Abstract
Background: Antimicrobial peptides (AMPs) play important roles in innate lung defense against pathogens, however high concentrations may enhance inflammation in COPD.
Aims: 1) Compare sputum levels of the two AMPs hCAP18/LL-37 and SLPI in COPD to controls, and stable COPD versus exacerbation 2) Examine factors associated with AMP levels.
Methods: Repeated measurements were collected in 426 stable and 355 COPD patients when exacerbating, and 233 controls during the 3-year study period. First available induced sputum sample was selected per subject for analyses of AMP levels (enzyme linked immunosorbent assay) and inflammatory markers (bead-based immunoassay). Associations were tested by the Wilcoxon rank-sum test and Spearman's rank correlation coefficient.
Results: 255 stable and 55 exacerbation sputum samples from patients and 45 sputum samples from controls were available.
While stable, COPD patients had significantly higher AMP levels compared to controls (p≤0.01) and male sex, higher age, GOLD stage, neutrophil count and IL-8 levels in sputum were associated with higher hCAP18/LL-37 levels in COPD.
During exacerbation, sputum hCAP18/LL-37 levels were higher and SLPI levels lower (p<0.001), and inversely correlated (r=-0.48, p<0.001) compared to stable COPD. The correlation remained between sputum hCAP18/LL-37 and IL-8 (r=0.33, p=0.01) and neutrophil count (r=0.46, p<0.001). SLPI were positively correlated with IL-6 (r=0.55, p<0.001) and negatively with neutrophil count (r=-0.42, p<0.01).
Conclusion: COPD is associated with altered AMP levels, which is further changed during exacerbation. Neutrophil recruitment during exacerbation may explain changes in AMP levels during exacerbation.
- Copyright ©ERS 2015
