Cadmium induces apoptosis partly via caspase-9 activation in HL-60 cells.
Cadmium (Cd), a potent immunotoxic metal, induces apoptosis both in vitro and in vivo. However, the mode of action remains unclear. We previously reported that Cd-induced apoptosis was partly dependent on mitochondria. In the present study, we investigated the involvement of caspase-9, which is the apex caspase in the mitochondoria-dependent apoptosis pathway, in Cd-induced apoptosis in human promyelocytic leukemia HL-60 cells. A specific inhibitor of caspase-9, Z-LEHD-FMK, partly inhibited DNA fragmentation induced by Cd treatment in HL-60 cells. Moreover, treatment of HL-60 cells with Cd resulted in the appearance of Cytochrome c (Cyt c), a potent activator of caspase-9, in the cytosol at 3 h, which closely paralleled the activation of caspase-9. Caspase-9 is an initiator caspase that is a potent activator of downstream effector caspases such as caspase-3. Caspase-3 activation was subsequent to the Cyt c release at 6 h. DNA fragmentation, an index of induction of apoptosis, also appeared 6 h after Cd treatment. The effects were more pronounced at 9 h after Cd addition. A broad-specificity inhibitor of caspases, Z-Asp-CH(2)-DCB, inhibited caspase-3 activation and DNA fragmentation induced by Cd in a dose-dependent fashion. The results suggest that Cd-induced apoptosis is partly caused by caspase-9 activation triggered by Cyt c.
Kondoh
Masuo
M
Faculty of Pharmaceutical Sciences, Tokushima Bunri University, 180 Yamashiro-cho, 770-8514, Tokushima, Japan.
Araragi
Saeko
S
Sato
Katsuya
K
Higashimoto
Minoru
M
Takiguchi
Masufumi
M
Sato
Masao
M
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002104:Cadmium / Q000633:toxicity*; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D011506:Proteins / Q000378:metabolism
D003574:Cytochrome c Group; D011506:Proteins; D002104:Cadmium; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases