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Jalali P, Nowroozi A, Moradi S, Shahlaei M. Exploration of lipid bilayer mechanical properties using molecular dynamics simulation. Arch Biochem Biophys 2024; 761:110151. [PMID: 39265694 DOI: 10.1016/j.abb.2024.110151] [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: 07/13/2024] [Revised: 08/22/2024] [Accepted: 09/09/2024] [Indexed: 09/14/2024]
Abstract
Important biological structures known for their exceptional mechanical qualities, lipid bilayers are essential to many cellular functions. Fluidity, elasticity, permeability, stiffness, tensile strength, compressibility, shear viscosity, line tension, and curvature elasticity are some of the fundamental characteristics affecting their behavior. The purpose of this review is to examine these characteristics in more detail by molecular dynamics simulation, elucidating their importance and the elements that lead to their appearance in lipid bilayers. Comprehending the mechanical characteristics of lipid bilayers is critical for creating medications, drug delivery systems, and biomaterials that interact with biological membranes because it allows one to understand how these materials respond to different stresses and deformations. The influence of mechanical characteristics on important lipid bilayer properties is examined in this review. The mechanical properties of lipid bilayers were clarified through the use of molecular dynamics simulation analysis techniques, including bilayer thickness, stress-strain analysis, lipid bilayer area compressibility, membrane bending rigidity, and time- or ensemble-averaged the area per lipid evaluation. We explain the significance of molecular dynamics simulation analysis methods, providing important new information about the stability and dynamic behavior of the bilayer. In the end, we hope to use molecular dynamics simulation to provide a comprehensive understanding of the mechanical properties and behavior of lipid bilayers, laying the groundwork for further studies and applications. Taken together, careful investigation of these mechanical aspects deepens our understanding of the adaptive capacities and functional roles of lipid bilayers in biological environments.
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Affiliation(s)
- Parvin Jalali
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Amin Nowroozi
- Pharmaceutical Sciences Research Center, Health Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Sajad Moradi
- Nano Drug Delivery Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Mohsen Shahlaei
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran.
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2
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Hagan ML, Balayan V, McGee-Lawrence ME. Plasma membrane disruption (PMD) formation and repair in mechanosensitive tissues. Bone 2021; 149:115970. [PMID: 33892174 PMCID: PMC8217198 DOI: 10.1016/j.bone.2021.115970] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/26/2021] [Accepted: 04/17/2021] [Indexed: 01/04/2023]
Abstract
Mammalian cells employ an array of biological mechanisms to detect and respond to mechanical loading in their environment. One such mechanism is the formation of plasma membrane disruptions (PMD), which foster a molecular flux across cell membranes that promotes tissue adaptation. Repair of PMD through an orchestrated activity of molecular machinery is critical for cell survival, and the rate of PMD repair can affect downstream cellular signaling. PMD have been observed to influence the mechanical behavior of skin, alveolar, and gut epithelial cells, aortic endothelial cells, corneal keratocytes and epithelial cells, cardiac and skeletal muscle myocytes, neurons, and most recently, bone cells including osteoblasts, periodontal ligament cells, and osteocytes. PMD are therefore positioned to affect the physiological behavior of a wide range of vertebrate organ systems including skeletal and cardiac muscle, skin, eyes, the gastrointestinal tract, the vasculature, the respiratory system, and the skeleton. The purpose of this review is to describe the processes of PMD formation and repair across these mechanosensitive tissues, with a particular emphasis on comparing and contrasting repair mechanisms and downstream signaling to better understand the role of PMD in skeletal mechanobiology. The implications of PMD-related mechanisms for disease and potential therapeutic applications are also explored.
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Affiliation(s)
- Mackenzie L Hagan
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA
| | - Vanshika Balayan
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA
| | - Meghan E McGee-Lawrence
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA; Department of Orthopaedic Surgery, Augusta University, Augusta, GA, USA.
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3
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Grazioli S, Dunn-Siegrist I, Pauchard LA, Blot M, Charles PE, Pugin J. Mitochondrial alarmins are tissue mediators of ventilator-induced lung injury and ARDS. PLoS One 2019; 14:e0225468. [PMID: 31756204 PMCID: PMC6874419 DOI: 10.1371/journal.pone.0225468] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Accepted: 11/05/2019] [Indexed: 12/14/2022] Open
Abstract
Rationale Endogenous tissue mediators inducing lung inflammation in the context of ventilator-induced lung injury (VILI) and acute respiratory distress syndrome (ARDS) are ill-defined. Objectives To test whether mitochondrial alarmins are released during VILI, and are associated with lung inflammation. Methods Release of mitochondrial DNA, adenosine triphosphate (ATP), and formyl-Met-Leu-Phe (fMLP) peptide-dependent neutrophil chemotaxis were measured in conditioned supernatants from human alveolar type II-like (A549) epithelial cells submitted to cyclic stretch in vitro. Similar measurements were performed in bronchoalveolar lavage fluids from rabbits submitted to an injurious ventilatory regimen, and from patients with ARDS. Measurements and main results Mitochondrial DNA was released by A549 cells during cell stretching, and was found elevated in BAL fluids from rabbits during VILI, and from ARDS patients. Cyclic stretch-induced interleukin-8 (IL-8) of A549 cells could be inhibited by Toll-like receptor 9 (TLR9) blockade. ATP concentrations were increased in conditioned supernatants from A549 cells, and in rabbit BAL fluids during VILI. Neutrophil chemotaxis induced by A549 cells conditioned supernatants was essentially dependent on fMLP rather than IL-8. A synergy between cyclic stretch-induced alarmins and lipopolysaccharide (LPS) was found in monocyte-derived macrophages in the production of IL-1ß. Conclusions Mitochondrial alarmins are released during cyclic stretch of human epithelial cells, as well as in BAL fluids from rabbits ventilated with an injurious ventilatory regimen, and found in BAL fluids from ARDS patients, particularly in those with high alveolar inflammation. These alarmins are likely to represent the proximal endogenous mediators of VILI and ARDS, released by injured pulmonary cells.
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Affiliation(s)
- Serge Grazioli
- Intensive Care Laboratory, Department of Microbiology and Molecular Medicine, University Hospitals of Geneva & Faculty of Medicine, Genève, Switzerland
- Department of Pediatrics, Division of Neonatal and Pediatric Intensive Care, University Hospital of Geneva, Genève, Switzerland
- * E-mail:
| | - Irène Dunn-Siegrist
- Intensive Care Laboratory, Department of Microbiology and Molecular Medicine, University Hospitals of Geneva & Faculty of Medicine, Genève, Switzerland
| | - Laure-Anne Pauchard
- Intensive Care Unit, University Hospital of Dijon, Dijon, France
- U.M.R. 1231, I.N.S.E.R.M, Burgundy University, Dijon, France
| | - Mathieu Blot
- Department of Infectious Diseases, University Hospital of Dijon, Dijon, France
| | - Pierre-Emmanuel Charles
- Intensive Care Unit, University Hospital of Dijon, Dijon, France
- U.M.R. 1231, I.N.S.E.R.M, Burgundy University, Dijon, France
| | - Jérôme Pugin
- Intensive Care Laboratory, Department of Microbiology and Molecular Medicine, University Hospitals of Geneva & Faculty of Medicine, Genève, Switzerland
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4
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Ayee MAA, LeMaster E, Teng T, Lee J, Levitan I. Hypotonic Challenge of Endothelial Cells Increases Membrane Stiffness with No Effect on Tether Force. Biophys J 2019; 114:929-938. [PMID: 29490252 DOI: 10.1016/j.bpj.2017.12.032] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 12/20/2017] [Accepted: 12/27/2017] [Indexed: 01/13/2023] Open
Abstract
Regulation of cell volume is a fundamental property of all mammalian cells. Multiple signaling pathways are known to be activated by cell swelling and to contribute to cell volume homeostasis. Although cell mechanics and membrane tension have been proposed to couple cell swelling to signaling pathways, the impact of swelling on cellular biomechanics and membrane tension have yet to be fully elucidated. In this study, we use atomic force microscopy under isotonic and hypotonic conditions to measure mechanical properties of endothelial membranes including membrane stiffness, which reflects the stiffness of the submembrane cytoskeleton complex, and the force required for membrane tether formation, reflecting membrane tension and membrane-cytoskeleton attachment. We find that hypotonic swelling results in significant stiffening of the endothelial membrane without a change in membrane tension/membrane-cytoskeleton attachment. Furthermore, depolymerization of F-actin, which, as expected, results in a dramatic decrease in the cellular elastic modulus of both the membrane and the deeper cytoskeleton, indicating a collapse of the cytoskeleton scaffold, does not abrogate swelling-induced stiffening of the membrane. Instead, this swelling-induced stiffening of the membrane is enhanced. We propose that the membrane stiffening should be attributed to an increase in hydrostatic pressure that results from an influx of solutes and water into the cells. Most importantly, our results suggest that increased hydrostatic pressure, rather than changes in membrane tension, could be responsible for activating volume-sensitive mechanisms in hypotonically swollen cells.
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Affiliation(s)
- Manuela Aseye Ayele Ayee
- Division of Pulmonary, Critical Care, Sleep, and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Elizabeth LeMaster
- Division of Pulmonary, Critical Care, Sleep, and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Tao Teng
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
| | - James Lee
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
| | - Irena Levitan
- Division of Pulmonary, Critical Care, Sleep, and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois.
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5
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Mori V, Smith BJ, Suki B, Bates JHT. Linking Physiological Biomarkers of Ventilator-Induced Lung Injury to a Rich-Get-Richer Mechanism of Injury Progression. Ann Biomed Eng 2018; 47:638-645. [PMID: 30421177 DOI: 10.1007/s10439-018-02165-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 11/01/2018] [Indexed: 01/11/2023]
Abstract
Mechanical ventilation is a crucial tool in the management of acute respiratory distress syndrome, yet it may itself also further damage the lung in a phenomenon known as ventilator-induced lung injury (VILI). We have previously shown in mice that volutrauma and atelectrauma act synergistically to cause VILI. We have also postulated that this synergy arises because of a rich-get-richer mechanism in which repetitive lung recruitment generates initial small holes in the blood-gas barrier which are then expanded by over-distension in a manner that favors large holes over small ones. In order to understand the causal link between this process and the derangements in lung mechanics associated with VILI, we developed a mathematical model that incorporates both atelectrauma and volutrauma to predict how the propensity of the lung to derecruit depends on the accumulation of plasma-derived fluid and proteins in the airspaces. We found that the model accurately predicts derecruitment in mice with experimentally induced VILI.
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Affiliation(s)
- Vitor Mori
- Department of Medicine, Vermont Lung Center, University of Vermont College of Medicine, 149 Beaumont Ave, HSRF 228, Burlington, VT, 05405, USA.,Department of Telecommunications and Control Engineering, University of Sao Paulo, Sao Paulo, Brazil
| | - Bradford J Smith
- Department of Bioengineering, University of Colorado Denver, Aurora, CO, 80045, USA
| | - Bela Suki
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | - Jason H T Bates
- Department of Medicine, Vermont Lung Center, University of Vermont College of Medicine, 149 Beaumont Ave, HSRF 228, Burlington, VT, 05405, USA.
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6
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Nagre N, Cong X, Ji HL, Schreiber JM, Fu H, Pepper I, Warren S, Sill JM, Hubmayr RD, Zhao X. Inhaled TRIM72 Protein Protects Ventilation Injury to the Lung through Injury-guided Cell Repair. Am J Respir Cell Mol Biol 2018; 59:635-647. [PMID: 29958015 PMCID: PMC6236686 DOI: 10.1165/rcmb.2017-0364oc] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 06/28/2018] [Indexed: 12/27/2022] Open
Abstract
Studies showed that TRIM72 is essential for repair of alveolar cell membrane disruptions, and exogenous recombinant human TRIM72 protein (rhT72) demonstrated tissue-mending properties in animal models of tissue injury. Here we examine the mechanisms of rhT72-mediated lung cell protection in vitro and test the efficacy of inhaled rhT72 in reducing tissue pathology in a mouse model of ventilator-induced lung injury. In vitro lung cell injury was induced by glass beads and stretching. Ventilator-induced lung injury was modeled by injurious ventilation at 30 ml/kg tidal volume. Affinity-purified rhT72 or control proteins were added into culture medium or applied through nebulization. Cellular uptake and in vivo distribution of rhT72 were detected by imaging and immunostaining. Exogenous rhT72 maintains membrane integrity of alveolar epithelial cells subjected to glass bead injury in a dose-dependent manner. Inhaled rhT72 decreases the number of fatally injured alveolar cells, and ameliorates tissue-damaging indicators and cell injury markers after injurious ventilation. Using in vitro stretching assays, we reveal that rhT72 improves both cellular resilience to membrane wounding and membrane repair after injury. Image analysis detected rhT72 uptake by rat alveolar epithelial cells, which can be inhibited by a cholesterol-disrupting agent. In addition, inhaled rhT72 distributes to the distal lungs, where it colocalizes with phosphatidylserine detection on nonpermeabilized lung slices to label wounded cells. In conclusion, our study showed that inhaled rhT72 accumulates in injured lungs and protects lung tissue from ventilator injury, the mechanisms of which include improving cell resilience to membrane wounding, localizing to injured membrane, and augmenting membrane repair.
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Affiliation(s)
- Nagaraja Nagre
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia
| | - Xiaofei Cong
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia
| | - Hong-Long Ji
- Texas Lung Injury Institute, the University of Texas Health Science Center at Tyler, Tyler, Texas
| | - John M. Schreiber
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia
| | - Hongyun Fu
- Division of Community Health and Research, Pediatrics Department and
| | - Ian Pepper
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia
| | - Seth Warren
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia
| | - Joshua M. Sill
- Division of Pulmonary and Critical Care, Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, Virginia; and
| | - Rolf D. Hubmayr
- Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota
| | - Xiaoli Zhao
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia
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7
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Self-induced mechanical stress can trigger biofilm formation in uropathogenic Escherichia coli. Nat Commun 2018; 9:4087. [PMID: 30291231 PMCID: PMC6173693 DOI: 10.1038/s41467-018-06552-z] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 09/06/2018] [Indexed: 11/08/2022] Open
Abstract
Bacterial biofilms represent an important medical problem; however, the mechanisms of the onset of biofilm formation are poorly understood. Here, using new controlled methods allowing high-throughput and reproducible biofilm growth, we show that biofilm formation is linked to self-imposed mechanical stress. In growing uropathogenic Escherichia coli colonies, we report that mechanical stress can initially emerge from the physical stress accompanying colony confinement within micro-cavities or hydrogel environments reminiscent of the cytosol of host cells. Biofilm formation can then be enhanced by a nutrient access-modulated feedback loop, in which biofilm matrix deposition can be particularly high in areas of increased mechanical and biological stress, with the deposited matrix further enhancing the stress levels. This feedback regulation can lead to adaptive and diverse biofilm formation guided by the environmental stresses. Our results suggest previously unappreciated mechanisms of the onset and progression of biofilm growth. Bacterial biofilms are an increasingly important medical problem but the mechanisms by which they develop remain largely unknown. Here, using a high-throughput approach, the authors show that biofilm formation is linked to self-imposed mechanical stress.
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8
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Boyd MA, Kamat NP. Visualizing Tension and Growth in Model Membranes Using Optical Dyes. Biophys J 2018; 115:1307-1315. [PMID: 30219285 DOI: 10.1016/j.bpj.2018.08.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 08/16/2018] [Accepted: 08/20/2018] [Indexed: 11/16/2022] Open
Abstract
Cells dynamically regulate their membrane surface area during a variety of processes critical to their survival. Recent studies with model membranes have pointed to a general mechanism for surface area regulation under tension in which cell membranes unfold or take up lipid to accommodate membrane strain. Yet we lack robust methods to simultaneously measure membrane tension and surface area changes in real time. Using lipid vesicles that contain two dyes isolated to spatially distinct parts of the membrane, we introduce, to our knowledge, a new method to monitor the processes of membrane stretching and lipid uptake in model membranes. Laurdan, located within the bilayer membrane, and Förster resonance energy transfer dyes, localized to the membrane exterior, act in concert to report changes in membrane tension and lipid uptake during osmotic stress. We use these dyes to show that membranes under tension take up lipid more quickly and in greater amounts compared to their nontensed counterparts. Finally, we show that this technique is compatible with microscopy, enabling real-time analysis of membrane dynamics on a single vesicle level. Ultimately, the combinatorial use of these probes offers a more complete picture of changing membrane morphology. Our optical method allows us to remotely track changes in membrane tension and surface area with model membranes, offering new opportunities to track morphological changes in artificial and biological membranes and providing new opportunities in fields ranging from mechanobiology to drug delivery.
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Affiliation(s)
- Margrethe A Boyd
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
| | - Neha P Kamat
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois; Center for Synthetic Biology, Northwestern University, Evanston, Illinois; Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois.
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9
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Ayee MA, Levitan I. Membrane Stiffening in Osmotic Swelling: Analysis of Membrane Tension and Elastic Modulus. CURRENT TOPICS IN MEMBRANES 2018; 81:97-123. [PMID: 30243442 PMCID: PMC6588289 DOI: 10.1016/bs.ctm.2018.07.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The effects of osmotic swelling on key cellular biomechanical properties are explored in this chapter. We present the governing equations and theoretical backgrounds of the models employed to estimate cell membrane tension and elastic moduli from experimental methods, and provide a summary of the prevailing experimental approaches used to obtain these biomechanical parameters. A detailed analysis of the current evidence of the effects of osmotic swelling on membrane tension and elastic moduli is provided. Briefly, due to the buffering effect of unfolding membrane reservoirs, mild hypotonic swelling does not change membrane tension or the adhesion of the membrane to the underlying cytoskeleton. Conversely, osmotic swelling causes the cell membrane envelope to stiffen, measured as an increase in the membrane elastic modulus.
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Affiliation(s)
| | - Irena Levitan
- University of Illinois at Chicago, Chicago, IL, United States
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10
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Higuita-Castro N, Nelson MT, Shukla V, Agudelo-Garcia PA, Zhang W, Duarte-Sanmiguel SM, Englert JA, Lannutti JJ, Hansford DJ, Ghadiali SN. Using a Novel Microfabricated Model of the Alveolar-Capillary Barrier to Investigate the Effect of Matrix Structure on Atelectrauma. Sci Rep 2017; 7:11623. [PMID: 28912466 PMCID: PMC5599538 DOI: 10.1038/s41598-017-12044-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 09/01/2017] [Indexed: 11/25/2022] Open
Abstract
The alveolar-capillary barrier is composed of epithelial and endothelial cells interacting across a fibrous extracelluar matrix (ECM). Although remodeling of the ECM occurs during several lung disorders, it is not known how fiber structure and mechanics influences cell injury during cyclic airway reopening as occurs during mechanical ventilation (atelectrauma). We have developed a novel in vitro platform that mimics the micro/nano-scale architecture of the alveolar microenvironment and have used this system to investigate how ECM microstructural properties influence epithelial cell injury during airway reopening. In addition to epithelial-endothelial interactions, our platform accounts for the fibrous topography of the basal membrane and allows for easy modulation of fiber size/diameter, density and stiffness. Results indicate that fiber stiffness and topography significantly influence epithelial/endothelial barrier function where increased fiber stiffness/density resulted in altered cytoskeletal structure, increased tight junction (TJ) formation and reduced barrier permeability. However, cells on rigid/dense fibers were also more susceptible to injury during airway reopening. These results indicate that changes in the mechanics and architecture of the lung microenvironment can significantly alter cell function and injury and demonstrate the importance of implementing in vitro models that more closely resemble the natural conditions of the lung microenvironment.
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Affiliation(s)
- N Higuita-Castro
- Biomedical Engineering Department, The Ohio State University, Columbus, Ohio, United States.,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States
| | - M T Nelson
- Biomedical Engineering Department, The Ohio State University, Columbus, Ohio, United States
| | - V Shukla
- Biomedical Engineering Department, The Ohio State University, Columbus, Ohio, United States.,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States
| | - P A Agudelo-Garcia
- Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio, United States
| | - W Zhang
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States
| | - S M Duarte-Sanmiguel
- Biomedical Engineering Department, The Ohio State University, Columbus, Ohio, United States.,Human Nutrition Program, The Ohio State University, Columbus, Ohio, United States
| | - J A Englert
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States
| | - J J Lannutti
- Department of Material Sciences and Engineering, The Ohio State University, Columbus, Ohio, United States
| | - D J Hansford
- Biomedical Engineering Department, The Ohio State University, Columbus, Ohio, United States
| | - S N Ghadiali
- Biomedical Engineering Department, The Ohio State University, Columbus, Ohio, United States. .,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States. .,Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States.
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11
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Elsaadany M, Yan KC, Yildirim-Ayan E. Predicting cell viability within tissue scaffolds under equiaxial strain: multi-scale finite element model of collagen-cardiomyocytes constructs. Biomech Model Mechanobiol 2017; 16:1049-1063. [PMID: 28093648 DOI: 10.1007/s10237-017-0872-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 01/03/2017] [Indexed: 12/11/2022]
Abstract
Successful tissue engineering and regenerative therapy necessitate having extensive knowledge about mechanical milieu in engineered tissues and the resident cells. In this study, we have merged two powerful analysis tools, namely finite element analysis and stochastic analysis, to understand the mechanical strain within the tissue scaffold and residing cells and to predict the cell viability upon applying mechanical strains. A continuum-based multi-length scale finite element model (FEM) was created to simulate the physiologically relevant equiaxial strain exposure on cell-embedded tissue scaffold and to calculate strain transferred to the tissue scaffold (macro-scale) and residing cells (micro-scale) upon various equiaxial strains. The data from FEM were used to predict cell viability under various equiaxial strain magnitudes using stochastic damage criterion analysis. The model validation was conducted through mechanically straining the cardiomyocyte-encapsulated collagen constructs using a custom-built mechanical loading platform (EQUicycler). FEM quantified the strain gradients over the radial and longitudinal direction of the scaffolds and the cells residing in different areas of interest. With the use of the experimental viability data, stochastic damage criterion, and the average cellular strains obtained from multi-length scale models, cellular viability was predicted and successfully validated. This methodology can provide a great tool to characterize the mechanical stimulation of bioreactors used in tissue engineering applications in providing quantification of mechanical strain and predicting cellular viability variations due to applied mechanical strain.
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Affiliation(s)
| | - Karen Chang Yan
- Department of Mechanical Engineering, The College of New Jersey, Ewing, NJ, USA
| | - Eda Yildirim-Ayan
- Department of Bioengineering, University of Toledo, Toledo, OH, USA.
- Department of Orthopaedic Surgery, University of Toledo Medical Center, Toledo, OH, USA.
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Abstract
Prevention of ventilator-induced lung injury (VILI) can attenuate multiorgan failure and improve survival in at-risk patients. Clinically significant VILI occurs from volutrauma, barotrauma, atelectrauma, biotrauma, and shear strain. Differences in regional mechanics are important in VILI pathogenesis. Several interventions are available to protect against VILI. However, most patients at risk of lung injury do not develop VILI. VILI occurs most readily in patients with concomitant physiologic insults. VILI prevention strategies must balance risk of lung injury with untoward side effects from the preventive effort, and may be most effective when targeted to subsets of patients at increased risk.
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13
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Abstract
Abstract
Background
The ventilator works mechanically on the lung parenchyma. The authors set out to obtain the proof of concept that ventilator-induced lung injury (VILI) depends on the mechanical power applied to the lung.
Methods
Mechanical power was defined as the function of transpulmonary pressure, tidal volume (TV), and respiratory rate. Three piglets were ventilated with a mechanical power known to be lethal (TV, 38 ml/kg; plateau pressure, 27 cm H2O; and respiratory rate, 15 breaths/min). Other groups (three piglets each) were ventilated with the same TV per kilogram and transpulmonary pressure but at the respiratory rates of 12, 9, 6, and 3 breaths/min. The authors identified a mechanical power threshold for VILI and did nine additional experiments at the respiratory rate of 35 breaths/min and mechanical power below (TV 11 ml/kg) and above (TV 22 ml/kg) the threshold.
Results
In the 15 experiments to detect the threshold for VILI, up to a mechanical power of approximately 12 J/min (respiratory rate, 9 breaths/min), the computed tomography scans showed mostly isolated densities, whereas at the mechanical power above approximately 12 J/min, all piglets developed whole-lung edema. In the nine confirmatory experiments, the five piglets ventilated above the power threshold developed VILI, but the four piglets ventilated below did not. By grouping all 24 piglets, the authors found a significant relationship between the mechanical power applied to the lung and the increase in lung weight (r2 = 0.41, P = 0.001) and lung elastance (r2 = 0.33, P < 0.01) and decrease in Pao2/Fio2 (r2 = 0.40, P < 0.001) at the end of the study.
Conclusion
In piglets, VILI develops if a mechanical power threshold is exceeded.
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14
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Tian Y, Gawlak G, O'Donnell JJ, Mambetsariev I, Birukova AA. Modulation of Endothelial Inflammation by Low and High Magnitude Cyclic Stretch. PLoS One 2016; 11:e0153387. [PMID: 27128976 PMCID: PMC4851399 DOI: 10.1371/journal.pone.0153387] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 03/29/2016] [Indexed: 11/29/2022] Open
Abstract
Excessive mechanical ventilation exerts pathologic mechanical strain on lung vascular endothelium and promotes endothelial cell (EC) inflammatory activation; however, the specific mechanisms underlying EC inflammatory response caused by mechanical ventilation related cyclic stretch (CS) remain unclear. This study investigated the effects of chronic exposure to CS at physiologic (5%) and pathologic (18%) magnitude on pulmonary EC inflammatory status in control conditions and bacterial lipopolysacharide (LPS)-stimulated conditions. EC exposure to high or low CS magnitudes for 28–72 hrs had distinct effects on EC inflammatory activation. 18% CS increased surface expression of endothelial adhesion molecule ICAM1 and release of its soluble form (sICAM1) and inflammatory cytokine IL-8 by CS-stimulated pulmonary endothelial cells (EC). EC inflammatory activation was not observed in EC exposed to 5% CS. Chronic exposure to 18% CS, but not to 5% CS, augmented ICAM1 and IL-8 production and EC monolayer barrier disruption induced by LPS. 18% CS, but not 5% CS, stimulated expression of RhoA GTPase-specific guanine nucleotide exchange factor GEF-H1. GEF-H1 knockdown using gene-specific siRNA abolished 18% CS-induced ICAM1 expression and sICAM1 and IL-8 release by EC. GEF-H1 knockdown also prevented disruption of EC monolayer integrity and attenuated sICAM1 and IL-8 release in the two-hit model of EC barrier dysfunction caused by combined stimulation with 18% CS and LPS. These data demonstrate that exacerbation of inflammatory response by pulmonary endothelium exposed to excessive mechanical stretch is mediated by CS-induced induction of Rho activating protein GEF-H1.
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Affiliation(s)
- Yufeng Tian
- Lung Injury Center, Section of Pulmonary and Critical Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637, United States of America
| | - Grzegorz Gawlak
- Lung Injury Center, Section of Pulmonary and Critical Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637, United States of America
| | - James J. O'Donnell
- Lung Injury Center, Section of Pulmonary and Critical Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637, United States of America
| | - Isa Mambetsariev
- Lung Injury Center, Section of Pulmonary and Critical Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637, United States of America
| | - Anna A. Birukova
- Lung Injury Center, Section of Pulmonary and Critical Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637, United States of America
- * E-mail:
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15
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Cressoni M, Chiumello D, Chiurazzi C, Brioni M, Algieri I, Gotti M, Nikolla K, Massari D, Cammaroto A, Colombo A, Cadringher P, Carlesso E, Benti R, Casati R, Zito F, Gattinoni L. Lung inhomogeneities, inflation and [18F]2-fluoro-2-deoxy-D-glucose uptake rate in acute respiratory distress syndrome. Eur Respir J 2015; 47:233-42. [DOI: 10.1183/13993003.00885-2015] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 08/05/2015] [Indexed: 01/17/2023]
Abstract
The aim of the study was to determine the size and location of homogeneous inflamed/noninflamed and inhomogeneous inflamed/noninflamed lung compartments and their association with acute respiratory distress syndrome (ARDS) severity.In total, 20 ARDS patients underwent 5 and 45 cmH2O computed tomography (CT) scans to measure lung recruitability. [18F]2-fluoro-2-deoxy-d-glucose ([18F]FDG) uptake and lung inhomogeneities were quantified with a positron emission tomography-CT scan at 10 cmH2O. We defined four compartments with normal/abnormal [18F]FDG uptake and lung homogeneity.The homogeneous compartment with normal [18F]FDG uptake was primarily composed of well-inflated tissue (80±16%), double-sized in nondependent lung (32±27% versus 16±17%, p<0.0001) and decreased in size from mild, moderate to severe ARDS (33±14%, 26±20% and 5±9% of the total lung volume, respectively, p=0.05). The homogeneous compartment with high [18F]FDG uptake was similarly distributed between the dependent and nondependent lung. The inhomogeneous compartment with normal [18F]FDG uptake represented 4% of the lung volume. The inhomogeneous compartment with high [18F]FDG uptake was preferentially located in the dependent lung (21±10% versus 12±10%, p<0.0001), mostly at the open/closed interfaces and related to recruitability (r2=0.53, p<0.001).The homogeneous lung compartment with normal inflation and [18F]FDG uptake decreases with ARDS severity, while the inhomogeneous poorly/not inflated compartment increases. Most of the lung inhomogeneities are inflamed. A minor fraction of healthy tissue remains in severe ARDS.
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16
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Abstract
Asthma is characterized by chronic inflammation, airway hyperresponsiveness, and progressive airway remodeling. The airway epithelium is known to play a critical role in the initiation and perpetuation of these processes. Here, we review how excessive epithelial stress generated by bronchoconstriction is sufficient to induce airway remodeling, even in the absence of inflammatory cells.
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Affiliation(s)
- Jin-Ah Park
- Harvard T. H. Chan School of Public Health, Boston, Massachussetts
| | | | - Jeffrey M Drazen
- Harvard T. H. Chan School of Public Health, Boston, Massachussetts
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17
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Camilo LM, Ávila MB, Cruz LFS, Ribeiro GCM, Spieth PM, Reske AA, Amato M, Giannella-Neto A, Zin WA, Carvalho AR. Positive end-expiratory pressure and variable ventilation in lung-healthy rats under general anesthesia. PLoS One 2014; 9:e110817. [PMID: 25383882 PMCID: PMC4226529 DOI: 10.1371/journal.pone.0110817] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 09/13/2014] [Indexed: 11/25/2022] Open
Abstract
Objectives Variable ventilation (VV) seems to improve respiratory function in acute lung injury and may be combined with positive end-expiratory pressure (PEEP) in order to protect the lungs even in healthy subjects. We hypothesized that VV in combination with moderate levels of PEEP reduce the deterioration of pulmonary function related to general anesthesia. Hence, we aimed at evaluating the alveolar stability and lung protection of the combination of VV at different PEEP levels. Design Randomized experimental study. Setting Animal research facility. Subjects Forty-nine male Wistar rats (200–270 g). Interventions Animals were ventilated during 2 hours with protective low tidal volume (VT) in volume control ventilation (VCV) or VV and PEEP adjusted at the level of minimum respiratory system elastance (Ers), obtained during a decremental PEEP trial subsequent to a recruitment maneuver, and 2 cmH2O above or below of this level. Measurements and Main Results Ers, gas exchange and hemodynamic variables were measured. Cytokines were determined in lung homogenate and plasma samples and left lung was used for histologic analysis and diffuse alveolar damage scoring. A progressive time-dependent increase in Ers was observed independent on ventilatory mode or PEEP level. Despite of that, the rate of increase of Ers and lung tissue IL-1 beta concentration were significantly lower in VV than in VCV at the level of the PEEP of minimum Ers. A significant increase in lung tissue cytokines (IL-6, IL-1 beta, CINC-1 and TNF-alpha) as well as a ventral to dorsal and cranial to caudal reduction in aeration was observed in all ventilated rats with no significant differences among groups. Conclusions VV combined with PEEP adjusted at the level of the PEEP of minimal Ers seemed to better prevent anesthesia-induced atelectasis and might improve lung protection throughout general anesthesia.
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Affiliation(s)
- Luciana M. Camilo
- Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Mariana B. Ávila
- Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Luis Felipe S. Cruz
- Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Gabriel C. M. Ribeiro
- Laboratory of Pulmonary Engineering, Biomedical Engineering Program, Alberto Luis Coimbra Institute of Post-Graduation and Research in Engineering, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Peter M. Spieth
- Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Medicine, Technische Universität Dresden, Germany
| | - Andreas A. Reske
- Department of Anesthesiology and Intensive Care Medicine, University of Leipzig, Leipzig, Germany
| | - Marcelo Amato
- Cardio-Pulmonary Department, Pulmonary Division, Hospital das Clínicas, Universidade de São Paulo, São Paulo, Brazil
| | - Antonio Giannella-Neto
- Laboratory of Pulmonary Engineering, Biomedical Engineering Program, Alberto Luis Coimbra Institute of Post-Graduation and Research in Engineering, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Walter A. Zin
- Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Alysson R. Carvalho
- Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Laboratory of Pulmonary Engineering, Biomedical Engineering Program, Alberto Luis Coimbra Institute of Post-Graduation and Research in Engineering, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- * E-mail:
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18
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Stress et strain : application au cours du syndrome de détresse respiratoire aiguë. MEDECINE INTENSIVE REANIMATION 2014. [DOI: 10.1007/s13546-014-0906-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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Mellander LJ, Kurczy ME, Najafinobar N, Dunevall J, Ewing AG, Cans AS. Two modes of exocytosis in an artificial cell. Sci Rep 2014; 4:3847. [PMID: 24457949 PMCID: PMC3900996 DOI: 10.1038/srep03847] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 12/31/2013] [Indexed: 01/24/2023] Open
Abstract
The details of exocytosis, the vital cell process of neuronal communication, are still under debate with two generally accepted scenarios. The first mode of release involves secretory vesicles distending into the cell membrane to release the complete vesicle contents. The second involves partial release of the vesicle content through an intermittent fusion pore, or an opened or partially distended fusion pore. Here we show that both full and partial release can be mimicked with a single large-scale cell model for exocytosis composed of material from blebbing cell plasma membrane. The apparent switching mechanism for determining the mode of release is demonstrated to be related to membrane tension that can be differentially induced during artificial exocytosis. These results suggest that the partial distension mode might correspond to an extended kiss-and-run mechanism of release from secretory cells, which has been proposed as a major pathway of exocytosis in neurons and neuroendocrine cells.
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Affiliation(s)
- Lisa J Mellander
- University of Gothenburg, Department of Chemistry and Molecular Biology, 412 96 Gothenburg, Sweden
| | - Michael E Kurczy
- Chalmers University of Technology, Department of Chemical and Biological Engineering, 412 96 Gothenburg, Sweden
| | - Neda Najafinobar
- Chalmers University of Technology, Department of Chemical and Biological Engineering, 412 96 Gothenburg, Sweden
| | - Johan Dunevall
- Chalmers University of Technology, Department of Chemical and Biological Engineering, 412 96 Gothenburg, Sweden
| | - Andrew G Ewing
- 1] University of Gothenburg, Department of Chemistry and Molecular Biology, 412 96 Gothenburg, Sweden [2] Chalmers University of Technology, Department of Chemical and Biological Engineering, 412 96 Gothenburg, Sweden
| | - Ann-Sofie Cans
- Chalmers University of Technology, Department of Chemical and Biological Engineering, 412 96 Gothenburg, Sweden
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20
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Haase K, Pelling AE. Resiliency of the plasma membrane and actin cortex to large-scale deformation. Cytoskeleton (Hoboken) 2013; 70:494-514. [PMID: 23929821 DOI: 10.1002/cm.21129] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 07/23/2013] [Accepted: 07/29/2013] [Indexed: 01/05/2023]
Abstract
The tight coupling between the plasma membrane and actin cortex allows cells to rapidly change shape in response to mechanical cues and during physiological processes. Mechanical properties of the membrane are critical for organizing the actin cortex, which ultimately governs the conversion of mechanical information into signaling. The cortex has been shown to rapidly remodel on timescales of seconds to minutes, facilitating localized deformations and bundling dynamics that arise during the exertion of mechanical forces and cellular deformations. Here, we directly visualized and quantified the time-dependent deformation and recovery of the membrane and actin cortex of HeLa cells in response to externally applied loads both on- and off-nucleus using simultaneous confocal and atomic force microscopy. The local creep-like deformation of the membrane and actin cortex depends on both load magnitude and duration and does not appear to depend on cell confluency. The membrane and actin cortex rapidly recover their initial shape after prolonged loading (up to 10 min) with large forces (up to 20 nN) and high aspect ratio deformations. Cytoplasmic regions surrounding the nucleus are shown to be more resistant to long-term creep than nuclear regions. These dynamics are highly regulated by actomyosin contractility and an intact actin cytoskeleton. Results suggest that in response to local deformations, the nucleus does not appear to provide significant resistance or play a major role in cell shape recovery. The membrane and actin cortex clearly possess remarkable mechanical stability, critical for the transduction of mechanical deformation into long term biochemical signals and cellular remodeling.
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Affiliation(s)
- Kristina Haase
- Department of Physics, University of Ottawa, MacDonald Hall, 150 Louis Pasteur, Ottawa, Ontario, Canada
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21
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Jabaraj DJ, Jaafar MS. Vibration Analysis of Circular Membrane Model of Alveolar Wall in Examining Ultrasound-induced Lung Hemorrhage. J Med Ultrasound 2013. [DOI: 10.1016/j.jmu.2013.04.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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22
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Dipaolo BC, Davidovich N, Kazanietz MG, Margulies SS. Rac1 pathway mediates stretch response in pulmonary alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2013; 305:L141-53. [PMID: 23686855 DOI: 10.1152/ajplung.00298.2012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alveolar epithelial cells (AECs) maintain the pulmonary blood-gas barrier integrity with gasketlike intercellular tight junctions (TJ) that are anchored internally to the actin cytoskeleton. We have previously shown that AEC monolayers stretched cyclically and equibiaxially undergo rapid magnitude- and frequency-dependent actin cytoskeletal remodeling to form perijunctional actin rings (PJARs). In this work, we show that even 10 min of stretch induced increases in the phosphorylation of Akt and LIM kinase (LIMK) and decreases in cofilin phosphorylation, suggesting that the Rac1/Akt pathway is involved in these stretch-mediated changes. We confirmed that Rac1 inhibitors wortmannin or EHT-1864 decrease stretch-stimulated Akt and LIMK phosphorylation and that Rac1 agonists PIP3 or PDGF increase phosphorylation of these proteins in unstretched cells. We also confirmed that Rac1 pathway inhibition during stretch modulated stretch-induced changes in occludin content and monolayer permeability, actin remodeling and PJAR formation, and cell death. As further validation, overexpression of Rac GTPase-activating protein β2-chimerin also preserved monolayer barrier properties in stretched monolayers. In summary, our data suggest that constitutive activity of Rac1, which is necessary for stretch-induced activation of the Rac1 downstream proteins, mediates stretch-induced increases in permeability and PJAR formation.
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Affiliation(s)
- Brian C Dipaolo
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
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23
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Liu D, Wang L, Wang Z, Cuschieri A. Magnetoporation and magnetolysis of cancer cells via carbon nanotubes induced by rotating magnetic fields. NANO LETTERS 2012; 12:5117-5121. [PMID: 22950948 DOI: 10.1021/nl301928z] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Weak magnetic fields (40 and 75 mT) were used either to enhance cell membrane poration (magnetoporation) or to ablate cultured human tumor cells (magnetolysis) by polymer-coated multiwalled carbon nanotubes, which form rotating bundles on exposure to magnetic fields. Findings of this study have potential clinical applications including enhanced tumor cell poration for targeted cancer chemotherapy and mechanical ablation of tumors.
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Affiliation(s)
- Dun Liu
- Institute for Medical Science and Technology, University of Dundee, Dundee Medipark, Dundee, United Kingdom
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24
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García-Delgado M, Navarrete-Sánchez I, Chamorro-Marín V, Díaz-Monrové JC, Esquivias J, Fernández-Mondéjar E. Alveolar overdistension as a cause of lung injury: differences among three animal species. ScientificWorldJournal 2012; 2012:985923. [PMID: 22645503 PMCID: PMC3356768 DOI: 10.1100/2012/985923] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 12/21/2011] [Indexed: 11/17/2022] Open
Abstract
This study analyses characteristics of lung injuries produced by alveolar overdistension in three animal species. Mechanical ventilation at normal tidal volume (10 mL/Kg) and high tidal volume (50 mL/Kg) was applied for 30 min in each species. Data were gathered on wet/dry weight ratio, histological score, and area of alveolar collapse. Five out of six rabbits with high tidal volume developed tension pneumothorax, and the rabbit results were therefore not included in the histological analysis. Lungs from the pigs and rats showed minimal histological lesions. Pigs ventilated with high tidal volume had significantly greater oedema, higher neutrophil infiltration, and higher percentage area of alveolar collapse than rats ventilated with high tidal volume. We conclude that rabbits are not an appropriate species for in vivo studies of alveolar overdistension due to their fragility. Although some histological lesions are observed in pigs and rats, the lesions do not appear to be relevant.
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Affiliation(s)
- Manuel García-Delgado
- Intensive Care Unit, Hospital Universitario Virgen de las Nieves, 18014 Granada, Spain.
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25
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Plasma membrane disruptions with different modes of injurious mechanical ventilation in normal rat lungs*. Crit Care Med 2012; 40:869-75. [PMID: 22001586 DOI: 10.1097/ccm.0b013e318232da2b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
OBJECTIVES Plasma membrane disruptions are caused by excessive mechanical stress and thought to be involved in inflammatory mediator upregulation. Presently, plasma membrane disruption formation has been studied only during mechanical ventilation with large tidal volumes and limitedly to subpleural alveoli. No information is available concerning the distribution of plasma membrane disruptions within the lung or the development of plasma membrane disruptions during another modality of injurious mechanical ventilation, i.e., mechanical ventilation with eupneic tidal volume (7 mL · kg) at low end-expiratory lung volume. The aim of this study is to assess whether 1) mechanical ventilation with eupneic tidal volume at low end-expiratory lung volume causes plasma membrane disruptions; and 2) the distribution of plasma membrane disruptions differs from that of mechanical ventilation with large tidal volume at normal end-expiratory lung volume. DESIGN Experimental animal model. SUBJECTS Sprague-Dawley rats. INTERVENTIONS Plasma membrane disruptions have been detected as red spots in gelatin-included slices of rat lungs stained with ethidium homodimer-1 shortly after anesthesia (control) after prolonged mechanical ventilation with eupneic tidal volume at low end-expiratory lung volume followed or not by the restoration of physiological end-expiratory lung volume and after prolonged mechanical ventilation with large tidal volumes and normal end-expiratory lung volume. MEASUREMENTS AND MAIN RESULTS Plasma membrane disruptions increased during mechanical ventilation at low end-expiratory lung volume, mainly at the bronchiolar level. Resealing of most plasma membrane disruptions occurred on restoration of normal end-expiratory lung volume. Mechanical ventilation with large tidal volume caused the appearance of plasma membrane disruptions, both bronchiolar and parenchymal, the latter to a much greater extent than with mechanical ventilation at low end-expiratory lung volume. The increase of plasma membrane disruptions correlated with the concomitant increase of airway resistance with both modes of mechanical ventilation. CONCLUSIONS : Amount and distribution of plasma membrane disruptions between small airways and lung parenchyma depends on the type of injurious mechanical ventilation. This could be relevant to the release of inflammatory mediators.
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26
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Zhou EH, Xu F, Quek ST, Lim CT. A power-law rheology-based finite element model for single cell deformation. Biomech Model Mechanobiol 2012; 11:1075-84. [PMID: 22307682 DOI: 10.1007/s10237-012-0374-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 01/14/2012] [Indexed: 10/14/2022]
Abstract
Physical forces can elicit complex time- and space-dependent deformations in living cells. These deformations at the subcellular level are difficult to measure but can be estimated using computational approaches such as finite element (FE) simulation. Existing FE models predominantly treat cells as spring-dashpot viscoelastic materials, while broad experimental data are now lending support to the power-law rheology (PLR) model. Here, we developed a large deformation FE model that incorporated PLR and experimentally verified this model by performing micropipette aspiration on fibroblasts under various mechanical loadings. With a single set of rheological properties, this model recapitulated the diverse micropipette aspiration data obtained using three protocols and with a range of micropipette sizes. More intriguingly, our analysis revealed that decreased pipette size leads to increased pressure gradient, potentially explaining our previous counterintuitive finding that decreased pipette size leads to increased incidence of cell blebbing and injury. Taken together, our work leads to more accurate rheological interpretation of micropipette aspiration experiments than previous models and suggests pressure gradient as a potential determinant of cell injury.
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Affiliation(s)
- E H Zhou
- Program in Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard School of Public Health, Boston, MA 02115, USA.
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27
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Induction of cellular antioxidant defense by amifostine improves ventilator-induced lung injury. Crit Care Med 2012; 39:2711-21. [PMID: 21765345 DOI: 10.1097/ccm.0b013e3182284a5f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVES To test the hypothesis that preconditioning animals with amifostine improves ventilator-induced lung injury via induction of antioxidant defense enzymes. Mechanical ventilation at high tidal volume induces reactive oxygen species production and oxidative stress in the lung, which plays a major role in the pathogenesis of ventilator-induced lung injury. Amifostine attenuates oxidative stress and improves lipopolysaccharide-induced lung injury by acting as a direct scavenger of reactive oxygen and nitrogen species. This study tested effects of chronic amifostine administration on parameters of oxidative stress, lung barrier function, and inflammation associated with ventilator-induced lung injury. DESIGN Randomized and controlled laboratory investigation in mice and cell culture. SETTING University laboratory. SUBJECTS C57BL/6J mice. INTERVENTIONS Mice received once-daily dosing with amifostine (10-100 mg/kg, intraperitoneal injection) 3 days consecutively before high tidal volume ventilation (30 mL/kg, 4 hrs) at day 4. Pulmonary endothelial cell cultures were exposed to pathologic cyclic stretching (18% equibiaxial stretch) and thrombin in a previously verified two-hit model of in vitro ventilator-induced lung injury. MEASUREMENTS AND MAIN RESULTS Three-day amifostine preconditioning before high tidal volume attenuated high tidal volume-induced protein and cell accumulation in the alveolar space judged by bronchoalveolar lavage fluid analysis, decreased Evans Blue dye extravasation into the lung parenchyma, decreased biochemical parameters of high tidal volume-induced tissue oxidative stress, and inhibited high tidal volume-induced activation of redox-sensitive stress kinases and nuclear factor-kappa B inflammatory cascade. These protective effects of amifostine were associated with increased superoxide dismutase 2 expression and increased superoxide dismutase and catalase enzymatic activities in the animal and endothelial cell culture models of ventilator-induced lung injury. CONCLUSIONS Amifostine preconditioning activates lung tissue antioxidant cell defense mechanisms and may be a promising strategy for alleviation of ventilator-induced lung injury in critically ill patients subjected to extended mechanical ventilation.
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28
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Waters CM, Roan E, Navajas D. Mechanobiology in lung epithelial cells: measurements, perturbations, and responses. Compr Physiol 2012; 2:1-29. [PMID: 23728969 PMCID: PMC4457445 DOI: 10.1002/cphy.c100090] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Epithelial cells of the lung are located at the interface between the environment and the organism and serve many important functions including barrier protection, fluid balance, clearance of particulate, initiation of immune responses, mucus and surfactant production, and repair following injury. Because of the complex structure of the lung and its cyclic deformation during the respiratory cycle, epithelial cells are exposed to continuously varying levels of mechanical stresses. While normal lung function is maintained under these conditions, changes in mechanical stresses can have profound effects on the function of epithelial cells and therefore the function of the organ. In this review, we will describe the types of stresses and strains in the lungs, how these are transmitted, and how these may vary in human disease or animal models. Many approaches have been developed to better understand how cells sense and respond to mechanical stresses, and we will discuss these approaches and how they have been used to study lung epithelial cells in culture. Understanding how cells sense and respond to changes in mechanical stresses will contribute to our understanding of the role of lung epithelial cells during normal function and development and how their function may change in diseases such as acute lung injury, asthma, emphysema, and fibrosis.
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29
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Moosavi Nejad S, Hosseini SHR, Akiyama H, Tachibana K. Optical observation of cell sonoporation with low intensity ultrasound. Biochem Biophys Res Commun 2011; 413:218-23. [PMID: 21875577 DOI: 10.1016/j.bbrc.2011.08.072] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 08/13/2011] [Indexed: 11/18/2022]
Abstract
Sonoporation is a promising drug delivery technique with great potential in medicine. However, its applications have been limited mostly by the lack of understanding its underlying biophysical mechanism, partly due to the inadequacy of the existing models for coupling with highly sensitive imaging techniques to directly observe the actual precursor events of cell-microbubble interaction under low intensity ultrasound. Here, we introduce a new in vitro method utilizing capillary-microgripping system and micro-transducer to achieve maximum level of experimental flexibility for capturing real time highly magnified images of cell-microbubble interaction, hitherto unseen in this context. Insonation of isolated single cells and microbubbles parallel with high speed microphotography and fluorescence microscopy allowed us to identify dynamic responses of cell-membrane/microbubble in correlation with sonoporation. Our results showed that bubble motion and linear oscillation in close contact with the cell membrane can cause local deformation and transient porosity in the cell membrane without rupturing it. This method can also be used as an in situ gene/drug delivery system of targeted cells for non-invasive clinical applications.
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Affiliation(s)
- Seyedeh Moosavi Nejad
- Department of Anatomy, Fukuoka University School of Medicine, 7-45-1 Nanakuma, Jonan, Fukuoka 814-0180, Japan.
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30
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Site-specific sonoporation of human melanoma cells at the cellular level using high lateral-resolution ultrasonic micro-transducer arrays. Biosens Bioelectron 2011; 27:25-33. [PMID: 21783355 DOI: 10.1016/j.bios.2011.05.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 05/09/2011] [Accepted: 05/12/2011] [Indexed: 11/23/2022]
Abstract
We developed a new instrumental method by which human melanoma cells (LU1205) are sonoporated via radiation pressures exerted by highly-confined ultrasonic waves produced by high lateral-resolution ultrasonic micro-transducer arrays (UMTAs). The method enables cellular-level site-specific sonoporation within the cell monolayer due to UMTAs and can be applicable in the delivery of drugs and gene products in cellular assays. In this method, cells are seeded on the biochip that employs UMTAs for high spatial resolution and specificity. UMTAs are driven by 30-MHz sinusoidal signals and the resulting radiation pressures induce sonoporation in the targeted cells. The sonoporation degree and the effective lateral resolution of UMTAs are determined by performing fluorescent microscopy and analysis of carboxylic-acid-derivatized CdSe/ZnS quantum dots passively transported into the cells. Models representing the transducer-generated ultrasound radiation pressure, the ultrasound-inflicted cell membrane wound, and the transmembrane transport through the wound are developed to determine the ultrasound-pressure-dependent wound size and enhanced cellular uptake of nanoparticles. Model-based calculations show that the effective wound size and cellular uptake of nanoparticles increase linearly with increasing ultrasound pressure (i.e., at applied radiation pressures of 0.21, 0.29, and 0.40 MPa, the ultrasound-induced initial effective wound radii are 150, 460, and 650 nm, respectively, and the post-sonoporation intracellular quantum-dot concentrations are 7.8, 22.8, and 29.9 nM, respectively) and the threshold pressure required to induce sonoporation in LU1205 cells is ∼0.12 MPa.
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31
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Li N, Li Q, Zhou XD, Kolosov VP, Perelman JM. Chronic mechanical stress induces mucin 5AC expression in human bronchial epithelial cells through ERK dependent pathways. Mol Biol Rep 2011; 39:1019-28. [PMID: 21556755 DOI: 10.1007/s11033-011-0827-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 05/03/2011] [Indexed: 11/24/2022]
Abstract
Mucus hypersecretion is a common pathological change in chronic inflammatory diseases of the airway. These conditions are usually accompanied by chronic mechanical stress due to airway constriction. Our objective was to study the molecular mechanisms and physical effects of chronic mechanical stress on mucin 5AC (MUC5AC) expression in airway epithelial cells. We exposed normal human bronchial epithelial (NHBE) cells cultured at an air-liquid interface to different degrees of chronic compressive mechanical stress (10, 20, 30 cmH(2)O) for 7 days(1 h per day). MUC5AC protein content was detected by enzyme-linked immunosorbent assay (ELISA). MUC5AC mRNA expression was detected by reverse transcription PCR (RT-PCR) and real-time PCR. The effects of chronic mechanical stress on phosphorylated ERK1/2 (p-ERK1/2), phosphorylated JNK (p-JNK), phosphorylated P38 (p-P38), and phosphorylation of FAK at Tyr397 (p-FAK-Y397), were assessed by Western blot. We also assessed the impact of, an EGFR kinase inhibitor (AG1478), an ERK kinase inhibitor (PD-98059), and short interfering RNA (siRNA) targeted to FAK. We found that transcriptional and protein expression levels of MUC5AC were elevated significantly in the 30 cmH(2)O compressive stress group. p-ERK1/2 increased significantly in response to compressive stress and PD-98059 could attenuated stress-induced MUC5AC expression. p-FAK-Y397 increased significantly in response to compressive stress and FAK siRNA attenuated stress-induced ERK activation strongly. AG1478 attenuated stress-induced ERK activation and MUC5AC expression significantly, but incompletely. Combination of FAK siRNA and AG1478 led to complete attenuation of ERK activation and MUC5AC expression. These results suggest that chronic mechanical stress can enhance MUC5AC expression in human bronchial epithelial cells through the ERK signal transduction pathway. Both FAK and EGFR mediate the mitogenic response induced by mechanical stress in human bronchial epithelial cells through an ERK signaling cascade.
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Affiliation(s)
- Na Li
- Division of Respiratory Medicine, Second Affiliated Hospital, Chongqing Medical University, No.74, Linjiang Road, Chongqing 400010, China
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Perchiazzi G, Rylander C, Vena A, Derosa S, Polieri D, Fiore T, Giuliani R, Hedenstierna G. Lung regional stress and strain as a function of posture and ventilatory mode. J Appl Physiol (1985) 2011; 110:1374-83. [DOI: 10.1152/japplphysiol.00439.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During positive-pressure ventilation parenchymal deformation can be assessed as strain (volume increase above functional residual capacity) in response to stress (transpulmonary pressure). The aim of this study was to explore the relationship between stress and strain on the regional level using computed tomography in anesthetized healthy pigs in two postures and two patterns of breathing. Airway opening and esophageal pressures were used to calculate stress; change of gas content as assessed from computed tomography was used to calculate strain. Static stress-strain curves and dynamic strain-time curves were constructed, the latter during the inspiratory phase of volume and pressure-controlled ventilation, both in supine and prone position. The lung was divided into nondependent, intermediate, dependent, and central regions: their curves were modeled by exponential regression and examined for statistically significant differences. In all the examined regions, there were strong but different exponential relations between stress and strain. During mechanical ventilation, the end-inspiratory strain was higher in the dependent than in the nondependent regions. No differences between volume- and pressure-controlled ventilation were found. However, during volume control ventilation, prone positioning decreased the end-inspiratory strain of dependent regions and increased it in nondependent regions, resulting in reduced strain gradient. Strain is inhomogeneously distributed within the healthy lung. Prone positioning attenuates differences between dependent and nondependent regions. The regional effects of ventilatory mode and body positioning should be further explored in patients with acute lung injury.
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Affiliation(s)
- Gaetano Perchiazzi
- Emergency and Organ Transplant, Bari University, Bari, Italy
- Medical Sciences–Clinical Physiology, Uppsala University, Uppsala, Sweden
| | - Christian Rylander
- Anaesthesia and Intensive Care Medicine, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Antonio Vena
- Intensive Care Unit, SS Annunziata Hospital, Taranto, Italy; and
| | - Savino Derosa
- Emergency and Organ Transplant, Bari University, Bari, Italy
| | - Debora Polieri
- Emergency and Organ Transplant, Bari University, Bari, Italy
| | - Tommaso Fiore
- Emergency and Organ Transplant, Bari University, Bari, Italy
| | - Rocco Giuliani
- Emergency and Organ Transplant, Bari University, Bari, Italy
| | - Göran Hedenstierna
- Medical Sciences–Clinical Physiology, Uppsala University, Uppsala, Sweden
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Letsiou E, Kitsiouli E, Nakos G, Lekka ME. Mild stretch activates cPLA2 in alveolar type II epithelial cells independently through the MEK/ERK and PI3K pathways. Biochim Biophys Acta Mol Cell Biol Lipids 2010; 1811:370-6. [PMID: 21185392 DOI: 10.1016/j.bbalip.2010.12.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 12/15/2010] [Accepted: 12/16/2010] [Indexed: 10/18/2022]
Abstract
Alveolar epithelial type II cells (AT II) in which lung surfactant synthesis and secretion take place, are subjected to low magnitude stretch during normal breathing. The aim of the study was to explore the effect of mild stretch on phospholipase A(2) (PLA(2)) activation, an enzyme known to be involved in surfactant secretion. In A549 cells (a model of AT II cells), we showed, using a fluorometric assay, that stretch triggers an increase of total PLA(2) activity. Western blot experiments revealed that the cytosolic isoform cPLA(2) is rapidly phosphorylated under stretch, in addition to a modest increase in cPLA(2) mRNA levels. Treatment of A549 cells with selective inhibitors of the MEK/ERK pathway significantly attenuated the stretch-induced cPLA(2) phosphorylation. A strong interaction of cPLA(2) and pERK enzymes was demonstrated by immunoprecipitation. We also found that inhibition of PI3K pathway attenuated cPLA(2) activation after stretch, without affecting pERK levels. Our results suggest that low magnitude stretch can induce cPLA(2) phosphorylation through the MEK/ERK and PI3K-Akt pathways, independently.
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Affiliation(s)
- Eleftheria Letsiou
- Biochemistry Laboratory, Chemistry Department, University of Ioannina, 45110, Ioannina, Greece
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Surfactant properties differentially influence intravascular gas embolism mechanics. Ann Biomed Eng 2010; 38:3649-63. [PMID: 20625830 DOI: 10.1007/s10439-010-0120-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Accepted: 06/28/2010] [Indexed: 10/19/2022]
Abstract
Gas bubble motion in a blood vessel causes temporal and spatial gradients of shear stress at the cell surface lining the vessel wall as the bubble approaches the cell, moves over it and passes it by. Rapid reversals occur in the sign of the shear stress imparted to the cell surface during this motion. These may result in injury to the cell. The presence of a soluble surfactant in the bulk medium reduces the level of the shear stress gradients imparted to the cell surface as compared to an equivalent surfactant-free system and is an important therapeutic aid. This is particularly true for a very small vessel. In this study, we analyze various physical and chemical properties of any given soluble surfactant to ascertain the relative significance of the property of the surfactant on the reduction in the level of the shear stress gradients imparted to the cell surface in such a vessel. While adsorption, desorption, and maximum possible monolayer interface surfactant concentration significantly impact the shear stress levels, physical properties such as the bulk or surface diffusivity do not appear to have large effects. At a given diameter, surfactants with k(a)/(k(d)d>O(10)⁻⁵ and Γ(∞)/C(0)d>9.5 x 10⁻⁴ are noted to be preferable from the point of view of an increased gap size between the bubble and vessel wall, and a corresponding reduction in the shear stress level imparted to an endothelial cell. The shear stress characteristics of nearly occluding bubbles, in contrast with smaller sized bubbles under identical conditions, are most affected by the introduction of a surfactant in regard to shear stress levels. These observations could form a basis for choosing surfactants in treating gas embolism related illnesses.
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Brégeon F, Steinberg JG, Andreotti N, Sabatier JM, Delpierre S, Ravailhe S, Jammes Y. Substance P receptor blockade decreases stretch-induced lung cytokines and lung injury in rats. J Physiol 2010; 588:1309-19. [PMID: 20176632 DOI: 10.1113/jphysiol.2010.187658] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Overdistension of lung tissue during mechanical ventilation causes cytokine release, which may be facilitated by the autonomic nervous system. We used mechanical ventilation to cause lung injury in rats, and studied how cervical section of the vagus nerve, or substance P (SP) antagonism, affected the injury. The effects of 40 or 25 cmH(2)O high airway pressure injurious ventilation (HV(40) and HV(25)) were studied and compared with low airway pressure ventilation (LV) and spontaneous breathing (controls). Lung mechanics, lung weight, gas exchange, lung myeloperoxidase activity, lung concentrations of interleukin (IL)-1 beta and IL-6, and amounts of lung SP were measured. Control rats were intact, others were bivagotomized, and in some animals we administered the neurokinin-1 (NK-1) receptor blocking agent SR140333. We first determined the durations of HV(40) and HV(25) that induced the same levels of lung injury and increased lung contents of IL-1 beta and IL-6. They were 90 min and 120 min, respectively. Both HV(40) and HV(25) increased lung SP, IL-1 beta and IL-6 levels, these effects being markedly reduced by NK-1 receptor blockade. Bivagotomy reduced to a lesser extent the HV(40)- and HV(25)-induced increases in SP but significantly reduced cytokine production. Neither vagotomy nor NK-1 receptor blockade prevented HV(40)-induced lung injury but, in the HV(25) group, they made it possible to maintain lung injury indices close to those measured in the LV group. This study suggests that both neuronal and extra-neuronal SP might be involved in ventilator-induced lung inflammation and injury. NK-1 receptor blockade could be a pharmacological tool to minimize some adverse effects of mechanical ventilation.
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Affiliation(s)
- Fabienne Brégeon
- UMR MD2 P2COE, Institut Fédératif de Recherche Jean-Roche, Université de la Méditerranée Aix-Marseille II, Marseille, France.
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Swaminathan TN, Mukundakrishnan K, Ayyaswamy PS, Eckmann DM. Effect of a soluble surfactant on a finite sized bubble motion in a blood vessel. JOURNAL OF FLUID MECHANICS 2010; 642:509-539. [PMID: 20305744 PMCID: PMC2841450 DOI: 10.1017/s0022112009992692] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We present detailed results for the motion of a finite sized gas bubble in a blood vessel. The bubble (dispersed phase) size is taken to be such as to nearly occlude the vessel. The bulk medium is treated as a shear thinning Casson fluid and contains a soluble surfactant that adsorbs and desorbs from the interface. Three different vessel sizes, corresponding to a small artery, a large arteriole, and a small arteriole, in normal humans, are considered. The hematocrit (volume fraction of RBCs) has been taken to be 0.45. For arteriolar flow, where relevant, the Fahraeus-Lindqvist effect is taken into account. Bubble motion cause temporal and spatial gradients of shear stress at the cell surface lining the vessel wall as the bubble approaches the cell, moves over it and passes it by. Rapid reversals occur in the sign of the shear stress imparted to the cell surface during this motion. Shear stress gradients together with sign reversals are associated with a recirculation vortex at the rear of the moving bubble. The presence of the surfactant reduces the level of the shear stress gradients imparted to the cell surface as compared to an equivalent surfactant-free system. Our numerical results for bubble shapes and wall shear stresses may help explain phenomena observed in experimental studies related to gas embolism, a significant problem in cardiac surgery and decompression sickness.
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Affiliation(s)
- T. N. Swaminathan
- Department of Anesthesiology and Critical Care, University of Pennsylvania
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
| | - K. Mukundakrishnan
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
| | - P. S. Ayyaswamy
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
| | - D. M. Eckmann
- Department of Anesthesiology and Critical Care, University of Pennsylvania
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Abstract
Blood vessels respond to changes in mechanical load from circulating blood in the form of shear stress and mechanical strain as the result of heart propulsions by changes in intracellular signaling leading to changes in vascular tone, production of vasoactive molecules, and changes in vascular permeability, gene regulation, and vascular remodeling. In addition to hemodynamic forces, microvasculature in the lung is also exposed to stretch resulting from respiratory cycles during autonomous breathing or mechanical ventilation. Among various cell signaling pathways induced by mechanical forces and reported to date, a role of reactive oxygen species (ROS) produced by vascular cells receives increasing attention. ROS play an essential role in signal transduction and physiologic regulation of vascular function. However, in the settings of chronic hypertension, inflammation, or acute injury, ROS may trigger signaling events that further exacerbate smooth muscle hypercontractility and vascular remodeling associated with hypertension and endothelial barrier dysfunction associated with acute lung injury and pulmonary edema. These conditions are also characterized by altered patterns of mechanical stimulation experienced by vasculature. This review will discuss signaling pathways regulated by ROS and mechanical stretch in the pulmonary and systemic vasculature and will summarize functional interactions between cyclic stretch- and ROS-induced signaling in mechanochemical regulation of vascular structure and function.
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Affiliation(s)
- Konstantin G Birukov
- Section of Pulmonary and Critical Care, Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
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38
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Birukov KG. Small GTPases in mechanosensitive regulation of endothelial barrier. Microvasc Res 2008; 77:46-52. [PMID: 18938185 DOI: 10.1016/j.mvr.2008.09.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 09/08/2008] [Indexed: 12/31/2022]
Abstract
Alterations in vascular permeability are defining feature of diverse processes including atherosclerosis, inflammation, ischemia/reperfusion injury, and ventilator-induced lung injury. Clinical observations and experimental studies support an essential role of mechanical forces in pathophysiologic regulation of lung barrier. Accumulating data demonstrate that decreased levels of blood flow and increased cyclic stretch of lung tissues associated with lung mechanical ventilation at high tidal volumes increase vascular permeability, activate inflammatory cytokine production, alveolar flooding, leukocyte infiltration, and hypoxemia, and increase morbidity and mortality. Potential synergism between pathologic mechanical stimulation and inflammatory molecules resulting in vascular leak and lung injury becomes increasingly recognized. This review will discuss a role of Rho family of small GTPases in the mechanochemical regulation of pulmonary endothelial permeability associated with ventilator induced lung injury.
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Affiliation(s)
- Konstantin G Birukov
- Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA.
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Mukundakrishnan K, Ayyaswamy PS, Eckmann DM. Finite-sized gas bubble motion in a blood vessel: non-Newtonian effects. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:036303. [PMID: 18851139 PMCID: PMC2761631 DOI: 10.1103/physreve.78.036303] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 06/30/2008] [Indexed: 05/26/2023]
Abstract
We have numerically investigated the axisymmetric motion of a finite-sized nearly occluding air bubble through a shear-thinning Casson fluid flowing in blood vessels of circular cross section. The numerical solution entails solving a two-layer fluid model--a cell-free layer and a non-Newtonian core together with the gas bubble. This problem is of interest to the field of rheology and for gas embolism studies in health sciences. The numerical method is based on a modified front-tracking method. The viscosity expression in the Casson model for blood (bulk fluid) includes the hematocrit [the volume fraction of red blood cells (RBCs)] as an explicit parameter. Three different flow Reynolds numbers, Reapp=rholUmaxdmicroapp , in the neighborhood of 0.2, 2, and 200 are investigated. Here, rhol is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and microapp is the apparent viscosity of whole blood. Three different hematocrits have also been considered: 0.45, 0.4, and 0.335. The vessel sizes considered correspond to small arteries, and small and large arterioles in normal humans. The degree of bubble occlusion is characterized by the ratio of bubble to vessel radius (aspect ratio), lambda , in the range 0.9< or =lambda< or =1.05 . For arteriolar flow, where relevant, the Fahraeus-Lindqvist effects are taken into account. Both horizontal and vertical vessel geometries have been investigated. Many significant insights are revealed by our study: (i) bubble motion causes large temporal and spatial gradients of shear stress at the "endothelial cell" (EC) surface lining the blood vessel wall as the bubble approaches the cell, moves over it, and passes it by; (ii) rapid reversals occur in the sign of the shear stress (+ --> - --> +) imparted to the cell surface during bubble motion; (iii) large shear stress gradients together with sign reversals are ascribable to the development of a recirculation vortex at the rear of the bubble; (iv) computed magnitudes of shear stress gradients coupled with their sign reversals may correspond to levels that cause injury to the cell by membrane disruption through impulsive compression and stretching; and (v) for the vessel sizes and flow rates investigated, gravitational effects are negligible.
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Affiliation(s)
- Karthik Mukundakrishnan
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, USA
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Portonovo S. Ayyaswamy
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - David M. Eckmann
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, USA
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Birukova AA, Moldobaeva N, Xing J, Birukov KG. Magnitude-dependent effects of cyclic stretch on HGF- and VEGF-induced pulmonary endothelial remodeling and barrier regulation. Am J Physiol Lung Cell Mol Physiol 2008; 295:L612-23. [PMID: 18689603 DOI: 10.1152/ajplung.90236.2008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mechanical ventilation at high tidal volumes compromises the blood-gas barrier and increases lung vascular permeability, which may lead to ventilator-induced lung injury and pulmonary edema. Using pulmonary endothelial cell (ECs) exposed to physiologically [5% cyclic stretch (CS)] and pathologically (18% CS) relevant magnitudes of CS, we evaluated the potential protective effects of hepatocyte growth factor (HGF) on EC barrier dysfunction induced by CS and vascular endothelial growth factor (VEGF). In static culture, HGF enhanced EC barrier function in a Rac-dependent manner and attenuated VEGF-induced EC permeability and paracellular gap formation. The protective effects of HGF were associated with the suppression of Rho-dependent signaling triggered by VEGF. Five percent CS promoted HGF-induced enhancement of the cortical F-actin rim and activation of Rac-dependent signaling, suggesting synergistic barrier-protective effects of physiological CS and HGF. In contrast, 18% CS further enhanced VEGF-induced EC permeability, activation of Rho signaling, and formation of actin stress fibers and paracellular gaps. These effects were attenuated by HGF pretreatment. EC preconditioning at 5% CS before HGF and VEGF further promoted EC barrier maintenance. Our data suggest synergistic effects of HGF and physiological CS in the Rac-mediated mechanisms of EC barrier protection. In turn, HGF reduced the barrier-disruptive effects of VEGF and pathological CS via downregulation of the Rho pathway. These results support the importance of HGF-VEGF balance in control of acute lung injury/acute respiratory distress syndrome severity via small GTPase-dependent regulation of lung endothelial permeability.
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Affiliation(s)
- Anna A Birukova
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
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41
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Féréol S, Fodil R, Pelle G, Louis B, Isabey D. Cell mechanics of alveolar epithelial cells (AECs) and macrophages (AMs). Respir Physiol Neurobiol 2008; 163:3-16. [PMID: 18565804 DOI: 10.1016/j.resp.2008.04.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Revised: 04/22/2008] [Accepted: 04/29/2008] [Indexed: 01/16/2023]
Abstract
Cell mechanics provides an integrated view of many biological phenomena which are intimately related to cell structure and function. Because breathing constitutes a sustained motion synonymous with life, pulmonary cells are normally designed to support permanent cyclic stretch without breaking, while receiving mechanical cues from their environment. The authors study the mechanical responses of alveolar cells, namely epithelial cells and macrophages, exposed to well-controlled mechanical stress in order to understand pulmonary cell response and function. They discuss the principle, advantages and limits of a cytoskeleton-specific micromanipulation technique, magnetic bead twisting cytometry, potentially applicable in vivo. They also compare the pertinence of various models (e.g., rheological; power law) used to extract cell mechanical properties and discuss cell stress/strain hardening properties and cell dynamic response in relation to the structural tensegrity model. Overall, alveolar cells provide a pertinent model to study the biological processes governing cellular response to controlled stress or strain.
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Affiliation(s)
- Sophie Féréol
- Inserm, UMR 841, Biomécanique Cellulaire et Respiratoire, Créteil F-94010, France
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Lee HS, Wang Y, Maciejewski BS, Esho K, Fulton C, Sharma S, Sanchez-Esteban J. Interleukin-10 protects cultured fetal rat type II epithelial cells from injury induced by mechanical stretch. Am J Physiol Lung Cell Mol Physiol 2008; 294:L225-32. [DOI: 10.1152/ajplung.00370.2007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mechanical ventilation plays a central role in the pathogenesis of bronchopulmonary dysplasia. However, the mechanisms by which excessive stretch of fetal or neonatal type II epithelial cells contributes to lung injury are not well defined. In these investigations, isolated embryonic day 19 fetal rat type II epithelial cells were cultured on substrates coated with fibronectin and exposed to 5% or 20% cyclic stretch to simulate mechanical forces during lung development or lung injury, respectively. Twenty percent stretch of fetal type II epithelial cells increased necrosis, apoptosis, and proliferation compared with control, unstretched samples. By ELISA and real-time PCR (qRT-PCR), 20% stretch increased secretion of IL-8 into the media and IL-8 gene expression and inhibited IL-10 release. Interestingly, administration of recombinant IL-10 before 20% stretch did not affect cell lysis but significantly reduced apoptosis and IL-8 release compared with stretched samples without IL-10. Collectively, our studies suggest that IL-10 may play an important role in protection of fetal type II epithelial cells from injury secondary to stretch.
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Hammerschmidt S, Kuhn H, Gessner C, Seyfarth HJ, Wirtz H. Stretch-Induced Alveolar Type II Cell Apoptosis. Am J Respir Cell Mol Biol 2007; 37:699-705. [PMID: 17630321 DOI: 10.1165/rcmb.2006-0429oc] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Apoptosis of alveolar type II (ATII) cells in response to high-amplitude mechanical stretch represents an important mechanism of ventilation-induced lung injury. Previously, it was demonstrated in an in vitro model that stretch-induced ATII cell apoptosis was prevented by angiotensin-converting enzyme (ACE) inhibitors. This study investigates the mechanism by which ACE inhibitors prevent stretch-induced apoptosis and elucidates the role of bradykinin as an endogenous anti-apoptotic factor. Rat ATII cells cultured on flexible membranes were subjected to cyclic stretch (40 cycles/min; 30% increase in surface area) and compared with static controls. Angiotensinogen, the bradykinin precursor T-kininogen, and bradykinin receptor expression were measured by RT-PCR; Angiotensin II and phosphoinositol 3 OH-kinase (PI3K) activity (as phospho-Akt) were measured by enzyme-linked immunosorbent assay; and Bcl-2 and Bcl-X(L) were measured by Western blot. Stretch did not influence angiotensinogen expression or induce angiotensin II generation. The angiotensin II receptor antagonist saralasin did not prevent stretch-induced apoptosis, whereas ACE inhibitors did. Stretch reduced ATII cell bradykinin release (T-kininogen expression and bradykinin supernatant concentration), and subsequently led to reduced PI3K activity and decreased concentrations of the anti-apoptotic proteins Bcl-2/Bcl-X(L). Bradykinin substitution or addition of keratinocyte or hepatocyte growth factor prevented stretch-induced decrease in PI3K activity and Bcl-2/Bcl-X(L) and reduced stretch-induced apoptosis. Mechanical stretch impairs a constitutively expressed, autocrine anti-apoptotic ATII cell survival signal involving bradykinin-mediated stimulation of the PI3K-Akt-Bcl-2/Bcl-X(L) pathway. Restoration of this pathway prevents stretch-induced apoptosis. This may be beneficial when mechanical ventilation cannot completely avoid alveolar overdistension to maintain oxygenation.
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Jain M, Sznajder JI. Bench-to-bedside review: distal airways in acute respiratory distress syndrome. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2007; 11:206. [PMID: 17306039 PMCID: PMC2151900 DOI: 10.1186/cc5159] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Distal airways are less than 2 mm in diameter, comprising a relatively large cross-sectional area that allows for slower, laminar airflow. The airways include both membranous bronchioles and gas exchange ducts, and have been referred to in the past as the 'quiet zone', in part because these structures were felt to contribute little to lung mechanics and in part because they were difficult to study directly. More recent data suggest that distal airway dysfunction plays a significant role in acute respiratory distress syndrome. In addition, injurious mechanical ventilation strategies may contribute to distal airway dysfunction. The presence of elevated airway resistance, intrinsic positive end-expiratory pressure or a lower inflection point on a pressure–volume curve of the respiratory system may indicate the presence of impaired distal airway function. There are no proven specific treatments for distal airway dysfunction, and protective ventilation strategies to minimize distal airway injury may be the best therapeutic approach at this time.
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Affiliation(s)
- Manu Jain
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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46
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Mijailovich SM, Hamada K, Tsuda A. IL-8 Response of Cyclically Stretching Alveolar Epithelial Cells Exposed to Non-fibrous Particles. Ann Biomed Eng 2007; 35:582-94. [PMID: 17242997 DOI: 10.1007/s10439-006-9233-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Accepted: 11/13/2006] [Indexed: 10/23/2022]
Abstract
Using a cell stretcher device, we have previously shown that A549 cells exposed to asbestos fibers gave significantly increased cytokine responses (IL-8) when they were cyclically stretched [Tsuda, A., B. K. Stringer, S. M. Mijailovich, R. A. Rogers, K. Hamada, and M. L. Gray. Am. J. Respir. Cell Mol. Biol. 21(4):455-462, 1999]. In the present study, cell stretching experiments were performed using non-fibrous riebeckite particles, instead of fibrous particles. Riebeckite particles are ground asbestos fibers with the size of a few microns and non-fibrous shape, and are often used as "non-toxic" control particles in the studies of fibrous particle-induced pathogenesis. Although it is generally assumed that riebeckite particles do not elicit strong biological responses, in our studies in cyclically stretched cell cultures, the riebeckite particles coated with adhesion proteins induced significant IL-8 responses, but in static cell cultures the treatment with adhesion protein-coated riebeckite did not induce comparable cytokine responses. To interpret these data, we have developed a simple mathematical model of adhesive interactions between a cell layer and rigid fibrous/non-fibrous particles that were subjected to external tensile forces. The analysis showed that because of considerable dissimilarity in deformations (i.e., strain mismatch) between the cells and particles during breathing, the attachment of particles as small as 1 micro in size could induce significant mechanical forces on the cell surface receptors, which may trigger subsequent adverse cell response under dynamic stretching conditions.
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Affiliation(s)
- S M Mijailovich
- Physiology Program, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
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Fisher JL, Margulies SS. Modeling the effect of stretch and plasma membrane tension on Na+-K+-ATPase activity in alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2007; 292:L40-53. [PMID: 16891387 DOI: 10.1152/ajplung.00425.2005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
While a number of whole cell mechanical models have been proposed, few, if any, have focused on the relationship among plasma membrane tension, plasma membrane unfolding, and plasma membrane expansion and relaxation via lipid insertion. The goal of this communication is to develop such a model to better understand how plasma membrane tension, which we propose stimulates Na+-K+-ATPase activity but possibly also causes cell injury, may be generated in alveolar epithelial cells during mechanical ventilation. Assuming basic relationships between plasma membrane unfolding and tension and lipid insertion as the result of tension, we have captured plasma membrane mechanical responses observed in alveolar epithelial cells: fast deformation during fast cyclic stretch, slower, time-dependent deformation via lipid insertion during tonic stretch, and cell recovery after release from stretch. The model estimates plasma membrane tension and predicts Na+-K+-ATPase activation for a specified cell deformation time course. Model parameters were fit to plasma membrane tension, whole cell capacitance, and plasma membrane area data collected from the literature for osmotically swollen and shrunken cells. Predictions of membrane tension and stretch-stimulated Na+-K+-ATPase activity were validated with measurements from previous studies. As a proof of concept, we demonstrate experimentally that tonic stretch and consequent plasma membrane recruitment can be exploited to condition cells against subsequent cyclic stretch and hence mitigate stretch-induced responses, including stretch-induced cell death and stretch-induced modulation of Na+-K+-ATPase activity. Finally, the model was exercised to evaluate plasma membrane tension and potential Na+-K+-ATPase stimulation for an assortment of traditional and novel ventilation techniques.
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Affiliation(s)
- Jacob L Fisher
- Department of Bioengineering, University of Pennsylvania, 3320 Smith Walk, Philadelphia, PA 19104-6392, USA
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Budker VG, Subbotin VM, Budker T, Sebestyén MG, Zhang G, Wolff JA. Mechanism of plasmid delivery by hydrodynamic tail vein injection. II. Morphological studies. J Gene Med 2006; 8:874-88. [PMID: 16718734 DOI: 10.1002/jgm.920] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND The efficient delivery of plasmid DNA (pDNA) to hepatocytes by a hydrodynamic tail vein (HTV) procedure has greatly popularized the use of naked nucleic acids. The hydrodynamic process renders onto the tissue increased physical forces in terms of increased pressures and shear forces that could lead to transient or permanent membrane damage. It can also trigger a series of cellular events to seal or reorganize the stretched membrane. Our goal was to study the uptake mechanism by following the morphological changes in the liver and correlate these with the fate of the injected plasmid DNA. METHODS We utilized both light microscopic (LM) and electron microscopic (EM) techniques to determine the effect of the HTV procedure on hepatocytes and non-parenchymal cells at various times after injection. The LM studies used paraffin-embedded livers with hematoxylin and eosin (H&E) staining. The immune-EM studies used antibodies labeled with sub-nanometer gold particles followed by silver enhancement to identify the location of injected pDNA at the subcellular level. The level of overall damage to liver cells was estimated based on alanine aminotransferase (ALT) release and clearance. RESULTS Both the LM and EM results showed the appearance of large vesicles in hepatocytes as early as 5 min post-injection. The number of vesicles decreased by 20-60 min. Plasmid DNA molecules often appeared to be associated with or inside such vesicles. DNA could also be detected in the space of Disse, in the cytoplasm and in nuclei. Non-parenchymal cells also contained DNA, but HTV-induced vesicles could not be observed in them. CONCLUSIONS Our studies suggest an alternative or additional pathway for naked DNA into hepatocytes besides direct entry via membrane pores. It may be difficult to prove which of these pathways lead to gene expression, but the membrane pore hypothesis alone appears insufficient to explain why expression happens preferentially in hepatocytes. Further study is needed to delineate the importance of each of these putative pathways and their interrelationship in enabling oligonucleotide (siRNA) activity and pDNA expression.
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Affiliation(s)
- Vladimir G Budker
- Department of Pediatrics and Medical Genetics, Waisman Center, University of Wisconsin-Madison, 1500 Highland Ave., Madison, WI 53705, USA
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Birukova AA, Chatchavalvanich S, Rios A, Kawkitinarong K, Garcia JGN, Birukov KG. Differential regulation of pulmonary endothelial monolayer integrity by varying degrees of cyclic stretch. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 168:1749-61. [PMID: 16651639 PMCID: PMC1606576 DOI: 10.2353/ajpath.2006.050431] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Ventilator-induced lung injury is a life-threatening complication of mechanical ventilation at high-tidal volumes. Besides activation of proinflammatory cytokine production, excessive lung distension directly affects blood-gas barrier and lung vascular permeability. To investigate whether restoration of pulmonary endothelial cell (EC) monolayer integrity after agonist challenge is dependent on the magnitude of applied cyclic stretch (CS) and how these effects are linked to differential activation of small GTPases Rac and Rho, pulmonary ECs were subjected to physiologically (5% elongation) or pathologically (18% elongation) relevant levels of CS. Pathological CS enhanced thrombin-induced gap formation and delayed monolayer recovery, whereas physiological CS induced nearly complete EC recovery accompanied by peripheral redistribution of focal adhesions and cortactin after 50 minutes of thrombin. Consistent with differential effects on monolayer integrity, 18% CS enhanced thrombin-induced Rho activation, whereas 5% CS promoted Rac activation during the EC recovery phase. Rac inhibition dramatically attenuated restoration of monolayer integrity after thrombin challenge. Physiological CS preconditioning (5% CS, 24 hours) enhanced EC paracellular gap resolution after step-wise increase to 18% CS (30 minutes) and thrombin challenge. These results suggest a critical role for the CS amplitude and the balance between Rac and Rho in mechanochemical regulation of lung EC barrier.
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Affiliation(s)
- Anna A Birukova
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, Illinois 60637, USA
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Abstract
Patients with severe acute respiratory distress syndrome who die usually succumb to multiorgan failure as opposed to hypoxia. Despite appropriate resuscitation, some patients' symptoms persist on a downward spiral, apparently propagated by an uncontained systemic inflammatory response. This phenomenon is not well understood. However, a novel hypothesis to explain this observation proposes that it is related to the life-saving ventilatory support used to treat the respiratory failure. According to this hypothesis, mechanical ventilation per se, by altering both the magnitude and the pattern of lung stretch, can cause changes in gene expression and/or cellular metabolism that ultimately can lead to the development of an overwhelming inflammatory response-even in the absence of overt structural damage. This mechanism of injury has been termed biotrauma. In this review we explore the biotrauma hypothesis, the causal relationship between biophysical injury and organ failure, and its implications for the future therapy and management of critically ill patients.
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Affiliation(s)
- Claudia C dos Santos
- Department of Medicine, St. Michael's Hospital, Toronto, Ontario M5B 1W8, Canada.
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