Apoptosis in pyrogallol-treated Calu-6 cells is correlated with the changes of intracellular GSH levels rather than ROS levels

We investigated the involvement of glutathione (GSH) and reactive oxygen species (ROS) such as H₂O₂ and O₂{radical dot}^- in the deaths of pyrogallol-treated Calu-6 cells. Pyrogallol inhibited the growth of Calu-6 cells with an IC₅₀ of approximately 50 μM. Levels of intracellular H₂O₂ were not altered or were decreased in pyrogallol-treated Calu-6 cells at 72 h. However, levels of O₂{radical dot}^- were increased. Treatment with pyrogallol also reduced the intracellular GSH content. The activity of SOD was down-regulated, but the activity of catalase was up-regulated by pyrogallol at 72 h. ROS scavengers, including Tempol, Tiron, Trimetazidine, and N-acetylcysteine (NAC), did not reduce the levels of the intracellular O₂{radical dot}^-. Tempol showing the recovery of GSH depletion in pyrogallol-treated cells significantly prevented apoptosis, while Tiron prevented the loss of mitochondrial transmembrane potential (ΔΨ_m). In contrast, treatment with NAC showing an increased effect on O₂{radical dot}^- levels and depletion of GSH intensified pyrogallol-induced apoptosis. In addition, treatment with SOD and catalase significantly prevented the loss of mitochondrial transmembrane potential (ΔΨ_m) in pyrogallol-treated Calu-6 cells. However, only catalase showing a decreased effect on O₂{radical dot}^- levels and depletion of GSH prevented pyrogallol-induced apoptosis. Taken together, apoptosis in pyrogallol-treated Calu-6 cells is correlated with the changes of intracellular GSH levels rather than ROS levels.