Tracheal Mucus Research Articles

Novel triple neurokinin receptor antagonist CS-003 inhibits respiratory disease models in guinea pigs

Neurokinins are known to induce neurogenic inflammation related to respiratory diseases. The effects of CS-003 ([1-{2-[( 2R)-(3,4-dichlorophenyl)-4-(3,4,5-trimethoxybenzoyl)morpholin-2-yl]ethyl}spiro[benzo[ c]thiophene-1( 3H),4'-piperidine]-( 2S)-oxide hydrochloride]), a novel triple neurokinin receptor antagonist, on several respiratory disease models were evaluated in guinea pigs. As we have already shown that CS-003 is intravenously effective, we first determined if CS-003 was orally effective. CS-003 dose-dependently inhibited substance P-induced tracheal vascular hyperpermeability, neurokinin A- and neurokinin B-induced bronchoconstriction with ID 50 values of 3.6, 1.3 and 0.89 mg/kg (p.o.), respectively. CS-003 (10 mg/kg, p.o.) inhibited the number of coughs induced by capsaicin aerosol ( P < 0.01) and the antitussive effect was comparable to that of codeine. CS-003 (10 mg/kg, p.o.) also inhibited airway hyperresponsiveness to methacholine chloride in ovalbumin-induced asthma models ( P < 0.01), a milder one and a severer one. On the other hand, montelukast (10 mg/kg, p.o.), a leukotriene receptor antagonist, significantly inhibited the hyperresponsiveness only in the milder model ( P < 0.05). In an ovalbumin-induced rhinitis model, oral administration of CS-003 inhibited nasal blockade in a dose-dependent manner and the inhibitory effect was comparable to that of dexamethasone (10 mg/kg, p.o.). CS-003 (i.v.) also dose-dependently inhibited cigarette smoke-induced bronchoconstriction, tracheal vascular hyperpermeability and mucus secretion. These data show that CS-003, a potent orally active triple neurokinin receptor antagonist, may be useful for the treatment of respiratory diseases associated with neurokinins, such as allergic asthma, allergic rhinitis, chronic obstructive pulmonary disease and cough.

Increased mucus accumulation in horses chronically affected with recurrent airway obstruction is not associated with up-regulation of CLCA1, EGFR, MUC5AC, Bcl-2, IL-13 and INF-γ expression

The mechanisms leading to mucus accumulation in equine inflammatory airway disease (IAD) and recurrent airway obstruction (RAO) are unclear. In airways of human patients with asthma and/or chronic obstructive pulmonary disease as well as in animal models of these diseases, associations of mucus hyperproduction with increased calcium-activated chloride channel 1 (CLCA1), epidermal growth factor receptor (EGFR), mucin 5AC (MUC5AC), B-cell lymphoma 2 (Bcl-2), interleukin (IL)-13 and interferon (IFN)-γ expression have been reported. We hypothesized that increased mucus accumulation in RAO and IAD are associated with alterations in inflammatory cytokine (IL-13 and IFN-γ) and epithelial gene (CLCA1, EGFR, Bcl-2 and MUC5AC) profiles. Therefore, mRNA expression of these genes in cell pellets extracted from bronchoalveolar lavage fluid (BALF) and bronchial epithelial brushing (BEB) was compared between 11 clinically healthy (Control group), 7 IAD- and 12 RAO-affected horses by reverse transcription polymerase chain reaction. We also performed arterial blood gas analysis, endoscopic scoring of mucus accumulation in the trachea and cytology of tracheo-bronchial secretions (TBS) and of BALF. Tracheal mucus accumulation, along with TBS and BALF neutrophils were significantly increased and arterial pO 2 was decreased in RAO-affected horses compared to the Control group. IL-13 in BALF samples was significantly lower in the RAO group. None of the other genes’ relative mRNA levels displayed significant differences between groups. Our findings suggest that mucus production in equine RAO is induced by pathways independent of IL-13, CLCA1, EGFR, MUC5AC and Bcl-2 up-regulation.

Pathology of Specific-Pathogen-Free Chickens Inoculated with H5N1 Avian Influenza Viruses Isolated in Japan in 2004

Specific-pathogen-free chickens inoculated with H5N1 highly pathogenic avian influenza (HPAI) viruses isolated in Japan in 2004 were investigated pathologically. The chickens inoculated intravenously with the viruses died within 26 hr after inoculation. Macroscopically, minimal necrosis of the tip of the comb, and hemorrhages of the palpebral conjunctiva, liver, cerebellum, and muscles were rarely observed. Histologically, dead chickens had minimal focal necrosis of hepatocytes with fibrinous thrombi in sinusoids, mild necrosis of splenic ellipsoids with fibrinous exudation, minimal necrosis of the brain, mild necrosis of epidermal cells of the comb with congestion of the lamina propria, and hemorrhages and edema of the lamina propria of the conjunctiva. Virus antigens were seen in the sinusoidal endothelial cells and hepatocytes in the liver, the capillary endothelial cells of the spleen, the capillary endothelial cells and cardiac myocytes in the heart, the capillary endothelial cells and necrotic nerve cells in the brain, the capillary endothelial cells in the lamina propria of the comb, the renal tubular epithelial cells, and the pancreatic acinar cells. The chickens inoculated by natural infectious routes died within 1-4 days after inoculation. Macroscopically, some chickens had hemorrhages in the conjunctiva, edematous swelling of the face and wattles, hydropericardium, hemorrhages of the proventriculus and bursa of Fabricius, increased secretion of tracheal mucus, and congestion and edema of lungs. Histologic lesions by natural infectious routes were similar to those by intravenous inoculation, except for the pancreatic necrosis. This study suggests H5N1 HPAI viruses isolated in Japan in 2004 cause pathologic conditions similar to natural cases.

Following tracheal intubation, mucus flow is reversed in the semirecumbent position: Possible role in the pathogenesis of ventilator–associated pneumonia

Critically ill intubated patients are positioned in the semirecumbent position to prevent pneumonia. In tracheally intubated sheep, we investigated the effects of gravitational force on tracheal mucus transport and on bacterial colonization of the respiratory system. Prospective randomized animal study. Animal research facility at the National Institutes of Health. Sixteen healthy sheep. Spontaneously breathing or mechanically ventilated sheep were randomized to be positioned with the orientation of the trachea above (40 degrees, trachea-up) or below (5 degrees, trachea-down) horizontal. Tracheal mucus velocity was measured through radiographic tracking of radiopaque tantalum disks, insufflated into the trachea. After 24 hrs, sheep were euthanized, and samples from the airways and lungs were taken for microbiological analysis. The proximal trachea was colonized in all sheep. In trachea-down sheep, all mucus moved toward the glottis at a mean velocity of 2.1 +/- 1.1 mm/min. When mucus reached the endotracheal tube, it either entered the endotracheal tube or was lodged at the inflated endotracheal tube cuff. In all trachea-up sheep, abnormal tracheal mucus clearance was found. Mucus, mostly on the nondependent part of the trachea, moved toward the glottis at an average velocity of 2.2 +/- 2.0 mm/min and constantly accumulated at the inflated endotracheal tube cuff. From the proximal trachea, mucus eventually moved toward the lungs on the dependent part of the trachea, leading to an "intratracheal route" of colonization of the lungs. Pneumonia was found in 6/8 of trachea-up sheep and the same microorganisms were isolated from the lungs and the proximal trachea. No pneumonia was found in trachea-down sheep (p = .007). The study indicates that following tracheal intubation gravitational force influences tracheal mucus clearance. When the trachea is oriented above horizontal, a flow of mucus from the proximal trachea toward the lungs is highly associated with bacterial colonization of the airways and pneumonia.

Lower respiratory tract disease in Thoroughbred racehorses: Analysis of endoscopic data from a UK training yard

There has been much research directed at potential causative agents and the epidemiology of lower respiratory tract disease (LRTD), but few reports of the clinical progression and outcome. To define clinical features of LRTD in racehorses, including association with age and average duration of disease, through the analysis of endoscopic data. A retrospective analysis of records from a single training yard of endoscopic examinations undertaken over a 2-year period was performed. Horses were subjected to regular endoscopic examination for a variety of reasons, and all horses placed on antibiotic therapy for lower respiratory tract disease were rescoped following treatment. Data analysed included a 0-8 tracheal mucus score based on visible endoscopic mucus and gross tracheal lavage turbidity, as well as age and treatment duration and type. A total of 522 endoscopic examinations undertaken on 123 horses and tracking 169 episodes of lower respiratory tract disease were recorded. Mean duration of disease episode was 15.5 days (median = 11 days, range = 4-61 days). Horses age 2 years were significantly more likely than those age > or=3 years to have at least one episode of respiratory disease (P<0.001). There was a direct association between initial tracheal mucus score and rescope score after treatment. Lower respiratory tract disease was more common in 2-year-olds than in older horses. Affected horses had endoscopic evidence of increased tracheal mucus accumulation for an average of 15.5 days per episode, a considerably shorter period than that suggested by previous studies. Endoscopic examinations permit longitudinal tracking of lower respiratory tract disease in Thoroughbred racehorses. A prolonged duration of disease, sometimes extending for months, can be expected in a small proportion of cases, some of which appear to be refractory to treatment. There is a clear need for evidence-based analysis of treatment regimes to assist clinicians in decision making when managing disease in both individual and group situations.

A new paradigm in respiratory hygiene: modulating respiratory secretions to contain cough bioaerosol without affecting mucus clearance

BackgroundSeveral strategies and devices have been designed to protect health care providers from acquiring transmissible respiratory diseases while providing care. In modulating the physical characteristics of the respiratory secretions to minimize the aerosolization that facilitates transmission of airborne diseases, a fundamental premise is that the prototype drugs have no adverse effect on the first line of respiratory defense, clearance of mucus by ciliary action.MethodsTo assess and demonstrate the primary mechanism of our mucomodulators (XLs), we have built our evidence moving from basic laboratory studies to an ex-vivo model and then to an in-vivo large animal model. We exposed anesthetized dogs without hypersecretion to different dose concentrations of aerosolized XL "B", XL "D" and XL "S". We assessed: cardio-respiratory pattern, tracheal mucus clearance, airway patency, and mucus viscoelastic changes.ResultsExposure of frog palate mucus to XLs did not affect the clearance of mucus by ciliary action. Dogs maintained normal cardio-respiratory pattern with XL administration. Tracheal mucociliary clearance in anesthetized dogs indicated a sustained 40% mean increase. Tracheal mucus showed increased filance, and there was no mucus retention in the airways.ConclusionThe ex-vivo frog palate and the in-vivo mammalian models used in this study, appear to be appropriate and complement each other to better assess the effects that our mucomodulators exert on the mucociliary clearance defence mechanism. The physiological function of the mucociliary apparatus was not negatively affected in any of the two epithelial models. Airway mucus crosslinked by mucomodulators is better cleared from an intact airway and normally functioning respiratory system, either due to enhanced interaction with cilia or airflow-dependent mechanisms. Data obtained in this study allow us to assure that we have complied with the fundamental requirement criteria established in the initial phase of developing the concept of mucomodulation: Can we modulate the physical characteristics of the respiratory secretions to reduce aerosolization without affecting normal mucociliary clearance function, or even better improving it?

Hyaluronan blocks porcine pancreatic elastase-induced mucociliary dysfunction in allergic sheep

Neutrophil elastase is a mediator common to asthma, chronic obstructive pulmonary disease, and cystic fibrosis and thought to contribute to the pathophysiology of these diseases. Previously, we found that inhaled hyaluronan blocked elastase-induced bronchoconstriction in allergic sheep through its control of tissue kallikrein. Here, we extend those studies by determining if inhaled hyaluronan can protect against the elastase-induced depression in tracheal mucus velocity, a surrogate marker of whole lung mucociliary clearance. We measured tracheal mucus velocity in allergic sheep before, and sequentially for 6 h after, aerosol challenge with porcine pancreatic elastase alone and after pretreatment with 1.5 or 6 mg aerosolized hyaluronan. Elastase (2.55 U) decreased tracheal mucus velocity. Pretreatment with 6 mg, but not 1.5 mg, hyaluronan inhibited the elastase-induced decrease in tracheal mucus velocity. Hyaluronan (6 mg) given 1 h after elastase challenge was ineffective, suggesting the involvement of secondary mediators. The elastase-induced depression in mucus transport appeared to be mediated, in part, by reactive oxygen species and bradykinin because pretreatment with either aerosolized catalase (38 mg/3 ml) or the bradykinin B2-receptor antagonist HOE140 (400 nM/kg) was also effective in blocking the response. These latter two findings are consistent with oxygen radical-induced degradation of hyaluronan with concomitant loss of its regulatory effect on tissue kallikrein, resulting in kinin generation. This hypothesis is supported by the demonstration that hyaluronan failed to block the oxygen radical-induced fall in tracheal mucus velocity resulting from xanthine-xanthine oxidase challenge and that inhaled bradykinin itself can slow mucociliary transport.

Prevalence of inflammatory airway disease in National Hunt horses referred for investigation of poor athletic performance

Inflammatory airway disease (IAD) is thought to be an important cause of poor performance in young Thoroughbred racehorses. However, little study has been made of IAD in older National Hunt (NH) horses. To determine the prevalence of IAD in NH racehorses referred for investigation of poor athletic performance and identify some of the risk factors that may be associated with IAD in this group of horses. Tracheal mucus was graded, and tracheal wash (TW) and bronchoalveolar lavage (BAL) performed after treadmill exercise in 91 NH horses referred to the University of Bristol. Comparisons were made between the different methods for diagnosing IAD and potential risk factors investigated. Tracheal mucus was observed in 68% and lower airway inflammation identified in 70% of horses. There was poor agreement between TW and BAL techniques for a diagnosis of IAD. The prevalence of increased proportions of neutrophils in TW was 40% compared with 59% in BAL. There was a significant association between presence of tracheal mucus and increased neutrophils in TW but not between tracheal mucus and BAL cytology. No significant association between IAD and age, EIPH or URT obstruction was observed. Inflammatory airway disease was a common finding in NH horses referred for investigation of poor performance. In contrast to studies in younger, flat racehorses the prevalence of disease did not decrease with increasing age. Horses of all ages presented for investigation of poor performance require a thorough clinical investigation of the lower airways. The collection of both TW and BAL samples is indicated in order to confirm a diagnosis of IAD.

The Prevalence of Laryngeal Disease in a Large Population of Competition Draft Horses

(1) To determine the effect of age, height, weight, breed, sex, and specific use on the prevalence of idiopathic left laryngeal hemiplegia (ILH) in a population of draft performance horses; (2) to determine the association between tracheal mucus and laryngeal dysfunction, and the prevalence of exercise-induced pulmonary hemorrhage (EIPH) in a population of draft performance horses. Cross-sectional. Draft horses competing at the 2005 Michigan Great Lakes Draft Horse Show. Endoscopic examinations were performed on horses competing at the 2005 Michigan Great Lakes Draft Horse Show. Signalment, height, and weight were obtained from the owners and trainers. Belgian, Percheron, and Clydesdale horses (n=183) were studied. Prevalence of ILH was 35%. Horse height was significantly associated with the risk of ILH in Belgian and Percheron horses but not Clydesdales. There was a significantly different prevalence of ILH among the breeds such that 42% Belgians, 31% Percherons, and 17% Clydesdales were affected. Laryngeal disease was a risk factor for increased tracheal mucus. None of the horses had acute evidence of EIPH. The prevalence of ILH in draft horses has increased or is higher in competition horses compared with previously studied groups. Tracheal and/or pulmonary inflammation may be more common in draft horses with ILH based on our findings that horses with ILH have more tracheal mucus than horses with normal laryngeal function. Selection pressure for large, taller, longer-necked horses may be responsible for a seemingly increased incidence of ILH in competitive draft horses.

Comparative Effects of Salmeterol, Albuterol, and Ipratropium on Normal and Impaired Mucociliary Function in Sheep

We measured tracheal mucus velocity (TMV), a marker of mucociliary clearance (MCC), in sheep before and for 12 h after treatment with salmeterol, albuterol, ipratropium, or vehicle to determine the effects on normal MCC. We also determined if these agents could reverse the depression in TMV caused by inhaled human neutrophil elastase (HNE), a model of abnormal MCC. Study 1: TMV was measured initially and then for 6 h after metered-dose inhaler treatment with salmeterol (42 microg), albuterol (180 microg), ipratropium bromide (36 microg), or vehicle. After 6 h, the sheep in the albuterol and ipratropium treatment arms were administered a second dose of drug, whereas the salmeterol and vehicle treatment arms received vehicle. TMV was measured for another 6 h. Study 2: Six sheep inhaled HNE aerosol, which significantly reduced TMV by 2 h. At this point, the sheep were treated with either salmeterol, albuterol, ipratropium, or vehicle, and the effects on TMV were measured for another 6 h. This experiment was repeated in four sheep using only salmeterol and albuterol, but the posttreatment measurements were extended to 12 h. Study 1: Only salmeterol and albuterol increased TMV (p < 0.05) during the initial 6-h period. From 6 to 12 h only, the salmeterol-treated sheep had TMV that remained at or above the initial TMV for the entire time, although both albuterol and ipratropium showed enhancement of TMV compared to vehicle. Study 2: Salmeterol and albuterol reversed the HNE-induced depression in TMV to a similar degree over the 6-h time course. However, the protection afforded by salmeterol was more prolonged than that seen with albuterol if the posttreatment interval was extended to 12 h. Ipratropium and vehicle had no effect. We conclude that salmeterol and albuterol can stimulate normal MCC and reverse HNE-induced mucociliary dysfunction and that salmeterol has a longer duration of action in these models of normal and abnormal MCC.

Effects of acute hypovolaemia by furosemide on tracheal transepithelial potential difference and mucus in dogs

Furosemide is a potent diuretic that affects water transfer across the respiratory epithelium, which is closely related to the transepithelial potential difference (PD). Water is a critical factor that determines mucus transport; an important lung defence mechanism that removes particles and microorganisms from the respiratory system. The aim of the present study was to investigate the acute effects of furosemide and hypovolaemia on tracheal PD and mucus properties. A total of 36 male mixed-breed dogs were submitted to anaesthesia, mechanical ventilation and haemodynamic monitoring. They were randomly assigned to three groups consisting of: a control group, a furosemide (40 mg i.v.) + hypovolaemia group, and a furosemide (40 mg i.v.) + volume replacement group. Tracheal PD and mucus samples were collected at time 0, 1 and 2 h after intervention. Mucus properties were analysed by means of a magnetic microrheometer and in vitro mucociliary transportability on the frog palate. Compared to controls, furosemide decreased PD to intermediate values, and only significantly when associated with hypovolaemia (-13+/-5 and -8+/-2 mV, time 0 and 2 h, respectively). In addition to the direct effect of furosemide, these results indicate that hypovolaemia also affects ion transport in the tracheal membrane. Furosemide and hypovolemia have no acute effects on respiratory mucus properties.

Endoscopic scoring of mucus quantity and quality: observer and horse variance and relationship to inflammation, mucus viscoelasticity and volume

Endoscopic scoring of airway mucus quantity and quality has not been critically assessed. To evaluate mucus scores for 1) observer- and horse-related variance and 2) association with inflammation, mucus viscoelasticity and measured volume. Variance of scoring within and between observers and over time within horses were determined for airway mucus accumulation, apparent viscosity, localisation and colour, and correlations of mucus accumulation scores with neutrophil ratios in secretions. The relationship of accumulation score to measured volumes of 'artificial mucus' was investigated. Correlations of mucus accumulation, apparent viscosity and colour scores with measured viscoelasticity were tested. Viscoelasticity was compared between tracheal secretion samples collected ventrally and dorsally. Mucus accumulation scoring showed excellent interobserver agreement and moderate horse-related variance, was related to measured volumes of 'artificial mucus', and correlated well with neutrophilic airway inflammation. Scores of mucus viscosity, colour and localisation showed high observer-related variance. Mucus accumulation, apparent viscosity and colour scores did not correlate with measured tracheal mucus viscoelasticity, but dorsally-localised mucus showed 2-fold higher measured viscoelasticity than ventrally-localised samples. Mucus accumulation scores are a reproducible measure of mucus volumes in the trachea. Endoscopic scoring of mucus accumulation is a reliable clinical and research tool. In contrast, apparent viscosity, localisation and colour scores should be interpreted with caution.

Airway responses to aerosolized brevetoxins in an animal model of asthma.

Florida red tide brevetoxins are sodium channel neurotoxins produced by the dinoflagellate Karenia brevis. When aerosolized, the toxin causes airway symptoms in normal individuals and patients with airway disease, but systematic exposures to define the pulmonary consequences and putative mechanisms are lacking. Here we report the effects of airway challenges with lysed cultures of Karenia brevis (crude brevetoxin), pure brevetoxin-2, brevetoxin-3, and brevetoxin-tbm (brevetoxin-2 minus the side chain) on pulmonary resistance and tracheal mucus velocity, a marker of mucociliary clearance, in allergic and nonallergic sheep. Picogram concentrations of toxin caused bronchoconstriction in both groups of sheep. Brevetoxin-tbm was the least potent, indicating the importance of the side chain for maximum effect. Both histamine H(1)- and cholinergic-mediated pathways contributed to the bronchoconstriction. A synthetic antagonist, beta-naphthoyl-brevetoxin-3, and brevenal, a natural antagonist, inhibited the bronchoconstriction. Only crude brevetoxin and brevetoxin-3 decreased tracheal mucus velocity; both antagonists prevented this. More importantly, picomolar concentrations of the antagonists alone improved tracheal mucus velocity to the degree seen with mM concentrations of the sodium channel blocker amiloride. Thus, Karenia brevis, in addition to producing toxins that adversely affect the airways, may be a source of agents for treating mucociliary dysfunction.

Evaluation of second generation amiloride analogs as therapy for cystic fibrosis lung disease.

Epithelial sodium channel (ENaC) blockers have been proposed as a therapy to restore mucus clearance (MC) in cystic fibrosis (CF) airways. The therapeutic effects of the first generation ENaC blocker, amiloride, in CF patients, however, were minimal. Because the failure of amiloride reflected both its low potency and short duration of action on airway surfaces, we investigated whether the increased potency of benzamil and phenamil would produce more favorable pharmacodynamic properties. In vitro potency, maximal efficacy, rate of recovery from maximal block of ENaC, and rate of drug absorption were compared for amiloride, benzamil, and phenamil in cultured human and ovine bronchial epithelial cells. In both human and ovine bronchial epithelia, the rank order of potency was benzamil > phenamil >> amiloride, the maximal efficacy was benzamil = phenamil = amiloride, the recovery to baseline sodium transport was phenamil < benzamil << amiloride, and the rate of drug absorption was phenamil > benzamil >> amiloride. Based on greater potency, benzamil was compared with amiloride in in vivo pharmacodynamic studies in sheep, including tracheal mucus velocity (TMV) and MC. Benzamil enhanced MC and TMV, but acute potency or duration of effect did not exceed that of amiloride. In conclusion, our data support the hypothesis that ENaC blocker aerosol therapy increases MC. However, rapid absorption of benzamil from the mucosal surface offset its greater potency, making it equieffective with amiloride in vivo. More potent, less absorbable, third generation ENaC blockers will be required for an effective aerosol CF pharmacotherapy.

Roles of anti-hemagglutinin IgA and IgG antibodies in different sites of the respiratory tract of vaccinated mice in preventing lethal influenza pneumonia

The roles of IgA and IgG antibodies (Abs) against hemagglutinin (HA) in the prevention of lethal influenza pneumonia in vaccinated mice were examined in terms of distribution and concentration of the Abs in the mucus or the serous fluid in different sites of the respiratory tract (RT), mucosa of the nose, trachea, bronchi and bronchioli and the alveolar epithelia of pulmonary acinus. First, the surface areas of the tracheal, bronchial and bronchiolar mucosa and alveolar epithelia were measured to be 20, 260 and 217,433 mm 2, respectively, using serial tissue sections of the trachea and lungs. Then, the volumes of the tracheal mucus, the bronchial and bronchiolar mucus and the serous fluid of alveolar epithelia were estimated to be 0.2, 2.6 and 21.7 mm 3, respectively, by calculating each from the surface area and an assumed thickness of the mucus layer (0.01 mm) or that of the serous fluid (0.0001 mm). Next, anti-HA IgA and IgG Ab responses in the nasal wash, the trachea-lung wash and the trachea wash were measured in BALB/c mice immunized intranasally with an adjuvant-combined A/PR/8/34 (H1N1) virus vaccine and challenged with a lethal dose of the virus. Then the values of Ab responses were converted to the mucus and serous fluid Ab concentration based on two premises that the serum Abs diffuse at a constant rate to the surface of the tracheal, bronchial and bronchiolar mucosa, and that the active transepithelial transport of IgA Abs does not work in the alveolar epithelia. Results showed that 21.4 μg/ml IgA Abs and 3.6 μg/ml IgG Abs in the tracheal mucus (19.1 and 0.3% of the trachea-lung wash IgA and IgG Ab amounts, respectively), 5.9 μg/ml IgA Abs and 3.6 μg/ml IgG Abs in the bronchial and bronchiolar mucus (66.0 and 3.4% of the trachea-lung wash IgA and IgG Ab amounts, respectively) and about 0.1 μg/ml IgA Abs and 12.3 μg/ml IgG Abs in the serous fluid of alveolar epithelia (14.9 and 96.3% of the trachea-lung wash IgA and IgG Ab amounts, respectively) were present in the vaccinated mice, at which concentrations influenza pneumonia was prevented. Thus, 96.3% of anti-HA IgG Abs in the trachea-lung wash work on the alveolar epithelia, whose surface area is about 800 times larger than that of tracheal, bronchial and bronchiolar mucosa and seem to play a more important role than the mucosal IgA Abs in the prevention of lethal influenza pneumonia.

Comparison of Mucociliary Clearance Velocities in Human and Rat Lungs for Extrapolation Modeling

Mucociliary clearance velocities in bronchial airway generations were calculated in asymmetric multiple-path models of the bronchial tree by solving mass transport equations based on the assumption of conservation of mucus volume and normalized to measured tracheal mucus velocities of 5.5 mm/min for humans and 1.9 mm/min for rats. Average mucus velocities decreased in a roughly exponential fashion with increasing airway generation number in the human lung and displayed a distinct two-exponential relationship in the rat lung due to its asymmetric branching. In contrast to the human lung, mucus velocities in single airways of the rat lung exhibited a significant statistical relationship with airway diameters but not with generation numbers, illustrating the monopodial nature of the branching pattern in the rat lung. Retention curves reflecting the combined effects of deposition and clearance were computed for particle diameters of 0.1, 1 and 2 μm for resting breathing conditions. These retention curves indicated that ~10–15% of the particles initially deposited in the bronchial tree were still retained in the human lung after 24 h, while all particles in the rat bronchial tree were cleared after ~6–8 h.

Effects of mechanical ventilation on platelet microparticles in bronchoalveolar lavage fluid

Introduction: Mechanical ventilation (MV) is considered to contribute to lung injury. Platelet membrane-derived microparticles (PMPs) are procoagulant and participate in the inflammatory process. The bronchoalveolar space could, besides plasma, be a site of origin of these microparticles. We evaluated the presence of these PMPs and two prostaglandin-derived metabolites in bronchoalveolar lavage fluid (BALF) regarding their possible relation to MV. Materials and methods: Before and after 1 h of MV, PMPs and prostaglandin metabolites were analyzed, in BALF from 14 anesthetized pigs, by flow cytometry and RIA, respectively. Tracheal mucus from five humans was analyzed for PMPs at extubation after surgery. Results: Activated PMPs and prostaglandin metabolites were present in all BALF samples. The time needed to count 5000 cellular events was prolonged six-fold after 1 h of mechanical ventilation ( p<0.001). The relative content of PMPs was constant in all samples. The PMPs were thrombogenic, i.e. they were fibrinogen, p-selectin and von Willebrand factor positive. Lavage did not per se affect the period necessary to count 5000 cellular events. PMPs in human tracheal mucus were in the same range as in the pig after 1 h of MV aiming at a PaCO 2 between 5.0 and 5.5 kPa. Conclusions: Activated PMPs are present in the pulmonary air–liquid interface. The prolongation of the time needed to count 5000 cellular events in BALF after MV indicates activation and adherence. Adherent microparticles bind neutrophils, which may aggravate pathological processes leading to pulmonary dysfunction. Evaluation of PMPs in BALF may be useful in evaluating strategies for lung-protective ventilator treatment.

Montelukast prevents antigen-induced mucociliary dysfunction in sheep.

The cysteinyl leukotrienes are potent proinflammatory mediators that, in addition to their bronchospastic actions, can also contribute to mucociliary dysfunction, a central component of the pathophysiology of asthma. In this study, we determined whether montelukast, a cysteinyl leukotriene 1 receptor antagonist, could prevent and/or reverse antigen-induced mucociliary dysfunction in allergic sheep. We measured tracheal mucus velocity, a marker of mucociliary clearance, before and for 8 hours after antigen challenge in six animals treated with montelukast (0.15 mg/kg, intravenously) 30 minutes before, 1 hour after, or 4 hours after antigen challenge. In the control trial, the sheep received 0.9% saline intravenously at each of the previously mentioned time points. The maximum decrease in tracheal mucus velocity seen in the control trial was 56 +/- 4% (mean +/- SE) of baseline at 8 hours. Pretreatment with montelukast significantly protected against this reduction. However, treatment at 1 and 4 hours neither protected against nor reversed the allergen-induced fall in tracheal mucus velocity. We conclude that the early release of cysteinyl leukotrienes may contribute to the fall in tracheal mucus velocity that follows acute antigen challenge and that pretreatment with montelukast reduces this impairment.

Evidence of an association between inflammatory airway disease and EIPH in young Thoroughbreds during training.

In an epidemiological study of risk factors for exercise-induced pulmonary haemorrhage (EIPH) in young Thoroughbreds in the UK, in which 148 horses contributed 1614 horse-months of data, there were 64 (4%) episodes of endoscopically visible tracheal bleeding and 824 (51%) episodes of increased quantities of haemosiderophages in tracheal washes. There were increases in prevalence and risk of EIPH by both definitions with age from < or = 2- > or = 4 years, season of sampling from winter (Nov-Jan) to autumn (Aug-Oct) and several different measures of airway inflammation, including tracheal mucus, neutrophil proportion, inflammation score and fungal material in tracheal washes. There was considerable variability in the prevalence of EIPH between trainers. EIPH in the preceding month significantly increased the risk of the condition the following month. There was no evidence that EIPH was associated with infection of the airways with even large numbers of Streptococcus zooepidemicus or Pasteurella-like spp., which are significantly associated with airway inflammation in younger racehorses. Multiple logistic regression modelling that took account of random variability between horses and the effects of each trainer and an episode the preceding month, confirmed that after controlling for the other risk factors, EIPH was still significantly associated with increasing age, different seasons, airway inflammation and evidence of airway fungal material.

Intratracheal pulmonary ventilation keeps tracheal tubes clean without impairing mucociliary transport

Background : Intratracheal pulmonary ventilation (ITPV) is a form of tracheal gas insufflation through a reverse thrust catheter that facilitates expiration and enhances CO 2 removal. Tracheas of sheep mechanically ventilated for 3 days with gas delivered through the reverse-thrust catheter remained free of secretions, without suctioning. It was hypothesized that: 1) The expiratory flow from the lungs, combined with continuous cephalad flow from the reversethrust catheter keeps endotracheal tubes clean; and 2) tracheal mucus velocity is not impaired by ITPV. Methods : A model trachea connected to a test lung and to a ventilator, via an 8-mm endotracheal tube, was used. Inspiratory and expiratory peak flow velocities and the movement of mucus in the model trachea and in the endotracheal tube were measured during conventional mechanical ventilation and ITPV. Tracheal mucus velocity was measured radiographically, using tantalum discs as markers, in seven intubated sheep ventilated for one hour with volume-controlled ventilation, and with ITPV. One millilitre Evans Blue dye was introduced into the trachea, to visualize mucus transport into the endotracheal tube. Results : Peak expiratory flow velocity exceeded peak inspiratory flow velocity by 100% during ITPV. During volume-controlled ventilation, flow velocities were equal. During ITPV, there was slow, then rapid cephalad movement of mucus in the model trachea, 0.5 cm distal to the tip of the endotracheal tube, the velocity increasing once mucus entered the endotracheal tube. During volume-controlled ventilation, no movement of mucus was found. Baseline tracheal mucus velocity was equal during volume-controlled ventilation and ITPV. Secretions stained with Evans Blue dye entered the endotracheal tube and were rapidly expelled from within the endotracheal tubes during ITPV; only traces of mucus were found in two sheep during volume-controlled ventilation. Conclusion : The enhanced expiratory flow during ITPV expels secretions from the endotracheal tube through entraining of mucus at the tip of the endotracheal tube. Tracheal mucus velocity is not influenced by ITPV.