Zhang Y, Goodyer C, LeBlanc A
Department of Neurology, McGill University, Montreal, Quebec, Canada H3A 1W9.
J Neurosci. 2000 Nov 15;20(22):8384-9. doi: 10.1523/JNEUROSCI.20-22-08384.2000.
We have shown previously that caspase-6 is activated in serum deprivation-mediated human neuronal cell death and correlates with increased production of Alzheimer's disease (AD) amyloid beta peptide (Abeta). Here, we show by direct microinjection of recombinant active enzymes that caspase-6 (>0.5 pg/cell) induces a protracted course of apoptosis in neurons in a caspase-specific, dose- and time-dependent manner in the presence of serum. Only transient activation of caspase-6 is required to initiate apoptosis. Caspase-6 induces apoptosis directly without the activation of other caspase effectors. Doses of caspase-6 of <0.25 pg/cell induce only 20% cell death within 16 d but render neurons vulnerable to oxidative stress, indicating that caspase activation affects neurons despite the absence of cell death. Caspase-3 induces neuronal apoptosis in 20% of the cells, whereas caspase-7 or -8 do not induce apoptosis. In contrast, astrocytes undergo apoptosis within 24 hr when microinjected with caspase-3 but not caspase-6, -7, or -8. These results show cell type-specific vulnerability to caspases in the CNS. The results suggest that activation of caspases in human neurons does not lead to an immediate and rapid process of cell death but provokes a protracted form of apoptosis. Activation of caspases in human neurons may participate in the long-term overproduction of Abeta and other potential toxic fragments resulting from caspase-mediated proteolysis. These results are consistent with the protracted and age-dependent nature of AD.
我们之前已经表明，半胱天冬酶-6在血清剥夺介导的人类神经元细胞死亡中被激活，并且与阿尔茨海默病（AD）淀粉样β肽（Aβ）产量增加相关。在此，我们通过直接显微注射重组活性酶表明，在有血清存在的情况下，半胱天冬酶-6（>0.5 pg/细胞）以半胱天冬酶特异性、剂量和时间依赖性方式诱导神经元发生长时间的凋亡过程。启动凋亡仅需要半胱天冬酶-6的短暂激活。半胱天冬酶-6直接诱导凋亡，无需激活其他半胱天冬酶效应器。剂量<0.25 pg/细胞的半胱天冬酶-6在16天内仅诱导20%的细胞死亡，但使神经元易受氧化应激影响，这表明尽管没有细胞死亡，半胱天冬酶激活仍会影响神经元。半胱天冬酶-3在20%的细胞中诱导神经元凋亡，而半胱天冬酶-7或-8不诱导凋亡。相反，当显微注射半胱天冬酶-3而非半胱天冬酶-6、-7或-8时，星形胶质细胞在24小时内发生凋亡。这些结果表明中枢神经系统中细胞类型对半胱天冬酶具有特异性易损性。结果表明，人类神经元中半胱天冬酶的激活不会导致立即和快速的细胞死亡过程，而是引发一种长时间形式的凋亡。人类神经元中半胱天冬酶的激活可能参与了由半胱天冬酶介导的蛋白水解导致的Aβ和其他潜在毒性片段的长期过量产生。这些结果与AD的长期和年龄依赖性性质一致。
