β - sitosterol promotes the SUMOylation of DRP1 in alveolar macrophages and alleviates sepsis-associated acute lung injury.

Acute lung injury (ALI) represents the most frequent complication of sepsis; however, effective drug-based interventions are still unavailable. β-sitosterol (BS) has demonstrated anti-inflammatory effects and protective properties on alveolar epithelial barriers. This study investigated the mechanism by which BS targets alveolar macrophages to attenuate sepsis-associated acute lung injury (SALI) via in vivo and in vitro experiments. Sepsis was induced in mice through cecal ligation and puncture (CLP), and BS was administered orally. An in vitro model of lipopolysaccharide (LPS)-induced MH-S cell infection validated the proposed mechanism. Macrophage polarization and mitochondrial function were assessed using flow cytometry, electron microscopy, and Western blot analysis. Results showed that BS suppressed reactive oxygen species (ROS) production and M1 macrophage polarization in LPS-stimulated MH-S cells. Mechanistically, BS promoted lysosomal degradation of dynamin-related protein 1 (DRP1) via SUMO2/3-mediated SUMOylation, preserving mitochondrial integrity and function. Transfection of MH-S cells with DRP1 plasmid abolished the BS-mediated mitochondrial protection mechanism, reducing inhibition of oxidative stress and M1 polarization. In summary, BS inhibits M1 polarization of alveolar macrophages by promoting DRP1 SUMOylation, effectively alleviating SALI in mice. These findings support BS as a potential therapeutic agent for SALI, providing a theoretical basis for clinical application.