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Cellular & Molecular Biology Letters Nov 2023The pulmonary surfactant that lines the air-liquid surface within alveoli is a protein-lipid mixture essential for gas exchange. Surfactant lipids and proteins are...
BACKGROUND
The pulmonary surfactant that lines the air-liquid surface within alveoli is a protein-lipid mixture essential for gas exchange. Surfactant lipids and proteins are synthesized and stored in the lamellar body (LB) before being secreted from alveolar type II (AT2) cells. The molecular and cellular mechanisms that regulate these processes are incompletely understood. We previously identified an essential role of general control of amino acid synthesis 5 like 1 (GCN5L1) and the biogenesis of lysosome-related organelle complex 1 subunit 1 (BLOS1) in surfactant system development in zebrafish. Here, we explored the role of GCN5L1 in pulmonary surfactant regulation.
METHOD
GCN5L1 knockout cell lines were generated with the CRISPR/Cas9 system. Cell viability was analyzed by MTT assay. Released surfactant proteins were measured by ELISA. Released surfactant lipids were measured based on coupled enzymatic reactions. Gene overexpression was mediated through lentivirus. The RNA levels were detected through RNA-sequencing (RNA-seq) and quantitative reverse transcription (qRT)- polymerase chain reaction (PCR). The protein levels were detected through western blotting. The cellular localization was analyzed by immunofluorescence. Morphology of the lamellar body was analyzed through transmission electron microscopy (TEM), Lysotracker staining, and BODIPY phosphatidylcholine labeling.
RESULTS
Knocking out GCN5L1 in MLE-12 significantly decreased the release of surfactant proteins and lipids. We detected the downregulation of some surfactant-related genes and misregulation of the ROS-Erk-Foxo1-Cebpα axis in mutant cells. Modulating the activity of the axis or reconstructing the mitochondrial expression of GCN5L1 could partially restore the expression of these surfactant-related genes. We further showed that MLE-12 cells contained many LB-like organelles that were lipid enriched and positive for multiple LB markers. These organelles were smaller in size and accumulated in the absence of GCN5L1, indicating both biogenesis and trafficking defects. Accumulated endogenous surfactant protein (SP)-B or exogenously expressed SP-B/SP-C in adenosine triphosphate-binding cassette transporterA3 (ABCA3)-positive organelles was detected in mutant cells. GCN5L1 localized to the mitochondria and LBs. Reconstruction of mitochondrial GCN5L1 expression rescued the organelle morphology but failed to restore the trafficking defect and surfactant release, indicating specific roles associated with different subcellular localizations.
CONCLUSIONS
In summary, our study identified GCN5L1 as a new regulator of pulmonary surfactant that plays a role in the biogenesis and positioning/trafficking of surfactant-containing LBs.
Topics: Animals; Mice; Alveolar Epithelial Cells; Lamellar Bodies; Lipids; Pulmonary Surfactants; RNA; Surface-Active Agents; Zebrafish
PubMed: 37936104
DOI: 10.1186/s11658-023-00506-0 -
Nano Letters Nov 2023Lung-targeting RNA-carrying lipid nanoparticles (LNPs) are often intravenously administered and accumulate in the pulmonary endothelium. However, most respiratory... (Review)
Review
Lung-targeting RNA-carrying lipid nanoparticles (LNPs) are often intravenously administered and accumulate in the pulmonary endothelium. However, most respiratory diseases are localized in the airway or the alveolar epithelium. Inhalation has been explored as a more direct delivery method, but it presents its own challenges. We believe that one reason LNPs have failed to transfect RNA into alveolar epithelial cells is their interaction with the lung surfactant (LS). We propose that inhalable LNP design should take inspiration from biological agents and other nanoparticles to overcome this barrier. Screening should first focus on LS penetration and then be optimized for cell uptake and endosomal release. This will enable more efficient applications of RNA-LNPs in lung diseases.
Topics: Surface-Active Agents; Pulmonary Surfactants; Lung; Nanoparticles; Genetic Therapy; RNA; RNA, Small Interfering
PubMed: 37930273
DOI: 10.1021/acs.nanolett.3c03547 -
Seminars in Fetal & Neonatal Medicine Dec 2023Surfactant is a pivotal neonatal drug used both for respiratory distress syndrome due to surfactant deficiency and for more complex surfactant dysfunctions (such as in... (Review)
Review
Surfactant is a pivotal neonatal drug used both for respiratory distress syndrome due to surfactant deficiency and for more complex surfactant dysfunctions (such as in case of neonatal acute respiratory distress syndrome). Despite its importance, indications for surfactant therapy are often based on oversimplified criteria. Lung biology and modern monitoring provide several diagnostic tools to assess the patient surfactant status and they can be used for a personalized surfactant therapy. This is desirable to improve the efficacy of surfactant treatment and reduce associated costs and side effects. In this review we will discuss these diagnostic tools from a pathophysiological and multi-disciplinary perspective, focusing on the quantitative or qualitative surfactant assays, lung mechanics or aeration measurements, and gas exchange metrics. Their biological and technical characteristics are described with practical information for clinicians. Finally, available evidence-based data are reviewed, and the diagnostic accuracy of the different tools is compared. Lung ultrasound seems the most suitable tool for assessing the surfactant status, while some other promising tests require further research and/or development.
Topics: Infant, Newborn; Humans; Surface-Active Agents; Pulmonary Surfactants; Lung; Respiratory Distress Syndrome, Newborn; Lipoproteins
PubMed: 38016825
DOI: 10.1016/j.siny.2023.101494 -
American Journal of Respiratory and... Jan 2023Coronavirus disease 2019 (COVID-19) can lead to acute respiratory distress syndrome with fatal outcomes. Evidence suggests that dysregulated immune responses, including...
Coronavirus disease 2019 (COVID-19) can lead to acute respiratory distress syndrome with fatal outcomes. Evidence suggests that dysregulated immune responses, including autoimmunity, are key pathogenic factors. To assess whether IgA autoantibodies target lung-specific proteins and contribute to disease severity. We collected 147 blood, 9 lung tissue, and 36 BAL fluid samples from three tertiary hospitals in Switzerland and one in Germany. Severe COVID-19 was defined by the need to administer oxygen. We investigated the presence of IgA autoantibodies and their effects on pulmonary surfactant in COVID-19 using the following methods: immunofluorescence on tissue samples, immunoprecipitations followed by mass spectrometry on BAL fluid samples, enzyme-linked immunosorbent assays on blood samples, and surface tension measurements with medical surfactant. IgA autoantibodies targeting pulmonary surfactant proteins B and C were elevated in patients with severe COVID-19 but not in patients with influenza or bacterial pneumonia. Notably, pulmonary surfactant failed to reduce surface tension after incubation with either plasma or purified IgA from patients with severe COVID-19. Our data suggest that patients with severe COVID-19 harbor IgA autoantibodies against pulmonary surfactant proteins B and C and that these autoantibodies block the function of lung surfactant, potentially contributing to alveolar collapse and poor oxygenation.
Topics: Humans; Pulmonary Surfactants; COVID-19; Bronchoalveolar Lavage Fluid; Surface-Active Agents; Autoantibodies; Immunoglobulin A
PubMed: 35926164
DOI: 10.1164/rccm.202201-0011OC -
Biophysical Journal Jun 2024The 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... (Review)
Review
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.
Topics: Pulmonary Surfactants; Humans; Animals; Models, Biological; Adsorption; Biophysical Phenomena; Surface Tension
PubMed: 38664968
DOI: 10.1016/j.bpj.2024.04.021 -
American Journal of Perinatology Jan 2024The standard of care in treating respiratory distress syndrome in preterm infants is respiratory support with nasal continuous positive airway pressure or a combination... (Review)
Review
The standard of care in treating respiratory distress syndrome in preterm infants is respiratory support with nasal continuous positive airway pressure or a combination of continuous positive airway pressure and exogenous surfactant replacement. Endotracheal intubation, the conventional method for surfactant administration, is an invasive procedure associated with procedural and mechanical ventilation complications. The INSURE (intubation, surfactant administration, and extubation soon after) technique is an accepted method aimed at reducing the short-term complications and long-term morbidities related to mechanical ventilation but does not eliminate risks associated with endotracheal intubation and mechanical ventilation. Alternative methods of surfactant delivery that can overcome the problems associated with the INSURE technique are surfactant through a laryngeal mask, surfactant through a thin intratracheal catheter, and aerosolized surfactant delivered using nebulizers. The three alternative methods of surfactant delivery studied in the last two decades have advantages and limitations. More than a dozen randomized controlled trials have aimed to study the benefits of the three alternative techniques of surfactant delivery compared with INSURE as the control arm, with promising results in terms of reduction in mortality, need for mechanical ventilation, and bronchopulmonary dysplasia. The need to find a less invasive surfactant administration technique is a clinically relevant problem. Before broader adoption in routine clinical practice, the most beneficial technique among the three alternative strategies should be identified. This review aims to summarize the current evidence for using the three alternative techniques of surfactant administration in neonates, compare the three techniques, highlight the knowledge gaps, and suggest future directions. KEY POINTS: · The need to find a less invasive alternative method of surfactant delivery is a clinically relevant problem.. · Clinical trials that have studied alternative surfactant delivery methods have shown promising results but are inconclusive for broader adoption into clinical practice.. · Future studies should explore novel clinical trial methodologies and select clinically significant long term outcomes for comparison..
Topics: Infant, Newborn; Humans; Infant, Premature; Surface-Active Agents; Pulmonary Surfactants; Respiration, Artificial; Continuous Positive Airway Pressure; Respiratory Distress Syndrome, Newborn; Intubation, Intratracheal; Randomized Controlled Trials as Topic
PubMed: 36539205
DOI: 10.1055/a-2001-9139 -
Colloids and Surfaces. B, Biointerfaces Feb 2022Pulmonary fungal infections lead to damage of the endogenous lung surfactant system. However, the molecular mechanism underlying surfactant inhibition is unknown....
Pulmonary fungal infections lead to damage of the endogenous lung surfactant system. However, the molecular mechanism underlying surfactant inhibition is unknown. β-D-glucan is the major component of pathogenic fungal cell walls and is also present in organic dust, which increases the risk of respiratory diseases. The objective of this study was to characterize the interaction of this D-glucopyranose polymer with pulmonary surfactant. Our results show that β-D-glucan induced a concentration-dependent inhibition of the surface adsorption, respreading, and surface tension-lowering activity of surfactant preparations containing surfactant proteins SP-B and SP-C. Our data support a new mechanism of surfactant inhibition that consists in the extraction of phospholipid molecules from surfactant membranes by β-D-glucan. As a result, surfactant membranes became more fluid, as demonstrated by fluorescence anisotropy, and showed decreased T and transition enthalpy. Surfactant preparations containing surfactant protein A (SP-A) were more resistant to β-D-glucan inhibition. SP-A bound to different β-D-glucans with high affinity (K = 1.5 ± 0.1 nM), preventing and reverting β-D-glucan inhibitory effects on surfactant interfacial adsorption and partially abrogating β-D-glucan inhibitory effects on surfactant's reduction of surface tension. We conclude that β-D-glucan inhibits the biophysical function of surfactant preparations lacking SP-A by subtraction of phospholipids from surfactant bilayers and monolayers. The increased resistance of SP-A-containing surfactant preparations to β-D-glucan reinforces its use in surfactant replacement therapy.
Topics: Glucans; Phospholipids; Pulmonary Surfactant-Associated Protein A; Pulmonary Surfactant-Associated Protein B; Pulmonary Surfactants
PubMed: 34836708
DOI: 10.1016/j.colsurfb.2021.112237 -
Biomaterials Dec 2023Idiopathic pulmonary fibrosis (IPF) stands as a highly heterogeneous and deadly lung disease, yet the available treatment options remain limited. Combining myofibroblast...
Idiopathic pulmonary fibrosis (IPF) stands as a highly heterogeneous and deadly lung disease, yet the available treatment options remain limited. Combining myofibroblast inhibition with ROS modulation in damaged AECs offers a comprehensive strategy to halt IPF progression, but delivering drugs separately to these cell types is challenging. Inspired by the successful application of pulmonary surfactant (PS) replacement therapy in lung disease treatment, we have developed PS nano-biomimetic liposomes (PSBs) to utilize its natural transport pathway for targeting AECs while reducing lung tissue clearance. In this collaborative pulmonary drug delivery system, PSBs composed of DPPC/POPG/DPPG/CHO (20:9:5:4) were formulated for inhalation. These PSBs loaded with ROS-scavenger astaxanthin (AST) and anti-fibrosis drug pirfenidone (PFD) were aerosolized for precise quantification and mimicking patient inhalation. Through aerosol inhalation, the lipid membrane of PSBs gradually fused with natural PS, enabling AST delivery to AECs by hitchhiking with PS circulation. Simultaneously, PFD was released within the PS barrier, effectively penetrating lung tissue to exert therapeutic effects. In vivo results have shown that PSBs offer numerous therapeutic advantages in mice with IPF, particularly in terms of lung function recovery. This approach addresses the challenges of drug delivery to specific lung cells and offers potential benefits for IPF patients.
Topics: Humans; Mice; Animals; Pulmonary Surfactants; Liposomes; Reactive Oxygen Species; Biomimetics; Respiratory Aerosols and Droplets; Idiopathic Pulmonary Fibrosis; Lung; Pyridones
PubMed: 37992600
DOI: 10.1016/j.biomaterials.2023.122404 -
Immunological Reviews Aug 2023The pulmonary surfactant system of the lung is a lipid and protein complex, which regulates the biophysical properties of the alveoli to prevent lung collapse and the... (Review)
Review
The pulmonary surfactant system of the lung is a lipid and protein complex, which regulates the biophysical properties of the alveoli to prevent lung collapse and the innate immune system in the lung. Pulmonary surfactant is a lipoprotein complex consisting of 90% phospholipids and 10% protein, by weight. Two minor components of pulmonary surfactant phospholipids, phosphatidylglycerol (PG) and phosphatidylinositol (PI), exist at very high concentrations in the extracellular alveolar compartments. We have reported that one of the most dominant molecular species of PG, palmitoyl-oleoyl-phosphatidylglycerol (POPG) and PI inhibit inflammatory responses induced by multiple toll-like receptors (TLR2/1, TLR3, TLR4, and TLR2/6) by interacting with subsets of multiprotein receptor components. These lipids also exert potent antiviral effects against RSV and influenza A, in vitro, by inhibiting virus binding to host cells. POPG and PI inhibit these viral infections in vivo, in multiple animal models. Especially noteworthy, these lipids markedly attenuate SARS-CoV-2 infection including its variants. These lipids are natural compounds that already exist in the lung and, thus, are less likely to cause adverse immune responses by hosts. Collectively, these data demonstrate that POPG and PI have strong potential as novel therapeutics for applications as anti-inflammatory compounds and preventatives, as treatments for broad ranges of RNA respiratory viruses.
Topics: Animals; Humans; Phospholipids; Pulmonary Surfactants; Antiviral Agents; Toll-Like Receptor 2; COVID-19; SARS-CoV-2; Lung; Anti-Inflammatory Agents; Phosphatidylglycerols
PubMed: 37144896
DOI: 10.1111/imr.13207 -
Advances in Colloid and Interface... Oct 2020Particulate matter (PM), which is the primary contributor to air pollution, has become a pervasive global health threat. When PM enters into a respiratory tract, the... (Review)
Review
Particulate matter (PM), which is the primary contributor to air pollution, has become a pervasive global health threat. When PM enters into a respiratory tract, the first body tissues to be directly exposed are the cells of respiratory tissues and pulmonary surfactant. Pulmonary surfactant is a pivotal component to modulate surface tension of alveoli during respiration. Many studies have proved that PM would interact with pulmonary surfactant to affect the alveolar activity, and meanwhile, pulmonary surfactant would be adsorbed to the surface of PM to change the toxic effect of PM. This review focuses on recent studies of the interactions between micro/nanoparticles (synthesized and environmental particles) and pulmonary surfactant (natural surfactant and its models), as well as the health effects caused by PM through a few significant aspects, such as surface properties of PM, including size, surface charge, hydrophobicity, shape, chemical nature, etc. Moreover, in vitro and in vivo studies have shown that PM leads to oxidative stress, inflammatory response, fibrosis, and cancerization in living bodies. By providing a comprehensive picture of PM-surfactant interaction, this review will benefit both researchers for further studies and policy-makers for setting up more appropriate regulations to reduce the adverse effects of PM on public health.
Topics: Animals; Health; Humans; Nanoparticles; Particulate Matter; Pulmonary Surfactants
PubMed: 32871405
DOI: 10.1016/j.cis.2020.102244