Sputum metalloproteinase-9/tissue inhibitor of metalloproteinase-1 ratio correlates with airflow obstruction in asthma and chronic bronchitis

Asthma and chronic bronchitis are inflammatory diseases with extracellular matrix (ECM) remodeling and collagen deposition. Collagen homeostasis is controlled by metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). We evaluated MMP and TIMP balance in induced sputum of 10 control, 31 untreated asthmatic, and 16 chronic bronchitic subjects. We first performed zymographic analysis to identify the profile of MMPs. Zymography revealed a similar MMPs profile in all populations studied and that MMP-9 was the major enzyme released. We then measured, using enzyme immunoassay, the concentrations of MMP-9 and of its inhibitor TIMP-1 and evaluated whether airflow limitation may be associated with an imbalance between these enzymes. MMP-9 and TIMP-1 concentrations were greater in sputum of patients with asthma and chronic bronchitis than in control subjects. The molar ratio between MMP-9 and TIMP-1 was lower in asthmatics and chronic bronchitics than in control subjects, and positively correlated with FEV1 values. In asthma, MMP-9 levels were significantly correlated with the number of macrophages and neutrophils. This study shows that airway inflammation in asthma and chronic bronchitis is associated with an imbalance between MMP-9 and TIMP-1 which may have a role in the pathogenesis of ECM remodeling and airflow obstruction.

Expired nitric oxide levels during treatment of acute asthma

Nitric oxide (NO) is known to be present in measurable quantities in the exhaled air of normal subjects and at higher concentrations in asthmatic subjects not treated with glucocorticoids. We confirmed these findings by analyzing the mean mixed expired NO concentrations of 43 stable asthmatics and 90 normal subjects; NO levels were higher in the asthmatic population (13.9 parts per billion [ppb] versus 6.2 ppb, p < 0.001). Although the effects of glucocorticoids on the NO content of mixed expired air are known, it is not known if beginning systemic glucocorticoid therapy reduces exhaled NO levels in a given individual. To examine this question, seven patients needing emergency therapy for asthma underwent repeated measurements of mixed expired NO levels during their course of treatment with glucocorticoids. All patients had a reduction in mixed expired NO concentration (p = 0.002) and an accompanying improvement in airway obstruction. The decrease in exhaled NO was evident as early as 48 h after the initiation of therapy (p = 0.05). These data suggest mixed expired NO concentrations may prove useful as an index of asthma severity and treatment efficacy for an individual patient.

Increased glucocorticoid receptor beta in airway cells of glucocorticoid-insensitive asthma

Glucocorticoid (GC)-insensitive asthma is a challenging clinical problem that can be associated with life-threatening disease progression. The molecular basis of GC insensitivity is unknown. Alternative splicing of the GC receptor (GCR) pre-mRNA generates a second GCR, termed GCRbeta, which does not bind GC but antagonizes the transactivating activity of the classic GCR. Thus increased expression of GCRbeta could account for glucocorticoid insensitivity. Bronchoalveolar lavage (BAL) cells and peripheral blood mononuclear cells (PBMC) were examined for GCRbeta immunoreactivity using a GCRbeta-specific antibody by immunohistochemical staining. Cell localization of GCRbeta expression was performed using a double immunostaining technique. Patients with GC-insensitive asthma expressed a significantly higher number of GCRbeta-immunoreactive cells in their BAL and peripheral blood than GC-sensitive asthmatics or normal control subjects. Furthermore, GCRbeta expression in GC-insensitive asthma was particularly high in airway T cells, which are thought to play a major role in the pathogenesis of asthma. We also examined the expression of GCRbeta in specimens from the airways of patients with chronic bronchitis. In chronic bronchitis, few cells were GCRbeta-positive and their numbers did not differ significantly from normal control subjects. We conclude that GC-insensitive asthma is associated with increased expression of GCRbeta in airway T cells.

Exhaled nitric oxide correlates with airway hyperresponsiveness in steroid-naive patients with mild asthma

Endogenously released nitric oxide (NO) has been detected in the exhaled air of humans. Exhaled NO (NOexh) levels have been significantly increased in patients with inflammatory airways disorders such as asthma, and NOexh has been suggested to be a usable marker of airway inflammation. In the present study, NOexh levels were measured both in steroid-treated and untreated subjects with mild asthma, and were correlated with the degree of airway hyperresponsiveness (AHR), measured as the dose of histamine that produced a 20% decrease in FEV1 (PC20histamine). NOexh levels, which were significantly increased in steroid-naive patients (Group A1: NOexh = 21 +/- 11 ppb; n = 56) in comparison with levels in control subjects (Group B: NOexh = 10 +/- 2 ppb; n = 20; p < 0.001), correlated significantly with the PC20histamine (r = -0.65; p < 0.0001). The NOexh level was significantly lower in patients with chronic cough of other causes than bronchial asthma (Group A2: NOexh = 11 +/- 3 ppb; n = 18) when compared with the level in subjects with mild asthma (Group A1: p < 0.001). Therefore, the noninvasive measurement of NOexh allowed us to discriminate, among patients with respiratory complaints, between those with and without AHR. In asthmatic subjects treated with inhaled steroids, the NOexh levels were significantly lower (Group A3: NOexh = 13 +/- 5 ppb; n = 25) than in untreated subjects (Group A1; p < 0.01), and there was no relationship with the PC20histamine (r = -0.18, p = NS). These findings confirm that NOexh reflects AHR in patients with mild asthma who have not already been treated with inhaled steroids. Patients treated with inhaled steroids had an NOexh level comparable to levels in control subjects, although AHR could still be demonstrated.

Levels of endothelin in the bronchoalveolar lavage fluid of patients with symptomatic asthma and reversible airflow obstruction

We have previously demonstrated that human bronchial smooth muscle cells possess a single class of specific binding sites for the potent bronchoconstrictive peptide, endothelin 1, and that human bronchial epithelial cells constitutively release an endothelin-like material in culture, which binds to smooth muscle cell receptors with a kinetic analogous to that observed with the authentic peptide. To evaluate the potential role of endothelin in the pathogenesis of asthma, we examined in this study the release of endothelin in the airways of six patients with asthma, both at the time when they were symptomatic and had reversible airflow obstruction and during the remission phase of the disease induced by treatment. Five normal volunteers and five patients with chronic bronchitis and airflow obstruction unaffected by bronchodilators were tested as control subjects. The release of endothelin in airway mucosa was assessed by RIA with the bronchoalveolar lavage fluid recovered during bronchoscopy. Patients with asthma had increased amounts of immunoreactive endothelin in bronchoalveolar lavage fluid than normal control subjects or subjects with chronic bronchitis (p less than 0.05) in absence of any significant alteration in the levels of circulating peptide. Treatment of patients with asthma with oral corticosteroids and inhaled beta-agonists for 15 days resulted in improvement of airflow obstruction and in more than threefold reduction in the contents of endothelin in lavage fluid. Our findings indicate that the potent bronchoconstrictive substance, endothelin, may contribute to the pathogenesis of airflow obstruction in asthma.

The metabolic syndrome in patients with chronic obstructive pulmonary disease

PURPOSE

This study was undertaken to evaluate the presence of the metabolic syndrome in COPD patients who participated in a cardiopulmonary rehabilitation program. The metabolic syndrome is characterized by the presence of abdominal obesity, atherogenic dyslipidemia, raised blood pressure, presence of insulin resistance, and prothrombotic and inflammatory states that predispose to cardiovascular diseases.

METHODS

Thirty-eight COPD patients (age: 66 +/- 7 years, [mean +/- SD], FEV1: 43 +/- 16% predicted) and 34 control participants matched for age and gender are included in this study. The criteria for the identification of the metabolic syndrome include 3 or more of the following features: abdominal obesity (waist circumference: > 102 cm in men, > 88 cm in women), triglycerides levels (>or= 1.69 mmol/L), high-density lipoprotein cholesterol levels (< 1.0 mmol/L in men, < 1.3 mmol/L in women), blood pressure (>or= 130/ >or= 85 mm Hg), and fasting glucose levels (>or= 6.1 mmol/L).

RESULTS

Forty-seven percent of COPD patients and 21% of control participants presented 3 or more determinants of the metabolic syndrome.

CONCLUSIONS

The presence of metabolic syndrome is frequent in patients with COPD who participated in a cardiopulmonary program. Hence, this population should be considered for screening for the metabolic syndrome.

Increased urinary excretion of the prostaglandin D2 metabolite 9 alpha, 11 beta-prostaglandin F2 after aspirin challenge supports mast cell activation in aspirin-induced airway obstruction

Prostaglandin (PG)D2 is a major product of arachidonic acid metabolism in pulmonary mast cells. We therefore attempted to determine whether measurement of the stable urinary metabolite of PGD2, 9 alpha, 11 beta-PGF2, could serve as a marker of mast cell activation in the lungs. A commercially available enzyme immunoassay was validated and found to be specific and sensitive when applied to unpurified urine. There was no diurnal variation in the levels of 9 alpha, 11 beta-PGF2 in healthy volunteers. Morning baseline values of urinary 9 alpha, 11 beta-PGF2 were measured in three groups--healthy volunteers (n = 9), patients with atopic asthma (n = 14), and aspirin-intolerant patients with asthma (n = 12)--and found to be very similar, 54 +/- 9, 62 +/- 6, and 71 +/- 15 ng/mmol creatinine, respectively (means +/- SEM). Urinary excretion of 9 alpha, 11 beta-PGF2 was increased threefold immediately after allergen-induced bronchoconstriction in nine patients with atopic asthma. Bronchial challenge with inhaled lysine aspirin in eight aspirin-intolerant patients with asthma produced bronchoconstriction without extrapulmonary symptoms and was also followed by a significant increase in the urinary excretion of 9 alpha, 11 beta-PGF2. In addition, challenge with a higher dose of aspirin produced an even greater increase in urinary 9 alpha, 11 beta-PGF2, supporting dose-dependent release of PGD2 during aspirin-induced bronchoconstriction. In contrast, the postchallenge levels of urinary 9 alpha, 11 beta-PGF2 were not increased when bronchoconstriction was induced by histamine challenge in the aspirin-intolerant patients with asthma. The study confirms mast cell involvement in allergen-induced bronchoconstriction and provides novel data, which strongly support the hypothesis that pulmonary mast cells are activated during aspirin-induced airway obstruction. It is finally suggested that measurement of urinary 9 alpha, 11 beta-PGF2 with enzyme immunoassay may be used as a new noninvasive strategy to monitor mast cell activation in vivo.

Chronic inflammation in the cystic fibrosis lung: alterations in inter- and intracellular signaling

A vicious cycle of airway obstruction, infection, and inflammation continues to cause most of the morbidity and mortality in cystic fibrosis (CF). Mutations that result in decreased expression or function of the membrane Cl(-) channel, cystic fibrosis transmembrane regulator (CFTR), result in a decrease in the volume (and hence the depth) of liquid on the airway surface, impaired ciliary function, and dehydrated glandular secretions. In turn, these abnormalities contribute to a milieu, which promotes chronic infection with a limited but unique spectrum of microorganisms. Defects in CFTR also perturb regulation of several intracellular signaling pathways including signal transducers and activator of transcription, I-kappaB and nuclear factor-kappa B, and low molecular weight GTPases. Together, these abnormalities result in excessive production of NF-kappaB dependent cytokines such as interleukin (IL)-1, tumor necrosis factor (TNF), IL-6, and IL-8. There are decreased responses to interferon gamma and transforming growth factor beta leading to decreased production of iNOS and NO. Abnormalities of lipid mediators and decreased secretion of counter/regulatory cytokines have also been reported. Together, these effects combine to create a chronic inflammatory process, which damages and obstructs the airways, and eventually claims the life of the patient.

Mechanisms of persistent NF-kappa B activity in the bronchi of an animal model of asthma

In most cells trans-activating NF-kappaB induces many inflammatory proteins as well as its own inhibitor, IkappaB-alpha, thus assuring a transient response upon stimulation. However, NF-kappaB-dependent inflammatory gene expression is persistent in asthmatic bronchi, even after allergen eviction. In the present report we used bronchial brushing samples (BBSs) from heaves-affected horses (a spontaneous model of asthma) to elucidate the mechanisms by which NF-kappaB activity is maintained in asthmatic airways. NF-kappaB activity was high in granulocytic and nongranulocytic BBS cells. However, NF-kappaB activity highly correlated to granulocyte percentage and was only abrogated after granulocytic death in cultured BBSs. Before granulocytic death, NF-kappaB activity was suppressed by simultaneous addition of neutralizing anti-IL-1beta and anti-TNF-alpha Abs to the medium of cultured BBSs. Surprisingly, IkappaB-beta, whose expression is not regulated by NF-kappaB, unlike IkappaB-alpha, was the most prominent NF-kappaB inhibitor found in BBSs. The amounts of IkappaB-beta were low in BBSs obtained from diseased horses, but drastically increased after addition of the neutralizing anti-IL-1beta and anti-TNF-alpha Abs. These results indicate that sustained NF-kappaB activation in asthmatic bronchi is driven by granulocytes and is mediated by IL-1beta and TNF-alpha. Moreover, an imbalance between high levels of IL-1beta- and TNF-alpha-mediated IkappaB-beta degradation and low levels of IkappaB-beta synthesis is likely to be the mechanism preventing NF-kappaB deactivation in asthmatic airways before granulocytic death.

Expired nitric oxide after bronchoprovocation and repeated spirometry in patients with asthma

Compared with normal individuals, subjects with asthma have elevated levels of expired nitric oxide (NO). These levels are hypothesized to reflect the degree of airway inflammation. Expired NO levels rise during the late phase of allergen challenge and decrease in asthmatics after steroid treatment. Isocapnic cold air hyperventilation (ISH) is believed to cause airway narrowing through noninflammatory mechanisms. We measured mixed expired NO in 10 individuals with atopic asthma who underwent both ISH challenge and allergen challenge, and compared these measurements with the change in expired NO that occurred after serial spirometry alone. We found that ambient NO levels affected mixed expired NO. Controlling for inspired NO, we found that repeated spirometry alone produced a significant fall in mixed expired NO (p < 0.01) that was maximal after 30 min (36.6 +/- 8.5% fall). After allergen and ISH challenges, expired NO was elevated relative to levels after repeated spirometry (p < 0.01 and p = 0.065, respectively). In addition, we found that prechallenge expired NO levels were significantly correlated with the magnitude of the late fall in FEV1 following allergen challenge (r = 0.80, p < 0.01). These data demonstrate that repeated spirometry results in reduced mixed expired NO and suggest that both ISH and allergen-induced bronchoconstriction share pathobiologic mechanisms that produce increases in mixed expired NO.

Deleterious effect of tracheal obstruction on type II pneumocytes in fetal sheep

It was previously shown that tracheal obstruction accelerated fetal lung growth and eventually reversed the pulmonary hypoplasia in experimental diaphragmatic hernia. We have successfully developed a reversible tracheal obstruction technique in fetal sheep using balloon occlusion and showed that 3 wk of obstruction induced significant lung growth of the same magnitude as the tracheal ligation. The purpose of this study was to examine the effects of 1 and 3 wk of tracheal occlusion on the alveolar cell population with specific attention to the type II pneumocytes. We first showed that 1 wk of occlusion induced a significant increase in lung weight and in alveolar surface area. We then used the surfactant protein C (SP-C) mRNA as a specific marker of differentiated type II pneumocytes. Total RNA was isolated from fetal sheep lung with or without tracheal occlusion, and Northern blots were hybridized with a cDNA probe specific for the sheep SP-C. The results show a dramatic decrease in SP-C mRNA expression (8.8-fold, p < 0.01). In situ hybridization showed a marked decrease in the density of cells expressing SP-C, as well as the amount of SP-C mRNA expressed by the cells. The effect was present as early as 1 wk of occlusion. The sparseness of type II pneumocytes was further confirmed by electron microscopy. We thus conclude that tracheal obstruction causes a profound decrease in the number of type II pneumocytes in the lungs. Given the crucial role of type II pneumocytes in surfactant production, we could speculate that, if tracheal occlusion is able to accelerate lung growth, the final product is probably surfactant-deficient.

RSV-encoded NS2 promotes epithelial cell shedding and distal airway obstruction

Respiratory syncytial virus (RSV) infection is the major cause of bronchiolitis in young children. The factors that contribute to the increased propensity of RSV-induced distal airway disease compared with other commonly encountered respiratory viruses remain unclear. Here, we identified the RSV-encoded nonstructural 2 (NS2) protein as a viral genetic determinant for initiating RSV-induced distal airway obstruction. Infection of human cartilaginous airway epithelium (HAE) and a hamster model of disease with recombinant respiratory viruses revealed that NS2 promotes shedding of infected epithelial cells, resulting in two consequences of virus infection. First, epithelial cell shedding accelerated the reduction of virus titers, presumably by clearing virus-infected cells from airway mucosa. Second, epithelial cells shedding into the narrow-diameter bronchiolar airway lumens resulted in rapid accumulation of detached, pleomorphic epithelial cells, leading to acute distal airway obstruction. Together, these data indicate that RSV infection of the airway epithelium, via the action of NS2, promotes epithelial cell shedding, which not only accelerates viral clearance but also contributes to acute obstruction of the distal airways. Our results identify RSV NS2 as a contributing factor for the enhanced propensity of RSV to cause severe airway disease in young children and suggest NS2 as a potential therapeutic target for reducing the severity of distal airway disease.

Sputum ECP levels correlate with parameters of airflow obstruction

Growing evidence suggests that eosinophils play an important role as proinflammatory cells in asthma, possibly by releasing toxic cationic proteins. In this study concentrations of serum and sputum eosinophil cationic protein (ECP) from 134 patients with productive cough and a history suggestive of airflow obstruction were measured by radioimmunoassay. Small sputum volumes were suspended in saline, vortexed, and centrifuged and ECP measured in the supernatant. Serum ECP levels ranged from 0.002 to 0.095 mg/L (0.016 +/- 0.0014), whereas sputum ECP concentrations were between 0.024 and 5.66 mg/L ECP per g sputum (0.878 +/- 0.092). Only 17 of the 134 patients (14 asthma, one cystic fibrosis, one bronchiectasis, and one bronchitis) had not been pretreated with corticosteroids. Sputum but not serum ECP levels of the 14 patients with asthma were inversely correlated with impairment of FEV1 (r = -0.73). Airway resistance (Raw) (r = 0.71) as well as the change in FEV1 (r = 0.79) and Raw (r = 0.84) after inhalation of 0.2 mg albuterol were positively correlated. This relationship was not observed in the remaining 117 patients on topical and/or systemic corticosteroids, suggesting that corticosteroid treatment influences sputum ECP levels. Also, sputum ECP levels and the degree of sputum eosinophilia were not correlated in any of the patient groups. Neither did serum ECP levels predict sputum ECP concentrations. We conclude that sputum ECP concentrations serve as a marker of eosinophil degranulation in the sputum, and this marker correlates with airflow obstruction. Sputum ECP levels are more closely related to lung function parameters than serum ECP concentrations and/or microscopic sputum analysis.

Utility of monitoring capnography, pulse oximetry, and vital signs in the detection of airway mishaps: a hyperoxemic animal model

This study was undertaken to determine the time interval for changes in end-tidal CO2, oxygen saturation (SaO2), heart rate (HR), and blood pressure (BP) in response to an acute airway obstruction or hypopharyngeal extubation in a hyperoxemic model. Complete and partial airway obstructions were simulated with complete and partial cross-clamping of an endotracheal (ET) tube in five anesthetized, nonparalyzed, mechanically ventilated Yorkshire minipigs with initial PAo2 of > 400 mm Hg. Placement of the ET tube into the hypopharynx was performed to simulate accidental extubation. Both sidestream (SS) and mainstream (MS) capnography were used. Continuous pulse oximetry monitored SaO2, femoral arterial catheter monitored systolic BP, and electrocardiograph monitored HR. The time intervals for the capnograph wave to flatten and for the monitor to display zero were recorded after each airway alteration. The time interval to a change in the initial HR of 10 beats/min, a change of initial systolic BP of 10 mm Hg, and a change of initial SaO2 of 5% were recorded. Experiments were carried out for 180 seconds, and 25 trials were performed. HR, systolic BP, and SaO2 did not change for the 180-second duration of the trials. Complete obstruction produced a flattening of the SS and MS waveform in 8 +/- 2 seconds and 6 +/- 2 seconds, respectively. The SS and MS monitors displayed zero in 19 +/- 1 seconds and 68 +/- 7 seconds, respectively. Partial obstruction did not produce flattening of the wave or a monitor displaying zero. Hypopharyngeal extubation produced a flattening of the SS and MS waveform in 7 +/- 1 seconds and 7 +/- 2 seconds, respectively. The SS and MS monitors displayed zero in 18 +/- 3 seconds and 76 +/- 16 seconds, respectively. Continuous end-tidal CO2 capnography detects acute airway obstruction and hypopharyngeal extubation more rapidly than does pulse oximetry or vital sign monitoring in a hyperoxemic porcine model.

Leukotrienes as mediators of airway obstruction

The cysteinyl leukotrienes are potent mediators of airway narrowing derived from the lipoxygenation of arachidonic acid and the adduction of glutathione to this eicosanoid backbone. In lower animals and humans, the cysteinyl leukotrienes are among the most potent airway contractile substances ever identified. Furthermore, these moieties can be recovered from the urine during induced or spontaneous asthma attacks. Most important, inhibition of the synthesis of the leukotrienes or prevention of their action at the CysLT1 receptor is associated with an improvement in the airway dysfunction that occurs in both induced and spontaneous asthma. These data indicate that the cysteinyl leukotrienes have a clinically significant role in the airway obstruction that characterizes asthma.

Inhibition of mucin secretion with MARCKS-related peptide improves airway obstruction in a mouse model of asthma

Allergic asthma is associated with airway epithelial cell mucous metaplasia and mucin hypersecretion, but the consequences of mucin hypersecretion on airway function are unclear. Recently, a peptide derived from the myristoylated alanine-rich C kinase substrate protein NH(2)-terminal sequence (MANS) was shown to inhibit methacholine (MCh)-induced mucin secretion from airway mucous cells by >90%. We studied the effect of intranasal pretreatment with this peptide on specific airway conductance (sGaw) during challenge with MCh in mice with allergen-induced mucous cell metaplasia. sGaw was noninvasively measured in spontaneously breathing restrained mice, using a double-chamber plethysmograph. Pretreatment with MANS peptide, but not a control peptide [random NH(2)-terminal sequence (RNS)], resulted in partial inhibition of the fall in sGaw induced by 60 mM MCh (mean +/- SE; baseline 1.15 +/- 0.06; MANS/MCh 0.82 +/- 0.05; RNS/MCh 0.55 +/- 0.05 cmH(2)O/s). The protective effect of MANS was also seen in mice challenged with allergen for 3 consecutive days to increase airway hyperresponsiveness, although the degree of protection was less (baseline 1.1 +/- 0.08; MANS/MCh, 0.65 +/- 0.06; RNS/MCh 0.47 +/- 0.03 cmH(2)O/s). Because routine sGaw measurement in mice includes nasal airways, the effectiveness of MANS was also confirmed in mice breathing through their mouths after nasal occlusion (baseline 0.92 +/- 0.05; MANS/MCh 0.83 +/- 0.06; RNS/MCh 0.61 +/- 0.03 cmH(2)O/s). In all instances, sGaw in the MANS-pretreated group was approximately 35% higher than in RNS-treated controls, and mucous obstruction accounted for approximately 50% of the MCh-induced fall in sGaw. In summary, mucin secretion has a significant role in airway obstruction in a mouse model of allergic asthma, and strategies to inhibit mucin secretion merit further investigation.

Pulmonary rehabilitation that includes arm exercise reduces metabolic and ventilatory requirements for simple arm elevation

Simple arm elevation results in increased metabolic and ventilatory requirements in patients with chronic airflow obstruction (CAO). These demands contribute to the dyspnea that is frequently reported when these patients perform activities of daily living involving the arms. We hypothesized that a comprehensive pulmonary rehabilitation (PR) program that includes upper extremity training would lower the ventilatory requirement for arm elevation. Metabolic and ventilatory responses to 2 min of simple arm elevation were studied in 14 patients with CAO before and after PR. Respiratory muscle strength was determined in 11 patients by measurement of maximal transdiaphragmatic pressure (Pdimax). Oxygen uptake (VO2), carbon dioxide production (VCO2), heart rate (HR), minute ventilation (VE), tidal volume (VT), and respiratory rate were measured at rest with the arms down and during 2 min of arm elevation. Before PR, arm elevation led to significant increases in VO2, VCO2, HR, and VE. After PR, pulmonary function, Pdimax, and resting metabolic and ventilatory parameters with the arms down were unchanged; however, during arm elevation, VO2, VCO2, and VE were significantly less than they were before PR. We conclude that a comprehensive PR program that includes upper extremity exercises leads to a reduction in the ventilatory requirement for simple arm elevation. This type of program may allow patients with CAO to perform sustained upper extremity activities with less dyspnea.

Relationship between surface tension of upper airway lining liquid and upper airway collapsibility during sleep in obstructive sleep apnea hypopnea syndrome

Lowering surface tension (gamma) of upper airway lining liquid (UAL) reduces upper airway opening (anesthetized humans) and closing (anesthetized rabbits) pressures. We now hypothesize that in sleeping obstructive sleep apnea hypopnea syndrome (OSAHS) patients lowering gamma of UAL will enhance upper airway stability and decrease the severity of sleep-disordered breathing. Nine OSAHS patients [respiratory disturbance index (RDI): 49 +/- 8 (SE) events/h, diagnostic night] participated in a two-part, one-night, polysomnography study. In the first part, upper airway closing pressures (during non-rapid eye movement sleep, Pcrit) were measured and samples of UAL (awake) were obtained before and after 2.5 ml of surfactant (Exosurf, Glaxo Smith Kline) was instilled into the posterior pharynx. The gamma of UAL was determined with the use of the "pull-off" force technique. In the second part, subjects received a second application of 2.5 ml of surfactant and then slept the remainder of the night (205 +/- 30 min). Instillation of surfactant decreased the gamma of UAL from 60.9 +/- 3.1 mN/m (control) to 45.2 +/- 2.5 mN/m (surfactant group) (n = 9, P < 0.001). Pcrit decreased from 1.19 +/- 1.14 cmH2O (control) to -0.56 +/- 1.15 cmH2O (surfactant group) (n = 7, P < 0.02). Compared with the second half of diagnostic night, surfactant decreased RDI from 51 +/- 8 to 35 +/- 8 events/h (n = 9, P < 0.03). The fall in RDI (deltaRDI) correlated with the fall in gamma of UAL (deltagamma) (deltaRDI = 1.8 x deltagamma, r = 0.68, P = 0.04). Hypopneas decreased approximately 50% from 42 +/- 8 to 20 +/- 5 events/h (n = 9, P < 0.03, paired t-test). The gamma of UAL measured the next morning remained low at 49.5 +/- 2.7 mN/m (n = 9, P < 0.001, ANOVA, compared with control). In conclusion, instillation of surfactant reduced the gamma of UAL in OSAHS patients and decreased Pcrit and the occurrence of hypopneas. Therapeutic manipulation of gamma of UAL may be beneficial in reducing the severity of sleep-disordered breathing in OSAHS patients.

Rat model of chronic recurrent airway obstructions to study the sleep apnea syndrome

STUDY OBJECTIVES

To implement a chronic rat model of recurrent airway obstructions to study the obstructive sleep apnea (OSA) syndrome.

DESIGN

Prospective controlled animal study.

SETTING

University laboratory.

PATIENTS OR PARTICIPANTS

24 male Sprague-Dawley rats (250-300 g).

INTERVENTIONS

The rats were placed in a setup consisting of a body chamber and a head chamber separated by a neck collar specially designed to apply recurrent airway obstructions with OSA patterns. Rats in the Obstruction group (n=8) were subjected to 5-s obstructions at a rate of 60 per hour, 6 h/day during 4 weeks. Sham rats (n=8) were placed in the setup but no obstructions were applied. Naive rats (n=8) were subjected to no intervention.

MEASUREMENTS AND RESULTS

Breathing flow, pressure, CO2 air concentration, and SpO2 showed that the model mimicked OSA respiratory events (obstructive apneas, increased respiratory efforts, and oxygen saturation dips). Animal stress, assessed by body weight and plasma corticosterone, was not significantly different across Obstruction and Sham groups. This supports the concept that this novel model does not introduce a significant burden of stress in the rat after acclimatization to the chamber. Thromboxane-B2/6-keto-Prostaglandin-Flalpha ratio in plasma, which is an index of vasoconstriction, was significantly increased in the rats subjected to obstructions.

CONCLUSIONS

The designed animal model of chronic recurrent airway obstructions is feasible and potentially useful to study the mechanisms involved in the cardiovascular consequences of OSA.

Indices of oxidative stress in blood and pulmonary epithelium lining fluid in horses suffering from recurrent airway obstruction

To test the hypothesis that reactive oxygen species could be associated to the lower airway disorders occurring in horses suffering from recurrent airway obstruction (RAO), indices of oxidative stress were studied in blood and pulmonary epithelium lining fluid in 5 RAO horses either in clinical remission or 24 h after the onset of a crisis of bronchospasm and in 5 healthy horses. Venous blood and bronchoalveolar lavage fluid (BALF) samples were collected and analysed for reduced glutathione (GSH), oxidised glutathione (GSSG), total glutathione (TGSH), glutathione redox ratio (GRR) in blood haemolysate and pulmonary epithelium lining fluid (PELF). The haemolysate concentrations of GSH, GSSG, TGSH and GRR were similar in the 3 groups. The PELF glutathione status was significantly different in the RAO horses in acute crisis compared to healthy horses, indicating the occurrence of an oxidative stress. When RAO horses were in crisis their GSH and TGSH remained unchanged but their GSSG and GRR were significantly increased compared to the remission. These results support the hypothesis that oxidative stress is associated with lower airway disorders occurring in horses suffering from RAO.

Mycoplasma pneumoniae induces host-dependent pulmonary inflammation and airway obstruction in mice

Respiratory tract infections result in wheezing in a subset of patients. Mycoplasma pneumoniae is a common etiologic agent of acute respiratory infection in children and adults that has been associated with wheezing in 20-40% of individuals. The current study was undertaken to elucidate the host-dependent pulmonary and immunologic response to M. pneumoniae respiratory infection by studying mice with different immunogenetic backgrounds (BALB/c mice versus C57BL/6 mice). After M. pneumoniae infection, only BALB/c mice developed significant airway obstruction (AO) compared with controls. M. pneumoniae-infected BALB/c mice manifested significantly elevated airway hyperresponsiveness (AHR) compared with C57BL/6 mice 4 and 7 d after inoculation as well as BALB/c control mice. Compared with C57BL/6 mice, BALB/c mice developed worse pulmonary inflammation, including greater peribronchial infiltrates. Infected BALB/c mice had significantly higher concentrations of tumor necrosis factor-alpha, interferon-gamma, interleukin (IL)-1beta, IL-6, IL-12, KC (functional IL-8), and macrophage inflammatory protein 1alpha in the bronchoalveolar lavage fluid compared with infected C57BL/6 mice. No differences in IL-2, IL-4, IL-5, IL-10, and granulocyte/macrophage colony-stimulating factor concentrations were found. The mice in this study exhibited host-dependent infection-related AO and AHR associated with chemokine and T-helper type (Th)1 pulmonary host response and not Th2 response after M. pneumoniae infection.

Mineral dusts directly induce epithelial and interstitial fibrogenic mediators and matrix components in the airway wall

Exposure to mineral dusts is associated with the development of chronic airflow obstruction, probably mediated in part by dust-induced fibrosis of the small airways. To investigate the mechanism of fibrosis, we exposed rat tracheal explants to amosite asbestos, iron oxide, or titanium dioxide. Explants were then maintained in air organ culture, and the expression of genes encoding for various mediators and matrix components assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). At 7 d, all dusts produced significant increases in platelet-derived growth factor-A (PDGF-A) and transforming growth factor-beta1 (TGF-beta1) gene expression compared with control; asbestos and titanium dioxide produced increases in PDGF-B, and titanium dioxide increased TGF-alpha expression. Only asbestos caused increases in procollagen expression. No dust increased expression of tumor necrosis factor-alpha (TNF-alpha), fibronectin, or tropoelastin. Elevations in these factors coincided temporally with transport of particles into the epithelium and then to the subepithelial space. By in situ hybridization, TGF-beta gene expression was found in both the epithelium and subepithelial (interstitial) space, and PDGF-B and procollagen gene expression in the subepithelial space. Chemical analysis showed a small increase in hydroxyproline, a measure of collagen content, in asbestos-treated explants. We conclude that mineral dusts can induce airway wall fibrosis by directly upregulating proliferative and fibrogenic mediators as well as matrix components in the airway epithelium and interstitium, and that neither airspace nor circulating inflammatory cells are required for these effects. Different mineral dusts produce different patterns of reaction.

The effects of tracheal occlusion and release on type II pneumocytes in fetal lambs

Fetal tracheal occlusion (TO) has been shown to lead to lung hyperplasia in various animal models, and this procedure has already been carried out in human fetuses with congenital diaphragmatic hernia (CDH). However, the authors previously showed that TO caused a decrease in type II pneumocytes.

PURPOSE

The aim of this study is to examine the effects of TO and release on type II pneumocytes.

METHOD

To was carried out with a Swan Ganz or Fogarty catheter in fetal sheep at 116 to 118 days of gestation. TO was maintained for 2 weeks followed by deflation of the balloon for 1 week before delivery, in group 1; in group 2, TO was maintained for 19 days and released 2 days before delivery. Group 3 consisted of previously reported animals who had TO maintained until birth. Unoperated twins served as controls. All specimens were analyzed using the surfactant protein C (SP-C) mRNA as a specific marker for type II pneumocytes. We used Northern Blot and in situ hybridization techniques to quantify total SP-C and the density of type II cells. Electron microscopy (EM) was also used to evaluate and quantitate type II cells.

RESULTS

TO resulted in significant lung growth in all groups. In situ hybridization and Northern Blot analysis showed that there was a complete recovery of type II cells in group 1 versus controls. Quantitative EM analysis confirmed these findings. In group 2 the number of type II cells was decreased but there was an increase in SP-C content per type II cell versus group 3.

CONCLUSION

Lung growth after TO appears to occur at the expense of type II cell differentiation. This effect is reversible with the release of TO before birth in this animal model.

Piceatannol, a Syk-selective tyrosine kinase inhibitor, attenuated antigen challenge of guinea pig airways in vitro

Activation of nontransmembrane protein tyrosine kinases, such as Lyn and Syk, has been shown to be the earliest detectable signaling response to Fc receptor (Fc epsilon RI) cross-linking on mast cells leading to mast cell degranulation. The present study examined the effects of piceatannol (3,4,3',5'-tetrahydroxy-trans-stilbene, 10-100 microM), a Syk-selective tyrosine kinase inhibitor, on ovalbumin-induced anaphylactic contraction of isolated guinea pig bronchi and release of histamine and peptidoleukotrienes from chopped lung preparations. Pretreatment with piceatannol slightly suppressed ovalbumin-induced peak anaphylactic bronchial contraction but markedly (P<0.05) facilitated relaxation of the anaphylactically contracted bronchi. Piceatannol did not inhibit direct histamine-, leukotriene D(4)- or KCl-induced bronchial contraction, nor revert an existing anaphylactic bronchial contraction. Piceatannol, at 30 microM and above, significantly (P<0.05) prevented ovalbumin-induced release of both histamine and peptidoleukotrienes from lung fragments. Piceatannol did not inhibit exogenous arachidonic acid-induced release of peptidoleukotrienes from lung fragments. Our data show for the first time that inhibition of Syk tyrosine kinase can attenuate anaphylactic bronchial contraction in vitro, probably via inhibition of mast cell degranulation.