β-防御素-2在机械通气相关性肺炎发病机制中的作用

目的观察铜绿假单胞菌（PA）机械通气相关性肺炎（VAP）前后肺组织β-防御素-2（BD-2）基因和蛋白质表达的变化，探讨肺组织的BD-2在机械通气相关性肺炎发病机制中的作用。方法90只健康清洁级雄性成年SD大鼠随机分成对照组、机械通气组（MV）和高盐抑制组（HS）。MV组中大鼠机械通气24h后气管内注入PA复制肺部感染模型。分别于接种细菌后8个时间点取3只大鼠处死，取肺组织进行病理学检测和测定大鼠肺组织中BD-2基因和蛋白质表达的变化。结果MV组中BD-2基因和蛋白质的表达水平的上调在3h后各时段均显著低于对照组（均P〈0．05）。MV组支气管肺泡灌洗液（BALF）、血细菌培养阳性率和重度肺部感染率均高于对照组（均P〈0．05）。HS组PA血细菌培养阳性率为76．2％，明显高于对照组和MV组（均P〈0．05）。对照组5d存活率为100％．MV组为50％．HS组为0。结论BD-2在机体呼吸系统中发挥重要抗感染作用．机械通气引起BD-2基因表达上调水平的下降可能与VAP的发生和发展有关。

Rat Beta-defensin-2 Gene and Protein Expression in the Pathogenesis of Ventilator-associated Pneumonia

Objective To study the changes in the expression of rat beta-defensin-2(BD-2) gene and protein in lung tissues before and after P.aeruginose(PA)-induced ventilator-associated pneumonia(VAP) to investigate the role of BD-2 in the pathogenesis of VAP.Methods A total of 90 normal healthy Sprague-Dawley rats were randomly divided into control,conventional mechanical ventilation(MV) and high salt(HS) groups.The rats in the MV group received ventilation through tracheal tube for 24 h followed by intra-tracheal challenge with PA(1 mol/L,0.2 ml) to establish the model of pulmonary infection.The samples of lung were collected and examined under light microscopy at 0 h,1.5 h,3.0 h,6.0 h,12.0 h,24.0 h,48.0 h and 72.0 h after injecting bacteria.The expression levels of BD-2 mRNA and protein in the rat lung were detected.Results The expression of BD-2 mRNA and protein was significantly lower at 3.0 h,6.0 h,12.0 h,24.0 h,48.0 h and 72.0 h in the MV group than in the control and HS groups(P<0.05).The positive rate of BALF and blood bacterial culture in MV and HS groups was significantly higher than in the control group(P<0.05).The incidence of severe pulmonary pathologic changes in MV and HS groups was also significantly higher than in the control group(P<0.05).The positive rate of blood bacterial culture in HS group was 76.2%,significantly higher than in the control group and MV group(both P<0.05).The 5-day survival rate in the control group was 100%,50% in MV group,and 0 in HS group respectively.Conclusion The changes that BD-2 gene and protein expression in the MV group was lower 3.0 h after bacteria injection than in control group might be one of the main factors causing VAP.