From the Cerebrovascular Diseases Research Institute, Xuanwu Hospital of Capital Medical University, Beijing, China (Y.Z., F.Y., J.Y., W.S., Z.Q., Y.F., Y.H., S.L., Y.L., X.J., K.J.L.).
Beijing Geriatric Medical Research Center, Beijing Key Laboratory of Translational Medicine for Cerebrovascular Diseases, China (Y.Z., F.Y., W.S., Z.Q., Y.F., Y.H., S.L., Y.L., X.J., K.J.L.).
Stroke. 2018 Sep;49(9):2200-2210. doi: 10.1161/STROKEAHA.118.021179.
Background and Purpose- Although intracellular zinc accumulation has been shown to contribute to neuronal death after cerebral ischemia, the mechanism by which zinc keeps on accumulating to cause severe brain damage remains unclear. Herein the dynamic cause-effect relationships between zinc accumulation and reactive oxygen species (ROS) production during cerebral ischemia/reperfusion are investigated. Methods- Rats were treated with zinc chelator, ROS scavenger, mitochondria-targeted ROS inhibitor, or NADPH oxidase inhibitor during a 90-minute middle cerebral artery occlusion. Cytosolic labile zinc, ROS level, cerebral infarct volume, and neurological functions were assessed after ischemia/reperfusion. Results- Zinc and ROS were colocalized in neurons, leading to neuronal apoptotic death. Chelating zinc reduced ROS production at 6 and 24 hours after reperfusion, whereas eliminating ROS reduced zinc accumulation only at 24 hours. Furthermore, suppression of mitochondrial ROS production reduced the total ROS level and brain damage at 6 hours after reperfusion but did not change zinc accumulation, indicating that ROS is produced mainly from mitochondria during early reperfusion and the initial zinc release is upstream of ROS generation after ischemia. Suppression of NADPH oxidase decreased ROS generation, zinc accumulation, and brain damage only at 24 hours after reperfusion, indicating that the majority of ROS is produced by NADPH oxidase at later reperfusion time. Conclusions- This study provides the direct evidence that there exists a positive feedback loop between zinc accumulation and NADPH oxidase-induced ROS production, which greatly amplifies the damaging effects of both. These findings reveal that different ROS-generating source contributes to ischemia-generated ROS at different time, underscoring the critical importance of spatial and temporal factors in the interaction between ROS and zinc accumulation, and the consequent brain injury, after cerebral ischemia/reperfusion.
背景与目的- 尽管细胞内锌积累已被证明会导致脑缺血后的神经元死亡，但锌持续积累导致严重脑损伤的机制仍不清楚。在此，研究了脑缺血/再灌注过程中锌积累与活性氧（ROS）产生之间的动态因果关系。方法- 在 90 分钟大脑中动脉闭塞期间，用锌螯合剂、ROS 清除剂、线粒体靶向 ROS 抑制剂或 NADPH 氧化酶抑制剂处理大鼠。缺血/再灌注后评估细胞质可溶锌、ROS 水平、脑梗死体积和神经功能。结果- 锌和 ROS 在神经元中发生共定位，导致神经元凋亡性死亡。螯合锌可减少再灌注后 6 和 24 小时的 ROS 产生，而消除 ROS 仅在 24 小时后减少锌积累。此外，抑制线粒体 ROS 产生可降低再灌注后 6 小时的总 ROS 水平和脑损伤，但不会改变锌积累，表明再灌注早期 ROS 主要来自线粒体，而缺血后 ROS 的初始锌释放是上游的。抑制 NADPH 氧化酶可减少 ROS 生成、锌积累和再灌注后 24 小时的脑损伤，表明再灌注后期 NADPH 氧化酶产生的大部分 ROS。结论- 本研究提供了直接证据，证明锌积累与 NADPH 氧化酶诱导的 ROS 产生之间存在正反馈循环，这大大放大了两者的破坏性作用。这些发现表明，不同的 ROS 产生源在不同的时间对缺血产生的 ROS 有贡献，强调了空间和时间因素在脑缺血/再灌注后 ROS 和锌积累相互作用以及随之而来的脑损伤中的重要性。
