Pyrogallol as a glutathione depletor induces apoptosis in HeLa cells

Pyrogallol, a polyphenol, is known to be a superoxide anion (O₂^•-) generator. We investigated the involvement of glutathione (GSH) and reactive oxygen species (ROS) in pyrogallol-induced HeLa cell death. We measured the changes of ROS levels, GSH levels, sub-G1 cells, annexin V/PI staining cells and mitochondria membrane potential (ΔΨ_m) in HeLa cells treated with pyrogallol and/or ROS scavenger. The intracellular ROS levels were decreased or increased depending on the concentration of pyrogallol. The level of O₂^•- was significantly increased and superoxide dismutase (SOD) activity was down-regulated by pyrogallol. Pyrogallol reduced intracellular GSH content in HeLa cells. The ROS scavengers, Tempol, Tiron, Trimetazidine and N-acetylcysteine (NAC), did not down-regulate the production of O₂•^-. However, treatment with NAC showed the recovery of GSH depletion and significantly rescued cells from pyrogallol-induced apoptosis. In addition, the recovery of GSH depletion by SOD and catalase was accompanied by the decrease of apoptosis levels. Furthermore, NAC and SOD significantly inhibited CMF-negative (GSH-depleted) and PI-positive cells induced by pyrogallol. Taken together, pyrogallol potently increased intracellular O₂•^- levels and decreased GSH content in HeLa cells, and NAC, SOD and catalase significantly rescued HeLa cells from pyrogallol-induced apoptosis accompanied by the recovery of GSH depletion.