Effects of formoterol and ipratropium bromide in COPD: a 3-month placebo-controlled study

The aim of this study was to compare the effects of formoterol, ipratropium bromide and a placebo on walking distance, lung function, symptoms and quality of life (QoL) in chronic obstructive pulmonary disease (COPD) patients. A total of 183 patients (mean age 64 yrs, 86 female) with moderate-to-severe nonreversible COPD participated in this randomised, double-blind, parallel-group study. After a 2-week placebo run-in, patients were randomised to formoterol Turbuhaler 18 microg b.i.d. (delivered dose), ipratropium bromide 80 microg t.i.d. via a pressurised metered dose inhaler, or placebo for 12 weeks. Inhaled short-acting beta2-agonists were allowed as relief medication and inhaled glucocorticosteroids were allowed at a constant dose. The primary variable was walking distance in the shuttle walking test (SWT). Baseline mean SWT distance was 325 m, mean forced expiratory volume in one second (FEV1) was 40% predicted. Clinically significant improvements in SWT (>30 m) were seen in 41, 38 and 30% of formoterol, ipratropium and placebo patients, respectively (not significant). Mean increases from run-in were 19, 17 and 5 m in the formoterol, ipratropium and placebo groups, respectively. Both active treatments significantly improved FEV1, forced vital capacity, peak expiratory flow and daytime dyspnoea score compared with placebo. Formoterol reduced relief medication use compared with placebo. Neither active treatment improved QoL. Formoterol and ipratropium improved airway function and symptoms, without significant improvements in the shuttle walking test.

Quality of life in patients with chronic alveolar hypoventilation

Measurements of health-related quality of life (HRQL) have not been reported in patients with chronic alveolar hypoventilation (CAH) before starting home mechanical ventilation. The purpose of this study was to investigate quality of life in a population of such patients. Forty-four consecutive patients with CAH due to previous polio, scoliosis, healed pulmonary tuberculosis or neuromuscular disease answered a battery of condition specific and generic (Sickness Impact Profile, Hospital Anxiety and Depression scale, Mood Adjective Check List) self-report questionnaires. Spirometry, arterial blood gases and overnight oxygen saturation were measured. Patients with untreated CAH had significantly impaired HRQL compared to historical data from a healthy reference population. Sleep-related problems were frequent. Age, underlying disease, and standard bicarbonate correlated significantly with HRQL measures, albeit with modest levels of explained variance (8-37%). Patients with chronic alveolar hypoventilation due to neuromuscular or restrictive chest wall disorders had severely impaired health-related quality of life. Age, the underlying disease and severity of hypoventilation are each related to the health-related quality of life decrements. Health-related quality of life measurements add important information to traditional clinical observations.

Neutrophil-associated activation markers in healthy smokers relates to a fall in DL(CO) and to emphysematous changes on high resolution CT

Smoking is a risk factor for developing chronic obstructive pulmonary disease (COPD), but there are no good indicators for early identification of subjects who will develop symptomatic COPD. The aim of this study was to investigate inflammatory mechanisms related to changes in lung function and emphysematous changes on high resolution computed tomography (HRCT) in 'healthy' smokers. Subjects were 60-year-old men from a population study. Bronchoscopy was performed in 30 smokers and 18 who had never smoked. Blood tests, lung function measurements and HRCT were carried out in 58 and 34 subjects, respectively. In comparison with never-smokers, smokers had higher levels of myeloperoxidase (MPO), human neutrophil lipocalin (HNL), eosinophil cationic protein (ECP) and lysozyme in blood, higher levels of MPO, interleukin-8 (IL-8) and HNL in bronchial lavage (BL), and of IL-8, HNL and interleukin-lbeta (IL-1beta) in bronchoalveolar lavage (BAL). Smokers also had lower levels of Clara cell protein 16 (CC-16) in blood. HNL in BL and BAL showed strong correlations to other inflammatory markers (MPO, IL-8, IL-1beta). The variations in MPO in BL were explained by variations in HNL (R2 =0.69), while these variations in BAL were explained by variations in HNL and IL-1beta (R2 = 0.76). DL(CO) was the lung function variable most closely related to MPO and IL-8 in BL and BAL and to IL-1beta in BAL. In a multiple regression analysis, MPO, IL-1beta, IL-8 and CC-16 in BL and MPO in BAL contributed to the explanation of variations in DL(CO) to 41% and 22%. respectively, independent of smoking habits. In smokers with emphysematous lesions on HRCT, HNL in BAL correlated to emphysema score (r(s) = 0.71). We conclude that 'healthy' smoking men with a near normal FEV1 show signs of inflammation in the lower airways that are related to a decrease in DL(CO) and to emphysematous lesions on HRCT. This inflammation seems to be the result of both monocyte/macrophage and neutrophil activation.

Exudation of plasma and production of thromboxane in human bronchi after local bradykinin challenge

Plasma exudation has been suggested to be an important component of the inflammatory response in asthma. Bradykinin elicits many of the features of asthma, including bronchoconstriction, cough, plasma exudation and mucus secretion. In an attempt to quantify local plasma exudation, we have employed a novel low-trauma technique with the aim of challenging and lavaging a central part of the bronchial tree, by selecting a medium sized bronchus. A fibreoptic bronchoscopy was performed in non-smoking healthy volunteers. The instrument was placed proximally in the right upper lobe bronchus. A plastic catheter, equipped with an inflatable latex balloon, was inflated with air (2-4 cmH2O). A solution (100 microl of either two different concentrations of bradykinin: 0.09 and 0.9 mg ml(-1) or normal saline) was instilled through the catheter and distal to the balloon. Eight minutes later a lavage procedure with 10 ml of saline was performed through the catheter. The procedure was then repeated twice, with the other solutions, but from the lingular and middle lobe bronchi. All solutions were given in a blinded fashion, and two different studies were performed. Lavage concentrations of albumin and IgG were quantified as measurements of plasma exudation. In our first study we found that bradykinin challenge significantly increased concentrations of albumin and IgG. In study two, there was no numeric increase in plasma proteins after local bradykinin challenge, but the concentration of thromboxane was significantly increased in lavages from bradykinin-challenged bronchi. Thus, local bronchial administration of bradykinin has the capacity to induce exudation of large plasma macromolecules into the bronchial lumen, as well as local thromboxane production.

Respiratory symptoms relate to physiological changes and inflammatory markers reflecting central but not peripheral airways. A study in 60-year-old 'healthy' smokers and never-smokers

The aim of this study was to evaluate the relationship between respiratory symptoms, lung function and inflammatory markers in 'healthy' smokers. The study population was recruited from an epidemiological study with subjects of the same age, 60 years. Only smokers who considered themselves healthy (n=58) and a random sample of never-smokers (n=34) were investigated. All subjects underwent lung function tests--spirometry, carbon monoxide transfer (DLco) and the single-breath N2 method (N2 test)--together with high-resolution computed tomography (HRCT). A flexible bronchoscopy with a bronchoalveolar lavage (BAL) was performed in 30 smokers and 18 never-smokers. Bronchial biopsies were also taken. Smokers who reported non-specific respiratory problems, chronic bronchitis and wheezing in a symptom questionnaire had a lower forced expiratory volume in 1 sec (FEV1), FEV% and specific airway conductance (sGaw), lung function tests supposed to reflect the more central airways, than smokers without respiratory symptoms. A limited number of smokers with occasional non-specific respiratory problems also had more cytotoxic T cells (CD8) in bronchial biopsies. No differences were found in DLCO and the N2 test, lung function tests supposed to reflect the more peripheral airways including the alveoli, HRCT-diagnosed emphysema or inflammatory markers in blood and BAL between smokers with and without respiratory symptoms. It is concluded that even when smokers consider themselves 'healthy' they have mild symptoms that are related more to physiological changes and inflammatory markers that may reflect events in the central airways than to changes that may reflect events in the peripheral airways.

Ventilatory response to CO2 re-breathing before and after nocturnal nasal intermittent positive pressure ventilation in patients with chronic alveolar hypoventilation

Long-term nocturnal nasal intermittent positive pressure ventilation (NIPPV) has beneficial effects on daytime PaCO2 in patients with chronic alveolar hypoventilation. Our aim was to investigate if these beneficial effects are related to improved respiratory drive as measured by ventilatory response to CO2. In 17 hypoventilated patients (mean age 62 years) we obtained daytime arterial blood gases, nocturnal transcutaneous oxygen saturation, nocturnal transcutaneous PaCO2 ventilatory response to CO2 re-breathing, spirometry and indices of respiratory muscle strength before and after 9 months of NIPPV. Patients served as their own controls. After 9 months of NIPPV day-time PaCO2 decreased from 7.1 kPa to 6.3 kPa, (P<0.001) and PaO2 increased from 8.1 kPa to 9.3 kPa, (P<0.01). The changes in morning and daytime PaCO2 and in nocturnal transcutaneous oxygen saturation were significantly correlated to the changes in several variables derived from the ventilatory response to CO2 re-breathing. In patients with substantial improvement in daytime PaCO2 we found significant improvements in ventilatory response to CO2 re-breathing. The present study confirms the beneficial effect of long-term NIPPV on daytime arterial blood gases. The results are consistent with the hypothesis that the improvement of daytime PaCO2 is related to improved respiratory drive observed after NIPPV.

The economic impact of asthma and chronic obstructive pulmonary disease (COPD) in Sweden in 1980 and 1991

This study was carried out to estimate the direct and indirect costs associated with asthma and chronic obstructive pulmonary disease (COPD) in Sweden in 1980 and 1991, and to identify trends in the use of outpatient care, drugs and inpatient care, and the development of temporary morbidity, permanent disability and mortality for asthma and COPD. Routinely published administrative and population data were used to estimate the costs of asthma and COPD, and these figures were compared to corresponding estimates and trends for all respiratory diseases as well as for all diseases. Asthma and COPD each accounted for about SEK 3 billion, together roughly 2% of the economic cost of all diseases. Although the total costs associated with each disease were similar, the distribution of the different cost components and changes in each component over time differed. During the 1980s, the cost of drugs and out-patient care increased for both diseases. The cost of inpatient care for asthma decreased, whereas that for COPD increased. This study shows that asthma therapy has changed from inpatient to ambulatory care in Sweden, while the treatment of COPD to a higher degree still is based on inpatient care.

Increased elastase and myeloperoxidase activity associated with neutrophil recruitment by IL-17 in airways in vivo

BACKGROUND

A recent study demonstrated that intratracheal administration of the T-lymphocyte cytokine IL-17 recruits neutrophils into airways in vivo by C-X-C chemokine release. It is not known whether IL-17 may also activate airway neutrophils.

OBJECTIVE

Our purpose was to evaluate whether IL-17 activates neutrophils in airways in vivo and, if so, whether the proinflammatory cytokine IL-1beta modulates this action of IL-17.

METHODS

Intratracheal administration of human (h) IL-17 or rat (r) IL-1beta or hIL-17 plus rIL-1beta in anesthetized, spontaneously breathing rats was followed by bronchoalveolar lavage (BAL) 6 hours later. The BAL fluid was characterized in terms of neutrophil count, of the activity for myeloperoxidase (MPO), and in some cases of the activity for elastase (ELA). Isolated rat neutrophils were stimulated with hIL-17 in vitro, followed by characterization of MPO activity in the cell medium.

RESULTS

hIL-17 (1 microg) increased the ELA and the MPO activity, as well as the neutrophil count in BAL fluid, whereas the proinflammatory cytokine rIL-1beta (2.5 ng) did not. Pretreatment with rIL-1beta enhanced IL-17induced ELA and MPO activity, without increasing the neutrophil count. The BAL ELA activity was inhibited by a specific inhibitor of neutrophil serine proteases. Stimulation with hIL-17 in vitro did not increase MPO activity in isolated neutrophils.

CONCLUSION

IL-17 can activate neutrophils in association with their recruitment into the airways in vivo and this effect is probably achieved through induced release of mediators from other airway cells.

Bronchial hyperresponsiveness and airway wall remodelling induced by exposure to allergen for 9 weeks

Prolonged exposure to allergen has been proposed to be important for the development of bronchial hyperresponsiveness and airway remodelling in asthma. The present study was designed to examine the effect of chronic allergen exposure on bronchial responsiveness, eosinophil infiltration, and airway remodelling. We sensitized brown Norway rats with the occupational allergen trimellitic anhydride (TMA) and exposed the animals to TMA conjugated to rat serum albumin (TMA-RSA) on 5 consecutive days each week for 9 weeks, starting 4 weeks after sensitization. IgE and IgG anti-TMA antibodies in serum and bronchial responsiveness to acetylcholine were evaluated before and at weeks 3, 6, and 9 of allergen exposure. Thickness of the airway wall, airway luminal narrowing, and the number of goblet cells and eosinophils in the airway wall were evaluated with an image analysis system in lungs resected after the last assessment of bronchial responsiveness, at the end of the 9-week allergen exposure. All rats developed IgE and IgG anti-TMA antibodies after sensitization. The levels of antibodies increased with allergen exposure until week 6, and then declined. Bronchial hyperresponsiveness to acetylcholine was induced in allergen-exposed rats without ongoing airway eosinophilia. Bronchial hyperresponsiveness induced by chronic allergen exposure via inhalation was accompanied by significantly increased thickness of smooth muscle and airway narrowing in the small airways, and goblet cell hyperplasia in the large airways. We conclude that chronic exposure to allergen can induce bronchial hyperresponsiveness and airway wall remodelling. Airway wall remodelling may contribute to bronchial hyperresponsiveness.

Randomized placebo-controlled study comparing a leukotriene receptor antagonist and a nasal glucocorticoid in seasonal allergic rhinitis

Allergic rhinitis is an inflammatory disorder associated with local leukotriene release during periods of symptoms. Therefore, it has been suggested that antileukotrienes may be beneficial in the treatment of this disease. Leukotriene receptor antagonists have recently become available for asthma treatment, but little is known of their effects on allergic rhinitis. We have evaluated the effects of the leukotriene receptor antagonist zafirlukast versus placebo in patients with allergic rhinitis during the grass pollen season, using the nasal glucocorticoid beclomethasone dipropionate (BDP) as a positive treatment control. Thirty-three patients with seasonal allergic rhinitis were in a double-blind, double-dummy fashion randomized to treatments with oral zafirlukast (20 mg twice a day), intranasal beclomethasone dipropionate (200 microg twice a day), or placebo. The treatment was initiated 3 wk prior to the expected beginning of the grass pollen season. Patients completed a daily symptom-score list for sneezing, rhinorrhea, nasal itch, and nasal blockage during the 50-d treatment period. Nasal biopsies for quantification of local tissue eosinophilia (immunohistochemistry; EG2) were taken 1 mo before initiation of treatment and immediately after the peak of grass pollen season. Patients receiving treatment with zafirlukast had degrees of nasal symptoms similar to those in the placebo group, whereas the BDP group had significantly less symptoms compared with both treatments (p = 0.01 and p = 0.005, respectively). The numbers of activated eosinophils in the nasal tissue increased significantly during the pollen season in both the zafirlukast and the placebo groups, but not in the BDP group. These results obtained with a limited number of patients do not support any clinical efficacy of regular treatment with an oral antileukotriene in seasonal allergic rhinitis but rather favor the use of a nasal glucocorticoid.

Effect of nedocromil sodium on non-adrenergic, non-cholinergic neural responses in guinea pig bronchi in vitro

OBJECTIVE

Nedocromil sodium (nedocromil) improves the clinical condition of asthmatic subjects but its mechanism of action is not fully understood. This study aimed to determine whether nedocromil alters the ability of contractile and relaxant non-adrenergic, non-cholinergic neural (NANC) responses to stabilise tone by inhibiting or potentiating these responses in bronchial smooth muscle and, if so, whether the action is on a pre- or postjunctional level.

RESULTS

Nedocromil attenuated contractile but not relaxant NANC responses (elicited by electric field stimulation) significantly (P < 0.05) in guinea pig main bronchi in vitro. However, the ability of NANC responses to stabilise tone (convergence effect) was not significantly impaired by nedocromil. Furthermore, nedocromil did not significantly shift the concentration response curve (-log EC50) to neurokinin A (NKA), the dominating contractile NANC transmitter, or alter the maximum response to NKA (P > 0.05). Submaximum or maximum contractile responses to histamine were not markedly affected by nedocromil (P > 0.05).

CONCLUSIONS

Nedocromil exerts selective neural inhibition of the contractile but not of the relaxant NANC responses on a pre-junctional level in bronchial smooth muscle. Nedocromil does not, however, markedly impair the ability of NANC response to stabilise bronchial smooth muscle tone.

Neutrophil recruitment by interleukin-17 into rat airways in vivo. Role of tachykinins

We determined whether neutrophil recruitment induced by the T-lymphocyte cytokine, interleukin-17 (IL-17) is modulated by tachykinins in airways in vivo. Cell recruitment into airways was induced by either human (h) IL-17 (1 microgram) or rat (r) IL-1beta (2. 5 ng), instilled intratracheally in rats (n = 5 to 7). Six hours after instillation, hIL-17 (3.1 +/- 1.2 x 10(6) cells/ml) and rIL-1beta (4.1 +/- 0.5 x 10(6) cells/ml), respectively, induced a significant and selective increase in neutrophil count in bronchoalveolar lavage fluid (BAL) when compared with vehicle (0.6 +/- 0.2 x 10(6) cells/ml). For hIL-17, this effect was dose-dependent. Inhalation of peptidase inhibitors (phosphoramidon plus captopril) potentiated the effect of both hIL-17 and rIL-1beta. Inhalation of a neutral endopeptidase inhibitor (phosphoramidon) alone also increased the neutrophil count for hIL-17, whereas an angiotensin-converting enzyme inhibitor (captopril) alone did not. A selective neurokinin (NK)-1 receptor antagonist (SR 140333) reduced the neutrophil count, both with and without phosphoramidon pretreatment. In conclusion, IL-17 selectively recruits neutrophils into rat airways in vivo and this effect is modulated by endogenous tachykinins acting via NK-1 receptors.

Neutrophil recruitment by human IL-17 via C-X-C chemokine release in the airways

IL-17 is a recently discovered cytokine that can be released from activated human CD4+ T lymphocytes. This study assessed the proinflammatory effects of human (h) IL-17 in the airways. In vitro, hIL-17 increased the release of IL-8 in human bronchial epithelial and venous endothelial cells, in a time- and concentration-dependent fashion. This effect of hIL-17 was inhibited by cotreatment with an anti-hIL-17 Ab and was potentiated by hTNF-alpha. In addition, hIL-17 increased the expression of hIL-8 mRNA in bronchial epithelial cells. Conditioned medium from hIL-17-treated bronchial epithelial cells increased human neutrophil migration in vitro. This effect was blocked by an anti-hIL-8 Ab. In vivo, intratracheal instillation of hIL-17 selectively recruited neutrophils into rat airways. This recruitment of neutrophils into the airways was inhibited by an anti-hIL-17 Ab and accompanied by increased levels of rat macrophage inflammatory protein-2 (rMIP-2) in bronchoalveolar lavage (BAL) fluid. The BAL neutrophilia was also blocked by an anti-rMIP-2 Ab. The effect of hIL-17 on the release of hIL-8 and rMIP-2 was also inhibited by glucocorticoids, in vitro and in vivo, respectively. These data demonstrate that hIL-17 can specifically and selectively recruit neutrophils into the airways via the release of C-X-C chemokines from bronchial epithelial cells and suggest a novel mechanism linking the activation of T-lymphocytes to recruitment of neutrophils into the airways.

Relationship between systemic blood pressure, airway blood flow and plasma exudation in guinea-pig

Plasma exudation in the airways is mainly dependent on microvascular permeability of the tracheobronchial circulation and may be affected by local blood flow. Aortic blood pressure provides the major inflow pressure to tracheobronchial circulation. Therefore, systemically administered vasoconstrictors, in doses enough to increase systemic blood pressure, may theoretically increase the blood flow in the tracheobronchial circulation by enhancing inflow pressure. Consequently, this may influence plasma exudation induced by inflammatory mediators in the airways. To test this hypothesis, we used guinea-pigs to study: (1) the effects of i.v. vasoconstrictors (methoxamine and angiotensin II) on blood flow in the tracheal mucosa and in the leg skeletal muscle (Laser-Doppler flowmetry); (2) the effects of i.v. vasoconstrictors on plasma exudation induced by tracheal administration of the inflammatory mediator bradykinin (150 nmol). We found that i.v. methoxamine and angiotensin II significantly increase tracheal mucosa blood flow and systemic blood pressure. The increase in tracheal mucosa blood flow was, in the case of angiotensin II, found to be significantly related to the increase in systemic blood pressure. In separate experiments, pre-treatment with i.v. methoxamine and angiotensin II significantly potentiates Evan's Blue dye exudation induced by bradykinin in the trachea and main bronchi. We conclude that i.v. methoxamine and angiotensin II potentiate bradykinin-induced plasma exudation in the guinea-pig airways, possibly by increasing the local blood flow. The increase in the local blood flow is most likely induced by enhanced systemic blood pressure (inflow pressure), owing to a redistribution of the total body blood flow.

Effect of a novel PACAP-27 analogue on muscarinic airway responsiveness in guinea-pigs in vivo

A recent study showed that the novel pituitary adenylate cyclase-activating peptide (PACAP)-27 analogue [Arg15,20,21,Leu17]-PACAP-27-Gly-Lys-Arg-NH2 causes sustained airway smooth muscle relaxation in vitro. This study examined whether this analogue also has bronchoprotective effects, by inhibiting muscarinic airway responsiveness in vivo. Total lung resistance was measured in anaesthetized, tracheostomized and ventilated guinea-pigs. Increasing doses of acetylcholine were given i.v. once before and thereafter repeatedly each hour after intratracheal instillation of either the PACAP-27 analogue or the clinical beta2-agonist bronchodilator salbutamol. Mean arterial blood pressure (MAP) was monitored to detect cardiovascular side-effects. Both the PACAP-27 analogue and salbutamol significantly attenuated the airway responsiveness to acetylcholine. The total inhibitory effect of the PACAP-27 analogue (350 nmol) corresponded to that of salbutamol (35 nmol). The inhibitory effect of salbutamol (35 nmol) peaked during the second hour and disappeared prior to 5 h after administration. In contrast, the corresponding effect of the analogue (350 nmol) gradually increased and peaked during the fifth hour after administration, whereas it did not fade during the observation period. Both the PACAP-27 analogue (350 nmol) and salbutamol (35 nmol) produced a transient decrease in MAP within 6 min after administration. In conclusion, the novel pituitary adenylate cyclase-activating peptide-27 analogue has bronchoprotective properties, by decreasing muscarinic airway responsiveness in guinea pigs in vivo. The time course of its effect is compatible with a more sustained duration of action compared with salbutamol.

An intranasal glucocorticoid inhibits the increase of specific IgE initiated during birch pollen season

BACKGROUND

Recent in vitro findings show that glucocorticoids in combination with IL-4 can induce the synthesis of IgE, indicating that glucocorticoids may promote allergy.

OBJECTIVE

A double-blind, placebo-controlled study was performed to evaluate the effect of an intranasal glucocorticoid on the levels of birch pollen-specific IgE antibodies in serum from patients with allergic rhinitis.

METHODS

Eighteen patients with allergic rhinitis received treatment with an intranasal glucocorticoid (beclomethasone dipropionate, 400 microg/day) or placebo for 5 weeks, starting from the beginning of the birch pollen season. Blood samples for anti-birch IgE evaluation were taken before treatment was initiated and at 2 and 5 weeks after the beginning of the study.

RESULTS

The beclomethasone group (n = 9) had significantly lower symptom scores when compared with the placebo group (n = 9) (0.86 +/- 0.26 vs 2.79 +/- 0.76, p value = 0.01). Both the treatment group and the placebo group showed a trend of an increase in anti-birch IgE levels 2 weeks after the beginning of the treatment (from 33.1 +/- 13.1 kU/L to 44.9 +/- 20.9 kU/L in the beclomethasone group and from 53.2 +/- 18.9 kU/L to 64.1 +/- 22.1 kU/L in the placebo group). Treatment with beclomethasone returned anti-birch IgE levels to baseline by the end of the study, whereas in the placebo group the anti-birch IgE levels continued to increase (final values, 33.1 +/- 11.9 kU/L vs 72.6 +/- 23.2 kU/L, respectively). The change in IgE antibody levels in the placebo group was significantly higher than that in the beclomethasone group. No statistically significant changes in total IgE or soluble CD23 levels were detected.

CONCLUSION

We conclude that treatment with an intranasal glucocorticoid initiated at the beginning of the pollen season inhibits the induced increase in specific IgE.

Bronchial hyperresponsiveness, epithelial damage, and airway eosinophilia after single and repeated allergen exposure in a rat model of anhydride-induced asthma

Bronchial hyperresponsiveness (BHR) and damage of the epithelium, as well as eosinophilia in the airway wall, induced by trimellitic anhydride (TMA) in sensitized brown Norway rats were studied. Rats were challenged once or seven times with aerosol of TMA conjugated to rat serum albumin (TMA-RSA) 3 weeks after intradermal TMA sensitization. Airway responsiveness (-log PC300 of acetylcholine i.v.) was measured 24 h after allergen challenge. Epithelial lesion and eosinophil infiltration in the airway walls were quantified under light microscopy, and TMA-specific IgE and IgG in serum were evaluated with ELISA. High levels of TMA-specific IgE and IgG were found in all rats in the sensitized groups compared to nonsensitized groups (P < 0.001). Repeated allergen challenges of 0.03% TMA-RSA for 7 consecutive days enhanced the level of TMA-specific IgG, compared to single challenge (P < or = 0.05). Single allergen challenge of 0.3% TMA-RSA had a nonsignificant tendency to produce BHR in sensitized rats compared to nonsensitized rats (P = 0.06). However, repeated allergen challenges (0.003% and 0.03% TMA-RSA for 7 consecutive days) produced significant BHR in sensitized rats (P < 0.05). Furthermore, repeated low-dose (0.003%) TMA-RSA challenge produced more BHR than a 10 times higher single dose (0.03%) (P < 0.05). Slight damage of the airway epithelium was seen in sensitized and repeat-challenged groups. However, bronchial eosinophilia was found in the sensitized and single-challenged groups, but not in nonsensitized nonchallenged, and sensitized repeat-challenged groups (P < 0.005). We conclude that the brown Norway rat can be sensitized with TMA, and that repeated low-dose allergen challenges produce slight epithelial damage and BHR which is independent of ongoing eosinophilia in the airway wall.

Different effects of a thromboxane mimetic on blood flow and plasma exudation in guinea pig airways and skeletal muscle

Thromboxane A2 (TXA2) is a potent constrictor of both airway and vascular smooth muscle. In addition, plasma exudation is induced in the airways by a thromboxane mimetic (U-46619). Because plasma exudation is associated with a local vasodilatation and increased local blood flow, we hypothesized that the general vasoconstrictor effect of U-46619 would be weaker in the airways than in other vascular beds, perhaps resulting in increased local airway blood flow. We studied the effects of i.v. U-46619 on blood pressure, lung resistance as well as blood flow, plasma exudation in airways and leg skeletal muscle in guinea pigs. We found (1) i.v. U-46619 increases the systemic blood pressure, blood flow in tracheal mucosa but decreases blood flow in leg skeletal muscle; (2) i.v. U-46619 induces plasma exudation in the airways, but not in the leg skeletal muscle; (3) a positive relationship between blood pressure and tracheal blood flow as well as airway plasma exudation, a negative relationship between blood pressure and blood flow in leg skeletal muscle; (4) i.v. U-46619 significantly increases lung resistance. We conclude that i.v. U-46619 induces plasma exudation in airways but not in skeletal muscle, and that this plasma exudation is associated with the increased local blood flow, which in turn is caused by increased inflow pressure and redistribution of the total body blood flow to the airways.

Development of antigen-specific IgE after sensitisation with trimellitic anhydride in rats is attenuated by glucocorticoids and cyclosporin A

BACKGROUND

Trimellitic anhydride (TMA) is a low-molecular-weight compound capable of inducing occupational asthma in man. We have characterized the TMA-induced antibody responses in Brown-Norway rats (BNR) and evaluated the effects of treatment with the glucocorticoid betamethasone or with cyclosporin A (CsA) on this response.

METHODS

Animals were sensitised by two intradermal injections of 0.1 ml TMA suspended in corn oil, and development of specific antibodies was assessed using ELISA.

RESULTS

Both IgE and IgG anti-TMA antibodies started to rise between weeks 1 and 3 after immunisation, reached their highest levels 7 weeks after sensitisation with 3% of TMA and then started to decline. Betamethasone and CsA given orally over the time of sensitisation (8 days in total) inhibited the development of specific IgE and IgG anti-TMA antibodies. Betamethasone given 10-17 days after sensitisation attenuated the IgE and IgG antibody responses as well while treatment with CsA after sensitisation had no effect on the production of specific antibodies. Levels of total IgE and IgG were not affected except for a small decrease in total IgE using medium-dose betamethasone after sensitisation.

CONCLUSION

We conclude that TMA-sensitised BNR develop specific IgE and IgG anti-TMA antibodies, and that glucocorticoids and CsA attenuate this response.

8-Epi-PGF2alpha induces airflow obstruction and airway plasma exudation in vivo

8-Epi-prostaglandin F2alpha (8-epi-PGF2alpha) is an F2-isoprostane formed mainly via noncyclooxygenase pathways in vivo. We investigated whether 8-epi-PGF2alpha has any effect on airflow obstruction and plasma exudation in vivo. Airflow obstruction was quantified by measuring lung resistance (RL) in anesthetized and ventilated guinea pigs, and plasma exudation was quantified by the Evans Blue dye method (20 mg/kg intravenously). Intratracheal instillation of 8-epi-PGF2alpha (1 nmol or 10 nmol) caused dose-related increases in RL. Furthermore, the higher dose of 8-epi-PGF2alpha produced Evans Blue dye extravasation in main bronchi and intrapulmonary airways. A prostanoid TP-receptor antagonist, BAY u3405 (1 mg/kg intravenously), abolished the airway effects of 8-epi-PGF2alpha (10 nmol). A thromboxane A2 (TxA2) synthase inhibitor, OKY-406 (30 mg/kg intravenously), significantly attenuated these effects of 8-epi-PGF2alpha (10 nmol). The level of TxB2, a stable TxA2 metabolite, increased in bronchoalveolar lavage fluid (BALF) after 8-epi-PGF2alpha instillation. We conclude that 8-epi-PGF2alpha causes airflow obstruction and plasma exudation in vivo. This effect may be mediated primarily via prostanoid TP-receptors, and a secondary generation of TxA2 may be involved in part of the airway responses in 8-epi-PGF2alpha in the guinea pig.

Inflammatory responses in skin and airways after allergen challenge in brown Norway rats sensitized to trimellitic anhydride

Trimellitic anhydride (TMA) is a low-molecular-weight compound which causes occupational allergy. Brown Norway rats were sensitized to TMA injected intradermally (0.3% TMA suspended in oil). Three weeks later, we examined responses to either free TMA injected intradermally, or TMA conjugated to rat serum albumin (TMA-RSA) given by inhalation (0.5%, nebulized for 15 min). Twenty-one days after the sensitization, Evans blue dye was given i.v. (20 mg/kg), and extravasation of dye in skin was measured 30 min after oil or TMA injections (0.03-10% in oil). In a separate series of experiments, we evaluated the accumulation of eosinophils in the skin after single and repeated injections of TMA (0.03-0.3%). The injection sites were removed and fixed in formalin 18-24 h after the last injection. In a third series of experiments, we evaluated the effects of airway exposure to TMA-RSA (0.5% in 0.9% saline) on the accumulation of eosinophils in the bronchial wall counted with quantitative light microscopy. Intradermal injections of free TMA caused a dose-dependent increase of Evans blue dye extravasation which was significantly higher in sensitized animals than in controls. Skin histology revealed a significant and dose-dependent increase in eosinophils after repeated TMA injections in sensitized animals. Exposure to aerosolized TMA-RSA caused a significant increase of eosinophils in the bronchial wall of sensitized rats compared with nonsensitized rats. Sensitized animals showed significantly higher levels of specific IgG and IgE. We conclude that brown Norway rats can be used as a model of TMA-induced allergic inflammation, mimicking occupational asthma.

U46619 (a thromboxane A2 mimetic) induces airflow obstruction and airway plasma extravasation in the guinea pig: the role of histamine, cyclooxygenase metabolites, leukotrienes and PAF

The aim of the present study was to characterize the airway effects of U46619, a stable thromboxane A2 mimetic, instilled into the trachea of guinea pigs in vivo, and to investigate the role of different mediators in these effects. The airflow obstruction was evaluated by measurement of airway insufflation pressure (P1) and plasma extravasation by quantification of Evans Blue dye (EBD) in airways. U46619, given as a single dose to each animal (1 pmol-10 nmol), caused a dose-dependent increase in P1 and extravasation of EBD. The threshold dose required to induce an increase in P1 was 30 times lower than the threshold dose necessary to evoke EBD extravasation. The role of inflammatory mediators was studied when 10 pmol (inducing only the increase in P1) or 10 nmol (inducing the increase in both P1 and EBD extravasation) of U46619 was administered. The effects of both doses of U46619 were abolished by ICI192,605, an antagonist of prostanoid receptor for thromboxane A2 (0.5 mg/kg i.v.). The airflow obstruction induced by 10 nmol of U46619 was potentiated by indomethacin, a cyclo-oxygenase inhibitor (10 mg/kg i.v.). EBD extravasation induced by 10 nmol U46619 was attenuated by BW70C (6 mg/kg i.v.), a selective 5-lipoxygenase inhibitor, by ICI198,615 (0.5 microgram/kg i.v.), a leukotriene D4/E4 receptor antagonist and by WEB2086 (1 mg/kg i.v.) a platelet-activating factor receptor antagonist. Pyrilamine (2 mg/kg i.v.), a histamine H1 receptor antagonist, did not have any influence on U46619-induced airway effects. We conclude that U46619 possesses a higher potency in the induction of airflow obstruction than in the induction of plasma extravasation and that U46619-induced plasma extravasation may be partly mediated via leukotrienes and platelet-activating factor.

Extent of salmeterol-mediated reassertion of relaxation in guinea-pig trachea pretreated with aliphatic side chain structural analogues

1. Salmeterol is a potent, selective and long acting beta 2-adrenoceptor agonist. In vitro, salmeterol exerts 'reassertion' relaxation of airways smooth muscle. Reassertion relaxation refers to the capacity of salmeterol to cause repeated functional antagonism of induced contraction when airway smooth muscle is intermittently exposed to, then washed free from, beta-adrenoceptor antagonists such as sotalol. The mechanism(s) underlying reassertion relaxation are unknown but may relate to high affinity binding of the long aliphatic side chain of salmeterol to an accessory site, distinct from the agonist recognition site, in or near the beta 2-adrenoceptor (exosite binding hypothesis). 2. In order to test the exosite hypothesis, three pure analogues of salmeterol, each exactly preserving the molecular structure of the aliphatic side chain but with zero or low efficacy at the beta 2-adrenoceptor were synthesized. The effect of pre-incubating guinea-pig tracheal smooth muscle with these analogues on salmeterol-induced reassertion relaxation was determined. 3. Computer Assisted Molecular Modelling of these molecules revealed that each of them exactly preserved the low energy linear conformation of the aliphatic side chain of salmeterol. Measurement of lipophilicity (octanol:water partition coefficient; log P) and direct partition into synthetic membranes (membrane partition coefficient; Kpmem) showed that all compounds had high affinity for lipids and membranes. In particular the biophysical properties of CGP 59162 (log P 1.89, Kpmem 16500) were very similar to salmeterol (log P 1.73, Kpmem 16800). 4. Two of the analogues, CGP 54103 and D 2543 (1 microM), which are structural mimics of the side chain of salmeterol, differing slightly in their length, did not prevent either the initial relaxation induced by salmeterol (0.1 microM) or the reassertion relaxation; however, it was not possible to determine whether either of these molecules occupied the beta 2-adrenoceptor. 5. The third analogue, CGP 59162, which has the substituents on the active saligenin head group of salmeterol in transposed positions, itself exerted a weak beta 2-adrenoceptor-mediated relaxation antagonized by ICI 118551 (beta 2-selective antagonist) but not CGP 20712 (beta 1-selective antagonist) and, at higher concentrations CGP 59162 caused reassertion relaxation suggesting that it may occupy and activate the beta 2-adrenoceptor in a manner analogous to salmeterol. 6. CGP 59162, at concentrations up to ten fold molar excess, did not prevent or reduce salmeterol-induced reassertion relaxation. 7. In conclusion these data are not consistent with the existence of a distinct 'exosite' recognising the aliphatic side chain of salmeterol mediating reassertion.

Airway effects of salmeterol in healthy individuals

The long-acting beta 2-agonist salmeterol has been shown in several in vitro studies to produce non-beta-mediated relaxant effects. The aim of the present study was to investigate whether these effects have any relevance in humans in vivo. Thirteen healthy individuals were studied in a randomized, double-blind, cross-over study on five separate days. The subjects were pre-treated orally with either propranolol 400 mg in order to block beta-adrenoceptor mediated effects or placebo. Two hours after drug intake, three increasing doses of salmeterol (25 + 50 + 100 micrograms), salbutamol (100 + 200 + 400 micrograms) or placebo were given from matched meter dose inhalers at 1-h intervals between doses. Specific airway conductance (sGAW) was measured in a body plethysmograph at the beginning of the experiment and 30 and 60 min after each inhaled dose of the beta-agonists. Salmeterol and salbutamol produced the same maximal increase in sGAW and had the same area under the dose-response curves. Pre-treatment with propranolol totally inhibited the effect of both drugs. In conclusion, salmeterol at clinically used doses did not produce any non-beta-mediated bronchodilating effect in normal individuals, measured as sGAW. Salmeterol and salbutamol showed the same efficacy but salmeterol was four times more potent than salbutamol.

Airway responses following intradermal sensitization to different types of allergens: ovalbumin, trimellitic anhydride and Dermatophagoides farinae

Sensitization of guinea pigs by intradermal injections of the occupational allergen trimellitic anhydride (TMA) in oily vehicle has been shown to be very reproducible. We studied the effect of intradermal sensitization with ovalbumin (OA) in oily vehicle on immune and airway responses in guinea pigs. We also compared airway responses to trimellitic anhydride or Dermatophagoides farinae (DF; mite) with those to OA in guinea pigs intradermally sensitized to respective allergens. Three to four weeks after sensitization, the animals were challenged with intratracheal instillation of these allergens. Intradermal injections with OA developed dose-dependently specific IgG1 antibodies to OA demonstrated by ELISA. In animals sensitized with different doses of OA in corn oil vehicle, a challenge with OA induced a reversely dose-dependent airflow obstruction and airway plasma exudation. In contrast, animals sensitized with OA in saline vehicle had dose-dependent airway responses to OA. Challenge with OA caused an immediate peak and subsequently persistent airflow obstruction, whereas this response to either TMA guinea pig serum albumin or Df was slowly progressive in animals sensitized to respective allergens. The animals sensitized to TMA or Df may show a different profile of airway responses following the challenge compared to OA. Intradermal sensitization may be a valuable method of sensitization for the development of an animal model of airway allergy to different types of allergens, including chemicals or mites.

Induction of nitric oxide synthase in a model of allergic occupational asthma

We have studied the induction of nitric oxide during late allergic responses, using a guinea pig model of trimellitic anhydride (TMA)-induced airway allergy. TMA is a low molecular weight chemical which can cause occupational asthma. The activity of nitric oxide synthase (NOS) was investigated by the detection of 3H-labeled citrulline formation from 3H-labeled arginine. In sensitized animals, challenge with TMA conjugated to guinea pigs albumin (TMA-GPSA) increased the activity of Ca(2+)-independent NOS (inducible NOS; iNOS) in lung and bronchial tissues at 15-17 h after challenge compared to nonsensitized animals. The induction of iNOS activity was associated with an associated with an increased level of nitrite, an end metabolite of the l-arginine-NO pathway, in bronchoalveolar lavage fluid. In contrast to iNOS, the activity of Ca(2+)-dependent NOS (constitutive NOS; cNOS) was not affected by the allergen challenge. These results demonstrate that iNOS in bronchial tissue is induced late after allergen challenge in sensitized guinea pig.

Bradykinin-induced release of thromboxane B2 into bronchoalveolar lavage fluid of guinea pigs: relationship to airflow obstruction

The aim of this study was to evaluate the role of thromboxane A2 in bradykinin-induced airflow obstruction in guinea pig in vivo. Airway insufflation pressure (Pi) was measured to assess airflow obstruction and the thromboxane B2 (a stable metabolite of thromboxane A2) concentration in bronchoalveolar lavage fluid was determined by radioimmunoassay. The animals were pretreated with propranolol (1 mg/kg i.v.) and suxamethonium (5 mg i.v.) prior to bradykinin administration. Bradykinin instillation into the trachea (300 nmol) induced a Pi increase (47.5 +/- 8.3 cm H2O versus 23.8 +/- 1.5 in sham) and significant thromboxane B2 release into bronchoalveolar lavage fluid (79 +/- 19 pg/ml versus 19 +/- 6 in sham). A thromboxane synthase inhibitor (OKY-046, 30 mg/kg i.v.; ((E-E)-3-[p(1H-imidazole-1-yl-methyl) phenyl]-2-propenoic acid hydrochloride mono-hydrate)) or a thromboxane A2 receptor antagonist (ICI192,605, 0.5 mg/kg i.v.; (4-(Z)-6-(2-o-chloro-phenyl-4-o-hydroxyphenyl-1,3-dioxan-cis-5-yl) hexenoic acid)) reduced the Pi increase evoked by bradykinin (38.7 +/- 3.8 and 40.6 +/- 3.8 cm H2O, respectively). OKY-046 abolished the thromboxane B2 release. A platelet-activating factor receptor antagonist, WEB2086 (1 mg/kg i.v.; (3-[4-(chlorophenyl)-9-methyl-6H-thienol [3,2-f][1,2,4]trizolo-[4,3-a][1,4] diazepin-2-yl]1-4-(4-morpholinyl)-1-propanon) did not significantly affect any measured parameter. We conclude that, in guinea pigs, bradykinin-induced airway effects are associated with a local thromboxane A2 release.

Different effects of salmeterol, formoterol and salbutamol on cholinergic responses in the ferret trachea

1. In the present study, the inhibitory effects of the selective beta 2-adrenoceptor agonists, salmeterol, formoterol and salbutamol, have been investigated on contractions of ferret trachea induced both by endogenous and exogenous acetylcholine. The aim of the study was to evaluate quantitative and/or qualitative differences in response which may indicate both pre- and post-junctional sites of action. The non-selective beta-antagonist, sotalol, was used to estimate beta-adrenoceptor involvement. 2. Isometric tension was measured in ferret isolated tracheal strips. The inhibitory effects of the drugs were studied on tonic contractions induced by pre-junctional activation with electrical field stimulation (EFS) (2 Hz, 700 mA) or post-junctional activation with exogenous acetylcholine (ACh) (0.5 microM, about EC80), giving a similar degree of smooth muscle response. 3. Concentration-response experiments were performed with formoterol (0.3 nM-0.3 microM) and salmeterol and salbutamol (10 nM-10 microM). The experiments ended with the addition of sotalol (10 microM). 4. All three beta-agonists inhibited the contractions in a concentration-dependent manner. Salbutamol, formoterol and salmeterol inhibited the EFS-induced contractions by 66(8)%, 105(5)% and 103(8)% (mean(s.e. mean)) respectively. ACh-induced contractions were inhibited by 37(6)%, 72(11)% and 33(8)%. Theophylline (10 nM-3 mM) inhibited the contractions to the same degree. 5. beta-Adrenoceptor blockade by sotalol significantly antagonized the inhibitory effects of salbutamol and formoterol on both EFS- and ACh-induced contractions. The effect of salmeterol on ACh-induced contraction was also significantly antagonized, whereas the inhibition of EFS-induced contraction was virtually unaffected. 6. In conclusion, salbutamol, salmeterol and formoterol produced greater inhibitory effects in preparations contracted by EFS than in preparations contracted by exogenously-added ACh. In the case of formoterol and salbutamol, the effects on both levels are most probably due to beta-adrenoceptor stimulation, whereas for salmeterol the dominant pre-junctional effect is probably not mediated via beta-adrenoceptors. This non-beta-mediated effect could represent an additional relaxant mechanism for salmeterol.

Palpable lymph nodes of the neck in Swedish schoolchildren

We studied 3592 Swedish schoolchildren, 8 or 9 years old, examined for palpable submandibular, cervical and supraclavicular lymph nodes. All children were skin tested with 2 TU PPD RT23 and with 0.1 microgram of Mycobacterium avium sensitin or 0.1 microgram of M. scrofulaceum sensitin. A total of 991 children had palpable lymph nodes in any of the three locations. Among them, 811 had lymph nodes in one location, 162 in two locations and 18 in three. In 312 children, the lymph nodes were > or = 5 mm in size in any location. The most common location was submandibular. Boys had a significantly higher prevalence of palpable lymph nodes than girls. There was also seasonal variation. Children infected by atypical mycobacteria (sensitin reaction > or = 6 mm) did not have a higher prevalence of palpable lymph nodes than those not infected.

Effect of maturation on airway plasma exudation induced by eicosanoids in guinea pig

Airway reactivity to bronchoconstrictor mediators changes with age. We studied the effects of maturational change on airway responses induced by a thromboxane A2 mimetic, U-46619 (2, 6 and 20 nmol/kg; i.v.), leukotriene D4 (0.6 and 2 nmol/kg; i.v.) or vehicle (0.9% NaCl; i.v.) in immature (196 +/- 3 g: 2 weeks) and adult guinea pigs (512 +/- 5 g: 11 weeks). In the same animals, we measured both lung resistance (RL) to monitor airflow obstruction and extravasation of Evans Blue dye (20 mg/kg) to quantify airway plasma exudation. For a comparison, changes in RL in response to acetylcholine (5, 15 and 50 nmol/kg; i.v.) were also examined in both age groups. The order of potency to induce an increase in RL did not change with age (leukotriene D4 > U-46619 > acetylcholine). In immature animals, the peak RL after U-46619 (2, 6 and 20 nmol/kg; P < 0.05, P < 0.005 and P < 0.01, respectively) and leukotriene D4 (2 nmol/kg; P < 0.01) was significantly higher than in adult animals. U-46619 and leukotriene D4 produced significant extravasation of Evans Blue dye in both immature and adult animals. The order of potency to induce extravasated dye also did not change with age (leukotriene D4 > U-46619). The amount of extravasation of Evans Blue dye after U-46619 (6 and 20 nmol/kg) and leukotriene D4 (0.6 and 2 nmol/kg) was significantly smaller in immature animals than adults at all airway levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of eicosanoids in airflow obstruction and airway plasma exudation induced by trimellitic anhydride-conjugate in guinea-pigs 3 and 8 weeks after sensitization

Trimellitic anhydride (TMA) is a low molecular weight chemical which can cause occupational asthma. We studied the role of eicosanoids in airway responses to TMA at different times after sensitization in actively sensitized guinea-pigs. Sensitization was performed by two intradermal injections of free TMA (0.1 ml of 0.3% TMA in corn oil). At 3 and 8 weeks after sensitization, the guinea-pigs were anaesthetized and challenged with intratracheal instillation of 0.5% TMA conjugated to guinea-pig serum albumin (TMA-GPSA; 50 microliters). Lung resistance (RL) was measured to assess airflow obstruction, and the tissue content of Evans Blue dye was measured to assess airway plasma exudation. Intratracheal instillation of TMA-GPSA induced a slowly progressing increase in RL, reaching a peak at approximately 3.5 min after the challenge (6.0 +/- 2.0 cm H2O/ml/s in the 3-week group and 3.8 +/- 0.6 in the 8-week group). Pretreatment before challenge with pyrilamine (anti-histamine: 2 mg/kg, intravenously) slowed the onset of the increase in RL following challenge with TMA-GPSA, and significantly attenuated the peak response. A combination of pyrilamine and ICI-192,605 (thromboxane receptor antagonist; 0.5 mg/kg, intravenously) completely abolished the increase in RL in both week groups. A combination of pyrilamine and ICI-198,615 (leukotriene C4/D4/E4 receptor antagonist: 0.5 mg/kg, intravenously) did not further attenuate the increase in RL compared with pretreatment with pyrilamine alone, but the induced Evans Blue dye extravasation was completely inhibited in the 3-week group, whereas a remaining extravasation was observed in the 8-week group.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment with cyclosporin A during sensitization with trimellitic anhydride attenuates the airway responses to allergen challenge three weeks later

The present studies examined the effects of oral treatment with cyclosporin A, betamethasone or azelastine administered over the time of sensitization with trimellitic anhydride on allergen-induced airway responses, compared to those of control animals given corn oil alone. Drugs were given for 8 days. The animals were sensitized with trimellitic anhydride (0.1 ml of 0.3% w/v) in corn oil given intradermally on days 4 and 5 of drug treatment. Three to four weeks after sensitization with free trimellitic anhydride, the animals were anesthetized, tracheostomized and challenged with trimellitic anhydride conjugated to guinea pig serum albumin (trimellitic anhydride-guinea pig serum albumin; 0.5%; 50 microliters) instilled via the airway route. In the same animal, we measured both lung resistance (RL) to monitor airflow obstruction, and extravasation of Evans Blue dye (20 mg/kg) to quantify airway plasma exudation. In control animals, instillation of trimellitic anhydride-guinea pig serum albumin into the tracheal lumen caused a slowly progressing increase in RL over the observation period (6 min), in addition to extravasation of Evans Blue dye at all airway levels. In animals treated with 50 mg/kg of cyclosporin A, both the allergen-induced increase in RL and extravasation of Evans Blue dye in intrapulmonary airways were significantly attenuated. However, neither betamethasone nor azelastine significantly affected these responses. We conclude that cyclosporin A may influence the immune system in the guinea pig during the induction of allergy, thus leading to attenuation of allergen-induced airway obstruction at later time points.

Sensitivity to sensitins and tuberculin in Swedish children. Part 5: A study of school children in an inland rural area

SETTING

Since 1986 we have tested approximately 7000 non-BCG-vaccinated Swedish children with tuberculin and with Mycobacterium avium or M. scrofulaceum sensitin. In Göteborg, an urban coastal area, 25% of 8-9-year-old school children reacted to M. avium sensitin and 32% of M. scrofulaceum sensitin using a 6 mm cut-off.

OBJECTIVE

To evaluate if geographical factors have an influence on the prevalence of children reacting to tuberculin and sensitins.

DESIGN

2000 schoolchildren of the same age as those in Göteborg but living in an inland rural area were Mantoux-tested in a similar way (simultaneously on separate arms with PPD RT23 and either of the two sensitins).

RESULTS

15% reacted to PPD RT23, 9.7% to M. avium and 13.9% to M. scrofulaceum sensitin. None of the children with a PPD RT23 reaction > = 6 mm showed signs of tuberculosis or had any known exposure. A reaction to PPD RT23 was usually combined with a still larger sensitin reaction.

CONCLUSION

There was a considerable geographic difference in sensitin reactivity, low in an inland rural area compared to a coastal urban area. Children reacting to PPD RT23 had probably not been infected by M. tuberculosis but more likely by atypical mycobacteria. The reactions should be interpreted as cross-reactions.

Bradykinin-induced airflow obstruction and airway plasma exudation: effects of drugs that inhibit acetylcholine, thromboxane A2 or leukotrienes

1. The mechanisms behind bradykinin-induced effects in the airways are considered to be largely indirect. The role of cholinergic nerves and eicosanoids, and their relationship in these mechanisms were investigated in guinea-pigs. 2. The role of cholinergic nerves was studied in animals given atropine (1 mg kg-1, i.v.), hexamethonium (2 mg kg-1, i.v.), or vagotomized. To study the role of eicosanoids, animals were pretreated with a thromboxane A2 (TxA2) receptor antagonist (ICI 192,605; 10(-6) mol kg-1, i.v.) or with a leukotriene (LT) receptor C4/D4/E4 antagonist (ICI 198,615; 10(-6) mol kg-1, i.v.). 3. After pretreatment with a drug, bradykinin (150 nmol) was instilled into the tracheal lumen. We measured both airway insufflation pressure (Pi), to assess airway narrowing, and the content of Evans blue dye in airway tissue, to assess plasma exudation. 4. Bradykinin instillation into the trachea caused an increase in Pi and extravasation of Evans blue dye. The increase in Pi was significantly attenuated by atropine or the TxA2 receptor antagonist, but not by hexamethonium, vagotomy or the LT receptor antagonist. 5. The bradykinin-induced exudation of Evans blue dye was significantly attenuated in the intrapulmonary airways by the TxA2 receptor antagonist, but not by atropine, hexamethonium, cervical vagotomy or the LT receptor antagonist. 6. A thromboxane-mimetic U-46619 (20 nmol kg-1, i.v. or 10 nmol intratracheally), caused both an increase in Pi and extravasation of Evans blue dye at all airway levels. Atropine pretreatment slightly attenuated the peak Pi after the intratracheal administration of U-46619, but not after i.v. administration. 7. We conclude that peripheral cholinergic nerves are involved in bradykinin-induced airflow obstruction but not plasma exudation, and that TxA2 is involved in both airflow obstruction and airway plasma exudation induced by bradykinin given via the airway route. TxA2-induced airflow obstruction is mediated only to a minor degree, via the release of acetylcholine in the airways.

Airway allergy to trimellitic anhydride in guinea pigs: different time courses of IgG1 titer and airway responses to allergen challenge

BACKGROUND

Trimellitic anhydride (TMA) is a low molecular weight chemical that may cause occupational asthma in human beings. The objectives of this study were to determine the time course of immune and airway responses to TMA in guinea pigs and to relate the immunologic response to the immediate responses in lung resistance (RL) and plasma exudation induced by allergen challenge.

METHODS

We studied the effects of time course after sensitization on airway response to TMA in guinea pigs actively sensitized to free TMA, given by intradermal injection (0.1 ml of 0.3% TMA in corn oil). During weeks 1, 2, 3, 5, and 8 after sensitization, anesthetized animals were challenged with TMA conjugated to guinea pig serum albumin (TMA-GPSA), instilled via the airway route. Nonsensitized animals were challenged with the same amount of conjugate 4 weeks after intradermal injection of corn oil only. In the same animal, we measured both RL to monitor airflow obstruction and extravasation of Evans blue dye (20 mg/kg) to quantify airway plasma exudation.

RESULTS

Instillation of TMA-GPSA (0.5%; 50 microliters) into the tracheal lumen caused a significant increase in RL, reaching a maximum at 2.5 minutes after the instillation in the 1-week group (9.0 +/- 5.9 cm H2O/ml/sec) and between 5 and 6 minutes in the 2-, 3-, 5-, and 8-week groups (9.4 +/- 4.8, 12.7 +/- 5.5, 3.7 +/- 1.1, and 1.7 +/- 0.2 cm H2O/ml/sec, respectively). The maximal increase in RL after the challenge in nonsensitized animals was 0.39 +/- 0.05 cm H2O/ml/sec. TMA-GPSA also produced significant extravasation of Evans blue dye at all airway levels in the sensitized groups, and the amount of dye in the peripheral airways was significantly greater than that in the trachea. Furthermore, the level of Evans blue dye in airway tissue increased with the time after sensitization, up to the latest time point tested (8 weeks). Specific IgG1 antibodies to TMA-GPSA demonstrated by ELISA were detected in all animals in the 3-, 5-, and 8-week groups, with maximal levels 5 weeks after sensitization. Specific IgG1 titers to TMA-GPSA significantly correlated with the level of Evans blue dye induced by challenge with TMA-GPSA but not with the increase in RL.

CONCLUSIONS

Intradermal sensitization to free TMA induces specific airway allergy for a long period after sensitization. Specific IgG1 antibodies to allergen may influence allergen-induced plasma exudation rather than the airflow obstruction in this animal model of TMA-induced asthma.

Leukotriene D4- and prostaglandin F2 alpha-induced airflow obstruction and airway plasma exudation in guinea-pig: role of thromboxane and its receptor

1. We studied the effects of a thromboxane A2 receptor (TP receptor) antagonist, ICI-192,605 (0.5 mg kg-1, i.v.) and a selective thromboxane (Tx) synthetase inhibitor, OKY-046 (30 mg kg-1, i.v.), on airway responses induced by leukotriene D4 (LTD4; 0.2 nmol) or prostaglandin F2 alpha (PGF2 alpha; 20 nmol) instilled via the airways route to anaesthetized guinea-pigs. For a comparison, airway responses to a TxA2-mimetic, U-46619 (0.02 nmol) were also studied. We measured both lung resistance (RL) to monitor airflow obstruction, and extravasation of Evans Blue dye to quantify airway plasma exudation. 2. Instilled LTD4 into the tracheal lumen induced an immediate peak and subsequently persistent increase in RL and produced a large amount of extravasation of Evans Blue dye at all airway levels. Both ICI-192,605 and OKY-046 significantly attenuated the persistent increase in RL following the immediate response and reduced LTD4-induced extravasation of Evans Blue dye in the trachea and proximal intrapulmonary airway. Instilled LTD4 produced significant increases in immunoreactive TxB2 in bronchoalveolar lavage fluid obtained 1.5 min after instillation of LTD4. 3. Instilled PGF2 alpha into the tracheal lumen induced an immediate increase in RL which peaked at approximately 15 s. We also observed a delayed sustained increase in RL, reaching a second peak at approximately 4 min. PGF2 alpha produced small but significant increases in the amount of Evans Blue dye at all airway levels. As with PGF2 alpha, instillation of U-46619 produced a biphasic increase in RL and extravasation of Evans Blue dye. The potency of PGF2a, in inducing these airway responses was about 1000 times less than U-46619. ICI-192,605 abolished both the immediate and the delayed increase in RL after PGF2a, and also blocked PGF2a,-induced extravasation of Evans Blue dye. However, OKY-046 had no inhibitory effects on these responses.4. We conclude that airflow obstruction and airway plasma exudation induced by instilled LTD4 is, in part, mediated via TxA2 generation and subsequent activation of TP-receptors. On the other hand,instilled PGF2a, while inducing similar responses, does so primarily by direct activation of TP receptors,rather than via TxA2 generation.

Non-adrenergic, non-cholinergic neural activation in guinea-pig bronchi: powerful and frequency-dependent stabilizing effect on tone

1. We examined non-adrenergic, non-cholinergic (NANC) stimulation for its stabilizing effect on bronchial smooth-muscle tone with respect to its regulatory power and the effect of variations in neural impulse frequency. 2. The guinea-pig isolated main bronchus (n = 4-12) was pretreated with indomethacin (10 microM) and incubated with atropine (1 microM) and guanethidine (10 microM). Electrical field stimulation (EFS: 1200 mA, 0.5 ms, 240 s) was applied at various levels of tone prior to EFS: first without tone, then at a moderate tone induced by histamine (0.3 microM) and, finally, at a high tone induced by histamine (6 microM). Three different stimulation frequencies (1, 3 or 10 Hz) were used in order to produce moderate to near-maximum contractile and relaxant NANC neural responses. Both the contractile and the relaxant NANC responses were tetrodotoxin-sensitive in the guinea-pig isolated main bronchus (3 Hz). 3. Without tone prior to EFS, NANC activation (1, 3 or 10 Hz) induced a pronounced contractile response. At a moderate level of tone prior to EFS, NANC activation induced a less pronounced contractile response. At the highest level of tone prior to EFS, NANC activation induced a relaxant response. All these NANC responses adjusted the tone towards a similar level and this 'stabilization level' was 56(6)% at 1 Hz, 65(3)% at 3 Hz and 56(5)% at 10 Hz, expressed as a percentage of the maximum histamine-induced (0.1 mM) tone in each airway preparation. 4. There was a difference of approximately 90% of maximum between the highest and the lowest tone level prior to NANC activation. This difference was reduced by the converging contractile and relaxantNANC responses and the magnitude of this 'convergence effect' was 40(8)% at 1 Hz, 72(4)% at 3 Hz and 90(2)% at 10 Hz.5. These findings indicate that NANC neural activation stabilizes bronchial smooth-muscle tone via a contraction when the tone is low prior to activation and via a relaxation when the tone is high prior to activation. The NANC stabilizing effect on tone appears to be powerful and its magnitude can be controlled by the neural impulse frequency. The level of tone towards which the NANC responses converge does not appear to be markedly altered by variations in the impulse frequency. Our findings are consistent with a regulatory role for NANC responses in the control of bronchial smooth-muscle tone.

Role of arachidonic acid metabolites in airway responses induced by trimellitic anhydride in actively sensitized guinea pigs

We studied the role of arachidonic acid metabolites, histamine, and 5-HT in airway responses to trimellitic anhydride (TMA) in actively sensitized guinea pigs. Sensitization was produced by two intradermal injections of free TMA (0.1 ml of 0.3% TMA in corn oil). After 21 to 28 days, guinea pigs were anesthetized and challenged with intratracheal instillation of 0.5% TMA conjugated to guinea pig serum albumin (TMA-GPSA; 50 microliters). Lung resistance (RL) was measured to assess airflow obstruction, and the tissue content of Evans blue dye was measured to assess airway plasma exudation. Before challenge, sensitized animals were pretreated intravenously with inhibitors of different mediators: pyrilamine (antihistamine: 2 mg/kg, indomethacin (cyclooxygenase inhibitor: 10 mg/kg), OKY-046 (thromboxane synthetase inhibitor: 30 mg/kg), ICI-198,615 (leukotriene receptor antagonist: 10(-6) mol/kg), ketanserin (5-HT2 receptor antagonist: 1 mg/kg), or azelastine ("antiallergic agent": 1 mg/kg). Intratracheal instillation of TMA-GPSA induced a slowly progressing increase in RL and produced extravasation of Evans blue dye at all airway levels in sensitized animals. Pyrilamine and azelastine abolished the increase in RL induced by TMA-GPSA until 2.5 min after the challenge. Indomethacin and OKY-046 significantly attenuated the increase in RL 3 min after the challenge. ICI-198,615 and ketanserin did not significantly affect the increase in RL. Extravasation of Evans blue dye induced by TMA-GPSA was decreased by pyrilamine, azelastine and ICI-198,615 in main bronchi and intrapulmonary airways. Indomethacin, OKY-046 and ketanserin did not significantly affect the extravasation of dye into the airway tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Salmeterol, formoterol, and salbutamol in the isolated guinea pig trachea: differences in maximum relaxant effect and potency but not in functional antagonism

BACKGROUND

Formoterol and salmeterol are new long acting beta 2 adrenoceptor agonists. The maximum relaxant effect, potency and functional antagonism against carbachol induced contraction for salmeterol, formoterol and salbutamol have been compared in the guinea pig isolated trachea. In addition, the possibility of inducing a non-beta adrenoceptor mediated relaxation by salmeterol was studied.

METHODS

Concentration response experiments were conducted with isolated tracheal preparations (n = 4-6 in all experiments), precontracted by carbachol to cause either 40% (60 nmol/l), 80% (0.3 mumol/l) or 100% (3 mumol/l, supramaximal) of the maximum contraction. Each beta agonist was added cumulatively at each level of precontraction. Additional cumulative concentration response experiments were conducted for salmeterol alone at the highest level of precontraction, with and without beta blockade by sotalol (1 mmol/l). With the drug concentrations which produced the maximum response and the highest level of precontraction, the relaxation of formoterol (10 nmol/l) and salmeterol (1 mumol/l) was also compared non-cumulatively. Finally, with the corresponding drug concentrations and precontraction, the relaxant effect was compared for formoterol (10 nmol/l) in salmeterol relaxed airways with that of salmeterol (1 mumol/l) in formoterol relaxed airways.

RESULTS

The increase in carbachol concentration from 60 nmol/l to 3 mumol/l induced a rightward shift in the mean (SE) concentration (log steps) causing 50% maximum relaxation for salmeterol (0.73 (0.17)), formoterol (0.85 (0.18)), and salbutamol (1.13 (0.11)). Significant differences in the maximum relaxant effect were shown at the highest level of precontraction only, with a remaining active tension of percentage precontraction of 27% (4%) for 1 mumol/l salbutamol and 35% (3%) for 10 nmol/l formoterol compared with 50% (2%) for 1 mumol/l salmeterol. The rank order of potency was: formoterol > salbutamol approximately salmeterol at all levels of precontraction (-log EC50: 9.32 (0.05) for formoterol, 7.82 (0.08) for salbutamol, and 7.50 (0.13) for salmeterol at 80% maximum precontraction). Beta blockade by sotalol (1 mmol/l) significantly inhibited the relaxation induced by salmeterol (1 mumol/l) (remaining active tension: 104% (1%) v 71% (11%) of precontraction) but not the relaxation induced by salmeterol (10 mumol/l) (remaining active tension: 75% (5%) v 71% (12%) of precontraction). In the non-cumulative experiments, formoterol displayed more relaxant effect than salmeterol (remaining active tension: 51% (6%) v 65% (6%) of precontraction). Finally, formoterol significantly relaxed salmeterol relaxed airways (relaxant effect: 22% (8%) of precontraction) whereas there was no significant response to salmeterol in formoterol relaxed airways (relaxant effect: 5% (12%) of precontraction).

CONCLUSIONS

In the guinea pig isolated trachea, formoterol and salbutamol produce more relaxant effect than salmeterol, suggesting that salmeterol is a partial beta 2 agonist. Very high concentrations of salmeterol may induce non-beta adrenoceptor mediated relaxation. Formoterol is more potent than both salbutamol and salmeterol. There is no pronounced difference in the magnitude of antagonism against carbachol induced contractions between salmeterol, formoterol, and salbutamol.

Nonadrenergic, noncholinergic responses stabilize smooth muscle tone, with and without parasympathetic activation, in guinea-pig isolated airways

In guinea-pig isolated airways, nonadrenergic, noncholinergic (NANC) neural responses converge towards a similar level of smooth muscle tone, via a contraction when the tone is low prior to stimulation, and via a relaxation when the tone is high prior to stimulation. We wanted to assess the effect of simultaneous parasympathetic activation on these converging NANC responses, with and without the addition of sympathetic activation. In guinea-pig isolated airways, the spontaneous airway tone was initially abolished by indomethacin (10 microM). In one series, adrenergic depletion by guanethidine (10 microM) was then established, with and without cholinergic blockade by atropine (1 microM). In another series, either cholinergic blockade by atropine (1 microM) or no blockade was utilized. Responses to electrical field stimulation (1,200 mA, 0.5 ms, 3 Hz for 240 s) were studied with no induced tone, at a moderate (0.3 microM) and at a near-maximum (6 microM), histamine-induced tone. The mean level of the tonus equilibrium (% of maximum tone) was higher with the simultaneous NANC and parasympathetic activation than with NANC activation alone (75% compared with 44%, in the main bronchus, n = 8). The level of the tonus equilibrium was also higher with the simultaneous NANC, sympathetic and parasympathetic activation than with NANC and sympathetic activation only (49% compared with 21%, in the main bronchus, n = 8). The pattern was similar in the distal trachea. In conclusion, NANC neural responses can stabilize smooth muscle tone, and this stabilizing effect can be modulated by both parasympathetic and sympathetic activation, in guinea-pig isolated airways.

Nonadrenergic, noncholinergic responses stabilize smooth muscle tone, with and without parasympathetic activation, in guinea-pig isolated airways

In guinea-pig isolated airways, nonadrenergic, noncholinergic (NANC) neural responses converge towards a similar level of smooth muscle tone, via a contraction when the tone is low prior to stimulation, and via a relaxation when the tone is high prior to stimulation. We wanted to assess the effect of simultaneous parasympathetic activation on these converging NANC responses, with and without the addition of sympathetic activation. In guinea-pig isolated airways, the spontaneous airway tone was initially abolished by indomethacin (10 microM). In one series, adrenergic depletion by guanethidine (10 microM) was then established, with and without cholinergic blockade by atropine (1 microM). In another series, either cholinergic blockade by atropine (1 microM) or no blockade was utilized. Responses to electrical field stimulation (1,200 mA, 0.5 ms, 3 Hz for 240 s) were studied with no induced tone, at a moderate (0.3 microM) and at a near-maximum (6 microM), histamine-induced tone. The mean level of the tonus equilibrium (% of maximum tone) was higher with the simultaneous NANC and parasympathetic activation than with NANC activation alone (75% compared with 44%, in the main bronchus, n = 8). The level of the tonus equilibrium was also higher with the simultaneous NANC, sympathetic and parasympathetic activation than with NANC and sympathetic activation only (49% compared with 21%, in the main bronchus, n = 8). The pattern was similar in the distal trachea. In conclusion, NANC neural responses can stabilize smooth muscle tone, and this stabilizing effect can be modulated by both parasympathetic and sympathetic activation, in guinea-pig isolated airways.