Croute Françoise, Beau Bernadette, Murat Jean-Claude, Vincent Christian, Komatsu Hiroyoshi, Obata Fumiya, Soleilhavoup Jean-Pierre
Laboratoire de Biologie Cellulaire et Pollution, Faculté de Médecine Toulouse-Purpan, Toulouse, France.
J Toxicol Environ Health A. 2005 May 14;68(9):703-18. doi: 10.1080/15287390590925447.
This study was designed to explain the basis for Cd-acquired tolerance of A549 cells cultured in the presence of Cd. Thirty-day exposure of cultured human pneumocytes (A549 cell line) to 10 microM Cd was previously found to induce an acquired resistance persisting over several weeks of culture. Moreover, these Cd-resistant cells (R-cells) were found to proliferate faster than controls. No difference was found between R-cells and control cells (S-cells) concerning the basal and Cd-induced level of metallothioneins expression. However, after exposure to Cd, cell glutathione levels were unchanged in R-cells while they were either increased (at 10 microM Cd) or decreased (at 25 microM Cd) in S-cells. cDNA array analysis showed that genes encoding for (GPx1) glutathione peroxidase, glutathione reductase, catalase, and superoxide dismutase were similarly expressed in R- and S-cells, whereas the gene of (GPx2) glutathione peroxidase was overexpressed in R-cells. Most genes encoding stress proteins were similarly expressed, except for HSP27 and GRP94 genes, which were respectively under- (ratio 0.5 +/- 0.1) and over- (1.8 +/- 0.5) expressed in R-cells. Acute exposure to Cd was found to trigger the upregulation of genes encoding the chaperone proteins HSP90A, HSP27, HSP40, GRP78, HSP72, and HO-1 in S-cells. In R-cells, only HO-1 and HSP72 were overexpressed but at a lower level. This suggests that the Cd-related adverse conditions, leading to protein misfolding, are lowered in R-cells. It is likely that the upregulation of GPx2 in R-cells leads to a higher antioxidant defense in these cells.
本研究旨在解释在镉存在的情况下培养的A549细胞对镉获得耐受性的基础。先前发现，将培养的人肺细胞（A549细胞系）暴露于10微摩尔/升的镉中30天，可诱导出持续数周培养的获得性抗性。此外，发现这些抗镉细胞（R细胞）比对照细胞增殖更快。在金属硫蛋白表达的基础水平和镉诱导水平方面，R细胞和对照细胞（S细胞）之间未发现差异。然而，暴露于镉后，R细胞中的细胞谷胱甘肽水平未发生变化，而S细胞中的细胞谷胱甘肽水平要么升高（在10微摩尔/升镉时），要么降低（在25微摩尔/升镉时）。cDNA阵列分析表明，编码谷胱甘肽过氧化物酶（GPx1）、谷胱甘肽还原酶、过氧化氢酶和超氧化物歧化酶的基因在R细胞和S细胞中的表达相似，而谷胱甘肽过氧化物酶（GPx2）的基因在R细胞中过表达。除HSP27和GRP94基因外，大多数编码应激蛋白的基因表达相似，这两个基因在R细胞中分别低表达（比率为0.5±0.1）和高表达（1.8±0.5）。发现急性暴露于镉会触发S细胞中编码伴侣蛋白HSP90A、HSP27、HSP40、GRP78、HSP72和HO-1的基因上调。在R细胞中，只有HO-1和HSP72过表达，但水平较低。这表明在R细胞中，导致蛋白质错误折叠的与镉相关的不利条件有所降低。R细胞中GPx2的上调可能导致这些细胞具有更高的抗氧化防御能力。
