We previously found that
ziram, a
carbamate fungicide, significantly induced apoptosis and
necrosis in human NK-92MI, a natural killer cell line. To investigate whether other
carbamate pesticides also induce apoptosis and
necrosis in human natural killer cell, we conducted further experiments with NK-92CI, a human natural killer cell line using a more sensitive assay. NK-92CI cells were treated with
ziram,
thiram,
maneb or
carbaryl at 0.031-40 microM for 2-24 h in the present study. Apoptosis and
necrosis were determined by
FITC-
Annexin-V/PI staining. To explore the mechanism of apoptosis, intracellular levels of active
caspases 3 and mitochondrial
cytochrome-c release were determined by flow cytometry. We found that
ziram and
thiram also induced apoptosis and
necrosis in a time- and dose-dependent manner; however,
maneb and
carbaryl induced apoptosis and
necrosis only at higher doses in NK-92CI cells. The strength of the apoptosis-inducing effect differed among the pesticides, and the order was as follows:
thiram >
ziram greater than
maneb greater than
carbaryl. NK-92CI was more sensitive to
ziram than NK-92MI. Moreover,
ziram and
thiram significantly increased the intracellular level of active
caspase 3 in NK-92CI and
caspase inhibitor significantly inhibited the apoptosis.
Ziram and
thiram significantly caused mitochondrial
cytochrome-c release in NK-92CI. These findings indicate that
carbamate pesticides can induce apoptosis in natural killer cells, and the apoptosis is mediated by both the
caspase-cascade and mitochondrial
cytochrome-c pathways.