Eotaxin-2 activates chemotaxis-related events and release of reactive oxygen species via pertussis toxin-sensitive G proteins in human eosinophils

B-cell depletion induces a shift in self antigen specific B-cell repertoire and cytokine pattern in patients with bullous pemphigoid

Bullous Pemphigoid is the most common auto-immune bullous skin disease. It is characterized by the production of auto-antibodies directed against 2 proteins of the hemi-desmosome (BP180 and BP230). We assessed the efficacy and mechanisms of action of rituximab, an anti-CD20 monoclonal antibody, in 17 patients with severe and relapsing type of bullous pemphigoid. The phenotype, cytokine gene expression, and rearrangement of BP180-specific B-cell receptor genes were performed over 2 years following treatment. At the end of the study, 5 patients had died, 3 had withdrawn from the study, and 9 patients were in complete remission. The one- and two-year relapse rates were 44.1% (95% Confidence Interval (CI): 21.0-76.0%) and 66.5%, (95% CI: 38.4-91.4%), respectively. Phenotypic analyses confirmed dramatic B-cell depletion, which lasted for 9 to 12 months. The ELISA values of serum anti-BP180 antibodies and the frequency of BP180-specific circulating B cells decreased dramatically following treatment, which paralleled the improvement of skin lesions. During B-cell reconstitution, a polyclonal IgM repertoire appeared and a shift in the rearrangement of the B-cell receptor genes of BP180-specific circulating B cells was observed. Concurrently, we observed a decrease of IL-15, IL-6 and TNFα expressing BP180-specific B cells, and the emergence of IL-10 and IL-1RA-expressing BP180-specific IgM+ B cells in patients in complete remission off therapy, suggesting the functional plasticity of BP180-specific auto-immune B cells after rituximab treatment.

Proteomic analysis of the aqueous humor in patients with wet age-related macular degeneration

PURPOSE

A number of studies have shown that the levels of some proteins in the aqueous humor (AH) are altered and correlate with the mechanisms or prognosis of many eye diseases. To identify the possible mechanisms that lead to the development of wet age-related macular degeneration (AMD), a proteomic analysis of the AH composition from wet AMD patients was performed and compared with that from non-AMD cataract patients.

EXPERIMENTAL DESIGN

Six wet AMD and six non-AMD cataract patients were enrolled. A proteomic approach which included two-dimensional electrophoresis coupled with MS and bioinformatics methods were used to identify AH proteins with altered expression in wet AMD compared with non-AMD patients. An ELISA was used to validate the proteomic results.

RESULTS

We separated 78 protein spots and identified 68 that were differently expressed in the wet AMD group and controls. Numerous proteins identified in this study are implicated in inflammation, apoptosis, angiogenesis, and oxidative stress.

CONCLUSIONS AND CLINICAL RELEVANCE

The AH protein composition was significantly different between wet AMD and non-AMD patients. The proteins identified in this study may be potential biomarkers of wet AMD development and might play a role in the mechanisms of wet AMD.

Control of extravillous trophoblast function by the eotaxins CCL11, CCL24 and CCL26

STUDY QUESTION

What are the effects of the eotaxin group of chemokines (CCL11, CCL24 and CCL26) on extravillous trophoblast (EVT) functions important during uterine decidual vessel remodelling?

SUMMARY ANSWER

CCL11, CCL24 and CCL26 can regulate EVT migration, invasion and adhesion, highlighting a potential regulatory role for these chemokines during uterine decidual spiral arteriole remodelling in the first trimester of human pregnancy.

WHAT IS KNOWN ALREADY

A successful human pregnancy depends on adequate remodelling of the uterine decidual spiral arterioles, a process carried out by EVT which invade from the placenta. The invasion by EVT into the maternal uterine decidual vessels is regulated by the interaction of many factors including members of the chemokine subfamily of cytokines.

STUDY DESIGN, SIZE, DURATION

This study used the HTR8/SVneo cell line as a model for invasive EVT. All experiments were repeated on at least three separate occasions.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The effect of recombinant human CCL11, CCL24 and CCL26 on EVT migration and invasive potential was measured using the xCELLigence real-time system, wound-healing and Matrigel invasion assays, zymography to measure MMP activity and reverse zymography to measure TIMP activity. A commercially available adhesion assay was used to assess EVT adhesion to extracellular matrix proteins.

MAIN RESULTS AND THE ROLE OF CHANCE

All the three eotaxins were found to significantly stimulate migration of the EVT-derived cell line HTR8/SVneo (P < 0.05) with no significant changes in cell number following treatment with each chemokine (P > 0.05). All the three eotaxins significantly increased HTR8/SVneo invasion (P < 0.05) and MMP2 activity (P < 0.05) without any effects on TIMP2 activity (P > 0.05). All the three eotaxins significantly increased HTR8/SVneo cell binding to collagen IV (P < 0.05) and fibronectin (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This work has been conducted in vitro with a commonly used cell line model of EVT, HTR8/SVneo.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the first to comprehensively examine the effects of the eotaxin group of chemokines on EVT functions and demonstrates that all the three eotaxins have the ability to regulate EVT functions critical to their role in vessel remodelling. This identifies a new role for the eotaxin group of chemokines during placentation.

Interleukin-15 expression is increased in human eosinophilic esophagitis and mediates pathogenesis in mice

BACKGROUND & AIMS

Quantitative microarray analyses have shown increased expression of interleukin-15 (IL-15) messenger RNA in the esophagus of patients with eosinophilic esophagitis (EoE), a recently recognized allergic disorder with poorly understood pathogenesis.

METHODS

Quantitative polymerase chain reaction and enzyme-linked immunosorbent assay analyses were performed to examine protein and transcript levels in tissue samples from patients with EoE. Tissues from IL-15Ra-deficient and wild-type (control) mice were also examined. Tissue eosinophilia was determined by immunostaining for major basic protein and flow cytometry for cell-surface receptors.

RESULTS

Quantitative polymerase chain reaction analyses showed that levels of IL-15 and its receptor IL-15Ra were increased approximately 6- and approximately 10-fold, respectively, in tissues from patients with EoE and approximately 3- and approximately 4-fold, respectively, in mice with allergen-induced EoE. A >2-fold increase in serum IL-15 protein levels was also detected in human EoE samples compared with those from healthy individuals. Human IL-15 messenger RNA levels correlated with esophageal eosinophilia (P < .001). IL-15Ra-deficient mice were protected from allergen-induced esophageal eosinophilia compared with controls (P < .001), even though similar levels of airway eosinophilia were observed in all mice. IL-15 activated STAT5 and CD4(+) T cells to produce cytokines that act on eosinophils. Incubation of primary esophageal epithelial cells from mice and humans with IL-15 caused a dose-dependent increase in the mRNA expression and protein levels of eotaxin-1, -2, and -3.

CONCLUSIONS

IL-15 mediates in the pathogenesis of EoE. IL-15 activates CD4(+) T cells to produce cytokines that act on eosinophils.

Protective effect of eotaxin-2 inhibition in adjuvant-induced arthritis

Eotaxin-2 is a potent chemoattractant for eosinophils, basophils and T helper type 2 (Th2) lymphocytes. The eotaxin-2/CCL24 receptor CCR3 is expressed in human brain, skin, endothelium and macrophages. The aim of the current study was to evaluate the protective effect of a monoclonal anti-eotaxin-2 antibody on the development of adjuvant-induced arthritis in rats (AIA). Adjuvant arthritis was induced in Lewis rats by intradermal injection of incomplete Freund's adjuvant +Mycobacterium tuberculosis. Rats were treated by intraperitoneal (i.p.) injection with three monoclonal antibodies against eotaxin-2 (G7, G8, D8) three times per week. Controls were treated with total mouse immunoglobulin G (IgG), methotrexate (MTX) or phosphate-buffered saline (PBS). Arthritis severity was evaluated by measuring ankle swelling, arthritic score, whole animal mobility and body weight. Sample joints were obtained for pathological evaluation and postmortem X-ray of ankle joints was performed to document erosions. Significant inhibition of arthritis was observed in rats treated with anti-eotaxin-2 antibodies compared to those treated with immunoglobulin or PBS. Inhibition was manifest in ankle diameter, arthritic score and mobility score. The antibody marked D8 showed the greatest efficacy. The effect was observed both in animals treated before the appearance of arthritis and in those where treatment was begun after development of joint inflammation. Combined treatment with D8 and MTX caused additional protection. Significant reduction of inflammation in D8-treated animals was also demonstrated in pathological and X-ray examinations. Inhibition of eotaxin-2 by monoclonal antibodies has a significant protective effect in adjuvant arthritis. These results may introduce a novel therapeutic target in rheumatoid arthritis and additional inflammatory joint disorders.

A new paradigm of eosinophil granulocytes: neuroimmune interactions

Eosinophil granulocytes have long been regarded as potent effector cells with the potential to release an array of inflammatory mediators involved in cytotoxicity to helminths and tissue destruction in chronic inflammatory diseases such as asthma. However, it has become evident that eosinophils are also involved in regulatory mechanisms modulating local tissue immune responses. Eosinophils take part in remodelling and repair mechanisms and contribute to the localized innate and acquired immune response as well as systemic adaptive immunity. In addition, eosinophils are involved in neuroimmune interactions modulating the functional activity of peripheral nerves. Neuromediators can also modulate the functional activity of eosinophils, revealing bidirectional interactions between the two cell types. Eosinophils are tissue-resident cells and have been found in close vicinity of peripheral nerves. This review describes neuroimmune interactions between eosinophil granulocytes and peripheral nerves and highlights why eosinophils are important in allergic diseases such as asthma.

Caffeic acid phenethyl ester attenuates allergic airway inflammation and hyperresponsiveness in murine model of ovalbumin-induced asthma

Caffeic acid phenethyl ester (CAPE) is a biologically active ingredient of propolis, which has several interesting biological properties, including antioxidant and anti-inflammatory; however, its anti-allergic effects are poorly understood. The objective of this study was to determine whether treatment with CAPE results in significant inhibition of asthmatic reactions in a mouse model. Mice sensitized and challenged with ovalbumin (OVA) had the following typical asthmatic reactions: an increase in the number of eosinophils in bronchoalveolar lavage (BAL) fluid; a marked influx of inflammatory cells into the lung around blood vessels and airways, and airway luminal narrowing; the development of airway hyperresponsiveness (AHR); the presence of tumor necrosis factor-alpha (TNF-alpha) and Th2 cytokines, including IL-4 and IL-5, in the BAL fluid; and the presence of allergen-specific IgE in the serum. Five successive intraperitoneal administrations of CAPE before the last airway OVA challenge resulted in significant inhibition of characteristic asthmatic reactions. We determined that increased generation of reactive oxygen species (ROS) by inhalation of OVA was diminished via the administration of CAPE in BAL fluid, as well as nuclear factor-kappaB (NF-kappaB) DNA binding activity. These findings indicate that oxidative stress may have a crucial function in the pathogenesis of bronchial asthma, and that CAPE may be useful as an adjuvant therapy for the treatment of bronchial asthma.

The role of the complement anaphylatoxins in the recruitment of eosinophils

Eosinophils are blood and tissue immune cells that participate in a diverse range of activities normally beneficial for the host defense, but in circumstances of untoward inflammatory conditions these cells can be responsible for pathological responses. Accordingly the transit of eosinophils from the blood to tissues is a subject of considerable importance in immunology. In this article we review how the complement anaphylatoxins, C3a and C5a bring about eosinophil extravasation. These mediators do not merely provide a chemotactic or haptotactic gradient but are responsible for orchestrating innumerable responses by other cells types, including of endothelial cells, mast cells, and basophils in order to create an environment that is conducive for eosinophil infiltration. C5a has the capacity to prime the endothelium directly to present P-selectin, and C5a stimulated generation of eosinophil hydrogen peroxide and other oxidants can cause additional upregulation of endothelial P-selectin and ICAM-1. Moreover, the anaphylatoxins have the ability to recruit mast cells and basophils and can stimulate these cells to release IL-4 and IL-13, which by augmenting endothelial VCAM-1, convey some selectivity for eosinophils. The anaphylatoxins also have the capability to evoke the release and activation of eosinophil MMP-9, which is employed by this cell type to digest its way past the subendothelial matrix. Finally, because C3a and C5a can stimulate the generation of nitric oxide along with the secretion of histamine and LTC4 from several cell types, the anaphylatoxins can bring about an increase in vascular permeability that facilitates eosinophil accumulation at sites of allergic inflammation.

Epigallocatechin-3-gallate protects toluene diisocyanate-induced airway inflammation in a murine model of asthma

Epigallocatechin-3-gallate (EGCG), a major form of tea catechin, has anti-allergic properties. To elucidate the anti-allergic mechanisms of EGCG, we investigated its regulation of matrix metalloproteinase (MMP-9) expression in toluene diisocyanate (TDI)-inhalation lung tissues as well as TNF-alpha and Th2 cytokine (IL-5) production in BAL fluid. Compared with untreated asthmatic mice those administrated with EGCG had significantly reduced asthmatic reaction. Also, increased reactive oxygen species (ROS) generation by TDI inhalation was diminished by administration of EGCG in BAL fluid. These results suggest that EGCG regulates inflammatory cell migration possibly by suppressing MMP-9 production and ROS generation, and indicate that EGCG may be useful as an adjuvant therapy for bronchial asthma.

Intranasal mite allergen induces allergic asthma-like responses in NC/Nga mice

Airway responses induced by intranasal administration of mite allergen without adjuvant were studied in NC/Nga mice. A crude extract of Dermatophagoides farinae (Df) was administered for 5 consecutive days and a single intranasal challenge booster dose was given 1 week after the last sensitization. 24 h after the single challenge, the airway hyperresponsiveness (AHR) was measured and the bronchoalveolar lavage fluid (BALF) was analyzed for numbers of eosinophils and neutrophils, and both cytokine and chemokine levels. There were marked increases in number of eosinophils in the BALF, AHR, Th2 cytokines (IL-5 and IL-13), and chemokine (eotaxin-1 and eotaxin-2) levels in the BALF following Df exposure. C57BL/6N, A/J, BALB/c, and CBA/JN mouse strains were also exposed to Df crude extract, but all of the measured responses were strongest in NC/Nga mice. Furthermore, Df-exposed NC/Nga mice showed the goblet cell hyperplasia, pulmonary eosinophilic inflammation, and increases in both total serum IgE and Df-specific IgG1. After intranasal exposure of NC/Nga mice to crude extract of Dermatophagoides pteronyssinus, the BALF eosinophilia and AHR were similar to responses induced by Df. None of the study parameters were increased in response to intranasal exposure to ovalbumin. These data demonstrated that NC/Nga mice developed allergic asthma-like responses after intranasal exposure to mite allergens.

CXCL9 inhibits eosinophil responses by a CCR3- and Rac2-dependent mechanism

Recently, inhibitory cytokine pathways for leukocyte chemoattraction and activation have been identified, but there is little insight into the operational mechanisms except for models that rely on simple receptor antagonism. We have previously identified the existence of a murine eosinophil inhibitory pathway mediated by the CXC chemokine ligand 9 (CXCL9, Mig [monokine induced by interferon-gamma]) that impressively blocks eosinophil chemoattraction and function, but the mechanism has remained elusive. We now demonstrate that Mig's inhibitory action extends beyond receptor antagonism alone. Notably, in addition to inhibiting eotaxin-induced filamentous actin (F-actin) formation and chemoattraction, Mig potently blocks platelet activating factor (PAF)- and leukotriene B4 (LTB4)-induced responses. Remarkably, Mig-treated eosinophils display an abnormal F-actin assembly in the absence of agonist stimulation. Additionally, Mig pretreatment inhibits eotaxin-induced activation of the Rho-guanosine triphosphatase (GTPase) Rac, and Rac2-deficient eosinophils demonstrate an impaired transmigration and actin polymerization response to eotaxin stimulation. Furthermore, Mig was unable to inhibit eotaxin-induced responses in Rac2-deficient eosinophils. Finally, using CCR3 gene-targeted cells, Mig's inhibitory activity is demonstrated to be mediated by CC chemokine receptor 3 (CCR3). Thus, by altering agonist-induced signaling and abrogating cytoskeletal reorganization by a Rac2-dependent mechanism, Mig markedly inhibits eosinophil responses to diverse stimuli. These results establish evidence that distinct chemokines can use CCR3 to induce opposing signals in eosinophils.

CD28 and secretory immunoglobulin A-dependent activation of eosinophils: inhibition of mediator release by the anti-allergic drug, suplatast tosilate

BACKGROUND

Eosinophils are major effector cells in allergic diseases. After their recruitment to sites of inflammation, they contribute to the pathophysiology of the disease by releasing granule proteins and cytokines. Suplatast tosilate (IPD-1151T), a new anti-allergic agent, has shown beneficial effect in the treatment of asthma, associated with reduced bronchoalveolar lavage eosinophil infiltration and eosinophilic cationic protein (ECP) release in serum and sputum.

OBJECTIVE

We investigated whether suplatast tosilate could exert direct effects on human eosinophil activation.

METHODS

Eosinophils from hypereosinophilic patients or normal donors were purified by Percoll gradient and the magnetic cell separation system. Chemotaxis was studied using the Boyden chamber technique using three chemoattractants, formyl-methionine-leucine-phenylalanine (fMLP), IL-5 and eotaxin. Oxidative metabolism was determined by a luminol-dependent chemiluminescence assay after activation with eotaxin or secretory IgA (sIgA). The release of ECP and eosinophil derived neurotoxin (EDN) was measured by radioimmunoassay and cytokine production was determined by ELISA following activation with sIgA or anti-CD28.

RESULTS

The chemotactic response to fMLP, IL-5 and eotaxin was significantly inhibited by IPD-1151T. Suplatast tosilate was partially inhibiting the release of reactive oxygen species (ROS) induced by eotaxin and sIgA. Activation by sIgA and CD28 ligation resulted in the release of ECP and EDN, which was inhibited by IPD-1151T. Upon activation by anti-CD28, only IL-13 production was inhibited by IPD-1151T, whereas release of IL-2 and IFN-gamma was not affected. IL-10 release induced by sIgA was also inhibited by IPD-1151T. Additionally, the pro-inflammatory cytokine IL-6, which was secreted following anti-CD28 and sIgA stimulation, was strongly inhibited by IPD-1151T.

CONCLUSION

Through inhibition of chemotaxis, IPD-1151T might limit the number of eosinophils at the inflammation site. Furthermore, it could reduce the pathological potential of eosinophils by inhibiting the release of ROS and cationic proteins, main inflammatory mediators produced by eosinophils. Moreover, the inhibition of immunoregulatory cytokines released by eosinophils could locally modify the immune response.

Chemokine receptor antagonists: a novel therapeutic approach in allergic diseases

The aim of this review is to give an overview of the role of chemokines, particularly ligands of the CC chemokine receptor CCR3, in allergic diseases and to show the new concept in the treatment of allergies using chemokine receptor antagonists. Allergic diseases such as allergic asthma, allergic rhinitis and atopic dermatitis are characterized by a complex interaction of different cell types and mediators. Among this, Th2 cells, mast cells, basophils and eosinophils are found in the inflamed tissue due to the attraction of chemokines. Of all the known chemokine receptors, the chemokine receptor CCR3 seems to play the major role in allergic diseases which is supported by the detection of this receptor on the cell types mentioned above. Therefore, academic and industrial research focus on compounds to block this receptor. To date, certain chemokine receptor antagonists derived from peptides and small molecules exist to block the chemokine receptor CCR3. However, the in vivo data about these compounds and the mechanisms of receptor interaction are poorly understood, as yet. For the development of additional chemokine receptor antagonists, more details about the interaction between the ligands and their receptors are required. Therefore, additional studies will lead to the identification of novel CCR3 chemokine receptor antagonists, which can be therapeutically used in allergic asthma, allergic rhinitis, and atopic dermatitis.

Immunopathogenesis of experimental ulcerative colitis is mediated by eosinophil peroxidase

The precise role that individual inflammatory cells and mediators play in the development of gastrointestinal (GI) dysfunction and extraintestinal clinical manifestations of ulcerative colitis (UC) is unknown. In this study, we have used a mouse model of UC to establish a central role for eotaxin and, in turn, eosinophils in the development of the immunopathogenesis of this disease. In this model the administration of dextran sodium sulfate (DSS) induces a prominent colonic eosinophilic inflammation and GI dysfunction (diarrhea with blood and shortening of the colon) that resembles UC in patients. GI dysfunction was associated with evidence of eosinophilic cytolytic degranulation and the release of eosinophil peroxidase (EPO) into the colon lumen. By using IL-5 or eotaxin-deficient mice, we show an important role for eotaxin in eosinophil recruitment into the colon during experimental UC. Furthermore, using EPO-deficient mice and an EPO inhibitor resorcinol we demonstrate that eosinophil-derived peroxidase is critical in the development of GI dysfunction in experimental UC. These findings provide direct evidence of a central role for eosinophils and EPO in GI dysfunction and potentially the immunopathogenesis of UC.

Chemokines in eosinophil-associated gastrointestinal disorders

Eosinophil-associated gastrointestinal disorders (EGDs) are characterized by a pronounced cellular inflammation. Recent clinical and experimental investigations have implicated a family of molecules known as chemokines in the regulation of leukocyte recruitment in these diseases. The underlying cellular and molecular mechanisms involved in chemokine-mediated cellular infiltration are largely unknown. In this review, we describe the role of CD4+ T cells and eosinophils in the clinical manifestations of EGDs and discuss the current understanding of the role of chemokines in the recruitment of these cells in the expression of diseases.

Eotaxin-2 and IL-5 cooperate in the lung to regulate IL-13 production and airway eosinophilia and hyperreactivity

BACKGROUND

Eotaxin-2 is a member of the eotaxin subfamily of CC chemokines that display eosinophil-specific, chemotactic properties and has been associated with allergic disorders. However, the contribution of eotaxin-2 to the development of defined pathogenic features of allergic disease remains to be defined.

OBJECTIVE

We sought to determine whether eotaxin-2 was a cofactor with IL-5 for the regulation of pulmonary eosinophilia and to identify the combined role of these molecules in the induction of phenotypic characteristics of allergic lung disease.

METHODS

We instilled recombinant eotaxin-2 into the airways of wild-type mice that had been treated systemically with IL-5 or into IL-5-transgenic mice and characterized pulmonary eosinophil numbers, IL-13 production, and airway hyperreactivity (AHR) to methacholine. Mice deficient in the IL-4 receptor alpha-chain, IL-13, and signal transducers and activators of transcription 6 or mice treated with anti-CCR3 monoclonal antibody were also used.

RESULTS

Eotaxin-2 and IL-5 cooperatively promoted eosinophil accumulation, IL-13 production, and AHR to methacholine. Neither eotaxin-2 nor IL-5 alone induced these features of allergic disease. IL-13 production was critically dependent on eotaxin-2- and IL-5-regulated eosinophilia, which predisposed to the development of AHR. AHR was dependent on IL-13 and signaling through the IL-4R alpha-chain and signal transducers and activators of transcription 6 pathways and the presence of eosinophils in the lung.

CONCLUSION

These investigations demonstrate important cooperativity between eotaxin-2, IL-5, and IL-13 signaling systems and eosinophils for the development of hallmark features of allergic disease of the lung.

Significant elevation of serum levels of eotaxin-3/CCL26, but not of eotaxin-2/CCL24, in patients with atopic dermatitis: serum eotaxin-3/CCL26 levels reflect the disease activity of atopic dermatitis

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease characterized by the predominant infiltration of T cells, eosinophils and macrophages in lesional skin. Recently, eotaxin-2/CCL24 and eotaxin-3/CCL26 were identified as CC chemokines that signal exclusively via the CCR3 receptor and have eosinophil-selective chemoattractant activity, as does eotaxin/CCL11. We previously reported that serum levels of thymus and activation-regulated chemokine (TARC)/CCL17 and macrophage-derived chemokine (MDC)/CCL22 were correlated with the severity of AD. In this report, we investigated the participation of eotaxin-2/CCL24 and eotaxin-3/CCL26 in AD, first measuring the serum levels of eotaxin-2/CCL24 and eotaxin-3/CCL26 in 30 patients with AD, 20 patients with psoriasis vulgaris and 20 healthy controls. The serum levels of eotaxin-3/CCL26 (but not eotaxin-2/CCL24) were significantly higher in patients with AD than in either healthy controls or patients with psoriasis vulgaris; furthermore, the eotaxin-3/CCL26 levels in patients with moderate and severe AD were significantly higher than eotaxin-3/CCL26 levels in patients with mild AD. The serum eotaxin-3/CCL26 levels tended to decrease after treatment, but there was no significant difference between groups. Moreover, the serum eotaxin-3/CCL26 levels were significantly correlated with the serum TARC/CCL17 and MDC/CCL22 levels, eosinophil numbers in peripheral blood and the scoring AD (SCORAD) index. Our study strongly suggests that serum levels of eotaxin-3/CCL26, but not of eotaxin-2/CCL24, have a notable correlation with disease activity of AD and that eotaxin-3/CCL26, as well as TARC/CCL17 and MDC/CCL22, may be involved in the pathogenesis of AD.

Inhibition of CCL11, CCL24, and CCL26-induced degranulation in HL-60 eosinophilic cells by specific inhibitors of MEK1/MEK2, p38 MAP kinase, and PI 3-kinase

Eosinophilic leukocytes are the cellular hallmark of allergic inflammation. Apart from being potent eosinophils chemoattractants, the eotaxins CCL11, CCL24 and CCL26 are capable of activating eosinophils to generate reactive oxygen species, lipid mediators of inflammation and degranulation of toxic granule proteins. Due to their central role in eosinophil trafficking and activation, understanding the signal transduction mechanism of the eotaxin-induced eosinophil effector functions may provide an innovative therapeutic strategy for eosinophil-associated diseases. Thus, these investigations were conducted to delineate signal transduction mechanisms of CCL11, CCL24 and CCL26-induced eosinophil peroxidase (EPO) degranulation following pretreatment of cells with or without a specific inhibitor of MEK1/MEK2 (U0126), inhibitor of p38 MAP kinase (SB203580) or a specific inhibitor of PI 3-kinase (LY294002). Results have shown that CCR3-mediated eotaxin-induced eosinophilic degranulation was concentration-dependently reduced by specific inhibitors of ERK1/ERK2, p38 MAP kinase and PI 3-kinase. However, the rank order of U0126 with respect to inhibition of chemokine-induced degranulation was CCL11 = CCL24 > CCL26. Potentiation of eotaxin-induced EPO degranulation by IL-5 was also seen. These investigations have not only confirmed the reported co-operativity between IL-5 and the eotaxins but also showed that the eosinophil-degranulating capabilities of the eotaxin CCL11, CCL24 and CCL26 is a consequence of activation of ERK1/ERK2, p38 MAP kinase and PI 3-kinase. Thus, these signaling molecules may provide the biochemical basis for mechanism-based therapy of allergic inflammatory diseases.

Inhibitory effects of ketotifen on eotaxin-dependent activation of eosinophils: consequences for allergic eye diseases

BACKGROUND

The aim of this study was to investigate the effects of ketotifen on different parameters of human eosinophil functions, namely chemotaxis, oxidative metabolism and mediator release, induced after activation.

METHODS

Eosinophils from hypereosinophilic patients or normal donors were purified by Percoll gradient and the magnetic cell separation system. Chemotaxis was studied using the Boyden chamber technique using three potent chemoattractants: formyl-methionine-leucine-phenylalanine (fMLP), interleukin (IL)-5 and eotaxin. Oxidative metabolism was determined by a luminol-dependent chemiluminescence assay after activation with eotaxin or secretory immunoglobulin A (sIgA). The release of eosinophil cationic protein (ECP) and eosinophil derived neurotoxin (EDN) was measured by radioimmunoassay after activation with sIgA.

RESULTS

At pharmacologically active concentrations and in a dose-dependent manner, ketotifen significantly inhibited the chemotaxis of eosinophils to fMLP, IL-5 and eotaxin. The production of reactive oxygen species induced by eotaxin and sIgA was decreased by ketotifen, showing a more pronounced effect when cells were activated by eotaxin. Activation by sIgA resulted in ECP and EDN release, which was partially inhibited by ketotifen.

CONCLUSIONS

Through inhibition of chemotaxis, ketotifen might limit the number of eosinophils at the inflammation site during allergic reaction. Furthermore, inhibition by ketotifen of main inflammatory mediators release suggests a potential role of the drug in limiting the pathological potential of eosinophils.

Regulatory effects of eotaxin, eotaxin-2, and eotaxin-3 on eosinophil degranulation and superoxide anion generation

Eosinophilic leukocytes have been implicated as primary effector cells in inflammatory and allergic diseases. When activated by cytokines, human eosinophils secrete and produce a variety of proinflammatory or tissue damaging substances. Although well known for their chemoattractant effects, little is known about the precise contribution of the eosinophil-selective chemokines, eotaxin, eotaxin-2, and eotaxin-3 to the effector functions of eosinophils. This forms the central focus of these investigations for which clone 15-HL-60 human eosinophilic cells were used as the in vitro model. Investigation results suggest that all three subtypes of eotaxin directly stimulate eosinophil superoxide anion generation that is inhibited by neutralizing eotaxin antibody or pretreatment of cells with the receptor antibody anti-CCR3. Pretreatment or co-treatment with each of the eotaxins augmented phorbol myristate-induced superoxide generation. Concentration-dependent degranulation of eosinophil peroxidase was noted for all three chemokines, and potentiation of calcium ionophore-induced degranulation was observed with eotaxin pretreatments. Results of interleukin-5 pretreatment studies suggest that the eotaxin chemokines may act cooperatively to enhance effector functions of eosinophils. Collectively, the present studies have advanced knowledge of the eotaxin family of chemokines to include eosinophil priming and modulation of eosinophil activation and secretion effector functions.

Experimental analysis of eosinophil-associated gastrointestinal diseases

Eosinophil infiltration into the gastrointestinal tract occurs in a wide range of diseases. However, the underlying cellular and molecular mechanisms involved in eosinophil migration and the role of eosinophils in disease pathogenesis are largely unknown. Recent studies using experimental models of eosinophil-associated gastrointestinal allergy have revealed differential roles for IL-5 and eotaxin in the modulation of eosinophil accumulation into various regions of the gastrointestinal tract. Furthermore, such studies have revealed a possible role for eosinophils in the pathogenesis of gastrointestinal disorders. The present review describes the clinical manifestations of various eosinophil-associated gastrointestinal disorders and the current understanding of the role of IL-5 and eotaxin in the allergic inflammatory response, and the participation of the eosinophilic granulocyte in the expression of disease.

Antichemokine immunotherapy for allergic diseases

Chemokines have emerged as critical regulators of leukocyte function and as such represent attractive new targets for the therapy of allergic diseases. Recent studies have revealed important roles for the chemokine family in both the afferent and efferent limbs of the immune system, orchestrating and integrating innate and acquired immune responses. A subset of chemokines including eotaxin-1 (also called CCL11), eotaxin-2 (CCL24), eotaxin-3 (CCL26), MCP (monocyte chemoattractant protein)-3 (CCL7), MCP (monocyte chemoattractant protein)-4 (CCL13), TARC (thymus- and activation-regulated chemokine) (CCL17), and MDC (macrophage-derived chemokine) (CCL22) are highly expressed in allergic inflammation and are regulated by T helper type 2 cytokines. Receptors for these chemokines, including CCR3 (CC chemokine receptor 3), CCR4 (CC chemokine receptor 4) and CCR8 (CC chemokine receptor 8) are expressed on key leukocytes associated with allergic inflammation, such as T helper type 2 cells, eosinophils, mast cells and basophils, establishing a subset of chemokine/chemokine receptors potentially important in allergic inflammation. Recent data using inhibitory antibodies and chemokine antagonists support the concept that interfering with this subset of chemokines and their receptors represents a new approach to allergy immunotherapy.

Chemokine receptors

Although chemokines were originally defined as host defense proteins it is now clear that their repertoire of functions extend well beyond this role. For example chemokines such as MGSA have growth regulatory properties while members of the CXC chemokine family can be mediators or inhibitors of angiogenesis and may be important targets for oncology. Recent work shows that the chemokine receptor CXCR4 and its cognate ligand SDF play important roles in the development of the immune, circulatory and central nervous systems. In addition, chemokine receptors play an important role in the pathogenesis of the AIDS virus, HIV-1. Taken together these findings expand the biological importance of chemokines from that of simple immune modulators to a much broader biological role than was at first appreciated and these and other properties of the chemokine receptor family are discussed in detail in this review.

Detection of mRNA for eotaxin-2 and eotaxin-3 in human dermal fibroblasts and their distinct activation profile on human eosinophils

As many new biologically active chemokines have been cloned exploring the genomic DNA sequence database in the vicinity of already known chemokine sequences without demonstrating their natural origin, it is important to transfer findings from in vitro experiments with chemokines into the in vivo situation. With respect to eosinophils and fibroblasts that play an important part in the pathogenesis of allergic and autoimmune diseases, the role of the recently discovered members of the eotaxin family, eotaxin-2 and eotaxin-3, is not really understood. In order to elucidate the origin and biologic potency of the eotaxin family this study was performed. Conventional reverse transcription-polymerase chain reaction analysis was suitable to detect mRNA for eotaxin and eotaxin-3 but not for eotaxin-2 in dermal fibroblasts. In contrast to conventional reverse transcription-polymerase chain reaction, LightCycler analysis revealed that dermal fibroblasts constitutively expressed mRNA not only for eotaxin and eotaxin-3 but also for eotaxin-2. Moreover, with this technique we investigated mRNA expression levels after stimulation of fibroblasts with interleukin-4 and interleukin-4 plus tumor necrosis factor-alpha: the rank order of expression levels within the eotaxin family was eotaxin > eotaxin-3 > eotaxin-2. To address the question of the efficacy of eotaxin-3, we compared its activity with eotaxin, eotaxin-2, monocyte chemotactic protein-3, monocyte chemotactic protein-4, and RANTES in different test systems for eosinophils. The efficacy of the CC chemokines at equimolar concentrations with respect to the chemotactic response of human eosinophils was eotaxin-3 = eotaxin = eotaxin-2 > RANTES > monocyte chemotactic protein-4. The rank order of activity with respect to actin polymerization and release of toxic reactive oxygen species was eotaxin-3 = eotaxin = eotaxin-2 and eotaxin = eotaxin-2 > eotaxin-3 = monocyte chemotactic protein-3 = monocyte chemotactic protein-4 = RANTES, respectively. This study indicated a distinct profile in expression levels of the members of the eotaxin family in dermal fibroblasts. Indeed, all three eotaxin ligands demonstrated activation of human eosinophils with similar efficacies for chemotaxis, cytoskeletal rearrangements, activation of Gi proteins and transients of [Ca2+]i, but a distinct profile of activity with respect to the binding to CCR3 and the release of toxic reactive oxygen species. These findings may help to understand further the role of CC chemokines in fibroblast/eosinophil activation, which is of interest particularly in allergic and autoimmune diseases.

Characterization of the CC chemokine receptor 3 on human keratinocytes

CC chemokine receptors are expressed on hematopoietic cells, and these may impart selective homing of monocyte, leukocyte, and lymphocyte subsets to sites of inflammation. CC chemokine receptor 3 is the major receptor on eosinophils and is also expressed on other inflammatory cells suggesting its important role for allergic diseases such as atopic dermatitis and bronchial asthma. Eotaxin, eotaxin-2 and eotaxin-3 have been identified as ligands that only activate CC chemokine receptor 3. CC chemokine receptor 3 is also activated by other promiscuous ligands, however, such as RANTES and monocyte chemotactic protein 4. To date, CC chemokine receptor 3 has not been reported to be expressed on nonhematopoietic cells. In this study, we investigated whether keratinocytes possess autocrine and paracrine mechanisms for CC chemokine secretion and receptor expression as reported for the expression of interleukin 8 and its receptors. Reverse transcriptase polymerase chain reaction analysis demonstrated that CC chemokine receptor 3 mRNA is expressed constitutively in cultured keratinocytes. The signal quantities of the CC chemokine receptor 3 amplicons showed lower intensities for keratinocytes than for eosinophils. In situ hybridization techniques exhibited that basal cell layers of the epidermis were stained homogeneously for CC chemokine receptor 3 mRNA with a decreasing signal to the upper epidermis showing that differentiating and proliferating keratinocytes did express mRNA specific for CC chemokine receptor 3. Immunohistochemical studies confirmed low expression of CC chemokine receptor 3 protein on epidermal keratinocytes compared to the high level observed on infiltrating eosinophils. Furthermore, stimulation of cultured keratinocytes with eotaxin resulted in an increased [3H]thymidine incorporation indicating a role of CC chemokine receptor 3 in epidermal proliferation and differentiation. These data demonstrate that CC chemokine receptor 3 is expressed not only on hematopoietic cells but also on keratinocytes as nonhematopoietic cells with ectodermal origin. Therefore, the identification of CC chemokine receptor 3 on epidermal keratinocytes may indicate a role for CC chemokine receptor 3 and its ligands in skin physiology and pathophysiology.

The CC chemokine receptor 3 CCR3 is functionally expressed on eosinophils but not on neutrophils

The chemokine subclasses differ in their biological activity to stimulate different kinds of effector cells via distinct chemokine receptors. Controversial results about the expression of the CC chemokine receptor CCR3 on the surface of human neutrophils have been described. To find out whether eosinophil contamination might be responsible for these diverse observations, CCR3 expression on highly purified neutrophils and eosinophils was investigated. We enriched neutrophils from a heterogeneous granulocyte population with immunomagnetic beads coated with various anti-CD52 monoclonal antibodies. This procedure was suitable to enrich neutrophils with a purity of up to 99.85%. Reverse transcriptase-PCR revealed that CCR3 mRNA was not expressed by CD52-negative selected neutrophils. In contrast to these cells, CCR3 mRNA could be detected in a heterogeneous granulocyte population and CD16-negative selected eosinophils. In addition, spectrofluorometric measurement of intracellular calcium concentration ([Ca2+]i) demonstrated that CD52-negative selected neutrophils did not show a transient [Ca2+]i increase following stimulation with the CCR3 ligand eotaxin, whereas the heterogeneous granulocyte population as well as eosinophils did respond. Therefore, previous studies demonstrating the expression of CCR3 on human neutrophils have to be re-evaluated because CCR3 mRNA detection on human neutrophils due to contamination by mRNA from eosinophils could not be excluded.

Are chemokines essential or secondary participants in allergic responses?

OBJECTIVES

This review will provide a concise and critical overview of the rapidly evolving concepts in chemokine biology with a special relevance to allergic responses. The article is intended for clinicians with little or no expertise in chemokine biology.

DATA SOURCES

A detailed literature search was performed through MEDLINE (PubMed). Those reports considered important and relevant to the topic were critically reviewed and their conclusions included.

RESULTS

Chemokines are a group of structurally related small proteins with a common biological activity of inducing directional migration (chemotaxis) of various cell types. Chemokines such as eotaxins and MCP-4 play a key role in selective eosinophil recruitment to sites of inflammation in allergies and asthma. Several other chemokine activities relevant to allergic responses are: activation of basophils and eosinophils to release inflammatory mediators, regulation of IgE responses, and Th1/Th2-type cytokine balance. A number of therapeutic strategies aimed at inhibiting chemokine function are being tested in animal models of allergies and asthma.

CONCLUSIONS

Chemokines have been widely viewed as pathogenic mediators of acute and chronic inflammation and tissue damage in allergies and asthma. On the other hand, recent evidence suggests that endogenous production of certain chemokines might be beneficial to the host in preventing allergic response. Met-RANTES, a modified antagonist of RANTES, and eotaxin receptor (CCR3) antagonists, represent promising novel therapeutic agents potentially useful in atopic disorders. Thus, suppression of chemokines may interrupt the sequence of signals culminating in an allergic response. Whether chemokines are actually essential for an allergic response awaits confirmation with gene knockout animal experiments.

Chemokine receptors and their role in inflammation and infectious diseases

Chemokines are small peptides that are potent activators and chemoattractants for leukocyte subpopulations and some nonhemopoietic cells. Their actions are mediated by a family of 7-transmembrane G-protein–coupled receptors, the size of which has grown considerably in recent years and now includes 18 members. Chemokine receptor expression on different cell types and their binding and response to specific chemokines are highly variable. Significant advances have been made in understanding the regulation of chemokine receptor expression and the intracellular signaling mechanisms used in bringing about cell activation. Chemokine receptors have also recently been implicated in several disease states including allergy, psoriasis, atherosclerosis, and malaria. However, most fascinating has been the observation that some of these receptors are used by human immunodeficiency virus type 1 in gaining entry into permissive cells. This review will discuss structural and functional aspects of chemokine receptor biology and will consider the roles these receptors play in inflammation and in infectious diseases.

Chemokine receptors and their role in inflammation and infectious diseases

Chemokines are small peptides that are potent activators and chemoattractants for leukocyte subpopulations and some nonhemopoietic cells. Their actions are mediated by a family of 7-transmembrane G-protein–coupled receptors, the size of which has grown considerably in recent years and now includes 18 members. Chemokine receptor expression on different cell types and their binding and response to specific chemokines are highly variable. Significant advances have been made in understanding the regulation of chemokine receptor expression and the intracellular signaling mechanisms used in bringing about cell activation. Chemokine receptors have also recently been implicated in several disease states including allergy, psoriasis, atherosclerosis, and malaria. However, most fascinating has been the observation that some of these receptors are used by human immunodeficiency virus type 1 in gaining entry into permissive cells. This review will discuss structural and functional aspects of chemokine receptor biology and will consider the roles these receptors play in inflammation and in infectious diseases.

The coupling of 5-oxo-eicosanoid receptors to heterotrimeric G proteins

5-Oxo-eicosatetraenoic acid (5-oxoETE) stimulated human neutrophil (PMN) and eosinophil chemotaxis, PMN hexose uptake, and PMN membrane GTP/GDP exchange. Pertussis toxin (PT), a blocker of heterotrimeric G proteins (GP), completely inhibited these responses, but proved far less effective on the same responses when elicited by leukotriene B4, C5a, FMLP, platelet-activating factor, IL-8, or RANTES chemotactic factors. 5-OxoETE also specifically bound to the membrane preparations that conducted GTP/GDP exchange. This binding was down-regulated by GTPgammaS, but not ADPgammaS, and displaced by 5-oxoETE analogues, but not by leukotriene B4, lipoxin A4, or lipoxin B4. Finally, PMN expressed PT-sensitive GP alphaiota2 and PT-resistant GP alphaq/11- and alpha13-chains; eosinophils expressed only alphai2 and alphaq/11. We conclude that 5-oxoETE activates granulocytes through a unique receptor that couples preferentially to PT-sensitive GP. The strict dependency of this putative receptor on PT-sensitive GP may underlie the limited actions of 5-oxoETE, compared with other CF, and help clarify the complex relations between receptors, GP, cell signals, and cell responses.

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.

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.

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.

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.

Cu/Zn superoxide dismutase in excretory-secretory products of the human hookworm Necator americanus. An electron paramagnetic spectrometry study

EPR spectrometry was used to investigate the effect of excretory/secretory product from Necator americanus on superoxide radical anions generated by xanthine/xanthine oxidase as a measure of excretory/secretory product superoxide dismutase activity. Using 1,1',5,5'-dimethylpyrollidine-N-oxide (DMPO) as a superoxide spin-trapping agent a 12-line EPR spectrum characteristic of the DMPO-OOH adduct was observed to decrease in the presence of excretory/secretory product. Superoxide dismutase activity was proportional to excretory/secretory protein concentration, was inhibited with cyanide treatment and was progressively destroyed with increasing time of heat denaturation of excretory/secretory product. Using a purpose-built chamber the superoxide dismutase activity of excretory/secretory product from live worms in culture was shown to accumulate with time to a maximum at 4 h. The electron paramagnetic resonance spectrum obtained for the frozen excretory/secretory product of N. americanus recorded at 77 K is typical of Cu(II) in a protein matrix. The results are consistent with the presence of an active Cu/Zn superoxide dismutase in excretory/secretory product from N. americanus and demonstrate a method for the unequivocal determination of the fate of superoxide anions in the presence of live worms.

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.

The CC chemokine receptor antagonist met-RANTES inhibits eosinophil effector functions

Eosinophils play an important role in allergic diseases such as allergic asthma, rhinoconjunctivitis and atopic dermatitis. Recruitement of eosinophils to the side of inflammation, the release of reactive oxygen species, leading to tissue damage, and the propagation of the inflammatory response are mediated by chemokines. Thus, the applicability of agents able to inhibit or antagonize chemokine-induced eosinophil activation seems to be of interest in the treatment of allergic diseases. Therefore, the effect of the CC chemokine antagonist, Met-RANTES, on its effect on human eosinophil effector functions in response to RANTES, MCP-3 and eotaxin was investigated. Met-RANTES had no intrinsic activity on [Ca2+]i transients in eosinophils and was able to dose-dependently inhibit [Ca2+]i transients in eosinophils following stimulation with RANTES, MCP-3 and eotaxin. Besides its effect on [Ca2+]i transients, Met-RANTES dose-dependently inhibited actin polymerization in eosinophils and the release of reactive oxygen species following stimulation with RANTES, MCP-3 and eotaxin. The results of this study lead to the conclusion that Met-RANTES is an effective and powerful compound to antagonize effector functions of human eosinophils following stimulation with RANTES, MCP-3 and eotaxin and is therefore a promising therapeutic approach to prevent the invasion and destructive power of eosinophils in allergic diseases.