Microglia/macrophages have been identified to be highly polarized after ischemia. Interestingly, the polarization of these microglia/macrophages varies immensely under differing disease conditions. Post-conditioning using sevoflurane, a volatile anesthetic, could provide long-term neuroprotection to neonatal rats after hypoxic-ischemic brain injury (HIBI). Thus, the current study aimed at investigating the effects of sevoflurane post-conditioning (SPC) on microglia/macrophage polarization after HIBI induction in neonatal rats. Additionally, we aimed at identifying the underpinning mechanisms specifically related to autophagy and lysosomal protease enzyme, cathepsin B. To develop a HIBI model, 7-day-old Sprague–Dawley rats underwent left common carotid artery ligation followed by 2 h of hypoxia. The role of microglia/macrophages in the neuroprotection conferred by SPC was examined by left-side intra-cerebroventricular injection with adenovirus vector carrying catB-GFP or rapamycin. The number of interleukin (IL)-1β⁺ cells, cathepsin B⁺ cells, light chain 3B positive (LC3B⁺) cells among ionized calcium binding adaptor molecule 1(Iba1⁺)cells to investigate microglia polarization, neuronal apoptosis to assess neuronal death in the acute phase were tested at 24 h after HIBI. Behavioral tests including suspension test, Morris water maze tests were performed to investigate the long-term effects of SPC, at 21 to 34 days post HIBI. Nissl staining and myelin basic protein (MBP) immunostaining to assess the long-term neuronal and myelin damage were performed at 34 days after HIBI. Based on the obtained results post HIBI, we observed the cells that were positive for IL-1β, cathepsin B, and LC3B among Iba1 positive cell population in the hippocampus were significantly decreased after SPC treatment. SPC significantly attenuated the HIBI-induced increase in neuronal apoptosis, improved long-term cognitive function, and attenuated HI-induced decrease of Nissl-positive cells and MBP expression. However, these trends were reversed by injection of adenovirus vector carrying catB-GFP and rapamycin. SPC attenuated microglia polarization towards neurotoxic phenotypes, alleviates neuronal death and axon demyelination after HIBI in neonatal rats by regulating microglia autophagy and cathepsin B expression, and therefore provided long-term cognitive, learning and memory protection.

已确定小胶质细胞/巨噬细胞在缺血后高度极化。有趣的是，这些小胶质细胞/巨噬细胞的极化在不同的疾病条件下变化很大。使用挥发性麻醉剂七氟醚进行后处理可以为缺氧缺血性脑损伤 (HIBI) 后的新生大鼠提供长期的神经保护。因此，本研究旨在研究七氟醚后处理 (SPC) 对新生大鼠 HIBI 诱导后小胶质细胞/巨噬细胞极化的影响。此外，我们旨在确定与自噬和溶酶体蛋白酶组织蛋白酶 B 相关的基础机制。为了开发 HIBI 模型，7 天大的 Sprague-Dawley 大鼠接受左颈总动脉结扎，然后缺氧 2 小时。通过左侧脑室内注射携带 catB-GFP 或雷帕霉素的腺病毒载体检查小胶质细胞/巨噬细胞在 SPC 赋予的神经保护中的作用。白细胞介素（IL）-1β的数量⁺细胞、组织蛋白酶 B ⁺细胞、离子化钙结合衔接分子 1(Iba1 ⁺中的轻链 3B 阳性 (LC3B ^{+ ) 细胞}) 在 HIBI 后 24 小时测试用于研究小胶质细胞极化、评估急性期神经元死亡的神经元凋亡的细胞。在 HIBI 后 21 至 34 天进行行为测试，包括悬浮测试、Morris 水迷宫测试以研究 SPC 的长期影响。在 HIBI 后 34 天进行 Nissl 染色和髓鞘碱性蛋白 (MBP) 免疫染色以评估长期神经元和髓鞘损伤。根据 HIBI 后获得的结果，我们观察到海马 Iba1 阳性细胞群中 IL-1β、组织蛋白酶 B 和 LC3B 阳性的细胞在 SPC 处理后显着减少。SPC 显着减弱 HIBI 诱导的神经元凋亡增加，改善长期认知功能，并减弱 HI 诱导的 Nissl 阳性细胞和 MBP 表达的减少。然而，通过注射携带 catB-GFP 和雷帕霉素的腺病毒载体逆转了这些趋势。SPC 通过调节小胶质细胞自噬和组织蛋白酶 B 的表达，减弱小胶质细胞对神经毒性表型的极化，减轻新生大鼠 HIBI 后的神经元死亡和轴突脱髓鞘，从而提供长期的认知、学习和记忆保护。