Polybrominated diphenyl ethers (
PBDEs) are used extensively as
flame-retardants and are ubiquitous in the environment and in wildlife and human tissue. Recent studies have shown that
PBDEs induce neurotoxic effects in vivo and apoptosis in vitro. However, the signaling mechanisms responsible for these events are still unclear. In this study, we investigated the action of a commercial mixture of
PBDEs (pentabrominated
diphenyl ether,
DE-71) on a human
neuroblastoma cell line, SK-N-SH. A cell viability test showed a dose-dependent increase in
lactate dehydrogenase leakage and 3-(4,5-dimethylthia-zol-2-yl)-2,5-diphenyl-tetrazolium
bromide reduction. Cell apoptosis was observed through morphological examination, and
DNA degradation in the cell cycle and cell apoptosis were demonstrated using flow cytometry and
DNA laddering. The formation of
reactive oxygen species was not observed, but
DE-71 was found to significantly induce
caspase-3, -8, and -9 activity, which suggests that apoptosis is not induced by oxidative stress but via a
caspase-dependent pathway. We further investigated the intracellular
calcium ([Ca(2+)](i)) levels using flow cytometry and observed an increase in the intracellular Ca(2+) concentration with a time-dependent trend. We also found that the
N-methyl d-aspartate (
NMDA) receptor antagonist
MK801 (3 microM) significantly reduced DE-71-induced cell apoptosis. The results of a Western blotting test demonstrated that
DE-71 treatment increases the level of Bax translocation to the mitochondria in a dose-dependent fashion and stimulates the release of
cytochrome c (Cyt c) from the mitochondria into the cytoplasm. Overall, our results indicate that
DE-71 induces the apoptosis of [Ca(2+)](i) in SK-N-SH cells via Bax insertion, Cyt c release in the mitochondria, and the
caspase activation pathway.