[ODP-175] Neutrophil-derived ectosomes with antibacterial potential ameliorate mouse sepsis
Sepsis is a life-threatening multiple organ dysfunction caused by systemic dysregulated inflammatory responses to infection. Since sepsis is still a major cause of mortality worldwide despite a large number of curative trials, we have been seeking for a novel effective therapeutic approach, using cecum ligation and puncture (CLP) septic mouse model. LL-37, a host-defense peptide, stimulated neutrophils to release extracellular vesicles (EV) including exosomes (50-200 nm in size) and ectosomes (200-1000 nm). The EV reduced the bacterial burden and mitigated inflammatory responses in CLP mice. In particular, ectosome-enriched fraction separated by differential centrifugation contained neutrophil-derived antimicrobial peptides and constituted a major portion of the antibacterial potential of EV. Indeed, the ectosomes reduced the bacterial load of CLP mice and improved their survival. LL-37 triggered calcium influx in neutrophils, and co-stimulation with calcium ionophore further enhanced the release of ectosomes with higher antibacterial activity. Moreover, it was shown that the ectosome secretion was mediated by CXCR2 chemokine receptor and formyl peptide receptor 2, and that calpain and ROCK kinase were involved in the downstream signaling. The signaling axis associated with ectosome induction gives an insight in bioengineering for EV with higher potential of sepsis-protection.