Protection against nonylphenol-induced cell death by DJ-1 in cultured Japanese medaka (Oryzias latipes) cells

The Japanese medaka (Oryzias latipes) has been used to investigate diverse aspects of toxicology, genetics and developmental biology and to monitor biological changes caused by endocrine disruptors. In this study, we analyzed a medaka homolog of human DJ-1 (meDJ-1) in cultured medaka cells into which nonylphenol (NP) was added. Like human DJ-1, meDJ-1 was found to be oxidized by treatment with H2O2 and its pI was shifted to acidic points. NP was found to induce cell death with kinetics similar to that of H2O2 in cultured medaka OLHE-13 cells. After OLHE-13 cells had been treated with sub-lethal concentrations of H2O2 and NP, production of reactive oxygen species and oxidation of meDJ-1 were observed. meDJ-1 knockdown by short interfering RNA rendered OLHE-13 cells susceptible to H2O2 and NP-induced cell death, suggesting a protective role of DJ-1 against oxidative stress-induced cell death in medaka cells. These results suggest that meDJ-1 is a suitable biomarker for oxidative stress reactions in medaka.