Ye Yaozu, Quijano Celia, Robinson Kristine M, Ricart Karina C, Strayer Amy L, Garner Mary Anne, Shacka John J, Kirk Marion, Barnes Stephen, Accavitti-Loper Mary Ann, Radi Rafael, Beckman Joseph S, Estévez Alvaro G
Burke Medical Research Institute, White Plains, New York 10605, USA.
J Biol Chem. 2007 Mar 2;282(9):6324-37. doi: 10.1074/jbc.M610800200. Epub 2007 Jan 2.
Although peroxynitrite stimulates apoptosis in many cell types, whether peroxynitrite acts directly as an oxidant or the induction of apoptosis is because of the radicals derived from peroxynitrite decomposition remains unknown. Before undergoing apoptosis because of trophic factor deprivation, primary motor neuron cultures become immunoreactive for nitrotyrosine. We show here using tyrosine-containing peptides that free radical processes mediated by peroxynitrite decomposition products were required for triggering apoptosis in primary motor neurons and in PC12 cells cultures. The same concentrations of tyrosine-containing peptides required to prevent the nitration and apoptosis of motor neurons induced by trophic factor deprivation and of PC12 cells induced by peroxynitrite also prevented peroxynitrite-mediated nitration of motor neurons, brain homogenates, and PC12 cells. The heat shock protein 90 chaperone was nitrated in both trophic factor-deprived motor neurons and PC12 cells incubated with peroxynitrite. Tyrosine-containing peptides did not affect the induction of PC12 cell death by hydrogen peroxide. Tyrosine-containing peptides should protect by scavenging peroxynitrite-derived radicals and not by direct reactions with peroxynitrite as they neither increase the rate of peroxynitrite decomposition nor decrease the bimolecular peroxynitrite-mediated oxidation of thiols. These results reveal an important role for free radical-mediated nitration of tyrosine residues, in apoptosis induced by endogenously produced and exogenously added peroxynitrite; moreover, tyrosine-containing peptides may offer a novel strategy to neutralize the toxic effects of peroxynitrite.
尽管过氧亚硝酸盐可刺激多种细胞类型发生凋亡，但过氧亚硝酸盐是直接作为氧化剂发挥作用，还是其诱导凋亡是由于过氧亚硝酸盐分解产生的自由基所致，目前尚不清楚。在因营养因子剥夺而发生凋亡之前，原代运动神经元培养物对硝基酪氨酸呈免疫反应性。我们在此表明，使用含酪氨酸的肽，过氧亚硝酸盐分解产物介导的自由基过程是触发原代运动神经元和PC12细胞培养物凋亡所必需的。预防营养因子剥夺诱导的运动神经元以及过氧亚硝酸盐诱导的PC12细胞的硝化作用和凋亡所需的相同浓度的含酪氨酸肽，也可预防过氧亚硝酸盐介导的运动神经元、脑匀浆和PC12细胞的硝化作用。热休克蛋白90伴侣在营养因子剥夺的运动神经元和用过氧亚硝酸盐孵育的PC12细胞中均被硝化。含酪氨酸的肽不影响过氧化氢诱导的PC12细胞死亡。含酪氨酸的肽应通过清除过氧亚硝酸盐衍生的自由基来发挥保护作用，而不是通过与过氧亚硝酸盐直接反应，因为它们既不增加过氧亚硝酸盐的分解速率，也不降低过氧亚硝酸盐介导的硫醇双分子氧化速率。这些结果揭示了自由基介导的酪氨酸残基硝化在由内源性产生和外源性添加的过氧亚硝酸盐诱导的凋亡中的重要作用；此外，含酪氨酸的肽可能提供一种中和过氧亚硝酸盐毒性作用的新策略。
