Cadmium induces apoptosis partly via caspase-9 activation in HL-60 cells

• Published in: Toxicology (Amsterdam) 2002-01, Vol.170 (1), p.111-117
• Main Authors: Kondoh, Masuo, Araragi, Saeko, Sato, Katsuya, Higashimoto, Minoru, Takiguchi, Masufumi, Sato, Masao
• Format: Article
• Language: English
• Subjects: Apoptosis; Apoptosis - drug effects; Biological and medical sciences; Blotting, Western; Cadmium; Cadmium - toxicity; Caspase 9; Caspases - metabolism; Chemical and industrial products toxicology. Toxic occupational diseases; Cytochrome c; Cytochrome c Group - metabolism; DNA Fragmentation - drug effects; Enzyme Activation - drug effects; HL-60 Cells; Humans; Medical sciences; Metals and various inorganic compounds; Mitochondria; Mitochondria - drug effects; Mitochondria - enzymology; Proteins - metabolism; Toxicology
• ISSN: 0300-483X; 1879-3185
• DOI: 10.1016/S0300-483X(01)00536-4

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.