Neutrophils augment LPS-mediated pro-inflammatory signaling in human lung epithelial cells

Biochim Biophys Acta. 2012 Jul;1823(7):1151-62. doi: 10.1016/j.bbamcr.2012.04.012. Epub 2012 May 1.


Background: The role of polymorphonuclear neutrophils in pulmonary host defense is well recognized. The influence of a pre-existing inflammation driven by neutrophils (neutrophilic inflammation) on the airway epithelial response toward pro-inflammatory exogenous triggers, however, is still poorly addressed. Therefore, the aim of the present study is to investigate the effect of neutrophils on lipopolysaccharide (LPS)-induced pro-inflammatory signaling in lung epithelial cells. Additionally, underlying signaling pathways are examined.

Methods: Human bronchial epithelial cells (BEAS-2B) were co-incubated with human peripheral blood neutrophils or bone-marrow derived neutrophils from either C57BL/6J wild type or nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase deficient (p47(phox-/-)) mice. Upon stimulation with LPS, interleukin (IL)-8 production and reactive oxygen species (ROS) generation were measured. Additionally, activation of the extracellular signal-regulated kinases (ERK) 1/2 and nuclear factor (NF)-κB signaling pathways was analyzed.

Results: Our studies show that the presence of neutrophils synergistically increases LPS-induced IL-8 and ROS production by BEAS-2B cells without inducing cytotoxicity. The observed IL-8 response to endotoxin increases in proportion to time, LPS-concentration and the number of neutrophils present. Moreover, this synergistic IL-8 production strongly correlated with the chemotactic properties of the co-incubations and significantly depended on a functional neutrophilic NADPH oxidase. The presence of neutrophils also augments LPS-induced phosphorylation of ERK1/2 and IκBα as well as NF-κB RelA DNA binding activity in BEAS-2B cells.

Conclusions: Our results indicate that the pro-inflammatory effects of LPS toward lung epithelial cells are amplified during a pre-existing neutrophilic inflammation. These findings support the concept that patients suffering from pulmonary neutrophilic inflammation are more susceptible toward exogenous pro-inflammatory triggers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cell Separation
  • Chemotactic Factors / pharmacology
  • DNA / metabolism
  • Epithelial Cells / drug effects*
  • Epithelial Cells / enzymology
  • Epithelial Cells / pathology*
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Humans
  • I-kappa B Proteins / metabolism
  • Inflammation / pathology*
  • Interleukin-8 / biosynthesis
  • Lipopolysaccharides / pharmacology*
  • Lung / pathology*
  • Mice
  • Models, Biological
  • NADPH Oxidases / metabolism
  • NF-KappaB Inhibitor alpha
  • Neutrophils / drug effects
  • Neutrophils / enzymology
  • Neutrophils / pathology*
  • Phosphorylation / drug effects
  • Protein Binding / drug effects
  • Reactive Oxygen Species / metabolism
  • Signal Transduction / drug effects*
  • Transcription Factor RelA / metabolism


  • Chemotactic Factors
  • I-kappa B Proteins
  • Interleukin-8
  • Lipopolysaccharides
  • NFKBIA protein, human
  • Nfkbia protein, mouse
  • Reactive Oxygen Species
  • Transcription Factor RelA
  • NF-KappaB Inhibitor alpha
  • DNA
  • NADPH Oxidases
  • Extracellular Signal-Regulated MAP Kinases