U. Alkner

The‘nasal pool’device applies controlled concentrations of solutes on human nasal airway mucosa and samples its surface exudations/secretions

A‘nasal pool’(NP) device, a compressible plastic container with an adapted nozzle, was used to perform a continuous 10‐min nasal provocation and lavage. This novel technique brings known concentrations of agents into contact with a large and defined area of the nasal mucosal surface for extended periods of time. Simultaneously, the surface exudations/secretions of the same nasal mucosa are effectively sampled by the NP fluid. A concentration‐response study of histamine (80, 400 and 2000 μg/ml) was performed in 12 normal subjects on three different occasions. Exudation of plasma albumin into the lavage fluid was measured to quantitate the histamine‐induced airway inflammation. The effect of the dwell time on exudation was examined using histamine (400 μg/ml) instilled in the nasal cavity for time periods from 10 sec to 10 min. The time course of histamine‐induced plasma exudation response was studied by exposing the mucosa to histamine (400 μg/ml) for 12 min, with the NP renewed every minute. Allergen‐provocations were performed in subjects with hay fever and TAME‐esterase activity in the returned lavage fluid was determined to indicate the degree of response. Histamine produced a concentration‐dependent increase in albumin levels in the NP fluid; 123·3 ± 25·6, 213·8 ± 19·7 and 430·2 ± 32·0 μg/ml (mean ± s.e.m.), respectively. The time‐course study demonstrated that plasma exudation into the lumen occurred promptly and that the exudation response reached a maximum after exposure to histamine for 6–10 min. The dwell‐time experiments supported this finding. After 10 min the exudation appeared to decline despite the continued presence of histamine. Allergen provocation resulted in a concentration‐dependent increase in TAME‐esterase activity of the NP‐fluids. It is concluded that the NP technique provides new possibilities in studies of pathophysiology and pharmacology of human airway mucosa. With the NP technique controlled concentrations of mediators, drugs, tracers, etc. can be applied for desirable lengths of time on a well‐defined mucosal surface area. This particular area is gently and effectively lavaged during the presence of the NP fluid and when the fluid is recovered by decompressing the NP device.

Plasma exudation as a first line respiratory mucosal defence

A great variety of provocations of the airway mucosa produce extravasation of plasma from the abundant subepithelial microvessels. A plasma exudate has important actions through its volume, its specific and unspecific binding proteins, its enzyme systems, and its potent peptides (of kinin. complement, coagulation, fibrinolysis and other systems). If allowed to operate on the surface of an intact mucosa the plasma exudale would have important roles in normal airway defence. Recent observations in guinea‐pig tracheo‐bronchial airways and in human nasal airways suggest that the mucosal exudation of plasma into the airway lumen is a non‐injurious fully reversible process. Threshold exudative responses thus resulted in the appearance of an ‘unfiltered’ plasma exudate not only in the lamina propria but also on the surface of an undisrupted mucosa. Even after extensive luminal entry of exudate the epithelial lining was intact, as judged by light, fluorescence and electron microscopy. Hence, the epithelial barrier was reversibly permeable when approached from beneath by the plasma exudate. This was a distinct increase in outward permeability, because even during the exudation of plasma the mucosa remained a barrier to luminal solutes. It is possible that the exudate itself, by a slight compressive action on the basolateral aspect of epithelial cells, creates intercellular pathways for its entry into the lumen. Contrary to current beliefs, we propose that plasma exudation should be considered a first line respiratory defence mechanism operating together with other systems of the mucosal surface.

Albumin, bradykinins, and eosinophil cationic protein on the nasal mucosal surface in patients with hay fever during natural allergen exposure

This study examined plasma- and eosinophil-derived products in nasal lavage fluids obtained from patients with hay fever during natural allergen exposure. Nine patients with strictly seasonal allergic rhinitis and five normal, nonallergic subjects (control group) were studied. Nasal lavages were performed twice weekly, starting 1 week before the expected birch-pollen season and continuing for 6 weeks, thereby covering the entire birch-pollen season. Nasal symptoms and pollen counts were recorded daily. The lavage fluid was analyzed for it content of albumin, bradykinins, and eosinophil cationic protein (ECP). During the pollen season, each of these solutes was significantly increased in the nasal lavage fluid from the allergic patients (p less than 0.05) but not from the control subjects. Albumin, bradykinins, and ECP generally correlated better between themselves than with symptoms and pollen counts. We conclude that natural exposure to allergens induces plasma exudation and increased levels of ECP on the human nasal mucosa.

Reversibility and reproducibility of histamine induced plasma leakage in nasal airways.

Plasma exudation is one cardinal factor in airways defence and inflammation. In inflammatory airway diseases such as rhinitis and asthma, however, plasma leakage may also have a pathogenetic role. Experimental data from animals indicate that highly sensitive, active, and reversible processes regulate the vascular and mucosal permeability to macromolecules. With the use of a nasal lavage model for the recovery of liquids on the mucosal surface the effect of histamine on the macromolecular permeability of the airway endothelial-epithelial barriers was studied in normal subjects. The concentrations of albumin, kinins, and N-alpha-beta-tosyl-L-arginine-methyl esterase (TAME) in nasal lavage fluid were measured and nasal symptoms assessed by a scoring technique. The reproducibility of three repeated challenges with 30 minute intervals on the same day was studied in 12 subjects and compared with the same procedure (three challenges) on a different day. Sneezing decreased significantly (p less than 0.05) after the first histamine challenge but was maintained thereafter. Otherwise, the mean values for symptoms and for markers of vascular leakage were very similar both for the three challenges in the same session and for the two challenge sessions on a different day. Sneezing, blockage, and secretions were associated with increased concentrations of TAME esterase (maximum 9000 cpm/ml), kinins (1.4 ng/ml), and albumin (0.3 g/l) in lavage fluid. Both the symptoms and the measures of plasma exudation were reversible and reproducible in the three repeat histamine challenges and at two challenge sessions on different days. These findings support the view that non-injurious, active processes regulate the inflammatory flow of macromolecules across airways endothelial-epithelial barriers. The present experimental approach would be suitable for studies of the modulatory effects of inflammatory stimulus induced plasma leakage and symptoms in human airways.

Mucosal Exudation of Fibrinogen in Coronavirus-induced Common Colds

We studied the mucosal exudation of plasma in relation to pathophysiological events during an induced common cold. Coronavirus 229E was inoculated nasally in 20 healthy volunteers under controlled conditions. Ten volunteers developed the common cold, determined by symptom scores and serology. The bulk plasma exudate was monitored, using fibrinogen (MW 340 kD) in nasal lavage fluids as an endogenous marker. Following inoculation, anterior rhinoscopy and objective registrations of nasal mucosal temperature, nasal discharge weight, and nasal blockage index by peak expiratory air flow, were followed twice daily for 6 days. Mucosal plasma exudation, as assessed by fibrinogen in lavage fluids, increased hundredfold after virus inoculation, concomitantly with the subjective symptoms and objective physiological changes. We propose that this exudation reflects the degree of subepithelial inflammation, and suggests that plasma bulk exudate, including all potent plasma protein systems may be involved in the resolution of acute viral rhinitis--common cold.

Glucocorticoid-induced attenuation of mucosal exudation of fibrinogen and bradykinins in seasonal allergic rhinitis

The mucosal plasma exudate with its proteins, enzymes, derived peptides, and matrix molecules is an important factor in inflammatory airway diseases. This study investigated whether topical glucocorticosteroid treatment influences mucosal exudation of bulk plasma (fibrinogen) and the generation of plasma‐derived mediators (bradykinins) in seasonal allergic rhinitis. Twenty‐two patients with birch‐pollen‐induced allergic rhinitis participated in a double‐blind, randomized, placebo‐controlled study during the birch pollen season in 1989. After a 2‐week run‐in period, the participants received treatment with budesonide (200 μg per nasal cavity and day) or placebo. The patients kept a diary to record their daily nasal symptoms (itching, sneezing, nasal blockage, and secretion). The amount of birch pollen in the air was determined with the aid of a Burkhard pollen trap. A nasal lavage was performed once a week, and the levels of bradykinins and fibrinogen were determined in the lavage fluid samples. The birch pollen season was very mild, resulting in only minor nasal symptoms. In spite of the low pollen exposure, treatment with budesonide reduced the lavage fluid levels of both bradykinins and fibrinogen. The present results show that topical glucocorticosteroid treatment attenuates plasma exudation and the generation of plasma‐derived mediators in seasonal allergic rhinitis. This action may not result from simple vascular antipermeability effects of the drug but may rather reflect the anti‐inflammatory efficacy of topical glucocorticoids in the airway mucosa.

Topical vasoconstrictor (oxymetazoline) does not affect histamine-induced mucosal exudation of plasma in human nasal airways

Mucosal exudation of almost unfiltered plasma proteins, plasma‐derived mediators and fluid has recently been advanced as a major respiratory defence mechanism. Oxymetazoline chloride is a commonly used decongestant agent. By reducing blood flow it may reduce mucosal exudation and thus compromise the mucosal defence capacity. This study examines the effect of topically applied oxymetazoline on histamine‐induced plasma exudation into human nasal airways. Twelve normal volunteers participated in a double‐blind, randomized, cross‐over and placebo‐controlled study with pretreatment with a single dose oxymetazoline chloride (5 μg or 50 μg; a dose previously known to reduce nasal mucosal blood flow by almost 50%) prior to the histamine challenge sequence. Nasal lavages were performed every 10 min for 140 min, and three histamine challenges were performed at 30‐min intervals during this period. The concentrations of two exudative indices, N‐alpha‐tosyl‐l‐arginine methyl ester (TAME)‐esterase activity and albumin, were measured in the nasal lavage fluids. Nasal symptoms (sneezing, nasal secretion and blockage) were assessed by a scoring technique.

Microvascular exudative hyperresponsiveness in human coronavirus-induced common cold.

BACKGROUND--The inflammatory response of the airway microcirculation in rhinitis and asthma may be recorded as luminal entry of plasma macromolecules (mucosal exudation). This study examines the exudative responsiveness of the subepithelial microvessels in subjects with and without common cold after inoculation with coronavirus. METHODS--The airway mucosa was exposed to exudative concentrations of histamine (40 and 400 micrograms/ml) before and six days after inoculation. To assess whether mucosal penetration of a topically applied agent was altered, nasal absorption of chromium-51 labelled ethylene diamine tetraacetic acid (51Cr-EDTA, MW 372) was also examined. A nasal pool technique kept the challenge and tracer solutes in contact with the same ipsilateral mucosal surface. Concentrations of albumin in lavage fluids were measured as an index of mucosal exudation of plasma. Nasal absorption of 51Cr-EDTA was determined by the cumulated 24 hour urinary excretion of radioactivity. RESULTS--Nine subjects developed common cold after coronavirus inoculation and 10 remained healthy. Histamine produced concentration dependent mucosal exudation of plasma in all subjects before and after coronavirus inoculation. In subjects with common cold, however, the histamine-induced mucosal exudation was significantly augmented compared with the group without common cold. This exudative hyperresponsiveness is not explained by an increased baseline exudation because the lavage regimen used produced comparably low baseline exudation in both groups of subjects, nor is it explained by an increased penetration of topical histamine because the ability of the nasal mucosa to absorb 51Cr-EDTA was not significantly increased in the subjects with common cold. CONCLUSIONS--An increased proclivity of the airway subepithelial microcirculation to respond with plasma exudation develops during coronavirus-induced common cold. This specific exudative hyperresponsiveness may be a feature of inflammatory airway diseases.

Antiallergic actions of high topical doses of terbutaline in human nasal airways.

It is debatable whether β2‐receptor agonists produce antiallergic effects in human airways. This question has been addressed in the present study by examination of both mast‐cell indices and the physiologic response to allergen challenge in human nasal airways. Twelve asymptomatic patients with seasonal allergic rhinitis were investigated outside the pollen season. Intranasal allergen provocation was carried out with diluent and three increasing doses of allergen. Topical terbutaline sulfate (1.0 mg) was given 5 min prior to each allergen challenge and nasal lavage was carried out 10 min after each challenge. The study design was double‐blind, placebo‐controlled, crossover, and randomized. The allergen challenge‐induced mast‐cell activation and the ensuing physiologic response of the airway tissue were investigated by measuring a mast‐cell‐derived mediator (tryptase) and plasma proteins (albumin and α2 macroglobulin), respectively, in the lavage fluids. Allergen provocation produced dose‐dependent increments of nasal symptoms and lavage fluid levels of tryptase, albumin and α2‐macroglobulin. Both nasal symptoms (p≤0.05) and lavage fluid levels of tryptase (p≤0.05), albumin (p≤0.05), and α2‐macroglobulin (p≤0.01) were reduced by pretreatment with topical terbutaline sulfate. We conclude that high doses of topical terbutaline may produce significant antiallergic effects in human airways by equally reducing both tryptase release and plasma exudation in the acute allergic reaction in human airways. Further studies are now warranted to determine whether microvascular antipermeability effects of (β2‐receptor stimulation contribute to the present observations.

Anti-IgE-induced accumulation of leukocytes, mediators, and albumin in skin chamber fluid from healthy and atopic subjects

The aim of this study was to examine potential differences between healthy and atopic subjects with regard to IgE-mediated cutaneous inflammation. For this purpose, we analyzed histamine, tryptase, leukotriene B4, albumin, eosinophils, and total leukocytes in skin chamber fluid after challenge with anti-human IgE. We also measured gross skin reactivity (wheal, flare, and late-phase reactions), circulating IgE, and eosinophils, as well as the state of eosinophil activation. It was found that despite having more circulating IgE, the skin responsiveness of the atopic subjects did not differ significantly from that of the nonatopic subjects with respect to mediator release, albumin extravasation, or total recruitment of leukocytes. Moreover, the sizes of anti-IgE-induced wheal, flare, and late-phase reactions were very similar in the two groups. On the other hand, significant recruitment of eosinophils during the IgE-mediated reaction was more or less restricted to the atopic group. Yet the recruited eosinophils, of which the majority was in an early state of activation before degranulation, did not seem to contribute significantly to the IgE-mediated delayed skin edema. Furthermore, the eosinophil count in anti-IgE chambers of the atopic subjects did not correlate with any of the other parameters monitored. Thus because the anti-IgE-induced recruitment of eosinophils appeared to be unrelated to factors such as the number of peripheral blood eosinophils, the degree of mast cell activation, the intensity of inflammatory skin changes, and the level of circulating IgE, it is apparent that the mechanisms for and pathophysiologic role of IgE-mediated dermal eosinophil accumulation in atopic subjects require further investigation.