Cadmium-dependent generation of reactive oxygen species and mitochondrial DNA breaks in photosynthetic and non-photosynthetic strains of Euglena gracilis.
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.
Watanabe
Masumi
M
Division of Life Sciences, Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan. m-wata@fish.hokudai.ac.jp
Henmi
Kenji
K
Ogawa
Ken'ichi
K
Suzuki
Tetsuya
T
D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D004249:DNA Damage; D053938:DNA Fragmentation; D004272:DNA, Mitochondrial / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005056:Euglena gracilis; D005434:Flow Cytometry; D020287:In Situ Nick-End Labeling; D010788:Photosynthesis / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013045:Species Specificity
D004272:DNA, Mitochondrial; D017382:Reactive Oxygen Species; D002104:Cadmium