Lin Eva, Cavanaugh Jane E, Leak Rehana K, Perez Ruth G, Zigmond Michael J
Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
J Neurosci Res. 2008 Jan;86(1):108-17. doi: 10.1002/jnr.21478.
Isoforms of the mitogen-activated protein kinase ERK have been implicated in both cell survival and cell death. In the present study we explored their role in cell viability in response to oxidative stress. Using the dopaminergic MN9D cell line, we determined that cell death occurred in a concentration-dependent manner after exposure to 6-hydroxydopamine (6-OHDA). The toxicity of 6-OHDA was mediated through generation of reactive oxygen species and was accompanied by a large increase in phosphorylated ERK1/2 but no significant increase in phosphorylated ERK5. 6-OHDA produced a distinct temporal pattern of ERK1/2 activation, with phosphorylated ERK1/2 peaks occurring after 10-15 min (25-fold increase) and 6-24 hr (13-fold increase). Inhibition of the early phosphorylated ERK1/2 peak with U0126 increased the generation of reactive oxygen species by 6-OHDA as well as 6-OHDA-induced toxicity, whereas inhibition of the late peak did not affect 6-OHDA-induced cell death. The time course of phosphorylation of the prosurvival protein CREB mimicked the temporal profile of ERK1/2 activation after 6-OHDA, and blocking the early phospho-ERK1/2 peak also abolished CREB activation. In contrast, activation of caspase-3 by 6-OHDA was delayed, occurring after about 6 hr, and this activation was increased by inhibition of the first phosphorylated ERK1/2 peak. These results suggest that the rapid activation of ERK1/2 in dopaminergic cells by oxidative stress serves as a self-protective response, reducing the content of reactive oxygen species and caspase-3 activity and increasing downstream ERK1/2 substrates.
丝裂原活化蛋白激酶ERK的亚型与细胞存活和细胞死亡均有关联。在本研究中，我们探讨了它们在细胞对氧化应激反应中的细胞活力方面的作用。使用多巴胺能MN9D细胞系，我们确定在暴露于6-羟基多巴胺（6-OHDA）后，细胞死亡呈浓度依赖性发生。6-OHDA的毒性是通过活性氧的产生介导的，并且伴随着磷酸化ERK1/2的大幅增加，但磷酸化ERK5没有显著增加。6-OHDA产生了一种独特的ERK1/2激活时间模式，磷酸化ERK1/2峰值出现在10-15分钟后（增加25倍）和6-24小时后（增加13倍）。用U0126抑制早期磷酸化ERK1/2峰值会增加6-OHDA产生的活性氧以及6-OHDA诱导的毒性，而抑制晚期峰值并不影响6-OHDA诱导的细胞死亡。促存活蛋白CREB的磷酸化时间进程模仿了6-OHDA后ERK1/2激活的时间概况，并且阻断早期磷酸化ERK1/2峰值也消除了CREB激活。相反，6-OHDA对caspase-3的激活延迟，大约在6小时后发生，并且这种激活通过抑制第一个磷酸化ERK1/2峰值而增加。这些结果表明，氧化应激在多巴胺能细胞中快速激活ERK1/2作为一种自我保护反应，减少活性氧含量和caspase-3活性，并增加下游ERK1/2底物。
