Cisplatin-induced inhibition of receptor-mediated endocytosis of protein in the kidney

Abstract

Background. Administration of cisplatin, cis-diamminedichloroplatinum (II) (CDDP), causes a severe impairment of renal function, including increases in urinary excretion of proteins. We recently found that CDDP inhibits vacuolar H+-ATPase, which plays an important role in receptor-mediated endocytosis in the renal proximal tubules. Therefore, CDDP-induced proteinuria may be due to an inhibition of the receptor-mediated endocytosis in the renal proximal tubules following a decrease in vacuolar H+-ATPase activity by the drug. Methods. Effects of CDDP on receptor-mediated endocytosis of albumin in opossum kidney (OK) epithelial cells, and on urinary excretion of albumin and vitamin D binding protein, which are reabsorbed in the renal proximal tubules by endocytosis, in rats were examined. Results. CDDP inhibited uptake of fluorescein-isothiocyanate (FITC)-albumin, a receptor-mediated endocytosis marker, by OK cells in a time- and concentration-dependent fashion. In contrast, CDDP treatment did not affect the uptake of FITC-inulin, a fluid-phase endocytosis marker. CDDP caused a decrease in the affinity and in the maximal velocity of FITC-albumin uptake. The adenosine 5′-triphosphate (ATP) content in OK cells was not changed by CDDP at concentrations that inhibited FITC-albumin uptake. The endosomal pH in OK cells was increased by CDDP treatment. Administration of CDDP to rats increased the urinary excretion of albumin and vitamin D binding protein. Conclusions. These results suggest that CDDP decreases the receptor-mediated endocytosis of protein following the inhibition of vacuolar H+-ATPase in the renal proximal tubules, and the inhibition of receptor-mediated endocytosis would be the mechanisms underlying the proteinuria induced by CDDP.