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S123 The effects of electronic cigarette flavourings on macrophage cytokine release and phagocytosis
  1. RL Dacie,
  2. KB Belchamber,
  3. LE Donnelly
  1. National Heart and Lung Institute, Imperial College, London, UK


Background Electronic cigarettes (e-cigarettes) are marketed as an alternative to tobacco cigarettes, but little is known regarding their biological effects. Studies to date have produced varying results, reflecting varying chemical compositions of different e-liquids.

Chronic tobacco smoking is known to alter macrophage function, resulting in impaired bacterial phagocytosis and increased release of cytokines including TNFα, CXCL8 and IL-6. To date, there is little understanding of the effects of e-cigarettes on human macrophages. It was hypothesised that e-cigarettes would produce effects on macrophage function comparable to those of tobacco cigarettes.

Methods Six e-liquids were investigated: tobacco-flavoured e-liquid (± nicotine), banoffee-pie-flavoured e-liquid (± nicotine), e-liquid vehicle (propylene glycol + vegetable glycerine) and nicotine-vehicle solution. Effects of e-cigarette vapour extracts (e-CVEs) were compared with cigarette smoke extract (CSE) from a tobacco cigarette. Monocyte-derived macrophages (MDMs) from healthy subjects (n = 6) were cultured for 24 h with e-CVEs or CSE then incubated for 4h with Streptococcus pneumoniae or Haemophilus influenzae. Cell viability was determined and phagocytosis was quantified using fluorimetry. Release of TNFα, CXCL8 and IL-6 was measured by ELISA. Expression of macrophage receptor with collagenous structure (MARCO) and toll-like receptors (TLRs) 2 and 4 was measured by flow cytometry.

Results Neither CSE nor any of the e-CVEs had any significant effect on cell viability. In addition, none of the exposures produced any significant effect on phagocytosis, though higher concentrations of CSE displayed a trend towards reduced phagocytosis.

CSE significantly reduced TNFα release (by approximately 70%; p < 0.05). Tobacco- and banoffee pie-flavoured e-CVEs also caused significant reductions in TNFα release (by 30–50%; p < 0.05), while nicotine and the e-liquid vehicle had no effect. Minimal effects were observed on CXCL8 and IL-6 release (0–30% reduction; p > 0.05) with CSE and e-CVEs. Expression of MARCO and TLR4 were unaffected by all cell treatments. TLR2 expression appeared to be slightly increased by e-CVEs, but was not statistically significant.

Conclusion Effects of e-CVEs on MDMs differed from those of CSE. E-liquid flavourings appeared to be responsible for changes in MDM function, while the e-liquid vehicle and nicotine solution had minimal effects. More research is needed to improve understanding of the biological effects of e-cigarette flavourings.

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