title: Pulmonary endothelial activation caused by extracellular histones contributes to neutrophil activation in acute respiratory distress syndrome.
abstract: During the acute respiratory distress syndrome (ARDS), neutrophils play a central role in the pathogenesis, and their activation requires interaction with the endothelium. Extracellular histones have been recognized as pivotal inflammatory mediators. This study was to investigate the role of pulmonary endothelial activation during the extracellular histone-induced inflammatory response in ARDS.
  
  
  
  ARDS was induced in male C57BL/6 mice by intravenous injection with lipopolysaccharide (LPS) or exogenous histones. Concurrent with LPS administration, anti-histone H4 antibody (anti-H4) or non-specific IgG was administered to study the role of extracellular histones. The circulating von Willebrand factor (vWF) and soluble thrombomodulin (sTM) were measured with ELISA kits at the preset time points. Myeloperoxidase (MPO) activity in lung tissue was measured with a MPO detection kit. The translocation of P-selectin and neutrophil infiltration were measured by immunohistochemical detection. For in vitro studies, histone H4 in the supernatant of mouse lung vascular endothelial cells (MLVECs) was measured by Western blot. The binding of extracellular histones with endothelial membrane was examined by confocal laser microscopy. Endothelial P-selectin translocation was measured by cell surface ELISA. Adhesion of neutrophils to MLVECs was assessed with a color video digital camera.
  
  
  
  The results showed that during LPS-induced ARDS extracellular histones caused endothelial and neutrophil activation, as seen by P-selectin translocation, release of vWF, an increase of circulating sTM, lung neutrophil infiltration and increased MPO activity. Extracellular histones directly bound and activated MLVECs in a dose-dependent manner. On the contrary, the direct stimulatory effect of exogenous histones on neutrophils was very limited, as measured by neutrophil adhesion and MPO activity. With the contribution of activated endothelium, extracellular histones could effectively activating neutrophils. Both inhibiting the endothelial activation with an anti-toll like receptor (TLR) antibody and inhibiting the interaction of the endothelium with neutrophil using an anti-P-selectin antibody decreased the degree of neutrophil activation.
  
  
  
  Extracellular histones are pro-inflammatory mediators in LPS-induced ARDS in mice. In addition to direct action to neutrophils, extracellular histones promote neutrophil adhesion and subsequent activation by first activating the pulmonary endothelium via TLR signaling. Thus, endothelial activation is important for extracellular histone-induced inflammatory injury.
authors.affiliation: Research Center of Occupational Medicine, Third Hospital of Peking University, No.49 North Garden Road, Haidian District, Beijing, 100191, People's Republic of China.
authors.forename: Yanlin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Research Center of Occupational Medicine, Third Hospital of Peking University, No.49 North Garden Road, Haidian District, Beijing, 100191, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Guan
authors.affiliation: Research Center of Occupational Medicine, Third Hospital of Peking University, No.49 North Garden Road, Haidian District, Beijing, 100191, People's Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Yu
authors.affiliation: Research Center of Occupational Medicine, Third Hospital of Peking University, No.49 North Garden Road, Haidian District, Beijing, 100191, People's Republic of China.
authors.forename: Zanmei
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Research Center of Occupational Medicine, Third Hospital of Peking University, No.49 North Garden Road, Haidian District, Beijing, 100191, People's Republic of China.
authors.forename: Lijun
authors.initials: L
authors.lastname: Mao
authors.affiliation: Research Center of Occupational Medicine, Third Hospital of Peking University, No.49 North Garden Road, Haidian District, Beijing, 100191, People's Republic of China. shuqiangli@263.net.
authors.forename: Shuqiang
authors.initials: S
authors.lastname: Li
authors.affiliation: Research Center of Occupational Medicine, Third Hospital of Peking University, No.49 North Garden Road, Haidian District, Beijing, 100191, People's Republic of China. zhaojinyuan@sina.com.
authors.forename: Jinyuan
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D002448:Cell Adhesion; D004727:Endothelium / Q000187:drug effects / Q000503:physiopathology; D006657:Histones / Q000037:antagonists & inhibitors / Q000276:immunology / Q000494:pharmacology*; D007074:Immunoglobulin G / Q000276:immunology; D008070:Lipopolysaccharides; D008168:Lung / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018375:Neutrophil Activation / Q000187:drug effects*; D019007:P-Selectin / Q000037:antagonists & inhibitors / Q000378:metabolism; D012128:Respiratory Distress Syndrome / Q000139:chemically induced / Q000503:physiopathology*; D018180:Thrombomodulin / Q000378:metabolism; D051193:Toll-Like Receptors / Q000037:antagonists & inhibitors
chemical_list: D019138:Antibodies, Blocking; D006657:Histones; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D019007:P-Selectin; D018180:Thrombomodulin; D051193:Toll-Like Receptors
keywords: Acute respiratory distress syndrome; Endothelium; Extracellular histones; Inflammation; Neutrophil