Objective:To evaluate the relationship between inositol-requiring enzyme 1α-X box-binding protein 1 (IRE1α-XBP1) signaling pathway in endoplasmic reticulum and neutrophil extracellular traps during endotoxin-induced acute lung injury (ALI) in mice.Methods:Forty-eight SPF healthy male C57BL/6 mice, aged 6-8 weeks, weighing 25-30 g, were divided into 4 groups ( n=12 each) using a random number table method: control group (C group), STF-083010 group (ST group), lipopolysaccharide (LPS)-induced ALI group (ALI group) and LPS-induced ALI + STF-083010 group (ALI+ ST group). The ALI model was established by inhaling aerosolized LPS in ALI group and ALI+ ST group. The equal volume of aerosolized normal saline was inhaled in C and ST groups. IRE1α inhibitor STF-083010 50 mg/kg was intraperitoneally injected at 1 h before developing the model in ST and ALI+ ST groups, and the equal volume of normal saline was intraperitoneally injected in the other two groups. The mice were sacrificed after anesthesia at 24 h after developing the model. Bronchoalveolar lavage fluid (BALF) and lung tissues were collected for determination of the pathological changes (by light microscopy) which were scored, wet/dry lung weight (W/D) ratio, concentrations of interleukin-1beta (IL-1β), IL-18 and myeloperoxidase (MPO) in the BALF supernatant, and expression of phosphorylated IRE1α(p-IRE1α), XBP1s and citrullinated histone H3 (Cit H3) in lung tissues (using Western blot). Results:Compared to group C, the lung injury scores and W/D ratio were significantly increased at 24 h after developing the model, the concentrations of IL-1β, IL-18 and MPO in BALF were increased, and the expression of p-IRE1α, XBP1s and Cit H3 in lung tissues was up-regulated in ALI and ALI+ ST groups. Compared to group L, the lung injury scores and W/D ratio were significantly decreased at 24 h after developing the model, the concentrations of IL-1β, IL-18 and MPO in BALF were decreased, and the expression of p-IRE1α, XBP1s and Cit H3 in lung tissues was down-regulated in group ALT+ ST ( P<0.05). Conclusions:The IRE1α-XBP1 signaling pathway in endoplasmic reticulum is involved in endotoxin-induced ALI by up-regulating the expression of neutrophil extracellular traps in mice.