Watanabe Masumi, Henmi Kenji, Ogawa Ken'ichi, Suzuki Tetsuya
Division of Life Sciences, Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
Comp Biochem Physiol C Toxicol Pharmacol. 2003 Feb;134(2):227-34. doi: 10.1016/s1532-0456(02)00253-3.
The photosynthetic strain Z of Euglena gracilis is more susceptible to cadmium chloride (Cd) than the non-photosynthetic strain SMZ. We investigated the correlation of intracellular reactive oxygen species (ROS) levels with Cd-induced cellular damage. Flow cytometry with dihydrorhodamine 123 showed that strain Z generated higher levels of ROS, probably H(2)O(2) and/or ONOO(-), than strain SMZ, and that this difference between the two strains became more pronounced with increasing Cd dose. The levels of ROS increased at cytotoxic concentrations of Cd, at over 10 microM Cd for Z and 50 microM Cd for SMZ. These results show an association of Cd cytotoxicity with ROS generation. Considering that strain SMZ is non-photosynthetic, the higher levels of ROS in strain Z might be due to blockage of photosynthetic electron flow by Cd. Using terminal deoxyribonucleotidyl transferase-mediated dUTP nick end-labeling analysis in combination with 4',6-diamidino-2-phenylindole, dihydrochloride staining, we observed DNA breaks in the mitochondria of both strains after Cd exposure. The results suggest that the mitochondrion is the primary target organelle of Cd in E. gracilis cells.
纤细裸藻的光合菌株Z比非光合菌株SMZ对氯化镉（Cd）更敏感。我们研究了细胞内活性氧（ROS）水平与镉诱导的细胞损伤之间的相关性。用二氢罗丹明123进行的流式细胞术表明，菌株Z产生的ROS水平高于菌株SMZ，可能是H₂O₂和/或ONOO⁻，并且随着镉剂量的增加，这两种菌株之间的差异变得更加明显。在细胞毒性浓度的镉下，ROS水平升高，对于Z来说是超过10微摩尔/升的镉，对于SMZ来说是50微摩尔/升的镉。这些结果表明镉的细胞毒性与ROS的产生有关。考虑到菌株SMZ是非光合的，菌株Z中较高水平的ROS可能是由于镉对光合电子流的阻断。使用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记分析结合4',6-二脒基-2-苯基吲哚二盐酸盐染色，我们在镉暴露后观察到两种菌株的线粒体中都有DNA断裂。结果表明线粒体是纤细裸藻细胞中镉的主要靶细胞器。
