Hempel S L, Buettner G R, Wessels D A, Galvan G M, O'Malley Y Q
Department of Veterans Affairs Medical Center, University of Iowa, Iowa City, IA 52242, USA.
Arch Biochem Biophys. 1996 Jun 15;330(2):401-8. doi: 10.1006/abbi.1996.0268.
We hypothesized that exposure of cells to H2O2 plus Fe2+ would increase formation of cell-derived lipid peroxides that would inactivate prostaglandin H synthase, resulting in decreased prostaglandin synthesis. Therefore, we treated human endothelial cells with 0-100 microM H2O2 followed immediately by addition of 0-200 microM Fe2+. After oxidant exposure, cells were stimulated with 20 microM arachidonic acid to induce prostaglandin I2 (PGI2) synthesis. Adding 100 microM H2O2 prior to arachidonic acid decreased PGI2 synthesis more than 80%. However, to our surprise, the addition of Fe2+, in increasing amounts, progressively protected PGI2 synthesis against the harmful effects of H2O2. A ratio of one part H2O2 to two parts Fe2+ offered almost complete protection, whereas Fe3+ did not protect PGI2 synthesis from H2O2. We found that 100 microM H2O2 was not cytolytic; however, 250 microM H2O2 was cytolytic; Fe2+ protected against this cytotoxicity. In addition, extracellular Fe2+ prevented the rise in intracellular calcium caused by H2O2 and extracellular Fe2+ preserved intracellular glutathione in H2O2-exposed cells. Electron paramagnetic resonance spin trapping demonstrated that extracellular Fe2+ generated the hydroxyl free radical, HO. outside the cell. We speculate that extracellular Fe2+ protects the intracellular space from H2O2 by initiating the Fenton reaction outside the cell. This reductive cleavage of H2O2 generates HO. in the extracellular space, where much of the HO. will react with noncellular components, thereby protecting the cell interior.
我们推测，将细胞暴露于过氧化氢（H₂O₂）和亚铁离子（Fe²⁺）中会增加细胞源性脂质过氧化物的形成，这些脂质过氧化物会使前列腺素H合酶失活，从而导致前列腺素合成减少。因此，我们用0 - 100微摩尔的H₂O₂处理人内皮细胞，随后立即加入0 - 200微摩尔的Fe²⁺。在暴露于氧化剂后，用20微摩尔的花生四烯酸刺激细胞以诱导前列腺素I₂（PGI₂）的合成。在花生四烯酸之前加入100微摩尔的H₂O₂会使PGI₂的合成减少超过80%。然而，令我们惊讶的是，增加Fe²⁺的添加量能逐渐保护PGI₂的合成免受H₂O₂的有害影响。一份H₂O₂与两份Fe²⁺的比例几乎能提供完全保护，而Fe³⁺不能保护PGI₂的合成免受H₂O₂的影响。我们发现100微摩尔的H₂O₂没有细胞毒性；然而，250微摩尔的H₂O₂具有细胞毒性；Fe²⁺能防止这种细胞毒性。此外，细胞外的Fe²⁺可防止H₂O₂引起的细胞内钙浓度升高，并且细胞外的Fe²⁺能在暴露于H₂O₂的细胞中保存细胞内谷胱甘肽。电子顺磁共振自旋捕获实验表明，细胞外的Fe²⁺在细胞外产生羟基自由基（·OH）。我们推测，细胞外的Fe²⁺通过在细胞外启动芬顿反应来保护细胞内空间免受H₂O₂的影响。这种H₂O₂的还原裂解在细胞外空间产生·OH，其中大部分·OH会与非细胞成分反应，从而保护细胞内部。
