Outer Membrane Vesicles Derived From Regulate Neutrophil Migration by Induction of Endothelial IL-8.

Outer membrane vesicles (OMVs) are spherical, proteolipid nanostructures that are constitutively released by Gram-negative bacteria including . Although it has been shown that administration of OMVs stimulates a strong pulmonary inflammatory response with infiltration of neutrophils into the lungs , the mechanism of OMV-mediated neutrophil recruitment is poorly characterized. In this study, we observed significant infiltration of neutrophils into the mouse lung tissues , with increased expression of the neutrophil chemoattractant CXCL1, a murine functional homolog of human IL-8, on intraperitoneal administration of OMVs. In addition, OMVs and CD31-positive endothelial cells colocalized in the mouse lungs. Moreover, results showed that OMVs significantly increased IL-8 release from human microvascular endothelial cells and toll-like receptor (TLR)4 was found to be the main component for recognizing OMVs among human endothelial cell-associated TLRs. Furthermore, the transmigration of neutrophils was suppressed in the lung tissues obtained from TLR4 knockout mice treated with OMVs. Taken together, our data demonstrated that OMVs potently recruit neutrophils into the lung via the release of IL-8/CXCL1 from endothelial cells in TLR4- and NF-κB-dependent manners.