Tribble D L, Jones D P, Edmondson D E
Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322.
Mol Pharmacol. 1988 Sep;34(3):413-20.
Toxicity of t-butylhydroperoxide (t-BuOOH) was studied at different steady state O2 concentrations under conditions at which O2 deficiency alone did not cause cell death. t-BuOOH-induced cell death was more rapid in hypoxic than normoxic cells; the maximal rate of cell death occurred in anoxic cells. t-BuOOH elimination was independent of O2 concentration and was complete within 15 min; t-Butanol was produced at the same rate and was the only product detected by gas chromatography. Measurement of radical production by formation of adducts of the spin-trapping agent N-tert-butylphenylnitrone showed that the amount of radicals trapped was 0.02% of the amount of peroxide added and was the same under anoxic and oxygenated (214 microM O2) conditions. These results show that the O2 dependence of t-BuOOH-induced toxicity is not related to quantitative alterations in its metabolism. Lipid peroxidation was lowest in anoxic cells and increased as the O2 concentration was increased to 1.07 mM O2, showing that enhanced toxicity during hypoxia and anoxia was not due to enhanced lipid peroxidation. In contrast, O2 deficiency impaired the ability of cells to maintain and recovery GSH and NADPH pools after addition of t-BuOOH. GSH was decreased to a greater extent in anoxic cells than in normoxic cells, and the GSH content remained lower in these cells for up to 30 min. This decrease was due both to a decrease in the rate of synthesis and to decreased supply of the NADPH needed for the reduction of GSSG. Taken together, these results show that O2 deficiency has little effect on metabolism of t-BuOOH but impairs the ability of cells to maintain cellular GSH and renders them more susceptible to injury from oxidizing agents. This suggests that oxidative injury under hypoxia or following ischemia may not require a marked stimulation in generation of oxidative species but may occur as a consequence of the impaired ability to tolerate or repair oxidative injury.
在仅缺氧不会导致细胞死亡的条件下，研究了不同稳态氧气浓度下叔丁基过氧化氢（t-BuOOH）的毒性。t-BuOOH诱导的细胞死亡在缺氧细胞中比在常氧细胞中更快；最大细胞死亡率出现在无氧细胞中。t-BuOOH的消除与氧气浓度无关，在15分钟内完成；叔丁醇以相同的速率产生，是气相色谱检测到的唯一产物。通过自旋捕获剂N-叔丁基苯基硝酮加合物的形成来测量自由基产生，结果表明捕获的自由基量为添加过氧化物量的0.02%，在无氧和充氧（214 microM O2）条件下相同。这些结果表明，t-BuOOH诱导毒性对氧气的依赖性与其代谢的定量变化无关。脂质过氧化在无氧细胞中最低，随着氧气浓度增加到1.07 mM O2而增加，这表明缺氧和无氧期间毒性增强并非由于脂质过氧化增强。相反，缺氧会损害细胞在添加t-BuOOH后维持和恢复谷胱甘肽（GSH）和烟酰胺腺嘌呤二核苷酸磷酸（NADPH）池的能力。GSH在无氧细胞中的降低程度比在常氧细胞中更大，并且这些细胞中的GSH含量在长达30分钟内保持较低水平。这种降低既是由于合成速率降低，也是由于还原氧化型谷胱甘肽（GSSG）所需的NADPH供应减少。综上所述，这些结果表明缺氧对t-BuOOH的代谢影响很小，但会损害细胞维持细胞内GSH的能力，使其更容易受到氧化剂的损伤。这表明缺氧或缺血后的氧化损伤可能不需要氧化物种生成的显著刺激，而是可能由于耐受或修复氧化损伤的能力受损而发生。
