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Hall SB, Zuo YY. The biophysical function of pulmonary surfactant. Biophys J 2024; 123:1519-1530. [PMID: 38664968 PMCID: PMC11213971 DOI: 10.1016/j.bpj.2024.04.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 04/08/2024] [Accepted: 04/22/2024] [Indexed: 05/12/2024] Open
Abstract
The type II pneumocytes of the lungs secrete a mixture of lipids and proteins that together acts as a surfactant. The material forms a thin film on the surface of the liquid layer that lines the alveolar air sacks. When compressed by the decreasing alveolar surface area during exhalation, the films reduce surface tension to exceptionally low levels. Pulmonary surfactant is essential for preserving the integrity of the barrier between alveolar air and capillary blood during normal breathing. This review focuses on the major biophysical processes by which endogenous pulmonary surfactant achieves its function and the mechanisms involved in those processes. Vesicles of pulmonary surfactant adsorb rapidly from the alveolar liquid to form the interfacial film. Interfacial insertion, which requires the hydrophobic surfactant protein SP-B, proceeds by a process analogous to the fusion of two vesicles. When compressed, the adsorbed film desorbs slowly. Constituents remain at the surface at high interfacial concentrations that reduce surface tensions well below equilibrium levels. We review the models proposed to explain how pulmonary surfactant achieves both the rapid adsorption and slow desorption characteristic of a functional film.
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Affiliation(s)
- Stephen B Hall
- Pulmonary and Critical Care Medicine, Oregon Health & Science University, Portland, Oregon.
| | - Yi Y Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii
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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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3
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Buckley A, Warren J, Hussain R, Smith R. Synchrotron radiation circular dichroism spectroscopy reveals that gold and silver nanoparticles modify the secondary structure of a lung surfactant protein B analogue. NANOSCALE 2023; 15:4591-4603. [PMID: 36763129 DOI: 10.1039/d2nr06107d] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Inhaled nanoparticles (NPs) depositing in the alveolar region of the lung interact initially with a surfactant layer and in vitro studies have demonstrated that NPs can adversely affect the biophysical function of model pulmonary surfactants (PS), of which surfactant protein B (SP-B) is a key component. Other studies have demonstrated the potential for NPs to modify the structure and function of proteins. It was therefore hypothesised that NPs may affect the biophysical function of PS by modifying the structure of SP-B. Synchrotron radiation circular dichroism (SRCD) spectroscopy was used to explore the effect of various concentrations of gold nanoparticles (AuNPs) (5, 10, 20 nm), silver nanoparticles (AgNPs) (10 nm) and silver citrate on the secondary structure of surfactant protein B analogue, SP-B1-25, in a TFE/PB dispersion. For Au and Ag NPs the SRCD spectra indicated a concentration dependent reduction in the α-helical structure of SP-B1-25 (5 nm AuNP ≈ 10 nm AgNP ≫ 10 nm AuNP > 20 nm AuNP). For AuNPs the effect was greater for the 5 nm size, which was not fully explained by consideration of surface area. The impact of the 10 nm AgNPs was greater than that of the 10 nm AuNPs and the effect of AgNPs was greater than that of silver citrate at equivalent Ag mass concentrations. For 10 nm AuNPs, SRCD spectra for dispersions in, the more physiologically relevant, DPPC showed a similar concentration dependent pattern. The results demonstrate the potential for inhaled NPs to modify SP-B1-25 structure and thus potentially adversely impact the physiological function of the lung, however, further studies are necessary to confirm this.
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Affiliation(s)
- Alison Buckley
- Toxicology Department, UK Health Security Agency, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0RQ, UK.
| | - James Warren
- Toxicology Department, UK Health Security Agency, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0RQ, UK.
| | - Rohanah Hussain
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
| | - Rachel Smith
- Toxicology Department, UK Health Security Agency, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0RQ, UK.
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Tripathi A, Kumar B, Sagi SSK. Hypoxia-mediated alterations in pulmonary surfactant protein expressions: Beneficial effects of quercetin prophylaxis. Respir Physiol Neurobiol 2021; 291:103695. [PMID: 34052411 DOI: 10.1016/j.resp.2021.103695] [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: 12/22/2020] [Revised: 03/26/2021] [Accepted: 05/17/2021] [Indexed: 10/21/2022]
Abstract
We have compared the prophylactic efficacies of quercetin and salbutamol in preventing pulmonary surfactants oxidation under hypoxia. Male SD rats supplemented orally with quercetin (50 mg/Kg BW) and salbutamol (2 mg/Kg BW) were exposed to hypobaric hypoxia (7,620 m for 6 h). Hypoxia-mediated elevation in oxidative stress, inflammation, and extravasations of LDH & albumin content in BALF of rats were assessed. Western blotting and mRNA studies determined the differential expressions of Nrf-2, HO-1, and associated surfactant proteins (SP-A, SP-B, SP-C, & SP-D) in rat lungs. Later, the lung configuration under hypoxia was assessed histopathologically. Quercetin and salbutamol pretreatment considerably restored the expressions of Nrf-2, HO-1, and surfactant proteins to normal by attenuating the increase in oxidative stress, inflammation, and extravasations of plasma proteins in the animals under hypoxia. The histopathology has also evidenced the protective effect of quercetin in retaining normal lung architecture under hypoxia over salbutamol. The present study indicates the effectiveness of quercetin prophylaxis in preventing pulmonary surfactants oxidation under hypoxia over salbutamol.
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Affiliation(s)
- Ankit Tripathi
- Nutrition Division, Defence Institute of Physiology and Allied Sciences, Lucknow Road, Timarpur, Delhi, 110054, India.
| | - Bhuvnesh Kumar
- Nutrition Division, Defence Institute of Physiology and Allied Sciences, Lucknow Road, Timarpur, Delhi, 110054, India.
| | - Sarada S K Sagi
- Nutrition Division, Defence Institute of Physiology and Allied Sciences, Lucknow Road, Timarpur, Delhi, 110054, India.
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5
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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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Andreev K, Martynowycz MW, Kuzmenko I, Bu W, Hall SB, Gidalevitz D. Structural Changes in Films of Pulmonary Surfactant Induced by Surfactant Vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:13439-13447. [PMID: 33080138 PMCID: PMC8754419 DOI: 10.1021/acs.langmuir.0c01813] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
When compressed by the shrinking alveolar surface area during exhalation, films of pulmonary surfactant in situ reduce surface tension to levels at which surfactant monolayers collapse from the surface in vitro. Vesicles of pulmonary surfactant added below these monolayers slow collapse. X-ray scattering here determined the structural changes induced by the added vesicles. Grazing incidence X-ray diffraction on monolayers of extracted calf surfactant detected an ordered phase. Mixtures of dipalmitoyl phosphatidylcholine and cholesterol, but not the phospholipid alone, mimic that structure. At concentrations that stabilize the monolayers, vesicles in the subphase had no effect on the unit cell, and X-ray reflection showed that the film remained monomolecular. The added vesicles, however, produced a concentration-dependent increase in the diffracted intensity. These results suggest that the enhanced resistance to collapse results from enlargement by the additional material of the ordered phase.
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Affiliation(s)
- Konstantin Andreev
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Michael W Martynowycz
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States
- X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Ivan Kuzmenko
- X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Wei Bu
- The Center for Advanced Radiation Sources (CARS), University of Chicago, Chicago, Illinois 60637, United States
| | - Stephen B Hall
- Pulmonary & Critical Care Medicine, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - David Gidalevitz
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States
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7
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Xu L, Yang Y, Zuo YY. Atomic Force Microscopy Imaging of Adsorbed Pulmonary Surfactant Films. Biophys J 2020; 119:756-766. [PMID: 32702292 DOI: 10.1016/j.bpj.2020.06.033] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 06/17/2020] [Accepted: 06/26/2020] [Indexed: 12/22/2022] Open
Abstract
Pulmonary surfactant (PS) is a lipid-protein complex that adsorbs to the air-water surface of the lung as a thin film. Previous studies have suggested that the adsorbed PS film is composed of an interfacial monolayer, plus a functionally attached vesicular complex, called the surface-associated surfactant reservoir. However, direct visualization of the lateral structure and morphology of adsorbed PS films using atomic force microscopy (AFM) has been proven to be technically challenging. To date, all AFM studies of the PS film have relied on the model of Langmuir monolayers. Here, we showed the first, to our knowledge, AFM imaging of adsorbed PS films under physiologically relevant conditions using a novel, to our knowledge, experimental methodology called constrained drop surfactometry. In conjunction with a series of methodological innovations, including subphase replacement, in situ Langmuir-Blodgett transfer, and real-time surface tension control using closed-loop axisymmetric drop shape analysis, constrained drop surfactometry allowed the study of lateral structure and topography of animal-derived natural PS films at physiologically relevant low surface tensions. Our data suggested that a nucleation-growth model is responsible for the adsorption-induced squeeze-out of the PS film, which likely results in an interfacial monolayer enriched in dipalmitoylphosphatidylcholine with the attached multilayered surface-associated surfactant reservoir. These findings were further supported by frequency-dependent measurements of surface dilational rheology. Our study provides novel, to our knowledge, biophysical insights into the understanding of the mechanisms by which the PS film attains low surface tensions and stabilizes the alveolar surface.
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Affiliation(s)
- Lu Xu
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii
| | - Yi Yang
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii
| | - Yi Y Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii; Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii.
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8
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Baer B, Souza LMP, Pimentel AS, Veldhuizen RA. New insights into exogenous surfactant as a carrier of pulmonary therapeutics. Biochem Pharmacol 2019; 164:64-73. [DOI: 10.1016/j.bcp.2019.03.036] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 03/26/2019] [Indexed: 01/03/2023]
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Koehn JT, Beuning CN, Peters BJ, Dellinger SK, Van Cleave C, Crick DC, Crans DC. Investigating Substrate Analogues for Mycobacterial MenJ: Truncated and Partially Saturated Menaquinones. Biochemistry 2019; 58:1596-1615. [DOI: 10.1021/acs.biochem.9b00007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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10
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Prince LS. FGF10 and Human Lung Disease Across the Life Spectrum. Front Genet 2018; 9:517. [PMID: 30429870 PMCID: PMC6220039 DOI: 10.3389/fgene.2018.00517] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 10/12/2018] [Indexed: 02/01/2023] Open
Abstract
Lung diseases impact patients across the lifespan, from infants in the first minutes of life through the aged population. Congenital abnormalities of lung structure can cause lung disease at birth or make adults more susceptible to chronic disease. Continuous inhalation of atmospheric components also requires the lung to be resilient to cellular injury. Fibroblast growth factor 10 (FGF10) regulates multiple stages of structural lung morphogenesis, cellular differentiation, and the response to injury. As a driver of lung airway branching morphogenesis, FGF10 signaling defects during development lead to neonatal lung disease. Alternatively, congenital airway abnormalities attributed to FGF10 mutations increase the risk of chronic airway disease in adulthood. FGF10 also maintains progenitor cell populations in the airway and promotes alveolar type 2 cell expansion and differentiation following injury. Here we review the cellular and molecular mechanisms linking FGF10 to multiple lung diseases, from bronchopulmonary dysplasia in extremely preterm neonates, cystic fibrosis in children, and chronic adult lung disorders. Understanding the connections between FGF10 and lung diseases may lead to exciting new therapeutic strategies.
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Affiliation(s)
- Lawrence S Prince
- Department of Pediatrics, University of California, San Diego, Rady Children's Hospital, San Diego, CA, United States
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Hernandez C, Nieves L, de Leon AC, Advincula R, Exner AA. Role of Surface Tension in Gas Nanobubble Stability Under Ultrasound. ACS APPLIED MATERIALS & INTERFACES 2018; 10:9949-9956. [PMID: 29494124 PMCID: PMC8994853 DOI: 10.1021/acsami.7b19755] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Shell-stabilized gas nanobubbles have recently captured the interest of the research community for their potential application as ultrasound contrast agents for molecular imaging and therapy of cancer. However, the very existence of submicron gas bubbles (especially uncoated bubbles) has been a subject of controversy in part due to their predicted Laplace overpressure reaching several atmospheres, making them supposedly thermodynamically unstable. In addition, the backscatter resulting from ultrasound interactions with nanoparticles is not predicted to be readily detectable at clinically relevant frequencies. Despite this, a number of recent reports have successfully investigated the presence and applications of nanobubbles for ultrasound imaging. The mechanism behind these observations remains unclear but is thought to be, in part, influenced heavily by the biophysical properties of the bubble-stabilizing shell. In this study, we investigated the effects of incorporating the triblock copolymer surfactant, Pluronic, into the lipid monolayer of nanobubbles. The impact of shell composition on membrane equilibrium surface tension was investigated using optical tensiometry, using both pendant drop and rising drop principles. However, these techniques proved to be insufficient in explaining the observed behavior and stability of nanobubbles under ultrasound. Additionally, we sought to investigate changes in membrane surface tension (surface pressure) at different degrees of compression (analogous to the bubble oscillations in the ultrasound field) via Langmuir-Blodgett experiments. Results from this study show a significant decrease ( p < 0.0001) in the nanobubble equilibrium surface tension through the incorporation of Pluronic L10, especially at a ratio of 0.2, where this value decreased by 28%. However, this reduction in surface pressure was seen only for specific compositions and varied with monolayer structure (crystalline phase or liquid-crystalline packing). These results indicate a potential for optimization wherein surface pressure can be maximized for both contraction and expansion phases with the proper lipid to Pluronic balance and microstructure.
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Affiliation(s)
- Christopher Hernandez
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Lenitza Nieves
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Al C. de Leon
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Rigoberto Advincula
- Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Agata A. Exner
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio 44106, United States
- Corresponding Author
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The Cerebral Surfactant System and Its Alteration in Hydrocephalic Conditions. PLoS One 2016; 11:e0160680. [PMID: 27656877 PMCID: PMC5033422 DOI: 10.1371/journal.pone.0160680] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 07/24/2016] [Indexed: 01/06/2023] Open
Abstract
Introduction Pulmonary Surfactant reduces surface tension in the terminal airways thus facilitating breathing and contributes to host’s innate immunity. Surfactant Proteins (SP) A, B, C and D were recently identified as inherent proteins of the CNS. Aim of the study was to investigate cerebrospinal fluid (CSF) SP levels in hydrocephalus patients compared to normal subjects. Patients and Methods CSF SP A-D levels were quantified using commercially available ELISA kits in 126 patients (0–84 years, mean 39 years). 60 patients without CNS pathologies served as a control group. Hydrocephalus patients were separated in aqueductal stenosis (AQS, n = 24), acute hydrocephalus without aqueductal stenosis (acute HC w/o AQS, n = 16) and idiopathic normal pressure hydrocephalus (NPH, n = 20). Furthermore, six patients with pseudotumor cerebri were investigated. Results SP A—D are present under physiological conditions in human CSF. SP-A is elevated in diseases accompanied by ventricular enlargement (AQS, acute HC w/o AQS) in a significant manner (0.67, 1.21 vs 0.38 ng/ml in control, p<0.001). SP-C is also elevated in hydrocephalic conditions (AQS, acute HC w/o AQS; 0.87, 1.71 vs. 0.48 ng/ml in controls, p<0.001) and in Pseudotumor cerebri (1.26 vs. 0.48 ng/ml in controls, p<0.01). SP-B and SP-D did not show significant alterations. Conclusion The present study confirms the presence of SPs in human CSF. There are significant changes of SP-A and SP-C levels in diseases affecting brain water circulation and elevation of intracranial pressure. Cause of the alterations, underlying regulatory mechanisms, as well as diagnostic and therapeutic consequences of cerebral SP’s requires further thorough investigations.
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Chakraborty A, Hui E, Waring AJ, Dhar P. Combined effect of synthetic protein, Mini-B, and cholesterol on a model lung surfactant mixture at the air-water interface. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:904-12. [PMID: 26775740 DOI: 10.1016/j.bbamem.2016.01.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 12/22/2015] [Accepted: 01/05/2016] [Indexed: 11/25/2022]
Abstract
The overall goal of this work is to study the combined effects of Mini-B, a 34 residue synthetic analog of the lung surfactant protein SP-B, and cholesterol, a neutral lipid, on a model binary lipid mixture containing dipalmitolphosphatidylcholine (DPPC) and palmitoyl-oleoyl-phosphatidylglycerol (POPG), that is often used to mimic the primary phospholipid composition of lung surfactants. Using surface pressure vs. mean molecular area isotherms, fluorescence imaging and analysis of lipid domain size distributions; we report on changes in the structure, function and stability of the model lipid-protein films in the presence and absence of varying composition of cholesterol. Our results indicate that at low cholesterol concentrations, Mini-B can prevent cholesterol's tendency to lower the line tension between lipid domain boundaries, while maintaining Mini-B's ability to cause reversible collapse resulting in the formation of surface associated reservoirs. Our results also show that lowering the line tension between domains can adversely impact monolayer folding mechanisms. We propose that small amounts of cholesterol and synthetic protein Mini-B can together achieve the seemingly opposing requirements of efficient LS: fluid enough to flow at the air-water interface, while being rigid enough to oppose irreversible collapse at ultra-low surface tensions.
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Affiliation(s)
- Aishik Chakraborty
- Department of Chemical Engineering, University of Kansas, KS 66045, United States
| | - Erica Hui
- Department of Chemical Engineering, University of Kansas, KS 66045, United States
| | - Alan J Waring
- Department of Medicine, Harbor UCLA Medical Center - LA BioMed, CA 90502, United States; Department of Physiology and Biophysics, University of California, Irvine, CA 92697, United States
| | - Prajnaparamita Dhar
- Department of Chemical Engineering, University of Kansas, KS 66045, United States.
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Dagan MP, Hall SB. The Equilibrium Spreading Tension of Pulmonary Surfactant. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:13063-7. [PMID: 26583569 PMCID: PMC4896737 DOI: 10.1021/acs.langmuir.5b03094] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Monomolecular films at an air/water interface coexist at the equilibrium spreading tension (γ(e)) with the bulk phase from which they form. For individual phospholipids, γ(e) is single-valued, and separates conditions at which hydrated vesicles adsorb from tensions at which overcompressed monolayers collapse. With pulmonary surfactant, isotherms show that monolayers compressed on the surface of bubbles coexist with the three-dimensional collapsed phase over a range of surface tensions. γ(e) therefore represents a range rather than a single value of surface tension. Between the upper and lower ends of this range, rates of collapse for spread and adsorbed films decrease substantially. Changes during adsorption across this narrow region of coexistence between the two- and three-dimensional structures at least partially explain how alveolar films of pulmonary surfactant become resistant to collapse.
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Affiliation(s)
| | - Stephen B. Hall
- Corresponding Author Address: Pulmonary and Critical Care Medicine, Mail Code UHN-67, OHSU, Portland, OR 97239-3098. Telephone: 503-494-6667;
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15
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Melbourne J, Clancy A, Seiffert J, Skepper J, Tetley TD, Shaffer MSP, Porter A. An investigation of the carbon nanotube--Lipid interface and its impact upon pulmonary surfactant lipid function. Biomaterials 2015; 55:24-32. [PMID: 25934449 DOI: 10.1016/j.biomaterials.2015.03.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 03/08/2015] [Accepted: 03/15/2015] [Indexed: 11/16/2022]
Abstract
Multiwalled carbon nanotubes (MWCNTs) are now synthesized on a large scale, increasing the risk of occupational inhalation. However, little is known of the MWCNT-pulmonary surfactant (PS) interface and its effect on PS functionality. The Langmuir-Blodgett trough was used to evaluate the impact of MWCNTs on fundamental properties of PS lipids which influence PS function, i.e. compression resistance and maximum obtainable pressure. Changes were found to be MWCNT length-dependent. 'Short' MWCNTs (1.1 μm, SD = 0.61) penetrated the lipid film, reducing the maximum interfacial film pressure by 10 mN/m (14%) in dipalmitoylphosphatidylcholine (DPPC) and PS, at an interfacial MWCNT-PS lipid mass ratio range of 50:1 to 1:1. 'Long' commercial MWCNTs (2.1 μm, SD = 1.2) caused compression resistance at the same mass loadings. 'Very long' MWCNTs (35 μm, SD = 19) sequestered DPPC and were squeezed out of the DPPC film. High resolution transmission electron microscopy revealed that all MWCNT morphologies formed DPPC coronas with ordered arrangements. These results provide insight into how nanoparticle aspect ratio affects the interaction mechanisms with PS, in its near-native state at the air-water interface.
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Affiliation(s)
- Jodie Melbourne
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
| | - Adam Clancy
- Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK
| | - Joanna Seiffert
- National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK
| | - Jeremy Skepper
- Multi-Imaging Centre, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Teresa D Tetley
- National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK
| | - Milo S P Shaffer
- Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK
| | - Alexandra Porter
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
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Lysophospholipid acyltransferases mediate phosphatidylcholine diversification to achieve the physical properties required in vivo. Cell Metab 2014; 20:295-305. [PMID: 24981836 DOI: 10.1016/j.cmet.2014.05.019] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 04/18/2014] [Accepted: 05/13/2014] [Indexed: 12/19/2022]
Abstract
The acyl-chain composition of the major mammalian phospholipid phosphatidylcholine (PC) is distinct in various tissues. Although it was classically suggested that PC diversity is acquired through acyl-chain remodeling, the mechanisms and biological relevance of acyl-chain diversity remain unclear. Here, we show that differences in the substrate selectivity of lysophospholipid acyltransferases regulate tissue PC acyl-chain composition through contribution of both the de novo and remodeling pathways, depending on the fatty acid species. Unexpectedly, while dipalmitoyl-PC (DPPC) is enriched through the remodeling pathway, several polyunsaturated PC molecules accumulate during the de novo pathway. We confirmed this concept for DPPC in pulmonary surfactant and showed that the biophysical properties of this lipid are important to prevent the early onset of acute lung injury. We propose a model of harmonized processes for phospholipid diversification to satisfy in vivo requirements, with an example of its biological relevance.
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17
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Structural modelling and dynamics of proteins for insights into drug interactions. Adv Drug Deliv Rev 2012; 64:323-43. [PMID: 22155026 DOI: 10.1016/j.addr.2011.11.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 11/17/2011] [Accepted: 11/24/2011] [Indexed: 12/27/2022]
Abstract
Proteins are the workhorses of biomolecules and their function is affected by their structure and their structural rearrangements during ligand entry, ligand binding and protein-protein interactions. Hence, the knowledge of protein structure and, importantly, the dynamic behaviour of the structure are critical for understanding how the protein performs its function. The predictions of the structure and the dynamic behaviour can be performed by combinations of structure modelling and molecular dynamics simulations. The simulations also need to be sensitive to the constraints of the environment in which the protein resides. Standard computational methods now exist in this field to support the experimental effort of solving protein structures. This review presents a comprehensive overview of the basis of the calculations and the well-established computational methods used to generate and understand protein structure and function and the study of their dynamic behaviour with the reference to lung-related targets.
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18
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Holten-Andersen N, Michael Henderson J, Walther FJ, Waring AJ, Ruchala P, Notter RH, Lee KYC. KL₄ peptide induces reversible collapse structures on multiple length scales in model lung surfactant. Biophys J 2011; 101:2957-65. [PMID: 22208194 DOI: 10.1016/j.bpj.2011.10.050] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 09/27/2011] [Accepted: 10/06/2011] [Indexed: 10/14/2022] Open
Abstract
We investigated the effects of KL₄, a 21-residue amphipathic peptide approximating the overall ratio of positively charged to hydrophobic amino acids in surfactant protein B (SP-B), on the structure and collapse of dipalmitoylphosphatidylcholine and palmitoyl-oleoyl-phosphatidylglycerol monolayers. As reported in prior work on model lung surfactant phospholipid films containing SP-B and SP-B peptides, our experiments show that KL₄ improves surfactant film reversibility during repetitive interfacial cycling in association with the formation of reversible collapse structures on multiple length scales. Emphasis is on exploring a general mechanistic connection between peptide-induced nano- and microscale reversible collapse structures (silos and folds).
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Affiliation(s)
- Niels Holten-Andersen
- Department of Chemistry, Institute for Biophysical Dynamics, and the James Franck Institute, University of Chicago, Chicago, Illinois, USA
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19
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Bernhard W, Raith M, Pynn CJ, Gille C, Stichtenoth G, Stoll D, Schleicher E, Poets CF. Increased palmitoyl-myristoyl-phosphatidylcholine in neonatal rat surfactant is lung specific and correlates with oral myristic acid supply. J Appl Physiol (1985) 2011; 111:449-57. [DOI: 10.1152/japplphysiol.00766.2010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Surfactant predominantly comprises phosphatidylcholine (PC) species, together with phosphatidylglycerols, phosphatidylinositols, neutral lipids, and surfactant proteins-A to -D. Together, dipalmitoyl-PC (PC16:0/16:0), palmitoyl-myristoyl-PC (PC16:0/14:0), and palmitoyl-palmitoleoyl-PC (PC16:0/16:1) make up 75–80% of mammalian surfactant PC, the proportions of which vary during development and in chronic lung diseases. PC16:0/14:0, which exerts specific effects on macrophage differentiation in vitro, increases in surfactant during alveolarization (at the expense of PC16:0/16:0), a prenatal event in humans but postnatal in rats. The mechanisms responsible and the significance of this reversible increase are, however, not understood. We hypothesized that, in rats, myristic acid (C14:0) enriched milk is key to lung-specific PC16:0/14:0 increases in surfactant. We found that surfactant PC16:0/14:0 in suckling rats correlates with C14:0 concentration in plasma chylomicrons and lung tissue triglycerides, and that PC16:0/14:0 fractions reflect exogenous C14:0 supply. Significantly, C14:0 was increased neither in plasma PC, nor in liver triglycerides, free fatty acids, or PC. Lauric acid was also abundant in triglycerides, but was not incorporated into surfactant PC. Comparing a C14:0-rich milk diet with a C14:0-poor carbohydrate diet revealed increased C14:0 and decreased C16:0 in plasma and lung triglycerides, respectively. PC16:0/14:0 enrichment at the expense of PC16:0/16:0 did not impair surfactant surface tension function. However, the PC profile of the alveolar macrophages from the milk-fed animals changed from PC16:0/16:0 rich to PC16:0/14:0 rich. This was accompanied by reduced reactive oxygen species production. We propose that nutritional supply with C14:0 and its lung-specific enrichment may contribute to decreased reactive oxygen species production during alveolarization.
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Affiliation(s)
| | | | - Christopher J. Pynn
- Departments of 1Neonatology and
- Natural and Medical Sciences Institute, Reutlingen, Germany
| | | | - Guido Stichtenoth
- Childrens Hospital, University Clinic Schleswig-Holstein, Lübeck; and
| | - Dieter Stoll
- Natural and Medical Sciences Institute, Reutlingen, Germany
| | - Erwin Schleicher
- Internal Medicine IV, Faculty of Medicine, Eberhard-Karls University, Tübingen
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20
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Zhang H, Wang YE, Fan Q, Zuo YY. On the low surface tension of lung surfactant. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:8351-8. [PMID: 21650180 PMCID: PMC4849879 DOI: 10.1021/la201482n] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Natural lung surfactant contains less than 40% disaturated phospholipids, mainly dipalmitoylphosphatidylcholine (DPPC). The mechanism by which lung surfactant achieves very low near-zero surface tensions, well below its equilibrium value, is not fully understood. To date, the low surface tension of lung surfactant is usually explained by a squeeze-out model which predicts that upon film compression non-DPPC components are gradually excluded from the air-water interface into a surface-associated surfactant reservoir. However, detailed experimental evidence of the squeeze-out within the physiologically relevant high surface pressure range is still lacking. In the present work, we studied four animal-derived clinical surfactant preparations, including Survanta, Curosurf, Infasurf, and BLES. By comparing compression isotherms and lateral structures of these surfactant films obtained by atomic force microscopy within the physiologically relevant high surface pressure range, we have derived an updated squeeze-out model. Our model suggests that the squeeze-out originates from fluid phases of a phase-separated monolayer. The squeeze-out process follows a nucleation-growth model and only occurs within a narrow surface pressure range around the equilibrium spreading pressure of lung surfactant. After the squeeze-out, three-dimensional nuclei stop growing, thereby resulting in a DPPC-enriched interfacial monolayer to reduce the air-water surface tension to very low values.
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Affiliation(s)
- Hong Zhang
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Department of Respiratory Medicine, Peking University First Hospital, Beijing, China 100034
| | - Yi E. Wang
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Qihui Fan
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Yi Y. Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Corresponding Author. ; Tel: 808-956-9650; Fax: 808-956-2373
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21
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Lipid polymorphism induced by surfactant peptide SP-B(1-25). Biophys J 2011; 99:1773-82. [PMID: 20858421 DOI: 10.1016/j.bpj.2010.06.076] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 06/24/2010] [Accepted: 06/28/2010] [Indexed: 01/09/2023] Open
Abstract
Pulmonary surfactant protein B (SP-B) is an essential protein for lowering surface tension in the alveoli. SP-B(1-25), a peptide comprised of the N-terminal 25 amino-acid residues of SP-B, is known to retain much of the biological activity of SP-B. Circular dichroism has shown that when SP-B(1-25) interacts with negatively charged lipid vesicles, it contains significant helical structure for the lipid compositions and peptide/lipid ratios studied here. The effect of SP-B(1-25) on lipid organization and polymorphisms was investigated via DSC, dynamic light scattering, transmission electron microscopy, and solid-state NMR spectroscopy. At 1-3 mol% peptide and physiologic temperature, SP-B(1-25) partitions at the interface of negatively charged PC/PG lipid bilayers. In lipid mixtures containing 1-5 mol% peptide, the structure of SP-B(1-25) remains constant, but (2)H and (31)P NMR spectra show the presence of an isotropic lipid phase in exchange with the lamellar phase below the T(m) of the lipids. This behavior is observed for both DPPC/POPG and POPC/POPG lipid mixtures as well as for both the PC and PG components of the mixtures. For 1-3 mol% SP-B(1-25), a return to a single lamellar phase above the lipid mixture T(m) is observed, but for 5 mol% SP-B(1-25) a significant isotropic component is observed at physiologic temperatures for DPPC and exchange broadening is observed in (2)H and (31)P NMR spectra of the other lipid components in the two mixtures. DLS and TEM rule out the formation of micellar structures and suggest that SP-B(1-25) promotes the formation of a fluid isotropic phase. The ability of SP-B(1-25) to fuse lipid lamellae via this mechanism, particularly those enriched in DPPC, suggests a specific role for the highly conserved N-terminus of SP-B in the packing of lipid lamellae into surfactant lamellar bodies or in stabilizing multilayer structures at the air-liquid interface. Importantly, this behavior has not been seen for the other SP-B fragments of SP-B(8-25) and SP-B(59-80), indicating a critical role for the proline rich first seven amino acids in this protein.
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22
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Pynn CJ, Picardi MV, Nicholson T, Wistuba D, Poets CF, Schleicher E, Perez-Gil J, Bernhard W. Myristate is selectively incorporated into surfactant and decreases dipalmitoylphosphatidylcholine without functional impairment. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1306-16. [DOI: 10.1152/ajpregu.00380.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lung surfactant mainly comprises phosphatidylcholines (PC), together with phosphatidylglycerols and surfactant proteins SP-A to SP-D. Dipalmitoyl-PC (PC16:0/16:0), palmitoylmyristoyl-PC (PC16:0/14:0), and palmitoylpalmitoleoyl-PC (PC16:0/16:1) together comprise 75–80% of surfactant PC. During alveolarization, which occurs postnatally in the rat, PC16:0/14:0 reversibly increases at the expense of PC16:0/16:0. As lipoproteins modify surfactant metabolism, we postulated an extrapulmonary origin of PC16:0/14:0 enrichment in surfactant. We, therefore, fed rats (d19–26) with trilaurin (C12:03), trimyristin (C14:03), tripalmitin (C16:03), triolein (C18:13) or trilinolein (C18:23) vs. carbohydrate diet to assess their effects on surfactant PC composition and surface tension function using a captive bubble surfactometer. Metabolism was assessed with deuterated C12:0 (ω-d3-C12:0) and ω-d3-C14:0. C14:03 increased PC16:0/14:0 in surfactant from 12 ± 1 to 45 ± 3% and decreased PC16:0/16:0 from 47 ± 1 to 29 ± 2%, with no impairment of surface tension function. Combined phospholipase A2 assay and mass spectrometry revealed that 50% of the PC16:0/14:0 peak comprised its isomer 1-myristoyl-2-palmitoyl-PC (PC14:0/16:0). While C12:03 was excluded from incorporation into PC, it increased PC16:0/14:0 as well. C16:03, C18:13, and C18:23 had no significant effect on PC16:0/16:0 or PC16:0/14:0. d3-C14:0 was enriched in lung PC, either via direct supply or via d3-C12:0 elongation. Enrichment of d3-C14:0 in surfactant PC contrasted its rapid turnover in plasma and liver PC, where its elongation product d3-C16:0 surmounted d3-C14:0. In summary, high surfactant PC16:0/14:0 during lung development correlates with C14:0 and C12:0 supply via specific C14:0 enrichment into lung PC. Surfactant that is high in PC16:0/14:0 but low in PC16:0/16:0 is compatible with normal respiration and surfactant function in vitro.
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Affiliation(s)
- Christopher J. Pynn
- Departments of 1Neonatology and
- Internal Medicine IV, Faculty of Medicine, and
| | - M. Victoria Picardi
- Department of Bioquimica y Biologia Molecular, Universidad Complutense, Madrid, Spain
| | - Tim Nicholson
- Department of Chemistry, Eberhard-Karls-University, Tübingen, Germany; and
| | - Dorothee Wistuba
- Department of Chemistry, Eberhard-Karls-University, Tübingen, Germany; and
| | | | | | - Jesus Perez-Gil
- Department of Bioquimica y Biologia Molecular, Universidad Complutense, Madrid, Spain
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23
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Perez-Gil J, Weaver TE. Pulmonary surfactant pathophysiology: current models and open questions. Physiology (Bethesda) 2010; 25:132-41. [PMID: 20551227 DOI: 10.1152/physiol.00006.2010] [Citation(s) in RCA: 173] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary surfactant is an essential lipid-protein complex that stabilizes the respiratory units (alveoli) involved in gas exchange. Quantitative or qualitative derangements in surfactant are associated with severe respiratory pathologies. The integrated regulation of surfactant synthesis, secretion, and metabolism is critical for air breathing and, ultimately, survival. The goal of this review is to summarize our current understanding and highlight important knowledge gaps in surfactant homeostatic mechanisms.
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Affiliation(s)
- Jesús Perez-Gil
- Department Bioquímica, Faculty Biología, Universidad Complutense, Madrid, Spain.
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24
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Hane F, Moores B, Amrein M, Leonenko Z. Effect of SP-C on surface potential distribution in pulmonary surfactant: Atomic force microscopy and Kelvin probe force microscopy study. Ultramicroscopy 2009; 109:968-73. [DOI: 10.1016/j.ultramic.2009.03.046] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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25
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Arnberg N. Adenovirus receptors: implications for tropism, treatment and targeting. Rev Med Virol 2009; 19:165-78. [PMID: 19367611 DOI: 10.1002/rmv.612] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Adenoviruses (Ads) are the most frequently used viral vectors in gene therapy and cancer therapy. Obstacles to successful clinical application include accumulation of vector and transduction in liver cells, coupled with poor transduction of target cells and tissues such as tumours. Many host molecules, including coagulation factor X, have been identified and suggested to serve as mediators of Ad liver tropism. This review summarises current knowledge concerning these molecules and the mechanisms used by Ads to bind to target cells, and considers the prospects of designing vectors that have been detargeted from the liver and retargeted to cells and tissues of interest in the context of gene therapy and cancer therapy.
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Affiliation(s)
- Niklas Arnberg
- Division of Virology, Department of Clinical Microbiology, Umeå University, Umeå, SE-901 85, Sweden.
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26
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Saleem M, Meyer MC, Breitenstein D, Galla HJ. The Surfactant Peptide KL4 in Lipid Monolayers. J Biol Chem 2008; 283:5195-207. [DOI: 10.1074/jbc.m705944200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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27
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Bernhard W, Schmiedl A, Koster G, Orgeig S, Acevedo C, Poets CF, Postle AD. Developmental changes in rat surfactant lipidomics in the context of species variability. Pediatr Pulmonol 2007; 42:794-804. [PMID: 17659602 DOI: 10.1002/ppul.20657] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Lung surfactant comprises mainly phosphatidylcholine (PC) species together with phosphatidylglycerols and surfactant proteins (SP) SP-A to -D. Changes in the concentrations of its principal components dipalmitoyl-PC, palmitoylmyristoyl-PC, palmitoylpalmitoleoyl-PC relative to developmental, structural and physiological differences are only partially understood. Particularly, their attribution to differences in air-liquid interface curvature, compared with dynamic parameters, such as respiratory rate, are controversial. We postulated that during alveolarization the changes in these principal PC components of surfactant differ from those in other phospholipid parameters, and that across endothermic vertebrates their concentrations are related to lung physiology rather than structure. We therefore investigated in rats from postnatal day (d)1 to d42 the pattern of surfactant phospholipids relative to alveolarization (d4-d14), and we discuss these changes in terms of molecular adaptation to pulmonary structure or physiology. Contrary to mammals with advanced alveolarization and increased respiratory rate (RR) at term, concentrations of dipalmitoyl-PC (49-52%) and palmitoylmyristoyl-PC (7-9%) in lung lavage fluid were identical at d1 and d42. At d7-d14, when in rats RR is increased, palmitoyl-myristoyl-PC transiently increased by 2.5- to 3.9-fold at the expense of dipalmitoyl-PC (-32% to 34%) and palmitoyl-palmitoleoyl-PC (-16%). Other lipidomic changes followed essentially different patterns of increase or decrease. Palmitoyl-myristoyl-PC was increased in large aggregates suggesting that it is an integral component of active surfactant. In the overall context of vertebrates, irrespective of age and lung structure, fractions of palmitoyl-myristoyl-PC, dipalmitoyl-PC and palmitoyl-palmitoleoyl-PC correlate with differences in RR rather than alveolar curvature. In adult mammals, however, only concentrations of palmitoyl-palmitoleoyl-PC correlate with RR.
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Affiliation(s)
- Wolfgang Bernhard
- Department of Neonatology, Faculty of Medicine, Eberhard-Karls-University, Tübingen, Germany.
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28
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Seurynck-Servoss SL, Brown NJ, Dohm MT, Wu CW, Barron AE. Lipid composition greatly affects the in vitro surface activity of lung surfactant protein mimics. Colloids Surf B Biointerfaces 2007; 57:37-55. [PMID: 17287113 DOI: 10.1016/j.colsurfb.2007.01.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2006] [Revised: 01/02/2007] [Accepted: 01/03/2007] [Indexed: 10/23/2022]
Abstract
A crucial aspect of developing a functional, biomimetic lung surfactant (LS) replacement is the selection of the synthetic lipid mixture and surfactant proteins (SPs) or suitable mimics thereof. Studies elucidating the roles of different lipids and surfactant proteins in natural LS have provided critical information necessary for the development of synthetic LS replacements that offer performance comparable to the natural material. In this study, the in vitro surface-active behaviors of peptide- and peptoid-based mimics of the lung surfactant proteins, SP-B and SP-C, were investigated using three different lipid formulations. The lipid mixtures were chosen from among those commonly used for the testing and characterization of SP mimics--(1) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol 7:3 (w/w) (PCPG), (2) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol:palmitic acid 68:22:9 (w/w) (TL), and (3) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol:palmitoyloleoyl phosphatidylethanolamine:palmitoyloleoyl phosphatidylserine:cholesterol 16:10:3:1:3:2 (w/w) (IL). The lipid mixtures and lipid/peptide or lipid/peptoid formulations were characterized in vitro using a Langmuir-Wilhelmy surface balance, fluorescent microscopic imaging of surface film morphology, and a pulsating bubble surfactometer. Results show that the three lipid formulations exhibit significantly different surface-active behaviors, both in the presence and absence of SP mimics, with desirable in vitro biomimetic behaviors being greatest for the TL formulation. Specifically, the TL formulation is able to reach low-surface tensions at physiological temperature as determined by dynamic PBS and LWSB studies, and dynamic PBS studies show this to occur with a minimal amount of compression, similar to natural LS.
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Affiliation(s)
- Shannon L Seurynck-Servoss
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
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29
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Morrow MR, Temple S, Stewart J, Keough KMW. Comparison of DPPC and DPPG environments in pulmonary surfactant models. Biophys J 2007; 93:164-75. [PMID: 17434940 PMCID: PMC1914421 DOI: 10.1529/biophysj.106.102681] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Deuterium nuclear magnetic resonance was used to monitor lipid acyl-chain orientational order in suspensions of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) containing Ca(2+) and the lung surfactant proteins SP-A and SP-B separately and together. To distinguish between protein-lipid interactions involving the PC and PG lipid headgroups and to examine whether such interactions might influence spatial distribution of lipids within the bilayer, acyl chains on either the DPPC or the DPPG component of the mixture were deuterated. The lipid components of the resulting mixtures were thus either DPPC-d(62)/DPPG (7:3) or DPPC/DPPG-d(62) (7:3), respectively. SP-A had little effect on DPPC-d(62) chain order but did narrow the temperature range over which DPPG-d(62) ordered at the liquid-crystal-to-gel transition. No segregation of lipid components was seen for temperatures above or below the transition. Near the transition, though, there was evidence that SP-A promoted preferential depletion of DPPG from liquid crystalline domains in the temperature range over which gel and liquid crystal domains coexist. SP-B lowered average chain order of both lipids both above and below the main transition. The perturbations of chain order by SP-A and SP-B together were smaller than by SP-B alone. This reduction in perturbation of the lipids by the additional presence of SP-A likely indicated a strong interaction between SP-A and SP-B. The competitive lipid-lipid, lipid-protein, and protein-protein interactions suggested by these observations presumably facilitate the reorganization of surfactant material inherent in the transformation from lamellar bodies to a functional surfactant layer.
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Affiliation(s)
- Michael R Morrow
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.
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30
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Sáenz A, Cañadas O, Bagatolli LA, Sánchez-Barbero F, Johnson ME, Casals C. Effect of surfactant protein A on the physical properties and surface activity of KL4-surfactant. Biophys J 2006; 92:482-92. [PMID: 17056727 PMCID: PMC1751418 DOI: 10.1529/biophysj.106.090217] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
SP-A, the major protein component of pulmonary surfactant, is absent in exogenous surfactants currently used in clinical practice. However, it is thought that therapeutic properties of natural surfactants improve after enrichment with SP-A. The objective of this study was to determine SP-A effects on physical properties and surface activity of a new synthetic lung surfactant based on a cationic and hydrophobic 21-residue peptide KLLLLKLLLLKLLLLKLLLLK, KL(4). We have analyzed the interaction of SP-A with liposomes consisting of DPPC/POPG/PA (28:9:5.6, w/w/w) with and without 0.57 mol % KL(4) peptide. We found that SP-A had a concentration-dependent effect on the surface activity of KL(4)-DPPC/POPG/PA membranes but not on that of an animal-derived LES. The surface activity of KL(4)-surfactant significantly improved after enrichment with 2.5-5 wt % SP-A. However, it worsened at SP-A concentrations > or =10 wt %. This was due to the fluidizing effect of supraphysiological SP-A concentrations on KL(4)-DPPC/POPG/PA membranes as determined by fluorescence anisotropy measurements, calorimetric studies, and confocal fluorescence microscopy of GUVs. High SP-A concentrations caused disappearance of the solid/fluid phase coexistence of KL(4)-surfactant, suggesting that phase coexistence might be important for the surface adsorption process.
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Affiliation(s)
- Alejandra Sáenz
- Department of Biochemistry and Molecular Biology I, Complutense University of Madrid, Madrid, Spain
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31
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Adhangale PS, Gaver DP. Equation of state for a coarse-grained DPPC monolayer at the air/water interface. Mol Phys 2006; 104. [PMID: 24179252 DOI: 10.1080/00268970600935101] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Pulmonary surfactant, a complex mixture of phospholipids and proteins, secreted by the type II epithelial cells in the lungs, is crucial to reducing the effort required for breathing. A lack of adequate amounts of pulmonary surfactant in underdeveloped lungs of premature infants results in infant respiratory distress syndrome (RDS). Surfactant replacement therapy (SRT) is the approved method of mitigating the effects of RDS. The development of new SRT regimens requires a fundamental understanding of the links between surfactant biochemistry and functionality. We use a coarse-grained (CG) model to predict the surface pressure-surface concentration relationship (equation of state) for pure DPPC, which is a major component of endogenous and synthetic pulmonary surfactant mixtures. We show that the model can be efficiently used to predict the equation of state in excellent agreement with experimental results. We also study the structure of the monolayer as a function of the surface tension of the system. We show that a decrease in the applied surface tension results in an increase in order in the head group region and a decrease in order in the tail region of DPPC. This technique may be useful in the prediction of equations of state for surfactant replacements.
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Affiliation(s)
- Parag S Adhangale
- Department of Biomedical Engineering, Tulane University, Lindy Boggs Center Suite 500, New Orleans, LA 70118, USA
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32
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Serrano AG, Pérez-Gil J. Protein-lipid interactions and surface activity in the pulmonary surfactant system. Chem Phys Lipids 2006; 141:105-18. [PMID: 16600200 DOI: 10.1016/j.chemphyslip.2006.02.017] [Citation(s) in RCA: 208] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2005] [Accepted: 02/20/2006] [Indexed: 11/30/2022]
Abstract
Pulmonary surfactant is a lipid-protein complex, synthesized and secreted by the respiratory epithelium of lungs to the alveolar spaces, whose main function is to reduce the surface tension at the air-liquid interface to minimize the work of breathing. The activity of surfactant at the alveoli involves three main processes: (i) transfer of surface active molecules from the aqueous hypophase into the interface, (ii) surface tension reduction to values close to 0 mN/m during compression at expiration and (iii) re-extension of the surface active film upon expansion at inspiration. Phospholipids are the main surface active components of pulmonary surfactant, but the dynamic behaviour of phospholipids along the breathing cycle requires the necessary participation of some specific surfactant associated proteins. The present review summarizes the current knowledge on the structure, disposition and lipid-protein interactions of the hydrophobic surfactant proteins SP-B and SP-C, the two main actors participating in the surface properties of pulmonary surfactant. Some of the methodologies currently used to evaluate the surface activity of the proteins in lipid-protein surfactant preparations are also revised. Working models for the potential molecular mechanism of SP-B and SP-C are finally discussed. SP-B might act in surfactant as a sort of amphipathic tag, directing the lipid-protein complexes to insert and re-insert very efficiently into the air-liquid interface along successive breathing cycles. SP-C could be essential to maintain association of lipid-protein complexes with the interface at the highest compressed states, at the end of exhalation. The understanding of the mechanisms of action of these proteins is critical to approach the design and development of new clinical surfactant preparations for therapeutical applications.
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Affiliation(s)
- Alicia G Serrano
- Departamento de Bioquímica y Biología Molecular I, Facultad de Biología, Universidad Complutense, Jose Antonio Novais 2, Madrid, Spain
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Stichtenoth G, Jung P, Walter G, Johansson J, Robertson B, Curstedt T, Herting E. Polymyxin B/pulmonary surfactant mixtures have increased resistance to inactivation by meconium and reduce growth of gram-negative bacteria in vitro. Pediatr Res 2006; 59:407-11. [PMID: 16492980 DOI: 10.1203/01.pdr.0000200806.32822.e6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Pulmonary surfactant is inactivated in meconium aspiration syndrome and neonatal pneumonia. Development of an exogenous surfactant less sensitive to inactivation might be useful for treating these diseases. We investigated in vitro whether addition of the cationic cyclic membrane cross-linking peptide polymyxin B (PxB) and/or calcium chloride (CaCl2) to modified porcine surfactant Curosurf increases resistance to meconium-induced inactivation of surface activity while antimicrobial activity of PxB is maintained. To study bacterial proliferation, Escherichia coli, group B streptococci (GBS), or Staphylococcus aureus were incubated 0-5 h in saline or in meconium in the presence or absence of Curosurf with or without PxB. PxB and CaCl2 improved spreading and adsorption of Curosurf. Curosurf plus CaCl2/PxB needed a 4-fold increase of meconium concentration to increase dynamic surface tension significantly compared with Curosurf plus CaCl2 alone, indicating that PxB further increases the resistance of Curosurf to meconium-induced inactivation. Meconium alone like meconium/Curosurf promoted growth of E. coli and GBS, but addition of Curosurf/PxB or PxB alone significantly reduced the growth of E. coli. Biophysical and antibacterial properties of Curosurf and PxB may be combined into a useful adjunct in the treatment of neonatal Gram-negative pneumonia and/or meconium aspiration syndrome.
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Affiliation(s)
- Guido Stichtenoth
- Department of Clinical Chemistry, Laboratory for Surfactant Research, Karolinska Hospital, Sweden.
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Wüstneck R, Perez-Gil J, Wüstneck N, Cruz A, Fainerman VB, Pison U. Interfacial properties of pulmonary surfactant layers. Adv Colloid Interface Sci 2005; 117:33-58. [PMID: 16120435 DOI: 10.1016/j.cis.2005.05.001] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2004] [Revised: 02/16/2005] [Accepted: 05/20/2005] [Indexed: 11/25/2022]
Abstract
The composition of the pulmonary surfactant and the border conditions of normal human breathing are relevant to characterize the interfacial behavior of pulmonary layers. Based on experimental data methods are reviewed to investigate interfacial properties of artificial pulmonary layers and to explain the behavior and interfacial structures of the main components during compression and expansion of the layers observed by epifluorescence and scanning force microscopy. Terms like over-compression, collapse, and formation of the surfactant reservoir are discussed. Consequences for the viscoelastic surface rheological behavior of such layers are elucidated by surface pressure relaxation and harmonic oscillation experiments. Based on a generalized Volmer isotherm the interfacial phase transition is discussed for the hydrophobic surfactant proteins, SP-B and SP-C, as well as for the mixtures of dipalmitoylphosphatidylcholine (DPPC) with these proteins. The behavior of the layers depends on both the oligomerisation state and the secondary structure of the hydrophobic surfactant proteins, which are controlled by the preparation of the proteins. An example for the surface properties of bronchoalveolar porcine lung washings of uninjured, injured, and Curosurf treated lavage is discussed in the light of surface behavior. An outlook summarizes the present knowledge and the main future development in this field of surface science.
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Affiliation(s)
- R Wüstneck
- Charité, Campus Virchow-Klinikum, Universitätsmedizin Berlin, Klinik für Anästhesiologie und operative Intensivmedizin, Spandauer Damm 130, 14050 Berlin, Germany.
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Bachofen H, Gerber U, Gehr P, Amrein M, Schürch S. Structures of pulmonary surfactant films adsorbed to an air–liquid interface in vitro. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1720:59-72. [PMID: 16405864 DOI: 10.1016/j.bbamem.2005.11.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Revised: 10/20/2005] [Accepted: 11/09/2005] [Indexed: 11/28/2022]
Abstract
Phospholipid films can be preserved in vitro when adsorbed to a solidifiable hypophase. Suspensions of natural surfactant, lipid extract surfactants, and artificial surfactants were added to a sodium alginate solution and filled into a captive bubble surfactometer (CBS). Surfactant film was formed by adsorption to the bubble of the CBS for functional tests. There were no discernible differences in adsorption, film compressibility or minimal surface tension on quasi-static or dynamic compression for films formed in the presence or absence of alginate in the subphase of the bubble. The hypophase-film complex was solidified by adding calcium ions to the suspension with the alginate. The preparations were stained with osmium tetroxide and uranyl acetate for transmission electron microscopy. The most noteworthy findings are: (1) Surfactants do adsorb to the surface of the bubble and form osmiophilic lining layers. Pure DPPC films could not be visualized. (2) A distinct structure of a particular surfactant film depends on the composition and the concentration of surfactant in the bulk phase, and on whether or not the films are compressed after their formation. The films appear heterogeneous, and frequent vesicular and multi-lamellar film segments are seen associated with the interfacial films. These features are seen already upon film formation by adsorption, but multi-lamellar segments are more frequent after film compression. (3) The rate of film formation, its compressibility, and the minimum surface tension achieved on film compression appear to be related to the film structure formed on adsorption, which in turn is related to the concentration of the surfactant suspension from which the film is formed. The osmiophilic surface associated surfactant material seen is likely important for the surface properties and the mechanical stability of the surfactant film at the air-fluid interface.
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Affiliation(s)
- H Bachofen
- Division of Pneumology, University Hospital of Berne, 3010 Berne, Switzerland
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Gunasekara L, Schürch S, Schoel WM, Nag K, Leonenko Z, Haufs M, Amrein M. Pulmonary surfactant function is abolished by an elevated proportion of cholesterol. Biochim Biophys Acta Mol Cell Biol Lipids 2005; 1737:27-35. [PMID: 16216549 DOI: 10.1016/j.bbalip.2005.09.002] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Revised: 08/17/2005] [Accepted: 09/06/2005] [Indexed: 10/25/2022]
Abstract
A molecular film of pulmonary surfactant strongly reduces the surface tension of the lung epithelium-air interface. Human pulmonary surfactant contains 5-10% cholesterol by mass, among other lipids and surfactant specific proteins. An elevated proportion of cholesterol is found in surfactant, recovered from acutely injured lungs (ALI). The functional role of cholesterol in pulmonary surfactant has remained controversial. Cholesterol is excluded from most pulmonary surfactant replacement formulations, used clinically to treat conditions of surfactant deficiency. This is because cholesterol has been shown in vitro to impair the surface activity of surfactant even at a physiological level. In the current study, the functional role of cholesterol has been re-evaluated using an improved method of evaluating surface activity in vitro, the captive bubble surfactometer (CBS). Cholesterol was added to one of the clinically used therapeutic surfactants, BLES, a bovine lipid extract surfactant, and the surface activity evaluated, including the adsorption rate of the substance to the air-water interface, its ability to produce a surface tension close to zero and the area compression needed to obtain that low surface tension. No differences in the surface activity were found for BLES samples containing either none, 5 or 10% cholesterol by mass with respect to the minimal surface tension. Our findings therefore suggest that the earlier-described deleterious effects of physiological amounts of cholesterol are related to the experimental methodology. However, at 20%, cholesterol effectively abolished surfactant function and a surface tension below 15 mN/m was not obtained. Inhibition of surface activity by cholesterol may therefore partially or fully explain the impaired lung function in the case of ALI. We discuss a molecular mechanism that could explain why cholesterol does not prevent low surface tension of surfactant films at physiological levels but abolishes surfactant function at higher levels.
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Affiliation(s)
- Lasantha Gunasekara
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada
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37
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Seurynck SL, Brown NJ, Wu CW, Germino KW, Kohlmeir EK, Ingenito EP, Glucksberg MR, Barron AE, Johnson M. Optical monitoring of bubble size and shape in a pulsating bubble surfactometer. J Appl Physiol (1985) 2005; 99:624-33. [PMID: 15790687 DOI: 10.1152/japplphysiol.00748.2004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The pulsating bubble surfactometer (PBS) is often used for in vitro characterization of exogenous lung surfactant replacements and lung surfactant components. However, the commercially available PBS is not able to dynamically track bubble size and shape. The PBS therefore does not account for bubble growth or elliptical bubble shape that frequently occur during device use. More importantly, the oscillatory volume changes of the pulsating bubble are different than those assumed by the software of the commercial unit. This leads to errors in both surface area and surface tension measurements. We have modified a commercial PBS through the addition of an image-acquisition system, allowing real-time determination of bubble size and shape and hence the accurate tracking of surface area and surface tension. Compression-expansion loops obtained with the commercially available PBS software were compared with those provided by the image-analysis system for dipalmitoylphosphatidylcholine, Infasurf, and Tanaka lipids (dipalmitoylphosphatidylcholine-palmitoyloleoylphosphatidyl-glycerol-palmitic acid, 68:22:9) at concentrations of 0.1 and 1.0 mg/ml and at frequencies of 1 and 20 cycles/min. Whereas minimum surface tension as determined by the image-analysis system is similar to that measured by the commercially available software, the maximum surface tension and the shapes of the interfacial area-surface tension loops are quite different. Differences are attributable to bubble drift, nonsinusoidal volume changes, and variable volume excursions seen with the modified system but neglected by the original system. Image analysis reveals that the extent of loop hysteresis is greatly overestimated by the commercial device and that an apparent, rapid increase in surface tension upon film expansion seen in PBS loops is not observed with the image-analysis system. The modified PBS system reveals new dynamic characteristics of lung surfactant preparations that have not previously been reported.
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Affiliation(s)
- Shannon L Seurynck
- Northwestern University, Dept. of Biomedical Engineering, 2145 Sheridan Road, Evanston, IL 60208, USA
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Miller NJ, Postle AD, Schürch S, Michael Schoel W, Daniels CB, Orgeig S. The development of the pulmonary surfactant system in California sea lions. Comp Biochem Physiol A Mol Integr Physiol 2005; 141:191-9. [PMID: 15964230 DOI: 10.1016/j.cbpb.2005.05.035] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Revised: 05/09/2005] [Accepted: 05/09/2005] [Indexed: 11/27/2022]
Abstract
Pulmonary surfactant has previously been shown to change during development, both in composition and function. Adult pinnipeds, unlike adult terrestrial mammals, have an altered lung physiology to cope with the high pressures associated with deep diving. Here, we investigated how surfactant composition and function develop in California sea lions (Zalophus californianus). Phosphatidylinositol was the major anionic phospholipid in the newborn, whereas phosphatidylglycerol was increased in the adult. This increase in phosphatidylglycerol occurred at the expense of phosphatidylinositol and phosphatidylserine. There was a shift from long chain and polyunsaturated phospholipid molecular species in the newborn to shorter chain and mono- and disaturated molecular species in the adult. Cholesterol and SP-B concentrations were also higher in the adult. Adult surfactant could reach a lower equilibrium surface tension, but newborn surfactant could reach a lower minimum surface tension. The composition and function of surfactant from newborn California sea lions suggest that this age group is similar to terrestrial newborn mammals, whereas the adult has a "diving mammal" surfactant that can aid the lung during deep dives. The onset of diving is probably a trigger for surfactant development in these animals.
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Affiliation(s)
- Natalie J Miller
- Environmental Biology, School of Earth and Environmental Sciences, Darling Building, University of Adelaide, North Tce, Australia
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Miller NJ, Daniels CB, Schürch S, Schoel WM, Orgeig S. The surface activity of pulmonary surfactant from diving mammals. Respir Physiol Neurobiol 2005; 150:220-32. [PMID: 16476655 DOI: 10.1016/j.resp.2005.03.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 03/17/2005] [Accepted: 03/19/2005] [Indexed: 11/27/2022]
Abstract
Pinnipeds (seals and sea lions) have developed a specialised respiratory system to cope with living in a marine environment. They have a highly reinforced lung that can completely collapse and reinflate during diving without any apparent side effects. These animals may also have a specialised surfactant system to augment the morphological adaptations. The surface activity of surfactant from four species of pinniped (California sea lion, Northern elephant seal, Northern fur seal and Ringed seal) was measured using a captive bubble surfactometer (CBS), and compared to two terrestrial species (sheep and cow). The surfactant of Northern elephant seal, Northern fur seal and Ringed seal was unable to reduce surface tension (gamma) to normal levels after 5 min adsorption (61.2, 36.7, and 46.2 +/- 1.7 mN/m, respectively), but California sea lion was able to reach the levels of the cow and sheep (23.4 mN/m for California sea lion, 21.6 +/- 0.3 and 23.0 +/- 1.5 mN/m for cow and sheep, respectively). All pinnipeds were also unable to obtain the very low gamma(min) achieved by cow (1.4 +/- 0.1 mN/m) and sheep (1.5 +/- 0.4 mN/m). These results suggest that reducing surface tension to very low values is not the primary function of surfactant in pinnipeds as it is in terrestrial mammals, but that an anti-adhesive surfactant is more important to enable the lungs to reopen following collapse during deep diving.
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Affiliation(s)
- Natalie J Miller
- Environmental Biology, School of Earth and Environmental Sciences, University of Adelaide, North Tce, Adelaide, SA 5005, Australia
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Cruz A, Vázquez L, Vélez M, Pérez-Gil J. Effect of pulmonary surfactant protein SP-B on the micro- and nanostructure of phospholipid films. Biophys J 2004; 86:308-20. [PMID: 14695272 PMCID: PMC1303794 DOI: 10.1016/s0006-3495(04)74106-5] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Monolayers of dipalmitoylphosphatidylcholine (DPPC) and DPPC/dipalmitoylphosphatidylglycerol (DPPG) (7:3, w/w) in the absence or in the presence of 2, 5, 10, or 20 weight percent of porcine surfactant protein SP-B were spread at the air-liquid interface of a surface balance, compressed up to surface pressures in the liquid-expanded/liquid-condensed (LE-LC) plateau of the isotherm, transferred onto mica supports, and analyzed by scanning force microscopy. In the absence of protein, the films showed micrometer-sized condensed domains with morphology and size that were analogous to those observed in situ at the air-liquid interface by epifluorescence microscopy. Scanning force microscopy permits examination of the coexisting phases at a higher resolution than previously achieved with fluorescent microscopy. Both LE and LC regions of DPPC films were heterogeneous in nature. LC microdomains contained numerous expanded-like islands whereas regions apparently liquid-expanded were covered by a condensed-like framework of interconnected nanodomains. Presence of increasing amounts of pulmonary surfactant protein SP-B affected the distribution of the LE and LC regions of DPPC and DPPC/DPPG films both at the microscopic and the nanoscopic level. The condensed microdomains became more numerous but their size decreased, resulting in an overall reduction of the amount of total LC phase in both DPPC and DPPC/DPPG films. At the nanoscopic level, SP-B also caused a marked reduction of the size of the condensed-like nanodomains in the LE phase and an increase in the length of the LE/LC interface. SP-B promotes a fine nanoscopic framework of lipid and lipid-protein nanodomains that is associated with a substantial mechanical resistance to film deformation and rupture as observed during film transference and manipulation. The effect of SP-B on the nanoscopic structure of the lipid films was greater in DPPC/DPPG than in pure DPPC films, indicating additional contributions of electrostatic lipid-protein interactions. The alterations of the nanoscopic structures of phospholipid films by SP-B provide the structural framework for the protein simultaneously sustaining structural stability as well as dynamical flexibility in surfactant films at the extreme conditions imposed by the respiratory mechanics. SP-B also formed segregated two-dimensional clusters that were associated with the boundaries between LC microdomains and the LE regions of DPPC and DPPC/DPPG films. The presence of these clusters at protein-to-lipid proportions above 2% by weight suggests that the concentration of SP-B in the surfactant lipid-protein complexes may be close to the solubility limit of the protein in the lipid films.
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Affiliation(s)
- Antonio Cruz
- Departamento de Bioquímica, Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain
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Morrow MR, Abu-Libdeh N, Stewart J, Keough KMW. Interaction of pulmonary surfactant protein SP-A with DPPC/egg-PG bilayers. Biophys J 2004; 85:2397-405. [PMID: 14507703 PMCID: PMC1303464 DOI: 10.1016/s0006-3495(03)74663-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
In the mixture of lipids and proteins which comprise pulmonary surfactant, the dominant protein by mass is surfactant protein A (SP-A), a hydrophilic glycoprotein. SP-A forms octadecamers that interact with phospholipid bilayer surfaces in the presence of calcium. Deuterium NMR was used to characterize the perturbation by SP-A, in the presence of 5 mM Ca(2+), of dipalmitoyl phosphatidylcholine (DPPC) properties in DPPC/egg-PG (7:3) bilayers. Effects of SP-A were uniformly distributed over the observed DPPC population. SP-A reduced DPPC chain orientational order significantly in the gel phase but only slightly in the liquid-crystalline phase. Quadrupole echo decay times for DPPC chain deuterons were sensitive to SP-A in the liquid-crystalline mixture but not in the gel phase. SP-A reduced quadrupole splittings of DPPC choline beta-deuterons but had little effect on choline alpha-deuteron splittings. The observed effects of SP-A on DPPC/egg-PG bilayer properties differ from those of the hydrophobic surfactant proteins SP-B and SP-C. This is consistent with the expectation that SP-A interacts primarily at bilayer surfaces.
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Affiliation(s)
- Michael R Morrow
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X9 Canada.
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Rau GA, Vieten G, Haitsma JJ, Freihorst J, Poets C, Ure BM, Bernhard W. Surfactant in Newborn Compared with Adolescent Pigs. Am J Respir Cell Mol Biol 2004; 30:694-701. [PMID: 14578213 DOI: 10.1165/rcmb.2003-0351oc] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Surfactant composition and function differ between vertebrates, depending on pulmonary anatomy and respiratory physiology. Because pulmonary development in pigs is similar to that in humans, we investigated surface tension function, composition of phospholipid molecular species, and concentrations of surfactant protein (SP)-A to -D in term newborn pigs (NP) compared with adolescent pigs (AP), using the pulsating bubble surfactometer, mass spectrometry, high-performance liquid chromatography, and immunoblot techniques (IT). NP was more potent than AP surfactant in reaching minimal surface tension values near zero mN/m. Whereas SP-A and SP-D were comparable, SP-B and SP-C were increased 3- to 4-fold in NP surfactant. Moreover, fluidizing phospholipids such as palmitoylmyristoyl-PC (PC16:0/14:0) and palmitoylpalmitoleoyl-PC (PC16:0/16:1) were increased at the expense of PC16:0/16:0 (32.4 +/- 0.6 versus 44.5 +/- 3.2%, respectively). Whereas concentrations of total anionic phospholipids were similar in NP and AP surfactant (9.9 +/- 0.3 and 12.0 +/- 0.3%, respectively), phosphatidylinositol was the predominant anionic phospholipid in NP surfactant. We conclude that, compared with AP, NP surfactant displays better surface tension function under dynamic conditions, which is associated with increased concentrations of SP-B and SP-C, as well as fluidizing phospholipids at the expense of PC16:0/16:0.
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Affiliation(s)
- Gunnar A Rau
- Department of Pediatric Pulmonology, Hannover Medical School, Hannover, Germany
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Abstract
A number of conditions, such as pneumonia, trauma, or systemic sepsis arising from the gut, may result in the acute respiratory distress syndrome (ARDS). Because of its significant morbidity and mortality, ARDS has been the focus of extensive research. One specific area of interest has been the investigation of the role of the surfactant system in the pathophysiology of this disease. Several studies have demonstrated that alterations of surfactant contribute to the lung dysfunction associated with ARDS, which has led to investigations into the use of exogenous surfactant as a therapy for this syndrome. Clinical experience with surfactant therapy has been variable owing to a number of factors including the nature of the injury at the time of treatment, the specific surfactant preparation utilized, the dose and delivery method chosen, the timing of surfactant administration over the course of the disease, and the mode of ventilation used during and after surfactant administration.
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Affiliation(s)
- James F Lewis
- Department of Medicine, Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada.
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ten Brinke A, van Golde LMG, Batenburg JJ. Palmitoylation and processing of the lipopeptide surfactant protein C. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1583:253-65. [PMID: 12176392 DOI: 10.1016/s1388-1981(02)00248-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Pulmonary surfactant, a mixture of lipids and proteins, reduces the surface tension at the air-water interface of the lung alveoli by forming a surface active film. This way, it prevents alveoli from collapsing and facilitates the work of breathing. Surfactant protein C (SP-C) plays an important role in this surfactant function. SP-C is expressed as a proprotein (proSP-C), which becomes posttranslationally modified with palmitate and undergoes several rounds of proteolytical cleavage. This results in the formation of mature SP-C, which is stored in the lamellar bodies (LB) and finally secreted into the alveolar space. Recently, new insights into the sorting, processing and palmitoylation of proSP-C have been obtained by mutagenesis studies. Moreover, reports on the association of development of lung disease with SP-C deficiency have led to new insights into the importance of SP-C for proper surfactant homeostasis. In addition, new information has become available on the role of the palmitoyl chains of SP-C in surface activity. This review summarizes these recent developments in the processing and function of SP-C, with particular emphasis on the signals for and role of palmitoylation of SP-C.
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Affiliation(s)
- Anja ten Brinke
- Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, and Institute of Biomembranes, Utrecht University, P.O. Box 80176, 3508 TD Utrecht, The Netherlands
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