Neuronal and glial responses in the brain under hypoxic stress

二酰基甘油激酶（DGK）通过调节脂质信使二酰基甘油的水平，在病理生理细胞反应中起关键作用。在DGK同工酶中，DGKζ定位于各种细胞的细胞核，如神经元。我们之前报道过，海马CA1锥体神经元DGKζ在短暂前脑缺血20分钟后从细胞核转移到细胞质。在这项研究中，我们检查了DGKζ易位的潜在机制，使用暴露于氧-葡萄糖剥夺（OGD）的海马切片来模拟脑缺血模型。在OGD 20 min后，CA1锥体神经元dgk - ζ-免疫反应性逐渐从细胞核向细胞质转变，再氧化后细胞核中未检测到dgk - ζ-免疫反应性。有趣的是，DGKζ在OGD 10分钟时在细胞核中检测到，而随后的60分钟再氧化诱导DGKζ的完全细胞质易位。形态计量学分析显示DGKζ细胞质易位与核收缩相关，表明神经元变性的早期过程。OGD条件下的易位被NMDA受体（NMDAR）抑制剂阻断，并由NMDAR激活诱导。细胞外Ca（2+）的螯合作用阻断了OGD条件下的易位。这些结果表明，DGKζ细胞质易位是由NMDAR的激活和随后的细胞外Ca（2+）内流触发的。此外，在OGD条件下，PKC活性的抑制导致DGKζ在约三分之一的神经元中的核保留，这表明PKC活性部分调节DGKζ的细胞质易位。这些发现为进一步研究谷氨酸在海马神经元中的兴奋毒性机制提供了线索。

Diacylglycerol kinase (DGK) plays a key role in pathophysiological cellular responses by regulating the levels of a lipid messenger diacylglycerol. Of DGK isozymes, DGKζ localizes to the nucleus in various cells such as neurons. We previously reported that DGKζ translocates from the nucleus to the cytoplasm in hippocampal CA1 pyramidal neurons after 20 min of transient forebrain ischemia. In this study, we examined the underlying mechanism of DGKζ translocation using hippocampal slices exposed to oxygen-glucose deprivation (OGD) to simulate an ischemic model of the brain. DGKζ-immunoreactivity gradually changed from the nucleus to the cytoplasm in CA1 pyramidal neurons after 20 min of OGD and was never detected in the nucleus after reoxygenation. Intriguingly, DGKζ was detected in the nucleus at 10 min OGD whereas the following 60 min reoxygenation induced complete cytoplasmic translocation of DGKζ. Morphometric analysis revealed that DGKζ cytoplasmic translocation correlated with nuclear shrinkage indicative of an early process of neuronal degeneration. The translocation under OGD conditions was blocked by NMDA receptor (NMDAR) inhibitor, and was induced by activation of NMDAR. Chelation of the extracellular Ca(2+) blocked the translocation under OGD conditions. These results show that DGKζ cytoplasmic translocation is triggered by activation of NMDAR with subsequent extracellular Ca(2+) influx. Furthermore, inhibition of PKC activity under OGD conditions led to nuclear retention of DGKζ in about one-third of the neurons, suggesting that PKC activity partially regulates DGKζ cytoplasmic translocation. These findings provide clues to guide further investigation of glutamate excitotoxicity mechanisms in hippocampal neurons.