mesna and aldophosphamide

Renal Fanconi syndrome occurs in about 1-5% of all children treated with Ifosfamide (Ifo) and impairment of renal phosphate reabsorption in about 20-30% of them. Pathophysiological mechanisms of Ifo-induced nephropathy are ill defined. The aim has been to investigate whether Ifo metabolites affect the type IIa sodium-dependent phosphate transporter (NaPi-IIa) in viable opossum kidney cells. Ifo did not influence viability of cells or NaPi-IIa-mediated transport up to 1 mM/24 h. Incubation of confluent cells with chloroacetaldehyde (CAA) and 4-hydroperoxyIfosfamide (4-OH-Ifo) led to cell death by necrosis in a concentration-dependent manner. At low concentrations (50-100 microM/24 h), cell viability was normal but apical phosphate transport, NaPi-IIa protein, and -mRNA expression were significantly reduced. Coincubation with sodium-2-mercaptoethanesulfonate (MESNA) prevented the inhibitory action of CAA but not of 4-OH-Ifo; DiMESNA had no effect. Incubation with Ifosfamide-mustard (Ifo-mustard) did alter cell viability at concentrations above 500 microM/24 h. At lower concentrations (50-100 microM/24 h), it led to significant reduction in phosphate transport, NaPi-IIa protein, and mRNA expression. MESNA did not block these effects. The effect of Ifo-mustard was due to internalization of NaPi-IIa. Cyclophosphamide-mustard (CyP-mustard) did not have any influence on cell survival up to 1000 microM, but the inhibitory effect on phosphate transport and on NaPi-IIa protein was the same as found after Ifo-mustard. In conclusion, CAA, 4-OH-Ifo, and Ifo- and CyP-mustard are able to inhibit sodium-dependent phosphate cotransport in viable opossum kidney cells. The Ifo-mustard effect took place via internalization and reduction of de novo synthesis of NaPi-IIa. Therefore, it is possible that Ifo-mustard plays an important role in pathogenesis of Ifo-induced nephropathy.

Topics: Acetaldehyde; Animals; Antineoplastic Agents, Alkylating; Biological Transport; Cell Death; Cell Line; Dose-Response Relationship, Drug; Gene Expression Regulation; Ifosfamide; Kidney; Mesna; Opossums; Phosphates; Phosphoramide Mustards; RNA, Messenger; Sodium-Phosphate Cotransporter Proteins, Type IIa

31P NMR and cell perfusion techniques were used to investigate the conversion of the individual enantiomers of aldophosphamide (AP) to carboxyphosphamide (CBP) as catalyzed by aldehyde dehydrogenase in human erythroleukemia K562 cells. R- and S-cyclophosphamides (CPs) were treated with ozone and hydrogen peroxide to yield Rp- and Sp-cis-4-hydroperoxycyclophosphamides (Rp- and Sp-cis-4-HO2-CP); reduction of each hydroperoxide gave the corresponding enantiomer of AP [along with its tautomer 4-hydroxycyclophosphamide (4-HO-CP)]. In separate experiments, K562 cells embedded in agarose gel threads were perfused at pH 7.4, 21 +/- 1 degrees, with solutions of 1.4 mM Rp- and Sp-4-HO-CP/AP, both with and without added mesna (an acrolein scavenger). A comparison of the 31P NMR spectral data derived from the experiments revealed little statistical difference (+/- 10-20% error limits) in the normalized intensities of the CBP peaks arising from the individual AP enantiomers [with added mesna, the ratio Rp-CBP:Sp-CBP was 1.00:1.24 +/- 0.13 (average deviation); without mesna, the same ratio was 1.00:1.35]. Using conventional methods for evaluating the in vitro drug toxicities, CP-resistant L1210 cells were treated in separate experiments with Rp- and Sp-cis-4-HO2-CP; there were no significant differences between the toxicities exhibited by the stereoisomers.

Topics: Aldehyde Dehydrogenase; Animals; Cyclophosphamide; Humans; Magnetic Resonance Spectroscopy; Mesna; Mice; Oxidation-Reduction; Phosphoramide Mustards; Stereoisomerism; Tumor Cells, Cultured