Prabhakaran Krishnan, Li Li, Mills Edward M, Borowitz Joseph L, Isom Gary E
Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907-1333, USA.
J Pharmacol Exp Ther. 2005 Sep;314(3):1338-45. doi: 10.1124/jpet.105.088625. Epub 2005 Jun 3.
Uncoupling protein 2 (UCP-2) regulates mitochondrial function by increasing proton leak across the inner membrane to dissociate respiration from ATP synthesis and reduce reactive oxygen species generation. A number of studies have shown that UCP-2 expression protects cells from oxidative stress mediated injuries. In the current study, we show UCP-2-mediated reduction in mitochondrial function contributes to the mitochondrial dysfunction and the necrotic death of primary cultured mesencephalic cells (MCs) after exposure to cyanide, a complex IV inhibitor. The necrotic cell death was directly related to the level of mitochondrial dysfunction, as shown by reduction in ATP levels and decreased mitochondrial membrane potential. Treatment with cyanide for 6 h or longer upregulated UCP-2 expression. Blockade of up-regulation with a transcription or a translational inhibitor reduced the response to cyanide. Knockdown with RNAi or transfection with a UCP-2 dominant-negative interfering mutant reduced the cyanide-induced mitochondrial dysfunction and cell death, showing that constitutive expression of UCP-2 plays a role in the response to cyanide. Overexpression of UCP-2 by transfection with human full-length cDNA potentiated the cyanide toxicity. These findings indicate that UCP-2 can serve as a regulator of mitochondria-mediated necrotic cell death, in which enhanced expression can increase the vulnerability of primary MCs to injury due to complex IV-mediated inhibition by cyanide.
解偶联蛋白2（UCP - 2）通过增加质子跨线粒体内膜的泄漏来调节线粒体功能，从而使呼吸与ATP合成解离，并减少活性氧的产生。多项研究表明，UCP - 2的表达可保护细胞免受氧化应激介导的损伤。在本研究中，我们发现UCP - 2介导的线粒体功能降低会导致原代培养的中脑神经元细胞（MCs）在暴露于氰化物（一种复合体IV抑制剂）后出现线粒体功能障碍和坏死性死亡。坏死性细胞死亡与线粒体功能障碍的程度直接相关，这表现为ATP水平降低和线粒体膜电位下降。用氰化物处理6小时或更长时间会上调UCP - 2的表达。用转录或翻译抑制剂阻断这种上调会降低对氰化物的反应。用RNAi敲低或用UCP - 2显性负性干扰突变体转染会减少氰化物诱导的线粒体功能障碍和细胞死亡，表明UCP - 2的组成性表达在对氰化物的反应中起作用。用人全长cDNA转染过表达UCP - 2会增强氰化物的毒性。这些发现表明，UCP - 2可作为线粒体介导的坏死性细胞死亡的调节因子，其中其表达增强会增加原代MCs因氰化物介导的复合体IV抑制而受到损伤的易感性。
