Amelioration of acute lung injury by Salvia miltiorrhiza-derived extracellular vesicles: through repair of the vascular barrier and modulation of lung microbiota

BACKGROUND: Acute lung injury (ALI) is a severe respiratory disease characterized by diffuse lung injury, vascular barrier dysfunction, and inflammatory responses. Its current treatments such as corticosteroids often involve adverse effects, highlighting the need for alternative therapies. Salvia miltiorrhiza-derived extracellular vesicles (SMEVs) have shown a potential therapeutic value for ALI due to their anti-inflammatory and barrier-protective properties, but the specific mechanisms remain unclear. METHODS: SMEVs were extracted and purified through differential centrifugation coupled with sucrose density gradient centrifugation, and were analyzed by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Biosafety assessment was then conducted in zebrafish embryos, mouse organs, and human umbilical vein endothelial cells (HUVEC). Subsequently, the treatment efficacy of SMEV on LPS-induced HUVEC inflammation was evaluated in vitro. LPS-induced ALI mice were then treated with SMEVs to further evaluate the posttreatment lung histopathology, vascular barrier markers, and microbial composition using metagenomics in vivo. RESULTS: SMEVs exhibited a typical bilayer structure (average size: 177.7 nm) and excellent biosafety properties. In vitro, SMEVs effectively reduced LPS-induced inflammation (IL-1β, IL-6, TNF-α) and promoted wound healing in HUVEC, while in vivo, SMEVs ameliorated pulmonary edema and inflammation, and restored the VE-cadherin expression. Metagenomic analysis revealed that SMEVs were capable of regulating lung microbiota and reducing the pathogenic bacterial (e.g., g-Listeria, g-Streptococcus) and microbial diversity and richness after LPS stimulation. CONCLUSION: SMEVs can ameliorate ALI by repairing the vascular barrier and modulating lung microbiota, offering a novel therapeutic strategy for this disease. Future research may focus on the SMEV-microbiota-immune interaction targeting ALI treatment.