Objective: To investigate the protective effects of acetaldehyde dehydrogenase 2 (ALDH2) against lipopolysaccharide (LPS)- induced acute lung injury (ALI) in mice and explore the possible mechanisms.
Methods: Sixty C57BL/6J mice were equally randomized into Sham group, LPS group, LPS + Alda-1 (an ALDH2 agonist) group, and LPS + Daidzin (an ALDH2 inhibitor) group. After the treatment, the wet/dry lung mass ratio of the mice was measured, and the lung permeability was evaluated with Evans Blue (EB). The lung tissue pathologies were evaluated with HE staining and transmission electron microscopy. Serum levels of 4-hydroxynonenal (4-HNE) were measured with ELISA, and malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) levels were determined to measure oxidative stress levels. The expressions of ALDH2, ZO-1, Occludin, Mfn2, OPA1, Drp1, Fis1, and nuclear Nrf2 and HO-1 proteins in the lung tissues were detected using Western blotting.
Results: The mice with LPS-induced ALI showed severe disruption of the lung tissue structure and endothelial cell tight junctions with significantly increased the lung permeability (P<0.01), increased levels of 4-HNE and MDA (P<0.01), decreased activities of CAT and SOD (P<0.01), lowered expressions of ALDH2, ZO-1, Occludin, Mfn2, and OPA1 proteins, and increased expressions of Drp1, Fis1, and nuclear Nrf2 and HO-1 proteins (P<0.05, P<0.01). Treatment with Alda-1 significantly improved lung tissue pathologies and mitochondrial damage in ALI mice (P<0.01), increased the expressions of ALDH2, ZO-1, Occludin, OPA1, Mfn2, and nuclear Nrf2 and HO-1 proteins, and lowered the expressions of Drp1 and Fis1 proteins (P<0.05, P<0.01). Compared with Alda-1, treatment with Daidzin significantly increased the lung permeability, exacerbated mitochondrial damage, decreased the expression of ALDH2, ZO-1, Occludin, Mfn2, OPA1, and nuclear Nrf2 and HO-1 proteins, and increased expressions of Drp1 and Fis1 proteins (P<0.05, P<0.01).
Conclusion: ALDH2 can ameliorate LPSinduced lung endothelial barrier damage in ALI mice by maintaining the balance of mitochondrial dynamics and inhibiting oxidative stress, and the mechanism may be related to the Nrf2/HO-1 pathway.
目的: 探讨乙醛脱氢酶2(ALDH2)在脂多糖(LPS)致小鼠急性肺损伤(ALI)中的作用及潜在机制。
方法: 60只C57BL/6J小鼠随机分为Sham组、LPS组、LPS+ALDH2激动剂Alda-1组(LPS+Alda-1)、LPS+ALDH2抑制剂Daidzin组(LPS+ Daidzin), 15只/组。实验结束后检测肺湿干重比, 伊文思蓝(EB)检测渗透量; HE染色和透射电镜观察肺组织病理变化及超微结构改变; ELISA检测血清中4-羟基壬烯醛(4-HNE)的水平, 氧化应激试剂盒测定丙二醛(MDA)和超氧化物歧化酶(SOD)、过氧化氢酶(CAT)水平; Western blot检测ALDH2、紧密连接蛋白ZO-1、Occludin、线粒体融合蛋白Mfn2、OPA1和分裂蛋白Drp1、Fis1以及Nrf2核蛋白和HO-1蛋白的表达。
结果: 与Sham组相比较, LPS组小鼠肺组织湿干重比, EB渗透均增高(P<0.01);肺组织结构、内皮细胞间紧密连接及线粒体损伤严重; 4-HNE、MDA含量升高, CAT及SOD活性下降(P<0.01); ALDH2、紧密连接蛋白ZO-1和Occludin、线粒体融合蛋白Mfn2和OPA1表达降低, 而线粒体分裂蛋白Drp1和Fis1表达升高(P<0.05, P<0.01);此外, Nrf2核蛋白和HO-1蛋白表达均增高(P<0.01)。应用Alda-1干预后, 小鼠肺组织结构、内皮细胞间紧密连接及线粒体损伤明显改善(P<0.01);ALDH2、ZO-1、Occludin、OPA1和Mfn2蛋白表达增高, Drp1和Fis1蛋白表达降低(P<0.05, P<0.01);Nrf2核蛋白和HO-1蛋白表达均上调(P<0.05, P<0.01)。相比LPS+Alda-1组, LPS+Daidzin组肺部通透性增加, 线粒体损伤明显; 并伴有ALDH2、ZO-1、Occludin、Mfn2、OPA1、Nrf2核蛋白和HO-1蛋白表达降低, Drp1和Fis1蛋白表达升高(P<0.05, P<0.01)。
结论: ALDH2可通过维持线粒体动力学平衡, 抑制氧化应激, 改善LPS诱导的ALI小鼠肺内皮屏障损伤, 其机制可能与Nrf2/HO-1通路有关。
Keywords: Nrf2/HO-1; acetaldehyde dehydrogenase 2; acute lung injury; lipopolysaccharide; lung endothelial barrier damage; mitochondrial dynamics.