Arsenic trioxide induces human pulmonary fibroblast cell death via increasing ROS levels and GSH depletion

Arsenic trioxide (ATO; As₂O₃) induces apoptotic cell death in various cancer cells including lung cancer via the induction of reactive oxygen species (ROS). However, little is known about the toxicological effects of ATO on normal primary lung cells. Here, we investigated the effects of N-acetyl cysteine (NAC) and vitamin C (well-known antioxidants) or L-buthionine sulfoximine (BSO; an inhibitor of GSH synthesis) on ATO-treated human pulmonary fibroblast (HPF) cells in relation to cell death, ROS and glutathione (GSH). ATO induced growth inhibition and death in HPF cells, accompanied by the loss of mitochondrial membrane potential (MMP; ΔΨ_m). ATO increased ROS levels including O₂ ^•- and GSH depleted cell numbers. NAC attenuated the growth inhibition, death and MMP (ΔΨ_m) loss in ATO-treated HPF cells and also decreased the ROS levels in these cells. However, vitamin C enhanced the growth inhibition, death, MMP (ΔΨ_m) loss and GSH depletion by ATO and even strongly increased mitochondrial O ₂^•- levels in ATO-treated HPF cells. BSO showed a strong increase in ROS levels in ATO-treated HPF cells and intensified the growth inhibition, cell death, MMP (ΔΨ_m) loss and GSH depletion. Moreover, superoxide dismutase (SOD2) or thioredoxin (TXN) siRNAs attenuated HPF cell death by ATO, which was not correlated with ROS and GSH level changes. In conclusion, ATO induced the growth inhibition and death of HPF cells, accompanied by increasing ROS levels and GSH depletion. NAC attenuated HPF cell death by ATO whereas vitamin C and BSO enhanced the death.