Cadmium induces caspase-mediated cell death: suppression by Bcl-2.
Apoptosis is a process of active cell death and is characterized by activation of caspases, DNA fragmentation, and biochemical and morphological changes. To better understand apoptosis, we have characterized the dose- and time-dependent toxic effects of cadmium in Rat-1 fibroblasts. Staining of cells with phosphatidylserine (PS)-annexin V, Hoechst 33258 or Rhodamine 123 and Tunel assays showed that incubating cells with 10 microM cadmium induced a form of cell death exhibiting typical characteristics of apoptosis, including cell shrinkage, externalization of PS, loss of mitochondria membrane potential, nuclear condensation and DNA fragmentation. Expression of Bcl-2 or CrmA each suppressed cadmium-induced cell death although Bcl-2 was somewhat more effective than CrmA. In vitro assay of caspase activity carried out using poly(ADP-ribose) polymerase (PARP) as a substrate as well as intracellular caspase assays using a fluorigenic caspase-3 substrate confirmed that caspase-3 is activated in Rat-1 cells undergoing cadmium-induced apoptosis. Both Asp-Glu-Val-Asp-aldehyde (DEVD-cho) and Tyr-Val-Ala-Asp-chloromethylketone (YVAD-cmk), selective inhibitors of caspase-3 and caspase-1, respectively, suppressed significantly cadmium-induced cell death. However, the nonselective caspase inhibitor, z-Val-Ala-Asp-floromethylketone (zVAD-fmk), was the most efficacious agent, almost completely blocking cadmium-induced cell death. Taken together, these results demonstrate that as in other forms of apoptosis, caspases play a central role in cadmium-induced cell death.
Kim
M S
MS
Department of Life Science, Kwangju Institute of Science and Technology, 1 Oryong-dong, Puk-gu, Kwangju, South Korea.
Kim
B J
BJ
Woo
H N
HN
Kim
K W
KW
Kim
K B
KB
Kim
I K
IK
Jung
Y K
YK
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002104:Cadmium / Q000633:toxicity*; D020169:Caspases / Q000502:physiology*; D002478:Cells, Cultured; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D051381:Rats
D019253:Proto-Oncogene Proteins c-bcl-2; D002104:Cadmium; D020169:Caspases