DDT-induced oxidative damage in human blood mononuclear cells

Recent work indicates that DDT and its metabolites induce apoptosis in different cellular types. However, the mechanism by which DDT generates apoptosis has not been elucidated. In this study, our data demonstrate that the apoptosis induction by DDT and its metabolites in human peripheral blood mononuclear cells (PBMC) is preceded by an increase in the levels of reactive oxygen species (ROS). Cells isolated from healthy individuals were incubated for different intervals of time (0-24 h) and in the presence of increasing concentrations of p'p-DDT, p'p-DDE, or p'p-DDD (0-80 microg/ml). The induction of oxidative stress was then determined by flow cytometry, using the compound 2',7'-dichlorofluorescein diacetate. The control level of ROS was 4.46+/-0.96 IFM, for DDT- and DDD-treated cells we obtained a 19.0-fold increment, whereas for DDE, the increment was 25-fold. ROS induction by DDT and DDE was observed after 1 h of incubation, while for DDD such levels began to be detected at 3 h of incubation; a maximum effect on the ROS production for the three compounds was found at 6 h of treatment. A significant level of ROS was induced by DDT, DDE, and DDD only at 60 and 80 microg/ml. Finally, to find an association between generation of ROS and apoptosis induction, cells incubated with DDT, DDE, and DDD were evaluated for apoptosis induction and generation of oxidative stress. Our results show that an increase in ROS was accompanied by apoptosis of PBMC in vitro. Moreover, N-acetyl-L-cysteine significantly inhibits the apoptosis induction.