Food Allergy Herbal Formula-1 (FAHF-1) blocks peanut-induced anaphylaxis in a murine model.

BACKGROUND: Peanut allergy is a major cause of fatal and near-fatal anaphylactic reactions to foods. There is no curative therapy for this condition. Traditional Chinese medicines have been reported to have antiallergic properties, which might be useful for treating peanut allergy. OBJECTIVE: The purpose of this study was to investigate the effects of a Chinese herbal formula, FAHF-1, on peanut anaphylactic reactions in a mouse model of peanut allergy. METHODS: Mice were sensitized with freshly ground whole peanut in the presence of cholera toxin and boosted 1 and 3 weeks later. FAHF-1 treatment was initiated 1 week later and continued for 7 weeks. After treatment, mice were challenged with peanut, and anaphylactic symptoms, body temperatures, and plasma histamine and IgE levels were measured. T-cell proliferative responses and cytokine production were also determined. RESULTS: FAHF-1 completely blocked peanut-induced anaphylactic symptoms and markedly reduced mast cell degranulation and histamine release. Peanut-specific serum IgE levels were significantly reduced by 2 weeks of treatment at the time of challenge, and they remained lower 4 weeks after discontinuation of treatment. FAHF-1 significantly reduced peanut-induced lymphocyte proliferation as well as IL-4, IL-5, and IL-13 synthesis but not IFN-gamma synthesis. No toxic effects on liver or kidney functions were observed, nor was there any overall immune suppression. CONCLUSION: FAHF-1 protected peanut-sensitized mice from anaphylactic reactions and significantly reversed established IgE-mediated peanut allergy. This suggests that FAHF-1 might prove valuable for the treatment of peanut allergy.

Oral administration of IL-12 suppresses anaphylactic reactions in a murine model of peanut hypersensitivity.

There is no satisfactory therapeutic intervention for peanut allergy, which accounts for most life-threatening food allergic reactions. Since IL-12 has been found to inhibit allergic airway responses in a mouse model of asthma and to cure Th2 cytokine-mediated murine schistosomiasis, we hypothesized that IL-12 treatment might also inhibit peanut allergic reactions. Consequently, we investigated the effects of oral IL-12 treatment in a murine model of peanut allergy and found that oral administration of liposome encapsulated rIL-12 could both prevent and reverse peanut hypersensitivity and could reduce histamine release, peanut-specific serum IgE and IgG1, and fecal IgA levels. Oral IL-12 treatment also increased IFN-gamma but did not decrease IL-4 or IL-5 levels. We conclude that oral rIL-12 treatment has therapeutic as well as preventive effects on peanut allergy, which are associated with increased IFN-gamma production.

Experimental autoimmune myocarditis in A/J mice is an interleukin-4-dependent disease with a Th2 phenotype.

Myocarditis in humans is often associated with an autoimmune process in which cardiac myosin (CM) is a major autoantigen. Experimental autoimmune myocarditis (EAM) is induced in mice by immunization with CM. We found that EAM in A/J mice exhibits a Th2-like phenotype demonstrated by the histological picture of the heart lesions (eosinophils and giant cells) and by the humoral response (association of IgG1 response with disease and up-regulation of total IgE). Blocking interleukin (IL)-4 with anti-IL-4 monoclonal antibody (mAb) reduced the severity of EAM. This reduction in severity was associated with a shift from a Th2-like to a Th1-like phenotype represented by a reduction in CM-specific IgG1; an increase in CM-specific IgG2a; an abrogation of total IgE response; a decrease in IL-4, IL-5, and IL-13; as well as a dramatic increase in interferon (IFN)-gamma production in vitro. Based on the latter finding, we hypothesized that IFN-gamma limits disease. Indeed, IFN-gamma blockade with a mAb exacerbated disease. The ameliorating effect of IL-4 blockade was abrogated by co-administration of anti-IFN-gamma mAb. Thus, EAM represents a model of an organ-specific autoimmune disease associated with a Th2 phenotype, in which IL-4 promotes the disease and IFN-gamma limits it. Suppression of IFN-gamma represents at least one of the mechanisms by which IL-4 promotes EAM.

Immune responses in tuberculosis: antibodies and CD4-CD8 lymphocytes with vascular adhesion molecules and cytokines (chemokines) cause a rapid antigen-specific cell infiltration at sites of bacillus Calmette-Guérin reinfection.

Rabbit primary dermal bacillus Calmette-Guérin (BCG) lesions were compared with reinfection BCG lesions in order to gain insight into how immune responses protect against clinical tuberculosis. As early as 3 hr, a marked infiltration of macrophages and lymphocytes occurred in the reinfection group, while very little cell infiltration occurred in the primary group. It seems that only an antigen-antibody reaction could produce such an immediate pronounced antigen-specific chemotactic effect, because very few lymphocytes are normally present in the skin. Therefore, antibodies hasten the accumulation of an expanded antigen-specific T-lymphocyte population (memory cells) at sites of bacillary lodgement. By 1-2 days, the primary and reinfection BCG lesions differed 400- to 500-fold in size. By 4-5 days, the size of the reinfection lesions had declined, while the size of the primary lesions had increased, so that, grossly, both types of lesion were similar. At 8 days in reinfection lesions and at 12 days in primary lesions, small secondary peaks in size occurred, which were probably caused by cell-mediated immune responses. In rabbits with primary BCG lesions, skin tests with Old Tuberculin were positive at 9 days, accompanied by a rise in the levels of antibodies to the secreted antigen, phosphate-specific transport protein 1, but the levels of antibodies to the constitutive antigens, purified protein derivative and heat-shock protein 65, did not increase appreciably until some time after 23 days. In tissue sections of reinfection BCG lesions, the percentage of mononuclear cells labelled, by in situ hybridization techniques, for the mRNA of monocyte chemoattractant protein 1 (MCP-1), a chemokine, peaked at 3 hr and then was down-regulated, whereas in primary lesions, this percentage was down-regulated only after 2 days. [The percentage in the tissue sections for the mRNAs of interleukins 1beta and 8, as well as the proteins of MCP-1 and tumor necrosis factor alpha (TNF-alpha), followed a somewhat similar time-course to that of MCP-1 mRNA.] A high percentage of mononuclear cells containing the MCP-1 mRNA 'factory' would favour enlargement of the lesions and a low percentage would favour their regression. At 5 days, the percentage of CD4 and CD8 lymphocytes, stained by immunohistochemical techniques, and the amount of microvasculature stained similarly for vascular cell adhesion molecule 1 were higher in the reinfection group, indicating that prior immunization caused a more rapid (antigen-dependent) up-regulation of these factors. Tuberculin reactions resembled early reinfection BCG lesions in almost every factor evaluated herein. In brief, the production of chemokines began soon after BCG reinfection, peaked within a few hours and was markedly down-regulated by 24 hr, a time at which the lesions of reinfection were of maximal size. Therefore, the amount of cell infiltration was tightly controlled, probably by the variety of mechanisms listed herein.

CpG oligodeoxynucleotides can reverse Th2-associated allergic airway responses and alter the B7.1/B7.2 expression in a murine model of asthma.

CpG oligodeoxynucleotides (CpG-ODN) administered during Ag sensitization or before Ag challenge can inhibit allergic pulmonary inflammation and airway hyperreactivity in murine models of asthma. In this study, we investigated whether CpG-ODN can reverse an ongoing allergic pulmonary reaction in a mouse model of asthma. AKR mice were sensitized with conalbumin followed by two intratracheal challenges at weekly intervals. CpG-ODN was administered 24 h after the first Ag challenge. CpG-ODN administration reduced Ag-specific IgE levels, bronchoalveolar lavage fluid eosinophils, mucus production, and airway hyperreactivity. We found that postchallenge CpG-ODN treatment significantly increased IFN-gamma concentrations and decreased IL-13, IL-4, and IL-5 concentrations in bronchoalveolar lavage fluids and spleen cell culture supernatants. Postchallenge CpG-ODN treatment also increased B7.1 mRNA expression and decreased B7.2 mRNA expression in lung tissues. These results suggest that CpG-ODN may have potential for treatment of allergic asthma by suppressing Th2 responses during IgE-dependent allergic airway reactions. The down-regulation of Th2 responses by CPG-ODN may be associated with regulation of the costimulatory factors B7.1 and B7.2.

The chinese herbal medicine formula MSSM-002 suppresses allergic airway hyperreactivity and modulates TH1/TH2 responses in a murine model of allergic asthma.

BACKGROUND: Asthma is a major public health problem worldwide, and the morbidity and mortality of asthma have increased in the past two decades. The reputed efficacy, low cost, and relative absence of side effects of traditional Chinese medicines (TCMs) have led to increasing interest in the use of TCMs for the treatment of asthma in Western countries. However, there are few well-controlled scientific studies on the efficacy, safety, and mechanisms of action of TCMs used to treat asthma. OBJECTIVE: The goal of this study was to investigate the effects of the Chinese herbal medicine formula MSSM-002, derived from TCMs used to treat allergic asthma, on a well-characterized mouse model of allergic asthma. METHODS: Mice sensitized intraperitoneally and challenged intratracheally with conalbumin were treated with MSSM-002 24 hours after the first intratracheal challenge. Dexamethasone-treated, saline solution sham-treated, and naive mice served as controls. The effects of MSSM-002 on allergic airway hyperreactivity, inflammation, antigen-specific antibody production, lung histologic features, and cytokine profiles were evaluated. RESULTS: MSSM-002 treatment virtually eliminated airway hyperreactivity and markedly reduced the total number of cells and the percent eosinophils in bronchoalveolar lavage fluids compared with the sham-treated group. Lung histologic features showed that MSSM-002 reduced inflammation and mucus production. These effects were equivalent to the effects of dexamethasone, but in contrast to the overall immunosuppressive effects of dexamethasone MSSM-002 treatment decreased antigen-specific IgE, IL-4, IL-5, and IL-13 levels without suppressing IgG2a and IFN-gamma synthesis. CONCLUSION: MSSM-002 exhibits anti-airway hyperresponsiveness, anti-airway inflammation, and immunoregulatory effects on T(H)1/T(H)2 responses, which may be useful for treatment of allergic asthma.

A murine model of peanut anaphylaxis: T- and B-cell responses to a major peanut allergen mimic human responses.

BACKGROUND: Peanut allergy affects 0.6% of the US population. At the present time, allergen avoidance is the only therapeutic option. Animal models of food-induced anaphylaxis would facilitate attempts to design novel immunotherapeutic strategies for the treatment of peanut allergy. OBJECTIVE: The purpose of this study was to develop a murine model of IgE-mediated peanut hypersensitivity that closely mimics human peanut allergy. METHODS: C3H/HeJ mice sensitized orally with freshly ground whole peanut and cholera toxin as adjuvant were challenged orally 3 and 5 weeks later with crude peanut extract. Anaphylactic reactions were determined. T- and B-cell responses to Ara h 1 and Ara h 2, the major peanut allergens, were characterized by evaluating splenocyte proliferative responses and IgE antibody concentrations. Furthermore, IgE antibodies in the sera of patients with peanut allergy and mice were compared for antibody binding to Ara h 2 isoforms and allergenic epitopes. RESULTS: Peanut-specific IgE was induced by oral peanut sensitization, and hypersensitivity reactions were provoked by feeding peanut to sensitized mice. The symptoms were similar to those seen in human subjects. Ara h 1- and Ara h 2-specific antibodies were present in the sera of mice with peanut allergy. Furthermore, these Ara h 2-specific IgE antibodies bound the same Ara h 2 isoforms and major allergenic epitopes as antibodies in the sera of human subjects with peanut allergy. Splenocytes from mice with peanut allergy exhibited proliferative responses to Ara h 1 and Ara h 2. CONCLUSION: This murine model of peanut allergy mimics the clinical and immunologic characteristics of peanut allergy in human subjects and should be a useful tool for developing immunotherapeutic approaches for the treatment of peanut allergy.

Strain-dependent induction of allergic sensitization caused by peanut allergen DNA immunization in mice.

To investigate the potential application of allergen gene immunization in the modulation of food allergy, C3H/HeSn (C3H) mice received i.m. injections of pAra h2 plasmid DNA encoding one of the major peanut allergens, Ara h2. Three weeks following pDNA immunization, serum Ara h2-specific IgG2a, IgG1, but not IgE, were increased significantly in a dose-dependent manner. IgG1 was 30-fold higher in multiply compared with singly immunized mice. Ara h2 or peanut protein injection of immunized mice induced anaphylactic reactions, which were more severe in multiply immunized mice. Heat-inactivated immune serum induced passive cutaneous anaphylaxis, suggesting that anaphylaxis in C3H mice was mediated by IgG1. IgG1 responses were also induced by intradermal injection of pAra h2, and by i.m. injection of pOMC, the plasmid DNA encoding the major egg allergen protein, ovomucoid. To elucidate whether the pDNA immunization-induced anaphylaxis was a strain-dependent phenomenon, AKR/J and BALB/c mice also received multiple i.m. pAra h2 immunizations. Injection of peanut protein into these strains at weeks 3 or 5 following immunization did not induce reactions. Although IgG2a was increased significantly from week 2 in AKR/J mice and from week 4 in BALB/c mice and remained elevated for at least 6 wk, no IgG1 or IgE was detected. These results indicate that the type of immune responses to pDNA immunization in mice is strain dependent. Consequently, models for studying human allergen gene immunization require careful selection of suitable strains. In addition, this suggests that similar interindividual variation is likely in humans.

A murine model of IgE-mediated cow's milk hypersensitivity.

BACKGROUND: Cow's milk allergy (CMA) is one of the leading causes of food allergy in children. Understanding the mechanisms involved in the development of CMA has been hampered by the lack of suitable animal models. OBJECTIVE: We sought to develop a mouse model of IgE-mediated cow's milk hypersensitivity (CMH) that mimics the clinical features of immediate CMA in humans. METHODS: Three-week-old C3H/HeJ mice were sensitized by intragastric administration of cow's milk (CM) plus cholera toxin and boosted 5 times at weekly intervals. RESULTS: CM-specific IgE antibody levels were significantly increased at 3 weeks and peaked at 6 weeks after the initial feeding. Intragastric challenge with CM at week 6 elicited systemic anaphylaxis accompanied by vascular leakage, significantly increased plasma histamine, and increased intestinal permeability to casein. Histologic examination of intestinal tissue revealed marked vascular congestion, edema, and sloughing of enterocytes. The role of IgE in mediating CMH was confirmed by abrogation of passive cutaneous anaphylaxis reactions by heat inactivation of immune sera. Development of IgE-mediated CMH in this model is likely to be TH2 cell mediated because in vitro stimulation of spleen cells from mice allergic to CM induced significant increases in the levels of IL-4 and IL-5, but not IFN-gamma. CONCLUSION: This model should provide a useful tool for evaluating the immunopathogenic mechanisms involved in CMA and for exploring new therapeutic approaches.

Induction of pulmonary allergic responses by antigen-specific Th2 cells.

The development of pulmonary allergic responses was examined in mice following pulmonary transfer of Ag (conalbumin)-specific Th2 cells. The levels of serum-specific IgE, cellular infiltrates, airway mucus goblet cells, and airway responsiveness were analyzed and compared with those in Ag-sensitized and -challenged mice. Pulmonary transfer of the conalbumin-specific Th2 clone (D10) induced, in an Ag-specific manner, high levels of the Th2 cytokines IL-4 and IL-5 in the bronchoalveolar lavage fluids and mucosal eosinophils, concomitant with an increase in airway responsiveness. The D10 cell-induced responses were seen in the absence of serum specific IgE. In the presence of Ag, the transferred D10 cells not only remained in the lungs, but also increased in number 72 h post-cell transfer. Although significantly higher levels of IL-4 and IL-5 in the bronchoalveolar lavage fluids were found in D10-transferred mice, the levels of pulmonary eosinophilia, mucus goblet cells, and airway responsiveness were significantly lower than those in Ag-sensitized and -challenged mice. These results demonstrate that although Ag-specific activation of Th2 cells at mucosal sites is able to mediate the recruitment of eosinophils and the subsequent induction of airway hyper-responsiveness, the more severe pulmonary allergic responses were observed only in mice sensitized and challenged with Ag.

Localization of eosinophils to airway nerves and effect on neuronal M2 muscarinic receptor function.

Neuronal M2 muscarinic receptors inhibit acetylcholine release from pulmonary parasympathetic nerves but are dysfunctional in antigen-challenged animals and asthmatics. Deletion of pulmonary eosinophils protects M2 receptor function in antigen-challenged guinea pigs. Therefore, the association of eosinophils with airway nerves was investigated. Nerve-associated eosinophils were significantly increased in challenged animals compared with controls (0.75 +/- 0.05 vs. 0.28 +/- 0.05 eosinophils/nerve). In antigen-challenged animals, eosinophil density was greatest around airway nerves, suggesting recruitment to the nerves. M2 receptor function was inversely correlated with the number of eosinophils per nerve, thus eosinophils are associated with airway nerves in antigen-challenged guinea pigs, where they impair M2 receptor function. In airways from three patients with fatal asthma, 196 of 637 eosinophils (30%) were associated with nerves, and release of eosinophil major basic protein was evident; conversely, in three control patients 1 of 11 (9%) eosinophils were in contact with nerves. Thus eosinophils and their granule proteins are also seen in association with airway nerves in patients with asthma.

Interleukin-4 receptor blockade prevents airway responses induced by antigen challenge in mice.

The functional role of interleukin (IL)-4 in the development of airway hyperresponsiveness (AHR) and pulmonary eosinophilia in response to sensitization and challenge of mice with sheep red blood cells (SRBC) was examined. Control- and SRBC-sensitized A/J mice were treated with an antibody to the murine IL-4 receptor (anti-IL-4R) 3 days before intratracheal challenge with the antigen or vehicle only. Blockade of IL-4R significantly reduced antigen-induced AHR and prevented increases in goblet cells and bronchoalveolar lavage (BAL) eosinophils. Treatment with anti-IL-4R did not affect antigen-induced increases in lung mRNA and BAL protein levels of IL-5 and interferon-gamma or IL-4 mRNA but did significantly increase IL-4 protein levels. Antigen-induced AHR was not reduced by treatment with antibodies to the adhesion molecules, vascular cell adhesion molecule-1 and very late activation antigen-4. Administration of IL-4 over a 7-day period did not increase airway reactivity or induce any changes in BAL cell numbers in naive mice. These results demonstrate that IL-4 is necessary for in vivo development of antigen-induced AHR, goblet cell metaplasia, and pulmonary eosinophilia.

Cavitary tuberculosis produced in rabbits by aerosolized virulent tubercle bacilli.

Liquefaction of solid caseous tuberculous lesions and the subsequent cavity formation are probably the most dangerous processes in the pathogenesis of human pulmonary tuberculosis. In liquefied caseum, the tubercle bacilli grow extracellularly for the first time since the onset of the disease and can reach such large numbers that mutants with antimicrobial resistance may develop. From a cavity, the bacilli enter the bronchial tree and spread to other parts of the lung and also to other people. Of the commonly used laboratory animals, the rabbit is the only one in which cavitary tuberculosis can be readily produced. This report is the first to describe and analyze the complete course of cavitary tuberculosis, produced by aerosolized virulent bovine-type tubercle bacilli in commercially available New Zealand white rabbits. After the inhalation of 220 to 880 bacillary units, all of the rabbits were overtly well until they were sacrificed at 33 weeks. After the inhalation of 3,900 to 5,800 bacillary units, half of the rabbits died of progressive tuberculosis between 5 and 9 weeks and the other half lived until they were sacrificed at 18 weeks. Pulmonary cavities developed in both low- and high-dose groups, some beginning as early as 6 weeks. Bacilli from primary cavities sometimes caused nearby secondary cavities, but more frequently, they ascended the bronchial escalator, were swallowed, and caused secondary tubercles in the lymphoid tissue of the appendix and ileocecal junction. Histologically, and by culture, the number of bacilli found in the liquefied caseum varied from many to comparatively few. Strong tuberculin reactions at 4 weeks after infection were associated with fewer primary lesions, while strong tuberculin reactions at 33 weeks were associated with more cavitary lesions. In the tuberculous granulation tissue surrounding caseous and liquefied pulmonary foci and cavities, we found many mature epithelioid macrophages that contained high levels of the proteinase cathepsin D. Therefore, cathepsin D probably plays a major role in the liquefaction of solid caseous material and in the subsequent cavity formation.

Mucosal IFN-gamma gene transfer inhibits pulmonary allergic responses in mice.

Th2 cytokines are associated with the airway inflammation and hyperreactivity in allergic asthma and are potential targets for developing novel therapies. The efficacy of a mucosal cytokine-gene transfer approach was examined in a mouse model for allergic asthma. We showed first that mucosal IFN-gamma gene transfer results in a significant expression of IFN-gamma in the pulmonary epithelium. Significantly, this approach inhibits both Ag- and Th2-cell-induced pulmonary eosinophilia and airway hyperreactivity. These findings suggest that mucosal IFN-gamma gene transfer is effective in modulating pulmonary allergic responses and provides a basis for developing a novel therapeutic approach.

Expression of ICAM-1 in airway epithelium after acute ozone exposure in the mouse.

We investigated the time course and regional distribution of the expression of intercellular adhesion molecule-1 (ICAM-1) on airway epithelial cells and the polymorphonuclear leukocyte (PMN) inflammatory response in the lung after acute exposure to ozone (O3). C57BL/6J mice were exposed to air or 2 ppm O3 for 3 h and killed immediately or 3, 6, 9, or 21 h after exposure. Expression of ICAM-1 was examined by immunohistochemical staining of frozen sections. PMN influx was evaluated by lavage and by histochemical staining of myeloperoxidase (MPO) and measurement of tissue MPO activity. ICAM-1 expression exhibited regional selectivity and temporal patterns that were unique to each region. Upregulation of ICAM-1 expression on the epithelial cells in the trachea, and to a lesser extent in the lobar and segmental bronchi, was observed 3-9 h after exposure and remained present at 21 h. Enhanced ICAM-1 expression in bronchioles and terminal bronchiole/alveolar duct regions was evident earlier (immediately to 3 h after exposure) but returned to baseline levels by 21 and 9 h, respectively. Maximal ICAM-1 expression and PMN influx in the lung parenchyma were concurrently observed at 3 h, followed by transepithelial migration of PMNs to the airway lumen. These results demonstrate regional variations in airway inflammatory activity and are supportive of the notion that upregulation of ICAM-1 on the airway epithelium may play a role in local regulation of PMN influx to the airways after acute O3 exposure.

The effect of bronchial blood flow on hyperpnea-induced airway obstruction and injury.

We examined the effect of bronchial blood flow (BBF) on hyperpnea-induced airway obstruction (HIAO) in dogs. HIAO in in situ isolated pulmonary lobes with or without BBF was monitored via a bronchoscope. An intravascular tracer in conjunction with morphometric analysis was used to document the efficacy of our occlusion technique. We found that (a) Occlusion of the bronchial artery abolished bronchovascular leakage, but did not alter HIAO; (b) HIAO occurred in postmortem dogs, and was attenuated by cooling; (c) absence of BBF did not cause mucosal damage, although hyperpnea-induced injury was enhanced in airways lacking BBF; (d) BBF did not affect either goblet/ ciliated cell ratios or hyperpnea-induced goblet cell degranulation; (e) ligation of the bronchial artery and hyperpnea each caused mast cell degranulation, and these effects were additive; (f) hyperpnea-induced leukocyte infiltration was reduced in the absence of BBF; and (g) ligation of the bronchial artery and hyperpnea with dry air each increased airway vessel diameter, and these effects were additive. We conclude that either impairment or absence of BBF abolishes bronchovascular leakage and increases hyperpnea-induced mucosal injury, but fails to affect HIAO. Based on these results we speculate that bronchovascular leakage protects the bronchial mucosa from excessive losses of heat and water, and inhibits mucosal damage.

A beta 2-adrenergic agonist inhibits dry air-induced injury in canine peripheral airways.

We examined the effects of a beta 2-agonist on dry air-induced injury in canine peripheral airways. Dry air-induced bronchoconstriction (AIB) was assessed by measuring peripheral airway resistance in anesthetized dogs. Salbutamol reduced AIB by approximately 75% compared with control values. Colloidal carbon was used to detect bronchovascular leakage in contralateral sublobar segments that were pretreated with saline or salbutamol. About 87% of the perimeter of bronchi was damaged after dry air challenge in saline-treated segments. Salbutamol reduced mucosal damage by approximately 30% (P < 0.05). The mucosa of bronchioles was not injured. The average goblet-to-ciliated cell ratio (which reflects mucosal perturbation) in bronchi decreased from 0.38 in control bronchi to 0.15 in challenged bronchi, and this effect was also evident in bronchioles. Salbutamol did not affect this decrement. Dry air challenge also caused degranulation of mast cells located below damaged mucosa, dilation of bronchial vessels, and leakage from capillaries and venules located below normal ciliated and damaged mucosa of bronchi. Thus, we conclude that salbutamol attenuates epithelial damage and AIB but fails to inhibit mast cell degranulation and vascular hyperpermeability.

Hyperpnea with dry air causes time-dependent alterations in mucosal morphology and bronchovascular permeability.

This study examines the morphological and physiological changes that occur in canine peripheral airways after hyperpnea with dry air. Peripheral airways were exposed to a 5-min 2,000 ml/min dry air challenge (DAC) at 24, 6, 2, or 1 h before or 60 s after (0 h) the injection of colloidal carbon. After recording the dry air-induced increase in peripheral airway resistance, the lungs were removed and prepared for morphometric analysis (n = 5). Light microscopy revealed that 50% of the airway perimeter appeared damaged at 0, 1, and 2 h after DAC, and repair was evident 6-24 h after the challenge. The average goblet-to-ciliated cell ratio decreased from 0.34 before DAC to 0.15 after DAC and recovered within 24 h. Dry air-induced bronchovascular leakage occurred immediately after DAC and persisted for > or = 24 h. DAC decreased mast cell number only in regions where the mucosa was damaged, and this decrease was inversely correlated with bronchovascular leakage. Finally, leukocyte infiltration was evident 1-2 h after DAC and continued throughout the 24-h period. We conclude that hyperpnea with dry air causes mucosal injury, inflammation, and microvascular leakage and that these dry air-induced effects persist for > or = 24 h after DAC.

Dry air-induced mucosal cell injury and bronchovascular leakage in canine peripheral airways.

The purpose of this study was to examine the relationship between hyperpnea-induced mucosal injury, bronchovascular hyperpermeability, and airway reactivity. Hyperpnea-induced bronchoconstriction was assessed by measuring peripheral airway resistance (Rp) in anesthetized mechanically ventilated male mongrel dogs. Either colloidal carbon or monastral blue was used to localize bronchovascular leakage after a 5-min exposure to either a 1000 ml/min dry, 2000 ml/min wet, or 2000 ml/min dry air challenge. Morphometric analyses of cross-sectioned bronchi revealed that hyperpnea with dry air stimulated goblet cell degranulation, damaged the bronchial mucosa, and increased bronchovascular permeability. Exposure to only a 2000 ml/min dry air challenge produced marked mucosal injury when compared with control. Regardless of treatment, bronchial vessels lying below normal mucosa characterized by goblet/ciliated cell (G/C) ratios > or = 0.3 did not leak. A G/C transition zone between 0 and 0.3 separated normal from damaged mucosa. Within this zone, vascular permeability was inversely correlated with G/C ratio. In addition, airflow-induced changes in Rp were inversely related to G/C ratio and positively correlated with bronchovascular leakage. Although these correlations are consistent with the speculation that bronchovascular leakage and edema formation are responsible for the dry air-induced changes in Rp, it is equally plausible that bronchovascular leakage is not the cause of but occurs in concert with airway narrowing to protect cells in the bronchial mucosa from excessive losses of heat and water.

Histochemical demonstration of hydrogen peroxide production by leukocytes in fixed-frozen tissue sections of inflammatory lesions.

The production of H2O2 by cells in cold paraformaldehyde-fixed frozen sections of inflammatory lesions was histochemically demonstrated by incubating them with diaminobenzidine (DAB) for 2 to 6 h. Catalase (150 micrograms/ml, about 1400 U/ml) inhibited the reaction, indicating that H2O2 was required to produce the chromogenic DAB product. Granulocytes (PMNs and eosinophils) were the main types of cells stained by the DAB reaction. Positive staining of macrophages was less frequent. The H2O2 was produced by metabolic enzymes that were still active after cell death and mild fixation. An atmosphere of 95 to 100% oxygen enhanced the specific DAB reaction, and an atmosphere of 100% nitrogen eliminated it. The DAB histochemical reaction to detect H2O2 requires the presence of peroxidases to produce the colored reaction product. Within our tissue sections, such peroxidases were evidently present in excess, because addition of low concentrations of H2O2 significantly increased the reaction product. Although some of the H2O2 produced by the granulocytes may have been derived from the dismutation of superoxide (O2-), the NADPH oxidase pathway for O2- formation did not seem to be involved: NADPH oxidase, a rather labile enzyme, should not be active after mild fixation, and diphenyleneiodonium (100 microM), an inhibitor of flavine-requiring NADPH oxidase, did not inhibit the reaction. Reactive nitrogen intermediates were also not involved, because NG-monomethyl-L-arginine and NG-nitro-L-arginine methyl ester, inhibitors of nitric oxide synthetase, did not appreciably inhibit the reaction. We conclude that stable, non-flavine-requiring oxidases, possibly cyclooxygenases or lipoxygenases, produced the H2O2 measured histochemically by our DAB reaction. These studies were made on tissue sections of acute dermal inflammatory lesions produced in rabbits by the topical application of 1% sulfur mustard [bis(2-chloroethyl) sulfide] in methylene chloride. Both intact PMNs and disintegrating PMNs in the base of the crust produced H2O2. Despite the production of H2O2 and the presence of peroxidase activity, no tissue damage was seen microscopically near the H2O2-producing cells, which indicates that the tissues are well protected by the antioxidants present in this self-limiting inflammatory reaction.