Kowaltowski Alicia J, Fenton Robert G, Fiskum Gary
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
Free Radic Biol Med. 2004 Dec 1;37(11):1845-53. doi: 10.1016/j.freeradbiomed.2004.09.005.
Bcl-2 family proteins protect against a variety of forms of cell death, including acute oxidative stress. Previous studies have shown that overexpression of the antiapoptotic protein Bcl-2 increases cellular redox capacity. Here we report that cell lines transfected with Bcl-2 paradoxically exhibit increased rates of mitochondrial H(2)O(2) generation. Using isolated mitochondria, we determined that increased H(2)O(2) release results from the oxidation of reduced nicotinamide adenine dinucleotide-linked substrates. Antiapoptotic Bcl-2 family proteins Bcl-xL and Mcl-1 also increase mitochondrial H(2)O(2) release when overexpressed. Chronic exposure of cells to low levels of the mitochondrial uncoupler carbonyl cyanide 4-(triflouromethoxy)phenylhydrazone reduced the rate of H(2)O(2) production by Bcl-xL overexpressing cells, resulting in a decreased ability to remove exogenous H(2)O(2) and enhanced cell death under conditions of acute oxidative stress. Our results indicate that chronic and mild elevations in H(2)O(2) release from Bcl-2, Bcl-xL, and Mcl-1 overexpressing mitochondria lead to enhanced cellular antioxidant defense and protection against death caused by acute oxidative stress.
Bcl-2家族蛋白可抵御多种形式的细胞死亡，包括急性氧化应激。先前的研究表明，抗凋亡蛋白Bcl-2的过表达可提高细胞的氧化还原能力。在此我们报告，转染了Bcl-2的细胞系却反常地表现出线粒体H₂O₂生成速率增加。利用分离的线粒体，我们确定H₂O₂释放增加是由还原型烟酰胺腺嘌呤二核苷酸连接底物的氧化所致。抗凋亡Bcl-2家族蛋白Bcl-xL和Mcl-1过表达时也会增加线粒体H₂O₂释放。细胞长期暴露于低水平的线粒体解偶联剂羰基氰4-(三氟甲氧基)苯腙，会降低过表达Bcl-xL的细胞的H₂O₂产生速率，导致清除外源性H₂O₂的能力下降，并在急性氧化应激条件下增强细胞死亡。我们的结果表明，Bcl-2、Bcl-xL和Mcl-1过表达的线粒体中H₂O₂释放的慢性轻度升高会导致细胞抗氧化防御增强，并抵御急性氧化应激引起的死亡。
