TNF-α mediated increase of HIF-1α inhibits VASP expression, which reduces alveolar-capillary barrier function during acute lung injury (ALI)

PLoS One. 2014 Jul 22;9(7):e102967. doi: 10.1371/journal.pone.0102967. eCollection 2014.

Abstract

Acute lung injury (ALI) is an inflammatory disorder associated with reduced alveolar-capillary barrier function and increased pulmonary vascular permeability. Vasodilator-stimulated phosphoprotein (VASP) is widely associated with all types of modulations of cytoskeleton rearrangement-dependent cellular morphology and function, such as adhesion, shrinkage, and permeability. The present studies were conducted to investigate the effects and mechanisms by which tumor necrosis factor-alpha (TNF-α) increases the tight junction permeability in lung tissue associated with acute lung inflammation. After incubating A549 cells for 24 hours with different concentrations (0-100 ng/mL) of TNF-α, 0.1 to 8 ng/mL TNF-α exhibited no significant effect on cell viability compared with the 0 ng/mL TNF-α group (control group). However, 10 ng/mL and 100 ng/mL TNF-α dramatically inhibited the viability of A549 cells compared with the control group (*p<0.05). Monolayer cell permeability assay results indicated that A549 cells incubated with 10 ng/mL TNF-α for 24 hours displayed significantly increased cell permeability (*p<0.05). Moreover, the inhibition of VASP expression increased the cell permeability (*p<0.05). Pretreating A549 cells with cobalt chloride (to mimic a hypoxia environment) increased protein expression level of hypoxia inducible factor-1α (HIF-1α) (*p<0.05), whereas protein expression level of VASP decreased significantly (*p<0.05). In LPS-induced ALI mice, the concentrations of TNF-α in lung tissues and serum significantly increased at one hour, and the value reached a peak at four hours. Moreover, the Evans Blue absorption value of the mouse lung tissues reached a peak at four hours. The HIF-1α protein expression level in mouse lung tissues increased significantly at four hours and eight hours (**p<0.001), whereas the VASP protein expression level decreased significantly (**p<0.01). Taken together, our data demonstrate that HIF-1α acts downstream of TNF-α to inhibit VASP expression and to modulate the acute pulmonary inflammation process, and these molecules play an important role in the impairment of the alveolar-capillary barrier.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Lung Injury / chemically induced
  • Acute Lung Injury / genetics*
  • Acute Lung Injury / physiopathology
  • Animals
  • Blotting, Western
  • Capillaries / metabolism*
  • Capillaries / physiopathology
  • Cell Adhesion Molecules / genetics*
  • Cell Adhesion Molecules / metabolism
  • Cell Line, Tumor
  • Cell Membrane Permeability / drug effects
  • Cell Membrane Permeability / genetics
  • Cell Survival / drug effects
  • Cell Survival / genetics
  • Dose-Response Relationship, Drug
  • Gene Expression / drug effects*
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics*
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Lipopolysaccharides
  • Mice, Inbred BALB C
  • Microfilament Proteins / genetics*
  • Microfilament Proteins / metabolism
  • Phosphoproteins / genetics*
  • Phosphoproteins / metabolism
  • Pulmonary Alveoli / blood supply
  • Pulmonary Alveoli / metabolism
  • Pulmonary Alveoli / physiopathology
  • RNA Interference
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Necrosis Factor-alpha / metabolism
  • Tumor Necrosis Factor-alpha / pharmacology*

Substances

  • Cell Adhesion Molecules
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Lipopolysaccharides
  • Microfilament Proteins
  • Phosphoproteins
  • Tumor Necrosis Factor-alpha
  • vasodilator-stimulated phosphoprotein

Grants and funding

This work was supported by the National Natural Science Foundation of China under Grant No. 81172043, the Hubei Science Foundation under Grant 2009CDA074, the Fundamental Research Funds for the Central Universities No. 2012301020208 and the laboratory and equipment administration of Wuhan University under project “Open Experimentation Program of Experimental Teaching Center of Wuhan University”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.