Origin of cadmium-induced reactive oxygen species production: Mitochondrial electron transfer versus plasma membrane NADPH oxidase

Abstract

• Cadmium (Cd2+) is an environmental pollutant that causes increased reactive oxygen species (ROS) production. To determine the site of ROS production, the effect of Cd2+ on ROS production was studied in isolated soybean (Glycine max) plasma membranes, potato (Solanum tuberosum) tuber mitochondria and roots of intact seedlings of soybean or cucumber (Cucumis sativus). • The effects of Cd2+ on the kinetics of superoxide (), hydrogen peroxide (H2O2) and hydroxyl radical ( •OH) generation were followed using absorption, fluorescence and spin-trapping electron paramagnetic resonance spectroscopy. • In isolated plasma membranes, Cd2+ inhibited production. This inhibition was reversed by calcium (Ca2+) and magnesium (Mg2+). In isolated mitochondria, Cd2+ increased and H2O2 production. In intact roots, Cd2+ stimulated H2O 2 production whereas it inhibited and •OH production in a Ca2+-reversible manner. • Cd2+ can be used to distinguish between ROS originating from mitochondria and from the plasma membrane. This is achieved by measuring different ROS individually. The immediate (≤ 1 h) consequence of exposure to Cd2+ in vivo is stimulation of ROS production in the mitochondrial electron transfer chain and inhibition of NADPH oxidase activity in the plasma membrane. © The Authors (2008).