Selected Contribution: Mechanical strain increases force production and calcium sensitivity in cultured airway smooth muscle cells

2000 ◽  
Vol 89 (5) ◽  
pp. 2092-2098 ◽  
Author(s):  
Paul G. Smith ◽  
Chaity Roy ◽  
Steven Fisher ◽  
Qi-Quan Huang ◽  
Frank Brozovich
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Airway Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Force Production ◽  
Muscle Cells ◽  
Calcium Sensitivity ◽  
Airway Smooth Muscle Cells ◽  
Maximal Force

Cultured airway smooth muscle cells subjected to cyclic deformational strain have increased cell content of myosin light chain kinase (MLCK) and myosin and increased formation of actin filaments. To determine how these changes may increase cell contractility, we measured isometric force production with changes in cytosolic calcium in individual permeabilized cells. The pCa for 50% maximal force production was 6.6 ± 0.4 in the strain cells compared with 5.9 ± 0.3 in control cells, signifying increased calcium sensitivity in strain cells. Maximal force production was also greater in strain cells (8.6 ± 2.9 vs. 5.7 ± 3.1 μN). The increased maximal force production in strain cells persisted after irreversible thiophosphorylation of myosin light chain, signifying that increased force could not be explained by differences in myosin light chain phosphorylation. Cells strained for brief periods sufficient to increase cytoskeletal organization but insufficient to increase contractile protein content also produced more force, suggesting that strain-induced cytoskeletal reorganization also increases force production.

Serum deprivation induces a unique hypercontractile phenotype of cultured smooth muscle cells

1998 ◽  
Vol 274 (5) ◽  
pp. C1206-C1214 ◽  
Author(s):  
Xuefei Ma ◽  
Ying Wang ◽  
Newman L. Stephens
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Cultured Cells ◽  
Muscle Cells ◽  
Serum Deprivation ◽  
Airway Smooth Muscle Cells ◽  
Shortening Velocity ◽  
Isolated Cells

Chronic asthma is characterized by hypertrophy and hyperplasia of airway smooth muscle cells (SMC) that limit airflow by a geometric effect. Whether contractility of airway SMC is altered is not clear. Cultured cells were used as a model of hyperplasia. Phenotypic changes seen indicated conversion to a synthetic, weakly contractile type. At confluence, although limited reversal of protein changes was seen, no restoration in contractility occurred. Phenotypic modulation of postconfluent cultured airway SMC under prolonged serum deprivation (arrested cells) is reported here. Two phenotypically distinct groups of cells were identified in primary airway SMC cultures: 1) elongated spindle-shaped cells, which expressed large amounts of smooth muscle contractile and regulatory proteins, and 2) flat and stellate cells, which expressed very little. The first group showed a surprising shortening capacity and a velocity that was even greater than that of the freshly isolated cells, whereas the second group became spherical and noncontractile. Even more surprising was that the myosin heavy chain (MHC) isoform (SM-B) generally said to be associated with the higher shortening velocity disappeared from the cell, while the content of the key rate-limiting regulating enzyme, myosin light chain kinase (MLCK), increased 30-fold. We conclude that a functional, contractile phenotype of airway SMC can be obtained by prolonged serum deprivation. We speculate that the increased contractility could be the result of increased phosphorylation of the 20-kDa myosin light chain resulting from increased content of smooth muscle MLCK rather than any increase in endogenous MHC ATPase activity. This model may be useful for study of SMC differentiation and contraction.

Mechanical strain increases velocity and extent of shortening in cultured airway smooth muscle cells

1999 ◽  
Vol 277 (2) ◽  
pp. L343-L348 ◽  
Author(s):  
Paul G. Smith ◽  
Chaity Roy ◽  
Jamie Dreger ◽  
Frank Brozovich
Keyword(s):  
Smooth Muscle ◽  
Mechanical Stress ◽  
Airway Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Mechanical Strain ◽  
Airway Smooth Muscle Cells ◽  
Maximal Velocity ◽  
Cell Contractility ◽  
Cell Shortening

Abnormal mechanical stress on lung tissue is associated with increased mass and contractility of airway smooth muscle (ASM). We have reported that cultured ASM cells subjected to cyclic strain exhibit increased myosin light chain kinase (MLCK) and stress filaments. Increased MLCK may increase contractile velocity, whereas increased stress filaments could impede cell shortening by increasing the cell’s internal load. To study strain-induced changes in cell contractility, the time course of shortening of individual cells exposed to 90 mM KCl was recorded. Length vs. time plots revealed significantly greater maximal velocity of shortening in strain cells than control (no strain). This correlated with an increase in MLCK and myosin light chain phosphorylation measured in strain cells in separate experiments. The extent of cell shortening tended to be greater in the strain cells so that increased impedance to shortening was not detected. Mechanical stress may therefore increase the contractility of ASM by increasing the content of MLCK.

Sign in / Sign up

Export Citation Format

Share Document