Cell-Specific DNA Methylation Signatures in Asthma

Asthma is a complex trait, often associated with atopy. The genetic contribution has been evidenced by familial occurrence. Genome-wide association studies allowed for associating numerous genes with asthma, as well as identifying new loci that have a minor contribution to its phenotype. Considering the role of environmental exposure on asthma development, an increasing amount of literature has been published on epigenetic modifications associated with this pathology and especially on DNA methylation, in an attempt to better understand its missing heritability. These studies have been conducted in different tissues, but mainly in blood or its peripheral mononuclear cells. However, there is growing evidence that epigenetic changes that occur in one cell type cannot be directly translated into another one. In this review, we compare alterations in DNA methylation from different cells of the immune system and of the respiratory tract. The cell types in which data are obtained influences the global status of alteration of DNA methylation in asthmatic individuals compared to control (an increased or a decreased DNA methylation). Given that several genes were cell-type-specific, there is a great need for comparative studies on DNA methylation from different cells, but from the same individuals in order to better understand the role of epigenetics in asthma pathophysiology.

Targeted HAS2 Expression Lessens Airway Responsiveness in Chronic Murine Allergic Airway Disease

Hyaluronan (HA), a major component of the extracellular matrix, is secreted by airway structural cells. Airway fibroblasts in allergic asthma secrete elevated levels of HA in association with increased HA synthase 2 (HAS2) expression. Thus, we hypothesized that HA accumulation in the airway wall may contribute to airway remodeling and hyperresponsiveness in allergic airways disease. To examine this hypothesis, transgenic mice in which the α-smooth muscle actin (α-SMA) promoter drives HAS2 expression were generated. Mixed male and female α-SMA-HAS2 mice (HAS2+ mice, n = 16; HAS2- mice, n = 13) were sensitized via intraperitoneal injection and then chronically challenged with aerosolized ovalbumin (OVA) for 6 weeks. To test airway responsiveness, increasing doses of methacholine were delivered intravenously and airway resistance was measured using the forced oscillation technique. HA, cytokines, and cell types were analyzed in bronchoalveolar lavage fluid, serum, and whole lung homogenates. Lung sections were stained using antibodies specific for HA-binding protein (HABP) and α-SMA, as well as Masson's trichrome stain. Staining of lung tissue demonstrated significantly increased peribronchial HA, α-SMA, and collagen deposition in OVA-challenged α-SMA-HAS2+ mice compared with α-SMA-HAS2- mice. Unexpectedly, OVA-challenged α-SMA-HAS2+ mice displayed significantly reduced airway responsiveness to methacholine compared with similarly treated α-SMA-HAS2- mice. The total numbers of inflammatory cell types in the bronchoalveolar lavage fluid did not differ significantly between OVA-challenged α-SMA-HAS2+ mice and α-SMA-HAS2- mice. We conclude that allergen-challenged mice that overexpress HAS2 in myofibroblasts and smooth muscle cells develop increased airway fibrosis, which lessens airway hyperresponsiveness to bronchoconstrictors.

Expression of CysLT2 receptors in asthma lung, and their possible role in bronchoconstriction

BACKGROUND

The expression and functional role of CysLT2 receptors in asthma have not been clarified. In this study, we evaluated CysLT2 receptors expression, and effects of CysLT2-and CysLT1/2-receptor antagonists on antigen-induced bronchoconstriction using isolated lung tissues from both asthma and non-asthma subjects.

METHODS

CysLT1 and CysLT2 receptors expression in asthma and non-asthma lung tissue preparations was examined in immunohistochemistry experiments, and their functional roles in antigen-induced bronchoconstriction were assessed using ONO-6950, a dual CysLT1/2-receptor antagonist, montelukast, a CysLT1 receptor antagonist, and BayCysLT2RA, a CysLT2 receptor-specific antagonist.

RESULTS

CysLT1 receptors were expressed on the bronchial smooth muscle and epithelium, and on alveolar leukocytes in 5 in 5 non-asthma subjects and 2 in 2 asthma subjects. On the other hand, although degrees of CysLT2 receptors expression were variable among the 5 non-asthma subjects, the expression in the asthma lung was detected on bronchial smooth muscle, epithelium and alveolar leukocytes in 2 in 2 asthma subjects. In the non-asthma specimens, antagonism of CysLT2 receptors did not affect antigen-induced bronchial contractions, even after pretreatment with the CysLT1-receptor specific antagonist, montelukast. However, in the bronchus isolated from one of the 2 asthma subjects, antagonism of CysLT2 receptors suppressed contractions, and dual antagonism of CysLT1 and CysLT2 receptors resulted in additive inhibitory effect on anaphylactic contractions.

CONCLUSIONS

CysLT2 receptors were expressed in lung specimens isolated from asthma subjects. Activation of CysLT2 receptors may contribute to antigen-induced bronchoconstriction in certain asthma population.

[Non-specific bronchial hyper-responsiveness and polymorphysm of xenobiotics biotransformation GSTM1 and GSTT1 genes under neutrophilic bronchial asthma in children]

With a view to study the effect of genes GSTT1 and GSTM1 deletion on the non-specific bronchial hyperresponsiveness in children with neutrophilic bronchial asthma (BA) 46 school age children having neutrophilic BA (1st clinical group) and their 48 coevals with eosinophilic phenotype of the disease (2nd clinical group) were subjected to a complex examination at the pulmo-allergologic department of the regional child clinical hospital of Chernivtsi. The study proved that genotype T1+M1del was more frequently registered in patients with the neutrophilic phenotype of the disease, and genotype T1delM1del was equifrequent in patients with different types of the inflammation of the respiratory ways. In patients with neutrophilic BA and deletion polymorphism of genes GSTT1 and GSTM1, there was a tendency to decreasing of the bronchial lability index through the decrease of bronchodilation, and bronchial response to histamine occurred to be higher than in children with the absence of polymorphism of the referred genes of the xenobiotics biotransformation system.

A possible association between ZNRD1 and aspirin-induced airway bronchoconstriction in a Korean population

BACKGROUND

The etiology of aspirin-exacerbated respiratory disease (AERD) has been attributed to the combination of environmental and genetic risk factors. Although widely investigated in various diseases associated with immune dysfunction, the human zinc ribbon domain containing 1 (ZNRD1) gene is thought to play a role in the pathogenesis of AERD by altering the mechanisms involved in disease development.

METHODS

We selected 6 single-nucleotide polymorphisms (SNPs) for genotyping from the International HapMap database in order to analyze the association between polymorphisms in ZNRD1 and AERD in a Korean asthma cohort. Genotyping was carried out using the TaqMan assay, and differences in genotype frequency distributions were analyzed using logistic regression models.

RESULTS

Nominal associations were found between ZNRD1 rs1150740 and risk ofAERD via codominant and dominant genetic inheritance (P=.03; odds ratio, 1.14 [1.14-10.16]). The same polymorphism was found to be significantly associated with a decrease in forced expiratory volume in the first second of expiration, an important diagnostic marker of AERD, even after multiple testing corrections (P=.006, P(corr)=.03 in codominant and dominant models).

CONCLUSIONS

These preliminary findings suggest a possible relationship between ZNRD1 and aspirin-induced respiratory dysfunctions in a Korean population and provide essential information on the etiology of AERD.

Transgenic expression of human S100A12 induces structural airway abnormalities and limited lung inflammation in a mouse model of allergic inflammation

BACKGROUND

The calcium-binding protein S100A12 is highly up-regulated in the serum and sputum of patients with allergic asthma and is suggested to be a biomarker and pathologic mediator of asthma.

OBJECTIVE

To test the role of S100A12 in mediating airway inflammation in a mouse model of allergic lung inflammation.

METHODS

Transgenic (TG) mice that express human S100A12 and wild-type (WT) littermates were sensitized and challenged with ovalbumin (OVA) and assessed for inflammation, lung structure, and function.

RESULTS

Following OVA sensitization and challenge, S100A12 TG mice showed reduced peribronchial and perivascular inflammation, mucus production, and eosinophilia as well as attenuated airway responsiveness to contractile agonist compared with WT sensitized and challenged animals. This is explained, at least in part, by remodelled airways in S100A12 TG mice with thinning of the airway smooth muscle. S100A12 exposure induced Fas expression and activation of caspase 3 in cultured airway smooth muscle cells, suggesting that airway smooth muscle abnormalities observed in S100A12 TG mice may be mediated through myocyte apoptosis.

CONCLUSION AND CLINICAL RELEVANCE

S100A12 is one of the most abundant proteins found in the airways of human asthmatics, and it was postulated that S100A12 could mediate the inflammatory process. Our study shows for the first time that TG expression of S100A12 in the lung of mice does not exacerbate lung inflammation in a model of OVA-induced allergic inflammation. We speculate that the high levels of S100/calgranulins found in bronchoalveolar lavage fluid of asthmatics and of OVA-treated TG S100A12 mice do not significantly mediate pulmonary inflammation.

Kinetics of in vitro bronchoconstriction in an elastolytic mouse model of emphysema

Thin-slice videomicroscopy was used to examine the kinetics of constriction in small airways in situ. Balb/C mice inhaled elastase (0-20 IU), and were then left to recover for 14 days before euthanisation and lung removal. Cholinergic responsiveness was assessed in thin lung slices. Magnitude and velocity of narrowing in response to 10(-5) M acetylcholine (ACh), as well as the full concentration-response relationship for ACh (10(-8)-10(-5) M) were assessed. In vivo exposure to elastase was accompanied by statistically significantly decreased magnitudes and velocities of contraction, but no change in the ACh concentration-response relationship. Conversely, overnight, in vitro exposure of slices from control animals to elastase (2.5 microg.mL(-1)) resulted in increased magnitudes and velocities of airway narrowing, with impaired relaxation, as well as marked tearing of the airways from the surrounding parenchyma. These changes are characteristic of decreased tethering forces on the airway wall. Thus, the lung slice technique coupled with videomicroscopic analysis of airway contraction velocities provides a powerful tool to study airway-parenchymal interactions. The elastolytic model of emphysema, which manifests with airspace enlargement and loss of parenchymal attachments, is accompanied by decreased airway contraction kinetics. The mechanism(s) underlying this loss of function remain to be elucidated.

Transcriptional response to persistent beta2-adrenergic receptor signaling reveals regulation of phospholamban, which alters airway contractility

Beta(2)-Adrenergic receptors (beta(2)AR) are expressed on airway smooth muscle cells and act to relax the airway on activation by beta-agonists. These agents are utilized for treating asthma but are associated with adverse outcomes. To ascertain the effects of persistent beta(2)AR activation on gene expression, cultured airway smooth muscle cells derived from wild-type (WT) and transgenic mice overexpressing beta(2)AR were subjected to DNA microarray analysis; 319 genes were increased and 164 were decreased. Differential expression was observed in genes from 22 Gene Ontology Slim categories, including those associated with ion transport and calcium ion binding. A 60% decrease (P = 0.008) in phospholamban (PLN), an intracellular Ca(2+) concentration ([Ca(2+)]i)-handling protein that is at a signaling nodal point in cardiomyocytes, was observed in beta(2)AR-overexpressing cells and confirmed at the protein level. To isolate the physiological effect of decreased PLN in airway smooth muscle, airway contraction and relaxation responses were studied in WT and PLN(-/-) mice. PLN(-/-) mice had a markedly reduced constrictive response to methacholine. In contrast, the bronchodilatory effect of beta-agonist was not different between WT and PLN(-/-) mice. These results revealed an unanticipated therapeutic effect of beta-agonists, PLN downregulation, which acts to decrease airway hyperreactivity. Thus agents that inhibit PLN may act synergistically with the bronchodilating action of beta-agonists. A number of other genes related to [Ca(2+)]i are also differentially regulated by beta(2)AR activity, some of which may act to oppose, or augment, the efficacy of chronic beta-agonists. These genes or pathways may also represent additional targets in the treatment of asthma and related obstructive lung diseases.

Tidal breathing pattern differentially antagonizes bronchoconstriction in C57BL/6J vs. A/J mice

There is abundant evidence that tidal breathing, and especially tidal breathing at elevated minute ventilation, antagonizes the development and persistence of airflow obstruction during bronchoconstrictor stimulation in normal animals and people. Here, we studied the antiobstructive effect of different tidal breathing patterns in C57Bl/6J and A/J mice during bronchoconstriction induced by continuous or bolus infusion of methacholine. Anesthetized, paralyzed mice were mechanically ventilated at 1,500 ml.kg(-1).min(-1), using each of three breathing patterns: 5 ml/kg, 300 breath/min; 10 ml/kg, 150 breath/min; or 20 ml/kg, 75 breath/min. Changing from 10 ml/kg, 150 breath/min to 20 ml/kg, 75 breath/min, breathing functionally antagonized bronchoconstriction, reducing the level of airflow obstruction induced by methacholine infusion or boluses equivalently in both strains. In marked contrast, changing from 10 ml/kg, 150 breath/min to 5 ml/kg, 300 breath/min, breathing substantially exacerbated methacholine-induced airflow obstruction in A/J mice, whereas it had no significant effect in C57Bl/6J mice. Our results therefore demonstrate that 1) even at moderate, fixed minute ventilation, the precise breathing pattern can influence the degree of airflow obstruction substantially, and 2) the influence of breathing pattern on bronchoconstriction differs considerably between genetically diverse inbred mouse strains. These findings imply that differences in antiobstructive effects of breathing can contribute to differences in apparent airway constrictor responsiveness. Much attention has been placed on dysregulation of contractile function of airway smooth muscle in human disease. We suggest that important pathophysiology might also be found in impairment of the functional antagonist effect of tidal breathing on airflow obstruction.

Subacute hypoxia decreases voltage-activated potassium channel expression and function in pulmonary artery myocytes

Chronic hypoxia results in both structural changes in the pulmonary artery and a sustained increase in pulmonary vascular tone. This study investigated the effects of subacute moderate hypoxia on expression and function of potassium (K+) channels in rat pulmonary artery myocytes (PASMCs). The rats were kept at 0.67 atmospheres for 6, 12, or 24 h. We found that the expression of mRNA for voltage-activated K+ channels (Kv)1.2, Kv1.5, and Kv2.1 is reduced after less than 24 h of this moderate hypoxia. K+ current (Ik) is significantly inhibited in PASMCs from rats hypoxic for 24 h, resting membrane potential is depolarized and cytosolic [Ca2+] is increased in these cells. In addition, antibodies to Kv1.2, Kv1.5, and Kv2.1 inhibit Ik, cause membrane depolarization and attenuate both hypoxia- and 4-AP-induced elevation in [Ca2+]i in PASMCs from normoxic rats but not from 24 h hypoxic rats. Subacute hypoxia does not completely remove the mRNA for Kv1.2, Kv1.5, and Kv2.1, but antibodies against these channels no longer alter Ik or cytosolic calcium, suggesting that subacute hypoxia may inactivate the channels as well as reduce expression. As the expression of mRNA for Kv1.2, Kv1.5, and Kv2.1 is sensitive to subacute hypoxia and decreased expression/function of these channels has physiologic effects on membrane potential and cytosolic calcium, it seems likely that these Kv channels may also be involved in the mechanism of high-altitude pulmonary edema and possibly in the signaling of chronic hypoxic pulmonary hypertension.

Role of muscarinic receptor subtypes in the constriction of peripheral airways: studies on receptor-deficient mice

In the airways, increases in cholinergic nerve activity and cholinergic hypersensitivity are associated with chronic obstructive pulmonary disease and asthma. However, the contribution of individual muscarinic acetylcholine receptor subtypes to the constriction of smaller intrapulmonary airways that are primarily responsible for airway resistance has not been analyzed. To address this issue, we used videomicroscopy and digital imaging of precision-cut lung slices derived from wild-type mice and mice deficient in either the M1 (mAChR1-/- mice), M2 (mAChR2-/- mice), or M3 receptor subtype (mAChR3-/- mice) or lacking both the M2 and M3 receptor subtypes (mAChR2/3-/- double-knockout mice). In peripheral airways from wild-type mice (mAChR+/+ mice), muscarine induced a triphasic concentration-dependent response, characterized by an initial constriction, a transient relaxation, and a sustained constriction. The bronchoconstriction was diminished by up to 60% in mAChR3-/- lungs and was completely abolished in mAChR2/3-/- lungs. The sustained bronchoconstriction was reduced in mAChR2-/- bronchi, and, interestingly, the transient relaxation was absent; the bronchoconstriction in response to 10-8 M muscarine was increased by 158% in mAChR1-/- mice. Quantitative reverse transcriptase-polymerase chain reaction analysis revealed that the disruption of specific mAChR genes had no significant effect on the expression levels of the remaining mAChR subtypes. These results demonstrate that cholinergic constriction of murine peripheral airways is mediated by the concerted action of the M2 and M3 receptor subtypes and suggest the existence of pulmonary M1 receptor activation, which counteracts cholinergic bronchoconstriction. Given the important role of muscarinic cholinergic mechanisms in pulmonary disease, these findings should be of considerable therapeutic relevance.

Concomitant occasional use of salbutamol influences bronchoprotective responsiveness afforded by formoterol in patients with the glycine-16 genotype

BACKGROUND

Predisposition to subsensitivity with long-acting beta(2)-agonists (LABA) or regular short-acting beta(2)-agonists (SABA) is related to polymorphisms at codon 16 of the beta(2)-adrenoceptor.

OBJECTIVE

To determine whether the use of occasional SABA induces further baseline downregulation of the beta(2)-adrenoceptor to that of endogenous catecholamines alone, in Gly-16 patients.

METHODS

A post-hoc analysis of two studies was performed. Twenty-three homozygous Gly-16 asthmatic patients received 12 microg inhaled formoterol either o.d. or b.i.d. for 2 weeks. Patients had been supplied with ipratropium bromide (IB) to use as reliever therapy preferentially over salbutamol. Spirometry and adenosine monophosphate (AMP) bronchial challenge was performed after 7-14 days of placebo and after active treatment.

RESULTS

A review of domiciliary diary card data indicated 13 patients (mean FEV(1): 76.8% pred., AMP PC(20): 23.4 mg/ml) did not require salbutamol, and 10 patients (mean FEV(1): 77.9% pred., AMP PC(20): 27.9 mg/ml) required occasional salbutamol (1.67 puffs/day) during run-in and/or formoterol periods. No significant difference in spirometry or AMP PC(20) were found between the populations after placebo. After formoterol, compared with placebo, patients requiring occasional salbutamol had no improvement in AMP PC(20) [geometric mean PC(20) (and 95% CI): 28.0 mg/ml (20.5-38.4) versus 34.46 mg/ml (25.1-47.3)], while those patients not requiring salbutamol had a significant ( p<0.05) improvement in AMP PC(20) with formoterol compared with placebo [89.9 mg/ml (52.4-154.3) versus 30.6 mg/ml (17.8-52.5)]. This amounted to a 3.12-fold (95% CI: 0.16-6.07) geometric mean fold difference between groups.

CONCLUSIONS

Our results indicate that homozygous Gly-16 patients using occasional salbutamol have reduced responsiveness to formoterol in terms of bronchoprotection to AMP than patients not using salbutamol. Patients expressing the homozygous gly-16 genotype of the beta(2)-adrenoceptor genotype receiving a LABA may benefit from the substitution of their usual SABA for an alternative reliever.

Early phase bronchoconstriction in the mouse requires allergen-specific IgG

Allergen provocation of allergic asthma patients is often characterized by an initial period of bronchoconstriction, or early phase reaction (EPR), that leads to maximal airway narrowing within 15-30 min, followed by a recovery period returning airway function to baseline within 1-2 h. In this study, we used a defined OVA provocation model and mice deficient for specific leukocyte populations to investigate the cellular/molecular origins of the EPR. OVA-sensitized/challenged wild-type (C57BL/6J) mice displayed an EPR following OVA provocation. However, this response was absent in gene knockout animals deficient of either B or T cells. Moreover, transfer of OVA-specific IgG, but not IgE, before the OVA provocation, was capable of inducing the EPR in both strains of lymphocyte-deficient mice. Interestingly, an EPR was also observed in sensitized/challenged mast cell-deficient mice following an OVA provocation. These data show that the EPR in the mouse is an immunologically based pathophysiological response that requires allergen-specific IgG but occurs independent of mast cell activities. Thus, in the mouse the initial period of bronchoconstriction following allergen exposure may involve neither mast cells nor IgE-mediated events.

Transgenic overexpression of beta(2)-adrenergic receptors in airway epithelial cells decreases bronchoconstriction

Airway epithelial cells express beta(2)-adrenergic receptors (beta(2)-ARs), but their role in regulating airway responsiveness is unclear. With the Clara cell secretory protein (CCSP) promoter, we targeted expression of beta(2)-ARs to airway epithelium of transgenic (CCSP-beta(2)-AR) mice, thereby mimicking agonist activation of receptors only in these cells. In situ hybridization confirmed that transgene expression was confined to airway epithelium, and autoradiography showed that beta(2)-AR density in CCSP-beta(2)-AR mice was approximately twofold that of nontransgenic (NTG) mice. Airway responsiveness measured by whole body plethysmography showed that the methacholine dose required to increase enhanced pause to 200% of baseline (ED(200)) was greater for CCSP-beta(2)-AR than for NTG mice (345 +/- 34 vs. 157 +/- 14 mg/ml; P < 0.01). CCSP-beta(2)-AR mice were also less responsive to ozone (0.75 ppm for 4 h) because enhanced pause in NTG mice acutely increased to 77% over baseline (P < 0.05) but remained unchanged in the CCSP-beta(2)-AR mice. Although both groups were hyperreactive to methacholine 6 h after ozone exposure, the ED(200) for ozone-exposed CCSP-beta(2)-AR mice was equivalent to that for unexposed NTG mice. These findings show that epithelial cell beta(2)-ARs regulate airway responsiveness in vivo and that the bronchodilating effect of beta-agonists results from activation of receptors on both epithelial and smooth muscle cells.

In vitro airway responsiveness of Flinders sensitive and resistant line rats

Recently, we reported that freely moving Flinders sensitive line rats (FSL, selectively bred for their cholinergic hyperresponsiveness) are more susceptible to allergen-induced airway hyperresponsiveness than their control counterparts-Flinders resistant line (FRL) rats. In this study the two Flinders lines were compared for responsiveness of excised tracheal and primary bronchial smooth muscle in vitro. FSL tissues were slightly but significantly more sensitive to cholinergic stimulation than FRL tissues (slightly lower EC(50) value for carbachol) but the FRL tissues were more responsive, exhibiting larger amplitude of response. Surprisingly, previous exposure to allergen challenge was accompanied by reduced in vitro responses to spasmogens in both rat lines. We conclude that FSL and FRL airways do not differ greatly with respect to sensitivity to cholinergic stimulation in vitro and that inflamed airways show reduced in vitro responses to spasmogens. The discrepancy between the in vivo and in vitro findings suggests that responsiveness of airway smooth muscle involves regulation from both proximal and distal sites.

Bronchial responsiveness and angiotensin-converting enzyme gene polymorphism in sarcoidosis patients

BACKGROUND

Angiotensin-converting enzyme (ACE) inactivates bradykinin and tachykinins, which are potent bronchoconstrictors and mediators of inflammatory reactions. It has recently been shown that an insertion (I)/deletion (D) polymorphism in the ACE gene accounts for variation in serum ACE level. We investigated bronchial responsiveness in patients with sarcoidosis to determine whether it might be associated with ACE gene polymorphism.

SUBJECTS

Bronchial responsiveness was assessed in 21 patients with sarcoidosis, 21 patients with asthma, and 18 healthy control subjects. ACE polymorphism was also examined in the 21 patients with sarcoidosis.

METHODS

Bronchial responsiveness was measured by recording respiratory resistance with continuous inhalation of methacholine from 49 to 25,000 microg/mL in concentration. The ACE genotype was determined using the polymerase chain reaction.

RESULTS

We found a significant increase in bronchial responsiveness in sarcoidosis patients as compared with healthy control subjects (p<0.01). In the sarcoidosis group, patients with the II genotype demonstrated significantly more coughing (p<0.05) and a greater bronchial responsiveness (p<0.05) than did those with DI or DD genotypes.

CONCLUSION

Patients with sarcoidosis have increased bronchial responsiveness to some extent, the degree apparently depending on the ACE genotype.

Genetic susceptibility to atracurium-induced bronchoconstriction

The goal of this study was to develop a murine model of atracurium-induced bronchoconstriction in which to evaluate the mechanism of action of this airway response. We evaluated nine inbred strains of mice for the development of atracurium-induced bronchoconstriction. The maximal difference in the magnitude of the airway response to atracurium noted between the highly responsive DBA/2 mice and the minimally responsive SJL mice was greater than 20-fold. This phenotype appears to reflect an intrinsic difference in the lungs of these animals because the extent of neuromuscular blockade was not significantly different in DBA/2 and SJL mice. Atracurium-induced airway hyperresponsiveness in DBA/2 mice was eliminated in a dose-dependent manner by pretreatment with atropine or pancuronium. These data are consistent with a postganglionic vagal efferent mechanism which produces a differential pulmonary response to this neuromuscular blocker. A genetic predisposition to atracurium-induced bronchoconstriction appears to exist in certain inbred strains of mice. Thus, a mouse model may be useful for mapping the gene(s) that control this trait and for suggesting responsible candidate genes. Our results suggest that the inbred laboratory mouse will be useful to study the mechanism by which atracurium produces bronchoconstriction.

Prednisolone treatment in asthma is associated with modulation of bronchoalveolar lavage cell interleukin-4, interleukin-5, and interferon-gamma cytokine gene expression

Although corticosteroids are effective in improving asthma symptoms and bronchial responsiveness, their mechanism of action is unknown. We examined whether changes in bronchial responsiveness with corticosteroid therapy of asthma are accompanied by a reduction in cytokine gene expression and eosinophil infiltration in the airways. Bronchoalveolar lavage (BAL) was performed in 18 patients with moderate asthma before and after 2 wk of treatment with prednisolone, 0.6 mg/kg/day, or matched placebo in a randomized double-blind parallel group study. Cells were counted in BAL cytocentrifuge preparations, and the numbers of cells expressing cytokine mRNA were assessed by in situ hybridization using 35S-labeled RNA probes. When the actively treated and placebo groups were compared, there was a decrease in airway methacholine responsiveness (p < 0.01) after prednisolone. This was accompanied by a decrease in bronchoalveolar lavage eosinophils (p < 0.05), a reduction in the numbers of BAL cells per 1,000 expressing mRNA for interleukin-4 (IL-4, p < 0.01) and interleukin-5 (IL-5, p < 0.005), and an increase in numbers of cells expressing mRNA for interferon-gamma (p < 0.005). These results are compatible with the hypothesis that the beneficial effects of corticosteroids in asthma may result from modulation of cytokine production, with consequent inhibition of local bronchial eosinophilia.