HUVEC-derived exosomes alleviate lipopolysaccharide-induced acute lung injury inflammation by restoring the balance of mitochondrial fusion and division

BACKGROUND: Sepsis is a life-threatening condition with high morbidity and mortality, where acute lung injury (ALI) is one of the earliest and most severe complications. Macrophage-mediated overactivation of inflammation and subsequent release of pro-inflammatory cytokines cause significant damage to pulmonary epithelial cells, playing a critical role in the progression of sepsis-induced ALI. This study successfully investigated the role of HUVEC-derived exosomes in the treatment of ALI and designed a novel engineered vesicle for therapeutic application. RESULTS: We successfully isolated and characterized HUVEC-derived exosomes. These exosomes were found to reduce inflammatory cytokine release from macrophages and restore the viability of lung epithelial cells. Furthermore, extracellular vesicles derived from HUVECs effectively suppress proinflammatory cytokine release from M1-polarized macrophages. Significantly, HUVEC-derived exosomes improved the balance between mitochondrial fusion and fission, reducing the release of mitochondrial DNA (mtDNA) and nuclear translocation of NF-κB. miRNA profiling and subsequent inhibition experiments identified miR-520d-3p as a key factor delivered by HUVEC exosomes. This miRNA was shown to decrease the expression of MARCH5, inhibiting ubiquitination of the mitochondrial fusion protein Mfn1, thus promoting mitochondrial fusion and reducing mtDNA release. In addition, we designed and synthesized a novel engineered vesicle, exosome@IPR, by encapsulating ipratropium bromide within HUVEC-derived exosomes to target mitochondrial fusion. This engineered vesicle significantly reduced lung injury and improved the survival rate in mice. CONCLUSION: Our findings uncover a novel therapeutic mechanism by which miR-520d-3p delivered via HUVEC-derived exosomes alleviates inflammation in sepsis-induced ALI. This occurs through modulation of mitochondrial dynamics, specifically by restoring the balance between mitochondrial fusion and fission, thereby mitigating macrophage-induced lung injury in sepsis. Our findings revealed that extracellular vesicles derived from HUVECs act as a natural therapeutic agent by restoring the balance between mitochondrial fusion and fission. Building on this, we designed and synthesized an engineered vesicle named exosome@IPR that more effectively reverses the LPS-induced imbalance in mitochondrial dynamics, reduces inflammation, and improves survival in mice.