Suarez N, Walum E, Eriksson H
Department of Neurochemistry and Neurotoxicology, Stockholm University, S-10691 Stockholm, Sweden; IIBCE, Instituto de Investigacions, Biologicas Clemente Estable, Montevideo, Uruguay.
Toxicol In Vitro. 1995 Oct;9(5):717-21. doi: 10.1016/0887-2333(95)00062-d.
Previous studies have shown that cellular uptake of manganese is related to its binding to transferrin. However, it is not known how transferrin binding influences manganese toxicity. Therefore, the cytotoxic activity of manganese bound as manganic ion to either transferrin or pyrophosphate was investigated in the cloned human neuroblastoma cell line SH-SY5Y. The toxicity of the two compounds was studied as changes in cell growth and survival by lipid and protein determinations. There was a significant difference in the toxicity between the two complexes after 72 hr of exposure. The toxicity of the manganic-pyrophosphate (MnPPi) complex differed from that of the manganic-transferrin (MnTf) complex by a factor of 2 (IC(50): 26 +/- 2.6 and 65 +/- 2.4 mum, respectively). After 3 days of exposure to MnPPi and MnTf, the mitochondrial integrity was monitored by the mitochondrial dehydrogenase activity. The two manganese complexes reduced the enzyme activity to the same extent. Measurements of membrane integrity, using (3)[H]-2-deoxy-d-glucose as a probe, showed an increase in the membrane permeability of cells exposed to MnPPi for 60 min. Exposure to MnTf did not result in any significant change in membrane permeability. These findings suggest that transferrin not only mediates manganese transport into the neurone, but also protects the cell from damage caused by the manganic ion. The increase in cell membrane permeability after MnPPi exposure indicates that this complex may enter the cell. Furthermore, the results show that inhibited mitochondrial function is part of the mechanism of manganese neurotoxicity.
先前的研究表明，细胞对锰的摄取与其与转铁蛋白的结合有关。然而，尚不清楚转铁蛋白结合如何影响锰的毒性。因此，在克隆的人神经母细胞瘤细胞系SH-SY5Y中研究了以锰离子形式与转铁蛋白或焦磷酸结合的锰的细胞毒性活性。通过脂质和蛋白质测定，研究了这两种化合物的毒性对细胞生长和存活的影响。暴露72小时后，两种复合物的毒性存在显著差异。锰-焦磷酸盐（MnPPi）复合物的毒性与锰-转铁蛋白（MnTf）复合物的毒性相差2倍（IC50分别为26±2.6和65±2.4 μmol）。暴露于MnPPi和MnTf 3天后，通过线粒体脱氢酶活性监测线粒体完整性。两种锰复合物对酶活性的降低程度相同。使用[3H]-2-脱氧-D-葡萄糖作为探针测量膜完整性，结果显示暴露于MnPPi 60分钟的细胞的膜通透性增加。暴露于MnTf不会导致膜通透性发生任何显著变化。这些发现表明，转铁蛋白不仅介导锰转运到神经元中，还保护细胞免受锰离子造成的损伤。MnPPi暴露后细胞膜通透性的增加表明该复合物可能进入细胞。此外，结果表明线粒体功能受抑制是锰神经毒性机制的一部分。
