小胶质细胞作为抗炎治疗靶点预防蛛网膜下腔出血（SAH）后二次脑损伤。
Microglia as target for anti-inflammatory approaches to prevent secondary brain injury after subarachnoid hemorrhage (SAH).
机构信息
Experimental Neurosurgery, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.
Department of Experimental Neurology and Center for Stroke Research, Charité - Universitätsmedizin Berlin, Berlin, Germany.
出版信息
J Neuroinflammation. 2021 Jan 30;18(1):36. doi: 10.1186/s12974-021-02085-3.
BACKGROUND
Microglia-driven cerebral spreading inflammation is a key contributor to secondary brain injury after SAH. Genetic depletion or deactivation of microglia has been shown to ameliorate neuronal cell death. Therefore, clinically feasible anti-inflammatory approaches counteracting microglia accumulation or activation are interesting targets for SAH treatment. Here, we tested two different methods of interference with microglia-driven cerebral inflammation in a murine SAH model: (i) inflammatory preconditioning and (ii) pharmacological deactivation.
METHODS
7T-MRI-controlled SAH was induced by endovascular perforation in four groups of C57Bl/6 mice: (i) Sham-operation, (ii) SAH naïve, (iii) SAH followed by inflammatory preconditioning (LPS intraperitoneally), and (iv) SAH followed by pharmacological microglia deactivation (colony-stimulating factor-1 receptor-antagonist PLX3397 intraperitoneally). Microglia accumulation and neuronal cell death (immuno-fluorescence), as well as activation status (RT-PCR for inflammation-associated molecules from isolated microglia) were recorded at day 4 and 14. Toll-like receptor4 (TLR4) status was analyzed using FACS.
RESULTS
Following SAH, significant cerebral spreading inflammation occurred. Microglia accumulation and pro-inflammatory gene expression were accompanied by neuronal cell death with a maximum on day 14 after SAH. Inflammatory preconditioning as well as PLX3397-treatment resulted in significantly reduced microglia accumulation and activation as well as neuronal cell death. TLR4 surface expression in preconditioned animals was diminished as a sign for receptor activation and internalization.
CONCLUSIONS
Microglia-driven cerebral spreading inflammation following SAH contributes to secondary brain injury. Two microglia-focused treatment strategies, (i) inflammatory preconditioning with LPS and (ii) pharmacological deactivation with PLX3397, led to significant reduction of neuronal cell death. Increased internalization of inflammation-driving TLR4 after preconditioning leaves less receptor molecules on the cell surface, providing a probable explanation for significantly reduced microglia activation. Our findings support microglia-focused treatment strategies to overcome secondary brain injury after SAH. Delayed inflammation onset provides a valuable clinical window of opportunity.
背景
小胶质细胞驱动的大脑扩散性炎症是蛛网膜下腔出血（SAH）后继发性脑损伤的关键因素。已经证明，小胶质细胞的基因耗竭或失活可以改善神经元细胞死亡。因此，针对小胶质细胞聚集或激活的临床可行的抗炎方法是治疗 SAH 的有趣靶点。在这里，我们在小鼠 SAH 模型中测试了两种不同的干扰小胶质细胞驱动的大脑炎症的方法：（i）炎症预处理和（ii）药理学失活。
方法
通过血管内穿孔在四组 C57Bl/6 小鼠中诱导 7T-MRI 控制的 SAH：（i）假手术，（ii）SAH 未处理，（iii）SAH 后进行炎症预处理（LPS 腹腔内注射），和（iv）SAH 后进行药理学小胶质细胞失活（集落刺激因子-1 受体拮抗剂 PLX3397 腹腔内注射）。在第 4 天和第 14 天记录小胶质细胞聚集和神经元细胞死亡（免疫荧光）以及分离的小胶质细胞中炎症相关分子的 RT-PCR 记录的激活状态。使用 FACS 分析 Toll 样受体 4（TLR4）状态。
结果
在 SAH 后，发生了明显的大脑扩散性炎症。小胶质细胞聚集和促炎基因表达伴随着神经元细胞死亡，SAH 后第 14 天达到最大值。炎症预处理和 PLX3397 治疗导致小胶质细胞聚集和激活以及神经元细胞死亡明显减少。预处理动物中 TLR4 表面表达减少，表明受体激活和内化。
结论
SAH 后小胶质细胞驱动的大脑扩散性炎症导致继发性脑损伤。两种针对小胶质细胞的治疗策略，（i）用 LPS 进行炎症预处理和（ii）用 PLX3397 进行药理学失活，可显著减少神经元细胞死亡。预处理后炎症驱动的 TLR4 内化增加，导致细胞表面的受体分子减少，这可能是小胶质细胞激活明显减少的原因。我们的研究结果支持针对小胶质细胞的治疗策略，以克服 SAH 后的继发性脑损伤。延迟炎症发作为临床提供了宝贵的机会窗口。
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