NF-κB在机械通气和内毒素肺损伤中的作用机制

Study on Role of NF-κB in Lung Injury by Mechanical Ventilation and Endotoxion

目的探讨幼兔机械通气、内毒素及机械通气复合内毒素肺损伤时,肺组织核因子-κB(NF-κB)活化及其对TNF-α和IL-8表达的影响。方法60只普通级幼兔随机等分为对照组(NMV)、大潮气量组(LVMV)、内毒素组(ENMV)和复合损伤组(EMV)(n=15),检测各时相肺组织NF-κB活性、IκBα含量、TNF-α和IL-8的基因表达和蛋白含量变化,并观察肺组织病理改变。结果NF-κB活性在NMV较底,ENMV致伤后2 h NF-κB活性达最高,而LVMV通气4 h NF-κB活性达高峰;EMV伤后各时相点NF-κB活性强度显著高于其它两组(P<0.01)。IκBα含量在NMV较高,ENMV致伤后4 h IκBα含量降至最低;出现显著下降的时间早于LVMV;EMV在通气后2、4、6 h的IκBα含量降低程度显著大于其它两组(P<0.01)。TNF-α、IL-8 mRNA和蛋白含量在NMV较低,在ENMV和EMV肺组织伤后TNF-α、IL-8 mRNA和蛋白含量峰值早于LVMV,EMV伤后2、4、6 h TNF-αmRNA表达和蛋白含量显著高于其它两组(P<0.05,P<0.01)。结论机械通气和内毒素可能通过不同的途径使NF-κB活化,启动致炎细胞因子的转录,导致肺损伤。机械通气和内毒素先后作用于机体对NF-κB的活化可能有相互反应后效应的加强,加重肺损伤。

Objective To investigate changes of NF-κB activation in lung tissues and expression of cytokines in homogenate from lung tissues in mechanical ventilation（MV） ,and endotoxin and MV combined with endotoxin in infant rabbits. Methods Sixty healthy infant rabbits were randomly divided into four groups（n = 15 each） ：combined non ventilation as controls（NMV） , MV with large tidal volume（LVMV） ,endotoxin with no MV（ENMV） and MV co- bined with endotoxin （ EMV）. NF-κB activation in nuclear protein from lung tissues was measured in different groups with EMSA. IκBα in lung tissues was analyzed with Western blot method, while genetic expression and protein quantity of TNF-α and IL-8 in homogenate from lung tissue were analyzed with RT-PCR and ELISA, and the pathological changes were examined. Results The activation of NF-KB reached peak at 2 h after occurrence of tissue injury caused by endotoxin and at 4 h caused by MV. Active strength of NF-κB at different time points after lung injury in EMV was significantly higher than that in the other 2 groups （P 〈0.01 ）. The lowest quantity of IκBα was found at 4 h after lung injury in ENMV, and 6 h in MV. Dropping of IκBα quantity at 2, 4, 6 h in EMV was very significantly faster than that of in the other 2 groups（P 〈0.01）. The expressions of TNF-α and IL-8 mRNA and their protein quantity in lung tissues reached peaks in ENMV and EMV earlier than in LVMV. They were significantly higher at 2, 4, 6 h after injury in EMV than that in the other 2 groups （P 〈 0.01 and P 〈 0.05） , respectively. Conclusion Both MV and endotoxin could enhance NF-κB activation through different ways and thus induce transcription of proinflammatory cytokines causing lung injury. The effects of the MV and endotoxin on the body earlier or later promote the activation of NF-κB to be more aggressive by their mutual reaction and accelerate lung injury.