Zhu Xiaoping, Sato Eisuke F, Wang Yi, Nakamura Hajime, Yodoi Junji, Inoue Masayasu
Department of Biochemistry & Molecular Pathology, Osaka City University Medical School, 1-4-3 Asahimachi, Abeno, Osaka 545-8585, Japan.
Arch Biochem Biophys. 2008 Oct 15;478(2):154-60. doi: 10.1016/j.abb.2008.07.024. Epub 2008 Aug 7.
To elucidate the mechanism by which L-carnitine and related metabolites inhibited mitochondria-dependent apoptosis, we used conditional TRX2-knockout DT40 cells (TRX2(-/-)) and compared the properties of signaling pathways leading to apoptosis in the wild and TRX2(-/-) cells. Caspase-3 and 9, but not caspase-8, were strongly activated in TRX2(-/-) cells but not in wild cells. TRX2(-/-) cells generated large amounts of reactive oxygen species that markedly decreased cellular glutathione levels both in cytosol and mitochondria. We found that the critical thiol groups of adenine nucleotide translocator (ANT) were oxidized more easily in TRX2(-/-) cells than in wild cells and that the reduced form, but not oxidized form, of ANT selectively bound to TRX2. Cytochrome c and SOD1 were released from mitochondria more easily in TRX2(-/-) cells than in wild cells. All these phenomena observed with TRX2(-/-) cells were effectively inhibited by acetyl-L-carntine but not L-carnitine. Thus, acetyl-L-carnitine effectively suppressed the oxidative stress in and around mitochondria thereby preventing mitochondrial signaling pathway leading to apoptosis.
为了阐明左旋肉碱及其相关代谢产物抑制线粒体依赖性凋亡的机制，我们使用了条件性TRX2基因敲除的DT40细胞（TRX2(-/-)），并比较了野生型细胞和TRX2(-/-)细胞中导致凋亡的信号通路特性。在TRX2(-/-)细胞中，半胱天冬酶-3和9被强烈激活，但半胱天冬酶-8未被激活，而在野生型细胞中则不然。TRX2(-/-)细胞产生大量活性氧，显著降低了细胞质和线粒体中的细胞谷胱甘肽水平。我们发现，腺嘌呤核苷酸转位酶（ANT）的关键巯基在TRX2(-/-)细胞中比在野生型细胞中更容易被氧化，并且ANT的还原形式而非氧化形式选择性地与TRX2结合。与野生型细胞相比，TRX2(-/-)细胞中的细胞色素c和超氧化物歧化酶1更容易从线粒体中释放出来。在TRX2(-/-)细胞中观察到的所有这些现象都被乙酰左旋肉碱有效抑制，而左旋肉碱则无此作用。因此，乙酰左旋肉碱有效抑制了线粒体及其周围的氧化应激，从而防止了导致凋亡的线粒体信号通路。
