肿瘤坏死因子-α在七氟醚后处理减轻体外循环犬肺损伤中的作用

The role of tumor necrosis factor-α in sevoflurane postconditioning alleviating cardiopulmonary bypass related lung injury in dogs

目的通过观察七氟醚后处理对体外循环（CPB）犬肺组织肿瘤坏死因子-α（TNF-α）表达的影响,探讨七氟醚后处理减轻CPB肺损伤的机制。方法健康杂种犬18只随机分为3组每组6只（n=6）：单纯手术组（A组）、体外循环缺血再灌注组（B组）、七氟醚后处理组（C组）。3组犬麻醉固定后行双腔气管插管机械通气。经胸骨正中切口开胸,B、C组建立犬体外循环单肺缺血再灌注损伤模型。C组在开放左肺动脉即刻通过人工膜肺给予呼气末2%七氟醚后处理30 min,A组只开胸不做其他处理。B、C组CPB前（T1）、开放左肺动脉后（T2）及实验结束时（T3）;A组与B、C组相同时间的3个时间点抽取股动脉血行血气分析计算氧合指数（OI）和呼吸指数（RI）;取左肺组织保存,HE染色光镜观察形态学变化;采用ELISA法检测肺组织TNF-α的含量。结果①肺功能指标的变化：3组内不同时点比较结果发现,A组各时点OI、RI未见明显改变（P〉0.05）,B、C组T1-T3时点OI逐渐降低,而RI则逐渐升高（P〈0.05）。3组间同时点比较结果显示,T1时刻,3组犬之间OI、RI无明显差异（P〉0.05）;T2、T3时刻,与A组比较,B、C组OI显著减低,RI则明显升高（P〈0.05）,其中C组在T_3时刻OI明显高于B组,而RI则相反（P〈0.05）。②肺组织光镜形态学观察：各组T_1-T_3时点,肺组织结构损伤逐渐加重。T_3时刻A组肺组织损伤程度较B、C组轻,而C组又明显较B组轻。③肺组织TNF-α含量的变化：3组内各时点比较结果显示,A组各时点肺组织TNF-α含量未见明显改变（P〉0.05）;B、C组T1-T3时点肺组织TNF-α含量逐渐增加（P〈0.05）。3组间同时点比较结果显示,T1时刻3组犬肺组织TNF-α含量无明显差异（P〉0.05）;T2、T3时刻,与A组比较,B、C组肺组织TNF-α含量明显增加（P〈0.05）,其中C组在T_3时刻TNF-α含量明显低于B组（P〈0.05）。结论CPB,后随着犬肺组织TNF-α含量的增加,肺组织结构破坏严重,肺功能降低,肺组织TNF-α含量的增加可能是加重肺损伤的重要原因。七氟醚后处理后肺功能明显改善,肺组织破坏程度减轻,对CPB犬肺损伤有一定保护作用。七氟醚后处理减轻CPB肺损伤的作用可能与抑制肺组织TNF-α表达有关。

Objective To observe the effect of sevoflurane postconditioning on expression of TNF- α in lungs of dogs during cardiopulmonary bypass（CPB） and explore mechanisms of sevoflurane postconditioning alleviating CPB- induced lung injury.Methods Eighteen healthy dogs were randomly divided into 3 groups（n = 6 each）：simple operation group（group A）,left lung ischemia- reperfusion injury of CPB group（group B）,sevoflurane postconditioning group（group C）.All dogs received intraperitoneal injection of 2.5%sodium pentobarbital and double lumen bronchial tube intubation.After cutting the sternum,the left pulmonary artery was separated and blocked to establish lung ischemia reperfusion injury model in B and C group.In C group,2%sevoflurane was administrated for 30 minutes at the onset of opening left pulmonary artery.In A group,sternotomy was completed without other treatments.Arterial blood was collected before CPB（T1）,at the onset of opening artery（T2） and2 h after CPB（T3） to calculate oxygenation index（OI） and respiration index（RI）.Left lung tissues were taken to measure following indexes.Hematoxylin- eosin staining was performed to observe the pathological changes.The expression of TNF-α was measured with enzyme linked immunosorbent assay method（ELISA）.Results（1） The changes of lung function index：In A group,there was no significant difference among three time points（P〈0.05）;The value of OI was gradually decreased at T1- TI and RI in every group at T1 time（P〈0.05）.The value of OI in the group B and C were obviously lower than that of group A at T2 and T3 time,while RI showed a contrary trend（P〈0.05）.C groups＇ OI values were obviously higher than group B（P〈0.05）,and RI values were obviously lower than group B（P〈0.05）.（2） Pathological changes under optical microscope：The damage of lung tissue was gradually aggravated at T1-T3 in all groups.At T3,the injury of lung tissue in A group was lower than that in B and C group,while the C group was significantly lower than the B group.（3） The expression changes of TNF-α：There were no changes at any time in group A（P〈0.05）.The changes of TNF-α was gradually decreased at T1-T3 in B and C group（P〈0.05）.The changes at the same time in the three groups：There were no obviously difference in every group at T1 time（P〈0.05）.The expression in the B and C group was obviously higher than that in group A at T2、T3 time（P〈0.05）,while the C group was significantly lower than the B group（P〈0.05）.Conclusion With the increase of TNF-α during CPB,the damage of lung tissue was severe and the lung function reduced,It indicates that the content of TNF-α could lead to lung injury.During CPB,sevoflurane postconditioning exerts protective effects on the lung indicated by improved lung function,alleviated pulmonary damage.The protective effect of sevoflurane postconditioning against lung injury caused by CPB is related with inhibition of TNF-α.