微量肺源性内毒素对大鼠呼吸机相关性肺损伤的影响

目的 评价微量肺源性内毒素对大鼠呼吸机相关性肺损伤的影响.方法 成年雄性SD大鼠32只,体重370～390 g,随机分为4组(n=8):自主呼吸组(C组)、内毒素+自主呼吸组(LC组)、机械通气组(M组)和内毒素+机械通气组(LM组).LC组和LM组气管内滴入内毒素100 μg/kg;M组和LM组行机械通气,潮气量20 ml/kg,呼气末正压0,1:E 1:1,维持P_(ET)CO_235～45 mm Hg;C组和LC组保持自主呼吸.于机械通气前、机械通气1、2和3 h时行血气分析,并记录血液动力学指标.机械通气3 h时放血处死大鼠,测定肺组织病理学损伤评分、湿/干重比(W/D比)、支气管肺泡灌洗液(BALF)中白细胞计数和肺蛋白透性系数,采用ELISA法检测血浆TNF-α和巨噬细胞炎性蛋白-2(MIP-2)的浓度.C组和M组采用RT-PCR法测定肺组织CD14 mRNA的表达水平,免疫组化法测定BALF中CD14的表达水平.结果 C组和M组血浆中未检测到TNF-α;与C组比较,LC组肺组织病理学损伤评分、W/D比、BALF中自细胞计数、肺蛋白透性系数和血浆MIP-2浓度差异无统计学意义(P>0.05),血浆TNF-α浓度升高,M组肺组织病理学损伤评分、BALF中白细胞计数和血浆MIP-2浓度升高,LM组肺组织病理学损伤评分、W/D比和BALF中白细胞计数、肺蛋白透性系数、血浆MIP-2和TNF-α的浓度升高(P<0.05或0.01);与M组比较,LM组肺组织病理学损伤评分、W/D比、BALF中自细胞计数、肺蛋白透性系数、血浆MIP-2和TNF-α的浓度升高(P<0.05或0.01).与C组比较,M组BALF中CD14表达和肺组织CD14 mRNA表达上调(P

Effects of minute quantity of endogenous endotoxin from the lung on ventilator-induced lung injury in rats

Objective To investigate the effects of minute quantity of endogenous endotoxin originating from the lung on ventilator-induced lung injury in rats. Methods Thirty-two pathogen-free male adult SD rats weighing 370-390 g were randomly divided into 4 groups ( n = 8 each): group I spontaneous breathing (group C) ; group Ⅱ spontaneous breathing + IPS (group CL) ; group IE mechanical ventilation (group M) and group IV mechanical ventilation + LPS (group ML). The animals were anesthetized with intraperitoneal 20% urethane 0.8 ml/100 g. Right common carotid artery and left femoral vein were cannulated for BP monitoring and fluid and drug administration. The animals were tracheostomized. In group CL and ML LPS 100μg /kg was instilled into trachea. In group M and ML the animals were mechanically ventilated (V_T 20 ml/kg, PEEP=0, I = E = 1:1). P_(ET) CO_2 was maintained at 35-45 nun Hg by adjusting respiratory rate. The animals were breathing or ventilated with room air,and ECG, BP, HR and P_(ET)CO_2 were continuously monitored. Blood gases were analyzed at the beginning and 1, 2 and 3 h of experiment. The animals were sacrificed at 3 h of experiment. The lungs were removed for microscopic examination. The pathological changes of the lung were scored (0 = normal,3 = severe change) . Wet/dry lung weight ratio was determined. The left lung was lavaged. The broncho-alveolar lavage fluid (BALF) was collected. WBCs in BALF were counted. Pulmonary albumin permeability (PAP) (BALF protein concentration/plasma protein concentration) was determined. Plasma TNF-a and macrophage inflammatory protein 2 (MIP-2) concentrations were detected with ELISA. The endotoxin receptor CD14 mRNA expression in lung tissue was determined by RT-PCR and the macrophage CD14 expression in BALF was determined by immuno histochemistry in group C and M. Results Wet/dry lung weight ratio and PAP were significantly higher in group ML than in group M and C. WBC count in BALF, the pathological score and plasma MIP-2 concentration were significantly higher in group M and ML than in group C and were significantly higher in group ML than in group M. TNF-a concentration was significantly higher in group CL and ML and was not detected in group C and M. CD14mRNA expression in the lung tissue and CD14 expression in BALF macrophage were significantly higher in group M than in group C. Conclusion Minute amount of endogenous endotoxin from the lung can aggravate ventilator-induced lung injury in rats. Mechanical ventilation with large tidal volume sensitizes the lung to LPS stimulation through up-regulation of CD14 exexpression.