Toxicity of holotransferrin but not albumin in proximal tubule cells in primary culture

• Published in: Journal of the American Society of Nephrology Vol. 9; no. 1; pp. 77 - 84
• Main Authors: CHEN, L, BOADLE, R. A, HARRIS, D. C. H
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 1998
• Subjects: Animals; Biological and medical sciences; Cells, Cultured; Extracellular Space - metabolism; Hydrogen-Ion Concentration; Interstitial nephritis; Intracellular Membranes - metabolism; Iron - metabolism; Kidney Tubules, Proximal - cytology; Kidney Tubules, Proximal - drug effects; L-Lactate Dehydrogenase - metabolism; Lysine - pharmacology; Male; Malondialdehyde - metabolism; Medical sciences; Nephrology. Urinary tract diseases; Nephropathies. Renovascular diseases. Renal failure; Rats; Rats, Wistar; Serum Albumin - pharmacology; Transferrin - pharmacokinetics; Transferrin - poisoning; Kidney disease; Cell culture; Transferrin; Urinary system disease; Rat; Pathogenesis; Toxicity; Rodentia; Albumin; Experimental study; Kidney; Vertebrata; Renal tubule; Mammalia; Animal; Tubulointerstitial nephritis; Epithelial cell
• ISSN: 1046-6673; 1533-3450
• DOI: 10.1681/ASN.V9177

Proteinuria has been invoked as a cause of tubulointerstitial injury in chronic renal disease, and in vivo studies have suggested indirectly the particular nephrotoxicity of one urinary protein holotransferrin (Tf-Fe). However, to date there has been no direct evidence for the nephrotoxicity of Tf-Fe. To examine the potential cytotoxicity of Tf-Fe and the mechanism involved, and to compare this to another urinary protein albumin, rat proximal tubule cells were studied in primary culture. Tf-Fe at pH 6.0 caused functional and ultrastructural injury, but no cytotoxicity was seen with cells exposed to albumin, apotransferrin (transferrin), or Tf-Fe at pH 7.4. The influence of pH on Tf-Fe-induced cytotoxicity was not due to pH per se, but could be explained by an effect on Tf-Fe uptake. At pH 6.0, uptake of 125I-Tf-Fe (3.55 +/- 0.05 versus 1.25 +/- 0.10 fmol/dish, P < 0.01) and intracellular iron concentration (1.14 +/- 0.25 versus 0.46 +/- 0.23 nmol/dish, P < 0.01) were increased compared with values at pH 7.4. In contrast, pH 6.0 did not increase iron uptake from FeCl3. Lysine (100 mM) inhibited Tf-Fe uptake, decreased intracellular iron concentration, and attenuated Tf-Fe-induced cytotoxicity. The iron chelator des-ferrioxamine (200 microM) and hydroxyl radical scavenger dimethylpyrroline N-oxide (32 mM) abolished lactate dehydrogenase leakage induced by Tf-Fe at pH 6.0. Lipid peroxidation, as assessed by production of malondialdehyde, preceded lactate dehydrogenase leakage. In summary, holotransferrin, but not albumin, is toxic to rat proximal tubule cells, a pH-dependent effect involving its uptake into tubule cells, its iron moiety, and its lipid peroxidation.