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Torchio R, Gobbi A, Gulotta C, Antonelli A, Dellacà RL, Pellegrino GM, Pellegrino R, Brusasco V. Role of hyperpnea in the relaxant effect of inspired CO 2 on methacholine-induced bronchoconstriction. J Appl Physiol (1985) 2022; 132:1137-1144. [PMID: 35358399 DOI: 10.1152/japplphysiol.00763.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Inhaling carbon dioxide (CO2) in humans is known to cause inconsistent effects on airway function. These could be due to direct effects of CO2 on airway smooth muscle or to changes in minute ventilation (e). To address this issue, we examined the responses of the respiratory system to inhaled methacholine in healthy and mild asthmatics while breathing air or gas mixtures containing 2% or 4% CO2. Respiratory mechanics were measured by a forced oscillation technique at 5 Hz during tidal breathing. At baseline, respiratory resistance (R5) was significantly higher in asthmatics (2.53±0.38 cm H2O•L-1•s) than healthy subjects (2.11±0.42 cm H2O•L-1•s) (p=0.008) with room air. Similar values were observed with CO2 2% or 4% in the two groups. e, tidal volume (VT), and breathing frequency (BF) significantly increased with CO2-containing mixtures (p<0.001) with insignificant differences between groups. After methacholine, the increase in R5 and the decrease in respiratory reactance (X5) were significantly attenuated up to about 50% with CO2-containing mixtures instead of room air in both asthmatic (p<0.001) and controls (p<0.001). Mediation analysis showed that the attenuation of methacholine-induced changes in respiratory mechanics by CO2 was due to the increase in e (p=0.006 for R5 and p=0.014 for X5) independently of the increase in VT or BF, rather than a direct effect of CO2. These findings suggest that the increased stretching of airway smooth muscle by the CO2-induced increase in e is a mechanism through which hypercapnia can attenuate bronchoconstrictor responses in healthy and mild asthmatic subjects.
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Affiliation(s)
- Roberto Torchio
- Pneumologia-Fisiopatologia Respiratoria, Universitaria S. Luigi, VENARIA REALE, Italy
| | - Alessandro Gobbi
- TBM Lab, Dipartimento di Bioingegneria, Politecnico di Milano, Milano, Italy.,Restech Srl, Milano, Italy
| | - Carlo Gulotta
- Pneumologia-Fisiopatologia Respiratoria, Universitaria S. Luigi, VENARIA REALE, Italy
| | - Andrea Antonelli
- Allergologia e Fisiopatologia Respiratoria, ASO S. Croce e Carle, Cuneo, Italy
| | - Raffaele L Dellacà
- TBM Lab, Dipartimento di Bioingegneria, Politecnico di Milano, Milano, Italy
| | - Giulia Michela Pellegrino
- Respiratory Unit, ASST Santi Paolo eCarlo, Dipartimento Scienze della Salute, Università degli Studi di Milano, Milan, Italy.,Casa di Cura del Policlinico, Dipartimento di Scienze Neuroriabilitative, Milan, Italy
| | | | - Vito Brusasco
- Centro Polifunzionale di Scienze Motorie, Dipartimento di Medicina Sperimentale, Università di Genova, Genova, Italy
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Chung Y, Huang TY, Liao YH, Kuo YC. 12-Week Inspiratory Muscle Training Improves Respiratory Muscle Strength in Adult Patients with Stable Asthma: A Randomized Controlled Trial. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18063267. [PMID: 33809922 PMCID: PMC8004228 DOI: 10.3390/ijerph18063267] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 03/12/2021] [Accepted: 03/18/2021] [Indexed: 11/29/2022]
Abstract
This study aims to investigate and compare the effects of conventional breathing exercises and an inspiratory muscle training intervention on clinical symptoms in asthma patients. Sixty asthma patients (40–65 years old) were randomly assigned to either the conventional breathing exercises (BTE) or inspiratory muscle training (IMT) group for a 12-week intervention period. Outcome measurements were performed before and after the intervention, including the spirometry data, maximal inspiratory and expiratory pressures (PImax and PEmax), asthma control test, asthma control questionnaire, six-minute walk test, and three-day physical activity log, were recorded. PImax expressed as % of predicted value controlled for age and gender in healthy subjects (% predicted) increased by 16.92% (82.45% to 99.38%, p < 0.05) in the BTE group and by 29.84% (71.19% to 101.03%, p < 0.05) in the IMT group. Except for forced vital capacity, which was reduced in the BTE group, all other measured variables improved in both groups, and no statistically significant between-group differences were found. IMT appears to be more effective than breathing exercise intervention in promoting improvements in respiratory muscle strength. IMT may act as an alternative to conventional breathing exercises for middle-aged and elderly asthma patients.
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Affiliation(s)
- Yi Chung
- College of Human Development and Health, National Taipei University of Nursing and Health Sciences, Taipei 112, Taiwan;
| | - Ting-Yu Huang
- Department of Exercise and Health Science, National Taipei University of Nursing and Health Sciences, Taipei 112, Taiwan; (T.-Y.H.); (Y.-H.L.)
| | - Yi-Hung Liao
- Department of Exercise and Health Science, National Taipei University of Nursing and Health Sciences, Taipei 112, Taiwan; (T.-Y.H.); (Y.-H.L.)
| | - Yu-Chi Kuo
- College of Human Development and Health, National Taipei University of Nursing and Health Sciences, Taipei 112, Taiwan;
- Department of Exercise and Health Science, National Taipei University of Nursing and Health Sciences, Taipei 112, Taiwan; (T.-Y.H.); (Y.-H.L.)
- Correspondence:
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3
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Evaristo KB, Mendes FAR, Saccomani MG, Cukier A, Carvalho-Pinto RM, Rodrigues MR, Santaella DF, Saraiva-Romanholo BM, Martins MA, Carvalho CRF. Effects of Aerobic Training Versus Breathing Exercises on Asthma Control: A Randomized Trial. THE JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY-IN PRACTICE 2020; 8:2989-2996.e4. [PMID: 32773365 DOI: 10.1016/j.jaip.2020.06.042] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Revised: 06/19/2020] [Accepted: 06/22/2020] [Indexed: 11/30/2022]
Abstract
BACKGROUND Aerobic training and breathing exercises are interventions that improve asthma control. However, the outcomes of these 2 interventions have not been compared. OBJECTIVE To compare the effects of aerobic training versus breathing exercises on clinical control (primary outcome), quality of life, exercise capacity, and airway inflammation in outpatients with moderate-to-severe asthma. METHODS Fifty-four asthmatics were randomized into either the aerobic training group (AG, n = 29) or the breathing exercise group (BG, n = 25). Both interventions lasted for 24 sessions (2/week, 40 minutes/session). Asthma clinical control (Asthma Control Questionnaire [ACQ]), quality of life (Asthma Quality of Life Questionnaire), asthma symptom-free days (ASFD), airway inflammation, exercise capacity, psychological distress (Hospital Anxiety and Depression Scale), daily-life physical activity (DLPA), and pulmonary function were evaluated before, immediately after, and 3 months after the intervention. RESULTS Both interventions presented similar results regarding the ACQ score, psychological distress, ASFD, DLPA, and airway inflammation (P > .05). However, participants in the AG were 2.6 times more likely to experience clinical improvement at the 3-month follow-up than participants in the BG (P = .02). A greater proportion of participants in the AG also presented a reduction in the number of days without rescue medication use compared with BG (34% vs 8%; P = .04). CONCLUSIONS Outpatients with moderate-to-severe asthma who participated in aerobic training or breathing exercise programs presented similar results in asthma control, quality of life, asthma symptoms, psychological distress, physical activity, and airway inflammation. However, a greater proportion of participants in the AG presented improvement in asthma control and reduced use of rescue medication.
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Affiliation(s)
- Karen B Evaristo
- Department of Physical Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Felipe Augusto Rodrigues Mendes
- Department of Physical Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil; Department of Physical Therapy, Universidade Ibirapuera, São Paulo, Brazil
| | - Milene G Saccomani
- Department of Physical Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Alberto Cukier
- Department of Pulmonary Division (InCor), School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Regina M Carvalho-Pinto
- Department of Pulmonary Division (InCor), School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Marcos R Rodrigues
- Department of Sports, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Danilo F Santaella
- Department of Sports, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Beatriz M Saraiva-Romanholo
- Department of Medicine, School of Medicine, University of São Paulo, São Paulo, Brazil; Department of Physical Therapy, University City of Sao Paulo (UNICID), São Paulo, Brazil
| | - Milton A Martins
- Department of Sports, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Celso R F Carvalho
- Department of Physical Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil.
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Chen B, Moore TV, Li Z, Sperling AI, Zhang C, Andrade J, Rodriguez A, Bahroos N, Huang Y, Morrisey EE, Gruber PJ, Solway J. Gata5 deficiency causes airway constrictor hyperresponsiveness in mice. Am J Respir Cell Mol Biol 2014; 50:787-95. [PMID: 24199649 DOI: 10.1165/rcmb.2013-0294oc] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Gata5 is a transcription factor expressed in the lung, but its physiological role is unknown. To test whether and how Gata5 regulates airway constrictor responsiveness, we studied Gata5(-/-), Gata5(+/-), and wild-type mice on the C57BL/6J background. Cholinergic airway constrictor responsiveness was assessed invasively in mice without and with induction of allergic airway inflammation through ovalbumin sensitization and aerosol exposure. Gata5-deficient mice displayed native airway constrictor hyperresponsiveness (AHR) in the absence of allergen-induced inflammation. Gata5-deficient mice retained their relatively greater constrictor responsiveness even in ovalbumin-induced experimental asthma. Gata5 deficiency did not alter the distribution of cell types in bronchoalveolar lavage fluid, but bronchial epithelial mucus metaplasia was more prominent in Gata5(-/-) mice after allergen challenge. Gene expression profiles revealed that apolipoprotein E (apoE) was the fifth most down-regulated transcript in Gata5-deficient lungs, and quantitative RT-PCR and immunostaining confirmed reduced apoE expression in Gata5(-/-) mice. Quantitative RT-PCR also revealed increased IL-13 mRNA in the lungs of Gata5-deficient mice. These findings for the first time show that Gata5 regulates apoE and IL-13 expression in vivo and that its deletion causes AHR. Gata5-deficient mice exhibit an airway phenotype that closely resembles that previously reported for apoE(-/-) mice: both exhibit cholinergic AHR in native and experimental asthma states, and there is excessive goblet cell metaplasia after allergen sensitization and challenge. The Gata5-deficient phenotype also shares features that were previously reported for IL-13-treated mice. Together, these results indicate that Gata5 deficiency induces AHR, at least in part, by blunting apoE and increasing IL-13 expression.
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5
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Parameswaran H, Lutchen KR, Suki B. A computational model of the response of adherent cells to stretch and changes in substrate stiffness. J Appl Physiol (1985) 2014; 116:825-34. [PMID: 24408996 DOI: 10.1152/japplphysiol.00962.2013] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cells in the body exist in a dynamic mechanical environment where they are subject to mechanical stretch as well as changes in composition and stiffness of the underlying extracellular matrix (ECM). However, the underlying mechanisms by which cells sense and adapt to their dynamic mechanical environment, in particular to stretch, are not well understood. In this study, we hypothesized that emergent phenomena at the level of the actin network arising from active structural rearrangements driven by nonmuscle myosin II molecular motors play a major role in the cellular response to both stretch and changes in ECM stiffness. To test this hypothesis, we introduce a simple network model of actin-myosin interactions that links active self-organization of the actin network to the stiffness of the network and the traction forces generated by the network. We demonstrate that such a network replicates not only the effect of changes in substrate stiffness on cellular traction and stiffness and the dependence of rate of force development by a cell on the stiffness of its substrate, but also explains the physical response of adherent cells to transient and cyclic stretch. Our results provide strong indication that network phenomena governed by the active reorganization of the actin-myosin structure plays an important role in cellular mechanosensing and response to both changes in ECM stiffness and externally applied mechanical stretch.
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6
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Abstract
Excessive narrowing of the airways due to airway smooth muscle (ASM) contraction is a major cause of asthma exacerbation. ASM is therefore a direct target for many drugs used in asthma therapy. The contractile mechanism of smooth muscle is not entirely clear. A major advance in the field in the last decade was the recognition and appreciation of the unique properties of smooth muscle--mechanical and structural plasticity, characterized by the muscle's ability to rapidly alter the structure of its contractile apparatus and cytoskeleton and adapt to the mechanically dynamic environment of the lung. This article describes a possible mechanism for smooth muscle to adapt and function over a large length range by adding or subtracting contractile units in series spanning the cell length; it also describes a mechanism by which actin-myosin-actin connectivity might be influenced by thin and thick filament lengths, thus altering the muscle response to mechanical perturbation. The new knowledge is extremely useful for our understanding of ASM behavior in the lung and could provide new and more effective targets for drugs aimed at relaxing the muscle or keeping the muscle from excessive shortening in the asthmatic airways.
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Affiliation(s)
- Chun Y Seow
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
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7
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Lundblad LKA. Issues determining direct airways hyperresponsiveness in mice. Front Physiol 2012; 3:408. [PMID: 23097643 PMCID: PMC3477826 DOI: 10.3389/fphys.2012.00408] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 10/03/2012] [Indexed: 12/28/2022] Open
Abstract
Airways hyperresponsiveness (AHR) is frequently a primary outcome in mouse models of asthma. There are, however, a number of variables that may affect the outcome of such measurements and the interpretation of the results. This article highlights issues that should be kept in mind when designing experiments using AHR as an outcome by reviewing techniques commonly used to assess AHR (unrestrained plethysmography and respiratory input impedance using forced oscillations), discussing the relationship between structure and function and, then exploring how the localization of AHR evolves over time, how the airway epithelium may affect the kinetics of methacholine induced AHR and finally how lung volume and positive end expiratory pressure (PEEP) can be used as tools assessing respiratory mechanics.
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Affiliation(s)
- Lennart K A Lundblad
- Department of Medicine, Vermont Lung Center, The University of Vermont Burlington, VT, USA
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8
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Ferreira CM, Chen JL, Li J, Shimomura K, Yang X, Lussier YA, Pinto LH, Solway J. Genetic interactions between chromosomes 11 and 18 contribute to airway hyperresponsiveness in mice. PLoS One 2012; 7:e29579. [PMID: 22253740 PMCID: PMC3254621 DOI: 10.1371/journal.pone.0029579] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Accepted: 11/30/2011] [Indexed: 01/28/2023] Open
Abstract
We used two-dimensional quantitative trait locus analysis to identify interacting genetic loci that contribute to the native airway constrictor hyperresponsiveness to methacholine that characterizes A/J mice, relative to C57BL/6J mice. We quantified airway responsiveness to intravenous methacholine boluses in eighty-eight (C57BL/6J X A/J) F2 and twenty-seven (A/J X C57BL/6J) F2 mice as well as ten A/J mice and six C57BL/6J mice; all studies were performed in male mice. Mice were genotyped at 384 SNP markers, and from these data two-QTL analyses disclosed one pair of interacting loci on chromosomes 11 and 18; the homozygous A/J genotype at each locus constituted the genetic interaction linked to the hyperresponsive A/J phenotype. Bioinformatic network analysis of potential interactions among proteins encoded by genes in the linked regions disclosed two high priority subnetworks - Myl7, Rock1, Limk2; and Npc1, Npc1l1. Evidence in the literature supports the possibility that either or both networks could contribute to the regulation of airway constrictor responsiveness. Together, these results should stimulate evaluation of the genetic contribution of these networks in the regulation of airway responsiveness in humans.
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Affiliation(s)
- Caroline M. Ferreira
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois, United States of America
| | - James L. Chen
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Jianrong Li
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Kazuhiro Shimomura
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois, United States of America
| | - Xinan Yang
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Yves A. Lussier
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Lawrence H. Pinto
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois, United States of America
| | - Julian Solway
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
- * E-mail:
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9
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Bronchodilation induced by muscular contraction in spontaneously breathing rabbits: neural or mechanical? Respir Physiol Neurobiol 2011; 180:311-5. [PMID: 22210464 DOI: 10.1016/j.resp.2011.12.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 11/24/2011] [Accepted: 12/14/2011] [Indexed: 11/22/2022]
Abstract
The respective contribution of mechanical and neural mechanisms to the bronchodilation occurring during exercise is not fully identified in spontaneously breathing animals. The airway response to electrically induced muscular contractions (MC) was studied after vagal cold block in 9 spontaneously breathing rabbits. The forced oscillation respiratory system resistance (Rrs) was measured at vagal nerve temperatures 37°C, 8°C and 4°C. Rrs was found to decrease significantly during MC in all conditions. The occasional occurrence of a deep breath was responsible for a sudden decrease in Rrs. However, when the deep breath was absent - after vagal cooling and in some experiments at 37°C - the bronchodilation was frequently dissociated from the change in breathing pattern, most likely illustrating a neural mechanism. Altogether, while some bronchodilation may be ascribed to the mechanical stretching of the airways, Rrs decreasing with little change in breathing pattern is likely related to a reflex effect, possibly a sympathetic-borne mechanism.
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10
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Vaickus LJ, Bouchard J, Kim J, Natarajan S, Remick DG. Assessing pulmonary pathology by detailed examination of respiratory function. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 177:1861-9. [PMID: 20724595 PMCID: PMC2947281 DOI: 10.2353/ajpath.2010.100053] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/18/2010] [Indexed: 12/12/2022]
Abstract
Pulmonary inflammation causes multiple alterations within the lung, including mucus production, recruitment of inflammatory cells, and airway hyperreactivity (AHR). Measurement of AHR by direct, invasive means (eg, mechanical ventilation) or noninvasive techniques, like whole body plethysmography (WBP), assesses the severity of pulmonary inflammation in animal models of inflammatory lung disease. Direct measurement of AHR is acknowledged as the most accurate method for assessing airway mechanics, but analysis of all data obtained from WBP may offer insights into which inflammatory aspects of the lung are altered along with AHR. Using WBP, we compared the respiratory parameters of two groups of mice sensitized with cockroach allergen. One group was treated with dexamethasone (Dex) before final challenge (Dex-Asthma), while the other group received vehicle treatment (Asthma). Respiratory parameters from plethysmography revealed that Dex-Asthma mice compensated to maintain high minute ventilation, whereas Asthma mice showed significant impairment in minute ventilation despite increased peak expiratory flow (103 ± 5 ml/min vs. 69 ± 70 ml/min). The WBP data suggest that enhanced air exchange in the Dex-Asthma mice results from significant decreases in airway mucus production. Additional studies with quantitative morphometry of histological sections confirmed that Dex reduced airway mucus. In conclusion, a detailed examination of WBP parameters can accurately assess the respiratory health of mice and will help direct additional studies.
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Affiliation(s)
| | | | | | | | - Daniel G. Remick
- Department of Pathology, Boston University School of Medicine, Boston, Massachusetts
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11
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Chapman DG, Berend N, King GG, Salome CM. Can we cure airway hyperresponsiveness with a gym membership? J Appl Physiol (1985) 2010; 109:267-8. [DOI: 10.1152/japplphysiol.00582.2010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- David G. Chapman
- Woolcock Institute of Medical Research, Camperdown, New South Sales
- University of Sydney, Sydney; and
| | - Norbert Berend
- Woolcock Institute of Medical Research, Camperdown, New South Sales
- Cooperative Research Centre for Asthma, Camperdown, New South Wales
- University of Sydney, Sydney; and
| | - Gregory G. King
- Woolcock Institute of Medical Research, Camperdown, New South Sales
- Cooperative Research Centre for Asthma, Camperdown, New South Wales
- University of Sydney, Sydney; and
- Department of Respiratory Medicine, Royal North Shore Hospital, St Leonards, New South Wales, Australia
| | - Cheryl M. Salome
- Woolcock Institute of Medical Research, Camperdown, New South Sales
- Cooperative Research Centre for Asthma, Camperdown, New South Wales
- University of Sydney, Sydney; and
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12
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Krishnan R, Trepat X, Nguyen TTB, Lenormand G, Oliver M, Fredberg JJ. Airway smooth muscle and bronchospasm: fluctuating, fluidizing, freezing. Respir Physiol Neurobiol 2008; 163:17-24. [PMID: 18514592 PMCID: PMC2591927 DOI: 10.1016/j.resp.2008.04.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 04/08/2008] [Accepted: 04/10/2008] [Indexed: 11/24/2022]
Abstract
We review here four recent findings that have altered in a fundamental way our understanding of airways smooth muscle (ASM), its dynamic responses to physiological loading, and their dominant mechanical role in bronchospasm. These findings highlight ASM remodeling processes that are innately out-of-equilibrium and dynamic, and bring to the forefront a striking intersection between topics in condensed matter physics and ASM cytoskeletal biology. By doing so, they place in a new light the role of enhanced ASM mass in airway hyper-responsiveness as well as in the failure of a deep inspiration to relax the asthmatic airway. These findings have established that (i) ASM length is equilibrated dynamically, not statically; (ii) ASM dynamics closely resemble physical features exhibited by so-called soft glassy materials; (iii) static force-length relationships fail to describe dynamically contracted ASM states; (iv) stretch fluidizes the ASM cytoskeleton. Taken together, these observations suggest that at the origin of the bronchodilatory effect of a deep inspiration, and its failure in asthma, may lie glassy dynamics of the ASM cell.
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Affiliation(s)
- Ramaswamy Krishnan
- Program in Molecular and Integrative Physiological Sciences, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, United States
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13
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Taylor JT, Davis E, Dabisch P, Horsmon M, Matson K, Crouse C, Mioduszewski R. Acute toxic effects of inhaled dichlorvos vapor on respiratory mechanics and blood cholinesterase activity in guinea pigs. Inhal Toxicol 2008; 20:465-72. [PMID: 18368617 DOI: 10.1080/08958370701805709] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Using a modified noninvasive volume-displacement plethysmography system, we investigated the effects of inhaled dichlorvos (2,2-dimethyl-dichlorovinyl phosphate, or DDVP) vapor on the respiratory mechanics and blood cholinesterase activity of guinea pigs. Data revealed significant dose-dependent changes in several pulmonary parameters. Animals exposed to a DDVP concentration of 35 mg/m(3) did not show any significant changes in frequency, tidal volume, or minute ventilation. However, animals exposed to 55 mg/m(3) DDVP showed significantly decreased respiratory frequency and significantly increased tidal volume with no significant changes in minute ventilation. Similarly, animals exposed to 75 mg/m(3) DDVP showed significantly decreased respiratory frequency along with significantly increased tidal volume. The decreased respiratory frequency was large enough in the high exposure group to offset the increased tidal volume. This effect resulted in significantly decreased minute ventilation by the end of exposure, which remained attenuated 10 min after exposure. An analysis of whole-blood cholinesterase activity revealed significantly decreased activity for both acetylcholinesterase (AChE) and butyl-cholinesterase (BChE). Peak inhibition occurred for both enzymes at the end of exposure for all three concentrations and rapidly recovered within several minutes of exposure. Analysis of blood samples using gas chromatography-mass spectroscopy (GC-MS) revealed that minute ventilation may only play a minimal role in the dosimetry of inhaled DDVP vapor.
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Affiliation(s)
- James T Taylor
- National Academy of Sciences-National Research Council, Washington, DC, USA.
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14
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Abstract
A novel physical perspective of molecular interactions within the cytoskeleton of the airway smooth muscle cell may help to explain why the most efficacious of all known bronchodilatory agencies-a simple deep inspiration-becomes abrogated during the spontaneous asthma attack and leads thereby to excessive airway narrowing. This perspective invites us to think of airway smooth muscle not only biochemically as a nidus of traditional cell signaling and immune modulation or mechanically as a motor for generation of active forces but also physically as a phase of soft condensed matter that can restrict airway stretch and dilation. This is perhaps a risky path and is surely an unconventional one, but it is where the trail of evidence leads. This line of investigation is unlikely by itself to provide an asthma cure but will lead to a new conceptual framework without which novel pathways, unsuspected phase transitions, and unanticipated mechanisms of action of target molecules would almost surely remain hidden. Glassy dynamics of the cytoskeleton are likely to be important in a wide range of biological functions and disease processes, but had it not been for their preeminent role in bronchospasm, they might never have been discovered.
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15
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Force fluctuation-induced relengthening of acetylcholine-contracted airway smooth muscle. Ann Am Thorac Soc 2008; 5:68-72. [PMID: 18094087 DOI: 10.1513/pats.200705-058vs] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Superimposition of force fluctuations on contracted tracheal smooth muscle (TSM) has been used to simulate normal breathing. Breathing has been shown to reverse lung resistance of individuals without asthma and animals given methacholine to contract their airways; computed tomography scans also demonstrated bronchial dilation after a deep inhalation in normal volunteers. This reversal of airway resistance and bronchial constriction are absent (or much diminished) in individuals with asthma. Many studies have demonstrated that superimposition of force oscillations on contracted airway smooth muscle results in substantial smooth muscle lengthening. Subsequent studies have shown that this force fluctuation-induced relengthening (FFIR) is a physiologically regulated phenomenon. We hypothesized that actin filament length in the smooth muscle of the airways regulates FFIR of contracted tissues. We based this hypothesis on the observations that bovine TSM strips contracted using acetylcholine (ACh) demonstrated amplitude-dependent FFIR that was sensitive to mitogen-activated protein kinase (p38 MAPK) inhibition- an upstream regulator of actin filament assembly. We demonstrated latrunculin B (sequesters actin monomers thus preventing their assimilation into filaments resulting in shorter filaments) greatly increases FFIR and jasplakinolide (an actin filament stabilizer) prevents the effects of latrunculin B incubation on strips of contracted canine TSM. We suspect that p38 MAPK inhibition and latrunculin B predispose to shorter actin filaments. These studies suggest that actin filament length may be a key determinant of airway smooth muscle relengthening and perhaps breathing-induced reversal of agonist-induced airway constriction.
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16
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Gil FR, Lauzon AM. Smooth muscle molecular mechanics in airway hyperresponsiveness and asthma. Can J Physiol Pharmacol 2007; 85:133-40. [PMID: 17487252 DOI: 10.1139/y06-096] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Asthma is a respiratory disorder characterized by airway inflammation and hyperresponsiveness associated with reversible airway obstruction. The relative contributions of airway hyperresponsiveness and inflammation are still debated, but ultimately, airway narrowing mediated by airway smooth muscle contraction is the final pathway to asthma. Considerable effort has been devoted towards identifying the factors that lead to the airway smooth muscle hypercontractility observed in asthma, and this will be the focus of this review. Airway remodeling has been observed in severe and fatal asthma. However, it is unclear whether remodeling plays a protective role or worsens airway responsiveness. Smooth muscle plasticity is a mechanism likely implicated in asthma, whereby contractile filament rearrangements lead to maximal force production, independent of muscle length. Increased smooth muscle rate of shortening via altered signaling pathways or altered contractile protein expression has been demonstrated in asthma and in numerous models of airway hyperresponsiveness. Increased rate of shortening is implicated in counteracting the relaxing effect of tidal breathing and deep inspirations, thereby creating a contracted airway smooth muscle steady-state. Further studies are therefore required to understand the numerous mechanisms leading to the airway hyperresponsiveness observed in asthma as well as their multiple interactions.
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Affiliation(s)
- Fulvio R Gil
- Meakins-Christie Laboratories, McGill University, 3626 St-Urbain Street, Montréal, QC H2X 2P2, Canada
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