〔Abstract〕 Objective To explore the mechanism of ferroptosis induced by endoplasmic reticulum stress(ERs) in acute respiratory distress syndrome(ARDS).Methods In order to determine the effects of LPS on oxidative stress and Fe2+level of mouse capillary alveolar epithelial cells(MLE12 cells),the cells were treated with LPS(0,1,2,5 μg/ml) for 24 h.To verify the role of ferroptosis in lipopoly saccharide(LPS)-induced cell death,MLE12cells were divided into control(Con) group,iron removal inhibitor(Fer-1) group,LPS group and LPS+Fer-1group.LPS+Fer-1 group was pretreated with 10 μmol/L Fer-1 for 6 h,then the cells were exposed to 5 μg/ml LPS for 24 h.Con group was treated with solvent DMSO for 24 h.Fer-1 group was pretreated with 10 μmol/L Fer-1 for 6 h,and then treated with DMSO for 24 h.The cells in LPS group were exposed to 5 μg/ml LPS for 24 h.The MLE12 cells were divided into three groups:Con+Vector group,Con+sequence similarity family 134 member B(FAM134B) group,LPS+Vector group and LPS+FAM134B group.After transfected with vector or FAM134B overexpression plasmid for 48 h,the cells were exposed or not exposed to 5 μg/ml LPS for 24 h.Cell viability was measured by CCK-8.The levels of malondialdehyde(MDA),glutathione and iron,the protein levels of ferroptosis markers [cyclooxygenase 2(PTGS2),glutathione peroxidase 4(GPX4)] and ERs markers [glucose regulatory protein 78(GRP78),activated transcription factor 4(ATF4) and C/EBP homologous protein(CHOP)]were measured in different groups.In order to further confirm the results of in vitro cell experiments,40 mice were randomly divided into Con+Vector group,Con+FAM134B group,LPS+Vector group and LPS+FAM134B group,with 10 mice in each group.LPS-induced sepsis models were established in LPS+Vector group and LPS+FAM134B group,and the levels of GPX4 and ERs in lung tissue were evaluated by immunofluorescence staining and protein blot.Results LPS treatment increased the levels of PTGS2 and MDA,and decreased the levels of GPX4 and GSH in MLE12 cells in a dose-dependent manner.Compared with LPS group,the cell viability,GPX4and GSH levels in LPS+Fer-1 group increased significantly(P<0.05),while the PTGS2 protein level and MDA level decreased significantly(P<0.05).Compared with LPS+Vector group,LPS+FAM134B group significantly increased cell viability(P<0.05),decreased PTGS2 protein level(P<0.05) and increased GPX4 level(P<0.05).At the same time,the level of MDA in LPS+FAM134B group was lower than that in LPS+Vector group(P<0.05),and the level of GSH was higher than that in LPS+Vector group(P<0.05).In animal experiment,compared with LPS+Vector group,the expression levels of 4-HNE,ATF4 and CHOP in lung tissue of LPS+FAM134B group decreased significantly(P<0.05),and the expression levels of GPX4,FAM134B group increased significantly(P<0.05).Conclusion LPS induces ferroptosis and ERs in MLE12 cells in a dose-dependent manner.Activating the endoplasmic reticulum autophagy associated FAM134B receptor helps to inhibit ERs and alleviate cell ferroptosis.