Suberoylanilide hydroxamic acid-induced HeLa cell death is closely correlated with oxidative stress and thioredoxin 1 levels

Suberoylanilide hydroxamic acid (SAHA) is a histone deacetylase (HDAC) inhibitor which has anticancer effects. We evaluated the growth inhibitory effects of SAHA on HeLa cervical cancer cells in relation to reactive oxygen species (ROS) levels. SAHA inhibited the growth of HeLa cells with an IC50 of approximately 10 mu M at 24 h, and induced apoptosis which was accompanied by the cleavage of PARP, caspase-3 activation and loss of mitochondrial membrane potential (MMP;Delta Psi(m)). All the tested caspase inhibitors prevented HeLa cell death induced by SAHA whereas TNF-alpha intensified apoptotic cell death in SAHA-treated HeLa cells. With respect to ROS and glutathione (GSH) levels, SAHA increased ROS levels, especially mitochondrial O-2(center dot-) in HeLa cells and also induced GSH depletion. Caspase inhibitors reduced the levels of ROS and GSH depletion in SAHA-treated HeLa cells whereas TNF-alpha enhanced the levels in these cells. The well-known antioxidant N-acetyl cysteine (NAC) attenuated cell death and an increase in ROS levels was caused by SAHA. Moreover, SAHA decreased the levels of thioredoxin 1 (Trx1) in HeLa cells. While the downregulation of Trx1 enhanced cell death and ROS levels in SAHA-treated HeLa cells, the overexpression of Trx1 attenuated the levels in these cells. In conclusion, SAHA inhibited the growth of HeLa cell via caspase-dependent apoptosis, which was influenced by the mitochondrial O-2(center dot-) and Trx1 levels.