Characterization of the inflammatory response to inhaled lipopolysaccharide in mild to moderate chronic obstructive pulmonary disease

Abstract

AIMS: Lipopolysaccharide (LPS) inhalation causes increased airway and systemic inflammation. We investigated LPS inhalation in patients with chronic obstructive pulmonary disease (COPD) as a model of bacterial exacerbations. We studied safety, changes in sputum and systemic biomarkers. We have also investigated interleukin (IL)-17 concentrations in this model. METHODS: Twelve COPD patients inhaled 5 μg LPS. Safety was monitored over 24 h. Sputum was induced at baseline, 6 and 24 h for cells and IL-8, IL-17, neutrophil elastase, monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1β (MIP-1β) in supernatants. Serum was collected at baseline, 4, 8 and 24 h for IL-6, C-reactive protein (CRP) and Clara cell protein (CC-16) concentrations. Peripheral blood mononuclear cells (PBMCs) were isolated at baseline and 4 h for systemic IL-17 analysis. RESULTS: LPS 5 μg was well tolerated. The greatest FEV1 change was 11.7% (mean) at 1 h (95% CI 5.1-18.2%). There was a large range in maximal fall (2.5-37.7%). Total sputum cell count and neutrophil count significantly increased 6 and 24 h post-LPS. There was no change in sputum supernatant mediators. IL-6, CRP and CC-16 increased post-inhalation, with different temporal patterns. CD4+ and CD8+ cell associated IL-17 significantly increased at 4 h. CONCLUSIONS: Inhaled LPS in COPD patients safely causes increased airway and systemic inflammation. This may be a model for studying COPD exacerbations.