Brambilla L, Sestili P, Guidarelli A, Palomba L, Cantoni O
Istituto di Farmacologia e Farmacognosia, Università di Urbino, Italy.
J Pharmacol Exp Ther. 1998 Mar;284(3):1112-21.
The toxicity of a short-term exposure to tert-butylhydroperoxide in U937 cells was markedly reduced by chemically or experimentally induced respiratory deficiency. Rotenone mitigated the lethal effects of the hydroperoxide over the same concentration-range in which the complex I inhibitor inhibited oxygen utilization. U937 cells that were made respiration deficient by growing them in the presence of either chloramphenicol or ethidium bromide, were in both circumstances highly resistant to tert-butylhydroperoxide. The improved survival was not a direct consequence of the absence of electron transport, but rather was attributable to the large amounts of NADH which accumulate in the mitochondria of chemically hypoxic or respiration-deficient cells. Indeed, the toxicity elicited by tert-butylhydroperoxide was also abolished by supplementation with either of two different NADH-linked substrates, namely pyruvate or beta-hydroxybutyrate. Accumulation of intramitochondrial NADH, and the resulting cytoprotective effects, was associated with prevention of the loss of nonprotein sulphydryls and mitochondrial membrane potential. Neither rotenone nor pyruvate reduced the toxicity of tert-butylhydroperoxide in thiol-depleted cells. Taken together, these results indicate that depletion of mitochondrial NADH is a critical event in the cytotoxic response to tert-butylhydroperoxide since this pyridine nucleotide prevents mitochondrial dysfunction and cell death caused by the hydroperoxide. As a consequence, in hydroperoxide-treated cells electron transport is highly detrimental since it consumes mitochondrial NADH.
化学或实验诱导的呼吸缺陷可显著降低U937细胞短期暴露于叔丁基过氧化氢时的毒性。鱼藤酮在与复合体I抑制剂抑制氧利用相同的浓度范围内减轻了过氧化氢的致死作用。在氯霉素或溴化乙锭存在下培养而导致呼吸缺陷的U937细胞，在这两种情况下对叔丁基过氧化氢都具有高度抗性。存活率的提高并非电子传递缺失的直接结果，而是归因于化学性缺氧或呼吸缺陷细胞线粒体中积累的大量NADH。实际上，补充两种不同的与NADH相关的底物（即丙酮酸或β-羟基丁酸）中的任何一种也可消除叔丁基过氧化氢引起的毒性。线粒体内NADH的积累以及由此产生的细胞保护作用与防止非蛋白巯基的丢失和线粒体膜电位有关。鱼藤酮和丙酮酸都不会降低硫醇耗竭细胞中叔丁基过氧化氢的毒性。综上所述，这些结果表明线粒体NADH的耗竭是对叔丁基过氧化氢细胞毒性反应中的关键事件，因为这种吡啶核苷酸可防止由过氧化氢引起的线粒体功能障碍和细胞死亡。因此，在过氧化氢处理的细胞中，电子传递非常有害，因为它消耗线粒体NADH。
