Neutrophil-derived exosomes promote sepsis-related multiple organ dysfunction through the induction of neutrophil extracellular trap formation.

Our previous studies have demonstrated that neutrophils play a key role in septic organ injury partly through the excessive formation of neutrophil extracellular traps (NETs) and that exosomes participate in the regulation of NET formation during sepsis. Therefore, this study aimed to determine whether neutrophil-derived exosomes promote the formation of NETs and induce multiple organ dysfunction during sepsis. Initially, polymorphonuclear neutrophil (PMN)-derived exosomes following in vitro stimulation with PBS or LPS (1 μg/mL) for 6 h. In vivo, PMN-derived exosomes were intravenously administered to wild-type C57BL/6 mice. Then, histopathological injury and NET formation in multiple organs were evaluated. In vitro, PMN-derived exosomes were cocultured with PMNs freshly isolated from healthy volunteers, and subsequently, NET formation and activation of associated molecular pathways were detected. Administration of LPS-stimulated PMN-derived exosomes in mice significantly enhanced NET formation, resulting in multi-organ inflammation and tissue injury. In vitro coculture experiments also demonstrated that exosomes from LPS-stimulated PMNs promote ROS-dependent NET formation. Proteomic analysis revealed enrichment of matrix metalloproteinase 9 (MMP9) expression in exosomes from LPS-stimulated PMNs, and further mechanistic investigations showed that exosomal MMP9 induced NET formation through the p38 MAPK pathway. Clinical data analysis suggests a close association between sepsis severity/prognosis and plasma-derived exosomal MMP9 expression levels. PMN-derived exosomes facilitate the excessive formation of NETs in sepsis, leading to the subsequent development of multiple organ dysfunction. This discovery reveals a novel role for PMN-derived exosomes in the pathogenesis of sepsis-related multiple organ dysfunction and suggests their potential as prognostic indicators for this condition.