Superoxide anion burst and taxol production induced by Ce 4+ in suspension cultures of Taxus cuspidata

Abstract

Generation of reactive oxygen species (ROS) induced by Ce 4+ in suspension cultures of Taxus cuspidata was investigated. The burst of superoxide anions (O 2 −) occurred rapidly after the addition of Ce 4+ 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 O 2 − burst. The pretreatment of the suspension cultures with diphenylene iodonium (DPI), a suicide inhibitor of the NADPH oxidase, blocked the O 2 − burst, inhibiting the cell apoptosis and taxol production induced by Ce 4+. These results show that NADPH oxidase played a key role in O 2 − burst and O 2 − served as a mediator of Ce 4+ for cell apoptosis and taxol production. The pretreatments of the suspension cultures with anthracene-9-carboxylate, an ion-channel blocker, nifedipine, a Ca 2+-channel blocker, neomycin, a phospholipase C (PLC) inhibitor, or suramin, a G-protein inhibitor, decreased O 2 − burst induced by Ce 4+. It is thus inferred that Ce 4+-induced O 2 − burst, which mediated cell apoptosis and taxol production by activating the ion-channels, PLC, G-proteins and NADPH oxidase.