Objective To investigate the effect of long non-coding RNA growth arrest-specific transcript 5(lncRNA GAS5)on lung tissue cell apoptosis in acute lung injury(ALI)rats via regulation of the miR-452-5p/myeloid cell leukemia sequence 1(Mcl-1)pathway.Methods SD rats were randomly separated into 6 groups(10 in each group):control group,model group,pUC57 lncRNA GAS5 group,miR-452-5p antagonist group,pUC57 NC+miR-452-5p NC group,and pUC57 lncRNA GAS5+miR-452-5p agonist group.The ALI model was constructed via the intraperitoneal injection of lipopolysaccharide in the model group and drug intervention group,whereas the control group rats were intraperitoneally injected with an equal dose of physio-logical saline.At the same time,the intervention was performed,and the lung function of the rats was subsequently meas-ured.The forced vital capacity(FVC),forced expiratory volume in 0.3 second(FEV0.3)/FVC,and tidal volume(VT)were com-pared among the groups.HE staining was used to observe pathological damage in the lung tissue,and the degree of damage was evaluated via the Holfbauer score.An enzyme-linked immunosorbent assay(ELISA)was used to measure the levels of bronchoal-veolar lavage fluid(BALF)and the serum inflammatory factors interleukin-18 and IL-1β in the rats.Immunoblotting was used to detect the expression of pyroptosis-related indicator proteins[(GSDMD),nucleotide binding oligomeric domain-like receptor protein 3(NLRP3),cysteine-containing aspartate-specific protease(Caspase-1),and Caspase-11]and Mcl-1 in rat lung tissue.Real-time fluorescence quantitative PCR was used to detect the expression of lncRNA GAS5 and miR-452-5p in rat lung tissue.A dual-luciferase reporter gene experiment was performed to validate the targeted regulation of miR-452-5p by lncRNA GAS5 in rat alveolar epithelial cell L2.Results Compared with those in the control group,the FVC,FEV0.3/FVC,expression of lncRNA GAS5,expression of Mcl-1 protein and mRNA in the model group decreased(P＜0.05),and the VT,Holfbauer score,IL-18 and IL-1β levels,GSDMD,NLRP3,Caspase-1 and Caspase-11 protein expression,and miR-452-5p expression were elevated(all P＜0.05).Compared with those in the model group,the FVC,FEV0.3/FVC,expression of Mcl-1 protein and mR-NA in the pUC57 lncRNA GAS5 group and the miR-452-5p antagonist group were increased(all P＜0.05),and the VT,Holf-bauer score,IL-18 and IL-1β levels,GSDMD,NLRP3,Caspase-1 and Caspase-11 protein expression,and miR-452-5p expression were reduced(all P＜0.05).There was no obvious difference in various indicators in the pUC57-NC+miR-452-5p-NC group(all P＞0.05).Compared with those in the pUC57 lncRNA GAS5 group,the FVC,FEV0.3/FVC,expression of Mcl-1 protein and mRNA in the pUC57 lncRNA GAS5+miR-452-5p agonist group decreased(all P＜0.05),and the VT,Holfbauer score,IL-18 and IL-1β levels,GSDMD,NLRP3,Caspase-1 and Caspase-11 protein expression,and miR-452-5p expression were elevated(all P＜0.05).Conclusion lncRNA GAS5 can promote Mcl-1 expression by down-regulating miR-452-5p,thereby inhibiting the in-flammatory response and lung tissue cell pyroptosis in ALI rats,ultimately reducing lung injury and improving lung function.