Cadmium affects tobacco cells by a series of three waves of reactive oxygen species that contribute to cytotoxicity.
Cadmium is suspected to exert its toxic action on cells through oxidative damage. However, the transition metal is unable to directly generate reactive oxygen species (ROS) via redox reactions with molecular oxygen in a biological environment. Here, we show that bright yellow-2 (BY-2) tobacco cells exposed to millimolar concentrations of CdCl(2) developed cell death within 2-3 h. The death process was preceded by two successive waves of ROS differing in their nature and subcellular localization. Firstly, these consisted in the transient NADPH oxidase-dependent accumulation of H(2)O(2) followed by the accumulation of O(2) (-*) in mitochondria. A third wave of ROS consisting in fatty acid hydroperoxide accumulation was concomitant with cell death. Accumulation of H(2)O(2) was preceded by an increase in cytosolic free calcium concentration originating from internal pools that was essential to activate the NADPH oxidase. The cell line gp3, impaired in NADPH oxidase activity, and that was unable to accumulate H(2)O(2) in response to Cd(2+), was nevertheless poisoned by the metal. Therefore, this first wave of ROS was not sufficient to trigger all the cadmium-dependent deleterious effects. However, we show that the accumulation of O(2) (-*) of mitochondrial origin and membrane peroxidation are key players in Cd(2+)-induced cell death.
Garnier
Lionel
L
Commissariat à l'Energie Atomique, Centre de Cadarache, DSV-DEVM, Laboratoire de Radiobiologie Végétale, 13108 Saint-Paul lez Durance Cedex, France.
Simon-Plas
Françoise
F
Thuleau
Patrice
P
Agnel
Jean-Pierre
JP
Blein
Jean-Pierre
JP
Ranjeva
Raoul
R
Montillet
Jean-Luc
JL
D001483:Base Sequence; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers; D006706:Homeostasis; D006861:Hydrogen Peroxide / Q000378:metabolism; D008969:Molecular Sequence Data; D019255:NADPH Oxidases / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014026:Nicotiana / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism
D017931:DNA Primers; D017382:Reactive Oxygen Species; D002104:Cadmium; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium