Acute exposure to traffic-related air pollution can lead to lower airway neutrophils to release of neutrophil extracellular traps (NETs), which is linked to chronic obstructive pulmonary disease (COPD) severity and airflow limitations, according to study results published in the European Respiratory Journal.
Exposure to traffic-related air pollution (TRAP) is a significant contributor to respiratory morbidity and mortality, especially among individuals living with COPD, although the mechanism is unknown. Neutrophils are recruited to the lung following diesel exhaust exposure, a model of TRAP, but their functional role in this response is unknown.
Therefore, researchers conducted a controlled human exposure crossover study to assess the effects of acute diesel exhaust exposure on neutrophil function in never-smokers (n=7), ex-smokers (n=4), and patients with mild to moderate COPD (n=7) with support from additional in vitro studies. The participants were exposed to diesel exhaust and filtered air for 2 hours on separate occasions, and neutrophil function in blood (0h and 24h postexposure) and bronchoalveolar lavage (24h postexposure) were assessed.
They found that compared with filtered air, diesel exhaust exposure reduced the proportion of circulating band cells at 0h, which was exaggerated in patients with COPD. Diesel exhaust increased the amount of NETs in the lung across participants, and patients with COPD had increased peripheral neutrophil activation following diesel exhaust. The researchers also found that in vitro, suspended diesel exhaust particles increased the amount of NETs measured in isolated neutrophils.
In the first controlled human TRAP exposure study directly comparing at-risk phenotypes (patients with COPD and ex-smokers) with lower-risk (never-smokers), the investigators concluded that, “We propose NET formation as a possible mechanism through which TRAP exposure affects airway pathophysiology.”
They added that patients with COPD “may be more prone to an activated inflammatory state following exposure.”
Wooding DJ, Ryu MH, Li H, Alexis NE, Pena O, Carlsten C. Acute air pollution exposure alters neutrophils in never-smokers and at-risk humans [published online December 5, 2019]. Eur Respir J. doi:10.1183/13993003.01495-2019