Corticosteroids alleviate lipopolysaccharide‐induced inflammation and lung injury via inhibiting NLRP3‐inflammasome activation

The role of corticosteroids in acute lung injury (ALI) remains uncertain. This study aims to determine the underlying mechanisms of corticosteroid treatment for lipopolysaccharide (LPS)‐induced inflammation and ALI. We used corticosteroid treatment for LPS‐induced murine ALI model to investigate the effect of corticosteroid on ALI in vivo. Moreover, LPS‐stimulated macrophages were used to explore the specific anti‐inflammatory effects of corticosteroids on NLRP3‐inflammasome in vitro. We found corticosteroids attenuated LPS‐induced ALI, which manifested in reduction of the alveolar structure destruction, the infiltration of neutrophils and the inflammatory cytokines release of interleukin‐1β (IL‐1β) and interleukin‐18 (IL‐18) in Lung. In vitro, when NLRP3‐inflammasome was knocked out, inflammatory response of caspase‐1 activation and IL‐1β secretion was obviously declined. Further exploration, our results showed that when corticosteroid preprocessed macrophages before LPS primed, it obviously inhibited the activation of caspase‐1 and the maturation of IL‐1β, which depended on inhibiting the nuclear factor‐κB (NF‐κB) signal pathway activation. However, when corticosteroids intervened the LPS‐primed macrophages, it also negatively regulated NLRP3‐inflammasome activation through suppressing mitochondrial reactive oxygen species (mtROS) production. Our results revealed that corticosteroids played a protection role in LPS‐induced inflammation and ALI by suppressing both NF‐κB signal pathway and mtROS‐dependent NLRP3 inflammasome activation.