Author(s): Little SA, Mirkes PE
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Abstract Previously we showed that teratogen-induced cell death in mouse embryos is apoptotic in nature, i.e., involves the release of cytochrome c from mitochondria and the subsequent activation of caspase-3, cleavage of poly (ADP-ribose) polymerase (PARP), and internucleosomal DNA fragmentation. Herein we show that hyperthermia, 4-hydroperoxycyclophosphamide, and staurosporine also activate caspase-9, the apical caspase in the mitochondrial apoptotic pathway. Activation of procaspase-9 is associated with the cleavage of this proenzyme and the generation of two forms of the large subunit, primarily a 39-kDa subunit (p39) but also a lesser amount of a 37-kDa subunit (p37). We also present data that support the idea that the teratogen-induced formation of the p37 subunit in vivo occurs by the cytochrome c-mediated processing of procaspase-9, whereas the p39 subunit is formed by an amplification loop involving caspase-3. We also previously showed that the release of cytochrome c, activation of caspase-3, cleavage of PARP, and DNA fragmentation are blocked in cells of the developing heart, which are resistant to teratogen-induced cell death. We now show that this block in the mitochondrial apoptotic pathway in heart cells extends to the activation of procaspase-9. Thus, our cumulative data indicate that hyperthermia, 4-hydroperoxycyclophosphamide, and staurosporine induce cell death in Day 9 mouse embryos by activating the mitochondrial apoptotic pathway. In addition, our data suggest that cells of the Day 9 mouse embryo that are resistant to teratogen-induced cell death possess multiple mechanisms for inhibiting the mitochondrial apoptotic pathway after a teratogenic exposure.
This article was published in Toxicol Appl Pharmacol
and referenced in Journal of Cell Science & Therapy