Teratogen-induced activation of caspase-9 and the mitochondrial apoptotic pathway in early postimplantation mouse embryos.
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.
Little
Sally A
SA
Birth Defects Research Laboratory, University of Washington, Seattle, Washington 98195, USA.
Mirkes
Philip E
PE
D000014:Abnormalities, Drug-Induced / Q000201:enzymology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis*; D003520:Cyclophosphamide / Q000031:analogs & derivatives* / Q000633:toxicity; D004622:Embryo, Mammalian / Q000187:drug effects* / Q000201:enzymology; D004625:Embryo, Nonmammalian; D004791:Enzyme Inhibitors / Q000633:toxicity; D006321:Heart / Q000187:drug effects / Q000196:embryology; D006979:Hyperthermia, Induced / Q000009:adverse effects; D066298:In Vitro Techniques; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology*; D009206:Myocardium / Q000166:cytology / Q000201:enzymology; D019311:Staurosporine / Q000633:toxicity; D013723:Teratogens / Q000633:toxicity*
D004791:Enzyme Inhibitors; D013723:Teratogens; D003520:Cyclophosphamide; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; D019311:Staurosporine; C011272:perfosfamide