Hydrogen peroxide induces cell death in human TRAIL-resistant melanoma through intracellular superoxide generation

Abstract

Intracellular reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) are thought to mediate apoptosis induced by death receptor ligands, including tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). However, the role of H2O2 is controversial, since some evidence suggests that H2O2 acts as an anti-apoptotic factor. Here, we show that exogenously applied H 2O2 (30-100 μM) induces cell death in TRAIL-resistant human melanoma cells via intracellular superoxide (O2-) generation. H2O2 induced apoptotic or necrotic cell death, depending on the concentration of the oxidant applied; low concentrations of H2O2 preferentially activated the caspase-dependent apoptotic pathway, while high concentrations of H2O2 induced apoptotic and necrotic cell death in a caspase-independent manner. The H2O2-induced cell death was associated with increased mitochondrial membrane potential collapse and caspase-3/7 activation and ER stress responses including caspase-12 and X-box-binding protein-1 (XBP-1) activation. H2O2 induced intracellular O2- generation even within the mitochondria, while TRAIL did not. The superoxide dismutase mimetic antioxidant MnTBaP [Mn (III) tetrakis (4-benzonic acid) porphyrin chloride] inhibited the H2O2-induced O2- generation, apoptosis and XBP-1 and caspase-12 activation at comparable concentrations. Importantly, H 2O2 treatment caused minimal O2- generation and apoptosis in normal primary melanocytes. These data show that H2O2 induces endoplasmic reticulum-associated cell death via intracellular O2- generation and that malignant melanoma cells are more susceptible than normal cells to this oxidative cell death. The findings suggest that H2O2 has therapeutic potential in the treatment of TRAIL-resistant melanoma.