RIP3 dependent NLRP3 inflammasome activation is implicated in acute lung injury in mice

Background: NLRP3 inflammasome is involved in the inflammatory responses during acute lung injury (ALI). RIP3 triggered NLRP3 inflammasome activation independent of necroptosis induction has recently been documented. In this study, the role of RIP3 in the activation of NLRP3 inflammasome in the development of ALI was investigated. Methods: A selective RIP3 inhibitor GSK872 was used to investigate the roles of RIP3 in NLRP3 inflammasome activation in the lipopolysaccharide (LPS) induced ALI mouse model. The mechanism of NLRP3 inflammasome activation was investigated in the human monocytic cell line THP-1. NLRP3 inflammasome and necroptosis were measured by flow cytometry or western blot. RIP3-NLRP3 interaction was interrogated using immunoprecipitation and the Duolink (R) In situ detection. Results: Significant upregulation of both necroptosis and NLRP3 inflammasome pathways were observed in the lungs of mice with LPS induced ALI. GSK872 significantly suppressed the activation of necroptosis and NLRP3 activation with reduction of IL-1 beta and IL-18 production and inflammatory cells infiltration, resulting in a significant amelioration of lung injury. These two processes were shown to be active in interstitial macrophages and CD11b(+) monocyte-macrophages/dendritic cells. In THP-1 cells, RIP3 and NLRP3 interaction was enhanced by LPS/ATP stimulation resulting in IL-1 beta and IL-18 production. This RIP3-NLRP3 interaction was significantly inhibited by GSK872. Conclusion: Taking together, these results show that RIP3 participates in the NLRP3 inflammasome activation in infiltrating macrophages in ALI induced by LPS. This process plays a significant pathogenic role in LPS-induced lung injury.