title: Toll-like receptor 4 mediates acute lung injury induced by high mobility group box-1.
abstract: BACKGROUND
  Acute lung injury (ALI) is considered to be the major cause of respiratory failure in critically ill patients. Clinical studies have found that in patients with sepsis and after hemorrhage, the elevated level of high mobility group box-1(HMGB-1) in their circulation is highly associated with ALI, but the underlying mechanism remains unclear. Extracellular HMGB-1 has cytokine-like properties and can bind to Toll-like Receptor-4 (TLR4), which was reported to play an important role in the pathogenesis of ALI. The aim of this study was to determine whether HMGB-1 directly contributes to ALI and whether TLR4 signaling pathway is involved in this process.
  
  
  METHODS
  Recombinant human HMGB-1 (rhHMGB-1) was used to induce ALI in male Sprague-Dawley rats. Lung specimens were collected 2 h after HMGB-1 treatment. The levels of TNF-α, IL-1β, TLR4 protein, and TLR4 mRNA in lungs as well as pathological changes of lung tissue were assessed. In cell studies, the alveolar macrophage cell line, NR8383, was collected 24 h after rhHMGB-1 treatment and the levels of TNF-α and IL-1β in cultured medium as well as TLR4 protein and mRNA levels in the cell were examined. TLR4-shRNA-lentivirus was used to inhibit TLR4 expression, and a neutralizing anti-HMGB1 antibody was used to neutralize rhHMGB-1 both in vitro and in vivo.
  
  
  RESULTS
  Features of lung injury and significant elevation of IL-1β and TNF-α levels were found in lungs of rhHMGB-1-treated animals. Cultured NR8383 cells were activated by rhHMGB-1 treatment and resulted in the release of IL-1β and TNF-α. TLR4 expression was greatly up-regulated by rhHMGB-1. Inhibition of TLR4 or neutralization of HMGB1 with a specific antibody also attenuated the inflammatory response induced by HMGB-1 both in vivo and in vitro.
  
  
  CONCLUSIONS
  HMGB-1 can activate alveolar macrophages to produce proinflammatory cytokines and induce ALI through a mechanism that relies on TLR-4.
authors.affiliation: Department of Anesthesiology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yuxiao
authors.initials: Y
authors.lastname: Deng
authors.forename: Zhongwei
authors.initials: Z
authors.lastname: Yang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Huan
authors.initials: H
authors.lastname: Xu
authors.forename: Beijie
authors.initials: B
authors.lastname: Zheng
authors.forename: Min
authors.initials: M
authors.lastname: Jiang
authors.forename: Jin
authors.initials: J
authors.lastname: Xu
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: He
authors.forename: Xiangrui
authors.initials: X
authors.lastname: Wang
mesh_terms: D055371:Acute Lung Injury / Q000139:chemically induced* / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D057134:Antibodies, Neutralizing / Q000378:metabolism; D015153:Blotting, Western; D017931:DNA Primers / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D024243:HMGB1 Protein / Q000235:genetics / Q000276:immunology / Q000633:toxicity*; D006652:Histological Techniques; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism; D008264:Macrophages; D008297:Male; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000235:genetics / Q000633:toxicity*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D057134:Antibodies, Neutralizing; D017931:DNA Primers; D024243:HMGB1 Protein; D053583:Interleukin-1beta; D011994:Recombinant Proteins; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha