[Role of autophagy in liver injury induced by lung ischemia/ reperfusion in rats].

Objective: To investigate the liver injury induced by lung ischemia / reperfusion(LI/R) and the role of autophagy in its prevention and treatment. Methods: The lung ischemia/reperfusion injury(LI/RI) model was prepared by anesthetizing the rats, cutting the trachea for mechanical ventilation, and using an arterial clamp to close the pulmonary hilum to simulate the ischemic process, and releasing the arterial clamp after 30 min to resume perfusion for 3 h. SD rats(n=24)were randomly divided into sham operation(sham)group,ischemia/reperfusion(I/R)group,solvent(DMSO)group and autophagy inhibitor (3-MA) group, 6 rats in each group. The rats were intraperitoneally injected with medicine before operation. After the rat LI/RI model was established,the rats were killed, and the lung wet/dry weight ratio was used to evaluate the success of modeling, the venous blood was collected to measure the contents of ALT and AST, and the liver tissues were collected. Light and electron microscopes were used to observed the liver tissues and cell shapes. The protein and mRNA expression levels of autophagy related proteins were determined by Western blot and RT-qPCR to suggest autophagy levels. Results: Compared with sham group, the lung wet/dry weight ratios in other groups were elevated, and the liver tissues of other groups were damaged significantly. Serum levels of AST and ALT were increased significantly and liver tissue damage was obvious, especially in I/R group. The light microscopy showed that the arrangement of hepatic cords was disordered or broken, hepatic sinuses were dilated, and edema of liver cells were observed; transmission electron microscopy showed varying degrees of mitochondria swelling up in liver cells in the other groups. At the same time, the expressions of AMPK, Beclin 1 and LC3 mRNA were increased, but the expressions of mTOR and p62 mRNA were decreased; the protein expressions of p-AMPK, Beclin 1, LC3-B were increased significantly, but those of p-mTOR and p62 were decreased (all P＜0.05). Compared with DMSO group, the injury of liver tissue in 3-MA group was alleviated, the damage degree of mitochondrial ultrastructure was lower, the levels of AST and ALT were decreased, the transcription and protein expression levels of autophagy related protein in liver tissue were decreased (P＜0.05). However, the injury degree of IR and DMSO groups were similar, and there was no significant differences in each index (P＞0.05). Conclusion: Lung ischemia/reperfusion can cause liver injury in rats. Autophagy can mediate liver injury induced by lung ischemia / reperfusion in rats and inhibiting autophagy can effectively reduce liver injury induced by LI/R in rats.目的: 探讨肺缺血/再灌注(LI/R)时肝脏损伤的影响,并初步探索细胞自噬(Autophagy)在其中发挥的作用。方法: 构建大鼠缺血/再灌注肺损伤(LI/RI)模型,模型制备方法为大鼠麻醉后切开气管进行机械通气,使用动脉夹将肺门夹闭模拟缺血过程,30 min后松开动脉夹,恢复灌注3 h。24只大鼠随机分为伪手术组(Sham组)、缺血/再灌注组(I/R组)、溶剂组(DMSO组)和自噬抑制剂组(3-MA组),每组均6只,后2组大鼠术前分别腹腔注射DMSO和3-MA,造模结束后使用肺湿/干重比判断造模是否成功;抽取静脉血测定肝脏转氨酶指标ALT与AST;取肝脏组织,光镜下观察肝脏形态改变,以及电镜下观察肝细胞超微结构;使用RT-qPCR和Western blot实验分别检测肝脏组织细胞中自噬相关蛋白的基因mRNA表达水平和蛋白表达水平。结果: 与Sham组相比,其余各组肺湿/干重比均升高;血AST和ALT均有大幅升高且肝脏组织损伤明显,其中以I/R组升高最为明显,光镜下组织形态学及电镜下细胞微细结构均有不同程度的破坏;肝脏中自噬相关蛋白的基因表达水平与蛋白表达水平均有明显不同,表现为自噬上升 (P＜0.01或P＜0.05)。I/R组和DMSO组肝脏组织均有较重损伤,肝细胞结构破坏严重,自噬小体形成,而AST、ALT、自噬相关蛋白转录和表达水平等各项指标均无统计学差异(P＞0.05)。而相较于DMSO组,3-MA组肝脏组织损伤有所减轻,肝细胞微细结构损伤程度低,且无自噬小体形成,血中AST和ALT下降,肝脏组织内自噬水平均下降 (P＜0.05)。结论: 肺缺血/再灌注可引起大鼠肝损伤;细胞自噬可介导大鼠肺缺血/再灌注引起的肝损伤,抑制细胞自噬可以有效减轻大鼠LI/R引起的肝损伤。.