Increase of chemokine levels in sputum precedes exacerbation of acute asthma attacks

Differences in Inflammatory Cytokine Profile in Obesity-Associated Asthma: Effects of Weight Loss

Obesity and asthma are associated with systemic inflammation maintained by mediators released by adipose tissue and lung. This study investigated the inflammatory serum mediator profile in obese subjects (O) (n = 35), non-obese asthma (NOA) patients (n = 14), obese asthmatics (OA) (n = 21) and healthy controls (HC) (n = 33). The effect of weight loss after bariatric surgery (BS) was examined in 10 OA and 31 O subjects. We analyzed serum markers including leptin, adiponectin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, ST2, IL-5, IL-9, and IL-18. Compared with HC subjects, the O group showed increased levels of leptin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, and ST2; the OA group presented increased levels of MCP-1, ezrin, YKL-40, and IL-18, and the NOA group had increased levels of ezrin, YKL-40, IL-5, and IL-18. The higher adiponectin/leptin ratio in NOA with respect to OA subjects was the only significant difference between the two groups. IL-9 was the only cytokine with significantly higher levels in OA with respect to O subjects. TNFR2, ezrin, MCP-1, and IL-18 concentrations significantly decreased in O subjects after BS. O, OA, and NOA showed distinct patterns of systemic inflammation. Leptin and adiponectin are regulated in asthma by obesity-dependent and -independent mechanisms. Combination of asthma and obesity does not result in significant additive effects on circulating cytokine levels.

CXCR1 and CXCR2 Inhibition by Ladarixin Improves Neutrophil-Dependent Airway Inflammation in Mice

Rationale

Increased IL-8 levels and neutrophil accumulation in the airways are common features found in patients affected by pulmonary diseases such as Asthma, Idiopathic Pulmonary Fibrosis, Influenza-A infection and COPD. Chronic neutrophilic inflammation is usually corticosteroid insensitive and may be relevant in the progression of those diseases.

Objective

To explore the role of Ladarixin, a dual CXCR1/2 antagonist, in several mouse models of airway inflammation with a significant neutrophilic component.

Findings

Ladarixin was able to reduce the acute and chronic neutrophilic influx, also attenuating the Th2 eosinophil-dominated airway inflammation, tissue remodeling and airway hyperresponsiveness. Correspondingly, Ladarixin decreased bleomycin-induced neutrophilic inflammation and collagen deposition, as well as attenuated the corticosteroid resistant Th17 neutrophil-dominated airway inflammation and hyperresponsiveness, restoring corticosteroid sensitivity. Finally, Ladarixin reduced neutrophilic airway inflammation during cigarette smoke-induced corticosteroid resistant exacerbation of Influenza-A infection, improving lung function and mice survival.

Conclusion

CXCR1/2 antagonist Ladarixin offers a new strategy for therapeutic treatment of acute and chronic neutrophilic airway inflammation, even in the context of corticosteroid-insensitivity.

Sputum Inflammometry to Manage Chronic Obstructive Pulmonary Disease Exacerbations: Beyond Guidelines

Quantitative sputum cytometry facilitates in assessing the nature of bronchitis associated with exacerbations of chronic obstructive pulmonary disease (COPD). This is not assessed in most clinical trials that evaluate the effectiveness of strategies to prevent or to treat exacerbations. While up to a quarter of exacerbations may be associated with raised eosinophil numbers, the vast majority of exacerbations are associated with neutrophilic bronchitis that may indicate airway infections. While eosinophilia may be a predictor of response to corticosteroids (oral and inhaled), the limited efficacy of anti-interleukin 5 therapies would suggest that eosinophils may not directly contribute to those exacerbations. However, they may contribute to airspace enlargement in patients with COPD through various mechanisms involving the interleukin 13 and matrix metalloprotease pathways. The absence of eosinophils may facilitate in limiting the unnecessary use of corticosteroids. The presence of neutrophiia could prompt an investigation for the specific pathogens in the airway. Additionally, sputum measurements may also provide insight into the mechanisms of susceptibility to airway infections. Iron within sputum macrophages, identified by hemosiderin staining (and by more direct quantification) may impair macrophage functions while the low levels of immunoglobulins in sputum may also contribute to airway infections. The assessment of sputum at the time of exacerbations thus would facilitate in customizing treatment and treat current exacerbations and reduce future risk of exacerbations.

Association between MCP-1 -2518A>G polymorphism and asthma susceptibility: a meta-analysis

The published data on the association between MCP-1 -2518A>G polymorphism and asthma susceptibility are inconclusive. Therefore, we performed a meta-analysis to estimate the impact of MCP-1 -2518A>G polymorphism on asthma susceptibility. PubMed, Web of Science, Wanfang, and China National Knowledge Infrastructure (CNKI) databases were used to identify eligible studies. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to calculate the strength of association. Sensitivity analysis was performed to evaluate the influence of individual studies on the estimates of overall effect, and funnel plots and Egger's test were used to assess publication bias. Eight publications with 1562 asthma patients and 1574 controls were finally identified. Overall, we found no significant association between MCP-1 -2518A>G polymorphism and asthma susceptibility in any of the genetic model comparisons. After stratified analysis by ethnicity, the results showed that a significant association with asthma risk was found in Caucasians in all the genetic models. However, a protective association was found in Africans under the dominant model. The present meta-analysis suggested that the MCP-1 -2518 A>G polymorphism is a risk factor for asthma in the Caucasian population, nevertheless it has a protective effect in the African population.

IL-8 Gene Variants and Expression in Childhood Asthma

PURPOSE

To examine the IL-8 expression levels and association of genetic variants with the risk of childhood persistent asthma prognosis.

METHODS

Overall, 170 asthmatic children and 170 healthy controls were included in this case-control study. The human IL-8 serum levels were measured using ELISA. The IL-8 mRNA expression levels were assessed by a real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods.

RESULTS

The IL-8 expression at both protein and mRNA levels was found to be significantly elevated in asthmatic children compared to healthy subjects (P < 0.0001, P = 0.004; respectively). Higher levels of IL-8 mRNA are detected in subjects with moderate to severe asthma. The presence of IL8-251 A/T (rs4073) and + 781C/T (rs2227306) polymorphisms was significantly associated with an increased risk of asthma (P = 0.002, P = 0.036, respectively). In addition, we noted a significant association between these polymorphisms and an elevated risk of atopic asthma (P < 0.05). For rs2227306 SNP, the highest median level of IgE was detected for the presence of TT genotype (865 ± 99.74 IU/mL). Although, the rs4073 polymorphism conferred a higher risk to develop asthma at an advanced stage of severity (P = 0.008). The rs4073 T and rs2227306 C alleles are considered as risk factors for asthma development. The rs4073 T allele is represented also as a risk factor for asthma severity in Tunisian children.

CONCLUSIONS

Both IL-8 gene and protein expression may play a key role in asthma pathogenesis.

Activity of sputum p38 MAPK is correlated with airway inflammation and reduced FEV1 in COPD patients

BACKGROUND

Inflammation and remodeling of the small airways are major determinants of the progression and severity of COPD. The present study explored the correlation between sputum p38 mitogen-activated protein kinase (MAPK) activity and airway inflammation and reduction of lung function in the patients with chronic obstructive pulmonary disease (COPD).

MATERIAL AND METHODS

Sputum samples were collected from 48 COPD patients and 12 healthy persons. Sputum p38 MAPK activity was measured by Western blotting and sputum levels of CXCL8 and neutrophil, and lung function was measured. The correlation between p38MAPK activity and airway inflammation and reduction of lung function was analyzed.

RESULTS

Our results showed the significantly increased expression of phospho-p38 MAPK and CXCL8 in the sputum samples of the COPD patients. The p38 MAPK activity was remarkably correlated with the CXCL8 level and neutrophils infiltration in the airway, and the decline of lung function in the COPD patients.

CONCLUSIONS

These findings suggest the pivotal role of p38 MAPK in the airway inflammation of COPD patients. We propose p38 MAPK as a potential target for the treatment of COPD.

CXCR2: From Bench to Bedside

Leukocyte recruitment to sites of infection or tissue damage plays a crucial role for the innate immune response. Chemokine-dependent signaling in immune cells is a very important mechanism leading to integrin activation and leukocyte recruitment. CXC chemokine receptor 2 (CXCR2) is a prominent chemokine receptor on neutrophils. During the last years, several studies were performed investigating the role of CXCR2 in different diseases. Until now, many CXCR2 inhibitors are tested in animal models and clinical trials and promising results were obtained. This review gives an overview of the structure of CXCR2 and the signaling pathways that are activated following CXCR2 stimulation. We discuss in detail the role of this chemokine receptor in different disease models including acute lung injury, COPD, sepsis, and ischemia-reperfusion-injury. Furthermore, this review summarizes the results of clinical trials which used CXCR2 inhibitors.

3D-QSAR studies on CCR2B receptor antagonists: Insight into the structural requirements of (R)-3-aminopyrrolidine series of molecules based on CoMFA/CoMSIA models

Objective:

Monocyte chemo attractant protein-1 (MCP-1) is a member of the CC-chemokine family and it selectively recruits leukocytes from the circulation to the site of inflammation through binding with the chemotactic cytokine receptor 2B (CCR2B). The recruitment and activation of selected populations of leukocytes is a key feature in a variety of inflammatory conditions. Thus MCP-1 receptor antagonist represents an attractive target for drug discovery. To understand the structural requirements that will lead to enhanced inhibitory potencies, we have carried out 3D-QSAR (quantitative structure–activity relationship) studies on (R)-3-aminopyrrolidine series of molecules as CCR2B receptor antagonists.

Materials and Methods:

Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were performed on a series of (R)-3-aminopyrrolidine derivatives as antagonists of CCR2B receptor with Sybyl 6.7v.

Results:

We have derived statistically significant model from 37 molecules and validated it against an external test set of 13 compounds. The CoMFA model yielded a leave one out r² (r²_loo) of 0.847, non-cross-validated r² (r²_ncv) of 0.977, F value of 267.930, and bootstrapped r² (r²_bs) of 0.988. We have derived the standard error of prediction value of 0.367, standard error of estimate 0.141, and a reliable external predictivity, with a predictive r² (r²_pred) of 0.673. While the CoMSIA model yielded an r²_loo of 0.719, r²_ncv of 0.964,F value of 135.666, r²_bs of 0.975, standard error of prediction of 0.512, standard error of estimate of 0.180, and an external predictivity with an r²_pred of 0.611. These validation tests not only revealed the robustness of the models but also demonstrated that for our models r²_pred, based on the mean activity of test set compounds can accurately estimate external predictivity.

Conclusion:

The QSAR model gave satisfactory statistical results in terms of q² and r² values. We analyzed the contour maps obtained, to study the activity trends of the molecules. We have tried to demonstrate structural features of compounds to account for the activity in terms of positively contributing physicochemical properties such as steric, electrostatic, hydrophobic, hydrogen bond donor, and acceptor fields. These contour plots identified several key features, which explain the wide range of activities. The results obtained from models offer important structural insight into designing novel CCR2B antagonists before their synthesis.

Serum chemokines RANTES and monocyte chemoattractant protein-1 in Egyptian patients with atopic asthma: relationship to disease severity

BACKGROUND AND AIMS

Asthma is a highly prevalent, complex inflammatory disease of the airways often associated with bronchial hyperreactivity and atopy. The chemokine RANTES (regulated upon activation, normal T -cell expressed and secreted) is an important element for the chemotaxis at the site of allergic inflammation. This study aimed to assess the serum levels of the chemokines RANTES and monocyte chemoattractant protein-1 (MCP-1) in Egyptian patients with atopic asthma and to evaluate their possible relation t the severity of airway obstruction.

METHODS

The study included 60 Egyptian patients with atopic asthma and 20 healthy volunteers. Serum levels of the chemokines RANTES and MCP-1 were measured. Total serum IgE level and absolute eosinophil counts were determined. The severity of airway obstruction was assessed using spirometric measurement (FEV(1)).

RESULTS

The serum levels of RANTES were significantly higher in all asthmatic patients than the controls (p <0.001). Moreover, RANTES levels were significantly increased in patients with moderate and severe asthma as compared to those with mild asthma (p <0.001). Serum RANTES correlated positively with absolute eosinophil counts and total serum IgE and negatively with FEV(1), whereas there was no significant correlation with serum MCP-1 in all asthmatic patients.

CONCLUSIONS

Serum RANTES may be used as a useful noninvasive marker of airway obstruction and a potential diagnostic tool for monitoring asthma severity. In this regard, identification and blocking of this chemokine and/or its receptor may be a promising therapeutic approach to asthmatic patients.

Lack of association between chemokine receptor 5 (CCR5) δ32 mutation and pathogenesis of asthma in Iranian patients

BACKGROUND

Chemokines and their receptors are clinically important mediators, as the chemokine receptors are expressed on almost all immune cells. They play pivotal roles in pathogenesis of almost all clinical situations including asthma. Correspondingly, MIP-1α (CCL3), MIP-1β (CCL4), and RANTES (CCL5) are among the important chemokines involved in the pathogenesis of asthma. These chemokines bind to the CCR5 (their related receptor) on the cell surfaces. Attachment of related chemokine ligands to CCR5 plays an important role in the pathogenesis of asthma; hence, this study aimed to analyze δ32 mutations in CCR5 in asthmatic patients.

MATERIAL AND METHODS

This experimental study was undertaken on 162 asthmatic patients and 200 healthy controls during February to June 2008 at Rafsanjan University of Medical Sciences. The Gap-PCR method was applied to analyze the δ32 mutation in the CCR5 gene, and demographic data (eg, age, sex, occupation, socio-economic status) were collected using a questionnaire.

RESULTS

The findings of this study indicated that none of the asthmatic patients exhibited δ32 mutation in CCR5 chemokine receptor while only 3 (1.5%) of controls had the heterozygotic form of this mutation.

DISCUSSION

Several research groups analyzed δ32 mutations in CCR5 in different diseases, including asthma. Some investigations reported a significant relation between asthma and δ32 mutations in CCR5, but there are also many reports which failed to find a relation between asthma and this mutation. Based on the results of this study and others, it seems that the δ32 mutation does not affect the pathogenesis of asthma.

Genetic associations with asthma and virus-induced wheezing: a systematic review

Various wheezing phenotypes can be identified based on differences in natural histories, risk factors and responses to treatment. In epidemiologic studies, atopic asthma or virus-induced wheezing can be discriminated by the presence or the absence of sensitization to allergens. Children with asthma have been shown to present lower levels of lung function. Patients with viral respiratory infections evolve from normal lung function to enhanced airway reactivity. The objective of this study was to identify genes and polymorphisms associated with different wheezing phenotypes. Using data obtained from the Genetic Association Database, we systematically reviewed studies on genes and polymorphisms that have been associated with virus-induced wheezing or atopic asthma. The research was carried out in February of 2009. Genes associated with the studied outcomes in more than three studies were included in the analysis. We found that different genes and loci have been associated with virus-induced wheezing or atopic asthma. Virus-induced wheezing has frequently been associated with IL-8 polymorphisms, whereas atopic asthma and atopy have frequently been associated with Th2 cytokine gene (CD14 and IL-13) polymorphisms on chromosome 5. This review provides evidence that different wheezing disorders in childhood can be differently affected by genetic variations, considering their role on airway inflammation and atopy. Future studies of genetic associations should consider the different wheezing phenotypes in infancy. In addition, stratified analyses for atopy can be useful for elucidating the mechanisms of the disease.

Repression of TNF-alpha-induced IL-8 expression by the glucocorticoid receptor-beta involves inhibition of histone H4 acetylation

Increased expression of a number of proinflammatory genes, including IL-8, is associated with inflammatory conditions such as asthma. Glucocorticoid receptor (GR)beta, one of the GR isoforms, has been suggested to be upregulated in asthma associated with glucocorticoid insensitivity and to work as a dominant negative inhibitor of wild type GRalpha. However, recent data suggest that GRbeta is not a dominant negative inhibitor of GRalpha in the transrepressive process and has its own functional role. We investigated the functional role of GRbeta expression in the suppressive effect of glucocorticoids on tumor necrosis factor (TNF)-alpha-induced IL-8 release in an airway epithelial cell line. GRbeta expression was induced by treatment of epithelial cells with either dexamethasone or TNF-alpha. GRbeta was able to inhibit glucocorticoid-induced transcriptional activation mediated by binding to glucocorticoid response elements (GREs). The suppressive effect of dexamethasone on TNF-alpha-induced IL-8 transcription was not affected by GRbeta overexpression, rather GRbeta had its own weak suppressive activity on TNF-alpha-induced IL-8 expression. Overall histone deacetylase activity and histone acetyltransferase activity were not changed by GRbeta overexpression, but TNF-alpha-induced histone H4 acetylation at the IL-8 promoter was decreased with GRbeta overexpression. This study suggests that GRbeta overexpression does not affect glucocorticoid-induced suppression of IL-8 expression in airway epithelial cells and GRbeta induces its own histone deacetylase activity around IL-8 promoter site.

Fiber-optic microsphere-based antibody array for the analysis of inflammatory cytokines in saliva

Antibody microarrays have emerged as useful tools for high-throughput protein analysis and candidate biomarker screening. We describe here the development of a multiplexed microsphere-based antibody array capable of simultaneously measuring 10 inflammatory protein mediators. Cytokine-capture microspheres were fabricated by covalently coupling monoclonal antibodies specific for cytokines of interest to fluorescently encoded 3.1 microm polymer microspheres. An optical fiber bundle containing approximately 50,000 individual 3.1 microm diameter fibers was chemically etched to create microwells in which cytokine-capture microspheres could be deposited. Microspheres were randomly distributed in the wells to produce an antibody array for performing a multiplexed sandwich immunoassay. The array responded specifically to recombinant cytokine solutions in a concentration-dependent fashion. The array was also used to examine endogenous mediator patterns in saliva supernatants from patients with pulmonary inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD). This array technology may prove useful as a laboratory-based platform for inflammatory disease research and diagnostics, and its small footprint could also enable integration into a microfluidic cassette for use in point-of-care testing.

CXCR2 antagonists for the treatment of pulmonary disease

Chemokines have long been implicated in the initiation and amplification of inflammatory responses by virtue of their role in leukocyte chemotaxis. The expression of one of the receptors for these chemokines, CXCR2, on a variety of cell types and tissues suggests that these receptors may have a broad functional role under both constitutive conditions and in the pathophysiology of a number of acute and chronic diseases. With the development of several pharmacological, immunological and genetic tools to study CXCR2 function, an important role for this CXC chemokine receptor subtype has been identified in chronic obstructive pulmonary disease (COPD), asthma and fibrotic pulmonary disorders. Interference with CXCR2 receptor function has demonstrated different effects in the lungs including inhibition of pulmonary damage induced by neutrophils (PMNs), antigen or irritant-induced goblet cell hyperplasia and angiogenesis/collagen deposition caused by lung injury. Many of these features are common to inflammatory and fibrotic disorders of the lung. Clinical trials evaluating small molecule CXCR2 antagonists in COPD, asthma and cystic fibrosis are currently underway. These studies hold considerable promise for identifying novel and efficacious treatments of pulmonary disorders.

CARMA3 mediates lysophosphatidic acid-stimulated cytokine secretion by bronchial epithelial cells

NF-kappaB activation in bronchial epithelial cells is important for the development of allergic airway inflammation, and may control the expression of critical mediators of allergic inflammation such as thymic stromal lymphopoietin (TSLP) and the chemokine CCL20. Members of the caspase recruitment domain (CARD) family of proteins are differentially expressed in tissue and help mediate NF-kappaB activity in response to numerous stimuli. Here we demonstrate that CARMA3 (CARD10) is specifically expressed in human airway epithelial cells, and that expression of CARMA3 in these cells leads to activation of NF-kappaB. CARMA3 has recently been shown to mediate NF-kappaB activation in embryonic fibroblasts after stimulation with lysophosphatidic acid (LPA), a bioactive lipid-mediator that is elevated in the lungs of individuals with asthma. Consistent with this, we demonstrate that stimulation of airway epithelial cells with LPA leads to increased expression of TSLP and CCL20. We then show that inhibition of CARMA3 activity in airway epithelial cells reduces LPA-mediated NF-kappaB activity and the production of TSLP and CCL20. In conclusion, these data demonstrate that LPA stimulates TSLP and CCL20 expression in bronchial epithelial cells via CARMA3-mediated NF-kappaB activation.

Loss of Control of Asthma Following Inhaled Corticosteroid Withdrawal Is Associated With Increased Sputum Interleukin-8 and Neutrophils

BACKGROUND

The role of neutrophils in exacerbations of asthma is poorly understood. We examined the effect of withdrawal of inhaled corticosteroids on sputum inflammatory indexes in a double-blind study in patients with moderate, stable asthma.

METHODS

Following a 2-week run in period, 24 subjects were randomized to receive either budesonide (400 microg bid) or placebo, and the study was continued for another 10 weeks.

RESULTS

Loss of asthma control developed in 8 of 12 patients over the 10-week period of steroid withdrawal, whereas only 1 of 10 patients with budesonide treatment had exacerbations. Those with an exacerbation had increased sputum interleukin (IL)-8 (p < 0.0001) and increased sputum neutrophil numbers (p < 0.0001) compared to those without an exacerbation. The significant elevation in sputum IL-8 and neutrophil counts initially occurred 2 weeks prior to an exacerbation. Sputum neutrophilia correlated positively with changes in IL-8 levels (r(2) = 0.76, p = 0.01).

CONCLUSIONS

Rapid withdrawal of inhaled corticosteroids results in an exacerbation of asthma that is preceded by an increase in sputum neutrophils and IL-8 concentrations, in contrast to an increase in eosinophils reported in previous studies in which inhaled steroids are slowly tapered.

Polymorphisms in interleukin 8 and its receptors (IL8, IL8RA and IL8RB) and association of common IL8 receptor variants with peripheral blood eosinophil counts

Airway inflammation is a major factor in the pathogenesis of asthma. Interleukin 8 (IL8) is a potent proinflammatory cytokine that interacts with its receptors, IL8RA and IL8RB. We investigated the genetic polymorphisms in IL8, IL8RA, and IL8RB for any association with risk of asthma and peripheral blood eosinophil counts in a Korean population. By carrying out direct sequencing in 24 individuals, we identified 20 sequence variants within exons and their flanking regions, including the 1.5 kb promoter regions of IL8, IL8RA, and IL8RB. Among them, seven common single-nucleotide polymorphisms (SNPs) were selected for genotyping in our asthma cohort (n = 1,439). Two common haplotypes in IL8 and three in IL8RA and IL8RB (defined as one block) were identified. Although none of the polymorphisms showed a significant association with risk of asthma, IL8RA-B ht2 showed a significant association with the peripheral blood eosinophil counts (%) among asthma patients, e.g., lower eosinophil levels among individuals with the homozygous IL8RA-B ht2 (3.55 +/- 3.39%) than among other asthmatic patients (5.52 +/- 5.55%; P (corr) = 0.018). Our findings suggest that polymorphisms and haplotypes in IL8RA and IL8RB might be among the genetic factors underlying production of peripheral blood eosinophil.

The role of interleukin-8 and its receptors in inflammatory lung disease: implications for therapy

Neutrophils have been implicated in the pathogenesis of many inflammatory lung diseases, including the acute respiratory distress syndrome, chronic obstructive pulmonary disease and asthma. The CXC chemokine interleukin (IL)-8, is a potent neutrophil recruiting and activating factor and the detection of IL-8 in clinical samples from patients with these diseases has led clinicians to believe that antagonism of IL-8 may be a practicable therapeutic strategy for disease management.

Work over the last decade has concentrated on both the molecular mechanisms by which IL-8 is produced in the inflammatory setting and also on the manner in which IL-8 activates the neutrophil. Expression of the IL-8 gene appears to be controlled by several components of the inflammatory milieu. Whilst lipopolysaccharide, IL-1β and tumor necrosis factor-α are capable of augmenting IL-8 production, IL-10 is a potent inhibitor of IL-8 synthesis and appears to play an auto-regulatory role. Regulation of the IL-8 gene is under the control of nuclear factor κB which appears to be a primary target for corticosteroid-mediated repression of IL-8 production.

IL-8 exerts is effects on neutrophils by binding with high affinity to two receptors on its cell surface, the chemokine receptors CXCR1 and CXCR2. These closely related receptors belong to the superfamily of G-protein coupled receptors, proteins that historically have proved amenable to antagonism by small molecules. The recent descriptions in the literature of highly potent small molecule antagonists of CXCR2 and their success in blocking in vivo trafficking of neutrophils suggest that antagonsim of IL-8 at the receptor level is a viable therapeutic strategy. Clinical trials of such compounds will ultimately provide crucial information currently lacking and will define whether or not IL-8 blockade provides future therapy in pulmonary disease.

MCP-1 gene regulatory region polymorphism in Chinese children with mild, moderate and near-fatal asthma

BACKGROUND

A polymorphism in the monocyte chemoattractant protein 1 (MCP-1) gene regulatory region has been associated with asthma in Caucasians. This polymorphism is possibly endemic to the Asian region, but its impact on Asian populations is unclear. In addition, the relationship of this marker with life-threatening asthma has not been clarified. The aim of this study was to test the genetic association between the MCP-1 -2518A/G polymorphism and asthma/atopy in a cohort of Chinese children, with particular emphasis on those patients who had experienced life-threatening asthma attacks.

METHODS

Forty-eight children with near-fatal asthma, 134 mild-to-moderate asthmatics, 69 allergic-disorder cases without asthma, and 107 nonasthmatic, nonatopic control children were genotyped by a polymerase chain reaction-based assay.

RESULTS

Comparison of the four groups of children (n = 358) revealed no detectable differences in genotype or allele frequencies of the MCP-1 -2518A/G polymorphism. There was no evidence of association between the polymorphism and any of the outcomes of interest including clinical severity, blood eosinophil count, atopy, total serum IgE levels, and degree of bronchial hyper-responsiveness.

CONCLUSION

These results suggest that the MCP-1 -2518A/G polymorphism is not a risk factor for near-fatal asthma. Furthermore, this polymorphism seems to play no role in the development of asthma or atopy in Chinese subjects, possibly as a result of the genetic heterogeneity between Asian and Caucasian populations with respect to regulation of MCP-1 expression. Our results underscore the necessity of accounting for ethnic background in the investigation of asthma-predisposition genes.

N-Benzylindole-2-carboxylic acids: potent functional antagonists of the CCR2b chemokine receptor

Screening of the corporate database led to the discovery of a novel series of N-benzylindole-2-carboxylic acid CCR2b chemokine receptor antagonists. These compounds demonstrate high affinity and functional inhibition of the CCR2b receptor. A discussion of the structure-activity relationships is presented, together with evidence for a highly selective receptor binding profile.

Pathophysiological roles of interleukin-8/CXCL8 in pulmonary diseases

Fifteen years have passed since the first description of interleukin (IL)-8/CXCL8 as a potent neutrophil chemotactic factor. Accumulating evidence has demonstrated that various types of cells can produce a large amount of IL-8/CXCL8 in response to a wide variety of stimuli, including proinflammatory cytokines, microbes and their products, and environmental changes such as hypoxia, reperfusion, and hyperoxia. Numerous observations have established IL-8/CXCL8 as a key mediator in neutrophil-mediated acute inflammation due to its potent actions on neutrophils. However, several lines of evidence indicate that IL-8/CXCL8 has a wide range of actions on various types of cells, including lymphocytes, monocytes, endothelial cells, and fibroblasts, besides neutrophils. The discovery of these biological functions suggests that IL-8/CXCL8 has crucial roles in various pathological conditions such as chronic inflammation and cancer. Here, an overview of its protein structure, mechanisms of production, and receptor system will be discussed as well as the pathophysiological roles of IL-8/CXCL8 in various types of lung pathologies.

Rapid response of circulating myeloid dendritic cells to inhaled allergen in asthmatic subjects

BACKGROUND

Dendritic cells (DC) are thought to play a key role in the initiation and maintenance of T cell immunity to inhaled antigens. While the density of DC within the bronchial mucosa is increased in stable asthma, there is little information currently available concerning the effects of allergen inhalation on DC in subjects with asthma.

OBJECTIVES

To enumerate changes in the numbers of circulating CD33(+) myeloid DC in asthmatics, before and after allergen challenge.

METHODS

Blood DC numbers were enumerated by flow cytometry before and at 3, 6 and 24 h after inhaled allergen and diluent in 10 mild, allergic asthmatic subjects.

RESULTS

Blood DC numbers rapidly fell from 3.42 +/- 0.30 x 10(7)/L at baseline, to 2.10 +/- 0.17 x 10(7)/L by 3 h post-challenge (P < 0.01), and remained significantly below baseline values at both 6 and 24 h following allergen challenge. No such changes in DC numbers were noted after diluent challenge. A similar, early fall in circulating lymphocytes was also noted post-allergen challenge, whereas changes in circulating eosinophil and neutrophil numbers occurred more slowly.

CONCLUSIONS

A significant proportion of myeloid DC rapidly 'disappear' from the circulation following allergen inhalation, suggesting that margination of circulating myeloid DC, and their recruitment into the airway mucosa, is an important feature of the immune response to inhaled allergen.

The generation and characterisation of antagonist RNA aptamers to MCP-1

Monocyte chemoattractant protein-1 (MCP-1) has been implicated as a powerful pro-inflammatory mediator and may represent a potentially important, therapeutic opportunity for treatment of inflammatory disease and atherosclerosis. To further investigate the role of MCP-1 in inflammatory disorders we have isolated a series of RNA aptamers that bind specifically to mouse MCP-1. The highest affinity aptamers, designated ADR7 and ADR22, have been functionally characterised in vitro and in cell based assays. ADR7 and ADR22 have an affinity of 180 pM and 370 pM respectively for mouse MCP-1, they can antagonise MCP-1 binding to heparin and specifically antagonise MCP-1 induced chemotaxis in a cell based assay. An interesting feature of ADR22 but not ADR7 is that it is capable of antagonising the function of human MCP-1, demonstrating the high level of specificity of these aptamers and that the aptamers recognise MCP-1 in different ways. The aptamers may be used as a tool to further investigate the role of MCP-1 in inflammatory disorders and may also have a role as a therapeutic agent.

Antifungal and airway remodeling roles for murine monocyte chemoattractant protein-1/CCL2 during pulmonary exposure to Asperigillus fumigatus conidia

Asperigillus fumigatus spores or conidia are quickly eliminated from the airways of nonsensitized individuals but persist in individuals with allergic pulmonary responsiveness to fungus. A. fumigatus-induced allergic airway disease is characterized by persistent airway hyperreactivity, inflammation, and fibrosis. The present study explored the role of CCR2 ligands in the murine airway response to A. fumigatus conidia. Nonsensitized and A. fumigatus-sensitized CBA/J mice received an intratracheal challenge of A. fumigatus conidia, and pulmonary changes were analyzed at various times after conidia. Whole lung levels of monocyte chemoattractant protein-1 (MCP-1/CCL2), but neither MCP-3/CCL7 nor MCP-5/CCL12, were significantly elevated at days 3 and 7 after conidia in nonsensitized mice. MCP-1/CCL2 was significantly increased in lung samples from A. fumigatus-sensitized mice at days 14 and 30 after a conidia challenge. Administration of anti-MCP-1/CCL2 antiserum to nonsensitized mice for14 days after the conidia challenge attenuated the clearance of conidia and significantly increased airway hyperreactivity, eosinophilia, and peribronchial fibrosis compared with nonsensitized mice that received conidia and normal serum. Adenovirus-directed overexpression of MCP-1/CCL2 in A. fumigatus-sensitized mice markedly reduced the number of conidia, airway inflammation, and airway hyperresponsiveness at day 7 after the conidia challenge in these mice. Immunoneutralization of MCP-1/CCL2 levels in A. fumigatus-sensitized mice during days14-30 after the conidia challenge did not affect the conidia burden but significantly reduced airway hyperreactivity, lung IL-4 levels, and lymphocyte recruitment into the airways compared with the control group. These data suggest that MCP-1/CCL2 participates in the pulmonary antifungal and allergic responses to A. fumigatus conidia.

Identification of the binding site for a novel class of CCR2b chemokine receptor antagonists: binding to a common chemokine receptor motif within the helical bundle

Monocyte chemoattracant-1 (MCP-1) stimulates leukocyte chemotaxis to inflammatory sites, such as rheumatoid arthritis, atherosclerosis, and asthma, by use of the MCP-1 receptor, CCR2, a member of the G-protein-coupled seven-transmembrane receptor superfamily. These studies identified a family of antagonists, spiropiperidines. One of the more potent compounds blocks MCP-1 binding to CCR2 with a K(d) of 60 nm, but it is unable to block binding to CXCR1, CCR1, or CCR3. These compounds were effective inhibitors of chemotaxis toward MCP-1 but were very poor inhibitors of CCR1-mediated chemotaxis. The compounds are effective blockers of MCP-1-driven inhibition of adenylate cyclase and MCP-1- and MCP-3-driven cytosolic calcium influx; the compounds are not agonists for these pathways. We showed that glutamate 291 (Glu(291)) of CCR2 is a critical residue for high affinity binding and that this residue contributes little to MCP-1 binding to CCR2. The basic nitrogen present in the spiropiperidine compounds may be the interaction partner for Glu(291), because the basicity of this nitrogen was essential for affinity; furthermore, a different class of antagonists, a class that does not have a basic nitrogen (2-carboxypyrroles), were not affected by mutations of Glu(291). In addition to the CCR2 receptor, spiropiperidine compounds have affinity for several biogenic amine receptors. Receptor models indicate that the acidic residue, Glu(291), from transmembrane-7 of CCR2 is in a position similar to the acidic residue contributed from transmembrane-3 of biogenic amine receptors, which may account for the shared affinity of spiropiperidines for these two receptor classes. The models suggest that the acid-base pair, Glu(291) to piperidine nitrogen, anchors the spiropiperidine compound within the transmembrane ovoid bundle. This binding site may overlap with the space required by MCP-1 during binding and signaling; thus the small molecule ligands act as antagonists. An acidic residue in transmembrane region 7 is found in most chemokine receptors and is rare in other serpentine receptors. The model of the binding site may suggest ways to make new small molecule chemokine receptor antagonists, and it may rationalize the design of more potent and selective antagonists.

Eotaxin in induced sputum of asthmatics: relationship with eosinophils and eosinophil cationic protein in sputum

BACKGROUND

Eosinophilic inflammation is a crucial aspect of allergic diseases such as bronchial asthma. An eosinophil-active chemokine, eotaxin, may play a role in the pathogenesis of the tissue eosinophilia accompanying asthma.

METHODS

Induced sputa were obtained from 53 patients with atopic asthma and six healthy subjects, and the concentration of eotaxin in the sputum was measured by ELISA. We investigated whether the sputum content of eotaxin is related to 1) asthma status or corticosteroid therapy, and 2) other sputum indices, including percentage of eosinophils and concentration of eosinophil cationic protein (ECP).

RESULTS

The patients with stable or unstable asthma showed significantly higher concentrations of sputum eotaxin than the normal controls. The level of sputum eotaxin demonstrated a positive correlation with the percentage of eosinophils in stable asthmatics not receiving corticosteroid therapy, but not in stable patients treated with corticosteroids, or in unstable patients. Sputum eotaxin demonstrated a positive correlation with ECP in asthmatic patients who were either in a stable state or not receiving steroid therapy.

CONCLUSIONS

The elevated level of eotaxin detected in association with increased eosinophils and ECP in the sputum of asthmatics suggests that eotaxin is involved in the pathogenesis of eosinophilic airway inflammation. The relationship of eotaxin to airway eosinophilia may be modified by the stability status of asthma and corticosteroid therapy.

Differential roles of IL-18 in allergic airway disease: induction of eotaxin by resident cell populations exacerbates eosinophil accumulation

Cytokine regulation during an allergic response can dictate the severity of the inflammation and resulting injury. In the present study, we have examined the systemic and local effects of IL-18, a Th1-associated cytokine, on a cockroach allergen-induced airway response. In initial studies, temporal increases in IL-18 levels were observed within the lungs. When IL-18 was neutralized systemically the allergen-associated eosinophil accumulation was significantly accelerated 5-fold by 8 h postchallenge, suggesting a regulatory role for IL-18. Recombinant IL-18 (200 ng) was instilled into the airway at the time of allergen challenge to examine whether a direct impact on local eosinophil accumulation could be induced. When IL-18 was instilled, a significant increase in peribronchial eosinophil accumulation was observed in allergic mice as well as in nonallergic mice. A possible mechanism was observed in a significant increase in eotaxin, but not other eosinophil chemotactic factors, in bronchoalveolar lavage fluid after IL-18 instillation. The role of eotaxin was confirmed using eotaxin -/- mice, which demonstrated significantly less eosinophil accumulation compared with littermate controls. IL-18 was subsequently shown to induce eotaxin production from bronchial epithelial cells and isolated macrophages in in vitro assays. The clinical relevance of these findings was determined in treated mice and demonstrated that neutralization of IL-18 exacerbated, whereas exogenous IL-18 had no effect on airway hyperreactivity. Altogether, these data demonstrate that IL-18 may have multiple functions during an immune response that differ depending upon the local or systemic effects.

NF-κB/Rel Transcription Factors: c-Rel Promotes Airway Hyperresponsiveness and Allergic Pulmonary Inflammation

The NF-κB/Rel family of transcription factors induces many genes involved in immune and inflammatory responses. Mice with germline deletions of individual NF-κB/Rel subunits have different phenotypes, suggesting that the NF-κB/Rel transcription factors have different functions. We tested whether c-Rel promotes allergic asthma using a murine model of allergen-induced pulmonary inflammation and airway hyperresponsiveness. Our investigation focused on c-Rel, which is expressed in lymphoid cells and is important for lymphocyte activation. In response to allergen sensitization and challenge, c-Rel-deficient mice did not develop increases in pulmonary inflammation, bronchoalveolar lavage fluid eosinophilia, or total serum IgE. c-Rel deficiency also prevented the induction of airway hyperresponsiveness. Allergen-treated wild-type mice had increased DNA binding to an NF-κB consensus site. Chemokine expression was altered in allergen-treated c-Rel-deficient mice. Monocyte chemoattractant protein-1, which is regulated by NF-κB, was decreased in allergen-treated c-Rel-deficient mice relative to wild-type controls. The increase in NF-κB/Rel transcription factors after allergen challenge in wild-type mice and the decrease in allergen reactivity found in c-Rel-deficient mice indicate that c-Rel promotes allergic inflammation. Alteration of pulmonary chemokine expression in c-Rel-deficient mice may inhibit allergen-induced pulmonary inflammation and airway hyperresponsiveness.

Identification of surface residues of the monocyte chemotactic protein 1 that affect signaling through the receptor CCR2

The CC chemokine, monocyte chemotactic protein, 1 (MCP-1) functions as a major chemoattractant for T-cells and monocytes by interacting with the seven-transmembrane G protein-coupled receptor CCR2. To identify which residues of MCP-1 contribute to signaling though CCR2, we mutated all the surface-exposed residues to alanine and other amino acids and made some selective large changes at the amino terminus. We then characterized the impact of these mutations on three postreceptor pathways involving inhibition of cAMP synthesis, stimulation of cytosolic calcium influx, and chemotaxis. The results highlight several important features of the signaling process and the correlation between binding and signaling: The amino terminus of MCP-1 is essential as truncation of residues 2-8 ([1+9-76]hMCP-1) results in a protein that cannot stimulate chemotaxis. However, the exact peptide sequence may be unimportant as individual alanine mutations or simultaneous replacement of residues 3-6 with alanine had little effect. Y13 is also important and must be a large nonpolar residue for chemotaxis to occur. Interestingly, both Y13 and [1+9-76]hMCP-1 are high-affinity binders and thus affinity of these mutants is not correlated with ability to promote chemotaxis. For the other surface residues there is a strong correlation between binding affinity and agonist potency in all three signaling pathways. Perhaps the most interesting observation is that although Y13A and [1+9-76]hMCP are antagonists of chemotaxis, they are agonists of pathways involving inhibition of cAMP synthesis and, in the case of Y13A, calcium influx. These results demonstrate that these two well-known signaling events are not sufficient to drive chemotaxis. Furthermore, it suggests that specific molecular features of MCP-1 induce different conformations in CCR2 that are coupled to separate postreceptor pathways. Therefore, by judicious design of antagonists, it should be possible to trap CCR2 in conformational states that are unable to stimulate all of the pathways required for chemotaxis.

Identification of residues in the monocyte chemotactic protein-1 that contact the MCP-1 receptor, CCR2

The CC chemokine, MCP-1, has been identified as a major chemoattractant for T cells and monocytes, and plays a significant role in the pathology of inflammatory diseases. To identify the regions of MCP-1 that contact its receptor, CCR2, we substituted all surface-exposed residues with alanine. Some residues were also mutated to other amino acids to identify the importance of charge, hydrophobicity, or aromaticity at specific positions. The binding affinity of each mutant for CCR2 was assayed with THP-1 and CCR2-transfected CHL cells. The majority of point mutations had no effect. Residues at the N-terminus of the protein, known to be crucial for signaling, contribute less than a factor of 10 to the binding affinity. However, two clusters of primarily basic residues (R24, K35, K38, K49, and Y13), separated by a 35 A hydrophobic groove, reduced the level of binding by 15-100-fold. A peptide fragment encompassing residues 13-35 recapitulated some of the mutational data derived from the intact protein. It exhibited modest binding as a linear peptide and dramatically improved affinity when the region which adopts a single turn of a 3(10)-helix in the protein, which includes R24, was constrained by a disulfide bond. Additional constraints at the ends of the peptide, corresponding to the disulfide between the first and third cysteines in MCP-1, yielded further improvements in affinity. Together, these data suggest a model in which a large surface area of MCP-1 contacts the receptor, and the accumulation of a number of weak interactions results in the 35 pM affinity observed for the wild-type (WT) protein. The receptor binding site of MCP-1 also is significantly different from the binding sites of RANTES and IL-8, providing insight into the issue of receptor specificity. It was previously shown that the N-terminus of CCR2 is critical for binding MCP-1 [Monteclaro, F. S., and Charo, I. F. (1996) J. Biol. Chem. 271, 19084-92; Monteclaro, F. S., and Charo, I. F. (1997) J. Biol. Chem. 272, 23186-90]. Point mutations of six acidic residues in this region of the receptor were made to test their role in ligand binding. This identified D25 and D27 of the DYDY motif as being important. On the basis of our data, we propose a model in which the receptor N-terminus lies along the hydrophobic groove in an extended fashion, placing the DYDY motif near the basic cluster involving R24 and K49 of MCP-1. This in turn orients the signaling residues (Y13 and the N-terminus) for productive interaction with the receptor.

Aggregation of RANTES is responsible for its inflammatory properties. Characterization of nonaggregating, noninflammatory RANTES mutants

The biology of RANTES (regulated on activation normal T cell expressed) aggregation has been investigated using RANTES and disaggregated variants, enabling comparison of aggregated, tetrameric, and dimeric RANTES forms. Disaggregated variants retain their G(i)-type G protein-coupled receptor-mediated biological activities. A correlation between RANTES aggregation and cellular activation has been demonstrated. Aggregated RANTES, but not disaggregated RANTES, activates human T cells, monocytes, and neutrophils. Dimeric RANTES has lost its cellular activating activity, rendering it noninflammatory. Macrophage inflammatory protein 1alpha, macrophage inflammatory protein-1beta, and erythrocytes are potent natural antagonists of aggregated RANTES-induced cellular activation. There is a clear difference in the signaling properties of aggregated and disaggregated RANTES forms, separating the dual signaling pathways of RANTES and the enhancing and suppressive effects of RANTES on human immunodeficiency virus infection. Disaggregated RANTES will be a valuable tool to explore the biology of RANTES action in human immunodeficiency virus infection and in inflammatory disease.

Immunomodulatory Role of C10 Chemokine in a Murine Model of Allergic Bronchopulmonary Aspergillosis

The immunomodulatory role of the chemokine C10 was explored in allergic airway responses during experimental allergic bronchopulmonary aspergillosis (ABPA). The intratracheal delivery of Asperigillus fumigatus Ag into A. fumigatus-sensitized mice resulted in significantly increased levels of C10 within the bronchoalveolar lavage, and these levels peaked at 48 h after A. fumigatus challenge. In addition, C10 levels in BAL samples were greater than 5-fold higher than levels of other chemokines such as monocyte-chemoattractant protein-1, eotaxin, and macrophage-inflammatory protein-1α. From in vitro studies, it was evident that major pulmonary sources of C10 may have included alveolar macrophages, lung fibroblasts, and vascular smooth muscle cells. Experimental ABPA was associated with severe peribronchial eosinophilia, bronchial hyperresponsiveness, and augmented IL-13 and IgE levels. The immunoneutralization of C10 with polyclonal anti-C10 antiserum 2 h before the intratracheal A. fumigatus challenge significantly reduced the airway inflammation and hyperresponsiveness in this model of ABPA, but had no effect on IL-10 nor IgE levels. Taken together, these data suggest that C10 has a unique role in the progression of experimental ABPA.

Fourteen-member macrolides inhibit interleukin-8 release by human eosinophils from atopic donors

Macrolide antibiotics such as erythromycin have been reported to be effective for asthma. However, the precise mechanisms of this effect remain unclear. We studied the effect of erythromycin, clarithromycin, josamycin, and other antibiotics on the release by eosinophils of interleukin-8 (IL-8), a potent chemokine for inflammatory cells, including eosinophils themselves. Human eosinophils were isolated from atopic patients, and the effects of the drugs on IL-8 release were evaluated. Only 14-member macrolides (erythromycin and clarithromycin) showed a concentration-dependent suppressive effect on IL-8 release (control, 100%; erythromycin at 1 microgram/ml, 67.82% +/- 3.45% [P < 0.01]; clarithromycin at 5 micrograms/ml, 56.81% +/- 9.61% [P < 0.01]). The effect was found at therapeutic concentrations and appeared to occur at the posttranscriprtional level. In contrast, a 16-member macrolide (josamycin) had no significant effect. We suggest that 14-member macrolides inhibit IL-8 release by eosinophils and may thereby prevent the autocrine cycle necessary for the recruitment of these cells into the airways.

Interleukin-8 inhalation directly provokes bronchoconstriction in guinea pigs

BACKGROUND

Although it has been reported that the concentration of interleukin (IL)-8 in nasal lavage fluid and sputum and its production in bronchial epithelium were increased in asthmatic subjects, the direct effects of IL-8 on the airways in vivo is unclear.

METHODS

We examined bronchoconstriction in response to IL-8 inhalation through an endotracheal cannula in anesthetized, artificially ventilated guinea pigs.

RESULTS

Inhalation of IL-8 at concentrations of 1 and 10 microg/ml caused significant bronchoconstriction, as revealed by the elevation of pressure at the airway opening. Moreover, the bronchoconstriction induced by IL-8 was significantly inhibited by the antihistamines diphenhydramine and terfenadine, suggesting the involvement of histamine release in the IL-8-induced bronchoconstriction. No significant leukocyte infiltration was observed in the bronchoalveolar lavage fluid or histologic findings 25 min after the first IL-8 inhalation.

CONCLUSIONS

IL-8 provokes bronchoconstriction without leukocyte accumulation in the airways, mediated in part by histamine release, in guinea pigs.

Regulation of interleukin-8 binding and function by heparin and alpha2-macroglobulin

BACKGROUND

Increased expression of interleukin-8 (IL-8), a potent neutrophil chemoattractant, is associated with a number of inflammatory diseases. Interleukin-8 binds to the glycosaminoglycan (GAG) heparin and the protease inhibitor alpha2-macroglobulin, molecules which regulate the function of a number of cytokines. Heparan sulphate was previously shown to enhance neutrophil chemotactic responses to IL-8.

OBJECTIVE

The purpose of this study was to investigate the effect of heparin, heparan sulphate and alpha2-macroglobulin on IL-8 binding to neutrophils and subsequent functional effects in vitro.

METHODS

The binding of 125I-IL-8 to normal neutrophils at 4 degrees C was studied and the IL-8 induced neutrophil chemotactic response was investigated using micro-Boyden chambers. Complexation of IL-8 with alpha2-macroglobulin was confirmed using gel filtration chromatography.

RESULTS

Heparin, but not heparan sulphate, inhibited the binding of 125I-IL-8 to neutrophils (IC50=26 microg/mL) and IL-8 induced neutrophil chemotactic responses (IC50=4 microg/mL). The specific inhibitory effect of heparin was apparently due to an interaction with IL-8 which was charge-dependent, since dextran sulphate had a greater inhibitory effect on chemotactic responses (IC50=2 microg/mL) and FITC-heparin did not bind to neutrophils. The heparin-induced inhibition of IL-8 binding and chemotactic responses was reversed in a dose-dependent manner in the presence of alpha2-macroglobulin. The binding of 125I-IL-8 to neutrophils in the presence of alpha2-macroglobulin appears to be, in part, through the specific IL-8 receptor.

CONCLUSION

These results point to an anti-inflammatory role for heparin and a novel, potentially, pro-inflammatory role for alpha2-macroglobulin which together indicate the importance of cytokine-binding macromolecules in determining net cytokine function.

The c-kit Ligand Stem Cell Factor and Anti-IgE Promote Expression of Monocyte Chemoattractant Protein-1 in Human Lung Mast Cells

Recent data suggest that mast cells (MC) are involved in the regulation of leukocyte accumulation in inflammatory reactions. In this study, expression of leukocyte-chemotactic peptides (chemokines) in purified human lung MC (n = 16) and a human mast cell line, HMC-1, was analyzed. Northern blotting and reverse transcriptase-polymerase chain reaction (RT-PCR) showed baseline expression of monocyte chemoattractant protein (MCP)-1 mRNA in unstimulated MC. Exposure of MC to recombinant stem cell factor (rhSCF, 100 ng/mL) or anti-IgE (10 μg/mL) was followed by a substantial increase in expression of MCP-1 mRNA. Neither unstimulated nor stem cell factor (SCF )-stimulated lung MC expressed transcripts for interleukin-8 (IL-8), macrophage inflammatory protein-1α (MIP-1α), MIP-1β, or RANTES by Northern blotting. The mast cell line HMC-1, which contains a mutated and intrinsically activated SCF-receptor, was found to express high levels of MCP-1 mRNA in a constitutive manner. Exposure of HMC-1 cells to rhSCF resulted in upregulation of MCP-1 mRNA expression, and de novo expression of MIP-1β mRNA. The SCF-induced upregulation of MCP-1 mRNA in lung MC and HMC-1 was accompanied by an increase in immunologically detectable MCP-1 in cell supernatants (sup) (lung MC [<98%], control medium, 1 hour: 159 ± 27 v SCF, 100 ng/mL, 1 hour: 398 ± 46 pg/mL/106 cells; HMC-1: control, 1 hour: 894 ± 116 v SCF, 1 hour: 1,536 ± 265 pg/mL/106). IgE-dependent activation was also followed by MCP-1 release from MC. MC-sup and HMC-1–sup induced chemotaxis in blood monocytes (Mo) (control: 100% ± 12% v 2-hour–MC-sup: 463% ± 38% v HMC-1–sup: 532% ± 12%), and a monoclonal antibody (MoAb) to MCP-1 (but not MoAb to IL-8) inhibited Mo-chemotaxis induced by MC-sup or HMC-1–sup (39% to 55% inhibition, P < .05). In summary, our study identifies MCP-1 as the predominant CC-chemokine produced and released in human lung MC. MCP-1 may be a crucial mediator in inflammatory reactions associated with MC activation and accumulation of MCP-1–responsive leukocytes.

The c-kit Ligand Stem Cell Factor and Anti-IgE Promote Expression of Monocyte Chemoattractant Protein-1 in Human Lung Mast Cells

Recent data suggest that mast cells (MC) are involved in the regulation of leukocyte accumulation in inflammatory reactions. In this study, expression of leukocyte-chemotactic peptides (chemokines) in purified human lung MC (n = 16) and a human mast cell line, HMC-1, was analyzed. Northern blotting and reverse transcriptase-polymerase chain reaction (RT-PCR) showed baseline expression of monocyte chemoattractant protein (MCP)-1 mRNA in unstimulated MC. Exposure of MC to recombinant stem cell factor (rhSCF, 100 ng/mL) or anti-IgE (10 μg/mL) was followed by a substantial increase in expression of MCP-1 mRNA. Neither unstimulated nor stem cell factor (SCF )-stimulated lung MC expressed transcripts for interleukin-8 (IL-8), macrophage inflammatory protein-1α (MIP-1α), MIP-1β, or RANTES by Northern blotting. The mast cell line HMC-1, which contains a mutated and intrinsically activated SCF-receptor, was found to express high levels of MCP-1 mRNA in a constitutive manner. Exposure of HMC-1 cells to rhSCF resulted in upregulation of MCP-1 mRNA expression, and de novo expression of MIP-1β mRNA. The SCF-induced upregulation of MCP-1 mRNA in lung MC and HMC-1 was accompanied by an increase in immunologically detectable MCP-1 in cell supernatants (sup) (lung MC [<98%], control medium, 1 hour: 159 ± 27 v SCF, 100 ng/mL, 1 hour: 398 ± 46 pg/mL/106 cells; HMC-1: control, 1 hour: 894 ± 116 v SCF, 1 hour: 1,536 ± 265 pg/mL/106). IgE-dependent activation was also followed by MCP-1 release from MC. MC-sup and HMC-1–sup induced chemotaxis in blood monocytes (Mo) (control: 100% ± 12% v 2-hour–MC-sup: 463% ± 38% v HMC-1–sup: 532% ± 12%), and a monoclonal antibody (MoAb) to MCP-1 (but not MoAb to IL-8) inhibited Mo-chemotaxis induced by MC-sup or HMC-1–sup (39% to 55% inhibition, P < .05). In summary, our study identifies MCP-1 as the predominant CC-chemokine produced and released in human lung MC. MCP-1 may be a crucial mediator in inflammatory reactions associated with MC activation and accumulation of MCP-1–responsive leukocytes.

Animal models of asthma: role of chemokines

In studies of disease processes, increasing knowledge leads to an increased awareness of the complexity of the underlying mechanisms. The intense research activity in the chemokine field has made this acutely manifest. Numerous chemokines have been discovered through the use of (1) bioassay of in vitro cell culture supernatants and in vivo exudates from animal models of inflammation and (2) molecular biology techniques. Any one chemokine can often be produced by a number of different cell types and exert its effects on different target cells. This has been interpreted by some as implying a high degree of redundancy. Although this is understandable, in disease processes parallel and sequential mechanisms are possible, and potentially important therapeutic targets have emerged. There is compelling evidence from animal and clinical studies that eosinophils are important effector cells in asthma, but this relationship is as yet unproven in the human disease. Two possible targets to prevent eosinophil recruitment to the lung are IL-5 and its receptor, which are important in several aspects of eosinophil biology, and eotaxin and its receptor, CCR3. The eotaxin receptor is particularly attractive as a target as it is expressed in high numbers on eosinophils, but not other leukocytes, and appears to be the major detector of the eosinophil for eotaxin and other chemokines such as MCP-4. Eotaxin and CCR3 knockout mice are being developed, and animal models will continue to be invaluable when antagonists are available. In the shape of receptor antagonists, the chemokine field may yet provide the final proof of concept for the long-established eosinophil theory of asthma in humans.

Effect of thromboxane A2 antagonists on bronchial hyperresponsiveness induced immediately after interleukin-8 inhalation in guinea-pigs

1. Although repeated intranasal administration of interleukin-8 (IL-8) causes bronchial hyperresponsiveness (BHR) mediated via thromboxane A2 (TXA2) and airway neutrophil accumulation in guinea-pigs, the acute effect of inhaled IL-8 is unclear. We performed this study to clarify the acute effect of IL-8 on bronchial responsiveness and the role of TXA2. 2. The effects of inhaled IL-8 on bronchial responsiveness and of the TXA2 antagonists, S-1452 (0.01 and 0.1 mg kg-1) and ONO-NT-126 (1.0 or 10 micrograms kg-1), on IL-8-induced BHR were examined by use of a modified Konzett-Rössler method in guinea-pigs. 3. Inhaled IL-8 at 100 ng ml-1, 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 micrograms ml-1) of methacholine and histamine, suggesting the potentiating effect of IL-8 on bronchial responsiveness. No significant leukocyte infiltration was observed histologically sixteen minutes after the IL-8 inhalation. Both S-1452 and ONO-NT-126 reduced the IL-8-induced BHR. 4. In conclusion, IL-8 rapidly causes BHR via TXA2 release in guinea-pigs.