Department of Neurology, MIND Institute, University of California at Davis, Sacramento, California.
Department of Aerospace and Diving, Nautical and Aviation Medical Center, Navy General Hospital, Beijing, China.
J Neuropathol Exp Neurol. 2018 Mar 1;77(3):260-265. doi: 10.1093/jnen/nly003.
Our previous study demonstrated caspase independent DNA fragmentation after very brief cerebral ischemia, the mechanism of which was unclear. In this study, we explore whether actin is cleaved following focal cerebral ischemia, and whether these structural changes of actin might modulate DNA fragmentation observed following focal ischemia. Results showed that a cleaved β-actin fragment was identified in brains of rats 24 hours following 10-minute and 2-hour focal ischemia. Though granzyme B and caspase-3 cleaved β-actin in vitro, the fragment size of β-actin cleaved by granzyme B was the same as those found after 10-minute and 2-hour focal ischemia. This was consistent with increases of granzyme B activity after 10-minute and 2-hour ischemia compared with controls. Cerebral extracts from 10-minute and 2-hour ischemic brains degraded DNA in vitro. Adding intact β-actin to these samples completely abolished DNA degradation from the 10-minute ischemia group but not from the 2-hour ischemia group. We concluded that β-actin is likely cleaved by granzyme B by 24 hours following 10-minute and 2-hour focal cerebral ischemia. Intact β-actin inhibits DNase, and cleavage of β-actin activates DNase, which leads to DNA fragmentation observed in the brain following very brief focal ischemia.
我们之前的研究表明，短暂性脑缺血后会发生 caspase 非依赖性 DNA 片段化，但具体机制尚不清楚。在这项研究中，我们探讨了局灶性脑缺血后是否会发生肌动蛋白的切割，以及肌动蛋白的这些结构变化是否会调节局灶性缺血后观察到的 DNA 片段化。结果显示，在 10 分钟和 2 小时局灶性缺血后 24 小时的大鼠脑中鉴定出了一种切割的β-肌动蛋白片段。尽管 granzyme B 和 caspase-3 在体外切割β-肌动蛋白，但 granzyme B 切割的β-肌动蛋白片段的大小与 10 分钟和 2 小时局灶性缺血后发现的相同。这与 10 分钟和 2 小时缺血后 granzyme B 活性的增加与对照组相比一致。体外培养来自 10 分钟和 2 小时缺血脑的脑提取物可降解 DNA。向这些样本中添加完整的β-肌动蛋白完全抑制了 10 分钟缺血组的 DNA 降解，但不抑制 2 小时缺血组的 DNA 降解。我们得出结论，10 分钟和 2 小时局灶性脑缺血后 24 小时内，β-肌动蛋白可能被 granzyme B 切割。完整的β-肌动蛋白抑制 DNase，而β-肌动蛋白的切割激活了 DNase，这导致了短暂局灶性缺血后大脑中观察到的 DNA 片段化。
