Airway smooth muscle relaxation results from a reduction in the frequency of Ca(2+ )oscillations induced by a cAMP-mediated inhibition of the IP(3 )receptor

BACKGROUND: It has been shown that the contractile state of airway smooth muscle cells (SMCs) in response to agonists is determined by the frequency of Ca(2+ )oscillations occurring within the SMCs. Therefore, we hypothesized that the relaxation of airway SMCs induced by agents that increase cAMP results from the down-regulation or slowing of the frequency of the Ca(2+ )oscillations. METHODS: The effects of isoproterenol (ISO), forskolin (FSK) and 8-bromo-cAMP on the relaxation and Ca(2+ )signaling of airway SMCs contracted with methacholine (MCh) was investigated in murine lung slices with phase-contrast and laser scanning microscopy. RESULTS: All three cAMP-elevating agents simultaneously induced a reduction in the frequency of Ca(2+ )oscillations within the SMCs and the relaxation of contracted airways. The decrease in the Ca(2+ )oscillation frequency correlated with the extent of airway relaxation and was concentration-dependent. The mechanism by which cAMP reduced the frequency of the Ca(2+ )oscillations was investigated. Elevated cAMP did not affect the re-filling rate of the internal Ca(2+ )stores after emptying by repetitive exposure to 20 mM caffeine. Neither did elevated cAMP limit the Ca(2+ )available to stimulate contraction because an elevation of intracellular Ca(2+ )concentration induced by exposure to a Ca(2+ )ionophore (ionomycin) or by photolysis of caged-Ca(2+ )did not reverse the effect of cAMP. Similar results were obtained with iberiotoxin, a blocker of Ca(2+)-activated K(+ )channels, which would be expected to increase Ca(2+ )influx and contraction. By contrast, the photolysis of caged-IP(3 )in the presence of agonist, to further elevate the intracellular IP(3 )concentration, reversed the slowing of the frequency of the Ca(2+ )oscillations and relaxation of the airway induced by FSK. This result implied that the sensitivity of the IP(3)R to IP(3 )was reduced by FSK and this was supported by the reduced ability of IP(3 )to release Ca(2+ )in SMCs in the presence of FSK. CONCLUSION: These results indicate that the relaxant effect of cAMP-elevating agents on airway SMCs is achieved by decreasing the Ca(2+ )oscillation frequency by reducing internal Ca(2+ )release through IP(3 )receptors

Properties of the δ\delta Scorpii Circumstellar Disk from Continuum Modeling

We present optical $WBVR$ and infrared $JHKL$ photometric observations of the Be binary system $\delta$ Sco, obtained in 2000--2005, mid-infrared (10 and $18 \mu$m) photometry and optical ($\lambda\lambda$ 3200--10500 \AA) spectropolarimetry obtained in 2001. Our optical photometry confirms the results of much more frequent visual monitoring of $\delta$ Sco. In 2005, we detected a significant decrease in the object's brightness, both in optical and near-infrared brightness, which is associated with a continuous rise in the hydrogen line strenghts. We discuss possible causes for this phenomenon, which is difficult to explain in view of current models of Be star disks. The 2001 spectral energy distribution and polarization are succesfully modeled with a three-dimensional non-LTE Monte Carlo code which produces a self-consistent determination of the hydrogen level populations, electron temperature, and gas density for hot star disks. Our disk model is hydrostatically supported in the vertical direction and radially controlled by viscosity. Such a disk model has, essentially, only two free parameters, viz., the equatorial mass loss rate and the disk outer radius. We find that the primary companion is surrounded by a small (7 $R_\star$), geometrically-thin disk, which is highly non-isothermal and fully ionized. Our model requires an average equatorial mass loss rate of 1.5\times 10^{-9} M_{\sun} yr$^{-1}$.Comment: 27 pages, 9 figures, submitted to Ap

Airway smooth muscle as a target of asthma therapy: history and new directions

Ultimately, asthma is a disease characterized by constriction of airway smooth muscle (ASM). The earliest approach to the treatment of asthma comprised the use of xanthines and anti-cholinergics with the later introduction of anti-histamines and anti-leukotrienes. Agents directed at ion channels on the smooth muscle membrane (Ca(2+ )channel blockers, K(+ )channel openers) have been tried and found to be ineffective. Functional antagonists, which modulate intracellular signalling pathways within the smooth muscle (β-agonists and phosphodiesterase inhibitors), have been used for decades with success, but are not universally effective and patients continue to suffer with exacerbations of asthma using these drugs. During the past several decades, research energies have been directed into developing therapies to treat airway inflammation, but there have been no substantial advances in asthma therapies targeting the ASM. In this manuscript, excitation-contraction coupling in ASM is addressed, highlighting the current treatment of asthma while proposing several new directions that may prove helpful in the management of this disease

Nebulisation of synthetic lamellar lipids mitigates radiation-induced lung injury in a large animal model

Item originally deposited in University of Edinburgh, Edinburgh Research Explorer Repository at: https://www.research.ed.ac.uk/portal/en/publications/nebulisation-of-synthetic-lamellar-lipids-mitigates-radiationinduced-lung-injury-in-a-large-animal-model(ab917c99-7e7f-4fa1-8d1e-40511ca9abd3).htmlMethods to protect against radiation-induced lung injury (RILI) will facilitate the development of more effective radio-therapeutic protocols for lung cancer and may provide the means to protect the wider population in the event of a deliberate or accidental nuclear or radiological event. We hypothesised that supplementing lipid membranes through nebulization of synthetic lamellar lipids would mitigate RILI. Following pre-treatment with either nebulised lamellar lipids or saline, anaesthetised sheep were prescribed fractionated radiotherapy (30 Gray (Gy) total dose in five 6 Gy fractions at 3–4 days intervals) to a defined unilateral lung volume. Gross pathology in radio-exposed lung 37 days after the first radiation treatment was consistent between treatment groups and consisted of deep red congestion evident on the pleural surface and firmness on palpation. Consistent histopathological features in radio-exposed lung were subpleural, periarteriolar and peribronchial intra-alveolar oedema, alveolar fibrosis, interstitial pneumonia and type II pneumocyte hyperplasia. The synthetic lamellar lipids abrogated radiation-induced alveolar fibrosis and reduced alpha-smooth muscle actin (ASMA) expression in radio-exposed lung compared to saline treated sheep. Administration of synthetic lamellar lipids was also associated with an increased number of cells expressing dendritic cell-lysosomal associated membrane protein throughout the lung.This work was supported by Grant MRC/CIC3/025 awarded to D.C., J.L., J.M., G.M. & J.P. The authors wish to acknowledge the assistance of Dryden Animal Services in the conduct of this work, and the assistance of Dr Helen Brown in relation to experimental design and statistical analysis. The authors are grateful to Lamellar Biomedical Ltd., Strathclyde Business Park, Bellshill, Scotland, United Kingdom, for the supply of LAMELLASOME™ used in this research.8pubpubArticle no: 1331

Ca²⁺-signaling in airway smooth muscle cells is altered in T-bet knock-out mice

<p>Abstract</p> <p>Background</p> <p>Airway smooth muscle cells (ASMC) play a key role in bronchial hyperresponsiveness (BHR). A major component of the signaling cascade leading to ASMC contraction is calcium. So far, agonist-induced Ca²⁺-signaling in asthma has been studied by comparing innate properties of inbred rat or mouse strains, or by using selected mediators known to be involved in asthma. T-bet knock-out (KO) mice show key features of allergic asthma such as a shift towards T_H2-lymphocytes and display a broad spectrum of asthma-like histological and functional characteristics. In this study, we aimed at investigating whether Ca²⁺-homeostasis of ASMC is altered in T-bet KO-mice as an experimental model of asthma.</p> <p>Methods</p> <p>Lung slices of 100 to 200 μm thickness were obtained from T-bet KO- and wild-type mice. Airway contraction in response to acetylcholine (ACH) was measured by video-microscopy and Ca²⁺-signaling in single ASMC of lung slices was assessed using two-photon-microscopy.</p> <p>Results</p> <p>Airways from T-bet KO-mice showed increased baseline airway tone (BAT) and BHR compared to wild-type mice. This could be mimicked by incubation of lung slices from wild-type mice with IL-13. The increased BAT was correlated with an increased incidence of spontaneous changes in intracellular Ca²⁺-concentrations, whereas BHR correlated with higher ACH-induced Ca²⁺-transients and an increased proportion of ASMC showing Ca²⁺-oscillations. Emptying intracellular Ca²⁺-stores using caffeine or cyclopiazonic acid induced higher Ca²⁺-elevations in ASMC from T-bet KO- compared to wild-type mice.</p> <p>Conclusion</p> <p>Altered Ca²⁺-homeostasis of ASMC contributes to increased BAT and BHR in lung slices from T-bet KO-mice as a murine asthma model. We propose that a higher Ca²⁺-content of the intracellular Ca²⁺-stores is involved in the pathophysiology of these changes.</p