PREVENTION OF IFOSFAMIDE INDUCED NEPHROTOXICITY

异环磷酰胺（IFO）是一种烷基化的恶氮磷，已被发现对复发实体瘤和其他化疗药物治疗后反应不良的患者非常有效。然而，IFO的疗效受到肾毒性高发生率的严重限制。该建议需要对IFO诱导的肾损伤的未知机制进行全面调查，并通过给药甘氨酸（Gly）预防这种损伤，我们发现甘氨酸在体外和体内都是一种有效的细胞保护剂。我们的最终目标是开发一种临床适用的方案，涉及甘氨酸与IFO的管理，以预防使用这种抗肿瘤药物治疗的癌症患者的肾毒性。要探讨的主要假设是，IFO治疗期间肾损伤的诱导是通过IFO的一种或多种活性代谢物，即4-羟基IFO （4- OH-IFO）和/或异磷酰胺芥（IPM）在肾皮质的积累介导的，继发性的是氯乙醛（CAA）和/或丙烯醛（ACR）对[GSH]的消耗。这些代谢物可能与质膜或线粒体膜蛋白的sh基团发生反应，从而破坏细胞的完整性。另一种但并非相互排斥的假设是，IFO治疗期间引起肾损伤的主要机制是通过CAA和/或ACR抑制线粒体氧化代谢介导的，从而导致能量产生缺陷，多种代谢异常，从而导致细胞损伤。然而，与IFO同时口服补充Gly将通过维持肾近端小管的完整性而减弱IFO引起的肾毒性，而不会减弱IFO的抗肿瘤作用。当前提案的独特之处在于：(a)成功开发了用于研究ifo引起的肾毒性的大鼠模型系统；(b)利用核磁共振（NMR）、气相色谱-质谱（GC-MS）、LC-MS-MS、激光扫描共聚焦显微镜和分子生物学技术探索ifo诱导肾损伤的生化/分子病变；(c)通过口服补充Gly来预防这种伤害。所提出的研究具有临床和科学意义。所产生的数据对于预防与癌症化疗相关的肾功能障碍具有潜在的重要意义，从而提高治疗效果，提高癌症患者的生存率。

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.