PREVENTION OF IFOSFAMIDE INDUCED NEPHROTOXICITY

异环磷酰胺(IFO)是一种烷基化的恶唑膦，已被发现对复发的实体肿瘤和其他化疗药物治疗后反应差的患者非常有效。然而，肾毒性的高发生率严重限制了IFO的疗效。本研究对异丙肾上腺素(IFO)致肾损伤的机制(S)进行了全面的研究，并通过给予甘氨酸(Gly)来预防这种损伤，我们发现甘氨酸在体内和体外都是有效的细胞保护剂。我们的最终目标是开发一种临床适用的方案，包括在IFO中给予甘氨酸，以防止使用这种抗肿瘤药物治疗的癌症患者发生肾毒性。需要探讨的主要假设是，在IFO治疗过程中，肾脏损伤的诱导是通过IFO的一个或多个活性代谢物，即4-羟基-IFO(4-OH-IFO)和/或异磷酰胺芥末(IPM)的积聚，继而通过氯乙醛(CAA)和/或丙烯醛(ACR)耗尽[GSH]而介导的。这些代谢物可能会与质膜或线粒体膜蛋白的SH基团反应，从而破坏细胞的完整性。另一种但不是相互排斥的假说是，IFO治疗过程中引起肾脏损伤的主要机制是通过CAA和/或ACR抑制线粒体氧化代谢，导致能量产生缺陷，多种代谢异常，从而导致细胞损伤。然而，同时口服Gly和IFO可以在不削弱IFO抗肿瘤作用的情况下，通过维持肾近端小管的完整性来减轻IFO引起的肾毒性。本建议的特点是：(A)成功建立了研究异烟肼肾毒性的大鼠模型系统；(B)利用核磁共振、气相色谱-质谱仪、LC-MS、激光扫描共聚焦显微镜和分子生物学技术，探索异烟肼所致肾脏损伤的生化/分子损伤；以及(C)通过口服甘氨酸预防这种损伤。建议的研究既具有临床意义，也具有科学意义。将产生的数据可能对预防与癌症化疗相关的肾功能障碍具有相当重要的意义，从而允许更好的治疗效果和提高癌症患者的存活率。

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.