The regulation of interleukin-8 by hypoxia in human macrophages--a potential role in the pathogenesis of the acute respiratory distress syndrome (ARDS)

Mol Med. 2001 Oct;7(10):685-97.

Abstract

Background: The acute respiratory distress syndrome (ARDS) represents a form of severe acute inflammatory lung disease. We have previously demonstrated significantly raised interleukin-8 (IL-8) levels in the lungs of at-risk patients that progress to ARDS, and identified the alveolar macrophage as an important source of this chemokine. We wished to extend this study in a well-defined group of patients with major trauma, and to investigate potential mechanisms for rapid intrapulmonary IL-8 generation.

Materials and methods: Patients with major trauma underwent bronchoalveolar lavage (BAL) and IL-8 levels were measured in BAL fluid by ELISA. Human macrophages were derived from peripheral blood monocytes from healthy volunteers. Rabbit alveolar macrophages were obtained from ex-vivo lavage of healthy rabbit lungs. Macrophages were culture under normoxic or hypoxic (PO2 26 mmHg) conditions. IL-8 and other proinflammatory mediator expression was measured by ELISA, northern blotting or multi-probe RNase protection assay.

Results: In patients with major trauma, IL-8 levels were significantly higher in patients that progressed to ARDS compared to those that did not (n = 56, P = 0.0001). High IL-8 levels negatively correlated with PaO2/FiO2 (r = -0.56, P < 0.001). In human monocyte derived macrophages hypoxia rapidly upregulated IL-8 protein (within 2 hours) and mRNA expression (within 30 mins). Acute hypoxia also increased rabbit alveolar macrophage IL-8 expression. Hypoxia increased DNA binding activity of AP-1 and C/EBP but not NF-kappaB. Hypoxia induced HIF-1 expression, but cobaltous ions and desferrioxamine did not mimic hypoxic IL-8 induction. Hypoxia downregulated a range of other proinflammatory mediators, including MCP-1 and TNF-alpha. Both the pattern of cytokine expression and transcription factor activation by hypoxia was different to that seen with endotoxin.

Conclusions: Rapidly raised intrapulmonary IL-8 levels are associated with ARDS progression in patients with major trauma. Acute hypoxia, a clinically relevant stimulus, rapidly and selectively upregulates IL-8 in macrophages associated with a novel pattern of transcription factor activation. Acute hypoxia may represent one of potentially several proinflammatory stimuli responsible for rapid intrapulmonary IL-8 generation in patients at-risk of ARDS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Blotting, Northern
  • Bronchoalveolar Lavage Fluid / chemistry
  • Cells, Cultured
  • DNA Primers / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Humans
  • Hypoxia / metabolism*
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Immunoblotting
  • Interleukin-8 / genetics
  • Interleukin-8 / metabolism*
  • Macrophages / metabolism*
  • Male
  • Middle Aged
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • RNA / metabolism
  • Rabbits
  • Respiratory Distress Syndrome / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription Factor AP-1 / genetics
  • Transcription Factor AP-1 / metabolism
  • Transcription Factors*

Substances

  • DNA Primers
  • DNA-Binding Proteins
  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Interleukin-8
  • NF-kappa B
  • Nuclear Proteins
  • Transcription Factor AP-1
  • Transcription Factors
  • RNA