Department of Pharmacology and Laboratory of Aging and Nervous Diseases, Soochow University School of Medicine, Suzhou, China.
J Neurosci Res. 2009 Dec;87(16):3600-10. doi: 10.1002/jnr.22152.
In vivo administration of the mitochondrial inhibitor 3-nitropropionic acid (3-NP) produces striatal pathology mimicking Huntington's disease (HD). However, the mechanisms of cell death induced by metabolic impairment are not fully understood. Previous studies showed that 3-NP triggered p53-depedent autophagy activation and cell death. The present study investigated the contribution of the Bcl-2 signaling pathway to autophagy activation and cell death induced by 3-NP. Rat striatum was intoxicated with 3-NP by stereotaxic injection. 3-NP up-regulated the expression of the autophagic protein beclin 1 but down-regulated the expression of the antiapoptotic protein Bcl-2. Pretreatment with the autophagy inhibitor 3-methyladenine (3-MA) significantly inhibited the 3-NP-induced alterations in beclin 1 and Bcl-2 protein levels. Similarly, the 3-NP-induced decline in Bcl-2 was also prevented by the lysosomal inhibitor E64, indicating degradation of Bcl-2 by lysosomes. In agreement with the time course of 3-NP-induced cell death, an increase in the release of cytochrome c from mitochondria was observed. 3-MA also attenuated the 3-NP-induced release of cytochrome c. On the other hand, 3-NP-induced elevations in proapoptotic protein Bax and autophagic protein beclin 1 and LC3-II were significantly enhanced by the Bcl-2-specific inhibitor HA14-1. Furthermore, HA14-1 increased the release of cytochrome c and 3-NP-induced striatal damage. These results suggest that induction of autophagy leads to degradation of Bcl-2. Meanwhile, down-regulation of Bcl-2 amplifies autophagy activation and apoptotic signaling. Bcl-2 thus plays important roles in mitochondria dysfunction-induced apoptotic death of stritatal neurons by modulating both autophagic and apoptotic processes.
体内给予线粒体抑制剂 3-硝基丙酸（3-NP）可产生类似于亨廷顿病（HD）的纹状体病变。然而，代谢损伤诱导细胞死亡的机制尚不完全清楚。先前的研究表明，3-NP 触发了依赖 p53 的自噬激活和细胞死亡。本研究探讨了 Bcl-2 信号通路对 3-NP 诱导的自噬激活和细胞死亡的贡献。通过立体定向注射使大鼠纹状体中毒 3-NP。3-NP 上调自噬蛋白 beclin 1 的表达，但下调抗凋亡蛋白 Bcl-2 的表达。自噬抑制剂 3-甲基腺嘌呤（3-MA）预处理显著抑制了 3-NP 诱导的 beclin 1 和 Bcl-2 蛋白水平的改变。同样，溶酶体抑制剂 E64 也阻止了 3-NP 诱导的 Bcl-2 下降，表明 Bcl-2 被溶酶体降解。与 3-NP 诱导的细胞死亡的时间进程一致，观察到线粒体细胞色素 c 的释放增加。3-MA 也减弱了 3-NP 诱导的细胞色素 c 释放。另一方面，3-NP 诱导的促凋亡蛋白 Bax 和自噬蛋白 beclin 1 和 LC3-II 的升高被 Bcl-2 特异性抑制剂 HA14-1 显著增强。此外，HA14-1 增加了细胞色素 c 的释放和 3-NP 诱导的纹状体损伤。这些结果表明，自噬的诱导导致 Bcl-2 的降解。同时，Bcl-2 的下调增强了自噬的激活和凋亡信号。因此，Bcl-2 通过调节自噬和凋亡过程，在纹状体神经元线粒体功能障碍诱导的凋亡死亡中发挥重要作用。
