Cadmium induces Ca2+-dependent necrotic cell death through calpain-triggered mitochondrial depolarization and reactive oxygen species-mediated inhibition of nuclear factor-kappaB activity.
This study investigates the mechanism of cell death induced by cadmium (Cd) in Chinese hamster ovary (CHO) cells. Cells exposed to 4 microM Cd for 24 h did not show signs of apoptosis, such as DNA fragmentation and caspase-3 activation. The pro-apoptotic (Bax) or anti-apoptotic (Bcl-2 and Bcl-xL) protein levels in the Bcl-2 family were not altered. However, an increase in propidium iodide uptake and depletion of ATP, characteristics of necrotic cell death, were observed. Cd treatment increased the intracellular calcium (Ca2+) level. Removal of the Ca2+ by a chelator, BAPTA-AM, efficiently inhibited Cd-induced necrosis. The increased Ca2+ subsequently mediated calpain activation and intracellular ROS production. Calpains then triggered mitochondrial depolarization resulting in cell necrosis. Cyclosporin A, an inhibitor of mitochondrial permeability transition, recovered the membrane potential and reduced the necrotic effect. The generated ROS reduced basal NF-kappaB activity and led cells to necrosis. An increase of NF-kappaB activity by its activator, PMA, attenuated Cd-induced necrosis. Calpains and ROS act cooperatively in this process. The calpain inhibitor and the ROS scavenger synergistically inhibited Cd-induced necrosis. Results in this study suggest that Cd stimulates Ca2+-dependent necrosis in CHO cells through two separate pathways. It reduces mitochondrial membrane potential by activating calpain and inhibits NF-kappaB activity by increasing the ROS level.
Yang
Pei-Ming
PM
Department of Life Science, National Tsing Hua University, Hsinchu 300, Taiwan.
Chen
Hung-Chi
HC
Tsai
Jia-Shiuan
JS
Lin
Lih-Yuan
LY
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D015153:Blotting, Western; D016466:CHO Cells; D002104:Cadmium / Q000037:antagonists & inhibitors / Q000633:toxicity*; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002154:Calpain / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000737:chemistry / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D017930:Genes, Reporter / Q000235:genetics; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology*; D051336:Mitochondrial Membranes / Q000187:drug effects* / Q000502:physiology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D009336:Necrosis; D010957:Plasmids / Q000235:genetics; D017382:Reactive Oxygen Species / Q000633:toxicity*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D016328:NF-kappa B; D017382:Reactive Oxygen Species; D002104:Cadmium; D000255:Adenosine Triphosphate; D004247:DNA; D002154:Calpain; D053148:Caspase 3; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium