Papa Luena, Rockwell Patricia
Department of Biological Sciences, Hunter College of The City University of New York, 695 Park Ave, New York, NY 10021, USA.
Apoptosis. 2008 Apr;13(4):588-99. doi: 10.1007/s10495-008-0182-0.
Oxidative stress, proteasome impairment and mitochondrial dysfunction are implicated as contributors to ageing and neurodegeneration. Using mouse neuronal cells, we showed previously that the reversible proteasome inhibitor, [N-benzyloxycarbonyl-Ile-Glu (O-t-bytul)-Ala-leucinal; (PSI)] induced excessive reactive oxygen species (ROS) that mediated mitochondrial damage and a caspase-independent cell death. Herein, we examined whether this insult persists in neuronal cells recovering from inhibitor removal over time. Recovery from proteasome inhibition showed a time and dose-dependent cell death that was accompanied by ROS overproduction, caspase activation and mitochondrial membrane permeabilization with the subcellular relocalizations of the proapoptotic proteins, Bax, cytochrome c and the apoptosis inducing factor (AIF). Caspase inhibition failed to promote survival indicating that cell death was caspase-independent. Treatments with the antioxidant N-acetyl-cysteine (NAC) were needed to promote survival in cell recovering from mild proteasome inhibition while overexpression of the antiapoptotic protein Bcl-xL together with NAC attenuated cell death during recovery from potent inhibition. Whereas inhibitor removal increased proteasome function, cells recovering from potent proteasome inhibition showed excessive levels of ubiquitinated proteins that required the presence of NAC for their removal. Collectively, these results suggest that the oxidative stress and mitochondrial inhibition induced by proteasome inhibition persists to influence neuronal cell survival when proteasome function is restored.
氧化应激、蛋白酶体损伤和线粒体功能障碍被认为是衰老和神经退行性变的促成因素。我们之前使用小鼠神经元细胞表明，可逆性蛋白酶体抑制剂[N-苄氧羰基-Ile-Glu（O-t-丁基）-Ala-亮氨醛；（PSI）]诱导过量的活性氧（ROS），介导线粒体损伤和非半胱天冬酶依赖性细胞死亡。在此，我们研究了这种损伤在从抑制剂去除后随时间恢复的神经元细胞中是否持续存在。从蛋白酶体抑制中恢复显示出时间和剂量依赖性的细胞死亡，同时伴有ROS过度产生、半胱天冬酶激活和线粒体膜通透性改变，以及促凋亡蛋白Bax、细胞色素c和凋亡诱导因子（AIF）的亚细胞重新定位。半胱天冬酶抑制未能促进细胞存活，表明细胞死亡是非半胱天冬酶依赖性的。用抗氧化剂N-乙酰半胱氨酸（NAC）处理对于促进从轻度蛋白酶体抑制中恢复的细胞的存活是必要的，而抗凋亡蛋白Bcl-xL的过表达与NAC一起可减轻从强效抑制中恢复期间的细胞死亡。虽然去除抑制剂可增加蛋白酶体功能，但从强效蛋白酶体抑制中恢复的细胞显示出过量的泛素化蛋白水平，这些蛋白需要NAC的存在才能被清除。总的来说，这些结果表明，当蛋白酶体功能恢复时，蛋白酶体抑制诱导的氧化应激和线粒体抑制持续影响神经元细胞存活。
