Intralysosomal iron: a major determinant of oxidant-induced cell death.
Intralysosomal iron: a major determinant of oxidant-induced cell death.
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DOI：
10.1016/s0891-5849(03)00109-6
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发表时间：
2003-05
影响因子：
7.4
通讯作者：
Zhengquan Yu;Lennart Persson;J. Eaton;U. Brunk
中科院分区：
文献类型：
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作者：
Zhengquan Yu;Lennart Persson;J. Eaton;U. Brunk
由于含铁金属蛋白的持续消化，正常细胞内的溶酶体含有一池不稳定的、氧化还原活性的、低分子量的铁，这可能使这些细胞器特别容易受到氧化损伤。氧化剂介导的溶酶体膜的不稳定，水解酶释放到细胞质中，可导致一系列事件，最终导致细胞死亡（凋亡或坏死，取决于损伤的程度）。为了评估溶酶体内氧化还原活性铁池的重要性，我们通过将细胞暴露于溶酶体嗜碱性剂氯化铵（NH4Cl）暂时阻断溶酶体消化。溶酶体pH随之升高（从4.5到0.6），抑制了溶酶体内的蛋白水解，因此，活性铁持续流入这个池。J774细胞用10 mM NH4Cl预孵育4小时，可显著降低随后暴露于H2O2引起的凋亡死亡，其保护作用与强效铁螯合剂去铁胺（可能主要定位于溶酶体腔室）的保护作用一样大。铁的硫化物-银细胞化学检测显示，暴露于NH4Cl后，溶酶体中氧化还原活性铁的含量明显下降，这可能是由于溶酶体内含铁物质的消化减少，同时铁继续从该细胞器输出。电子顺磁共振实验显示，羟基自由基的形成在加入h2o2后的对照细胞中很容易检测到，而在预先暴露于10 mM NH4Cl的细胞中则不存在。因此，具有氧化还原活性的低分子量铁的主要储存库可能位于溶酶体内。在许多临床情况下，减少溶酶体内铁的量或反应性的药理学策略应该能有效地预防氧化诱导的细胞死亡。
As a result of continuous digestion of iron-containing metalloproteins, the lysosomes within normal cells contain a pool of labile, redox-active, low-molecular-weight iron, which may make these organelles particularly susceptible to oxidative damage. Oxidant-mediated destabilization of lysosomal membranes with release of hydrolytic enzymes into the cell cytoplasm can lead to a cascade of events eventuating in cell death (either apoptotic or necrotic depending on the magnitude of the insult). To assess the importance of the intralysosomal pool of redox-active iron, we have temporarily blocked lysosomal digestion by exposing cells to the lysosomotropic alkalinizing agent, ammonium chloride (NH4Cl). The consequent increase in lysosomal pH (from ca. 4.5 to > 6) inhibits intralysosomal proteolysis and, hence, the continuous flow of reactive iron into this pool. Preincubation of J774 cells with 10 mM NH4Cl for 4 h dramatically decreased apoptotic death caused by subsequent exposure to H2O2, and the protection was as great as that afforded by the powerful iron chelator, desferrioxamine (which probably localizes predominantly in the lysosomal compartment). Sulfide-silver cytochemical detection of iron revealed a pronounced decrease in lysosomal content of redox-active iron after NH4Cl exposure, probably due to diminished intralysosomal digestion of iron-containing material coupled with continuing iron export from this organelle. Electron paramagnetic resonance experiments revealed that hydroxyl radical formation, readily detectable in control cells following H2O2addition, was absent in cells preexposed to 10 mM NH4Cl. Thus, the major pool of redox-active, low-molecular-weight iron may be located within the lysosomes. In a number of clinical situations, pharmacologic strategies that minimize the amount or reactivity of intralysosomal iron should be effective in preventing oxidant-induced cell death.