目的 考察右美托咪定（Dex）对脂多糖（LPS）诱导的大鼠急性肺损伤（ALI）的影响，并探讨可能与PI3K/Akt信号通路改变的相关机制。方法 将80只SD大鼠根据建模方法随机分为5组：对照组、模型组、Dex低剂量组、Dex高剂量组、Dex+LY294002组，建模24 h时处死并分离肺组织，观察组织病理切片，检查肺水肿程度及微血管通透性，采用Western blotting法检测Akt及其磷酸化蛋白以及线粒体凋亡信号相关蛋白的表达水平，检查线粒体细胞色素C、膜电位及ATP含量，并用电镜观察线粒体形态，采用流式细胞术检测肺组织细胞凋亡情况，采用DCFH-DA探针荧光显微镜法检测细胞内的活性氧（ROS）水平。结果 LPS滴注24 h后，病理切片表现有明显的ALI特征，Dex在50 μg/kg剂量时可明显改善LPS诱导的ALI病理特征；以对照组为参照，p-Akt（Thr308）与p-Akt（Ser473）的相对表达量模型组未发生明显变化，Dex组则均显著增高（P<0.001），在Dex+LY294002组的表达水平较Dex组显著降低（P<0.001）；模型组的Bax与Bcl-2蛋白较对照组的相对表达量分别显著升高与降低（P<0.001），Dex组分别降低与升高至接近对照组水平，Dex+LY294002组又分别回升与回降；对照组、模型组、Dex组、Dex+LY294002组的肺组织细胞凋亡率分别为2.4%、19.5%、6.7%、13.1%；各组的ROS水平变化与肺组织细胞凋亡情况一致性良好。结论 Dex可通过激活PI3K/Akt信号通路减轻LPS诱导的肺组织细胞凋亡及线粒体凋亡信号激活，继而改善ALI，发挥肺保护作用。

Objective To investigate the effect of dexmedetomidine (Dex) on LPS-induced acute lung injury (ALI) in rats, and to explore the possible mechanism of PI3K/Akt signaling pathway changes. Methods Eighty SD rats were randomly divided into five groups:control group, model group, Dex low-dose group, Dex high-dose group and Dex + LY294002 group. After 24 h of modeling, the lung tissues were separated. Histopathological sections were observed to examine the degree of pulmonary edema and microvascular permeability. Western blotting was used to detect the expression of Akt, its phosphorylated protein and mitochondrial apoptotic signal-related protein. The levels of cytochrome C, membrane potential and ATP in mitochondria were examined. The morphology of mitochondria was observed by electron microscopy. The apoptosis of lung cells was detected by flow cytometry. The ROS level in cells was detected by DCFH-DA probe fluorescence microscopy. Results After 24 h of LPS infusion, the pathological sections showed obvious ALI characteristics. Dex could significantly improve the pathological characteristics of LPS-mediated ALI at the dose of 50 ug/kg. Compared with the control group, the relative expression of p-Akt (Thr308) and p-Akt (Ser473) did not change significantly in model group, but increased significantly in Dex group (P<0.05), and the expression level of p-Akt (Thr308) and p-Akt (Ser473) in Dex + LY294002 group was significantly lower than that in the Dex group (P<0.05). The relative expression of Bax and Bcl-2 protein in model group was significantly higher and lower than that in control group (P<0.05). The expression of Bax and Bcl-2 protein in Dex group was lower and higher than that in model group, while that in Dex +LY294002 group was higher and lower. The apoptotic rates of lung tissue in control group, model group, Dex group and Dex +LY294002 group were 2.4%, 19.5%, 6.7% and 13.1% respectively, the changes of ROS levels in each group were in good agreement with the apoptosis of lung cells. Conclusion Dex can alleviate LPS-mediated apoptosis of lung tissue and mitochondrial apoptosis by activating PI3K/Akt signaling pathway, and then improve ALI to play a protective role in lung.

R974

河南省医学科技攻关计划项目（2018020351）