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Rietdorf K, Bootman MD, Sanderson MJ. Spontaneous, pro-arrhythmic calcium signals disrupt electrical pacing in mouse pulmonary vein sleeve cells. PLoS One 2014; 9:e88649. [PMID: 24586364 PMCID: PMC3930634 DOI: 10.1371/journal.pone.0088649] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 01/08/2014] [Indexed: 11/18/2022] Open
Abstract
The pulmonary vein, which returns oxygenated blood to the left atrium, is ensheathed by a population of unique, myocyte-like cells called pulmonary vein sleeve cells (PVCs). These cells autonomously generate action potentials that propagate into the left atrial chamber and cause arrhythmias resulting in atrial fibrillation; the most common, often sustained, form of cardiac arrhythmia. In mice, PVCs extend along the pulmonary vein into the lungs, and are accessible in a lung slice preparation. We exploited this model to study how aberrant Ca(2+) signaling alters the ability of PVC networks to follow electrical pacing. Cellular responses were investigated using real-time 2-photon imaging of lung slices loaded with a Ca(2+)-sensitive fluorescent indicator (Ca(2+) measurements) and phase contrast microscopy (contraction measurements). PVCs displayed global Ca(2+) signals and coordinated contraction in response to electrical field stimulation (EFS). The effects of EFS relied on both Ca(2+) influx and Ca(2+) release, and could be inhibited by nifedipine, ryanodine or caffeine. Moreover, PVCs had a high propensity to show spontaneous Ca(2+) signals that arose via stochastic activation of ryanodine receptors (RyRs). The ability of electrical pacing to entrain Ca(2+) signals and contractile responses was dramatically influenced by inherent spontaneous Ca(2+) activity. In PVCs with relatively low spontaneous Ca(2+) activity (<1 Hz), entrainment with electrical pacing was good. However, in PVCs with higher frequencies of spontaneous Ca(2+) activity (>1.5 Hz), electrical pacing was less effective; PVCs became unpaced, only partially-paced or displayed alternans. Because spontaneous Ca(2+) activity varied between cells, neighboring PVCs often had different responses to electrical pacing. Our data indicate that the ability of PVCs to respond to electrical stimulation depends on their intrinsic Ca(2+) cycling properties. Heterogeneous spontaneous Ca(2+) activity arising from stochastic RyR opening can disengage them from sinus rhythm and lead to autonomous, pro-arrhythmic activity.
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Affiliation(s)
- Katja Rietdorf
- Department of Microbiology and Physiological Systems, University of Massachusetts, Medical School, Worcester, Massachusetts, United States of America
- Department of Life, Health and Chemical Science, The Open University, Milton Keynes, United Kingdom
- * E-mail:
| | - Martin D. Bootman
- Department of Life, Health and Chemical Science, The Open University, Milton Keynes, United Kingdom
- Signalling Programme, The Babraham Institute, Cambridge, United Kingdom
| | - Michael J. Sanderson
- Department of Microbiology and Physiological Systems, University of Massachusetts, Medical School, Worcester, Massachusetts, United States of America
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102
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Paddenberg R, Mermer P, Goldenberg A, Kummer W. Videomorphometric analysis of hypoxic pulmonary vasoconstriction of intra-pulmonary arteries using murine precision cut lung slices. J Vis Exp 2014:e50970. [PMID: 24458260 PMCID: PMC4089409 DOI: 10.3791/50970] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Acute alveolar hypoxia causes pulmonary vasoconstriction (HPV) - also known as von Euler-Liljestrand mechanism - which serves to match lung perfusion to ventilation. Up to now, the underlying mechanisms are not fully understood. The major vascular segment contributing to HPV is the intra-acinar artery. This vessel section is responsible for the blood supply of an individual acinus, which is defined as the portion of lung distal to a terminal bronchiole. Intra-acinar arteries are mostly located in that part of the lung that cannot be selectively reached by a number of commonly used techniques such as measurement of the pulmonary artery pressure in isolated perfused lungs or force recordings from dissected proximal pulmonary artery segments(1,2). The analysis of subpleural vessels by real-time confocal laser scanning luminescence microscopy is limited to vessels with up to 50 µm in diameter(3). We provide a technique to study HPV of murine intra-pulmonary arteries in the range of 20-100 µm inner diameters. It is based on the videomorphometric analysis of cross-sectioned arteries in precision cut lung slices (PCLS). This method allows the quantitative measurement of vasoreactivity of small intra-acinar arteries with inner diameter between 20-40 µm which are located at gussets of alveolar septa next to alveolar ducts and of larger pre-acinar arteries with inner diameters between 40-100 µm which run adjacent to bronchi and bronchioles. In contrast to real-time imaging of subpleural vessels in anesthetized and ventilated mice, videomorphometric analysis of PCLS occurs under conditions free of shear stress. In our experimental model both arterial segments exhibit a monophasic HPV when exposed to medium gassed with 1% O2 and the response fades after 30-40 min at hypoxia.
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Affiliation(s)
| | - Petra Mermer
- Institute of Anatomy and Cell Biology, Justus-Liebig-University
| | - Anna Goldenberg
- Institute of Anatomy and Cell Biology, Justus-Liebig-University
| | - Wolfgang Kummer
- Institute of Anatomy and Cell Biology, Justus-Liebig-University
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103
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Nichols JE, Niles JA, Vega SP, Cortiella J. Novel in vitro respiratory models to study lung development, physiology, pathology and toxicology. Stem Cell Res Ther 2013; 4 Suppl 1:S7. [PMID: 24565038 PMCID: PMC4028843 DOI: 10.1186/scrt368] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Detailed studies of lung pathology in patients during the course of development of acute lung injury or respiratory distress are limited, and in the past information related to lung-specific responses has been derived from the study of lungs from patients who died at autopsy or from animal models. Development of good in vitro human tissue models would help to bridge the gap in our current knowledge of lung responses and provide a better understanding of lung development, physiology and pathology. In vitro models of simple one-cell or two-cell culture systems as well as complex multicellular lung analogs that reproduce defined components of specific human lung responses have already been realized. A benefit of current in vitro lung models is that hypotheses generated from review of data from human or animal disease studies can be tested directly in engineered human tissue models. Results of studies done using simple in vitro lung systems or more complex three-dimensional models have already been used to examine cell-based responses, physiologic functions, pathologic changes and even drug toxicity or drug responses. In the future we will create models with specific genetic profiles to test the importance of single gene products or pathways of significance. Recent development of microfluidics-based models that support high-throughput screening will allow early-stage toxicity testing in human systems and faster development of new and innovative medical products. Model design in the future will also allow for evaluation of multiple organ systems at once, providing a more holistic or whole-body approach to understanding human physiology and responses.
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104
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Jain N, Miu B, Jiang JK, McKinstry KK, Prince A, Swain SL, Greiner DL, Thomas CJ, Sanderson MJ, Berg LJ, Kang J. CD28 and ITK signals regulate autoreactive T cell trafficking. Nat Med 2013; 19:1632-7. [PMID: 24270545 PMCID: PMC4005518 DOI: 10.1038/nm.3393] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2013] [Accepted: 10/04/2013] [Indexed: 01/07/2023]
Abstract
Activation of self-reactive T cells and their trafficking to target tissues leads to autoimmune organ destruction. Mice lacking the co-inhibitory receptor cytotoxic T lymphocyte antigen-4 (CTLA-4) develop fatal autoimmunity characterized by lymphocytic infiltration into nonlymphoid tissues. Here, we demonstrate that the CD28 co-stimulatory pathway regulates the trafficking of self-reactive Ctla4(-/-) T cells to tissues. Concurrent ablation of the CD28-activated Tec family kinase ITK does not block spontaneous T cell activation but instead causes self-reactive Ctla4(-/-) T cells to accumulate in secondary lymphoid organs. Despite excessive spontaneous T cell activation and proliferation in lymphoid organs, Itk(-/-); Ctla4(-/-) mice are otherwise healthy, mount antiviral immune responses and exhibit a long lifespan. We propose that ITK specifically licenses autoreactive T cells to enter tissues to mount destructive immune responses. Notably, ITK inhibitors mimic the null mutant phenotype and also prevent pancreatic islet infiltration by diabetogenic T cells in mouse models of type 1 diabetes, highlighting their potential utility for the treatment of human autoimmune disorders.
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Affiliation(s)
- Nitya Jain
- Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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105
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FitzPatrick M, Donovan C, Bourke JE. Prostaglandin E2 elicits greater bronchodilation than salbutamol in mouse intrapulmonary airways in lung slices. Pulm Pharmacol Ther 2013; 28:68-76. [PMID: 24291048 DOI: 10.1016/j.pupt.2013.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 10/23/2013] [Accepted: 11/18/2013] [Indexed: 10/26/2022]
Abstract
BACKGROUND Current asthma therapy may not adequately target contraction of smaller intrapulmonary airways, which are a major site of airway obstruction and inflammation. The aim of this study was to characterise responses of mouse intrapulmonary airways to prostaglandin E(2) (PGE(2)) and compare its dilator efficacy with the β(2)-adrenoceptor agonist salbutamol in situ, using lung slices. METHODS Lung slices (150 μm) were prepared from male Balb/C mice. Changes in intrapulmonary airway lumen area were recorded and analysed by phase-contrast microscopy. Relaxation to PGE(2) and salbutamol were assessed following various levels of pre-contraction with methacholine, serotonin or endothelin-1, as well as following overnight incubation with PGE(2) or salbutamol. The mechanism of PGE(2)-mediated relaxation was explored using selective EP antagonists (EP(1/2) AH6809; EP(4) L-161982) and Ca(2+)-permeabilized slices, where airway responses are due to regulation of Ca(2+)-sensitivity alone. RESULTS PGE2 elicited EP(1/2)-mediated relaxation of intrapulmonary airways. PGE(2) was more potent than salbutamol in opposing submaximal pre-contraction to all constrictors tested, and only PGE(2) opposed maximal pre-contraction with endothelin-1. Relaxation to PGE(2) was maintained when contraction to methacholine was mediated via increased Ca(2+)-sensitivity alone. PGE(2) was less sensitive to homologous or heterologous desensitization of its receptors than salbutamol. CONCLUSION The greater efficacy and potency of PGE(2) compared to salbutamol in mouse intrapulmonary airways supports further investigation of the mechanisms underlying this improved dilator responsiveness for the treatment of severe asthma.
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Affiliation(s)
- M FitzPatrick
- Lung Health Research Centre, Department of Pharmacology and Therapeutics, University of Melbourne, Parkville, Victoria 3010, Australia.
| | - C Donovan
- Lung Health Research Centre, Department of Pharmacology and Therapeutics, University of Melbourne, Parkville, Victoria 3010, Australia.
| | - J E Bourke
- Lung Health Research Centre, Department of Pharmacology and Therapeutics, University of Melbourne, Parkville, Victoria 3010, Australia.
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106
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Donovan C, Royce SG, Esposito J, Tran J, Ibrahim ZA, Tang MLK, Bailey S, Bourke JE. Differential effects of allergen challenge on large and small airway reactivity in mice. PLoS One 2013; 8:e74101. [PMID: 24040180 PMCID: PMC3765301 DOI: 10.1371/journal.pone.0074101] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 07/30/2013] [Indexed: 01/21/2023] Open
Abstract
The relative contributions of large and small airways to hyperresponsiveness in asthma have yet to be fully assessed. This study used a mouse model of chronic allergic airways disease to induce inflammation and remodelling and determine whether in vivo hyperresponsiveness to methacholine is consistent with in vitro reactivity of trachea and small airways. Balb/C mice were sensitised (days 0, 14) and challenged (3 times/week, 6 weeks) with ovalbumin. Airway reactivity was compared with saline-challenged controls in vivo assessing whole lung resistance, and in vitro measuring the force of tracheal contraction and the magnitude/rate of small airway narrowing within lung slices. Increased airway inflammation, epithelial remodelling and fibrosis were evident following allergen challenge. In vivo hyperresponsiveness to methacholine was maintained in isolated trachea. In contrast, methacholine induced slower narrowing, with reduced potency in small airways compared to controls. In vitro incubation with IL-1/TNFα did not alter reactivity. The hyporesponsiveness to methacholine in small airways within lung slices following chronic ovalbumin challenge was unexpected, given hyperresponsiveness to the same agonist both in vivo and in vitro in tracheal preparations. This finding may reflect the altered interactions of small airways with surrounding parenchymal tissue after allergen challenge to oppose airway narrowing and closure.
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Affiliation(s)
- Chantal Donovan
- Lung Health Research Centre, Department of Pharmacology & Therapeutics, University of Melbourne, Parkville, Victoria, Australia
| | - Simon G. Royce
- Department of Pediatrics, University of Melbourne, Parkville, Victoria, Australia
- Department of Allergy & Immunology, Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia
| | - James Esposito
- Lung Health Research Centre, Department of Pharmacology & Therapeutics, University of Melbourne, Parkville, Victoria, Australia
| | - Jenny Tran
- Lung Health Research Centre, Department of Pharmacology & Therapeutics, University of Melbourne, Parkville, Victoria, Australia
| | - Zaridatul Aini Ibrahim
- Lung Health Research Centre, Department of Pharmacology & Therapeutics, University of Melbourne, Parkville, Victoria, Australia
| | - Mimi L. K. Tang
- Department of Pediatrics, University of Melbourne, Parkville, Victoria, Australia
- Department of Allergy & Immunology, Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia
| | - Simon Bailey
- Lung Health Research Centre, Department of Pharmacology & Therapeutics, University of Melbourne, Parkville, Victoria, Australia
- Faculty of Veterinary Science, University of Melbourne, Parkville, Victoria, Australia
| | - Jane E. Bourke
- Lung Health Research Centre, Department of Pharmacology & Therapeutics, University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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107
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ECM modulated early kidney development in embryonic organ culture. Biomaterials 2013; 34:6670-82. [DOI: 10.1016/j.biomaterials.2013.05.031] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 05/18/2013] [Indexed: 01/17/2023]
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108
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Mukherjee S, Trice J, Shinde P, Willis RE, Pressley TA, Perez-Zoghbi JF. Ca2+ oscillations, Ca2+ sensitization, and contraction activated by protein kinase C in small airway smooth muscle. ACTA ACUST UNITED AC 2013; 141:165-78. [PMID: 23359281 PMCID: PMC3557311 DOI: 10.1085/jgp.201210876] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Protein kinase C (PKC) has been implicated in the regulation of smooth muscle cell (SMC) contraction and may contribute to airway hyperresponsiveness. Here, we combined optical and biochemical analyses of mouse lung slices to determine the effects of PKC activation on Ca2+ signaling, Ca2+ sensitivity, protein phosphorylation, and contraction in SMCs of small intrapulmonary airways. We found that 10 µM phorbol-12-myristate-13-acetate or 1 µM phorbol 12,13-dibutyrate induced repetitive, unsynchronized, and transient contractions of the SMCs lining the airway lumen. These contractions were associated with low frequency Ca2+ oscillations in airway SMCs that resulted from Ca2+ influx through L-type voltage-gated Ca2+ channels and the subsequent release of Ca2+ from intracellular stores through ryanodine receptors. Phorbol ester stimulation of lung slices in which SMC intracellular Ca2+ concentration ([Ca2+]i) was “clamped” at a high concentration induced strong airway contraction, indicating that PKC mediated sensitization of the contractile response to [Ca2+]i. This Ca2+ sensitization was accompanied by phosphorylation of both the PKC-potentiated PP1 inhibitory protein of 17 kD (CPI-17) and the regulatory myosin light chain. Thrombin, like the phorbol esters, induced a strong Ca2+ sensitization that was inhibited by the PKC inhibitor GF-109203X and also potentiated airway contraction to membrane depolarization with KCl. In conclusion, we suggest that PKC activation in small airways leads to both the generation of Ca2+ oscillations and strong Ca2+ sensitization; agents associated with airway inflammation, such as thrombin, may activate this pathway to sensitize airway smooth muscle to agonists that cause membrane depolarization and Ca2+ entry and induce airway hyperresponsiveness.
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Affiliation(s)
- Seema Mukherjee
- Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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109
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Dixon RE, Santana LF. A Ca2+- and PKC-driven regulatory network in airway smooth muscle. ACTA ACUST UNITED AC 2013; 141:161-4. [PMID: 23359280 PMCID: PMC3557310 DOI: 10.1085/jgp.201210953] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Rose E Dixon
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
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110
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Davidovich N, Huang J, Margulies SS. Reproducible uniform equibiaxial stretch of precision-cut lung slices. Am J Physiol Lung Cell Mol Physiol 2012; 304:L210-20. [PMID: 23275624 DOI: 10.1152/ajplung.00224.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Simulating ventilator-induced lung injury (VILI) in the laboratory requires stretching of lung alveolar tissue. Whereas precision-cut lung slices (PCLSs) are widely used for studying paracrine signaling pathways in the lungs, their use in stretch studies is very limited because of the technical challenge of fixing them to a stretchable substrate, stretching them uniformly, or holding them in a stretch device without causing rupture. We describe a novel method for attaching PCLSs to silicone membranes by stitching them together in a star-shaped pattern. Using a device that was previously designed in our laboratory for stretching primary alveolar epithelial cell monolayers, we demonstrate that in the central region of the PCLSs stretch is uniform, equibiaxial, and, after a short preconditioning period, also reproducible. The stitched and stretched PCLSs showed equal or better viability outcomes after 60 min of cyclic stretch at different magnitudes of physiological stretch compared with primary pulmonary alveolar epithelial cell monolayers. Preparing and stitching the PCLSs before stretch is relatively easy to perform, yields repeatable outcomes, and can be used with tissue from any species. Together with the ensuring uniform and equibiaxial stretch, the proposed methods provide an optimal model for VILI studies with PCLSs.
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Affiliation(s)
- N Davidovich
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
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111
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Mfge8 suppresses airway hyperresponsiveness in asthma by regulating smooth muscle contraction. Proc Natl Acad Sci U S A 2012; 110:660-5. [PMID: 23269839 DOI: 10.1073/pnas.1216673110] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Airway obstruction is a hallmark of allergic asthma and is caused primarily by airway smooth muscle (ASM) hypercontractility. Airway inflammation leads to the release of cytokines that enhance ASM contraction by increasing ras homolog gene family, member A (RhoA) activity. The protective mechanisms that prevent or attenuate the increase in RhoA activity have not been well studied. Here, we report that mice lacking the gene that encodes the protein Milk Fat Globule-EGF factor 8 (Mfge8(-/-)) develop exaggerated airway hyperresponsiveness in experimental models of asthma. Mfge8(-/-) ASM had enhanced contraction after treatment with IL-13, IL-17A, or TNF-α. Recombinant Mfge8 reduced contraction in murine and human ASM treated with IL-13. Mfge8 inhibited IL-13-induced NF-κB activation and induction of RhoA. Mfge8 also inhibited rapid activation of RhoA, an effect that was eliminated by an inactivating point mutation in the RGD integrin-binding site in recombinant Mfge8. Human subjects with asthma had decreased Mfge8 expression in airway biopsies compared with healthy controls. These data indicate that Mfge8 binding to integrin receptors on ASM opposes the effect of allergic inflammation on RhoA activity and identify a pathway for specific inhibition of ASM hypercontractility in asthma.
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112
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Fujioka H, Halpern D, Gaver DP. A model of surfactant-induced surface tension effects on the parenchymal tethering of pulmonary airways. J Biomech 2012; 46:319-28. [PMID: 23235110 DOI: 10.1016/j.jbiomech.2012.11.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 11/10/2012] [Accepted: 11/13/2012] [Indexed: 12/21/2022]
Abstract
We developed a computational model of lung parenchyma, which is comprised of individual alveolar chamber models. Each alveolus is modeled by a truncated octahedron. Considering the force balance between the elastin and collagen fibers laying on the alveolar membrane and the pressures acting on the membrane, we computed the deformations of the parenchyma with a finite element method. We focused on the effect of surfactant on the force of parenchymal tethering an airway. As the lung inflates, the parenchyma becomes stiffer and the tethering force becomes stronger. As the alveolar surfactant concentration is reduced, the lung volume at a fixed alveolar pressure decreases, and thus, the tethering force becomes weaker. The distortion of parenchyma caused by the deformation of an airway extends widely around the airway. The displacement of parenchyma decays with distance from the airway wall, but deviates from the prediction based on a theory for a continuum material. Using results obtained from the present lung parenchyma model, we also developed a simple 1-dimensional model for parenchyma tethering force on an airway, which could be utilized for the analysis of liquid/gas transports in an axis-symmetric elastic airway. The effective shear modulus was calculated from the pressure-volume relation of parenchyma. By manipulating the pressure-volume curve, this simple model may be used to predict the parenchyma tethering force in diseased lungs.
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Affiliation(s)
- Hideki Fujioka
- Center for Computational Science, Tulane University, New Orleans, LA 70118, USA.
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113
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Ma B, Sanderson M, Bates JHT. Airway-parenchymal interdependence in the lung slice. Respir Physiol Neurobiol 2012; 185:211-6. [PMID: 23128069 DOI: 10.1016/j.resp.2012.10.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 09/28/2012] [Accepted: 10/29/2012] [Indexed: 10/27/2022]
Abstract
The explanted lung slice has become a popular in vitro system for studying how airways contract. Because the forces of airway-parenchymal interdependence are such important modulators of airway narrowing, it is of significant interest to understand how the parenchyma around a constricting airway in a lung slice behaves. We have previously shown that the predictions of the 2-dimensional distortion field around a constricting airway are substantially different depending on whether the parenchyma is modeled as an elastic continuum versus a network of hexagonally arranged springs, which raises the question as to which model best explains the lung slice. We treated lung slices with methacholine and then followed the movement of a set of parenchymal landmarks around the airway as it narrowed. The resulting parenchymal displacement field was compared to the displacement fields predicted by the continuum and hexagonal spring network models. The predictions of the continuum model were much closer to the measured data than were those of the hexagonal spring network model, suggesting that the parenchyma in the lung slice behaves like an elastic continuum rather than a network of discrete springs. This may be because the alveoli of the lung slice are filled with agarose in order to provide structural stability, causing the parenchyma in the slice to act like a true mechanical continuum. How the air-filled parenchyma in the intact lung behave in vivo remains an open question.
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Affiliation(s)
- Baoshun Ma
- College of Medicine, University of Vermont, Burlington, VT 05405, United States
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114
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Poole JA, Romberger DJ, Bauer C, Gleason AM, Sisson JH, Oldenburg PJ, West WW, Wyatt TA. Protein kinase C epsilon is important in modulating organic-dust-induced airway inflammation. Exp Lung Res 2012; 38:383-95. [PMID: 22897707 DOI: 10.3109/01902148.2012.714841] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Organic dust samples from swine confinement facilities elicit pro-inflammatory cytokine/chemokine release from bronchial epithelial cells and monocytes, dependent, in part, upon dust-induced activation of the protein kinase C (PKC) isoform, PKCε. PKCε is also rapidly activated in murine tracheal epithelial cells following in vivo organic dust challenges, yet the functional role of PKCε in modulating dust-induced airway inflammatory outcomes is not defined. Utilizing an established intranasal inhalation animal model, experiments investigated the biologic and physiologic responses following organic dust extract (ODE) treatments in wild-type (WT) and PKCε knock-out (KO) mice. We found that neutrophil influx increased more than twofold in PKCε KO mice following both a one-time challenge and 3 weeks of daily challenges with ODE as compared with WT mice. Lung pathology revealed increased bronchiolar and alveolar inflammation, lymphoid aggregates, and T cell influx in ODE-treated PKCε KO mice. Airway hyperresponsiveness to methacholine increased in PKCε KO + ODE to a greater magnitude than WT + ODE animals. There were no significant differences in cytokine/chemokine release elicited by ODE treatment between groups. However, ODE-induced nitric oxide (NO) production differed in that ODE exposure increased nitrate levels in WT mice but not in PKCε KO mice. Moreover, ODE failed to upregulate NO from ex vivo stimulated PKCε KO lung macrophages. Collectively, these studies demonstrate that PKCε-deficient mice were hypersensitive to organic dust exposure and suggest that PKCε is important in the normative lung inflammatory response to ODE. Dampening of ODE-induced NO may contribute to these enhanced inflammatory findings.
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Affiliation(s)
- Jill A Poole
- Pulmonary, Critical Care, Sleep and Allergy Division, Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska 68198-5300, USA.
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115
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Lauzon AM, Bates JHT, Donovan G, Tawhai M, Sneyd J, Sanderson MJ. A multi-scale approach to airway hyperresponsiveness: from molecule to organ. Front Physiol 2012; 3:191. [PMID: 22701430 PMCID: PMC3371674 DOI: 10.3389/fphys.2012.00191] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 05/21/2012] [Indexed: 12/13/2022] Open
Abstract
Airway hyperresponsiveness (AHR), a characteristic of asthma that involves an excessive reduction in airway caliber, is a complex mechanism reflecting multiple processes that manifest over a large range of length and time scales. At one extreme, molecular interactions determine the force generated by airway smooth muscle (ASM). At the other, the spatially distributed constriction of the branching airways leads to breathing difficulties. Similarly, asthma therapies act at the molecular scale while clinical outcomes are determined by lung function. These extremes are linked by events operating over intermediate scales of length and time. Thus, AHR is an emergent phenomenon that limits our understanding of asthma and confounds the interpretation of studies that address physiological mechanisms over a limited range of scales. A solution is a modular computational model that integrates experimental and mathematical data from multiple scales. This includes, at the molecular scale, kinetics, and force production of actin-myosin contractile proteins during cross-bridge and latch-state cycling; at the cellular scale, Ca2+ signaling mechanisms that regulate ASM force production; at the tissue scale, forces acting between contracting ASM and opposing viscoelastic tissue that determine airway narrowing; at the organ scale, the topographic distribution of ASM contraction dynamics that determine mechanical impedance of the lung. At each scale, models are constructed with iterations between theory and experimentation to identify the parameters that link adjacent scales. This modular model establishes algorithms for modeling over a wide range of scales and provides a framework for the inclusion of other responses such as inflammation or therapeutic regimes. The goal is to develop this lung model so that it can make predictions about bronchoconstriction and identify the pathophysiologic mechanisms having the greatest impact on AHR and its therapy.
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Affiliation(s)
- Anne-Marie Lauzon
- Meakins-Christie Laboratories, Department of Medicine, McGill University Montreal, QC, Canada
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116
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Lavoie TL, Krishnan R, Siegel HR, Maston ED, Fredberg JJ, Solway J, Dowell ML. Dilatation of the constricted human airway by tidal expansion of lung parenchyma. Am J Respir Crit Care Med 2012; 186:225-32. [PMID: 22679010 DOI: 10.1164/rccm.201202-0368oc] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
RATIONALE In the normal lung, breathing and deep inspirations potently antagonize bronchoconstriction, but in the asthmatic lung this salutary effect is substantially attenuated or even reversed. To explain these findings, the prevailing hypothesis focuses on contracting airway smooth muscle and posits a nonlinear dynamic interaction between actomyosin binding and the tethering forces imposed by tidally expanding lung parenchyma. OBJECTIVE This hypothesis has never been tested directly in bronchial smooth muscle embedded within intraparenchymal airways. Our objective here is to fill that gap. METHODS We designed a novel system to image contracting intraparenchymal human airways situated within near-normal lung architecture and subjected to dynamic parenchymal expansion that simulates breathing. MEASUREMENTS AND MAIN RESULTS Reversal of bronchoconstriction depended on the degree to which breathing actually stretched the airway, which in turn depended negatively on severity of constriction and positively on the depth of breathing. Such behavior implies positive feedbacks that engender airway instability. OVERALL CONCLUSIONS These findings help to explain heterogeneity of airflow obstruction as well as why, in people with asthma, deep inspirations are less effective in reversing bronchoconstriction.
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Affiliation(s)
- Tera L Lavoie
- Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA
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Park SJ, Yoo HY, Kim HJ, Kim JK, Zhang YH, Kim SJ. Requirement of Pretone by Thromboxane A(2) for Hypoxic Pulmonary Vasoconstriction in Precision-cut Lung Slices of Rat. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2012; 16:59-64. [PMID: 22416221 PMCID: PMC3298827 DOI: 10.4196/kjpp.2012.16.1.59] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 01/22/2012] [Accepted: 01/25/2012] [Indexed: 01/28/2023]
Abstract
Hypoxic pulmonary vasoconstriction (HPV) is physiologically important response for preventing mismatching between ventilation and perfusion in lungs. The HPV of isolated pulmonary arteries (HPV-PA) usually require a partial pretone by thromboxane agonist (U46619). Because the HPV of ventilated/perfused lungs (HPV-lung) can be triggered without pretone conditioning, we suspected that a putative tissue factor might be responsible for the pretone of HPV. Here we investigated whether HPV can be also observed in precision-cut lung slices (PCLS) from rats. The HPV in PCLS also required partial contraction by U46619. In addition, K+ channel blockers (4AP and TEA) required U46619-pretone to induce significant contraction of PA in PCLS. In contrast, the airways in PCLS showed reversible contraction in response to the K+ channel blockers without pretone conditioning. Also, the airways showed no hypoxic constriction but a relaxation under the partial pretone by U46619. The airways in PCLS showed reliable, concentration-dependent contraction by metacholine (EC50, ~210 nM). In summary, the HPV in PCLS is more similar to isolated PA than V/P lungs. The metacholine-induced constriction of bronchioles suggested that the PLCS might be also useful for studying airway physiology in situ.
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Affiliation(s)
- Su Jung Park
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea
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Precision-Cut Vibratome Slices Allow Functional Live Cell Imaging of the Pulmonary Neuroepithelial Body Microenvironment in Fetal Mice. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 758:157-66. [DOI: 10.1007/978-94-007-4584-1_22] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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