scholarly journals Emergence of airway smooth muscle functions related to structural malleability

2011 ◽  
Vol 110 (4) ◽  
pp. 1130-1135 ◽  
Author(s):  
Chun Y. Seow ◽  
Jeffrey J. Fredberg
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Molecular Interactions ◽  
Indirect Evidence ◽  
Emergent Properties ◽  
Structural Elements ◽  
Molecular Events ◽  
Cell Dimensions ◽  
Active Interaction ◽  
Force Relationship

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.

On the terminology for describing the length-force relationship and its changes in airway smooth muscle

2004 ◽  
Vol 97 (6) ◽  
pp. 2029-2034 ◽  
Author(s):  
Tony R. Bai ◽  
Jason H. T. Bates ◽  
Vito Brusasco ◽  
Blanca Camoretti-Mercado ◽  
Pasquale Chitano ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Underlying Mechanism ◽  
Force Generation ◽  
Dynamic Nature ◽  
Optimal Length ◽  
Maximal Force ◽  
Reference Length ◽  
Force Relationship

The observation that the length-force relationship in airway smooth muscle can be shifted along the length axis by accommodating the muscle at different lengths has stimulated great interest. In light of the recent understanding of the dynamic nature of length-force relationship, many of our concepts regarding smooth muscle mechanical properties, including the notion that the muscle possesses a unique optimal length that correlates to maximal force generation, are likely to be incorrect. To facilitate accurate and efficient communication among scientists interested in the function of airway smooth muscle, a revised and collectively accepted nomenclature describing the adaptive and dynamic nature of the length-force relationship will be invaluable. Setting aside the issue of underlying mechanism, the purpose of this article is to define terminology that will aid investigators in describing observed phenomena. In particular, we recommend that the term “optimal length” (or any other term implying a unique length that correlates with maximal force generation) for airway smooth muscle be avoided. Instead, the in situ length or an arbitrary but clearly defined reference length should be used. We propose the usage of “length adaptation” to describe the phenomenon whereby the length-force curve of a muscle shifts along the length axis due to accommodation of the muscle at different lengths. We also discuss frequently used terms that do not have commonly accepted definitions that should be used cautiously.

Rat airway smooth muscle cell during actin modulation: rheology and glassy dynamics

2005 ◽  
Vol 289 (6) ◽  
pp. C1388-C1395 ◽  
Author(s):  
Rachel E. Laudadio ◽  
Emil J. Millet ◽  
Ben Fabry ◽  
Steven S. An ◽  
James P. Butler ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Protein Interactions ◽  
Airway Smooth Muscle Cell ◽  
Protein Protein Interactions ◽  
Molecular Events ◽  
Glassy Systems ◽  
Latrunculin A ◽  
Before And After

Although changes of cytoskeleton (CSK) stiffness and friction can be induced by diverse interventions, all mechanical changes reported to date can be scaled onto master relationships that appear to be universal. To assess the limits of the applicability of those master relationships, we focused in the present study on actin and used a panel of actin-manipulating drugs that is much wider than any used previously. We focused on the cultured rat airway smooth muscle (ASM) cell as a model system. Cells were treated with agents that directly modulate the polymerization (jasplakinolide, cytochalasin D, and latrunculin A), branching (genistein), and cross linking (phallacidin and phalloidin oleate) of the actin lattice. Contractile (serotonin, 5-HT) and relaxing (dibutyryl adenosine 3′,5′-cyclic monophosphate, DBcAMP) agonists and a myosin inhibitor (ML-7) were also tested for comparison, because these agents may change the structure of actin indirectly. Using optical magnetic twisting cytometry, we measured elastic and frictional moduli before and after treatment with each agent. Stiffness increased with frequency as a weak power law, and changes of friction paralleled those of stiffness until they approached a Newtonian viscous limit. Despite large differences in the mechanism of action among the interventions, all data collapsed onto master curves that depended on a single parameter. In the context of soft glassy systems, that parameter would correspond to an effective temperature of the cytoskeletal matrix and reflect the effects of molecular crowding and associated molecular trapping. These master relationships demonstrate that when the mechanical properties of the cell change, they are constrained to do so along a special trajectory. Because mechanical characteristics of the cell shadow underlying molecular events, these results imply special constraints on the protein-protein interactions that dominate CSK mechanical properties.

Ultrastructural basis of airway smooth muscle contractionThis article is one of a selection of papers published in the Special Issue on Recent Advances in Asthma Research.

2007 ◽  
Vol 85 (7) ◽  
pp. 659-665 ◽  
Author(s):  
Chun Y. Seow ◽  
Peter D. Paré
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Future Research ◽  
Contractile Apparatus ◽  
Muscle Ultrastructure ◽  
Cell Dimensions ◽  
Sliding Filament Theory ◽  
Selection Of

The sliding filament theory of contraction that was developed for striated muscle is generally believed to be also applicable to smooth muscle. However, the well-organized myofilament lattice (i.e., the sarcomeric structure) found in striated muscle has never been clearly delineated in smooth muscle. There is evidence that the myofilament lattice in some smooth muscles, such as airway smooth muscle, is malleable; it can be reshaped to fit a large range of cell dimensions while the maximal overlap between the contractile filaments is maintained. In this review, some early models of the structurally static contractile apparatus of smooth muscle are described. The focus of the review, however, is on the recent findings supporting a model of structurally dynamic contractile apparatus and cytoskeleton for airway smooth muscle. A list of unanswered questions regarding smooth muscle ultrastructure is also proposed in this review, in the hope that it will provide some guidance for future research.

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