SIRT4 knockout exacerbates lung injury in septic mice by activating TLR4/MYD88/NFκB pathway

Sepsis-induced acute lung injury (ALI) is a major cause of patient mortality, and its pathological mechanism is closely associated with dysregulated inflammatory responses. SIRT4 is a mitochondrial-localized deacylase whose role in metabolism regulation is well-established; however, its specific function and molecular mechanism in septic lung injury remain unclear. This study aims to investigate the role of SIRT4 in septic lung injury and its underlying regulatory mechanism.

Sepsis models were established in C57 and SIRT4^-/- mice using cecal ligation and puncture (CLP). Mice survival rates, lung wet/dry weight ratios, histopathological injury, apoptosis, and inflammatory cytokine expression were assessed. In vitro, human alveolar epithelial cells (A549) were stimulated with lipopolysaccharide (LPS) to simulate an inflammatory environment. Key signaling pathways were screened via transcriptome sequencing (RNA-seq), and validated using Western blot and immunofluorescence assays.

The expression of SIRT4 was significantly downregulated in both lung tissues of CLP mice and A549 cells stimulated with LPS. Compared with C57 mice, SIRT4^-/- mice exhibited decreased survival, more severe lung tissue damage, and excessive release of pro-inflammatory cytokines after CLP surgery. Transcriptomic and molecular biological analyses revealed that SIRT4 deficiency markedly activated the TLR4/MYD88/NF-κB inflammatory signaling pathway. Ex-vivo experiments further confirmed that knocking down SIRT4 expression enhanced LPS-induced activation of the TLR4/MYD88/NF-κB pathway; conversely, inhibition of TLR4 effectively reversed both NF-κB translocation and cellular injury resulting from SIRT4 deficiency.

This study demonstrates that SIRT4 knockout exacerbates lung injury in septic mice by activating the TLR4/MYD88/NF-κB signaling pathway, suggesting that SIRT4 may serve as a potential therapeutic target for sepsis-associated lung injury.