Human neutrophil peptides sputum levels in symptomatic smokers and COPD patients

Human Neutrophil Peptides (HNP) are major neutrophils' products which may contribute to the airway inflammation and lung remodelling during chronic obstructive pulmonary disease (COPD). We aimed to assess whether HNP sputum concentrations could be used as indicators of airway inflammation and progression towards pulmonary functional impairment, and correlate with the degree of airways obstruction.

We measured, by ELISA tests, HNP concentrations from 37 symptomatic smokers and 34 COPD patients. All participants underwent pulmonary function tests. Sputum samples were collected at the enrolment, and 6 months after smoking cessation. Differences between groups and correlation coefficients between variables were determined using non parametric tests.

Sputum HNP concentrations were higher in COPD patients as compared to symptomatic smokers (14 +/- 1.5 microg/ml vs 1.6 +/- 0.4 microg/ml; p < 0.0001). Among COPD patients HNP concentrations were higher in individuals with severe obstruction than in patients with mild to moderate COPD (19.9 +/- 2.3 microg/ml vs 10.3 +/- 0.8 microg/ml, p = 0.003). A negative correlation was observed between HNP levels and FEV1 (rho = -0.38, p = 0.02), and FEV1/FVC (rho = -0.42, p = 0.01). No differences were found in HNP levels before and after 6 months of smoking withdrawal (1.1 microg/ml +/- 0.3 vs 1.1 microg/ml +/- 0.3 for symptomatic smokers, p = 0.9, and 14.4 microg/ml +/- 1 vs 16 microg/ml +/- 1.1 for COPD, p = 0.6).

Sputum levels of HNP may represent a marker of severity of functional impairment in COPD. Our data support the hypothesis that HNP may have a role in smoking- and COPD-related lung inflammation.