Inhibition of IRE1α/XBP1 axis alleviates LPS-induced acute lung injury by suppressing TXNIP/NLRP3 inflammasome activation and ERK/p65 signaling pathway

BackgroundAcute lung injury or acute respiratory distress syndrome (ALI/ARDS) is a devastating clinical syndrome with high incidence and mortality rates. IRE1 alpha-XBP1 pathway is one of the three major signaling axes of endoplasmic reticulum stress that is involved in inflammation, metabolism, and immunity. The role and potential mechanisms of IRE1 alpha-XBP1 axis in ALI/ARDS has not well understood.MethodsThe ALI murine model was established by intratracheal administration of lipopolysaccharide (LPS). Hematoxylin and eosin (H&E) staining and analysis of bronchoalveolar lavage fluid (BALF) were used to evaluate degree of lung injury. Inflammatory responses were assessed by ELISA and RT-PCR. Apoptosis was evaluated using TUNEL staining and western blot. Moreover, western blot, immunohistochemistry, and immunofluorescence were applied to test expression of IRE1 alpha, XBP1, NLRP3, TXNIP, IL-1 beta, ERK1/2 and NF-kappa B p65.ResultsThe expression of IRE1 alpha significantly increased after 24 h of LPS treatment. Inhibition of the IRE1 alpha-XBP1 axis with 4 mu 8C notably improved LPS-induced lung injury and inflammatory infiltration, reduced the levels of IL-6, IL-1 beta, and TNF-alpha, and decreased cell apoptosis as well as the activation of the NLRP3 inflammasome. Besides, in LPS-stimulated Beas-2B cells, both 4 mu 8C and knockdown of XBP1 diminished the mRNA levels of IL-6 and IL-1B, inhibited cell apoptosis and reduced the protein levels of TXNIP, NLRP3 and secreted IL-1 beta. Mechanically, the phosphorylation and nuclear translocation of ERK1/2 and p65 were significantly suppressed by 4 mu 8C and XBP1 knockdown.ConclusionsIn summary, our findings suggest that IRE1 alpha-XBP1 axis is crucial in the pathogenesis of ALI/ARDS, whose suppression could mitigate the pulmonary inflammatory response and cell apoptosis in ALI through the TXNIP/NLRP3 inflammasome and ERK/p65 signaling pathway. Our study may provide new evidence that IRE1 alpha-XBP1 may be a promising therapeutic target for ALI/ARDS.