Abstract: By using the tobacco (Nicotiana tabacum cv. Bright Yellow-2) cell suspension culture, we studied the roles of extracellular H₂O₂ and NADPH oxidase in the copper-induced cell death. With the increase of exogenous CuCl₂ from 0 to 700 μmol·L^-1, the level of cell death were increased followed by the increase of extracellular H₂O₂. In the cell subjected to 300 μmol·L^-1 CuCl₂, the addition of exogenous dimethyl thiourea (DMTU, a scavenger of H₂O₂) alleviated the increases of both the cell death level and the production of extracellular H₂O₂, which were induced by CuCl₂(300 μmol·L^-1). The copperinduced increase in the cell death was associated with the increase of extracellular H₂O₂. The CuCl₂(300 μmol·L^-1) stress induced an increase of the activity of NADPH oxidase. The addition of diphenylene iodonium (DPI, an inhibitor of NADPH oxidase) alleviated the increases of both the cell death level and the production of extracellular H₂O₂, which were induced by CuCl₂ (300 μmol·L^-1). Our results indicate that extracellular H₂O₂ and NADPH oxidase are involved in the copper-induced cell death.

Key words: cell death, copper, extracellular H₂O₂, NADPH oxidase