scholarly journals Increased mechanical strain imposed on murine lungs during ventilation in vivo depresses airway responsiveness and activation of protein kinase Akt

2013 ◽  
Vol 114 (11) ◽  
pp. 1506-1510 ◽  
Author(s):  
Z. Xue ◽  
W. Zhang ◽  
L. P. Desai ◽  
H. Gao ◽  
S. J. Gunst ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Mechanical Strain ◽  
Airway Responsiveness ◽  
Negative Regulator ◽  
High Peep ◽  
Mechanical Loads ◽  
Akt Activation ◽  
Isolated Lung

Continuous positive airway pressure (CPAP) administered to tracheostomized rabbits and ferrets for 4 days or 2 wk suppresses bronchial reactivity in vivo and suppresses airway reactivity in lobes and tracheal segments isolated from these animals. In vitro studies of canine tracheal smooth muscle tissues indicate that mechanical loading suppresses the activation of the growth regulatory kinase, Akt, and that Akt is a negative regulator of smooth muscle differentiation. The transduction of mechanical signals in the tracheal tissues in vitro is mediated by integrin-associated adhesion complexes. To determine whether airway responsiveness and Akt activation are modulated by mechanical loads applied for short time periods to the airways of living animals in vivo, mice were mechanically ventilated for 2 h with high (5 cmH2O) or low (0–1 cmH2O) positive end-expiratory pressure (PEEP) and then ventilated at low PEEP for 30 min. Ventilation of mice with PEEP in vivo for 2 h depressed airway responsiveness to methacholine measured in vivo subsequent to the PEEP treatment. Airway narrowing in vitro in intraparenchymal airways in isolated lung slices and contractile responses of isolated tracheal segments in vitro were suppressed for at least 6 h subsequent to the in vivo exposure to PEEP. Tracheal segments isolated from high PEEP-treated mice exhibited significantly lower levels of Akt activation than tracheae from low PEEP-treated mice. The results indicate that mechanical loads imposed in vivo result in physiological and biochemical changes in the airway tissues after a relatively short 2-h period of in vivo loading.

Airway smooth muscle tone increases airway responsiveness in healthy young adults

2017 ◽  
Vol 312 (3) ◽  
pp. L348-L357 ◽  
Author(s):  
Morgan Gazzola ◽  
Katherine Lortie ◽  
Cyndi Henry ◽  
Samuel Mailhot-Larouche ◽  
David G. Chapman ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Airway Responsiveness ◽  
High Dose ◽  
Forced Oscillation Technique ◽  
Single High Dose ◽  
Healthy Humans

Force adaptation, a process whereby sustained spasmogenic activation (viz., tone) of airway smooth muscle (ASM) increases its contractile capacity, has been reported in isolated ASM tissues in vitro, as well as in mice in vivo. The objective of the present study was to assess the effect of tone on airway responsiveness in humans. Ten healthy volunteers underwent methacholine challenge on two occasions. One challenge consisted of six serial doses of saline followed by a single high dose of methacholine. The other consisted of six low doses of methacholine 5 min apart followed by a higher dose. The cumulative dose was identical for both challenges. After both methacholine challenges, subjects took a deep inspiration (DI) to total lung capacity as another way to probe ASM mechanics. Responses to methacholine and the DI were measured using a multifrequency forced oscillation technique. Compared with a single high dose, the challenge preceded by tone led to an elevated response measured by respiratory system resistance (Rrs) and reactance at 5 Hz. However, there was no difference in the increase in Rrs at 19 Hz, suggesting a predominant effect on smaller airways. Increased tone also reduced the efficacy of DI, measured by an attenuated maximal dilation during the DI and an increased renarrowing post-DI. We conclude that ASM tone increases small airway responsiveness to inhaled methacholine and reduces the effectiveness of DI in healthy humans. This suggests that force adaptation may contribute to airway hyperresponsiveness and the reduced bronchodilatory effect of DI in asthma.

scholarly journals Molecular Mechanisms for the Mechanical Modulation of Airway Responsiveness

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Wenwu Zhang ◽  
Susan J. Gunst
Keyword(s):  
Extracellular Matrix ◽  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Actin Polymerization ◽  
Molecular Mechanisms ◽  
Airway Responsiveness ◽  
Small Gtpase ◽  
Cortical Actin

The smooth muscle of the airways is exposed to continuously changing mechanical forces during normal breathing. The mechanical oscillations that occur during breathing have profound effects on airway tone and airway responsiveness both in experimental animals and humans in vivo and in isolated airway tissues in vitro. Experimental evidence suggests that alterations in the contractile and mechanical properties of airway smooth muscle tissues caused by mechanical perturbations result from adaptive changes in the organization of the cytoskeletal architecture of the smooth muscle cell. The cytoskeleton is a dynamic structure that undergoes rapid reorganization in response to external mechanical and pharmacologic stimuli. Contractile stimulation initiates the assembly of cytoskeletal/extracellular matrix adhesion complex proteins into large macromolecular signaling complexes (adhesomes) that undergo activation to mediate the polymerization and reorganization of a submembranous network of actin filaments at the cortex of the cell. Cortical actin polymerization is catalyzed by Neuronal-Wiskott–Aldrich syndrome protein (N-WASP) and the Arp2/3 complex, which are activated by pathways regulated by paxillin and the small GTPase, cdc42. These processes create a strong and rigid cytoskeletal framework that may serve to strengthen the membrane for the transmission of force generated by the contractile apparatus to the extracellular matrix, and to enable the adaptation of smooth muscle cells to mechanical stresses. This model for the regulation of airway smooth muscle function can provide novel perspectives to explain the normal physiologic behavior of the airways and pathophysiologic properties of the airways in asthma.

Increased in vitro airway responsiveness in sheep following repeated exposure to antigen in vivo

1985 ◽  
Vol 59 (6) ◽  
pp. 1874-1878 ◽  
Author(s):  
E. M. Wagner ◽  
S. R. Kleeberger ◽  
E. W. Spannhake ◽  
G. K. Adams
Keyword(s):  
Smooth Muscle ◽  
Thromboxane A2 ◽  
Airway Responsiveness ◽  
Tracheal Smooth Muscle ◽  
Prostaglandin F2 Alpha ◽  
Peripheral Airway ◽  
Exposure In Vivo ◽  
Thromboxane A2 Analogue

We have studied the effect of repeated in vivo antigen exposure on in vitro airway responsiveness in sensitized sheep. Fourteen sheep underwent five biweekly exposures to aerosolized Ascaris suum antigen or saline. Following this exposure regimen, the animals were killed and tracheal smooth muscle and lung parenchymal strips were prepared for in vitro studies of isometric contraction in response to histamine, methacholine, prostaglandin F2 alpha, and a thromboxane A2 analogue. No alteration in tracheal smooth muscle responsiveness was observed between saline- and antigen-exposed tissue. In contrast, by use of lung parenchymal strips as an index of peripheral airway responsiveness, significant increases in responsiveness to histamine and a thromboxane A2 analogue (10(-6) and 10(-5) M) were observed in antigen-exposed tissue compared with saline controls. These results demonstrate that repeated antigen exposure in vivo selectively increase the responsiveness of peripheral lung smooth muscle to certain chemical mediators of anaphylaxis.

scholarly journals Comparison of in vivo airway responsiveness and in vitro smooth muscle sensitivity to methacholine in man.

Thorax ◽  
1984 ◽  
Vol 39 (11) ◽  
pp. 837-843 ◽  
Author(s):  
J A Roberts ◽  
D Raeburn ◽  
I W Rodger ◽  
N C Thomson
Keyword(s):  
Smooth Muscle ◽  
Airway Responsiveness

Chronic inflation of ferret lungs with CPAP reduces airway smooth muscle contractility in vivo and in vitro

2008 ◽  
Vol 104 (3) ◽  
pp. 610-615 ◽  
Author(s):  
Z. Xue ◽  
L. Zhang ◽  
Y. Liu ◽  
S. J. Gunst ◽  
R. S. Tepper
Keyword(s):  
Smooth Muscle ◽  
Mechanical Stress ◽  
Chronic Stress ◽  
Airway Smooth Muscle ◽  
Structural Changes ◽  
Airway Responsiveness ◽  
Wall Structure ◽  
Airway Wall

The mechanical stress imposed on the lungs during breathing is an important modulator of airway responsiveness in vivo. Our recent study demonstrated that continuous positive airway pressure applied to the lungs of nonanesthetized, tracheotomized rabbits for 4 days decreased lower respiratory system responsiveness to challenge with ACh (Xue Z, Zhang L, Ramchandani R, Liu Y, Antony VB, Gunst SJ, Tepper RS. J. Appl Physiol 99: 677–682, 2005). In addition, airway segments excised from the lungs of these animals and studied in vitro exhibited reduced contractility. However, the mechanism for this reduction in contractility was not determined. The stress-induced decrease in airway responsiveness could have resulted from alterations in the excitation-contraction coupling mechanisms of the smooth muscle cells, or it might reflect changes in the structure and/or composition of the airway wall tissues. In the present study, we assessed the effect of prolonged chronic stress of the lungs in vivo on airway smooth muscle force generation, myosin light chain phosphorylation, and airway wall structure. To enhance the potential development of stress-induced structural changes, we applied mechanical stress for a prolonged period of time of 2–3 wk. Our results demonstrate a direct connection between the decreased airway responsiveness caused by chronic mechanical stress of the lungs in vivo and a persistent decrease in contractile protein activation in the airway smooth muscle isolated from those lungs. The chronic stress also caused an increase in airway size but no detectable changes in the composition of the airway wall.

Airway closure with high PEEP in vivo

2000 ◽  
Vol 89 (3) ◽  
pp. 956-960 ◽  
Author(s):  
Robert H. Brown ◽  
Wayne Mitzner
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Functional Residual Capacity ◽  
Lung Volume ◽  
Transpulmonary Pressure ◽  
High Peep ◽  
Airway Closure ◽  
Residual Capacity

When airway smooth muscle is contracted in vitro, the airway lumen continues to narrow with increasing concentrations of agonist until complete airway closure occurs. Although there remains some controversy regarding whether airways can close in vivo, recent work has clearly demonstrated that, if the airway is sufficiently stimulated with contractile agonists, complete closure of even large cartilaginous conducting airways can readily occur with the lung at functional residual capacity (Brown RH and Mitzner W. J Appl Physiol 85: 2012–2017, 1998). This result suggests that the tethering of airways in situ by parenchymal attachments is small at functional residual capacity. However, at lung volumes above functional residual capacity, the outward tethering of airways should increase, because both the parenchymal shear modulus and tethering forces increase in proportion to the transpulmonary pressure. In the present study, we tested whether we could prevent airway closure in vivo by increasing lung volume with positive end-expiratory pressure (PEEP). Airway smooth muscle was stimulated with increasing methacholine doses delivered directly to airway smooth muscle at three levels of PEEP (0, 6, and 10 cmH2O). Our results show that increased lung volume shifted the airway methacholine dose-response curve to the right, but, in many airways in most animals, airway closure still occurred even at the highest levels of PEEP.

Pharmacological characterization of airway smooth muscle responses to antigen in ascaris-sensitive dogs

1986 ◽  
Vol 64 (11) ◽  
pp. 1361-1367 ◽  
Author(s):  
M. S. Kannan ◽  
C. Davis ◽  
A. Sankaranarayanan ◽  
A. R. C. Ladenius ◽  
L. Kannan
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Smooth Muscle Contraction ◽  
Airway Responsiveness ◽  
Antigen Challenge ◽  
Minor Role ◽  
Pharmacological Characterization ◽  
A Minor

The dog model of ascaris airway sensitivity was chosen because of its frequency and its immunologic similarity to the human atopic asthmatic state. We studied the mediators of the antigen-induced airway response in vitro and the alterations in the in vivo and in vitro responsiveness to spasmogens evoked by antigen challenge. A myogenic basis of altered reactivity was suggested by the following: (i) tetrodotoxin-insensitive spontaneous active tone; (ii) phasic contractions of airway smooth muscle; and (iii) responsiveness to leukotrienes C4 and D4. The pharmacologic characteristics of the antigen-induced airway smooth muscle contraction in vitro were similar to those induced by arachidonic acid and the leukotrienes only in some respects but were clearly different from those induced by compound 48/80. This suggested a predominant role for arachidonate lipoxygenase products. Histamine apeared to play a minor role in the antigen response. Comparisons were made between antigen-induced responses of actively and passively sensitized airways tissues. In the latter, histamine release appeared to contribute to the initial antigen-induced contraction and, unlike in actively sensitized airways, the responses were easily densensitized to repeated challenge. Alterations of airway responsiveness were demonstrated in vivo to acetylcholine and 5-HT following antigen challenge of highly ascaris-sensitive dogs. In vitro studies of passively sensitized muscle showed selectively enhanced response to 5-HT following antigen challenge. These studies suport the presence of altered myogenic properties of airway smooth muscle and nonspecific increased airway responsiveness in this animal model.

scholarly journals Ndfip1 regulates nuclear Pten import in vivo to promote neuronal survival following cerebral ischemia

2012 ◽  
Vol 196 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Jason Howitt ◽  
Jenny Lackovic ◽  
Ley-Hian Low ◽  
Adam Naguib ◽  
Alison Macintyre ◽  
...  
Keyword(s):  
Cerebral Ischemia ◽  
Tumor Suppression ◽  
Negative Regulator ◽  
Nuclear Entry ◽  
Interacting Protein ◽  
Akt Activation ◽  
Phosphorylated Akt ◽  
Phosphatase And Tensin Homologue

PTEN (phosphatase and tensin homologue deleted on chromosome TEN) is the major negative regulator of phosphatidylinositol 3-kinase signaling and has cell-specific functions including tumor suppression. Nuclear localization of PTEN is vital for tumor suppression; however, outside of cancer, the molecular and physiological events driving PTEN nuclear entry are unknown. In this paper, we demonstrate that cytoplasmic Pten was translocated into the nuclei of neurons after cerebral ischemia in mice. Critically, this transport event was dependent on a surge in the Nedd4 family–interacting protein 1 (Ndfip1), as neurons in Ndfip1-deficient mice failed to import Pten. Ndfip1 binds to Pten, resulting in enhanced ubiquitination by Nedd4 E3 ubiquitin ligases. In vitro, Ndfip1 overexpression increased the rate of Pten nuclear import detected by photobleaching experiments, whereas Ndfip1−/− fibroblasts showed negligible transport rates. In vivo, Ndfip1 mutant mice suffered larger infarct sizes associated with suppressed phosphorylated Akt activation. Our findings provide the first physiological example of when and why transient shuttling of nuclear Pten occurs and how this process is critical for neuron survival.

scholarly journals Sp1-dependent activation of KLF4 is required for PDGF-BB-induced phenotypic modulation of smooth muscle

2009 ◽  
Vol 296 (4) ◽  
pp. H1027-H1037 ◽  
Author(s):  
Rebecca A. Deaton ◽  
Qiong Gan ◽  
Gary K. Owens
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Smooth Muscle ◽  
Vascular Injury ◽  
Marker Gene ◽  
Negative Regulator ◽  
Phenotypic Modulation ◽  
Marker Gene Expression

There is clear evidence that the phenotypic modulation of smooth muscle cells (SMCs) contributes to the pathophysiology of vascular disease. Phenotypic modulation refers to the unique ability of SMCs to alter their phenotype in response to extracellular stimuli and is hallmarked by the loss of SMC marker gene expression. The transcription factor Krüppel-like factor 4 (KLF4) is a known powerful negative regulator of SMC marker gene expression that works, in part, by decreasing the expression of the serum response factor (SRF) myocardin. KLF4 is not expressed in healthy adult SMCs but is increased in SMCs in response to vascular injury in vivo or PDGF-BB treatment in vitro. The aim of the present study was to determine the molecular mechanisms that regulate the expression of KLF4 in phenotypically modulated SMCs. The results demonstrated that the transcription factor stimulating protein-1 (Sp1) regulated the expression of KLF4 in SMCs. The KLF4 promoter contains three consensus Sp1 binding sites. Using a series of truncated KLF4 promoters, we showed that only fragments containing these Sp1 sites could be activated by PDGF-BB. In addition, overexpression of Sp1 alone was sufficient to increase the activity of the KLF4 promoter. Moreover, inhibiting Sp1 expression with small-interfering RNA attenuated the effects of PDGF-BB on KLF4 expression. Mutation of the three Sp1 sites within the KLF4 promoter abolished both baseline and PDGF-BB-induced activity. Finally, the results demonstrated enhanced Sp1 binding to the KLF4 promoter in SMCs treated with PDGF-BB in vitro and following vascular injury in vivo. Taken together, the results suggest a novel role for Sp1 in increasing the expression of KLF4 in phenotypically modulated SMCs.

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