LAUSR

Exogenous hydrogen peroxide (H2O2) induces oxidative stress and apoptosis in cancer cells. This study evaluated the antiapoptotic effects of pan-caspase and caspase-3, -8, or -9 inhibitors on H2O2-treated Calu-6 and A549 lung cancer cells in relation to reactive oxygen species (ROS) and glutathione (GSH). Treatment with 50–500 μM H2O2 inhibited the growth of Calu-6 and A549 cells at 24 h and induced apoptosis in these cells. All the tested caspase inhibitors significantly prevented cell death in H2O2-treated lung cancer cells. H2O2 increased intracellular ROS levels, including that of O2·−, at 1 and 24 h. It also increased the activity of catalase but decreased the activity of SOD. In addition, H2O2 triggered GSH deletion in Calu-6 and A549 cells at 24 h. It reduced GSH levels in Calu-6 cells at 1 h but increased them at 24 h. Caspase inhibitors decreased O2·− levels in H2O2-treated Calu-6 cells at 1 h and these inhibitors decreased ROS levels, including that of O2·−, in H2O2-treated A549 cells at 24 h. Caspase inhibitors partially attenuated GSH depletion in H2O2-treated A549 cells and increased GSH levels in these cells at 24 h. However, the inhibitors did not affect GSH deletion and levels in Calu-6 cells at 24 h. In conclusion, H2O2 induced caspase-dependent apoptosis in Calu-6 and A549 cells, which was accompanied by increases in ROS and GSH depletion. The antiapoptotic effects of caspase inhibitors were somewhat related to the suppression of H2O2-induced oxidative stress and GSH depletion.