Superoxide anion burst and taxol production induced by Ce4+ in suspension cultures of Taxus cuspidata

Generation of reactive oxygen species (ROS) induced by Ce4+ in suspension cultures of Taxus cuspidata was investigated. The burst of superoxide anions (O2−) occurred rapidly after the addition of Ce4+ and reached maximum at 4.3 h, while the total level of the cellular reactive oxygen species maintained unchanged. The intracellular superoxide dismutase (SOD) and catalase (CAT) were activated while the intra/extracellular peroxidases (PODs) were inhibited accompanying the O2− burst. The pretreatment of the suspension cultures with diphenylene iodonium (DPI), a suicide inhibitor of the NADPH oxidase, blocked the O2− burst, inhibiting the cell apoptosis and taxol production induced by Ce4+. These results show that NADPH oxidase played a key role in O2− burst and O2− served as a mediator of Ce4+ for cell apoptosis and taxol production. The pretreatments of the suspension cultures with anthracene-9-carboxylate, an ion-channel blocker, nifedipine, a Ca2+-channel blocker, neomycin, a phospholipase C (PLC) inhibitor, or suramin, a G-protein inhibitor, decreased O2− burst induced by Ce4+. It is thus inferred that Ce4+-induced O2− burst, which mediated cell apoptosis and taxol production by activating the ion-channels, PLC, G-proteins and NADPH oxidase.