α7nAChR激动剂经内质网应激调控NLRP3炎症小体改善缺氧缺血性脑损伤的分子机制研究

Molecular mechanism of NLRP3 inflammasome regulated by α7nAChR agonist via endoplasmic reticulum stress to ameliorate hypoxic-ischemic brain damage

摘要:

目的 探究α7nAChR激动剂通过介导内质网应激（ERS）调控NLRP3炎症小体表达对缺氧缺血性脑损伤（HIBD）的影响及可能机制。方法 选择出生7 d左右的SPF级SD雄性大鼠48只，随机分为假手术组（S组）、模型组（HIBD组）、HIBD+α7nAChR激动剂PNU282987组（HP组），每组16只。HIBD组和HP组大鼠均进行HIBD模型复制；S组进行假手术，不做结扎和缺氧处理。HP组模型复制成功后1 h腹腔注射0.8 mg/kg PNU282987，HIBD组和S组同时间腹腔注射等量生理盐水。模型复制48 h后采用水迷宫实验检测大鼠学习记忆能力；酶联免疫吸附试验（ELISA）检测血清白细胞介素-18（IL-18）、白细胞介素-1β（IL-1β）水平；HE染色观察脑组织病理变化；TTC染色法检测脑梗死面积；TUNEL法检测大脑皮质、海马CA1区神经细胞凋亡；Western blotting检测脑组织中NLRP3蛋白及葡萄糖调节蛋白78（GRP78）、C/EBP同源蛋白（CHOP）的相对表达量。结果 水迷宫实验结果显示，3组大鼠逃避潜伏期、穿越圆台次数比较，差异有统计学意义（P <0.05）；ELISA检测结果显示，HIBD组和HP组大鼠血清IL-18、IL-1β水平较S组升高（P <0.05），HP组大鼠血清IL-18、IL-1β水平较HIBD组降低（P <0.05）；HE染色结果显示，S组脑皮层完整，细胞排列正常，无明显神经元损伤，HIBD组可见脑皮层神经元排列较为紊乱，细胞间隙变宽，细胞膜破裂，HP组神经元排列紊乱，水肿程度、坏死程度较HIBD组轻；TTC染色结果显示，S组无明显梗死灶，HIBD组和HP组均可见白色梗死灶，其中HP组梗死面积占比明显低于HIBD组（P <0.05）；TUNEL法结果显示，HIBD组和HP组大鼠脑皮层和海马CA1区神经细胞凋亡率较S组升高（P <0.05），HP组大鼠脑皮层和海马CA1区神经细胞凋亡率较HIBD组降低（P <0.05）；Western blotting检测结果显示，HIBD组和HP组大鼠NLRP3、GRP78、CHOP蛋白相对表达量较S组升高（P <0.05），HP组NLRP3、GRP78、CHOP蛋白相对表达量较HIBD组降低（P <0.05）。结论 α7nAChR激动剂可改善大鼠HIBD，其机制可能与其能抑制ESR途径、降低NLRP3炎症小体表达有关。

Abstract:

Objective To investigate the effect of α7nAChR agonist on hypoxic-ischemic brain damage (HIBD) by regulating NLRP3 inflammasome expression mediated by endoplasmic reticulum stress (ERS) and its possible mechanism.Methods Forty-eight SPF SD rats at about 7 days after birth were randomly divided into a sham operation group (S group), a model group (HIBD group) and a HIBD + α7nAChR agonist PNU282987 group (HP group). HIBD model was established in HP group and HIBD group, and sham operation was performed in S group without ligation and hypoxia treatment. 0.8 mg/kg PNU282987 was injected intraperitoneally one hour after successful modeling in HP group, and the same amount of normal saline was injected intraperitoneally in HIBD group and S group. 48 h after modeling, the brain function of rats was detected by water maze test. The levels of interleukin-18 (IL-18) and interleukin-1β (IL-1β) expression in peripheral blood were detected by ELISA, the cerebral infarction area was detected by TTC staining, the pathological changes of brain tissue were observed by HE staining, the apoptosis of nerve cells in the cerebral cortex and CA1 region of the hippocampus was detected by TUNEL assay, and the expression of NLRP3 protein and glucose-regulated protein 78 (GRP78) and CCAAT/enhancer binding protein (CHOP) in brain tissue was detected by Western blotting.Results The escape latency, times of crossing round table, serum IL-18, IL-1β, proportion of cerebral infarction area, proportion of neuronal apoptosis in cerebral cortex and hippocampal CA1 area, expression of NLRP3, GRP78, chop protein of s group, HIBD group and HP group was compared, and the difference was statistically significant by analysis of variance (P < 0.05); There was no obvious infarction in the brain of rats in group S, obvious white infarction was observed in HIBD group, and the proportion of infarct size in HP group was significantly lower than that in HIBD group (P < 0.05). HE staining results showed that there was no obvious neuronal injury in group S, obvious neuronal lesions in CA1 region and cortex of hippocampus were observed in HIBD group, and the degree of brain tissue lesions in HP group was milder than that in HIBD group. Compared with the S group, Escape latency, peripheral blood IL-18, IL-1β, the proportion of neuronal apoptosis, NLRP3, GRP78, and CHOP protein expression in the cortex and CA1 region of the hippocampus were increased in the HIBD group and the HP group (P < 0.05), the number of crossing round platform is reduced in the HIBD group and the HP group (P < 0.05); compared with the HIBD group, Escape latency, peripheral blood IL-18, IL-1β, the proportion of neuronal apoptosis, NLRP3, GRP78 and CHOP protein expression in the cortex and CA1 region of the hippocampus were decreased in the HP group (P < 0.05), the number of times of crossing round platform were increased in the HP group (P < 0.05).Conclusions The mechanism of α7nAChR agonist improving HIBD in rats may be related to the inhibition of ER stress pathway, the decrease of NLRP3 expression, the alleviation of inflammatory injury and neuronal apoptosis in brain tissue.