Chronic obstructive pulmonary disease patients have greater systemic responsiveness to ex vivo stimulation with swine dust extract and its components versus healthy volunteers

Abstract

Chronic obstructive pulmonary disease (COPD) is characterized by an airway and systemic inflammatory response. Bioaerosols/organic dusts are important agricultural pollutants that may lead to COPD. These environments are complex, containing a rich source of various microbial components. The objective of this study was to determine whether individuals with COPD have enhanced systemic responsiveness to settled swine facility organic dust extract (ODE) or its main pathogenic components (peptidoglycan [PGN], lipopolysaccharide [LPS]) versus healthy volunteers. A modified whole blood assay (WBA) that included occupational levels of ODE and concentrations of LPS and PGN found in ODE was used to determine systemic responsiveness (mediator release), and sputum inflammatory markers were measured to explore for systemic and airway associations. Sputum samples were evaluated for cell counts, and tumor necrosis factor (TNF)-α, interleukin (IL)-8/CXCL8, IL-6, and IL-10. Ex vivo whole blood stimulation with ODE, LPS, and PGN each resulted in significant mediator release in all subjects, with the highest occurring with ODE; PGN resulted in significantly enhanced TNF-α and IL-8 as compared to LPS. COPD subjects demonstrated greater systemic responsiveness using the modified WBA versus healthy controls. Within COPD subjects, blood baseline TNF-α, IL-8, and IL-10 and ODE-, PGN-, and LPS-stimulated IL-8 levels significantly correlated with lung function. In conclusion, dust-induced mediator release was robust, and PGN, in part, resembled dust-induced mediator release. Subjects with COPD demonstrated increased mediator release following ex vivo whole blood stimulation with bioaerosol components, suggesting that circulating blood cells in COPD subjects may be primed to respond greater to microbial/inflammatory insult.

Trial registration: ClinicalTrials.gov NCT00871637.

Figures

Figure 1

(A-D).Ex vivo whole blood stimulation with high and low organic dust extract (ODE), lipopolysaccharide (LPS), and peptidoglycan (PGN) resulted in significant cytokine/chemokine release in all subjects as compared to baseline (*p<0.001). Results of cell-free supernatant release of TNF-α (A) IL-8/CXCL8 (B), IL-10 (C), and IL-6 (D) release following 24hr incubation with high and low concentrations of ODE (1%, 0.1%) and comparable concentrations of LPS (100 and 10 ng/ml) and PGN (10 and 1 μg/ml) by ELISA. Unstimulated (baseline) levels are also shown. Data are presented as mean concentration (ng/ml) with standard error bars shown (N=20 subjects). By Bonferroni adjustment, a) denotes significant difference as compared to LPS stimulation, and b) denotes significant difference as compared to PGN stimulation.

Figure 2

(A-D). Differences in TNF-α (A), IL-8/CXCL8 (B), IL-10 (C), and IL-6 (D)-hyper-responsiveness to organic dust extract (ODE), lipopolysaccharide (LPS), and peptidoglycan (PGN) stimulated whole blood from subjects with COPD as compared to healthy controls are depicted. Unstimulated (baseline) levels are also shown. Data are presented as mean concentration (pg/ml) with standard error bars shown (N=10/group). P values <0.10 are given, and * denotes statistically significant (p<0.05).