Mohrmann M, Küpper N, Schönfield B, Brandis M
Kinderklinik der Albert-Ludwigs-Universität, Freiburg, Deutschland.
Ren Physiol Biochem. 1995 May-Jun;18(3):118-27. doi: 10.1159/000173909.
Ifosfamide (IF) is an alkylating cytostatic with urotoxic and tubulotoxic side effects which may result in the development of Fanconi syndrome in children. While the urotoxicity of IF is effectively prevented by the uroprotective thiol compound sodium-2-mercaptoethanesulfonate (Mesna), tubulo-toxicity of IF may occur even in the presence of Mesna and in the absence of any signs of urotoxicity. Using the renal tubular cell line LLC-PK1, we investigated whether there is a protective effect of Mesna or of its major dimeric metabolite Dimesna against metabolites of IF with respect to the Na/H exchanger activity. We tested the major IF metabolites 4-hydroperoxy-IF (4-OOH-IF), chloroacetaldehyde (CAA), and acrolein. All metabolites significantly inhibit the Na/H exchanger activity. Half-maximal inhibition of transport occurs at concentrations of 120 mumol/l (4-OOH-IF), 80 (CAA), and 60 mumol/l (acrolein) after 2 h of incubation. The onset of the inhibitory effect of all three metabolites is rapid. Complete inhibition of Na/H exchange by acrolein and CAA is present after a 6-hour exposure to 100 mumol/l of the respective metabolite, while 100 mumol/l 4-OOH-IF causes only 50% inhibition after 24 h of incubation. Dimesna, which the proximal tubular cell has to reduce to Mesna at the expense of intracellular glutathione before it exerts a uroprotective effect, has no protective effect in LLC-PK1 cells. Dimesna (0.3 mmol/l) displaces the dose-response curve for acrolein to the left, indicating an increased toxicity of the combination of acrolein plus Dimesna. Mesna (0.3 mmol/l) has a complete protective effect with respect to acrolein and CAA, while the protective effect versus 100 mumol/l of 4-OOH-IF is incomplete. We conclude that the function of the Na/H exchanger in LLC-PK1 cells is altered by metabolites of IF. The incomplete protection against the toxic effect of 4-OOH-IF by Mesna may explain the pathomechanism by which IF causes tubulotoxicity in the absence of urotoxicity.
异环磷酰胺（IF）是一种具有泌尿毒性和肾小管毒性副作用的烷化剂类细胞抑制剂，可能导致儿童发生范科尼综合征。虽然泌尿保护硫醇化合物2-巯基乙烷磺酸钠（美司钠）可有效预防IF的泌尿毒性，但即使存在美司钠且无任何泌尿毒性迹象时，IF仍可能发生肾小管毒性。我们使用肾小管细胞系LLC-PK1，研究了美司钠或其主要二聚体代谢产物二巯基丁二酸钠对IF代谢产物在钠氢交换体活性方面是否具有保护作用。我们测试了IF的主要代谢产物4-氢过氧异环磷酰胺（4-OOH-IF）、氯乙醛（CAA）和丙烯醛。所有代谢产物均显著抑制钠氢交换体活性。孵育2小时后，转运的半数最大抑制浓度分别为120μmol/L（4-OOH-IF）、80μmol/L（CAA）和60μmol/L（丙烯醛）。这三种代谢产物的抑制作用起效迅速。丙烯醛和CAA在暴露于100μmol/L各自代谢产物6小时后可完全抑制钠氢交换，而100μmol/L 4-OOH-IF在孵育24小时后仅引起50%的抑制。二巯基丁二酸钠在近端肾小管细胞发挥泌尿保护作用之前必须以细胞内谷胱甘肽为代价还原为美司钠，在LLC-PK1细胞中它没有保护作用。二巯基丁二酸钠（0.3mmol/L）使丙烯醛的剂量反应曲线左移，表明丙烯醛加二巯基丁二酸钠组合的毒性增加。美司钠（0.3mmol/L）对丙烯醛和CAA具有完全保护作用，而对100μmol/L 4-OOH-IF的保护作用不完全。我们得出结论，LLC-PK1细胞中钠氢交换体的功能被IF的代谢产物改变。美司钠对4-OOH-IF毒性作用的不完全保护可能解释了IF在无泌尿毒性时导致肾小管毒性的发病机制。
