Nasal secretions and exudations : collection and approaches to analysis

Nasal and bronchoalveolar lavage techniques, as well as sputum inductiontechniques, are frequently used for sampling of airway mucosal surface liquids, together with their contents of cell products, plasma proteins, glandular secretions and cells. These techniques continue to provide new information on the nature and pharmacology of airway inflammation in rhinitis and asthma. The relative ease and safety by which nasal lavage techniques can be employed, their repeatability, and the possibility for control of important factors, make it advantageous to use the nose in clinical studies of airway disease mechanisms. The nasal airway thus offers the attractive possibility of exploring gross as well as molecular events directly in the complex, but relevant, disease biosystem. A patient-orientated m vivo focus is also needed, we think, for original discovery of important airway disease mechanisms. This need seems increasingly urgent since many central airway in vivo events have been incompletely researched and since concepts built on data from reductive test systems, such as cell culture and mouse models, may not always translate well into human in vivo events (1,2). Additionally, the nasal studies are important because they may provide insights into the biology, physiology, and pharmacology of human mucosal mechanisms, also of other parts of the respiratory tract, notably the difficult-to-reach bronchial mucosa (3).

Secretoneurin is released into human airways by topical histamine but not capsaicin

BACKGROUND

The neuropeptide secretoneurin, with potential relevance to leukocyte trafficking, is present in nerves of the nasal mucosa in allergic rhinitis and may be released in response to allergen and histamine exposure. There is no information on the occurrence and mechanisms of release of secretoneurin in healthy human airways.

METHODS

The presence of secretoneurin in nasal biopsies and its release in response to nasal capsaicin and histamine challenges were examined. Symptoms and lavage fluid levels of fucose were recorded as markers of effects in part produced by neural activity. Bronchial histamine challenges followed by sputum induction and analysis of secretoneurin were also carried out.

RESULTS

Nerves displaying secretoneurin immunoreactivity abounded in the nasal mucosa. Nasal capsaicin challenge produced local pain (P <0.05) and increased the levels of fucose (P <0.05), but failed to affect the levels of secretoneurin. Nasal histamine challenge produced symptoms (P <0.05) and increased the mucosal output of secretoneurin (P <0.05) and fucose (P <0.05). Bronchial histamine challenge increased the sputum levels of secretoneurin (P <0.05).

CONCLUSIONS

We conclude that secretoneurin is present in healthy human airways and that histamine evokes its release in both nasal and bronchial mucosae. The present observations support the possibility that secretoneurin is involved in histamine-dependent responses of the human airway mucosa.

Rapid and efficient clearance of airway tissue granulocytes through transepithelial migration

BACKGROUND

Clearance of tissue granulocytes is central to the resolution of airway inflammation. To date the focus has been on apoptotic mechanisms of cell removal and little attention has been given to alternative processes. The present study explores transepithelial migration as a mechanism of cell clearance.

METHOD

Guinea pig tracheobronchial airways where eosinophils are constitutively present in the mucosal tissue were studied. A complex topical stimulus (allergen challenge) was applied and the fate of the eosinophils was determined by selective tracheobronchial lavage and histological examination of the tissue.

RESULTS

Within 10 minutes of the allergen challenge, massive migration of eosinophils into the airway lumen occurred together with a reduction in tissue eosinophil numbers. Cell clearance into the lumen continued at high speed and by 30 and 60 minutes the tissue eosinophilia had been reduced by 63% and 73%, respectively. The marked transepithelial migration (estimated maximal speed 35,000 cells/min x cm2 mucosal surface) took place ubiquitously between epithelial cells without affecting epithelial integrity as assessed by transmission and scanning electron microscopy. Eosinophil apoptosis was not detected but occasional cytolytic eosinophils occurred.

CONCLUSION

This study shows that luminal entry has a remarkably high capacity as a granulocyte elimination process. The data also suggest that an appropriate stimulus of transepithelial migration may be used therapeutically to increase the resolution of inflammatory conditions of airway tissues.

Gut mucosal uptake and retention characteristics contribute to the high intestinal selectivity of budesonide compared with prednisolone in the rat

BACKGROUND

Budesonide and prednisolone are both effective for the treatment of inflammatory bowel disease, but budesonide produces fewer adverse systemic effects. High first-pass hepatic inactivation of budesonide partially explains its favourable ratio between topical and systemic activity, but it is probable that its uptake and retention in intestinal target tissues are also contributory.

AIM

To compare the uptake and retention of radio-labelled budesonide and prednisolone in rat ileal mucosa in vivo.

METHODS

3H-Budesonide and 3H-prednisolone were applied for 10 min directly to a perfused segment of rat ileum in vivo, followed by saline lavage every 10 min. Steroid uptake into the mucosa and submucosa was assessed at 20 min and 4 h. The uptake of budesonide was also measured in allergen-challenged animals vs. saline-challenged controls to assess whether inflammation of the mucosa with ongoing plasma exudation would impair its uptake.

RESULTS

Budesonide was better absorbed into ileal tissue (15-fold at 20 min) than prednisolone and better retained (50-fold at 4 h) after topical administration. The uptake of budesonide was not impaired by exudation processes following allergen challenge.

CONCLUSIONS

The higher uptake and retention characteristics of budesonide in gut mucosa should contribute to its greater intestinal selectivity compared with that of prednisolone.

Lung tissue eosinophils may be cleared through luminal entry rather than apoptosis: effects of steroid treatment

Spontaneous or steroid-induced eosinophil apoptosis occurring in vitro has not been demonstrated in lung tissues in vivo. This study examines cell apoptosis in rat lungs using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) technique and transmission electron microscopy (TEM). After establishing sustained lung edema and eosinophilia by challenge with Sephadex beads intratracheally, budesonide treatment was started intratracheally. Sephadex alone increased the total number of apoptotic cells, which were not efficiently engulfed by macrophages or other cells, in vivo. Yet apoptotic tissue eosinophils were exceedingly rare (1 of 360 TEM-analyzed eosinophils). By contrast, approximately 20% of eosinophils in the airway lumen were apoptotic, and unengulfed. Budesonide promptly inhibited edema but 3 d of steroid treatment were required to reduce the established tissue eosinophilia. Not at any time point did budesonide induce eosinophil apoptosis (0 of 318 TEM-analyzed tissue eosinophils). We conclude that (1) eosinophil apoptosis can occur but is a rare event in vivo in respiratory tract tissues; (2) airway tissue eosinophils, rather than undergoing apoptosis, are eliminated by migration into airway lumen followed by apoptosis and mucociliary clearance; (3) anti-inflammatory steroid treatment may not increase eosinophil apoptosis in vivo nor may it affect the luminal entry of eosinophils; (4) steroids permit elimination of eosinophils into airway lumen and slowly resolve established lung eosinophilia.

Topical and oral anti-inflammatory activity of budesonide compared with oral prednisolone in an animal model using allergen-induced gut mucosal exudation of plasma as a marker

BACKGROUND

Development of topically active glucocorticosteroids with minimal systemic effects is paramount in improving therapy in inflammatory bowel disease. Our experimental model in the rat has proved useful for assessing topical versus systemic anti-inflammatory potency of glucocorticosteroids on the inflamed gut.

METHODS

Experiments were performed on allergen-sensitized perfused rat ileum in vivo. Mucosal exudation of plasma, induced by local allergen perfusion, was measured as the appearance of circulating 125I-labelled albumin in the gut lumen. Experiments compared the anti-exudative effects of oral budesonide (0.1 mg/kg) with oral prednisolone (1, 3.3 or 10 mg/kg) and saline, given by oral gavage 24 h prior to allergen challenge, and of topical budesonide (3 x 10(-5) mol/L) with saline, administered in the perfusate 4 h prior to allergen challenge. Systemic glucocorticosteroid activity was assessed by weighing thymus glands after sacrifice.

RESULTS

Allergen-induced plasma exudation was significantly reduced by oral budesonide, oral prednisolone (dose-dependently) and topically applied budesonide; topical budesonide was effective within 4 h. While prednisolone significantly reduced the relative thymus weight at both 3.3 and 10 mg/kg, budesonide given orally, 0.1 mg/kg, or topically, 3 x 10(-5) mol/L, had no significant effect.

CONCLUSION

Budesonide, administered orally or topically, shows higher selectivity for the gut mucosa than prednisolone and produces local anti-inflammatory responses comparable to prednisolone, without the accompanying systemic effects.

Mucosal output of eotaxin in allergic rhinitis and its attenuation by topical glucocorticosteroid treatment

BACKGROUND

Eotaxin is a chemokine that attracts and activates eosinophils. The present study examines the occurrence of eotaxin in nasal mucosal surface liquids in patients with seasonal allergic rhinitis without allergen exposure and during repeat allergen challenge with and without topical glucocorticosteroid treatment. The number of subepithelial eosinophils and mucosal outputs of bulk plasma (alpha2-macroglobulin) and eosinophil cationic protein (ECP) are also examined.

METHODS

Twelve patients underwent daily allergen challenges for 6 days. Separately, 14 patients, who were receiving budesonide and placebo in a parallel group design, also underwent allergen challenge for 6 days. Nasal biopsies were obtained before and 24 h after the allergen challenge series, and lavages were carried out before and 15 min after selected allergen challenges.

RESULTS

At baseline nasal lavage fluid levels of eotaxin correlated to levels of alpha2-macroglobulin and ECP. After the first allergen challenge there was a correlation between nasal lavage fluid levels of eotaxin and ECP. Repeat allergen exposure increased the mucosal output of eotaxin (P <0.05) and ECP (P <0.01) as well as eosinophil numbers (P <0.01), but no correlation was found between increased eosinophil numbers and eotaxin. Budesonide reduced eotaxin levels during repeat allergen challenge (P <0.05).

CONCLUSIONS

Repeat allergen exposure in allergic rhinitis is associated with increased mucosal output of eotaxin. Topical budesonide attenuates this effect, suggesting the possibility that inhibitory effects on mucosal eotaxin may contribute to anti-eosinophilic actions of topical glucocorticosteroids.

Degranulation patterns of eosinophil granulocytes as determinants of eosinophil driven disease

BACKGROUND

Degranulation of eosinophils in target tissues is considered a key pathogenic event in major chronic eosinophilic diseases. However, because of a lack of appropriate methods, little is known about degranulation of eosinophils in common eosinophilic diseases.

METHODS

Using transmission electron microscopic (TEM) analysis, a novel approach has been devised and validated to quantify eosinophil degranulation in human tissues (assessed in individual cells as percentage granules with structural signs of protein release). Biopsy specimens from patients with inflammatory bowel disease, allergic rhinitis, asthma, and nasal polyposis were evaluated.

RESULTS

All conditions displayed a similar degree of local tissue eosinophilia, with no differences being observed in eosinophil numbers in the airway mucosa of patients with airway diseases and the colonic mucosa of those with inflammatory bowel disease (IBD). In contrast, marked differences in the mean (SE) extent of eosinophil degranulation were observed between the patient groups; IBD 9.3 (1.4)% altered granules, artificial and natural allergen challenge induced allergic rhinitis 67.8 (6.8)% and 86.6 (3.0)%, respectively, asthma 18.1 (2)%, and nasal polyposis 46.6 (7.6)%.

CONCLUSIONS

This study provides the first quantitative data which show that different eosinophilic conditions, despite having similar numbers of tissue eosinophils, may exhibit markedly different degranulation patterns. The present assessment of piecemeal degranulation would thus make it possible to delineate the conditions under which eosinophils are likely to contribute to disease processes. This novel type of analysis may also guide and validate anti-eosinophilic treatment options.

Prevalence of nasal symptoms and their relation to self-reported asthma and chronic bronchitis/emphysema

Little information is available on associations between rhinitis and chronic bronchitis/emphysema (CBE). Self-reported upper airway symptoms, asthma, and CBE were examined in 12,079 adults living in southern Sweden. The response rate was 70% (n=8,469), of whom 33% reported significant nasal symptoms: a blocked nose was reported by 21%; sneezing by 18%; nasal discharge by 17%; and thick yellow nasal discharge by 5.7%. Nasal symptoms and combined nasal and self-reported bronchial disease were generally more common among smokers than nonsmokers. There was little overlap between asthma and CBE, but 46% of those with asthma and 40% of those with CBE had significant nasal symptoms. Best predicting factors (odds ratios >3) for asthma and CBE were nasal symptoms due to exposure to animals and damp/cold air, respectively. One-third of an adult, southern Swedish population, had significant allergic and/or nonallergic nasal symptoms. Nasal symptoms were frequently found to coexist with both asthma and chronic bronchitis/emphysema, suggesting that pan-airway engagement is common in both diseases. Differing associations between types of nasal symptoms and allergic and irritant triggers of nasal symptoms, with regard to asthma and chronic bronchitis/emphysema, emphasize the different natures of these bronchial diseases.

Degranulation status of airway tissue eosinophils in mouse models of allergic airway inflammation

Eosinophil degranulation is a characteristic feature of asthma and allergic rhinitis. However, degranulated eosinophils have not been convincingly demonstrated in the common mouse models of these airway diseases. This study uses eosinophil peroxidase (EPO) histochemistry and transmission electron microscopy (TEM) analysis to assess eosinophil degranulation in the airways of ovalbumin (OVA)-sensitized and challenged BALB/c and C57BL/6 mice. Using TEM we also examined mouse and human blood eosinophils after in vitro incubation with formyl-Met-Leu-Phe (fMLP) or phorbol myristate acetate (PMA). Although OVA exposure induced significant nasal and lung eosinophilia, we did not observe any of the known cellular processes by which eosinophils release their granule products, i.e., eosinophil cytolysis, piecemeal degranulation, and exocytosis. The occurrence of other allergen-induced degranulation events was ruled out because no difference in granule morphology was observed between lung-tissue eosinophils and blood or bone-marrow eosinophils from control animals. Accordingly, there was no detectable extracellular EPO in lung tissues of allergic mice. Similarly, mouse blood eosinophils remained nondegranulated in vitro in the presence of fMLP and PMA, whereas the same treatment of human eosinophils resulted in extensive degranulation. This investigation indicates that OVA-induced airway inflammation in the present mouse strains does not involve significant eosinophil degranulation. It is speculated that this dissimilarity from the human disease may be due to a fundamental difference in the regulation of mouse and human eosinophils.

Immediate effect of topical budesonide on allergen challenge-induced nasal mucosal fluid levels of granulocyte-macrophage colony-stimulating factor and interleukin-5

The nasal antiinflammatory effects produced by maintenance treatment with topical steroids include reduced production of cytokines. The present study explored nasal mucosal effects induced during the first 9 h after a single dose of topical budesonide. Nine subjects with allergic rhinitis due to birch or timothy pollen were given budesonide (256 microg; Rhinocort Aqua) or placebo in a double-blind, randomized, crossover (4 wk washout) manner. Nasal allergen challenges were performed 30 min after the steroid/placebo pretreatment. Before and 30 min, 1, 3, 5, 7, and 9 h after challenge, filter paper strips were placed on the nasal septum and inferior turbinates for 10 min to sample undiluted mucosal fluids. Strips were then extracted in 1 ml buffer for cytokine analysis (ELISA). Allergen challenge produced acute nasal symptoms that peaked at 30 min and then tapered off. Conversely, both GM-CSF and IL-5 were increased only at 3, 5, 7 and 9 h (p < 0.05 compared with baseline). Budesonide did not affect the nasal symptoms but inhibited (p < 0. 05; compared with placebo treatment) the allergen challenge-induced mucosal output of GM-CSF and IL-5. These data demonstrate that GM-CSF and IL-5 are induced in a nonsymptomatic, late phase response to nasal allergen challenge, and that this cytokine response is prevented by single dose budesonide pretreatment.

Effects of benzalkonium chloride on innate immunity physiology of the human nasal mucosa in vivo

OBJECTIVE

Benzalkonium chloride (BC) is a preservative commonly used in nasal decongestant sprays. It has been suggested that BC may be harmful to the nasal mucosa. The present study, involving healthy volunteers, examines effects of BC on nasal mucosal end-organ functions.

METHODS

Isotonic saline and BC (0.1 mg/mL) were administered acutely to the nasal mucosa using a nasal pool device. Nasal symptoms were determined. Nasal lavage fluid levels of alpha2-macroglobulin and fucose were measured as indices of plasma exudation and glandular secretion, respectively. In addition, BC (0.1 mg/mL) was given as single actuations of 100 microL per nasal cavity three times daily for 10 days. The ability of histamine (0.4 mg/mL) to evoke nasal symptoms and plasma exudation responses was determined before and after the repeated BC administration series.

RESULTS

BC produced immediate nasal smart or pain (P < .05), but tolerance to this response developed by repeated administrations. BC increased nasal mucosal output of fucose (P < .05), whereas nasal lavage fluid levels of alpha2-macroglobulin were unaffected. Histamine produced significant symptoms and mucosal exudation of alpha2-macroglobulin (P values < .01), equally before and after the 10 days of BC exposure.

CONCLUSIONS

BC in dosages commonly used as preservative in nasal decongestant sprays produced short-term glandular secretion and nasal smart or pain. However, 10 days' frequent exposure to BC was not associated with untoward symptomatic effects, nor was a sensitive mucosal variable such as histamine-induced exudative responsiveness affected by this repeated exposure 1 BC.

Allergen challenge-induced acute exudation of IL-8, ECP and alpha2-macroglobulin in human rhinovirus-induced common colds

Rhinovirus infections cause exacerbations of eosinophilic airway disease. The acute effects of allergen‐challenge on nasal interleukin‐8 (IL‐8), eosinophil cationic protein (ECP), and α₂‐macroglobulin were examined in atopic subjects with common cold symptoms.

Twenty‐three patients with seasonal allergic rhinitis were inoculated with human rhinovirus 16 outside the pollen season. Diluent and allergen challenges, followed by nasal lavages, were carried out about 3 months before and 4 days after virus inoculation.

Seventeen patients developed significant common cold symptoms with increased nasal lavage fluid levels of α₂‐macroglobulin, IL‐8, and ECP at baseline (p<0.001–0.05 versus before inoculation), and were further increased by allergen challenge (p<0.001–0.05); IL‐8 and ECP levels were correlated (r=0.63, p<0.001). Before inoculation, the six patients who later did not develop common cold symptoms had high levels of IL‐8 and myeloperoxidase (MPO), and exhibited strong allergen‐induced plasma exudation responses (α₂‐macroglobulin). After inoculation, IL‐8 and ECP did not increase in these symptomless subjects.

In conclusion, high nasal interleukin‐8 and myeloperoxidase levels and exudative hyperresponsiveness may protect against infection. The association between nasal interleukin‐8 and eosinophil cationic protein in common cold, particularly that observed in nasal lavage fluids after allergen‐induced acute exudation of plasma, suggests the involvement of interleukin‐8 in exacerbation of airway mucosal eosinophil activity.

Role of macrophage migration inhibitory factor (MIF) in allergic and endotoxin-induced airway inflammation in mice

Macrophage migration inhibitory factor (MIF) has recently been forwarded as a critical regulator of inflammatory conditions, and it has been hypothesized that MIF may have a role in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD). Hence, we examined effects of MIF immunoneutralization on the development of allergen-induced eosinophilic inflammation as well as on lipopolysaccharide (LPS)-induced neutrophilic inflammation in lungs of mice. Anti-MIF serum validated with respect to MIF neutralizing capacity or normal rabbit serum (NRS) was administered i.p. repeatedly during allergen aerosol exposure of ovalbumin (OVA)-immunized mice in an established model of allergic asthma, or once before instillation of a minimal dose of LPS into the airways of mice, a tentative model of COPD. Anti-MIF treatment did not affect the induced lung tissue eosinophilia or the cellular composition of bronchoalveolar lavage fluid (BALF) in the asthma model. Likewise, anti-MIF treatment did not affect the LPS-induced neutrophilia in lung tissue, BALF, or blood, nor did it reduce BALF levels of tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-1alpha (MIP-1alpha). The present data suggest that MIF is not critically important for allergen-induced eosinophilic, and LPS-induced neutrophilic responses in lungs of mice. These findings do not support a role of MIF inhibition in the treatment of inflammatory respiratory diseases.

Experimental common cold increases mucosal output of eotaxin in atopic individuals

BACKGROUND

In view of recent observations demonstrating that rhinovirus infections are associated with increased local activity of eosinophils, we hypothesized that eotaxin, a selective eosinophil chemoattractant, may be involved in eosinophil recruitment/activation in common cold infections.

METHODS

Twenty-three patients with seasonal allergic rhinitis were inoculated with human rhinovirus 16 (HRV 16) outside the pollen season. Sequential diluent and allergen (10(3) SQ-U) challenges, each followed by nasal lavage, were carried out about 3 months before and 4 days after virus inoculation.

RESULTS

Seventeen patients developed common cold and were further analyzed. Lavage fluid levels of eotaxin were increased at the height of active common cold (day 4 after inoculation) both at baseline (after diluent challenge) (P<0.01) and acutely after allergen challenge (P<0.05).

CONCLUSIONS

Common cold symptoms after nasal HRV 16 inoculation are associated with increased nasal mucosal output of eotaxin, suggesting that this chemokine is partly responsible for recruitment/activation of airway mucosal eosinophils in common cold infections.

Allergen-induced eosinophil cytolysis is a primary mechanism for granule protein release in human upper airways

Cytotoxic eosinophil granule proteins are considered important in the pathogenesis of allergic airway diseases such as rhinitis and asthma. To explore the cellular mechanisms behind eosinophil granule release in human allergic airways, 16 symptom-free patients with seasonal allergic rhinitis were challenged daily with allergen during 1 wk. Nasal lavage samples and biopsies, obtained before and 24 h after the last allergen exposure, were processed for immunohistochemical and electron microscopic analysis. The allergen challenges produced nasal symptoms, marked tissue eosinophilia, and an increase in lavage fluid levels of eosinophil cationic protein (ECP). The nasal mucosa areas with intense extracellular immunoreactivity for ECP were associated with abundant free eosinophil granules. Electron microscopy confirmed the free granules and revealed that all mucosal eosinophils were involved in granule release, either by cytolysis (33%) or piecemeal degranulation (PMD) (67%). Resting or apoptotic eosinophils were not observed. Cytolytic eosinophils had less signs of intracellular granule release (p < 0. 001) and a higher content of intact granules (p < 0.001) compared with viable eosinophils in the same tissue. This study demonstrates eosinophil cytolysis (ECL) as a distinct mechanism for granule mediator release in human allergic airway mucosa. The nature and extent of the ECL and its product (i.e., protein-laden extracellular granules) indicate that allergen-induced cytolysis is a primary and major mechanism for the release of eosinophil proteins in human allergic airway inflammation in vivo.

Effects of hydrogen peroxide on the guinea-pig tracheobronchial mucosa in vivo

Lumenal entry of plasma (mucosal exudation) is a key feature of airway inflammation. In airways challenged with histamine-type mediators and allergen the mucosal exudation response occurs without causing epithelial derangement and without increased airway absorption. In contrast, reactive oxygen metabolites may cause mucosal damage. In this study, involving guinea-pig airways, we have examined effects of H2O2 on airway exudation and absorption in vivo. Vehicle or H2O2 (0.1 and 0.5 M) was superfused onto the tracheobronchial mucosal surface through an oro-tracheal catheter. 125I-albumin, given intravenously, was determined in tracheobronchial tissue and in lavage fluids 10 min after challenge as an index of mucosal exudation of plasma. The tracheobronchial mucosa was also examined by scanning electron microscopy. In separate animals, 99mTc-DTPA was superfused 20 min after vehicle or H2O2 (0.1 and 0.5 M) had been given. A gamma camera determined the disappearance rate of 99mTc-DTPA from the airways as an index of airway absorption. The high dose of H2O2 (0.5 M) produced epithelial damage, increased the absorption of 99mTc-DTPA (P < 0.001), and increased the exudation of plasma (P < 0.001). Notably, it appeared that all extravasated plasma had entered the airway lumen within 10 min. These data demonstrate that H2O2 differs from exudative autacoids such as histamine by causing both epithelial damage and plasma exudation responses. These data also agree with the view that the epithelial lining determines the rate of absorption and is responsible for the valve-like function that allows lumenal entry of extravasated bulk plasma without any increased inward perviousness.

Circulating eosinophil/basophil progenitors and nasal mucosal cytokines in seasonal allergic rhinitis

Accumulation of eosinophils in the airways is characteristic of allergic rhinitis and asthma. The tissue eosinophilia may involve both recruitment of mature eosinophils and proliferation of their progenitors. This study examines mature eosinophils (nasal and circulating), their circulating progenitors, and a potential role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in stimulating these progenitors. Twelve subjects with a history of seasonal allergic rhinitis and positive skin prick test for birch pollen were studied during four periods: shortly before, in the early and intense phase, at the end, and well after the Swedish birch-pollen season. Nasal mucosal and circulating eosinophils were examined in both nasal brushings and peripheral blood samples. Eosinophil/basophil progenitors were determined by counting colony-forming units in nonadherent mononuclear blood-cell cultures in methylcellulose at 14 days. The nasal mucosal cytokines GM-CSF, interleukin (IL)-1beta, IL-3, IL-5, IL-6, IL-8, and RANTES were analyzed (ELISA) in nasal lavage (NAL) fluids. All patients developed severe symptoms of rhinitis at the height of the season, with increased numbers of eosinophils in the nasal mucosa (P<0.05) and in the circulation (P<0.05). At this time point, the number of circulating progenitors (P<0.05) and the NAL fluid level of GM-CSF (P<0.05) were also increased. In contrast, there was no change in the NAL fluid levels of IL-1beta, IL-3, IL-6, or IL-8. Neither IL-5 nor RANTES could be detected in any of the NAL fluids. At the end of or after the season, there was no increase in nasal eosinophils or circulating eosinophils or progenitors (P>0.05). Ex vivo addition of GM-CSF (10-100 U) increased the number of blood progenitors grown before (P<0.01) and after (P<0.05) the season, compared with during the season. The in vitro GM-CSF responsiveness of progenitors may be related to whether or not these already have been stimulated endogenously by GM-CSF. Taken together, our data thus suggest that GM-CSF may play a role in vivo to increase production of eosinophilic progenitors in allergic airway disease.

Alpha2-macroglobulin and eosinophil cationic protein in the allergic airway mucosa in seasonal allergic rhinitis

As previously demonstrated in seasonal allergic rhinitis, increased microvascular permeability and eosinophil activation are key features of allergic airway inflammation. In the present study, the hypothesis that exudation of alpha2-macroglobulin may cause the appearance of eosinophil cationic protein (ECP) in the airway lumen was explored. Nasal lavages were carried out using the nasal pool device before and during the pollen season both at baseline and after histamine challenge in 10 children with allergic rhinitis. Nasal lavage fluid levels of alpha2-macroglobulin and ECP were determined. All patients experienced nasal symptoms of allergic rhinitis during the pollen season (p<0.01-0.05). Baseline nasal lavage fluid levels of alpha2-macroglobulin and ECP were increased during the season (p<0.01-0.05) and were found to be well correlated (p<0.0001). Histamine produced concentration-dependent plasma exudation before and during the pollen season, but it was only during the pollen season that this caused an increase in the lavage fluid levels of ECP (p<0.05). These data suggest that exudation of plasma and increased tissue levels and output of eosinophil cationic protein characterize nasal mucosal inflammation in children with seasonal allergic rhinitis. The plasma exudation process in part may account for lumenal entry of eosinophil cationic protein molecules that have been released in mucosal tissue compartments. A combination of induced exudation and nasal lavage may improve the yield of important markers of inflammation in studies of nasal diseases.

Natural killer cells determine development of allergen-induced eosinophilic airway inflammation in mice

The earliest contact between antigen and the innate immune system is thought to direct the subsequent antigen-specific T cell response. We hypothesized that cells of the innate immune system, such as natural killer (NK) cells, NK1.1(+) T cells (NKT cells), and gamma/delta T cells, may regulate the development of allergic airway disease. We demonstrate here that depletion of NK1.1(+) cells (NK cells and NKT cells) before immunization inhibits pulmonary eosinophil and CD3(+) T cell infiltration as well as increased levels of interleukin (IL)-4, IL-5, and IL-12 in bronchoalveolar lavage fluid in a murine model of allergic asthma. Moreover, systemic allergen-specific immunoglobulin (Ig)E and IgG2a levels and the number of IL-4 and interferon gamma-producing splenic cells were diminished in mice depleted of NK1.1(+) cells before the priming regime. Depletion of NK1.1(+) cells during the challenge period only did not influence pulmonary eosinophilic inflammation. CD1d1 mutant mice, deficient in NKT cells but with normal NK cells, developed lung tissue eosinophilia and allergen-specific IgE levels not different from those observed in wild-type mice. Mice deficient in gamma/delta T cells showed a mild attenuation of lung tissue eosinophilia in this model. Taken together, these findings suggest a critical role of NK cells, but not of NKT cells, for the development of allergen-induced airway inflammation, and that this effect of NK cells is exerted during the immunization. If translatable to humans, these data suggest that NK cells may be critically important for deciding whether allergic eosinophilic airway disease will develop. These observations are also compatible with a pathogenic role for the increased NK cell activity observed in human asthma.

Demonstration of bronchial eosinophil activity in seasonal allergic rhinitis by induced plasma exudation combined with induced sputum

BACKGROUND

Patients with seasonal allergic rhinitis may develop bronchial hyperresponsiveness during the active disease period. Eosinophil activation may occur in the bronchial mucosa and may be reflected by increased sputum levels of eosinophil cationic protein (ECP), especially when ECP binding proteins such as alpha 2-macroglobulin pass through the lamina propria and across the epithelium into the airway lumen. A study was therefore undertaken to determine histamine airway responsiveness (FEV1) and bronchovascular responsiveness (exudation of alpha 2-macroglobulin) to histamine in subjects with seasonal allergic rhinitis, and to explore whether sputum ECP levels are increased by the use of induced exudation followed by induced sputum.

METHODS

Eleven patients with seasonal allergic rhinitis were examined before and during a birch pollen season. Sputum was induced by inhalation of 4.5% saline twice before and twice during the pollen season. Histamine inhalations were given before the second of each pair of sputum inductions at increasing concentrations until FEV1 was reduced by 20%. Sputum levels of alpha 2-macroglobulin and ECP were determined as indices of bronchial exudation of plasma and activation of bronchial eosinophils, respectively.

RESULTS

Bronchomotor responsiveness increased during the pollen season (median difference in the reduction of FEV1 9% (95% confidence interval (CI) -3 to 26)) but histamine induced exudation of plasma was not increased. Baseline sputum levels of alpha 2-macroglobulin and ECP did not increase. Histamine induced exudation of alpha 2-macroglobulin was associated with increased sputum levels of ECP exclusively during the pollen season (median difference 8.2 ng/ml (95% CI 0.4 to 562.0)).

CONCLUSION

Bronchial hyperresponsiveness in seasonal allergic rhinitis may not be associated with bronchovascular exudative hyperresponsiveness. Sputum levels of ECP were increased only during the season, and only after induced exudation (potentially moving ECP to the mucosal surface). It is suggested that the combined method of induced exudation and induced sputum may significantly improve the yield of some markers of inflammation in sputum samples.

Allergen challenge-induced acute exudation of IL-8, ECP and alpha2-macroglobulin in human rhinovirus-induced common colds

Rhinovirus infections cause exacerbations of eosinophilic airway disease. The acute effects of allergen-challenge on nasal interleukin-8 (IL-8), eosinophil cationic protein (ECP), and alpha2-macroglobulin were examined in atopic subjects with common cold symptoms. Twenty-three patients with seasonal allergic rhinitis were inoculated with human rhinovirus 16 outside the pollen season. Diluent and allergen challenges, followed by nasal lavages, were carried out about 3 months before and 4 days after virus inoculation. Seventeen patients developed significant common cold symptoms with increased nasal lavage fluid levels of alpha2-macroglobulin, IL-8, and ECP at baseline (p<0.001-0.05 versus before inoculation), and were further increased by allergen challenge (p< 0.001-0.05); IL-8 and ECP levels were correlated (r = 0.63, p<0.001). Before inoculation, the six patients who later did not develop common cold symptoms had high levels of IL-8 and myeloperoxidase (MPO), and exhibited strong allergen-induced plasma exudation responses (alpha2-macroglobulin). After inoculation, IL-8 and ECP did not increase in these symptomless subjects. In conclusion, high nasal interleukin-8 and myeloperoxidase levels and exudative hyperresponsiveness may protect against infection. The association between nasal interleukin-8 and eosinophil cationic protein in common cold, particularly that observed in nasal lavage fluids after allergen-induced acute exudation of plasma, suggests the involvement of interleukin-8 in exacerbation of airway mucosal eosinophil activity.

Lack of systemic anaphylaxis and aeroallergen-induced airway plasma extravasation in allergic immunoglobulin-deficient mice

BACKGROUND

In Ig-deficient mice allergen challenge-induced pulmonary late phase inflammation is at least as pronounced as in wild-type animals. This study investigates immediate hypersensitivity responses in these mice.

METHODS

To examine the acute plasma extravasation response in airway tissue, immunized Ig-deficient and wild-type mice and sham-immunized wild-type controls were subjected to 15 min ovalbumin aerosol challenge. 125I-albumin was injected (i.v.) 1 min prior to challenge. Immediately after challenge 131I-albumin was injected and the experiment was terminated. Plasma and trachea were analyzed for 125I and 131I, and the amount of extravasated plasma in the trachea was calculated. To study the development of systemic anaphylaxis immunized Ig-deficient and wild-type animals received intravenous allergen challenge followed by determination of mast cell responses and plasma histamine levels.

RESULTS

Allergen aerosol-exposed immunized wild-type mice exhibited marked plasma extravasation in the trachea (pd0.01 vs. wild-type controls), but in the corresponding Ig-deficient mice there was no increased extravasation. Immunized Ig-deficient mice receiving intravenous allergen challenge were resistant to anaphylactic shock. By contrast, the wild-type animals developed systemic anaphylaxis, accompanied by plasma extravasation, mast cell degranulation, elevated plasma histamine and rapid death.

CONCLUSION

The present data are evidence that immunoglobulins are crucial for the development of immediate (type 1) responses. These findings together with our previous observations on late-phase pulmonary responses suggest that immediate hypersensitivity processes are unimportant for development of the late phase inflammation in the respiratory tract of mice.

Effects of formoterol on histamine induced plasma exudation in induced sputum from normal subjects

BACKGROUND

A number of studies have shown that beta 2 agonists, including formoterol, inhibit plasma exudation induced by the inflammatory stimulus in animal airways. Whether clinical doses of beta 2 agonists inhibit plasma exudation in human bronchial airways is unknown.

METHODS

In order to explore the microvascular permeability and its potential inhibition by beta 2 agonists in human bronchial airways a dual induction method was developed: plasma exudation induced by histamine inhalation followed by sputum induction by hypertonic saline (4.5%) inhalation. Sixteen healthy subjects received formoterol (18 micrograms) in a placebo controlled, double blind, crossover study. Sputum was induced on five occasions: once at baseline and four times after histamine challenge (30 minutes and eight hours after both formoterol and placebo treatments). Sputum levels of alpha 2-macroglobulin were determined to indicate microvascular-epithelial exudation of bulk plasma.

RESULTS

Histamine induced plasma exudation 30 minutes after placebo was considerably greater than at baseline (median difference 11.3 micrograms/ml (95% confidence interval 0.9 to 90.0)). At 30 minutes after formoterol the effect of histamine was reduced by 5.1 (0.9 to 61.9) micrograms/ml compared with placebo. At eight hours histamine produced less exudation and inhibition by formoterol was not demonstrated.

CONCLUSION

This study shows for the first time an anti-exudative effect of a beta 2 agonist in healthy human bronchial airways. Through its physical and biological effects, plasma exudation is of multipotential pathogenic importance in asthma. If the present findings translate to disease conditions, it suggests that an anti-exudative effect may contribute to the anti-asthmatic activity of formoterol.

Allergen challenge-induced extravasation of plasma in mouse airways

BACKGROUND

Mouse models are extensively used to study genetic and immunological mechanisms of potential importance to inflammatory airway diseases, e.g. asthma. However, the airway pathophysiology in allergic mice has received less attention. For example, plasma extravasation and the ensuing tissue-deposition of plasma proteins, which is a hallmark of inflammation, has not been examined in allergic mice.

OBJECTIVE

This study aims to examine the vascular permeability and the distribution of plasma proteins in mouse airways following exposure to allergen and serotonin.

METHODS

Extravasated plasma was quantified by a dual isotop technique using intravascular (131I-albumin) and extrasvascular (125I-albumin) plasma tracers. Histological visualization of fibrinogen and colloidal gold revealed the tissue distribution of extravasated plasma.

RESULTS

Allergen aerosol exposure (3% OVA, 15min) of sensitized animals resulted in a marked plasma extravasation response in the trachea (P < 0.01) and the bronchi but not in the lung parenchyma. A similar extravasation response was induced by serotonin (P<0.001). Extravasating vessels (assessed by Monastral blue dye) were identified as intercartilaginous venules. Extravasated plasma abounded in the subepithelial tissue but was absent in the epithelium and airway lumen. The allergen-induced response was dose-dependently inhibited by iv administration of formoterol (P < 0.001), a vascular antipermeability agent.

CONCLUSION

The present study demonstrates that serotonin and allergen challenge of sensitized mice increase airway venular permeability to cause transient extravasation and lamina propria distribution of plasma in the large airways. We suggest that the extravasation response is a useful measure of the intensity and the distribution of active inflammation

Effects of orally inhaled budesonide in seasonal allergic rhinitis

It has previously been demonstrated that topical nasal treatment with glucocorticosteroids has significant effects on the bronchial airways. Less is known about effects on nasal disease by topical bronchial treatment with these drugs. The present study examined effects on nasal allergic disease of inhaled budesonide (avoiding nasal deposition of the drug). Patients with seasonal allergic rhinitis, but without asthma, were thus given inhalations of budesonide (600 microg b.i.d.) or placebo. The aim of the design was to allow the study of eosinophilic airway disease in a part of the airway other than the directly treated locus. Moderate to high birch pollen levels were recorded during the study season, and nasal symptoms were significantly increased in both treatment groups, although they were milder in patients receiving budesonide than in the placebo group (p<0.05). Nasal brush eosinophils and nasal lavage fluid levels of eosinophil cationic protein as well as blood eosinophils were increased during the season (p<0.05), but these increases were prevented by the inhaled budesonide. Nasal lavage fluid levels of alpha2-macroglobulin were particularly elevated in the placebo group but did not differ between patients receiving placebo and budesonide. Budesonide prevented the seasonal development of increased bronchoconstrictor responses to methacholine challenge (p<0.05). In conclusion, budesonide reduced the seasonal eosinophilia both in the circulation and in the nose along with an attenuation of seasonal nasal symptoms. Hence, at a daily dose of 600 microg b.i.d., known to cause no, or minimal, adverse effects, inhaled budesonide produces clinically significant anti-inflammatory effects in the entire airways, including the nasal mucosa, which is not exposed topically to the drug. We suggest that nasal and systemic anti-eosinophil actions are produced at commonly employed dose levels of orally inhaled budesonide.

Plasma-derived proteins in airway defence, disease and repair of epithelial injury

One significant characteristic of the airway mucosa in vivo, that cannot easily be mimicked in vitro, is its microcirculation, which generates a highly dynamic, biologically active milieu of plasma-derived molecules that may pass to the airway lumen in vivo. New data on the mechanisms of airway mucosal exudation indicate that the protein systems of circulating plasma may contribute significantly to the biology and immunology of the lamina propria, its surface epithelium and the luminal surface, not only in injured airways, but also in airways that are activated but display no sign of oedema, epithelial disruption, or increased absorption capacity. We suggest that present knowledge of the mechanisms of plasma exudation, together with rapidly emerging information (not detailed herein) on receptors, target cells and cellular responses to the plasma-derived molecules, must be considered in any realistic model that investigates "immuno-inflammatory" mechanisms of the airway mucosa.

Effects of topical budesonide and levocabastine on nasal symptoms and plasma exudation responses in seasonal allergic rhinitis

This study compares the effects of two topical nasal treatments for allergic rhinitis, budesonide and levocabastine, on symptom development during seasonal pollen exposure. Additionally, the protective effects of drug treatments on allergen-challenge-induced responses (symptoms and microvascular exudation of plasma) are examined late into the pollen season. Forty-four patients with seasonal allergic rhinitis to birch pollen participated in this single-blind, randomized, and placebo-controlled study. Topical nasal treatment with either levocabastine (200 microg b.i.d.; n = 16), budesonide (200 microg b.i.d.; n = 16), or placebo (n = 12) was instituted before the start of the pollen season and continued for 5 weeks until the end of the birch pollen season. The participants kept diaries for scores of nasal and ocular symptoms. Nasal allergen challenges with increasing doses of a birch pollen extract (10[2], 10[3], and 10[4] SQ-U) were carried out both before, when patients were asymptomatic and without treatment, and late into the pollen season. A nasal lavage followed each challenge, and the lavage fluid levels of albumin were measured as an index of the acute inflammatory response of the allergic mucosa. The birch pollen season was rather mild, producing only small increases in nasal symptoms. Budesonide treatment reduced the total nasal symptoms compared to placebo (P<0.01) and to levocabastine (P<0.05), while levocabastine treatment did not differ significantly from placebo. Ocular symptoms and use of rescue medication did not differ between placebo and the active treatments. At the end of the pollen season, both treatments reduced allergen-challenge-induced nasal symptoms compared to placebo (P<0.01). Only budesonide reduced allergen-challenge-induced increments of albumin levels in postchallenge nasal lavage fluids (P<0.05, in comparison with placebo). The results suggest that budesonide reduces both seasonal and allergen-challenge-induced nasal symptoms, while levocabastine is effective against allergen-challenge-induced symptoms also during the season. In addition, the topical steroid treatment, but not the antihistamine, inhibits the inflammatory exudation evoked by allergen challenge in patients with active seasonal disease.

Contribution of plasma-derived molecules to mucosal immune defence, disease and repair in the airways

This review discusses recent observations, in health and disease, on the release and distribution of plasma-derived molecules in the airway mucosa. Briefly, the new data on airway mucosal exudation mechanisms suggest that the protein systems of plasma contribute significantly to the mucosal biology, not only in injured airways but also in such mildly inflamed airways that lack oedema and exhibit no sign of epithelial derangement. Plasma as a source of pluripotent growth factor, adhesive, leucocyte-activating, etc., molecules may deserve a prominent position in schemes that claim to illustrate immunological and inflammatory mechanisms of the airway mucosa in vivo.

Generation of clusters of free eosinophil granules (Cfegs) in seasonal allergic rhinitis

Generation of clusters of free eosinophil granules (Cfegs), through lysis of eosinophils, has recently been proposed as a major paradigm for ultimate activation of airway mucosal eosinophils. In the present study involving patients with seasonal allergic rhinitis, we have investigated whether generation of Cfegs in the nasal mucosa is a feature of allergic rhinitis. Nasal mucosal biopsies were obtained before and late in a birch-pollen season, and were subjected to histochemical staining of eosinophil peroxidase. In biopsies obtained before the pollen season, a few, intact eosinophils were observed, and Cfegs were scarce. In biopsies taken during the pollen season, the numbers of eosinophils were increased about 10-fold (P < 0.05) and the Cfegs about 25-fold (P < 0.05). We conclude that generation of Cfegs is a significant feature of seasonal allergic rhinitis and that this process represents the ultimate activation of mucosal eosinophils in this disease.

Nasal mucosal endorgan hyperresponsiveness

Nonspecific hyperresponsiveness of the upper and lower airways is a well-known characteristic of different inflammatory airway diseases but the underlying mechanisms have not yet been satisfactorily explained. In attempts to elucidate the relation of hyperresponsiveness to disease pathophysiology we have particularly examined the possibility that different airway endorgans may alter their function in allergic airway disease. The nose, in contrast to the bronchi, is an accessible part of the airways where in vivo studies of airway mucosal processes can be carried out in humans under controlled conditions. Different endorgans can be defined in the airway mucosa: subepithelial microvessels, epithelium, glands, and sensory nerves. Techniques may be applied further in the nose to determine selectively the responses/function of these endorgans. Topical challenge with methacholine will induce a glandular secretory response, and topical capsaicin activates sensory c-fibers and induces nasal smart. Topical histamine induces extravasation of plasma from the subepithelial microvessels. The plasma exudate first floods the lamina propria and then moves up between epithelial cells into the airway lumen. This occurs without any changes in the ultrastructure or barrier function of the epithelium. We have therefore forwarded the view of mucosal exudation of bulk plasma as a physiological airway tissue response with primarily a defense function. Since the exudation is specific to inflammation, we have also suggested mucosal exudation as a major inflammatory response among airway endorgan functions. Using a "nasal pool" device for concomitant provocation with histamine and lavage of the nasal mucosa we have assessed exudative responses by analyzing the levels of plasma proteins (e.g., albumin alpha 2-macroglobulin) in the returned lavage fluids. A secretory hyperresponsiveness occurs in both experimental and seasonal allergic rhinitis. This type of nasal hyperreactivity may develop already 30 minutes after allergen challenge. It is attenuated by topical steroids and oral antihistamines. We have demonstrated that exudative hyperresponsiveness develops in both seasonal allergic rhinitis and common cold, indicating significant changes of this important microvascular response in these diseases. An attractive hypothesis to explain airway hyperresponsiveness has been increased mucosal absorption permeability due to epithelial damage, possibly secondary to the release of eosinophil products. However, neither nonspecific nor specific endorgan hyperresponsiveness in allergic airways may be explained by epithelial fragility or damage since nasal absorption permeability (measured with 51CR-EDTA and dDAVP) was decreased or unchanged in our studies of allergic and virus-induced rhinitis, respectively. Thus, the absorption barrier of the airway mucosa may become functionally tighter in chronic eosinophilic inflammation.

The mouse trap

Mouse models of asthma are now being used extensively in drug research. However, the successful unravelling of combinatorial interplays of cells and molecules in the murine airways may not be matched by equally successful demonstrations of an asthma-like pathophysiology. Here, Carl Persson, Jonas Erjefält, Magnus Korsgren and Frank Sundler discuss the fact that major features of asthma may still need to be demonstrated in the airways of allergic mice.

Permeation of polysucrose 15000 across the human nasal mucosa in vivo

Studies of the nasal permeation of small molecules (< 1000 Da) have yielded important information about the integrity of the human airway mucosa in health and disease. In this study, we used a much larger tracer molecule, polysucrose (PS) 15,000 (approx. 14,700 Da), to predict the mucosal permeation of inhalational allergens. PS 15,000 (50 mg/ml; 15 ml), with or without a detergent type of permeation enhancer (dioctyl sodium sulfosuccinate 10 mg/ml), was maintained for 15 min in one nasal cavity of 12 healthy nonatopic subjects by employment of a nasal-pool device. Permeation as determined by the 24-h urine recovery of PS (micro-ELISA analysis assay) was expressed as percentage of nasal instillate. Mean baseline permeation was 0.044% (range 0.009-0.250%). In the presence of the detergent, permeation increased to 0.600% (range 0.007-2.260%) (P < 0.01). After oral intake of 750 mg of PS 15,000 (50 micrograms/ml; 15 ml), the 24-h urinary recovery was 0.013% (range 0.004-0.023%). Our study thus demonstrates a measurable baseline permeation of PS 15,000, an elevated permeation rate in the presence of an epithelium-damaging detergent molecule, and a negligible permeation by the oral route. These properties support the utility of PS 15,000 as a nasal airway permeation tracer. Its size further suggests that its permeation may reflect mucosal perviousness to many allergens.

Prompt epithelial damage and restitution processes in allergen challenged guinea-pig trachea in vivo

BACKGROUND

Little is known about the induction and the morphology of epithelial damage, and of the ensuing epithelial restitution processes in allergic airways.

OBJECTIVE

To examine epithelial damage and restitution in allergen challenged guinea-pig trachea.

METHODS

Whole-mount techniques, transmission and scanning electron microscopy, cryosectioning, and histochemical staining were used. Cell proliferation was monitored by BrdU-immunohistochemistry.

RESULTS

Allergen challenge produced patchy, crater-like, and leucocyte-rich epithelial damage sites. At 1, 5, and 24 h damage was associated with poorly differentiated epithelial restitution cells. Already at 1 h the epithelial craters had a floor of flattened restitution cells and the damaged areas comprised < 1% of the mucosal surface area (whole-mount preparations). In contrast, cryo sections displayed large areas (approximately 20%, 1 h) of denudation. Epithelial, and subepithelial (fibroblasts, smooth muscle) proliferation was increased 5 and 24 h after challenge (P < 0.01).

CONCLUSION

Within 1 h allergen challenge has induced patchy damage sites where epithelial restitution is already advanced; although easily produced by cryosectioning frank denudation was not evident in whole-mount preparations. The present findings may explain the well maintained, functional tightness of allergic airways displaying epithelial damage, shedding, and even denudation. The present data also suggest the possibility that epithelial damage-restitution may be causative to allergic airway remodelling.

Effects of inhaled histamine, methacholine and capsaicin on sputum levels of alpha 2-macroglobulin

BACKGROUND

Plasma exudation-derived proteins and peptides contribute significantly to inflammation in the airway mucosa in vivo. In the guinea pig trachea both histamine and the neurogenic stimulant capsaicin produce acute mucosal tissue distribution and luminal entry of bulk plasma, whereas cholinergic agonists fail to produce this effect. Of these agents, only histamine induces mucosal exudation of plasma in human nasal airways. The exudative effect of the above agents on human bronchi remains unknown.

METHODS

The bronchial exudative responses to inhalation of histamine, methacholine, and capsaicin were examined in two groups of healthy volunteers. Sputum was induced on three occasions in each study group by inhalation of hypertonic saline (4.5%) given as an aerosol for 40 minutes using an ultrasonic nebuliser. The second and third occasions were preceded by histamine and capsaicin challenges in the first study group, and by histamine and methacholine challenges in the second study group. Histamine and methacholine were given in cumulative doses (total doses 3160 micrograms, respectively) or until a 20% reduction in forced expiratory volume in one second (FEV1) was achieved. Cumulative doses of capsaicin were inhaled until coughing prevented the subjects from drawing a full breath. Sputum levels of alpha 2-macroglobulin (729 kDa) were measured as an index of mucosal exudation of bulk plasma.

RESULTS

Histamine increased mean (SE) sputum levels of alpha 2-macroglobulin from 2.72 (1.01) micrograms/ml (95% confidence interval (CI) 0.49 to 4.94) to 18.38 (8.03) micrograms/ml (95% CI 0.49 to 36.27) in the first group, and from 1.66 (0.84) micrograms/ml (95% CI -0.18 to 3.49) to 9.43 (3.63) micrograms/ml (95% CI 1.59 to 17.27) in the second group. In contrast, capsaicin evoked no exudation (sputum levels of alpha 2-macroglobulin 1.21 (0.28) micrograms/ml (95% CI 0.59 to 1.83)) and methacholine produced a minor increase in sputum levels of alpha 2-macroglobulin (2.90 (0.92) micrograms/ml (95% CI 0.90 to 4.89)).

CONCLUSIONS

These results indicate that histamine is a useful agent for studying bronchial exudative responsiveness in man and that exudative effects are only of marginal importance in the cough and bronchoconstriction produced by capsaicin and methacholine.

Association between inflammation and epithelial damage-restitution processes in allergic airways in vivo

BACKGROUND

Associations between allergen challenge-induced sites of epithelial damage and the distribution of leucocytes and extravasated plasma remain unexplored.

OBJECTIVE

To study neutrophils, eosinophils, and fibrinogen at allergen challenge-induced patchy epithelial damage-restitution sites in guinea-pig trachea.

METHODS

After local challenge tracheal tissue (cryo sections and whole-mounts) and lumen (selective tracheal lavage) were examined at 1, 5, and 24 h. Eosinophils, neutrophils and fibrinogen were identified by histochemistry.

RESULTS

Neutrophils increased markedly in tracheal lavage fluids and in tissue and were strongly associated with the challenge-induced epithelial craters of damage-restitution. At 1 and 24 h eosinophils were increased in the tracheal lumen whereas the surrounding tissue displayed a reversed pattern. Gels rich in fibrinogen, neutrophils, and eosinophils were present in epithelial crater areas, protruding into the lumen. Clusters of free eosinophil granules, Cfegs, released through lysis of eosinophils, and neutrophils with long cytoplasmatic protrusions abounded in these crater areas.

CONCLUSION

The present findings provide important new insights into allergic airways where sites of epithelial damage-restitution processes emerge as the major loci for eosinophil, neutrophil, and plasma protein activities, the latter likely causing leukocyte adhesion and activation in vivo. The distribution of eosinophils in this study suggests roles of these cells both in airway mucosa and in regional lymph nodes. Based on the present study we also propose that lysis of eosinophils and Cfegs generation are a major paradigm for activation of these cells in vivo.

Airway epithelial repair: breathtakingly quick and multipotentially pathogenic

Epithelial shedding, even to the point of airway denudation, had already been described as a common and unifying feature of asthma by the latter half of the 19th century. However, the repair processes that specifically follow the shedding-like loss of epithelial cells have only recently been examined in vivo. This paper discusses the exceedingly fast epithelial restitution and the potential pathogenic sequelae to epithelial shedding alone that have been unravelled. Epithelial cytoprotection emerges as an important property of future therapeutic drugs for the treatment of airways inflammatory conditions.

Reduced airway absorption in seasonal allergic rhinitis

The common notion that increased mucosal absorption characterizes allergic and inflamed airways is poorly supported by physiologic in vivo data. We have now examined whether the airway mucosa of patients with seasonal allergic rhinitis develop a change in absorption during their active disease period. Twelve patients with birch pollen rhinitis were examined twice, prior to and late into a Swedish birch pollen season. Ten healthy subjects were examined once. A nasal pool device was used to fill the unilateral nasal cavity with fluid containing 1-deamino-8-D-arginine vasopressin (desmopressin, 20 micrograms/ml) as absorption tracer. The peptide tracer solution was removed after 15 min, and absorption was determined by analysis of the peptide in the 24-h urine sample. Nasal absorption did not differ between healthy subjects and symptom-free patients outside the season. After 3 wk of symptom-producing seasonal allergic rhinitis, absorption of the peptide across the nasal mucosa was less (p < 0.05) than outside the season. These data indicate that hyperresponsiveness and disease progression in seasonal allergic rhinitis are not due to a compromise of the mucosal barrier that would permit increased absorption of mucosally deposited solutes. The reduced absorption may in part reflect the ability of the airway epithelium in vivo to maintain and potentially improve its barrier function by efficient epithelial restitution processes.

Effects of topical platelet activating factor on the guinea-pig tracheobronchial mucosa in vivo

Platelet activating factor (PAF) has been reported to produce a variety of airway effects including epithelial damage and increased airway-lung absorption of hydrophilic tracers. The present study examines effects of PAF on the guinea-pig tracheobronchial mucosa in vivo. Vehicle with and without PAF (4.0 and 8.0 nmol) was superfused onto the tracheobronchial mucosa. The levels of 125I-albumin, previously given intravenously, were determined in tracheobronchial lavage fluids as an index of mucosal exudation of plasma. The mucosa was also examined by scanning electron microscopy. In separate animals, 99mTc-DTPA (a low molecular weight, 492 Da, hydrophilic tracer) was superfused onto the mucosal surface through an oro-tracheal catheter, together with vehicle or PAF (8.0 nmol). A gamma camera determined the disappearance rate of 99mTc-DTPA from the airways as an index of mucosal absorption. PAF produced dose-dependent mucosal exudation of plasma up to 20-fold greater than control (P < 0.001). However, PAF did not damage the epithelium and the absorption ability of the airway mucosa was unaffected. The results, in contrast to previous reports, suggest that PAF may not readily damage the airway mucosa even at large exudative doses of the agent. The present finding support the view that the plasticity of the epithelial junctions allows the creation of valve-like paracellular pathways for unidirectional clearance of extravasated plasma into the airway lumen. We suggest that endogenous PAF may participate in first line respiratory defence reactions by causing lumenal entry of bulk plasma without harming the epithelium.