MAPK inhibitors, particularly the JNK inhibitor, increase cell death effects in H₂O₂-treated lung cancer cells via increased superoxide anion and glutathione depletion

Reactive oxygen species (ROS), especially hydrogen peroxide (H₂O₂), induce apoptosis in cancer cells by regulating mitogen-activated protein kinase (MAPK) signaling pathways. The present study investigated the effects of MAPK inhibitors on cell growth and death as well as changes in ROS and glutathione (GSH) levels in H₂O₂-treated Calu-6 and A549 lung cancer cells. H₂O₂ inhibited growth and induced death of Calu-6 and A549 lung cancer cells. All MAPK inhibitors appeared to enhance growth inhibition in H₂O₂-treated Calu-6 and A549 lung cancer cells and increased the percentage of Annexin V-FITC-positive cells in these cancer cells. Among the MAPK inhibitors, a JNK inhibitor significantly augmented the loss of mitochondrial membrane potential (MMP;m) in H₂O₂-treated Calu-6 and A549 lung cancer cells. Intracellular ROS levels were significantly increased in the H₂O₂-treated cells at 1 and 24 h. Only the JNK inhibitor increased ROS levels in the H₂O₂-treated cells at 1 h and all MAPK inhibitors raised superoxide anion levels in these cells at 24 h. In addition, H₂O₂ induced GSH depletion in Calu-6 and A549 cells and the JNK inhibitor significantly enhanced GSH depletion in H₂O₂-treated cells. Each of the MAPK inhibitors altered ROS and GSH levels differently in the Calu-6 and A549 control cells. In conclusion, H₂O₂ induced growth inhibition and death in lung cancer cells through oxidative stress and depletion of GSH. The enhanced effect of MAPK inhibitors, especially the JNK inhibitor, on cell death in H₂O₂-treated lung cancer cells was correlated with increased O₂- levels and GSH depletion.