BACKGROUND Cardiac arrest survivors suffer from neurological dysfunction including cognitive impairment. Cerebral mast cells, the key regulators of neuroinflammation contribute to neuroinflammation-associated cognitive dysfunction. Mast cell tryptase was demonstrated to have a proinflammatory effect on microglia via the activation of microglial protease-activated receptor-2 (PAR-2). This study investigated the potential anti-neuroinflammatory effect of mast cell tryptase inhibition and the underlying mechanism of PAR-2/p-p38/NFκB signaling following asphyxia-induced cardiac arrest in rats. METHODS Adult male Sprague-Dawley rats resuscitated from 10 min of asphyxia-induced cardiac arrest were randomized to four separate experiments including time-course, short-term outcomes, long-term outcomes and mechanism studies. The effect of mast cell tryptase inhibition on asphyxial cardiac arrest outcomes was examined after intranasal administration of selective mast cell tryptase inhibitor (APC366; 50 μg/rat or 150 μg/rat). AC55541 (selective PAR-2 activator; 30 μg/rat) and SB203580 (selective p38 inhibitor; 300 μg/rat) were used for intervention. Short-term neurocognitive functions were evaluated using the neurological deficit score, number of seizures, adhesive tape removal test, and T-maze test, while long-term cognitive functions were evaluated using the Morris water maze test. Hippocampal neuronal degeneration was evaluated by Fluoro-Jade C staining. RESULTS Mast cell tryptase and PAR-2 were dramatically increased in the brain following asphyxia-induced cardiac arrest. The inhibition of mast cell tryptase by APC366 improved both short- and long-term neurological outcomes in resuscitated rats. Such behavioral benefits were associated with reduced expressions of PAR-2, p-p38, NFκB, TNF-α, and IL-6 in the brain as well as less hippocampal neuronal degeneration. The anti-neuroinflammatory effect of APC366 was abolished by AC55541, which when used alone, indeed further exacerbated neuroinflammation, hippocampal neuronal degeneration, and neurologic deficits following cardiac arrest. The deleterious effects aggregated by AC55541 were minimized by p38 inhibitor. CONCLUSIONS The inhibition of mast cell tryptase attenuated neuroinflammation, led to less hippocampal neuronal death and improved neurological deficits following cardiac arrest. This effect was at least partly mediated via inhibiting the PAR-2/p-p38/NFκB signaling pathway. Thus, mast cell tryptase might be a novel therapeutic target in the management of neurological impairment following cardiac arrest.

中文翻译：

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大鼠窒息性心脏骤停后，肥大细胞类胰蛋白酶的抑制可通过PAR-2 / p38 /NFκB途径减弱神经炎症。

背景技术心脏骤停幸存者患有神经功能障碍，包括认知障碍。脑肥大细胞是神经炎症的关键调节因子，与神经炎症相关的认知功能障碍有关。肥大细胞类胰蛋白酶被证明通过激活小胶质蛋白酶激活受体2（PAR-2）对小胶质细胞有促炎作用。这项研究调查了窒息性大鼠心脏骤停后肥大细胞类胰蛋白酶抑制作用的潜在抗神经炎作用以及PAR-2 / p-p38 /NFκB信号传导的潜在机制。方法将窒息性心跳骤停10分钟后复苏的成年雄性Sprague-Dawley大鼠随机分为四个独立的实验，包括时程，短期结果，长期结果和机制研究。在鼻内施用选择性肥大细胞类胰蛋白酶抑制剂（APC366； 50μg/大鼠或150μg/大鼠）后，检查肥大细胞类胰蛋白酶抑制对窒息性心脏骤停结果的影响。AC55541（选择性PAR-2激活剂； 30μg/大鼠）和SB203580（选择性p38抑制剂； 300μg/大鼠）用于干预。短期神经认知功能通过神经功能缺损评分，癫痫发作次数，胶带去除测试和T迷宫测试进行评估，而长期认知功能通过莫里斯水迷宫测试进行评估。通过Fluoro-Jade C染色评估海马神经元变性。结果窒息性心脏骤停后脑中肥大细胞类胰蛋白酶和PAR-2显着增加。APC366对肥大细胞类胰蛋白酶的抑制作用可改善复苏大鼠的短期和长期神经功能。这种行为上的好处与大脑中PAR-2，p-p38，NFκB，TNF-α和IL-6的表达减少以及海马神经元变性减少有关。AC55541取消了APC366的抗神经炎作用，当单独使用时，确实会进一步加重心脏骤停后神经炎症，海马神经元变性和神经功能缺损。p38抑制剂可将AC55541聚集的有害作用减至最小。结论抑制肥大细胞类胰蛋白酶可减轻神经炎症，减少海马神经元死亡并改善心脏骤停后的神经功能缺损。该作用至少部分地通过抑制PAR-2 / p-p38 /NFκB信号传导途径来介导。因此，肥大细胞类胰蛋白酶可能是心脏骤停后神经系统损伤管理中的新型治疗靶标。