地塞米松对内毒素性肺损伤大鼠肺水通道蛋白1和5表达的影响

Effect of dexamethasone on the expression of aquaporin 1 and 5 in the LPS-induced lung injury in rats

目的探讨内毒素（LPS）所致急性肺损伤（ALI）大鼠肺水通道蛋白1、5（AQP1、AQP5）表达的变化及不同剂量地塞米松（DEX）对其干预作用。方法将Wistar大鼠随机分为五组：对照组（NC）、ALI组、三种剂量的DEX干预组（小剂量0．5mg／kg、中剂量1．0mg／kg、大剂量5．0mg／kg）。ALI组通过尾静脉注射LPS，干预组注射LPS后给予不同剂量的DEX，于2、6、12和24h采集标本。HE染色观察肺组织病理，测定肺湿／干质量比（W／D）、肺通透指数，ELISA检测血清TNF-α、MIP-1α水平；Western blot、免疫组化和Real—TimePCR法检测肺AQPl、AQP5蛋白和mRNA变化。结果与对照组比较，AL1组TNF—α、MIP—1α均明显升高（P〈0．01），至24h逐渐恢复；与ALI组比较，DEX干预各组上述炎症因子随时间延长逐渐下降（Pc0．05）。ALI组出现肺泡和间质水肿，炎性细胞浸润，以12h最明显；而DEX干预各组肺损伤病理明显减轻。经LPS处理各组肺W／D比值、肺通透指数均较对照组明显升高（P〈0．05），12h达峰值；与ALI组比较，DEX干预各组上述指标随时间延长逐渐下降（P〈0．05），但各干预组间比较差异无统计学意义（P〉0．05）。Au组各时间点肺AQP1及AQP5表达均较对照组明显下调（P〈0．01），以12h时间点下降最明显；与ALI组比较，DEX干预各组AQP表达上调，随时间延长，AQP表达逐渐恢复，但各干预组间比较差异无统计学意义（P〉0．05）。结论LPS能诱导大鼠ALI，DEX对肺损伤具有保护作用，其作用机制可能与DEX上调AQP1、AQP5的表达有关，与DEX剂量无量效关系。

Objective To investigate the expression changes of Aquaporin （AQP） 1, 5 in acute lung injury induced by lipopolysaccharide （LPS） and the effect of different doses of dexamethasone on them. Methods Wistar rats were randomly divided into 5 groups： control-group （NC）, acute lung injury （ALI） group, 3 doses of dexamethasone （DEX） intervention group （small dose 0.5 mg/kg, medium dose 1 mg/kg, large dose 5 mg/kg）. The ALI-group was injected with LPS by tail vein, and the intervention group was given DEX after LPS injection. Rats were sacrificed in 2, 6, 12 and 24 h, and the samples were collected after the successful modeling. Lung HE-staining morphological changes were observed; lung wet/dry weight ratio （W/D） and lung permeability index were detected; TNF-α, MIP-1α level were detected by ELISA methods. At the same time, AQP1, AQP5 protein and mRNA content changes were detected through Western blot, immunohistochemistry and real-time PCR. Results Comparedwith control group, the TNF-α, MIP-1α level in ALI group were significantly elevated at 2, 6 and 12 h （P 〈 0.01 ） , and gradually down to normal level to 24 h point. Compared with the ALI group, the inflammatory factors in Dex-intervention group were decreased gradually （P 〈 0.05）. In ALI-group, alveolar and interstitial edema and inflammatory cell infiltration were observed, 12 h was the most obvious but the pathological changes were significantly alleviated in Dex-group. The W/D and lung permeability index were significantly higher in LPS-group than those in the control-group （P 〈 0.05 ）, and reached the peak in 12 h, while the Dex-intervention group was significantly decreased （P 〈 0.05）, but there was no statistical significance among the three Dex-groups （P 〉 0.05）. The expression of AQP1 and AQP5 was significantly lower in ALI-group than that in control-group （P 〈 0.01 ）, and the most obvious decline in 12 h points while the expression of AQPs was significantly increased in Dex-group than that in ALI-group, but there was no statistical significance among the three Dex-groups （P 〉 0.05）. Conclusion LPS can induce rats acute lung injury. Dexamethasone has a protective effect on lung inju- ry, the mechanism of action may be related to the increase expression of AQP1 and AQP5, while has not dose-effect relationship with dexamethasone.