The macrophage scavenger receptor 1 (MSR1)-induced resolution of neuroinflammation may be a novel therapeutic strategy for ischemic stroke. Our previous study showed that the neuroprotective and anti-inflammatory effects of phthalide are associated with the inhibition of the post-ischemic damage-associated molecular pattern (DAMP)/Toll-like receptor 4 (TLR4) pathway. This study investigated the effects of the phthalide derivative CD21 on ischemic brain injury and the mechanism underlying MSR1-induced resolution of neuroinflammation. Using a rat model of 2 h transient middle cerebral artery occlusion (MCAO), MSR1-induced peroxiredoxin1 (PRX1) clearance in RAW264.7 macrophages were investigated. We show here that CD21 significantly ameliorated infarct volumes and neurological deficits in a dose-dependent manner with a ≥ 12 h therapeutic time window. Moreover, administration of 5 mg/kg/day CD21 over 24 h significantly reduced pathological damages, with associated inhibition of PRX1 expression, reduced TLR4/nuclear factor-κB activation and the suppression of the inflammatory response in MCAO rats. Furthermore, the expression of MAFB/MSR1 in the ischemic brain was elevated and the phagocytosis of PRX1 in CD68-positive macrophages isolated from the ischemic brain was enhanced. Further in vitro studies show that CD21 (20 μM) strongly enhanced the Msr1 mRNA and MSR1 protein levers in RAW264.7 cells and PRX1 internalization in cellular lysosomes, which were significantly reversed by N-acetylcysteine treatment. These results suggest that CD21 may exert neuroprotective and anti-inflammatory effects with a wide time window for the treatment of ischemic stroke. The anti-stroke effects of CD21 appear to be mediated partially via the induction of MSR1-promoted DAMP (PRX1) clearance, TLR4/nuclear factor-κB pathway inhibition, and the resolution of inflammation.

The neuroprotective action of CD21 was associated with the resolution of neuroinflammation through enhancement of the MAFB-MSR1 pathway that leads to DAMP (PRX1) phagocytosis and TLR4 pathway inhibition. Red solid arrows represent promotion, red dotted arrow represents the positive correlation, green arrows represent inhibition.

巨噬细胞清道夫受体 1 (MSR1) 诱导的神经炎症消退可能是缺血性中风的新治疗策略。我们之前的研究表明，苯酞的神经保护和抗炎作用与抑制缺血后损伤相关分子模式 (DAMP)/Toll 样受体 4 (TLR4) 通路有关。本研究调查了苯酞衍生物 CD21 对缺血性脑损伤的影响以及 MSR1 诱导的神经炎症消退的机制。使用 2 小时短暂大脑中动脉闭塞 (MCAO) 的大鼠模型，研究了 RAW264.7 巨噬细胞中 MSR1 诱导的过氧化物酶 1 (PRX1) 清除。我们在此表明​​ CD21 以剂量依赖性方式显着改善梗死体积和神经功能缺损，治疗时间窗≥12 小时。此外，在 24 小时内施用 5 mg/kg/天 CD21 可显着减少病理损伤，同时抑制 PRX1 表达，减少 TLR4/核因子-κB 激活并抑制 MCAO 大鼠的炎症反应。此外，缺血脑中 MAFB/MSR1 的表达升高，并且从缺血脑中分离出的 CD68 阳性巨噬细胞中 PRX1 的吞噬作用增强。进一步的体外研究表明，CD21 (20 μM) 强烈增强 RAW264.7 细胞中的 Msr1 mRNA 和 MSR1 蛋白水平以及细胞溶酶体中的 PRX1 内化，而 N-乙酰半胱氨酸处理显着逆转了这些作用。这些结果表明，CD21 可能发挥神经保护和抗炎作用，治疗缺血性中风的时间窗口很宽。

CD21 的神经保护作用与通过增强导致 DAMP (PRX1) 吞噬作用和 TLR4 通路抑制的 MAFB-MSR1 通路解决神经炎症有关。红色实心箭头代表促进，红色虚线箭头代表正相关，绿色箭头代表抑制。