Lymphokine-induced airway hyperresponsiveness in the rat

Kinetics of respiratory system elastance after airway challenge in dogs

We compared the time courses of lung mechanical changes with intravenous (iv) injection vs. aerosol administration of histamine, methacholine, and ACh in dogs. We interpret these results in terms of a spring-and-dashpot model of airway smooth muscle receiving activation via a tissue compartment when agonist is delivered by the iv route and through an additional airway wall compartment when it is delivered by the aerosol route. The model accurately accounts for the principal features of the respiratory system elastance response curves. It also accounts for the differences between iv and aerosol responses, supporting the notion that agonist delivered by aerosol has to traverse a longer pathway to the airway smooth muscle than does agonist delivered iv. The time constants representing diffusive exchange of agonist between compartments were not significantly different for the three agonists, suggesting that the three agonists shared a common principal means of clearance, which was presumably blood flow.

IL-5 and IL-5 receptor in asthma

Eosinophils, along with mast cells are key cells involved in the innate immune response against parasitic infection whereas the adaptive immune response is largely dependent on lymphocytes. In chronic parasitic disease and in chronic allergic disease, IL-5 is predominantly a T cell derived cytokine which is particularly important for the terminal differentiation, activation and survival of committed eosinophil precursors. The human IL-5 gene is located on chromosome 5 in a gene cluster that contains the evolutionary related IL-4 family of cytokine genes. The human IL-5 receptor complex is a heterodimer consisting of a unique alpha subunit (predominantly expressed on eosinophils) and a beta subunit which is shared between the receptors for IL-3 & GM-CSF (more widely expressed). The alpha subunit is required for ligand-specific binding whereas association with the beta subunit results in increased binding affinity. The alternative splicing of the alpha IL-5R gene which contains 14 exons can yield several alpha-IL-5R isoforms including a membrane-anchored isoform (alpha IL-5Rm) and a soluble isoform (alpha IL-5Rs). Cytokines such as IL-5 produce specific and non-specific cellular responses through specific cell membrane receptor mediated activation of intracellular signal transduction pathways which, to a large part, regulate gene expression. The major intracellular signal transduction mechanism is activation of non-receptor associated tyrosine kinases including JAK and MAP kinases which can then transduce signals via a novel family of transcriptional factors named signal transducers and activators of transcription (STATS). JAK2, STAT1, and STAT5 appear to be particularly important in IL-5 mediated eosinophil responses. Asthma is characterized by episodic airways obstruction, increased bronchial responsiveness, and airway inflammation. Several studies have shown an association between the number of activated T cells and eosinophils in the airways and abnormalities in FEV1, airway reactivity and clinical severity in asthma. It has now been well documented that IL-5 is highly expressed in the bronchial mucosa of atopic and intrinsic asthmatics and that the increased IL-5 mRNA present in airway tissues is predominantly T cell derived. Immunocytochemical staining of bronchial biopsy sections has confirmed that IL-5 mRNA transcripts are translated into protein in asthmatic subjects. Furthermore, the number of activated CD4 + T cells and IL-5 mRNA positive cells are increased in asthmatic airways following antigen challenge and studies that have examined IL-5 expression in asthmatic subjects before and after steroids have shown significantly decreased expression following oral corticosteroid treatment in steroid-sensitive asthma but not in steroid resistant and chronic severe steroid dependent asthma. The link between T cell derived IL-5 and eosinophil activation in asthmatic airways is further strengthened by the demonstration that there is an increased number of alpha IL-5R mRNA positive cells in the bronchial biopsies of atopic and non-atopic asthmatic subjects and that the eosinophil is the predominant site of this increased alpha IL-5R mRNA expression. We have also shown that the subset of activated eosinophils that expressed mRNA for membrane bound alpha IL-5r inversely correlated with FEV1, whereas the subset of activated eosinophils that expressed mRNA for soluble alpha IL-5r directly correlated with FEV1. Hence, not only does this data suggest that the presence of eosinophils expressing alpha IL-5R mRNA contribute towards the pathogenesis of bronchial asthma, but also that the eosinophil phenotype with respect to alpha IL-5R isoform expression is of central importance. Finally, there are several animal, and more recently in vitro lung explant, models of allergen induced eosinophilia, late airway responses (LARS), and bronchial hyperresponsiveness (BHR)--all of which support a link between IL-5 and airway eosinophilia and bronc

Cellular immunity is activated and a TH-2 response is associated with early wheezing in infants after bronchiolitis

OBJECTIVE

To determine whether abnormalities of cellular immunity are present and linked to early wheezing after bronchiolitis.

METHODS

We prospectively studied 26 infants hospitalized for a first episode of bronchiolitis and without any prior immune, cardiac, or respiratory disease. Blood was obtained at the time of enrollment and 5 months later for the assessment of the total cellular and differential counts, CD4+ (helper) and CD8+ (suppressor/cytotoxic) lymphocytes, and the activation markers CD23 (low-affinity immunoglobulin E receptor) and CD25 (interleukin-2 (IL-2) receptor). The cytokines interferon gamma (T-helper (TH) type-1 cytokine) and IL-4 (TH-2) were measured in plasma and in vitro after stimulation with IL-2 or with the house-dust mite (Dermatophagoides farinae) antigen. A daily log of episodes of wheezing was kept by parents after discharge.

RESULTS

We found an increase in blood eosinophils, an increased percentage of CD4+, CD25+, and CD23+ lymphocytes in subjects at 5 months compared with the time of bronchiolitis and with healthy subjects of the same age (p < 0.05). Plasma IL-4 levels, although not different from those of healthy subjects, also increased significantly. Peripheral blood lymphocytes from infants who wheezed produced more IL-4 in vitro, 5 months after bronchiolitis, in response to D. farinae antigen. In babies who wheezed, a positive correlation was found between the total number of days that wheezing occurred and the blood eosinophil count. Babies who wheezed more often (> 20 days) had more peripheral blood basophils and eosinophils, and peripheral blood lymphocytes obtained from these subjects at the time of bronchiolitis produced less interferon gamma on stimulation with IL-2.

CONCLUSIONS

Bronchiolitis is followed by activation of cellular immunity, and early wheezing in infants is associated with a TH-2 response.

A computer-controlled research ventilator for small animals: design and evaluation

The understanding of the mechanical properties of the mammalian respiratory system and how they change under the influence of drugs and in disease are frequently pursued in small animals, since they can be easily obtained in large numbers as pure-bred strains. However, conventional experimental set-ups for studying small animals are generally limited in their ability to measure gas flow into the lungs. In this paper, we present a computer-controlled research ventilator for small animals which can provide conventional mechanical ventilation as well as arbitrary flow perturbations with a bandwidth from 0-55 Hz. Respiratory impedance is estimated from the displacement of the piston and the pressure it generates, thereby obviating the need for a direct flow measurement. The performance of the device was tested on mechanical loads whose impedances were calculated theoretically. The measured and predicted loads agreed within less than 5% up to 30 Hz. Furthermore, the measured impedance of two mechanical loads in series precisely matched the sum of their individual impedances.

Interleukin-2 and soluble interleukin-2 receptor in bronchoalveolar lavage fluid from patients with bronchial asthma

To clarify the interrelation between interleukin-2 (IL-2) and soluble IL-2R receptor (sIL-2R), as products of T-cell activation in the bronchial tree of patients with bronchial asthma, we measured the concentration of IL-2, sIL-2R, and the cellular composition in bronchoalveolar lavage (BAL) fluid. We also measured physiologic parameters, including provocation concentration of histamine required to reduce the forced expiratory volume in 1 s by 20 percent of the prechallenge baseline (PC20). The concentrations of IL-2 and sIL-2R were higher in BAL fluid of symptomatic patients with bronchial asthma than those of normal subjects and asymptomatic patients. There was a significant correlation between IL-2 and sIL-2 concentrations in BAL fluid of the patients with bronchial asthma. Patients with other lung diseases had significantly higher concentration of IL-2 than normal control; however, sIL-2R was not detected in their BAL fluids. The concentration of IL-2 inversely correlated with FEV1 in symptomatic bronchial asthma. Among the inflammatory cells in BAL fluid, percentages of eosinophils showed significant correlation with the concentrations of IL-2 and sIL-2R in BAL fluid of the patients with bronchial asthma. In conclusion, IL-2 within the bronchial tree appears to be associated with eosinophil infiltration. This leads to physiologic changes in symptomatic patients with bronchial asthma, which may be influenced by the presence of sIL-2R in BAL fluid.

Detection of cytokines and their cell sources in bronchial biopsy specimens from asthmatic patients. Relationship to atopic status, symptoms, and level of airway hyperresponsiveness

This study evaluated immunoreactivity for several cytokines in bronchial tissue of asthmatic patients and related this to the clinical and functional characteristics. Patients were allocated into two different groups on the basis of their atopic status (atopic and nonatopic), with two subgroups of symptomatic and asymptomatic subjects in each. Five healthy volunteers were tested as control subjects. After clinical and functional assessment, all of the subjects underwent bronchoscopy. Several biopsy specimens were obtained for immunohistochemical and immunoelectron microscopic evaluation. Symptomatic asthmatic subjects had increased expression of immunoreactive interleukin (IL) 1 beta, IL-2, IL-3, IL-5, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor alpha (TNF alpha) when compared to the asymptomatic patients or normal control subjects. The cell sources of IL-1 beta were monocytes and dendritic cells in atopic patients and monocytes alone in nonatopic asthmatic subjects. The CD4+ T lymphocytes from atopic asthmatic subjects predominantly expressed IL-3, IL-4, IL-5, and GM-CSF immunoreactivity, whereas CD4+ T cells from nonatopic patients predominantly expressed IL-2, IL-3, and IL-5, and GM-CSF immunoreactivity. Mast cells showed immunoreactivity for TNF alpha, IL-3, IL-5, and GM-CSF. Immunostaining for TNF alpha and GM-CSF was also detected in bronchial epithelial cells and monocytes. Tissue eosinophilia and the level of airway hyperresponsiveness more closely correlated with IL-5 immunoreactivity in atopic asthmatic subjects and with IL-2 and GM-CSF immunoreactivity in nonatopic patients.

Effect of dexamethasone on airway inflammation and responsiveness after antigen challenge of the rat

The purpose of this study was to examine the effects of dexamethasone on airway responsiveness and lung inflammation of rats at 8 h, 32 h, and 7 d after allergen challenge. Brown-Norway male rats, 7 to 8 wk old, were actively sensitized to ovalbumin (OA) and challenged 14 d later. The rats were divided into a control group (n = 31) and a test group (n = 34) that received dexamethasone (DEXA) (0.3 mg/kg intraperitoneally) 14 h and 2 h before saline or OA challenge. For challenge, rats were anesthetized with pentobarbital and intubated endotracheally. Aerosols of OA (5% wt/vol in saline) were administered for 5 min. Responsiveness to inhaled aerosols of methacholine and the total and differential leukocyte counts in the large airways (generations 0 to 5), small airways, and parenchyma isolated by tissue mincing and digestion were measured at 8 h, 32 h, and 7 d after OA challenge. The cellular influx into the airways and parenchyma was highest at 8 h and decreased progressively over 7 d. DEXA significantly inhibited the cellular influx after allergen challenge. At 8 h, cellular return from the large airways was 3.61 +/- 0.5 x 10(6) (controls) versus 1.0 +/- 0.2 x 10(6) (DEXA), and from the small airways and parenchyma was 31.7 +/- 2.8 x 10(6) (controls) versus 21.9 +/- 2.9 x 10(6) (DEXA) (p < 0.05). The differences were attributable mostly to decreases in neutrophils in DEXA-treated animals. In control animals, neutrophil yield fell between 8 and 32 h, whereas eosinophils and 32 h, whereas eosinophil and lymphocyte counts increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of NZ-107 on airway inflammation and cell activation in guinea-pigs

The effects of NZ-107 on some airway inflammation models and the generation of superoxide anion (O2-) were studied in guinea-pigs. Airway inflammation was caused by intra-tracheal injection of murine recombinant interleukin-5 (mrIL-5, 15 micrograms/animal), inhalation of platelet-activating factor (PAF, 0.003%) and intra-tracheal injection of leukotriene B4 (LTB4, 10 micrograms/animal). NZ-107 (4-bromo-5-(3-ethoxy-4-methoxybenzylamino)-3(2H)-pyridazinone) at a dose of 50 mg kg-1, intraperitoneally reduced mrIL-5- and PAF-induced eosinophilia. This compound at a dose of 25 and 50 mg kg-1 also suppressed LTB4-induced eosinophilia and neutrophilia in bronchoalveolar lavage fluid (BALF). On the other hand, prednisolone at a dose of 20 mg kg-1, i.p., prevented the increased number of macrophages, eosinophils and neutrophils induced by mrIL-5, the increased number of eosinophils induced by PAF and the increased number of eosinophils and neutrophils induced by LTB4 in BALF. Furthermore, both drugs reduced mrIL-5- or PAF-induced increase in the number of airway epithelial cells in BALF. The generation of O2- was measured by the method of cytochrome C reduction. NZ-107 (10-100 micrograms mL-1) attenuated PAF- and FMLP-induced O2- production from macrophages and reduced PAF-induced O2- generation by eosinophils but had no effect on that from neutrophils. These results indicate that NZ-107 prevents the increased number of pulmonary eosinophils and airway epithelial cells and the activation of macrophages and eosinophils, suggesting that NZ-107 may be useful as a remedy for airway inflammatory diseases such as bronchial asthma.