Ifosfamide (IFO), an alkylating oxazaphosphorine, has been found to be very effective for the treatment of relapsed solid tumors and in patients who respond poorly following treatment with other chemotherapeutic agents. However, the efficacy of IFO is severely limited by a high incidence of nephrotoxicity. This proposal entails a comprehensive investigation of the as yet unknown mechanism(s) involved in IFO- induced renal injury and prevention of such injury by administration of glycine (Gly), which we found to be an effective cytoprotective agent both in vitro and in vivo. Our ultimate goal is to develop a clinically applicable protocol involving administration of glycine with IFO to prevent nephrotoxcity in cancer patients treated with this antineoplastic drug. The main hypothesis to be explored is that the induction of renal injury during IFO treatment is mediated via accumulation in the kidney cortex of one or more of the active metabolites of IFO, i.e., 4-hydroxy-IFO (4- OH-IFO) and/or isophosphoramide mustard (IPM), secondary to depletion of [GSH] by chloroacetaldehyde (CAA) and/or acrolein (ACR). These metabolites may react with SH-groups of the plasma membrane or mitochondrial membrane proteins, thereby damaging cellular integrity. An alternative, but not mutually exclusive hypothesis is that the primary mechanism in evoking renal injury during IFO treatment is mediated via inhibition of mitochondrial oxidative metabolism by CAA and/or ACR, resulting in defective energy production, multiple metabolic abnormalities, and thereby, cellular damage. However, concomitant oral supplementation of Gly with IFO will attenuate IFO-induced nephrotoxicity by maintaining the renal proximal tubule integrity without diminishing the antitumor action of IFO. Unique features of the current proposal are: (a) the successful development of a rat model system for investigation of IFO-induced renal toxicity; (b) the use of Nuclear Magnetic Resonance (NMR), Gas Chromatography-Mass Spectrometry (GC-MS), LC-MS-MS, Laser- Scanning Confocal Microscopy and techniques of molecular biology to explore the biochemical/molecular lesions responsible for IFO-induced renal injury; and (c) a prevention of such injury by oral supplementation of Gly. The proposed studies are of clinical as well as scientific significance. The data to be generated will potentially have considerable importance for prevention of renal dysfunction associated with cancer chemotherapy, and thus allow for a greater therapeutic efficacy and enhanced survival of cancer patients.
