Calcium associated resistance to H(2)O(2) in Chinese hamster V79 cells.
To investigate whether the difference in cellular sensitivity of Chinese hamster V79 and their H(2)O(2)-resistant variant cells (Hpr-4) to H(2)O(2) relates to the difference in intracellular Ca(2+) concentration in these cells, we measured Ca(2+) concentration by calcium ion analysis after loading these cells with Fura-2/AM. Intracellular Ca(2+) concentration increased in both Chinese hamster V79 and Hpr-4 cells as extracellular Ca(2+) concentration increased. However, the increase in intracellular Ca(2+) concentration in response to extracellular H(2)O(2) was more pronounced in Hpr-4 than V79 cells. H(2)O(2) cytotoxicity of Hpr-4 but not V79 cells was also decreased in response to the increase in extracellular Ca(2+) concentration. In parallel with the decrease in cytotoxicity in response to increasing extracellular Ca(2+) concentration, the frequency of mitochondrial DNA single strand breaks (SSB) in Hpr-4 cells also decreased without producing observable nuclear DNA SSB. Use of permeabilized V79 and Hpr-4 cells exposed to H(2)O(2) showed that mitochondrial DNA SSB decreased when extramitochondrial Ca(2+) concentration increased. These findings indicate that elevated intracellular Ca(2+) concentration may protect against H(2)O(2)-induced mitochondrial damage and cytotoxicity in these cells.
Kaneko
M
M
Biophysics Division, National Cancer Center Research Institute, Tsukiji 5-1-1, Chuo-ku, Tokyo, Japan. mkaneko@ncc.go.jp
Inoue
F
F
Oda
T
T
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels; D006224:Cricetinae; D004249:DNA Damage; D006861:Hydrogen Peroxide / Q000633:toxicity*; D008928:Mitochondria / Q000502:physiology*; D016877:Oxidants / Q000633:toxicity*; D017382:Reactive Oxygen Species
D015220:Calcium Channels; D016877:Oxidants; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D002118:Calcium