Cloning of the human eosinophil chemoattractant, eotaxin. Expression, receptor binding, and functional properties suggest a mechanism for the selective recruitment of eosinophils

CCL chemokines and asthma

Airway eosinophilia is a characteristic of bronchial asthma. Eosinophils are considered to cause tissue damage through the release of toxic proteases, lipid mediators, cytokines and oxygen free radicals. The discovery of chemokines and the demonstration that some members of this cytokine superfamily are implicated in the recruitment of eosinophils offers an opportunity for a novel therapeutic approach in asthma.

Migration of eosinophils across endothelial cell monolayers: interactions among IL-5, endothelial-activating cytokines, and C-C chemokines

Eosinophils are the predominant cell type recruited in inflammatory reactions in response to allergen challenge. The mechanisms of selective eosinophil recruitment in allergic reactions are not fully elucidated. In this study, the ability of several C-C chemokines to induce transendothelial migration (TEM) of eosinophils in vitro was assessed. Eotaxin, eotaxin-2, monocyte chemotactic protein (MCP)-4, and RANTES induced eosinophil TEM across unstimulated human umbilical vein endothelial cells (HUVEC) in a concentration-dependent manner with the following rank order of potency: eotaxin approximately eotaxin-2 > MCP-4 approximately RANTES. The maximal response induced by eotaxin or eotaxin-2 exceeded that of RANTES or MCP-4. Preincubation of eosinophils with anti-CCR3 Ab (7B11) completely blocked eosinophil TEM induced by eotaxin, MCP-4, and RANTES. Activation of endothelial cells with IL-1beta or TNF-alpha induced concentration-dependent migration of eosinophils, which was enhanced synergistically in the presence of eotaxin and RANTES. Anti-CCR3 also inhibited eotaxin-induced eosinophil TEM across TNF-alpha-stimulated HUVEC. The ability of eosinophil-active cytokines to potentiate eosinophil TEM was assessed by investigating eotaxin or RANTES-induced eosinophil TEM across resting and IL-1beta-stimulated HUVEC in the presence or absence of IL-5. The results showed synergy between IL-5 and the chemokines but not between IL-5 and the endothelial activator IL-1beta. Our data suggest that eotaxin, eotaxin-2, MCP-4, and RANTES induce eosinophil TEM via CCR3 with varied potency and efficacy. Activation of HUVEC by IL-1beta or TNF-alpha or priming of eosinophils by IL-5 both promote CCR3-dependent migration of eosinophils from the vasculature in conjunction with CCR3-active chemokines.

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.

Eotaxin and RANTES expression by the dermal endothelium is associated with eosinophil infiltration after ivermectin treatment of onchocerciasis

The roles of eotaxin, RANTES, and MCP-3 expression in eosinophil recruitment to the site of parasite killing that occurs following ivermectin treatment of onchocerciasis were assessed in the skin of 13 Onchocerca volvulus-infected subjects and two noninfected controls before and after ivermectin treatment. Adverse reactions in infected subjects were associated with the appearance of eosinophils in the dermis as part of a perivascular inflammatory infiltrate. Although no expression of RANTES and eotaxin was seen in dermal vascular endothelial cells in biopsies taken before treatment (nor at any time in the skin of uninfected controls), endothelial expression of both eotaxin and RANTES was noted by 24 h following treatment. While RANTES expression was transient, eotaxin expression increased in parallel with increasing eosinophil recruitment up to 60 h posttreatment. These observations indicate that endothelial expression of eotaxin and RANTES may have an important role in eosinophil recruitment into the skin during helminth-killing reactions.

Eotaxin induces degranulation and chemotaxis of eosinophils through the activation of ERK2 and p38 mitogen-activated protein kinases

Eotaxin and other CC chemokines acting via CC chemokine receptor-3 (CCR3) are believed to play an integral role in the development of eosinophilic inflammation in asthma and allergic inflammatory diseases. However, little is known about the intracellular events following agonist binding to CCR3 and the relationship of these events to the functional response of the cell. The objectives of this study were to investigate CCR3-mediated activation of the mitogen-activated protein (MAP) kinases extracellular signal-regulated kinase-2 (ERK2), p38, and c-jun N-terminal kinase (JNK) in eosinophils and to assess the requirement for MAP kinases in eotaxin-induced eosinophil cationic protein (ECP) release and chemotaxis. MAP kinase activation was studied in eotaxin-stimulated eosinophils (more than 97% purity) by Western blotting and immune-complex kinase assays. ECP release was measured by radioimmunoassay. Chemotaxis was assessed using Boyden microchambers. Eotaxin (10−11 to 10−7 mol/L) induced concentration-dependent phosphorylation of ERK2 and p38. Phosphorylation was detectable after 30 seconds, peaked at about 1 minute, and returned to baseline after 2 to 5 minutes. Phosphorylation of JNK above baseline could not be detected. The kinase activity of ERK2 and p38 paralleled phosphorylation. PD980 59, an inhibitor of the ERK2-activating enzyme MEK (MAP ERK kinase), blocked phosphorylation of ERK2 in a concentration-dependent manner. The functional relevance of ERK2 and p38 was studied using PD98 059 and the p38 inhibitor SB202 190. PD98 059 and SB202 190 both caused inhibition of eotaxin-induced ECP release and chemotaxis. We conclude that eotaxin induces a rapid concentration-dependent activation of ERK2 and p38 in eosinophils and that the activation of these MAP kinases is required for eotaxin-stimulated degranulation and directed locomotion.

Correlation between deposition of immuno-components and infiltration pattern of polymorphonuclear leukocytes in the lesions of chronic urticaria

Urticaria is often associated with perivascular infiltration of leukocytes into the lesions. Although mast cell-derived chemical mediators are considered to play crucial roles in the infiltration of leukocytes as well as in the dermal edema, other mechanisms for the leukocyte infiltration have not been well defined. This study revealed that approximately 25% of the cases of chronic idiopathic urticaria in whom wheals had continued for more than 12 h had deposition of immuno-components in the lesions, although histological examination of the lesions did not show leukocytoclastic vasculitis. In these lesions with deposition of immuno-components, both neutrophils and eosinophils had infiltrated at a constant ratio (approximately 2:1), whereas, in the lesions without deposition, a variable population of leukocytes was seen. This result suggests that activation of complements occurs in the lesions of a considerable percentage of patients with chronic idiopathic urticaria and that the complement fragments influence the infiltration patterns of polymorphonuclear leukocytes.

Interleukin-13 and tumour necrosis factor-alpha synergistically induce eotaxin production in human nasal fibroblasts

BACKGROUND

There is increasing evidence that eotaxin is a key mediator in the development of tissue eosinophilia. However, the mechanism involved in the production of eotaxin has yet to be clarified. Most recently, it has been shown that interleukin (IL) -4 induces eotaxin in dermal fibroblasts. A novel cytokine termed IL-13, which binds to the alpha-chain of the IL-4 receptor, shares many biological activities with IL-4. It is known that fibroblasts express the IL-4 receptor and produce collagen type I upon stimulation with IL-4.

OBJECTIVE

We investigated whether IL-13, as well as IL-4, are able to induce eotaxin production in human nasal mucosal fibroblasts (HNMFs). Furthermore, we investigated the effect of costimulation of IL-13 and TNFalpha on eotaxin production.

METHODS

HNMFs, isolated from inferior nasal mucosa samples, were stimulated by various kind of cytokines for 1-36 h at 37 degrees C in 5% CO2. The change in the expression of eotaxin mRNA was then evaluated by reverse transcriptase-polymerase chain reaction and the Southern blot analysis. The amount of eotaxin in the culture media was measured by ELISA.

RESULTS

IL-13 as well as IL-4 dose-dependently induced eotaxin expression in HNMFs. Furthermore, IL-13 and TNFalpha synergistically induced eotaxin expression in HNMFs, while they hardly induced eotaxin expression in endothelial cells, epithelial cells or eosinophils. The synergy was observed when pre-incubation of HNMFs with IL-13 was followed by a stimulation with TNFalpha, or HNMFs were simultaneously stimulated with IL-13 and TNFalpha.

CONCLUSION

These results strongly indicate that IL-13, as well as IL-4, may be important in eotaxin-mediated eosinophilic inflammation in nasal mucosa. In addition, in nasal mucosa, fibroblasts are the major cell source for eotaxin.

Eotaxin synthesis by nasal polyp fibroblasts

Nasal polyps is a chronic inflammatory disease of the upper airway characterized by structural abnormalities including stromal fibrosis. Fibroblasts are a rich source of cytokines and inflammatory mediators and are thought to play an important role in the development of fibrosis. In addition, there is considerable evidence for the participation of eosinophils in the pathophysiology of nasal polyps. Although increased numbers of eosinophils are present in nasal polyps, the mechanisms responsible for their selective accumulation are not completely clear. Eotaxin is a chemokine that promotes the selective recruitment of eosinophils. Thus, it may be an important molecule for the recruitment of eosinophils in nasal polyps. The purpose of this study was to investigate whether nasal polyp fibroblasts synthesize eotaxin after stimulation with lipopolysaccharide, IL-1beta or TNF-alpha. Using primary nasal polyp tissue-derived fibroblast lines, we demonstrated that LPS, IL-1beta and TNF-alpha induced the gene expression and protein production of eotaxin in nasal polyp fibroblasts. This responsiveness to LPS, IL-1beta and TNF-alpha was time- and dose-dependent. These findings support the hypothesis that fibroblasts could play an important role in the recruitment of eosinophils in nasal polyps through the production of eotaxin.

Interleukin-5 enhances eosinophil adhesion to bronchial epithelial cells

BACKGROUND

Eosinophil-bronchial epithelial cell interactions are thought to be central to the pathogenesis of asthma, both in terms of the epithelium as a source of pro-inflammatory mediators and as a target for eosinophil-mediated damage. We have therefore investigated adhesion interactions between these two cell types.

OBJECTIVES

To determine the role of eosinophil and epithelial activation on eosinophil adhesion to bronchial epithelium and to characterize the adhesion receptors mediating eosinophil adhesion.

METHODS

Eosinophils were purified from human peripheral blood by immunomagnetic selection and adhesion to confluent cultures of the airway epithelial cell lines A549 and BEAS-2B was studied.

RESULTS

Stimulation of A549 cells with TNFalpha, IFNgamma or a combination of 50 ng/mL of TNFalpha, IFNgamma and IL-1 (cytomix) did not effect eosinophil binding despite an increase in ICAM-1 expression. Similarly stimulation of eosinophils with PAF or IL-5 had no effect on eosinophil binding to medium- or cytokine-treated A549 cells. In contrast stimulation of BEAS-2B cells with cytomix caused a significant increase in eosinophil adhesion. This was associated with an increase in expression of ICAM-1 and induced expression of VCAM-1. Treatment of eosinophils with Mn2+ and IL-5 but not eotaxin, RANTES or PAF also significantly enhanced eosinophil adhesion to medium-treated BEAS-2B cells. Using blocking mAbs we were able to demonstrate that the increased adhesion resulting from stimulation of eosinophils or BEAS-2B cells was in both cases mediated by a combination of CD18 and alpha4 integrins.

CONCLUSIONS

This study demonstrates a selective role for IL-5 in mediating integrin-dependent eosinophil adhesion to airway epithelium and once again emphasizes the importance of this cytokine in controlling eosinophil activation in diseases such as asthma.

Molecular analysis of CCR-3 events in eosinophilic cells

CCR-3 is a major receptor involved in regulating eosinophil trafficking. Initial analysis of chemokine receptors has demonstrated unique receptor events in different cell types, indicating the importance of investigating CCR-3 events in eosinophilic cell lines. We now report that the eosinophilic cell line, acute myelogenous leukemia (AML) 14.3D10, expresses eosinophil granule proteins and eotaxin, but has no detectable expression of eosinophil chemokine receptors. Treatment of the cell line with butyric acid and IL-5 results in a dose-dependent synergistic induction of CCR-3 and, to a lesser extent, CCR-1 and CCR-5. Interestingly, using a luciferase reporter construct under the control of the hCCR-3 promoter, the uninduced and induced cells display high, but comparable, levels of promoter activity. Differentiated AML cells developed enhanced functional activation, as indicated by adhesion to respiratory epithelial cells and chemokine-induced transepithelial migration. Chemokine signaling did not inhibit adenylate cyclase activity even though calcium transients were blocked by pertussis toxin. Additionally, chemokine-induced calcium transients were inhibited by pretreatment with PMA, but not forskolin. Eotaxin treatment of differentiated AML cells resulted in marked down-modulation of CCR-3 expression for at least 18 h. Receptor internalization was not dependent upon chronic ligand exposure and was not accompanied by receptor degradation. Thus, CCR-3 is a late differentiation marker on AML cells and uses a signal transduction pathway involving rapid and prolonged receptor internalization, calcium transients inhibitable by protein kinase C but not protein kinase A, and the paradoxical lack of inhibition of adenylate cyclase activity.

Effects of reactive oxygen and nitrogen metabolites on eotaxin-induced eosinophil chemotactic activity in vitro

Peroxynitrite, an oxidant generated by the interaction between superoxide and nitric oxide (NO), has been implicated in the etiology of numerous disease processes. Several studies have shown that peroxynitrite-induced protein nitration may compromise enzyme and protein function. We hypothesized that peroxynitrite may regulate cytokine function during inflammation. To test this hypothesis, the eosinophil chemotactic responses of eotaxin incubated with and without peroxynitrite were evaluated. Peroxynitrite attenuated eotaxin-induced eosinophil chemotactic activity (ECA) in a dose-dependent manner (P < 0.05). The inhibitory effects were not significant on ECA induced by leukotriene B(4) or complement-activated serum incubated with peroxynitrite. The reducing agents deferoxamine and dithiothreitol reversed the ECA inhibition by peroxynitrite, and exogenous L-tyrosine abrogated the inhibition by peroxynitrite. PAPA-NONOate (an NO donor) or a combination of xanthine and xanthine oxidase to generate superoxide did not show an inhibitory effect on ECA induced by eotaxin. In contrast, 3-morpholinosydnonimine, a peroxynitrite generator, caused a concentration-dependent inhibition of ECA by eotaxin. Consistent with its capacity to reduce ECA, peroxynitrite treatment reduced eotaxin binding to eosinophils. Nitrotyrosine was detected in the eotaxin incubated with peroxynitrite. These findings are consistent with nitration of tyrosine by peroxynitrite with subsequent inhibition of eotaxin binding to eosinophils and a reduction in ECA. These data demonstrate that peroxynitrite modulates the eosinophil migration by eotaxin, and suggest that oxidants may play an important role in regulation of eotaxin-induced eosinophil chemotaxis.

CCR3 blockade as a new therapy for asthma

Among the inflammatory cells infiltrating the lungs of asthmatic patients, eosinophils and Th2 cells are thought to play a central role in the pathogenesis of this disease. Several studies have implicated that chemokines are prime candidates for being responsible for the selective recruitment of the leukocyte subsets found in atopic diseases. Regulated upon activation, normal T-cell-expressed and secreted (RANTES), monocyte chemoattractant protein-3 (MCP-3), MCP-4 and the eotaxins, for example, have been shown in vitro to potently induce eosinophil chemotaxis as well as initiate several other pro-inflammatory activities such as integrin activation, lipid mediator biosynthesis and degranulation. Ligand binding and chemotaxis experiments with these chemokines demonstrated that a G-protein coupled-receptor (GPCR) cloned from eosinophils, termed CCR3, was responsible for producing a chemokine selectivity profile identical to that of eosinophils. In addition, blocking CCR3 on eosinophils, with a monoclonal antibody, completely abolished eosinophil responses to these chemokines. Together these studies strongly suggest a central role for this receptor in eosinophil trafficking. CCR3 has also been found on in vitro derived Th2 cells and on T-cells co-localising with eosinophils in diseased tissue, thus revealing a possible pathogenic mechanism for T-cell recruitment into the airways. Therefore, blockade of CCR3 represents a highly attractive and innovative strategy for asthma therapy.

Intranasal administration of eotaxin increases nasal eosinophils and nitric oxide in patients with allergic rhinitis

BACKGROUND

Nitric oxide (NO) plays an important role as an inflammatory mediator in the airways. Inducible NO synthase in the nasal mucosa is upregulated in perennial allergic rhinitis, and nasal NO is reduced after treatment with topical corticosteroids. A previous study has suggested that there is a significant correlation between exhaled NO and sputum eosinophils in patients with asthma.

OBJECTIVE

We investigated the ability of intranasal administration of eotaxin, a potent chemoattractant for eosinophils, to induce eosinophil accumulation and the relationship between eosinophil recruitment in the nasal mucosa and nasal NO production in patients with allergic rhinitis.

METHODS

Nine patients with allergic rhinitis were studied. Eotaxin or diluent was delivered intranasally in patients by using a metered spray pump. Nasal NO, symptom scores, and the influx of inflammatory cells in nasal lavage fluid were assessed before and after the challenge. Immunoreactivity for inducible NO synthase and nitrotyrosine was evaluated in nasal lavage cells.

RESULTS

Eotaxin induced a significant influx of eosinophils (P <.05) with mild symptoms of rhinitis. There was neither significant migration of lymphocytes, basophils, and macrophages into nasal lavage fluid nor a shedding of nasal epithelial cells after eotaxin challenge. Nasal NO was increased significantly (P <.05) 8 hours after eotaxin challenge compared with diluent challenge. Nitrotyrosine immunoreactivity was moderately elevated in nasal epithelial cells after the challenge.

CONCLUSION

We have shown that eotaxin causes chemotaxis of eosinophils with a clinically symptomatic inflammatory response in the nasal mucosa and that eosinophil recruitment accompanies an increase in nasal NO, contributing to oxidative stress.

Chemokines and their role in airway hyper-reactivity

Airway hyper-reactivity is a characteristic feature of many inflammatory lung diseases and is defined as an exaggerated degree of airway narrowing. Chemokines and their receptors are involved in several pathological processes that are believed to contribute to airway hyper-responsiveness, including recruitment and activation of inflammatory cells, collagen deposition and airway wall remodeling. These proteins are therefore thought to represent important therapeutic targets in the treatment of airway hyper-responsiveness. This review highlights the processes thought to be involved in airway hyper-responsiveness in allergic asthma, and the role of chemokines in these processes. Overall, the application of chemokines to the prevention or treatment of airway hyper-reactivity has tremendous potential.

Molecular pathology of allergic disease: I: lower airway disease

Asthma is a complex disorder associated with eosinophil infiltration and the activation of T lymphocytes within the airways. Recent advances in the pathophysiologic mechanisms of asthma point to the importance of eosinophil-basophil progenitor cells and a family of transcription factors that underlie the development of T(H)2-type responses. Further research is needed to address the development of chronic inflammatory changes, the role of profibrotic cytokines, and especially their reliance on eosinophils in the lungs.

Chemokine production by the BEAS-2B human bronchial epithelial cells: differential regulation of eotaxin, IL-8, and RANTES by TH2- and TH1-derived cytokines

BACKGROUND

Bronchial epithelial cells produce many types of chemokines and may contribute to lung inflammation by recruiting inflammatory cells. The CC chemokine eotaxin is a potent, eosinophil-specific chemoattractant that has been detected in the bronchial epithelium of patients with asthma.

OBJECTIVES

The aim of this study was to investigate the regulatory mechanisms of chemokine production from bronchial epithelium by inflammatory cytokines, especially T(H)2- and T(H)1-derived cytokines, in bronchial asthma.

METHODS

BEAS-2B human bronchial epithelial cells were cultured with TNF-alpha, IL-4, IL-13, and IFN-gamma alone or in combination, after which supernatants were assayed for eotaxin, IL-8, and RANTES proteins with ELISA. Reverse transcription-PCR was also performed.

RESULTS

TNF-alpha induced production of eotaxin, IL-8, and RANTES in a concentration-dependent manner. Both IL-4 and IL-13 synergistically enhanced TNF-alpha-induced eotaxin production, whereas IL-8 production induced by TNF-alpha was significantly down-regulated by the T(H)2-derived cytokines. IFN-gamma, a T(H)1 cytokine, counteracted the enhancing effects of IL-4 and IL-13 on eotaxin production. RANTES production by TNF-alpha was not affected by IL-4 and IL-13 but was markedly enhanced by IFN-gamma.

CONCLUSIONS

These results suggest that T(H)2 cytokines are involved in preferential recruitment of eosinophils in bronchial asthma by enhancing eotaxin and reducing IL-8 production from bronchial epithelial cells and that T(H)1 cytokines counteract the effects of T(H)2 cytokines by reducing eotaxin production.

Activation of Eotaxin Gene Transcription by NF-κB and STAT6 in Human Airway Epithelial Cells

The C-C chemokine eotaxin is a potent chemoattractant for eosinophils and probably plays an important role in the pathogenesis of asthma, although the mechanisms of its regulation are not well known. Airway epithelial cells express eotaxin mRNA and protein after stimulation with a variety of cytokines. We focused on the molecular mechanisms of eotaxin gene regulation by TNF-α and IL-4 in the airway epithelial cell line, BEAS-2B. Cells were transfected with luciferase reporter plasmids, which contained up to 1363 bp of the eotaxin promoter. Eotaxin promoter activity was increased by TNF-α (2.5-fold) and IL-4 (1.5-fold), respectively. The combination of TNF-α and IL-4 produced 3.6-fold activation of the eotaxin promoter. The eotaxin promoter contains overlapping consensus binding sites for transcription factors, NF-κB and STAT6, which are known to mediate responses to TNF-α and IL-4, respectively. Electrophoretic mobility shift assays revealed NF-κB binding after TNF-α stimulation and STAT6 binding after IL-4 stimulation using a DNA probe derived from the eotaxin promoter. Mutant plasmids were generated to define the roles of these transcription factors in eotaxin promoter activity. TNF-α stimulation, but not IL-4 stimulation, was lost in plasmids mutated at the NF-κB binding site, whereas IL-4 stimulation, but not TNF-α stimulation, was lost in plasmids mutated at the STAT6 binding site. When both sites were mutated, all transcriptional activation was lost. These results imply that TNF-α and IL-4 stimulate expression of the eotaxin gene by activating NF-κB and STAT6.

Eosinophil activation by eotaxin--eotaxin primes the production of reactive oxygen species from eosinophils

BACKGROUND

The CC chemokine eotaxin has been shown to possess selective chemotactic activity for eosinophils, the major effector cells in allergic inflammation. Reactive oxygen species (ROS) from eosinophils may damage cells or tissue, such as the mucosal epithelium. In this study, we examined the effect of eotaxin on ROS from eosinophils and compared its activity with RANTES and interleukin (IL)-5. Moreover, we examined the signal transduction of eotaxin and the effect of dexamethasone on ROS from eosinophils.

METHODS

Eosinophils were isolated by modified CD16-negative selection. ROS in luminol-dependent or lucigenin-dependent chemiluminescence reaction were examined. Calcium ionophore A23187 was added to the mixture of eosinophils with luminol or lucigenin, and then ROS were determined.

RESULTS

Eotaxin primed the production of ROS in a dose-dependent manner. ROS from untreated eosinophils evoked with calcium ionophore A23187 in luminol-dependent chemiluminescence gave a maximal value of 4957+/-1035 intensity counts (IC) (mean+/-SE, n=7) and an integral value of 15.75+/-3.14 IC (x10(-4)), while eosinophils that were treated with eotaxin gave maximal values of 11 142+/-2300 IC (10 nM) and 29165+/-3718 IC (100 nM) and integral values of 41.07+5.44 IC (x10(-4)) (10 nM) and 152.90+/-22.38 IC (x10(-4))(100 nM). Moreover, eotaxin was less effective as a priming agent with lucigenin-sensitive pathways than luminol-sensitive pathways. Among several kinds of eosinophils activating cytokines and chemokines, the priming effect of eotaxin on RO5 was the most potent. Eotaxin-primed ROS were inhibited by pertussis toxin, which ADP-ribolysates G proteins; wortmannin, a phosphatidylinositol-3-kinase inhibitor; and genistein, a tyrosine kinase inhibitor, suggesting the involvement of pertussis toxin-sensitive G proteins, phosphatidylinositol-3-kinase, and tyrosine kinase in the signal transduction of eotaxin. Moreover, dexamethasone inhibited ROS from not only untreated eosinophils but also eosinophils treated with eotaxin.

CONCLUSION

Eotaxin may play an important role in the pathogenesis of allergic inflammation through eosinophil activation by priming of eosinophil oxidative metabolism, as well as by involvement in selective eosinophil chemotaxis.

Eosinophil Chemotactic Chemokines (Eotaxin, Eotaxin-2, RANTES, Monocyte Chemoattractant Protein-3 (MCP-3), and MCP-4), and C-C Chemokine Receptor 3 Expression in Bronchial Biopsies from Atopic and Nonatopic (Intrinsic) Asthmatics

Atopic (AA) and nonatopic (NAA) asthma are characterized by chronic inflammation and local tissue eosinophilia. Many C-C chemokines are potent eosinophil chemoattractants and act predominantly via the CCR3. We examined the expression of eotaxin, eotaxin-2, RANTES, monocyte chemoattractant protein-3 (MCP-3), MCP-4, and CCR3 in the bronchial mucosa from atopic (AA) and nonatopic (intrinsic; NAA) asthmatics and compared our findings with atopic (AC) and nonatopic nonasthmatic controls (NC). Cryostat sections were processed for immunohistochemistry (IHC), in situ hybridization (ISH), and double IHC/ISH. Compared with AC and NC, the numbers of EG2+ cells and the cells expressing mRNA for eotaxin, eotaxin-2, RANTES, MCP-3, MCP-4, and CCR3 were significantly increased in AA and NAA (p &lt; 0.01). Nonsignificant differences in these variants were observed between AA and NAA and between AC and NC. Significant correlations between the cells expressing eotaxin or CCR3 and EG2+ eosinophils in the bronchial tissue were also observed for both AA (p &lt; 0.01) and NAA (p = 0.01). Moreover, in the total asthmatic group (AA + NAA) there was a significant inverse correlation between the expression of eotaxin and that of the histamine PC20 (p &lt; 0.05). Sequential IHC/ISH showed that cytokeratin+ epithelial cells, CD31+ endothelial cells, and CD68+ macrophages were the major sources of eotaxin, eotaxin-2, RANTES, MCP-3, and MCP-4. There was no significantly different distribution of cells expressing mRNA for these chemokines between atopic and nonatopic asthma. These findings suggest that multiple C-C chemokines, acting at least in part via CCR3, contribute to bronchial eosinophilia in both atopic and nonatopic asthma.

Eotaxin expression in Sephadex-induced lung injury in rats

The CC chemokine eotaxin is a potent and specific eosinophil chemoattractant. Eosinophil-dependent tissue injury has been shown to contribute to airway inflammation such as that in asthma. In the present study, We investigated eotaxin expression in a rat model of pulmonary inflammation (featuring accumulation of eosinophils) induced by intratracheal instillation of cross-linked dextran beads (Sephadex G200). Intratracheal instillation of 5 mg/kg Sephadex caused a time-dependent eosinophil infiltration into the lung, reaching a peak at 24 hours. Eotaxin mRNA in the lung paralleled the eosinophil influx. Eotaxin protein in bronchoalveolar (BAL) fluids and lung homogenates was shown by Western blot and immunostaining to be maximally expressed by 24 hours. Sephadex-induced lung injury, as measured by (125)I-labeled albumin leakage from the pulmonary vasculature, developed in a time-dependent manner. Intravenous injection of blocking antibody to eotaxin significantly decreased eosinophil infiltration and lung permeability. These data suggest that, in the Sephadex model of lung inflammation, eotaxin up-regulation mediates intrapulmonary accumulation of eosinophils and the development of lung injury.

The equine herpesvirus 2 E1 open reading frame encodes a functional chemokine receptor

Several herpesviruses contain open reading frames (ORFs) that encode potential homologs of eucaryotic genes. Equine herpesvirus 2 (EHV-2) is a gammaherpesvirus related to other lymphotropic herpesviruses such as herpesvirus saimiri and Epstein-Barr virus. The E1 ORF of EHV-2, a G protein-coupled receptor homolog, shows 31 to 47% amino acid identity with known CC chemokine receptors. To investigate whether E1 may encode a functional receptor, we cloned the E1 ORF and expressed it in stably transfected cell lines. We report here the identification of the CC chemokine eotaxin as a functional ligand for the EHV-2 E1 receptor. Chemokines are likely to play a role in the regulation of immune functions in equine hosts during EHV-2 infection and, via interaction with E1, may affect viral replication and/or escape from immune responses.

Differential Regulation of Epithelial-Derived C-C Chemokine Expression by IL-4 and the Glucocorticoid Budesonide

Airway epithelial cells are a rich source of eosinophil-selective C-C chemokines. We investigated whether cytokines and the topical glucocorticoid budesonide differentially regulate RANTES, monocyte chemoattractant protein-4 (MCP-4), and eotaxin mRNA and protein expression in the human bronchial epithelial cell line BEAS-2B and in primary human bronchial epithelial cells by Northern blot analysis and ELISAs. Eotaxin and MCP-4 mRNA expression induced by TNF-α alone or in combination with IFN-γ was near-maximal after 1 h, peaked at 4 and 8 h, respectively, remained unchanged up to 24 h, and was protein synthesis independent. In contrast, RANTES mRNA was detectable only after 2 h and slowly increased to a peak at 24 h, and was protein synthesis dependent. Induction of eotaxin and MCP-4 mRNA showed a 10- to 100-fold greater sensitivity to TNF-α compared with RANTES mRNA. IL-4 and IFN-γ had selective effects on chemokine expression; IL-4 selectively up-regulated the expression of eotaxin and MCP-4 and potentiated TNF-α-induced eotaxin, while IFN-γ markedly potentiated only the TNF-α-induced expression of RANTES. Although budesonide inhibited the expression of chemokine mRNA to a variable extent, it effectively inhibited production of eotaxin and RANTES protein. Budesonide inhibited both RANTES- and eotaxin promoter-driven reporter gene activity. Budesonide also selectively accelerated the decay of eotaxin and MCP-4 mRNA. These results point to IL-4 as a possible mediator by which Th2 cells may induce selective production of C-C chemokines from epithelium and indicate that glucocorticoid inhibit chemokine expression through multiple mechanisms of action.

Calcium ionophore upregulation of AUUUA-specific binding protein activity is contemporaneous with granulocyte macrophage colony-stimulating factor messenger RNA stabilization in AML14.3D10 cells

Eosinophils produce granulocyte macrophage colony-stimulating factor (GM-CSF), which enhances their survival and function. In T cells and fibroblasts, GM-CSF production is controlled predominantly by variable messenger RNA (mRNA) stability involving 3' untranslated region (3' UTR) adenosine-uridine-rich elements (AREs) and sequence-specific mRNA binding proteins. However, the mode of regulation of this critical cytokine remains unknown in eosinophils. Therefore, we measured GM-CSF mRNA decay in an eosinophil-like cell line (AML14.3D10) and, with a radiolabeled GM-CSF RNA probe, asked whether ARE-specific, mRNA binding proteins were present in cytoplasmic lysates of these cells. Human GM-CSF mRNA transfected into unstimulated AML14.3D10 cells decayed with a half-life of 6 min, which increased to 14 min after 1 h, and to 22 min after 2 h, of ionophore-mediated activation. GM-CSF RNA mobility shift assays using cytoplasmic extracts from resting or ionophore-stimulated AML14.3D10 cells revealed multiple RNA-protein complexes of 55, 60, 85, 100, and 125 kD. A 47-kD complex was also detected with an 80-base RNA probe containing four consecutive AUUUA motifs. On the basis of competition studies, all of the observed binding protein activities interacted with the 3' UTR AREs. In addition, binding activity increased 2.5-fold in cytoplasmic lysates from cells stimulated with calcium ionophore for 2 h, contemporaneous with GM-CSF mRNA stabilization. These data provide direct evidence that ionophore stabilizes GM-CSF mRNA in AML14.3D10 cells and simultaneously increases the activity of a series of AUUUA-specific mRNA binding proteins. We conclude that the interaction of AU-specific binding proteins may stabilize GM-CSF mRNA in activated eosinophil-like cell lines.

Experimental common cold increases mucosal output of eotaxin in atopic individuals

BACKGROUND

In view of recent observations demonstrating that rhinovirus infections are associated with increased local activity of eosinophils, we hypothesized that eotaxin, a selective eosinophil chemoattractant, may be involved in eosinophil recruitment/activation in common cold infections.

METHODS

Twenty-three patients with seasonal allergic rhinitis were inoculated with human rhinovirus 16 (HRV 16) outside the pollen season. Sequential diluent and allergen (10(3) SQ-U) challenges, each followed by nasal lavage, were carried out about 3 months before and 4 days after virus inoculation.

RESULTS

Seventeen patients developed common cold and were further analyzed. Lavage fluid levels of eotaxin were increased at the height of active common cold (day 4 after inoculation) both at baseline (after diluent challenge) (P<0.01) and acutely after allergen challenge (P<0.05).

CONCLUSIONS

Common cold symptoms after nasal HRV 16 inoculation are associated with increased nasal mucosal output of eotaxin, suggesting that this chemokine is partly responsible for recruitment/activation of airway mucosal eosinophils in common cold infections.

Characterization of eosinophils and detection of eotaxin in skin chamber fluid after challenge with relevant allergen in patients with mild asthma

BACKGROUND

A selective recruitment of eosinophils to sites of allergic inflammation is suggested to be controlled by regulation of cytokines, chemokines and adhesion molecules.

OBJECTIVE

The aim of this study was to examine whether allergen challenge in skin chambers, applied on patients with allergic rhinitis and mild asthma, results in a selective influx of activated eosinophils and detectable levels of cytokines/chemokines related to eosinophil recruitment, such as interleukin (IL)-5 and eotaxin.

METHODS

A skin blister was induced on the volar aspect of each forearm; one contained PBS-heparin buffer (control) and the other was challenged with relevant allergen. Peripheral blood was drawn before the allergen was applied to the skin chamber, and the expression of CD9, CD11b and EG2-epitope on intracellular eosinophil cationic protein (ECP) was analysed in eosinophils. Chamber fluid was collected 8 h after allergen application and analysed for differential cell counts, expression of eosinophil activity markers, the presence of ECP, eotaxin, and IL-5.

RESULTS

The number of recruited leucocytes was equal in the allergen-challenged chambers and in controls. However, the number of eosinophils was significantly increased in the allergen-challenged chambers, and elevated levels of released ECP were measured. Moreover, the eosinophils recruited were activated, as shown by increased expression of EG2 and CD11b, and decreased expression of CD9, in comparison with blood eosinophils. In the skin chamber fluids, higher levels of eotaxin were detected in the allergen-challenged chambers than in controls, but there were no detectable levels of IL-5.

CONCLUSION

We have demonstrated a selective recruitment of eosinophils, and higher levels of released ECP and eotaxin, in skin chambers stimulated with allergen, as compared with control chambers. Allergen challenge in skin chambers is a useful tool for studies of eosinophil recruitment, their state of activation, and their involvement in the allergic inflammatory response.

Novel association of the src family kinases, hck and c-fgr, with CCR3 receptor stimulation: A possible mechanism for eotaxin-induced human eosinophil chemotaxis

The chemokine eotaxin is a potent and relatively eosinophil-specific chemoattractant implicated in the cell migration to inflammatory sites in allergic diseases. Eotaxin exerts its activity solely through the CCR3 receptor, but the signaling pathways are poorly defined. In this study, we show that eotaxin induces an increase in tyrosine phosphorylation of multiple cellular proteins in normal human eosinophils. Eotaxin-dependent tyrosine phosphorylation was detected 1 min after stimulation and increased for at least 15 min with kinetics similar to those of eotaxin-induced cell shape changes. Herbimycin A, a tyrosine kinase inhibitor, blocked both eotaxin-induced tyrosine phosphorylation and cell shape changes as well as chemotaxis. Immunofluorescence microscopy analyses showed that eotaxin-induced cell shape changes were accompanied by redistribution of tyrosine-phosphorylated proteins and F-actin reorganization that were sensitive to herbimycin A. Coimmunoprecipitation studies revealed that binding of eotaxin to CCR3 greatly enhanced association of the Src family kinases, Hck and c-Fgr, with CCR3 after internalization of CCR3. These results may indicate that recruitment of Hck and c-Fgr to CCR3 in a compartment triggers tyrosine phosphorylation, leading to rapid cell shape changes required for cell migration.

Characterization of chemokine CCR3 agonist-mediated eosinophil recruitment in the Brown-Norway rat

1. The ability of various C-C chemokines to elicit tissue eosinophil infiltration following intradermal injection or peripheral blood eosinophilia following intravenous injection were compared in the Brown-Norway rat. 2. Eotaxin (0.1 - 3 microg site-1) of human and murine origin produced equivalent, dose-dependent increases in eosinophil peroxidase activity in rat dermis 4 h post-injection. 3. Human eotaxin-2 was equipotent with human eotaxin in terms of dermal eosinophil recruitment. Other human CCR3 agonists, such as MCP-3, RANTES and MCP-4 failed to increase dermal eosinophil peroxidase activity at doses up to 1 microg site-1 whereas the latter did produce a small effect at 3 microg site-1. 4. Consistent with observations in vivo, human eotaxin displaced [125I]-eotaxin from rat spleen membranes more potently (IC50=2 nM) than did MCP-4 (IC50=500 nM). RANTES did not compete with the radiolabelled chemokine at concentrations up to 1 microM. 5. Human eotaxin (5 microg) administered intravenously increased circulating eosinophils approximately 3 fold whereas MCP-4 (5 microg i.v.) increased circulating monocytes approximately 3 fold without affecting eosinophil numbers. 6. Dexamethasone pretreatment inhibited eotaxin-induced dermal eosinophil influx only at a steroid dose (0.1 mg kg-1, s.c.) which significantly reduced circulating eosinophil numbers. The steroid also reduced eosinophilia in peripheral blood resulting from systemic eotaxin administration (5 microg, i.v.). 7. These data suggest differences in rat CCR3 relative to other species as surmised from a distinctive rank order of chemokine potency. In addition to its chemotactic effects eotaxin, but not MCP-4, promotes eosinophil recruitment into the circulation. One of the mechanisms by which glucocorticoids, such as dexamethasone, acutely inhibits eotaxin-induced dermal eosinophil influx is to diminish the circulating numbers of these cells available for tissue recruitment.

Dermal fibroblasts represent a potent major source of human eotaxin: In vitro production and cytokine-mediated regulation

Accumulating evidence indicates that eotaxin plays an integral role in tissue recruitment of eosinophils in humans as well as in animals. To clarify which types of cells are actually important as sources of human eotaxin, we used a specific enzyme-linked immunosorbent assay (ELISA) to compare various types of hemopoietic and nonhemopoietic cells for the ability to produce eotaxin protein. Regardless of various conditioning, we failed to determine any significant eotaxin generation by peripheral leukocytes and vein endothelial cells (less than 20 pg/ml). A small amount of immunoreactive eotaxin was detected in cultures of A549 bronchial epithelial cell line cells. In contrast, dermal fibroblasts were capable of generating extremely high, and potentially biologically relevant, amounts of eotaxin protein (on the order of ng/ml). The eotaxin generation was induced by tumour necrosis factor alpha (TNF-alpha) or IL-4, and the production was drastically increased by combined use of these cytokines. Because fibroblasts are ideally situated within the interstium at the sites of allergic responses, our finding that these cells represent an important cellular source of eotaxin suggests that fibroblast-derived eotaxin may act to regulate eosinophil recruitment in a paracrine fashion.

Advances in the immunobiology of eosinophils and their role in disease

Eosinophils play a protective role in host immunity to infections by parasitic worms and, detrimentally, are involved in the pathophysiology of asthma and other allergic diseases. Airway inflammation is central to the pathology of asthma and is characterized by infiltration of the bronchial mucosa by large numbers of proinflammatory cells, amongst which the eosinophil is prominent despite being a minority constituent of circulating leukocytes. Crucial steps in eosinophilic inflammation include augmented production of eosinophils in the bone marrow, their increased release into the circulation, and their selective accumulation in the conducting airways. The eosinophil has a potent armory of proinflammatory mediators, including cytotoxic granule proteins, cytokines and lipid mediators with considerable potential to initiate and sustain an inflammatory response. Thus there is much interest in the elucidation of the mechanisms responsible for eosinophil accumulation, persistence, activation and ultimate fate. This article reviews our current understanding of the role of the eosinophil in human disease and the immunobiology of this important proinflammatory cell.

Backbone dynamics of the human CC chemokine eotaxin: fast motions, slow motions, and implications for receptor binding

Eotaxin is a member of the chemokine family of about 40 proteins that induce cell migration. Eotaxin binds the CC chemokine receptor CCR3 that is highly expressed by eosinophils, and it is considered important in the pathology of chronic respiratory disorders such as asthma. The high resolution structure of eotaxin is known. The 74 amino acid protein has two disulfide bridges and shows a typical chemokine fold comprised of a core of three antiparallel beta-strands and an overlying alpha-helix. In this paper, we report the backbone dynamics of eotaxin determined through 15N-T1, T2, and [1H]-15N nuclear Overhauser effect heteronuclear multidimensional NMR experiments. This is the first extensive study of the dynamics of a chemokine derived from 600, 500, and 300 MHz NMR field strengths. From the T1, T2, and NOE relaxation data, parameters that describe the internal motions of eotaxin were derived using the Lipari-Szabo model free analysis. The most ordered regions of the protein correspond to the known secondary structure elements. However, surrounding the core, the regions known to be functionally important in chemokines show a range of motions on varying timescales. These include extensive subnanosecond to picosecond motions in the N-terminus, C-terminus, and the N-loop succeeding the disulfides. Analysis of rotational diffusion anisotropy of eotaxin and chemical exchange terms at multiple fields also allowed the confident identification of slow conformational exchange through the "30s" loop, disulfides, and adjacent residues. In addition, we show that these motions may be attenuated in the dimeric form of a synthetic eotaxin. The structure and dynamical basis for eotaxin receptor binding is discussed in light of the dynamics data.

C-C Chemokines in Allergen-Induced Late-Phase Cutaneous Responses in Atopic Subjects: Association of Eotaxin with Early 6-Hour Eosinophils, and of Eotaxin-2 and Monocyte Chemoattractant Protein-4 with the Later 24-Hour Tissue Eosinophilia, and Relationship to Basophils and Other C-C Chemokines (Monocyte Chemoattractant Protein-3 and RANTES)

The relationship of expression of the C-C chemokines eotaxin, eotaxin 2, RANTES, monocyte chemoattractant protein-3 (MCP-3), and MCP-4 to the kinetics of infiltrating eosinophils, basophils, and other inflammatory cells was examined in allergen-induced, late-phase allergic reactions in the skin of human atopic subjects. EG2+ eosinophils peaked at 6 h and correlated significantly with eotaxin mRNA and protein, whereas declining eosinophils at 24 h correlated significantly with eotaxin-2 and MCP-4 mRNA. In contrast, no significant correlations were observed between BB1+ basophil infiltrates, which peaked at 24 h, and expression of eotaxin, eotaxin-2, RANTES, MCP-3, and MCP-4 or elastase+ neutrophils (6-h peak), CD3+ and CD4+ T cells (24 h), and CD68+ macrophages (72 h). Furthermore, 83% of eosinophils, 40% of basophils, and 1% of CD3+ cells expressed the eotaxin receptor CCR3, while eotaxin protein was expressed by 43% of macrophages, 81% of endothelial cells, and 6% of T cells (6%). These data suggest that 1) eotaxin has a role in the early 6-h recruitment of eosinophils, while eotaxin-2 and MCP-4 appear to be involved in later 24-h infiltration of these CCR3+ cells; 2) different mechanisms may guide the early vs late eosinophilia; and 3) other chemokines and receptors may be involved in basophil accumulation of allergic tissue reactions in human skin.

Chemokines and allergic disease

Understanding the chemokine network has become one of the great challenges for researchers interested in inflammatory mechanisms and inflammation-based diseases. The complexity and diversity of the system provide not only a daunting task for its comprehension but also numerous opportunities for development of new, targeted therapies. It is now certain that chemokines are involved as important mediators of allergic inflammation; the fine details and scope of their roles are now under investigation. Presumably, because of distinct pressures on the immune systems of people living in different geographic regions, genetic variation of ligands, receptors, and regulatory regions in the network have emerged. Establishing the roles of these polymorphisms in determining disease susceptibility or progression among individuals and in distinct ethnic groups will provide a basis for improved understanding and treatment of allergic diseases.

Hodgkin/Reed-Sternberg Cells Induce Fibroblasts to Secrete Eotaxin, a Potent Chemoattractant for T Cells and Eosinophils

Hodgkin’s disease is histopathologically characterized by the relative scarcity of neoplastic Hodgkin and Reed-Sternberg cells and for yet unknown reasons by an abundant reactive background of T lymphocytes and often eosinophils. Eotaxin is a CC-chemokine attracting eosinophils and T helper 2 (Th2) cells in allergic inflammation. We now report that eotaxin is strongly expressed in fibroblasts of Hodgkin’s disease tissues, whereas Hodgkin/Reed-Sternberg cells do not express this chemokine. In tissue culture, Hodgkin’s disease tumor cells induce eotaxin expression in cocultured dermal fibroblasts in a concentration leading to a specific chemotactic response of a Th2 cell clone. Production of tumor necrosis factor- (TNF-) by Hodgkin/Reed-Sternberg cells appears to be responsible for this induction, because blocking of TNF- by neutralizing antibodies prevented fibroblast eotaxin expression. Our data suggest that eotaxin is involved in the pathobiology of Hodgkin’s disease by contributing to eosinophil and T-lymphocyte recruitment.

Hodgkin/Reed-Sternberg Cells Induce Fibroblasts to Secrete Eotaxin, a Potent Chemoattractant for T Cells and Eosinophils

Hodgkin’s disease is histopathologically characterized by the relative scarcity of neoplastic Hodgkin and Reed-Sternberg cells and for yet unknown reasons by an abundant reactive background of T lymphocytes and often eosinophils. Eotaxin is a CC-chemokine attracting eosinophils and T helper 2 (Th2) cells in allergic inflammation. We now report that eotaxin is strongly expressed in fibroblasts of Hodgkin’s disease tissues, whereas Hodgkin/Reed-Sternberg cells do not express this chemokine. In tissue culture, Hodgkin’s disease tumor cells induce eotaxin expression in cocultured dermal fibroblasts in a concentration leading to a specific chemotactic response of a Th2 cell clone. Production of tumor necrosis factor- (TNF-) by Hodgkin/Reed-Sternberg cells appears to be responsible for this induction, because blocking of TNF- by neutralizing antibodies prevented fibroblast eotaxin expression. Our data suggest that eotaxin is involved in the pathobiology of Hodgkin’s disease by contributing to eosinophil and T-lymphocyte recruitment.

Up-Regulation of CCR2 Chemokine Receptor Expression and Increased Susceptibility to the Multitropic HIV Strain 89.6 in Monocytes Exposed to Glucocorticoid Hormones

Glucocorticoid hormones (GC) are potent antiinflammatory agents widely used in the treatment of diverse human diseases. The present study was aimed at assessing the effect of GC on chemokine receptor expression in human monocytes. Dexamethasone (Dex) up-regulated mRNA expression of the monocyte chemotactic protein (MCP-1, CCL2) chemokine receptor CCR2. The effect was selective in that other chemokine receptors were not substantially affected. Stimulation by Dex was observed after 4 h of exposure at concentrations of 10−7 to 10−5 M. Steroids devoid of GC activity were inactive, and the GC receptor antagonist, RU486, inhibited stimulation. Dex did not affect the rate of nuclear transcription, but augmented the CCR2 mRNA half-life. Augmentation of CCR2 expression by Dex was associated with increased chemotaxis. Finally, Dex treatment induced productive replication of the HIV strain 89.6, which utilizes CCR2 as entry coreceptor, in freshly isolated monocytes. Together with previous findings, these results indicate that at least certain pro- and antiinflammatory molecules have reciprocal and divergent effects on expression of a major monocyte chemoattractant, MCP-1, and of its receptor (CCR2). Augmentation of monocyte CCR2 expression may underlie unexplained in vivo effects of GC as well as some of their actions on HIV infection.

Interleukin (IL)-5 downregulates tumor necrosis factor (TNF)-induced eotaxin messenger RNA (mRNA) expression in eosinophils. Induction of eotaxin mRNA by TNF and IL-5 in eosinophils

An eotaxin is a chemoattractant specific for eosinophils that are known to play a role in helminth infection and allergic responses. Although several cellular sources have been reported to produce eotaxin, it would be interesting to know whether eosinophils are able to produce their own eotaxin and participate in recruitment of themselves in response to inflammation. To this end, a cloned eotaxin complementary DNA was transcribed in vitro to use as a probe for detecting eotaxin messenger RNA (mRNA), and eotaxin protein levels were determined by enzyme-linked immunosorbent assay. Eotaxin mRNA was, as analyzed by in situ hybridization, rarely detectable in unstimulated eosinophils, but was strongly induced in eosinophils when stimulated with tumor necrosis factor (TNF). Interleukin (IL)-5, which is known to be a major factor of eosinophil survival in vivo and in vitro, was also able to induce a modest level of eotaxin mRNA but inhibited TNF-induced eotaxin mRNA expression in a dose-response manner. Dexamethasone inhibited TNF-induced eotaxin mRNA expression. This result was consistent with that from reverse transcription/polymerase chain reaction followed by Southern blot analysis. Unlike the little expression of eotaxin mRNA in the absence of stimuli, the measurement of eotaxin protein revealed that a considerable amount of eotaxin protein was constitutively produced in unstimulated eosinophils. Its expression was upregulated by TNF and IL-5 as well. However, the inhibitory effect of IL-5 on TNF-mediated eotaxin protein production was not as pronounced as that on eotaxin mRNA induction. Collectively, these data reflect the complex physiology of eosinophils in the expression of eotaxin gene upon the exposure to their survival and/or death factors.

Eosinophil chemotaxis by chemokines: a study by a simple photometric assay

BACKGROUND

The effects of a panel of 15 chemokines on eosinophil chemotaxis were studied by a new photometric assay which is both less tedious and less laborious than the conventional manual counting methods. Approximately 40 chemokines have been identified to date, but there is little information on the eosinophil migration-inducing ability of chemokines other than CC chemokine receptor (CCR) 3 ligands.

METHODS

Eosinophil migration was measured by the Boyden chamber technique with a 96-well multiwell chamber and polycarbonate membrane filter. Eosinophil migration was assessed by determination of the eosinophil peroxidase (EPO) activity, and photometric measurement was performed with a microtiter plate reader.

RESULTS

The assay was sensitive enough to detect 200 eosinophils, and the time required was within 4 h. CCR3 ligands, i.e., regulated on activation normal T-cell expressed and secreted (RANTES), eotaxin, eotaxin-2, and monocyte chemoattractant protein (MCP)-3, induced significant migration, while other chemokines showed no significant migration-inducing ability. Although the chemotaxis induction by these chemokines was efficiently inhibited by anti-CCR3 mAb, anti-CCR1 mAb failed to show any inhibitory effects.

CONCLUSIONS

The photometric assay is suitable for analyzing a large number of samples. CCR3 ligands are the most important chemokines inducing eosinophil chemotaxis; thus, CCR3 represents a possible therapeutic target for the treatment of allergic diseases.

Immunopathogenesis of human gastrointestinal infection by Anisakis simplex

BACKGROUND

Anisakis simplex is a parasite of fish, and in the case of human infestation, it should be considered as a possible cause of gastrointestinal disease, especially in countries where raw or undercooked fish is a frequent food. Clinical features of anisakiasis may simulate acute abdominal pain, such as that found in patients with gastric ulcers, appendicitis, and Crohn's disease. Furthermore, many cases of anisakiasis are diagnosed as eosinophilic gastroenteritis, which is a broad term for a specific disease.

OBJECTIVE

The purpose of this study was to investigate the immunopathogenesis of human gastrointestinal infestation by A simplex.

METHODS

Thirteen intestinal biopsy specimens from patients with anisakiasis were analyzed for the presence of messenger (m)RNA for different cytokines and inflammatory mediators by RT-PCR. Specific IgE, eosinophil cationic protein, eosinophil protein X, and tryptase levels were measured in each patient's serum. Also, cell cultures were set up with lymphocytes from some patients and stimulated in vitro with Anisakis and Ascaris antigens.

RESULTS

We performed immunologic phenotyping in 13 patients. All patients underwent biopsy after emergency surgery caused by episodes of acute abdominal pain. In all cases inflammatory infiltrate composed of eosinophils and lymphocytes was found in the intestinal wall. We demonstrated that after infestation, a T(H2)-type immune response occurred. Also, major basic protein, nitric oxide, and eotaxin were found in the tissue, and eosinophil cationic protein and eosinophil protein X levels were elevated in sera.

CONCLUSION

These data and in vitro lymphocyte cultures indicate that a T(H2) mechanism plays an important role in the inflammatory infiltrate produced by the anchorage of parasites in the gastrointestinal wall.

Airway epithelial cell-induced activation of monocytes and eosinophils in respiratory syncytial viral infection

The early inflammatory events in respiratory syncytial viral (RSV) infection are likely to be crucial in the development of clinical disease, which is characterized by bronchiolitis with mononuclear cell inflammation, some eosinophil involvement and airway hyperreactivity. Since RSV replication is restricted to airway epithelial cells, our working hypothesis is that inflammatory cell recruitment by the infected cells will set the stage for late immunopathology. We have identified the selective induction and release of mononuclear cell and eosinophil-attracting beta-chemokines MIP-1alpha and RANTES, but not eotaxin, by RSV-infected airway epithelial cells and herein demonstrated the recruitment of eosinophils and monocytes, but not neutrophils, in response to chemokines produced by infected epithelial cells during viral replication and dissemination. The chemotactic response of both eosinophils and monocytes was inhibited by antibodies to RANTES but not to MIP-1alpha. Interaction of eosinophils or monocytes with RSV-infected epithelial cells resulted in the production of additional beta-chemokines MCP-1 and MIP-1beta, and increased levels of MIP-1alpha. The monocyte containing cultures produced >10 fold the amount of these chemokines compared to eosinophil containing cultures. On the other hand, the levels of RANTES and the lack of eotaxin were not altered in the cocultures, RSV-infected monocytes appeared to be the main source of MIP-1alpha and MIP-1beta, while MCP-1 was derived from monocytes as well as epithelial cells following coculture. These data implicate RANTES as the primary chemokine responsible for selectively recruiting eosinophils and monocytes to the site of RSV infection. This inflammatory response results in the production of high levels of additional chemokines capable of setting up a full-fledged inflammatory response including lymphocytes.

Chemokines and chemokine receptors: their role in allergic airway disease

One of the hallmarks of allergic pulmonary disorders is the accumulation of an abnormally large number of leukocytes including eosinophils, neutrophils, lymphocytes, basophils, and macrophages in the lung. There is now substantial evidence that eosinophils, under the control of T lymphocytes, are major effector cells in the pathogenesis of asthma. Therefore, understanding the mechanisms by which eosinophils accumulate and are activated in tissues is a fundamental question very relevant to allergic diseases. Another characteristic of allergic inflammation is the activation of leukocytes resulting in the release of biologically active mediators, such as histamine from mast cells and basophils. It is now apparent that chemokines are potent leukocyte chemoattractants, cellular activating factors, histamine releasing factors, and regulators of homeostatic immunity, making them particularly important in the pathogenesis of airway inflammation in asthma. In this regard, chemokines are attractive new therapeutic targets for the treatment of allergic disease. This article focuses on recently emerging data on the importance of chemokines and their receptors in allergic airway inflammation.

Monocyte Chemoattractant Protein-1 Mediates Cockroach Allergen-Induced Bronchial Hyperreactivity in Normal But Not CCR2−/− Mice: The Role of Mast Cells

Bronchial eosinophil and mononuclear cell infiltrates are a hallmark of the asthmatic lung and are associated with the induction of reversible airway hyperreactivity. In these studies, we have found that monocyte chemotactic protein-1 (MCP-1), a CC (β) chemokine, mediates airway hyperreactivity in normal and allergic mice. Using a murine model of cockroach Ag-induced allergic airway inflammation, we have demonstrated that anti-MCP-1 Abs inhibit changes in airway resistance and attenuate histamine release into the bronchoalveolar lavage, suggesting a role for MCP-1 in mast cell degranulation. In normal mice, instillation of MCP-1 induced prolonged airway hyperreactivity and histamine release. In addition, MCP-1 directly induced pulmonary mast cell degranulation in vitro. These latter effects would appear to be selective because no changes were observed when macrophage-inflammatory protein-1α, eotaxin, or MCP-3 were instilled into the airways of normal mice or when mast cells were treated in vitro. Airway hyperreactivity was mediated by MCP-1 through CCR2 because allergen-induced as well as direct MCP-1 instilled-induced changes in airway hyperreactivity were significantly attenuated in CCR2 −/− mice. The neutralization of MCP-1 in allergic animals and instillation of MCP-1 in normal animals was related to leukotriene C4 levels in the bronchoalveolar lavage and was directly induced in pulmonary mast cells by MCP-1. Thus, these data identify MCP-1 and CCR2 as potentially important therapeutic targets for the treatment of hyperreactive airway disease.

A Novel Human CC Chemokine, Eotaxin-3, Which Is Expressed in IL-4-Stimulated Vascular Endothelial Cells, Exhibits Potent Activity Toward Eosinophils

IL-4 has been shown to be involved in the accumulation of leukocytes, especially eosinophils, at sites of inflammation by acting on vascular endothelial cells. To identify novel molecules involved in the IL-4-dependent eosinophil extravasation, cDNA prepared from HUVEC stimulated with IL-4 was subjected to differential display analysis, which revealed a novel CC chemokine designated as eotaxin-3. The human eotaxin-3 gene has been localized to chromosome 7q11.2, unlike most other CC chemokine genes. The predicted mature protein of 71 aa showed 27–42% identity to other human CC chemokines. The recombinant protein induced a transient increase in the cytosolic Ca2+ concentration and in vitro chemotaxis on eosinophils. Furthermore, in cynomolgus monkeys, the accumulation of eosinophils was observed at the sites where the protein was injected. Eotaxin-3 inhibited the binding of 125I-eotaxin, but not 125I-macrophage inflammatory protein-1α, to eosinophils and acted on cell lines transfected with CCR-3, suggesting that eotaxin-3 recognized CCR-3. IL-13 as well as IL-4 up-regulated eotaxin-3 mRNA in HUVEC, whereas neither TNF-α, IL-1β, IFN-γ, nor TNF-α plus IFN-γ did. The expression profile of eotaxin-3 is different from those of eotaxin, RANTES, and monocyte chemoattractant protein-4, which are potent eosinophil-selective chemoattractants and are induced by either TNF-α or TNF-α plus IFN-γ. These results suggest that eotaxin-3 may contribute to the eosinophil accumulation in atopic diseases.

Prevention of experimental autoimmune encephalomyelitis by MIP-1alpha and MCP-1 naked DNA vaccines

Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated autoimmune disease of the central nervous system (CNS). RT-PCR verified by Southern blotting and sequencing of PCR products of two C-C chemokines, MIP-1alpha and MCP-1, was performed on brain samples from EAE rats to evaluate mRNA transcription of these chemokines at different stages of disease. mRNA transcription in of each chemokine peaked after the onset of disease and declined during its remission. Each PCR product was then used as a construct for naked DNA vaccination. The subsequent in vivo immune response to MIP-1alpha or MCP-1 DNA vaccines prevented EAE. Immunization of CFA without the encephalitogenic epitope did not elicit an anti-C-C chemokine regulatory response in DNA- vaccinated rats. Thus, modulation of EAE with C-C chemokine DNA vaccines is dependent on targeting chemokines that are highly transcribed at the site of inflammation at the onset of disease.

Glucocorticosteroids Inhibit mRNA Expression for Eotaxin, Eotaxin-2, and Monocyte-Chemotactic Protein-4 in Human Airway Inflammation with Eosinophilia

How eosinophils are preferentially recruited to inflammatory sites remains elusive, but increasing evidence suggests that chemokines that bind to the CCR3 participate in this process. In this study, we investigated the transcript levels and chemotactic activity of CCR3-binding chemokines in nasal polyps, a disorder often showing prominent eosinophilia. We found that mRNA expression for eotaxin, eotaxin-2, and monocyte-chemotactic protein-4 was significantly increased in nasal polyps compared with turbinate mucosa from the same patients, or histologically normal nasal mucosa from control subjects. Interestingly, the novel CCR3-specific chemokine, eotaxin-2, showed the highest transcript levels. Consistent with these mRNA data, polyp tissue fluid exhibited strong chemotactic activity for eosinophils that was significantly inhibited by a blocking Ab against CCR3. When patients were treated systemically with glucocorticosteroids, the mRNA levels in the polyps were reduced to that found in turbinate mucosa for all chemokines. Together, these findings suggested an important role for CCR3-binding chemokines in eosinophil recruitment to nasal polyps. Such chemokines, therefore, most likely contribute significantly in the pathogenesis of eosinophil-related disorders; and the reduced chemokine expression observed after steroid treatment might reflect, at least in part, how steroids inhibit tissue accumulation of eosinophils.

Activation of Mitogen-Activated Protein Kinase Regulates Eotaxin-Induced Eosinophil Migration

Eotaxin is a potent eosinophil chemoattractant that plays an important role in regulating eosinophil tissue levels both in healthy individuals and in diseases associated with significant eosinophil infiltrates, such as the allergic inflammation observed in asthma. Here, we demonstrate that treatment of eosinophils with eotaxin induces the phosphorylation of the mitogen-activated protein kinases (MAPKs) p42 and p44, leading to kinase activation. Blockade of MAPK activation by the MAPK kinase inhibitor PD98059 leads to a dramatic decrease in eotaxin-induced eosinophil rolling in vivo and chemotaxis in vitro. This blockade in the leukocyte migration process is consistent with the observed inhibition of actin polymerization and rearrangement within the eosinophil following treatment with MAPK inhibitor. It is suggested, therefore, that the intrinsic mechanism of eotaxin-induced eosinophil rolling and migration involves activation of the p42/p44 MAPK, possibly through regulation of the cytoskeletal rearrangements necessary for chemotaxis.