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目的:探讨氯化钡（BaCl 2）预处理是否对脂多糖（LPS）诱导的急性呼吸窘迫综合征（ARDS）小鼠具有保护作用及其可能的作用机制。 方法:将60只8~12周龄健康C57BL/6雄性小鼠随机分为假手术组、ARDS模型组和BaCl 2预处理组，每组20只。BaCl 2预处理组提前3 d连续经尾静脉注射BaCl 2 4 mg/kg，其余两组不进行预处理。采用气管内滴注LPS 3 mg/kg的方法制备小鼠ARDS模型；假手术组则给予等体积0.9%生理盐水。制模成功后24 h，将部分小鼠处死取肺组织，分离右肺下叶于光镜下观察各组小鼠肺组织病理改变，取小鼠剩余肺组织称重，观察各组小鼠肺组织湿/干质量（W/D）比值；部分小鼠经尾静脉注射伊文思蓝（EB），2 h后处死取肺组织，观察肺微血管通透性变化；剩余小鼠行肺泡灌洗，采用酶联免疫吸附试验（ELISA）检测支气管肺泡灌洗液（BALF）中肿瘤坏死因子-α（TNF-α）水平变化。 结果:与假手术组比较，ARDS模型组小鼠表现出典型的ARDS病理变化，该组小鼠肺W/D比值明显升高（4.951±0.161比3.449±0.299， P<0.01），每克肺组织中EB含量明显增加（μg/g：0.130±0.027比0.085±0.011， P<0.01），光镜下显示肺泡壁结构被明显破坏、肺淤血及肺泡内渗出液明显增多、炎症细胞大量浸润，肺损伤病理评分明显升高（分：10.33±1.15比1.67±0.58， P<0.01），BALF中TNF-α水平明显升高（ng/L：900.85±247.80比68.21±5.79， P<0.01）。与ARDS模型组比较，BaCl 2预处理组小鼠肺W/D比值明显降低（4.620±0.125比4.951±0.161， P<0.01），每克肺组织中EB含量明显减少（μg/g：0.108±0.011比0.130±0.027， P<0.01），光镜下显示肺组织损伤程度较ARDS模型组减轻，肺损伤病理评分明显降低（分：5.00±1.00比10.33±1.15， P<0.01），BALF中TNF-α水平明显降低（ng/L：169.16±73.33比900.85±247.80， P<0.01）。 结论:BaCl 2预处理可通过减轻肺毛细血管通透性和局部炎症反应改善LPS诱导的ARDS模型小鼠的肺组织病理学改变，对ARDS小鼠具有保护作用。

Objective:To explore whether barium chloride (BaCl 2) preconditioning has the protective effect on lipopolysaccharide (LPS)-induced acute respiratory distress syndrome (ARDS) model in mice and the possible mechanism. Methods:Sixty 8-12 week old healthy C57BL/6 male mice were randomly divided into control group, ARDS model group and BaCl 2 pretreatment group, with 20 mice in each group. The BaCl 2 pretreatment group was continuously injected with BaCl 2 (4 mg/kg through the tail vein) for 3 days before ARDS model establishment. ARDS model was established by intratracheally injecting (3 mg/kg) LPS. The control group was intratracheally given the same volume of 0.9% normal saline. On 24th hour after ARDS model establishment, some mice were sacrificed for obtaining fresh lung tissue. And the right lower lobe of the lung was separated for observing the pathological changes of lung tissue while the left lung tissue was used to measure the wet/dry weight ratio (W/D) of the lung. Some mice were sacrificed for observing pulmonary microvascular permeability at 2nd hours after injecting Evans blue (EB) through tail vein. The left mice were killed for alveolar lavage to measure the levels of tumor necrosis factor-α (TNF-α) via enzyme linked immunosorbent assay (ELISA). Results:Comparing with the control group, ARDS model group showed typical ARDS pathological changes, which included the increased W/D ratio (4.951±0.161 vs. 3.449±0.299, P < 0.01) and the content of EB in the lung tissue (μg/g: 0.130±0.027 vs. 0.085±0.011, P < 0.01), the damaged alveolar wall structure, lung congestion and exudates in the alveoli, as well as amounts of inflammatory cells. The pathological score of lung injury (10.33±1.15 vs. 1.67±0.58) and the level of TNF-α in BALF (ng/L: 900.85±247.80 vs. 68.21±5.79) were significantly increased in the ARDS model group (both P < 0.01). Comparing with the ARDS model group, the lung W/D ratio (4.620±0.125 vs. 4.951±0.161) and the EB content in the lung tissue (μg/g: 0.108±0.011 vs. 0.130±0.027) of BaCl 2 pretreatment group were significantly reduced (both P < 0.01). And the damaged pulmonary structural BaCl 2 pretreatment group were significantly alleviated. In addition, the pulmonary pathological score (5.00±1.00 vs. 10.33±1.15) and the level of TNF-α in BALF (ng/L: 169.16±73.33 vs. 900.85±247.80) were significantly decreased (both P < 0.01). Conclusion:Barium chloride pretreatment can improve the lung histopathological changes of ARDS model mice induced by LPS by reducing the permeability of pulmonary capillaries and local inflammatory reaction.Barium chloride has the protective effect against LPS attack in mice model of ARDS.