title: VEGF Production by Ly6C+high Monocytes Contributes to Ventilator-Induced Lung Injury.
abstract: BACKGROUND
  Mechanical ventilation is a life-saving procedure for patients with acute respiratory failure, although it may cause pulmonary vascular inflammation and leakage, leading to ventilator-induced lung injury (VILI). Ly6C+high monocytes are involved in the pathogenesis of VILI. In this study, we investigated whether pulmonary infiltrated Ly6C+high monocytes produce vascular endothelial growth factor (VEGF) and contribute to VILI.
  
  
  METHODS
  A clinically relevant two-hit mouse model of VILI, with intravenous lipopolysaccharide (LPS, 20 ng/mouse) immediately before high tidal volume (HTV, 20 mL/kg) ventilation (LPS+HTV), was established. Blood gas and respiratory mechanics were measured to ensure the development of VILI. Flow cytometry and histopathological analyses revealed pulmonary infiltration of leukocytes subsets. Clodronate liposomes were intravenously injected to deplete pulmonary monocytes. In vitro endothelial cell permeability assay with sorted Ly6C+high monocytes condition media assessed the role of Ly6C+high monocytes in vascular permeability.
  
  
  RESULTS
  LPS+HTV significantly increased total proteins, TNF-α, IL-6, vascular endothelial growth factor (VEGF) and mononuclear cells in the bronchoalveolar lavage fluid (BALF). Pulmonary Ly6C+high monocytes (SSClowCD11b+F4/80+Ly6C+high), but not Ly6C+low monocytes (SSClowCD11b+F4/80+Ly6C+low), were significantly elevated starting at 4 hr. Clodronate liposomes were able to significantly reduce pulmonary Ly6C+high monocytes, and VEGF and total protein in BALF, and restore PaO2/FiO2. There was a strong correlation between pulmonary Ly6C+high monocytes and BALF VEGF (R2 = 0.8791, p<0.001). Moreover, sorted Ly6C+high monocytes were able to produce VEGF, resulting in an increased permeability of endothelial cell monolayer in an in vitro endothelial cell permeability assay.
  
  
  CONCLUSIONS
  VEGF produced by pulmonary infiltrated Ly6C+high monocytes regulates vasculature permeability in a two-hit model of HTV-induced lung injury. Ly6C+high monocytes play an important role in the pathogenesis of VILI.
authors: Graduate Institute of Clinical Medicine Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan.|Division of Urology, Department of Surgery, Chang Gung Memorial Hospital, Chiayi, Taiwan.
authors: Chung-Sheng
authors: CS
authors: Shi
authors: Department of Respiratory Therapy, Chang Gung Memorial Hospital, Chiayi, Taiwan.
authors: Tzu-Hsiung
authors: http://orcid.org/0000-0002-8783-1645
authors: TH
authors: Huang
authors: The Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan.
authors: Chin-Kuo
authors: CK
authors: Lin
authors: Graduate Institute of Clinical Medicine Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors: Jhy-Ming
authors: JM
authors: Li
authors: Graduate Institute of Clinical Medicine Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors: Mei-Hsin
authors: MH
authors: Chen
authors: Department of Physiology, Medical College, National Cheng Kung University, Tainan, Taiwan.
authors: Mei-Ling
authors: ML
authors: Tsai
authors: Department of Environmental and Occupational Health, Medical College, National Cheng Kung University, Tainan, Taiwan.
authors: Chih-Ching
authors: CC
authors: Chang
mesh_terms: D000818:Animals; D000950:Antigens, Ly / Q000378:metabolism*; D001784:Blood Gas Analysis; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D008168:Lung / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012044:Regression Analysis; D012121:Respiration, Artificial / Q000009:adverse effects; D012720:Severity of Illness Index; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D055397:Ventilator-Induced Lung Injury / Q000378:metabolism / Q000473:pathology*
chemical_list: D000950:Antigens, Ly; D015850:Interleukin-6; D008070:Lipopolysaccharides; C494192:Ly-6C antigen, mouse; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A