Sirtuin 3 attenuates sepsis-induced acute lung injury by suppressing NF-κB/NLRP3/GSDMD-mediated pyroptotic signaling

BACKGROUND Sepsis is a major global health threat and frequently leads to acute lung injury (ALI). Pyroptosis has been increasingly implicated in the inflammatory progression of sepsis-induced ALI. Sirtuin 3 (Sirt3), a mitochondrial deacetylase, can regulate inflammatory injury and cellular stress responses. However, its role in sepsis-induced ALI and pulmonary pyroptosis remains incompletely understood. METHODS Sirt3 expression was measured in peripheral blood mononuclear cells (PBMCs) and neutrophils from septic patients (n=10) and healthy controls (n=5). Wild-type (WT) and Sirt3 knockout (Sirt3^-/- ) mice were subjected to cecal ligation and puncture (CLP). Lung injury, inflammatory responses, transcriptomic changes, and nuclear factor-κB (NF-κB)/NLRP3/gasdermin D (GSDMD)-related signaling were evaluated. In vitro, human umbilical vein endothelial cells (HUVECs) were used to assess the effects of Sirt3 knockdown and overexpression on lipopolysaccharides (LPS)/nigericin-induced pyroptotic injury. RESULTS Sirt3 expression was reduced in circulating immune cells from septic patients. In mice, CLP decreased pulmonary Sirt3 expression, and Sirt3 deficiency aggravated lung histological injury, pulmonary edema, and systemic inflammatory responses. Transcriptomic analysis revealed enrichment of immune- and pyroptosis-related pathways in septic lungs from Sirt3^-/- mice. Consistently, Sirt3 deficiency increased NF-κB/NLRP3/GSDMD-associated signaling, as shown by increased p-NF-κB/NF-κB, NOD-like receptor family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC), cleaved caspase-1, N-terminal gasdermin D (N-GSDMD), and GSDMD levels. In HUVECs, Sirt3 knockdown exacerbated LPS/nigericin-induced cell injury, whereas Sirt3 overexpression preserved cell viability and reduced lactate dehydrogenase (LDH) release. CONCLUSION Sirt3 downregulation is associated with aggravated sepsis-induced ALI and enhanced NF-κB/NLRP3/GSDMD-related pyroptotic signaling. These findings suggest that Sirt3 may serve as a potential regulatory node in endothelial inflammatory injury during sepsis-induced ALI.