Current smoking alters phospholipid- and surfactant protein A levels in small airway lining fluid: An explorative study on exhaled breath

PLoS One. 2021 Jun 25;16(6):e0253825. doi: 10.1371/journal.pone.0253825. eCollection 2021.

Abstract

Small airways are difficult to access. Exhaled droplets, also referred to as particles, provide a sample of small airway lining fluid and may reflect inflammatory responses. We aimed to explore the effect of smoking on the composition and number of exhaled particles in a smoker-enriched study population. We collected and chemically analyzed exhaled particles from 102 subjects (29 never smokers, 36 former smokers and 37 current smokers) aged 39 to 83 years (median 63). A breathing maneuver maximized the number exhaled particles, which were quantified with a particle counter. The contents of surfactant protein A and albumin in exhaled particles was quantified with immunoassays and the contents of the phospholipids dipalmitoyl- and palmitoyl-oleoyl- phosphatidylcholine with mass spectrometry. Subjects also performed spirometry and nitrogen single breath washout. Associations between smoking status and the distribution of contents in exhaled particles and particle number concentration were tested with quantile regression, after adjusting for potential confounders. Current smokers, compared to never smokers, had higher number exhaled particles and more surfactant protein A in the particles. The magnitude of the effects of current smoking varied along the distribution of each PEx-variable. Among subjects with normal lung function, phospholipid levels were elevated in current smokers, in comparison to no effect of smoking on these lipids at abnormal lung function. Smoking increased exhaled number of particles and the contents of lipids and surfactant protein A in the particles. These findings might reflect early inflammatory responses to smoking in small airway lining fluid, also when lung function is within normal limits.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Breath Tests
  • Exhalation*
  • Female
  • Humans
  • Lung / metabolism*
  • Male
  • Middle Aged
  • Phosphatidylcholines / metabolism*
  • Pulmonary Surfactant-Associated Protein A / metabolism*
  • Smokers*
  • Smoking / metabolism*

Substances

  • Phosphatidylcholines
  • Pulmonary Surfactant-Associated Protein A

Grants and funding

This research was supported by the Swedish Research Council for Health, Working Life and Welfare (A-CO, Grant nr:201600419, https://forte.se/en/), by the Heart and Lung foundation Sweden (A-CO, Grant nr: 20180209, https://www.hjart-lungfonden.se/), and by the Centre for Allergy Research Highlights Asthma Markers of Phenotype consortium (A-CO) which is funded by the Swedish Foundation for Strategic Research, the Karolinska Institute, AstraZeneca & Science for Life Laboratory Joint Research Collaboration, and the Vårdal Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.