Porwol T, Ehleben W, Zierold K, Fandrey J, Acker H
Max Planck Institut für molekulare Physiologie, Dortmund, Germany.
Eur J Biochem. 1998 Aug 15;256(1):16-23. doi: 10.1046/j.1432-1327.1998.2560016.x.
Cobalt and nickel stimulate, as does hypoxia, the production of erythropoietin (EPO) in HepG2 cells. Under hypoxic conditions, a decrease in the level of intracellular reactive oxygen species (ROS) is thought to stimulate EPO expression. Cobalt and nickel may interact with the putative oxygen sensor by changing the redox state of the central iron atom of heme proteins, similar to the effects of hypoxia. It was investigated, therefore, whether cobalt and nickel interact with hemeproteins or ROS scavenging systems in the control of intracellular ROS level. Cobalt chloride (100 microM, 24 h) oxidized non respiratory as well respiratory hemeproteins and increased the oxygen consumption. In contrast, nickel chloride (300 microM, 24 h) primarily reduced respiratory hemeproteins and decreased the oxygen consumption. In HepG2 cells treated with CoCl2, iron and cobalt were localized in cytosolic granules close to the cell nucleus and in mitochondria at concentrations up to 12 mM or 41 mM, respectively. Intracellular nickel was not measurable. Three-dimensional reconstruction of confocal laser microscopy images revealed hot spots of hydroxyl radical generation by a Fenton reaction at the sites of cytosolic iron accumulation. The .OH levels decreased in cobalt-treated (to 81%) as well as in nickel-treated (to 67%) HepG2 cells, accompanied by an increase of EPO expression to 167% and 150%, respectively. Our results underline the importance of .OH formed by a Fenton reaction for triggerimg EPO production. Identification of the primary hemeprotein being the oxygen sensor was not possible due to the antagonistic effects of cobalt and nickel on the redox state of detectable hemeproteins.
钴和镍与缺氧一样，能刺激HepG2细胞中促红细胞生成素（EPO）的产生。在缺氧条件下，细胞内活性氧（ROS）水平的降低被认为会刺激EPO的表达。钴和镍可能通过改变血红素蛋白中心铁原子的氧化还原状态，与假定的氧传感器相互作用，类似于缺氧的影响。因此，研究了钴和镍在控制细胞内ROS水平时是否与血红素蛋白或ROS清除系统相互作用。氯化钴（100微摩尔，24小时）氧化非呼吸性和呼吸性血红素蛋白，并增加氧气消耗。相比之下，氯化镍（300微摩尔，24小时）主要还原呼吸性血红素蛋白并降低氧气消耗。在用CoCl2处理的HepG2细胞中，铁和钴分别以高达12毫摩尔或41毫摩尔的浓度定位于靠近细胞核的胞质颗粒和线粒体中。细胞内镍无法检测到。共聚焦激光显微镜图像的三维重建显示，在胞质铁积累部位通过芬顿反应产生羟基自由基的热点。在钴处理的HepG2细胞（降至81%）和镍处理的HepG2细胞（降至67%）中，·OH水平降低，同时EPO表达分别增加至167%和150%。我们的结果强调了芬顿反应形成的·OH对触发EPO产生的重要性。由于钴和镍对可检测血红素蛋白氧化还原状态的拮抗作用，无法确定作为氧传感器的主要血红素蛋白。
