Hiraishi H, Terano A, Ota S, Mutoh H, Razandi M, Sugimoto T, Ivey K J
Department of Medicine, Veterans Affairs Medical Center, Long Beach 90822.
Am J Physiol. 1991 Apr;260(4 Pt 1):G556-63. doi: 10.1152/ajpgi.1991.260.4.G556.
The gastric epithelium is exposed to oxygen species that are generated within the lumen. Reactive oxygen species, enzymatically generated, cause injury to cultured rat gastric mucosal cells. Much interest has been focused on the role of iron in producing oxidant-mediated injury to the gastric mucosa, because iron is a catalyst that promotes the production of .OH possibly from O2-. and H2O2 (Haber-Weiss reaction) or from H2O2 alone (Fenton reaction). With the use of an iron chelator and an iron binding protein, we examined the role of iron in producing oxidant-mediated injury to cultured gastric mucosal cells. Reactive oxygen species and H2O2 were generated by hypoxanthine-xanthine oxidase and glucose-glucose oxidase, respectively, in buffer without iron. Pretreatment with deferoxamine diminished hypoxanthine-xanthine oxidase-induced 51Cr release from prelabeled cells, dose dependently. Furthermore, addition of deferoxamine to the reactive oxygen species-generating system also protected against the injury. However, apotransferrin (which binds extracellular iron) failed to protect cells. Pretreatment with .OH scavengers was partially protective. Depletion of glutathione with diethyl maleate enhanced reactive oxygen species-mediated cytolysis; such cytolysis was inhibited by deferoxamine. Deferoxamine also decreased 51Cr release induced by glucose-glucose oxidase. We conclude that intracellular iron plays a crucial role in mediating oxygen radical damage to gastric mucosal cells. The .OH, produced from H2O2 by the iron-catalyzed Fenton reaction, seems to be the main mediator of oxidant-induced cytotoxicity to gastric mucosal cells in vitro.
胃上皮暴露于管腔内产生的氧物种。酶促产生的活性氧会对培养的大鼠胃黏膜细胞造成损伤。铁在对胃黏膜产生氧化介导损伤中的作用备受关注，因为铁是一种催化剂，可能促进从超氧阴离子（O2-）和过氧化氢（H2O2）产生羟基自由基（·OH）（哈伯-韦斯反应），或仅从过氧化氢产生羟基自由基（芬顿反应）。我们使用铁螯合剂和铁结合蛋白，研究了铁在对培养的胃黏膜细胞产生氧化介导损伤中的作用。在无铁的缓冲液中，分别通过次黄嘌呤-黄嘌呤氧化酶和葡萄糖-葡萄糖氧化酶产生活性氧和过氧化氢。去铁胺预处理可剂量依赖性地减少次黄嘌呤-黄嘌呤氧化酶诱导的预标记细胞中51Cr的释放。此外，向活性氧生成系统中添加去铁胺也能保护细胞免受损伤。然而，脱铁转铁蛋白（结合细胞外铁）未能保护细胞。用·OH清除剂预处理有部分保护作用。用马来酸二乙酯消耗谷胱甘肽可增强活性氧介导的细胞溶解；这种细胞溶解可被去铁胺抑制。去铁胺还可减少葡萄糖-葡萄糖氧化酶诱导的51Cr释放。我们得出结论，细胞内铁在介导氧自由基对胃黏膜细胞的损伤中起关键作用。由铁催化的芬顿反应从过氧化氢产生的·OH似乎是体外氧化诱导的对胃黏膜细胞细胞毒性的主要介质。
