Little Sally A, Mirkes Philip E
Birth Defects Research Laboratory, University of Washington, Seattle, Washington 98195, USA.
Toxicol Appl Pharmacol. 2002 Jun 1;181(2):142-51. doi: 10.1006/taap.2002.9414.
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.
此前我们发现，致畸剂诱导的小鼠胚胎细胞死亡本质上是凋亡性的，即涉及细胞色素c从线粒体释放，随后激活半胱天冬酶-3、切割聚（ADP-核糖）聚合酶（PARP）以及核小体间DNA片段化。在此我们表明，热疗、4-氢过氧环磷酰胺和星形孢菌素也能激活线粒体凋亡途径中的顶端半胱天冬酶——半胱天冬酶-9。原半胱天冬酶-9的激活与该酶原的切割以及产生两种形式的大亚基有关，主要是39 kDa的亚基（p39），但也有少量37 kDa的亚基（p37）。我们还提供了数据支持以下观点：致畸剂在体内诱导p37亚基的形成是通过细胞色素c介导的原半胱天冬酶-9的加工过程，而p39亚基是由涉及半胱天冬酶-3的放大环形成的。我们之前还表明，发育中心脏细胞中细胞色素c的释放、半胱天冬酶-3的激活、PARP的切割以及DNA片段化均被阻断，这些细胞对致畸剂诱导的细胞死亡具有抗性。我们现在表明，心脏细胞中线粒体凋亡途径的这种阻断延伸至原半胱天冬酶-9的激活。因此，我们的累积数据表明，热疗、4-氢过氧环磷酰胺和星形孢菌素通过激活线粒体凋亡途径诱导第9天小鼠胚胎细胞死亡。此外，我们的数据表明，第9天小鼠胚胎中对致畸剂诱导的细胞死亡具有抗性的细胞在致畸剂暴露后具有多种抑制线粒体凋亡途径的机制。
