Epsztejn S, Glickstein H, Picard V, Slotki I N, Breuer W, Beaumont C, Cabantchik Z I
Department of Biological Chemistry, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Isreal.
Blood. 1999 Nov 15;94(10):3593-603.
The labile iron pool (LIP) of animal cells has been implicated in cell iron regulation and as a key component of the oxidative-stress response. A major mechanism commonly implied in the downregulation of LIP has been the induced expression of ferritin (FT), particularly the heavy subunits (H-FT) that display ferroxidase activity. The effects of H-FT on LIP and other physiological parameters were studied in murine erythroleukemia (MEL) cells stably transfected with H-FT subunits. Clones expressing different levels of H-FT displayed similar concentrations of total cell iron (0.3 +/- 0.1 mmol/L) and of reduced/total glutathione. However, with increasing H-FT levels the cells expressed lower levels of LIP and reactive oxygen species (ROS) and ensuing cell death after iron loads and oxidative challenges. These results provide direct experimental support for the alleged roles of H-FT as a regulator of labile cell iron and as a possible attenuator of the oxidative cell response. H-FT overexpression was of no apparent consequence to the cellular proliferative capacity. However, concomitant with the acquisition of iron and redox regulatory capacities, the H-FT-transfectant cells commensurately acquired multidrug resistance (MDR) properties. These properties were identified as increased expression of MDR1 mRNA (by reverse transcription polymerase chain reaction [RT-PCR]), P-glycoprotein (Western immunoblotting), drug transport activity (verapamil-sensitive drug efflux), and drug cytotoxicity associated with increased MDR1 or PgP. Although enhanced MDR expression per se evoked no significant changes in either LIP levels or ROS production, it might be essential for the survival of H-FT transfectants, possibly by expediting the export of cell-generated metabolites.
动物细胞中的不稳定铁池（LIP）与细胞铁调节有关，并且是氧化应激反应的关键组成部分。LIP下调通常涉及的一个主要机制是铁蛋白（FT）的诱导表达，特别是具有铁氧化酶活性的重链亚基（H-FT）。在稳定转染了H-FT亚基的小鼠红白血病（MEL）细胞中研究了H-FT对LIP和其他生理参数的影响。表达不同水平H-FT的克隆显示出相似的总细胞铁浓度（0.3±0.1 mmol/L）以及还原型/总谷胱甘肽浓度。然而，随着H-FT水平的增加，细胞中LIP和活性氧（ROS）的水平降低，并且在铁负荷和氧化应激后细胞死亡减少。这些结果为H-FT作为不稳定细胞铁的调节剂以及氧化细胞反应的可能减弱剂的所谓作用提供了直接的实验支持。H-FT的过表达对细胞增殖能力没有明显影响。然而，伴随着铁和氧化还原调节能力的获得，H-FT转染细胞相应地获得了多药耐药（MDR）特性。这些特性表现为MDR1 mRNA表达增加（通过逆转录聚合酶链反应[RT-PCR]）、P-糖蛋白表达增加（蛋白质免疫印迹法）、药物转运活性增加（维拉帕米敏感的药物外排）以及与MDR1或PgP增加相关的药物细胞毒性增加。尽管MDR表达增强本身在LIP水平或ROS产生方面没有引起显著变化，但它可能对H-FT转染细胞的存活至关重要，可能是通过加速细胞产生的代谢产物的输出实现的。
