Neutrophil Activation in Severe, Early-Onset COPD Patients versus Healthy Non-Smoker Subjects in vitro: Effects of Antioxidant Therapy

Abstract

Background: Neutrophils and oxidative stress have been implicated in the pathogenesis of COPD. Severe, early-onset COPD is characterized by a rapid decline in the lung function at an early age; however, nothing is known about neutrophil activation in COPD patients. Objectives: The aim of this study was to evaluate peripheral blood neutrophil activation in severe, early-onset COPD patients versus healthy non-smokers and the effect of N-acetyl-L-cysteine (NAC) on neutrophil activation in vitro. Methods: Neutrophils were isolated from 15 severe, early-onset COPD patients and 15 age-matched healthy subjects and stimulated with N-formyl- Met-Leu-Phe (fMLP) in the presence or absence of NAC (10 µM to 10 mM). Neutrophil chemotaxis, elastase release, reactive oxygen species (ROS), intracellular thiols and apoptosis were measured by Boyden chamber, spectrofluorometry, CMFDA and H₂DCF-DA dyes and by annexin V-FITC, respectively. Results: Chemotaxis of peripheral blood neutrophils from COPD patients in response to fMLP was 30% more increased than that observed in healthy subjects. Elastase release in response to fMLP was 2-fold higher in neutrophils from COPD patients versus healthy subjects. Intracellular thiol levels were 30% lower in COPD and ROS was approximately 30% higher in COPD versus healthy neutrophils. Spontaneous apoptosis showed no differences in both groups of patients and fMLP-induced apoptosis was higher in COPD. Pre-treatment with the antioxidant NAC effectively attenuated neutrophil chemotaxis, elastase release and ROS as well as effectively increased thiol levels in COPD. Conclusions: Neutrophils in severe, early-onset COPD patients are highly activated and this is alleviated by NAC in vitro.

Neutrophil-Mediated Lung Damage: A New COPD Phenotype?

“…1 ). Whatever the cause of persistent lung inflammation in this group of COPD subjects, the findings from Milara et al [6] suggest that the circulating neutrophils of these patients remain activated years after smoking cessation. These neutrophils could provide a major source of ongoing elastolytic burden in the lungs, especially during acute exacerbations.…”

“…These neutrophils could provide a major source of ongoing elastolytic burden in the lungs, especially during acute exacerbations. The data from Milara et al [6] also offer hope. They provide tantalizing evidence that by pretreating these neutrophils with an antioxidant they can reverse their activated state.…”

“…However, this group of COPD subjects that develop severe disease at an early age may represent a unique COPD phenotype where activated circulating neutrophils significantly contribute to alveolar wall damage. The data by Milara et al [6] also suggest that targeting these activated neutrophils with antioxidants may ameliorate the course of COPD in these patients, providing new hope for millions of patients with COPD around the world.…”

“…In this issue of Respiration, Milara et al [6] offer new insights into the role of neutrophils in COPD that may in part explain the conundrum of disease progression in COPD in ex-smokers. The authors studied subjects with severe COPD developed at an early age ( !…”

“…Together, these data suggest that, even with smoking cessation, circulating neutrophils remain persistently activated and primed to unleash a cocktail of enzymes that can cause progressive lung injury in some COPD patients. The study by Milara et al [6] was not designed to address the question of why circulating neutrophils in these COPD patients remain activated and dysregulated. Several possibilities exist.…”