胰岛素调控丝氨酸/苏氨酸蛋白激酶-1信号通路对急性肺损伤小鼠肺水肿的清除作用

Clearance effect of regulation of serine/threonine protein kinase-1 signaling pathway by insulin on pulmonary edema in mice with acute lung injury

目的 探讨胰岛素通过丝氨酸/苏氨酸蛋白激酶-1(serine/threonine protein kinase-1,SGK1)减轻急性肺损伤(acute lung injury,ALI)小鼠肺水肿的机制。方法 将32只雄性成年C3H/HeN小鼠随机分为对照组(仅泵入与治疗组等量的生理盐水)、ALI组(建模后持续泵入与治疗组等量的生理盐水)、治疗组[建立ALI模型后,持续经颈静脉泵入胰岛素0.1 U/(kg·h)]和SGK1 siRNA组[建立ALI模型后,持续泵入胰岛素0.1 U/(kg·h)的同时,给予SGK1 siRNA(75μg SGK1 siRNA稀释于100μL生理盐水中)],每组8只。8 h后处死小鼠,进行动脉血气分析(模型建立1 h后),并检测血糖变化情况(0、1、4、8 h);收集支气管肺泡灌洗液(bronchoalveolar lavage fluid,BALF),检测其中总蛋白含量,并测定肺泡上皮通透性和肺水含量;观察肺组织病理学改变和肺上皮细胞凋亡情况;Western blot法测定肺泡上皮钠通道(epithelial sodium channel,ENaC)和α_(1)-钠/钾ATP酶(α_(1)-Na^(+),K^(+)-ATPase)蛋白表达以及SGK1磷酸化水平。结果 泵入胰岛素后0、1、4、8 h,ALI与治疗组小鼠血糖水平差异均无统计学意义(t分别为1.330 0、0.986 0、0.565 7和0.724 3,P分别为0.204 7、0.340 7、0.580 6和0.480 8)。与ALI组比较,治疗组小鼠动脉血氧分压显著升高(t=6.026,P <0.000 1),BALF蛋白含量、肺泡上皮通透性、肺水含量和肺上皮细胞凋亡显著减少(t分别为7.39、5.286、5.651和3.312,P分别为<0.000 1、0.000 4、0.000 2和0.007 8),肺组织中α-ENaC和α_(1)-Na^(+),K^(+)-ATPase蛋白表达及SGK1磷酸化水平显著升高(t分别为26、18.67和8.547,P分别为<0.000 1、<0.000 1和0.000 1);与治疗组比较,SGK1 siRNA组小鼠BALF蛋白含量、肺泡上皮通透性、肺水含量和肺上皮细胞凋亡显著增加(t分别为5.964、3.449、3.148和3.520,P分别为0.000 2、0.006 2、0.010 4和0.016 9),α-ENaC和α_(1)-Na^(+),K^(+)-ATPase蛋白表达及SGK1磷酸化水平显著降低(t分别为13、9.874和7.741,P分别为<0.000 1、<0.000 1和0.001 5)。结论 外源性胰岛素能减轻ALI小鼠的肺水肿,其机制可能是通过SGK1上调α-ENaC和α_(1)-Na^(+),K^(+)-ATPase的表达实现。

Objective To investigate the mechanism of insulin alleviating pulmonary edema in mice with acute lung injury(ALI)by serine/threonine protein kinase-1(SGK1).Methods 32 male adult C3H/HeN mice were randomly divided into control group(only pumped with the same amount of normal saline as the treatment group),ALI group(continuously pumped with the same amount of normal saline as the treatment group after modeling),treatment group[continuously pumped with 0.1 U/(kg·h)of insulin through jugular vein after establishing ALI model]and SGK1 siRNA group[continuously pumped with 0.1 U/(kg·h)of insulin and given SGK1 siRNA(75μg SGK1 siRNA diluted in 100μL saline)simultaneously after establishing ALI model]with 8 mice in each group.After 8 h,the mice were killed for arterial blood gas analysis(1 h after establishment of the model)and the changes of plasma glucose levels were detected(0,1,4and 8 h);The bronchoalveolar lavage fluid(BALF)was collected to detect the content of total protein,and the alveolar epithelial permeability and lung water content were measured;The pathological changes of lung tissue and apoptosis of lung epithelial cells were observed;The protein expressions of alveolar epithelial sodium channel(ENaC)and α_(1)-Na^(+),K^(+)-ATPase and the phosphorylation level of SGK1 were determined by Western blot.Results There was no significant difference in plasma glucose level of ALI and treatment group at 0,1,4 and 8 h after insulin infusion(t=1.3300,0.9860,0.5657 and 0.7243,P=0.2047,0.3407,0.5806 and 0.4808,respectively).Compared with ALI group,the partial pressure of oxygen in arterial blood in treatment group increased significantly(t=6.026,P 0.0001),while the BALF protein content,alveolar epithelial permeability,lung water content and lung epithelial cells apoptosis decreased significantly(t=7.39,5.286,5.651 and 3.312,P 0.0001,=0.0004,=0.0002 and=0.0078,respectively),and the expression ofα-ENaC and α_(1)-Na^(+),K^(+)-ATPase and the phosphorylation level of SGK1 in lung tissue significantly increased(t=26,18.67 and 8.547,P 0.0001,0.0001 and=0.0001,respectively);Compared with the treatment group,the BALF protein content,alveolar epithelial permeability,lung water content and lung epithelial cells apoptosis increased significantly in SGK1 siRNA group(t=5.964,3.449,3.148 and 3.520,P=0.0002,0.0062,0.0104 and0.0169,respectively),whileα-ENaC and α_(1)-Na^(+),K^(+)-ATPase protein expression and SGK1 phosphorylation level decreased significantly(t=13,9.874 and 7.741,P 0.0001,0.0001 and=0.0015,respectively).Conclusion Exogenous insulin can alleviate the pulmonary edema in ALI mice,which might be mediated via up-regulation of the expressions ofα-ENaC andα_(1)-Na^(+),K^(+)-ATPase by SGK1.