Wu Qing-ping, Yao Shang-long, Fang Xiang-ming
Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei, China.
Zhongguo Wei Zhong Bing Ji Jiu Yi Xue. 2005 Jun;17(6):353-6.
To study the changes in the expression of rat beta-defensin-2 (RBD-2) gene in the lung tissue with P. aeruginosa (PA) pneumonia following tracheal mechanical ventilation (MV), and to evaluate the pathogenesis of ventilator-associated pneumonia (VAP).
A total of 58 normal healthy Sprague-Dawley rats, weighing between 280 and 320 g, were randomly divided into the control group and the conventional MV group (CMV). A tracheal catheter was inserted via mouth in every rat under urethane anesthesia. PA (1 MIC, 0.2 ml) was instilled into the tracheal in the control group. Rats of CMV group received MV (V(T)=12 ml/kg) through tracheal tube for 24 hours, and then were challenged intra-tracheally with PA (1 MIC, 0.2 ml). Fluid loss was replenished through intravenous infusion. The arterial catheter was used for hemodynamics, parameters were monitored, and arterial blood gases were determined. Samples of lung were harvested at 0 hours, 15 hours, 3 hours, 6 hours, 12 hours, 1 day, 3 days and 5 days, respectively, after bacterial challenge. The mRNA of RBD-2 was detected by reverse transcription-polymerase chain reaction (RT-PCR), and the protein levels were analyzed by Western blotting.
Expression of RBD-2 mRNA and protein was lower in CMV group compared with the control 3 hours before instillation of bacteria. RBD-2 mRNA increased 3 hours after bacteria instillation, reaching the peak at 12-24 hours. No significant difference in RBD-2 expression between the control group and the CMV group within 3 hours, but it was significantly higher at 3 hours, 6 hours, 12 hours, 1 day, 3 days and 5 days in the control group than in the CMV group. The number of inflammatory cells infiltrating the bronchial submucous layer was significantly higher in the control group than in the CMV group (P<0.05). There was milder interstitial pulmonary edema and less red blood cells in the alveoli in the control group than in the CMV group. The mortality rate of the CMV group was 60%, which was significantly higher than that of the control group (20%, P<0.05). The positive rates of blood culture and bronchoalveolar lavage fluid (BALF) bacterial culture were also higher in the CMV group (P<0.05). The survival rate in CMV group (40%) was lower than that of the control group (P<0.05).
The lowering of BD-2 gene and protein expression in the CMV group 3 hours after bacteria challenge might be one of the contributory factors in causing VAP.
研究气管机械通气（MV）后铜绿假单胞菌（PA）肺炎大鼠肺组织中大鼠β-防御素-2（RBD-2）基因表达的变化，评估呼吸机相关性肺炎（VAP）的发病机制。
选取58只体重280～320 g的健康雄性Sprague-Dawley大鼠，随机分为对照组和传统MV组（CMV）。所有大鼠在乌拉坦麻醉下经口插入气管导管。对照组气管内注入PA（1 MIC，0.2 ml）。CMV组大鼠经气管插管进行MV（V(T)=12 ml/kg）24小时，然后气管内注入PA（1 MIC，0.2 ml）。通过静脉输液补充液体丢失。使用动脉导管监测血流动力学参数并测定动脉血气。在细菌攻击后0小时、3小时、6小时、12小时、1天、3天和5天分别采集肺组织样本。采用逆转录-聚合酶链反应（RT-PCR）检测RBD-2的mRNA，采用蛋白质印迹法分析蛋白质水平。
细菌注入前3小时，CMV组RBD-2 mRNA和蛋白表达低于对照组。细菌注入后3小时RBD-2 mRNA增加，在12～24小时达到峰值。注入细菌后3小时内对照组和CMV组RBD-2表达无显著差异，但对照组在注入细菌后3小时、6小时、12小时、1天、3天和5天的RBD-2表达明显高于CMV组。对照组支气管黏膜下层炎性细胞浸润数量明显高于CMV组（P<0.05）。对照组间质性肺水肿较轻，肺泡内红细胞较CMV组少。CMV组死亡率为60%，明显高于对照组（20%，P<0.05）。CMV组血培养和支气管肺泡灌洗液（BALF）细菌培养阳性率也较高（P<0.05）。CMV组生存率（40%）低于对照组（P<0.05）。
细菌攻击后3小时CMV组BD-2基因和蛋白表达降低可能是导致VAP的因素之一。
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