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Epidemiology and Prevention |
1 Children's Hospital of Philadelphia, Division of Child Development, Rehabilitation Medicine and Metabolic Disease and 2 Division of Oncology, Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
Requests for reprints: Itzhak Nissim, Division of Child Development, Abramson Pediatrics Research Center, Room-510C, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104-4318. Phone: 215-590-3392; Fax: 215-590-5199; E-mail: ssitz{at}mail.med.upenn.edu.
The efficacy of ifosfamide (IFO), an antineoplastic drug, is severely limited by a high incidence of nephrotoxicity of unknown etiology. We hypothesized that inhibition of complex I (C-I) by chloroacetaldehyde (CAA), a metabolite of IFO, is the chief cause of nephrotoxicity, and that agmatine (AGM), which we found to augment mitochondrial oxidative phosphorylation and ß-oxidation, would prevent nephrotoxicity. Our model system was isolated mitochondria obtained from the kidney cortex of rats treated with IFO or IFO + AGM. Oxidative phosphorylation was determined with electron donors specific to complexes I, II, III, or IV (C-I, C-II, C-III, or C-IV, respectively). A parallel study was done with 13C-labeled pyruvate to assess metabolic dysfunction. Ifosfamide treatment significantly inhibited oxidative phosphorylation with only C-I substrates. Inhibition of C-I was associated with a significant elevation of [NADH], depletion of [NAD], and decreased flux through pyruvate dehydrogenase and the TCA cycle. However, administration of AGM with IFO increased [cyclic AMP (cAMP)] and prevented IFO-induced inhibition of C-I. In vitro studies with various metabolites of IFO showed that only CAA inhibited C-I, even with supplementation with 2-mercaptoethane sulfonic acid. Following IFO treatment daily for 5 days with 50 mg/kg, the level of CAA in the renal cortex was
15 µmol/L. Taken together, these observations support the hypothesis that CAA is accumulated in renal cortex and is responsible for nephrotoxicity. AGM may be protective by increasing tissue [cAMP], which phosphorylates NADH:oxidoreductase. The current findings may have an important implication for the prevention of IFO-induced nephrotoxicity and/or mitochondrial diseases secondary to defective C-I. (Cancer Res 2006; 66(15): 7824-31)
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C. Li, I. Nissim, P. Chen, C. Buettger, H. Najafi, Y. Daikhin, I. Nissim, H. W. Collins, M. Yudkoff, C. A. Stanley, et al. Elimination of KATP Channels in Mouse Islets Results in Elevated [U-13C]Glucose Metabolism, Glutaminolysis, and Pyruvate Cycling but a Decreased {gamma}-Aminobutyric Acid Shunt J. Biol. Chem., June 20, 2008; 283(25): 17238 - 17249. [Abstract] [Full Text] [PDF] |
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I. Nissim, O. Horyn, I. Nissim, Y. Daikhin, S. L. Wehrli, and M. Yudkoff 3-Isobutylmethylxanthine Inhibits Hepatic Urea Synthesis: PROTECTION BY AGMATINE J. Biol. Chem., May 30, 2008; 283(22): 15063 - 15071. [Abstract] [Full Text] [PDF] |
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