1
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Walther FJ, Waring AJ. Structure and Function of Canine SP-C Mimic Proteins in Synthetic Surfactant Lipid Dispersions. Biomedicines 2024; 12:163. [PMID: 38255268 PMCID: PMC10813813 DOI: 10.3390/biomedicines12010163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 01/03/2024] [Accepted: 01/08/2024] [Indexed: 01/24/2024] Open
Abstract
Lung surfactant is a mixture of lipids and proteins and is essential for air breathing in mammals. The hydrophobic surfactant proteins B and C (SP-B and SP-C) assist in reducing surface tension in the lung alveoli by organizing the surfactant lipids. SP-B deficiency is life-threatening, and a lack of SP-C can lead to progressive interstitial lung disease. B-YL (41 amino acids) is a highly surface-active, sulfur-free peptide mimic of SP-B (79 amino acids) in which the four cysteine residues are replaced by tyrosine. Mammalian SP-C (35 amino acids) contains two cysteine-linked palmitoyl groups at positions 5 and 6 in the N-terminal region that override the β-sheet propensities of the native sequence. Canine SP-C (34 amino acids) is exceptional because it has only one palmitoylated cysteine residue at position 4 and a phenylalanine at position 5. We developed canine SP-C constructs in which the palmitoylated cysteine residue at position 4 is replaced by phenylalanine (SP-Cff) or serine (SP-Csf) and a glutamic acid-lysine ion-lock was placed at sequence positions 20-24 of the hydrophobic helical domain to enhance its alpha helical propensity. AI modeling, molecular dynamics, circular dichroism spectroscopy, Fourier Transform InfraRed spectroscopy, and electron spin resonance studies showed that the secondary structure of canine SP-Cff ion-lock peptide was like that of native SP-C, suggesting that substitution of phenylalanine for cysteine has no apparent effect on the secondary structure of the peptide. Captive bubble surfactometry demonstrated higher surface activity for canine SP-Cff ion-lock peptide in combination with B-YL in surfactant lipids than with canine SP-Csf ion-lock peptide. These studies demonstrate the potential of canine SP-Cff ion-lock peptide to enhance the functionality of the SP-B peptide mimic B-YL in synthetic surfactant lipids.
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Affiliation(s)
- Frans J. Walther
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA 90502, USA
- Department of Pediatrics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Alan J. Waring
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA 90502, USA
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
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2
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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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3
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Liekkinen J, Olżyńska A, Cwiklik L, Bernardino de la Serna J, Vattulainen I, Javanainen M. Surfactant Proteins SP-B and SP-C in Pulmonary Surfactant Monolayers: Physical Properties Controlled by Specific Protein-Lipid Interactions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:4338-4350. [PMID: 36917773 PMCID: PMC10061932 DOI: 10.1021/acs.langmuir.2c03349] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 02/07/2023] [Indexed: 06/18/2023]
Abstract
The lining of the alveoli is covered by pulmonary surfactant, a complex mixture of surface-active lipids and proteins that enables efficient gas exchange between inhaled air and the circulation. Despite decades of advancements in the study of the pulmonary surfactant, the molecular scale behavior of the surfactant and the inherent role of the number of different lipids and proteins in surfactant behavior are not fully understood. The most important proteins in this complex system are the surfactant proteins SP-B and SP-C. Given this, in this work we performed nonequilibrium all-atom molecular dynamics simulations to study the interplay of SP-B and SP-C with multicomponent lipid monolayers mimicking the pulmonary surfactant in composition. The simulations were complemented by z-scan fluorescence correlation spectroscopy and atomic force microscopy measurements. Our state-of-the-art simulation model reproduces experimental pressure-area isotherms and lateral diffusion coefficients. In agreement with previous research, the inclusion of either SP-B and SP-C increases surface pressure, and our simulations provide a molecular scale explanation for this effect: The proteins display preferential lipid interactions with phosphatidylglycerol, they reside predominantly in the lipid acyl chain region, and they partition into the liquid expanded phase or even induce it in an otherwise packed monolayer. The latter effect is also visible in our atomic force microscopy images. The research done contributes to a better understanding of the roles of specific lipids and proteins in surfactant function, thus helping to develop better synthetic products for surfactant replacement therapy used in the treatment of many fatal lung-related injuries and diseases.
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Affiliation(s)
- Juho Liekkinen
- Department
of Physics, University of Helsinki, FI-00560 Helsinki, Finland
| | - Agnieszka Olżyńska
- J.
Heyrovský Institute of Physical Chemistry, Czech Academy of
Sciences, CZ-18223 Prague, Czech Republic
| | - Lukasz Cwiklik
- J.
Heyrovský Institute of Physical Chemistry, Czech Academy of
Sciences, CZ-18223 Prague, Czech Republic
| | - Jorge Bernardino de la Serna
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
- NIHR
Imperial Biomedical Research Centre, London SW7 2AZ, U.K.
| | - Ilpo Vattulainen
- Department
of Physics, University of Helsinki, FI-00560 Helsinki, Finland
| | - Matti Javanainen
- Institute
of Biotechnology, University of Helsinki, FI-00790 Helsinki, Finland
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, CZ-16100 Prague 6, Czech Republic
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4
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Xu Y, Parra-Ortiz E, Wan F, Cañadas O, Garcia-Alvarez B, Thakur A, Franzyk H, Pérez-Gil J, Malmsten M, Foged C. Insights into the mechanisms of interaction between inhalable lipid-polymer hybrid nanoparticles and pulmonary surfactant. J Colloid Interface Sci 2023; 633:511-525. [PMID: 36463820 DOI: 10.1016/j.jcis.2022.11.059] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 10/15/2022] [Accepted: 11/11/2022] [Indexed: 11/16/2022]
Abstract
Pulmonary delivery of small interfering RNA (siRNA) using nanoparticle-based delivery systems is promising for local treatment of respiratory diseases. We designed dry powder inhaler formulations of siRNA-loaded lipid-polymer hybrid nanoparticles (LPNs) with aerosolization properties optimized for inhalation therapy. Interactions between LPNs and pulmonary surfactant (PS) determine the fate of inhaled LPNs, but interaction mechanisms are unknown. Here we used surface-sensitive techniques to study how physicochemical properties and pathological microenvironments influence interactions between siRNA-loaded LPNs and supported PS layers. PS was deposited on SiO2 surfaces as single bilayer or multilayers and characterized using quartz crystal microbalance with dissipation monitoring and Fourier-transform infrared spectroscopy with attenuated total reflection. Immobilization of PS as multilayers, resembling the structural PS organization in the alveolar subphase, effectively reduced the relative importance of interactions between PS and the underlying surface. However, the binding affinity between PS and LPNs was identical in the two models. The physicochemical LPN properties influenced the translocation pathways and retention time of LPNs. Membrane fluidity and electrostatic interactions were decisive for the interaction strength between LPNs and PS. Experimental conditions reflecting pathological microenvironments promoted LPN deposition. Hence, these results shed new light on design criteria for LPN transport through the air-blood barrier.
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Affiliation(s)
- You Xu
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark
| | - Elisa Parra-Ortiz
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark
| | - Feng Wan
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark
| | - Olga Cañadas
- Department of Biochemistry and Molecular Biology, Faculty of Biology, Complutense University, 28040 Madrid, Spain; Research Institute "Hospital 12 de Octubre (imas12)", Madrid, Spain
| | - Begoña Garcia-Alvarez
- Research Institute "Hospital 12 de Octubre (imas12)", Madrid, Spain; Department of Biochemistry and Molecular Biology, Faculty of Chemistry, Complutense University, 28040 Madrid, Spain
| | - Aneesh Thakur
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark
| | - Henrik Franzyk
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 162, 2100 Copenhagen Ø, Denmark
| | - Jesús Pérez-Gil
- Department of Biochemistry and Molecular Biology, Faculty of Biology, Complutense University, 28040 Madrid, Spain; Research Institute "Hospital 12 de Octubre (imas12)", Madrid, Spain
| | - Martin Malmsten
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark; Department of Physical Chemistry 1, University of Lund, SE-22100 Lund, Sweden
| | - Camilla Foged
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark.
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5
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Dixit G, Stowe RB, Bates A, Jaycox CK, Escobar JR, Harding BD, Drew DL, New CP, Sahu ID, Edelmann RE, Dabney-Smith C, Sanders CR, Lorigan GA. Purification and membrane interactions of human KCNQ1 100-370 potassium ion channel. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:184010. [PMID: 35870481 DOI: 10.1016/j.bbamem.2022.184010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 07/12/2022] [Accepted: 07/14/2022] [Indexed: 06/15/2023]
Abstract
KCNQ1 (Kv7.1 or KvLQT1) is a voltage-gated potassium ion channel that is involved in the ventricular repolarization following an action potential in the heart. It forms a complex with KCNE1 in the heart and is the pore forming subunit of slow delayed rectifier potassium current (Iks). Mutations in KCNQ1, leading to a dysfunctional channel or loss of activity have been implicated in a cardiac disorder, long QT syndrome. In this study, we report the overexpression, purification, biochemical characterization of human KCNQ1100-370, and lipid bilayer dynamics upon interaction with KCNQ1100-370. The recombinant human KCNQ1 was expressed in Escherichia coli and purified into n-dodecylphosphocholine (DPC) micelles. The purified KCNQ1100-370 was biochemically characterized by SDS-PAGE electrophoresis, western blot and nano-LC-MS/MS to confirm the identity of the protein. Circular dichroism (CD) spectroscopy was utilized to confirm the secondary structure of purified protein in vesicles. Furthermore, 31P and 2H solid-state NMR spectroscopy in DPPC/POPC/POPG vesicles (MLVs) indicated a direct interaction between KCNQ100-370 and the phospholipid head groups. Finally, a visual inspection of KCNQ1100-370 incorporated into MLVs was confirmed by transmission electron microscopy (TEM). The findings of this study provide avenues for future structural studies of the human KCNQ1 ion channel to have an in depth understanding of its structure-function relationship.
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Affiliation(s)
- Gunjan Dixit
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Rebecca B Stowe
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Alison Bates
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Colleen K Jaycox
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Jorge R Escobar
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Benjamin D Harding
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Daniel L Drew
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Christopher P New
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Richard E Edelmann
- Center for Advanced Microscopy and Imaging, Miami University, Oxford, OH 45056, USA
| | - Carole Dabney-Smith
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Charles R Sanders
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA.
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6
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Fluid Films as Models for Understanding the Impact of Inhaled Particles in Lung Surfactant Layers. COATINGS 2022. [DOI: 10.3390/coatings12020277] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Pollution is currently a public health problem associated with different cardiovascular and respiratory diseases. These are commonly originated as a result of the pollutant transport to the alveolar cavity after their inhalation. Once pollutants enter the alveolar cavity, they are deposited on the lung surfactant (LS) film, altering their mechanical performance which increases the respiratory work and can induce a premature alveolar collapse. Furthermore, the interactions of pollutants with LS can induce the formation of an LS corona decorating the pollutant surface, favoring their penetration into the bloodstream and distribution along different organs. Therefore, it is necessary to understand the most fundamental aspects of the interaction of particulate pollutants with LS to mitigate their effects, and design therapeutic strategies. However, the use of animal models is often invasive, and requires a careful examination of different bioethics aspects. This makes it necessary to design in vitro models mimicking some physico-chemical aspects with relevance for LS performance, which can be done by exploiting the tools provided by the science and technology of interfaces to shed light on the most fundamental physico-chemical bases governing the interaction between LS and particulate matter. This review provides an updated perspective of the use of fluid films of LS models for shedding light on the potential impact of particulate matter in the performance of LS film. It should be noted that even though the used model systems cannot account for some physiological aspects, it is expected that the information contained in this review can contribute on the understanding of the potential toxicological effects of air pollution.
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7
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Da Silva E, Vogel U, Hougaard KS, Pérez-Gil J, Zuo YY, Sørli JB. An adverse outcome pathway for lung surfactant function inhibition leading to decreased lung function. Curr Res Toxicol 2021; 2:225-236. [PMID: 34345865 PMCID: PMC8320609 DOI: 10.1016/j.crtox.2021.05.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 05/19/2021] [Accepted: 05/25/2021] [Indexed: 12/27/2022] Open
Abstract
Inhaled substances, such as consumer products, chemicals at the workplace, and nanoparticles, can affect the lung function in several ways. In this paper, we explore the adverse outcome pathway (AOP) that starts when inhaled substances that reach the alveoli inhibit the function of the lung surfactant, and leads to decreased lung function. Lung surfactant covers the inner surface of the alveoli, and regulates the surface tension at the air-liquid interface during breathing. The inhibition of the lung surfactant function leads to alveolar collapse because of the resulting high surface tension at the end of expiration. The collapsed alveoli can be re-opened by inspiration, but this re-opening causes shear stress on cells covering the alveoli. This can damage the alveolar-capillary membrane integrity, allowing blood components to enter the alveolar airspace. Blood components, such as albumin, can interact with the lung surfactant and further inhibit its function. The collapse of the alveoli is responsible for a decrease in the surface area available for blood oxygenation, and it reduces the volume of air that can be inhaled and exhaled. These different key events lead to decreased lung function, characterized by clinical signs of respiratory toxicity and reduced blood oxygenation. Here we present the weight of evidence that supports the AOP, and we give an overview of the methods available in vitro and in vivo to measure each key event of the pathway, and how this AOP can potentially be used in screening for inhalation toxicity.
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Key Words
- AO, adverse outcome
- AOP, adverse outcome pathway
- ARDS, acute respiratory distress syndrome
- Adverse outcome pathway
- Alternative method
- EAGMST, Extended Advisory Group on Molecular Screening and Toxicogenomics
- GHS, Globally Harmonized System of Classification and Labelling of Chemicals
- Inhalation
- KE, key event
- Lung surfactant
- MIE, molecular initiating event
- Nanomaterials
- New approach methodology
- OECD, Organisation for Economic Cooperation and Development
- OI, oxygenation index
- PaO2, dissolved oxygen in the plasma
- SaO2, percentage of hemoglobin saturated with oxygen
- Spray products
- TEER, trans epithelial electrical resistance
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Affiliation(s)
- Emilie Da Silva
- National Research Centre for the Working Environment, Copenhagen, Denmark
- DTU Environment, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Ulla Vogel
- National Research Centre for the Working Environment, Copenhagen, Denmark
- DTU Health Tech, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Karin S. Hougaard
- National Research Centre for the Working Environment, Copenhagen, Denmark
- Department of Public Health, University of Copenhagen, Denmark
| | - Jesus Pérez-Gil
- Faculty of Biology and Research Institute “12 de Octubre (imas12)”, Complutense University, Madrid, Spain
| | - Yi Y. Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, HI, United States
| | - Jorid B. Sørli
- National Research Centre for the Working Environment, Copenhagen, Denmark
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8
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Kiener M, Roldan N, Machahua C, Sengupta A, Geiser T, Guenat OT, Funke-Chambour M, Hobi N, Kruithof-de Julio M. Human-Based Advanced in vitro Approaches to Investigate Lung Fibrosis and Pulmonary Effects of COVID-19. Front Med (Lausanne) 2021; 8:644678. [PMID: 34026781 PMCID: PMC8139419 DOI: 10.3389/fmed.2021.644678] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 04/01/2021] [Indexed: 12/15/2022] Open
Abstract
The coronavirus disease 2019 (COVID-19) pandemic has caused considerable socio-economic burden, which fueled the development of treatment strategies and vaccines at an unprecedented speed. However, our knowledge on disease recovery is sparse and concerns about long-term pulmonary impairments are increasing. Causing a broad spectrum of symptoms, COVID-19 can manifest as acute respiratory distress syndrome (ARDS) in the most severely affected patients. Notably, pulmonary infection with Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), the causing agent of COVID-19, induces diffuse alveolar damage (DAD) followed by fibrotic remodeling and persistent reduced oxygenation in some patients. It is currently not known whether tissue scaring fully resolves or progresses to interstitial pulmonary fibrosis. The most aggressive form of pulmonary fibrosis is idiopathic pulmonary fibrosis (IPF). IPF is a fatal disease that progressively destroys alveolar architecture by uncontrolled fibroblast proliferation and the deposition of collagen and extracellular matrix (ECM) proteins. It is assumed that micro-injuries to the alveolar epithelium may be induced by inhalation of micro-particles, pathophysiological mechanical stress or viral infections, which can result in abnormal wound healing response. However, the exact underlying causes and molecular mechanisms of lung fibrosis are poorly understood due to the limited availability of clinically relevant models. Recently, the emergence of SARS-CoV-2 with the urgent need to investigate its pathogenesis and address drug options, has led to the broad application of in vivo and in vitro models to study lung diseases. In particular, advanced in vitro models including precision-cut lung slices (PCLS), lung organoids, 3D in vitro tissues and lung-on-chip (LOC) models have been successfully employed for drug screens. In order to gain a deeper understanding of SARS-CoV-2 infection and ultimately alveolar tissue regeneration, it will be crucial to optimize the available models for SARS-CoV-2 infection in multicellular systems that recapitulate tissue regeneration and fibrotic remodeling. Current evidence for SARS-CoV-2 mediated pulmonary fibrosis and a selection of classical and novel lung models will be discussed in this review.
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Affiliation(s)
- Mirjam Kiener
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department for BioMedical Research DBMR, Urology Research Laboratory, University of Bern, Bern, Switzerland
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Nuria Roldan
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Carlos Machahua
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department for BioMedical Research DBMR, Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Arunima Sengupta
- Organs-on-Chip Technologies, ARTORG Center for Biomedical Engineering, University of Bern, Bern, Switzerland
| | - Thomas Geiser
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department for BioMedical Research DBMR, Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Olivier Thierry Guenat
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Organs-on-Chip Technologies, ARTORG Center for Biomedical Engineering, University of Bern, Bern, Switzerland
- Department of General Thoracic Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Manuela Funke-Chambour
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department for BioMedical Research DBMR, Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Nina Hobi
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Marianna Kruithof-de Julio
- Department for BioMedical Research DBMR, Urology Research Laboratory, University of Bern, Bern, Switzerland
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
- Organoid Core, Department for BioMedical Research, University of Bern, Bern, Switzerland
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9
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Paget TL, Parkinson-Lawrence EJ, Trim PJ, Autilio C, Panchal MH, Koster G, Echaide M, Snel MF, Postle AD, Morrison JL, Pérez-Gil J, Orgeig S. Increased Alveolar Heparan Sulphate and Reduced Pulmonary Surfactant Amount and Function in the Mucopolysaccharidosis IIIA Mouse. Cells 2021; 10:849. [PMID: 33918094 PMCID: PMC8070179 DOI: 10.3390/cells10040849] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/18/2021] [Accepted: 03/24/2021] [Indexed: 02/07/2023] Open
Abstract
Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disease with significant neurological and skeletal pathologies. Respiratory dysfunction is a secondary pathology contributing to mortality in MPS IIIA patients. Pulmonary surfactant is crucial to optimal lung function and has not been investigated in MPS IIIA. We measured heparan sulphate (HS), lipids and surfactant proteins (SP) in pulmonary tissue and bronchoalveolar lavage fluid (BALF), and surfactant activity in healthy and diseased mice (20 weeks of age). Heparan sulphate, ganglioside GM3 and bis(monoacylglycero)phosphate (BMP) were increased in MPS IIIA lung tissue. There was an increase in HS and a decrease in BMP and cholesteryl esters (CE) in MPS IIIA BALF. Phospholipid composition remained unchanged, but BALF total phospholipids were reduced (49.70%) in MPS IIIA. There was a reduction in SP-A, -C and -D mRNA, SP-D protein in tissue and SP-A, -C and -D protein in BALF of MPS IIIA mice. Captive bubble surfactometry showed an increase in minimum and maximum surface tension and percent surface area compression, as well as a higher compressibility and hysteresis in MPS IIIA surfactant upon dynamic cycling. Collectively these biochemical and biophysical changes in alveolar surfactant are likely to be detrimental to lung function in MPS IIIA.
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Affiliation(s)
- Tamara L. Paget
- Mechanisms in Cell Biology and Disease Group, UniSA Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia; (T.L.P.); (E.J.P.-L.)
| | - Emma J. Parkinson-Lawrence
- Mechanisms in Cell Biology and Disease Group, UniSA Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia; (T.L.P.); (E.J.P.-L.)
| | - Paul J. Trim
- Proteomics, Metabolomics and MS-Imaging Core Facility, South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia; (P.J.T.); (M.F.S.)
| | - Chiara Autilio
- Department of Biochemistry, Faculty of Biology and Research Institute Hospital 12 de Octubre (Imas12), Complutense University, 28003 Madrid, Spain; (C.A.); (M.E.); (J.P.-G.)
| | - Madhuriben H. Panchal
- Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK; (M.H.P.); (G.K.); (A.D.P.)
| | - Grielof Koster
- Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK; (M.H.P.); (G.K.); (A.D.P.)
| | - Mercedes Echaide
- Department of Biochemistry, Faculty of Biology and Research Institute Hospital 12 de Octubre (Imas12), Complutense University, 28003 Madrid, Spain; (C.A.); (M.E.); (J.P.-G.)
| | - Marten F. Snel
- Proteomics, Metabolomics and MS-Imaging Core Facility, South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia; (P.J.T.); (M.F.S.)
| | - Anthony D. Postle
- Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK; (M.H.P.); (G.K.); (A.D.P.)
| | - Janna L. Morrison
- Early Origins Adult Health Research Group, Health and Biomedical Innovation, UniSA Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia;
| | - Jésus Pérez-Gil
- Department of Biochemistry, Faculty of Biology and Research Institute Hospital 12 de Octubre (Imas12), Complutense University, 28003 Madrid, Spain; (C.A.); (M.E.); (J.P.-G.)
| | - Sandra Orgeig
- Mechanisms in Cell Biology and Disease Group, UniSA Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia; (T.L.P.); (E.J.P.-L.)
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10
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Structural hallmarks of lung surfactant: Lipid-protein interactions, membrane structure and future challenges. Arch Biochem Biophys 2021; 703:108850. [PMID: 33753033 DOI: 10.1016/j.abb.2021.108850] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/20/2021] [Accepted: 03/16/2021] [Indexed: 11/23/2022]
Abstract
Lung surfactant (LS) is an outstanding example of how a highly regulated and dynamic membrane-based system has evolved to sustain a wealth of structural reorganizations in order to accomplish its biophysical function, as it coats and stabilizes the respiratory air-liquid interface in the mammalian lung. The present review dissects the complexity of the structure-function relationships in LS through an updated description of the lipid-protein interactions and the membrane structures that sustain its synthesis, secretion, interfacial performance and recycling. We also revise the current models and the biophysical techniques employed to study the membranous architecture of LS. It is important to consider that the structure and functional properties of LS are often studied in bulk or under static conditions, in spite that surfactant function is strongly connected with a highly dynamic behaviour, sustained by very polymorphic structures and lipid-lipid, lipid-protein and protein-protein interactions that reorganize in precise spatio-temporal coordinates. We have tried to underline the evidences available of the existence of such structural dynamism in LS. A last important aspect is that the synthesis and assembly of LS is a strongly regulated intracellular process to ensure the establishment of the proper interactions driving LS surface activity, while protecting the integrity of other cell membranes. The use of simplified lipid models or partial natural materials purified from animal tissues could be too simplistic to understand the true molecular mechanisms defining surfactant function in vivo. In this line, we will bring into the attention of the reader the methodological challenges and the questions still open to understand the structure-function relationships of LS at its full biological relevance.
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11
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Da Silva E, Autilio C, Hougaard KS, Baun A, Cruz A, Perez-Gil J, Sørli JB. Molecular and biophysical basis for the disruption of lung surfactant function by chemicals. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1863:183499. [PMID: 33137304 DOI: 10.1016/j.bbamem.2020.183499] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/29/2020] [Accepted: 10/19/2020] [Indexed: 02/06/2023]
Abstract
With the intention to move away from animal testing for the toxicological evaluation of chemicals comes the need to develop new approach methodologies which are mechanism-anchored and target relevant key events leading to an adverse outcome. To date, no validated alternative methods are available for studying the acute inhalation toxicity potential of airborne chemicals but the constrained drop surfactometer measuring the surface tension of a drop of lung surfactant presents as a promising candidate. Indeed, the correlation of the increase in minimum surface tension of lung surfactant in vitro with changes in the breathing patterns of mice after inhalation of test compounds has been shown in multiple studies. However, the causal factors leading to lung surfactant inactivation remain speculative. This paper combines molecular and biophysical methods (constrained drop and captive bubble surfactometers, Langmuir-Blodgett balance, epifluorescence microscopy, cryogenic transmission electron microscopy, and differential scanning calorimetry) applied to purified porcine lung surfactant and dipalmitoylphosphatidylcholine interfacial films to gain insights into the disruption of lung surfactant function by three chemicals known to show acute inhalation toxicity (trimethoxyoctylsilane, methyl 3-oxo-2-pentylcyclopentaneacetate, and diisopentyl ether). The results of this study suggest that the test chemicals intercalate between the phospholipids at the air-liquid interface, reduce the stability of the films, and decrease the cohesivity of interface-associated multilayered structures thereby perturbing the lung surfactant surface activity. These findings contribute to a better understanding of chemically-induced lung surfactant function disruption.
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Affiliation(s)
- Emilie Da Silva
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark; National Research Centre for the Working Environment, Copenhagen, Denmark
| | - Chiara Autilio
- Department of Biochemistry and Molecular Biology, Research Institute "Hospital 12 de Octubre (imas12)", Complutense University, Madrid, Spain
| | | | - Anders Baun
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Antonio Cruz
- Department of Biochemistry and Molecular Biology, Research Institute "Hospital 12 de Octubre (imas12)", Complutense University, Madrid, Spain
| | - Jesus Perez-Gil
- Department of Biochemistry and Molecular Biology, Research Institute "Hospital 12 de Octubre (imas12)", Complutense University, Madrid, Spain
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12
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Lopez-Rodriguez E, Ochs M. Reply to: Comments on “Air Space Distension Precedes Spontaneous Fibrotic Remodeling and Impaired Cholesterol Metabolism in the Absence of Surfactant Protein C”. Am J Respir Cell Mol Biol 2020; 63:399-402. [DOI: 10.1165/rcmb.2020-0158le] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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13
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Ruwisch J, Sehlmeyer K, Roldan N, Garcia-Alvarez B, Perez-Gil J, Weaver TE, Ochs M, Knudsen L, Lopez-Rodriguez E. Air Space Distension Precedes Spontaneous Fibrotic Remodeling and Impaired Cholesterol Metabolism in the Absence of Surfactant Protein C. Am J Respir Cell Mol Biol 2020; 62:466-478. [PMID: 31922895 DOI: 10.1165/rcmb.2019-0358oc] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Surfactant protein (SP)-C deficiency is found in samples from patients with idiopathic pulmonary fibrosis, especially in familial forms of this disease. We hypothesized that SP-C may contribute to fibrotic remodeling in aging mice and alveolar lipid homeostasis. For this purpose, we analyzed lung function, alveolar dynamics, lung structure, collagen content, and expression of genes related to lipid and cholesterol metabolism of aging SP-C knockout mice. In addition, in vitro experiments with an alveolar macrophage cell line exposed to lipid vesicles with or without cholesterol and/or SP-C were performed. Alveolar dynamics showed progressive alveolar derecruitment with age and impaired oxygen saturation. Lung structure revealed that decreasing volume density of alveolar spaces was accompanied by increasing of the ductal counterparts. Simultaneously, septal wall thickness steadily increased, and fibrotic wounds appeared in lungs from the age of 50 weeks. This remarkable phenotype is unique to the 129Sv strain, which has an increased absorption of cholesterol, linking the accumulation of cholesterol and the absence of SP-C to a fibrotic remodeling process. The findings of this study suggest that overall loss of SP-C results in an age-dependent, complex, heterogeneous phenotype characterized by a combination of overdistended air spaces and fibrotic wounds that resembles combined emphysema and pulmonary fibrosis in patients with idiopathic pulmonary fibrosis. Addition of SP-C to cholesterol-laden lipid vesicles enhanced the expression of cholesterol metabolism and transport genes in an alveolar macrophage cell line, identifying a potential new lipid-protein axis involved in lung remodeling.
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Affiliation(s)
- Jannik Ruwisch
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany.,BREATH (Biomedical Research in Endstage and Obstructive Lung Disease Hannover), Member of the German Center for Lung Research, Hannover, Germany
| | - Kirsten Sehlmeyer
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany.,BREATH (Biomedical Research in Endstage and Obstructive Lung Disease Hannover), Member of the German Center for Lung Research, Hannover, Germany
| | - Nuria Roldan
- Alveolix AG and ARTORG Center, University of Bern, Bern, Switzerland.,Biochemistry and Molecular Biology Department, Faculty of Biology, and Research Institute "Hospital 12 de Octubre," Complutense University Madrid, Madrid, Spain
| | - Begoña Garcia-Alvarez
- Biochemistry and Molecular Biology Department, Faculty of Biology, and Research Institute "Hospital 12 de Octubre," Complutense University Madrid, Madrid, Spain
| | - Jesus Perez-Gil
- Biochemistry and Molecular Biology Department, Faculty of Biology, and Research Institute "Hospital 12 de Octubre," Complutense University Madrid, Madrid, Spain
| | - Timothy E Weaver
- Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, Ohio; and
| | - Matthias Ochs
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany.,BREATH (Biomedical Research in Endstage and Obstructive Lung Disease Hannover), Member of the German Center for Lung Research, Hannover, Germany.,Institute of Vegetative Anatomy, Charité-Universitaetsmedizin Berlin, Berlin, Germany
| | - Lars Knudsen
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany.,BREATH (Biomedical Research in Endstage and Obstructive Lung Disease Hannover), Member of the German Center for Lung Research, Hannover, Germany.,Institute of Vegetative Anatomy, Charité-Universitaetsmedizin Berlin, Berlin, Germany
| | - Elena Lopez-Rodriguez
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany.,BREATH (Biomedical Research in Endstage and Obstructive Lung Disease Hannover), Member of the German Center for Lung Research, Hannover, Germany.,Institute of Vegetative Anatomy, Charité-Universitaetsmedizin Berlin, Berlin, Germany
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14
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Lipid-Protein and Protein-Protein Interactions in the Pulmonary Surfactant System and Their Role in Lung Homeostasis. Int J Mol Sci 2020; 21:ijms21103708. [PMID: 32466119 PMCID: PMC7279303 DOI: 10.3390/ijms21103708] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 12/12/2022] Open
Abstract
Pulmonary surfactant is a lipid/protein complex synthesized by the alveolar epithelium and secreted into the airspaces, where it coats and protects the large respiratory air–liquid interface. Surfactant, assembled as a complex network of membranous structures, integrates elements in charge of reducing surface tension to a minimum along the breathing cycle, thus maintaining a large surface open to gas exchange and also protecting the lung and the body from the entrance of a myriad of potentially pathogenic entities. Different molecules in the surfactant establish a multivalent crosstalk with the epithelium, the immune system and the lung microbiota, constituting a crucial platform to sustain homeostasis, under health and disease. This review summarizes some of the most important molecules and interactions within lung surfactant and how multiple lipid–protein and protein–protein interactions contribute to the proper maintenance of an operative respiratory surface.
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15
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Sehlmeyer K, Ruwisch J, Roldan N, Lopez-Rodriguez E. Alveolar Dynamics and Beyond - The Importance of Surfactant Protein C and Cholesterol in Lung Homeostasis and Fibrosis. Front Physiol 2020; 11:386. [PMID: 32431623 PMCID: PMC7213507 DOI: 10.3389/fphys.2020.00386] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 03/30/2020] [Indexed: 12/13/2022] Open
Abstract
Surfactant protein C (SP-C) is an important player in enhancing the interfacial adsorption of lung surfactant lipid films to the alveolar air-liquid interface. Doing so, surface tension drops down enough to stabilize alveoli and the lung, reducing the work of breathing. In addition, it has been shown that SP-C counteracts the deleterious effect of high amounts of cholesterol in the surfactant lipid films. On its side, cholesterol is a well-known modulator of the biophysical properties of biological membranes and it has been proven that it activates the inflammasome pathways in the lung. Even though the molecular mechanism is not known, there are evidences suggesting that these two molecules may interplay with each other in order to keep the proper function of the lung. This review focuses in the role of SP-C and cholesterol in the development of lung fibrosis and the potential pathways in which impairment of both molecules leads to aberrant lung repair, and therefore impaired alveolar dynamics. From molecular to cellular mechanisms to evidences in animal models and human diseases. The evidences revised here highlight a potential SP-C/cholesterol axis as target for the treatment of lung fibrosis.
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Affiliation(s)
- Kirsten Sehlmeyer
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover, Member of the German Centre for Lung Research, Hanover, Germany
| | - Jannik Ruwisch
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover, Member of the German Centre for Lung Research, Hanover, Germany
| | - Nuria Roldan
- Alveolix AG and ARTORG Center, University of Bern, Bern, Switzerland
| | - Elena Lopez-Rodriguez
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover, Member of the German Centre for Lung Research, Hanover, Germany
- Institute of Functional Anatomy, Charité – Universitätsmedizin Berlin, Berlin, Germany
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16
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Liekkinen J, Enkavi G, Javanainen M, Olmeda B, Pérez-Gil J, Vattulainen I. Pulmonary Surfactant Lipid Reorganization Induced by the Adsorption of the Oligomeric Surfactant Protein B Complex. J Mol Biol 2020; 432:3251-3268. [DOI: 10.1016/j.jmb.2020.02.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 02/22/2020] [Accepted: 02/24/2020] [Indexed: 12/11/2022]
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17
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Zuniga-Hertz JP, Patel HH. The Evolution of Cholesterol-Rich Membrane in Oxygen Adaption: The Respiratory System as a Model. Front Physiol 2019; 10:1340. [PMID: 31736773 PMCID: PMC6828933 DOI: 10.3389/fphys.2019.01340] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/08/2019] [Indexed: 12/14/2022] Open
Abstract
The increase in atmospheric oxygen levels imposed significant environmental pressure on primitive organisms concerning intracellular oxygen concentration management. Evidence suggests the rise of cholesterol, a key molecule for cellular membrane organization, as a cellular strategy to restrain free oxygen diffusion under the new environmental conditions. During evolution and the increase in organismal complexity, cholesterol played a pivotal role in the establishment of novel and more complex functions associated with lipid membranes. Of these, caveolae, cholesterol-rich membrane domains, are signaling hubs that regulate important in situ functions. Evolution resulted in complex respiratory systems and molecular response mechanisms that ensure responses to critical events such as hypoxia facilitated oxygen diffusion and transport in complex organisms. Caveolae have been structurally and functionally associated with respiratory systems and oxygen diffusion control through their relationship with molecular response systems like hypoxia-inducible factors (HIF), and particularly as a membrane-localized oxygen sensor, controlling oxygen diffusion balanced with cellular physiological requirements. This review will focus on membrane adaptations that contribute to regulating oxygen in living systems.
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Affiliation(s)
- Juan Pablo Zuniga-Hertz
- Department of Anesthesiology, VA San Diego Healthcare System, University of California, San Diego, San Diego, CA, United States
| | - Hemal H Patel
- Department of Anesthesiology, VA San Diego Healthcare System, University of California, San Diego, San Diego, CA, United States
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18
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Martínez-Calle M, Alonso A, Pérez-Gil J, Olmeda B. Native supramolecular protein complexes in pulmonary surfactant: Evidences for SP-A/SP-B interactions. J Proteomics 2019; 207:103466. [DOI: 10.1016/j.jprot.2019.103466] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/08/2019] [Accepted: 07/22/2019] [Indexed: 12/21/2022]
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19
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Tran N, Kurian J, Bhatt A, McKenna R, Long JR. Entropic Anomaly Observed in Lipid Polymorphisms Induced by Surfactant Peptide SP-B(1-25). J Phys Chem B 2017; 121:9102-9112. [PMID: 28872861 DOI: 10.1021/acs.jpcb.7b06538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The N-terminal 25 amino-acid residues of pulmonary surfactant protein B (SP-B1-25) induces unusual lipid polymorphisms in a model lipid system, 4:1 DPPC/POPG, mirroring the lipid composition of native pulmonary surfactant. It is widely suggested that SP-B1-25-induced lipid polymorphisms within the alveolar aqueous subphase provide a structural platform for rapid lipid adsorption to the air-water interface. Here, we characterize in detail the phase behavior of DPPC and POPG in hydrated lipid assemblies containing therapeutic levels of SP-B1-25 using 2H and 31P solid state NMR spectroscopy. The appearance of a previously observed isotropic lipid phase is found to be highly dependent on the thermal cycling of the samples. Slow heating of frozen samples leads to phase separation of DPPC into a lamellar phase whereas POPG lipids interact with the peptide to form an isotropic phase at physiologic temperature. Rapid heating of frozen samples to room temperature leads to strongly isotropic phase behavior for both DPPC and POPG lipids, with DPPC in exchange between isotropic and interdigitated phases. 31P T2 relaxation times confirm the isotropic phase to be consistent with a lipid cubic phase. The observed phases exhibit thermal stability up to physiologic temperature (37 °C) and are consistent with the formation of a ripple phase containing a large number of peptide-induced membrane structural defects enabling rapid transit of lipids between lipid lamellae. The coexistance of a lipid cubic phase with interdigitated lipids suggests a specific role for the highly conserved N-terminus of SP-B in stabilizing this unusual lipid polymorphism.
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Affiliation(s)
- Nhi Tran
- Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States
| | - Justin Kurian
- Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida 32610, United States
| | - Avni Bhatt
- Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida 32610, United States
| | - Robert McKenna
- Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida 32610, United States
| | - Joanna R Long
- Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida 32610, United States
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