclosporine A nephrotoxicity in rats.

OBJECTIVE: Multidrug resistance-related protein 2 (Mrp2) is expressed in apical membranes of renal proximal tubular cells and contributes to the renal secretion of cyclosporine A (CsA). Mrp2⁻/⁻ deficiency may lead to local renal CsA accumulation. We investigated whether kidney-specific Mrp2 deficiency enhances acute CsA nephrotoxicity in rats. METHODS: Kidney-specific Mrp2 deletion was achieved by bilateral nephrectomy and transplantation of a congenic Mrp2-deficient kidney into wild-type recipients. Controls received a wild-type kidney. Animals were treated with CsA (10 or 30 mg/kg/day) for 7 days. Renal hemodynamics and renal cortical mRNA expression profile, oxidative stress, and the abundance of multidrug resistance protein 1 (Mdr1) and Mrp2 were assessed. RESULTS: CsA accumulation and CsA-induced reduction in glomerular filtration rate were similar in wild-type and Mrp2⁻/⁻ kidneys. Renal vascular resistance and agonist-induced renal vascular responses were similar in both groups. A PCR array on 84 genes involved in the biotransformation and antioxidant defense revealed increased CsA-induced mRNA expression of genes involved in oxidative and metabolic stress, inflammation, and apoptosis. This gene expression pattern was similar in wild-type and Mrp2⁻/⁻ kidneys. CsA increased the renal cortical oxidized glutathione, did not affect xanthine oxidase-dependent superoxide formation, and decreased renal cortical NADPH oxidase-dependent superoxide formation. Furthermore, CsA increased Mdr1 protein abundance to a greater extent in Mrp2⁻/⁻ than in wild-type kidneys. CONCLUSION: Mrp2 is not critical for renal CsA disposition and its deficiency does not enhance acute CsA nephrotoxicity. The high Mdr1 abundance may at least in part prevent exaggerated CsA accumulation in Mrp2⁻/⁻ kidneys.