The fluorescent DNA-staining dye Hoechst 33342 was used to quantify total cell numbers. Intracellular levels of reactive oxygen species (ROS) were measured by the fluorescent probe 2鈥?7鈥?dichlorofluorescein diacetate (DCFH-DA). Apoptosis was determined by FACS analysis (Annexin V-FITC/propidium iodide), by measuring caspase-3/7 activity (ELISA) and by DNA laddering.
Our data show that CQ was dose-dependent cytotoxic and caused oxidative stress by inducing reactive oxygen species (ROS). The redistribution of phosphatidylserine (PS) to the outer layer of the plasma membrane, induction of caspase-3 enzyme activity and DNA fragmentation were also observed in CQ exposed cells. Interestingly, CQ-induced ROS generation enhanced by VL irradiation or a simultaneous treatment with DMT showed no quantitative effect on apoptosis. However, co-exposure of cells with GSH significantly reduced the intracellular ROS generation as well as apoptosis caused by CQ.
This is the first report showing that ROS-induced apoptosis, which is caused by CQ, is prevented by GSH.