Nath K A, Balla J, Croatt A J, Vercellotti G M
Department of Medicine, University of Minnesota, Minneapolis, USA.
Kidney Int. 1995 Feb;47(2):592-602. doi: 10.1038/ki.1995.75.
21-aminosteroids ("lazaroids") have recently excited much interest by virtue of their ability to inhibit lipid peroxidation in vitro and to protect against neural injury in vivo. We tested the effect of these compounds in models of heme protein-mediated renal injury in vitro and in vivo. We devised an in vitro model of heme protein-induced toxicity in which renal epithelial cells were exposed to heme proteins for one hour, after which they were subjected to glutathione depletion by 1-chloro-2,4-dinitrobenzene (CDNB). This model was associated with more than a threefold increase in lipid peroxidation (as measured by thiobarbituric acid reactive substances, TBARS) and a marked reduction in cellular glutathione content. In this model, 21-aminosteroids virtually prevented cytotoxicity as measured by the 51-chromium release assay, and significantly reduced TBARS in a dose-dependent manner. Catalase was partially protective in this model, thereby indicating hydrogen peroxide-dependent toxicity. While pursuing mechanisms accounting for enhanced cellular generation of hydrogen peroxide, we uncovered the first direct evidence that the heme prosthetic group per se directly stimulates cellular generation of hydrogen peroxide; complementing these findings is the remarkable efficacy of 21-aminosteroids in protecting against cytotoxicity induced by hydrogen peroxide. We also tested the capacity of 21-aminosteroids to protect against heme protein-mediated renal injury in vivo. Prior administration of 21-aminosteroids attenuated reductions in GFR and renal blood flow rates following the systemic infusion of methemoglobin in normal rats. 21-aminosteroids also attenuated renal injury observed over three successive days in the glycerol model of heme protein-mediated injury when this model was induced at a higher dose of glycerol (8 ml/kg body wt) but not at a lower dose (5 ml/kg body wt). We conclude that 21-aminosteroids protect against heme protein-mediated renal injury in vitro and in vivo. We suggest that these compounds are potentially useful in such clinical conditions as rhabdomyolysis, intravascular hemolysis and renal injury associated with hemoglobin-based red blood cell substitutes.
21-氨基类固醇（“拉扎罗ids”）最近因其在体外抑制脂质过氧化以及在体内预防神经损伤的能力而引起了广泛关注。我们在体外和体内血红素蛋白介导的肾损伤模型中测试了这些化合物的作用。我们设计了一种体外血红素蛋白诱导毒性模型，其中肾上皮细胞暴露于血红素蛋白1小时，之后用1-氯-2,4-二硝基苯（CDNB）使其谷胱甘肽耗竭。该模型与脂质过氧化（通过硫代巴比妥酸反应性物质，TBARS测定）增加三倍以上以及细胞谷胱甘肽含量显著降低有关。在该模型中，21-氨基类固醇通过51-铬释放试验测定实际上预防了细胞毒性，并以剂量依赖性方式显著降低了TBARS。过氧化氢酶在该模型中具有部分保护作用，从而表明存在过氧化氢依赖性毒性。在探究细胞内过氧化氢生成增加的机制时，我们发现了首个直接证据，即血红素辅基本身直接刺激细胞生成过氧化氢；与这些发现相补充的是，21-氨基类固醇在预防过氧化氢诱导的细胞毒性方面具有显著功效。我们还测试了21-氨基类固醇在体内预防血红素蛋白介导的肾损伤的能力。在正常大鼠全身输注高铁血红蛋白之前给予21-氨基类固醇可减轻肾小球滤过率（GFR）和肾血流速率的降低。当在较高剂量甘油（8 ml/kg体重）而非较低剂量（5 ml/kg体重）诱导血红素蛋白介导损伤的甘油模型时，21-氨基类固醇还减轻了连续三天观察到的肾损伤。我们得出结论，21-氨基类固醇在体外和体内均可预防血红素蛋白介导的肾损伤。我们认为这些化合物在诸如横纹肌溶解、血管内溶血以及与基于血红蛋白的红细胞替代物相关的肾损伤等临床病症中可能具有潜在用途。
