Bronchial hyperresponsiveness and airway neutrophil accumulation induced by interleukin-8 and the effect of the thromboxane A2 antagonist S-1452 in guinea-pigs

Interleukin-8 (IL-8) has been shown to be a chemotactic factor for neutrophils, T-lymphocytes and eosinophils, but it is unknown whether the IL-8-induced inflammatory cell accumulation into the airways can cause the bronchial hyperresponsiveness (BHR) characteristic of asthma. IL-8 at a dose of 0.5 or 5μg/kg was administered intranasally to guinea-pigs twice a week for 3 weeks. One day after the last administration, animals were anesthetized and artificially ventilated through tracheal cannula and lateral pressure at the cannula (Pao) was measured as an overall index of airway responses to increasing concentrations of inhaled histamine (25, 50, 100, and 200 μg/ml). The IL-8 treatment significantly enhanced bronchial responsiveness to histamine in a dose-dependent manner (ANOVA P < 0.01). The provocative concentration of histamine causing a 100% increase in Pao (PC100) at a dose of 0.5 and 5μg/kg of IL-8 was 68.1 (Gsem 1.12) and 35.6 (Gsem 1.25) μg/ml, respectively. The latter was significantly (P < 0.01) lower than that in control animals treated with PBS (93.3 [Gsem , 1.14] μg/ml)- The IL-8 treatment also induced a significant influx of neutrophils, but not eosinophils, in bronchoalveolar lavage (BAL) fluid (18.3 ± 8.8 and 30.6 ± 8.3% in animals treated with 0.5 and 5 μg/kg, respectively, of IL-8 vs 3.6 ± 0.7% in phosphate buffered saline-(PBS)-treated animals). Furthermore, we examined the effect of the thromboxane receptor antagonist S-1452 (0.01 or 0.1 mg/kg, i.p. 24 and 1 h before anesthesia) on this IL-8 induced BHR. S-1452 significantly inhibited the BHR dose-dependently (ANOVA P < 0.001). PC100 was 94.0 (Gsem 1.19), 137.4 (Gsem 1.17) and 43.0 (Gsem 1.24) μg/ml with S-1452 at doses of 0.01 and 0.1mg/ml and saline, respectively. We conclude that IL-8 causes BHR and airway neutrophil inflammation, and that thromboxane A₂ is important in the development of BHR induced by IL-8.     

Role of sensory neuropeptides in post-allergic propranolol-induced bronchoconstriction in guinea pigs in vivo

Background Administration of propranolol can provoke bronchoconstriction in asthmatic patients. We hypothesized that such bronchoconstriction may result from the inflammatory mediators released by an allergic reaction. We recently developed a guinea pig model for propranolol-induced bronchoconstriction (PIB). Neuropeptides which are released from C-fibre nerve endings have been postulated to induce bronchial hyperresponsiveness through neurogenic inflammation. Objective The purpose of this study was to examine whether sensory neuropeptides are involved in the development of PIB after allergic reaction. Methods Propranolol at a concentration of 10mg/ml was inhaled 20min after antigen challenge in passively sensitized, anaesthetized and artificially ventilated guinea pigs. The animals were treated intravenously with a NK₁ and NK₂ dual antagonist, FK224, in a dose of 1 or 10 mg/kg or vehicle or a selective NK₁ antagonist, FK888, in a dose of 1 or 10mg/kg or vehicle 10min before or 15min after antigen challenge. Results Propranolol inhaled 20 min after antigen challenge caused bronchoconstriction. FK224 or FK888 administered 15 min after antigen challenge as well as 10 min before antigen challenge did not reduce the PIB. Conclusion We conclude that neuropeptides such as neurokinin A and substance P do not directly contribute to the development of PIB after allergic reaction.     

Neurokinin-1 receptor antagonist inhibits short-term sulfuric-acid-induced airway hyperresponsiveness in sensitized guinea pigs

BACKGROUND: Tachykinins are involved in the development of bronchial inflammation and airway hyperresponsiveness (AHR); however, the role of the neurokinin-1 (NK(1)) receptor in acid-aerosol-induced bronchial impairment in asthmatic patients remains controversial. METHODS: To investigate the effects on the NK(1) receptor antagonist FK888 the neurokinin-2 (NK(2)) receptor antagonist SR48968 on sulfuric-acid (H(2)SO(4))-induced AHR in guinea pigs, specific airways resistance (sRaw) and airways responsiveness to methacholine (MCh) were measured before and after 6 h of exposure to H(2)SO(4) aerosol (pH 1.7, 82 mg/m(3)) in ovalbumin-sensitized guinea pigs. RESULTS: Airway responsiveness to MCh significantly increased (p<0. 05) after the exposure, however sRaw did not. Treatment with FK888 significantly inhibited (p<0.05) H(2)SO(4)-induced AHR in a dose-dependent manner, as did SR48968. CONCLUSIONS: These results suggest that not only NK(2) but also NK(1) receptors might have important roles in the development of acid-aerosol-induced AHR.     

Relationship between viral antibodies and bronchial hyperresponsiveness in 495 unselected children and adolescents

The purpose of this study was to investigate whether recent and previous subclinical viral respiratory infection can explain the presence of increased bronchial responsiveness to histamine. We studied a randomly selected population of 495 children and adolescents, aged 7–16 years, from Copenhagen. If the subjects had had symptoms of respiratory infection recently, the examination was postponed for at least 6 weeks. Bronchial hyperresponsiveness (BHR) to inhaled histamine was found in 79 (16%) of the subjects, of whom 28 had asthma. Forty-eight subjects (10%) had increased levels of serum IgM antibodies against either parainfluenza, influenza, adenovirus, or respiratory syncytial virus (RSV), reflecting a recently acquired infection. No association between BHR and antibodies against respiratory viruses was found, as 7 (8.9%) of the 79 subjects with BHR and 41 (9.9%) of the 416 subjects without BHR had viral antibodies. Furthermore, no association between degree of bronchial responsiveness and viral antibodies was found. Moreover, 251 individuals (51%) had signs of earlier RSV infection, i.e. IgG antibodies against RSV. No relationship was found between age of the subjects and the presence of antibodies against either respiratory viruses in general or IgG-RSV. No relationship was found between the presence of antibodies against RSV and BHR; furthermore, evidence of earlier RSV infection was unrelated to the level of lung function and degree of bronchial responsiveness. We conclude that increased bronchial responsiveness in asymptomatic, unselected schoolchildren and adolescents is not likely to be caused by recent or previous viral respiratory infections.     

Bronchial hyperresponsiveness in two populations of Australian schoolchildren. I. Relation to respiratory symptoms and diagnosed asthma

In order to explore the relationship between bronchial hyperresponsiveness (BHR) to inhaled histamine, respiratory symptoms and diagnosed asthma in children, we undertook a cross-sectional study of 2363 Australian schoolchildren aged 8–11 years. The methods used included a self-administered questionnaire to parents, which was shown to have a high degree of repeatability, and a histamine inhalation test to measure bronchial responsiveness (BR). The study showed that 17.9% of children had BHR, defined as a 20% fall in FEV₁ at a provoking dose of histamine (PD₂₀ FEV₁) of less than 7.8 μmol. The distribution of PD₂₀ FEV₁ appeared to be continuous. Most children with PD₂₀ FEV₁ values < 1.0μmol had symptoms of asthma. However, 6.7% of children had BHR without symptoms or a previous diagnosis of asthma and 5.6% had had a diagnosis of asthma but had no BHR. Although there was a good association between BHR and respiratory symptoms, questionnaire data of wheeze and diagnosed asthma do not reflect accurately the level of BHR in the community. We conclude that cross-sectional studies of BR to identify children with BHR probably do not reflect the prevalence of asthma in populations of children. However, the strong association between BHR and symptoms, particularly in children with severe and moderate BHR, suggests that measurements of BR in populations are useful for defining a group of children whose airways behave differently from those of the majority. Prospective studies are needed to define the level of BHR that is associated with important sequelae.     

Relationship between atopy and bronchial responsiveness to histamine in a random population

Although there are theoretical reasons to suggest that atopy might predispose to non-allergic bronchial hyperresponsiveness, previous studies have yielded conflicting results. We assessed this by determining the atopic status and bronchial responsiveness to inhaled histamine in 400 randomly selected college students. An atopy score was determined as the number of "+"s from a standard battery of seven allergy prick skin tests each graded from + to +, and the atopic status was graded as non-atopic (no +'s) mildly atopic (1 to 4 +'s), moderately atopic (5 to 8 +'s), or markedly atopic (greater than 8 +'s). Non-allergic bronchial responsiveness to inhaled histamine was measured with a standardized histamine inhalation test from which the histamine provocation concentration producing a 20% FEV1 fall (PC20) was calculated. The prevalence of bronchial hyperresponsiveness to histamine (PC20 less than or equal to 8 mg/ml) was 10.3% in the entire population. There was a progressive increase from 6.1% in the non-atopic group to 33% in the markedly atopic group (p less than 0.001). In 43 subjects with both measurable atopy score (greater than or equal to 1) and PC20 (less than or equal to 16 mg/ml), a regression of atopy score vs. log PC20 produced a small (r = -0.36) but significant (p less than 0.02) correlation. These data indicate a significant relationship exists between atopic status and increased non-allergic bronchial responsiveness to histamine. Although cause and effect cannot be inferred from this study, it is hypothesized that atopy is one factor, among others, which predisposes to non-allergic bronchial hyperresponsiveness.     

Peptide leukotrienes mediate acetaldehyde-induced bronchial hyper-responsiveness in guinea-pigs

Background We previously reported that inhaled acetaldehyde, a metabolite of ethanol atid a maiti factor in alcohol-induced asthma, causes bronchial hyper-responsiveness (BHR) in asthmatics. However, the mechanisms are unclear. Objective The purpose of this study was to investigate a role of a peptide leukotriene (LT) in acetaldehyde-induced BHR. Methods Effects of LT antagonists, ONO-1078 (O.l-l.Omg/kg) and ICI-198, 615 (0.03–0.3 mg/kg), on acetaldehyde-induced bronchoconstriction and BHR to inhaled methacho-line were examined using a modified Konzett-Rössler method in guinea pigs. Results Aeetaldehyde at 0.8mg/ml, which failed to induce significant changes in Pao (pressure at the airway opening), enhanced an increase in Pao induced by subsequent inhalations of ascending doses (50–200 μg/ml) of methacholine. suggesting a potentiating effect of acetaldehyde oti bronchial responsiveness. Although ONO-1078 had no inhibitory effect on bronchoconstriction caused by ascending doses (5.0–20 mg/ml) of acetaldehyde, ONO-1078 and ICI-198, 615 reduced the acetaldehyde-induced BHR. Conclusion Acetaldehyde causes BHR via LT release in guinea-pigs.     

Comparison of four different measures of bronchial responsiveness in asthmatic children

Although several tests are available to assess the presence and severity of bronchial hyperresponsiveness (BHR), there is no agreement on the most appropriate stimulus. The most commonly used stimuli are methacholine, histamine, and exercise. Daily peak expiratory flow (PEF) variation has been reported to correlate with the severity of BHR, and in recent years this has been widely used because of its noninvasiveness and ease of performance. This study was carried out to determine the relationship among these four commonly used measures of bronchial responsiveness in asthmatic children. For this purpose, 12 asthmatic children of varying disease severity were recruited. Subjects underwent three challenges on 3 separate days in 1 week. During the week preceding the challenges (methacholine, histamine, and exercise), patients recorded PEF three times a day. All patients had PC₂₀ less than 8 mg/ml with methacholine and histamine. Patients with PC₂₀ greater than 3.5 mg/ml for both methacholine or histamine had negative exercise challenges. The strongest correlation was between histamine and methacholine ( r =0.95). Exercise-induced bronchospasm had substantial and significant correlation with the other three measures. No significant correlation was observed between PEF variability and histamine or methacholine. The varying degrees of relationships among the four commonly used measures suggests that each method yields information on different but related phenomena. More than one measure may be required to detect the different aspects of asthmatic bronchial responsiveness.     

Histamine hyperresponsiveness of the extrathoracic airway in patients with asthmatic symptoms

Functional abnormalities of the extrathoracic airway (EA) may produce symptoms mimicking bronchial asthma. We assessed the bronchial (B) and EA responsiveness to inhaled histamine in 40 patients with asthmatic symptoms and in nine asymptomatic controls. FEV1 and maximal mid-inspiratory flow (MIF50) were used as index of bronchial and EA narrowing. Hyperresponsiveness of the intra-(BHR) or extra-(EA-HR) thoracic airway was diagnosed when the provocative concentrations of histamine (PC20FEV1 or PC25MIF50) were less than 8 mg/ml. Fiberoptic laryngoscopy was performed in nine patients and three controls. The glottal region was measured at mid-volume of maximal inspiration (AgMI) and expiration (AgME) before and after histamine. Predominant EA-HR was found in 13 patients, predominant BHR in 12, equivalent BHR and EA-HR in another 12; no significant airway narrowing was observed in three patients and in the nine controls. EA-HR was significantly associated with female sex, sinusitis, post-nasal drip, dysphonia; BHR with atopy, wheezing and lower MEF50. The percent change in AgMI after histamine was closely related to the PC25MIF50 (r = 0.87, P less than 0.001), that of AgME to the PC20FEV1 (r = 0.78, P less than 0.01). These findings suggest that the assessment of EA responsiveness may be useful in the evaluation of asthmatic symptoms, especially in patients with no BHR.     

Inhibition of bronchial hyperresponsiveness to histamine induced by intravenous administration of leukotriene C4 by novel thromboxane A2 receptor antagonists ONO-NT-126 and ONO-8809 in guinea-pigs

We studied the effect of intravenous administration of leukotriene (LT) C4 on bronchial responsiveness to histamine and airway wall thickening in guinea-pigs. Guinea-pigs were killed and the lungs were fixed in formalin. Slides from paraffin-embedded sections of the lungs were stained and the airways that were cut in transverse sections were measured by tracing enlarged images using a digitizer. Moreover, airway resistance (Raw) was determined by a pulmonary mechanics analyser and we calculated two indices, an index of airway wall thickening and the one of airway hyperresponsiveness to histamine, from changes of baseline-Raw and peak-Raw following intravenous administration of histamine before and after the intravenous administration of LTC4. Intravenous administration of 3 microg/kg LTC4 for 1 hr induced an increase of the relative thickness of the airway wall in peripheral bronchi by the histological examination. In analysis of airway function, intravenous administration of 3 microg/kg LTC4 for 1 hr induced airway hyperresponsiveness to histamine with airway wall thickening. Thromboxane A2 receptor antagonists ONO-NT-126 and ONO-8809 inhibited the LTC4-induced airway hyperresponsiveness to histamine in a dose-dependent manner, but not the airway wall thickening induced by LTC4, suggesting that the effect of LTC4 on bronchial hyperresponsiveness is likely to be mediated through TXA2.     

Increase in non-specific bronchial responsiveness after repeated inhalation of low doses of allergen

The development of bronchial hyperresponsiveness (BHR) in asthma is considered to be caused by inflammation of the airway. In IgE-mediated allergy BHR is related to the occurrence of late phase reactions. We have previously shown that exposure to low doses of allergen can cause isolated late reactions. These findings are potentially of clinical importance, since exposure to low, subclinical allergen doses may lead to bronchial inflammation and increasing bronchial responsiveness without necessarily causing immediate bronchoconstriction. This study was performed to investigate whether repeated exposure to low doses of allergen could induce a change in BHR. The trial comprised two groups of five and eight patients with a history of allergic asthma. They were submitted to a series of allergen inhalations for 5–7 days. They were given the same low allergen dose (1–10 biological units) each day. Before and after the allergen exposure period histamine challenges were performed. After the week of allergen inhalation the bronchial responsiveness was increased in 11 of 13 patients.     

Relationship between nasal and bronchial responsiveness in perennial allergic rhinitic patients with asthma

BACKGROUND: The nasal and bronchial mucosa present similarities and most patients with asthma also have rhinitis, suggesting the concept of 'one airway one disease'. Although many studies may suggest the relationship between nasal and bronchial responsiveness in patients with allergic rhinitis and asthma, few studies have been published which address this question directly. The aim of this study is to investigate whether the relationship between nonspecific nasal and bronchial responsiveness exists in perennial allergic rhinitic patients with asthma. METHODS: Fifty-one perennial allergic rhinitic patients with the definitive or suspected asthma underwent methacholine bronchial provocation tests and nasal histamine challenge tests. A slope of the absolute changes in nasal symptoms score/log concentrations of histamine was calculated by linear regression analysis. A ratio of the final absolute change in nasal symptoms score to the sum of all the doses of histamine given to the subject was also calculated. The degree of bronchial responsiveness to methacholine was categorized as positive bronchial hyperresponsiveness (BHR) if PC(20) (provocative concentration of methacholine resulting in 20% fall in FEV(1)) was <4 mg/ml, borderline BHR if PC(20) was >or=4 but 16 mg/ml. Another index of bronchial responsiveness (BRindex) was calculated as the log [(% decline in FEV(1)/log final methacholine concentration as mg/dl) + 10]. RESULTS: The geometric means of the slope (4.47 vs. 2.95, p < 0.05) and the ratio (1.68 vs. 0.54, p < 0.01) were higher in patients with positive BHR (n = 23) than in patients with negative BHR (n = 19), respectively. The geometric means of the slope (3.50) and the ratio (1.13) in patients with borderline BHR (n = 9) were between the two groups, respectively. In all patients, the log-slope (r = 0.48, p < 0.001) and the log-ratio (r = 0.51, p < 0.001) were correlated well with the BRindex, respectively. Even in allergic rhinitic patients with definitive asthma, the log-slope was correlated with the BRindex (r = 0.39, p < 0.05) or log-PC(20) (r = -0.36, p < 0.05). CONCLUSIONS: The nonspecific nasal responsiveness may be related to the nonspecific bronchial responsiveness in patients with allergic rhinitis and asthma, which may support the viewpoint that allergic rhinitis and asthma represent a continuum of inflammation involving one common airway.     

Characterization of allergen-induced bronchial hyperresponsiveness and airway inflammation in actively sensitized brown-Norway rats.

Bronchial responsiveness to inhaled acetylcholine (ACh) and inflammatory cell recruitment in bronchoalveolar lavage fluid (BALF) were studied in inbred Brown-Norway rats actively sensitized to, and later exposed to, ovalbumin (OA). We examined animals 21 days after initial sensitization at 18 to 24 hours, or 5 days after a single challenge, or after the last of seven repeated exposures administered every 3 days. BALF was examined as an index of inflammatory changes within the lung. Animals repeatedly exposed to OA aerosols had an increased baseline lung resistance and a significant increase in bronchial responsiveness to inhaled ACh compared to control animals at both 18 to 24 hours and 5 days after the last OA exposure. Sensitized animals receiving a single OA aerosol also demonstrated bronchial hyperresponsiveness (BHR) to inhaled ACh (p less than 0.01) at 18 to 24 hours of a similar order as the multiple-exposed group. There was a significant increase in eosinophils, lymphocytes, and neutrophils in BALF at 18 to 24 hours but not at 5 days after single or multiple exposure to OA aerosol in the sensitized groups. Control animals demonstrated no changes in bronchial responsiveness, although a small but significant increase in inflammatory cells was observed compared to saline-only treated animals. There was a significant correlation between bronchial responsiveness and eosinophil counts in the BALF in the single allergen-exposed group (Rs = 0.68; p less than 0.05). We conclude that (1) BHR after allergen exposure in sensitized rats is associated with the presence of pulmonary inflammation but persists despite the regression of inflammatory cells in BALF after multiple OA exposures, and (2) this rat model has many characteristics of human allergen-induced BHR.     

Effect of murine recombinant interleukin-5 on bronchial reactivity in guinea-pigs

We have reported that an intratracheal injection of murine recombinant interleukin-5 (mrIL-5, 15 μg/0.0 ml/animal) induces the increased number of inflammatory leucocytes and epithelial cells in bronchoaiveolar lavage fluid (BALF) 24 hr after administration of mrIL-5 in guinea-pigs [1]. In this paper, we have examined the effects of mrIL-5 on bronchial reactivity in guinea-pigs. An intratracheal injection of mrIL-5 (15 μg/0.0 ml/animal) induced airway hyperresponsiveness to acetytcholine (ACh) which was accompanied with eosinophilia and neutrophilia in blood at 24 hr in guinea-pigs. Bovine serum albumin (BSA, 15 μg/0.0 ml/animal) used as a reference material did not cause airway hyperresponsiveness, blood eosinophilia and neutrophilia. Prednisotone (20 mg/kg, i.p.) inhibited mrIL-5-induccd airway hyperresponsiveness, eosinophilia and neutrophilia. Ketotifen (2 mg/kg, i.p.) also reduced this airway hyperresponsiveness and neutrophilia but not eosinophilia. In contrast, the injection of 2% disodium cromoglycale (DSCG) into the trachea showed the tendency of inhibitory effects against mrIL-5-induced airway hyperresponsiveness, eosinophilia and neutrophilia. The present data indicate that mrIL-5 induces airway hyperresponsiveness, blood eosinophilia and neutrophilia in guinea-pigs and that prednisolone and ketotifen inhibit mrIL-5-induced airway hyperresponsiveness accompanied with reduction of the increased number of leucocytes, suggesting that eosinophils and neutrophilia in blood may be important for the onset of bronchial hyperresponsiveness caused by mrIL-5 in guinea-pigs.     

Distribution of radioactive aerosol in the airways of children and adolescents with bronchial hyper-responsiveness.

The purpose of this study was to examine the relationship between the pulmonary distribution of inhaled radioaerosol, bronchial responsiveness, and lung function in children and adolescents. The participating subjects (n = 39) were divided into three groups: (1) 14 asthmatics with bronchial hyper-responsiveness (BHR), (2) five non-asthmatic subjects with BHR, and (3) 20 controls without BHR. Pulmonary distribution of [99Tcm) albumin radioaerosol, maximal expiratory flow when 25% of forced vital capacity remain to be exhaled (MEF25), and bronchial responsiveness to inhaled histamine were measured. Twenty subjects (52%) had irregular central distribution and 19 subjects (48%) had regular distribution of radioaerosol in their lungs. No difference in distribution of radioaerosol was found between the three groups of children. The median MEF25 among non-asthmatic subjects (80% predicted) was lower than that found in controls (92% predicted) but higher than that found in asthmatic subjects (55% predicted). A relationship was found between reduced flow at the peripheral airways, as indicated by MEF25 and the degree of central distribution of radioaerosol. Furthermore, subjects with irregular central distribution of radioaerosol had an increased degree of bronchial responsiveness. In conclusion, children and adolescents who have flow rates in the peripheral airways or increased degree of bronchial responsiveness tend to have abnormal distribution of radioaerosols.     

Involvement of IL-9 in the bronchial phenotype of patients with nasal polyposis

BACKGROUND: Nasal polyposis (NP) is frequently associated with asthma. In this disease, asymptomatic bronchial hyperresponsiveness (BHR) is thought to precede the development of asthma. IL-9 and its receptor have been reported as candidate genes for asthma and to be associated with BHR. OBJECTIVE: The objective of this study was to assess the contribution of 11-9 to the pathogenesis of BHR in NP by comparing the expression of IL-9 and its receptor in bronchial biopsy specimens from three groups of patients with NP: NP without BHR, NP with asymptomatic BHR, and NP with BHR and asthma. METHODS: Bronchial biopsy specimens were examined in terms of cellular infiltration and in terms of expression of IL-9 protein and mRNA as well as of its receptor by using immunohistochemistry and in situ hybridization. RESULTS: Patients with NP with asthma as compared with the two other groups exhibited an increased bronchial infiltration of basophils, eosinophils, and T cells that correlated with the asthma score. The two groups of patients with NP with BHR showed an increased expression in IL-9 protein and mRNA as well as an increase in the expression of IL-9R mRNA at the epithelial level. These modifications were inversely correlated with the airway responsiveness to methacholine, producing a 20% fall in FEV1. There was a close association between IL-9+ cells, IL-5 mRNA expression, and eosinophil infiltration that correlated with each other. CONCLUSIONS: These results suggest an important role for IL-9 in the pathogenesis of BHR and a causal relation between IL-9 and the development of bronchial eosinophilia in asthma.     

Inhibitory effect of inhaled FK-506 on increased bronchial responsiveness and eosinophil infiltration in the airway mucosa]

We examined the effects of inhaled FK-506, a potent immunosuppressive agent, on increased bronchial responsiveness to acetylcholine and on eosinophil infiltration in a guinea pig models of asthma. The guinea pigs were sensitized by repeated inhalation of ovalbumin (OA). Twenty four hours after antigen challenge, bronchial responsiveness to acetylcholine significantly increased and a marked accumulation of eosinophils in the airways was observed. However, when the guinea pigs were treated with aerosolized FK (10 mg/ml) for 5 min per day for 6 successive days before antigen challenge, the increase in bronchial responsiveness was significantly suppressed and the eosinophil accumulation was strikingly reduced. Since inhaled FK significantly suppressed these responses, there is a possibility that inhaled FK may be a useful therapy for patients with chronic bronchial asthma in the future.     

Synergistic activation of human natural killer cell cytotoxicity by histamine and interleukin-2

Interleukin-2 (IL-2) is recognized as a major activating signal for human natural killer (NK) cells. The presence of monocytes alters NK cell responsiveness to IL-2. Thus, while IL-2 effectively augments NK cell cytotoxicity (NKCC) in monocyte-depleted NK effector cells, it is relatively ineffective or even suppressive for NK cells in monocyte-containing, NK-cell-enriched mononuclear cell fractions. Here we report that concomitant treatment with IL-2 and the biogenic amine histamine synergistically augmented NKCC against K562 and Daudi target cells of CD3-/CD16+ human NK cells in the presence but not in the absence of monocytes. Addition of peripheral-blood monocytes, recovered by countercurrent centrifugal elutriation, to purified NK cells abrogated IL-2 induced NK cell activation, reconstituted the synergistic, NK-activating effects of histamine and IL-2, and strongly reduced baseline NKCC. The effects of histamine on baseline NKCC and on NK cell responsiveness to IL-2 were related to counteraction of monocyte-mediated NK cell suppression. By contrast, histamine did not affect baseline or IL-2-induced NKCC in mixtures of NK cells and monocytes when the latter cells were recovered after adherence. The effect of histamine on NK cell responsiveness to IL-2 was mediated by H2-type histamine receptors, as judged by mimicry exerted by the specific H2 receptor agonist dimaprit, but not by an H2-receptor-inactive derivative of this compound, N-methyldimaprit, and blocking by the H2 receptor antagonist ranitidine. Experiments in which monocytes and nonadherent NK cells were separately pretreated with ranitidine prior to histamine treatment suggested that NK-regulatory effects of histamine were mediated by H2 receptors on monocytes. Our data suggest that histamine may provide an important signal in the regulation of NK cell responsiveness to IL-2.     

Inhibition by thromboxane antagonists of airway hyperresponsiveness to histamine induced by 13,14-dihydro-15-keto-PGF2α in guinea-pigs

Summary. We studied the effect of intravenous administration of 13,14-dihydro-15-keto-prostaglandin (PG) F_27alpha; on airway responsiveness to histamine and airway wall thickening in guinea-pigs. Guinea-pigs were killed and the lungs were fixed in formalin. Slides from paraffin-embedded sections of the lungs were stained and the airways that were cut in transverse section were measured by tracing enlarged images using a digitizer. Moreover, airway resistance (Raw) was determined by a pulmonary mechanics analyser and we calculated two indices, an index of airway wall thickening and the one of airway hyperresponsiveness to histamine, from changes of baseline-Raw and peak-Raw following intravenous administration of histamine before and after the intravenous administration of 13,14-dihydro-l5-keto-PGF_2n. Intravenous administration of 10/μg/kg 13,14-dihydro-15-keto-PGF_2α for 1 h did not induce an increase of the relative thickness of the airway wall by the histological examination. In analysis of airway function, intravenous administration of 10μg/kg 13,14-dihydro-15-keto-PGF_2α for 1 h induced airway hyperresponsiveness to histamine without airway wall thickening. Thromboxane A₂ (TXA₂) receptor antagonists ONO-NT-126 and ONO-8809 inhibited the 13,14-dihydro-15-keto-PGF_2α-induced airway hyperresponsiveness to histamine, suggesting that the effect of 13,14-dihydro-15-keto-PGF_2α on bronchial hyperresponsiveness is likely to be mediated through TXA₂.     

In vivo airway eosinophil accumulation induced by polymyxin-B reduces bronchial responsiveness in guinea pigs

BACKGROUND: Chronic desquamative eosinophilic bronchitis and bronchial hyperresponsiveness have been considered essential for bronchial asthma. However, it has not been studied whether airway eosinophils enhance or inhibit bronchial responsiveness in vivo. OBJECTIVE: This study was conducted to elucidate the influence of airway eosinophil accumulation on bronchial responsiveness in vivo. MATERIALS AND METHODS: Guinea pigs were transnasally treated with 75 microg/kg of polymyxin-B or vehicle twice a week for a total of 3 weeks. Guinea pigs were surgically cannulated and artificially ventilated 24 h after the last administration of polymyxin-B or vehicle. Ten minutes after the installation of artificial ventilation, ascending doses of methacholine, acetylcholine or histamine were inhaled for 20 s at intervals of 5 min. Subsequent study was conducted 20 min after treatment of 60 mg/kg of indomethacin in the same manner. Final study was conducted in naive guinea pigs after single inhalation of 75 microg/mL of polymyxin B. RESULTS: The proportion of eosinophils in bronchoalveolar lavage fluid significantly increased in guinea pigs treated with polymyxin-B compared with vehicle. Bronchial responsiveness to inhaled methacholine, acetylcholine and histamine was significantly decreased by the polymyxin-B treatment. This protective effect induced by polymyxin B was abolished by pretreatment of indomethacin. A significant increase in bronchial responsiveness was observed after a single inhalation of polymyxin B. CONCLUSION: These results suggest that in vivo airway eosinophils may reduce non-specific bronchial responsiveness through inhibitory or bronchoprotective prostanoids.