APOPTOSIS INDUCED BY CADMIUM

Cell death resulting from cadmium (Cd) intoxication has been confirmed to occur through apoptosis by morphological and biochemical studies, However it is still not clear whether Cd itself or metallothionein (MT ) induced by Cd is the major factor responsible for the apoptosis, Alt hough apoptosis is inducible by exposure of cells to various stimuli, the common pathway involved is generally accepted to be activation of endonucleases that induce internucleosomal cleavage of DNA, resulting in the 'ladder' formation observed upon agarose gel electrophoresis an d the chromatin condensation seen by electron microscopy. Cd does not seem to activate the endonuclease in vitro. However, Cd itself can be associated with apoptosis through indirect oxidative stress by inhibit ion of antioxidant enzymes and possible interaction with zinc finger p rotein, In addition to the direct effect of Cd, MT appears to play dua l roles in apoptosis induction: one as a Cd carrier by which Cd accumu lates in the nucleus, and the other as an inhibitor of zinc finger pro teins, which include transcriptional factors related to apoptosis such as the product of the apoptosis resistance gene A20. In this review, we demonstrated that the mode of cell death following Cd exposure is a ssociated with intracellular movement of Cd and MT. A possible mechani sm for Cd-induced apoptosis is also discussed.