CC chemokine receptor-3 undergoes prolonged ligand-induced internalization

CCR3-dependent eosinophil recruitment is regulated by sialyltransferase ST3Gal-IV

Eosinophil recruitment is a pathological hallmark of many allergic and helminthic diseases. Here, we investigated chemokine receptor CCR3-induced eosinophil recruitment in sialyltransferase St3gal4-/- mice. We found a marked decrease in eosinophil extravasation into CCL11-stimulated cremaster muscles and into the inflamed peritoneal cavity of St3gal4-/- mice. Ex vivo flow chamber assays uncovered reduced adhesion of St3gal4-/- compared to wild type eosinophils. Using flow cytometry, we show reduced binding of CCL11 to St3gal4-/- eosinophils. Further, we noted reduced binding of CCL11 to its chemokine receptor CCR3 isolated from St3gal4-/- eosinophils. This was accompanied by almost absent CCR3 internalization of CCL11-stimulated St3gal4-/- eosinophils. Applying an ovalbumin-induced allergic airway disease model, we found a dramatic reduction in eosinophil numbers in bronchoalveolar lavage fluid following intratracheal challenge with ovalbumin in St3gal4-deficient mice. Finally, we also investigated tissue-resident eosinophils under homeostatic conditions and found reduced resident eosinophil numbers in the thymus and adipose tissue in the absence of ST3Gal-IV. Taken together, our results demonstrate an important role of ST3Gal-IV in CCR3-induced eosinophil recruitment in vivo rendering this enzyme an attractive target in reducing unwanted eosinophil infiltration in various disorders including allergic diseases.

Eosinophils as potential biomarkers in respiratory viral infections

Eosinophils are bone marrow-derived granulocytes that, under homeostatic conditions, account for as much as 1-3% of peripheral blood leukocytes. During inflammation, eosinophils can rapidly expand and infiltrate inflamed tissues, guided by cytokines and alarmins (such as IL-33), adhesion molecules and chemokines. Eosinophils play a prominent role in allergic asthma and parasitic infections. Nonetheless, they participate in the immune response against respiratory viruses such as respiratory syncytial virus and influenza. Notably, respiratory viruses are associated with asthma exacerbation. Eosinophils release several molecules endowed with antiviral activity, including cationic proteins, RNases and reactive oxygen and nitrogen species. On the other hand, eosinophils release several cytokines involved in homeostasis maintenance and Th2-related inflammation. In the context of SARS-CoV-2 infection, emerging evidence indicates that eosinophils can represent possible blood-based biomarkers for diagnosis, prognosis, and severity prediction of disease. In particular, eosinopenia seems to be an indicator of severity among patients with COVID-19, whereas an increased eosinophil count is associated with a better prognosis, including a lower incidence of complications and mortality. In the present review, we provide an overview of the role and plasticity of eosinophils focusing on various respiratory viral infections and in the context of viral and allergic disease comorbidities. We will discuss the potential utility of eosinophils as prognostic/predictive immune biomarkers in emerging respiratory viral diseases, particularly COVID-19. Finally, we will revisit some of the relevant methods and tools that have contributed to the advances in the dissection of various eosinophil subsets in different pathological settings for future biomarker definition.

Acupuncture Alleviates Menstrual Pain in Rat Model via Suppressing Eotaxin/CCR3 Axis to Weak EOS-MC Activation

Introduction

Emerging data show that chemokine-mediated inflammation is involved in the occurrence and maintenance of pain. Recent evidence suggests that eotaxin levels rise when dysmenorrhea happens. The purpose of this study is to investigate whether eotaxin/CC chemokine receptor 3 (CCR3) axis, a key regulatory pathway for eosinophils (EOS) recruitment, is involved in acupuncture analgesia for dysmenorrhea.

Methods

After the cold congealing dysmenorrhea (CCD) rat model prepared, animals received perpendicular needling (PN) and transverse needling (TN) at SP6, respectively, for 20 min. The CCR3 agonist CCL11 was administered 30 min prior to acupuncture. Pain behavior was assessed via a writhing response. The uterine contraction test was detected by an electrophysiological method. Eotaxin, histamine (HIS), and interleukin-6 (IL-6) levels were evaluated by ELISA. The expression of CCR3 and histamine H1 receptor (H1R) was analyzed by RT-qPCR and Western blot. The expression of EOS, mast cells (MCs), eosinophil peroxidase (EPO), and eosinophil cationic protein (ECP) was assessed by hematoxylin-eosin staining (HE), Toluidine Blue staining (TB), and immunohistochemistry, respectively.

Results

Acupuncture prominently attenuated the menstrual pain in CCD rats, particularly TN technique. Electrophysiological recording data showed that the increased uterine contractility was ameliorated by acupuncture. In addition, TN decreased the release of eotaxin, HIS, IL-6, and the expression of CCR3 and H1R. HE, TB staining, and immunohistochemistry experiments showed that the increased expression of EOS, MCs, EPO, and ECP in uterine tissues was reversed by TN. Furthermore, we found that the effects of TN against CCD-induced menstrual pain, increased ECP expression, and HIS level were abolished by CCL11.

Conclusion

TN alleviated menstrual pain by improving the uterine inflammatory environment via suppressing eotaxin/CCR3 axis to weak EOS-MC activation in CCD rats. The study findings support the acupuncture as a promising approach for dysmenorrhea, meanwhile, indicating the importance of performing appropriate needling technique.

Stromal CCL5 Promotes Breast Cancer Progression by Interacting with CCR3 in Tumor Cells

Chemokines secreted from stromal cells have important roles for interactions with carcinoma cells and regulating tumor progression. C-C motif chemokine ligand (CCL) 5 is expressed in various types of stromal cells and associated with tumor progression, interacting with C-C chemokine receptor (CCR) 1, 3 and 5 expressed in tumor cells. However, the expression on CCL5 and its receptors have so far not been well-examined in human breast carcinoma tissues. We therefore immunolocalized CCL5, as well as CCR1, 3 and 5, in 111 human breast carcinoma tissues and correlated them with clinicopathological characteristics. Stromal CCL5 immunoreactivity was significantly correlated with the aggressive phenotype of breast carcinomas. Importantly, this tendency was observed especially in the CCR3-positive group. Furthermore, the risk of recurrence was significantly higher in the patients with breast carcinomas positive for CCL5 and CCR3 but negative for CCR1 and CCR5, as compared with other patients. In summary, the CCL5-CCR3 axis might contribute to a worse prognosis in breast cancer patients, and these findings will contribute to a better understanding of the significance of the CCL5/CCRs axis in breast carcinoma microenvironment.

Eosinophilic recruitment in thermally injured older animals is associated with worse outcomes and higher conversion to full thickness burn

BACKGROUND

Partial burn injury in older patients is associated with higher rates of morbidity, mortality, and conversion to full thickness burn (Finnerty et al., 2009; Pham et al., 2009). Both human and mouse models demonstrate an altered systemic immune response in older subjects, however less is known about the localized response (Jeschke et al., 2016; Farinas et al., 2018; Mohs et al., 2017). We hypothesized that a mouse model could demonstrate differences in the localized inflammatory response of the old.

METHODS

Six old (66 weeks) and young (8 weeks) mice received partial thickness thermal burns. Localized and systemic expression of nine chemokines (TNFalpha, MCP-1, MIP-2, S100A9, EGF, IL-10, RANTES, G-CSF, and EOTAXIN) were evaluated at day 3 after burn using Luminex analysis. Vimentin immunostaining was used to evaluate injury depth.

RESULTS

Vimentin staining demonstrated increased burn depth in old mice (449±38μm) as compared to young (166±18μm) (p<0.05). Both groups exhibited increased localized expression of EOTAXIN after burn (p<0.05), however expression in old mice (83.6±6.1pg/ml) was lower than that of young (126.8±18.7pg/ml) (p<0.05). Systemically, however, old mice had increased baseline EOTAXIN expression (1332.40±110.78pg/ml) compared to young (666.12±45.8pg/ml) (p<0.005).

CONCLUSIONS

EOTAXIN is one of the primary chemoattractants for selective eosinophilic recruitment and activation. While eosinophils are important for wound healing, a hyperactive eosinophilic response can result in tissue damage. We hypothesize that the increased baseline serum EOTAXIN in the old may prime their hyperactive response, and may contribute to their worse clinical outcomes. Long-term eosinophil activation requires further study, however our findings indicate a role for EOTAXIN and eosinophils in burn response.

Rat cytomegalovirus-encoded γ-chemokine vXCL1 is a highly adapted, species-specific agonist for rat XCR1-positive dendritic cells

Dendritic cells (DCs) expressing the chemokine receptor XCR1 are specialized in antigen cross-presentation to control infections with intracellular pathogens. XCR1-positive (XCR1⁺) DCs are attracted by XCL1, a γ-chemokine secreted by activated CD8⁺ T cells and natural killer cells. Rat cytomegalovirus (RCMV) is the only virus known to encode a viral XCL1 analog (vXCL1) that competes for XCR1 binding with the endogenous chemokine. Here we show that vXCL1 from two different RCMV strains, as well as endogenous rat XCL1 (rXCL1) bind to and induce chemotaxis exclusively in rat XCR1⁺ DCs. Whereas rXCL1 activates the XCR1 Gi signaling pathway in rats and humans, both of the vXCL1s function as species-specific agonists for rat XCR1. In addition, we demonstrate constitutive internalization of XCR1 in XCR1-transfected HEK293A cells and in splenic XCR1⁺ DCs. This internalization was independent of β-arrestin 1 and 2 and was enhanced after binding of vXCL1 and rXCL1; however, vXCL1 appeared to be a stronger agonist. These findings suggest a decreased surface expression of XCR1 during DC cultivation at 37°C, and subsequent impairment of chemotactic activity and XCR1⁺ DC function.

Severe Eosinophilic Asthma

Asthma is a heterogeneous disease with varying severity. Severe asthma is a subject of constant research because it greatly affects patients’ quality of life, and patients with severe asthma experience symptoms, exacerbations, and medication side effects. Eosinophils, although at first considered insignificant, were later specifically associated with features of the ongoing inflammatory process in asthma, particularly in the severe case. In this review, we discuss new insights into the pathogenesis of severe asthma related to eosinophilic inflammation and the pivotal role of cytokines in a spectrum that is usually referred to as “T2-high inflammation” that accounts for almost half of patients with severe asthma. Recent literature is summarized as to the role of eosinophils in asthmatic inflammation, airway remodeling, and airway hypersensitivity. Major advances in the management of severe asthma occurred the past few years due to the new targeted biological therapies. Novel biologics that are already widely used in severe eosinophilic asthma are discussed, focusing on the choice of the right treatment for the right patient. These monoclonal antibodies primarily led to a significant reduction of asthma exacerbations, as well as improvement of lung function and patient quality of life.

Novel peptide nanoparticle-biased antagonist of CCR3 blocks eosinophil recruitment and airway hyperresponsiveness

BACKGROUND

Chemokine signaling through CCR3 is a key regulatory pathway for eosinophil recruitment into tissues associated with allergic inflammation and asthma. To date, none of the CCR3 antagonists have shown efficacy in clinical trials. One reason might be their unbiased mode of inhibition that prevents receptor internalization, leading to drug tolerance.

OBJECTIVE

We sought to develop a novel peptide nanoparticle CCR3 inhibitor (R321) with a biased mode of inhibition that would block G protein signaling but enable or promote receptor internalization.

METHODS

Self-assembly of R321 peptide into nanoparticles and peptide binding to CCR3 were analyzed by means of dynamic light scattering and nuclear magnetic resonance. Inhibitory activity on CCR3 signaling was assessed in vitro by using flow cytometry, confocal microscopy, and Western blot analysis in a CCR3+ eosinophil cell line and blood eosinophils. In vivo effects of R321 were assessed by using a triple-allergen mouse asthma model.

RESULTS

R321 self-assembles into nanoparticles and binds directly to CCR3, altering receptor function. Half-maximal inhibitory concentration values for eotaxin-induced chemotaxis of blood eosinophils are in the low nanomolar range. R321 inhibits only the early phase of extracellular signal-regulated kinase 1/2 activation and not the late phase generally associated with β-arrestin recruitment and receptor endocytosis, promoting CCR3 internalization and degradation. In vivo R321 effectively blocks eosinophil recruitment into the blood, lungs, and airways and prevents airway hyperresponsiveness in a mouse eosinophilic asthma model.

CONCLUSIONS

R321 is a potent and selective antagonist of the CCR3 signaling cascade. Inhibition through a biased mode of antagonism might hold significant therapeutic promise by eluding the formation of drug tolerance.

Using biomaterials to modulate chemotactic signaling for central nervous system repair

Chemotaxis enables cellular communication and movement within the body. This review focuses on exploiting chemotaxis as a tool for repair of the central nervous system (CNS) damaged from injury and/or degenerative diseases. Chemokines and factors alone may initiate repair following CNS injury/disease, but exogenous administration may enhance repair and promote regeneration. This review will discuss critical chemotactic molecules and factors that may promote neural regeneration. Additionally, this review highlights how biomaterials can impact the presentation and delivery of chemokines and growth factors to alter the regenerative response.

Functional expression of CCL8 and its interaction with chemokine receptor CCR3

Background

Chemokines and their cognate receptors play important role in the control of leukocyte chemotaxis, HIV entry and other inflammatory diseases. Developing an effcient method to investigate the functional expression of chemokines and its interactions with specific receptors will be helpful to asses the structural and functional characteristics as well as the design of new approach to therapeutic intervention.

Results

By making systematic optimization study of expression conditions, soluble and functional production of chemokine C-C motif ligand 8 (CCL8) in Escherichia coli (E. coli) has been achieved with approx. 1.5 mg protein/l culture. Quartz crystal microbalance (QCM) analysis exhibited that the purified CCL8 could bind with C-C chemokine receptor type 3 (CCR3) with dissociation equilibrium constant (K_D) as 1.2 × 10⁻⁷ M in vitro. Obvious internalization of CCR3 in vivo could be detected in 1 h when exposed to 100 nM of CCL8. Compared with chemokine C-C motif ligand 11 (CCL11) and chemokine C-C motif ligand 24 (CCL24), a weaker chemotactic effect of CCR3 expressing cells was observed when induced by CCL8 with same concentration.

Conclusion

This study delivers a simple and applicable way to produce functional chemokines in E. coli. The results clearly confirms that CCL8 can interact with chemokine receptor CCR3, therefore, it is promising area to develop drugs for the treatment of related diseases.

Electronic supplementary material

The online version of this article (10.1186/s12865-017-0237-5) contains supplementary material, which is available to authorized users.

Host lung immunity is severely compromised during tropical pulmonary eosinophilia: role of lung eosinophils and macrophages

Eosinophils play a central role in the pathogenesis of tropical pulmonary eosinophilia, a rare, but fatal, manifestation of filariasis. However, no exhaustive study has been done to identify the genes and proteins of eosinophils involved in the pathogenesis of tropical pulmonary eosinophilia. In the present study, we established a mouse model of tropical pulmonary eosinophilia that mimicked filarial manifestations of human tropical pulmonary eosinophilia pathogenesis and used flow cytometry-assisted cell sorting and real-time RT-PCR to study the gene expression profile of flow-sorted, lung eosinophils and lung macrophages during tropical pulmonary eosinophilia pathogenesis. Our results show that tropical pulmonary eosinophilia mice exhibited increased levels of IL-4, IL-5, CCL5, and CCL11 in the bronchoalveolar lavage fluid and lung parenchyma along with elevated titers of IgE and IgG subtypes in the serum. Alveolar macrophages from tropical pulmonary eosinophilia mice displayed decreased phagocytosis, attenuated nitric oxide production, and reduced T-cell proliferation capacity, and FACS-sorted lung eosinophils from tropical pulmonary eosinophilia mice upregulated transcript levels of ficolin A and anti-apoptotic gene Bcl2,but proapoptotic genes Bim and Bax were downregulated. Similarly, flow-sorted lung macrophages upregulated transcript levels of TLR-2, TLR-6, arginase-1, Ym-1, and FIZZ-1 but downregulated nitric oxide synthase-2 levels, signifying their alternative activation. Taken together, we show that the pathogenesis of tropical pulmonary eosinophilia is marked by functional impairment of alveolar macrophages, alternative activation of lung macrophages, and upregulation of anti-apoptotic genes by eosinophils. These events combine together to cause severe lung inflammation and compromised lung immunity. Therapeutic interventions that can boost host immune response in the lungs might thus provide relief to patients with tropical pulmonary eosinophilia.

Topical corticosteroids do not revert the activated phenotype of eosinophils in eosinophilic esophagitis but decrease surface levels of CD18 resulting in diminished adherence to ICAM-1, ICAM-2, and endothelial cells

Swallowed topical corticosteroids are the standard therapy for eosinophilic esophagitis (EoE) in adults. Eosinophils in the blood of untreated EoE patients have an activated phenotype. Our aim was to determine if corticosteroids restore the phenotype of eosinophils to a healthy phenotype and if certain cell-surface molecules on blood eosinophils correlate with eosinophilic infiltration of the esophagus. Levels of eight surface markers on eosinophils from treated and untreated EoE patients were determined by flow cytometry and analyzed using multivariate methods of pattern recognition. Corticosteroid-treated EoE patients' eosinophils had decreased levels of CD18 compared to both untreated patients and healthy controls, but maintained their activated phenotype. CD18 expression correlated positively with eosinophil numbers in the esophagus and promoted the adherence of eosinophils to ICAM-1, ICAM-2, and to endothelial cells. The diminished expression of CD18 may be one mechanism behind the reduced entry of eosinophils into the esophagus in corticosteroid-treated EoE patients.

SOCS3 silencing attenuates eosinophil functions in asthma patients

Eosinophils are one of the key inflammatory cells in asthma. Eosinophils can exert a wide variety of actions through expression and secretion of multiple molecules. Previously, we have demonstrated that eosinophils purified from peripheral blood from asthma patients express high levels of suppressor of cytokine signaling 3 (SOCS3). In this article, SOCS3 gene silencing in eosinophils from asthmatics has been carried out to achieve a better understanding of the suppressor function in eosinophils. SOCS3 siRNA treatment drastically reduced SOCS3 expression in eosinophils, leading to an inhibition of the regulatory transcription factors GATA-3 and FoxP3, also interleukin (IL)-10; in turn, an increased STAT3 phosphorilation was observed. Moreover, SOCS3 abrogation in eosinophils produced impaired migration, adhesion and degranulation. Therefore, SOCS3 might be regarded as an important regulator implicated in eosinophil mobilization from the bone marrow to the lungs during the asthmatic process.

Targeting chemokines: Pathogens can, why can't we?

Chemoattractant cytokines, or chemokines, are the largest sub-family of cytokines. About 50 distinct chemokines have been identified in humans. Their principal role is to stimulate the directional migration of leukocytes, which they achieve through activation of their receptors, following immobilization on cell surface glycosaminoglycans (GAGs). Chemokine receptors belong to the G protein-coupled 7-transmembrane receptor family, and hence their identification brought great promise to the pharmaceutical industry, since this receptor class is the target for a large percentage of marketed drugs. Unfortunately, the development of potent and efficacious inhibitors of chemokine receptors has not lived up to the early expectations. Several approaches to targeting this system will be described here, which have been instrumental in establishing paradigms in chemokine biology. Whilst drug discovery programs have not yet elucidated how to make successful drugs targeting the chemokine system, it is now known that certain parasites have evolved anti-chemokine strategies in order to remain undetected by their hosts. What can we learn from them?

The role of CCL21/CCR7 chemokine axis in breast cancer-induced lymphangiogenesis

Background

Tumor-induced lymphangiogenesis facilitates breast cancer progression by generating new lymphatic vessels that serve as conduits for tumor dissemination to lymph nodes and beyond. Given the recent evidence suggesting the implication of C-C chemokine ligand 21/chemokine receptor 7 (CCL21/CCR7) in lymph node metastasis, the aim of our study was to define the role of this chemokine pair in breast cancer-associated lymphangiogenesis.

Methods

The expression analysis of CCL21/CCR7 pair and lymphatic endothelial cell (LEC) markers in breast cancer specimens was performed by means of quantitative real-time PCR. By utilizing CCR7 and CCL21 gene manipulated breast cancer cell implants into orthotopic sites of nude mice, lymphatic vessel formation was assessed through quantitative real-time PCR, immunohistochemistry and immunofluorescence assays. Finally, the lymphangiogenic potential of CCL21/CCR7 was assessed in vitro with primary LECs through separate functional assays, each attempting to mimic different stages of the lymphangiogenic process.

Results

We found that CCR7 mRNA expression in human breast cancer tissues positively correlates with the expression of lymphatic endothelial markers LYVE-1, podoplanin, Prox-1, and vascular endothelial growth factor-C (VEGF-C). We demonstrated that the expression of CCL21/CCR7 by breast cancer cells has the ability to promote tumor-induced lymph-vascular recruitment in vivo. In vitro, CCL21/CCR7 chemokine axis regulates the expression and secretion of lymphangiogenic factor VEGF-C and thereby promotes proliferation, migration, as well as tube formation of the primary human LECs. Finally, we showed that protein kinase B (AKT) signaling pathway is the intracellular mechanism of CCR7-mediated VEGF-C secretion by human breast cancer cells.

Conclusions

These results reveal that CCR7 and VEGF-C display a significant crosstalk and suggest a novel role of the CCL21/CCR7 chemokine axis in the promotion of breast cancer-induced lymphangiogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0306-4) contains supplementary material, which is available to authorized users.

HMGB1 contributes to allergen-induced airway remodeling in a murine model of chronic asthma by modulating airway inflammation and activating lung fibroblasts

The pro-inflammation factor high-mobility group box protein 1 (HMGB1) has been implicated in the pathogenesis of asthma. In this study, we used a murine model of chronic asthma to evaluate the effects of HMGB1 on airway remodeling. Female BALB/c mice were randomly divided into four groups: control, ovalbumin (OVA) asthmatic, OVA+isotype antibody and OVA+anti-HMGB1 antibody. Anti-HMGB1 antibody therapy was started on day 21 and was administered three times per week for 6 weeks before intranasal challenge with OVA. In this mouse model, HMGB1 expression is significantly elevated. The anti-HMGB1 antibody group exhibited decreased levels of immunoglobulin E (IgE) and inflammatory mediators and reduced inflammatory cell accumulation, airway hyperresponsiveness (AHR), mucus synthesis, smooth muscle thickness and lung collagen content compared with the OVA groups. Treatment with HMGB1 increased proliferation, migration, collagen secretion and α-smooth muscle actin (SMA) expression in MRC-5 cells. Treatment with the HMGB1/IL-1β complex significantly increased the expression and secretion of transforming growth factor (TGF-β1), matrix metalloproteinase (MMP)-9 and vascular endothelial growth factor (VEGF). Altogether, these results suggest that blocking HMGB1 activity may reverse airway remodeling by suppressing airway inflammation and modulating lung fibroblast phenotype and activation.

The Activity of CCL18 is Principally Mediated through Interaction with Glycosaminoglycans

The CC chemokine ligand 18 (CCL18) was first identified as a chemoattractant for naïve T cells. It has been reported to recruit T and B lymphocytes, and we show here, natural killer (NK) cells, but with low efficacy. Investigation of its ability to elicit G-protein-coupled signaling showed that it does not involve extracellular signal-regulated kinase (ERK) phosphorylation, and it is not able to induce receptor internalization, as assessed on CCR3. CCL18 has recently been reported to possess activities unrelated to cellular recruitment, but it had no effect on T lymphocyte proliferation. We postulated that a more potent chemoattractant may be produced under inflammatory conditions but only minor truncations were observed, with the major form being the full-length protein. In view of the lack of potent immunomodulatory properties, we wondered if binding to CCL18 by the tick chemokine binding proteins Evasin-1 and -4 was an artifact of the methods used, but complex formation was confirmed by size exclusion chromatography, and abrogation of its binding to, and antagonism of, CCR3. Its receptor has remained elusive since its cloning in 1997, although it has been reported to induce migration of breast cancer cells by signaling through PITPNM3, but we show that this receptor is not expressed on lymphocytes. We have developed a radiolabeled equilibrium competition binding assay and demonstrated that it bound with high affinity to peripheral blood leukocytes (PBLs), but the binding was displaced similarly by both unlabelled CCL18 as well as heparin. Both heparin binding and binding to PBLs are considerably abrogated by mutation of the BBXB motif in the 40s loop suggesting an essential role of the CCL18-glycosaminoglycan interaction.

The downstream regulation of chemokine receptor signalling: implications for atherosclerosis

Heterotrimeric G-protein-coupled receptors (GPCRs) are key mediators of intracellular signalling, control numerous physiological processes, and are one of the largest class of proteins to be pharmacologically targeted. Chemokine-induced macrophage recruitment into the vascular wall is an early pathological event in the progression of atherosclerosis. Leukocyte activation and chemotaxis during cell recruitment are mediated by chemokine ligation of multiple GPCRs. Regulation of GPCR signalling is critical in limiting vascular inflammation and involves interaction with downstream proteins such as GPCR kinases (GRKs), arrestin proteins and regulator of G-protein signalling (RGS) proteins. These have emerged as new mediators of atherogenesis by functioning in internalisation, desensitisation, and signal termination of chemokine receptors. Targeting chemokine signalling through these proteins may provide new strategies to alter atherosclerotic plaque formation and plaque biology.

Chemokine CCR3 ligands-binding peptides derived from a random phage-epitope library

Eosinophils are major effectors cells implicated in a number of chronic inflammatory diseases in humans, particularly bronchial asthma and allergic rhinitis. The human chemokine receptor C-C receptor 3 (hCCR3) provides a mechanism for the recruitment of eosinophils into tissue and thus has recently become an attractive biological target for therapeutic intervention. In order to develop peptides antagonists of hCCR3-hCCL11 (human eotaxin) interactions, a random bacteriophage hexapeptide library was used to map structural features of hCCR3 by determining the epitopes of neutralizing anti-hCCR3 mAb 7B11. This mAb t is selective for hCCR3 and exhibit potent antagonist activity in receptor binding and functional assays. After three rounds of biopanning, four mAb7B11-binding peptides were identified from a 6-mer linear peptide library. The phage bearing the peptides showed specific binding to immobilized mAb 7B11 with over 94% of phages bound being competitively inhibited by free synthetic peptides. In FACScan analysis all selected phage peptides were able to strongly inhibit the binding of mAb 7B11 to hCCR3-transfected preB-300-19 murine cells. Furthermore, synthetic peptides of the corresponding phage epitopes were effective in blocking the antibody-hCCR3 interactions and to inhibit the binding of hCCL11 to hCCR3 transfectants. Chemically synthesized peptides CKGERF, FERKGK, SSMKVK and RHVSSQ, effectively competed for (125)I-hCCL11 binding to hCCR3 with IC(50) ranging from 3.5 to 9.7μM. Calcium release and chemotaxis of hCCR3 transfectants or human eosinophils were inhibited by all peptides in a dose-dependent manner. Furthermore, they showed inhibitory effects on chemotaxis of human eosinophils induced by hCCL11, hCCL5, hCCL7, hCCL8, and hCCL24. Specificities of all selected peptides were assessed with hCXCR1, hCXCR2, hCXCR3, and hCCR5 receptors. Peptides CKGERF and FERKGK showed inhibitory effects on eosinophil chemotaxis in a murine model of mCCL11-induced peritoneal eosinophilia. The development of peptides inhibiting the interactions between hCCR3 and its chemokine ligands will facilitate the development of small peptides antagonists with the hope of ameliorating chronic inflammatory diseases in humans.

Interleukin-25 promotes basic fibroblast growth factor expression by human endothelial cells through interaction with IL-17RB, but not IL-17RA

BACKGROUND

Unlike other IL-17 family members, the Th2-derived cytokine IL-25 (IL-17E) induces (promotes) Th2 responses. One or both of the two receptors for IL-25 (IL-17RA, IL-17RB) is expressed on inflammatory cells and tissue structural cells, suggesting that in addition to promoting Th2-type inflammation IL-25 may also act on structural cells at sites of Th2-type inflammation such as in the asthmatic bronchial mucosa to promote remodelling changes.

OBJECTIVE

Our previous studies showed elevated expression of IL-25 and IL-17RB immunoreactivity in asthmatic airways with co-localization of the latter to endothelial cells. We therefore hypothesized that IL-25 acts on endothelial cells through this receptor to induce production of the key angiogenic and remodelling cytokine basic fibroblast growth factor (bFGF).

METHODS

Polymerase chain reaction (PCR) immunocytochemistry/immunohistochemistry and ELISA were employed to detect expression of IL-17RB, IL-17RA and bFGF by human vascular endothelial cells (HUVEC) and immunoreactivity for IL-25 and bFGF in asthmatic bronchial biopsies. Receptor-blocking antibodies, PCR and an in vitro angiogenesis assay were used to investigate whether IL-25 acts on IL-17RB or IL-17RA to induce bFGF expression and angiogenesis. PCR was also employed to investigate the signalling pathways involved in IL-25-mediated bFGF expression.

RESULTS

HUVEC constitutively expressed IL-17RB, IL-17RA and bFGF. Production of the latter was further increased by IL-25, but attenuated after blockade of the IL-17RB, but not the IL-17RA receptor. Neutralization of endogenous VEGF and bFGF completely abrogated IL-25-induced angiogenesis which was also inhibited by blocking IL-17RB, but not IL-17RA. The PI3K-specific inhibitor LY294002 also completely attenuated IL-25-induced bFGF expression. Immunoreactivity for IL-25 and bFGF was elevated in the asthmatic bronchial mucosa and the expression of each correlated with the other.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data support the hypothesis that IL-25 contributes to elevated bFGF in asthmatic airways by acting on the endothelial cell IL-17RB receptor through PI3K-signalling pathways. Targeting the pathways might benefit therapy of airways remodelling.

Cellular assays of chemokine receptor activation

This unit describes procedures for measuring the activation of chemokine receptors by their ligands. Chemokines are chemoattractant proteins and two assays are described for analyzing the chemoattractant properties (chemotaxis) of these proteins. Chemokine receptors are coupled to G proteins, and activation of the receptors results in the mobilization of intracellular Ca²⁺ stores. Two assays for the measurement of this activity are described which employ calcium-sensitive dyes, one for adherent and one for non-adherent cells. In addition, an assay for quantitating chemokine receptor downmodulation and subsequent recycling events is described. The assays are applicable to both purified leukocytes and stably expressed recombinant chemokine receptors.This unit describes procedures for measuring the activation of chemokine receptors by their ligands.

Carbon dioxide-enriched water inhalation in patients with allergic rhinitis and its relationship with nasal fluid cytokine/chemokine release

BACKGROUND AND AIMS

Allergic rhinitis is characterized by eosinophil infiltration and accumulation in the nasal mucosa mainly due to IL-3, IL-5, and eotaxin activities. We undertook this study to investigate a possible in vivo effect of carbon dioxide-enriched water inhalation in patients with allergic rhinitis.

METHODS

Twenty five consecutive patients inhaled carbon dioxide-enriched water at Fonti di Rabbi Spa Centre (Trento, Italy). Symptom scores for nasal obstruction, itching and sneezing were obtained before and after treatment. Nasal lavage was collected, and IL-3, IL-5, and eotaxin levels were assessed using the quantitative sandwich enzyme immunoassay technique. Cytometric analysis was performed on samples to measure total cell count, CD45+ cells, and percentages of polymorphonucleates and lymphocytes.

RESULTS

There were statistically significant differences in chemokine levels and in cell populations between patients and healthy controls before treatment. After carbon dioxide-enriched water inhalation, we observed statistically significant improvements in symptom scores, chemokine levels, and percentages of cell populations.

CONCLUSIONS

Our results seem to confirm the role of IL-3, IL-5, and eotaxin in the pathophysiology of allergy and the beneficial effect of carbon dioxide-enriched water inhalation in patients affected by allergic rhinitis.

Characterization of CCR9 expression and thymus-expressed chemokine responsiveness of the murine thymus, spleen and mesenteric lymph node

CC chemokine receptor 9 (CCR9) is a receptor expressed at high levels in immature thymocytes, small intestine trafficking T cells and IgA-producing plasma cells. CCR9 mediates chemotaxis in response to thymus-expressed chemokine (TECK) selectively expressed in the thymus and small intestine. CCR9 expression in different subpopulations of thymus, spleen and mesenteric lymph node (MLN) cells was analyzed by flow cytometry and TECK responsiveness of those lymphoid cells was assessed by a Transwell migration assay. CCR9 surface expression level did not completely correlate with cellular chemotaxis to its cognate ligand TECK. The active chemotaxis to TECK was observed in CD4 single positive thymocytes and CD4(-)B220(hi) splenocyte and MLN cells, which poorly expressed CCR9 on their surface. TECK responsiveness of CCR9-abundant subpopulations in the thymus and MLN was unremarkable except for CD4(+)B220(hi) subset of the MLN, and was evident in the CCR3(+) subsets of the thymus and spleen. Exposure to TECK did not affect CCR9 expression in the thymus, spleen and MLN, except for the CD4(+)CD8(+) thymocyte. CCR9 was exuberantly expressed in the cytoplasm of lymphoid cells. CCR9 may act in concert with CCR3 for in terms of TECK responsiveness. Its cytoplasmic location may allow precise regulation of leukocyte responsiveness to TECK.

The role of chemokines and their receptors in angiogenesis

Chemokines are a vertebrate-specific group of small molecules that regulate cell migration and behaviour in diverse contexts. So far, around 50 chemokines have been identified in humans, which bind to 18 different chemokine receptors. These are members of the seven-transmembrane receptor family. Initially, chemokines were identified as modulators of the immune response. Subsequently, they were also shown to regulate cell migration during embryonic development. Here, we discuss the influence of chemokines and their receptors on angiogenesis, or the formation of new blood vessels. We highlight recent advances in our understanding of how chemokine signalling might directly influence endothelial cell migration. We furthermore examine the contributions of chemokine signalling in immune cells during this process. Finally, we explore possible implications for disease settings, such as chronic inflammation and tumour progression.

Characterization of CXCR4 expression in chondrosarcoma of bone

CONTEXT

Alterations in molecular elements derived from the CXC chemokine receptor 4 (CXCR4)/stromal-derived factor 1 (SDF-1) cytokine system have been found to strongly correlate with neoplastic progression leading to metastasis in a number of tumors, including osteosarcoma. Excluding hematologic malignancies, chondrosarcoma of bone is the most common primary malignant tumor of bone in adults in the United States. Like osteosarcoma, chondrosarcoma preferentially metastasizes to lung, bone, and very rarely to regional lymph nodes. However, the role of the signal pathway(s) driving neoplastic progression in chondrosarcoma has not yet been clearly elucidated.

OBJECTIVE

To test whether CXCR4 was detectable in chondrosarcoma and whether CXCR4 expression levels correlated with chondrosarcoma grade.

DESIGN

Twenty-two chondrosarcoma samples banked at our institution between 2001 and 2006 were retrieved for study. By using invasive ductal carcinoma of the breast and osteosarcoma as the positive controls, immunohistochemistry was performed on paraffin-embedded tissue sections and the intensity of the tumor cells was analyzed by morphometric techniques.

RESULTS

All chondrosarcoma cases (22 of 22) were immunoreactive for CXCR4. However, the staining intensity of the CXCR4 between the low- and high-grade groups was significantly different. There was a higher staining intensity in high-grade chondrosarcoma cells (P < .001).

CONCLUSION

CXCR4 is expressed in chondrosarcomas. CXCR4 expression levels were higher in high-grade chondrosarcoma cells than in low-grade specimens. A larger number of cases will be required to confirm these results and expand the observation, but preliminary data would argue for CXCR4 immunohistochemistry as a potential marker for biologic aggressiveness in chondrosarcoma of bone.

Cannabinoids inhibit migration of microglial-like cells to the HIV protein Tat

Microglia are a population of macrophage-like cells in the central nervous system (CNS) which, upon infection by the human immunodeficiency virus (HIV), secrete a plethora of inflammatory factors, including the virus-specified trans-activating protein Tat. Tat has been implicated in HIV neuropathogenesis since it elicits chemokines, cytokines, and a chemotactic response from microglia. It also harbors a β-chemokine receptor binding motif, articulating a mode by which it acts as a migration stimulus. Since select cannabinoids have anti-inflammatory properties, cross the blood-brain barrier, and target specific receptors, they have potential to serve as agents for dampening untoward neuroimmune responses. The aim of this study was to investigate the effect of select cannabinoids on the migration of microglial-like cells toward Tat. Using a mouse BV-2 microglial-like cell model, it was demonstrated that the exogenous cannabinoids Delta-9-tetrahydrocannabinol (THC) and CP55940 exerted a concentration-related reduction in the migration of BV-2 cells towards Tat. A similar inhibitory response was obtained when the endogenous cannabinoid 2-arachidonoylglycerol (2-AG) was used. The CB(2) receptor (CB2R) antagonist SR144528, but not the CB(1) receptor (CB1R) antagonist SR141716A, blocked this inhibition of migration. Similarly, CB2R knockdown with small interfering RNA reversed the cannabinoid-mediated inhibition. In addition, the level of the β-chemokine receptor CCR-3 was reduced and its intracellular compartmentation was altered. These results indicate that cannabinoid-mediated inhibition of BV-2 microglial-like cell migration to Tat is linked functionally to the CB2R. Furthermore, the results indicate that activation of the CB2R leads to altered expression and compartmentation of the β-chemokine receptor CCR-3.

T-helper cell type 2 (Th2) memory T cell-potentiating cytokine IL-25 has the potential to promote angiogenesis in asthma

IL-25 (IL-17E) is a T-helper cell type 2 (Th2) cytokine best described as a potentiator of Th2 memory responses. Reports of expression of its receptor, IL-25R, on airways structural cells suggest a wider role for IL-25 in remodeling. We hypothesized that IL-25 stimulates local angiogenesis in the asthmatic bronchial mucosa. Immunoreactive IL-25(+), IL-25R(+), and CD31(+) (endothelial) cells in sections of bronchial biopsies from asthmatics and controls were detected by immunohistochemistry. The effect of IL-25 on angiogenesis was examined using an in vitro assay. Real-time PCR was used to detect expression of IL-25R and VEGF mRNA in cultured human vascular endothelial cells (HUVEC), and a cell proliferation kit (WST-8) was used to measure the effect of IL-25 on HUVEC proliferation. Immunostaining showed that IL-25(+), IL-25R(+), and CD31(+)/IL-25R(+) cells were significantly elevated in the bronchial mucosa of asthmatics compared with controls (P < 0.003). In asthmatics, the numbers of IL-25(+) cells correlated inversely with the forced expiratory volume in 1 s (r = -0.639; P = 0.01). In vitro, HUVEC constitutively expressed IL-25R, which was up-regulated further by TNF-α. IL-25 and TNF-α also increased expression of VEGF and VEGF receptors. IL-25 increased HUVEC proliferation and the number, length, and area of microvessel structures in a concentration-dependent manner in vitro. VEGF blockade, the PI3K-specific inhibitor LY294002, and the MAPK/ERK1/2 (MEK1/2)-specific inhibitor U0126 all markedly attenuated IL-25-induced angiogenesis, and the inhibitors also reduced IL-25-induced proliferation and VEGF expression. Our findings suggest that IL-25 is elevated in asthma and contributes to angiogenesis, at least partly by increasing endothelial cell VEGF/VEGF receptor expression through PI3K/Akt and Erk/MAPK pathways.

A single nucleotide polymorphism in the CCR3 gene ablates receptor export to the plasma membrane

BACKGROUND

The chemokine receptor CCR3 orchestrates the migration of eosinophils, basophils, T(H)2 lymphocytes, and mast cells during the allergic response, with CCR3 blockade a potential means of therapeutic intervention. Non-synonymous single nucleotide polymorphisms (SNPs) within the ccr3 gene have previously been described, with little information regarding their effects on CCR3 function.

OBJECTIVE

To characterize the effects of nonsynonymous SNPs within the ccr3 gene.

METHODS

Site-directed mutagenesis was used to generate N-terminally tagged mutant CCR3 constructs corresponding to reported SNPs. Cell transfectants expressing either wild-type or mutant CCR3 were studied by flow cytometry, Western blotting, and confocal microscopy and examined for their ability to migrate to the CC chemokine ligand CCL11/eotaxin.

RESULTS

An L324P mutant CCR3 protein corresponding to the previously identified T971C SNP was not expressed at the cell surface, and cells remained unresponsive to CCL11 in chemotaxis assays. Confocal microscopy confirmed that L324P-CCR3 had a predominantly intracellular distribution compared with wild-type CCR3. A L324A variant of CCR3 had an identical phenotype to the L324P mutant, suggesting that L324 per se is critical for successful trafficking of nascent CCR3 to the cell membrane. The processes involved appear to be specific for CCR3, because an identical mutation in the homologous receptor CCR1 had minor effects.

CONCLUSION

Trafficking to the cell surface of nascent CCR3 is critically dependent on a C-terminal leucine residue, suggestive of specific mechanisms for CCR3 export. Manipulation of these mechanisms may suggest novel means of antagonizing CCR3 function in the treatment of allergy.

Nuclear autoantigen CENP-B transactivation of the epidermal growth factor receptor via chemokine receptor 3 in vascular smooth muscle cells

OBJECTIVE

We have previously found that the CENP-B nuclear autoantigen, which is specifically targeted by autoantibodies in the limited cutaneous form of systemic sclerosis, behaved as a potent migratory factor for human pulmonary artery smooth muscle cells (PASMCs). Other recent studies have shown that several disease-associated autoantigens induced cell migration by interacting with various chemokine receptors. Prompted by this hypothesis, we undertook this study to determine whether CENP-B interacts with chemokine receptors on the surface of human PASMCs, to explore the relevant signaling pathways, and to characterize the effects of anti-CENP-B binding on SMC stimulation.

METHODS

To demonstrate the expression of specific chemokine receptors by human PASMCs at both the messenger RNA and protein levels, reverse transcription-polymerase chain reaction, immunoblotting, and flow cytometry analyses were performed. Desensitization studies and specific inhibitors were used to further identify the CENP-B target on the surface of human PASMCs.

RESULTS

Our data strongly suggested that CENP-B used chemokine receptor 3 (CCR3) to mediate human PASMCs signaling. Moreover, several lines of evidence indicated that CENP-B binding subsequently stimulated the cross-talk between CCR3 and epidermal growth factor receptor (EGFR) via a matrix metalloprotease-dependent mechanism that involved the processing of heparin-binding EGF-like growth factor. Transactivation of the EGFR through CCR3 was found to be a critical pathway that elicits MAP kinase activation and secretion of cytokines such as interleukin-8. Finally, anti-CENP-B autoantibodies were found to abolish this signaling pathway, thus preventing CENP-B from transactivating EGFR and exerting its cytokine-like activities toward vascular smooth muscle cells.

CONCLUSION

The identification of CENP-B as a CCR3 ligand opens up new perspectives for the study of the pathogenic role of anti-CENP-B autoantibodies.

Didecyldimethylammonium chloride induces pulmonary inflammation and fibrosis in mice

Didecyldimethylammonium chloride (DDAC) is used worldwide as a germicide, in antiseptics, and as a wood preservative, and can cause adverse pulmonary disease in humans. However, the pulmonary toxicity of DDAC has not yet been thoroughly investigated. Mice were intratracheally instilled with DDAC to the lung and the bronchoalveolar lavage (BAL) fluid and lung tissues were collected to assess dose- and time-related pulmonary injury. Exposure to 1500 μg/kg of DDAC caused severe morbidity with pulmonary congestive oedema. When the BAL fluid from survivors was examined on day 3 after treatment, exposure to 150 μg/kg of DDAC caused weakly induced inflammation, and exposure to 15μg/kg did not cause any visible effects. Next, we observed pulmonary changes that occurred up to day 20 after 150 μg/kg of DDAC exposure. Pulmonary inflammation peaked on day 7 and was confirmed by expression of interleukin-6, monocyte chemotactic protein-1, macrophage inflammatory protein (MIP)-1α, MIP-1β, and regulated upon activation, normal T-cell expressed and secreted in the BAL fluid; these changes were accompanied by altered gene expression of their chemokine (C-C motif) receptor (Ccr) 1, Ccr2, Ccr3, and Ccr5. Cytotoxicity evoked by DDAC was related to the inflammatory changes and was confirmed by an in vitro study using isolated mouse lung fibroblasts. The inflammatory phase was accompanied or followed by pulmonary remodeling, i.e., fibrosis, which was evident in the mRNA expression of type I procollagen. These results suggest that administering DDAC by intratracheal instillation causes pulmonary injury in mice, and occupational exposure to DDAC might be a potential hazard to human health.

Altered chemokine receptor expression in papillary thyroid cancer

BACKGROUND

Papillary thyroid cancer (PTC), the most prevalent type of differentiated thyroid carcinoma, displays a strikingly high frequency of lymph node metastasis (LNM). Recent data suggest that chemokines can play an important role in promoting tumor progression and metastatic migration of tumor cells. Here we have evaluated whether PTC tissues express a different pattern of chemokine receptors and if the expression of these receptors correlates with LNM.

METHODS

We assessed by immunohistochemistry and flow cytometry the expression of the chemokine receptors CCR3, CCR7, and CXCR4 in tumor and nonmalignant thyroid tissues from patients suffering from PTC. Expression of these receptors in PTC was correlated with the clinical pathological condition of PTC.

RESULTS

Our data show a significant enhancement of CCR3 (2.5 times higher, p = 0.038) and CXCR4 (1.7 times higher, p = 0.02) expression in PTC tissues as determined by immunohistochemical staining, and of CCR3 (3.5 times higher, p < 0.002) in the plasma membrane as determined by flow cytometric analyses, compared to controls. In addition, while CCR3 (100%) and CXCR4 (90%) were present in both tumor and control thyroid tissues, expression of CCR7 was scarcely detected in PTC cells (5-10%) and not found in control cells. CXCR4 expression correlated with the classical variant of PTC (p < 0.035) and extranodal extension (p < 0.010) in patients with LNM.

CONCLUSIONS

Our data support the notion that CCR3, CCR7, and CXCR4 are increasingly expressed in tumor cells from PTC and that CXCR4 expression in PTC could be a potential marker for enhanced tumor aggressiveness.

CCR5 signalling, but not DARC or D6 regulatory, chemokine receptors are targeted by herpesvirus U83A chemokine which delays receptor internalisation via diversion to a caveolin-linked pathway

Background

Herpesviruses have evolved chemokines and chemokine receptors, which modulate the recruitment of human leukocytes during the inflammatory response to infection. Early post-infection, human herpesvirus 6A (HHV-6A) infected cells express the chemokine receptor U51A and chemokine U83A which have complementary effects in subverting the CC-chemokine family thereby controlling anti-viral leukocyte recruitment. Here we show that, to potentiate this activity, the viral chemokine can also avoid clearance by scavenger chemokine receptors, DARC and D6, which normally regulate an inflammatory response. Conversely, U83A delays internalisation of its signalling target receptor CCR5 with diversion to caveolin rich membrane domains. This mechanism can redirect displaced human chemokines to DARC and D6 for clearance of the anti-viral inflammatory response, leaving the viral chemokine unchecked.

Methods

Cell models for competitive binding assays were established using radiolabeled human chemokines and cold U83A on CCR5, DARC or D6 expressing cells. Flow cytometry was used to assess specific chemotaxis of CCR5 bearing cells to U83A, and internalisation of CCR5 specific chemokine CCL4 after stimulation with U83A. Internalisation analyses were supported by confocal microscopy of internalisation and co-localisation of CCR5 with caveosome marker caveolin-1, after virus or human chemokine stimulation.

Results

U83A displaced efficiently human chemokines from CCR5, with a high affinity of 0.01nM, but not from DARC or D6. Signalling via CCR5 resulted in specific chemoattraction of primary human leukocytes bearing CCR5. However, U83A effective binding and signalling to CCR5 resulted in delayed internalisation and recycling up to 2 hours in the absence of continual re-stimulation. This resulted in diversion to a delayed caveolin-linked pathway rather than the rapid clathrin mediated endocytosis previously shown with human chemokines CCL3 or CCL4.

Conclusion

U83A diverts human chemokines from signalling, but not regulatory or scavenger, receptors facilitating their clearance, while occupying signalling receptors at the cell surface. This can enhance virus specific inflammation, facilitating dissemination to replication sensitive leukocytes while evading clearance; this has implications for linked neuro-inflammatory pathologies.

Eosinophil viability is increased by acidic pH in a cAMP- and GPR65-dependent manner

The microenvironment of the lung in asthma is acidic, yet the effect of acidity on inflammatory cells has not been well established. We now demonstrate that acidity inhibits eosinophil apoptosis and increases cellular viability in a dose-dependent manner between pH 7.5 and 6.0. Notably, acidity induced eosinophil cyclic adenosine 5'-monophosphate (cAMP) production and enhanced cellular viability in an adenylate cyclase-dependent manner. Furthermore, we identify G protein-coupled receptor 65 (GPR65) as the chief acid-sensing receptor expressed by eosinophils, as GPR65-deficient eosinophils were resistant to acid-induced eosinophil cAMP production and enhanced viability. Notably, GPR65(-/-) mice had attenuated airway eosinophilia and increased apoptosis in 2 distinct models of allergic airway disease. We conclude that eosinophil viability is increased in acidic microenvironments in a cAMP- and GPR65-dependent manner.

Role of eotaxin-1 signaling in ovarian cancer

PURPOSE

Tumor cell growth and migration can be directly regulated by chemokines. In the present study, the association of CCL11 with ovarian cancer has been investigated.

EXPERIMENTAL DESIGN AND RESULTS

Circulating levels of CCL11 in sera of patients with ovarian cancer were significantly lower than those in healthy women or women with breast, lung, liver, pancreatic, or colon cancer. Cultured ovarian carcinoma cells absorbed soluble CCL11, indicating that absorption by tumor cells could be responsible for the observed reduction of serum level of CCL11 in ovarian cancer. Postoperative CCL11 levels in women with ovarian cancer negatively correlated with relapse-free survival. Ovarian tumors overexpressed three known cognate receptors of CCL11, CC chemokine receptors (CCR) 2, 3, and 5. Strong positive correlation was observed between expression of individual receptors and tumor grade. CCL11 potently stimulated proliferation and migration/invasion of ovarian carcinoma cell lines, and these effects were inhibited by neutralizing antibodies against CCR2, CCR3, and CCR5. The growth-stimulatory effects of CCL11 were likely associated with activation of extracellular signal-regulated kinase 1/2, MEK1, and STAT3 phosphoproteins and with increased production of multiple cytokines, growth factors, and angiogenic factors. Inhibition of CCL11 signaling by the combination of neutralizing antibodies against the ligand and its receptors significantly increased sensitivity to cisplatin in ovarian carcinoma cells.

CONCLUSION

We conclude that CCL11 signaling plays an important role in proliferation and invasion of ovarian carcinoma cells and CCL11 pathway could be targeted for therapy in ovarian cancer. Furthermore, CCL11 could be used as a biomarker and a prognostic factor of relapse-free survival in ovarian cancer.

Ablation of type I hypersensitivity in experimental allergic conjunctivitis by eotaxin-1/CCR3 blockade

The immune response is regulated, in part, by effector cells whose activation requires multiple signals. For example, T cells require signals emanating from the T cell antigen receptor and co-stimulatory molecules for full activation. Here, we present evidence indicating that IgE-mediated hypersensitivity reactions in vivo also require cognate signals to activate mast cells. Immediate hypersensitivity reactions in the conjunctiva are ablated in mice deficient in eotaxin-1, despite normal numbers of tissue mast cells and levels of IgE. To further define the co-stimulatory signals mediated by chemokine receptor 3 (CCR3), an eotaxin-1 receptor, effects of CCR3 blockade were tested with an allergic conjunctivitis model and in ex vivo isolated connective tissue-type mast cells. Our results show that CCR3 blockade significantly suppresses allergen-mediated hypersensitivity reactions as well as IgE-mediated mast cell degranulation. We propose that a co-stimulatory axis by CCR3, mainly stimulated by eotaxin-1, is pivotal in mast cell-mediated hypersensitivity reactions.

2007 E. Mead Johnson award: scientific pursuit of the allergy problem

My research has focused on elucidating the allergy problem over the past two decades. The primary approach has been to uncover critical mechanisms of allergic inflammation, with particular focus on eosinophils, a hallmark cellular constituent of allergic responses. Molecular processes that bridge T helper cell type 2 (TH2) immunity with eosinophilia and key checkpoints for regulating eosinophilia have been uncovered. Notably, interleukin (IL)-5 (derived from TH2 cells) has been identified as the chief hematopoietin responsible for eosinophil expansion in the circulation. Pathways for selective eosinophil mobilization from the blood stream to the tissue have been uncovered by defining the role of the eotaxin subfamily of chemokines in eosinophil chemoattraction and activation. Finally, TH2 cell derived IL-4 and IL-13 have been defined as chief inducers of the eotaxins, and upstream orchestrators of eosinophilic inflammation. These translational studies have formulated novel therapeutic strategies (currently being tested) for a variety of eosinophilic conditions, with particular attention on hypereosinophilic syndromes and eosinophil-associated gastrointestinal disorders such as eosinophilic esophagitis.

Interplay of adaptive th2 immunity with eotaxin-3/c-C chemokine receptor 3 in eosinophilic esophagitis

BACKGROUND

Pediatric eosinophilic esophagitis (EE) is a recently described disorder associated with atopy. Although studies of esophageal tissue suggest that Th2 cytokines and eotaxin-3 may be crucial in disease pathogenesis, little is known about the systemic immunological phenotypes of children with EE.

OBJECTIVES

To define the phenotypes of peripheral blood eosinophils and lymphocytes in EE and to examine for correlations between these parameters and tissue eosinophil numbers and disease severity.

PATIENTS AND METHODS

Blood was collected from children with EE, atopic control children without EE, and nonatopic control children without EE. Flow cytometry was used to measure eosinophil expression of chemokine receptor 3 (CCR3) and interleukin-5 receptor-alpha (IL-5Ralpha), and intracellular lymphocyte expression of IL-4, IL-5, IL-13, interferon-gamma, and tumor necrosis factor-alpha. Eosinophil numbers and eotaxin-3 mRNA levels were quantitated in esophageal biopsy specimens.

RESULTS

Compared with nonatopic control children, EE patients with active disease had increased peripheral blood eosinophil percentages, mean channel of fluorescence (MCF) of CCR3 on eosinophils, and percentage of CD4+ T cells expressing IL-5. Notably, these parameters positively correlated with esophageal eosinophil numbers. Eotaxin-3 tissue expression positively correlated with esophageal eosinophil numbers and peripheral blood eosinophil CCR3 MCF. The percentage of peripheral blood eosinophils, eosinophil CCR3 MCF, and CD4+ T cell expression of IL-5 were lower in EE patients in disease remission than in patients with active disease.

CONCLUSIONS

Collectively, these studies demonstrate cooperation between systemic CD4+ Th2-cell-mediated immunity and an enhanced eosinophil-CCR3/eotaxin-3 pathway in EE pathogenesis. Furthermore, the imbalanced Th2 immunity and increased CCR3 expression are reversible with disease remission.

Eosinophils in the pathogenesis of allergic airways disease

Eosinophils are traditionally thought to form part of the innate immune response against parasitic helminths acting through the release of cytotoxic granule proteins. However, they are also a central feature in asthma. From their development in the bone marrow to their recruitment to the lung via chemokines and cytokines, they form an important component of the inflammatory milieu observed in the asthmatic lung following allergen challenge. A wealth of studies has been performed in both patients with asthma and in mouse models of allergic pulmonary inflammation to delineate the role of eosinophils in the allergic response. Although the long-standing association between eosinophils and the induction of airway hyper-responsiveness remains controversial, recent studies have shown that eosinophils may also promote airway remodelling. In addition, emerging evidence suggests that the eosinophil may also serve to modulate the immune response. Here we review the highly co-ordinated nature of eosinophil development and trafficking and the evolution of the eosinophil as a multi-factoral leukocyte with diverse functions in asthma.

Interactions between eotaxin and interleukin-5 in the chemotaxis of primed and non-primed human eosinophils

This study was designed to understand the relationship between interleukin-5 and eotaxin in modulating the chemotaxis of eosinophils obtained from healthy subjects and subjects with allergic rhinitis. Chemotaxis of eosinophils from patients with allergic rhinitis toward interleukin-5 (0.25 ng/ml) was 78% higher than that of healthy subjects. Incubation of eosinophils with eotaxin (100 ng/ml) did not change the interleukin-5-induced chemotaxis of eosinophils from healthy subjects, but it reversed the enhanced chemotaxis seen in eosinophils from allergic patients. Chemotaxis of eosinophils from patients with allergic rhinitis toward eotaxin (100 ng/ml) was 65% higher than that of eosinophils from healthy subjects. Incubation of eosinophils with interleukin-5 (100 ng/ml) significantly increased the eotaxin-induced chemotaxis in both subject groups, but such increases were markedly higher for cells from patients with allergic rhinitis. Our finding that eotaxin inhibits the enhanced eosinophil chemotaxis toward interleukin-5 in primed cells suggests that this chemokine may downregulate eosinophil accumulation in the nasal mucosa of allergic patients.

The alpha4bbeta7-integrin is dynamically expressed on murine eosinophils and involved in eosinophil trafficking to the intestine

BACKGROUND

Of the numerous adhesion molecules expressed by eosinophils, the alpha4-integrin has been identified as critically involved in eosinophil trafficking in the lung. Most studies have focused on the role of the alpha4beta1-adhesion complex, but eosinophils also express the alpha4beta7-integrin complex.

OBJECTIVE

To investigate the role of alpha4beta7, by assessing its membrane expression on eosinophils from different compartments using allergen-challenged mice and IL-4/IL-5 bi-transgenic mice. In addition, we aim to determine the impact of beta7-integrin deficiency on eosinophil recruitment to the lungs and intestine in specific experimental allergic models.

RESULTS

Evaluation of alpha4beta7 expression on bronchoalveolar lavage fluid (BALF) and lung tissue eosinophils revealed a down-regulation of this integrin as eosinophils migrate through the lungs. Indeed eosinophils isolated from the BALF and lung of allergic mice had low expression of the alpha4beta7-complex. While expression of the alpha4-chain remained unchanged, a significant decrease in beta7-surface expression was observed. Intestinal eosinophils, isolated from Peyer's patches, also displayed a down-regulation of the alpha4beta7-integrin, albeit only modest. In contrast, circulating eosinophils, isolated from the blood and spleen, expressed high levels of the alpha4beta7-integrin. However, eosinophil trafficking into the lungs of beta7-integrin-deficient mice was not significantly impaired in response to respiratory allergen challenges. In contrast, beta7-deficient mice had impaired eosinophil recruitment to the intestine.

CONCLUSION

Taken together, these results identify differential expression of the alpha4beta7-integrin on eosinophils and its critical role in regulating eosinophil responses in the intestine.

Alanine scanning mutagenesis of the chemokine receptor CCR3 reveals distinct extracellular residues involved in recognition of the eotaxin family of chemokines

Despite considerable differences in primary structure, the chemokines eotaxin-1/CCL11, eotaxin-2/CCL24 and eotaxin-3/CCL26 signal via a single receptor, CCR3, but exhibit different potencies and efficacies. To examine receptor/ligand interactions in more detail, we performed alanine scanning mutagenesis of 21 charged residues within the extracellular loops (ECLs) of CCR3. Following transient expression in the L1.2 cell line, CCR3 mutants were assessed for their ability to be expressed at the cell surface, bind CCL11 and induce chemotactic responses to CCL11, CCL24 and CCL26. The majority of constructs were well expressed at the cell surface and bound CCL11 with low nanomolar affinity. Exceptions to this rule included the mutants E175A and E176A (ECL2) which were poorly expressed and responded weakly to all three ligands in chemotaxis assays. In contrast, the mutants K26 (amino-terminus) E179 and E180 (ECL2) responded in chemotaxis assays to CCL11 and CCL24, but not to CCL26. Mutation of residues in ECL3 was informative, with the D272A, K277A and D280A mutants exhibiting reduced chemotactic responses to two or more of the three ligands examined, despite being expressed on the cell surface at levels similar to WT CCR3. This suggests a major role for ECL3 in the recognition of all three eotaxins. In summary, distinct acidic and basic residues within CCR3 determine both receptor expression and activation by the eotaxins. Determining how these chemokines interact with their receptor at the molecular level should increase our understanding of the process of chemokine receptor activation.

Differential pattern of CCR1 internalization in human eosinophils: prolonged internalization by CCL5 in contrast to CCL3

BACKGROUND

Whereas recent studies underlie the fundamental importance of the CC chemokine receptor 3 (CCR3) for the recruitment of eosinophils in allergic diseases, controversial data exist about the relevance of CCR1 on eosinophils. Therefore, the purpose of this study was to investigate the expression and regulation of CCR1 on eosinophils.

METHODS

Flow cytometric analysis of whole blood eosinophils and CD16-negative selected eosinophils from healthy nonatopic donors and from patients with atopic disorders was performed and CCR1 receptor internalization and re-expression were studied.

RESULTS

Flow cytometric analysis of whole blood eosinophils revealed that 17.8% of the donors expressed high levels of CCR1 (CCR1high) and 82.2% low levels of CCR1 (CCR1low). A significant down-regulation of CCR1 was induced by 24 h preincubation of isolated eosinophils from CCR1high donors either with IL-3, CC chemokine ligand 3 (CCL3), CCL5, CCL7, or CCL13. Internalization experiments using eosinophils from CCR1high donors revealed that CCL5 is more effective to induce CCR1 internalization than CCL3. Whereas CCR1 re-expression after stimulation with CCL3 reached prestimulation levels (120 min: 81.3% relative CCR1 surface expression) CCL5 induced a prolonged CCR1 internalization (120 min: 15.7%).

CONCLUSIONS

This study demonstrates a distinct pattern of CCR1 internalization and re-expression in human eosinophils between CCL3 and CCL5, as CCL5 induces a prolonged CCR1 internalization and the basic value is not reached after 24 h. Since prolonged receptor internalization plays a central role in chemokine-mediated inhibition of receptor function, CCR1 seems to be an attractive target on human eosinophils for chemokine receptor blockade besides CCR3.

Chemokine receptor internalization and intracellular trafficking

The internalization and intracellular trafficking of chemokine receptors have important implications for the cellular responses elicited by chemokine receptors. The major pathway by which chemokine receptors internalize is the clathrin-mediated pathway, but some receptors may utilize lipid rafts/caveolae-dependent internalization routes. This review discusses the current knowledge and controversies regarding these two different routes of endocytosis. The functional consequences of internalization and the regulation of chemokine receptor recycling will also be addressed. Modifications of chemokine receptors, such as palmitoylation, ubiquitination, glycosylation, and sulfation, may also impact trafficking, chemotaxis and signaling. Finally, this review will cover the internalization and trafficking of viral and decoy chemokine receptors.

The carboxyl terminus of the chemokine receptor CCR3 contains distinct domains which regulate chemotactic signaling and receptor down-regulation in a ligand-dependent manner

The chemokine receptor CCR3 regulates the chemotaxis of leukocytes implicated in allergic disease, such as eosinophils. Incubation of eosinophils with CCL11, CCL13 or CCL5 resulted in a rapid decrease of cell-surface CCR3 which was replicated using CCR3 transfectants. Progressive truncation of the CCR3 C terminus by 15 amino acids produced three constructs, Delta340, Delta325 and Delta310. Delta340 and Delta325 were able to bind CCL11 with affinities similar to wild-type CCR3. Delta340 transfectants exhibited enhanced migration and reduced receptor down-regulation in response to CCL11 and CCL13. Delta325 transfectants displayed chemotactic responses to CCL11 and CCL13 similar to wild-type CCR3, and had impaired down-regulation when stimulated with CCL13 but not CCL11. In contrast, neither the Delta325 nor Delta340 truncation affected chemotaxis or receptor down-regulation induced by CCL5. Delta310 transfectants bound CCL11 poorly and were biologically inactive. Inhibitors of p38 mitogen-activated protein kinase and PI3-kinase antagonized eosinophil shape change responses and chemotaxis of transfectants to CCL11 and CCL13. In contrast, shape change but not chemotaxis was sensitive to inhibition of the extracellular signal-regulated kinase kinase pathway suggesting differential regulation of the two responses. Thus, the CCR3 C terminus contains distinct domains responsible for the regulation of receptor desensitization and for coupling to chemotactic responses.

Cytokine-stimulated human lung alveolar epithelial cells release eotaxin-2 (CCL24) and eotaxin-3 (CCL26)

Asthma is a complex inflammatory disease characterized by a prolonged underlying airway inflammation resulting from cytokine-orchestrated signaling between many types of cells, including airway epithelial cells. Trafficking, recruitment, and activation of cells in airway disease are, in part, modulated by the newly discovered CC subfamily of chemokines, eotaxin (CCL11), eotaxin-2 (CCL24) and eotaxin-3 (CCL26), which transduce signals by acting as agonists for the CCR3 receptor. The specific cytokine stimuli that modulate CCL24 and CCL26 release in airway epithelial cells remain poorly defined. Thus, human 549 alveolar type II epithelium-like cells were stimulated singly and with combinations of 1-100 ng/ml tumor necrosis-factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-4, cytokines known to be elevated in the airways of asthmatics. Release of CCL11, CCL24, and CCL26 was quantified by ELISA, and CCR3 receptors monitored by immunocytochemistry and FACS analysis. Results suggest that epithelial cells release CCL11 during the first 24 h of stimulation, in contrast to a significant increase in CCL24 and CCL26 release after 24-48 h of stimulation. Differential release of the eotaxins in response to cytokine combinations was noted. The alveolar type II epithelial cells were found to possess constitutive CCR3 receptors, which increased after proinflammatory cytokine stimulation. The airway epithelium CCR3 receptor/eotaxin ligand signal transduction system may be an important target for development of novel mechanism-based adjunctive therapies designed to interrupt the underlying chronic inflammation in allergic and inflammatory disorders.