Effects of antioxidants and MAPK inhibitors on cell death and reactive oxygen species levels in H₂O₂-treated human pulmonary fibroblasts

H₂O₂-induced cytotoxicity in normal human pulmonary fibroblasts (HPFs) is of interest in toxicological research since HPFs are involved in lung inflammation, fibrosis and cancer. The present study investigated the cytotoxic effects of H₂O₂ on normal HPFs in relation to reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) using the well-known antioxidants N-acetyl cysteine (NAC) and propyl gallate (PG), as well as MAPK inhibitors. Treatment with 50 μM H₂O₂ inhibited the growth of the HPFs by ~45% in 24 h. H₂O₂ induced cell death via apoptosis and triggered the loss of mitochondrial membrane potential (MMP; Δψm) in the HPFs. H₂O₂ also increased the ROS levels, including O₂•-, in the HPFs and induced glutathione (GSH) depletion. NAC and PG attenuated the death of the HPFs and the loss of MMP (Δψm) through the use of H₂O₂. NAC decreased the ROS levels in the H₂O₂-treated HPFs and PG markedly prevented an increase in O₂•- levels in these cells. However, PG alone induced cell death in the HPF control cells and increased the ROS levels in these cells. None of the MAPK (MEK, JNK and p38) inhibitors affected cell growth inhibition or cell death by H₂O₂. In addition, these inhibitors did not significantly affect the ROS levels and GSH depletion in the H₂O₂-treated HPFs. In conclusion, H₂O₂ induced growth inhibition and cell death in the HPFs via GSH depletion. NAC and PG attenuated H₂O₂--induced HPF cell death but each regulated the ROS levels in a different manner. Treatment with MAPK inhibitors did not affect cell death or the ROS levels in the H₂O₂-treated HPFs.