Abstract: 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 LPS-induced 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.

Key words: acetaldehyde dehydrogenase 2; lipopolysaccharide; acute lung injury; lung endothelial barrier damage; mitochondrial dynamics; Nrf2/HO-1