乌司他丁预先给药对大鼠呼吸机相关性肺损伤时p-ERK表达的影响

Effect of ulinastatin pretreatment on expression of p-ERK during ventilator-induced lung injury in rats

目的 评价乌司他丁预先给药对大鼠呼吸机相关性肺损伤时磷酸化胞外信号调节激酶（p-ERK）表达的影响.方法 清洁级健康成年雄性SD大鼠45只,体重200 ～ 250 g.采用随机数字表法分为3组（n=15）：对照组（C组）、呼吸机相关性肺损伤组（VILI组）和乌司他丁预先给药组（UP组）.UP组于机械通气前10 min颈内静脉注射乌司他丁200 000 U/kg;C组和VILI组于机械通气前10 min颈内静脉注射等容量生理盐水.3组大鼠进行双肺机械通气,采用容量控制通气模式.VILI组和UP组机械通气参数：潮气量40 ml/kg,吸呼比1∶1,通气频率40次/min,吸入氧浓度50％.于机械通气4h时麻醉后处死大鼠取肺,称湿重、干重,计算肺湿重/干重（W/D）比值、肺水含量（TLW）,光镜下观察肺组织病理学结果,测定肺泡损伤率（IAR）,电镜下观察肺组织超微结构,分别采用TUNEL法检测肺组织细胞凋亡指数（AI）.采用RT-PCR法和Western blot法检测肺组织ERKmRNA和p-ERK的表达水平.采用Western blot法检测肺组织Bcl-2和Bax的表达水平.结果 与C组比较,VILI组肺W/D比值、TLW、IAR和AI升高,肺组织p-ERK、Bcl-2和Bax表达上调（P＜0.01）;与VILI组比较,UP组肺W/D比值、TLW、IAR和AI降低,肺组织Bax表达下调,p-ERK及Bcl-2表达上调（P＜0.01）.UP组肺组织病理学损伤较VILI组明显减轻.结论 乌司他丁预先给药减轻大鼠呼吸机相关性肺损伤的机制与激活ERK信号通路,抑制细胞凋亡有关.

Objective To evaluate the effect of ulinastatin pretreatment on the expression of phosphorylated extracellular signal-regulated kinase （p-ERK） during ventilator-induced lung injury （VILI） in the rats.Methods Forty-five pathogen-free healthy adult male Sprague-Dawley rats,weighing 200-250 g,were randomly divided into 3 groups using a random number table：control group （group C）,group VILI and ulinastatin pretreatment group （group UP）,with 15 rats in each group.Ulinastatin 200 000 U/kg was injected via the jugular vein at 10 min prior to mechanical ventilation in group UP.The equal volume of normal saline was injected via the jugular vein at 10 min prior to mechanical ventilation in C and VILI groups.Bilateral lungs were ventilated in volume-controlled mode in the 3 groups.Ventilator settings were adjusted to volume-controlled mode with a fixed tidal volume 40 ml/kg,inspiratory/expiratory ratio 1 ∶ 1,respiratory rate 40 breaths/min,and fraction of inspired oxygen 50%.The rats were anesthetized at 4 h of ventilation and sacrificed,and lungs were removed for determination of wet/dry lung weight ratio （W/D ratio）,total lung water content （TLW） and cell apoptosis （using TUNEL） and for examination of the pathologic changes （with light microscope） and ultrastructure of lung tissues （with electron microscope）.The injured alveolus rate （IAR） and apoptosis index （AI） were calculated.The expression of ERK mRNA and pERK in lung tissues was detected by real-time polymerase chain reaction and by Western blot,respectively.The expression of B-cell lymphoma/leukemia-2 （Bcl-2） and Bcl-2-associated X protein （Bax） in lung tissues was detected by Western blot.Results Compared to group C,the W/D ratio,TLW,IAR and AI were significantly increased,and the expression of p-ERK,Bcl-2 and Bax in lung tissues was significantly up-regulated in group VILI （P〈0.01）.Compared to group VILI,the W/D ratio,TLW,IAR and AI were significantly decreased,the expression of Bax in lung tissues was significantly down-regulated,and the expression of p-ERK and Bcl-2 in lung tissues was significantly up-regulated in group UP （P〈0.01）.The pathological changes of lung tissues were significantly attenuated in group UP as compared with group VILI.Conclusion The mechanism by which ulinastatin pretreatment mitigates VILI is related to activation of ERK signaling pathway and inhibition of cell apoptosis in rats.