Anti-apoptotic effect of caspase inhibitors on H₂O₂-treated HeLa cells through early suppression of its oxidative stress

Oxidative stress-induced cytotoxicity in cervical cancer cells may be of toxicological interest. In the present study, the effects of exogenous H₂O₂ on cell growth and death in HeLa cervical cancer cells were investigated, and the anti-apoptotic effects of various caspase (pan-caspase, caspase-3, -8 or -9) inhibitors on H₂O₂-treated HeLa cells were also evaluated with regard to reactive oxygen species (ROS) and glutathione (GSH) levels. Based on MTT assays, H₂O₂ inhibited the growth of HeLa cells with an IC50 value of ~75 μM at 24 h. H₂O₂ increased the number of dead cells and Annexin V-FITC-positive cells in the HeLa cells, which was accompanied by the activation of caspase-3 and the loss of mitochondrial membrane potential (MMP; δΩm). However, relatively higher doses of H₂O₂ induced necrosis in HeLa cells. Caspase inhibitors significantly prevented H₂O₂-induced HeLa cell death. H₂O₂ increased ROS including O2•- at 24 h and increased the activity of catalase in HeLa cells. H₂O₂ also increased the ROS level at 1 h, and several caspase inhibitors attenuated the increased level at 1 h but not at 6, 12 and 24 h. H₂O₂ decreased the GSH level in HeLa cells at 1 h, and several caspase inhibitors attenuated the decreased level of GSH at this time. H₂O₂ induced GSH depletion at 24 h. In conclusion, H₂O₂ inhibited the growth of HeLa cells via apoptosis and/or necrosis, which was accompanied by intracellular increases in ROS levels and GSH depletion. Caspase inhibitors are suggested to suppress H₂O₂-induced oxidative stress to rescue HeLa cells at the early time point of 1 h.