Saquinavir inhibits pyroptosis by regulating NLRP3 degradation to alleviate acute lung injury

BACKGROUND: In critically ill patients, sepsis can precipitate acute lung injury (ALI), a syndrome with high incidence in intensive care settings. Pyroptosis plays an important role in ALI, highlighting its potential as a drug target. The NLRP3-mediated classical pyroptosis pathway is notably implicated in this pathogenesis. Saquinavir (SQV), the first HIV protease inhibitor, is well-documented for its antiviral properties. However, its influence on macrophage pyroptosis during sepsis-induced ALI has not been fully elucidated. METHODS: To investigate the role of SQV in sepsis-induced ALI, in vitro models of pyroptosis in macrophage were established using PMA-differentiated human THP-1 macrophages and mouse RAW264.7 cells stimulated with LPS plus Nigericin. The effects of SQV on the NLRP3-mediated pyroptosis pathway and NLRP3 ubiquitination levels were assessed by ELISA, flow cytometry, confocal microscopy, western blotting, co-immunoprecipitation (Co-IP), and cellular thermal shift assay (CETSA). In vivo, a mouse model of sepsis-induced ALI was established by cecal ligation and puncture (CLP) to evaluate the effects of SQV on lung injury, inflammatory cytokines, the NLRP3 pyroptosis pathway, survival rate. The NLRP3 level in lung macrophages was detected by immunofluorescence staining. RESULTS: In vitro studies demonstrated that SQV inhibited macrophage pyroptosis by reducing NLRP3 protein levels. Further investigation revealed that SQV promoted NLRP3 ubiquitination and degradation by targeting OTUD6A, thereby suppressing macrophage pyroptosis mediated by the NLRP3-caspase-1-GSDMD cascade. In vivo experiments showed that, by suppressing the NLRP3-caspase-1-GSDMD signaling cascade, SQV improved survival rate in a murine model of sepsis-induced ALI, reduced levels of inflammatory cytokines, decreased lung histopathological scores, and inhibited pyroptosis in lung macrophages. CONCLUSIONS: SQV alleviates sepsis-induced ALI by targeting OTUD6A to promote NLRP3 ubiquitination and degradation, thereby inhibiting macrophage pyroptosis via the NLRP3-caspase-1-GSDMD axis.