Institute of Neuroanatomy, Medical Faculty, RWTH Aachen University, Aachen, Germany.
Department of Neurology, Medical Faculty, RWTH Aachen University, Aachen, Germany.
Mol Neurobiol. 2020 Jun;57(6):2588-2599. doi: 10.1007/s12035-020-01909-2. Epub 2020 Apr 1.
Post-hypoxic/ischemic neuroinflammation is selectively driven by sterile inflammation, which implies the interplay of brain-intrinsic immune cells with other neural cells and immigrated peripheral immune cells. The resultant inflammatory cascade evolves extra- and intracellular pathogen and danger-associated receptors. The latter interacts with multiprotein complexes termed inflammasomes. The NLRP3 inflammasome is one of the best-described inflammasomes. However, its impact on post-ischemic neuroinflammation and its role in neuroprotection after ischemic stroke are still under debate. Microglial cells are known to be the main source of neuroinflammation; hence, we depleted NLRP3 in BV-2 microglial cells using shRNA to investigate its role in IL-1β maturation and phagocytosis after hypoxia (oxygen-glucose-deprivation (OGD)). We also examined the expression profiles of other inflammasomes (NLRC4, AIM2, ASC) and caspase-1 activity after OGD. OGD triggered caspase-1 activity and increased IL-1β secretion in BV-2 cells with no alteration after NLRP3 depletion. The expression of the AIM2 inflammasome was significantly higher after OGD in NLRP3-depleted cells, whereas NLRC4 was unaltered in all groups. Interestingly, OGD induced a complete inactivation of phagocytic activity in wild-type cells, while in NLRP3-depleted BV-2, this inactivity was restored after hypoxia. Our findings indicate a minor role of NLRP3 in the inflammatory response after hypoxic/ischemic stimulus. However, NLRP3 seems to play a pivotal role in the regulation of post-ischemic phagocytosis. This might be a prerequisite for the putative neuroprotective effect.
缺氧/缺血后神经炎症是由无菌性炎症选择性驱动的，这意味着脑固有免疫细胞与其他神经细胞和迁移的外周免疫细胞相互作用。由此产生的炎症级联反应涉及细胞外和细胞内病原体和危险相关受体。后者与称为炎性体的多蛋白复合物相互作用。NLRP3 炎性体是描述最清楚的炎性体之一。然而，其对缺血后神经炎症的影响及其在缺血性中风后神经保护中的作用仍存在争议。小胶质细胞被认为是神经炎症的主要来源；因此，我们使用 shRNA 在 BV-2 小胶质细胞中耗尽 NLRP3，以研究其在缺氧（氧葡萄糖剥夺（OGD））后 IL-1β成熟和吞噬作用中的作用。我们还检查了其他炎性体（NLRC4、AIM2、ASC）和 OGD 后 caspase-1 活性的表达谱。OGD 在 BV-2 细胞中触发 caspase-1 活性并增加 IL-1β分泌，但 NLRP3 耗尽后无变化。在 NLRP3 耗尽的细胞中，OGD 后 AIM2 炎性体的表达明显更高，而 NLRC4 在所有组中均未改变。有趣的是，OGD 诱导野生型细胞吞噬活性完全失活，而在 NLRP3 耗尽的 BV-2 中，缺氧后这种失活得到恢复。我们的研究结果表明 NLRP3 在缺氧/缺血刺激后的炎症反应中作用较小。然而，NLRP3 似乎在调节缺血后吞噬作用中起关键作用。这可能是假定的神经保护作用的先决条件。
