Departments of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA.
NeuroVascular Protection Research Center, College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Korea.
J Neurochem. 2018 Jul;146(2):160-172. doi: 10.1111/jnc.14337. Epub 2018 May 16.
Ischemic postconditioning is increasingly being investigated as a therapeutic approach for cerebral ischemia. However, the majority of studies are focused on the acute protection of neurons per se. Whether and how postconditioning affects multiple cells in the recovering neurovascular unit remains to be fully elucidated. Here, we asked whether postconditioning may modulate help-me signaling between injured neurons and reactive microglia. Rats were subjected to 100 min of focal cerebral ischemia, then randomized into a control versus postconditioning group. After 3 days of reperfusion, infarct volumes were significantly reduced in animals treated with postconditioning, along with better neurologic outcomes. Immunostaining revealed that ischemic postconditioning increased expression of vascular endothelial growth factor (VEGF) in neurons within peri-infarct regions. Correspondingly, we confirmed that VEGFR2 was expressed on Iba1-positive microglia/macrophages, and confocal microscopy showed that in postconditioned rats, these cells were polarized to a ramified morphology with higher expression of M2-like markers. Treating rats with a VEGF receptor 2 kinase inhibitor negated these effects of postconditioning on microglia/macrophage polarization. In vitro, postconditoning after oxygen-glucose deprivation up-regulated VEGF release in primary neuron cultures, and adding VEGF to microglial cultures partly shifted their M2-like markers. Altogether, our findings support the idea that after postconditioning, injured neurons may release VEGF as a 'help-me' signal that promotes microglia/macrophage polarization into potentially beneficial phenotypes.
缺血后处理作为一种治疗脑缺血的方法越来越受到关注。然而，大多数研究都集中在神经元本身的急性保护上。后处理是否以及如何影响恢复中的神经血管单元中的多种细胞仍有待充分阐明。在这里，我们想知道后处理是否可以调节受损神经元和反应性小胶质细胞之间的“帮助信号”。大鼠接受 100 分钟的局灶性脑缺血，然后随机分为对照组和后处理组。再灌注 3 天后，后处理组动物的梗死体积明显减少，神经功能结局也更好。免疫染色显示，缺血后处理增加了梗死周围区域神经元中血管内皮生长因子（VEGF）的表达。相应地，我们证实 VEGFR2 在 Iba1 阳性小胶质细胞/巨噬细胞上表达，共聚焦显微镜显示，在经过后处理的大鼠中，这些细胞极化呈分支状形态，M2 样标志物表达更高。用 VEGF 受体 2 激酶抑制剂处理大鼠可消除后处理对小胶质细胞/巨噬细胞极化的这些影响。在体外，氧葡萄糖剥夺后的后处理增加了原代神经元培养物中 VEGF 的释放，向小胶质细胞培养物中添加 VEGF 部分改变了它们的 M2 样标志物。总之，我们的研究结果支持这样一种观点，即在缺血后处理后，受损神经元可能会释放 VEGF 作为一种“帮助信号”，促进小胶质细胞/巨噬细胞向潜在有益的表型极化。
