Salbutamol-induced lactic acidosis in status asthmaticus survivor.

BACKGROUND: Salbutamol-induced lactic acidosis is a rare presentation that could manifest in specific clinical context as acute asthmatic attack treatment. An increase of glycolysis pathway leading to pyruvate escalation is the mechanism of hyperlactatemia in ß2-adrenergic agonist drug. CASE PRESENTATION: A 40-year-old man who had poor-controlled asthma, presented with progressive dyspnea with coryza symptom for 6 days. He was intubated and admitted into medical intensive care unit due to deteriorated respiratory symptom. Severe asthmatic attack was diagnosed and approximate 1.5 canisters of salbutamol inhaler was administrated within 24 h of admission. Initial severe acidosis consisted of acute respiratory acidosis from ventilation-perfusion mismatch and acute metabolic acidosis resulting from bronchospasm and hypoxia-related lactic acidosis, respectively. The lactate level was normalized in 6 h after hypoxemia and ventilation correction. Given the lactate level re-elevated into a peak of 4.6 mmol/L without signs of tissue hypoxia nor other possible etiologies, the salbutamol toxicity was suspected and the inhaler was discontinued that contributed to rapid lactate clearance. The patient was safely discharged on the 6th day of admission. CONCLUSION: The re-elevation of serum lactate in status asthmaticus patient who had been administrated with the vast amount of ß2-adrenergic agonist should be considered for salbutamol-induced lactic acidosis and promptly discontinued especially when there were no common potentials.

The ß2-adrenergic receptor-ROS signaling axis: An overlooked component of ß2AR function?

ß2-Adrenergic receptor (ß2AR) agonists are clinically used to elicit rapid bronchodilation for the treatment of bronchospasms in pulmonary diseases such as asthma and COPD, both of which exhibit characteristically high levels of reactive oxygen species (ROS); likely secondary to over-expression of ROS generating enzymes and chronically heightened inflammation. Interestingly, ß2AR has long-been linked to ROS, yet the involvement of ROS in ß2AR function has not been as vigorously studied as other aspects of ß2AR signaling. Herein, we discuss the existing body of evidence linking ß2AR activation to intracellular ROS generation and importantly, the role of ROS in regulating ß2AR function. The reciprocal interplay of the ß2AR and ROS appear to endow this receptor with the ability to self-regulate signaling efficacy and ligand binding, hereby unveiling a redox-axis that may be unfavorably altered in pathological states contributing to both disease progression and therapeutic drug responses.

ß-Elemene inhibits the proliferation of primary human airway granulation fibroblasts by down-regulating canonical Wnt/ß-catenin pathway.

Benign airway stenosis is a clinical challenge because of recurrent granulation tissues. Our previous study proved that a Chinese drug, ß-elemene, could effectively inhibit the growth of fibroblasts cultured from hyperplastic human airway granulation tissues, which could slow down the progression of this disease. The purpose of the present study is to find out the mechanism for this effect. We cultured fibroblasts from normal human airway tissues and human airway granulation tissues. These cells were cultured with 160 µg/ml normal saline (NS), different doses of ß-elemene, or 10 ng/ml canonical Wnt/ß-catenin pathway inhibitor (Dickkopf-1, DKK-1). The proliferation rate of cells and the expression of six molecules involved in canonical Wnt/ß-catenin pathway, Wnt3a, glycogen synthase kinase-3ß (GSK-3ß), ß-catenin, α-smooth muscle actin (α-SMA), transforming growth factor-ß (TGF-ß), and Collagen I (Col-I), were measured. At last, we used canonical Wnt/ß-catenin pathway activator (LiCl) to further ascertain the mechanism of ß-elemene. Canonical Wnt/ß-catenin pathway is activated in human airway granulation fibroblasts. ß-Elemene didn't affect normal human airway fibroblasts; however, it had a dose-responsive inhibitive effect on the proliferation and expression of Wnt3a, non-active GSK-3ß, ß-catenin, α-SMA, TGF-ß, and Col-I of human airway granulation fibroblasts. More importantly, it had the same effect on the expression and nuclear translocation of active ß-catenin. All these effects were similar to 10 ng/ml DKK-1 and could be attenuated by 10 mM LiCl. Thus, ß-elemene inhibits the proliferation of primary human airway granulation fibroblasts by down-regulating canonical Wnt/ß-catenin pathway. This pathway is possibly a promising target to treat benign tracheobronchial stenosis.

Mechanistic link between diesel exhaust particles and respiratory reflexes.

BACKGROUND: Diesel exhaust particles (DEPs) are a major component of particulate matter in Europe's largest cities, and epidemiologic evidence links exposure with respiratory symptoms and asthma exacerbations. Respiratory reflexes are responsible for symptoms and are regulated by vagal afferent nerves, which innervate the airway. It is not known how DEP exposure activates airway afferents to elicit symptoms, such as cough and bronchospasm. OBJECTIVE: We sought to identify the mechanisms involved in activation of airway sensory afferents by DEPs. METHODS: In this study we use in vitro and in vivo electrophysiologic techniques, including a unique model that assesses depolarization (a marker of sensory nerve activation) of human vagus. RESULTS: We demonstrate a direct interaction between DEP and airway C-fiber afferents. In anesthetized guinea pigs intratracheal administration of DEPs activated airway C-fibers. The organic extract (DEP-OE) and not the cleaned particles evoked depolarization of guinea pig and human vagus, and this was inhibited by a transient receptor potential ankyrin-1 antagonist and the antioxidant N-acetyl cysteine. Polycyclic aromatic hydrocarbons, major constituents of DEPs, were implicated in this process through activation of the aryl hydrocarbon receptor and subsequent mitochondrial reactive oxygen species production, which is known to activate transient receptor potential ankyrin-1 on nociceptive C-fibers. CONCLUSIONS: This study provides the first mechanistic insights into how exposure to urban air pollution leads to activation of guinea pig and human sensory nerves, which are responsible for respiratory symptoms. Mechanistic information will enable the development of appropriate therapeutic interventions and mitigation strategies for those susceptible subjects who are most at risk.

Prostaglandin D2 and the role of the DP1, DP2 and TP receptors in the control of airway reflex events.

Prostaglandin D2 (PGD2) causes cough and levels are increased in asthma suggesting that it may contribute to symptoms. Although the prostaglandin D2 receptor 2 (DP2) is a target for numerous drug discovery programmes little is known about the actions of PGD2 on sensory nerves and cough. We used human and guinea pig bioassays, in vivo electrophysiology and a guinea pig conscious cough model to assess the effect of prostaglandin D2 receptor (DP1), DP2 and thromboxane receptor antagonism on PGD2 responses. PGD2 caused cough in a conscious guinea pig model and an increase in calcium in airway jugular ganglia. Using pharmacology and receptor-deficient mice we showed that the DP1 receptor mediates sensory nerve activation in mouse, guinea pig and human vagal afferents. In vivo, PGD2 and a DP1 receptor agonist, but not a DP2 receptor agonist, activated single airway C-fibres. Interestingly, activation of DP2 inhibited sensory nerve firing to capsaicin in vitro and in vivo. The DP1 receptor could be a therapeutic target for symptoms associated with asthma. Where endogenous PGD2 levels are elevated, loss of DP2 receptor-mediated inhibition of sensory nerves may lead to an increase in vagally associated symptoms and the potential for such adverse effects should be investigated in clinical studies with DP2 antagonists.

Pharmacological characterization of muscarinic receptors in the contractions of isolated bronchi in the horse.

We investigated the effects of nonselective muscarinic antagonist (atropine) and of selective muscarinic subtype 1 (M1), 2 (M2), 3 (M3) antagonists (VU0255035, methoctramine, pFHHSiD, respectively) on the contractions evoked by electrical field stimulation (EFS) or by exogenous ACh in isolated horse bronchial muscle. Atropine completely inhibited neurogenic contractions in a concentration-dependent fashion, whereas selective muscarinic antagonists induced relevant modifications only at the highest concentration tested. Experiments with selective muscarinic antagonists in combination showed that only the simultaneous blockade of M1 /M3 or M2 /M3 receptors was able to induce a nearly complete suppression of contractions. The contractions induced by exogenous ACh were competitively antagonized only by atropine (pA2 = 9.01 ± 0.05). M3 selective antagonist, up to 10(-6) m, caused a moderate concentration-dependent rightward shift of ACh curve (pA2 = 7.96 ± 0.10). These data show that M3 muscarinic receptors possess a central role in mediating cholinergic contraction of horse bronchi, while M1 and M2 receptors seem to have a cooperative role. Selective muscarinic antagonists seem unlikely to be useful against bronchoconstriction associated with airway diseases in horses. Conversely, compounds with selectivity for both M1 and M3 receptors could be as effective as traditional anticholinergics and induce fewer cardiac side effects.

Evaluation of gut modulatory and bronchodilator activities of Amaranthus spinosus Linn.

BACKGROUND: The aqueous-methanolic extract of Amaranthus spinosus (A. spinosus Linn.,) whole plant, was studied for its laxative, spasmolytic and bronchodilator activities to validate some of its medicinal uses. METHODS: The crude extract of A. spinosus was studied in-vivo for bronchodilator and laxative activities and in-vitro using isolated tissue preparations which were mounted in tissue baths assembly containing physiological salt solutions, maintained at 37°C and aerated with carbogen, to assess the spasmolytic effect and to find out the possible underlying mechanisms. RESULTS: In the in-vivo experiments in mice, the administration of A. spinosus increased fecal output at doses of 100 and 300 mg/kg showing laxative activity. It also inhibited carbachol-induced bronchospasm in anesthetized rats at 1, 3, 10 and 30 mg/kg indicative of bronchodilator activity. When tested on isolated gut preparations, the plant extract showed a concentration-dependent (0.01-10.0 mg/ml) spasmogenic effect in spontaneously contracting rabbit jejunum and guinea-pig ileum. The spasmogenic effect was partially blocked in tissues pretreated with atropine (0.1 µM). When tested on K+ (80 mM)-induced sustained contractions in isolated rabbit jejunum, the plant extract caused complete relaxation and also produced a shift in the Ca++ concentration-response curves (CRCs) towards right, similar to diltiazem. In rabbit trachea, the plant extract completely inhibited K+ (80 mM) and carbachol (CCh, 1 µM)-induced contractions at 1 mg/ml but pretreatment of tissue with propranolol (1 µM), caused around 10 fold shift in the inhibitory CRCs of the plant extract constructed against CCh-induced contraction. The plant extract (up to 0.3 mg/ml) also increased both force and rate of spontaneous contractions of isolated guinea-pig atria, followed by relaxation at higher concentration (1.0-5.0 mg/ml). The cardio-stimulant effect was abolished in the presence of propranolol, similar to that of isoprenaline. Activity-directed fractionation revealed that the spasmolytic component(s) was separated in the organic fraction, whereas the spasmogenic component was concentrated in the aqueous fraction. CONCLUSION: These results indicate that A. spinosus possesses laxative activity partially mediated through cholinergic action. The spasmolytic effect was mediated through calcium channel blocking (CCB), while bronchodilator activity through a combination of ß-adrenergic and CCB pathways, which may explain the traditional uses of A. spinosus in gut and airways disorders.

Exhaled RANTES and interleukin 4 levels after exercise challenge in children with asthma.

BACKGROUND: Despite the universality and clinical significance of exercise-induced bronchospasm (EIB), the mechanisms responsible for it are incompletely understood. OBJECTIVE: To investigate the role of exhaled RANTES (regulated on activation, normal T-cell expressed and secreted) and interleukin (IL) 4 in EIB in children with asthma. METHODS: Fifty-six children with asthma were evaluated with exercise challenge and exhaled RANTES and IL-4 levels. Exhaled breath condensate was collected before and 30 minutes after exercise challenge. RANTES and IL-4 concentrations were determined using a specific immunoassay kit. RESULTS: A significant increase was found in RANTES levels after exercise challenge in the asthmatic children (P<.001). A statistically significant increase in RANTES levels was noted after exercise challenge in both the asthmatic children with EIB (n=25, P=.007) and in the non-EIB asthmatic group (n=31, P=.005). Our study revealed that exhaled RANTES level correlates significantly well with percentage of forced expiratory volume in 1 second (FEV1), exacerbation frequency, serum IgE, and body mass index. No statistically significant increase was found in IL-4 levels after exercise challenge. The maximal postexercise decrease in FEV1 strongly correlated with total eosinophil count (P<.001, r = -0.61) and baseline ratio of FEV1 to forced vital capacity (FVC) (P=.002, r=0.40). Results from multivariate regression analysis adjusted for age, sex, and atopy as covariates showed that eosinophil count and FEV1/FVC ratio were significantly associated with EIB. CONCLUSION: We found that exercise challenge, leading to hyperosmolar stimulus, may increase exhaled RANTES levels in children with asthma. In addition, exhaled RANTES levels correlate well with serum IgE, severity of asthma, FEV1/FVC ratio, and body mass index. RANTES and IL-4 may not be independent predictors for EIB. Furthermore, eosinophil count and FEV1/FVC ratio may predict the presence and severity of EIB in asthmatic children.

A role for ATP in bronchoconstriction-induced activation of guinea pig vagal intrapulmonary C-fibres.

Activation of vagal afferent sensory C-fibres in the lungs leads to reflex responses that produce many of the symptoms associated with airway allergy. There are two subtypes of respiratory C-fibres whose cell bodies reside within two distinct ganglia, the nodose and jugular, and whose properties allow for differing responses to stimuli. We here used extracellular recording of action potentials in an ex vivo isolated, perfused lung-nerve preparation to study the electrical activity of nodose C-fibres in response to bronchoconstriction. We found that treatment with both histamine and methacholine caused strong increases in tracheal perfusion pressure that were accompanied by action potential discharge in nodose, but not in jugular C-fibres. Both the increase in tracheal perfusion pressure and action potential discharge in response to histamine were significantly reduced by functionally antagonizing the smooth muscle contraction with isoproterenol, or by blocking myosin light chain kinase with ML-7. We further found that pretreatment with AF-353 or 2',3'-O-(2,4,6-Trinitrophenyl)-adenosine-5'-triphosphate (TNP-ATP), structurally distinct P2X3 and P2X2/3 purinoceptor antagonists, blocked the bronchoconstriction-induced nodose C-fibre discharge. Likewise, treatment with the ATPase apyrase, in the presence of the adenosine A1 and A2 receptor antagonists 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and SCH 58261, blocked the C-fibre response to histamine, without inhibiting the bronchoconstriction. These results suggest that ATP released within the tissues in response to bronchoconstriction plays a pivotal role in the mechanical activation of nodose C-fibres.

[Bronchial hyperresponsiveness and factors of bronchial inflammation under the exercise-induced asthma in schoolchildren].

88 schoolchildren with bronchial asthma were observed at the department of pulmonary disease and allergology of the Chernivtsi regional children clinical hospital. The study showed that the content of aldehyde- and ketoderivatives of 2,4-dinitrophenylhydrazones of neutral character in the expired air condensate (AKDNPH) was presumably higher in patients with the exercise-induced bronchial asthma thus indicating the more significant activity of the inflammatory process in bronchi under the studied phenotype of the disease. Non-specific bronchial hyperresponsiveness was presumably higher in children suffering exercise-induced bronchial asthma due to bronchial hyperresponsiveness as well as hyperreactivity when compared with the patients having activity independent asthma attacks. The factor of bronchial spasm was significantly associated with the content of AKDNPH of the basic character and nitric oxide metabolites in the expired air condensate in the patients with the exercise-induced bronchial asthma.

[Analysis of L, E, and P selectins concentration in infants and young children with spastic bronchitis]. / Analiza stezenia selektyny L, E i P u niemowlat i malych dzieci chorych na obturacyjne zapalenie oskrzeli.

UNLABELLED: Spastic bronchitis in infants and young children is one of the most frequent causes of hospitalization in this age group. Both infectious and allergic inflammations lead to inflammation cells activation and their flow to the place of inflammation by the activation of adhesive molecules. One of groups of adhesive molecules are L, E and P selectins responsible for leucocytes migration through the vessel wall. The aim of the study was to assess the concentration of solved fractions of L, P and E selectins in infants and young children in the course of spastic bronchitis. MATERIAL AND METHODS: Fifty four patients with spastic bronchitis (group I) including 32 with the first bronchitis (group IA) and 22 patients with recurrent bronchitis (at last the third one--group IB) were included into the study. Comparative group (group II) was consisted of 26 patients hospitalized due to other causes and with no bronchitis in the past. Patients were from 1 to 36 months of age. Among all patients solved fractions of selectins L, E and P were analyzed by ELISA tests. RESULTS: Mean sL-selectin concentration in group I was 4126.3 ng/ml and in group II 4222.31 ng/ml and was not statistically significant. Concentrations of sL-selectin in the group of patients with the first episode of spastic bronchitis was 4099.37 ng/ml and in the group of patients with recurrent bronchitis was 4166 ng/ml and had no statistical difference. Mean sE-selectin concentration in group I was 205.49 ng/ml and in group II 214.50 ng/ml and was not statistically significant. Concentrations of sE-selectin in the group of patients with the first episode of spastic bronchitis was 195.22 ng/ml and in the group of patients with recurrent bronchitis was 220.43 ng/ml and had no statistical difference. Concentration of sP-selectin was assessed among 51 patients with bronchitis and among 26 patients from comparative group. Because of the lack of normal distribution values of sP-selectin concentrations were changed by decimal logarithm. Mean sP-selectin concentration in group I was 235.95 ng/ml and in group II 164.70 ng/ml. After logarithm change values of concentrations were: 2.249 and 2.005 and had statistical difference (p = 0.0221). Concentrations of sP-selectin in the group of patients with the first episode of spastic bronchitis was 234.0 ng/ml and in the group of patients with recurrent bronchitis was 238.20 ng/ml and after logarithm change concentrations were 2.26 in the group of patients with the first episode of spastic bronchitis and 2.24 in the group of patients with recurrent bronchitis and had no statistical difference. CONCLUSION: On the ground of our study in infants and young children with spastic bronchitis increase of sP-selectin concentration was observed and sE-selectin and sL-selectin concentrations were the same.

[Response mechanisms of the airway smooth muscle tissue in experimental bronchial spasm].

This investigation was aimed at the complex evaluation of the reactivity mechanisms of bronchial smooth muscle tissue (SMT) in experimental bronchial spasm. Morphometric, cytospectrophotometric and electron microscopical analysis demonstrated the presence of three types of smooth muscle cells (SMC) within the bronchial SMT (small, medium, large), that differed in their linear and metabolic parameters. The findings of this study indicate that under the conditions of experimental bronchial spasm development, the ratios of SMC in bronchial SMT are changed with the increase in proportion of small SMC and the elimination of large SMC. In the dynamics of experimental bronchial spasm development, the activation of cytoplasmic synthesis as well as of DNA synthesis was detected mainly in group of small SMC. The reactive-dystrophic changes were marked at the subcellular level, that were most often identified in large SMC resulting in their elimination from population in the dynamics of an experiment. The data obtained suggest that one of the important mechanisms of airway SMT adaptation to the bronchial spasm development is a dynamic reorganization of SMC population.

Antileukotrienes as adjunctive therapy in acute asthma.

The leukotriene receptor antagonists (LTRAs) are a comparatively new class of asthma drugs that exhibit both bronchodilator and anti-inflammatory properties. There is a substantial body of evidence for their benefit in the management of chronic asthma in both adults and children, and particularly in specific types of asthma such as exercise-induced and aspirin-sensitive asthma. Despite best practice using current treatment guidelines for the management of acute asthma, a significant proportion of patients require continued treatment and are unable to be discharged from the emergency department; many require a short course of oral corticosteroids. The relatively rapid onset of action of LTRAs after oral administration and their additive effect to beta(2)-adrenoceptor agonists led to the hypothesis that they might be of benefit in acute asthma. This review examines the available evidence for the effect of LTRAs in acute asthma. Although the evidence is limited, it suggests that treatment with LTRAs provides additional bronchodilator effect to nebulised and inhaled beta(2)-adrenoceptor agonists. Short-term therapy with LTRAs results in fewer treatment failures and readmissions for patients with acute asthma, and less need for additional therapies such as nebulisers and corticosteroids.

Crosstalk between Gi and Gq/Gs pathways in airway smooth muscle regulates bronchial contractility and relaxation.

Receptor-mediated airway smooth muscle (ASM) contraction via G(alphaq), and relaxation via G(alphas), underlie the bronchospastic features of asthma and its treatment. Asthma models show increased ASM G(alphai) expression, considered the basis for the proasthmatic phenotypes of enhanced bronchial hyperreactivity to contraction mediated by M(3)-muscarinic receptors and diminished relaxation mediated by beta(2)-adrenergic receptors (beta(2)ARs). A causal effect between G(i) expression and phenotype has not been established, nor have mechanisms whereby G(i) modulates G(q)/G(s) signaling. To delineate isolated effects of altered G(i), transgenic mice were generated overexpressing G(alphai2) or a G(alphai2) peptide inhibitor in ASM. Unexpectedly, G(alphai2) overexpression decreased contractility to methacholine, while G(alphai2) inhibition enhanced contraction. These opposite phenotypes resulted from different crosstalk loci within the G(q) signaling network: decreased phospholipase C and increased PKCalpha, respectively. G(alphai2) overexpression decreased beta(2)AR-mediated airway relaxation, while G(alphai2) inhibition increased this response, consistent with physiologically relevant coupling of this receptor to both G(s) and G(i). IL-13 transgenic mice (a model of asthma), which developed increased ASM G(alphai), displayed marked increases in airway hyperresponsiveness when G(alphai) function was inhibited. Increased G(alphai) in asthma is therefore a double-edged sword: a compensatory event mitigating against bronchial hyperreactivity, but a mechanism that evokes beta-agonist resistance. By selective intervention within these multipronged signaling modules, advantageous G(s)/G(q) activities could provide new asthma therapies.

Synthesis and pharmacological investigation of novel 1-substituted-4-(4-substituted phenyl)-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-ones as a new class of H1-antihistamine agents.

A series of novel 1-substituted-4-(4-substituted phenyl)-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-ones was synthesized by the cyclization of 2-hydrazino-3-(4-substituted phenyl)-3H-quinazolin-4-one with various one-carbon donors. The starting material, 2-hydrazino-3-(4-substituted phenyl)-3H-quinazolin-4-one, was synthesized from 4-substituted aniline by a novel innovative route. When tested for in-vivo H1-antihistamine activity on conscious guinea-pigs, all the test compounds significantly protected the animals against histamine-induced bronchospasm. The compound 1-methyl-4-(4-chloro phenyl)-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-one (VII) was more potent (72.71% protection), and 1-methyl-4-(4-methoxy phenyl)-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-one (II) was equipotent (71% protection), when compared with the reference standard, chlorpheniramine maleate (71% protection). Compounds II and VII showed negligible sedation (5% and 8% respectively) when compared with chlorpheniramine maleate (25%). Compounds II and VII could serve as prototype molecules for further development as a new class of H1-antihistamines.

[Influence of industrial pollutants on bronchial permeability].

The authors studied influence of chemical hazards with various characteristics on bronchial permeability. Workers exposed to organic chemicals demonstrated respiratory complaints and spirometric signs of bronchial obstruction 1.3-1.8 times more frequently. Longer length of service in hazardous conditions is associated with higher occurrence of bronchial obstruction and more intensive changes of lipid peroxidation.

Cytokine production from sputum cells after allergenic challenge in IgE-mediated asthma.

BACKGROUND: Th2 cytokine production from airway cells is thought to govern the eosinophilic airways inflammation in allergic asthma. Induced sputum has become a widely used technique to assess airways inflammation. METHODS: By applying the technique of induced sputum to collect airways cells, we have assessed the spontaneous production of a set of cytokines, including interleukin-4, 6, 10, interferon-gamma and tumour necrosis factor-alpha, 6 h after a bronchial allergenic challenge with Dermatophagoides pteronyssinus (Dpt) in 12 sensitized asthmatics and compared the results obtained after inhalation of saline as control. A group of eight healthy non-allergic subjects was enrolled to control for any non-specific effect of Dpt. Cytokines were measured by a dynamic immunoassay during a 24-h sputum cell culture. RESULTS: Allergen challenge in sensitized asthmatics caused an acute and a late bronchospasm together with a rise in sputum eosinophil counts. Afterwards allergen sputum cells from allergic asthmatics displayed a rise in their production of IL-4 (P < 0.01), IL-6 (P < 0.05) and IL-10 (P < 0.05) when compared to saline. By this time sputum generation of IL-4 in atopic asthmatics was greater than in healthy subjects (P < 0.001). Furthermore, in allergic asthmatics there was a strong correlation between the rise in interleukin-4 production from sputum cells and the rise in sputum eosinophils (r = 0.87, P < 0.001). CONCLUSIONS: Sputum cell culture is a useful model to assess cytokine production in allergic asthmatics who show a marked up-regulation of Th2 cytokines following acute allergen exposure. The rise in sputum eosinophil count following allergen challenge strongly correlates with the rise in IL-4 generation from sputum cells.

Perturbed equilibria of myosin binding in airway smooth muscle: bond-length distributions, mechanics, and ATP metabolism.

We carried out a detailed mathematical analysis of the effects of length fluctuations on the dynamically evolving cross-bridge distributions, simulating those that occur in airway smooth muscle during breathing. We used the latch regulation scheme of Hai and Murphy (Am. J. Physiol. Cell Physiol. 255:C86-C94, 1988) integrated with Huxley's sliding filament theory of muscle contraction. This analysis showed that imposed length fluctuations decrease the mean number of attached bridges, depress muscle force and stiffness, and increase force-length hysteresis. At frequencies >0.1 Hz, the bond-length distribution of slowly cycling latch bridges changed little over the stretch cycle and contributed almost elastically to muscle force, but the rapidly cycling cross-bridge distribution changed substantially and dominated the hysteresis. By contrast, at frequencies <0.033 Hz this behavior was reversed: the rapid cycling cross-bridge distribution changed little, effectively functioning as a constant force generator, while the latch bridge bond distribution changed substantially and dominated the stiffness and hysteresis. The analysis showed the dissociation of force/length hysteresis and cross-bridge cycling rates when strain amplitude exceeds 3%; that is, there is only a weak coupling between net external mechanical work and the ATP consumption required for cycling cross-bridges during the oscillatory steady state. Although these results are specific to airway smooth muscle, the approach generalizes to other smooth muscles subjected to cyclic length fluctuations.

Perturbed equilibrium of myosin binding in airway smooth muscle and its implications in bronchospasm.

In asthma, the mechanisms relating airway obstruction, hyperresponsiveness, and inflammation remain rather mysterious. We show here that regulation of airway smooth muscle length corresponds to a dynamically equilibrated steady state, not the static mechanical equilibrium that had been previously assumed. This dynamic steady state requires as an essential feature a continuous supply of external mechanical energy (derived from tidal lung inflations) that acts to perturb the interactions of myosin with actin, drive the molecular state of the system far away from thermodynamic equilibrium, and bias the muscle toward lengthening. This mechanism leads naturally to the suggestion that excessive airway narrowing in asthma may be associated with the destabilization of that dynamic process and its resulting collapse back to static equilibrium. With this collapse the muscle undergoes a phase transition and virtually freezes at its static equilibrium length. This mechanism may help to elucidate several unexplained phenomena including the multifactorial origins of airway hyperresponsiveness, how allergen sensitization leads to airway hyperresponsiveness, how hyperresponsiveness can persist long after airway inflammation is resolved, and the inability in asthma of deep inspirations to relax airway smooth muscle.