Acute nephrotoxicity of a carcinogenic iron chelate Selective inhibition of a proteolytic conversion of α_2U‐globulin to the kidney fatty acid‐binding protein

Abstract

The mechanism of acute nephrotoxicity of an iron chelate in vivo has been investigated. Administration of a renal carcinogen ferric nitrilotriacetate (Fe-NTA) (15 mg Fe/kg body weight, intraperitoneally) led to selective loss of a renal protein with an apparent molecular mass of 17 kDa. Analysis of the 17 kDa protein by NH2-terminal sequence demonstrated its identity over 16 NH2-terminal residues as a kidney fatty acid-binding protein (k-FABP) that is a proteolytically modified form of a2u-globulin, a major urinary protein of adult male rats. An immunochemical study using anti-a2u-globulin polyclonal antibodies confirmed that a single injection of Fe-NTA led to a decrease in k-FABP levels. However, a 19-kDa protein identical to the C~zu-globulin progressively appeared in the kidney, suggesting that the proteolytic processing of azu-globnlin in the renal proximal tubules was suppressed by the treatment with Fe-NTA. By monitoring k-FABP and its precursor Ot2u-globulin , it was determined that repeated exposure to Fe-NTA caused suppression of both proteolytic and endocytotic activity of the kidney. The implications of these data in relation to the nephrotoxicity of Fe-NTA are discussed.renal carcinogenesis mediated by Fe-NTA treatment, the role of iron or Fe-NTA has not been fully established, except for the induction of lipid peroxidation. Okada and his co-workers have shown that membrane lipid peroxidation, as seen biochemically by 2-thiobarbituric acid-reactive substances (TBARS) and histochemically by cold Schiff's method (detection of aldehydes), is one of the basic mechanisms of Fe-NTAinduced renal injury and is closely associated with renal carcinogenesis [10][11][12][13][14]. It can therefore be assumed that these renal oxidative injuries are associated with the alteration of the fundamental functions of the kidney, including reabsorption of filtered proteins from glomerular ultrafiltrate and their proteolysis.In the present paper, based on the identification of a major kidney-specific protein, we demonstrate the alteration of proteolytic and endocytotic functions of the renal brush border membrane caused by Fe-NTA treatment. Materials and methods

Decreased Tissue COX5B Expression and Mitochondrial Dysfunction during Sepsis‐Induced Kidney Injury in Rats

“…It is a precursor of a kidney fatty acid-binding protein, involved in mechanism of binding and transport of fatty acids ( http://www.uniprot.org/ ) and it is overexpressed in renal cortex rather than medulla [ 59 ]. This protein can strongly bind toxic agents like alkans [ 58 , 60 ] and is associated with the accumulation of hyaline droplet that leads to damage of the proximal tubular epithelium and renal cancer [ 61 , 62 ].…”

Decreased tissue COX5B expression and mitochondrial dysfunction during sepsis-induced kidney injury in rats

“…It is a precursor of a kidney fatty acidbinding protein, involved in mechanism of binding and transport of fatty acids (http://www.uniprot.org/) and it is overexpressed in renal cortex rather than medulla [59]. This protein can strongly bind toxic agents like alkans [58,60] and is associated with the accumulation of hyaline droplet that leads to damage of the proximal tubular epithelium and renal cancer [61,62]. In our sample, MUP5 spot was localized at a significantly more alkaline pI than the other analyzed protein spots featuring this protein, suggesting some kind of posttranslational modification and/or degradation of MUP5 between 24 h and 48 h of sepsis.…”

N-terminal processing of affinity-tagged recombinant proteins purified by IMAC procedures

“…nitriloacetic acid (NTA)) (Hochuli et al ., ; Arnold, ; Zachariou & Hearn, ; Derewenda, ). The metal ion stability constants (log β values) of many of these ligands are however relatively low, leading to metal ion leakage or metal ion transfer to the target protein depending on its structure (Sulkowski, ), whilst some of these ligands exhibit toxicity or carcinogenicity (Uchida et al ., ; Report on Carcinogens, ). Unlike many other tridentate ligands, 1,4,7‐triazacyclononane (tacn) and its analogues achieve chelation via electron donation from three nitrogen atoms and exhibit very much higher metal ion stability constants (e.g.…”