Suberoyl bishydroxamic acid-induced apoptosis in HeLa cells via ROS-independent, GSH-dependent manner

Suberoyl bishydroxamic acid (SBHA) is a HDAC inhibitor that can regulate many biological functions including apoptosis and proliferation in various cancer cells. Here, we evaluated the effect of SBHA on the growth of HeLa cervical cancer cells in relation to apoptosis, reactive oxygen species (ROS) and glutathione (GSH) levels. Dose-dependent inhibition of cell growth was observed in HeLa cells with an IC₅₀ of approximately 15 μM at 72 h. SBHA also induced apoptosis in HeLa cells, as evidenced by sub-G1 cells, annexin V-FITC staining cells, activations of caspase 3 and 8, and the loss of mitochondrial membrane potential (ΔΨ_m). In addition, all of the tested caspase inhibitors rescued some cells from SBHA-induced HeLa cell death. SBHA increased ROS levels including O ₂ ^•- and induced GSH depletion in HeLa cells. Generally, caspase inhibitors did not affect ROS levels in SBHA-treated HeLa cells, but they significantly prevented GSH depletion in these cells. Furthermore, while the well-known antioxidants, N-acetyl cysteine and vitamin C, did not affect cell death, ROS level or GSH depletion in SBHA-treated HeLa cells, l-buthionine sulfoximine, a GSH synthesis inhibitor, enhanced cell death and GSH depletion in these cells. In conclusion, SBHA inhibits the growth of HeLa cervical cancer cells via caspase-dependent apoptosis, and the inhibition is independent of ROS level changes, but dependent on GSH level changes.