1
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Martin A, Tempra C, Yu Y, Liekkinen J, Thakker R, Lee H, de Santos Moreno B, Vattulainen I, Rossios C, Javanainen M, Bernardino de la Serna J. Exposure to Aldehyde Cherry e-Liquid Flavoring and Its Vaping Byproduct Disrupt Pulmonary Surfactant Biophysical Function. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:1495-1508. [PMID: 38186267 PMCID: PMC10809783 DOI: 10.1021/acs.est.3c07874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 12/16/2023] [Accepted: 12/18/2023] [Indexed: 01/09/2024]
Abstract
Over the past decade, there has been a significant rise in the use of vaping devices, particularly among adolescents, raising concerns for effects on respiratory health. Pressingly, many recent vaping-related lung injuries are unexplained by current knowledge, and the overall implications of vaping for respiratory health are poorly understood. This study investigates the effect of hydrophobic vaping liquid chemicals on the pulmonary surfactant biophysical function. We focus on the commonly used flavoring benzaldehyde and its vaping byproduct, benzaldehyde propylene glycol acetal. The study involves rigorous testing of the surfactant biophysical function in Langmuir trough and constrained sessile drop surfactometer experiments with both protein-free synthetic surfactant and hydrophobic protein-containing clinical surfactant models. The study reveals that exposure to these vaping chemicals significantly interferes with the synthetic and clinical surfactant biophysical function. Further atomistic simulations reveal preferential interactions with SP-B and SP-C surfactant proteins. Additionally, data show surfactant lipid-vaping chemical interactions and suggest significant transfer of vaping chemicals to the experimental subphase, indicating a toxicological mechanism for the alveolar epithelium. Our study, therefore, reveals novel mechanisms for the inhalational toxicity of vaping. This highlights the need to reassess the safety of vaping liquids for respiratory health, particularly the use of aldehyde chemicals as vaping flavorings.
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Affiliation(s)
- Alexia Martin
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
| | - Carmelo Tempra
- Institute
of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague 6 160 00, Czech Republic
| | - Yuefan Yu
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
| | - Juho Liekkinen
- Department
of Physics, University of Helsinki, Helsinki 00560, Finland
| | - Roma Thakker
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
| | - Hayoung Lee
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
| | - Berta de Santos Moreno
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
| | - Ilpo Vattulainen
- Department
of Physics, University of Helsinki, Helsinki 00560, Finland
| | - Christos Rossios
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
| | - Matti Javanainen
- Institute
of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague 6 160 00, Czech Republic
- Institute
of Biotechnology, University of Helsinki, Helsinki 00790, Finland
| | - Jorge Bernardino de la Serna
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
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2
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Garavaglia ML, Bodega F, Porta C, Milzani A, Sironi C, Dalle-Donne I. Molecular Impact of Conventional and Electronic Cigarettes on Pulmonary Surfactant. Int J Mol Sci 2023; 24:11702. [PMID: 37511463 PMCID: PMC10380520 DOI: 10.3390/ijms241411702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 07/11/2023] [Accepted: 07/15/2023] [Indexed: 07/30/2023] Open
Abstract
The alveolar epithelium is covered by a non-cellular layer consisting of an aqueous hypophase topped by pulmonary surfactant, a lipo-protein mixture with surface-active properties. Exposure to cigarette smoke (CS) affects lung physiology and is linked to the development of several diseases. The macroscopic effects of CS are determined by several types of cell and molecular dysfunction, which, among other consequences, lead to surfactant alterations. The purpose of this review is to summarize the published studies aimed at uncovering the effects of CS on both the lipid and protein constituents of surfactant, discussing the molecular mechanisms involved in surfactant homeostasis that are altered by CS. Although surfactant homeostasis has been the topic of several studies and some molecular pathways can be deduced from an analysis of the literature, it remains evident that many aspects of the mechanisms of action of CS on surfactant homeostasis deserve further investigation.
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Affiliation(s)
| | - Francesca Bodega
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, 20133 Milan, Italy
| | - Cristina Porta
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, 20133 Milan, Italy
| | - Aldo Milzani
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milan, Italy
| | - Chiara Sironi
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, 20133 Milan, Italy
| | - Isabella Dalle-Donne
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milan, Italy
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3
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Dziura M, Castillo SR, DiPasquale M, Gbadamosi O, Zolnierczuk P, Nagao M, Kelley EG, Marquardt D. Investigating the Effect of Medium Chain Triglycerides on the Elasticity of Pulmonary Surfactant. Chem Res Toxicol 2023; 36:643-652. [PMID: 36926887 DOI: 10.1021/acs.chemrestox.2c00349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
In recent years, vaping has increased in both popularity and ease of access. This has led to an outbreak of a relatively new condition known as e-cigarette/vaping-associated lung injury (EVALI). This injury can be caused by physical interactions between the pulmonary surfactant (PS) in the lungs and toxins typically found in vaping solutions, such as medium chain triglycerides (MCT). MCT has been largely used as a carrier agent within many cannabis products commercially available on the market. Pulmonary surfactant ensures proper respiration by maintaining low surface tensions and interface stability throughout each respiratory cycle. Therefore, any impediments to this system that negatively affect the efficacy of this function will have a strong hindrance on the individual's quality of life. Herein, neutron spin echo (NSE) and Langmuir trough rheology were used to probe the effects of MCT on the mechanical properties of pulmonary surfactant. Alongside a porcine surfactant extract, two lipid-only mimics of progressing complexity were used to study MCT effects in a range of systems that are representative of endogenous surfactant. MCT was shown to have a greater biophysical effect on bilayer systems compared to monolayers, which may align with biological data to propose a mechanism of surfactant inhibition by MCT oil.
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Affiliation(s)
- Maksymilian Dziura
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Stuart R Castillo
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Mitchell DiPasquale
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Omotayo Gbadamosi
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Piotr Zolnierczuk
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Michihiro Nagao
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.,Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States.,Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, United States
| | - Elizabeth G Kelley
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Drew Marquardt
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada.,Department of Physics, University of Windsor, Windsor, ON N9B 3P4, Canada
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4
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E-cigarette aerosol exposure of pulmonary surfactant impairs its surface tension reducing function. PLoS One 2022; 17:e0272475. [PMID: 36350850 PMCID: PMC9645651 DOI: 10.1371/journal.pone.0272475] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 09/27/2022] [Indexed: 11/11/2022] Open
Abstract
Introduction E-cigarette (EC) and vaping use continue to remain popular amongst teenage and young adult populations, despite several reports of vaping associated lung injury. One of the first compounds that EC aerosols comes into contact within the lungs during a deep inhalation is pulmonary surfactant. Impairment of surfactant’s critical surface tension reducing activity can contribute to lung dysfunction. Currently, information on how EC aerosols impacts pulmonary surfactant remains limited. We hypothesized that exposure to EC aerosol impairs the surface tension reducing ability of surfactant. Methods Bovine Lipid Extract Surfactant (BLES) was used as a model surfactant in a direct exposure syringe system. BLES (2ml) was placed in a syringe (30ml) attached to an EC. The generated aerosol was drawn into the syringe and then expelled, repeated 30 times. Biophysical analysis after exposure was completed using a constrained drop surfactometer (CDS). Results Minimum surface tensions increased significantly after exposure to the EC aerosol across 20 compression/expansion cycles. Mixing of non-aerosolized e-liquid did not result in significant changes. Variation in device used, addition of nicotine, or temperature of the aerosol had no additional effect. Two e-liquid flavours, menthol and red wedding, had further detrimental effects, resulting in significantly higher surface tension than the vehicle exposed BLES. Menthol exposed BLES has the highest minimum surface tensions across all 20 compression/expansion cycles. Alteration of surfactant properties through interaction with the produced aerosol was observed with a basic e-liquid vehicle, however additional compounds produced by added flavourings appeared to be able to increase inhibition. Conclusion EC aerosols alter surfactant function through increases in minimum surface tension. This impairment may contribute to lung dysfunction and susceptibility to further injury.
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5
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Milad N, Morissette MC. Revisiting the role of pulmonary surfactant in chronic inflammatory lung diseases and environmental exposure. Eur Respir Rev 2021; 30:30/162/210077. [PMID: 34911693 DOI: 10.1183/16000617.0077-2021] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 08/05/2021] [Indexed: 12/12/2022] Open
Abstract
Pulmonary surfactant is a crucial and dynamic lung structure whose primary functions are to reduce alveolar surface tension and facilitate breathing. Though disruptions in surfactant homeostasis are typically thought of in the context of respiratory distress and premature infants, many lung diseases have been noted to have significant surfactant abnormalities. Nevertheless, preclinical and clinical studies of pulmonary disease too often overlook the potential contribution of surfactant alterations - whether in quantity, quality or composition - to disease pathogenesis and symptoms. In inflammatory lung diseases, whether these changes are cause or consequence remains a subject of debate. This review will outline 1) the importance of pulmonary surfactant in the maintenance of respiratory health, 2) the diseases associated with primary surfactant dysregulation, 3) the surfactant abnormalities observed in inflammatory pulmonary diseases and, finally, 4) the available research on the interplay between surfactant homeostasis and smoking-associated lung disease. From these published studies, we posit that changes in surfactant integrity and composition contribute more considerably to chronic inflammatory pulmonary diseases and that more work is required to determine the mechanisms underlying these alterations and their potential treatability.
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Affiliation(s)
- Nadia Milad
- Faculty of Medicine, Université Laval, Quebec City, QC, Canada.,Quebec Heart and Lung Institute - Université Laval, Quebec City, QC, Canada
| | - Mathieu C Morissette
- Quebec Heart and Lung Institute - Université Laval, Quebec City, QC, Canada .,Dept of Medicine, Faculty of Medicine, Université Laval, Quebec City, QC, Canada
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6
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Hayeck N, Zoghzoghi C, Karam E, Salman R, Karaoghlanian N, Shihadeh A, Eissenberg T, Zein El Dine S, Saliba NA. Carrier Solvents of Electronic Nicotine Delivery Systems Alter Pulmonary Surfactant. Chem Res Toxicol 2021; 34:1572-1577. [PMID: 33945261 PMCID: PMC8220501 DOI: 10.1021/acs.chemrestox.0c00528] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
![]()
In late 2019, hundreds
of users of electronic products that aerosolize
a liquid for inhalation were hospitalized with a variety of respiratory
and gastrointestinal symptoms. While some investigations have attributed
the disease to the presence of vitamin E acetate in liquids that also
contained tetrahydrocannabinol, some evidence suggests that chronic
inhalation of two common solvents used in electronic nicotine delivery
systems (ENDS), propylene glycol (PG) and vegetable glycerin (VG),
can interfere with the lipid components of pulmonary surfactant and
cause or exacerbate pulmonary injury. The interaction between PG,
VG, and lung surfactant is not yet understood. This study presents
an examination of the molecular interactions of PG and VG with lung
surfactant mimicked by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine
(DPPC). The interaction of DPPC and PG-VG is studied by attenuated
total reflectance fourier transform infrared spectroscopy. The results
showed that PG and VG altered the molecular alignment of the DPPC
surfactant. The orientation of the surfactant at the surface of the
lung affects the surface tension at the air–water interface,
thereby influencing breathing. These findings suggest that chronic
aerosolization of the primary solvents in ENDS might alter the function
of pulmonary surfactant.
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Affiliation(s)
- Nathalie Hayeck
- Chemistry Department, Faculty of Arts and Sciences, American University of Beirut, Beirut 1107-2020, Lebanon.,Center for the Study of Tobacco Products, Department of Psychology, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Carl Zoghzoghi
- Chemistry Department, Faculty of Arts and Sciences, American University of Beirut, Beirut 1107-2020, Lebanon
| | - Ebrahim Karam
- Center for the Study of Tobacco Products, Department of Psychology, Virginia Commonwealth University, Richmond, Virginia 23284, United States.,Mechanical Engineering Department, Maroun Semaan Faculty of Engineering and Architecture, American University of Beirut, 1107-2020 Beirut, Lebanon
| | - Rola Salman
- Center for the Study of Tobacco Products, Department of Psychology, Virginia Commonwealth University, Richmond, Virginia 23284, United States.,Mechanical Engineering Department, Maroun Semaan Faculty of Engineering and Architecture, American University of Beirut, 1107-2020 Beirut, Lebanon
| | - Nareg Karaoghlanian
- Center for the Study of Tobacco Products, Department of Psychology, Virginia Commonwealth University, Richmond, Virginia 23284, United States.,Mechanical Engineering Department, Maroun Semaan Faculty of Engineering and Architecture, American University of Beirut, 1107-2020 Beirut, Lebanon
| | - Alan Shihadeh
- Center for the Study of Tobacco Products, Department of Psychology, Virginia Commonwealth University, Richmond, Virginia 23284, United States.,Mechanical Engineering Department, Maroun Semaan Faculty of Engineering and Architecture, American University of Beirut, 1107-2020 Beirut, Lebanon
| | - Thomas Eissenberg
- Center for the Study of Tobacco Products, Department of Psychology, Virginia Commonwealth University, Richmond, Virginia 23284, United States.,Department of Psychology, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Salah Zein El Dine
- Department of Internal Medicine, Faculty of Medicine, American University of Beirut, 1107-2020 Beirut, Lebanon
| | - Najat A Saliba
- Chemistry Department, Faculty of Arts and Sciences, American University of Beirut, Beirut 1107-2020, Lebanon.,Center for the Study of Tobacco Products, Department of Psychology, Virginia Commonwealth University, Richmond, Virginia 23284, United States
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7
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Toxicology of flavoring- and cannabis-containing e-liquids used in electronic delivery systems. Pharmacol Ther 2021; 224:107838. [PMID: 33746051 DOI: 10.1016/j.pharmthera.2021.107838] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 03/11/2021] [Indexed: 12/15/2022]
Abstract
Electronic cigarettes (e-cigarettes) were introduced in the United States in 2007 and by 2014 they were the most popular tobacco product amongst youth and had overtaken use of regular tobacco cigarettes. E-cigarettes are used to aerosolize a liquid (e-liquid) that the user inhales. Flavorings in e-liquids is a primary reason for youth to initiate use of e-cigarettes. Evidence is growing in the scientific literature that inhalation of some flavorings is not without risk of harm. In this review, 67 original articles (primarily cellular in vitro) on the toxicity of flavored e-liquids were identified in the PubMed and Scopus databases and evaluated critically. At least 65 individual flavoring ingredients in e-liquids or aerosols from e-cigarettes induced toxicity in the respiratory tract, cardiovascular and circulatory systems, skeletal system, and skin. Cinnamaldehyde was most frequently reported to be cytotoxic, followed by vanillin, menthol, ethyl maltol, ethyl vanillin, benzaldehyde and linalool. Additionally, modern e-cigarettes can be modified to aerosolize cannabis as dried plant material or a concentrated extract. The U.S. experienced an outbreak of lung injuries, termed e-cigarette, or vaping, product use-associated lung injury (EVALI) that began in 2019; among 2,022 hospitalized patients who had data on substance use (as of January 14, 2020), 82% reported using a delta-9-tetrahydrocannabinol (main psychoactive component in cannabis) containing e-cigarette, or vaping, product. Our literature search identified 33 articles related to EVALI. Vitamin E acetate, a diluent and thickening agent in cannabis-based products, was strongly linked to the EVALI outbreak in epidemiologic and laboratory studies; however, e-liquid chemistry is highly complex, and more than one mechanism of lung injury, ingredient, or thermal breakdown product may be responsible for toxicity. More research is needed, particularly with regard to e-cigarettes (generation, power settings, etc.), e-liquids (composition, bulk or vaped form), modeled systems (cell type, culture type, and dosimetry metrics), biological monitoring, secondhand exposures and contact with residues that contain nicotine and flavorings, and causative agents and mechanisms of EVALI toxicity.
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8
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Sosnowski TR, Jabłczyńska K, Odziomek M, Schlage WK, Kuczaj AK. Physicochemical studies of direct interactions between lung surfactant and components of electronic cigarettes liquid mixtures. Inhal Toxicol 2018; 30:159-168. [PMID: 29932004 DOI: 10.1080/08958378.2018.1478916] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Direct physicochemical interactions between the major components of electronic cigarette liquids (e-liquids): glycerol (VG) and propylene glycol (PG), and lung surfactant (LS) were studied by determining the dynamic surface tension under a simulated breathing cycle using drop shape method. The studies were performed for a wide range of concentrations based on estimated doses of e-liquid aerosols (up to 2500 × the expected nominal concentrations) and for various VG/PG ratios. The results are discussed as relationships among mean surface tension, surface tension amplitude, and surface rheological properties (dilatational elasticity and viscosity) versus concentration and composition of e-liquid. The results showed that high local concentrations (>200 × higher than the estimated average dose after a single puffing session) may induce measurable changes in biophysical activity of LS; however, only ultra-high e-liquid concentrations inactivated the surfactant. Physiochemical characterization of e-liquids provide additional insights for the safety assessment of electronic nicotine delivery systems (ENDS).
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Affiliation(s)
- Tomasz R Sosnowski
- a Faculty of Chemical and Process Engineering , Warsaw University of Technology , Warsaw , Poland
| | - Katarzyna Jabłczyńska
- a Faculty of Chemical and Process Engineering , Warsaw University of Technology , Warsaw , Poland
| | - Marcin Odziomek
- a Faculty of Chemical and Process Engineering , Warsaw University of Technology , Warsaw , Poland
| | - Walter K Schlage
- b Philip Morris International R&D, Philip Morris Products S.A. (part of Philip Morris International group of companies) , Neuchâtel, Switzerland
| | - Arkadiusz K Kuczaj
- b Philip Morris International R&D, Philip Morris Products S.A. (part of Philip Morris International group of companies) , Neuchâtel, Switzerland.,c Department of Applied Mathematics, Faculty EEMCS , University of Twente , Enschede , The Netherlands
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9
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Davies MJ, Leach AG, Riley F. An investigation into drug partitioning behaviour in simulated pulmonary surfactant monolayers with associated molecular modelling. SURF INTERFACE ANAL 2018. [DOI: 10.1002/sia.6379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Michael J. Davies
- The School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
| | - Andrew G. Leach
- The School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
| | - Fatima Riley
- The School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
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10
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Davies MJ, Birkett JW, Court O, Mottram A, Zoroaster F. The impact of cannabis smoke on the performance of pulmonary surfactant under physiologically relevant conditions. SURF INTERFACE ANAL 2017. [DOI: 10.1002/sia.6357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Michael J. Davies
- The School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
| | - Jason W. Birkett
- The School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
| | - Olivia Court
- The School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
| | - Alicia Mottram
- The School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
| | - Farbod Zoroaster
- The School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
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11
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Electronic cigarette vapor alters the lateral structure but not tensiometric properties of calf lung surfactant. Respir Res 2017; 18:193. [PMID: 29149889 PMCID: PMC5693547 DOI: 10.1186/s12931-017-0676-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 10/25/2017] [Indexed: 12/24/2022] Open
Abstract
Background Despite their growing popularity, the potential respiratory toxicity of electronic cigarettes (e-cigarettes) remains largely unknown. One potential aspect of e-cigarette toxicity is the effect of e-cigarette vapor on lung surfactant function. Lung surfactant is a mixture of lipids and proteins that lines the alveolar region. The surfactant layer reduces the surface tension of the alveolar fluid, thereby playing a crucial role in lung stability. Due to their small size, particulates in e-cigarette vapor can penetrate the deep lungs and come into contact with the lung surfactant. The current study sought to examine the potential adverse effects of e-cigarette vapor and conventional cigarette smoke on lung surfactant interfacial properties. Methods Infasurf®, a clinically used and commercially available calf lung surfactant extract, was used as lung surfactant model. Infasurf® films were spread on top of an aqueous subphase in a Langmuir trough with smoke particulates from conventional cigarettes or vapor from different flavors of e-cigarettes dispersed in the subphase. Surfactant interfacial properties were measured in real-time upon surface compression while surfactant lateral structure after exposure to smoke or vapor was examined using atomic force microscopy (AFM). Results E-cigarette vapor regardless of the dose and flavoring of the e-liquid did not affect surfactant interfacial properties. In contrast, smoke from conventional cigarettes had a drastic, dose-dependent effect on Infasurf® interfacial properties reducing the maximum surface pressure from 65.1 ± 0.2 mN/m to 46.1 ± 1.3 mN/m at the highest dose. Cigarette smoke and e-cigarette vapor both altered surfactant microstructure resulting in an increase in the area of lipid multilayers. Studies with individual smoke components revealed that tar was the smoke component most disruptive to surfactant function. Conclusions While both e-cigarette vapor and conventional cigarette smoke affect surfactant lateral structure, only cigarette smoke disrupts surfactant interfacial properties. The surfactant inhibitory compound in conventional cigarettes is tar, which is a product of burning and is thus absent in e-cigarette vapor.
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