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BackgroundThe 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 methodsPatients 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.ResultsIn 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.ConclusionsRapidly 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.

Original publication

DOI

10.1007/bf03401959

Type

Journal article

Journal

Molecular medicine (Cambridge, Mass.)

Publication Date

10/2001

Volume

7

Pages

685 - 697

Addresses

The Respiratory Medicine Unit, Centre for Inflammation Research, University of Edinburgh, UK.

Keywords

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