Comparison of the effects of electronic cigarette vapours and tobacco smoke extracts on human neutrophils in vitro

Guy A Richards; Annette J Theron; Iman van den Bout; Ronald Anderson; Charles Feldman; Richard van Zyl Smit; Ju-Wei Chang; Gregory R Tintinger

doi:10.1183/23120541.00502-2022

Comparison of the effects of electronic cigarette vapours and tobacco smoke extracts on human neutrophils in vitro

ERJ Open Res. 2023 May 22;9(3):00502-2022. doi: 10.1183/23120541.00502-2022. eCollection 2023 May.

Authors

Guy A Richards¹, Annette J Theron², Iman van den Bout³, Ronald Anderson², Charles Feldman⁴, Richard van Zyl Smit⁵, Ju-Wei Chang⁵, Gregory R Tintinger⁶

Affiliations

¹ Division of Critical Care, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
² Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
³ Centre of Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
⁴ Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
⁵ Department of Medicine, University of Cape Town, Groote Schuur Hospital, Cape Town, South Africa.
⁶ Department of Internal Medicine, Steve Biko Academic Hospital and Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.

Abstract

Background: Electronic cigarettes (ECs) are electronic aerosol delivery systems composed of nicotine and various chemicals, which are widely used to facilitate smoking cessation. Although ECs are considered safer than cigarettes, they do, however, contain chemical toxicants, some of which may interact with cells of the host's innate immune system of which neutrophils constitute a key component.

Methods: The current study was designed to compare the effects of aqueous EC aerosol extracts (ECEs; with or without nicotine) with those of cigarette smoke extract (CSE) on neutrophil and platelet reactivity in vitro. Neutrophil reactivity is characterised by the generation of reactive oxygen species (ROS), degranulation (elastase release) and the release of extracellular DNA (neutrophil extracellular trap (NET) formation: NETosis), which were measured using chemiluminescence, spectrophotometric and microscopic procedures, respectively. Platelet reactivity was measured according to the magnitude of upregulated expression of the adhesion molecule CD62P on activated cells using a flow cytometric procedure.

Results: Exposure of neutrophils to either ECEs or CSE caused a significant inhibition of ROS generation and elastase release by N-formyl-l-methionyl-l-leucyl-l-phenylalanine (1 µM)-activated neutrophils. Pre-treatment of neutrophils with CSE also resulted in a marked attenuation of phorbol 12-myristate 13-acetate (6.25 nM)-mediated release of extracellular DNA, which was unaffected by the ECEs. Similarly, CSE, but not the ECEs, inhibited the expression of CD62P by platelets activated with ADP (100 µM).

Conclusions: These observations suggest that ECE aerosols may inhibit some of the immuno-protective activities of neutrophils such as ROS production and elastase release by activated cells, the effect of which was not enhanced by inclusion of nicotine. The inhibitory effects of CSE were significantly more pronounced than those of ECEs, especially so for suppression of NET formation and platelet activation. If operative in vivo, these harmful immunosuppressive effects of ECEs may compromise intrinsic pulmonary antimicrobial defence mechanisms, albeit less so than cigarette smoke.