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Zhang W, Wu Y, J Gunst S. Membrane adhesion junctions regulate airway smooth muscle phenotype and function. Physiol Rev 2023; 103:2321-2347. [PMID: 36796098 PMCID: PMC10243546 DOI: 10.1152/physrev.00020.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 02/09/2023] [Accepted: 02/15/2023] [Indexed: 02/18/2023] Open
Abstract
The local environment surrounding airway smooth muscle (ASM) cells has profound effects on the physiological and phenotypic properties of ASM tissues. ASM is continually subjected to the mechanical forces generated during breathing and to the constituents of its surrounding extracellular milieu. The smooth muscle cells within the airways continually modulate their properties to adapt to these changing environmental influences. Smooth muscle cells connect to the extracellular cell matrix (ECM) at membrane adhesion junctions that provide mechanical coupling between smooth muscle cells within the tissue. Membrane adhesion junctions also sense local environmental signals and transduce them to cytoplasmic and nuclear signaling pathways in the ASM cell. Adhesion junctions are composed of clusters of transmembrane integrin proteins that bind to ECM proteins outside the cell and to large multiprotein complexes in the submembranous cytoplasm. Physiological conditions and stimuli from the surrounding ECM are sensed by integrin proteins and transduced by submembranous adhesion complexes to signaling pathways to the cytoskeleton and nucleus. The transmission of information between the local environment of the cells and intracellular processes enables ASM cells to rapidly adapt their physiological properties to modulating influences in their extracellular environment: mechanical and physical forces that impinge on the cell, ECM constituents, local mediators, and metabolites. The structure and molecular organization of adhesion junction complexes and the actin cytoskeleton are dynamic and constantly changing in response to environmental influences. The ability of ASM to rapidly accommodate to the ever-changing conditions and fluctuating physical forces within its local environment is essential for its normal physiological function.
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Affiliation(s)
- Wenwu Zhang
- Department of Anatomy, Cell Biology and Physiology, Indiana University School of Medicine, Indianapolis, Indiana, United States
| | - Yidi Wu
- Department of Anatomy, Cell Biology and Physiology, Indiana University School of Medicine, Indianapolis, Indiana, United States
| | - Susan J Gunst
- Department of Anatomy, Cell Biology and Physiology, Indiana University School of Medicine, Indianapolis, Indiana, United States
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2
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Actomyosin Complex. Subcell Biochem 2022; 99:421-470. [PMID: 36151385 PMCID: PMC9710302 DOI: 10.1007/978-3-031-00793-4_14] [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: 01/03/2023]
Abstract
Formation of cross-bridges between actin and myosin occurs ubiquitously in eukaryotic cells and mediates muscle contraction, intracellular cargo transport, and cytoskeletal remodeling. Myosin motors repeatedly bind to and dissociate from actin filaments in a cycle that transduces the chemical energy from ATP hydrolysis into mechanical force generation. While the general layout of surface elements within the actin-binding interface is conserved among myosin classes, sequence divergence within these motifs alters the specific contacts involved in the actomyosin interaction as well as the kinetics of mechanochemical cycle phases. Additionally, diverse lever arm structures influence the motility and force production of myosin molecules during their actin interactions. The structural differences generated by myosin's molecular evolution have fine-tuned the kinetics of its isoforms and adapted them for their individual cellular roles. In this chapter, we will characterize the structural and biochemical basis of the actin-myosin interaction and explain its relationship with myosin's cellular roles, with emphasis on the structural variation among myosin isoforms that enables their functional specialization. We will also discuss the impact of accessory proteins, such as the troponin-tropomyosin complex and myosin-binding protein C, on the formation and regulation of actomyosin cross-bridges.
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3
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Sieck GC, Dogan M, Young‐Soo H, Osorio Valencia S, Delmotte P. Mechanisms underlying TNFα-induced enhancement of force generation in airway smooth muscle. Physiol Rep 2019; 7:e14220. [PMID: 31512410 PMCID: PMC6739507 DOI: 10.14814/phy2.14220] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 07/29/2019] [Accepted: 08/05/2019] [Indexed: 11/24/2022] Open
Abstract
Airway diseases such as asthma are triggered by inflammation and mediated by proinflammatory cytokines such as tumor necrosis factor alpha (TNFα). Our goal was to systematically examine the potential mechanisms underlying the effect of TNFα on airway smooth muscle (ASM) contractility. Porcine ASM strips were incubated for 24 h with and without TNFα. Exposure to TNFα increased maximum ASM force in response to acetylcholine (Ach), with an increase in ACh sensitivity (hyperreactivity), as reflected by a leftward shift in the dose-response curve (EC50 ). At the EC50 , the [Ca2+ ]cyt response to ACh was similar between TNFα and control ASM, while force increased; thus, Ca2+ sensitivity appeared to increase. Exposure to TNFα increased the basal level of regulatory myosin light chain (rMLC) phosphorylation in ASM; however, the ACh-dependent increase in rMLC phosphorylation was blunted by TNFα with no difference in the extent of rMLC phosphorylation at the EC50 ACh concentration. In TNFα-treated ASM, total actin and myosin heavy chain concentrations increased. TNFα exposure also enhanced the ACh-dependent polymerization of G- to F-actin. The results of this study confirm TNFα-induced hyperreactivity to ACh in porcine ASM. We conclude that the TNFα-induced increase in ASM force, cannot be attributed to an enhanced [Ca2+ ]cyt response or to an increase in rMLC phosphorylation. Instead, TNFα increases Ca2+ sensitivity of ASM force generation due to increased contractile protein content (greater number of contractile units) and enhanced cytoskeletal remodeling (actin polymerization) resulting in increased tethering of contractile elements to the cortical cytoskeleton and force translation to the extracellular matrix.
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Affiliation(s)
- Gary C. Sieck
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
| | - Murat Dogan
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
| | - Han Young‐Soo
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
| | - Sara Osorio Valencia
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
| | - Philippe Delmotte
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
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4
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Brozovich FV, Nicholson CJ, Degen CV, Gao YZ, Aggarwal M, Morgan KG. Mechanisms of Vascular Smooth Muscle Contraction and the Basis for Pharmacologic Treatment of Smooth Muscle Disorders. Pharmacol Rev 2016; 68:476-532. [PMID: 27037223 PMCID: PMC4819215 DOI: 10.1124/pr.115.010652] [Citation(s) in RCA: 298] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The smooth muscle cell directly drives the contraction of the vascular wall and hence regulates the size of the blood vessel lumen. We review here the current understanding of the molecular mechanisms by which agonists, therapeutics, and diseases regulate contractility of the vascular smooth muscle cell and we place this within the context of whole body function. We also discuss the implications for personalized medicine and highlight specific potential target molecules that may provide opportunities for the future development of new therapeutics to regulate vascular function.
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Affiliation(s)
- F V Brozovich
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - C J Nicholson
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - C V Degen
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - Yuan Z Gao
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - M Aggarwal
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - K G Morgan
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
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5
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Liu Y, Wang Y, Shi H, Jia L, Cheng J, Cui W, Li H, Li P, Du J. CARD9 mediates necrotic smooth muscle cell-induced inflammation in macrophages contributing to neointima formation of vein grafts. Cardiovasc Res 2015; 108:148-58. [PMID: 26243429 DOI: 10.1093/cvr/cvv211] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 07/27/2015] [Indexed: 12/11/2022] Open
Abstract
AIMS Inflammation plays an important role in the neointima formation of grafted veins. However, the initiation of inflammation in grafted veins is still unclear. Here, we investigated the role and underlying mechanism of an innate immunity signalling protein, caspase-associated recruitment domain 9 (CARD9) in vein grafts in mice. METHODS AND RESULTS In early murine vein grafts, we observed robust death of smooth muscle cells (SMCs), which was accompanied by infiltration of macrophages and expression of pro-inflammatory cytokines. Meanwhile, SMC necrosis was associated with the expression of pro-inflammatory cytokines in macrophages in vitro. To explore the mediators of necrotic SMC-induced inflammation in grafted veins from mice, we examined the expression of CARD family proteins and found CARD9 highly expressed in infiltrated macrophages of grafted veins. CARD9-knockout (KO) inhibited necrotic SMC-induced pro-inflammatory cytokine expression and NF-κB activation. Furthermore, CARD9-KO suppressed necrotic SMC-induced expression of VEGF in macrophages. Finally, CARD9-KO decreased neointima formation of grafted veins in mice. CONCLUSION The innate immune protein CARD9 in macrophages may mediate necrotic SMC-induced inflammation by activating NF-κB and contributed to neointima formation in the vein grafts.
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Affiliation(s)
- Yan Liu
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
| | - Ying Wang
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
| | - Hongtao Shi
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
| | - Lixin Jia
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
| | - Jizhong Cheng
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
| | - Wei Cui
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
| | - Huihua Li
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
| | - Ping Li
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
| | - Jie Du
- Beijing Anzhen Hospital, Capital Medical University, The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing Collaborative Innovative Research Center for Cardiovascular Diseases, Beijing 100029, China
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6
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Lan B, Deng L, Donovan GM, Chin LYM, Syyong HT, Wang L, Zhang J, Pascoe CD, Norris BA, Liu JCY, Swyngedouw NE, Banaem SM, Paré PD, Seow CY. Force maintenance and myosin filament assembly regulated by Rho-kinase in airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 2014; 308:L1-10. [PMID: 25305246 DOI: 10.1152/ajplung.00222.2014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Smooth muscle contraction can be divided into two phases: the initial contraction determines the amount of developed force and the second phase determines how well the force is maintained. The initial phase is primarily due to activation of actomyosin interaction and is relatively well understood, whereas the second phase remains poorly understood. Force maintenance in the sustained phase can be disrupted by strains applied to the muscle; the strain causes actomyosin cross-bridges to detach and also the cytoskeletal structure to disassemble in a process known as fluidization, for which the underlying mechanism is largely unknown. In the present study we investigated the ability of airway smooth muscle to maintain force after the initial phase of contraction. Specifically, we examined the roles of Rho-kinase and protein kinase C (PKC) in force maintenance. We found that for the same degree of initial force inhibition, Rho-kinase substantially reduced the muscle's ability to sustain force under static conditions, whereas inhibition of PKC had a minimal effect on sustaining force. Under oscillatory strain, Rho-kinase inhibition caused further decline in force, but again, PKC inhibition had a minimal effect. We also found that Rho-kinase inhibition led to a decrease in the myosin filament mass in the muscle cells, suggesting that one of the functions of Rho-kinase is to stabilize myosin filaments. The results also suggest that dissolution of myosin filaments may be one of the mechanisms underlying the phenomenon of fluidization. These findings can shed light on the mechanism underlying deep inspiration induced bronchodilation.
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Affiliation(s)
- Bo Lan
- Bioengineering College, Chongqing University, Chongqing, China; Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China; and Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Linhong Deng
- Bioengineering College, Chongqing University, Chongqing, China; Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China; and
| | - Graham M Donovan
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| | - Leslie Y M Chin
- Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Harley T Syyong
- Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Lu Wang
- Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Jenny Zhang
- Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Christopher D Pascoe
- Department of Medicine, University of British Columbia, Vancouver, Canada; Vancouver, Canada; Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Brandon A Norris
- Department of Medicine, University of British Columbia, Vancouver, Canada; Vancouver, Canada; Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Jeffrey C-Y Liu
- Department of Medicine, University of British Columbia, Vancouver, Canada; Vancouver, Canada; Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Nicholas E Swyngedouw
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada; Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Saleha M Banaem
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada; Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Peter D Paré
- Department of Medicine, University of British Columbia, Vancouver, Canada; Vancouver, Canada; Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
| | - Chun Y Seow
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada; Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, Canada
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7
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Prakash YS. Airway smooth muscle in airway reactivity and remodeling: what have we learned? Am J Physiol Lung Cell Mol Physiol 2013; 305:L912-33. [PMID: 24142517 PMCID: PMC3882535 DOI: 10.1152/ajplung.00259.2013] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 10/12/2013] [Indexed: 12/12/2022] Open
Abstract
It is now established that airway smooth muscle (ASM) has roles in determining airway structure and function, well beyond that as the major contractile element. Indeed, changes in ASM function are central to the manifestation of allergic, inflammatory, and fibrotic airway diseases in both children and adults, as well as to airway responses to local and environmental exposures. Emerging evidence points to novel signaling mechanisms within ASM cells of different species that serve to control diverse features, including 1) [Ca(2+)]i contractility and relaxation, 2) cell proliferation and apoptosis, 3) production and modulation of extracellular components, and 4) release of pro- vs. anti-inflammatory mediators and factors that regulate immunity as well as the function of other airway cell types, such as epithelium, fibroblasts, and nerves. These diverse effects of ASM "activity" result in modulation of bronchoconstriction vs. bronchodilation relevant to airway hyperresponsiveness, airway thickening, and fibrosis that influence compliance. This perspective highlights recent discoveries that reveal the central role of ASM in this regard and helps set the stage for future research toward understanding the pathways regulating ASM and, in turn, the influence of ASM on airway structure and function. Such exploration is key to development of novel therapeutic strategies that influence the pathophysiology of diseases such as asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis.
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Affiliation(s)
- Y S Prakash
- Dept. of Anesthesiology, Mayo Clinic, 4-184 W Jos SMH, 200 First St. SW, Rochester, MN 55905.
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8
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Seow CY. Passive stiffness of airway smooth muscle: the next target for improving airway distensibility and treatment for asthma? Pulm Pharmacol Ther 2012; 26:37-41. [PMID: 22776694 DOI: 10.1016/j.pupt.2012.06.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 06/25/2012] [Accepted: 06/27/2012] [Indexed: 10/28/2022]
Abstract
Reduced airway distensibility due to increased airway stiffness is a characteristic of asthma. Airway stiffness is determined by the property and structural organization of the various elements of the airway wall, and is often divided into active and passive components. Active stiffness is thought to be associated with activation of muscle cells in the airway wall. This component of stiffness can be inhibited when active force produced by the muscle is abolished. Passive stiffness, on the other hand, is thought to stem from non-muscle component of the airway wall, especially the collagen/elastin fibrous network of the extracellular matrix within which the muscle cells are embedded. In this brief review, the notion that passive stiffness is exclusively extracellular in origin is challenged. Recent evidence suggests that a substantial portion of the passive stiffness of an in vitro preparation of tracheal smooth muscle is calcium sensitive and is regulated by Rho-kinase, although the underlying mechanism and the details of regulation for the development of this intracellular passive stiffness are still largely unknown. To reduce airway stiffness different lines of attack must be tailored to different components of the stiffness. The regulatable passive stiffness is distinct from the relatively permanent stiffness of the extracellular matrix and the stiffness associated with active muscle contraction. To improve airway distensibility during asthma exacerbation, a comprehensive approach to reduce overall airway stiffness should therefore include a strategy for targeting the regulatable passive stiffness.
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Affiliation(s)
- Chun Y Seow
- Department of Pathology and Laboratory Medicine, The James Hogg Research Centre/St. Paul's Hospital, University of British Columbia, 1081 Burrard Street, Rm. 166, Vancouver, BC V6Z 1Y6, Canada.
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9
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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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10
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Speich JE, Southern JB, Henderson S, Wilson CW, Klausner AP, Ratz PH. Adjustable passive stiffness in mouse bladder: regulated by Rho kinase and elevated following partial bladder outlet obstruction. Am J Physiol Renal Physiol 2011; 302:F967-76. [PMID: 22205227 DOI: 10.1152/ajprenal.00177.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Detrusor smooth muscle (DSM) contributes to bladder wall tension during filling, and bladder wall deformation affects the signaling system that leads to urgency. The length-passive tension (L-T(p)) relationship in rabbit DSM can adapt with length changes over time and exhibits adjustable passive stiffness (APS) characterized by a L-T(p) curve that is a function of both activation and strain history. Muscle activation with KCl, carbachol (CCh), or prostaglandin E(2) at short muscle lengths can increase APS that is revealed by elevated pseudo-steady-state T(p) at longer lengths compared with prior T(p) measurements at those lengths, and APS generation is inhibited by the Rho Kinase (ROCK) inhibitor H-1152. In the current study, mouse bladder strips exhibited both KCl- and CCh-induced APS. Whole mouse bladders demonstrated APS which was measured as an increase in pressure during passive filling in calcium-free solution following CCh precontraction compared with pressure during filling without precontraction. In addition, CCh-induced APS in whole mouse bladder was inhibited by H-1152, indicating that ROCK activity may regulate bladder compliance during filling. Furthermore, APS in whole mouse bladder was elevated 2 wk after partial bladder outlet obstruction, suggesting that APS may be relevant in diseases affecting bladder mechanics. The presence of APS in mouse bladder will permit future studies of APS regulatory pathways and potential alterations of APS in disease models using knockout transgenetic mice.
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Affiliation(s)
- John E Speich
- Mechanical and Nuclear Engineering, Virginia Commonwealth University, 401 West Main St., Richmond, VA 23284-3015, USA.
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11
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Ijpma G, Lauzon AM. The rise of passive airway smooth muscle mechanics. J Appl Physiol (1985) 2011; 112:335-6. [PMID: 22052866 DOI: 10.1152/japplphysiol.01338.2011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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12
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Raqeeb A, Jiao Y, Syyong HT, Paré PD, Seow CY. Regulatable stiffness in relaxed airway smooth muscle: a target for asthma treatment? J Appl Physiol (1985) 2011; 112:337-46. [PMID: 21998272 DOI: 10.1152/japplphysiol.01036.2011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The airway smooth muscle (ASM) layer within the airway wall modulates airway diameter and distensibility. Even in the relaxed state, the ASM layer possesses finite stiffness and limits the extent of airway distension by the radial force generated by parenchymal tethers and transmural pressure. Airway stiffness has often been attributed to passive elements, such as the extracellular matrix in the lamina reticularis, adventitia, and the smooth muscle layer that cannot be rapidly modulated by drug intervention such as ASM relaxation by β-agonists. In this study, we describe a calcium-sensitive component of ASM stiffness mediated through the Rho-kinase signaling pathway. The stiffness of ovine tracheal smooth muscle was assessed in the relaxed state under the following conditions: 1) in physiological saline solution (Krebs solution) with normal calcium concentration; 2) in calcium-free Krebs with 2 mM EGTA; 3) in Krebs with calcium entry blocker (SKF-96365); 4) in Krebs with myosin light chain kinase inhibitor (ML-7); and 5) in Krebs with Rho-kinase inhibitor (Y-27632). It was found that a substantial portion of the passive stiffness could be abolished when intracellular calcium was removed; this calcium-sensitive stiffness appeared to stem from intracellular source and was not sensitive to ML-7 inhibition of myosin light chain phosphorylation, but was sensitive to Y-27632 inhibition of Rho kinase. The results suggest that airway stiffness can be readily modulated by targeting the calcium-sensitive component of the passive stiffness within the muscle layer.
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Affiliation(s)
- Abdul Raqeeb
- James Hogg Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
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13
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Syyong HT, Raqeeb A, Paré PD, Seow CY. Time course of isotonic shortening and the underlying contraction mechanism in airway smooth muscle. J Appl Physiol (1985) 2011; 111:642-56. [DOI: 10.1152/japplphysiol.00085.2011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the structure of the contractile unit in smooth muscle is poorly understood, some of the mechanical properties of the muscle suggest that a sliding-filament mechanism, similar to that in striated muscle, is also operative in smooth muscle. To test the applicability of this mechanism to smooth muscle function, we have constructed a mathematical model based on a hypothetical structure of the smooth muscle contractile unit: a side-polar myosin filament sandwiched by actin filaments, each attached to the equivalent of a Z disk. Model prediction of isotonic shortening as a function of time was compared with data from experiments using ovine tracheal smooth muscle. After equilibration and establishment of in situ length, the muscle was stimulated with ACh (100 μM) until force reached a plateau. The muscle was then allowed to shorten isotonically against various loads. From the experimental records, length-force and force-velocity relationships were obtained. Integration of the hyperbolic force-velocity relationship and the linear length-force relationship yielded an exponential function that approximated the time course of isotonic shortening generated by the modeled sliding-filament mechanism. However, to obtain an accurate fit, it was necessary to incorporate a viscoelastic element in series with the sliding-filament mechanism. The results suggest that a large portion of the shortening is due to filament sliding associated with muscle activation and that a small portion is due to continued deformation associated with an element that shows viscoelastic or power-law creep after a step change in force.
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Affiliation(s)
| | | | - Peter D. Paré
- James Hogg Research Centre/St. Paul's Hospital,
- Department of Medicine, and
| | - Chun Y. Seow
- James Hogg Research Centre/St. Paul's Hospital,
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Seow CY, Fredberg JJ. Emergence of airway smooth muscle functions related to structural malleability. J Appl Physiol (1985) 2010; 110:1130-5. [PMID: 21127211 DOI: 10.1152/japplphysiol.01192.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The function of a complex system such as a smooth muscle cell is the result of the active interaction among molecules and molecular aggregates. Emergent macroscopic manifestations of these molecular interactions, such as the length-force relationship and its associated length adaptation, are well documented, but the molecular constituents and organization that give rise to these emergent muscle behaviors remain largely unknown. In this minireview, we describe emergent properties of airway smooth muscle that seem to have originated from inherent fragility of the cellular structures, which has been increasingly recognized as a unique and important smooth muscle attribute. We also describe molecular interactions (based on direct and indirect evidence) that may confer malleability on fragile structural elements that in turn may allow the muscle to adapt to large and frequent changes in cell dimensions. Understanding how smooth muscle works may hinge on how well we can relate molecular events to its emergent macroscopic functions.
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Affiliation(s)
- Chun Y Seow
- Department of Pathology, James Hogg Research Centre, University of British Columbia, Vancouver, British Columbia, Canada.
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