USP48 promotes NLRP3-dependent pyroptosis of alveolar macrophages to exacerbate sepsis-induced acute lung injury.

BACKGROUND

Ubiquitination regulates diverse cellular processes and is implicated in various pathophysiological conditions, including sepsis-induced acute lung injury (ALI). Ubiquitin-specific peptidase 48 (USP48), a deubiquitinating enzyme, has been shown to promote pyroptosis in tumor cells. However, its role in sepsis-induced ALI has not been elucidated. This study aimed to investigate the function and underlying mechanism of USP48 in sepsis-induced ALI.

METHODS

A murine model of sepsis-induced ALI was established to assess USP48 expression in lung tissues. In parallel, USP48 levels were examined in lipopolysaccharide (LPS)-stimulated alveolar macrophages. USP48 was then knocked down both in vivo and in vitro to evaluate its functional role. Co-immunoprecipitation (Co-IP) was performed to examine the interaction between USP48 and NEK7. The effects of USP48 on NEK7 ubiquitination and stabilization were assessed in cell-based assays. To further delineate the mechanistic pathway, NEK7 was overexpressed following USP48 knockdown.

RESULTS

USP48 expression was significantly upregulated in the lung tissues of septic mice and in LPS-induced macrophages. In vivo knockdown of USP48 alleviated sepsis-induced ALI and reduced macrophage pyroptosis. In vitro, USP48 enhanced LPS-induced NLRP3 inflammasome activation and macrophage pyroptosis. Co-IP analysis confirmed a direct interaction between USP48 and NEK7. Mechanistically, USP48 promoted NEK7 stabilization by facilitating its deubiquitination. Furthermore, USP48-induced pyroptosis was dependent on NEK7-mediated NLRP3 inflammasome activation. In vivo, USP48 aggravated sepsis-induced ALI through the NEK7/NLRP3/caspase-1/GSDMD signaling axis.

CONCLUSIONS

USP48 exacerbates sepsis-induced ALI by promoting pyroptosis of alveolar macrophages through NEK7-mediated activation of the NLRP3 inflammasome, which is facilitated by USP48-induced deubiquitination of NEK7.