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Abstract
Pulmonary surfactant is a critical component of lung function in healthy individuals. It functions in part by lowering surface tension in the alveoli, thereby allowing for breathing with minimal effort. The prevailing thinking is that low surface tension is attained by a compression-driven squeeze-out of unsaturated phospholipids during exhalation, forming a film enriched in saturated phospholipids that achieves surface tensions close to zero. A thorough review of past and recent literature suggests that the compression-driven squeeze-out mechanism may be erroneous. Here, we posit that a surfactant film enriched in saturated lipids is formed shortly after birth by an adsorption-driven sorting process and that its composition does not change during normal breathing. We provide biophysical evidence for the rapid formation of an enriched film at high surfactant concentrations, facilitated by adsorption structures containing hydrophobic surfactant proteins. We examine biophysical evidence for and against the compression-driven squeeze-out mechanism and propose a new model for surfactant function. The proposed model is tested against existing physiological and pathophysiological evidence in neonatal and adult lungs, leading to ideas for biophysical research, that should be addressed to establish the physiological relevance of this new perspective on the function of the mighty thin film that surfactant provides.
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Affiliation(s)
- Fred Possmayer
- Department of Biochemistry, Western University, London, Ontario N6A 3K7, Canada
- Department of Obstetrics/Gynaecology, Western University, London, Ontario N6A 3K7, Canada
| | - Yi Y Zuo
- Department of Mechanical Engineering, University of Hawaii at Manon, Honolulu, Hawaii 96822, United States
- Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96826, United States
| | - Ruud A W Veldhuizen
- Department of Physiology & Pharmacology, Western University, London, Ontario N6A 5C1, Canada
- Department of Medicine, Western University, London, Ontario N6A 3K7, Canada
- Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Nils O Petersen
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada
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2
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Xu X, Li G, Zuo YY. Constrained drop surfactometry for studying adsorbed pulmonary surfactant at physiologically relevant high concentrations. Am J Physiol Lung Cell Mol Physiol 2023; 325:L508-L517. [PMID: 37642656 DOI: 10.1152/ajplung.00101.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 07/15/2023] [Accepted: 08/24/2023] [Indexed: 08/31/2023] Open
Abstract
Exogenous surfactant therapy has been used as a standard clinical intervention for treating premature newborns with respiratory distress syndrome. The phospholipid concentrations of exogenous surfactants used in clinical practice are consistently higher than 25 mg/mL; while it was estimated that the phospholipid concentration of endogenous surfactant is approximately in the range between 15 and 50 mg/mL. However, most in vitro biophysical simulations of pulmonary surfactants were only capable of studying surfactant concentrations up to 3 mg/mL, one order of magnitude lower than the physiologically relevant concentration. Using a new in vitro biophysical model, called constrained drop surfactometry, in conjunction with atomic force microscopy and other technological advances, we have investigated the biophysical properties, ultrastructure, and topography of the pulmonary surfactant film adsorbed from the subphase at physiologically relevant high surfactant concentrations of 10-35 mg/mL. It was found that the effect of surfactant concentration on the dynamic surface activity of the surfactant film was only important when the surface area of the surfactant film varied no more than 15%, mimicking normal tidal breathing. The adsorbed surfactant film depicts a multilayer conformation consisting of a layer-by-layer assembly of stacked bilayers with the height of the multilayers proportional to the surfactant concentration. Our experimental data suggest that the biophysical function of these multilayer structures formed after de novo adsorption is to act as a buffer zone to store surface-active materials ejected from the interfacial monolayer under extreme conditions such as deep breathing.NEW & NOTEWORTHY An in vitro biophysical model, called constrained drop surfactometry, was developed to study the biophysical properties, ultrastructure, and topography of the pulmonary surfactant film adsorbed from the subphase at physiologically relevant high surfactant concentrations of 10-35 mg/mL. These results suggest that the biophysical function of multilayers formed after de novo adsorption is to act as a buffer zone to store surface-active materials ejected from the interfacial monolayer under extreme conditions such as deep breathing.
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Affiliation(s)
- Xiaojie Xu
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
| | - Guangle Li
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
| | - Yi Y Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
- Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, United States
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Sinnberg T, Lichtensteiger C, Ali OH, Pop OT, Jochum AK, Risch L, Brugger SD, Velic A, Bomze D, Kohler P, Vernazza P, Albrich WC, Kahlert CR, Abdou MT, Wyss N, Hofmeister K, Niessner H, Zinner C, Gilardi M, Tzankov A, Röcken M, Dulovic A, Shambat SM, Ruetalo N, Buehler PK, Scheier TC, Jochum W, Kern L, Henz S, Schneider T, Kuster GM, Lampart M, Siegemund M, Bingisser R, Schindler M, Schneiderhan-Marra N, Kalbacher H, McCoy KD, Spengler W, Brutsche MH, Maček B, Twerenbold R, Penninger JM, Matter MS, Flatz L. Pulmonary Surfactant Proteins Are Inhibited by Immunoglobulin A Autoantibodies in Severe COVID-19. Am J Respir Crit Care Med 2023; 207:38-49. [PMID: 35926164 PMCID: PMC9952873 DOI: 10.1164/rccm.202201-0011oc] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Rationale: Coronavirus disease 2019 (COVID-19) can lead to acute respiratory distress syndrome with fatal outcomes. Evidence suggests that dysregulated immune responses, including autoimmunity, are key pathogenic factors. Objectives: To assess whether IgA autoantibodies target lung-specific proteins and contribute to disease severity. Methods: We collected 147 blood, 9 lung tissue, and 36 BAL fluid samples from three tertiary hospitals in Switzerland and one in Germany. Severe COVID-19 was defined by the need to administer oxygen. We investigated the presence of IgA autoantibodies and their effects on pulmonary surfactant in COVID-19 using the following methods: immunofluorescence on tissue samples, immunoprecipitations followed by mass spectrometry on BAL fluid samples, enzyme-linked immunosorbent assays on blood samples, and surface tension measurements with medical surfactant. Measurements and Main Results: IgA autoantibodies targeting pulmonary surfactant proteins B and C were elevated in patients with severe COVID-19 but not in patients with influenza or bacterial pneumonia. Notably, pulmonary surfactant failed to reduce surface tension after incubation with either plasma or purified IgA from patients with severe COVID-19. Conclusions: Our data suggest that patients with severe COVID-19 harbor IgA autoantibodies against pulmonary surfactant proteins B and C and that these autoantibodies block the function of lung surfactant, potentially contributing to alveolar collapse and poor oxygenation.
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Affiliation(s)
- Tobias Sinnberg
- Department of Dermatology,,Cluster of Excellence iFIT (EXC 2180) Image Guided and Functionally Instructed Tumor Therapies,,Department of Dermatology, Venereology and Allergology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, Berlin, Germany
| | | | - Omar Hasan Ali
- Institute of Immunobiology,,Department of Medical Genetics, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada;,Department of Dermatology
| | | | | | - Lorenz Risch
- Center of Laboratory Medicine, Vaduz, Liechtenstein;,Center of Laboratory Medicine, University Institute of Clinical Chemistry, University Hospital Bern, University of Bern, Bern, Switzerland;,Faculty of Medical Sciences, Private University in the Principality of Liechtenstein, Triesen, Liechtenstein
| | | | - Ana Velic
- Proteome Center Tübingen, Interfaculty Institute for Cell Biology
| | - David Bomze
- Institute of Immunobiology,,Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Philipp Kohler
- Division of Infectious Diseases and Hospital Epidemiology
| | | | | | - Christian R. Kahlert
- Division of Infectious Diseases and Hospital Epidemiology,,Department of Infectious Diseases and Hospital Epidemiology, Children’s Hospital of Eastern Switzerland, St. Gallen, Switzerland
| | | | | | | | - Heike Niessner
- Department of Dermatology,,Cluster of Excellence iFIT (EXC 2180) Image Guided and Functionally Instructed Tumor Therapies
| | - Carl Zinner
- Pathology, Institute of Medical Genetics and Pathology
| | - Mara Gilardi
- Pathology, Institute of Medical Genetics and Pathology
| | | | - Martin Röcken
- Department of Dermatology,,Cluster of Excellence iFIT (EXC 2180) Image Guided and Functionally Instructed Tumor Therapies
| | | | | | | | - Philipp K. Buehler
- Institute of Intensive Care Medicine, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | | | | | | | | | | | - Gabriela M. Kuster
- Department of Cardiology and Cardiovascular Research Institute Basel (CRIB)
| | - Maurin Lampart
- Department of Cardiology and Cardiovascular Research Institute Basel (CRIB)
| | - Martin Siegemund
- Intensive Care Unit, Department of Acute Medicine,,Department of Clinical Research, and
| | - Roland Bingisser
- Emergency Department, University Hospital Basel, University of Basel, Basel, Switzerland
| | | | | | - Hubert Kalbacher
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Kathy D. McCoy
- Snyder Institute for Chronic Disease, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Werner Spengler
- Department of Medical Oncology and Pneumology, University Hospital Tübingen, Tübingen, Germany
| | - Martin H. Brutsche
- Institute of Intensive Care Medicine, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Boris Maček
- Proteome Center Tübingen, Interfaculty Institute for Cell Biology
| | - Raphael Twerenbold
- Division of Pneumology, and,University Center of Cardiovascular Science and Department of Cardiology, University Heart and Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Partner Site Hamburg-Kiel-Lübeck, Hamburg, Germany; and
| | - Josef M. Penninger
- Department of Medical Genetics, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada;,Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna, Austria
| | | | - Lukas Flatz
- Department of Dermatology,,Institute of Immunobiology,,Department of Dermatology, Venereology, and Allergology, Cantonal Hospital St. Gallen, St. Gallen, Switzerland;,Department of Dermatology
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Liu JY, Sayes CM. Lung surfactant as a biophysical assay for inhalation toxicology. Curr Res Toxicol 2022; 4:100101. [PMID: 36687216 PMCID: PMC9849875 DOI: 10.1016/j.crtox.2022.100101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Revised: 11/21/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022] Open
Abstract
Lung surfactant (LS) is a mixture of lipids and proteins that forms a thin film at the gas-exchange surfaces of the alveoli. The components and ultrastructure of LS contribute to its biophysical and biochemical functions in the respiratory system, most notably the lowering of surface tension to facilitate breathing mechanics. LS inhibition can be caused by metabolic deficiencies or the intrusion of endogenous or exogenous substances. While LS has been sourced from animals or synthesized for clinical therapeutics, the biofluid mixture has also gained recent interest as a biophysical model for inhalation toxicity. Various methods can be used to evaluate LS function quantitatively or qualitatively after exposure to potential toxicants. A narrative review of the recent literature was conducted. Studies focused whether LS was inhibited by various environmental contaminants, nanoparticles, or manufactured products. A review is also conducted on synthetic lung surfactants (SLS), which have emerged as a promising alternative to conventional animal-sourced LS. The intrinsic advantages and recent advances of SLS make a strong case for more widespread usage in LS-based toxicological assays.
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Affiliation(s)
| | - Christie M. Sayes
- Corresponding author at: Baylor University, Department of Environmental Science, One Bear Place # 97266, Waco, TX 76798-7266.
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Wu M, Wang F, Chen J, Zhang H, Zeng H, Liu J. Interactions of model airborne particulate matter with dipalmitoyl phosphatidylcholine and a clinical surfactant Calsurf. J Colloid Interface Sci 2021; 607:1993-2009. [PMID: 34798708 DOI: 10.1016/j.jcis.2021.09.193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 09/29/2021] [Accepted: 09/30/2021] [Indexed: 12/31/2022]
Abstract
HYPOTHESIS Lung surfactant protects lung tissue and reduces the surface tension in the alveoli during respiration. Particulate matter with an aerodynamic diameter of less than 2.5 μm (PM2.5), which invades primely through inhalation, can deposit on and interact with the surfactant layer, leading to changes in the biophysical and morphological properties of the lung surfactant. EXPERIMENTS Langmuir monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and clinical surfactant Calsurf were investigated with a PM2.5 model injected into the water subphase, which were characterized by surface pressure-area isotherms, Brewster angle microscopy, atomic force microscopy, fluorescent microscopy, and x-ray photoelectron spectroscopy. The binding between DPPC/Calsurf and PM2.5 was studied using isothermal titration calorimetry. FINDINGS PM2.5 induced the expansion of the monolayers at low surface pressure (п) and film condensation at high п. Aggregation of PM2.5 mainly occurred at the interface of liquid expanded/liquid condensed (LE/LC) phases. PM2.5 led to slimmer and ramified LC domains on DPPC and the reduction of nano-sized condensed domains on Calsurf. Both DPPC and Calsurf showed fast binding with PM2.5 through complex binding modes attributed to the heterogeneity and amphiphilic property of PM2.5. This study improves the fundamental understanding of PM2.5-lung surfactant interaction and shows useful implications of the toxicity of PM2.5 through respiration process.
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Affiliation(s)
- Min Wu
- The Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong 510700, China; Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Feifei Wang
- The Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong 510700, China; Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Jingsi Chen
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Hao Zhang
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Hongbo Zeng
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
| | - Jifang Liu
- The Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong 510700, China.
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Herman L, De Smedt SC, Raemdonck K. Pulmonary surfactant as a versatile biomaterial to fight COVID-19. J Control Release 2021; 342:170-188. [PMID: 34813878 PMCID: PMC8605818 DOI: 10.1016/j.jconrel.2021.11.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 11/13/2021] [Accepted: 11/15/2021] [Indexed: 02/06/2023]
Abstract
The COVID-19 pandemic has wielded an enormous pressure on global health care systems, economics and politics. Ongoing vaccination campaigns effectively attenuate viral spreading, leading to a reduction of infected individuals, hospitalizations and mortality. Nevertheless, the development of safe and effective vaccines as well as their global deployment is time-consuming and challenging. In addition, such preventive measures have no effect on already infected individuals and can show reduced efficacy against SARS-CoV-2 variants that escape vaccine-induced host immune responses. Therefore, it is crucial to continue the development of specific COVID-19 targeting therapeutics, including small molecular drugs, antibodies and nucleic acids. However, despite clear advantages of local drug delivery to the lung, inhalation therapy of such antivirals remains difficult. This review aims to highlight the potential of pulmonary surfactant (PS) in the treatment of COVID-19. Since SARS-CoV-2 infection can progress to COVID-19-related acute respiratory distress syndrome (CARDS), which is associated with PS deficiency and inflammation, replacement therapy with exogenous surfactant can be considered to counter lung dysfunction. In addition, due to its surface-active properties and membrane-interaction potential, PS can be repurposed to enhance drug spreading along the respiratory epithelium and to promote intracellular drug delivery. By merging these beneficial features, PS can be regarded as a versatile biomaterial to combat respiratory infections, in particular COVID-19.
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Affiliation(s)
- Lore Herman
- Ghent Research Group on Nanomedicines, Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium.
| | - Stefaan C De Smedt
- Ghent Research Group on Nanomedicines, Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium.
| | - Koen Raemdonck
- Ghent Research Group on Nanomedicines, Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium.
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