南方医科大学学报

南方医科大学学报 ›› 2020, Vol. 40 ›› Issue (10): 1465-1471.doi: 10.12122/j.issn.1673-4254.2020.10.12

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白三烯B4在“肺保护性”通气致肺损伤中的作用机制 

袁凌跃，李 江，杨 泳，郭 欣，刘星玲，李丽莎，朱晓燕，刘 睿   

  • 出版日期:2020-10-20 发布日期:2020-10-20

Pathogenic role leukotriene B4 in lung injury induced by lung-protective mechanical ventilation in rabbits

  • Online:2020-10-20 Published:2020-10-20

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摘要： 目的 探讨白三烯B4（LTB4）在“肺保护性”机械通气（LPMV）致肺损伤中的作用机制。方法 32只健康日本大耳白兔随机平均分为：溶剂预处理+假手术组（S组）、乌苯美司（白三烯A4水解酶抑制剂）预处理+假手术组（BS组）、溶剂预处理+ LPMV组（PM组）和乌苯美司预处理+LPMV组（BPM组）。BS组和BPM组先实施连续5 d的乌苯美司8 mg/ （kg· d）灌胃预处理，S组和PM组则在相同时间点灌胃给予同等容积的溶剂。乌苯美司或溶剂预处理结束后，对PM组和BPM组实验动物实施时长为5 h的LPMV：潮气量（VT）=8 mL/kg，呼气末正压（PEEP）=5 cm H2O，吸气时间：呼气时间（I∶E）=1∶2，吸入氧浓度（FiO2）=0.5，调整呼吸频率（RR）维持呼末CO2在35~45 mmHg范围内；S组和BS组则保留自主呼吸。酶联免疫法用于检测实验动物肺组织LTB4和环一磷酸腺苷（cAMP）含量；肺组织cAMP含量、蛋白激酶A（PKA）蛋白表达水平和活化Rap1蛋白（Rap1-GTP）/总Rap1蛋白比值分别用于反映cAMP/PKA和Rap1信号通路活性变化情况；用肺通透性[肺通透性指数和肺湿/干（W/D）重比值]、肺炎症反应[支气管肺泡灌洗液（BALF）中多形核白细胞（PMN）计数和肺组织髓过氧化物酶（MPO）活性]和肺组织形态学评分对肺损伤的严重程度进行判断。结果 S组与BS组实验动物各检测指标无显著差异；除肺组织学评分无显著差异外，PM组和BPM组实验动物其余各指标均显著增高于S组（P<0.05）；与PM组相比，BPM组实验动物肺内LTB4生成明显减少（P<0.05），cAMP/PKA和Rap1信号通路活性进一步上调（P<0.05），肺炎症反应与肺通透性增加明显减轻（P<0.05）。结论 LPMV会造成实验动物肺内LTB4大量生成继而诱发肺炎症反应和肺通透性增加，LTB4在其中的作用机制与下调cAMP/PKA和Rap1信号通路活性有关；乌苯美司可通过抑制肺内LTB4的生成发挥抗LPMV诱导的肺炎症反应和肺通透性增加保护作用。

关键词: 机械通气, 肺损伤, 白三烯B4, 环一磷酸腺苷/蛋白激酶A信号通路, 环一磷酸腺苷/Rap1信号通路

Abstract: Objective To elucidate the pathogenic role of leukotriene B4 (LTB4) in pulmonary hyper-permeability and inflammation induced by lung-protective mechanical ventilation (LPMV) in rabbits. Methods Thirty-two healthy Japanese white rabbits were randomized into 4 groups for treatment with vehicle or bestatin (a leukotriene A4 hydrolase inhibitor that inhibits LTB4 production) administered intragastrically at the daily dose of 8 mg/kg for 5 days, followed by sham operation (group S and group BS, respectively, in which the rabbits were anesthetized only) or LPMV (group PM and group BPM, respectively, in which the rabbits received ventilation with 50% oxygen at a tidal volume of 8 mL/kg for 5 h). The concentrations of LTB4 and cyclic adenosine monophosphate (cAMP) in the lung tissues were analyzed by ELISA. cAMP content, protein kinase A (PKA) protein expression and the Rap1-GTP protein to total Rap1 protein ratio were determined to assess the activities of cAMP/PKA and Rap1 signaling pathways. The lung injury was evaluated by assessing lung permeability index, lung wet/dry weight ratio, polymorphonuclear leukocyte (PMN) count in bronchoalveolar lavage fluid (BALF), pulmonary myeloperoxidase (MPO) activity and lung histological scores. Results None of the examined parameters differed significantly between group S and group BS. All the parameters with the exception of lung histological score increased significantly in group PM and group BPM as compared to those in group S (P<0.05). Compared with those in PM group, the rabbits in group BPM showed significantly reduced LTB4 production in the lungs (P<0.05), up-regulated cAMP/ PKA and Rap1 signaling pathway activities (P<0.05), and alleviated lung hyper-permeability and inflammation (P<0.05).
Conclusion LPMV can induce LTB4 overproduction to down-regulate cAMP/PKA and Rap1 signaling pathways in the lungs of rabbits, which results in lung hyper-permeability and inflammation. Bestatin can inhibit LTB4 production in the lungs to protect against LPMV-induced lung hyper-permeability and inflammation. 

Key words: mechanical ventilation, lung injury, leukotriene B4, bestatin, cAMP/protein kinase A signaling pathway, AMP/Rap1 signaling pathway