過酸化水素の細胞毒性に対するコバルトの効果

Cytotoxicity by reactive oxygen species (ROS) are mainly resulted from the reaction with biological molecules. Recently, it was reported that mitochondrial DNA (mtDNA) damage was induced by CoCl₂ through ROS. However, there are only a few reports indicating cytotoxicity of CoCl₂ at the same concentration. Here, we evaluated cell growth, DNA damage and expression of hypoxia inducible factor-1α relevant to the treatment with CoCl₂ in order to determine the responses of 293 cells in detail. For the estimation of DNA damage, we used long PCR method for mtDNA and nuclear-encoded β-globin gene (nDNA). When cells were incubated with 0.4 mM H₂O₂ for 1 hr, mtDNA damage occurred but nDNA remained unchanged. The cell growth was suppressed completely 2 days after the treatment and cell number decreased within 4 days. In the case of CoCl₂ treatment at 100 μM for 24 hr, cell number was the same as that without any treatment throughout the experiment, suggesting that CoCl₂ did not cause cytotoxicity. Furthermore, western blots revealed the activation of hypoxia inducible factor-1α under the conditions. When cells was exposed to 100 μM CoCl₂ for 24 hr prior to 0.4 mM H₂O₂ treatment for 1 hr, we observed a transient growth arrest and the cell number increased after 4days of the treatment of H₂O₂. These data indicate that the pretreatment of CoCl₂ cause the suppression of cytotoxicity by H₂O₂ rather than the induction. [Jpn J Physiol 55 Suppl:S77 (2005)]