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Original article
Pro-inflammatory effects of e-cigarette vapour condensate on human alveolar macrophages
  1. Aaron Scott1,
  2. Sebastian T Lugg1,
  3. Kerrie Aldridge1,
  4. Keir E Lewis2,
  5. Allen Bowden3,
  6. Rahul Y Mahida1,
  7. Frances Susanna Grudzinska1,
  8. Davinder Dosanjh1,
  9. Dhruv Parekh1,
  10. Robert Foronjy4,
  11. Elizabeth Sapey1,
  12. Babu Naidu1,
  13. David R Thickett1
  1. 1 Birmingham Acute Care Research Group Institute of Inflammation and Ageing (IIA), University of Birmingham, Birmingham, UK
  2. 2 College of Medicine, Swansea University, Swansea, UK
  3. 3 Analytical Facility, School of Chemistry, University of Birmingham, Birmingham, UK
  4. 4 Division of Pulmonary and Critical Care Medicine,Department of Medicine, SUNY Downstate Medical Center, Brooklyn, New York, USA
  1. Correspondence to Dr David R Thickett, Institute of Inflammation and Ageing, University of Birmingham, Birmingham B15 2TH, UK; d.thickett{at}bham.ac.uk

Abstract

Objective Vaping may increase the cytotoxic effects of e-cigarette liquid (ECL). We compared the effect of unvaped ECL to e-cigarette vapour condensate (ECVC) on alveolar macrophage (AM) function.

Methods AMs were treated with ECVC and nicotine-free ECVC (nfECVC). AM viability, apoptosis, necrosis, cytokine, chemokine and protease release, reactive oxygen species (ROS) release and bacterial phagocytosis were assessed.

Results Macrophage culture with ECL or ECVC resulted in a dose-dependent reduction in cell viability. ECVC was cytotoxic at lower concentrations than ECL and resulted in increased apoptosis and necrosis. nfECVC resulted in less cytotoxicity and apoptosis. Exposure of AMs to a sub-lethal 0.5% ECVC/nfECVC increased ROS production approximately 50-fold and significantly inhibited phagocytosis. Pan and class one isoform phosphoinositide 3 kinase inhibitors partially inhibited the effects of ECVC/nfECVC on macrophage viability and apoptosis. Secretion of interleukin 6, tumour necrosis factor α, CXCL-8, monocyte chemoattractant protein 1 and matrix metalloproteinase 9 was significantly increased following ECVC challenge. Treatment with the anti-oxidant N-acetyl-cysteine (NAC) ameliorated the cytotoxic effects of ECVC/nfECVC to levels not significantly different from baseline and restored phagocytic function.

Conclusions ECVC is significantly more toxic to AMs than non-vaped ECL. Excessive production of ROS, inflammatory cytokines and chemokines induced by e-cigarette vapour may induce an inflammatory state in AMs within the lung that is partly dependent on nicotine. Inhibition of phagocytosis also suggests users may suffer from impaired bacterial clearance. While further research is needed to fully understand the effects of e-cigarette exposure in humans in vivo, we caution against the widely held opinion that e-cigarettes are safe.

  • respiratory infection
  • oxidative stress
  • macrophage biology

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/.

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Footnotes

  • Contributors Author Contributions: Concept and design: DRT, AS, STL, DD, KEL, BN, RF. Cell preparation, laboratory work and data analysis: AS, RM, STL, KA. GCFID- AB. Additional laboratory work: FSG. Patient recruitment: BN, DRT, DP, RM. Drafting manuscript: AS, DRT. ALL authors have read and approved the manuscript.

  • Funding DRT (G1100196/1), ES (MR/L008335/1), AS (MR/L002736/1) and RM (MR/N021185/1) were funded by the MRC. AS, STL and DD were supported by the British Lung Foundation (PPRG16-12).

  • Competing interests None declared.

  • Patient consent Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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